The use of activated carbons for removing organic

Archives of Environmental Protection
Vol. 43 no. 3 pp. 32–41
PL ISSN 2083-4772
DOI 10.1515/aep-2017-0031
© Copyright by Polish Academy of Sciences
and Institute of Environmental Engineering of the Polish Academy of Sciences,
Zabrze, Poland 2017
The use of activated carbons for removing organic matter
from groundwater
Jadwiga Kaleta, Małgorzata Kida, Piotr Koszelnik*, Dorota Papciak, Alicja Puszkarewicz,
Barbara Tchórzewska-Cieślak
Rzeszow University of Technology
* Corresponding author’s e-mail: pkoszel@prz.edu.pl
Keywords: groundwater, powdery activated carbon, granular activated carbon, organic matter, biosorption.
Abstract: The article presents research results of the introduction of powdery activated carbon to the existing
technological system of the groundwater treatment stations in a laboratory, pilot plant and technical scale. The
aim of the research was to reduce the content of organic compounds found in the treated water, which create toxic
organic chlorine compounds (THM) after disinfection with chlorine. Nine types of powdery active carbons were
tested in laboratory scale. The top two were selected for further study. Pilot plant scale research was carried out
for the filter model using CWZ-30 and Norit Sa Super carbon. Reduction of the organic matter in relation to the
existing content in the treated water reached about 30%. Research in technical scale using CWZ-30 carbon showed
a lesser efficiency with respect to laboratory and pilot-plant scale studies. The organic matter decreased by 15%.
Since filtration is the last process before the individual disinfection, an alternative solution is proposed, i.e. the
second stage of filtration with a granular activated carbon bed, operating in combined sorption and biodegradation
processes. The results of tests carried out in pilot scale were fully satisfactory with the effectiveness of 70–100%.
Introduction
Groundwater is often the only source of water for public
supply. The degree of contamination generally does not allow
for its immediate use. Primary groundwater contamination
is most often caused by common natural organic substances,
mainly humic compounds, which are very difficult to remove
with conventional treatment systems (aeration, sedimentation
and filtration) (Adamski and Szlachta 2011, Kalda and
Murias 2015, Pisarek and Głowacki 2015, Skoczko et al.
2016, Tchórzewska-Cieślak 2012). These contaminants are
toxic to humans but their presence in the water can affect the
biochemical transformations of elements binding other organic
substances and stimulating the development of organisms.
Furthermore, they can adsorb toxic compounds including
polychlorinated biphenyls, pesticides or phthalates. In addition,
humic substances impart the colour and turbidity of water and
can emit an undesirable odour (Hur et al. 2006, Grzegorczuk-Nowacka 2011). The danger arising from the presence of
humic substances in waters treated for municipal purposes
is associated primarily with the formation of oxidation and
disinfection of by-products. About 500 different disinfection
products are known, most of which are haloacetic acids
(HAA) and trihalomethanes (THMs), showing mutagenic and
carcinogenic effects for human and animal organisms (Rosińska
and Rakocz 2013, Adamski and Szlachta 2011, Grzegorczuk-Nowacka 2011). Consequently, the removal of natural organic
materials is a key operation in the development and operation
of water treatment processes intended for human consumption
(Kim and Yu 2007). Coagulation and adsorption on activated
carbon is used for the removal of these substances from water,
which involves the formation of biofilm on the surface thereof
(Meinel et al. 2010, Jasper et al. 2010, Kovalova et al. 2013,
Holc et al. 2016). Biofilm primarily increases the efficiency
of water purification and the operation time of carbon beds
(Górka et al. 2008, Bodzek and Rajca 2013).
The presence of natural organic matter accounting for the
needs of municipal waters is a problem faced by many treatment
plants. Hence, the research discussed in the article focused
on determining the effectiveness of the removal of humic
substances (TOC 14–20 mgC/L) from underground water in
the sorption process. The results of laboratory and pilot-plant
scale studies on the addition of the powdery activated carbon
(PAC) to the existing process water treatment station have been
presented.
As an alternative solution, the process of bio-sorption on
granular activated carbon (II degree of filtration) was tested in
pilot scale.
Materials and methods
Characteristics of drawn water (raw)
The Water Treatment Plant (WTP) is supplied from an
unconfined quaternary aquifer with a depth of about 15 m bgl
using 27 wells. The physicochemical composition of water
drawn and directed to the treatment station varies greatly,
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The use of activated carbons for removing organic matter from groundwater
because it depends essentially on the well included in the
operation and productivity (Table 1). Drawn water does not
meet sanitary requirements in terms of turbidity (8.0–14.0
NTU), colour (40–100 mgPt/L), the permanganate index
(11.0–18.1 mgO2/L), ammonium ion (1.20–1.98 mgNH4+/L),
iron (14.0–44.0 mgFe/L) and manganese (0.74–2.58 mgMn/L).
High water colour, which correlates with the elevated
permanganate index value and total organic carbon (TOC;
14–20 mgC/L), indicates the presence of water of natural
organic matter that may be present in combinations of complex
compounds of iron and manganese. Intakes of iron in the present
water are large and rarely seen in the municipal infrastructure. It
comes under medium hard water (4.0–9.4 meq/L), with 48–65%
of the hardness being carbonate hardness due to the hardness
of the generally drawn water. Raw water also has a high
concentration of sulphates (60–240 mgSO42/L). The physical
and chemical composition of the water drawn indicates the
difficulties that may arise in the treatment process.
Technology system for water treatment
The drawn water is directed to a collective well (stoppage time
of 2–4 hours, depending on the current water production). The
water is then directed to a cascade of oxygenation. A dispensing
potassium permanganate chemical-oxidant with a dose of
2.1–2.4 mg/L and a PAX-18 coagulant in the amount
of 120–140 mg/L is situated just below the cascade
(11.0–12.6 mgAl/L). Vertical coagulation-sedimentation
chambers with a contact time of 6–8 hours are the next stage of
the water treatment. Lime milk is dosed (about 10.0 mg/L) to
the water in the chambers, which is directed to horizontal settler
raising the pH. The retention time in the settlers is several hours.
The next step involves filtration of water at a speed of 1.5–3 m/h
and the final disinfection with sodium hypochlorite (Fig. 1).
Although the quality of the treated water which is directed
to the water supply meets the requirements of the Regulation
of the Minister of Health of 13 November 2015 relating to the
quality of water intended for human consumption (Journal of
Laws 2015, item. 1989), research has been carried out in order
to further reduce the content of organic substances in the treated
33
water of the following composition: TOC 7.00–11.00 mgC/L,
with a permanganate index of 4.7–5.0 mgO2/L and colouring of
10–16 mgPt/L.
The selection and dosing
of powdery activated carbons
Nine powdery activated carbons: Sorbotech LPW 90,
Sorbotech LPW 125 CA, CWZ-22, AKPA-22, CWZ-30,
Carbopol AP, Norit Sa Super, Hydraffin P 800 and Carbopol
MB 5 were examined in the preliminary laboratory tests and
were selected on the basis of product cards analysis. Carbon
doses amounted to 10, 15 and 20 mg/L and were dosed into
the treated water. The best results were obtained with a dose
of 20 mg/L, which was used in further tests. Sorbotech LPW
90 (Sorb-1), Sorbotech LPW 125 CA (Sorb-2), CWZ-22,
AKPA-22, CWZ-30, Norit Sa Super (Norit), and Carbopol MB
5 carbon proved to be the most effective sorbent of organic
compounds. The selected carbon was dosed to the collected
water from three sites of the technological system (Fig. 1):
– Point 1 – at the beginning of the technological process after
the addition of the KMnO4 oxidant (dose of 2.5 mgO2/L)
and the PAX–18 coagulant (dose of 130 mg/L),
– Point 2 – before the settlers and after the adjustment of
pH with help of Ca(OH)2 (dose of 10 mg/L),
– Point 3 – after the settlers, before precipitous filters.
Afterwards, mixing (100 rev/min) was carried out
for 60 minutes. The sample was subsequently allowed to
achieve an absorption balance for 24 hours. After this time,
the solutions were filtered and the effects of the removal of
organic compounds were evaluated by determining the colour,
permanganate index and the TOC.
Pilot-plant scale studies on the model filter
In order to make the laboratory tests involving powdery activated
carbons reflect real conditions, a model filter F1 (Fig. 2) was
made characterized by the construction and hydraulic parameters
consistent with the parameters of filters working in the treatment
plant. It consisted of a support layer with a height of 0.10 m and was
filled with a double-layer bed: the bottom layer comprised quartz
Table 1. Physicochemical parameters of water used in the test
Parameter
Colour
Turbidity
untreated water
treated water
mgPt/L
40–100
10–16
NTU
8.0–14.0
1.0
-
6.4–7.0
7.8–8.1
C
10.8–12.1
10.9–11.6
mgCaCO3/L
200–470
280–380
pH
Temperature
Total hardness
Sulfates
Conductivity
The range of values
Unit
o
mgSO4 /L
60–240
60–124
mS/cm
430–1016
648–891
2-
Alkalinity
mval/L
2.5–4.5
–
Iron
mgFe/L
14.0–44.0
<0.02
Manganese
mgMn/L
0.74–2.58
<0.02
Ammonium
mgNH4+/L
1.20-–1,98
0.09–0.28
Permanganate index
mgO2/L
11.0–18.1
4.7–5.0
TOC (±0.05)
mgC/L
14.00–20.00
7.00–11.00
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J. Kaleta, M. Kida, P. Koszelnik, D. Papciak, A. Puszkarewicz, B. Tchórzewska-Cieślak
Fig. 1. Technological flowchart for the Water Treatment Plant (1, 2, 3 – place of dosing powdery activated carbon
during the tests)
sand with a height of 1.0 m, whereas the top layer was anthracite
with a height of 0.4 m. Both of these layers were taken from the
bed of filters operating in the station. Water was supplied to the
sedimentation tanks on the model filter (Fig. 2, 3-point laboratory
testing), to which a powdery activated carbon was added. The
type and dose of carbon were selected on the basis of laboratory
tests. Two activated carbons: CWZ-30 and Norit Sa Super were
selected, both at a dose of 20 mg/L. The filtration speed fluctuated
in the range of 1.5–2 m/h. The filtration cycle lasted until the
appearance of PAC in the leakage, thus piercing the bed. The
filter was then rinsed with water and air. The effectiveness of the
introduction of PAC prior to the filtration process was analyzed
for TOC concentration reduction. The results of the conducted
filtration were obtained and compared with the quality of raw
water and water on filters working on the WTP.
Research in technical scale
Research in technical scale lasted for six weeks and was
carried out on a single filter chamber which was excluded from
the operation of the filter chamber. CWZ-30 dosed powdery
activated carbon with an optimum dose of 20 mg/L which was
directed to the water and into the filtration chamber. The purpose
of the research in technical scale was to confirm the efficiency
of water purification, evaluation of the efficiency of rinsing and
operation of the filter chamber. The effectiveness of the addition
before PAC filtration was analyzed in the aspect of lowering
the TOC concentration. Analysis was carried out two times per
week. Evaluation of the effectiveness of the process was carried
out on the basis of the average value of the TOC concentration
(calculated from 16 measurements) in the treated water.
Fig. 2. Diagram of the filter
models
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The use of activated carbons for removing organic matter from groundwater
Research on the bio-sorption model filter
The bio-sorption filter was filled with a bed of WD-extra granular
activated carbon and constituted II0 filtration, supplied with treated
water at the WTP station. The bio-filter F2 filling was chosen
earlier by the authors of the study, indicating that WD-extra carbon
proved to be the most effective in regard to the removal of organic
matter in the sorption processes (Kaleta et al. 2015).The bio-filter
was supplied with treated water. The operating parameters of
the bio-filter F2 (Fig. 2) were as presented in Table 2. Analyses
were carried out for water supply and water after the bio-filtration
process in terms of TOC, colour, turbidity, permanganate index
and dissolved oxygen. Bio-filter operational assessment was
carried out on the basis of EMS tests.
The EMS test is based on determining the value of the S
index of the specified ratio of changes in COD or permanganate
index to the loss of dissolved oxygen DO.
S=
ǻCOD
ǻDO
(1)
35
If:
S=1 adsorption and biodegradation occurs with the same
intensity
S>1 adsorption dominates
S<1 biodegredation dominates
S=0, ΔCOD=0, ΔDO>0 stop processes of sorption and
biodegradation S unmarked, ΔCOD >0, ΔDO=0 sorption
occurs, lack of biodegradation
ΔCOD=0, ΔDO=0 lack of sorption and biodegradation.
Results and discussion
The effectiveness of treating water by means
of powdery active carbons
The composition of the water used in the research, collected in
step 1 was as follows: colouring 40–60 mgPt/L, the permanganate
index of 13–14 mgO2/L, TOC 14.50–16.30 mgC/L (Table 3).
After the addition of powdery activated carbons, a significant
reduction of organic matter was obtained (Fig. 3).
Table 2. Parameters of the biofilter model and filter material
Operating parameters
Physical and chemical properties of the filter material
Height of the carbon bed, m
1.12
Granulation WD-Extra, mm
1–4
Diameter, m
0.055
Specific surface, m2/g
950–1050
Filtration velocity, m/h
1.5–2.0
The iodine value, mg/g
900–1000
Contact time, h
0.5
pH aqueous extract
10.4
Table 3. Physicochemical parameters of water after individual technological processes
Parameter
Unit
Colour
The range of values
untreated water
1*
2*
3*
treated water
mgPt/L
40–100
40–60
20
20
10–16
–
6.4–7.0
6.6–7.4
8.0–8.2
8.0–8.2
7.8–8.1
Permanganate index
mgO2/L
11.0–18.1
13.0–14.0
12.0
5.6
4.7–5.0
TOC (±0.05)
mgC/L
11.00–14.50
14.40–16.30
11.90
9.60
7.00–16.80
pH
* 1 – Point at the beginning of the technological process after the addition of the oxidant and the coagulant, 2 – Point before the settlers and after the
adjustment of pH, 3 – Point after the settlers, before precipitous filters
Fig. 3. Efficiency of removal of organic compounds – water after adding an oxidant and coagulant (point 1)
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36
J. Kaleta, M. Kida, P. Koszelnik, D. Papciak, A. Puszkarewicz, B. Tchórzewska-Cieślak
Reduction of colouring ranged from 50 to 70%, the
permanganate index was within 54.3–60% and the TOC in
the range of 23.4–39%. The best results were obtained using
CWZ-30 and Norit carbon after application and whose TOC
index value amounted to 8.9 and 8.4 mgO2/L.
In step 2 of the process, the water was characterized by the
following arrangement: colouring 20 mgPt/L, permanganate
index of 12 mgO2/L, TOC 11.90 mgC/L. The sorption organic
pollutants proceeded in a less effective manner (Fig. 4).
In this series of tests, reducing the analyzed indicators
varied within the following limits: colouring 0–25%,
permanganate index 41.6–45%, TOC 5–17.6%.
Similarly to the previous stage of research, CWZ-30 and
Norit carbon have proven to be the most effective carbons;
however, the results obtained were much lower than point 1.
The TOC values after the application of the carbon were 9.8
and 9.9 mg C/L, respectively.
Organic compound indicators in water collected in
section 3 accepted the following values: colouring 20 Hazen,
permanganate index of 5.6 mg O2/L TOC 9.6 mg C/L (Table
3). The results obtained from the use of powdery activated
carbons are shown in Figure 5.
After adding the powdery activated carbon to water before
filters, the compound indicators characterizing the content
of organic compounds were reduced respectively: colouring
– 25–75%, the permanganate index – 1.8–47%, TOC – 2–40%.
The greatest reduction of colouring and TOC was obtained by
using CWZ-30 carbon. In the case of the permanganate index,
the effectiveness of CWZ-30 and Norit were comparable.
Research undertaken has shown that the most effective
powdery activated carbons in removing the organic matter are
CWZ-30 and Norit.
Organic compounds are best removed during the insertion
of carbon into the water after the addition of an oxidant
and coagulant – point 1. Slightly worse, but comparable
performance was achieved for the water before precipitous
filters – point 3. The process of sorption was worst during
the dosage of carbon into the water, before the settlers and
after adjusting pH using Ca(OH)2 (Fig. 6 and Fig. 7). This
fact is confirmed in the literature; sorption of pollutants takes
place less efficiently in an alkaline environment (Kaleta et
al. 2013).
Due to technical conditions prevailing in the analyzed
underground water treatment plant (WTP), dosing the powdery
activated carbon into the water after settlers (before the filter)
was easier. The dosage site was selected as the most suitable
for the pilot-scale studies on the filter model and studies on
a technical scale.
Fig. 4. Efficiency of removal of organic compounds – water before settlers and after adjusting pH (point 2)
Fig. 5. Efficiency of removal of organic compounds –water before precipitous filters (point 3)
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The use of activated carbons for removing organic matter from groundwater
37
Fig. 6. The efficiency of the removal of organic compounds depending on the dosing sites of CWZ-30 carbon
(1 – Point at the beginning of the technological process after the addition of the oxidant and the coagulant,
2 – Point before the settlers and after the adjustment of pH, 3 – Point after the settlers, before precipitous filters)
Fig. 7. The efficiency of the removal of organic compounds depending on the dosage site of Norit carbon
(1 – Point at the beginning of the technological process after the addition of the oxidant and the coagulant,
2 – Point before the settlers and after the adjustment of pH, 3 – Point after the settlers, before precipitous filters)
Analysis of the model filter operation
TOC concentrations in the water after filters at the station and
after the model filter are shown in Table 1. The percentage
of organic compounds removed (efficiency process) was
calculated relative to the TOC concentration in the raw
water during the tests amounting to 13.1 mgC/L. In real
terms, the reduction of TOC was 22.1%. After entering the
dusty fraction of activated carbons and conducting filtration
through a model, more than double the TOC concentration
reduction was obtained. The effectiveness of the carbon was
comparable. TOC removal rates with the addition of PAC
were as follows: for CWZ; 30–48.9% for Norit SA Super
– 46.6% (Table 4).
Comparing the concentration of TOC in the water to the
filter station with the results obtained on the model filter, it
appeared that there was a TOC reduction of 31–34% activated
carbon organic compounds and it was retained in the bed.
Unfortunately, this resulted in a shortening cycle of filter (from
7 to 4 days) and the possibility of uncontrolled breakthrough
of the bed stopping the active carbon. There is always the risk
of penetrating the bed in this case, therefore, for safety reasons,
dosing of powdery activate carbon in technical conditions is
recommended before settling tanks.
Summing up the research in pilot-plant scale, it can be
stated that in order to increase the efficiency of TOC removal to
treatment technologies it is necessary to introduce the sorption
process on the powdery active carbons.
Research in technical scale
The effectiveness of using PAC in the technical conditions is
shown in Table 5. The addition of powdery activated carbon
(carbon cannot be put before the settlers) before the chamber
filter to the technological system resulted in a decrease of
organic matter present in the water by about 10 to 21%. Smaller
TOC removal efficiency (average 14.8%) in the technical
conditions could result from the difficulties in precise dosing
of carbon dust (imperfect mixing, clogging pumps, valves and
pipes supplying coal slurry).
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J. Kaleta, M. Kida, P. Koszelnik, D. Papciak, A. Puszkarewicz, B. Tchórzewska-Cieślak
Analysis of bio-filter operation
The measures taken towards the reduction of TOC content in
the treated water through the use of a second stage filtration
with granular activated WD-extra carbon proved to be effective.
TOC concentration at the outlet of the filter for a period of
approx. 6 months (184 days) was within a range of 0–1 mg
C/L (Fig.8). Starting from the 170th day, the filter operation
showed an increase in TOC after filtration to the value of about
3 mgC/L. Over the next two months, the filter operation of TOC
content in filtered water stabilized at a level of 3–4 mg C/L.
However, this was still lower than the current value obtained
for the WTP. A systematic study of the filtration bed confirmed
the growth of microorganisms, which gradually involved the
cycle of transformation of organic matter (Papciak et al.2016).
The increasing share of microorganisms in the removal of
organic matter rendered the evolution of the S indicator. The
value from the 170th day of filter operation was lesser than 1,
indicating a biodegradable advantage over the sorption process
(Fig. 9). The analyzed groundwater can be effectively devoid of
organic matter on the second degree of filtration on biologically
active carbon filters. The organic compounds in the purified
water were 100% absorbable and 70% biodegradable. The
combination of sorption process with biodegradation up to the
moment of exhaustion of the sorption capacity of the activated
carbon enabled the work in the initial stage of the carbon bed to
remove organic matter within approx. 100%. The colouring of
water after the bio-filtration process did not exceed 5 mgPt/L.
Other water parameters such as turbidity and the permanganate
index were below the limit of quantification (Table 6). Despite
the unfavorable development of the biofilm water temperature
targeting the bio-filter (about 11°C) there is a smooth transition
from the sorption process in bio-sorption. The formation of
biofilm allows to extend the filtration cycle and reduce the
TOC content by 70% i.e. from 10 mgC/L to 3–4 mgC/L. The
remaining organic carbon was not biodegradable.
Biological changes are often slow, but due to the adsorption
qualities of carbon, particles of organic compound may function
on the coal surface for long periods of time. Along with gradual
depletion of carbon sorption capacity, the microorganism
biomass takes over its function, sorbing the substances present
in water. The organic compounds cumulated in the biomass
are used for growth and breathing. Also a systematic growth
of the number of bacteria populating the biofilter filling has
been observed (Papciak el al. 2016). The total number of
mesophilic bacteria did not go over 5 fcu/ml and total number of
psychrophilic bacteria did not go over 14 fcu/ml in water after
the biofiltration process (Table 6). A small number of bacteria in
the water after biofiltration and the fluid transition from sorption
to biodegradation is a proof of well – chosen parameters for the
operation of the bioactive filter.
Table 4. Filtration efficiency in the reduction of TOC
Type of filtration
TOC ±0.05 (mgC/L)
Effectiveness (%)
Water after filters working on WTP
10.20
22.1
Norit Sa Super and filtration on the model filter
7.00
46.6
CWZ-30 and filtration on the model filter
6.70
48.9
Table 5. Lowering the TOC using CWZ-30 carbon
TOC (±0.05)
[mgC/L]
Well water
Without CWZ-30
Water treatment
Treated water supplemented with
CWZ-30
Min.
16.1
9.39
7.45
Max.
17.2
11.20
9.84
Av.
16.6
10.37
8.82
Fig. 8. Changes in organic matter content in water subjected to biofiltration process on model filter
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The use of activated carbons for removing organic matter from groundwater
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Fig. 9. Changes of S indicator during water filtration on WD-extra granulated active carbon
Table 6. Changes in water parameters in the process of biofiltration
(after 140 days of operation of the bed, 71 measuring points )
Parameter
TOC
[mgC/L]
DO
[mgO2/L]
Permanganate index
[mgO2/L]
Colour
[mgPt/L]
Turbidity
[NTU]
Temperature
o
C
Influent
Effluent
Min.
7.56
0.3
Max.
14.60
3.9
AV.
8.95
1.97
Med.
8.61
1.90
SD
1.43
1.41
Min.
7.67
2.77
Max.
8,94
7.63
AV.
8.36
4.46
Med.
8.3
3.2
SD
0.52
1.42
Min.
4.9
0.9
Max.
4.9
1
AV.
4.9
0,9
Med.
4.9
0,9
SD
0
0.05
Min.
5
0
Max.
16
5
AV.
11.9
1.63
Med.
12
0
SD
3.23
1.89
Min.
0.24
0.76
Max.
0.75
0.19
AV.
0.47
0.42
Med.
0.47
0.40
SD
0.13
0.13
Min.
9.1
9.6
Max.
12.1
14.5
AV.
10.6
11.5
Med.
10.6
11.3
SD
0.78
1.52
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J. Kaleta, M. Kida, P. Koszelnik, D. Papciak, A. Puszkarewicz, B. Tchórzewska-Cieślak
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Parameter
Total number
of mesophilic bacteria
37oC
[fcu/ml]
Total number
of psychrophilic bacteria
22oC
[fcu/ml]
Influent
Effluent
Min.
0
0
Max.
8
5
AV.
2
2
Med.
1
1
SD
2.5
2
Min.
0
0
Max.
43
14
AV.
8
5
Med.
3
5
SD
12
4
Conclusions
Introduction of the technological process to water collected
from three different points carried out at the WTP sorption
process with the use of powdery active carbons resulted in
a more effective removal of organic matter. During laboratory
tests, CWZ-30 and Norit proved to be the best carbons.
The best results were obtained when carbon was dosed
into the water collected at the beginning of the technological
process (after adding oxidant and coagulant), the rate of TOC
decreased by approx. 39%. Slightly worse but comparable
performance was achieved for the water taken in the settlers
(before precipitous filters), TOC reduction ranged from
29–40%. The adsorption process proceeded worst at a dosage
of carbon for water taken after settling tanks for pH adjustment
with help of Ca(OH)2. TOC reduction amounted to 17–34%.
The pH of water had an impact on the efficiency of
sorption process. The best results were obtained for the water
at pH=6.6–7.4, taken at the beginning of the technological
system, which was consistent with the literature reports (Kaleta
et al. 2013).
Research conducted in a pilot-scale confirmed the results
obtained in the laboratory. The concentration of TOC in the
water to the filter station was increased by 31–34% compared
to the addition of the powdery active carbons and filtration
through a model. The tested dusty activated carbons gave
comparable results. These absorbed organic compounds are
retained in the bed. However, this resulted in a shortening filter
cycle (from 7 to 4 days) and the possibility of uncontrolled
piercing of deposits.
Research on a technical scale did not confirm such a high
removal efficiency of organic matter, which was obtained at
the laboratory scale and pilot scale. The effectiveness of TOC
reduction was smaller and amounted to an average of about
15% in relation to the currently obtained at the WTP.
Groundwater may be effectively devoid of organic matter
in the second degree of filtration on biologically active carbon
filters in which the organic compounds in the purified water
was 70% biodegradable. The concentration of TOC after the
second stage of bio-filtration on granular activated carbon did
not exceed the value of 4.0 mg C/L.
In view of the fact that the parameters of the biofilter were
well matched, and physico-chemical quality of water supplied
to the biofilter was stable and conducive to the development of
biofilm (pH, oxygen); the only parameter which could improve
the effectiveness of the process is the temperature. However,
its increase in technical conditions is economically unjustified.
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Zastosowanie pylistych węgli aktywnych
do usuwania materii organicznej z wody podziemnej
Streszczenie: W artykule przedstawiono wyniki badań w skali laboratoryjnej, półtechnicznej i technicznej nad
wprowadzeniem do istniejącego układu technologicznego stacji uzdatniania wody podziemnej, pylistego węgla
aktywnego. Celem badań było obniżenie zawartości występujących w wodzie uzdatnionej związków organicznych,
które po procesie dezynfekcji chlorem tworzą toksyczne związki chloroorganiczne (THM). W skali laboratoryjnej
przebadano 9 rodzajów pylistych węgli aktywnych, z których dwa najlepsze wytypowano do dalszych badań.
Badania w skali półtechnicznej realizowano na filtrze modelowym z zastosowaniem węgli: CWZ-30 i Norit Sa
Super. Obniżenie materii organicznej w stosunku do jej dotychczasowej zawartości w wodzie uzdatnionej wynosiło
ok.30%. Badania w skali technicznej z zastosowaniem węgla CWZ-30 wykazały nieco mniejszą skuteczność
w odniesieniu do badań laboratoryjnych i badań w skali półtechnicznej. Obniżenie zawartości materii organicznej wyniosło ok. 15%. Ponieważ ostatnim procesem jednostkowym przed dezynfekcją jest filtracja, zaproponowano alternatywne rozwiązanie – drugi stopień filtracji ze złożem granulowanego węgla aktywnego, pracującego
w połączonych procesach sorpcji i biodegradacji. Rezultaty badań zrealizowanych w skali półtechnicznej były
w pełni zadowalające – skuteczność 70–100%.
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