S - P N

S - P N
STUDY ON ONE-STAGE PARTIAL
NITRITATION-ANAMMOX PROCESS IN
MOVING BED BIOFILM REACTORS: A
SUSTAINABLE NITROGEN REMOVAL
Andrea Bertino
December 2010
TRITA-LWR Degree Project
ISSN 1651-064X
LWR-EX-11-05
Andrea Bertino
TRITA LWR Degree Project
© Andrea Bertino 2010
Degree Project in the Master‟s program Water Systems Technology
Water System Technology
Department of Land and Water Resources Engineering
Royal Institute of Technology (KTH)
SE-100 44 STOCKHOLM, Sweden
Reference should be written as: Bertino, A. (2010) “Study on one-stage Partial Nitritation-Anammox process in Moving Bed Biofilm Reactors: a sustainable nitrogen removal” TRITA LWR
Degree Project
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Dedicated to my Family and Federica
"We forget that the water cycle and the life cycle are one." Jacques Cousteau
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TRITA LWR Degree Project
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
S UMMARY IN S WEDISH
Under det senaste decenniet har flera nya och kostnadseffektiva biologiska kvävereningstekniker
utvecklats. Upptäckten av anaerob ammoniumoxidation (Anammox), för ca 15 år sedan, har resulterat i
nya möjligheter för forskning och utveckling av hållbara kvävereningssystem. Jämfört med konventionell
nitrifikation/denitrifikation, eliminerar Anammox behovet av organisk kolkälla, har en mindre produktion
av överskottsslam, minskar efterfrågan på energi för luftning (upp till 60-90%) och CO2-utsläpp (upp till
90%). System baserade på Anammox kan vara till stor hjälp för att uppfylla strängare utsläppskrav för
avloppsvatten och minska miljöproblem som orsakas av utsläpp av näringsämnen (t.ex. eutrofiering).
Denna avhandling undersöker partiell nitritation/Anammox i ett enstegssystem under syrebegränsande
villkor (även kallad CANON eller Deammonifikation) och med Moving Bed Biofilm Reactor (MBBR™)
teknik. Anammoxprocessen kopplad till partiell nitritation kan vara särskilt lämpad för att behandla
ammoniumrikt avloppsvatten med lågt innehåll av biologiskt nedbrytbart organiskt material, som
rejektvatten från avvattning av rötslam, som vanligen recirkuleras tillbaka till huvudströmmen i
avloppsreningsverk och står för 15-20% av den totala kvävebelastningen.
Partiell nitritation/Anammoxprocessen testades framgångsrikt på en anläggning i pilotskala i fyra månader
vid 25 ° C, i en 200 L Continuous Stirred Tank Reactor (CSTR), fylld till 40% av Kaldnes bärarmedia
(modell K1). Vid en ammoniumytbelastning (ASL) på 3,.45 gN m-2 d-1, var kvävereningsgraden 2,85 gN
m-2 d-1. Avlägsningseffektiviteter på 95%, 85% och 83% uppnåddes för respektive NH4+-N, oorganiskt
kväve och Total kväve (TN). Bakterieaktiviteten bestämmdes med batchtester såsom S Specific
Anammoxaktivitet (SAA), syreupptagshastighet (OUR) och nitratupptagshastighet (NUR), som avslöjade
en ökning i aktiviteten för Nitrosomonas- och Anammoxbakterier i biofilmen. Koncentrationen löst
syrgas i vattenfasen var en avgörande parameter, medan pH och konduktivitet visade sig vara två
användbara verktyg för övervakning.
Två reaktorer i laboratorieskala drevs tidigare i två månader vardera, för att utvärdera en enstegs partiell
nitritation/Anammoxprocess med lägre ASL. En reaktor tillfördes utspätt rejektvatten, medan den andra
behandlade utflödet från UASB-reaktorn (Up-flow Anaerobic Sludge Blanket) efter sandfiltrering. Ganska
bra verkningsgrad (> 75%) uppnåddes, men i det sista fallet kan låg ammoniumkvävebelastningen
innebära ett problem för en stabil fullskaleinstallation och långsiktig tillväxt av Anammoxbakterier.
Några förslag för en fullskalig implementering och fortsatt forskning föreslås i det sista kapitlet i detta
examensarbete.
Nyckelord: Anammox Biofilm; Deammonifikation; CANON; Moving Bed Biofilm reaktor;
Rejektvatten.
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Andrea Bertino
TRITA LWR Degree Project
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
A CKNOWLEDGMENTS
It is a pleasure to thank my supervisor Professor Elżbieta Płaza who made this interesting thesis possible.
It allowed me to investigate a subject of current importance and to learn a lot, from both theoretical and
practical points of view. I am indeed grateful to you and I wish you good luck in the hope of achieving
rewarding results from this excellent research on the deammonification process.
The research on deammonification process was funded by Swedish Institute and Swedish Water Development (SVU).
I am heartily grateful to my teachers, Professors Giuseppe Genon and Maurizio Onofrio, who, despite the
problem of distance, have been always promptly available for me in order to help me and solve my doubts
during my study.
Jingjing Yang, PhD student at KTH (Department of Land and Water Resources Engineering) and friend,
deserves an enormous thank for her patience and helpful support provided during the whole study. I have
really appreciated your effort and your guidance that, especially at the beginning of the study, allowed me
to develop the necessary understanding of the subject. You have always been available to discuss issues of
experimentation with me and share your knowledge and views throughout the whole study. I do hope that
all your efforts will be rewarded in your professional carrier in the best way.
I would like to acknowledge Dr. Eng. Jozef Trela (KTH), the leader of the “deammonification project”
for his help and his knowledge.
Special thanks go to Dr. Eng. Christian Baresel and Dr. Eng. Lars Bengtsson from Swedish Environmental Research Institute (IVL), for their kindness, assistance and help when needed and for creating a friendly and pleasant atmosphere at the Hammarby Sjöstadsverk research facility.
I am also thankful Dr. Eng. Monika Żubrowska for sharing her experience about experimental work and
Rune Bergström for his contribution regarding the pilot plant reactor.
I would like to extend my gratitude to the excellent KTH Library service that allowed me to have access
to scientific literature necessary to carry out this Master Thesis.
Further thanks should also go to Politecnico of Turin (Servizio Gestione Didattica) for granting a scholarship for development of thesis abroad and EDISU (Ente regionale per il DIritto allo Studio Universitario),
Politecnico of Turin and European Union for the financial support within the ERASMUS programme.
Many thanks go also to my family for all their love, support and encouragement during my studies.
I am heartily thankful to my girlfriend Federica, who, even though I have been away for several months,
has always been present with her love, kindness and understanding. You are unique and I cannot thank
you enough.
A special thank you also to all my friends who have made my time in Stockholm enjoyable, with countless
memories. I am grateful for having shared with you this amazing international experience.
Finally, I want to thank everyone, both within and outside of the University, who has sparked my interest
in environmental issues including wastewater treatment and protection of water resources.
Thank you!
Stockholm, December 2010.
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TRITA LWR Degree Project
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
T ABLE OF C ONTEN TS
Summary in Swedish ....................................................................................................................v
Acknowledgments ..................................................................................................................... vii
Table of Contents ....................................................................................................................... ix
Acronyms and Symbols .............................................................................................................. xi
Abstract ........................................................................................................................................ 1
1
Introduction ....................................................................................................................... 1
1.1
1.2
Environmental problems related to nitrogen discharges .......................................... 3
Nitrogen removal in WWTPs...................................................................................... 6
1.2.1
1.2.2
1.2.3
1.2.4
1.2.5
1.2.6
1.2.7
1.2.8
1.2.9
1.3
Moving Bed Biofilm Reactor (MBBR) technology ................................................. 20
1.3.1
1.3.2
1.3.3
2
3
Physical - chemical methods ............................................................................................... 7
Conventional Nitrification/Denitrification ......................................................................... 9
Innovative and sustainable technologies for biological nitrogen removal .......................... 11
Nitritation-Denitritation (SHARON®) ............................................................................. 12
ANAMMOX® process ..................................................................................................... 13
Partial nitritation and ANAMMOX in separate reactors (2-reactor system) ....................... 15
Partial nitritation and ANAMMOX in one single reactor (1-reactor system) ..................... 16
DENAMMOX process .................................................................................................... 18
Bio-Augmentation BABE®............................................................................................... 18
Introduction of MBBR ..................................................................................................... 20
Advantages compared with activated and granular sludge and fixed biofilm systems ......... 21
Kaldnes Moving Bed™ Process ....................................................................................... 22
Aim of the present study ................................................................................................. 25
Material and Methods ..................................................................................................... 26
3.1
3.2
3.3
Hammarby Sjöstadsverk research facility ................................................................ 26
Overview of the experimental strategy ..................................................................... 27
Physical parameters monitoring ............................................................................... 28
3.3.1
3.3.2
3.3.3
3.4
3.5
Chemical analyses...................................................................................................... 29
Suspended solids measurements .............................................................................. 30
3.5.1
3.5.2
3.6
Total and volatile suspended solids as biofilm .................................................................. 30
Total and volatile suspended solids in the influent and inside the reactor .......................... 30
Batch tests .................................................................................................................. 31
3.6.1
3.6.2
3.6.3
4
Parameters description ..................................................................................................... 28
Measurements in laboratory-scale studies ......................................................................... 28
Measurements in pilot plant-scale studies ......................................................................... 29
Specific Anammox Activity (SAA) test ............................................................................. 31
Oxygen Uptake Rate (OUR) test ...................................................................................... 33
Nitrate Uptake Rate (NUR) test ....................................................................................... 35
Laboratory-scale studies ................................................................................................. 37
4.1
Laboratory-scale reactor treating diluted reject water ............................................ 37
4.1.1
4.1.2
4.1.3
4.1.4
4.2
Reactor operation and experimental set-up ....................................................................... 37
Analytical measurements and sampling procedures ........................................................... 39
Results and discussion ...................................................................................................... 39
Conclusions ..................................................................................................................... 44
Laboratory-scale reactor treating diluted reject water ............................................ 44
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
Treatment Line 3 - Anaerobic treatment with UASB ........................................................ 45
Characterization of the effluent from sand filter after anaerobic treatment with UASB ..... 45
Laboratory-scale reactor configuration and experimental set-up ....................................... 46
Analytical measurements and sampling procedures ........................................................... 47
Results and discussion ...................................................................................................... 47
Possibility to treat supernatant from UASB with deammonification process ..................... 52
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TRITA LWR Degree Project
Single Partial Nitritation/Anammox Pilot Plant Reactor ............................................ 53
5.1
Pilot plant reactor operation ..................................................................................... 53
5.1.1
5.1.2
5.1.3
5.1.4
5.2
Results and discussion .............................................................................................. 56
5.2.1
5.2.2
5.2.3
5.2.4
6
7
Pilot plant reactor design .................................................................................................. 53
Reject water characterization ............................................................................................ 53
Operational strategy ......................................................................................................... 55
Measurements and experimental procedure ...................................................................... 55
Physical parameters .......................................................................................................... 56
Biomass analyses. Total and volatile suspended solids and biofilm growth ........................ 57
Reactor performance evaluation and chemical analyses results .......................................... 59
Evaluation of biomass activity .......................................................................................... 67
Conclusions...................................................................................................................... 73
Suggestions for Full-Scale Implementation and Future Research .............................. 75
7.1
7.2
7.3
Partial nitrification/Anammox in municipal WWTPs ............................................ 75
Partial nitrification/Anammox for leachate treatment ........................................... 76
Future research .......................................................................................................... 77
8
References ........................................................................................................................ 78
Appendix I – Description of procedures for analyses and measurements ............................... I
Appendix II – Data from lab-scale reactor treating diluted supernatant .............................. IV
Appendix III – Data from lab-scale reactor treating effluent from anaerobic treatment with
UASB ....................................................................................................................................... VIII
Appendix IV –Data from pilot plant-scale reactor .................................................................XII
Appendix V –Batch tests on the pilot plant-scale reactor................................................... XXII
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
A CRONYMS A ND S YMBOLS
AOB = Ammonium Oxidizing Bacteria
ANAMMOX = ANaerobic AMMonium OXidation
ASL = Ammonium Surface Load
ATP = Adenosine-5'-triphosphate
BABE = Bio Augmentation Batch Enhanced
BOD = Biochemical Oxygen Demand (mg O2/l)
CANON = Completely Autotrophic Nitrogen Removal Over Nitrite
CBOD =Carbonaceous Biochemical Oxygen Demand (mg O2/l)
COD = Chemical Oxygen Demand (mg O2/l)
CSTR = Continuous Stirred-Tank Reactor
DEAMOX = DEnitrifying AMmonium Oxidation
DEMON = DEamMONification
DENAMMOX – DENitrification-anAMMOX
DO = Dissolved Oxygen
DNRA = Dissimilatory Nitrate Reduction to Ammonia
FA = Free ammonia
FISH = Fluorescent In Situ Hybridization
FNA = Free Nitrous Acid
HRT = Hydraulic Retention Time
HT = Heterotrophs
MAP = Magnesium Ammonium Phosphate
MBBR = Moving Bed Biofilm Reactor
MBR = Membrane Biological Reactor
MLSS = Mixed Liquor Suspended Solids
MLSS = Mixed Liquor Volatile Suspended Solids
NOB = Nitrite Oxidizing Bacteria
NUR = Nitrate Uptake Rate
ORP = Oxidation Reduction Potential
OUR = Oxygen Uptake Rate
p. e. = Population Equivalent
R = molar gas constant = 8.314 J mol-1 K-1
Rpm = Revolutions per minute
RBC = Rotating Biological Contactor
SAA = Specific Anammox Activity
SBR = Sequencing Batch Reactor
SHARON = Single Reactor for High Activity Ammonium Removal Over Nitrite
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S.D. = Standard Deviation
SRT = Sludge Retention Time
SS = Suspended Solids
T = Temperature
TKN= Total Kjeldahl-Nitrogen
TN = Total Nitrogen
TP = Total Phosphorus
TSS = Total Suspended Solids
UASB – Upflow Anaerobic Sludge Bed
VSS = Volatile Suspended Solids
WWTP = Wastewater Treatment Plant
μmax = maximum growth rate (day-1)
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
A BSTRACT
In the last decade, several novel and cost-effective biological nitrogen removal technologies have been
developed. The discovery of anaerobic ammonium oxidation (Anammox), about 15 years ago, has resulted
in new opportunities for research and development of sustainable nitrogen removal systems. Compared to
conventional nitrification/denitrification, Anammox eliminates necessity of external organic carbon
source, has a smaller production of excess sludge, reduces energy demand for aeration (up to 60-90%) and
CO2 emissions (up to 90%). Systems based on Anammox can be of great help to comply with stricter
wastewater discharge regulations and reduce environmental problems caused by nutrients discharges (e.g.
eutrophication).
This thesis investigates the partial nitritation/Anammox in one stage system under oxygen limited conditions (also called CANON or Deammonification) and with the Moving Bed Biofilm Reactor (MBBR™)
technology. Anammox process coupled with partial nitritation can be particularly suitable to treat ammonium-rich wastewater with low content of biodegradable organic matter, such as the reject water from
dewatering of digested sludge, which is usually recirculated back to the main stream of wastewater treatment plants, accounting for the 15-20% of the total nitrogen load.
Partial nitritation/Anammox process was successfully tested on a pilot plant scale for four months at
25°C, in a 200 L Continuous Stirred Tank Reactor (CSTR), filled with 40% of Kaldnes media (model K1).
At an Ammonium Surface Load (ASL) of 3.45 gN m-2 d-1, the removal rate was about 2.85 gN m-2 d-1.
Removal efficiencies of 95%, 85% and 83% were respectively achieved for NH 4+-N, inorganic nitrogen,
and Total Nitrogen (TN). Bacteria activity was followed by batch tests such as Specific Anammox Activity
(SAA), Oxygen Uptake Rate (OUR) and Nitrate Uptake Rate (NUR), which revealed an increase in activity for Nitrosomonas and Anammox bacteria within the biofilm. Dissolved oxygen concentration in the
bulk liquid was a crucial parameter, whereas pH and conductivity turned out to be two useful monitoring
tools.
Two laboratory-scale reactors were previously run for two months each, in order to evaluate the one-stage
partial nitritation/Anammox process with a lower ASL. One reactor was fed with diluted reject water,
whereas the other one treated the effluent from UASB (Up-flow Anaerobic Sludge Blanket) reactor after
sand filtration. Fairly good efficiency (>75%) were reached but, however, in the last case the low ammonium nitrogen load could represent a problem for a stable full-scale installation and long-term growth of
Anammox bacteria.
Some suggestions for full-scale implementation and further research are proposed in the last chapter of
this master thesis.
Key words: Anammox Biofilm; Deammonification; CANON; Moving Bed Biofilm Reactor; Reject water.
1 I NTRODUCTION
Nowadays the world is facing a steady increase in
world population and drink-ing water demand as
well as an increment of industrial sites. Therefore
a higher and higher pressure is applied on the
surrounding environment and ecosystem, which
has been affected by innumerable cases of pollution. In order to prevent further degradation
there is a strong need for sustainable technologies, cleaner production and wastewater treatment. These important concepts should also be
applied to effluent streams with unacceptable
levels of nitrogen.
Nitrogen is the most abundant element in the
atmosphere and the fourth most common ele-
ment found in cells as a building block of proteins and nucleic acids.
Nitrogen can be found in the environment under
several forms as shown in Table 1.
The nitrogen cycle is a complex biogeochemical
cycle in which nitrogen is converted from its inert
atmospheric molecular form (N2) into a form that
can be used in biological processes. The classical
nitrogen cycle includes:
 Nitrogen fixation: conversion of the inert form
N2 to an organic (or fixed) form which organism can use. Nitrogen fixation is mostly
carried out by biological processes (e.g. nitrogen-fixing bacteria such as Rhizobium or Azotobacter and cyanobacteria). A small amount
of nitrogen is 'fixed' through high-energy natural events such as lightning and forest fires.
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Andrea Bertino
TRITA Degree Project Thesis
Table 1. Forms of nitrogen in the environment
Unoxidized form
Oxidized form
Nitrogen Gas (N2)
Ammonia (NH4+, NH3)
Organic Nitrogen (urea, amino acids, peptides, proteins, etc...)
Nitrite NO2Nitrate NO3Nitrous Oxide (N2O)
Nitric Oxide (NO)
Nitrogen Dioxide (NO2)
Nitrogen can also be fixed through man-made
processes (e.g. ammonia and nitrogen-rich fertilizers, explosives or combustion of fossil
fuels which release NOx).
 Nitrification: conversion of ammonia into
nitrite (NO2-), and then into nitrate (NO3-),
which is the form that plants take up mostly.
It is carried out by nitrifying bacteria under
aerobic conditions.
 Assimilation: uptake of nitrogen compounds
(i.e. nitrate, nitrite, ammonia, and ammonium)
from soils by plants which used them for the
formation of proteins.
 Ammonification (or mineralization): is the conversion of organic nitrogen to ammonianitrogen. It is carried out by microorganism
(decomposers) which produce ammonium
(NH4+) from dead organic matter (plants and
animal tissues) and animal fecal matter.
 Denitrification: conversion of nitrate (NO3-)
back to gaseous nitrogen (N2) and, to a lesser
extent, nitrous oxide gas, which is a strong
greenhouse gas. It is carried out anaerobically
by denitrifying bacteria. Through denitrification nitrogen is removed from ecosystems and
it is a way to contrast the increased nitrogen
fixation.
 Dissimilatory Nitrate Reduction to Ammonia
(DNRA): it is a form of anaerobic respiration
process where nitrate (NO3-) is used as electron acceptor instead of oxygen and it is recycled to ammonia (NH4+). In contrast to denitrification, this process does not remove the
nitrogen from the habitat, but it remains available to primary producers. An example of dissimilatory nitrate reducer is Escherichia coli.
In this traditional version of the N-cycle, the
ammonium oxidation was assumed to take place
only under aerobic conditions and the possibility
of an anaerobic ammonium oxidation was not
contemplated. Recently it was discovered that
ammonium can also be oxidized under anaerobic
conditions. This new discover created a “shortcut” in the traditional nitrogen cycle (Fig. 1) and
was called (ANaerobic AMMonium Oxidation -
ANAMMOX), which is described in paragraph
1.2.5.
Over the last century, anthropogenic processes
(e.g. fertilizers production, fossil fuel combustion,
industrial production, livestock ranching and
cultivation of crops such as legumes and rice)
have substantially altered the global nitrogen
cycle by increasing both the availability and mobility of nitrogenous compounds in the environment including water systems (Kumar & Lin,
2010).
In this first section the environmental concerns
and risks connected to the discharge of nutrients
(e.g. nitrogen) in water bodies will be discussed.
In order to shed light upon the current situation
and give a general background of the nowadays
available technologies for nitrogen reduction
from wastewater, a second section will focus on
different strategies and treatment methods.
A particular attention will be devoted to biological processes with special regard to the new
promising sustainable technologies based on the
recently discovered ANAMMOX® (ANaerobic
AMMonium Oxidation), such as the one-stage
Partial Nitritation-Anammox process (also called
“Deammonification” or “CANON”), using the
Fig. 1. The updated nitrogen cycle following
the discovery of ANAMMOX (source:
http://aem.asm.org/cgi/content/full/69/1
1/6447).
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
moving bed biofilm technology. These technologies have proved to be particularly suitable to
treat wastewaters with high content of ammonium nitrogen and low content of biodegradable
organic compounds.
1.1 Environmental problems related to
nitrogen discharges
The discharge of nitrogen compounds can cause
environmental impacts on the surrounding ecosystem and receiving water bodies or watersheds.
The commonly nitrogen compounds present in a
wastewater treatment plant which may adversely
impact the receiving waters are:
 ammonium ions (NH4+);
 nitrite ions (NO2-);
 nitrate ions (NO3-).
The main risks related to the presence of these
compounds in concentrations above the water
quality standard or guidance values may cause:
 dissolved oxygen (O2) depletion;
 toxicity;
 eutrophication ;
 methemoglobinemia;
 deterioration of water aesthetic quality and
odors from decomposing algae.
Ammonium ions are oxidized to nitrite ions by
bacteria and nitrite ions are then oxidized to
nitrates ions. Both these two reactions (nitrification) require dissolved oxygen which is depleted and
reduced within the water.
Besides this, these three ions represent forms of
nitrogen nutrients which aquatic plants (i.e. algae)
can use for their growth. With their death, the
dead plants will induce an increment of organic
matter to be decomposed by bacteria, which will
lead to a further reduction of dissolved oxygen.
Moreover the water bodies might face the accumulation of parts of plants that do not decompose.
In the last decades several lakes, estuaries and
coastal zones have faced problems due to the
high nutrients contents, mainly deriving from
different sources and human activities such as
sewage discharges and the extensive use of fertilizer in agriculture.
This nutrient enrichment can lead to localized
eutrophication, which in turn is associated with
more frequent or severe algal blooms (WHO,
2000) with losses in ecological, commercial,
recreational and aesthetic value of these water
and changes in species composition and diversity
of plant and animal communities. Prolonged and
excessive eutrophication has also been responsible for algal blooms on a regional basis, such as
those in the Adriatic and Baltic seas in recent
years (WHO, 2000).
Eutrophication is defined by the European Commission – Environment as “the enrichment of
water by nutrients, especially compounds of
nitrogen and/or phosphorus, causing an accelerated growth of algae and higher forms of plant
life to produce an undesirable disturbance to the
balance of organisms present in the water and to
the quality of the water concerned”.
Eutrophication is recognized as a pollution problem in European, North American and Asian
lakes and reservoirs since the mid-20th century
(Rodhe, 1969).
Although nitrogen is an essential nutrient for
biological health and aquatic ecosystem integrity,
it becomes a pollutant if its amount is beyond the
natural capacity of the system to assimilate or
flush the excess. This is particularly true for water
bodies characterized by a low turnover rate (i.e.
lagoons, lakes, coastal areas). Human activities are
responsible for increasing and accelerating the
natural process of eutrophication in the surrounding watersheds (Bricker et al, 1999).
Table 2 - Pollution concerns related to excess of NH4+,NO2- and NO3- (Gerardi, 2002)
Nitrogenous ion
Pollution concerns
NH4+
Overabundant growth of aquatic plants
Dissolved Oxygen depletion
Toxicity as NH3
NO2-
Overabundant growth of aquatic plants
Dissolved Oxygen depletion
Toxicity
Methemoglobinemia
NO3-
Overabundant growth of aquatic plants
Toxicity
Methemoglobinemia
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Direct consequences of this enhanced growth in
a lake are a limited amount of light reaching the
lower regions (leading to a loss of submerged
aquatic vegetation), color, odor (associated with
the growth and death of aquatic plants) and,
above all, low levels of dissolved oxygen at the
bottom (i.e.hypolimnion), which, in very eutrophic lakes with high concentration of organic
matter could lead to the reduction of sulphate to
hydrogen sulphide, before the end of summer
stagnation. HS- is very toxic for aquatic organisms. .Recently it has been found that some cyanobacteria have the capacity to produce toxins
dangerous to human beings and cyanobacterial
toxins have become widely recognized as a human health problem arising as a consequence of
eutrophication (WHO, 1999). Besides this, cyanobacteria (”blue-green algae”) are nitrogenfixing bacteria which increase ammonium concentration in the aquatic ecosystem.
According to the Swedish Environmental Protection Agency (2000) total phosphorus, total
nitrogen and the nitrogen/phosphorus ratio are
parameters used to assess lakes”. The ratio
TN/TP shows the availability of nitrogen in
relation to phosphorus in lakes. When the ratio is
higher than 30, the production of algae is governed by availability of phosphorus.
The Total Nitrogen (TN) is the sum of dissolved
inorganic nitrogen (i.e. nitrate-nitrogen (NO3--N),
nitrite-nitrogen (NO2--N), ammonia-nitrogen
(NH4+-N)) and organic nitrogen (e.g. urea, peptides, proteins). Total Kjeldahl-Nitrogen (TKN)
is used to indicate the sum of organic N and
NH3, which are the two typical forms of nitrogen
in the sewage treatment plant inflow.
The nitrogenous ions can be toxic to aquatic life,
especially to fish. (Gerardi, 2002). Ammonium
ions and nitrite are extremely toxic, and nitrite
ions are the most toxic of the three nitrogenous
ions form. Ammonium ions, actually, are one of
the most preferred nitrogen nutrient for most
organisms, but they can be converted to ammonia with increasing pH of water (above 8-9),
which can toxic for aquatic life at concentration
as low as 0.025 mg/l NH3. The reference value
for water suitable for fish life is equal to 0.005
mg/l (Decreto Legislativo 152/2006 - allegato
alla parte terza). High temperature and low salinity (freshwater) are other parameters that can
contribute to a higher unionized-ammonia concentration in the water.
The toxic effects of nitrate exposure result from
the conversion of nitrate to nitrite. Methemoglobinemia is a well-recognized hazard of ingestion of
nitrates and nitrites (Comly H.H., 1945); nitrates
are reduced to nitrites in the digestive system and,
combining with the hemoglobin of the blood,
stop the transport mechanism of oxygen. Infants
younger than 4 months of age who are fed with
water from rural domestic wells are at highest
risks to developing health effects from nitrate
exposure (American Academy of Pediatrics
Committee on Nutrition, 1970).
The current legislations in Europe provide the
following requirements for discharges of nitrogen
from
urban
wastewater
treatment
plants (Table 3).
The current environmental legislation in Italy is
Decreto legislativo 3 aprile 2006, n. 152 -Norme in
materia ambientale and it contains also the limits for
nitrate-nitrogen
(NO3--N),
nitrite-nitrogen
(NO2 N) and ammonium (NH4+) (Table 4).
There are several typology of wastewater from
industrial production which can be sources of
high concentration of ammonium, nitrite and
nitrate ions. The main are listed in
Table 5 (Gerardi, 2002).
Table 3 - Requirements for discharges from urban waste water treatment plants. (Directive
91/271/EEC)
Population equivalents (p.e.) (1)
10.000-100.000
Nitrogenous specie (annual average)
Total Nitrogen
(1)
(2)
>100.000
Concentration
[mg/l]
% of reduction
(2)
Concentration
[mg/l]
% of reduction
(2)
≤ 15
70-80
≤ 10
70-80
1 unti PE = 0.2 m3/d (Henze et al, 2002)
Reduction in relation to the load of the influent.
4
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 4 - Discharge limit values in surface water and sewer. (D.Lgs 3 aprile 2006, n. 152 Norme in materia ambientale)
Concentration [mg/l]
Nitrogenous specie (annual average) (2)
Discharge into surface waters
Discharge into public sewers (1)
NH4+
< 15
< 30
NO2--N
< 0.6
< 0.6
NO3--N
< 20
< 30
(1)
The limits for discharge into the public sewer are required in the absence of limits established by the competent
authority or in the absence of a final treatment plant can meet the emission limits final discharge.
As regards discharges of urban waste waters, the limits indicated in Table 4 for sensitive areas are applied. As regards discharges of industrial waste water into the sensitive areas total nitrogen concentrations must be less than
10 mg/l.
(2)
Table 5 - Industrial streams containing relatively high concentrations of Ammonium, Nitrite
and Nitrate ions (modified after Gerardi, 2002)
Pollutant
NH4+
Industry
Concentrations [mg/l]
Reject water from a sludge digester
600 – 1600 mg/l TN
-
Landfill leachate
400-2500 mg/l TN
Chung et al, 2003
Molasses-based distillery wastewaters
1660–4200 mg/l TN
Pectin industry
1600 mg/l TN
Deng Peterson et al, 2003
Starch production
800-1100 mg/l TN
Abeling and Seyfried, 1993
Crude palm oil wastewater
770 mg/l TN
35 mg/l NH4+-N
Nemerow and Dasgupta, 1991
Livestock manure (e.g. piggery manure)
1000-5000 mg/l TN
Ahn et al, 2004
NH4+-N
5-80 mg/l
9-90mg/l TKN
Jørgensen, 1979
Slaughterhouse and packinghouse wastes
150-400 mg/l TN
113-324 mg/l org N
Zhan et al, 2008
Nemerow & Dasgupta, 1991
Tannery
128 – 185 mg/l TN
Murat et al, 2003
Wood-preservation
89 mg/l TN
32 mg/l NH4+-N
Middlebrooks, 1968
Automotive
-
Chemical
-
Coal
-
Fertilizer
-
Petrochemical
-
Ordnance
-
Metallurgical
-
Mining industries (blasting residuals)
-
Pharmaceutical
-
Corrosion inhibitor
1100 mg/l
NO2-
Meat (pre-treated)
Fertilizer Industry
http://www.environet.ene.gov.on.ca/
instruments/9430-725LUQ-14.pdf
-
Steel
NO3-
Mahimairaja & Bolan, 2004
Oil Refinery
Primary metal
NO2-
Reference
600-950 mg/l
NO3--N
Zala et al, 2004
Mining industries (blasting residuals)
-
Meat (flavoring)
-
Meat (pre-treated)
-
Steel
Electroplating plants
10-120 mg/l NO3--N
5
Jørgensen, 1979
Andrea Bertino
TRITA Degree Project Thesis
Table 6 – Centrifugated anaerobically digested sludge (reject water)
Parameter
Value / Range
References
pH
7.18 - 8.42
Marsalek et al, 2004
230
Helliga et al, 1999
BOD5 (mg/l)
109 ± 44
Vandaele et al, 2000
1400 - 2000
Galì Serra A., 2006
COD (mg/l)
650
Köz Utku, 2007
700 - 1000
Wett et al, 1998
BOD5/ COD
0.14 - 0.2
Vymazal, 2010
CODsol/ NH4+-N
0.29 - 1.19
Marsalek et al, 2004
943 - 1513
Marsalek et al, 2004
1180 ± 140
Van Dongen et al, 2001
800 - 900
Dosta et al, 2007
NH4+-N (mg/l)
TKN (mg/l)
450 - 750
Vymazal, 2010
1053
Helliga et al,1999
859
Vymazal, 2010
0-3
Vymazal, 2010
NO2--N, NO3--N (mg/l)
The effluent from the sludge line and the landfill
leachate are the two most important and common wastewater sources of high nitrogen load.
Anaerobic digestion of sludge and the sanitary
landfill under acid or methanogenic phases are
characterized by anaerobic conditions.
Regarding the sludge treatment, nitrogen is initially present as organic nitrogen bound in proteins of the biomass. During anaerobic digestion
proteins are broken down into amino acids (hydrolysis) which are further broken down releasing
ammonium (acidogenesis). The liquor effluent
from the digester can have concentrations around
1000 mg N/l. A similar process occurs within a
sanitary landfill, where, under acidogenic phase
ammonia nitrogen concentration may gradually
raise up to over 1000 mg/l.
The characterizations of these two kinds of
wastewater are shown with regard to nitrogen
forms and organic material in Table 6 and 7.
1.2 Nitrogen removal in WWTPs
Nowadays there are several ways to reduce nitrogen content from wastewater. This chapter deals
with treatments for nitrogen removal, considering
both the well-established techniques and the
innovative ones with greater chances of success,
and examines the advantages and drawbacks.
Most of the wastewater treatment plants carry out
nitrogen removal by biologi-cal methods rather
than physical-chemical ones. The main reasons
are, generally, the lower operational costs, the
lower complexity of the plant and management
and less use of chemicals.
In general, a municipal wastewater treatment
plant which removes organic matter and nutrients
can achieve concentrations in the effluent as the
ones shown in Table 8.
Regarding wastewater with high concentration of
nitrogen (i.e. leachate, reject water from dewatering of sludge, slurry from farms, etc.) a more
Table 7 – Landfill leachate (Ehrig, 1989; Nuovo Colombo - Manuale dell’Ingegnere 84° ed.
2003; Renou et al, 2008)
Parameter
Acidogenic phase
Methanogenic phase
mean
range
mean
range
pH
6.1
4.5 - 7.5
8
7.5 - 9
BOD5 (mg/l)
13000
4000 - 40000
180
20 - 550
COD (mg/l)
22000
6000 - 60000
3000
500 - 4500
BOD5/ COD
0.58
0.20 - 0.70
0.06
0.03 - 0.20
Organic N (mg/l)
600
10 - 4250
600
10 - 4250
NH4+ (mg/l)
750
30 - 3000
750
30 - 3000
TKN (mg/l)
1350
40 - 3425
1350
40 - 3425
NO2--N (mg/l)
0.5
0 - 25
0.5
0 - 25
NO3--N (mg/l)
3
0.1 - 50
3
0.1 - 50
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Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 8 - Range of concentration in urban sewage water before and after treatment to remove
organic matter and nutrient. (Nuovo Colombo - Manuale dell’Ingegnere 84a ed. 2003)
Concentration [mg/l]
Parameter
Raw sewage water
Effluent from biological treatment for removal
of organic matter and nitrogen
BOD5
150-300
5-20
40-120
COD
300-600
NH4+-N
20-40
0-3
NO2--N
0-1
0-0.5
NO3--N
0-5
5-10
Ntot
25-60
6-15
stringent treatment for nitrogen removal is necessary in order to reduce the high concentrations of
am-monia in the wastewater and prevent the high
potential impacts from discharge. These special
kinds of wastewater should be treated through an
appropriate treat-ment which can allow reducing
the high content of nitrogen and the presence of
any toxic compounds, before these effluents are
discharged to the sewage system and sent back to
the head of the municipal WWTP, for further
purification and nutrient reduction.
1.2.1
Physical - chemical methods
Here below some physical-chemical methods are
briefly discussed. Among them there are:
 Mechanical separation
 Membrane filtration
 Ammonia stripping
 Ion exchange
 Breakpoint chlorination
 Electrodialysis
 Struvite precipitation
Mechanical separation is mainly used for cattle slurry
treatments and is a physical separation, with the
goal to obtain an easier handling of the liquid by
concentrating it. The separation efficiency of the
process is rather low and removal rates for nutrients are less than 30% (Barker, 1993). In order
to obtain a higher separation a prior coagulation/flocculation step is required. Some examples
of mechanical separation are flotation separator
and horizontal centrifugal.
Membrane filtration includes Ultrafiltration (UF),
Nanofiltration (NF) and Reverse Osmosis (RO).
Ultrafiltration method uses membranes with a
pore size of 0.1-0.01 μm, whereas Nanofiltration
membranes have a pore size of 0.01-0.001 μm.
The removal mechanism of these two methods is
based on physical separation (i.e. size exclusion).
Reverse Osmosis removal mechanism is instead
based on a diffusive mechanism. A pressure (high
enough to exceed the osmotic pressure) is applied
to the side with high concentration to force water
to flow through the semi-permeable membrane in
the opposite direction of the natural osmotic flow
and the separation efficiency is dependent on
influent solute concentration, pressure and water
flux rate. Reverse Osmosis can achieve very high
level of purity. Nitrogen separation trials by RO
were performed on domestic wastewater and
combined domestic-industrial wastewater achieving a separation efficiency of 95% for total nitrogen (Bilstad T., 1995). The main disadvantages
are that it is expensive and can be subject to
membrane fouling (caused by deposits of inorganic, organic and colloidal and suspended substances on the membrane surface), which requires
maintenance and increases significantly operational costs. Some possible solutions to this
problem are pH adjustment, pre-filtration and
coagulation. Membrane technology is usually
used as polishing step. Another drawback is that
the concentrates obtained by means of membrane technology (UF, NF, RO) - although they
may theoretically be used as fertilizer - have a
high salt concentrations and it is unclear the type
of market that will have, and it should not be
excluded that they have to be "disposed" with
associated costs.
The use of a combination of membrane separation technology (micro-and ultrafiltration) and
bioreactors is steadily increasing and can contribute to very compact systems working with a
high biomass concentration and achieving a low
sludge production with a good effluent quality
(Van Dijk & Roncken, 1997). For instance, a
Membrane bioreactor (MBR), which combines
activated sludge process with micro- or ultrafiltration membranes, does not need for a secondary clarifier and can provide several advantages
such as a high efficiency of selectivity, an im7
Andrea Bertino
proved retention of the biomass and compact
dimension of the whole system. Moreover, in a
membrane assisted bioreactor excess sludge
production is lower than in conventional activated sludge systems (Ghyoot et al, 2000; Rols &
Goma, 1997).
Ammonia Stripping consist of removing ammonia
present as solute in wastewater and transfer it to
gaseous form by means of air flow. Nitrogen is
simply transferred from one form to another with
characteristics more suitable for further processing. Higher pH (10.5-11.5), temperature and
air flow, as well as greater packed bed depth,
increase the efficiency and the removal of ammonia from solution. Temperature can be increased by using steam instead of regular air.
Once the ammonia is removed from the wastewater, it can be concentrated as ammonium
sulfate or equal or can undergo thermal destruction. The first option is carried out through the
combination of a stripping tower and a scrubber
where the flow of air loaded with ammonia is
brought into contact with an acidic solution,
usually acid-based sulfuric acid, to obtain a salt,
ammonium sulphate. The ammonium salt thus
formed can be treated as spent solution or, less
frequently, crystallized, precipitated and handled
as solid form. Some of the main drawbacks are
the need to increase the pH (with lime) and then
the need to decrease it before discharge, the need
of large quantities of sulfuric acid, fouling (calcification) of the packed stripping tower, low efficiency of the process in cold weather, potential
for odors generation and release of ammonia
with potential environmental and health effects.
Carbonates precipitation due to high pH can be
prevented by acidifying the water and stripping
CO2 as pre-treatment, but this will increase the
use of chemicals (Henze, 2008). Ammonia stripping is a method widely established in industrial
applications and in the treatment of landfill
leachate (Piccinini et al, 2007). Ammonia stripping may be preceded by an anaerobic digestion
step, in order to reduce costs, where it is feasible.
Ion Exchange is a process in which ions on the
surface of a solid are exchanged for ammonium
ions in the wastewater. It can be carried out
through the use of materials with high affinity for
ammonium ion such as clinoptilolite, a naturally
occurring zeolite (Jorgensen & Weatherley, 2003;
Thornton et al, 2007). Ammonium ions are usually exchanged for ions with the same charge,
typically sodium. When all the exchange sites
have been replaced, the resin must be regenerated. Ion exchange is typically used for small
flows. The optimum ammonium exchange by
TRITA Degree Project Thesis
clinoptilolite occurs at pH between 4 and 8. If the
ammonium concentration is high or large volumes need to be treated, frequent regeneration
may be required, with an increase in operational
costs. A combined ion-exchange and nitrification
column can be an attractive solution.
Breakpoint chlorination is a process in which chlorine is added to the wastewater in an amount
sufficient to oxidize ammonia-nitrogen into
nitrogen gas. The ratio Cl2/NH3-N needed for
the oxidation is 10:1, which makes this technique
expensive. Another disadvantage is the addition
of chloride to the water, which might give chlorination by-products. On the other side, one advantage is represented by the low spatial requirement.
Electrodialysis is a process in which ions are transported through a semipermeable membrane
under the action of an electric field. Membranes
can be cation or anion-selective (i.e. positive ions
or negative ions can pass through them) and may
be arranged in series. The total nitrogen removal
efficiency is low compared to other treatment
methods (about 40-50%) (Halling-Sørensen &
Jørgensen, 1993). Some disadvantages are chemical precipitation of salts with low solubility on the
membrane surface, clogging of the membrane by
residual colloidal organic matter.
Struvite precipitation. Precipitation of nitrogen (in
the form of ammonia) as struvite. The efficiency
of nitrogen recovered as struvite can be beyond
70% (Shin & Lee, 1997) and time required for
reaction is very short (i.e. 10-15 minutes). Struvite
is an inorganic magnesium ammonium phosphate
(MAP) mineral with the chemical formula
Mg(NH4)PO4·6H2O. It is a valuable by product,
which can be used as slow-release fertilizer, as a
raw material for the phosphate industry, for use
in making fire-resistant panels and as binding
material in cements (Schuiling & Andrade, 1999;
Sarkar, 1990). One limiting factor to the application of this technology to wastewaters with high
content of ammonium nitrogen is the stoichiometry for the precipitation; for a molar ratio of
magnesium, ammonium and phosphate of 1:1:1,
ammonium is in large excess in the influent
wastewater and therefore additional magnesium
phosphate has to be added. One way to solve this
problem is to remove ammonium in precipitated
magnesium ammonium phosphate and then
recycle magnesium and phosphate ions to the
influent. Recycling can be based on chemical
dissolution and ammonia removal or dissolution
by bacteria as performed in introductory studies
at KTH (Hultman and Plaza, 2009). Another
8
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
alternative is to recover the ammonium from the
MAP sludge by heat treatment which makes
ammonium volatilize, allowing to a recover of
ammonium and a reuse of magnesium phosphate
in the treatment (Henze, 2008).
1.2.2
Conventional Nitrification/Denitrification
The
combined
process
of
Nitrification/Denitrification is the most common method
used for wastewater treatment at municipal
wastewater treatment plants nowadays. It is a
treatment process known and well established
and with high stability of operation.
This biological treatment consists of two steps
called Nitrification and Denitrification.
Nitrification is a biological process whereby free
and saline ammonia is oxidized to nitrite and then
nitrate. It is mediated by autotrophic organism
(nitrifying bacteria) which obtain their energy
requirement (catabolism) for biomass synthesis
from inorganic nitrogen compounds, oxidizing
ammonia to nitrite and nitrite to nitrate, and their
carbon requirement (anabolism) from dissolved
CO2 (Gerardi, 2002).
Nitrification is therefore made up of two sequential steps:
1) Ammonia is oxidized to nitrite (NO2-) by
Nitrosomonas spp. bacteria:
NH4+ + 1.5 O2 →NO2- + H2O + 2 H+
These bacteria are also called Ammonium
Oxidizing Bacteria (AOB).
2) Nitrite is converted to nitrate by Nitrobacter
spp. bacteria:
NO2- + 0.5 O2 → NO3These bacteria are also called Nitrite Oxidizing Bacteria (NOB).
The stoichiometric oxygen required for these
reactions is: 1.5·32/14= 3.43 mg O2/mg N for
ammonia oxidation and 0.5·32/14= 1.14 mg
O2/mg N for nitrite oxidation. The first reaction
consumes alkalinity (about 7.1 g of alkalinity as
CaCO3 for each gram of N-NH4+ oxidized).
The most commonly recognized genus of bacteria that carries out ammonia oxidation is Nitrosomonas; however, Nitrosococcus, Nitrosopira, Nitrosovibrio and Nitrosolobus are also able to oxidize ammonium to nitrite (Ahn, 2006).
The main responsible for nitrite oxidation is
Nitrobacter genus but several other genera such as
Nitrospira, Nitrospina, Nitrococcus, and Nitrocystis are
known to be involved (Ahn, 2006).
As mentioned by Gerardi (2002), recent molecular techniques have discovered that there are
several genera of nitrifying organisms (i.e. Proto-
zoa, Actinomycetes, Algae, Fungi, and other
bacteria such as Pseudomonas, Bacillus, Vibrio,
Proteus and Arthrobacter), but however, most of
nitrification is carried out by Nitrosomonas spp.
and Nitrobacter spp., whose rate of nitrification
is often 1000 to 10000 times greater than the
nitrification achieved by other organisms (Gerardi, 2002).
The main factors which might influence the
kinetics of nitrification are:
 pH; the two reactions mentioned above produce H+ and therefore lower the pH. The optimum pH for Nitrosomonas and Nitrobacter
is between 7.2 and 8.5. At pH of 6.0 normally
the nitrification stops. The pH also controls
the concentration of free ammonia (NH3) and
nitrous acid (HNO2) which are strong inhibitor of bacterial activity. Free ammonia can inhibit Nitrosomonas at concentration as low as
10 mg/l and Nitrobacter at concentration as
low as 0.1 mg/l. Free nitrous acid inhibits
them at concentrations as low as 1 mg/l (Gerardi, 2002). The pH can control these two
equilibria: NH4+ ↔ H+ + NH3 and
NO2- + H+ ↔ HNO2.
 DO; dissolved oxygen is an important parameter for nitrifiers growth. The DO concentration should be kept above 2-3 mg/l
(Nuovo Colombo - Manuale dell‟Ingegnere,
2003) in order to not unduly depress the rate
of removal. A DO between 0.5 and 2.5 mg/l
may limit the nitrification (NSF International
and US EPA, 2003) in suspended or attached
growth system under steady state conditions,
depending on the degree of diffusional resistance, especially in attached biomass growth
systems.
 Temperature; a too low temperature (below
10-15 °C) as well as sudden changes in temperature can decrease the removal rate. Nitrification reaches a maximum rate at temperatures between 30 and 35 °C.
 Heavy metals and organic compounds; some
heavy metals (Zn2+, Cd2+, Cr3+, Pb2+, Ni2+)
may exert their inhibitory action from concentration of 1 mg/l. Active carbon or acclimatization of biomass can reduce the inhibitory action of many compounds.
Denitrification is a biological process whereby
nitrate is reduced to nitrite and the produced
nitrite to nitrogen gas. It is mediated by heterotrophic microorganism (Denitrifying bacteria)
which uses organic matter as carbon (anabolism)
and energy source (catabolism). This results in a
9
Andrea Bertino
much higher biomass growth compared with
autotrophic bacteria (5-fold higher according to
Gerardi, 2002).
Among denitrifying bacteria, the most common
are Achromobater, Pseudomonas, Micrococcus,
Bacillus and Alcaligens. Other bacteria such as
Aerobacter, Proteus, Flavobacterium are only
able to convert NO3- to NO2-.
Denitrifying bacteria are facultative organisms
that can use either dissolved oxygen or nitrates as
source for metabolism and oxidation of organic
matter. In the case of simultaneous presence of
dissolved oxygen and nitrates, denitrifying bacteria use preferentially oxygen because the energy
generated per unit weight of organic matter metabolized, is higher.
Therefore it is important to keep dissolved oxygen as low as possible (less than 0.3-0.5 mg/l), at
least in the microenvironment surrounding the
bacteria. Under anoxic conditions, denitrification
reactions can be simplified as the sum of denitratation (1) and denitritation (2):
(1) NO3- + 1/3 CH3OH → NO2- + 1/3 CO2 +
2/3 H2O
(2) NO2- + 0.5 CH3OH → 0.5 N2 + 0.5 CO2 +
0.5 H2O + OHSince nitrogen gas has low water solubility, it is
released into the atmosphere without any environmental concern. The second reaction occurs
through the formation of nitrogen oxides (NO
and N2O) which are subsequently reduced to
nitrogen gas. A carbon source (shown in the
above equation as methanol, CH3OH) is required
for denitrification to occur. Organic matter may
be in the form of raw wastewater or external
carbon source (e.g. ethanol, molasses, distillery
stillage, buttermilk, methanol or acetate). Methanol has a high toxicity in humans, therefore the
use of another carbon source would be preferable. When these sources are not present in the
water, bacteria may depend on internal (endogenous) carbon reserves, but the nitrate removal
may be lower. Removal of nitrogen is also partly
due to the synthesis of new biomass and thus of
organic nitrogen. This amount is about 4% of the
total nitrogen removed (Nuovo Colombo Manuale dell‟Ingegnere, 2003).
The main factors which might affect the efficiency of denitrification are:
 DO; as dissolved oxygen increases, denitrification rates decreases, therefore anoxic condition should be maintained.
 presence of organic matter; the source of
available carbon can influence the denitrifica-
TRITA Degree Project Thesis
tion rate. The highest rate can be achieved by
adding an easily biodegradable and assimilated
carbon source, but this may implies costs for
its purchase. The highest removal rates occur
with the use of effluent from distillery and
food industries.
 pH and alkalinity; the optimum pH is between
7.5 and 9.1, but denitrification can occur also
at pH between 6 and 75. Alkalinity is produced during the process (about 3-3.5 g of alkalinity as CaCO3 for each gram of NO3- reduced).
 temperature; it affects the growth rate of
denitrifying organisms, with greater growth
rate at higher temperatures. Denitrification
can occur between 5 and 30°C.
 Heavy metals and organic compounds. Denitrifying organisms are generally less sensitive
to toxic chemicals than nitrifiers, and recover
from toxic shock loads quicker than nitrifiers.
In wastewater treatment plant, nitrification/denitrification can be performed through:
 suspended-growth biomass processes (e.g. conventional activated sludge, sequencing batch reactors-SBR);
 attached-growth systems (e.g. trickling filters,
rotating biological contactors-RBC).
In suspended-growth biomass processes, several
schemes and configurations can be adopted. The
main distinction is the choice of a:
 separate system configuration, in which nitrification
and denitrification are carried out in series
(post-denitrification) and in distinct stages
with their own clarifier and sludge recycling
system. The costs are higher as two clarifiers
are needed.
 combined system configuration, in which biomasses
are mixed in a single activated sludge.
If denitrification is carried out after the nitrification (i.e. “post-denitrification”), an external carbon
source is usually required, unless other configurations are adopted, as for instance, a post-denitrification with by-pass of part of the incoming
wastewater to the anoxic tank where denitrification takes place.
A common scheme in municipal wastewater
treatment plant is “pre-denitrification”, which provides a denitrification stage followed by a nitrification-oxidation stage with oxidation of organic
material and ammonia. The recirculation of nitrates provides the nitrates to the anoxic tank.
This configuration requires recirculation ratios up
to 4-5 times the inlet flow.
10
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
In conventional activated sludge nitrification/denitrification, the different treatment stages
(i.e. denitrification, oxidation-nitrification and
sedimentation) occur in separate tanks, thus
requiring the presence of pipes and recirculation
pumps. A valid alternative to conventional biological systems is the system SBR (sequencing batch
reactor) which requires only one reactor (or more
reactors in parallel) in which are created in succession, the proper conditions for the different
reactions.
The complete cycle may consist of six main steps:
1. filling with mixing, but without aeration
2. filling with aeration;
3. filling with mixing without aeration;
4. aeration;
5. settling;
6. drawing.
The control of aeration can be based on oxidation reduction potential in the reactor. The SBR
has several advantages compared to conventional
activated sludge:
 flexibility of operation and possibility to
control the duration of different phases;
 more compact footprint by eliminating secondary clarifier;
 no need for recirculation pipes;
 less sludge generation;
Although
conventional
nitrification/denitrification process has high stability and
reliability, it has several drawbacks:
 high costs of the process, due to the large
amount of energy required for aeration needed for nitrification;
 need for an external carbon source for denitrification;
 infeasibility to treat wastewaters with high
nitrogen concentrations or low C/N ratios;
 relatively high sludge generation.
These disadvantages can be overcome through
the use of innovative, sustainable and cost-effective nitrogen removal technologies, as those
described in the following paragraph.
1.2.3
Innovative and sustainable technologies
for biological nitrogen removal
Generally, the conventional biological nitrogen
removal process is used for treating wastewaters
with relatively low nitrogen concentrations (total
nitrogen concentration less than 100 mg N/l
(Van Hulle et al, 2010)).
Some wastewater streams such as anaerobic
digester effluents, landfill leachate, and some
industrial wastewaters (fertilizer industry, explosive industry, tannery industry, etc.) contain high
concentrations of nitrogen, usually in the form of
ammonium. If these streams are returned back to
the inlet of the municipal WWTP, the result is a
considerable increase in the ammonium loading
in the mainstream.
Although the volumetric flow of side-streams
such as the effluents from dewatering of digested
sludge by centrifuges or belt presses is a small
proportion of the total inflow to the WWTP
(usually less than 5%), their total nitrogen load
can be very high and up to 30% of the total Nload to the treatment plant (Siegrist, 1996; Janus
& van der Roest, 1997; Pearce et al, 2000;
Mackinnon et al, 2003; Thornton et al, 2006;
Henze, 2008), with consequent impacts on the
global efficiency and risk to not meet the effluent
discharge standards. At HimmerfjärdsverketGrödinge WWTP (Sweden) and RotterdamDokhaven WWTP (The Netherlands) it amounts
to 15% of the incoming nitrogen load (SYVAB,
Himmerfjärdsverket.
Available
at:
http://www.syvab.se/396/Vattnets-vag.html).
These stream are often highly concentrated with
ammonium consequently small tank volumes may
be required. In addition some of these flows has
high temperature (20-35°C) (van Haandel & van
der Lubbe, 2007) compared to the main treatment stream and thus bacteria activity is higher,
with consequent possibility to operate with shorter solid retention times (SRT).
Removing the ammonium with a separate treatment of these side-streams, can lead to a significant improvement of the final effluent quality
(Henze, 2008) and can be a valid option when
existing plants require upgrading due to more
stringent requirements or increased load.
Conventional biological nitrogen removal process
(denitrification-nitrification) is uneconomical and
complicated when treating high nitrogen contained wastewaters with low C/N ratio.
During the last decade, several new sustainable
and cost-effective alternatives have been discovered and studied and their implementation can be
a valid option to treat strong nitrogenous wastewaters characterized by high ammonium concentrations and low biodegradable organic matter
content.
The novel processes which have been recently
developed include:
 nitritation – denitritation (SHARON®);
11
Andrea Bertino
 partial nitritation and anaerobic ammonium
oxidation (ANAMMOX®) in two separate reactors (combined SHARON®-ANAMMOX®
processes);
 the combination of partial nitritation and
ANAMMOX® in one single reactor, also
called Deammonification, or CANON (completely autotrophic nitrogen removal over nitrite), or SNAP (single-stage nitrogen removal
using ANAMMOX and partial nitritation) or
DEMOX;
 the coupling of denitrification and
ANAMMOX® (called DENAMMOX or
DEAMOX);
 Bio-augmentation (BABE®)
These novel processes are described in the following paragraphs.
1.2.4
Nitritation-Denitritation (SHARON®)
Nitritation–denitritation process over nitrite (or
commonly called SHARON® process) is a more
sustainable alternative to the traditional nitrification/denitrification (Van Hulle et al, 2010).
SHARON stands for Single reactor High Activity
Ammonia Removal Over Nitrite. The
SHARON® process was developed in the late
1990s at the Delft University of Technology by
Hellinga et al (1998).
The SHARON® process is usually performed in
separate reactor compartments with continuous
flow. In this process, ammonium is oxidized
under aerobic conditions to nitrite (Nitritation)
and the produced nitrite is in turn reduced and
heterotrophically denitrified to nitrogen gas under
anoxic conditions by using an external carbon
source (Denitritation).
The bacteria culture is a mix of Nitrosomonas
TRITA Degree Project Thesis
and aerobic denitrifiers and the process is operated without any biomass retention. As the process functions without sludge retention there is
no influence of the presence of suspended solids
in the wastewater.
Ideally the reactions of the process are the following:
Nitritation:
NH4+ + 1.5 O2 → NO2− + 2 H2O + 2 H+
Denitritation:
NO2- + 0.5 CH3OH → 0.5 N2 + 0.5 CO2 +
0.5 H2O + OHThis process requires less oxygen and less organic
carbon in comparison with the traditional nitrification–denitrification. The reduction in the oxygen demand amount to 25 % and the reduction
of carbon demand to approximately 40% (Fig. 34). The sludge generation is lower compared to
the conventional denitrification/nitrification.
The main goal of this process was to arrest the
autotrophic nitrification (i.e. ammonium oxidation) at nitrite by creating unsuitable conditions
for subsequent oxidation process to nitrate, in
order to save costs for aeration and carbon
source.
Fig. 3. Nitrification/Denitrification (source:
H. D. Stensel, Sidestream treatment for
nitrogen removal, 2006).
Fig. 2. Schematic representation of
Nitritation/Denitritation
(SHARON®)
(source: Notenboom, Jacobs, van Kempen,
van Loosdrecht, 2002).
Fig. 4. Nitritation/Denitritation (source: H.
D. Stensel, Sidestream treatment for nitrogen removal, 2006).
12
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
The operating variables in order to obtain a stable
partial nitrification are:
 temperature;
 hydraulic retention time;
 dissolved oxygen;
 pH
 substrate and inhibitor concentration.
The process requires elevated temperatures
(above 25°C), at which the maximum specific
growth rate of the desired ammonium oxidizers is
higher than that of the “undesired” nitrite oxidizers. At the operational temperature of 35°C, the
maximum specific growth rate of nitrite oxidizers
is approximately only half of the one for the
ammonium oxidizers (0.5 and 1 day-1, respectively) (Khin & Annachhatre, 2004).
At temperatures of 25-35 °C ammonium oxidizers have a shorter minimum required sludge age
and a proper hydraulic retention time is chosen in
order to wash out nitrite oxidizers and keep the
ammonium oxidizers inside the reactor (Fig. 5).
Lower dissolved oxygen concentration limit the
growth of Nitrite Oxidizing Bacteria (NOB) due
to their lower oxygen affinity compared to AOB
(Wiesmann, 1994). Thus dissolved oxygen is a
key parameter of high importance.
As stated by Van Hulle et al (2007), free ammonia
(NH3) and free nitrous acid (HNO2) concentration are the actual substrate/inhibitor for ammonium and nitrite oxidation instead of ammonium
(NH4+) and nitrite (NO2−).
Nitrite oxidizers can be outcompeted at higher
pH (7.5–8), because the amount of nitrous acid
decreases and uncharged ammonia increases.
This promotes ammonium oxidizers and suppresses nitrite oxidizers.
However, at higher concentration uncharged
ammonia and nitrous acid may act as inhibitory
factors. Anthonisen et al stated that ammonia
oxidizers (AOB) are inhibited at NH3 concentrations of 8–120 mg N/l and HNO2 concentrations
of 0.2–2.8 mg N/l while inhibition of nitrite
oxidizing bacteria (NOB) is observed already at
NH3 concentration of 0.08–0.82 mg N/l and a
HNO2 concentration of 0.06–0.83 mg N/l.
However these thresholds are dependent on
bacteria adaptation. At higher pH values the free
ammonia concentration is higher, limiting the
growth of Nitrite Oxidizing Bacteria (NOB) due
to their higher sensitivity to free ammonia inhibition than Ammonia Oxidizing Bacteria (AOB)
(Anthonisen et al, 1976).
As mentioned by Van Hulle (2010), some authors
such as Guisasola et al (2005) and Wett & Rauch
(2002) reported a reduction in ammonia oxidizing
activity due to bicarbonate limitation and Nowak
et al (1996) reported a reduction of nitrite oxidation at phosphate concentrations below
0.2 mg P/l and of ammonium oxidation at
0.03 mg P/l. Some pollutant resulted more inhibitory to the oxidation of nitrite than to the
oxidation of ammonium. Some examples are
chlorate, formic, acetic, propionic and n-butyric
acid, cyanide, azide and hydrazine, bromide and
chloride (Van Hulle, 2010).
The first full-scale application was built in Rotterdam-Dokhaven in 1999. Between the years
2000-2005 four full-scale application have been
constructed in the Netherland with an average
total N removal efficiency of 88% and in 2007
the first one installation was built in New York.
The process can also be run in a single reactor
system using intermittent aeration. Fux et al,
(2006) obtained 85–90% nitrogen removal by
nitritation/denitritation
of
ammonium-rich
sludge dewatering liquor in a SBR with continuous loading (loading rate of 1.2 g NH4+-N m3 d-1). High process stability was achieved at a
total HRT of 1 day.
1.2.5
Fig. 5. Minimum residence time for ammonium and nitrite oxidizers at different temperatures (source: Notenboom et al, 2002).
ANAMMOX® process
The ANAMMOX® (ANaerobic AMMonium
OXidation) process is a novel and promising
alternative in which ammonium is directly oxidized to dinitrogen gas using nitrite as the electron acceptor under anoxic conditions (Jetten et
al, 1999). This process, although predicted more
than 30 years ago (Broda, 1977) on the base of
thermodynamic calculations (standard free energy
values of chemical reactions), was discovered
about 15 years ago, during experiments on a
denitrifying pilot plant of a multi-stage wastewater treatment system at Gist-Brocades (Delft, The
Netherlands) where it was noted that ammonium
13
Andrea Bertino
disappeared from the reactor effluent at the expense of nitrate with a concomitant increase in
dinitrogen gas production (Mulder et al,1995).
Later it was realized that nitrite rather nitrate was
the electron acceptor for this reaction.
The overall ANAMMOX reaction is (Strous et al,
1999):
NH4++ 1.32 NO2– + 0.066 HCO3– + 0.13 H+ →
1.02 N2 + 0.26 NO3– + 2.03 H2O
+0.066 CH2O0.5N0.15
Ammonium is converted to dinitrogen gas with
nitrite as electron acceptor in a ratio of 1:1.32,
without the need of oxygen or carbon source.
Small amount of nitrate are produced (about
10%). An analysis of mass balances by Strous
(1998) on an enriched culture of Anammox
microorganisms (Candidatus Brocadia anammoxidans) showed that the Anammox bacteria
uses CO2 as its carbon source to produce biomass (CH2O0.5N0.15) and that NO2– not only
functions as an electron acceptor for
NH4+oxidation, but also as an electron donor for
the reduction of carbon dioxide.
15N-labeling experiments showed that hydroxylamine and hydrazine are formed as intermediates. The mechanism involves the partial reduction of nitrite with the formation of hydroxylamine (NH2OH), which reacts further with
ammonium to form hydrazine (N2H4). Hydrazine
is further converted to nitrogen gas (N2). This
oxidation would give the necessary reducing
equivalents for the initial reduction of nitrite (Van
de Graaf, 1996; Jetten et al, 1999). The actual
substrate for Anammox bacteria is NH3 rather
than NH4+.
Anammox bacteria were found in several wastewater treatments plants, in coastal anoxic marine
sediments all over the world (e.g. Gullmarsfjorden in Sweden, Skagerrak in the North Sea,
Colne Estuary National Nature Reserve in United
Kingdom, Greenland Arctic Sea, Mertz Sea in
Antarctica, Benguela OMZ in Namibia, Chesapeake Bay in U.S.A.) or anoxic basins (e.g. in the
Black Sea and Golfo Dulce, Costa Rica). The
presence and activity of Anammox bacteria have
been detected in more than 30 natural freshwater
and marine ecosystems all over the world (Op
den Camp et al, 2006). In the sediments with low
organic carbon content, Anammox accounted for
20-79% of total N2 production (Op den Camp et
al, 2006).
The anaerobic ammonium oxidation is carried
out by chemolithoautotrophic bacteria belonging
to the order Planctomycetales. Five genera of
TRITA Degree Project Thesis
Anammox bacteria have been defined so far
(Table 9).
The Anammox biomass has a brown-reddish
color. These bacteria are characterized by slow
maximum specific growth rate (μ=0.00648 d-1)
with a doubling time of 10.6 days (Strous et al,
1998; Jetten et al, 1999; van Dongen; 2001) and
low biomass yield (0.11-0.13 g VSS/g NH4+-N)
(Strous et al, 1997). This means that a low
amount of sludge is produced but long start-up
period (up to one year) (Trigo et al, 2006) are
required to grow enough biomass if insufficient
seed sludge is available.
The maximum specific nitrogen consumption
rate is very high (0.82 gN/gVSS d-1) as well as the
affinity for the substrates ammonia and nitrite
(Ks<0.1 mgN/l).
The optimum pH range is 6.7-8.3 whereas the
optimum temperature is (20-43 °C) (Strous et al,
1999). Anammox activity was observed by Egli et
al (2001) only between pH 6.5 and 9, with an
optimum at pH 8 and a temperature optimum at
37 °C. A temperature of 45°C causes an irreversible decrease of the Anammox activity due to
biomass lysis. The possibility to operate the
Anammox process at lower temperature is object
of study. Cema et al (2007a) studied the Anammox process at 20 °C in a successfully operating
RBC (Rotating Biological Contactor).
Anammox activity is also sensitive to visible light
with a decrease in activity of 30 to 50% (van de
Graaf et al, 1996).
The reaction is strongly but reversibly inhibited
by dissolved oxygen (Jetten et al, 2001). It was
noticed that the growth of the Anammox bacteria
is reversibly inhibited by low oxygen concentrations between 0.25-2% air saturation (Strous et al,
1997, Egli et al, 2001).
The reaction is irreversibly inhibited by nitrite
when NO2--N exceeds a concentration of
70 mg NO2--N/l for several days (van Dongen et
al, 2001). Batch-scale experimental studies on the
effects of nitrite inhibition on Anammox bacteria
(Bettazzi et al, 2010) showed a short-term inhibition, with more than 25% maximum nitrite removal rate decrease at concentrations higher than
60 mg NO2--N/l and losses of activity were detected with nitrite concentrations higher than
30 mg NO2-N/l. Fux et al (2004) also reported
serious inhibition of Anammox activity when
nitrite was present at concentrations of 30-50
mg NO2--N/l for six days. Other authors obtained different threshold values of nitrite inhibition and there are still ongoing studies on this. It
seems also that different Anammox genera show
14
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 9 – Microbial species of ANAMMOX bacteria discovered up to date.
(Source: Kumar & Lin, 2010; Van Hulle et al, 2010)
Genus
Species
Sources
Brocadia
Candidatus Brocadia anammoxidans
Candidatus Brocadia fulgida
Wastewater
Wastewater
Kuenenia
Candidatus Kuenenia stuttgartiensis
Wastewater
Scalindua
Candidatus Scalindua brodae
Candidatus Scalindua wagneri
Candidatus Scalindua sorokinii
Candidatus Scalindua arabica
Wastewater
Wastewater
Seawater
Seawater
Jettenia
Candidatus Jettenia asiatica
Not reported
Anammoxoglobus
Candidatus Anammoxoglobus propionicus
Wastewater
different intolerance for nitrite. The inhibition
caused by free ammonia is limited and occurs
only at high ammonium concentration (> several
hundred mg NH4+-N/l) (van Haandel & van der
Lubbe, 2007). For these reasons, the Anammox
process must be operated under conditions of
nitrite limitation.
Anammox are chemolithoautotrophs bacteria
which utilize inorganic carbon as carbon source,
thus the influent bicarbonate concentration is an
important factor. Dexiang et al (2007) observed
low
Anammox
activity
at
bicarbonate/ammonium ratios of 2.3:1.
Anaerobic ammonium oxidation is more than
seven times slower than aerobic ammonia oxidation (Strous et al, 1998). Jetten et al (1999) observed that also “classical nitrifiers” Nitrosomonas
sp. are able to oxidize ammonium under anaerobic conditions, but at a specific rate 25-fold
lower than Anammox bacteria.
Many advantages can be obtained by the implementation of the ANAMMOX® process:
 No requirement for external organic carbon
source
 Smaller production of excess sludge
 High nitrogen removal
 Smaller reactor footprint (up to 50% less)
 Reduction of energy demand and power
consumption up to 60-90% (compared to
conventional nitrification/denitrification)
 Reduction of CO2 emission (up to 90%)
because during the process bicarbonate is
consumed instead of carbon dioxide produced
(as in conventional denitrification). Thus this
process has a much lower contribution to
greenhouse effect.
 N2O (strong greenhouse gas with a GWP =
298) is not an intermediate in the Anammox
reaction.
In order to remove ammonium nitrogen successfully from wastewater using the ANAMMOX®
process, a proper molar nitrite-ammonium ratio
(1.32:1) is needed, but such a ratio is rarely encountered in any wastewater and thus Anammox
process alone is not advisable in a WWTP but it
should always be combined with a preceding
aerobic partial nitritation process which can
produce nitrite. Anammox process is nowadays
studied in combination with other processes such
as partial nitrification in one-single reactor or in
two separate reactors.
1.2.6
Partial nitritation and ANAMMOX in
separate reactors (2-reactor system)
This process is also called “combined
SHARON®-ANAMMOX® processes” or “autotrophic nitrogen removal process”. The process is
run in two reactors in series. In the first aerobic
reactor about 50 % of ammonium is partially
nitrified to nitrite. The produced nitrite is in turn
reduced to nitrogen gas through the
ANAMMOX® process in a second anaerobic
reactor.
The ideal goal for the first reactor would be to
obtain a stable effluent suitable for the
ANAMMOX® reactor (i.e. with a molar ammonium/nitrite ratio of 1.32:1 according to the
stoichiometry of ANAMMOX® reaction proposed by Strous et al (1999)). In practice, however, this ratio is not produced, but it is kept
closer to 1:1 in order to prevent nitrite inhibition
in the second reactor by providing an excess of
ammonium (Fig. 6.).
The ideal reaction in the first reactor, which
produces the 50:50 mixture of nitrite and ammonium is:
NH4++ 0.75 O2 +HCO3– → 0.5 NH4+ + 0.5
NO2- + CO2+ 1.5 H2O
15
Andrea Bertino
TRITA Degree Project Thesis
Fig. 6. Schematic representation of combined
SHARON®-ANAMMOX®
processes (source: Khin et
al, 2004).
The operating variables for the SHARON®
reactor in order to obtain a stable ANAMMOXsuited effluent are temperature, oxygen conditions, pH, hydraulic retention time and selection
of the substrate availability. The sensitivities of
ammonium and nitrite oxidizer towards these
parameters are different (see paragraph 1.2.4).
Generally the operating conditions in the first
reactor are: pH 6.6–7.0, T=30–40 °C, HRT=1
day, no sludge retention (Ahn, 2006). In case of
treatment of digester effluent, no extra addition
of base is necessary since digester effluent generally contain enough alkalinity.
Absence of inhibiting factors in the
ANAMMOX® reactor is important for the successful operation of the combined process.
The combination of a partial nitritation and
ANAMMOX® process has been studied and
tested by several authors at a lab and pilot scale in
recent years (Fux et al, 2002; Van Dongen et al,
2001) with nitrogen removal efficiencies over
80%.
This sustainable alternative allows achieving high
saving costs in terms of aeration (40%) and carbon source (100%) respectively, compared to the
conventional nitrification–denitrification processes (Van Loosdrecht & Jetten, 1998; van Dongen,
2001). The overall nitrogen removal in the combined process requires less oxygen (1.9 kg O2/kg
N instead of 4.6 kg O2/kg N), no carbon source
(instead of 2.6 kg BOD/kg N) and low sludge
production (0.08 instead of approximately 1 kg
VSS/kg N) (Van Loosdrecht & Jetten, 1998).
Because the combined process does not require
any input of external carbon source, the COD
and nitrogen removal operations can be optimized and carried out separately, eliminating the
need for complex compromises between COD
and N-removal as in the conventional N-removal
process (Jetten et al, 1997; van Dongen et al,
2001). One possible solution is the adoption of a
denitrifying unit (anoxic) before the partial nitrification stage.
Compared
to
conventional
nitrification/denitrification, the combined system partial
nitritation/ANAMMOX® in two reactors reduces
CO2 emission by more than 100%, because the
combined process consumes CO2 (Van
Loosdrecht & Jetten, 1997). The combined process is 90% less expensive than the conventional
nitrification/denitrification processes (Dijkman &
Strous, 1999).
For full scale application a CSTR or a SBR are
recommended for the partial nitritation step as it
is easier to manipulate the SRT (sludge retention
time), whereas a biofilm or granular-based bioreactor is preferable since anammox bacteria
easily form sludge granules or biofilms obtaining
a high biomass concentration in the reactor (Van
Hulle, 2010).
1.2.7
Partial nitritation and ANAMMOX in one
single reactor (1-reactor system)
This process is called with several names: “Deammonification”, “CANON” (Completely Autotrophic Nitrogen removal Over Nitrite), “SNAP”
(Single-stage Nitrogen removal using the Anammox and Partial nitritation), “DEMON” or “aerobic/anoxic deammonification”.
In order to avoid confusion dealing with this
particular system, which is object of study of the
present thesis, this process will be called Deammonification or sometimes partial nitritationANAMMOX in one single reactor.
Compared with partial nitrification in series,
Deammonification process needs only one rector.
This implies a small footprint and less investment
costs. The disadvantage is the more complex
control of the overall process. The two stage
deammonification process has lower N2O emission (Kampschreur et al, 2009) and avoid the risk
of high toxic nitrite concentration for
ANAMMOX bacteria, but needs a control of the
nitrite/ammonium ratio in the inflow to the
ANAMMOX reactor and has a higher consumption of alkalinity compared to the one-stage
process.
16
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Deammonification process is based on the harmonious co-existence and cooperation of aerobic
(AOB) and anaerobic ammonium-oxidizing
(ANAMMOX) bacteria in one single reactor.
This can be established under oxygen-limited
conditions to avoid inhibition of ANAMMOX
bacteria by oxygen and to achieve appropriated
conditions to obtain partial nitritation. In practice
the main systems that can provide the favorable
microaerobic conditions for the co-existence of
these two bacteria species are the biofilm system
(moving bed biofilm reactors, MBBR), reactors
with an intermitted aeration (SBR or RBC) or
granular sludge.
The ammonium oxidizers (AOB) oxidize ammonium to nitrite. Under low concentration of
dissolved oxygen, the growth of nitrite oxidizing
bacteria NOB (and subsequent nitrate production) is usually small due to their lower affinity to
oxygen compared to AOB and for nitrite compared to ANAMMOX bacteria.
The optimal bulk oxygen concentration in the
liquid in a reactor that carries out deammonification with biofilm system may be different case by
case and depends mainly on different configuration of the reactors and lnfluent components. In
our case, biofilm thickness and density, boundary
layer thickness, the COD content of the influent
and the temperature need to be considered to
decide DO concentration inside the reactor (van
Hulle et al, 2010).
In this process part of the ammonium is oxidized
into nitrite (partial nitritation), which serves as
electron acceptor for NH4+oxidation, and the
remaining ammonium is converted to dinitrogen
gas by ANAMMOX bacteria. The nitrate (NO3–)
that is produced is primarily due to ANAMMOX
bacteria. The presence or activity of nitrite oxidizers (NOB) may affect the global efficiency and
a further oxidation of nitrite to nitrate should be
prevented or reduced at minimum. Some operation strategies are useful for the process monitoring and are based on different growth conditions of ammonia oxidizers (AOB) and nitrite
oxidizers (NOB). As described in paragraph
1.2.4, they are essentially dissolved oxygen (DO),
temperature, pH value, free ammonia (FA) and
sludge retention time (SRT).
Recent researches by a PhD student from KTH
(Cema et al, 2010) demonstrated that the nitrite
concentration was the rate-limiting factor for the
simultaneous nitritation/Anammox process.
Deammonification process is an autotrophic
nitrogen removal which offers a sustainable
alternative for treating highly loaded nitrogen
streams with an unfavorable carbon to nitrogen
ratio (C/N or COD/N), such as reject water
from dewatering of digested sludge. In fact during anaerobic digestion fast biodegradable organic content is converted to biogas and, as
consequence, only slow biodegradable organic
matter will be present in the effluent.
The overall reaction can be approximately written
as Third et al (2001):
1 NH4+ + 0.85 O2 → 0.13 NO3- + 0.435 N2 +
1.4 H+ + 1.43 H2O.
As the global process produces H+ (or similarly
consumes HCO3-), alkalinity is consumed. It is
clear that one candidate wastewater which can be
treated by this process is certainly the sludge
reject water. If this process is applied to the
treatment of reject water from anaerobic digester,
usually these wastewaters have enough alkalinity
to stand the potential decrease of pH and provide
a whole stability of the process.
The first full-scale application with Deammonification process is date back to April 2001 in a
moving bed reactor using Kaldnes® carriers at the
WWTP of Hattingen (Germany). One reactor
with a volume of 104 m3 and two reactors with a
volume of 67m3 each with a total effective biofilm surface area of 47200 m2 allow reaching
efficiency up to 70-80%. The load is 120 kg N/d
and the removal rate is 400 g N m−3 d−1. In this
case the oxygen concentration is kept below 1
mg/l.
Other full-scale plants for deammonification of
reject-water from digested sludge dewatering are
currently in operation in:
 Strass (Austria), treating the wastewater of
200.000 population equivalents (load up to
340 kg NH4+-N/d) by a sequencing batch reactor (SBR) of 500 m3 with NH4+-N and TN
removal efficiencies of 90% and 86% respectively (Wett, 2006).
 Glarnerland-Zurich (Switzerland) where a
suspended-growth sequencing batch (SBR) reactor of 400 m3 treats over 635 kg N/d (ammonium oxidation rates of about 500 g N m−3
d−1) with efficiency over 90% (Joss et al, 2009)
 Rotterdam Dokhaven (The Netherlands)
(620.000 p.e.) where granular sludge is used
and the load is around 700 kg N/d. The reactor is compact (volume = 72 m3) and with
NH4+-N and total N removal efficiencies of
95%
and
85%
respectively.
(http://www.paques.nl).
17
Andrea Bertino
 Himmerfjärden Grödinge (Sweden) (278.000
p.e.), which was started in April 2007. Two reactors of 900 m3 are run with intermittent aeration (40 min aerobic phase with DO set
point about 3-4 mg O2/l and 20 minutes anoxic phase) and treat 600 kg N/d (removal
rates
of
300
g
N
m−3
d−1)
(http://www.syvab.se).
1.2.8
DENAMMOX process
This process is also called DEAMOX (DEnitrifying AMmonium OXidation) and it is the coupling of denitrification and ANAMMOX® processes. Researches on this process are still
ongoing. It can be applied to the treatment of
wastewater with high nitrogen concentrations
with high organic carbon levels, such as landfill
leachate and wastewaters from digested animal
waste (Van Hulle et al, 2010).
Denitrifying bacteria and Anammox bacteria do
not need oxygen, therefore this process has a
high potential in term of costs saving for aeration
and DO control. The main issue is the co-existence of these two bacteria in a long-term perspective. As mentioned by Kumar and Lin (2010),
denitrifiers have higher growth yield (Yheterotrophs =
0.3 gVSS/gNH4+-N, whereas
Yanammox =
0.066±0.01 gVSS/gNH4+-N).
In wastewaters with high quantities of slowly
biodegradable organic carbon such as digested
liquor and landfill leachate, heterotrophic denitrifying growth is limited by the low availability of
easily biodegradable organic carbon and, as consequence, denitrifiers should not be able to dominate in these systems and outcompete Anammox bacteria.
Beyond certain amounts of organic carbon,
Anammox organisms may not longer be able to
compete for nitrite with denitrifiers. Moreover, as
reported by Van Hulle et al (2010) denitrification
reaction (∆G=−427 kJ/mol) is thermodynamically more favorable than anaerobic ammonium
oxidation (∆G=−355 kJ/mol) of Anammox
bacteria.
ANAMMOX reaction produce small amounts of
NO3- (according to the molar ratio
NO3-out/NH4+in=0.26) and the co-existence of
ANAMMOX and denitrification in one reactor
could be an aid to reduce this quantities of nitrates produced in the reactor. Besides this, the
denitrification produces nitrite as intermediate
which can be used by the Anammox bacteria for
the oxidation of ammonium. For this reasons,
DENAMMOX process could be a potential valid
TRITA Degree Project Thesis
option for simultaneous nitrogen and carbon
removal as claimed by Kumar et al (2010).
Some authors state that Anammox bacteria are
not longer able to compete with heterotrophic
denitrifying bacteria at COD/N ratio above 2
(Chamchoi et al, 2008).
Another thing to be kept into account is that
Anammox bacteria are irreversibly inhibited by
low concentrations of methanol (15 mg/l) and
ethanol (Güven et al, 2005). Methanol is often
used to remove nitrate in a post-denitrification
step.
Recently a new process called SNAD (Simultaneous partial Nitrification Anammox and Denitrification) has been developed. The main difference is the addition of the denitrification to the
partial nitrification/Anammox process (Chen et
al, 2009).
1.2.9
Bio-Augmentation BABE®
BABE stands for Bio-Augmentation Batch Enhanced. The main goals of this process are to
remove nitrogen in the concentrated side-stream
and to increase the nitrification capacity of the
main activated sludge system by “seeding” it with
the nitrifiers produced in the BABE reactor (van
Haandel & van der Lubbe, 2007) (Fig. 7). BABE®
process was developed and designed based on
model simulation.
The nitrifier seed enhances nitrification rate and
thus complete nitrification occurs at lower SRT.
It can be a useful upgrading option for system
with limited tank volume or high SRT (i.e. colder
climates) and thus limited nitrification capacity.
BABE is a small reactor where nitrifying bacteria
are cultivated. It is a reactor continuously inoculated with sludge from the aeration basin and fed
with digester effluent. It operates at higher temperatures than the main activated reactor, thus it
has a higher nitrogen removal rate.
On the next page a summary comparison of
some of the innovative systems is shown
(Table 10).
18
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Fig. 7. BABE configuration
for reject water from dewatering of digested sludge.
(source: Khin et al, 2004).
Table 10 – Comparison of the innovative processes for nitrogen removal (Jetten et al 2002;
Ahn, 2006)
Characteristic
Conventional
nitrification/ denitrification
Nitritation/ denitritation (SHARON®)
Partial nitritation
(50%) and
ANAMMOX in two
reactors
Partial nitritation and
ANAMMOX in one
single reactor
Number of reactors
2
2
2
1
Conditions
oxic/anoxic
oxic/anoxic
oxic/anoxic
oxygen limited
Oxygen requirement
[gO2/gN]
4.57 / 0
3.43 / 0
1.71 (1) / 0
1.94
% O2 saving (2)
-
24.9 %
62.6 %
57.5 %
Alkalinity consumption
[gCaCO3/gN]
7.07 / -3.57
7.07 / -3.57 (3)
3.57 / 0.24
3.68
pH control
yes
none
none
none
Carbon source requirement [gCOD/gN] (4)
3.7
2.3
0
0
% reduction in carbon
source requirement (2)
-
37.8 %
100 %
100 %
Main bacteria involved
Nitrifiers (AOB,NOB)
/ denitrifiers
AOB / denitrifiers
AOB / ANAMMOX
AOB / ANAMMOX
Biomass retention
none / none
none / none
none / yes
yes
Sludge production
high
low
low
low
(1) If the partial nitritation was carried on to 60% the oxygen requirement would be 2.06 g O 2/g N.
(2) Compared to conventional nitrification/denitrification.
(3) Alkalinity is produced in the heterotrophic denitrification and denitritation steps.
(4) Based on methanol.
19
Andrea Bertino
1.3 Moving Bed Biofilm
(MBBR) technology
1.3.1
TRITA Degree Project Thesis
Reactor
Introduction of MBBR
The Moving Bed Biofilm Reactor technology
(Fig. 8) is sometimes called “Hybrid Fixed Film
Process” in case of co-presence of activated
sludge. It has been developed to integrate the
advantages of both biofilm systems and suspended activated sludge in one process without
being restrained by their disadvantages.
It makes use of polymeric carriers, which are kept
in continuous movement in the reactor by aeration or simply mixing.
Several type of carriers (Fig. 9) have been developed (e.g. KaldnesTM), with the common goal to
provide optimal conditions and a large protected
surface area for the biomass, which grows as a
biofilm on the surfaces of them.
The MBBR technology does not require any
recirculation of the sludge and saves costs for the
sedimentation.
The relatively high concentration of maintained
biomass allows a higher load-ing rate, which
results in reduction in reactor volume or increase
of treatment capability within existing basins.
Fig. 8. MBBR - Moving Bed Biofilm Reactor with Kaldnes carriers
The main advantages of this system are:
 Higher biomass concentrations due to biofilm
process and carriers with high internal surface
area;
 Small reactor footprint (compact system);
 Low sludge generation;
 No sludge return;
 High ammonia removal in a single process;
 Suitable to create anoxic condition in the
inner part of the biofilm;
 Possibility to use this technology to enhance
or upgrade an existing system (i.e. activated
sludge);
 Economical attractive and low investment
costs;
 Minimal maintenance and simplicity of operation;
 No media clogging;
 Higher process stability under load variations;
 Lower sensitivity to toxic compounds;
 Customizable reactor shapes;
 Flexibility and suitability to different types of
wastewater treatments.
Fig. 9. Different carrier media used inside a
MBBR.
20
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
1.3.2
Advantages compared with activated and
granular sludge and fixed biofilm systems
In the activated sludge the biomass is suspended
inside the reactors as flocs. A great number of
existing wastewater treatment plants makes use of
this technology nowadays. However this conventional technology has several drawbacks compared to the recent technologies. It has relatively
poor settling characteristics (up to 1 m/h), low
permissible dry solid concentration in the aeration tank and low maximum hydraulic load of the
secondary clarifier and therefore large footprints
are required for the reactors and the sedimentation tanks. Moreover the biomass production is
higher compared to the other systems. This
technology has lower flexibility related to fluctuating loading rates and it is also vulnerable to
high concentrations or shock loads of toxic
compounds in the influent.
The granular sludge consists of microorganisms
which are compacted on dense biomass granules.
These granules have fast settling velocity and
high biomass density. This technology is usually
applied in sequencing batch reactors (SBR) which
enable the separation of sludge and effluent
inside the reactor itself. The high biomass retention (i.e. high sludge retention time) reduces the
sludge production. The high biomass concentration biomass concentration inside the reactor (up
to 10÷16 g VSS/l) makes the reactor very compact and with high biomass densities. Another
advantage is the improved settling ability (sludge
volume index (SVI) <50 ml/g). The sludge volume index (SVI) is the volume in milliliters
occupied by 1 g of a suspension after a settling
period of 30 minutes.
The diffusive processes are important for this
system, as well as for the biofilm systems. Extensive shear stress in the reactor (e.g. mechanical
Table 11 – Advantages and limitations of different reactor configurations.
System
Advantages
Disadvantages
Activated Sludge
- Conventional and common process
- Large surfaces
-
Granular sludge
-
No need for a clarifier if SBR is used.
Higher biomass retention
No sludge return
Higher settling ability
Co-existence of aerobic and anoxic microorganisms on granules
- Highest rate of reaction / m3
- More complex operation (in case of SBR)
- Discontinuous discharge (in case of SBR)
- Extensive shear stress may damage
granules
- Start up period may be long
Fixed film (RBC)
-
- May need maintenance
Fixed film (Trickling
filters)
- No need for a clarifier
- Problems of clogging and maintenance
MBBR
- No need for a clarifier or biomass recirculation
- Low sludge production
- High specific surface area and higher biomass
density
- High biomass retention (high sludge age)
- Small footprint
- Possibility to upgrade existing systems
- Co-existence of aerobic and anoxic microorganisms in biofilms
- More robust technology and resilient bacteria
population
- Possibility to handle high loads or temporary
limitations
- Easy to operate and simple design
- Low maintenance required
- No problem of clogging
- Longer start up period may be required
No need for a clarifier
Low energy consumption
Alternation of oxic and anoxic conditions
Co-existence of aerobic and anoxic microorganisms on the disks
21
Usually low sludge settling ability
Foaming and sludge bulking problems
High surplus biomass production
Vulnerable to shock loads or high concentrations of toxic compounds in the
influent
Andrea Bertino
mixing, aeration, etc.) might cause detachment of
biomass from the granules.
Fixed biofilm systems use a porous medium which
provides a static media (a “fixed bed”) as support
for the biomass film growth. The fixed bed can
be made of rocks, gravel, slag, polyurethane
foam, sphagnum peat moss, ceramic or plastic
media (Wikipedia, 2010). Some examples of fixed
film system are the trickling filters or the rotating
biological contactor (RBC). The latter consists of
disks which rotate slowly on a horizontal shaft
and have a 40% of their surface always submerged, thus allowing an alternation of aerobic
and anaerobic condition. Fixed film systems have
the capacity to handle shock loads. One serious
drawback of trickling filters is the clogging and
the risks to have septic conditions even under
moderate loading conditions.
The Moving Bed Biofilm Reactor technology is an
attached growth biological wastewater treatment
process. It combines the advantages of activated
sludge and biofilm systems without being restrained by their disadvantages.
A MBBR operates continuously and it is not
affected by problem of clogging that may require
need for backwashing or maintenance. Compared
to the fixed film system, the moving bed biofilm
systems have much higher specific surface area
for the biofilm. The specific surface area are 500
m2/m3 (Kaldnes K1 media) or 1200 m2/m3
(Kaldnes Flat Chip), whereas a trickling filter
media has a specific surface area of 46-60 m2/m3
(rocks) or 90-150 m2/m3 (plastic) and a rotating
biological contactor of about 100-150 m2/m3
(Weiss et al, 2005). The main reason of this difference lies in the fact that the MBBRs utilize the
whole tank volume for biomass and not only the
fixed bed. The carriers can occupy up to 70% of
the reactor volume on a bulk volume basis. Experience has shown that mixing efficiency decreases
at higher percentage fills (Weiss et al, 2005). This
process is more robust compared to activated
sludge because the biofilm is protected by the
biocarriers design. This system has lower sensitivity and better recovery from shock loading.
For example it can tolerate higher concentration
of NO2-. The advantages of MBBR compared to
activated sludge are the lower sludge production,
low loss of biomass, higher process stability
under load variations, no need for sludge return
and lower costs.
1.3.3
TRITA Degree Project Thesis
good performance and operation of the reactor
over time.
The media should be carefully designed to have a
long service life and a large protected internal
surface which acts as a carrier for the biomass
growth. In these experimental studies the Kaldnes Moving Bed™ process was used.
This particular technology was developed in
Norway by Kaldnes Miljøteknologi AS in the late
1980s and early 1990s and it has been patented.
The Kaldnes Moving Bed™ consists of polyethylene rings (or “wheels”) with a stable internal
cross and a density slightly lower than water
(0.95 g/cm3) which allows easy movement of the
carrier material in the completely mixed reactor.
The small difference from the water density
avoids negative buoyancy effects.
The type of media chosen for the operation is
Kaldnes K1 media (Fig. 10) which provides a
high specific internal surface area of 500 m2/m3.
It is shaped like a cylinder with a cross inside the
cylinder and fins on the outside. The shape allows
a small amount of water to flow through the
carrier.
The total surface area (Table 12) consists of both
inner and outer surface while the protected surface area is the effective internal area where the
biofilm seems to attach and grow as shown in
figure 10.
As suggested by Ødegaard et al (2000) the performance of a biofilm reactor is primarily dependent upon the biofilm growth surface area
(kgsubstrate/m2biofilm area/d) in the reactor and not on
the reactor volume.
In case of the one-stage partial nitritationANAMMOX process, it is composed by two
Kaldnes Moving Bed™ Process
The choice of the media for the Moving Bed
Biofilm Reactor is extremely important for a
Fig. 10. Kaldnes K1 media™ (Trela et al,
2008)
22
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 12 – Kaldnes K1 media™ (source: http://www.anoxkaldnes.com)
Model
Length
Diameter
Protected surface
Total surface
K1
7 mm
10 mm
500 m2/m3
800 m2/m3
main bacteria culture: the ammonium oxidizing
bacteria and the Anammox bacteria.
The ammonium oxidizers are mainly located in
the outer layers of the biofilm and they produce
the suitable anoxic conditions for the Anammox
bacteria sited in the inner layers, by reducing the
dissolved oxygen concentration in the bulk liquid
and providing nitrites ions necessary for the
ANAMMOX reaction. The thickness of biofilm
strongly influences bacteria composition; usually
the oxygen diffusion is lower in thicker biofilms
and therefore a larger anoxic layer is created,
where more Anammox bacteria can live and be
active. In biofilm systems mass transfer is usually
the limiting step. As underlined by Van Hulle et
al (2010), as long as ammonium concentrations
outside the biofilm are much higher than the
oxygen or nitrites concentrations, ammonium
diffusion into the biofilm does not limit the
process rate. If the nitrites produced in the outer
layer are mainly consumed in the inner layer,
oxygen is the main limiting factor controlling the
overall rate and its bulk concentration in the
liquid is crucial. A too high value may inhibit the
ANAMMOX reaction and increase the oxidation
of nitrite to nitrate by NOB (i.e. Nitrobacter),
whereas a too low value may reduce the production of nitrite by AOB (i.e. Nitrosomonas).
As shown if Fig .11, in the outer layer ammonium
is converted to nitrite by ammonium oxidizing
bacteria (AOB), while Anammox bacteria are
active in the inner layer. Anammox bacteria are
characterized by a low growth rate and this type
N2
  max
S
KS  S
where μmax is the maximum specific growth rate,
S is the concentration of the substrate (or limiting
nutrient) and Ks is the half saturation constant
N2
NH4+
Water phase
of attached growth system (Moving Bed Biofilm
reactor) ensures that they are not washed out but
are retained inside the reactor, attached at the
carriers.
Other bacteria may be present in minor amounts
such as nitrite oxidizing bacteria (NOB), denitrifiers (Fig. 11) and other heterotrophic bacteria.
It is difficult to suppress completely nitrite oxidizers even under oxygen-limited concentrations,
because it is difficult to subtly manipulate SRT in
one-stage partial nitrification-ANAMMOX process. This view is supported by the detection of
nitrite oxidizers in some CANON biofilm systems.
In biofilm system (i.e. Moving Bed Biofilm Reactor), the overall process performance is strongly
dependent on dissolved oxygen concentration,
nitrogen-surface load (ammonium loading rate),
temperature, biofilm thickness, pH and nitrite
concentrations.
Simplified growth of the main bacteria involved
in the partial Nitritation/ANAMMOX process
(i.e. ammonia oxidizing bacteria and Anammox
bacteria) could be approximately expressed with
an equation based on the kinetics model developed by Michaelis-Menten or Monod:
NH4+
NH4+
O2
AOB
Fig. 11. Simplified
scheme of the main
reactions within the
biofilm
NO2-
NOB
Aerobic zone
NO3-
interface
Biofilm
N2
DENITRIFIERS
NO2-
NO3-, N2
ANAMMOX
NH4+
Anaerobic zone
Carrier
diffusion
main reactions in the one-stage Partial Nitritation-Anammox reactor
some of the possible parallel reactions
23
Andrea Bertino
TRITA Degree Project Thesis
which represents the substrate concentration (in
mg/l) at which μ equals μmax/2.
The growth of ammonium oxidizer (AOB) can
be expressed as (Van Hulle et al, 2007):
  max

C NH3
C O2

C I , NH3

K NH 3  C NH3 K O2  C O2 K I , NH 3  C I , NH3
  f (C S , C e accept , K S , K e accept , DS , De accept , T , pH ,


C I , HNO2
K I , HNO 2  C I , HNO2
where CNH3 is the concentration of free ammonia
(which is the actual substrate), CO2 is the oxygen
concentration and CI,NH3 and CI,HNO2 are the
concentration of NH3 and HNO2 which can
inhibit the process at high concentrations. All
concentrations are to be considered as concentration diffused into the biofilm.
The growth of Anammox bacteria can be expressed as
  max 

C NH3

C NO2

C I ,O2
K NH 3  C NH3 K NO 2  C NO2 K I ,O 2  C I ,O2
C I , NH3

C I , HNO2
K I , NH 3  C I , NH3 K I , HNO 2  C I , HNO2
where CI,O2 is the oxygen concentration considered as inhibiting factor for Anammox bacteria.
The bacteria growth rate is thus a function of
many factors:



C Inhib , b )
where CS is the substrate concentration or energy
source (NH3 for both Anammox and Nitrosomonas), Ce- accept is the concentration of the electron acceptor (NH3 for Anammox and O2 for
Nitrosomonas), KS and Ke- accept are the affinity
constants for the substrate and electron acceptor
respectively, DS and De- accept are the diffusion
coefficients in the biofilm, T is the temperature,
Cinhib are the inhibitory factors such as free
HNO2, NH3, toxic compounds or O2 for Anammox bacteria and b is the biomass decay coefficient.
Below a comparison of the main physiological
parameters of different bacteria populations
(Table 13) is given, although the differences that
can be found among different reactors configurations.
Table 13 – Physiological parameters of different bacteria populations
Parameter
AOB
NOB
Heterotrophs
ANAMMOX
pH range
6.5-8.5 (6)
6.5-8.5 (6)
7.5-9.1 (3)
6.7-8.3 (2)
Optimum pH
7.9-8.2 (5)
7.8-8.0 (6)
7.6-7.8 (7)
7.2-7.6 (5)
7.3-7.5 (6)
7.9 (8)
6.5-7.5 (9)
7.0-7.5 (10)
8.0 (4)
T range [°C]
5-42 (11)
5-42
optimum T [°C]
25-30 (6)
35 (8)
25-30 (6)
38 (8)
20-35
Free energy [kJ/mol substrate]
-275 (1)
-74 (13)
-427 (12)
-357 (1)
Biomass yield
[g protein / g NH4+-N]
[molC / mol NH4+]
[gVSS / gN]
0.1 (1)
0.127 (17)
0.056 (17)
0.3 (32)
0.07 (1)
0.066 (14)
0.11-0.13 (18)
[g CODbiomass / gN]
0.15 (15)
0.18 (17)
0.04 (15)
0.08 (17)
0.67* (17)
1.6-1.8 **
-
Aerobic rate
[mmol NH4+ h-1 mg protein-1]
12-36 (1)
-
-
0 (1)
Anaerobic rate
[mmol NH4+ h-1 mg protein-1]
0.12 (1)
-
-
3.6 (1)
Maximum specific growth rate
μmax [d-1]
0.96 (11)
1.08 (15)
0.6-0.8 (16)
1.21 (17)
1.39 (22)
0.98 (24)
0.66-0.77 (28)
2.6 (15)
0.6-1.0 (16)
1.02 (17)
0.91 (23)
0.79 (25)
3-6 (20)
5-10 (21)
8.42 (17)
0.0648 (14)
Doubling time [d]
0.73 (1)
0.29-0.33 (27)
0.33-1.46 (33)
0.42-0.54 (27)
0.5-1.63 (33)
-
10.6 (1)
24
20-43 (2)
37 (4)
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 13 – Physiological parameters of different bacteria populations (continued)
Affinity constant KNH4+ [mg/l]
0.09-46.8 (1)
0.96 (24)
0.60 (29)
0.48-1.62 (28)
n/a
n/a
0.09 (1)
Affinity constant KNO2-[mg/l]
n/a
0.24 (34)
-
<0.23 (1)
Affinity constant KO2 [mg/l]
0.32-1.6 (1)
0.74 (9)
0.03-1.3 (17)
0.24-1.22 (28)
0.94 (24)
1.75 (9)
0.3-2.5 (17)
1.1 (31)
0.2 (26)
n/a
n/a = not applicable.
* = g biomass COD /g COD;
** = g biomass COD /g NO3--N
(1) Jetten et al, 2001.
(2) Strous et al, 1999.
(3) Manuale dell‟Ingegnere 84 ed., 2003.
(4) Egli et al, 2001.
(5) Paredes et al, 2007.
(6) Ramadan A. E. K., 2007
(7) Holt et al, 1993.
(8) Grunditz and Dalhammar, 2001.
(9) Wang et al, 2009.
(10) Gerardi, 2002.
(11) Ahn, 2006.
(12) Van Hulle et al, 2010.
(13) http://nitrification.org/
(14) Strous et al, 1998
(15) Ahn et al, 2008.
(16) Henze, 2002.
(17) Jubany Güell I., 2007. At 25°C and
pH 7.5
(18) Strous et al, 1997.
(19)
(20)
(21)
(22)
Van Hulle, 2005.
Henze et al, 2002. With organic matter in wastewater.
Henze et al, 2002. With methanol.
Calculated as:
max  2.22  1011  e(( 6.5  104 )/(8.314  ( T  273.15))  (8.21/(8.21  1  10 7.23 pH )
[d-1] at pH 7.5 and T=25°C. (Volcke et al, 2007)
(23) Calculated as:
max  4.5  1011  e(( 4.5  104 )/(8.314  ( T  273.15))  (8.21/(8.21  1  10 7.23 pH )
[d-1] at pH 7.5 and T=25°C. (Volcke et al, 2007)
(24) Van Hulle et al, 2007.
(25) Wiesmann, 1994. At 20°C.
(26) Henze et al, 2000.
(27) Philips et al, 2002.
(28) Park and Noguera, 2007.
(29) Helliga et al, 1999. At 35°C and pH 7.
(30) Brion & Billen, 1998.
(31) Zhang et al, 2008.
(32) Kumar & Lin, 2010.
(33) Prosser, 2005.
(34) Kornaros et al, 2010.
2 A IM OF T HE PRESENT STUDY
This study is carried out with the main objective
to better understand and evaluate the performance - on a lab and pilot-scale - of partial Nitritation and Anammox in one single reactor, which
has still few full-scale installations in the world.
General aims regarding the partial nitritation/Anammox process are:
 Review literature and recent publications
about innovative nitrogen removal from
wastewater;
 Get familiar with laboratory-scale and pilot
plant reactors operation and understand the
optimal conditions for bacteria growth and an
efficient nitrogen removal in the one-stage
partial nitritation/Anammox process;
 Evaluation of the process performance by
chemical analyses, physical parameters monitoring and biomass measurements. Perform
calibrations and cleaning of the portable and
on-line instruments;
With specific regard to the laboratory scale experiments:
 Check different nitrogen removal possibilities
of partial nitritation/Anammox process under
different nitrogen influent loads and different
type of influent wastewater;
 Monitor the evolution of Anammox bacteria
activity through SAA (Specific Anammox Activity) tests;
With specific regard to the pilot scale experiments:
 Try to find some correlations between physical parameters and chemical analyses results;
 Assess the evolution of Anammox bacteria
(Specific Anammox Activity) in the biofilm;
 Assess the evolution of Nitrosomonas, Nitrobacter and Heterotrophic bacteria activity in
the biofilm through OUR (Oxygen Uptake
Rate) tests;
 Assess the Nitrate Uptake Rate (NUR) by the
biofilm and its evolution;
25
Andrea Bertino
TRITA Degree Project Thesis
 Compare the activities of different bacteria in
the biofilm with their activity in the activated
sludge.
In the next chapter material and methods used
for the experimental studies are described.
In the fourth and fifth chapters the results from
the lab and pilot-scale reactors respectively will be
discussed and analyzed in detail.
In the last section conclusions will be drawn and
recommendation for full-scale installation and
further research will be presented.
3 M ATERIAL A ND M ETHODS
This chapter gives a brief introduction of Hammarby Sjöstadsverk research facility where the
research studies discussed in this master thesis
were carried out in the period of time between
April and September (chapter 3.1).
An overview of the parallel research studies
undertaken within the present thesis are shown in
chapter 3.2.
The following chapters deal with the methodology and materials used for these studies, such as:
 instruments, materials and procedure used to
monitor and follow the reactors operation
(chapter 3.3);
 materials and methods for analytical measures
such as chemical analyses and suspended solids measurements (chapters 3.4 and 3.5);
 methodology for batch test carried out on the
biomass such as OUR, NUR and SAA (chapter 3.6).
3.1 Hammarby
facility
Sjöstadsverk
research
Hammarby Sjöstadsverk is a research and demonstration facility for wastewater treatment. It
was built in 2003 and it is located on top of Henriksdals WWTP, in Stockholm. Henriksdals
underground WWTP is the biggest in Sweden
and serves a population equivalent of 700.000.
The plant Hammarby Sjöstadsverk is owned and
operated by a consortium lead by the Royal Institute of Technology (KTH) and IVL Swedish
Environmental Research Institute.
The facility contributes to develop knowledge
and skills in water treatment and it is used for
development and demonstrations of new solutions and equipment for industries and partners
and for researching and testing more sustainable
and effective technologies in the wastewater
purification field. The main activities at Hammarby Sjöstadsverk consist of research and de-
Fig. 12. Hammarby Sjöstadsverk research
facility
from
above
(source:
http://sjostad.ivl.se)
velopment on water treatment technology and
biogas production (source: IVL Swedish Environmental Research Institute).
At Hammarby Sjöstadsverk there are five parallel
lines in pilot plant scale, three main lines with a
capacity of 1-2 m³/h (i.e. line 1: Aerobic treatment with activated sludge and biological nitrogen and phosphorous removal; line 2: Aerobic
treatment with membrane bioreactor and reverse
osmosis; line 3-4 combined: Anaerobic treatment
with UASB, a line for sludge treatment (line 5)
and an anaerobic membrane bioreactor (MBR)
(line 6).
Hammarby Sjöstadsverk is also used for education, including a fair number o different degree
projects and PhD thesis, and for collaboration
with national and/or international research programs/projects and consultancy.
Several research projects are currently underway
at the facility, including the project “Control and
optimization of the deammonification process” under the
leadership of Jozef Trela and Elzbieta Plaza, from
Fig. 13. Hammarby Sjöstadsverk research
plant - part of the treatment line 1 (source:
http://www.sjostadsverket.se/; photo: Per
Westergård)
26
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
KTH (http://www.sjostadsverket.se/) within
which this master thesis has been developed.
KTH has been conducted research on the deammonification process since 1999, leading to the
first full-scale plant in Scandinavia, at Himmerfjärds WWTP, south of Stockholm, in Södertälje municipality.
The main goal of this new project is to gather
new knowledge, test different operation strategies
and determine the optimal parameters for an
efficient nitrogen removal with deammonification
process. This thesis is part of this project and it is
focused on the one-step partial nitrification/Anammox process in the moving bed biofilm reactor (MBBR) with Kaldnes carriers.
3.2 Overview
strategy
of
the
experimental
An overview of different studies undertaken
within the present thesis is shown in figure 14.
During the period 23rd March – 25th July two
different laboratory scale reactors were operated
whereas the pilot plant-scale reactor was started
the 27th May and followed for four months from
its start-up.
The main analyses carried out and the main parameters studied in each reactor operation are
briefly summarized in Table 14.
Table 14 – Experimental work and analyses carried out.
Reactor
Monitoring parameters and analytical measures
Laboratory-scale reactor
treating reject water diluted
1:2.5
Laboratory-scale reactor
treating effluent from UASB
reactor and sand filtration
Technical-scale pilot plant
reactor treating reject water
from sludge dewatering after
anaerobic digestion
Inflow: pH, conductivity, alkalinity, COD, NH4+-N, TOT-P, inflow rate.
Outflow/Reactor: pH, conductivity, DO, T, alkalinity, COD, NH4+-N,
NO2--N, NO3-N, TOT-P, TSS/VSS (biocarriers), TSS/VSS (activated
sludge).
Inflow: pH, conductivity, alkalinity, COD, NH4+-N, TOT-P, inflow rate.
Outflow/Reactor: pH, conductivity, DO, T, alkalinity, COD, NH4+-N,
NO2-N, NO3-N, TOT-P, TSS/VSS (biocarriers), TSS/VSS (activated
sludge & influent).
Inflow: pH, conductivity, ORP, alkalinity, COD, NH4+-N, NO2--N, NO3-N,
TOT-N, CBOD5, TOT-P, inflow rate.
Outflow/Reactor: pH, ORP, DO, T, conductivity, alkalinity, COD,
NH4+-N, NO2--N, NO3-N, TOT-N, TOT-P, TSS/VSS (biocarriers),
TSS/VSS (activated sludge & influent).
Batch Tests
SAA
SAA
SAA, OUR, NUR
Technical-scale pilot plant reactor treating reject water from sludge
dewatering after anaerobic digestion (from Bromma WWTP).
Laboratory-scale reactor treating effluent from
UASB reactor & sand filtration (treatment line 3
at Hammarby Sjöstadsverk )
Laboratory-scale reactor treating
reject water (from Bromma WWTP)
diluted 1:2.5
11th May 27th May
23rd March
7th May
28th September
31st May
25th July
Fig. 14. Different studies on 1-stage partial Nitritation/Anammox process during the experimental work carried out at Hammarby Sjöstadsverk
27
Andrea Bertino
3.3 Physical parameters monitoring
3.3.1
Parameters description
The physical parameters were measured to keep
the reactor operation under control and in the
optimum range for bacteria and biological reactions. Some of the parameters were mainly used
as a monitoring tool for the conditions in the
reactor but were never corrected (redox, potential, pH, conductivity), whereas other parameters
(DO, inflow rate) were used to actively control
the process. These parameters are briefly described below.
pH. The pH is a measure of the concentration of
hydrogen ions (H+ or H3O+) in a solution and it
is mathematically defined as: pH   log H   ,
where   denote activity. The activity is the
molar concentration (expressed as mol/l)
multiplied by the activity coefficient γ. For diluted
solutions, activity is identical to concentration.
The pH represents the degree of acidity or
alkalinity of a solution and its scale ranges
between 0 and 14. Its value is influenced by
temperature. It is an important parameter to
provide suitable conditions for bacteria and
biological reactions. Constant pH values may be
indicative of overall stability of the process.
Dissolved Oxygen (DO). The dissolved oxygen
concentration (mg/l) is a key parameter for
biological reaction and its concentration can
enhance a reaction rather than another, or even
inhibit a reaction as in the case of Anammox or
denitrification. If dissolved oxygen in the bulk
liquid is high, nitrifying bacteria can be very
active and dissolved oxygen diffusion in the
biofilm is higher, leading to inhibition of
Anammox bacteria. Dissolved oxygen is provided
by aeration, which is one of the biggest costs in
wastewater
biological
treatments.
DO
concentration is influenced by the temperature
(inversely proportional) and atmospheric pressure
(directly proportional).
Oxidation Reduction Potential (ORP/redox). The ORP is
also called redox potential or indicated as Eh. It is
a measure that can be useful for determining the
oxidizing or reducing conditions of a solution. It
is measured in millivolts (mV) or volts (V).
Reduced substances in water predominate when
the redox potential is negative and oxidized
substances predominate when the redox potential
is positive. In biological wastewater treatment the
ORP is a useful tool to assess the
aerobic/anoxic/anaerobic condition in the
reactor. A low and negative ORP (<200 mV)
indicates anaerobic and methanogenic conditions
TRITA Degree Project Thesis
whereas a high and positive value (above 200
mV) are usually typical of aerobic activated sludge
processes. The ORP could also be used as a
monitoring tool in a low dissolved oxygen
wastewater treatment process (Holman and
Warehem, 2000). ORP is dependent on
temperature and aeration, organic substrate and
activity of microorganisms in the reactor.
Conductivity. The electrical conductivity of a solution
is a measure of the ionic activity in term of its
capacity to transmit current. It is proportional to
the total amount of ions, their valence and
temperature. It is usually measured in µS/cm or
mS/cm. In these studies it was used as an easy
and direct monitoring parameter as indicator of
process performance and ammonium removal.
As suggested by Szatkowska et al (2007c) and
Levlin (2007), these monitoring parameters can
be used for wastewater treatment that causes
changes in total salt concentration (and thus in
conductivity) as in the case of partial nitrification
and Anammox process where the main ions –
NH4+ and HCO3- – are converted to CO2 and
N2.
Temperature.
The temperature was another
parameters for bacteria activity and rates of
biological reactions. It was kept constant at about
25°C during the reactors operations. Temperature
of the system may be a problem in cold areas
during winter season and could represents a cost
if heat need to be supplied to the system.
Inflow rate. The inflow rate (l/d) is closely related to
the nitrogen loading rate and determines the
hydraulic retention time at a fixed volume of the
reactor. A too high or too low inflow rate can
significantly influence the efficiency of the whole
process. The inflow rate was accurately checked
manually with a graduated cylinder, by measuring
the volume of the influent wastewater after 3
minutes.
3.3.2
Measurements in laboratory-scale studies
Measurements of physical parameters in laboratory-scale studies were carried out manually three
times per week if possible. The instruments
which were used are listed below:
 pH: WTW pH 330i with WTW SenTix 41
probe;
 DO: Hach Lange HQ 30d flexi together with
Hach Lange LDO (Dissolved Oxygen Luminescent) 101 sensor and/or YSI Model 57
Oxygen Meter with YSI 5905 BOD probe.
 Conductivity: WTW Cond 330i with WTW
tetraCon 325 sensor;
28
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
 Temperature: WTW Cond 330i with WTW
tetraCon 325 sensor or Hach Lange HQ 30d
flexi together with Hach Lange LDO (Dissolved Oxygen Luminescent) 101 sensor or a
digital thermometer with precision ± 0.1 °C.
The pH was calibrated once a month, whereas
the conductivity meter was calibrated only at the
beginning of the experimental studies (as it was
advised a calibration every six months). The DO
meter was calibrated each measurement. The
ORP was not measured in the lab-scale studies.
3.3.3
Measurements in pilot plant-scale studies
Regarding the pilot plant-scale reactor, the parameters were all measured online and data were
logged every 10 seconds. The control boxes
installed were two Cerlic BB2 central units
(Fig. 15) equipped with one Cerlic pHX sensor,
two Cerlic ReX sensors (one for inflow and one
inside the reactor) and one Cerlic O2X Dissolved
Oxygen sensor (Fig. 16). The conductivity was
measured by Dr Lange Analon Cond 10 Conductivity Monitor unit. The DO concentration
and the air flow supplied were controlled by a
Samson Trovis 6493 Compact PID Controller
with an electropneumatic actuator Samson type
3372 and valve Samson type 3321. The temperature was controlled by a Jumo dTRON 316 microprocessor PID controller. A float was used to
monitor the water level for safety reasons: if the
flow falls below a certain level, then the heater
would stop.
Regarding the DO, only the air calibration was
done, whereas the conductivity sensors were
calibrated with air and in few occasions with
DO sensor
Fig. 15. Online measurements and control
panel for the pilot plant-scale reactor.
standard solution 10 mS/cm. In the last six weeks
it was not possible to do the calibration with
standard solution anymore, probably because of
their usage. The Cerlic O2X sensor, however, do
not need a frequent calibration, as it is written in
the manual (once every six month). The inflow
rate was checked between once and thrice per
week.
3.4 Chemical analyses
Regarding the laboratory scale reactors, the
chemical analyses were usually per-formed once
per week for both inflow and outflow and within
a time equal to the hydraulic retention time of the
reactor. Regarding the pilot plant operation the
in-flow was analyzed once per week and the
outflow twice per week, in order to monitor the
performance more frequently. The two chemical
analyses on the outflow were usually performed
Fig. 16. Monitoring
instruments for the
pilot plant-scale reactor.
pH electrode
Inflow
pipe
ORP electrode
Air tube
Mechanical
stirrer
Conductivity sensor
29
Andrea Bertino
TRITA Degree Project Thesis
286 ml capacity and no seeding was needed. The
only difference is that, among the reagents
NH4Cl was not added because ammonium was
already present in the reject water and MgCl2 was
added instead of MgSO4. pH was adjusted to 7.2
with sulfuric acid (H2SO4) and ATU was used as
nitrification inhibitor. Dilutions were prepared in
graduate cylinders.
3.5 Suspended solids measurements
Fig. 17. Dr. Lange Cuvette Tests used for
chemical analyses.
two and four days after the measurement on the
inflow to the reactor.
The samples were taken from the outflow
tank/vessel after 20-30 minutes having emptied it
and filtered soon afterwards.
Dr. Lange Cuvette Tests (Fig. 17) were used for
the chemical analyses. The samples were filtered
with Schleicher & Schuell membrane filters 0.45
µm (mixed cellulose ester). If the chemical parameters were outside the measuring range, dilution
with distilled water was done. In a few occasions
samples were filtered, frozen and analyzed the
following day. The cuvettes were evaluated with
the Dr Lange XION 500 spectrophotometer.
Hach Lange Thermostat LT200 was used for
COD, TOT-N and TOT-P measurements.
The measurements on unfiltered samples were
done after having mixed carefully the samples.
The pipettes were checked regularly.
The cuvettes used are listed below:
 NH4+-N LCK 305, 1-12 mg/l
 NH4+-N LCK 303, 2-47 mg/l
 NH4+-N LCK 302, 47-130 mg/l
 NO2--N LCK 342, 0.6-6 mg/l
 NO3--N LCK 339, 0.23-13.50 mg/l
 NO3--N LCK 340, 5-35 mg/l
 TOT-N LCK 338, 20-100 mg/l
 TOT-P LCK 350, 2-20 mg/l
 Acid Capacity KS 4.3 LCK 362, 0.5-8.0 mmol/l
 COD LCK 314, 15-150 mg O2/l
 COD LCK 514, 100-2000 mg O2/l
The CBOD5 was measured only once on the
influent reject water to the pilot reactor according
to the procedure described in Standard Method
5210 B (5-day BOD Test). The bottles used were
Suspended solids measurements were carried out
in order to estimate the total and the volatile
suspended solids contents for both the biofilm
developed on the carriers and the liquid inside the
reactor. The suspended solids were measured
using filters with pore size 1.6 µm, because due to
problem with purchase was not possible to carry
out the analyses with filters with pore size 0.45
µm. The filtration was done by a vacuum filter.
The digital scale used for weighting was Acculab
LA-series with a precision of ± 0.1 mg. The
micro-glass fiber filters used were Munktell MG
A type. The aluminum plates used did not show
any loss of weight after having been left for 40
minutes at high temperatures. In one occasion a
box of filters show a decrease of weight, especially at high temperatures (-0.06 %). A sort of
calibration was done on eight filters in order to
estimate the average weight loss and correct the
results afterwards.
3.5.1
Total and volatile suspended solids as
biofilm
The total suspended solids (TSS) and the volatile
suspended solids (VSS) content of the biofilm
were estimated averaging the results from 4 sample rings taken randomly from inside the reactor
according to the procedure described in
APPENDIX I.
3.5.2 Total and volatile suspended solids in the
influent and inside the reactor
The total suspended solids (TSS) and the volatile
suspended solids (VSS) were measured according
to Standard methods 2540 D (Total Suspended
Solids Dried at 103-105°C) and 2540 E (Fixed
and Volatile Solids Ignited at 550°C) as described
in APPENDIX I.
The measurement of VSS (or sometimes indicated as MLVSS – Mixed Liquor Volatile Suspended Solids) is a rough approximation of the
amount of organic matter present in the solid
fraction. In presence of activated sludge it can be
an estimation of the biomass concentration.
However this conventional suspended solid
measurement includes both the living biomass
30
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
VSS
Living
biomass
Dead biomass
and
Inert Organics
TSS
Inert
Inorganics
Fig. 18. Suspended solids classification
(modified from Whalen, 2007).
and the dead biomass and inert organics as drawn
in figure 18.
New molecular techniques such as fluorescent in
situ hybridization (FISH), RNA analysis, DAPI
staining, and ATP analysis make possible to
measure directly and quantify the metabolically
active fraction of the activated sludge mixed
liquor.
3.6 Batch tests
Suspended solids measurements were carried out
in order to Batch tests were performed in order
to assess the activity of different bacteria populations present in the reactor and measure the
Anammox activity (SAA), the oxygen and nitrate
uptake rates (OUR and NUR). With regard to the
pilot plant-scale reactor, which was followed for a
longer period of time, the aim was also to assess
the presence of any trend in the bacterial activity.
3.6.1
Specific Anammox Activity (SAA) test
The SAA test has the aim to evaluate the Anammox bacteria activity. The tests were performed
according to the methodology described by
Dapena-Mora et al (2007). These batch tests are
based on the measurement of the increment of
pressure inside a closed volume, proportional to
the production of nitrogen gas by ANAMMOX
bacteria which use nitrite and ammonium as their
substrates (Strous et al, 1999):
NH4+ + 1.32 NO2– + 0.066 HCO3– + 0.13 H+ →
1.02 N2 + 0.26 NO3– + 2.03 H2O
+ 0.066 CH2O0.5N0.15
The analyses were carried out in vials with a total
volume of 38.0 ml and a volume of liquid of 25.0
ml, sealed tightly with rubber caps. The gas phase
was therefore equal to 13.0 ml.
Each vial was filled with phosphate buffer solution (0.14 g/l KH2PO4 and 0.75 g/l K2HPO4)
and 15 Kaldnes rings, which have been previously washed twice with buffer solution (Fig.
19). The total volume of phosphate buffer solution and the 15 rings was always equal to 24 ml,
Fig. 19. Vial with 15 Kaldnes carriers after
SAA analysis.
in order to have a constant gas phase. The initial
pH value was about 7.8.
The vials were closed and oxygen in the liquid
phase was removed by supplying N2 gas for
about three minutes by means of a needle inserted through the septum. Another needle was
used to remove the gas excess from the vials.
concentrations of NH4+-N and NO2--N inside
the bottles were 70 mg N/l. This concentration is
not inhibiting according to Strous et al (1999) and
Dapena-Mora et al (2007).
Then the vials were tightly closed and the pressure was equalized to the atmospheric one with
another needle. From that moment the test was
started. The pressure in the headspace was monitored with a time frequency depending on the
biomass activity (usually 30 minutes) by means of
a pressure transducer (Centrepoint Electronics
model PSI. 5) that measures the overpressure in a
range from 0 to 5 psi. The duration of the test
was about 2 hours. The final pH value was measured only in the first test and it was between 8
and 8.08, thus in the optimal range for the
Anammox activity. In the first months the SAA
test on the rings from the pilot plant reactor was
performed at both 25°C and 35°C. Regarding the
lab-scale studies SAA was carried out only at
35°C.
The total amount of N2 gas produced was calculated from the overpressure measured in the
headspace of each vial by using the ideal gas law
equation (Dapena-Mora et al, 2007). Ammonium,
nitrite and nitrate concentrations removed from
the liquid phase (or produced, in the case of
nitrate) were not measured in these experiments.
The accuracy of the test was estimated by
Dapena-Mora et al (2007) which measured the
31
Andrea Bertino
TRITA Degree Project Thesis
phosphate
buffer
solution
NH4Cl
NaNO2
pressure
transducer
Fig. 20. SAA material
and instruments.
vials
average errors from the balances and resulted
lower than 7%. Analysis of the produced biogas
composition by Dapena-Mora et al (2007) indicated that more than 99% of the produced gas
was N2.
The main inconvenient which may occur is the
nitrogen gas leakage from the cap if it has been
worn out by use. In those cases, the linearity of
the curves (pressure vs. time) obtained from the
experimental measures, show a fall or a sharp
change of slope and the data from those particular tests are not reliable.
A potential limitation of SAA test and its results
might be related to the possibility of denitrifiers
to produce nitrogen gas N2 (and other gases such
as nitrous oxide N2O and nitric oxide NO) by
consuming NO3- (that is produced by Anammox
bacteria) or NO2- and the COD stored by the
biomass, as electron donor. If this takes place, the
estimation of the nitrogen gas production might
be slightly overestimated.
The values of pressure measured by the pressure
transducer were given in mV. These values were
converted to mmHg by multiplying by a factor
equal to 2.65 based on a calibration.
The correctness of this value was later checked
Table 15 – Calculations for SAA tests on the biocarriers.
Result
Unit
Formulas
N2 gas production rate (dN2/dt)
mol N 2
min
SAA (Specific Anammox Activity)
g N2
m2 d
dN 2  VG

dt
R T
dN 2
 28
SAA  dt
 60  24
Sbiofilm
SAA (Specific Anammox Activity)
g N2
g VSS d
dN 2
 28
SAA  dt
 60  24
X
α = slope of the pressure increase inside the vial plotted versus time (atm/min);
VG = volume of the gas phase (0.013 l), calculated by subtracting the volume of liquid with 15 biocarriers (25 ml) from the
total volume of the vial (38 ml):
R = ideal gas constant 0.0820575 (atm l mol-1 K-1);
T = temperature (K);
28 = molecular weight of N2 (g N/mol);
60 and 24 = unit conversion factors from min to days.
Sbiofilm = surface area of 15 biocarriers = 7.00935∙10-3 m2, calculated as the product of the specific area of Kaldnes media and
the volume occupied by 15 rings (calculated by proportion on the base of the measurement that 107 rings occupy 100 ml):
Sbiofilm  500
m2
V15rings
m3
X = grams of biomass attached on 15 rings;
32
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 16 – Calculations for SAA tests on the activated sludge.
Result
Unit
Formulas
N2 gas production rate (dN2/dt)
mol N 2
min
dN 2  VG

dt
R T
SAA (Specific Anammox Activity)
g N2
g VSS  d
dN 2
 28
SAA  dt
 60  24
X VL
α = slope of the pressure increase inside the vial plotted versus time (atm/min);
VG = volume of the gas phase (0.013 l), calculated by subtracting the volume of liquid with 15 biocarriers (25 ml) from the
total volume of the vial (38 ml):
R = ideal gas constant 0.0820575 (atm l mol-1 K-1);
T = temperature (K);
28 = molecular weight of N2 (g N/mol);
60 and 24 = unit conversion factors from min to days.
X = biomass concentration inside the vial (g VSS/l);
VL = volume of the liquid phase in the vial (approximately 18.97 ml). It has been calculated as difference between 25 ml and
the equivalent volume occupied by carriers, based on the measurement that 4 l of rings occupy approximately a volume of 1.72
l.
and verified.
The pressure expressed in mmHg was then converted to atm by dividing by 760. The N2 gas
production rate  dN 2  was calculated through
 dt 
the ideal gas equation PV  nRT and assuming a
zero order kinetic dn  k for nitrogen gas prodt
duction. This hypothesis can be considered valid
because of the high initial concentrations of
nitrogen, the short duration of the experiment
(about 2 hours) and the experimental results
which showed that the pressure data plotted
versus time were aligned on a straight line.
The calculations used to estimate the SAA on the
biocarriers are summarized in Table 15.
In one occasion SAA analysis was carried out on
the activated sludge. In that case the vials used
were the same ones (38 ml) and the liquid phase
consisted of 24 ml of liquid from the reactor
(activated sludge), 0.5 ml of NH4Cl and 0.5 ml of
NaNO2. No buffer solution was added and no
pH value was measured in that experiment. The
SAA test was performed at 25°C.
N2 gas production rate and the SAA calculations
for the activated sludge (Table 16) have been
calculated similarly but referred to the biomass
concentration inside the vial expressed as
(g VSS/l).
3.6.2
Oxygen Uptake Rate (OUR) test
The OUR test has the aim to assess qualitatively
and quantitatively ammonia- and nitrite-oxidizing
bacteria (AOB and NOB) as well as heterotrophic activity. The tests were performed on the
base of the methodology described by Gut et
al (2005).
The principle of OUR test is to monitor the rate
of dissolved oxygen uptake by bacteria and selectively inhibit different bacterial populations during the test (Fig. 21).
The dissolved oxygen was measured by YSI
Model 57 Oxygen Meter with YSI 5905 BOD
probe and data were recorded every second by
TESTO® Comfort-Software 2004 v 3.4. The
batch test was performed in a glass bottle with a
volume of 1.56 l. The bottle was filled with reject
water (characterization is shown in paragraph
5.1.2.) previously diluted approximately 1:10 in
order to have a NH4+-N initial concentration of
about 100 mg/l. This value was measured before
starting the test. The bottle was placed in the
water bath until the temperature measured had
reached about 25°C. Then the bottle was vigorously shaken or, alternatively, air was supplied in
the reject water to reach a DO concentration
over 6.5-7 mg/l. The bottle was placed in the
water bath and on a magnetic stirrer, in order to
assure a proper mixing of the liquor. At this
point, the Kaldnes carriers, washed with the same
diluted reject water, were rapidly inserted into the
bottle. 107 Kaldnes carriers were used for the
test, which
correspond to a volume of approximately 100 ml. Larger amounts of Kaldnes
carriers were rejected in order to avoid the risk to
damage too much the biofilm bacteria culture
activity by the tests. The Kaldnes carriers were
usually taken directly from the reactor about one
hour before the test and kept in diluted reject
water. The reactor vessel was completely closed,
33
Andrea Bertino
TRITA Degree Project Thesis
NOB (Nitrite-oxidizing
bacteria)
Inhibited by NaClO3
Inhibited by NaClO3
NOB (Nitrite-oxidizing
bacteria)
NOB (Nitrite-oxidizing
bacteria)
+
Inhibited by ATU
AOB (Ammonia-oxidizing
bacteria)
AOB (Ammonia-oxidizing
bacteria)
+
+
HT (Heterotrophic
respiration)
AOB (Ammonia-oxidizing
bacteria)
HT (Heterotrophic
respiration)
HT (Heterotrophic
respiration)
time of the experiment
Fig. 21. Selective inhibitions of bacteria populations.
with rubber corks and parafilm, in order to avoid
air intrusion in the bottle, and test was started.
First, the total oxygen uptake was measured.
After about 4-5 minutes and depending on test
progress, 4 ml of sodium chlorate (NaClO3)
(solution 131.4 mg/100 ml) were added to the
mixed liquor in order inhibit NO2--N oxidation
by NOB. The final concentration in the bottle
was about 32.6 µM. This concentration was lower
than other values described in the literature studies. A ClO3 concentration above 1 mM inhibits
completely the NO2--N oxidation to NO3--N
(Peng and Zhu., 2006; Xu et al, 2010). SurmaczGórska et al (1996) suggested a concentration of
17 mM NaClO3 for NOB inhibition. Belser &
Mays (1980) observed that 10 mM NaClO3 does
not affect AOB, which are inhibited by sodium
chlorite NaClO2. However, according to Yang J.
and Zubrowska M. (personal information, not
published) which carried out some OUR tests on
a parallel pilot reactor in Hammarby Sjöstadsverk
on biocarriers with the same origin, the results
with the concentration used in this thesis were
not different from the results obtained with the
higher concentration that is mentioned in literature.
After about 5-6 minutes, 6 ml of Allylthiourea
(ATU) (C4H8N2S) (solution 390 mg/100 ml) were
added to the liquor. The final concentration in
the bottle was about 132.9 µM, which is higher
than the one suggested by the concentration
suggested in the 21st edition of Standard Methods for measuring CBOD (about 57.4 µM).
Probably a lower concentration was sufficient to
fully inhibit nitrification.
Fig. 22. Material and
equipment for OUR
tests
DO
probe
water
bath
magnetic
stirrer
recorder
107
rings
inhibitors
34
Andrea Bertino
TRITA Degree Project Thesis
Table 17 – Calculations for OUR tests on the biocarriers.
Result
Unit
Formulas
Dissolved oxygen uptake rate (dO2/dt)
g O2
m2  d
dO2  i VL 60  60  24


dt
Sbiofilm
1000
OUR - Nitrobacter
g O2
m2 d
OUR - Nitrosomonas
g O2
m2 d
OUR - Heterotrophs
g O2
m2 d
OUR NOB  
dO2 
 dO 
 2 

 dt  AOB  NOB  HT  dt  AOB  HT
OUR  AOB  
dO2 
 dO 
 2 

 dt  AOB  HT  dt HT
dO
OUR HT   2 
 dt HT
αi = slope of the dissolved oxygen concentration decrease inside the bottle plotted versus time (mg O 2 l-1 s-1). Subscript "i"
indicates the slope of the respective phase of the test (AOB+NOB+HT, HT+AOB or HT). The values of the three
slopes are the averages of the three OUR tests performed;
VL = volume of the liquid phase (about 1.517 l) calculated by subtracting from the total volume of the bottle (1.56 l), the equivalent volume of liquid displaced by 107 Kaldnes biocarriers (calculated by a simple proportion, on the base of the measurement that 4 l of biocarriers occupy approximately an equivalent volume of water of 1.72 l). The volume of the liquid
phase VL was slightly different during the three steps of the test because of the stepwise additions of inhibitors (4 ml and 6
ml); This was kept into account in the calculations and the volumes are approximately 1.507 l, 1.511 l and 1.517 l;
Sbiofilm = surface area of 107 biocarriers = 0.05 m2, calculated as the product of the specific area of Kaldnes media and the
volume occupied by 107 rings (i.e. 100 ml): S  500 m 2 V
;
 106
biofilm
m3
107rings
60, 60 and 24 = unit conversion factors from seconds to days;
1000 = unit conversion factors from mg to g.
The difference between the total OUR and the
one after NaClO3 addition was identified as the
oxygen uptake due to NOB (nitrite oxidizers),
whereas the difference between the OUR with
NaClO3 and the OUR after addition of ATU was
attributed to the oxygen consumption by AOB
(ammonium oxidizers). Ultimately, the OUR
measured in the presence of two chemicals represented the oxygen uptake of the heterotrophs
(HT).
The inhibitors were added by means of two
needles inserted in the rubber corks. The pH was
measured manually at the beginning and the end
of a couple of tests and it was between 8.05
and 8.25. The temperature was maintained
around 25 °C during the whole test. Three tests
were performed in order to obtain more reliable
results. The value in output from the recorder
was in mV and it was later converted to mg O2/l
on the basis of the calibration done before starting that specific OUR test.
As underlined by Gut et al (2005), a limitation of
this method is the impossibility to distinguish
between the oxygen consumption for substrate
oxidation and endogenous respiration of heterotrophic bacteria.
The dissolved oxygen uptake rate (OUR) was
calculated by linear regression from the slope of
the three curves (line segments) of the oxygen
uptake plotted versus time. The calculations used
to estimate the oxygen uptake rate (OUR) by
different bacterial populations on the biocarriers
are shown in Table 17.
In one occasion OUR test was carried out on the
activated sludge in order to have a term of comparison. In that case, the bottle was filled with
fresh activated sludge directly taken from the
reactor. The bottle was shaken vigorously and 9
ml NH4HCO3 were added to raise the NH4+-N
concentration up to 100 mg/l. Then the data
logging was started. The duration of the test was
shorter. The first inhibitor (NaClO3) was added
after 2 minutes and ATU about 1.5 minutes later.
The concentrations added were the same. The
oxygen uptake rate was calculated as shown in
Table 18.
3.6.3
Nitrate Uptake Rate (NUR) test
The NUR test has the aim to assess the NO3removal rate from the liquor. The bacteria responsible for nitrate removal are essentially denitrifying bacteria. However Anammox bacteria
(which may use the nitrite produced during denitrification) can act in the opposite direction,
leading to an underestimation of the nitrate removal rate by denitrifiers.
The test was performed in a 1.5 l plastic container, which was filled with 1 l of reject water
diluted with tap water (50-75% reject water and
50%-25% tap water), in order to have a slightly
lower initial pH and an initial COD concentration
Andrea Bertino
TRITA Degree Project Thesis
Table 18 – Calculations for OUR tests on the activated sludge.
Result
Unit
Formulas
Specific dissolved oxygen uptake
rate (dO2/dt)
g O2
g VSS  d
dO2  i

 60  60  24
dt
X
OUR - Nitrobacter
g O2
g VSS  d
OUR - Nitrosomonas
g O2
g VSS  d
OUR - Heterotrophs
g O2
g VSS  d
OUR NOB  
dO2 
 dO 
 2 

 dt  AOB  NOB  HT  dt  AOB  HT
OUR  AOB  
dO2 
 dO 
 2 

 dt  AOB  HT  dt HT
dO
OUR HT   2 
 dt HT
αi = slope of the dissolved oxygen concentration decrease inside the bottle plotted versus time (mg O2 l-1 s-1). Subscript "i"
indicates the slope of the respective phase of the test (AOB+NOB+HT, HT+AOB or HT). The values of the three
slopes are the averages of the three OUR tests performed;
X = biomass concentration inside the bottle (mg VSS/l); the biomass concentration inside the bottle was slightly different
during the test because of the stepwise dilutions made (9 ml NH4HCO3, 4 ml NaClO3 and 6 ml ATU). These changes
were kept into account in the calculations and the VSS concentration was recalculated according to the new volume of
liquid;
60, 60 and 24 = unit conversion factors from seconds to days;
of about 350-450 mg O2/l. The container was
placed in the water bath until the temperature
measured had reached about 25°C and on a
submersible magnetic stirrer in order to assure a
proper mixing of the liquor.
Afterwards, nitrogen gas (N2) was supplied into
the liquor to decrease the dissolved oxygen concentration below 0.5 mg/l and the container was
covered by parafilm. At this point, the Kaldnes
carriers, washed with the same diluted reject
water, were put into the container. 400 ml of
Kaldnes carriers were used for the test. The
Kaldnes carriers were usually taken directly from
the reactor about one hour before starting the
test and kept in diluted reject water in order to
prevent oxygen diffusion into the biofilm.
Then
10
ml
NaNO3
solution
(6 g NaNO3/100 ml) were added in order to
reach 100 mg/l NO3--N in the container. After
having waited about one minute that the solution
was spread in the liquor evenly, the first sample
was taken and filtered with 0.45 μm filter. A filter
with pore size 1.6 μm was used to prevent rapid
clogging of the
filter with smaller pores size. Nitrogen gas was
supplied during the whole test under parafilm, in
order to avoid oxygen diffusion into the liquor.
The duration of the test was about 4 hours and 5
sample were taken in total (one each hour). COD
and NO3--N were analyzed at the end of the test.
Fig. 22. Material and
equipment for NUR tests
parafilm
NaNO3
Syringe filters
36
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 19 – NUR calculations for the biocarriers and activated sludge.
Result
Unit
NUR (biocarriers)
g NO3  N
m2 d
NUR (activated sludge)
g NO3  N
g VSS  d
Formulas
NUR 
 VL
 1000  60  24
Sbiofilm
NUR 

 60  24
X
α = slope of the nitrate concentration consumption inside the container plotted versus time (mg NO 3--N l-1 min-1);
VL = volume of the liquid phase equal to 1l.
Sbiofilm = surface area of 400 ml biocarriers = 0.2 m2, calculated as the product of the specific area of Kaldnes media and the
volume of the rings: S  500 m 2  400  106 ;
biofilm
m3
X = biomass concentration inside the container (mg VSS/l);
60 and 24 = unit conversion factors from min to days;
1000 = deriving from conversion from mg to g and from ml to m3.
As the decrease of COD was found to be low,
only the first and last samples were analyzed for
COD. NO2--N initial concentration in the liquor
was close to zero. The pH was measured at the
beginning and the end of the test on a couple of
occasions and it ranged between 8 and 8.9.
The dissolved nitrate uptake rate (NUR) was
calculated by linear regression from the slope of
the curve (straight line) of the nitrate uptake
plotted versus time.
In one occasion NUR test was carried out on the
activated sludge in order to have a term of comparison. In that case the container was filled with
1 l of activated sludge directly taken from the
reactor. The container was placed in the water
bath at 25°C and nitrogen gas (N2) was supplied
into the liquor to decrease the dissolved oxygen
concentration below 0.5 mg/l. The container was
covered by parafilm and the magnetic stirred
assured proper mixing. There was no need to
increase the NO3--N concentration as it was
already 104 mg/l. The pH was measured at the
beginning and the end of the test and ranged
between 8 and 8.7.
4 L ABORATORY - SCALE S TUDIES
The laboratory-scale studies were carried out
during the first four months of thesis work (period April-June). These studies were conducted in
order to get practice with the whole one-stage
deammonification process, investigate the factors
influencing the process performance and assess
different possibilities of treatment.
Two different laboratory reactors were run:
 a laboratory scale reactor treating diluted
reject water (cfr. paragraph 4.1)
 a laboratory scale reactor treating the effluent
of the upflow anaerobic sludge blanket
(UASB) reactor (cfr. Paragraph 4.2).
4.1 Laboratory-scale reactor treating
diluted reject water
The laboratory-scale reactor was started on 23rd
March in the chemical labora-tory of the research
facility Hammarby Sjöstadsverk and run for two
months until the pilot plant scale reactor in the
facility was started.
4.1.1
Reactor operation and experimental setup
The laboratory-scale system consisted of one
single reactor filled with ap-proximately 40% of
Kaldnes™ carriers. The reactor was simply a
plastic bucket, open at the top (Fig. 24). The
outflow of the reactor consisted of an overflow
system. The reactor had a volume of 9.345 L and
it was filled with about 3.9 L of Kaldnes rings
(model K1) with a specific internal surface area of
500 m2/m3. The effective volume of liquid in the
reactor was 7.685 L.
The temperature was kept at about 25°C by an
electric water heater thermostat. The stirring was
assured by two electric submersible aquarium
water pumps located at the basis of the reactor in
order to avoid as much as possible sedimentation
of Kaldnes rings. Oxygen was supplied continuously by aeration through air stone connected
to the aeration pipe. The reactor was usually
covered by aluminum paper in order to avoid
possible effect of light and keep biocarriers in the
dark and it was also wrapped in insulating material to prevent heat loss and reduce electricity
consumption for heating.
37
Andrea Bertino
TRITA Degree Project Thesis
Fig. 24. Laboratory scale reactor treating diluted reject water.
The hydraulic retention time (HRT) was kept at
two days and the inflow rate was checked three
times per week in order to make sure the inflow
rate was maintained constant at about 3.78 l/d
and to prevent the occurrence of a decrease in
the inflow rate due to deposition of suspended
solids in the inflow pipe of small diameter.
The operational parameters are summarized in
Table 20.
The reactor was working as Continuous StirredTank Reactor (CSTR) and no sludge recycling
was provided. The Kaldnes™ carriers used for
the reactor start-up are shown in figure 25. They
were brought in January, from Himmerfjärden
Wastewater Treatment Plant where deammonification process is carried out using biocarriers
with a biofilm composed by Anammox and
Nitrosomonas bacteria. Before the use for the
laboratory scale studies here described, they have
been kept in anoxic conditions into a vessel for
two months as they were a “surplus” from another reactor that was started in January, 2010.
The supernatant used as inflow was periodically
taken from a storage tank in Hammarby
Sjöstadsverk and it was brought from Bromma
WWTP. The inflow vessel in the laboratory,
where the influent to the reactor was stored, was
refilled with about 20-30 liters two-three times
per week.
The reactor feed consisted of reject water from
sludge dewatering after anaerobic digestion which
was diluted 1:2.5 with tap water in order to have
an ammonia nitrogen (NH4+-N) concentration of
about 400 mg/l. Nitrate (NO3-) and nitrite (NO2-)
concentrations were very low and negligible.
The physical and chemical parameters of the
influent to the reactor are summarized in
Table 21. Unlike the pilot plant reactor described
in chapter 5, the total nitrogen, the suspended
solids in the influent and in the reactor have not
been measured in this laboratory study.
Table 20 – Operational parameters for the
laboratory-scale reactor.
Parameter
Unit
Value
Hydraulic Retention Time (HRT)
day
2.04
Reactor Volume (liquid)
l
7.69
3.78
Flow rate
l/d
Kaldnes carriers
l
3.9
Temperature
°C
25.4
Fig. 25. Biocarriers used for laboratory-scale
reactor start-up.
38
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 21 – Characterization of the influent diluted reject water 1:2.5.
Parameter
Unit
Mean±S.D.
Measurements
Ammonium NH4+
mg/l NH4+-N
399.1 ± 27.7
12
mmol/l Ks 4.3
36.5 ± 16.4
g/l CaCO3
1.82 ± 0.82
Alk/NH4+-N
mol Alk / mol N
1.06 ± 0.09
8
CODsoluble
mg O2/l
311 ± 48
8
CODtot
mg O2/l
496 ± 73
7
COD/ NH4+-N
-
0.79 ± 0.12
8
Total Phosphorus (unfilt.)
mg/l
2.10 ± 0.91
5
Conductivity
mS/cm
3.07 ± 0.27
39
pH
-
8.19 ± 0.38
38
Alkalinity
4.1.2
Analytical measurements and sampling
procedures
The physical parameters (pH, T, DO, conductivity) in the reactor and the inflow rate were
measured manually three-four times per week in
order to provide good and stable conditions for
bacteria and evaluate process efficiency with the
operating conditions.
The flow was kept constant during the whole
study but ammonia nitrogen in the influent
showed slight variations in concentration.
The chemical analyses were performed once per
week for both inflow and outflow and within two
days of each other. Between the inflow and outflow analyses the tank containing the influent
diluted supernatant was not refilled in order not
to change its composition between the two
measurements.
The main compounds and parameters monitored
were NH4+-N, NO2-N, NO3-N, COD (filtered
0.45μm and unfiltered) and alkalinity. The decrease of ammonia nitrogen in the reject water
over two days was negligible and only once it was
found to be higher (about 8.1 %) but that was
probably due to an analysis error because the
following times it was negligible (about 1%). The
outflow samples were taken from a small outflow
container after about 30-40 minutes having emptied it.
4.1.3
9
Results and discussion
Operational conditions
The results from measurements of physical parameters in the reactor are shown in the chart in
figure 26. The average values over the months of
operation are shown in Table 22 whereas the raw
table with all the physical parameters measured is
included in the APPENDIX II.
The dissolved oxygen was the most sensitive and
problematic parameter to keep stable and sometimes its concentration was not evenly distributed
in different parts of the reactor. This was mainly
due to the rather punctual aeration system which
was not the most suitable. Moreover the absence
of an online control system on the aeration supply device made it hard to regulate the aeration
and keep the dissolved oxygen at a constant
concentration without variations. Several times it
was needed to decrease aeration in order to bring
back the pH to higher values and to prevent
further oxidation to nitrate and other times there
was the need to increase aeration to enhance
nitritation. This was done according to the results
from the chemical analyses on the outflow and
the pH value measured in the reactor. High dissolved oxygen concentration effects seemed to be
reversible and they caused only accumulation of
nitrates in the reactor, resulting in a couple of
days of bad performance with higher concentrations of nitrates in the outflow.
The pH was found to be strongly dependent on
the dissolved oxygen concentration in the reactor.
Table 22 – Physical parameters in the laboratory scale reactor.
Parameter
Unit
Mean±S.D.
Measurements
pH
-
7.30 ± 0.54
35
DO
mg O2/l
1.13 ± 0.77
35
T
°C
25.45 ± 0.20
34
Conductivity
mS/cm
1.19 ± 0.49
33
39
Andrea Bertino
TRITA Degree Project Thesis
DO
conductivity IN
conductivity R
8,5
8,0
7,5
7,0
6,5
6,0
5,5
5,0
4,5
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
5,0
4,5
4,0
3,5
3,0
2,5
2,0
1,5
conductivity [mS/cm]
pH; DO [mgO2/l]
pH
1,0
0,5
0,0
Fig. 26. Physical parameters in the reactor: pH,date
DO and conductivity.
If the dissolved oxygen concentration was too
high, then, as a consequence, the pH tended to
decrease inevitably, due to an enhanced nitrification. During the 6th week of operation, for example, the pH dropped down to 6.1 due to a too
high aeration.
NH4-N in
N inorg out
The conductivity was used as a useful secondary
monitoring tool for the indication of the process
performance.
The temperature was slightly higher (about 2627°C) during the last two weeks of operation.
1
NH4-N out
NO2-N out
500
mg N l -1
400
300
200
100
0
Fig. 27. Results from the chemical analyses on inorganic nitrogen forms.
date
40
NO3-N out
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
N inorg loading rate
N inorg removal rate
1,0
0,9
0,8
g N m-2 d-1
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0,0
Fig. 28. Nitrogen loading and removal rates.
Date
Analyses of nitrogen compounds in the outflow and their
dependence on operational parameters
As discussed before, the results from the chemical analyses on the outflow where strongly related
to the conditions in the reactor, especially the
dissolved oxygen. The results are presented in
figure 27.
During the 2nd week (29th March - 4th April) the
ammonium nitrogen in the outflow was very low
(9.0 mg/l) as well as the alkalinity (1.26 mmol/l),
in contrast to nitrate nitrogen levels which were
high (50.7 mg/l). An alternation of periods of
consumption of ammonium and production of
nitrate was observed during the following weeks.
This was due to the sensitivity of the air supply
device and the strong dependence of the partial
nitritation/Anammox process on the dissolved
oxygen concentration in the reactor.
The chemical analyses were not performed on the
6th week (26th April - 2nd May) because conditions
N inorg removal eff.
NH4-N removal eff.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Date
Fig. 29. Removal efficiencies for inorganic nitrogen
and ammonia nitrogen.
41
Andrea Bertino
TRITA Degree Project Thesis
N inorg. removal rate [g N/m -2 d-1]
0,8
0,7
0,6
y = -0,2532x2 + 0,8272x
R² = 0,8113
0,5
0,4
0,3
0,2
0,1
0,0
0,0
0,5
1,0
1,5
2,0
2,5
3,0
DO [mg O2/l]
Fig. 30. Dissolved oxygen concentration influencing the nitrogen removal rate.
of the reactor were out of optimum range for
bacteria and low process efficiency was expected.
A too high aeration caused a pH drop down to
6.1 (due to acidification from nitrification process) and a very low alkalinity content of the
liquid in the reactor (0.52 mmol/l).
During 8th and 9th week (10th – 23rd May) low
dissolved
oxygen
concentrations
(about
0.7 mg O2/l) limited the nitritation and Anammox processes and ammonium was only partly
converted. In these two weeks, high pH (about
7.9), high conductivity (2.18 mS/cm) and high
alkalinity in the effluent (21.7 mmol/l) were
noticed.
A better view and analysis can be obtained from
the charts with the nitrogen load and nitrogen
removal rates (Fig. 28) and the chart with the
efficiencies of NH4+-N removal and inorganic
nitrogen removal (Fig. 29).
As the dissolved oxygen was the most important
parameter, an evaluation on its relations with
nitrogen removal efficiencies has been done
(Fig. 30).
The values of dissolved oxygen used are the
averages of available data from two or three days
before chemical analyses on the outflow were
done. A fairly good interpolation of the data was
found with parabolic equation with intercept set
equal to zero (which means that for values of
dissolved oxygen equal to zero, the nitrogen
removal is zero). From a first derivative calculation, the maximum of the parabolic fit was found
to be at 1.63 mg O2/l. Unfortunately no value
between 1.2 and 1.7 mg O2/l is available. Proba-
Table 23 – COD, Alkalinity and conductivity.
Parameter
Unit
Mean±S.D.
Samples
CODtot removed
mg/l
292.4 ± 76.4
5
CODtot removal
%
60.0 ± 5.7
5
COD soluble out
mg/l
167.1 ± 17.4
6
COD soluble removed
mg/l
132.8 ± 62.0
6
COD soluble removal
%
41.9 ± 13.1
6
CODtot removed / N inorg removed
-
0.80 ± 0.24
4
COD soluble removed / N inorg removed
-
0.34 ± 0.15
5
Alkalinity consumed
Alkalinity consumed / NH4+-N removed
Conductivity removed
mmol/l Ks 4.3
27.5 ± 5.1
g/l CaCO3
1.37 ± 0.25
5
mol Alk/mol N
1.07 ± 0.14
g CaCO3 / g NH4+-N
3.83 ± 0.49
5
mS/cm
1.85 ± 0.43
33
42
5
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
bly dissolved oxygen of about 1.5 mg O2/l could
have given slightly higher efficiencies. However
this was not proved because the laboratory reactor was stopped at the end of May and this relationship was studied later.
Calculations on COD removals, alkalinity consumptions and conductivity decrease are shown
in Table 23. The results showed in the table have
been obtained averaging the data from each
single week. The calculations include only the
first six weeks of operation, during which more
stable conditions were maintained.
The ratio COD removed/N inorg removed ranged between 0.54-1.17 and 0.15-0.59 considering the
COD unfiltered (CODtot) and filtered 0.45 μm
(CODsoluble) respectively.
Measurements of volatile suspended solids content in the
biofilm of Kaldnes carriers
In this study, measurements on the biomass were
carried out only on the biofilm of the Kaldnes
rings, in order to assess the growth on them. The
results (Fig. 31) show that no growth was observed in the first two months.
Unlike the pilot plant scale reactor, only one
analysis on the activated sludge and suspended
solids was carried out. The reason lay in the interest devoted to the biofilm, where Anammox
bacteria are supposed to be present and active,
and the activity of the Anammox bacteria during
the reactor operation. The result of the measurement, performed on the 21st May, gave the
following results: TSS = 905 mg/l and
VSS = 780 mg/l, which is a relatively high for a
MBBR. A reason may be a not very good mixing
from the two electric submersible aquarium water
pumps and thus a lower content of suspended
solids leaving the reactor through the overflow
system. Another cause could be the detachment
of biomass from the rings, as suggested from the
last measurement. However this hypothesis was
not verified by next measurements.
On the basis of the measurements of the
21st May, the total amount of suspended biomass
in the reactor has been compared with the biomass attached on the rings on the same day.
VSSbiofilm  10.85mg / ring  4173rings  45277.1mg
VSSact .sludge  780mg / l  7.69l  5998.2mg
where:
10.85 mg/ring = measurement of biomass on the
biocarriers (21st May);
4173 rings = estimated number of rings in the
reactor, on the basis that 107 biocarriers occupy
100 ml and the reactor was filled with 3.9 l of
rings.
Few days before the study on the reactor was
finished, the biomass in the activated sludge
accounted for the 11.07% of the total biomass
estimated in the reactor.
Results from Specific Anammox activity (SAA)
The Anammox bacteria activity was followed by
weekly measurements (SAA tests) in order to
assess whether there was an increase in AnamTSS
VSS
14
12
mg/ring
10
8
6
4
2
0
Fig. 31. No signs of biofilm growth.
date
43
Andrea Bertino
TRITA Degree Project Thesis
6
SAA [g N/m2/d]
5
4
3
2
1
0
25-Mar-10
04-Apr-10
14-Apr-10
24-Apr-10
04-May-10
14-May-10
24-May-10
Fig. 32. Activity of Anammox bacteria in the biofilmdate
(SAA test at 35°C)
mox bacteria activity during operation or not and
trying to quantify it. In total 10 series of SAA
analyses have been carried out. The tests were all
performed at 35°C and had a duration of about
120 minutes. The experimental data are included
in APPENDIX II. The results are summarized in
figure 32.
No particular increase of Anammox bacteria
activity was noticed during the two months of
reactor operation.
An average value of 4.3 g N m-2 d-1 can be assumed for the SAA tests carried out at 35°C.
4.1.4
Conclusions
Some conclusions can be drawn on the basis of
the obtained results on this laboratory scale
reactor. They are briefly summarized below:
 Dissolved oxygen is the key parameter for a
good efficiency and the overall stability of the
partial nitrification/Anammox process;
 An optimum DO concentration of 1.51.6 mg O2/l was probably the more appropriate for this reactor;
 A better system for DO control based on a
PID controller is strongly recommended in
order to avoid too high or too low aeration
periods and control the set point of dissolved
oxygen concentration in the reactor. An aeration system which bases the air supply on the
oxygen consumption could be more effective
than a system which supply a constant air
flow, as it was in this case;
 Conductivity could be an useful monitoring
tool for the indication of the process performance and the ammonia consumption between the inflow and the outflow;
 The low nitrite concentration in the reactor
suggests that nitrite was probably the limiting
factor for Anammox bacteria;
 The alkalinity/nitrogen in the inflow
(1.06 mol Alk/mol NH4+-N) was suitable to
stand the decrease in pH induced from nitrification during the reactor operation;
 The COD/NH4+-N in the influent was low
(about 0.79) and therefore suitable for the partial nitritation/Anammox process;
 A removal efficiency of about 80% of inorganic nitrogen has been achieved;
 SAA results did not show any particular evidence of increase/decrease in Anammox bacteria activity.
4.2 Laboratory-scale reactor treating
diluted reject water
The laboratory-scale reactor was started on
11th May in the chemical laboratory of the research facility Hammarby Sjöstadsverk and it was
run for two months until mid-July. This laboratory reactor was started in order to evaluate the
biological treatment of the effluent from the
treatment line 3 at Hammarby Sjöstadsverk research facility, through the deammonification
process (partial nitrification and Anammox in one
single reactor).
44
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
SAMPLING
POINT
GAS
GAS
DEGASSING
UASB 2 UNIT
PRESEDIMENTATION
SAND FILTER
REVERSE OSMOSIS
UASB 1
WATER
BACKWASH
EFFLUENT
MIXER
TANKS
CONCENTRATE
DIGESTER
GAS
FLUSH
WATER
DEWATERING
FILTRATE
TANK
SLUDGE
THICKENER
Fig. 33. Treatment Line 3 – Anaerobic treatment with UASB and sand filtration (modified from:
http://sjostad.ivl.se).
4.2.1
Treatment Line 3 - Anaerobic treatment
with UASB
The treatment line 3 at Hammarby Sjöstadsverk
is outlined in figure 33. The process line consists
of a pre-sedimentation step of the sewage water
which has already been preliminary treated by bar
screens and grit chamber.
The primary sedimentation is followed by an
anaerobic treatment with two UASB (Upflow
Anaerobic Sludge Blanket) reactors run in series
with granules and biogas production. The main
purpose is to reduce the COD content and produce a valuable energy product (biogas). The two
mixing chambers have the purpose to mix the
incoming wastewater with the recirculation from
the UASB reactors. The effluent from the reactors is sent to a degassing unit to separate the
residue gas and then to a slow sand filter for
solids and biomass separation. The filtrate water
undergoes a further polishing step for nutrients
removal consisting of reverse osmosis. However
in those months no reverse osmosis was carried
out and the effluent was discharged directly.
Nowadays reverse osmosis technology is still
expensive and this laboratory reactor was run
with the goal to make a preliminary assessment of
the possibility of using the deammonification
process as polishing step for nitrogen removal.
The influent wastewater to the laboratory-scale
reactor was taken downstream the sand filtration
as showed by the red circle. The filtered water is
used as backwash water for the regeneration of
the sand bed filter. The backwash effluent is then
sent back to the inlet of the treatment line. The
primary sludge from the pre-sedimentation
(mainly solid particles) is thickened, digested
anaerobically (for COD removal and biogas
production) and dewatered. The removed water
is then sent back to the precipitation and flocculation step.
4.2.2 Characterization of the effluent from sand
filter after anaerobic treatment with UASB
The influent to the laboratory scale reactor was
periodically taken from the tap of the treatment
line 3 located downstream the sand filtration and
stored in a tank of about 200 L. From this tank,
the wastewater was brought manually to the
adjacent chemical laboratory to refill the inflow
vessel with about 15-20 liters, two-three times per
week. Nitrate (NO3-) and nitrite (NO2-) were
Table 24 – Characterization of the influent diluted reject water 1:2.5.
Parameter
Unit
Mean±S.D.
Measurements
Ammonium NH4+
mg/l NH4+-N
43.7 ± 3.2
10
mmol/l Ks 4.3
5.68 ± 0.28
g/l CaCO3
0.284 ± 0.014
Alk/NH4+-N
mol Alk / mol N
1.80 ± 0.09
8
CODsoluble
mg O2/l
53.4 ± 2.9
7
CODtot
mg O2/l
90.1 ± 25.7
7
COD/ NH4+-N
-
1.22 ± 0.09
7
Alkalinity
8
Total Phosphorus (unfilt.)
mg/l
5.2 ± 0.8
8
Conductivity
mS/cm
0.772 ± 0.027
31
pH
-
7.83 ± 0.30
32
45
Andrea Bertino
measured once and the results were NO3--N =
0.176 mg/l and NO2--N < 0.2 mg/l, therefore
very low and negligible. The physical and chemical parameters of the influent to the reactor are
summarized in Table 24. Unlike the pilot plant
reactor described in chapter 5, the total nitrogen
has not been measured in this laboratory scale
study.
The only measurement of suspended solids was
performed with filters with a pore size of 1.6 μm
and the result was very low and less than 3 mg/l
for both total and volatile suspended solids.
4.2.3 Laboratory-scale reactor configuration
and experimental set-up
The laboratory-scale reactor was filled with approximately 40% of Kaldnes™ carriers. The
reactor (Fig. 34) was simply a plastic bucket open
at the top and slightly smaller but however similar
to the one described in paragraph 4.1. The reactor was filled with about 3.17 L of Kaldnes rings
(model K1) with a specific internal surface area of
500 m2/m3. The effective volume of liquid in the
reactor, measured with the biocarriers inside it,
was 6.74 L.
The temperature was kept at about 25°C by an
electric water heater thermostat. The stirring was
provided by two electric submersible aquarium
water pumps located at the basis of the reactor in
order to avoid sedimentation of Kaldnes rings
and provide a good mixing of the liquid inside
the reactor.
Oxygen was not supplied because the organic
matter and ammonium nitrogen of the incoming
wastewater was rather low and the monitored
dissolved oxygen concentration was around 1
mg/l and anyway it was never found to be less
than 0.35 mg/l. It is likely that part of the dissolved oxygen utilized by bacteria derived from
the action of refilling the inflow tank in the la-
TRITA Degree Project Thesis
boratory. The reactor was usually covered by
aluminum paper in order to avoid possible effect
of light and keep biocarriers in the dark and it
was also wrapped in insulating material to prevent
heat loss and reduce electricity demand for heating.
The hydraulic retention time (HRT) was chosen
to be kept at one day, with the purpose of increasing the load, because the ammonium nitrogen in the influent was lower (about only
44 mg/l) compared to the laboratory scale reactor
described in paragraph 4.1 (HRT = 2 days and
NH4-+N = 400 mg/l). As it will be stressed in the
discussion of the results, a shorter hydraulic
retention time would have been preferable. An
explanation for the choice of this hydraulic retention time and not a lower one was mainly due
to practical problems such as the small size of the
inflow tank in the chemical laboratory and the
unsuitable and too light inlet system.
The inflow rate was checked about two times per
week in order to make sure the inflow rate was
maintained constant. In the first six week of
operation the effluent from UASB digester and
sand filtration had a higher turbidity and higher
content of suspended solids. However, since the
25th June, the incoming wastewater prior to
treatment was clearer and with a lower turbidity.
Despite this, the flow was found to be slightly
higher or lower in some occasions, but however
this never happened the day before the chemical
analyses on the inflow and between the inflow
and outflow chemical analyses. For example, on
the 7th June, the inflow rate was decreased for
one day, on the 20th June no inflow to the reactor
was provided (probably since one or two days
before) and lastly the 3-4 days prior to the
13th July no inflow to the reactor was supplied
(owing to a my short return to Italy due to academic reasons).
Fig. 34. Laboratory scale reactor treating effluent supernatant from Line 3.
46
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
The reactor was run as Continuous Stirred-Tank
Reactor (CSTR) and no sludge recycling was
provided. The outflow consisted of an overflow
system. The operational parameters are summarized in Table 25.
The origin of the Kaldnes™ carriers used for the
reactor start-up is here below explained. The
biocarriers were the same as those ones used for
the laboratory scale reactor described in paragraph 4.1 and showed in figure 25. The main
difference is that during the period between the
23rd March and 7th May they had been used for a
trial study to assess the consequence of Anammox and partial nitritation process on raw sewage
water after sedimentation. Unfortunately that trial
study turned to be a process with characteristics
of heterotrophic denitrification and biofilm might
have undergone a slight change in composition or
activity. After that trial they have been stored for
four days in supernatant from dewatering of
anaerobic digester sludge, diluted with tap water,
before being used for the new laboratory scale
reactor described in this chapter.
4.2.4 Analytical measurements and sampling
procedures
The physical parameters (pH, T, DO, conductivity) in the reactor and the inflow rate were
measured manually three-four times per week
pH
DO
Table 25 – Operational parameters for the
laboratory-scale reactor.
Parameter
Unit
Value
day
1.00
Reactor Volume (liquid)
l
6.74
Flow rate
l/d
6.73
Hydraulic Retention Time (HRT)
Kaldnes carriers
l
3.17
Temperature
°C
26.77
when possible. The chemical analyses were usually performed once per week for both inflow and
outflow and within one day of each other. Between the inflow and outflow analyses the tank
containing the influent wastewater was not refilled in order to not change its composition
between the two measurements.
The main compounds and parameters monitored
were NH4+-N, NO2-N, NO3-N, COD (filtered
0.45μm and unfiltered) and alkalinity. The outflow samples were taken from a small outflow
container after about 20-30 minutes having
emptied it.
4.2.5
Results and discussion
Operational conditions in the reactor
The results from measurements of physical parameters in the reactor are shown in the chart in
figure 35.
conductivity IN
conductivity R
8,0
2,0
7,5
1,8
7,0
6,5
1,6
1,4
5,5
5,0
1,2
4,5
4,0
1,0
3,5
0,8
3,0
2,5
0,6
2,0
0,4
1,5
1,0
0,2
0,5
0,0
0,0
Fig. 35. Physical parameters in the reactor: pH,date
DO and conductivity.
47
conductivity [mS/cm]
pH; DO [mgO2/l]
6,0
Andrea Bertino
TRITA Degree Project Thesis
Table 26 – Physical parameters in the laboratory scale reactor.
Parameter
Unit
Mean±S.D.
Measurements
pH
-
7.24 ± 0.19
30
DO
mg O2/l
0.74 ± 0.23
28
T
°C
26.77 ± 1.67
28
Conductivity
mS/cm
0.57 ± 0.06
29
The average values of the parameters monitored
over the two months of operation are shown in
Table 26, whereas the raw table with all the physical parameters measured is included in the
APPENDIX III.
The pH and the dissolved oxygen (DO) were
easily kept stable during the whole operation. The
ratio alkalinity-ammonia nitrogen of the influent
to the reactor was sufficient to contrast pH drops
and acidification from the process. pH values
never dropped below 6.5.
The conductivity removal was fairly constant and
equal to 0.22 mS/cm. The average temperature
was slightly higher than the previous laboratory
reactor and it was around 26-27 °C, except the
period around the 7th week (20th June - 2nd July)
with a temperature of nearly 29°C. After those
days the heater was stopped because there was no
need of heating, due to warmer temperatures.
NH4-N in
N inorg out
Nitrogen removal performance and efficiency evaluation
The results from chemical analyses on the outflow are shown in figure 36.
After three weeks of operation the ammonia
nitrogen was almost completely depleted with
one day of retention time. An increase in nitrate
nitrogen in the outflow was noticed. No explanations has been found for the high value of nitrate
in the outflow measured on the 4th June, as the
pH was 7.11 and not particularly low, the dissolved oxygen concentration was just slightly
higher than usual (i.e. 1.06 mg O2/l) as well as the
alkalinity (1.46 mmol/l) in the reactor which was
not particularly low that day if compared to the
other weeks.
The nitrite NO2 was almost certainly the limiting
substrate for Anammox bacteria and the hydraulic retention time seemed to be too high for this
reactor operation, which resulted in a full depletion of nitrite in the reactor and a full conversion
of ammonium and nitrite to nitrate.
NH4-N out
NO2-N out
80
mg N l -1
60
40
20
0
Fig. 36. Chemical analyses results on the inorganic nitrogen forms.
date
48
NO3-N out
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
N inorg loading rate
N inorg removal rate
g N m-2 d-1
0,3
0,2
0,1
0,0
Fig. 37. Nitrogen loading and removal rates.
Date
Unfortunately, unlike the pilot plant reactor
operation, no measurements of redox potential
were done for a better understanding of the
oxidizing conditions inside the reactor.
Nitrogen load and nitrogen removal rates are
shown in figure 37, whereas the efficiencies of
NH4+-N removal and inorganic nitrogen removal
are summarized in figure 38. The nitrogen load-
ing and removal rates have been calculated according to APPENDIX I.
Considering the period 25th May – 16th July and
excluding the results from the chemical analyses
performed on the 4th June, the ratio between the
nitrogen loading rate and removal rate was
80.6 %.
N inorg removal eff.
NH4-N removal eff.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Fig. 38. Removal efficiencies for inorganic nitrogen
and ammonia nitrogen.
Date
49
Andrea Bertino
TRITA Degree Project Thesis
Table 27 – COD, Alkalinity and conductivity (data from 20th May).
Parameter
Unit
CODtot removed
CODtot removal
Mean±S.D.
Samples
mg/l
7.0 ± 20.1
5
%
11.9 ± 27.0
5
COD soluble out
mg/l
47.7 ± 4.0
6
COD soluble removed
mg/l
5.9 ± 5.7
6
COD soluble removal
%
10.7 ± 9.9
6
CODtot removed / N inorg removed
-
0.23 ± 0.60
5
COD soluble removed / N inorg removed
-
0.17 ± 0.21
6
mmol/l Ks 4.3
3.81 ± 1.12
g/l CaCO3
0.19 ± 0.06
Alkalinity consumed / NH4+-N removed
g CaCO3 / g NH4+-N
4.59 ± 0.77
7
Conductivity removed (1)
mS/cm
0.17 ± 0.15
33
Alkalinity consumed
Calculations on COD removed, alkalinity consumptions and conductivity decrease are shown
in Table 27.
The results have been obtained averaging the data
from each single week.
The ratio COD removed/N inorg removed was about
0.2. The COD consumption was very low for
COD measured both on samples unfiltered
(CODtot) and filtered 0.45μm (CODsoluble). The
low consumption of COD might have been due
to a low content of biodegradable organic substance. However the total influent COD was
already low and less than 100 mg O2/l. The low
COD concentration might have been a limiting
factor for heterotrophic denitrifying bacteria
activity. On one occasion (25th June) an increase
of unfiltered COD between outflow and inflow
was measured. A reason could be found in the
conductivity IN
7
sampling procedure or perhaps to a not perfectly
homogeneous conditions in the reactor. The ratio
alkalinity consumed and NH4+-N removed was
about 4.6 g CaCO3/g NH4+-N and perhaps
slightly high for the one-stage deammonification
process, but however, no pH drop below 6.6
were observed.
From the chart of conductivities in figure 39, it is
possible to have a confirmation of the results
obtained from the chemical analysis on the outflow. The start-up period for this reactor, before
achieving a stable nitrogen removal was about
two weeks (11th May – 26th May)
conductivity R
conductivity removed
0,9
0,8
0,7
mS/cm
0,6
0,5
0,4
0,3
0,2
0,1
0,0
12-May-10 19-May-10 26-May-10 2-Jun-10
9-Jun-10
Fig. 39. Conductivity decrement in the reactor.
16-Jun-10 23-Jun-10 30-Jun-10
Date
50
7-Jul-10
14-Jul-10
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
TSS
VSS
12
mg/ring
10
8
6
4
2
0
Fig. 40. Suspended solids as biofilm. No particular sign
date of growth or decay.
Measurements of volatile suspended solids content of the
biofilm and as activated sludge
In this study, measurements on the biomass were
carried out on the biofilm of the Kaldnes rings, in
order to assess the volatile solids in the biofilm,
and since the 1st June, also on the volatile suspended solids in the reactor as an estimate of the
biomass concentration in the activated sludge.
The results from the measurements on the biocarriers (Fig. 40) did not show any particular
trend of growth or decrease of the biomass
content.
Only four measurements on the suspended solids
were done (Fig. 42). Apart from the measurement
on the 1st June, the following three measurements gave similar results between 103 and
112 mg VSS/l.
On the basis of the measurements of the 1st and
25th June, 2nd and 16th July, the total amount of
suspended biomass in the reactor has been compared with the biomass attached on the rings on
the same days. The results are summarized in
Table 28.
TSS
VSS
175
150
125
[mg/l]
100
75
50
25
0
Fig. 42. Total and volatile suspended solids in the reactor
date
51
Andrea Bertino
TRITA Degree Project Thesis
Table 28 – Comparison between biomass attached on the carriers and as activated sludge.
Parameter
Unit
Result
Period
VSS biofilm (1)
mg VSS
28152.8
1st June
VSS act. sludge (2)
mg VSS
244.3
1st June
% VSS act. sludge
%
0.86 %
1st June
VSS biofilm (1)
mg VSS
31177.2
25 June – 16th July
VSS act. sludge (2)
mg VSS
734.7
25th June – 16th July
% VSS act. sludge
%
2.35 %
25th June – 16th July
th
(1) and (2), calculated according to APPENDIX I.
Results from Specific Anammox activity (SAA)
The Anammox bacteria activity was followed by
weekly measurements (SAA tests) in order to
evaluate the Anammox bacteria activity during
this operation at lower nitrogen load and check
whether there was a decrease or not. In total 6
series of SAA analyses have been carried out. The
tests were all performed at 35°C and had a duration of 70-80 minutes. The experimental data are
included in APPENDIX III. The results are
summarized in figure 43. The chart shows a
gradual reduction of Anammox bacteria activity.
A plausible reason of this decrement may be the
load that was too low and not suitable for
Anammox bacteria growth over time. The average SAA from the last five analyses is 3.8 g N m2 d-1.
4.2.6 Possibility to treat supernatant from
UASB with deammonification process
The main challenge for the partial nitritation/Anammox process run in reactors with a
low concentration of nitrogen in the influent is
related to the long-term stability of the process.
High ammonium removal efficiency can be easily
achieved as showed from the graphs, but a higher
load is strongly recommended for a good and
stable operation. Unfortunately, due to practical
reasons, this was not possible in this study. The
main problem lies in the fact that Anammox
bacteria have a low maximum specific growth
rate (about 0.065 d-1) and, as consequence, a too
low ammonia nitrogen load can limit the growth
of Anammox bacteria and their decay rate might
exceed their growth rate. Unfortunately this
reactor was not run for a long term, but only for
two months and the results from suspended
solids on the biocarriers did not show any clear
trend. The results from SAA analyses seem to
show a decrease in activity of Anammox biomass
attached on the rings.
However, if a short hydraulic retention time was
provided, and therefore a higher inflow load to
the reactor (>0.7-0.8 g N m-2 d-1), this technology
might represent an effective treatment of the
effluent from UASB reactor over time. A possibility to overcome this issue for the partial nitrification/Anammox step could be to treat a stream
which has been previously concentrated by technology such as ion exchange or reverse osmosis
(downstream degradation of organic matter and
particles removal) but, nevertheless, these tech-
6
SAA [g N/m2/d]
5
4
3
2
1
0
25-Mar-10
04-Apr-10
14-Apr-10
24-Apr-10
04-May-10
Fig. 43. Activity of Anammox bacteria in the biofilmdate
(SAA test at 35°C)
52
14-May-10
24-May-10
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
nologies might increase costs for the treatment
and frequent regenerations might be required if a
large volume is treated and the economic and
operational convenience of these alternative
solutions is questionable. More studies are therefore needed to achieve an effective partial nitritation/Anammox process which can fully replace
nitrification and denitrification or can be implemented in the main treatment line of a municipal
WWTP.
Another problem that should not be overlooked
is that the lower temperature of the process
(< 25°C used for this experimentation) compared
to the temperature of the reject water from the
sludge treatment line can significantly reduce
nitrogen removal efficiencies.
5 S INGLE P ARTIAL
N ITRITATION /A NAMMOX
P ILOT P LANT R EA CTOR
5.1 Pilot plant reactor operation
The most interesting and useful results in these
studies were obtained for the pilot plant reactor.
The technical scale pilot plant reactor was started
on the 27th May with the intention to study the
performance of the partial nitritation and Anammox process in one single reactor over a rather
long period of time under stable conditions. It
was installed at Hammarby Sjöstadsverk research
station in Stockholm. This master thesis evaluates
the performance of the pilot reactor over the first
four months (27th May – 28th September) at a
temperature of 25°C and a load of about
3.4 g N/m2/d.
5.1.1
Pilot plant reactor design
The technical-scale pilot plant reactor (Fig. 44)
was designed as a continuous stirred and aerated
Moving Bed Biofilm Reactor (MBBR) with Kaldnes™ carriers (model K1). The biocarriers used
in this study were brought from Himmerfjärden
Wastewater Treatment Plant (SYVAB Company)
where deammonification process was carried out
using biocarriers with a biofilm composed by
Anammox and Nitrosomonas bacteria.
There was no need for any long start-up period
because growth of biomass on the media was
already adequate as shown on Fig. 45.
The reactor was continuously fed with supernatant from sludge dewatering after anaerobic
digestion. It is assumed that it was operating as a
CSTR. The reject water used in the operation
came from Bromma Wastewater Treatment Plant
which serves the north-western parts of Stock-
Fig. 44. The one-stage pilot plant scale
reactor for partial Nitritation/Anammox.
holm area. The reactor was run without any
sludge recirculation.
5.1.2
Reject water characterization
The reject water had a high content of ammonium of about 1000 mg/l, high alkalinity (about
3700 mg/l CaCO3) and low content of biodegradable organic matter. Nitrate and nitrite concentrations were almost zero.
Fig. 45. Biocarriers used for pilot reactor
start-up.
53
Andrea Bertino
TRITA Degree Project Thesis
Table 29 – Characterization of the reject water from sludge dewatering after anaerobic
digestion at Bromma WWTP.
Parameter
Unit
Mean±S.D.
Measurements
Ammonium NH4+
mg/l NH4+-N
963.3 ± 75.9
21
< 0.1
5
2.0 ± 0.3
5
Nitrite
NO2-
mg/l
Nitrate NO3-
mg/l NO2--N
Alkalinity
mmol/l Ks 4.3
74.2 ± 6.3
g/l CaCO3
3.71 ± 0.31
18
Alk/NH4+-N
mol Alk / mol N
1.08 ± 0.09
18
Total Nitrogen (soluble)
mg/l
987.7 ± 89.8
12
Total Nitrogen (unfilt.)
mg/l
1142.7 ± 107.0
3
CODsoluble
mg O2/l
611 ± 115
17
CODtot
mg O2/l
1137 ± 179
15
-
0.63 ± 0.10
17
mg/l
1.63
1
COD/
NH4+-N
Total Phosphorus (soluble)
(1)
(2)
NO3--N
Total Phosphorus (unfilt.)
mg/l
9.31 ± 1.64
3
Conductivity
mS/cm
9.31 ± 0.69 (1)
online
pH
-
8.43 ± 0.05
13
ORP
mV
-469.6 ± 88.0 (1)
online
Total Suspended Solids (TSS)
mg/l
335.5 ± 51.6 (2)
11
Volatile Suspended Solids (VSS)
mg/l
272.1 ± 62.4 (2)
11
The mean value has been calculated from daily averages of the online measurements.
Determined by filtration 1.6 μm.
The main characteristics of the reject water from
Bromma WWTP are shown in Table 29. The
high alkalinity makes this stream suitable for the
deammonification process. The carbon to nitrogen ratio (expressed as the soluble ratio
COD/NH4+-N) is about 0.63 and low enough
for a potential good performance of the whole
process.
The reject water was delivered periodically, according to the required use by the pilot reactor
Online measurement and data storage
ORP,
conductivity
DO, pH, ORP, T
conductivity.
influent
pump
air
Storage tank 26 m3
Storage tank 1,3 m3
Pilot reactor 200L
Fig. 46. Simplified scheme of the pilot scale reactor.
54
Outflow tank
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
and other parallel installations, and stored in a big
tank of 26 m3 which was not stirred.
From this tank the reject water was regularly
pumped to a smaller tank of 1.3 m3 which was
not stirred either and pumped continuously to
the reactor by means of a volumetric pump, for
the treatment of the supernatant (Fig. 46).
5.1.3
Operational strategy
The reactor had a working volume of 200 l which
was filled with 80 l (about 40%) of Kaldnes rings
with a specific internal surface area of 500
m2/m3. The effective volume of liquid in the
reactor was about 166 l and it was measured at
the beginning of the operation, after biocarriers
introduction. The hydraulic retention time was
measured using 166 l as volume divided by the
V
166l
inflow rate: HRT  
[day].
Q l / day
The volume in the reactor was kept constant
during the whole study. An appropriate mixing
was provided by stirring and air supply. The
aeration was located at the bottom of the reactor
and the two-bladed stirrers were located, respectively, at about one-third and two-third of the
working height of the reactor.
In the first two months the operational strategy
was based on the flow rate, which was checked
on a regular basis. The flow was kept at around
144 l/d, regardless of the concentration of ammonia in the inflow, with the exception of the
first 18 days during which the flow was lower
(about 101 l/d).
In the last two months the reactor operation was
based on the operational strategy of maintain a
constant ammonium surface load (ASL) of slightly more than 3.4 mg N m-2 day-1 and the pump
rate was periodically set depending on the ammonia nitrogen concentration in the influent. The
reason of this choice was to minimize changes in
substrate (ammonium) loading rate. This resulted
in an average flow rate of 135.8 l/d, but the
ammonium in the reject water in this period was
slightly higher. The hydraulic retention time at
the higher load was kept constant at about 1.20
day (28.4 hours). In a couple of occasions the
flow had been noticeably different from the
Table 30 – Operational parameters for the
laboratory-scale reactor.
Parameter
Unit
Value
Reactor Total volume
l
approx 200
Reactor Volume (liquid)
l
166
Kaldnes carriers
l
80
average value and this was due to no inflow at the
inlet (13th July between 8.30 and 17.30; 8th August
the whole day), non-delivery of the reject water
(23rd the whole day until the 24th 10 a.m.) and
halving of the inflow rate to keep enough reject
water in the tank (between 17th afternoon and
21th September morning). In these occasions the
dissolved oxygen set point was decreased.
Except this the reactor was run in a stable way
and without any kind of particular problem.
During the whole study the reactor was heated up
and the temperature was maintained at an average
value of 25°C, varying between 24.4°C and
25.5°C. This range is below the optimum temperature of ANAMMOX bacteria and the operational temperature of the SHARON process,
therefore a reduction of the efficiency can be
expected. However running the process at a
temperature of 25°C has the clear advantage of
saving electricity needed for the heating, with the
possibility to exploit the heat content in the
supernatant from anaerobic digestion.
The DO concentration in the reactor was the
main operational parameter that was varied in
order to provide the suitable conditions for the
process and bacteria activity. The dissolved oxygen in the reactor was automatically maintained
constant at the value set in the control panel
through air insufflations by means of a stainless
steel sparger tube with minute perforations and
located at the bottom of the reactor. The inflow
rate was the parameter that was changed in order
to maintain a constant load of ammonia nitrogen
to the reactor. No pH adjustments and needs of
chemicals have ever been required, and this is a
good and promising sign for a long-term stability
of the one-stage process.
5.1.4
Measurements and experimental
procedure
Physical parameters in the reactor such as pH, T,
ORP, DO, conductivity were measured automatically every 10 seconds. These values have been
corrected according to a calibration based on
about twenty data because it was found that
during the data logging the values of the parameters were slightly lowered compared to the
ones showed in control panel in front of the
reactor. The correctness of this calibration had
been later verified.
The hydraulic retention time was measured manually as well as the pH of the reject water in
inflow.
The chemical analyses on the main compounds
of interest were usually carried out once per week
55
Andrea Bertino
for the inflow and twice per week for the outflow, if possible. It was assumed that the decrease
of ammonia nitrogen in the reject water over one
week was negligible. Its average decrease was
about 2.3% per week. The outflow samples were
taken from the outflow settling tank after about
20 minutes having emptied it.
5.2 Results and discussion
5.2.1
Physical parameters
Most of the pH variations were a direct consequence of voluntary changes in DO set point
with the aim to try to increase the efficiency of
the process (i.e. in case of a higher nitrates concentration in the outflow, the dissolved oxygen
concentration was decreased). The involuntary
pH fluctuations were mostly the consequence of
short anoxic periods (due to problems with DOmeter in few occasions) or momentary stopping
of the inflow. However these incidents were quite
rare. Temporary anoxic conditions resulted in an
increase of the pH, whereas stopping of inflow
(without change of dissolved oxygen concentration in the reactor) caused a decrease of pH.
TRITA Degree Project Thesis
The average values are shown in Table 31 and the
variations over time are shown in figure 47.
A detailed table of the physical parameters is
included in APPENDIX IV.
Some days the data logger was not recording and
those data are missing, but however the process
was monitored by reading the value from the
control panel during working hours.
Several periods can be observed from the chart.
The first period (27th May-12th June) was characterized by a lower inflow rate (100.8 l/d) in order
to avoid a too high load for the biomass and
perform a softer start-up. The DO was adjusted
manually until the 6th June by turning the DO
valve and the dissolved oxygen concentration was
read on the control panel. The second period
(13th June-22nd July) was the more unstable; the
redox potential showed high values with great
variations and pH varied between 6.5 and 7.4.
However the chemical analyses in this period did
not give any noticeable decrease in process efficiency. The flow rate was about 144-152.6 l/d,
except a problem with the pump on the 13th July.
In the third period (23rd July-22nd August) the pH
9,0
240
8,5
8,0
200
7,5
7,0
6,5
pH; DO (mgO2/l)
6,0
5,5
120
5,0
pH
redox
4,5
4,0
DO
flow rate
80
3,5
3,0
40
2,5
2,0
1,5
0
1,0
0,5
0,0
-40
Fig. 47. Daily averages of the main physical anddate
chemical parameters.
56
flow rate (l/d); ORP (mV)
160
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
value was maintained between 7.3 and 7.8 and the
dissolved oxygen at 2.5 mg/l. The reactor worked
under stable conditions. The sharp increase of
pH in between period 2 and 3 may have been due
to a too high inflow rate. The fourth period
(24th August-28th September) was also stable
(with the exception of a necessary reduction in
the inflow rate for some days due to external
causes), but the pH was slightly lower (7.4 and
7.5) as well as the DO (2.3 mg O2/l).
FISH method is applied to detect selectively
specific groups of microorganisms in a mixture
with others (e.g. the biofilm) and their spatial
distribution, by using their specific 16S rRNA
sequence. This technique exploits differences
between the ribosomal gene sequences of different bacteria. By using specific rRNA-targeted
oligonucleotide probes is possible to visualize
single species, whole genera of bacteria or even
phyla and domains (Amann et al, 1995 cited in
Arshad, 2008, p.31).
Total and Volatile Suspended solids in the influent and
activated sludge
The measurements were carried out with 1.6 μm
filters glass fiber filters. Unfortunately it was not
possible to measure the volatile suspended solids
content on not-cellulose 0.45 μm filters because
of delay with the purchase.
The suspended solids (volatile and not) in the
influent reject water showed wide variations mainly
depending on the time passed since the delivery
of the new reject water from Bromma WWTP,
because of the progressive sedimentation in the
tanks the following day after the delivery. A likely
average estimate of total suspended solids in the
influent can be 461.1 ± 565.5 mg/l, with 84.6%
of volatile solids content (389.9 ± 393.2 mg/l).
The activated sludge concentration inside the reactor was estimated by the measurement of the
volatile suspended solids concentration from a
mixed sample taken from the reactor (MLVSS
Mixed Liquor Volatile Suspended Solids, or
simply VSS). As suggested by many authors the
use of VSS measurement as a measure of biomass
5.2.2 Biomass analyses. Total and volatile
suspended solids and biofilm growth
Measures of total and volatile suspended solids
were carried out on the activated sludge and on
the biofilm, to assess the presence of any growth
of the biofilm. No quantitative evaluation of
biofilm thickness was carried out because of the
sometimes strong difference between biofilm on
the carriers and irregularity of the growth. FISH
method was performed by my colleague and PhD
student Jingjing Yang at Delft University of
Technology.
FISH (Fluorescence In Situ Hybridization) analysis
FISH analyses done by J. Yang and M.K. Winkler
(2010) at Delft University of Technology (The
Netherland) on some sample carriers taken from
the pilot plant reactor in July showed the coexistence of Nitrosomonas and ANAMMOX bacteria in the biofilm with only a small amount of
Nitrobacter. The ANAMMOX bacteria are mostly belonging to the species “Candidatus Brocadia
fulgida”. No quantitative information about the
different bacteria populations were communicated.
TSS
VSS
500
450
400
[mg/l]
350
300
250
200
150
100
50
0
27-May-10
10-Jun-10
24-Jun-10
8-Jul-10
22-Jul-10
5-Aug-10
Fig. 48. Activated sludge in the reactor (filtered 1.6 μm).
date
57
19-Aug-10
2-Sep-10
16-Sep-10
Andrea Bertino
TRITA Degree Project Thesis
is convenient but includes both endogenous and
inert volatile solids in the activated sludge. New
molecular techniques such as fluorescent in situ
hybridization (FISH), RNA analysis, DAPI staining, and ATP analysis make possible to measure
directly and quantify the metabolically active
fraction of the activated sludge mixed liquor.
A likely average estimate of total suspended
solids can be 334.3 ± 49.4 mg/l, with an 82% of
volatile solids content (273.5 ± 59.6 mg/l). A
chart is shown in figure 48.
No explanation has been found for the increment
measured on the 16th July except that a higher
inflow rate or a wrong measurement, whereas the
mea-surement on the 28th August was close to
the 23rd August, when the supernatant fed to the
reactor was denser and containing a higher load
of suspended solids as it was at the bottom of the
tank. Detailed tables of the suspended solids
measurements
are
included
in
the
APPENDIX IV.
Measurements on total suspended solids were
carried out also with filters with pores size of
0.45 μm and the resulting concentrations are
slightly higher. The average on total suspended
solids measurements is 347.5 ± 71.0 mg/l (based
on a total of 8 measurements during the four
months).
Bacteria growth as biofilm
Measurements of the volatile suspended solids on
the carriers were carried out in order to assess
whether there was any biofilm growth or not.
The results are shown in figure 49.
The measurements (expressed in mg/ring) show
an increase in the volatile solids content on the
carriers, especially from the end of July. The
lower result from the measurement on the 20th
August could be related to the random sampling
of the four carriers taken from reactor and used
to obtain an estimate of the volatile solids content on a single ring.
The reason of the decrease from the high percentage of volatile solids measured on the 5th day
of operation (99.3%) to the lower average percentage measured during next months of reactor
operation (85.3 ± 2.2 mg/l) was not found except
as a direct consequence of two different types of
reject water with which biocarriers were fed prior
to reactor start up and during pilot reactor operation.
Surprisingly, the growth observed on the biocarriers (+38.6% and about 4.8 mg/ring between the
22nd July and 10th September) resulted only in a
slight increase of process efficiency (+5.2%
calculated as inorganic nitrogen removed in g
N/m2 /d as comparison between the periods 18th
June-20th July and 23rd July-26th September). This
could be due to an increased diffusion resistance
for substrates (NO2- and NH4+) through the
thicker biofilm, or to an overestimation of the
metabolically active biomass by VSS measurements. Unfortunately no results from microbiology analyses on the grown biofilm are available in order to monitor and to assess quantitatively the composition of the new biofilm. The
increase of biomass attached on the carriers was
observed together with a decrease in the biomass
TSS
VSS
25
[mg/ring]
20
15
10
5
0
27-May-10 10-Jun-10 24-Jun-10
8-Jul-10
22-Jul-10
5-Aug-10
19-Aug-10
Fig. 49. Biomass attached on the Kaldnes carriersdays
(filtered 1.6 μm).
58
2-Sep-10
16-Sep-10
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Fig. 50. Comparison of
the biocarriers before
starting the pilot reactor
(left) and after 106 days
of operation (right).
concentration in the activated sludge. During that
period the mixer was working at about 27 rpm.
Probably this rotational speed was suitable for
bacteria growth and did not show effect of detachment of the biomass from the carriers. At the
beginning of September (around the 3rd September) the mixing was increased to 50 rpm.
According to results of the 10 measurements
carried out on the biomass attached on the rings
and the corresponding suspended biomass in the
reactor carried out on the same days, the activated sludge accounted for the 2.9% ± 0.8% of
the biomass attached on the rings (both expressed as mg VSS).
This apparently small amount of bacteria may
actually “cooperate” with Anammox biofilm on
Kaldnes rings, by removing dissolved oxygen
from the liquid and partly convert ammonium to
nitrite needed by Anammox bacteria, as stated by
Cema et al (2007b).
A visual comparison of the biofilm developed on
the Kaldnes carriers is shown below in figure 50.
The photos were taken on the start-up day
(27th May) and on the 10th September. As it can
be seen the growth of the biofilm was quite
irregular among the Kaldnes media and a lower
thickness of the biofilm on some rings might
have been a direct consequence of detachment
phenomena due to the mechanical stirring or
aeration on those carriers supporting a high
quantity of biomass.
5.2.3 Reactor performance evaluation and
chemical analyses results
The raw results from chemical analyses on the
inflow and outflow concentrations of the onestage pilot plant reactor for partial nitritation and
Anammox process are shown in figure 51. Detailed tables with all the chemical analyses results
for both inflow and outflow are included in the
APPENDIX IV.
The reactor performance during the four months
was satisfying. High nitrogen removal was
achieved and ammonium was greatly reduced as
well as total nitrogen concentration, with a hydraulic retention time of only about 1.16 ±
0.15 days (i.e. 27.9 hours), calculated from the
end of the first period with a lower inflow rate.
Two main phases can be identified from the
chemical analyses results. The first one that goes
until the 23rd July, during which the nitrate concentrations in the outflow were slightly higher
and with a mean value of 117.7 ± 23.8 mg/l. This
was probably due to a dissolved oxygen concentration in the bulk liquid slightly higher than
necessary and thus part of the produced nitrite
was oxidized to nitrate by Nitrobacters.
During the last two months with a constant load
of 3.4 g N m-2 d-1 the average nitrate nitrogen
concentration in the outflow was 82.9 ±
13.6 mg/l but an opposite slight increase of
ammonium nitrogen in the outflow was noticed.
This was equal to 76.0 ± 17.1 mg NH4+-N/l
instead of 62.3 ± 13.9 mg NH4+-N/l of the
previous period.
Perhaps a possible explanation of the reduced
production of nitrate in the second period might
be a lesser activity for Nitrobacter at pH=7.6-7.7
compared to pH=7, even though the average DO
concentrations during this period were slightly
higher than the previous period and ranging
between 2.3 and 2.5 mg/l.
The nitrite concentration in the reactor were
rather low and maintained constant at a mean
value of NO2--N = 7.3 ± 1.8 mg/l. It is likely that
nitrite nitrogen was the limiting factor for
Anammox bacteria.
The nitrate in the outflow was not so high if
compared with the global reaction for the deammonification process with a stoichiometric coefficient of 0.13, as showed on the next page.
59
Andrea Bertino
TRITA Degree Project Thesis
1 NH4+ + 0.85 O2 → 0.13 NO3- + 0.435 N2 +
1.4 H+ + 1.43 H2O.
The calculation can be performed on the last two
months of operation. Considering the average
inflow concentration of NH4+-N = 975.5 mg/l,
which corresponds to NH4+ = 1254.2 mg/l and
69.92 mmol NH4+/l, about 69.92·0.13 =
9.06 mmol NO3-/l should be expected in the
outflow. In the last two months of operation the
nitrate nitrogen in outflow was NO3-N =
89.2 mg/l which corresponds to NO3- =
395.0 mg/l and 6.37 mmol NO3-/l, that is less
than expected, but must be kept into account the
untreated ammonium (NH4+-N = 76.0 mg/l =
N inorg in
N inorg out
5.43 mmol NH4+/l) and the nitrite in outflow
(NO2--N = 7.9 mg/l = 0.56 mmol NO2--N /l).
Looking at the Fig. 52, removal efficiencies of
95%, 85% and 83% for NH4+-N, inorganic nitrogen, and Total Nitrogen (TN) respectively, have
been achieved by partial nitritation/ANAMMOX
process in one single reactor.
The ammonia nitrogen removal efficiency has
been found to be higher when the hydraulic
retention time and/or the dissolved oxygen
concentration were higher than predefined reactor conditions for those specific days.
NH4-N out
NO2-N out
NO3-N out
1100
1000
900
800
mg N l -1
700
600
500
400
300
200
100
0
Fig. 51. Inorganic forms of nitrogen in the inflow and
dateoutflow during the four months of evaluation of the process in the pilot plant reactor.
60
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
N inorg removal eff.
NH4-N removal eff.
TN removal eff.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Date
Fig. 52. Removal efficiencies for inorganic nitrogen
(sum of NH4+-N, NO3--N and NO2--N),
+
ammonia nitrogen (NH4 -N) and total nitrogen (TN, sum of inorganic and organic nitrogen).
Efficiencies have been calculated according to
APPENDIX I.
During the last days of study on pilot reactor
performance, the three removal efficiencies ana-
lyzed reached their highest values throughout all
the experimental period, if we exclude the first
days of reactor operation at a lower ammonium
load. The general trend was slight positive and
N inorg loading rate
N inorg removal rate
4,5
4,0
3,5
g N m-2 d-1
3,0
2,5
2,0
1,5
1,0
0,5
0,0
Dateremoval rate during the four months of pilot
Fig. 53. Nitrogen loading rate (ASL) and nitrogen
reactor operation.
61
Andrea Bertino
TRITA Degree Project Thesis
Table 32 – ASL, inorganic nitrogen loading and removal rates.
Parameter
Unit
Loading rate (ASL)
g N m-2 d-1
2.62 ± 0.07
27th May-12th June
Loading rate
mg N l-1 d-1
Mean±S.D
631.6 ± 16.0
27th May-12th June
-2
-1
2.25 ± 0.29
27th May-12th June
-1
-1
mg N l d
542.6 ± 26.8
27th May-12th June
%
86.0
27th May-12th June
-2
-1
gNm d
Removal rate
Ratio (loading rate)/(removal rate)
Period
Loading rate (ASL)
gNm d
3.44 ± 0.13
13th June-28th Sept.
Loading rate
mg N l-1 d-1
819.1 ± 95.3
13th June-28th Sept.
gNm d
2.78 ± 0.16
13th June-28th Sept.
mg N l-1 d-1
667.2 ± 76.8
13th June-28th Sept.
Ratio (loading rate)/(removal rate)
%
80.1
13th June-28th Sept.
Loading rate (ASL)
g N m-2 d-1
-2
Removal rate
Loading rate
-1
3.45 ± 0.14
21st July-28th Sept.
-1
-1
839.5 ± 60.2
21st July-28th Sept.
-2
-1
gNm d
2.85 ± 0.16
21st July-28th Sept.
mg N l-1 d-1
692.8 ± 58.9
21st July-28th Sept.
%
82.7
21st July-28th Sept.
mg N l d
Removal rate
Ratio (loading rate)/(removal rate)
efficiencies might have been even higher if the
reactor performance had been analyzed for a
couple of weeks more.
Considering the last two months the average
efficiencies were: 92%, 82.5% and 80% for
NH4+-N, inorganic nitrogen and TN respectively.
Decreases in efficiencies due to the flow rate
increase and thus ammonium loading rate rise
from 2.6 g N m-2 d-1 to about 3.4 g N m-2 d-1 were
noticed. The load was changed on the 13th June.
Comparing the first two weeks of operation
(influent load of 2.62 g N m-2 d-1) and the last two
weeks of June (3.44 g N m-2 d-1), efficiencies
decreased by -2.37% and -7.19% for inorganic
nitrogen and NH4+-N respectively (Fig. 52). After
a couple of weeks bacteria adaptation to the new
load was observed and probably in the last month
bacteria could have been ready to treat a higher
load, but this was not studied in this thesis.
A better evaluation of the process can be conducted by analyzing the nitrogen loading rate and
the nitrogen removal rate (Fig. 53).
The loading and removal rates have been calculated according to APPENDIX I. The loading
4.5
Ninorg removal rate [g N m-2 d-1]
4.0
y = 0.8127x
R² = 0.8497
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Ninorg loading rate [g N m-2 d-1]
Fig. 54. Rough estimate of nitrogen removal rate at higher ASL
62
3.5
4.0
4.5
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 33 – COD, Alkalinity and conductivity.
Parameter
Unit
Mean±S.D.
Samples
CODtot removed
mg/l
462.7 ± 182.7
11
CODtot removed
%
41.1 ± 12.0
11
CODsoluble out
mg/l
350.6 ± 42.6
13
CODsoluble removed
mg/l
246.1 ± 106.7
11
CODsoluble removed
%
39.9 ± 12.0
11
CODtot removed / N inorg removed
-
0.61 ± 0.26
11
COD soluble removed / N inorg removed
-
0.32 ± 0.14
11
mmol/l Ks 4.3
67.6 ± 7.6
g/l CaCO3
3.38 ± 0.38
Alkalinity consumed / NH4+-N removed
g CaCO3 / g NH4+-N
3.88 ± 0.34
13
Conductivity removed
mS/cm
7.32 ± 0.67
online
Alkalinity consumed
rate (g N m-2 d-1) is sometimes called ASL (ammonium surface load). A summary table on
loading rate and nitrogen removal rate for three
different period is shown in Table 32.
The first period (27th May-11th June) includes the
first two weeks at lower loading rate, the second
one is the whole period at higher load (13th June 28th September) and the third one is the period
(21th July - 28th September) where a more stable
operation and higher efficiencies were obtained.
As expected, the removal rate efficiency at the
loading rate of 3.4 g N m-2 d-1 was lower compared to the previous one at the loading rate of
2.6 g N m-2 d-1, but it was anyway above 80%.
A simplistic modeling approach (Fig. 54) tries to
predict the possible nitrogen removal rates at
higher ammonium loading rates. However at a
too high loading rate, efficiency will drop due to
the shorter hydraulic retention time. However
only two main group of nitrogen loading rate
were tested (2.6 and 3.4 g N m-2 d-1) with the
addition of a single point during which a higher
loading rate was provide for two days (22-23
September). In the chart the intercept of the
fitted line was set equal to zero.
Comparisons and average results of COD removals, alkalinity consumptions and conductivity decrement for the period at load of about
3.4 g N m-2 d-1 are shown in Table 33.
The COD removal [%] calculated as
COD out
had been lower during the last
1
COD in
month compared to the previous months (29.3 %
instead of 47.9 % for the COD unfiltered and
31.0 % instead of 45.0 % for the COD filtered
0.45 μm). Plausible hypothesis could be changes
in biodegradable organic matter content in the
reject water from dewatering of digested sludge
13
from Bromma WWTP, a reduced activity or
concentration of denitrifiers in the reactor or a
higher sedimentation in the reject water tank
prior to treatment.
The ratio COD removed/N inorg removed ranged between 0.22-1.01 and 0.14-0.55 considering the
COD unfiltered and filtered 0.45 μm respectively.
The drop of conductivity between inflow and in
the reactor is due to ammonia oxidation to nitrite
and nitrogen gas and alkalinity consumption in
the nitritation and Anammox processes.
The decrement of conductivity between inflow
and the outflow is shown in figure 55.
The COD in the outflow was fairly constant and
ranging between 300 and 400 mg O2/l (Fig. 56).
The curve of the soluble COD removed over
time seems to be parallel to the curve showing
the concentration of soluble COD in the influent
supernatant, whereas the soluble COD in the
reactor was rather constant.
A possible explanation might be that the biodegradable organic matter was a limiting factor for
heterotrophic bacteria and the percentage of
COD removed (about 40% as shown in
Table 33) was only the biodegradable fraction.
This hypothesis could be confirmed by the
CBOD5 measurement of the 14th September (the
procedure adopted is briefly described in chapter
3.4) determined on the influent reject water
which gave the result of:
D  D2
CBOD5  1
 173 mg/l,
0.01
where:
D1= DO of diluted sample immediately after
preparation (8.94 mg/l);
D2= DO of diluted sample after 5 d incubation
(7.21 mg/l);
0.01 = 1% dilution of the sample;
63
Andrea Bertino
TRITA Degree Project Thesis
conductivity IN
conductivity R
8-Jul-10
5-Aug-10 19-Aug-10 2-Sep-10 16-Sep-10
12
11
10
9
mS/cm
8
7
6
5
4
3
2
1
0
27-May-10 10-Jun-10 24-Jun-10
22-Jul-10
Date
Fig. 55. Conductivity decrement in the reactor (about
78.7 %).
Unfortunately the dilution did not result in a DO
uptake of at least 2 mg/l and the temperature
during the measurement reached 21.5 °C for a
couple of hours. The other dilution chosen
(0.5%) gave a too high and not reliable result
COD unf IN
COD 0.45 IN
probably due to a small presence of air bubbles in
the upper part of the bottle.
The DO uptake for the dilution water blank was
0.18 mg/l, thus less than 0.2 mg/l.
COD 0.45 out
COD 0.45 removed
2.000
mg O2/l
1.500
1.000
500
0
Fig. 56. COD prior to treatment, COD in the outflow
Dateand COD removed.
64
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
The result from CBOD5 measurement represents
the 34.1% of the soluble COD (0.45 μm) measured the same day on the same reject water.
However that week, the COD consumption was
only the 21.5 % of the soluble COD in the inflow.
The free ammonia (NH3) and free nitrous acid
(HNO2) concentrations in the reactor have been
approximately calculated using the equilibria at
25°C:
NH3(aq) + H2O ↔ NH4+(aq) + OH-(aq) ,
 NH 4   OH  
Kb= 
= 1.78·10-5;
NH
 3
HNO2(aq) + H2O ↔ NO2-(aq) + H+(aq) ,
 NO2    H  
Ka= 
= 4.57·10-4;
 HNO2 
From the concentration of ammonium and nitrite
in outflow, the average values of pH on that
specific day of outflow measurement and the
equilibrium constants the results obtained are:
 Free ammonia NH3 = (1.51 ± 1.05) mg/l with
a maximum value of 3.87 mg/l and a minimum of 0.29.
 Free nitrous acid HNO2 = (0.0024 ± 0.0016)
mg/l with a maximum value of 0.0079 mg/l.
It is likely that nitrite oxidizing bacteria (NOB)
might have been inhibited to some extent by free
ammonia (crf. paragraph 1.2.4). The concentrations calculated above might have been slightly
lower because the results have been calculated
with molar concentrations without activity corrections.
Total soluble phosphorus in the outflow (filtered
0.45 μm) was measured only once (27th July and
under stable conditions) and the result was about
0.7 mg/l (with an inflow concentration of about
1.6 mg/l).
Some relationships and correlations have been
studied and are here below presented (Fig. 5760). The following parameters showed a good
correlation in spite of possible small errors of
measurement or calibration and/or interferences
from changes in other parameters.
The conductivity was found to be a good parameter to monitor the performance of the process
and the ammonia nitrogen removal. Its advantage
is that it can be easily measured giving an immediate result. Most of the times, the lowest values
of conductivity were observed together with
higher ammonia nitrogen removal (Fig. 57) and
low NH4+-N concentration in outflow.
High conductivity removal was often associated
to a higher consumption of alkalinity (Fig. 58-59).
This is related to the hydrogen carbonate
(HCO3-) consumption as consequence of nitrification and Anammox reactions and the production of hydrogen ions.
Lower values of pH and pH drops were found
together with decrements of alkalinity of the
liquor in the reactor (Fig. 60). A consumption of
alkalinity, as a consequence of HCO3- removal,
leads to a lower buffer capacity and ability of the
liquor to withstand pH drops. pH drops in the
reactor can be provoked by higher DO concentrations (and thus an enhanced nitrification which
produces H+) or a lower inflow rate (and thus a
lower incoming of HCO3- and alkalinity).
Very often low values of pH were observed
together with high redox potential (ORP) as
showed in figure 61.
NH4+-N removed [mg/l]
1,200
Fig. 57. Conductivity
removed and NH4+-N
removed
y = 113.48x + 27.433
R² = 0.808
1,000
800
600
400
200
0
4.0
5.0
6.0
7.0
8.0
conductivity removed [mS/cm]
65
9.0
Andrea Bertino
TRITA Degree Project Thesis
alkalinity consumed [mmol/l]
90
Fig. 58. Conductivity
removed and alkalinity
consumption
y = 8.6625x + 1.3823
R² = 0.784
80
70
60
50
40
30
20
10
0
4.0
5.0
6.0
7.0
8.0
9.0
conductivity removed [mS/cm]
Fig. 59. Conductivity
and alkalinity in outflow
12.0
11.0
alkalinity out [mmol/l]
10.0
9.0
y = 10.977x - 15.101
R² = 0.7338
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
conductivity out [mS/cm]
alkalinity out [mmol/l]
12.0
10.0
Fig. 60. pH in the
reactor and alkalinity
in outflow
y = 7.8441x - 51.718
R² = 0.7271
8.0
6.0
4.0
2.0
0.0
6.6
6.8
7.0
7.2
7.4
7.6
pH out
66
7.8
8.0
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
180
Fig. 50. Comparison of
the biocarriers before
starting the pilot reactor
(left) and after 106 days
of operation (right).
160
140
120
redox [mV]
100
80
60
40
y = -97.767x + 764.47
R² = 0.6773
20
0
-20 5.5
6.0
6.5
7.0
7.5
8.0
8.5
-40
pH
Fig. 61. pH and redox (ORP) conditions in the reactor.
The main reason lies in the fact that both of these
two parameters are strongly dependent on the
DO concentration in biological treatment. Oxygen is a strong oxidizer in waters, which therefore
raises the redox potential and oxidizes ammonium and nitrite through nitrification process by
Nitrosomonas and Nitrobacters, leading to a
decrease of the pH. The values of these two
parameters – ORP and pH – within the reactor
are also influenced by the incoming flow of reject
water which tends to lower the redox potential
and contrast the pH decrease. The reject water
prior to treatment has, in fact, basic and reducing
conditions with a negative and low ORP (around
-470 mV) and high pH value (8.43).
The redox potential in the reactor may also be
influenced by other reductants/oxidants compounds concentrations such as NO3-, SO42- (oxidants) or NH4+, NH3, organic matter, HS-, Fe2+,
Mn2+ (reductants).
For example in figure 61, the nine points marked
in red and ranging between ORP value of 52.8
and 137.2, belong to the period 9th July – 15th July
during which the chemical analyses results on the
15th July gave lower values of DO (1.77 mg/l)
and NO3--N (87.6 mg/l) compared to other
chemical analyses performed with similar high
values of ORP. For instance the period
17-20 June, whose values are marked in blue, had
higher DO and NO3--N concentrations. According to the measurements on the 15th June
and 22nd June, NO3-N was expected to be in the
range 125-135 mg/l or even higher, because DO
concentration was around 2.53 mg/l and higher
than the previous and following days. Thus higher DO and NO3--N concentration resulted in a
higher ORP.
5.2.4
Evaluation of biomass activity
Three different kinds of batch tests (OUR, SAA,
NUR) were performed in order to evaluate and
monitor trends and changes in activity of different bacteria populations on the carriers during
the four months of pilot reactor operation. The
batch tests were carried out according to the
methodology described in chapter 3.6. In the last
days of study on pilot reactor a set of batch test
was carried out on the activated sludge, in order
to have a term of comparison with the bacterial
activity in the biofilm.
Oxygen Uptake Rate (OUR)
The oxygen uptake rate (OUR) tests (cfr. chapter
3.6.2) aimed to evaluate the oxygen consumption
by nitrifying bacteria (AOB, mainly Nitrosomonas spp., and NOB, mainly Nitrobacter spp.) and
heterotrophic bacteria. A higher oxygen uptake
rate by nitrifying bacteria reflects higher nitrification rate and ammonia consumption.
In total 9 series of OUR tests were performed
during the first four months of pilot plant-scale
reactor operation. The data from the tests are
shown in APPENDIX V. The results are summarized in figure 62. The oxygen uptake rates
were calculated according to the formulas described in chapter 3.6.2.
67
Andrea Bertino
TRITA Degree Project Thesis
AOB
HT
NOB
Lineare (AOB)
Lineare (HT)
Lineare (NOB)
6
5
g O2 / m2 / d
4
y = 0,0016x - 58,6621
3
y = -0,0059x + 239,9195
2
y = -0,0033x + 133,25
1
0
27-May
6-Jun
16-Jun
26-Jun
6-Jul
16-Jul
26-Jul
5-Aug
15-Aug
25-Aug
4-Sep
14-Sep
24-Sep
Fig. 62. Results from OUR tests on the biocarriers during the period June-September 2010
date
The pH was measured manually at the beginning
and the end of a couple of tests and it decreased
from about 8.25 to 8.05. The diluted reject water
had a NH4+-N initial concentration of 99.7 ±
3.4 mg/l and the tests were started with a DO
concentration above 6.5 mg/l. NO2--N and NO3-N concentrations were almost zero.
Analyzing the results from OUR tests during
these four months of pilot reactor operation, a
general increase of ammonia oxidizing bacteria
(AOB) was noticed at the expense of nitrite
oxidizing bacteria (NOB) and heterotrophic
bacteria (indicated as HT). This trend in the
biofilm activity was in the right direction for a
good performance of the partial nitritation/Anammox process.
A total increase in Nitrosomonas bacteria activity
was observed during August. The higher activity
of Nitrosomonas reflects the biomass growth on
the biocarriers observed during August by VSS
measurements. During that period of time, the
pH in the reactor was about 7.6, the DO concentration mostly between 2.4-2.5 mg/l and the
ORP average value was lower than 20 mV.
The decrease of Nitrosomonas activity observed
during July could have been due to a lower DO
concentration in the pilot plant reactor during the
first three weeks of July (DO about 1.7-1.8 mg/l).
The lower COD consumption during the last two
months of operation is evidenced by a decrease in
heterotrophic activity.
Despite that, three objections could be raised
about the results from these OUR tests. Firstly,
the concentration of sodium chlorate (NaClO3),
the inhibitor of NOB, was lower than the concentration reported in literature which was found
to fully inhibit Nitrobacter spp. This might have
led to an overestimation of AOB (calculated as
difference of DO consumption rate between the
second and third phase of the test) and an underestimation of NOB (calculated as difference of
DO consumption rate between the first and
second phase of the test). Secondly, the test was
started with a NO2- concentration almost zero,
and the rate of nitrification by NOB was probably limited to some extent by the oxidation of
NH4+ by AOB. This probably led to an underestimation of NOB. However nitrite limiting conditions are also present inside the pilot-scale
reactor. Moreover at the beginning of July, FISH
analysis confirmed that the Nitrobacter spp.
bacteria were few in the biofilm, and the results
from OUR tests seem to confirm that. Thirdly
the rather high pH above 8 was higher than the
real conditions in the reactor, and Nitrobacter
might have been inhibited by free ammonia to
some extent.
If the results are then expressed as specific oxygen uptake rate (SOUR) (gO2 gVSS-1 d-1), by
using the measurements of the biomass attached
on the rings which were obtained in the days
close to the date of OUR tests and estimate the
68
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
AOB
HT
NOB
Lineare (AOB)
Lineare (HT)
Lineare (NOB)
0.16
0.14
y = -0.0002x + 9.642
g O2 / g VSS / d
0.12
0.10
0.08
0.06
y = -0.0003x + 11.524
0.04
y = -0.0001x + 5.8207
0.02
0.00
27-May
6-Jun
16-Jun
26-Jun
6-Jul
16-Jul
26-Jul
5-Aug
15-Aug 25-Aug
4-Sep
14-Sep
24-Sep
date
Fig. 63. Specific Oxygen Uptake Rate (SOUR) of the
biofilm during the period June-September
2010
concentration in the bottle for OUR test, the
chart is slightly different (Fig. 63).
The chart shows a rather similar decrease in
activity for all the bacteria population. A likely
reason can be the increase of the biofilm thickness, and therefore a higher resistance to the
diffusion of substrates and dissolved oxygen
within the biofilm, or the presence of a small
amount of death biomass not metabolically active. That means for example that total activity of
Nitrosomonas bacteria has basically increased
because of the observed growth of Nitrosomonas
bacteria in the biofilm with time, but their specific activity per unit of weight of biomass seems
to have slightly decreased, probably because of
the reasons explained above.
During the last days of the studies on the pilot
plant reactor, on the 27th September, the OUR
test was performed on the activated sludge and
compared to the OUR results obtained on the
28th September. The specific oxygen consumption rates are summarized in Table 34.
The pH of the liquid from the reactor, and thus
the pH value of this series of three tests was
between 7.3-7.5. The test was performed on fresh
activated sludge taken directly from the reactor.
Table 34 – OUR test results performed
on activated sludge
OUR (AOB)
-1
OUR (NOB)
-1
-1
OUR (HT)
-1
g O2 g VSS d
g O2 g VSS d
g O2 g VSS-1 d-1
3.2781
1.0571
0.2716
A comparison with the OUR test carried out on
the 28th September on the biocarriers was done
(Table 36). The principle was to recalculate the
results from the OUR tests on the rings as
g O2 g VSS-1 d-1 (Table 35) and then adjust both
the results obtained inside the bottle of 1.56 l
with activated sludge and biocarriers to the reactor configuration that is 80 l of biocarriers in
166 l of liquid. The results obtained from the
tests on the activated sludge (calculated as
g O2 g VSS-1 d-1) have been simply multiplied by
the VSS concentration of the activated sludge in
the reactor on that day (284.74 mg VSS/l - average on three measurements). The results were
finally compared as g O2 m-3 d-1.
The comparison between the activity of AOB,
NOB and heterotrophs in the activated sludge
and the biocarriers (Table 36) confirms what the
theory suggested. Ammonium oxidizers (AOB)
are mainly attached on the carriers, whereas the
nitrite oxidizers (NOB) are more active in the
activated sludge. The heterotrophic bacteria
(among which the heterotrophic denitrifying
bacteria) are present and active to a greater extent
in the biofilm rather than in the activated sludge.
Few objections can be raised to this comparison.
The biomass concentration in the activated
sludge depends strongly on the hydraulic retention time of the period prior to the test. A higher
HRT may lead to a higher washing out of the
biomass from the reactor. Moreover the biomass
present as activated sludge is more sensitive to
shock loads or variations in the reactor.
69
Andrea Bertino
TRITA Degree Project Thesis
Table 35 – Recalculations of OUR results obtained for the Kaldnes rings.
Result
Unit
Formulas
Specific dissolved Oxygen Uptake Rate (dO2/dt)
g O2
g VSS  d
Dissolved oxygen uptake rate (d[O2]/dt)
g O2
m 3d
dO2  i

 60  60  24
dt
X
d O2 
dt

dO2 19.47mg / ring  85600rings

dt
166l
αi = slope of the dissolved oxygen concentration decrease inside the bottle plotted versus time (mg O 2 l-1 s-1). Subscript "i"
indicates the slope of the respective phase of the test (AOB+NOB+HT, HT+AOB or HT). The values of the three
slopes are the averages of the three OUR tests performed;
X = concentration of the biomass attached on the 107 rings inside the bottle (mg VSS/l), based on the concentration of
VSS on each ring measured on the 24th September (i.e. 19.47 mg/ring). The biomass concentration inside the bottle
was then adjusted to the stepwise dilutions made (4 ml NaClO3 and 6 ml ATU);
60, 60 and 24 = unit conversion factors from seconds to days;
19.47 mg/ring = biomass attached on the rings measured on the 24th September;
85600 rings = estimate of the total number of carriers inside the 166 l of liquid of the pilot reactor, calculated by proportion
and based on the measurement that 1070 carriers occupy a volume of 1 l and the reactor was filled with 80 l of carriers;
166 l = volume of liquor in the reactor.
Table 36 – OUR – comparison between biofilm and activated sludge
Object of the OUR test
OUR (AOB)
-3
Activated sludge (inside reactor)
Ratio biofilm / A.S. (inside reactor)
-3
g O2 m d
g O2 m-3 d-1
933.40
300.99
77.32
g O2 m d
g O2 m d
g O2 m-3 d-1
1092.32
223.39
421.08
1.17
0.74
5.45
Although the ammonia nitrogen concentration
was nearly the same, the COD was probably
different; in one case a dilution 1:10 was done for
the test on the biocarriers, whereas in the other
case the liquid was directly taken from the reactor, which had a higher COD concentration but
with a likely lower percentage of biodegradable
content.
Specific Anammox activity (SAA)
The main objective of the Specific Anammox
Activity (SAA) tests (cfr. chapter 3.6.1) was to
monitor the Anammox activity during the four
months of pilot plant-scale reactor operation.
In total 14 SAA analyses were performed (10 at a
temperature of 25°C and 4 at 35°C). The data
from the tests are shown in APPENDIX V.
The results are summarized in figure 64.
The tests carried out during the four months of
operation show a general increase of Anammox
bacteria activity over time. During the last two
months of operation the Anammox activity was
higher and about 4 g N m2 d-1. A total increase in
activity of 34.3 % was noticed from the test at
25°C, between the start and the end of the study
on the pilot reactor.
-1
-3
-1
OUR (HT)
g O2 m d
-3
Biofilm (inside reactor)
OUR (NOB)
-1
-1
The tests carried out at a higher temperature
(35°C), closer to the optimum temperature of
Anammox bacteria, showed a steeper increase in
activity over time compared to the tests carried
out at the reactor operating temperature of 25°C.
If the results are then expressed as Specific
Anammox Activity per grams of biomass attached as biofilm on 15 rings (by using the measurements on suspended volatile solids carried
out on days close to the SAA analyses), the SAA
does not show any increase and has an average
value of 0.0965 gN gVSS d-1 (Fig. 65).
A SAA test was carried out on the suspended
activated sludge taken directly from reactor and
the result is showed in APPENDIX V.
The Anammox activity resulted to be
0.1203 g N g VSS-1 d-1. This value has been transformed to g N m-3 d-1 by multiplying by the
volatile suspended solids concentration in the
reactor on that day (280.73 mg/l) and compared
to the result obtained on the biofilm adjusted to
the reactor characteristic (80 l of rings and 166 l
of liquor) and expressed as g N m-3 d-1. The
procedure is very similar to the one used for
OUR test before.
70
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
SAA 25C
SAA 35C
Lineare (SAA 25C)
Lineare (SAA 35C)
7
6
y = 0,0197x - 789,89
R² = 0,8203
SAA [g N/m2/d]
5
4
3
y = 0,0084x - 335,05
R² = 0,6969
2
1
0
27-mag
6-giu
16-giu
26-giu
6-lug
16-lug
26-lug
5-ago
15-ago 25-ago
4-set
14-set
24-set
Fig. 64. Activity of Anammox bacteria attacheddate
on the biocarriers during the period JuneSeptember 2010
From Table 37 is possible to verify that almost all
the activity of bacteria is concentrated in the
biofilm (>96.6%).
However this value could be even higher because
in the test on activated sludge denitrifiers were
able to have access to the COD (contained in the
liquor from the reactor), to the substrate
(70 mg/l NO2--N and about 100 mg/l NO3--N)
Serie1
and probably to a variety of other micronutrients
which were not present in the synthetic liquid
used for the SAA test on the biofilm.
Nitrate Uptake Rate (NUR)
NUR test was carried out to assess the NO3removal rate from the liquor. The method is
described in chapter 3.6.3. In total 10 NUR tests
were per-formed on the biocarriers during the
Lineare (Serie1)
0,12
SAA [g N/gVSS/d]
0,10
0,08
y = 4E-06x - 0,0801
R² = 0,0005
0,06
0,04
0,02
0,00
27-mag
6-giu
16-giu
26-giu
6-lug
16-lug
26-lug
5-ago
15-ago
25-ago
4-set
14-set
24-set
date during the period June-September 2010
Fig. 65. Specific Anammox Activity (25°C) of the biofilm
71
Andrea Bertino
TRITA Degree Project Thesis
Table 37 – SAA – comparison between biofilm and activated sludge
Object of the OUR test
Unit
SAA
Activated sludge (inside reactor)
g O2 m-3 d-1
33.77
Biocarriers (inside reactor)
g O2 m-3 d-1
956.01
% activity by biocarriers (inside reactor)
%
96.59
four months of evaluation of the pilot plant-scale
reactor.
The experimental data from the tests are shown
in APPENDIX V, while the results are summarized in figure 66.
Parallel to NUR test, COD analyses were carried
out and are presented below.
NUR tests results does not show any particular
tendency for the nitrate up-take rate by the denitrifiers in the biofilm. The low result obtained on
the 26th August may be due to the problems
occurred on the 23rd August when the reactor
could not be fed for one day. A part from this
value, the average Nitrate Uptake Rate in this
four month was approximately 0.84 g N m2 d-1.
Reduction in COD removal was observed during
the last two months (Fig. 66 and Fig. 56).
In some cases the COD removal was even negative and it was observed an increase in COD
between the beginning and the end of the NUR
test. A plausible reason of this may be an increase
of soluble COD due to solubilization of COD
initially present in insoluble form, that is the
condition which underlies the process of anaerobic fermentation. The decrease in NUR during
July is similar to the one reported by OUR tests.
In August an increase in nitrate uptake rate was
observed, consistent with the increase of volatile
solids on the biocarriers during those weeks.
No explanations were found for the low value
measured on 26th August, if not because of the
problems occurred on the 23rd August when no
inflow was provided to the reactor or a wrong
result from the test.
The last test (26th September) was followed by
measurements of inorganic nitrogen forms (three
samples for NH4+-N and NO2-.-N and five, as
usual, for NO3-.-N). After about 3 hours and
30 minutes, a decrease of 4.0% of NH4+-N was
noticed (i.e. from 748 mg/l to 718 mg/l), while
the removal of NO3--N was 25.0% (i.e. from
101.2 mg/l to 75.9 mg/l). The ammonia nitrogen
decrement might have been caused by ammonia
stripping phenomena due to nitrogen gas supply
during the whole test (the pH was about 8.25), or
to the consumption by Anammox bacteria which
might have been used, under anoxic conditions,
the nitrite produced during the denitrification
process, although the kinetic rate for the conversion of NO2- to N2, is usually higher than the for
NO3- to NO2-. The NO2-.-N was less than
0.15 mg/l during the whole test.
Thus a possible limitation of NUR test carried
out on reactors with a partial nitrita-
NO3-N uptake rate
Lineare (NO3-N uptake rate)
COD removal rate
1.3
2.0
1.5
1.0
0.8
y = -0.0002x + 9.0104
R² = 0.0027
0.5
0.5
0.0
0.3
-0.5
0.0
27-May 6-Jun
-1.0
16-Jun 26-Jun
6-Jul
16-Jul
26-Jul
5-Aug 15-Aug 25-Aug 4-Sep 14-Sep 24-Sep
Fig. 66. Results from NUR tests on the biofilm date
during the period June-September 2010
72
g COD/ m2/ d
g N/ m2/ d
1.0
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 38 – Recalculations from NUR results on the biocarriers.
Unit
Result
Formulas
Specific Nitrate Uptake Rate (dNO3- -N/dt)
g N
g VSS  d
Dissolved Nitrate Uptake Rate (d[O2]/dt)
g N
m 3d
dN 

 60  24  0.0196
dt
X
d  N  dN 19.47  85600


 197.17
dt
dt
166l
α = average slope of the nitrate concentration decrease plotted versus time (mg N l-1 min-1);
X = mg VSS of 400 ml of carriers inside 1 l container. The concentration of VSS on each ring measured on the
24th September (i.e. 19.47 mg/ring) was calculated by 107 and 4, based on the measurement that 107 carriers occupy a
volume of 100 ml. X  19.47mg / l  107  4 ;
1l
60 and 24 = unit conversion factors from seconds to days;
19.47 mg/ring = biomass attached on the rings measured on the 24th September;
85600 rings = estimate of the total number of carriers inside the 166 l of liquid of the pilot reactor, calculated by proportion
and based on the measurement that 1070 carriers occupy a volume of 1 l and the reactor was filled with 80 l of carriers;
166 l = volume of liquor in the reactor.
tion/Anammox process is that the nitrate uptake
rate by denitrifying bacteria may be slightly underestimated because of the opposite action
exerted by Anammox bacteria which produce
nitrates and may reduce the result of nitrate
uptake rate by denitrifiers.
On the 27th September the NUR test was performed on fresh activated sludge taken directly
from the reactor and compared to the NUR
results obtained on the 26th September. The
nitrate uptake rate (NUR) was found to be 0.139
g N gVSS-1 d-1 while the soluble COD increased
from 380 mg O2/l to 393 mg O2/l.
A comparison with the NUR test carried out on
the 26th September on the biocarriers was made
as g N m-3 d-1. The principle used to compare the
result is the same used previously for OUR test
and it is shown in Table 38.
The correspondent NUR on the activated sludge
has been multiplied by the VSS concentration of
the activated sludge used for the test (i.e. 296.18
mg VSS/l):
g N
g N
 296.18mgVSS / l  41.16 3
g VSS d
md
The
comparison
shows
a
ratio
NURbiocarriers/NURact. sludge = 4.79, therefore the
nitrate uptake is mostly carried out within the
biofilm, where anoxic conditions are favorable to
the nitrate uptake by denitrifiers. However this
ratio could actually be higher, because the negligible concentration of Anammox bacteria in
the activated sludge played a minimal role in the
production of nitrate during NUR test compared
to the NUR test carried out on the biocarriers
0.139
where Anammox bacteria are present and might
produce a small percentage of NO3- by using the
NO2-.produced during denitrification.
6 C ONCLUSIONS
These studies were carried out to investigate and
evaluate the partial nitritation/Anammox technology in moving bed biofilm reactors (onereactor system). Literature review and experimental work carried out in this thesis confirmed
the sustainability and the potential advantages of
the partial nitritation/Anammox as a viable option for the treatment of ammonium-rich wastewaters.
Two laboratory-scale reactors and a pilot plantscale reactor were studied. The laboratory scale
studies allowed understanding the parameters
involved in the process and directly examine their
influence on the process performance. Conclusions and findings concerning the laboratoryscale reactors are given in chapter 4. The pilot
plant-scale reactor, which was evaluated for a
longer period, allowed establishing a stable partial
nitritation/Anammox process with good and
promising results. The main conclusions given
below are largely related to this reactor.
The following conclusions can be stated:
 By varying and adjusting carefully operational
parameters such as DO concentration, temperature and HRT (i.e. inflow rate) is possible
to obtain high and stable efficiency of the
whole process.
 Efficiencies of 95%, 85% and 83% for NH4+N, inorganic nitrogen, and Total Nitrogen re73
Andrea Bertino
spectively have been simultaneously achieved
in the one-stage partial nitritation/Anammox
Moving Bed Biofilm Reactor filled with about
40% of Kaldnes rings and with an influent
load of 3.4 g N m-2 d-1. The maximum removal rate at this loading rate was about 2.9 g
N m-2 d-1.
 DO is a key parameter and the oxygen-limiting conditions must be provided for a good
performance of the process. A too high dissolved oxygen concentration resulted in a
temporarily accumulation of nitrates in the reactor, but its effects seemed to be reversible.
An average DO concentration in the reactor
of 2.2 mg/l was used in this study, providing
good results.
 Conductivity is a good parameter which can
be easily used to monitor the performance of
the process and the NH4+ removal. It gives an
immediate result without the need to perform
analyses.
 pH and, to a slightly lower extent, ORP can
give useful information about the conditions
in the reactor and the adequacy of the dissolved oxygen concentration provided by aeration; moreover, a low pH and high ORP
were usually noticed together with higher
NO3--N concentration in the reactor.
 An on-line control of physical parameters
with particular regard to DO and pH is advisable for a continuous and real-time monitoring of the process.
 A PID controller for aeration may be important to avoid peak concentrations of dissolved
oxygen, especially for research purpose.
 Ratios such as COD/N and Alkalinity/N in
the wastewater prior to treatment are extremely important for the stability of the process. A too high COD might enhance denitrifiers growth which could outcompete
Anammox bacteria on a long-term scale. A
too low alkalinity may not be sufficient to
cope with the general decrease in pH of the
partial nitritation/Anammox process.
 NO2- was the limiting factor for the Anammox bacteria in the one-stage partial nitritation/Anammox reactor and its concentration
inside the reactor was only the 11.6% the concentration on NH4+.
 Anammox bacteria are strongly influenced by
temperature and dissolved oxygen inhibition.
A higher temperature can result in higher
Anammox bacteria activity; however at a tem-
TRITA Degree Project Thesis
perature of 25°C it was already possible to obtain a satisfying nitrogen removal.
 If the reactor is run at 25°C, the heat deriving
from the anaerobic digestion of the sludge can
be exploited, with the advantage to save costs
for the heating.
 The coexistence of aerobic and anaerobic
ammonium oxidizers (i.e. Nitrosomonas and
Anammox) within the biofilm was confirmed
by FISH analyses. A smaller percentage of Nitrobacter was found to be present within the
biofilm.
 An increase of biofilm thickness was observed
on the biocarriers (+38.6% between the 22nd
July and 10th September) together with a
moderate increase of process efficiency
(+5.2%) and a decrease in biomass concentration as activated sludge.
 The suspended biomass in the reactor accounted for about 2.9% of the total biomass
in the reactor (activated sludge + biomass attached on the Kaldnes rings). However the
small percentage of aerobic activated sludge
with nitrifying bacteria may be important for
removing dissolved oxygen from the liquor
and converting NH4+ to NO2- and thus provide good conditions for anaerobic bacteria
(Anammox) in the biofilm.
 Batch tests such as SAA, OUR and NUR can
give useful information about evolution of
bacteria activity over time. In this thesis, these
tests have been carried out on the Kaldnes
rings from the pilot plant-scale reactor for a
period of four months.
 Results from the tests are highly dependent on
proper execution of tests. Test duration
should be kept as constant as possible between different tests. In a couple of tests
(NUR and especially SAA tests) a decrease in
the experimental curves slope was noted for
duration longer than about 90 and 180 minutes for SAA and NUR tests respectively.
 OUR tests carried out on the Kaldnes rings
showed a total increase in Nitrosomonas activity and a decrease in activity for Heterotrophs and Nitrobacter.
 Oxygen Uptake Rates (OUR) (at 25°C) of the
biofilm attached on the rings were estimated
of about 4.3 g O2 m-2 d-1 for Nitrosomonas,
2.1 g O2 m-2 d-1 for Heterotrophs and
0.8 g O2 m-2 d-1 for Nitrobacters.
 The calculated ratios between the OUR
(g O2 m-3 d-1) by the biofilm and the OUR
74
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
(g O2 m-3 d-1) by the activated sludge were
1.17 for Nitrosomonas, 5.45 for Heterotrophs
and 0.74 for Nitrobacters.
 SAA tests carried out on the Kaldnes rings at
25°C showed a constant increase in Anammox activity (+ 34.3 %) with a maximum value of 4.1 g N m-2 d-1.
 The Anammox bacteria activity is almost
entirely concentrated in the biofilm (>96.5%).
 A sufficiently high nitrogen loading rate is
required for a stable partial nitritation/Anammox process in order to not limit
the slow growth rate of Anammox bacteria. If
the load is too low the decay rate might exceed the Anammox bacteria growth rate.
 NUR results showed a slight decrease in nitrate uptake rate by the biofilm, probably due
to a decrease activity of denitrifiers. The average value was 0.84 g N m-2 d-1.
 The calculated ratio between the NUR
(g N m-3 d-1) by the biofilm and the NUR
(g N m-3 d-1) by the activated sludge was 4.79.
7 S UGGESTIONS FOR F ULL -S CALE
I MPLEMENTATION A ND
F UTURE R ES EARCH
In this chapter proposal for the implementation of partial nitrification/Anammox process using the moving bed biofilm technology are discussed both as an upgrading
option for existing WWTP (chapter 7.1) and
as an alternative for nitrogen removal from
leachate (chapter 7.2) or other stream with
high content of organic matter. A brief discussion is given about the possibility to use
the studied process within the main treatment line (chapter 7.3). A last section (chapter 7.4) deals with future research which is
needed to understand and generally improve
the scientific knowledge about these innovative wastewater treatment options.
7.1 Partial nitrification/Anammox in
municipal WWTPs
The pilot plant scale reactor seemed to work well
with the volume of carriers used for the operation and the influent reject water from dewatering
of the anaerobically digested sludge which fed the
reactor. High efficiencies, above 80%, were
reached. Removal efficiencies of 95% for NH4+N and 85% for inorganic nitrogen have been
achieved simultaneously. Based on the results
obtained during the last two months of study on
the pilot reactor and despite the large nitrogen
removal achieved from the high initial concentration of the reject water (974.3 mg/l NH4+-N),
average concentrations of 76.8 mg/l NH4+-N,
7.82 mg/l NO2--N and 83.4 mg/l NO3--N were
still present in the effluent. These values are
above the requirements for discharge, thus a
further treatment is needed.
An example of municipal WWTP (Fig. 67) consists of a primary treatment to remove solids, a
secondary treatment to reduce the organic content and nutrients (phosphorus and nitrogen) and
finally the treatment and handling of sludge
(anaerobically digested). In Fig 67 the secondary
treatment is depicted as a biological treatment
with enhanced biological phosphorus removal
(e.g. Johannesburg system). The partial nitrification/Anammox reactor in a full scale WWTP can
be located downstream the sludge treatment line.
In most cases, the supernatant from the dewatering of the digested sludge is suitable to undergo partial nitritation/Anammox process.
The small but highly concentrated side stream
with a relatively high temperature and through
the Moving Bed Biofilm Reactor (MBBR) technology make it possible to have a treatment
within a tank with a smaller and compact footprint. By upgrading an existing WWTP with the
partial nitritation/Anammox reactor large advantages in term of costs and sustainability can be
obtained compared to the recirculation of the
reject water from sludge dewatering directly to
the inlet of the WWTP without further treatment.
Economical and environmental benefits can be
gained, if compared to the conventional nitrification/denitrification. For instance, by treating the
side stream of the effluent from sludge dewatering by partial nitritation/Anammox technology,
a lower nitrogen load (-15-20%) is supplied to the
main treatment line, a lower aeration and additional carbon source are needed and less CO2
emissions are produced from the whole WWTP.
Several options can be adopted for the partial
nitritation/Anammox process in one-single
reactor. Here below (Fig. 68) an example of a
possible interesting configuration is illustrated.
Two MBBRs in series with bypass of part of
reject water allow achieving a large reduction of
the incoming nitrogen load. The reactors could
also work in parallel if are equally loaded with the
clarified effluent from the anoxic tank where
denitrification takes place in order to consume
the nitrates (NO3-) produced by Anammox and
Nitrobacters in partial nitritation/Anammox
75
Andrea Bertino
TRITA Degree Project Thesis
PRIMARY
SETTLER
SCREEN
Raw
wastewater
SECONDARY
CLARIFIER
GRIT CHAMBER
ANAEROBIC
AEROBIC
ANOXIC
TREATED
WASTEWATER
complying with
regulations
ANOXIC
Landfilling
Landfilling
THICKENER
THICKENER
ANAEROBIC
DIGESTION
bypass
CLARIFIER
PARTIAL
NITRITATION/
ANAMMOX
MBBR
technology
CONDITIONING
PARTIAL
NITRITATION/
ANAMMOX
MBBR
technology
CLARIFIER
DENITRIF.
SETTLING
TANK
(ANOXIC)
DEWATERING
HEAT DRYING
NO3--N
Landfilling
Fig. 67. A general overview of treatments in a municipal WWTP. Two MMBRs in series with
bypass and pre-denitrification could be implemented in the sludge line.
reactors. The treated effluent can be recirculated
back to the main treatment line or discharged if it
meets the requirements for discharge. The denitrifiers and the sludge from the partial nitritation/Anammox reactors can be used to seed the
denitrification and nitrification units of the main
stream treatment line or otherwise sent back to
the primary settler.
7.2 Partial nitrification/Anammox for
leachate treatment
The partial nitrification/Anammox MBBR could
also be used for treatment of landfill leachate
with low biodegradable content or after COD
removal. Particular regard should be paid to the
presence of high concentrations of inhibiting
substances or nitrification inhibitors (e.g. heavy
metals), which if present to some extent may
slow down or inhibit the whole process.
A chemical precipitation for metal removal is
usually carried out before the biological treatment.
A biological anaerobic treatment could be applied
prior to the biological treatment with partial
nitritation/Anammox in MBBRs as shown in the
overview of the line of treatment in figure 69.
The biogas produced is a valuable product and
the higher temperature from the anaerobic digestion can improve the process efficiencies. However, the most suitable option for the choice of a
treatment line must always be based on a casespecific decision.
The effluent from biological processes should be
able to meet requirements for nitrogen, but further treatment might be needed to comply discharge requirements for other pollutants.
Similar streams with high COD concentrations,
and especially the effluents from food industries
biogas
bypass
CaO
Al2(SO4)3
CLARIFIER
ANAEROBIC
DIGESTION
(UASB)
SETTLING
TANK
DENITRIFICATION
CLARIFIER
(ANOXIC)
PARTIAL
NITRITATION/
ANAMMOX
MBBR technology
PARTIAL
NITRITATION/
ANAMMOX
MBBR technology
CLARIFIER
Further
treatment
NO3-
Fig. 68. Anaerobic treatment, pre-denitrification and partial nitritation/Anammox reactor for
biological treatment of leachate.
76
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
which have a high biodegradable fraction of
COD, need a previous degradation of organic
matter by means of an anaerobic digestion, if a
partial nitritation/Anammox process is chosen as
option for the nitrogen removal.
 A detailed evaluation of the consequences of
the possibility to seed the main treatment line
with the produced sludge from the side
stream treatment are interesting in order to
evaluate the extent of the benefits.
7.3 Future research
 Online monitoring for nitrogen compounds
(NH4+, NO3-, NO2-) might be of great interest
for a monitoring and real-time control of the
process performance, without the need of
chemical analyses.
Future research and studies are still needed to
fully understand this novel technology and increase the scientific knowledge for its future fullscale installations.
A couple of directions for future research have
emerged from this study:
 Long term coexistence of denitrifiers and
Anammox bacteria and the stability of the
process must be further investigated, with
special regard to the implementation of
DEAMOX systems.
 Intermitted aeration in Moving Bed Biofilm
Reactors or Sequencing Batch Reactors must
be further studied in order to compare the
performance of different operational strategies with partial nitritation and Anammox
process.
 More research on acclimation of bacteria
populations responsible for partial nitritation
and Anammox process to lower temperatures
could provide a thorough understanding of
the perspectives to run this process at low
temperatures.
 More research is needed to fully understand
and provide models for the diffusion of substrates in biofilm systems and the degree of
influence of the biofilm thickness.
 COD fractionation (e.g. inert, biodegradable,
readily biodegradable, slowly biodegradable,
etc. fractions of COD) can give useful information about the wastewater which has to be
treated and about the COD removed by the
process.
 Further improvements and alternatives should
be investigated with the common aim to reduce costs (especially aeration) of the conventional nitrification and denitrification treatment.
 More research is needed in order to fully
replace traditional nitrification and denitrification with new innovative and sustainable
technologies for nitrogen removal. It will be a
challenge to make partial nitrification/Anammox process (or similar novel processes) suitable for the treatment of
wastewater with lower nitrogen concentrations and low temperatures.
 More studies are needed to study the slowdown in the biological kinetics due to the
mass transfer limitation inside the biofilm.
The kinetics could be evaluated in batch tests
varying concentrations of substrates in the
bulk liquid and the biofilm thickness. Different shape of the carriers should be studied
and compared in order to contain and minimize this problem.
 More research should be conducted towards
faster start-up strategies for Anammox-based
systems.
 Studies about N2O emission from the treatment are important in order to reduce and
minimize the impacts from the emission of
this strong greenhouse gas. In particular aeration strategy or gas recirculation should be investigated.
77
Andrea Bertino
TRITA Degree Project Thesis
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http://www.anoxkaldnes.com/Eng/c1prodc1/mbbr.htm
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http://www.sjostadsverket.se/
Lecture notes of the course: “Water and waste handling” (KTH)
Lecture notes of the course: “Reduction of wastewater treatment contribution to global warming” (KTH)
Lecture notes of the course Environmental Dynamics/Chemical Processes (KTH)
Lecture notes of the courses “Ingegneria sanitaria ambientale” and “Complementi di ingegneria sanitaria
ambientale” (Politecnico of Turin)
85
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
A PPENDIX I – D ES CRIPTION OF PROCED URES FOR ANAL YSES AN D
MEASUREMENTS
Total and volatile suspended solids as biofilm
The procedure followed was:
1. The filter and the aluminum plate were weighted before the filtration;
2. The biomass was carefully removed from the carriers by using a needle and distilled water;
3. The removed biomass was filtered with a micro glass fiber filters with pore size 1.6 µm;
4. The biomass retained on the filter was evaporated at 105°C over night. The increase in weight of the
filter represents the total suspended solids (TSS);
5. The residue from the point 4) was ignited to constant weight at 550°C for 40 minutes. The remaining
solids represents the fixed total, dissolved, or suspended solids while the weight loss on ignition is the
volatile solids (VSS).
The total suspended solids (TSS) were calculated as:
AB
mg TSS/ring = 4
where:
A = weight of filter and aluminum plate + dried residue [mg];
B = weight of filter and aluminum plate [mg];
4 = number of rings.
The volatile suspended solids (VSS) were calculated as:
AB
mg VSS/ring = 4
where:
A = weight of filter and aluminum plate + residue before ignition [mg];
B = weight of filter and aluminum plate + residue after ignition [mg];
4 = number of rings.
The ash content was calculated as:
TSS  VSS
 100
TSS
% ash =
Total and volatile suspended solids in the influent and inside the reactor
The procedure followed was:
1. The filter and the aluminum plate were weighted before the filtration;
2. A certain amount of mixed sample was filtered with a micro glass fiber filters with pore size 1.6 µm;
3. The residue retained on the filter was evaporated at 105°C over night. The increase in weight of the
filter represent the total suspended solids (TSS);
4. The residue from the point 4) was ignited to constant weight at 550°C for 40 minutes. The remaining
solids represent the fixed total, dissolved, or suspended solids while the weight loss on ignition is the
volatile solids (VSS).
The total suspended solids (TSS) were calculated as:
 A  B   1000
mg TSS/l = sample volume , ml
where:
A = weight of filter and aluminum plate + dried residue [mg];
I
Andrea Bertino
TRITA Degree Project Thesis
B = weight of filter and aluminum plate [mg];
The volatile suspended solids (VSS) were calculated as:
 A  B   1000
mg VSS/l = sample volume , ml
where:
A = weight of filter and aluminum plate + residue before ignition [mg];
B = weight of filter and aluminum plate + residue after ignition [mg];
The ash content was calculated as:
TSS  VSS
 100
TSS
% ash =
Estimate of the total suspended biomass and the total biomass as biofilm
The suspended biomass was calculated as :
VSSact .sludge   mgVSS / l  VR
where:
mg VSS/l = measurement of suspended biomass;
VR = volume of liquid in the reactor;
The total biomass attached on the Kaldness rings in the reactor was calculated as:
VSSbiofilm   mgVSS / ring   Nrings
where:
mg VSS/ring = measurement of average biomass attached on the Kaldnes rings;
Nrings = estimated number of rings in the reactor, on the basis that 107 biocarriers occupy 100 ml and the
reactor was filled with rings whose total volume was known because measured before starting the
study.
Samples (activated
sludge and inflow)
Al plate
+ filter
4 rings
Biomass removed
from rings
II
Fig. 1A. Material for the
measurements of suspended solids in the influent,
attached on the rings and
inside the reactor.
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Efficiencies for Lab-scale and Pilot Plant-scale reactors
 NH
N
4

inorg
N

TN 
 NH

 NH

4

4
 N in   NH 4   N out
 NH

4
 N in
 N in   N inorg 
 NH4   N in
;
;
out
TN in  TN out
.
TN in
Nitrogen loading and removal rates
N 
Q
Loading rate [g N m-2 d-1] = 1000 1000
 60  24
Vrings
m2
 500 3
1000
m
inorg in

N  N 
inorg in
inorg out
1000
Vrings
m2
 500 3
1000
m
Removal rate [g N m-2 d-1] =

Q
1000  60  24
where:
Ninorg = inorganic nitrogen [mg/l] in inflow (Ninorg)in , essentially NH4+-N, or outflow (Ninorg)out;
Q = inflow rate [ml/min], kept constant between inflow and outflow chemical analysis and measured
manually;
Vrings = bulk volume of biocarriers in the reactor (Lab-scale reactor treating diluted reject water: 3.9 l; Labscale reactor treating effluent from UASB reactor: 3.17 l; Pilot-plant scale reactor: 80 l;
500 m2/m3 = specific internal surface area of Kaldnes media (model 1);
1000 = unit conversion factors mg - g, ml - l and l - m3;
60 and 24 = unit conversion factors from min to days.
The loading and removal rates could also be expressed as mg N l-1 d-1, but this is usually less common for
biofilm systems. In this case they could be calculated as:
Loading rate [mg N l-1 d-1] =
N 
inorg in

166l
Q
1000  60  24
 N inorg    N inorg    Q
in
out  1000

Removal rate [mg N l-1 d-1] =
 60  24
166l
where:
166 l = liquid volume in the reactor (Lab-scale reactor treating diluted reject water: 7.69 l; Lab-scale reactor treating effluent from UASB reactor: 6.74 l; Pilot-plant scale reactor: 166 l);
1000 = unit conversion factors ml - l;
III
Andrea Bertino
TRITA Degree Project Thesis
A PPENDIX II – D A TA FROM LAB - SCALE REACTOR TREATI NG DILUTED
SUPERNATANT
Table 1A – Chemical analyses on the inflow to the reactor
Alkalinity
(mmol/l)
(0,45μm)
NH4-N
(mg/l)
(0,45μm)
TOT-P
(mg/l)
unfiltr
COD
(mg/l)
(0,45μm)
COD
(mg/l)
unfiltr
N load
(gN/m2/d)
23/03/2010
-
400
30/03/2010
79,9
341
-
-
-
0,7748
-
284
-
0,6605
05/04/2010
31,4
13/04/2010
29,5
421
-
247
452
0,8154
368
-
257
355
0,7128
21/04/2010
27/04/2010
30,1
418
1,82
298
576
0,8096
33,9
383
0,75
358
527
0,7418
03/05/2010
33,9
421
2,07
382
497
0,8154
05/05/2010
-
387
-
-
-
0,7496
12/05/2010
31,5
447
-
-
-
0,8658
19/05/2010
31,5
406
3,04
326
540
0,7864
21/05/2010
-
402
-
-
-
0,7786
26/05/2010
26,6
395
2,82
337
526
0,7651
Date
Table 2A – Chemical analyses on the outflow from the reactor
Date
Alkalinity
(mmol/l)
(0,45μm)
NH4-N
(mg/l)
(0,45μm)
NO2-N
(mg/l)
(0,45μm)
NO3-N
(mg/l)
(0,45μm)
TOT-P
(mg/l)
unfiltr.
COD
(mg/l)
(0,45μm)
COD
(mg/l)
unfiltr
Ninorg
removal
(gN/m2/d)
23/03/2010
-
-
-
-
-
-
-
-
25/03/2010
7,16
42,4
5,23
4,45
-
141
-
0,6739
30/03/2010
-
-
-
-
-
-
-
-
01/04/2010
1,26
8,97
7,2
50,7
-
178
-
0,5310
08/04/2010
6,35
68,3
1,81
19
-
196
197
0,6428
15/04/2010
4,88
35,6
3,51
47,3
-
158
166
0,5454
23/04/2010
8,14
77
2,96
19,16
-
168
187
0,6176
29/04/2010
0,522
-
-
-
-
158
191
-
05/05/2010
1,62
46,6
6,405
52,8
-
171
204
0,5776
14/05/2010
23,72
200
2,41
2,13
-
202
-
0,4696
21/05/2010
19,72
225,2
2,92
0,96
4,14
197
415
0,3388
28/05/2010
0,668
23,6
0,191
109,2
2,56
187
314
0,5075
IV
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 3A – Physical parameters
23/03/2010
24/03/2010
25/03/2010
26/03/2010
29/03/2010
30/03/2010
31/03/2010
01/04/2010
Influent
Cond
pH
(mS/cm)
7,38
3,18
7,66
3,16
7,96
3,04
8,26
3,09
8,49
2,94
8,49
2,91
8,50
2,83
8,57
2,24
Temp
(C)
24,6
24,5
24,5
24,8
25,1
24,4
25,2
25,3
Effluent
Cond
pH
(mS/cm)
7,90
1,24
7,42
0,87
7,64
0,82
7,46
1,07
7,62
1,07
7,19
0,72
6,80
0,88
7,70
7,48
7,03
7,48
7,57
7,63
7,03
6,72
02/04/2010
8,42
3,18
6,66
0,96
1,58
24,8
6,60
0,96
05/04/2010
06/04/2010
08/04/2010
09/04/2010
13/04/2010
15/04/2010
16/04/2010
8,36
8,47
8,85
8,48
8,83
8,32
8,02
2,90
2,87
2,76
2,93
2,71
3,18
3,14
6,67
7,05
7,65
7,62
6,96
7,32
6,44
0,85
0,90
1,02
0,85
0,94
1,04
0,70
1,29
0,71
0,68
1,05
2,15
0,18
24,2
24,5
26,2
25,8
25,6
24,4
24,5
6,54
7,04
-
0,87
0,88
-
21/04/2010
8
3,17
7,22
0,78
0,62
25,2
-
-
23/04/2010
8,28
3,01
7,63
1,17
0,32
24,6
7,78
1,11
26/04/2010
8,10
3,13
7,85
1,47
0,43
24,2
-
-
27/04/2010
7,86
3,05
6,84
0,64
26,1
-
-
8,11
8,48
8,30
2,77
2,98
2,67
3,02
6,11
6,39
0,87
2,00
0,79
27,4
-
-
7,83
1,49
0,51
27,2
26,0
7,80
1,33
Inflow rate was 2,541 l/min.
04/05/2010
8,27
3,15
7,72
1,19
24,0
7,60
1,13
Decreased aeration.
05/05/2010
8,47
8,35
2,90
3,41
7,55
1,05
25,0
7,58
0,97
Decreased aeration. Inflow rate
was 2,6 ml/min.
07/05/2010
-
-
-
-
-
-
-
-
New inflow (but dilution 1:2 on
7/5/2010).
10/05/2010
8,36
7,18
3,31
3,58
7,72
1,67
1,19
24,2
7,43
1,56
11/05/2010
7,26
3,58
7,91
1,99
0,54
25,4
-
-
12/05/2010
7,78
3,54
7,99
2,31
0,65
25,0
7,86
2,27
13/05/2010
7,79
3,50
7,97
2,36
1,00
25,4
7,84
2,30
18/05/2010
8,05
3,11
7,92
2,30
0,83
27,8
7,92
1,77
T high ( probably due to warm
days). Increased slightly aeration.
8,22
2,95
7,96
8,26
3,32
7,83
Calibrated pH meter. Flow was too
low (1,87 ml/min). T high (warm
days). Increased aeration
(changed air stone that supply air).
DO was not evenly distributed.
8,17
8,07
8,34
3,25
3,22
3,07
6,95
6,73
6,54
Date
pH
Inside reactor
Cond
DO
(mS/cm)
(mg/l)
1,60
1,90
0,93
2,50
0,86
1,05
0,86
0,70
1,04
0,80
1,11
0,74
3,80
0,83
2,83
1,40
29/04/2010
03/05/2010
21/05/2010
24/05/2010
26/05/2010
27/05/2010
1,05
1,3
1,0
1,55
0,80
0,58
1,96
29,2
8,00
1,90
26,2
26
26
7,03
6,96
-
1,30
0,79
-
0,57
1,1
0,82
0,908
0,80
1,10
0,77
V
Remark
Decreased aeration
Increased aeration
Decreased aeration
Decreased aeration
Inflow rate was too low. Increased
inflow rate. Changed position
stirrers.
Decrease aeration (1,77->0,80).
Increase aeration
Decrease aeration
Increased aeration. Cleaned pipes.
Decreased aeration
New DO-meter for measurement.
Calibrated pH-meter.
Parameters checked before new
inflow. Problem with DO, not
evenly distributed. (high close to
the aeration (>2,5mg/l)). Changed
many times.
Increased aeration. Added 28
rings.
Decreased aeration (1,40->1,05).
Decreased inflow (2,85ml/min ->
2,57 ml/min)
Decreased aeration. Inflow rate
was slightly lower.
Inflow rate was too low.
Increased aeration
Andrea Bertino
TRITA Degree Project Thesis
Table 4A – TSS & VSS as biofilm on the carriers (filtered 1.6 µm)
Date
Biocarriers
Empty plate
+ filter (g)
After 105
°C (g)
After 550
°C (g)
TSS
(mg/ring)
VSS
(mg/ring)
Ash
(%)
23/03/2010
4
1,0604
1,1104
1,0618
12,50
12,15
2,80%
01/04/2010
4
1,0606
1,1106
1,0617
12,50
12,23
2,20%
06/04/2010
4
0,8887
0,9392
0,8905
12,63
12,18
3,56%
16/04/2010
4
0,8984
0,948
0,9002
12,40
11,95
3,63%
23/04/2010
4
0,8918
0,9421
0,8935
12,58
12,15
3,38%
29/04/2010
4
0,8908
0,9565
0,8925
16,43
16,00
2,59%
05/05/2010
4
0,8987
0,9492
0,9004
12,63
12,20
3,37%
21/05/2010
4
0,9020
0,9493
0,9059
11,83
10,85
8,25%
Table 5A – TSS & VSS in the activated sludge (filtered 1.6 µm)
Date
Sample
Volume (ml)
Empty plate
+ filter (g)
After 105
C (g)
After 550
C (g)
TSS
(mg/l)
VSS
(mg/l)
Ash
(%)
21/05/2010
61
20
1,0696
1,0877
1,0721
905,0
780,0
SAA tests
200
200
150
y = 1,5229x + 35,586
R² = 0,9764
P (atm∙10 -3 )
250
P (atm∙10-3 )
250
150
100
y = 0,9616x + 29,457
R² = 0,9904
50
y = 1,5629x + 33,386
R² = 0,9501
100
50
0
0
0
30
60
90
120
0
30
Time (min)
60
90
120
Time (min)
Fig. 2A – 25 March 2010 (35°C)
Fig. 3A – 1 April 2010 (35°C)
250
250
y = 1,3919x + 81,406
R² = 0,7691
y = 1,4301x + 46,84
R² = 0,8771
200
P (atm∙10 -3 )
P (atm∙10-3 )
200
150
150
y = 1,3236x + 44,464
R² = 0,9613
100
y = 1,521x + 30,499
R² = 0,9315
100
50
50
0
0
0
30
60
90
0
120
30
60
90
Time (min)
Time (min)
Fig. 4A – 8 April 2010 (35°C)
Fig. 5A – 15 April 2010 (35°C)
VI
120
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
250
y = 1,5958x + 49,513
R² = 0,9587
200
200
P (atm∙10 -3 )
y = 1,2064x + 60,88
R² = 0,9046
150
100
y = 1,5086x + 42,261
R² = 0,9788
P (atm∙10-3 )
250
150
y = 1,3692x + 38,843
R² = 0,9878
100
y = 1,2622x + 60,601
R² = 0,9259
y = 1,4563x + 32,358
R² = 0,9939
50
50
0
0
0
30
60
90
0
120
30
60
90
120
Time (min)
Time (min)
Fig. 6A – 21 April 2010 (35°C)
250
Fig. 7A – 29 April 2010 (35°C)
250
y = 1,6135x + 58,221
R² = 0,8803
y = 1,7185x + 67,265
R² = 0,8987
200
y = 1,6386x + 64,933
R² = 0,9272
150
100
y = 1,6517x + 63,195
R² = 0,9147
P (atm∙10 -3 )
P (atm∙10 -3 )
200
150
100
y = 1,673x + 57,729
R² = 0,9111
50
50
0
0
0
30
60
90
120
0
30
60
Time (min)
90
120
Time (min)
Fig. 8A – 7 May 2010 (35°C)
Fig. 9A – 12 May 2010 (35°C)
250
250
200
200
150
y = 1,5133x + 23,571
R² = 0,9948
P (atm∙10 -3 )
P (atm∙10 -3 )
y = 1,4802x + 69,458
R² = 0,9633
150
100
y = 1,4348x + 25,245
R² = 0,996
100
y = 1,5761x + 61,578
R² = 0,9721
50
y = 1,318x + 26,291
R² = 0,9958
50
0
0
0
30
60
90
120
0
30
60
Time (min)
90
Time (min)
Fig. 10A – 19 May 2010 (35°C)
Fig. 11A – 28 May 2010 (35°C)
Table 6A – SAA results
Date
SAA (35°C)
(gN/m2/d)
Date
SAA (35°C)
(gN/m2/d)
25/03/2010
2,844
29/04/2010
4,273
01/04/2010
4,563
07/05/2010
4,855
08/04/2010
4,015
12/05/2010
4,407
15/04/2010
4,364
19/05/2010
4,519
21/04/2010
4,007
28/05/2010
4,206
VII
120
Andrea Bertino
TRITA Degree Project Thesis 09:11
A PPENDIX III – D A TA FROM LAB - SCALE REACTOR TREATI NG EFFLUENT
FROM ANAEROBIC TREAT MENT WITH UASB
Table 7A – Chemical analyses on the inflow to the reactor
Date
Alkalinity
(mmol/l)
(0,45μm)
NH4-N
(mg/l)
(0,45μm)
TOT-P
(mg/l)
unfiltr
COD
(mg/l)
(0,45μm)
COD
(mg/l)
unfiltr
N load
(gN/m2/d)
11/05/2010
5,83
44,6
3,45
52,5
107
0,1897
18/05/2010
-
40,3
-
-
-
0,1714
20/05/2010
5,23
40,7
4,98
57,6
59,8
0,1731
21/05/2010
-
42,6
-
-
-
0,1812
26/05/2010
5,83
49,3
5,79
55,9
63
0,2096
03/06/2010
5,33
43
5,7
52,3
70
0,1829
10/06/2010
5,59
41,8
5,6
50,6
126
0,1777
24/06/2010
5,72
40,8
5,8
49,7
98,5
0,1735
01/07/2010
6
48,2
5,4
55,3
106,5
0,2050
15/07/2010
5,93
46
5,07
-
-
0,1956
Table 8A – Chemical analyses on the outflow from the reactor
Date
Alkalinity
(mmol/l)
(0,45μm)
NH4-N
(mg/l)
(0,45μm)
NO2-N
(mg/l)
(0,45μm)
NO3-N
(mg/l)
(0,45μm)
TOT-P
(mg/l)
unfiltr.
COD
(mg/l)
(0,45μm)
COD
(mg/l)
unfiltr
Ninorg
removal
(gN/m2/d)
21/05/2010
3,35
27/05/2010
2,82
14,5
0,32
1,71
5,32
42,4
33,6
0,1068
7,26
0,304
1,92
5,35
54,2
-
0,1693
04/06/2010
11/06/2010
1,46
0,042
0,016
21,7
5,1
47,3
49
0,0903
1,86
0,811
0,034
7,01
4,78
48,2
120
0,1443
25/06/2010
1,6
0,552
0
10,4
7,69
48,9
125
0,1269
02/07/2010
0,7
0
0
5,6
5
45
98
0,1812
16/07/2010
1,2
1,05
0
8,4
4,43
-
-
0,1554
VIII
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 9A – Physical parameters
Flow
Date
HRT
Influent
Cond
pH
(mS/cm)
Temp
(°C)
Effluent
Cond
pH
(mS/cm)
Remarks
(ml/min)
(days)
12/05/2010
4,56
1,0264
7,52
0,700
7,33
0,700
0,75
26
7,68
0,690
13/05/2010
4,70
0,9959
7,5
0,690
7,32
0,680
0,98
26,4
7,53
0,690
18/05/2010
3,83
1,22
7,76
0,720
7,26
0,630
7,17
0,771
6,93
0,559
1,19
25,4
7,46
0,626
Flow was too low. Some rings were floating.
21/05/2010
4,68
1,00
7,43
0,802
7,12
7,61
0,800
7,25
0,637
0,66
27,2
7,61
0,626
Calibrated pH meter. Flow OK.
24/05/2010
7,5
0,760
7,20
0,590
0,55
25,2
2,27
0,620
26/05/2010
7,72
0,800
7,17
0,570
0,35
24,7
7,37
0,600
0,803
7,10
0,602
0,49
24,4
7,71
-
25,5
7,48
0,591
27/05/2010
31/05/2010
4,83
0,9684
4,93
0,9488
01/06/2010
02/06/2010
04/06/2010
4,6
1,0175
1,05
Increase pump
8,13
0,803
7,23
0,567
8,13
0,795
7,36
0,572
0,59
25,9
-
-
8,13
0,796
7,28
0,575
0,75
24,1
7,70
0,571
Calibrated pH meter. Decreased inflow rate
0,792
7,11
0,581
1,06
26,8
7,39
0,587
Increased inflow rate. Calibrated pH-meter.
0,780
7,19
0,581
26,7
7,66
0,570
Decreased inflow (because no inflow from the line 3).
26,9
-
-
8,28
8,32
8
07/06/2010
pH
Inside reactor
Cond
DO
(mS/cm)
(mg/l)
8,12
0,56
0,42
0,48
3,20
Calibrated pH meter. Decreased inflow rate.
Inflow stopped for 2h. Refilled tank. Changed stirrer.
08/06/2010
4.68
1,0001
7,47
0,765
7,20
0,587
10/06/2010
5,03
0,9299
7,85
0,764
7,29
0,577
0,59
25,6
7,77
0,582
7,77
0,770
7,53
0,600
0,75
25,4
7,74
0,590
8,03
0,774
7,86
0,777
7,40
0,555
-
25,2
-
-
Good mixing. DO inflow 0,95.
7,40
0,530
29,2
-
-
Inflow was finished. Filter was turned upside-down. Good
mixing. DO too high! Added 22 rings and took 14 out. Added
1-1,5 l new inflow in the reactor. Inflow too low. Increased
inflow rate.
12/06/2010
15/06/2010
4,68
1,0001
20/06/2010
4,17
1,1233
21/06/2010
-
23/06/2010
-
-
0,57
4,00
8,03
0,774
0,70
-
7,96
0,783
7,10
0,498
0,55
29,3
7,09
0,500
-
8,03
0,792
7,53
0,559
0,98
29,4
7,43
0,563
IX
Decrease T. Now inflow again (h 19). New inflow from line3.
Decreased pump
Andrea Bertino
24/06/2010
-
-
7,76
25/06/2010
4,93
0,9488
27/06/2010
5,27
0,8887
29/06/2010
4,64
1,0087
7,94
01/07/2010
-
-
02/07/2010
-
13/07/2010
TRITA Degree Project Thesis 09:11
0,753
7,21
0,526
0,67
29,3
7,20
0,557
7,36
0,535
0,87
29,1
7,89
0,542
Decreased T. Decreased inflow rate. New inflow very clear.
6,67
0,602
28,5
7,19
0,596
Decreased T. DO in the inflow tank about 1,90 mg/l. Changed
membrane for DO-meter. Decreased pump.
0,773
7,40
0,593
1,01
28,9
7,35
0,600
Decrease pump. HRT is after having set the pump.
7,85
0,781
7,37
0,557
0,57
28,4
7,4
0,560
-
7,65
0,754
7,42
0,493
0,79
28,1
7,45
0,500
Stopped heater.
4,62
1,0131
7,2
0,756
6,83
0,335
1,21
26,5
6,9
0,350
Increase pump. HRT is after having set the pump. No inflow
since a couple of days.
15/07/2010
-
-
7,86
0,779
7,31
0,547
0,8
25,8
7,34
0,600
16/07/2010
-
-
7,79
0,776
7,38
0,567
0,7
25,7
7,4
0,598
8,17
0,770
8,11
0,767
-
3,40
-
Decrease inflow rate
Table 10A – TSS & VSS as biofilm on the carriers (filtered 1.6 µm)
Date
Biocarriers
Empty plate
+ filter (g)
After 105
°C (g)
After 550
°C (g)
TSS
(mg/ring)
VSS
(mg/ring)
21/05/2010
4
0,8981
0,9434
0,9021
11,33
10,33
8,83%
01/06/2010
4
1,6760
1,7182
1,6850
10,55
8,30
21,33%
25/06/2010
4
1,7048
1,7492
1,7076
11,10
10,40
6,31%
02/07/2010
4
1,7013
1,7352
1,7049
8,48
7,58
10,62%
16/07/2010
4
1,7019
1,7443
1,7059
10,60
9,60
9,43%
Ash (%)
Table 11A – TSS & VSS in the activated sludge (filtered 1.6 µm)
Table 12A – SAA results
SAA (35°C)
Date
(gN/m2/d)
12/05/2010
5,726
19/05/2010
4,058
28/05/2010
3,815
23/06/2010
4,015
Date
Sample
Volume (ml)
Empty plate
+ filter (g)
After 105
C (g)
After 550
C (g)
TSS
(mg/l)
VSS
(mg/l)
Ash (%)
01/06/2010
80
1,7038
1,7071
1,7042
41,25
36,25
12,12%
25/06/2010
100
1,6698
1,6817
1,6714
119,00
103,00
13,45%
02/07/2010
50
1,6650
1,6718
1,6662
136,00
112,00
17,65%
01/07/2010
3,687
16/07/2010
50
1,6657
1,6729
1,6673
144,00
112,00
22,22%
15/07/2010
3,420
X
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
SAA tests
y = 2,1469x + 43,76
R² = 0,9534
200
y = 1,5307x + 75,595
R² = 0,9772
150
y = 1,7783x + 52,245
R² = 0,974
y = 1,2134x + 90,867
R² = 0,951
100
100
y = 1,8829x + 51,14
R² = 0,7817
50
0
0
30
60
90
y = 2,4844x + 42,133
R² = 0,9995
0
0
30
60
90
120
Fig. 13A – 19 May 2010 (35°C)
30
y = 1,3696x + 16,807
R² = 0,9869
100
y = 1,2009x + 19,736
R² = 0,9992
150
150
y = 1,2553x + 25,105
R² = 0,9348
100
100
y = 1,2064x + 25,593
R² = 0,9331
y = 1,1552x + 20,353
R² = 0,9836
50
y = 1,2222x + 15,184
R² = 0,9772
0
0
90
Time (min)
Fig. 15A – 23 June 2010 (35°C)
120
120
y = 1,0917x + 27,028
R² = 0,9533
y = 1,2779x + 22,316
R² = 0,9562
0
90
200
50
y = 1,5021x + 18,55
R² = 0,9721
60
Fig. 14A – 28 May 2010 (35°C)
P (atm∙10 -3 )
P (atm∙10 -3 )
150
60
0
Time (min)
200
30
y = 1,3407x + 19,526
R² = 0,9884
Time (min)
200
0
y = 1,2221x + 25,245
R² = 0,9933
0
120
y = 1,4558x + 19,875
R² = 0,9835
100
50
Fig. 12A – 12 May 2010 (35°C)
50
150
50
Time (min)
P (atm∙10 -3 )
P (atm∙10 -3 )
150
200
P (atm∙10 -3 )
P (atm∙10 -3 )
200
0
30
60
90
Time (min)
Fig. 16A – 1 July (35°C)
XI
120
0
30
60
90
Time (min)
Fig. 17A – 15 July 2010 (35°C)
120
Andrea Bertino
TRITA Degree Project Thesis 09:11
A PPENDIX IV –D A TA FROM PILOT PLANT - SCALE REACTOR
Table 13A – TSS & VSS in the influent reject water (filtered 1.6 µm)
Date
Sample
Volume
(ml)
Al plate +
filter (g)
After
105°C (g)
After
550°C (g)
TSS
(mg/l)
VSS
(mg/l)
Ash (%)
01/06/2010
30
1,7450
1,7591
1,7451
470,0
466,7
0,71%
27/06/2010
50
1,6663
1,6875
1,6671
424,0
408,0
3,77%
16/07/2010
35
1,6672
1,6856
1,6684
525,7
491,4
6,52%
22/07/2010
25
1,6636
1,6687
1,6637
204,0
200,0
1,96%
31/07/2010
25
1,6827
1,6946
1,6838
476,0
432,0
9,24%
06/08/2010
17
1,6864
1,7222
1,6968
2105,9
1494,1
29,05%
12/08/2010
22
1,6862
1,6901
1,6867
178,9
155,0
13,32%
20/08/2010
40
1,6862
1,6912
1,6866
125,9
115,3
8,42%
28/08/2010
35
1,6848
1,6919
1,6852
203,9
191,8
5,93%
10/09/2010
45
1,6851
1,6914
1,6858
140,8
124,7
11,42%
24/09/2010
20
1,6857
1,6900
1,6858
216,8
210,6
2,84%
Table 14A – TSS & VSS in the influent reject water (filtered 0.45 µm)
Date
Sample
Volume
(ml)
Al plate +
filter (g)
After
105°C (g)
After 550
°C (g)
TSS
(mg/l)
VSS
(mg/l)
Ash (%)
31/07/2010
10
1,6603
1,6664
-
610,0
-
-
06/08/2010
8
1,6604
1,6792
-
2350,0
-
-
12/08/2010
10
1,6654
1,6674
-
195,2
-
-
20/08/2010
9
1,6672
1,6700
-
305,9
-
-
28/08/2010
9
1,6617
1,6655
-
416,7
-
-
10/09/2010
7
1,6657
1,6686
-
407,5
-
-
Table 15A – TSS & VSS as biofilm on the carriers (filtered 1.6 µm)
Date
Biocarriers
Empty
plate +
filter (g)
After
105 °C
(g)
After
550 °C
(g)
TSS
(mg/ring)
VSS
(mg/ring)
Ash (%)
01/06/2010
4
1,7335
1,8012
1,734
16,9
16,8
0,74%
27/06/2010
4
1,6623
1,7375
1,6746
18,8
15,7
16,36%
16/07/2010
4
1,662
1,7324
1,6732
17,6
14,8
15,91%
22/07/2010
4
1,6627
1,7343
1,6739
17,9
15,1
15,64%
31/07/2010
4
1,7557
1,8353
1,7672
19,9
17,0
14,45%
06/08/2010
4
1,7337
1,8141
1,7419
20,1
18,0
10,16%
12/08/2010
4
1,7242
1,8152
1,7378
22,7
19,3
14,91%
20/08/2010
4
1,7307
1,8162
1,7454
21,4
17,7
17,16%
28/08/2010
4
1,7191
1,8125
1,7329
23,3
19,9
14,74%
10/09/2010
4
1,7263
1,8208
1,7371
23,6
20,9
11,39%
24/09/2010
4
1,7199
1,8129
1,7350
23,2
19,5
16,20%
XII
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 16A – TSS & VSS in the activated sludge (filtered 1.6 µm)
Date
Sample
Volume
(ml)
Empty
plate +
filter (g)
After
105 C
(g)
After
550 C
(g)
TSS
(mg/l)
VSS
(mg/l)
Ash (%)
02/06/2010
35
1,7382
1,7484
1,7437
291,4
134,3
53,92%
27/06/2010
50
1,6783
1,6938
1,6807
310,0
262,0
15,48%
16/07/2010
20
1,6800
1,6891
1,6815
456,7
380,6
16,68%
22/07/2010
25
1,6796
1,6870
1,6810
297,4
240,5
19,14%
31/07/2010
25
1,6788
1,6875
1,6805
349,4
280,6
19,69%
06/08/2010
25
1,6818
1,6895
1,6830
309,4
260,5
15,79%
12/08/2010
27
1,6811
1,6892
1,6823
301,3
256,1
15,01%
20/08/2010
25
1,7167
1,7237
1,7177
281,6
239,7
14,87%
28/08/2010
25
1,7163
1,7257
1,7176
377,6
323,7
14,26%
10/09/2010
26
1,6631
1,6726
1,6643
366,6
320,2
12,67%
25
1,7031
1,7118
1,7044
349,5
296,0
15,30%
averages on 5 measures on activated sludge
for batch test (OUR, NUR) carried out on 27th
Sept.
320,2
287,3
10,26%
Ash (%)
24/09/2010
27/09/2010
Table 17A – TSS & VSS in the activated sludge (filtered 0.45 µm)
Date
Sample
Volume
(ml)
Empty
plate +
filter (g)
After
105 C
(g)
After
550 C
(g)
TSS
(mg/l)
VSS
(mg/l)
27/06/2010
20
1,6579
1,6622
-
217,4
-
31/07/2010
15
1,7004
1,7058
-
360,0
-
06/08/2010
15
1,6495
1,6546
-
342,9
-
12/08/2010
15
1,6500
1,6550
-
336,2
-
20/08/2010
15
1,6536
1,6577
-
276,3
-
28/08/2010
12
1,6522
1,6573
-
428,7
-
10/09/2010
12
1,6654
1,6699
-
371,1
-
24/09/2010
13
1,6587
1,6618
-
242,1
XIII
Andrea Bertino
TRITA Degree Project Thesis 09:11
Table 18A – Chemical analyses on the reject water in inflow to Pilot Plant scale reactor
Date
Flow
(ml/min)
Alkalinity
(mmol/l)
(0.45μm)
COD
(mg/l)
(0.45μm)
COD
(mg/l)
(1.6
μm)
COD
(mg/l)
unfilt
27/05/2010
70
74,9
836
1011
02/06/2010
70
63,4
791
10/06/2010
70
70,6
16/06/2010
100
23/06/2010
28/06/2010
NH4+-N
(mg/l)
(0.45μm)
NO2--N
(mg/l)
(0.45μm)
NO3--N
(mg/l)
(0.45μm)
Ninorg
N load
(gN/m2/d)
-
1050
0
0
1050,0
2,6460
-
-
1060
0
0
1060,0
2,6712
1103
8,38
-
1010
-
-
1010,0
2,5452
-
1286
-
970
965
0,084
1,62
966,7
3,4802
650
-
1110
8,35
1094
960
0,084
1,62
961,7
3,4622
535
-
1015
-
-
940
0,084
1,62
941,7
3,3901
68,0
668
-
1074
-
913
874
0,084
1,62
875,7
3,3417
100
71,1
634
-
1429
-
-
945
0,084
1,62
946,8
3,4084
29/07/2010
106,7
70,1
546
-
1313
1,63
11,2
916
1030
884
0,084
1,62
885,7
3,4011
04/08/2010
106,7
67,9
503
-
1007
-
-
913
-
875,5
0,084
1,63
877,2
3,3685
06/08/2010
103,0
73,2
496
-
1840
-
-
947
1155
917
0,032
1,84
918,9
3,4073
10/08/2010
105,3
71,6
-
-
863
-
892
0,032
1,84
893,9
3,3896
18/08/2010
107,5
70,1
-
-
947
-
880
0,032
1,84
881,9
3,4128
24/08/2010
93,3
81,8
-
-
-
-
1010
0,113
2,37
1012,5
3,4020
26/08/2010
94,8
80,3
01/09/2010
94,0
07/09/2010
96,0
10/09/2010
91,7
14/09/2010
99,8
23/09/2010
100,0
24/09/2010
89,0
TOT-P
(mg/l)
unfilt
TN
(mg/L)
(0.45μm)
1452
-
872
1359
567
-
75,0
667
100
77,0
100
88,8
13/07/2010
66
21/07/2010
73,7
528
-
2146
TOT-P
(mg/l)
(0.45μm)
TN
(mg/L)
unfilt
501
-
967
-
-
1100
1243
1003,6
0,113
2,37
1006,1
3,4348
632
-
1012
-
-
-
-
1005,0
0,113
2,37
1007,5
3,4093
814
-
966
-
-
-
-
1006,0
0,113
2,37
1008,5
3,4855
-
-
-
948,2
0,113
2,37
950,7
3,4168
1095
0,011
2,15
1097,2
3,9498
1085
0,011
2,15
1087,2
3,4833
1082,4
73,3
84
507
505
-
946
-
-
976,8
1020
1130
XIV
-
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 19A – Chemical analyses on the outflow from Pilot Plant scale reactor
Date
Flow
(ml/min)
Alkalinity
(mmol/l)
(0.45μm)
COD
(mg/l)
(0.45μm)
COD
(mg/l)
(1.6
μm)
COD
(mg/l)
unfilt
TOT-P
(mg/l)
(0.45μm)
TOT-P
(mg/l)
unfilt
TN
(mg/L)
(0.45μm)
TN
(mg/L)
unfilt
NH4+-N
(mg/l)
(0.45μm)
NO2--N
(mg/l)
(0.45μm)
NO3--N
(mg/l)
(0.45μm)
Ninorg
N
removal
(gN/m2/d)
01/06/2010
70
8,62
419
509
616
-
-
-
-
59,5
11,50
81,3
152,3
2,2622
04/06/2010
70
-
-
-
-
-
-
-
30,9
8,54
144,0
183,4
2,2089
08/06/2010
70
7,72
-
-
-
-
-
-
44,8
7,58
101,0
153,4
2,2847
11/06/2010
70
-
-
-
-
-
-
-
44,5
5,42
106,2
156,1
2,1518
15/06/2010
100
7,65
-
778
-
-
-
-
78,0
7,78
128,0
213,8
2,8664
18/06/2010
100
-
-
-
-
-
-
-
81,0
6,89
125,0
212,9
2,7137
22/06/2010
100
7,32
-
760
-
52,5
5,32
135,0
192,8
2,7860
25/06/2010
100
-
-
-
-
8,78
-
630,0
46,7
6,38
158,0
211,1
2,7023
30/06/2010
100
4,32
-
514
-
-
-
-
60,5
7,30
144,0
211,8
2,6277
05/07/2010
100
-
-
-
-
-
-
-
50,2
3,80
140,0
194,0
2,6917
15/07/2010
106
2,00
-
469
-
-
162,0
-
75,5
2,76
87,6
165,9
2,5554
16/07/2010
106
-
-
-
-
-
-
-
64,3
5,56
91,2
161,1
2,5727
20/07/2010
106
6,32
-
609
-
-
164,4
-
73,4
7,70
106,6
187,7
2,6254
23/07/2010
100
-
-
-
-
-
-
-
79,5
8,88
125,8
214,2
2,7956
27/07/2010
100
5,65
-
670
0,735
5,57
183,4
202,4
48,3
7,59
93,5
149,4
2,8706
31/07/2010
113,3
-
-
-
-
-
-
-
94,2
8,58
66,5
169,3
2,7511
02/08/2010
113,3
9,75
313
-
595
-
-
233,4
390,0
90,9
8,28
73,8
173,0
2,9080
06/08/2010
103,0
-
326
-
631
-
-
-
-
58,0
8,04
68,0
134,0
2,8538
12/08/2010
105,0
8,52
384
-
603
-
-
195,5
232,5
97,2
8,25
91,5
197,0
2,6428
16/08/2010
105,0
-
-
-
-
-
-
-
89,1
8,52
75,0
172,6
2,7264
20/08/2010
107,5
9,06
333
-
641
-
-
186,9
-
90,9
8,16
64,8
163,9
2,7787
28/08/2010
94,2
3,98
363
-
785
-
-
206,0
226,8
49,2
7,96
106,8
164,0
2,8548
30/08/2010
94,2
-
-
-
-
-
-
-
73,2
7,96
90,8
172,0
2,8277
08/09/2010
96,0
10,95
-
580
-
-
-
-
84,8
6,81
88,1
179,7
2,8644
10/09/2010
91,7
8,43
84,6
7,23
77,7
169,5
2,7687
298
254
333
383
364
321
409
-
-
193,5
XV
Andrea Bertino
14/09/2010
99,8
16/09/2010
99,8
23/09/2010
100,0
26/09/2010
88,3
7,23
398
4,81
377
TRITA Degree Project Thesis 09:11
-
-
645
-
749
-
-
207,0
-
194,4
79,2
5,23
72,1
156,5
2,8542
66,0
9,64
88,8
164,4
3,3578
58,5
7,80
102,9
169,2
2,9169
Table 20A – Physical paramenters – daily average from on-line measurements on Pilot Plant scale reactor
Inflow
Flow
(ml/min)
Flow
(l/day)
HRT
(days)
27/05/2010
70
100,8
28/05/2010
70
29/05/2010
70
30/05/2010
Date
Inside Reactor
Remarks
ORP
(mV)
Cond
(mS/cm)
pH
DO
(mg/L)
ORP
(mV)
Cond
(mS/cm)
T (°C)
1,65
-500,9
10,005
8,46
2,5
60,8
4,145
25,2
100,8
1,65
-496,1
9,956
8,51
2,5
61,8
4,209
25,2
100,8
1,65
-532,5
9,900
8,45
2,5
57,9
3,951
25,2
70
100,8
1,65
-530,9
9,884
8,35
2,5
44,1
3,575
25,2
31/05/2010
70
100,8
1,65
-491,4
9,805
8,25
2,5
34,4
3,152
25,2
01/06/2010
70
100,8
1,65
-462,1
9,609
7,64
2,5
47,9
1,749
25,2
02/06/2010
70
100,8
1,65
-400,9
9,479
7,41
2,5
50,3
1,760
25,2
03/06/2010
70
100,8
1,65
-507,2
9,468
7,44
2,5
39,6
1,794
25,2
04/06/2010
70
100,8
1,65
-458,0
9,371
7,18
2,5
55,5
1,801
25,2
05/06/2010
70
100,8
1,65
2,5
25,2
06/06/2010
70
100,8
1,65
2,5
25,2
07/06/2010
70
100,8
1,65
-338,0
9,053
6,95
2,35
112,9
1,992
25,01
08/06/2010
70
100,8
1,65
-496,0
8,723
6,98
2,37
104,2
1,974
24,99
09/06/2010
70
100,8
1,65
-546,7
8,235
6,96
2,39
98,6
1,935
25,00
10/06/2010
70
100,8
1,65
11/06/2010
70
100,8
1,65
12/06/2010
70
100,8
1,65
pH
DO set point (2,5 mg/l) controlled manually.
Calibration pH-meter, redox-meter (INflow and Reactor), conductivity meter (IN and R). DO set point (2,5 mg/l) controlled manually.
DO set point (2,5 mg/l) controlled manually.
DO controlled automatically. DO set point 2,4 mg/l. Installed on-line
measurement for T.
New reject water. Calibration pH-meter, redox-meter (IN and R),
conductivity meter (IN and R).
8,37
XVI
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
13/06/2010
100
144
1,15
DO set point 2,0 mg/l
14/06/2010
100
144
1,15
DO set point 1,4 mg/l
15/06/2010
100
144
1,15
-223,0
8,797
7,34
1,39
75,4
1,945
25,05
16/06/2010
100
144
1,15
-224,3
8,755
7,23
1,93
127,0
1,840
25,01
17/06/2010
100
144
1,15
-299,4
8,738
6,93
2,55
159,6
1,833
24,97
18/06/2010
100
144
1,15
-376,4
8,719
6,81
2,55
167,8
1,928
25,00
19/06/2010
100
144
1,15
-497,8
8,691
6,77
2,55
152,8
1,997
24,98
20/06/2010
100
144
1,15
-515,2
8,694
6,76
2,48
139,6
2,045
24,99
21/06/2010
100
144
1,15
-302,1
8,387
7,04
1,53
53,5
2,081
24,98
Calibrationd DO-meter. DO set point 1,5 mg/l
22/06/2010
100
144
1,15
-409,6
8,500
7,35
1,62
60,5
2,079
24,99
DO set point 2,0 mg/l. Calibration Redox (IN), Cleaning conductivity meter (IN and R), pH-meter, redox-meter (R).
23/06/2010
100
144
1,15
-462,3
8,542
7,00
2,02
93,8
1,855
24,97
24/06/2010
100
144
1,15
-532,7
8,522
6,97
2,00
99,2
1,876
24,97
25/06/2010
100
144
1,15
-524,2
8,506
7,00
2,02
97,8
1,894
24,95
26/06/2010
100
144
1,15
-527,1
8,493
7,02
2,01
98,7
1,894
24,98
27/06/2010
100
144
1,15
-445,9
8,435
7,01
2,01
117,8
1,872
24,96
28/06/2010
100
144
1,15
-495,5
8,362
7,11
2,01
106,8
1,860
24,93
29/06/2010
100
144
1,15
-528,7
8,383
7,32
1,98
97,0
1,846
24,92
30/06/2010
100
144
1,15
-522,5
8,360
7,32
1,98
97,9
1,810
24,91
01/07/2010
100
144
1,15
-531,3
8,251
7,30
2,00
94,4
1,779
24,96
02/07/2010
100
144
1,15
-517,1
8,143
7,16
1,60
94,9
1,699
24,93
03/07/2010
100
144
1,15
-526,1
8,113
6,92
0,96
118,9
1,540
24,92
04/07/2010
100
144
1,15
-393,2
7,543
6,96
0,95
134,8
1,507
24,93
05/07/2010
100
144
1,15
-477,6
6,530
7,23
0,92
150,1
1,511
24,93
06/07/2010
100
144
1,15
-355,2
7,206
7,21
1,09
98,2
1,512
24,94
07/07/2010
106
152,6
1,09
-515,1
8,552
6,95
1,99
129,2
1,782
24,93
08/07/2010
106
152,6
1,09
-544,5
8,554
6,60
2,00
135,1
1,823
24,92
XVII
DO set point 2.3 mg/l
Calibration pH-meter, DO-meter, redox-meter (IN and R), conductivity-meter (IN and R). Increased pH probably due to anoxic
period (25 min) during DO calibration.
Add water in reject water (until 5/7). Decreased DO set point to 1
mg/l
New reject water. DO set back to 2mg/l. Calibration conductivity.meter (R).
Andrea Bertino
TRITA Degree Project Thesis 09:11
09/07/2010
106
152,6
1,09
-548,2
8,728
6,47
1,88
94,6
1,888
24,92
10/07/2010
106
152,6
1,09
-555,1
9,167
6,54
1,77
87,6
1,869
24,87
11/07/2010
106
152,6
1,09
-559,6
9,718
6,75
1,75
67,2
1,838
24,89
12/07/2010
106
152,6
1,09
-558,8
9,924
7,04
1,73
52,8
1,822
24,84
13/07/2010
66
95,04
1,75
9,596
6,48
1,75
92,0
1,712
24,89
14/07/2010
106
152,6
1,09
-491,9
8,759
6,91
1,74
59,7
1,713
24,86
15/07/2010
106
1,09
-497,9
8,834
6,83
1,77
60,3
1,650
24,85
16/07/2010
-465,6
8,747
7,17
1,78
36,2
1,762
24,89
17/07/2010
-485,9
8,690
7,73
1,77
10,0
2,105
24,90
18/07/2010
-438,0
8,646
7,94
1,77
0,9
2,241
24,91
152,6
DO set point 1.8 mg/l.
Inflow pipe was block since 8.30 until 17.30. pH dropped down to
5,22 and redox increased up to 215mV.
Calibration pH-meter, redox-meter (R), conductivity-meter (R).
Cleaning conductivity meter (IN), Redox-meter (IN) and DO-meter.
19/07/2010
106
152,6
1,09
-452,8
8,589
7,89
2,21
17,1
2,051
24,90
DO setpoint 2,5 mg/L
20/07/2010
100
144
1,15
-477,0
8,743
7,70
2,49
38,3
1,863
24,90
New reject water.
21/07/2010
100
144
1,15
-550,2
8,854
7,53
2,47
49,7
1,766
24,90
22/07/2010
100
144
1,15
-542,6
8,993
7,45
2,49
52,6
1,738
24,91
23/07/2010
100
144
1,15
-532,6
8,945
7,50
2,50
35,8
1,732
24,96
24/07/2010
100,0
144
1,15
-537,9
9,032
7,48
2,50
37,8
1,681
24,98
25/07/2010
100,0
144
1,15
-504,2
9,036
7,55
2,51
36,6
1,666
24,97
26/07/2010
100,0
144
1,15
-471,5
9,055
7,62
2,51
36,1
1,691
25,00
27/07/2010
100,0
144
1,15
-398,8
8,971
7,66
2,52
37,1
1,708
24,92
28/07/2010
100,0
144
1,15
-510,9
8,787
7,66
2,50
22,3
1,753
24,97
29/07/2010
106,7
153,6
1,08
-414,7
8,683
7,67
2,51
23,7
1,733
24,96
30/07/2010
106,7
153,6
1,08
-356,3
8,454
7,76
2,53
14,1
1,856
24,77
31/07/2010
113,3
163,2
1,02
-374,0
8,332
7,80
-2,1
1,976
01/08/2010
113,3
163,2
1,02
02/08/2010
113,3
163,2
1,02
-365,5
8,882
7,83
2,54
-1,3
2,233
24,78
03/08/2010
113,3
163,2
1,02
-375,3
8,934
7,84
2,54
1,2
2,287
24,99
8,38
8,41
XVIII
Calibration pH-meter, redox-meter (IN and R). Cleaning conductivity-meter (IN and R).
Calibration redox-meter (IN).
Calibration pH-meter, DO-meter.
Calibration conductivity-meter (R), redox-meter (IN and R). Cleaning pH-meter.
Single data because automatic data capture was off.
Calibration pH-meter, DO-meter, conductivity-meter (IN). Cleaning
redox-meter (IN and R).
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
04/08/2010
106,7
153,6
1,08
-401,7
8,960
7,82
2,49
5,9
2,328
24,93
05/08/2010
106,7
153,6
1,08
-421,5
8,619
7,74
2,52
11,3
2,152
24,86
06/08/2010
103,0
148,3
1,12
-387,0
8,775
7,64
2,51
24,9
1,901
24,85
07/08/2010
103,0
148,3
1,12
-331,8
9,443
7,69
2,54
22,1
2,000
24,97
08/08/2010
103,0
148,3
1,12
7,24
2,57
133,0
1,416
24,68
09/08/2010
103,2
148,6
1,12
9,677
7,45
2,53
100,4
1,716
23,05
10/08/2010
105,3
151,7
1,09
-467,0
9,635
7,71
2,53
6,3
2,155
24,98
11/08/2010
105,3
151,7
1,09
-492,4
9,631
7,65
2,53
3,7
2,087
24,95
12/08/2010
105,0
151,2
1,10
-540,5
9,594
7,68
2,51
1,7
2,153
24,93
13/08/2010
105,0
151,2
1,10
23,2
9,626
7,72
2,51
5,2
2,314
24,91
14/08/2010
105,0
151,2
1,10
-536,5
9,638
7,71
2,50
1,1
2,318
24,92
15/08/2010
105,0
151,2
1,10
-546,0
9,612
7,71
2,49
0,2
2,320
24,91
16/08/2010
105,0
151,2
1,10
-561,1
9,568
7,69
2,49
1,6
2,245
24,95
17/08/2010
105,0
151,2
1,10
-525,4
9,465
7,83
2,48
-9,5
2,336
24,92
Calibration pH-meter, DO-meter, redox-meter (IN and R), Problem
with calibration DO-meter. pH increased up to 7,85 due to two
anoxic period (20 min and 30 min) during DO calibration.
18/08/2010
107,5
154,8
1,07
-550,2
9,427
7,80
2,50
-2,3
2,248
24,95
Calibration (only air) conductivity-meter (IN and R). Problem to
calibrate with standard solution.
19/08/2010
107,5
154,8
1,07
-540,3
9,396
7,79
2,51
-2,6
2,262
24,96
20/08/2010
107,5
154,8
1,07
-483,1
9,302
7,77
2,51
4,8
2,193
24,98
21/08/2010
107,5
154,8
1,07
-505,6
9,219
7,80
2,51
-2,5
2,215
24,97
22/08/2010
107,5
154,8
1,07
-545,4
9,134
7,76
2,49
-3,9
2,138
24,96
8,46
8,49
8,47
8,49
XIX
New reject water. Cleaning pH-meter, redox-meter (IN and R),
conductivity-meter (IN and R) and DO-meter.
No inflow rate since 00.20 because the pipe in the tank was not
under the reject water level. T started to decrease since 17.41. pH
decresed to down to 7,20.
Progressive re-establishment of prevoius conditions from 11.50. T
dropped down to 21,4°C. Calibration pH-meter, DO-meter, redoxmeter (IN and R).
Calibration DO-meter. Cleaning redox-meter (IN and R), pH-meter,
conductivity-meter (IN and R).
Since 0.00 inflow rate probably started to decrease because the
reject water level in the tank was very low and reject water at the
bottom had a higher content of suspended solids.
Andrea Bertino
TRITA Degree Project Thesis 09:11
7,32
1,61
68,6
1,409
24,89
Reject water was finished. New reject water was not delivered
because problems with the truck. pH dropped down to 7,29 and
conductivity to 1,395mS/cm. NH4-N was probably depleted because pH did not decreased anymore (ammonia-elbow). Average
on data from 5pm. DO set point decreased to 1,6mg/l.
10,347
7,51
2,04
61,7
1,901
25,00
New reject water since 10 am. Calibration DO-meter, pH-meter,
redox-meter (IN and R). Conductivity-meter (IN and R) (only air).
Spilled some liquid from inside reactor. DO set point 2,4 mg/l.
-468,6
10,515
7,31
2,35
41,4
1,861
24,99
Decrease of pH from 7,6 to 7,0.
-479,2
10,432
7,14
2,28
37,9
1,794
25,01
DO set point decreased to 2,1 mg/l and before leaving to 2,0 mg/l.
-526,4
10,407
7,18
2,05
27,1
1,827
25,03
-533,0
10,337
7,27
2,04
21,2
1,870
25,03
1,22
-501,3
10,269
7,40
2,13
8,4
1,958
25,05
135,6
1,22
-519,7
10,201
7,51
2,26
0,9
2,030
25,02
135,6
1,22
-535,4
10,168
7,47
2,31
3,9
1,966
25,04
94,0
135,4
1,23
-555,6
10,111
7,44
2,29
11,2
1,926
25,03
02/09/2010
94,0
135,4
1,23
-425,3
10,075
7,40
2,29
10,4
1,962
25,06
Calibration DO-meter, pH-meter. Problem with DOmeter after
calibration. Between 14.41 and 16.37 no aeration and pH increased
from 7,35 to 7,50.
03/09/2010
94,0
135,4
1,23
-373,7
10,066
7,62
2,19
9,1
2,182
25,12
Probably problems with DO-meter and aeration stopped between
9.52 and 11.27 and pH increased up to 9,65. Calibration pH-meter.
Increased mixing 27 ->50 rpm
04/09/2010
94,0
135,4
1,23
-475,9
10,055
7,40
2,31
11,4
2,034
25,06
05/09/2010
94,0
135,4
1,23
-470,4
10,017
7,35
2,31
15,9
2,002
25,05
06/09/2010
94,0
135,4
1,23
-430,8
9,978
7,40
2,25
16,8
2,089
25,02
Problem with DO-meter No aeration between 19.44 and 20.23.pH
increased from 7,34 to 7,51. Calibration redox-meter (IN and R).
Cleaning pH-meter,, conductivity-meter (IN and R) and DO-meter.
07/09/2010
96,0
138,2
1,20
-515,0
9,958
7,58
2,25
-11,8
2,364
25,03
Problem with DO-meter. It seems there was no aeration between
2.29 and 3.39. pH increased from 7,52 to 7,61.
08/09/2010
96,0
138,2
1,20
-521,5
9,935
7,49
2,30
-9,7
2,183
25,04
09/09/2010
96,0
138,2
1,20
-567,7
9,910
7,47
2,30
-17,5
2,162
25,04
Calibration pH-meter, redox-meter (IN and R).
10/09/2010
91,7
132
1,26
9,861
7,49
2,3
17,8
2,141
25,05
Average on three data during the day because automatic data
capture was off.
11/09/2010
91,7
132
1,26
2,3
25,05
12/09/2010
91,7
132
1,26
2,3
25,05
23/08/2010
0,0
0,0
-
24/08/2010
93,3
134,4
1,24
25/08/2010
93,3
134,4
1,24
26/08/2010
94,8
136,6
1,22
27/08/2010
94,8
136,6
1,22
28/08/2010
94,2
135,6
1,22
29/08/2010
94,2
135,6
30/08/2010
94,2
31/08/2010
94,2
01/09/2010
8,43
8,48
8,39
XX
DO set point 2,1 mg/l. Increased pump rate; flow was 92 ml/min.
DO set point 2,3 mg/l
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
13/09/2010
93,3
134,4
1,24
-362,9
9,689
7,57
2,3
12,2
2,297
25,06
14/09/2010
99,8
143,8
1,15
-407,2
9,663
7,47
2,33
7,4
2,009
25,06
15/09/2010
99,8
143,8
1,15
-503,9
9,646
7,52
2,35
1,7
2,148
25,03
16/09/2010
99,8
143,8
1,15
-516,6
9,582
7,53
2,39
1,8
2,182
25,04
17/09/2010
18/09/2010
50,0
72
2,31
-420,6
9,466
7,48
2,11
20,0
2,045
25,04
50,0
72
2,31
-500,6
9,368
7,43
1,17
27,1
1,875
25,05
19/09/2010
50,0
72
2,31
-533,8
9,326
7,46
1,18
46,6
1,878
25,09
20/09/2010
50,0
72
2,31
-321,4
9,269
7,46
1,23
44,9
1,837
25,07
Calibration pH-meter, redox-meter (IN and R). DO set point to 1,3
mg/l.
21/09/2010
50,0
72
-404,8
9,917
7,50
1,64
22,7
1,774
25,08
New reject water. DO set point 2,3mg/l
22/09/2010
100,0
144
-524,3
10,337
7,55
2,31
21,1
2,026
25,09
23/09/2010
100,0
158,4
1,05
-434,2
10,386
7,47
2,29
31,0
2,067
25,08
24/09/2010
89,0
128,2
1,30
-463,7
10,537
7,51
2,28
24,9
2,231
25,05
25/09/2010
89,0
128,2
1,30
-551,2
10,631
7,37
2,19
26,1
2,008
25,05
26/09/2010
88,3
127,1
1,31
-535,3
10,572
7,32
2,22
29,4
1,995
25,06
27/09/2010
88,3
127,1
1,31
-528,3
10,510
7,30
2,22
29,9
1,999
25,06
28/09/2010
88,3
127,1
1,31
-489,3
9,844
7,36
2,17
21,9
1,987
8,40
8,37
8,50
XXI
Decreased inflow rate (half) and DO set point to 1,2 mg/l.
DO set point 2,2mg/l
Andrea Bertino
TRITA Degree Project Thesis 09:11
A PPENDIX V –B ATCH TESTS ON THE PI LOT PLANT - SCALE REACTOR
Table 21A – OUR tests on carriers – data and results from Pilot Plant scale reactor (*)
Date
Initial
NH4-N
(mg/l)
OUR (Nitrobacters +
Nitrosomonas +
Heterotrophic)
slope
[mg O2/l s]
average
[mg O2/l s]
OUR (Nitrosomonas +
Heterotrophic)
slope
[mg O2/l s]
average
[mg O2/l s]
OUR
(NOB+AOB+HT)
OUR
(AOB+HT)
OUR
(HT)
OUR
(AOB)
OUR
(NOB)
average
[mg O2/l s]
g O2 / m2 / d
g O2 / m2 / d
g O2 / m2 / d
g O2 / m2 / d
g O2 / m2 / d
-0,001109
7,7255
6,9831
2,9071
4,0760
0,7423
-0,000862
7,3787
6,5941
2,2596
4,3345
0,7846
-0,001248
7,9642
6,6907
3,2715
3,4192
1,2735
-0,000919
6,2472
5,6150
2,4082
3,2068
0,6323
-0,000910
6,8579
6,4884
2,3863
4,1020
0,3695
-0,000752
6,6865
6,2934
1,9721
4,3213
0,3931
-0,000739
7,1856
6,7573
1,9381
4,8192
0,4283
-0,000519
7,0610
6,2516
1,3596
4,8920
0,8094
-0,000694
6,7177
6,1524
1,8201
4,3323
0,5653
OUR (Heterotrophic)
slope
[mg O2/l s]
-0,003121
02/06/2010
104
-0,003069
-0,002967
-0,002710
-0,003623
28/06/2010
104
-0,002691
-0,002599
-0,002599
-0,000724
-0,002946
-0,003097
-0,002976
-0,002335
-0,000654
-0,002666
-0,002716
-0,000891
-0,001041
-0,003142
15/07/2010
97,6
-0,003192
-0,003058
-0,002841
04/08/2010
103
97,2
-0,002307
-0,002057
-0,002235
-0,002411
-0,001965
101,4
-0,002663
-0,002915
98,7
-0,002710
-0,000875
-0,002410
-0,002712
-0,002713
-0,002404
-0,000867
-0,000515
-0,002708
-0,002759
-0,002578
02/09/2010
-0,002459
-0,001004
-0,001031
-0,002150
-0,002785
104,4
-0,000696
-0,002280
-0,002622
-0,002568
-0,002416
26/08/2010
-0,002735
-0,000918
-0,001003
-0,001869
-0,002624
17/08/2010
-0,000835
-0,002151
-0,002656
-0,001041
-0,001252
-0,002244
-0,002399
-0,002396
-0,002611
-0,002563
-0,002615
-0,002494
22/07/2010
-0,002510
-0,000973
-0,002588
-0,000589
-0,002652
-0,000656
-0,002376
-0,000609
-0,002487
-0,002394
-0,002320
-0,000589
-0,000358
-0,000549
28/09/2010
98,4
-0,002640
-0,002896
-0,002768
-0,002459
-0,002352
-0,002406
-0,000670
-0,000781
(*) in blue are enlighten the measurements whose results are somewhat anomalous. The empty cells represent problems with DO probe, inhibitors or not reliable execution of the test.
XXII
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
Table 22A – OUR tests on activated sludge from Pilot Plant scale reactor
Initial
NH4-N
(mg/l)
Date
27/09/2010
VSS
(mg/l)
VSS (mg/l)
with 9ml
NH4HCO3
VSS (mg/l)
with 9ml
NH4HCO3
and 4 ml
NaClO3
VSS (mg/l)
with 9ml
NH4HCO3, 4
ml NaClO3
and 6 ml
ATU
OUR
(Nitrobacter +
Nitrosomonas +
Heterotrophic)
OUR
(Nitrosomonas +
Heterotrophic)
OUR
(Heterotrophic)
OUR
(Nitrobacter +
Nitrosomonas +
Heterotrophic)
OUR
(Nitrosomonas +
Heterotrophic)
OUR
(Heterotrophic)
[mg O2/l s]
[mg O2/l s]
[mg O2/l s]
gO2 gVSS-1 d-1
gO2 gVSS-1 d-1
gO2 gVSS-1 d-1
106,8
283,8
282,1
281,4
280,4
-0,014109
-0,010367
-0,000941
113,4
286,2
284,5
283,8
282,8
-0,014887
-0,011671
-0,000898
4,5205
3,5531
0,2900
0,2743
112,5
284,3
282,6
281,9
280,9
-0,015351
-0,011570
-0,000814
4,6930
3,5462
0,2504
4,6067
3,5496
0,2716
AVERAGE:
OUR (NOB)
-1
g O2 gVSS d
OUR (AOB)
-1
-1
g O2 gVSS d
1,0571
g O2 gVSS-1 d1
3,2781
0,2716
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
8
8
y = -0,003121x + 7,175136
R² = 0,971271
7
y = -0,003069x + 7,245150
R² = 0,970079
6
5
y = -0,002710x + 6,600405
R² = 0,964706
6
DO [mg/l]
7
DO [mg/l]
7
DO [mg/l]
OUR (HT)
-1
6
5
y = -0,002599x + 6,579606
R² = 0,964613
5
y = -0,000724x + 5,236281
R² = 0,752304
4
4
4
3
3
2
3
2
0
100
200
300
400
500
600
700
800
900 1000 1100 1200
time [s]
Fig. 18A - 2 June 2010 (I) (25°C)
2
0
200
400
600
800
1000
1200
1400
time [s]
Fig. 19A - 2 June 2010 (II) (25°C)
XXIII
1600
1800
0
100
200
300
400
500
600
700
800
900 1000 1100 1200
time [s]
Fig. 20A - 2 June 2010 (III) (25°C)
Andrea Bertino
TRITA Degree Project Thesis 09:11
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
7
7
7
6
5
4
6
y = -0,002335x + 6,507028
R² = 0,977804
5
4
3
DO [mg/l]
y = -0,002946x + 6,544311
R² = 0,993951
DO [mg/l]
3
y = -0,000654x + 4,277332
R² = 0,779997
2
200
400
600
800
1000
1200
1400
100
200
300
400
500
600
700
800
900 1000 1100 1200
0
Lineare (NOB, AOB, HT)
y = -0,003142x + 7,077338
R² = 0,815616
DO [mg/l]
5
4
3
2
400
500
600
500
700
800
900 1000 1100 1200
time [s]
Fig. 24A – 15 July 2010 (I) (25°C)
600
700
800
900 1000 1100 1200
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
9
y = -0,003192x + 7,774275
R² = 0,973440
y = -0,002510x + 7,552970
R² = 0,947212
7
y = -0,002841x + 8,315553
R² = 0,970562
y = -0,002615x + 8,255496
R² = 0,964623
8
6
y = -0,001041x + 6,540131
R² = 0,640706
5
7
6
y = -0,001252x + 7,356033
R² = 0,850140
5
4
4
3
3
2
300
400
NOB, AOB, HT
8
6
200
300
Fig. 23A - 28 June 2010 (III) (25°C)
9
100
200
time [s]
Fig. 22A - 28 June 2010 (II) (25°C)
8
0
100
time [s]
Fig. 21A - 28 June 2010 (I) (25°C)
7
y = -0,001041x + 5,428681
R² = 0,876388
2
0
time [s]
NOB, AOB, HT
5
3
2
0
y = -0,002716x + 6,682164
R² = 0,979415
4
y = -0,000891x + 5,343516
R² = 0,826324
DO [mg/l]
DO [mg/l]
6
DO [mg/l]
y = -0,002976x + 6,680878
R² = 0,972019
y = -0,002691x + 6,624887
R² = 0,981060
y = -0,003623x + 6,856237
R² = 0,992462
2
0
100
200
300
400
500
600
700
800
time [s]
Fig. 25A - 15 July 2010 (II) (25°C)
XXIV
900
1000
0
100
200
300
400
500
600
700
800
time [s]
Fig. 26A - 15 July 2010 (III) (25°C)
900
1000
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
y = -0,002494x + 7,822553
R² = 0,986806
y = -0,002244x + 7,658953
R² = 0,864671
6
DO [mg/l]
5
y = -0,000835x + 6,207847
R² = 0,905292
4
8
7
7
y = -0,002307x + 7,682639
R² = 0,984339
6
5
y = -0,000918x + 6,375693
R² = 0,715334
4
3
3
2
200
400
600
800
1000
1200
1400
1600
1800
2000
y = -0,001003x + 6,301559
R² = 0,760963
4
2
0
200
400
600
time [s]
800
1000
1200
1400
0
200
400
600
time [s]
Fig. 27A - 22 July 2010 (I) (25°C)
800
1000
1200
Fig. 29A - 22 July 2010 (III) (25°C)
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
8
y = -0,002656x + 7,508570
R² = 0,990391
6
8
y = -0,002611x + 7,323290
R² = 0,985818
7
DO [mg/l]
7
y = -0,002235x + 7,222294
R² = 0,976922
5
4
y = -0,000696x + 5,427976
R² = 0,755156
3
7
y = -0,002735x + 7,441613
R² = 0,977798
6
5
y = -0,001004x + 6,115412
R² = 0,902523
4
3
2
200
400
600
800
1000
1200
1400
time [s]
Fig. 30A – 4 August 2010 (I) (25°C)
1600
y = -0,001031x + 6,569806
R² = 0,896685
6
5
4
3
2
0
1400
time [s]
Fig. 28A - 22 July 2010 (II) (25°C)
8
DO [mg/l]
5
3
2
0
y = -0,002057x + 7,482005
R² = 0,817750
y = -0,002396x + 7,619939
R² = 0,983837
6
DO [mg/l]
DO [mg/l]
7
8
DO [mg/l]
8
2
0
100
200
300
400
500
600
700
800
900 1000 1100 1200
time [s]
Fig. 31A – 4 August 2010 (II) (25°C)
XXV
0
100
200
300
400
500
600
700
800
900 1000 1100 1200
time [s]
Fig. 32A - 4 August 2010 (III) (25°C)
Andrea Bertino
TRITA Degree Project Thesis 09:11
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
7
y = -0,002624x + 6,659541
R² = 0,981136
6
y = -0,002622x + 6,688445
R² = 0,970874
5
5
y = -0,002416x + 7,164672
R² = 0,930018
7
y = -0,002663x + 6,399807
R² = 0,920928
6
DO [mg/l]
DO [mg/l]
7
8
DO [mg/l]
8
y = -0,002459x + 6,195219
R² = 0,942471
y = -0,002150x + 7,042439
R² = 0,957754
6
5
y = -0,000515x + 5,585228
R² = 0,623948
4
4
4
y = -0,000875x + 4,959871
R² = 0,692369
3
3
2
y = -0,000867x + 4,507688
R² = 0,603518
2
0
200
400
600
800
1000
1200
1400
2
0
200
400
600
time [s]
800
1000
1200
1400
0
200
400
time [s]
Fig. 33A – 17 August 2010 (I) (25°C)
600
800
1000
1200
Fig. 35A – 17 August 2010 (III ) (25°C)
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
7
5
DO [mg/l]
y = -0,002708x + 7,144403
R² = 0,959555
y = -0,002404x + 6,491561
R² = 0,762718
5
y = -0,002578x + 6,881426
R² = 0,909665
7
6
DO [mg/l]
6
8
y = -0,002915x + 6,793308
R² = 0,889993
y = -0,002785x + 7,075862
R² = 0,968257
7
1400
time [s]
Fig. 34A – 17 August 2010 (II) (25°C)
8
DO [mg/l]
3
6
y = -0,002652x + 6,898258
R² = 0,976117
5
4
4
4
y = -0,000973x + 5,609506
R² = 0,762907
y = -0,000589x + 4,617614
R² = 0,157520
3
3
2
2
0
200
400
600
800
1000
1200
1400
time [s]
Fig. 36A – 26 August 2010 (I) (25°C)
1600
y = -0,000656x + 5,014863
R² = 0,659740
3
2
0
200
400
600
800
1000
1200
1400
time [s]
Fig. 37A – 26 August 2010 (II) (25°C)
XXVI
1600
0
200
400
600
800
1000
1200
time [s]
Fig. 38A – 26 August 2010 (III) (25°C)
1400
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
8
7
7
y = -0,002376x + 7,149238
R² = 0,879792
6
5
y = -0,000609x + 5,946064
R² = 0,402369
8
y = -0,002710x + 7,408454
R² = 0,958529
y = -0,002487x + 7,289639
R² = 0,933170
6
5
y = -0,000589x + 5,889587
R² = 0,448955
4
3
3
3
2
100
200
300
400
500
600
700
800
900 1000 1100 1200
y = -0,000358x + 5,116509
R² = 0,454196
2
0
100
200
300
400
500
time [s]
600
700
800
900 1000 1100 1200
0
100
200
300
400
500
time [s]
Fig. 39A – 2 September 2010 (III ) (25°C)
600
700
800
900 1000 1100 1200
time [s]
Fig. 40A – 2 September 2010 (III ) (25°C)
Fig. 41A – 2 September 2010 (III ) (25°C)
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
8
7
7
6
5
y = -0,000626x + 5,961817
R² = 0,557623
4
8
y = -0,002664x + 7,386310
R² = 0,943261
y = -0,002482x + 7,354814
R² = 0,933938
6
5
y = -0,000676x + 5,875877
R² = 0,503371
4
3
200
400
600
800
1000
1200
1400
1600
time [s]
Fig. 42A – 28 September 2010 (I) (25°C)
1800
5
y = -0,000781x + 5,954621
R² = 0,606705
3
2
0
y = -0,002352x + 7,122422
R² = 0,926631
6
4
3
2
y = -0,002896x + 7,256260
R² = 0,948118
7
DO [mg/l]
8
DO [mg/l]
DO [mg/l]
5
4
0
y = -0,002320x + 6,582154
R² = 0,938064
6
4
2
y = -0,002713x + 6,737749
R² = 0,967454
7
DO [mg/l]
8
DO [mg/l]
DO [mg/l]
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
2
0
200
400
600
800
1000
1200
time [s]
Fig. 43A – 28 September 2010 (I) (25°C)
XXVII
1400
0
200
400
600
800
1000
1200
time [s]
Fig. 44A – 28 September 2010 (I) (25°C)
1400
TRITA Degree Project Thesis 09:11
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
NOB, AOB, HT
AOB, HT
HT
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
Lineare (NOB, AOB, HT)
Lineare (AOB, HT)
Lineare (HT)
6
5
5
4
y = -0,000941x + 2,873276
R² = 0,787463
y = -0,014887x + 5,764239
R² = 0,965314
4
y = -0,011671x + 5,105303
R² = 0,983483
3
2
5
100
200
300
400
500
600
700
800
time [s]
4
y = -0,011570x + 5,244068
R² = 0,959229
3
y = -0,000898x + 2,696838
R² = 0,752782
2
0
y = -0,015351x + 5,583620
R² = 0,976388
y = -0,000814x + 2,723679
R² = 0,705420
2
0
100
200
300
400
500
600
700
800
0
100
200
300
time [s]
Fig. 45A – 27 Sept. 2010 (I) Act. sludge (25°C)
400
500
600
Fig. 46A – 27 Sept. 2010 (II) Act. sludge 25°C)
NUR tests
Fig. 47A – 27 Sept. 2010 (II) Act. sludge (25°C)
NO3-N
COD
Lineare (NO3-N)
120
500
Table 23A – NUR results
y = -0.1225x + 99.45
R² = 0.978
NUR
(g N / m2 / d)
02/06/2010
0,8820
24/06/2010
0,8544
28/06/2010
0,6588
15/07/2010
0,8846
22/07/2010
0,7452
04/08/2010
0,8051
17/08/2010
0,9795
26/08/2010
0,5063
02/09/2010
0,9250
26/09/2010
0,8182
NO3--N (mg/l)
100
Date
700
time [s]
450
400
80
350
300
60
250
40
200
150
20
100
0
50
0
30
60
90
120
150
180
210
Time (min)
Fig. 48A – 2 June 2010 (25°C)
XXVIII
240
COD (mg O2/l)
3
6
DO [mg/l]
6
DO [mg/l]
DO [mg/l]
Andrea Bertino
800
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
NO3-N
COD
Lineare (NO3-N)
NO3-N
120
COD
Lineare (NO3-N)
120
500
350
y = -0,1187x + 100,96
R² = 0,9502
60
300
250
40
COD (mg O2/l)
400
80
NO3--N (mg/l)
100
450
400
80
350
300
60
250
40
200
200
150
20
150
20
100
0
100
50
0
30
60
90
120
150
180
210
0
240
50
0
30
60
90
Time (min)
COD
120
150
180
210
240
Time (min)
Fig. 49A - 24 June 2010 (25°C)
NO3-N
Fig. 50A - 28 June 2010 (25°C)
NO3-N
Lineare (NO3-N)
COD
Lineare (NO3-N)
120
120
500
500
350
300
60
250
40
200
150
20
NO3--N (mg/l)
400
80
y = -0,1035x + 96,72
R² = 0,9965
100
450
400
80
350
300
60
250
40
200
150
20
100
100
0
50
0
30
60
90
120
150
180
210
0
50
0
240
30
60
90
120
150
180
Time (min)
Time (min)
Fig. 51A - 15 July 2010 (25°C)
Fig. 52A - 22 July 2010 (25°C)
XXIX
210
240
COD (mg O2/l)
450
y = -0,1229x + 97,886
R² = 0,9956
COD (mg O2/l)
100
NO3--N (mg/l)
COD (mg O2/l)
450
100
NO3--N (mg/l)
500
y = -0,0915x + 101,31
R² = 0,972
Andrea Bertino
NO3-N
TRITA Degree Project Thesis 09:11
COD
NO3-N
Lineare (NO3-N)
COD
Lineare (NO3-N)
120
120
500
500
350
300
60
250
40
NO3--N (mg/l)
400
80
y = -0,1258x + 97
R² = 0,9644
400
80
350
300
60
250
40
200
150
20
450
100
COD (mg O2/l)
200
150
20
100
100
0
0
50
0
30
60
90
120
150
180
210
50
0
240
30
60
90
Fig. 53A – 4 August 2010 (25°C)
COD
180
210
240
Fig. 54A– 17 August 2010 (25°C)
NO3-N
Lineare (NO3-N)
COD
Lineare (NO3-N)
120
120
500
500
450
350
300
60
250
40
200
150
20
COD (mg O2/l)
400
80
y = -0,1188x + 100,77
R² = 0,9205
100
NO3--N (mg/l)
y = -0,065x + 97,354
R² = 0,9934
100
NO3--N (mg/l)
150
Time (min)
Time (min)
NO3-N
120
450
400
80
350
300
60
250
40
200
150
20
100
100
0
0
50
0
30
60
90
120
150
180
210
50
0
240
30
60
90
120
150
180
210
Time (min)
Time (min)
Fig. 55A – 26 August 2010 (25°C)
Fig. 56A - 2 September 2010 (25°C)
XXX
240
COD (mg O2/l)
NO3--N (mg/l)
y = -0,1034x + 92,16
R² = 0,7945
COD (mg O2/l)
450
100
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
NO3-N
COD
NO3-N
Lineare (NO3-N)
COD
Lineare (NO3-N)
120
120
500
500
350
300
60
250
40
200
150
20
NO3--N (mg/l)
400
80
450
100
y = -0,0286x + 104,42
R² = 0,911
80
400
350
300
60
250
40
200
150
20
100
100
0
50
0
30
60
90
120
150
180
210
COD (mg O2/l)
450
y = -0,1136x + 96,823
R² = 0,8896
COD (mg O2/l)
NO3--N (mg/l)
100
0
50
0
240
30
60
90
120
150
180
210
240
Time (min)
Time (min)
Fig. 57A – 26 September 2010 (25°C)
Fig. 58A – 27 September 2010 – activated sludge (25°C)
XXXI
Andrea Bertino
TRITA Degree Project Thesis 09:11
SAA tests
200
200
y = 1,3023x + 95,261
R² = 0,9695
y = 0,9732x + 25,494
R² = 0,9961
100
y = 0,8972x + 31,154
R² = 0,9978
P (atm∙10 -3 )
150
P (atm∙10 -3 )
150
y = 1,0282x + 27,627
R² = 0,9964
50
y = 1,1332x + 93,447
R² = 0,9503
100
50
0
0
0
30
60
90
120
0
30
60
Time (min)
90
120
Time (min)
Fig. 59A - 25 May 2010 (25°C)
Fig. 60A - 25 May 2010 (35°C)
200
200
150
150
y = 1,1135x + 22,595
R² = 0,9812
P (atm∙10 -3 )
P (atm∙10 -3 )
y = 1,1823x + 22,213
R² = 0,9448
100
100
y = 1,2117x + 11,538
R² = 0,9788
50
y = 0,917x + 25,593
R² = 0,9585
50
0
0
0
30
60
90
120
0
30
60
Time (min)
90
120
Time (min)
Fig. 61A – 10 June 2010 (25°C)
Fig. 62A – 28 June 2010 (25°C)
200
200
y = 1,2064x + 78,977
R² = 0,9974
P (atm∙10 -3 )
100
y = 1,0356x + 28,278
R² = 0,9278
100
y = 1,3407x + 41,493
R² = 0,9873
50
y = 1,0681x + 29,778
R² = 0,9436
150
P (atm∙10 -3 )
150
y = 1,017x + 25,454
R² = 0,9361
50
y = 1,7364x + 21,967
R² = 0,9901
0
0
0
30
60
90
120
0
30
Time (min)
60
90
120
Time (min)
Fig. 63A – 28 June 2010 (35°C)
Fig. 64A - 15 July 2010 (25°C)
200
200
y = 1,1472x + 25,593
R² = 0,966
y = 1,4211x + 29,364
R² = 0,9311
150
150
P (atm∙10 -3 )
P (atm∙10 -3 )
y = 1,4545x + 22,316
R² = 0,9467
y = 1,1588x + 21,514
R² = 0,9948
100
100
y = 1,4303x + 24,548
R² = 0,9385
y = 1,2169x + 20,642
R² = 0,9585
50
50
0
0
0
30
60
90
0
120
30
60
Time (min)
Time (min)
Fig. 65A – 16 July 2010 (35°C)
Fig. 66A – 22 July 2010 (25°C)
XXXII
90
120
Study on one-stage Partial Nitritation-Anammox process in MBBRs: a sustainable nitrogen removal
200
200
y = 2,0796x + 27,93
R² = 0,9792
y = 1,2506x + 4,5678
R² = 0,9979
P (atm∙10 -3 )
150
P (atm∙10 -3 )
150
y = 1,5119x + 28,209
R² = 0,9265
100
y = 1,3947x + 23,362
R² = 0,9626
50
y = 1,2402x + 3,3822
R² = 0,9984
100
y = 1,3227x + 5,1605
R² = 0,999
50
0
0
0
30
60
90
120
0
30
60
Time (min)
Fig. 67A – 22 July 2010 (35°C)
200
y = 1,1925x + 4,2191
R² = 0,9976
P (atm∙10 -3 )
P (atm∙10 -3 )
y = 1,5807x + 4,9978
R² = 0,9988
150
y = 1,3843x + 2,3013
R² = 0,9939
100
120
Fig. 68A - 16 August 2010 (25°C)
200
150
90
Time (min)
y = 1,1332x + 6,625
R² = 0,9903
100
y = 1,2111x + 4,6026
R² = 0,9972
50
50
0
y = 1,1716x + 2,0224
R² = 0,9943
0
0
30
60
90
120
0
30
60
Time (min)
90
120
Time (min)
Fig. 69A – 23 August 2010 (25°C)
Fig. 70A – 3 September 2010 (25°C)
200
200
y = 1,6772x + 28,522
R² = 0,9626
150
y = 1,4386x + 10,671
R² = 0,9947
P (atm∙10 -3 )
P (atm∙10 -3 )
150
y = 1,6156x + 20,921
R² = 0,9864
100
100
50
y = 1,2432x + 7,4618
R² = 0,9822
y = 1,2122x + 7,8342
R² = 0,9968
50
0
0
30
60
90
120
0
30
60
Time (min)
90
Time (min)
Fig. 71A – 8 September 2010 (25°C)
Fig. 72A – 28 September 2010 (25°C)
200
150
P (atm∙10 -3 )
0
100
y = 0,0378x + 20,634
R² = 0,9946
50
0
0
30
60
90
120
Time (min)
Fig. 73A – 28 September 2010 (25°C) – Activated sludge
XXXIII
120
Andrea Bertino
TRITA Degree Project Thesis 09:11
Table 24A – SAA results from Pilot Plant scale reactor
Date
Anammox Biomass
SAA (25°C) (gN/m2/d)
SAA (35°C) (gN/m2/d)
28/05/2010
2,95
3,60
10/06/2010
3,66
28/06/2010
3,10
15/07/2010
3,18
4,22
16/07/2010
4,24
22/07/2010
3,59
16/08/2010
3,89
23/08/2010
3,86
03/09/2010
3,96
08/09/2010
4,12
23/09/2010
3,21
28/09/2010
3,97
4,92
7,12
XXXIV
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