Course 3 - Water and Health - Water and Wastewater Treatment

Course 3 - Water and Health - Water and Wastewater Treatment
Course 3 - Water and Health
Course 3 - Water and Health - Water and Wastewater Treatment
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Treatment Technologies for Water and Wastewater
Treatment Methods - Understanding the Basics
The fundamental aspects of treatment methods and technologies for drinking water are similar
to those used for wastewater.
Major differences are generally in how the technology is applied in the treatment of either
drinking water or wastewater.
Treatment Categories
Fundamental treatment methodologies can be grouped into either:
Physical treatment
Chemical treatment
Microbial
Advanced
The methodologies within each of these four categories can range from simple to complex.
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Water and Wastewater Physical Treatment
Heat
Boiling
–Disinfection
–coagulation
Distillation
–Removal of contaminants (inorganic and organic)
–Desalination (vacuum distillation, cogeneration)
–Solar distillation
Passive solar distillation kits are available
E.g., the WaterPod see: http://www.thesourcesit.com/english/the-waterpod/ (Internet Access required)
Water pod
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Water and Wastewater Physical Treatment
Filtration
Physical exclusion of particles.
Particles excluded depend on pore size of filter.
Filters can have large pore size and are intended to remove only large debris or they can be
designed to exclude particles in the micron to nanometre size.
Types of filtration technologies can vary from point-of-use technologies (e.g., ceramic pot
filters), community filters (e.g, skyhydrant, or more elaborate micro, ultra or nano-filtration
devices).
Also includes membrane-filtration technologies [microfiltration (MF), ultrafiltration (UF),
nanofiltration (NF), reverse osmosis (RO)].
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The Disinfection Process
Disinfection of drinking water involves:
Removal of pathogens through chemically assisted filtration or equivalent.
Inactivation through a chemical or physical treatment process.
Microorganisms
Chart of different particle sizes of contaminants and different pore sizes of different types of filters
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Disinfection - Counting Logs
Disinfection is measured in the amount of removal and inactivation of microbes.
The effectiveness of disinfection is expressed in tens of times (logs) or percentage of removal and
inactivation of microorganisms
Removal is dependent on the specific disinfection treatment and type of microorganisms (e.g.,
viruses, vegetative bacteria, mycobacteria, spore-forming microorganisms, protozoa, parasites, and
fungi).
–1 Log = 90 % inactivation = 10% alive
–2 Log = 99% inactivation = 1% alive
–3 Log = 99.9% inactivation = 0.1% alive
–4 Log = 99.99% inactivation = 0.01% alive
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Disinfection - Minimum Treatment Requirements
Groundwater:
A 2 log (99%) removal and inactivation of viruses
Surface Water or GUDI:
Chemically-assisted filtration (or equivalent),
AND
a 2 log (99%) removal and inactivation of Cryptosporidium;
a 3-log (99.9%) removal and inactivation of Giardia;
a 4-log (99.99%) removal and inactivation of viruses.
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Disinfection
Factors Affecting Disinfection
Dosage and type of chemical
Injection point and mixing
Contact time
Turbidity
Reducing Agents
pH
Temperature
Organic and Inorganic Material
Microorganisms
Cryptosporidium
CT Concept
Used to determine the appropriate dosage of chemical disinfectants in order to provide effective
pathogen inactivation to the required level.
Involves operating conditions such as flow, temperature, pH and contact time.
Calculated by multiplying the disinfectant residual concentration (in mg/L) by the disinfectant contact
time (in minutes).
CT = Concentration (mg/L) x Time (minutes)
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Disinfection By-Products (DBPs)
Disinfection
Disinfection By-Products
Agent
Free
Chlorine
Trihalomethanes, THMs
Haloacetic Acids, HAAs
Inorganic By-Products
Ozone
Organic Acids
Aldehydes
Assimilable organic carbon
Bromate
Chlorine
Dioxide
Inorganic by-products
Chlorite
Chlorate
Chloramines ?
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Filtration Pressure vs Particle Size
Increasingly greater applied pressure is required as the filter pore size decreases for the physical
removal of particles, including microrgansims, of increasingly smaller sizes.
Applied Pressure: Filtration< Microfitration < Ultrafiltration< Nanofiltration< Reverse Osmosis.
Particle Size Removal: Filtration> Microfiltration>Ultrafiltration>Nanofiltration> Reverse Osmosis.
Adapted from Meier et al., 2006
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Water Treatment - Microfiltration (MF)
MF pore size is generally between 10 µm to 0.1 µm.
MF does not always need pressure to operate, but some filters can operate under pressure.
MF can remove parasitic Giardia lamblia cysts and Cryptosporidium oocyts and bacteria if the filter
pore size rating is at least 0.2 µm or smaller.
Generally, MF requires backwashing to remove filter cake that can cause fouling of the filteration
unit.
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Water Treatment - Ultrafiltration (UF)
UF pore size is generally 0.1 µm to 0.001 µm.
UF will filter out:
Microorganisms
High molecular weight substances
Natural organic matter (NOM)
Dissolved organic matter (DOC)
Colloidal matter
Organic and inorganic polymeric molecules
Some disinfection by-products
UF will not filter out low molecular weight organics and freely dissolved ions such as,
sodium, calcium, magnesium chloride and sulfate.
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Water Treatment - Ultrafiltration (UF)
Pathogen removal:
UF membranes generally provide good removal rates for many pathogens, in particular Giarida
lamblia cysts and Cryptosporidium oocysts and various bacteria.
The retention of viruses on low-pressure membranes depends on the molecular weight cutoff
(MWCO) and other characteristics of the membrane, module design and the mode of operation
Studies have shown that virus retention can not be predicted by normal pore size alone or by
the MWCO.
Natural organic matter (NOM) is a major factor causing fouling on UF membranes.
UF membranes require cleaning. UF membranes must be cleaned or replaced to ensure
adequate performance.
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Water Treatment - Nanofiltration (NF)
NF is a relatively new addition to the family of membrane filters.
NF pore size is approximately 1 nm (typically rated by molecular weight cut-off “MWCO” which
is typically < 1000 atomic mass units (daltons)).
NF is used primarily to filter waters with a low total dissolved solids content.
NF primary purpose is to remove monovalent ions to soften water.
NF is commonly used for desalination.
NF requires pressure.
NF operates on the principle of cross-flow filtration technology.
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Water Treatment - Reverse Osmosis (RO)
Osmosis is the process where a solute moves from a high concentration across a semipermeable membrane to an area of low concentration.
Reverse osmosis (RO) is when an external pressure is exerted to reverse the direction of flow
(i.e., solute moves from a low concentration to a high concentration).
RO is often used for desalination.
Poor water yield and high manufacturing and operational costs have been a major hindrance to
the expansion of RO technology which restricts RO use to primarily developed countries.
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Water Treatment - Ultraviolet (UV)
UV rays can inactivate many bacteria and viruses.
The effectiveness of UV treatment to inactivate microorganisms and to disinfect water supplies is
limited by:
Water quality properties such as, turbidity, water hardness, iron and manganese
concentrations, organic compounds, colloidal OM and DOM.
Duration of UV exposure.
The absorbed UV wavelength.
The resistance of specific microorganisms to UV irradiation.
UV disinfection by-products can be formed by chemical phototransformation of organic compounds
in the water, and residual microbial contamination may occur from incomplete UV inactivation of
microorganisms, as well as microbial mutations caused by UV irradiation.
A commercial UV water treatment unit consists of a UV light source enclosed in a sleeve made of
quartz.
Water passes through a flow chamber; UV rays are emitted and absorbed into the stream of water.
Image:
UVB on DNA. Source: http://earthobservatory.nasa.gov/Library/UVB/ (Internet Access Required)
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UV spectrum
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Water Treatment - Aeration
Primarily used to off-gas volatile organic compounds.
Used to enhance microbial action.
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Water Treatment - Coagulation
The purpose of coagulation is to primarily reduce turbidity, with the added benefit of removing
other pollutants and microorganisms attached to the suspended matter and the removal of
dissolved organic matter and inorganic matter.
Coagulation can also be used to remove colloidal material when other membrane technologies
are used or when the removal of these this material is important for other technologies such as
UV irradiation or ozonation.
The removal of this colloidal material will often extend the life and enhance the performance of
the membrane devices, particularly for ultrafiltration, nanofiltration and reverse osmosis units.
Any remaining colloidal or dissolved matter can be further removed by membrane devices.
Ferric chloride is a coagulant that is particularly effective in the removal of natural organic
matter (NOM).
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Chemical Treatment Methods
This category includes:
Chlorine and chlorine based products
Iodine
Silver
Copper
Ion exchange
Activated carbon adsorption
Activated alumina
Ozonation
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Removal and Inactivation of Pathogens
The removal and inactivation of pathogenic microorganisms from water (i.e., waterborne pathogens) is a
major treatment objective for both drinking water and wastewater.
The selection of the appropriate inactivation process for drinking water is dependent on raw water
characteristics.
The choice should consider and balance the need to inactivate pathogens while minimizing the production of
disinfection-by-products.
The approach often utilizes both chemical and physical options.
Treatment method and log removal of pathogens
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Types of Disinfectants
Chemical Disinfection:
Physical Disinfection:
Ultraviolet (UV)
Chlorine: Sodium Hypochlorite;
Calcium Hypochlorite; Chlorine gas
Filtration
Heat (boiling water)
Chlorine Dioxide
Chloramines
Physical methods are not acceptable for secondary disinfection
because physical methods do not provide a persistent residual
disinfection.
Ozone
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Chlorination
Purpose of Chlorination
1.
The primary purpose of chlorination is for disinfection of water by inactivation of microbial
contaminants such as, the killing of pathogenic bacteria and viruses
2.
Secondary purposes of chlorination include its use as an oxidant to remove or assist in the
removal or conversion of undesired chemicals such as,
in the chemical breakdown of easily oxidized pesticides (e.g., aldicarb) and
in the oxidation of dissolved metal ions like manganese (II) to form insoluble
products that can be more easily removed by physical treatment.
Chlorination Process
Chlorination can be accomplished with the use of the following:
Liquefied Chlorine gas;
Sodium Hypochlorite solution
Calcium Hypochlorite granules
On-site Chlorine generator
Chlorine Residuals - Hypochlorous Acid (HOCl) and Hypochlorite Ion (OCl- )
All forms of chlorine dissolve in water, reacting with the H+ ions and the OH- ions of water,
producing hypochlorous acid (HOCl) and hypochlorite ion (OCl- ).
The free chlorine residuals, HOCl and OCl - formed when chlorine reacts with water are
two active disinfecting agents of chlorination.
HOCl is a more effective disinfectant than OCl - because it diffuses faster through the
bacterial cell wall, and therefore destroys organisms much quicker.
The ratio of HOCl to OCl - produced in chlorine treated water is dependent on the
temperature and the pH of the water,
The lower the pH, the more HOCl produced, and in general, the more effective is the
chlorination-disinfection process.
Water temperature is important because the free chlorine residual required for
adequate disinfection is more easily maintained in cold water.
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% free chlorine residuals vs pH
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Chlorinated Products Used in Water Treatment
Sodium Hypochlorite
A manufactured solution of sodium hypochlorite is released into the water using a metering pump.
The sodium hypochlorite solution is available as 12% or 5% available Cl2 .
The solution is corrosive; must keep the chlorine solution away from equipment that can be
damaged by corrosion.
The addition of sodium hypochlorite solution to water will increase the pH of the water.
The chlorine concentration in the solution will degrade over time. It is important to protect the
solution from exposure to light and heat during storage in order to minimize degradation and to
ensure adequate chlorine concentration necessary for disinfection.
Calcium Hypochlorite
A solution is prepared before use by mixing powdered or granulated calcium hypochlorite with water.
The prepared chlorine solution is then added to water.
Used by some municipal systems, but more commonly for post construction disinfection (new water
mains) and for swimming pools.
Chlorine tablets; chlorine pucks container
Other Chlorinated Products
Chloramines are produced when ammonia is added to chlorine.
The three basic forms of chloramines that can be produced are: monochloramine, dichloramine,
trichloramine.
Monochlorame is the most common and plentiful form.
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Monochloramine is often a desired product for secondary disinfection.
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Principles of Chlorination
Chlorine Demand
Each water source treated will have its own chlorine demand. This refers to the amount of
chlorine that is consumed in the oxidation and interaction of constituents found within the
water.
For example, those waters high in NOM will have a much higher chlorine demand than those
waters with a lower NOM content.
In order for the chlorine to be an effective disinfectant, the amount added must ensure that
there is free (unbounded, un-reacted) chlorine that remains in solution after all other chemical
reactions with other water constituents (such as NOM) have occurred.
The amount of chlorine left in a free state is often termed “residual chlorine”.
Many factors influence the consumption of chlorine and the presence of residual chlorine.
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Reaction of Chlorine with Water
Chlorine added to raw water
Chlorine demand of raw water
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Chlorine reaction with water
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Chlorination Methods
Different techniques of chlorination
A. Breakpoint Chlorination
The dose of chlorine used is sufficient to rapidly oxidize all ammonia nitrogen and to leave a residual
concentration of free chlorine to protect against re-infection.
The process of adding chlorine to water until the chlorine demand has been satisfied.
Further additions of chlorine after breakpoint result in an increase in the free chlorine residual.
The process occurs in the following four steps:
1.
The small amount of chlorine added, reacts with organic matter and inorganic materials
(ammonia, iron, manganese, etc.); disinfection does not occur and no chlorine residual is
formed.
2.
More chlorine is added, reacts with organics and ammonia to form chlororganics and
chloramines. Produces a combined chlorine residual.
3.
More chlorine is added (chlorine demand is satisfied – breakpoint chlorination is reached).
Chloramines and some chlororganics are destroyed.
4.
After breakpoint, the addition of chlorine will produce free residual chlorine (best residual for
disinfection).
B. Superchlorination / dechlorination
The addition of large dose of chlorine to achieve rapid disinfection; followed by the removal of all
excess free chlorine.
C. Marginal Chlorination
Used in high quality water for the purpose of ensuring a sufficient concentration of residual chlorine
is achieved.
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Breakpoint Chlorination
figure - breakpoint chlorination
Chlorine residual
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Chlorine Residuals
Free chlorine residual: Chlorine reacts with water to form hypochlorous acid (HOCl) and
hypochlorite ion (OCl-)
Combined chlorine residual: Chlorine also readily with ammonia (NH 3 -N) to form,
monochloramine (NH 2 Cl), dichloramine (NHCl 2 ), trichloramine (NCl3 )
Combined chlorine residual= total chlorine residual - free chlorine residual
Total chlorine residual = free chlorine residual + combined chlorine residual
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Free Chlorine Residuals
Water MUST have a minimum Free Residual of 0.2 mg/L when leaving a water treatment plant.
Water MUST have a minimum Free Residual of 0.05 mg/L at ALL points in the distribution
system.
The maximum chlorine residual at any time and/or location should not exceed 4 mg/L.
Depending on the size of the distribution systems, re-chlorination stations may be required.
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Degradation of Chlorine Solutions
Decay rate sodium hypochlorite
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Water Treatment Using Disinfectants (Biocides) Other than Chlorine
Iodine
Iodine is a biocide that has a long history of biocidal use in medicine and is used for short-term
disinfectant applications (e.g., point of use technologies).
Iodine is typically used as an emergency disinfectant of drinking water in the field, but is not
intended for long term use.
The maximum concentration of iodine in drinking water should not exceed 18 µg/L (0.018 mg/L).
Toxicity: Exposure to 16-130 mg of total iodine per kg of body weight can be fatal.
Silver
Silver has been long known for its biocidal properties and has a long history of biocidal use in
medicine, but some bacteria are resistance to silver.
The silver ion (Ag+) binds to proteins in the bacterial cell membrane causing damage to cell
structure and function and inhibition of bacterial cell growth.
The most common use of silver in water treatment is in point of use products such as, ceramic
filters coated with silver particles and fabric treated with nanosized silver.
In these products, the silver inhibits microbial growth to prevent clogging of the filter and does
not directly disinfect the filtered water.
Copper-Silver Ionization
Recent attention has been given to the combined use of copper and silver as a biocide for the
treatment of bacteria and control of bacterial biofilms.
The ionization of copper and silver ions has been demonstrated as an effective technique for
bacterial pathogens in hospitals such as Legionella sp.
An electrical charge from an electrode is needed in the process.
The procedure appears to be a relatively new treatment and as such regulatory agencies are
still trying to determine what human health effects could arise and what safeguards are needed
in terms of copper and silver ion exposure.
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Water Treatment - Other Methods
Ion Exchange
This process in its simplest form is when an unwanted ion is removed from solution and is
replaced by an ion with a weaker attraction for the solid matrix through a dissociation reaction;
hence the name ion exchange.
The most widely used applications involve passing water (i.e., solution) through an ion
exchange resin (i.e., solid matrix) that removes unwanted ions from the water (e.g., heavy
metals, ionic pesticides) by more strongly adsorbing them than less harmful ions weakly
adsorbed to the resin material (i.e., solid matrix).
Ion exchange resins are manufactured to be selective for the type of unwanted ion
intended to be removed.
The selectivity of the resin material is achieved by choosing the appropriate functional
group and pre-charging it with a more weakly adsorbing ion that has less harmful
properties than the targeted unwanted ion (e.g., heavy metals, pesticides).
Activated Carbon Adsorption
Activated carbon is an adsorptive filter.
Carbon is activated when exposed to steam and high temperatures (2300°F) without oxygen.
Activation produces many tiny pores and thus increases the overall surface area of the particle.
Can be used to remove some solvents, pesticides, chlorine, chloramines and compounds
producing unwanted taste and odour.
Activated Alumina
Activated alumina is an adsorptive filter.
Manufactured from aluminium hydroxide to produce aluminium oxide (Al 2 O 3 ) which is quite
porous and can have a surface area > 200 m 2 /g.
Often used to remove fluoride, arsenic, selenium and phosphorus.
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Water Treatment - Ozonation
Ozone (O3 ) is a powerful oxidant.
Ozone can be used as a primary disinfectant, but is often used as an oxidizing agent for the
removal of pesticides and other chemical contaminants.
Performance is related to achieving a desired concentration and duration of contact time.
The residual concentration of O 3 remaining in the water is short lived (virtually none); this is
because ozone is rapidly consumed by natural organics within the water and is quickly
volatilized to the atmosphere.
The typical dosing range is 2 – 5 mg of ozone/L to produce a remaining residual
concentration of approx 0.5 mg/L water after a contact time of up to 20 minutes (i.e., a loss
of the applied ozone dose of approximately 10-fold occurs within 20 minutes).
Low levels of chlorine may be added to water treated by ozonation in order to provide a
low residual concentration of chlorine to prevent re-contamination by microbial growth in
the O 3 treated water.
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Microbial Treatment of Wastewaters
The breakdown of organic molecules by microorganisms is often referred to as microbial
degradation or biodegradation, and is exploited in the treatment of wastewaters, particularly
treatment of domestic wastewaters.
The solubilisation and in some cases the mineralization of a wide range of organic and
inorganic compounds is carried out by microorganisms.
Wastewater treatment plants utilize micoorganisms (e.g., facultative bacteria) to digest many
different types of organic compounds and overall reduce the original volume of solids in the
wastewater.
Microorganisms are also important in key processes such as ammonification, nitrification and
denitrification.
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Water Treatment - Advanced Treatment Processes
Many advances have been made in the last one to two decades in the treatment of raw drinking
water and wastewater.
Much of this interest has been focussed on developing new technologies for the removal of
emerging contaminants of concern (COCs), primarily pharmaceuticals and personal care
products.
Public concern has fueled interest in determining more effective ways at removing these types
of compounds, primarily from drinking water supplies, but also from treated effluents released
to the environment.
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Drinking Water - The Protection of Raw Drinking Water Supplies (Source Water Protection).
Provision of Safe Drinking Water
A multi-barrier approach is often used by regulatory agencies to ensure the safety of drinking
water supplies.
The focus of this approach is to develop multiple points of control.
The intent is redundancy to ensure that multiple safe guards are in place to ensure continuity of
protection should one level (point of control) fail.
These levels of control often include: i) protection of the source, ii) water treatment, iii)
distribution network, iv) monitoring and surveillance of treated water.
Source Water Protection (SWP)
SWP refers to a methodology or an approach that is implemented to protect the raw (untreated)
drinking water supply in terms of both quality and quantity.
SWP is the first barrier in a multi-barrier approach.
In practical terms, SWP is a management tool to ensure that harmful pathogens and chemicals
do not contaminant raw water supplies and to ensure that raw water resources are not
unnecessarily depleted.
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Source Water Protection (SWP)
SWP refers to a methodology or an approach that is implemented to protect the raw (untreated)
drinking water supply in terms of both quality and quantity.
SWP is the first barrier in a multi-barrier approach.
In practical terms, SWP is a management tool to ensure that harmful pathogens and chemicals
do not contaminant raw water supplies and to ensure that raw water resources are not
unnecessarily depleted.
The Goals of a Source Water Protection are to…
1. Keep Drinking Water Supplies Clean and Plentiful
Preventing contaminants (pathogens, chemicals) from getting into the source water supplies
(e.g., lakes, rivers, ground water wells, reservoirs and cisterns from which drinking water is
obtained)
Conserving water supplies and taking safe guards for the prevention of needless depletion of
water quality and volume of water resources.
2. Develop Mitigation plans
Identify problems and threats and develop plans to mitigate them.
3. Develop Contingency Plans
Preparing a plan of action in the case of an emergency.
How to protect existing source waters and decrease the risks that threaten it? (what can
be done)
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Components of the SWP Approach
1. Characterizing the water source.
2. Identifying major problems and threats (risks).
3. Evaluate the risks.
4. Determine how to manage the risks.
5. Identify key needs within the community.
6. Development and implementation of a source water protection plan.
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WLC Template
Characterizing the Source Water
Source waters are best managed on a watershed basis.
Understanding where your water originates and the path it takes is key to protection.
Some important aspects for characterization include:
Topography, climate, soil and bedrock types.
Volume of drinking water supplies (both ground and surface).
Human development and use.
Water needs, potential conflicts and risks.
Diagram of source waters.
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WLC Template
Inventory (characterize) the Watershed
Physical Attributes
Surface water resources and groundwater
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C005IWS.htm[11/3/2014 7:38:04 PM]
WLC Template
Inventory (characterize) the Watershed
Climatic Attributes
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C006IWSCA.htm[11/3/2014 7:38:04 PM]
WLC Template
Characterizing the Watershed
Characterisation will identify vulnerable areas which need protection.
Groundwater:
Significant groundwater recharge areas.
Highly vulnerable aquifers (un-protective overburden).
Wellhead Protection Areas (WHPAs).
Future municipal supplies.
Surface Water:
Headwaters.
Drinking water intake sites (site specific, historical).
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WLC Template
Identifying Major Risks to Source Waters
SWP plans determine the boundaries of a protective zone around the source water.
Within the protective zone all activities that could degrade the quality or quantity of the source
water are identified and where possible mitigated or eliminated.
Information regarding the flow path and flow velocities are often used when determining the
boundary of the protective zone.
The size of the protective zone depends on the level of protection desired. Protective zones for
surface waters are often larger than those for ground water since the time required for water to
travel from a contamination source to the location where the drinking water is drawn can be
much shorter than the travel times for ground water resources.
Risk is an evaluation of the problem (hazard and threat) combined with the level of harm it could
cause and the probability (chance) of it happening.
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WLC Template
Delineation of Protection Zones around Drinking Water Supplies
Communities can provide protection of groundwater and surface water resources through the
establishment of source water protection zones.
Delineated zones that protect groundwater are called Wellhead Protection Areas (WHPAs), those that
protect surface waters are called Intake Protection Zones (IPZs)
Important Concept:
Jurisdictional authority of communities is limited (often can not protect everything within a
watershed)
Delineation identifies those sites that are most important in terms of providing supplies in the near
future (e.g, days-surface water to decade-groundwater)
Delineated zones are used to identify a physical location to be:
i) Inventoried for existing and potential problems (hazards and threats)
ii) Managed to mitigate impacts and risks of identified hazards and threats.
The delineation of protection zones are primarily based on two key factors:
1. Direction of water flow.
2. Speed of travel (also known as "Time-of-Travel").
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WLC Template
Two guiding principles
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WLC Template
Protection of Ground Water Supplies
Groundwater Protection Zones
The principles of 1) direction and 2) time-of-travel still operate for groundwater resources.
Groundwater movement and the size of the aquifer are more difficult to define than that for
surface waters such as, rivers and lakes.
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WLC Template
How is Time of Travel Estimated
Data Requirements:
Topography
surface and subsurface geology and lithology
surface water and groundwater conditions,
hydrodynamic parameters of the subsurface formations
climate data, etc.,
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WLC Template
Intake Protection Zones: Simple Set-back Method
Intake Protection
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WLC Template
Time of Travel Method
Assumptions:
Time zones provide assessment of dispersion rate or spread of a spill or discharge (vulnerability of water intakes in case of contamination event) (>time to reach the water intake =
less vulnerable).
Time zones give plant operators the time (warning) needed to shut off the tap.
Spills and other hazards and threats will be detected quickly.
Time of travel method
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WLC Template
Watershed Delineation and Zoning By-Laws
Delineation used to develop zoning by-laws.
Red Zone: most restrictive to the types of activities that are allowed.
Yellow Zone: least restrictive.
Anything beyond yellow zone not under bylaw restrictions.
Watershed delineation and zoning
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WLC Template
Wellhead Protection Areas
Wellhead Protection Areas: Arbitrary fixed radius method for delineation is based on distance from
the wellhead.
Wellhead protection areas
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WLC Template
WHPA: Calculated Fixed Radius Delineation
Diagram of well and volume calculation
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WLC Template
WHPA: Calculated Fixed Radius Delineation (3 years)
WHPA
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C017WHPA.htm[11/3/2014 7:38:06 PM]
WLC Template
WHPA: Calculated Fixed Radius Delineation (Six Years)
WHPA six years
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C018WHPA6.htm[11/3/2014 7:38:06 PM]
WLC Template
Calculated Fixed Radius Delineation
Calculated Fixed Radius Delineation expressed as time.
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C019FRD.htm[11/3/2014 7:38:07 PM]
WLC Template
Analytical Methods for Delineation
Analytical methods for delineation involved the development and application of computer models to
estimate groundwater flow patterns and delineation of areas for protection zones.
Digital photo groundwater flow and well
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WLC Template
Comparison of Delineation Approaches
Comparison of the calculated fixed radius delineation approach versus analytical methods and
applied computer models utilizing actual measurements of ground water movement.
Delineated zone comparisons
Delineated zone is based on actual ground water measurements and monitoring data.
Implications for stakeholders within identified zones.
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WLC Template
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C021CDA.htm[11/3/2014 7:38:07 PM]
WLC Template
Selecting a Delineation Method for Defining Source Water Protection Zones
What criteria should be applied in selecting a delineation method?
The followng criteria should be included and possibly others in the selection of a delineation method
for defining ground water protection zones and their implications for source protection plans for safe
drinking water.
1. What are the goals and objectives of the Source Water Protection Plan (SWPP)?
2. What are the identified hazards from past present and planned future sources of
contaminants (both naturally occurring and from human activities)? And where are point and
non-point sources of contaminants (biological, chemical and physical) located in relationship
to the water intake, upstream or downstream, up gradient or down gradient)?
3. What are the source water capacity requirements for the present and future community and
area? Taking into account the long term planning and development objectives in the community
in terms of its demographics growth and needs for drinking water and potable water supplies
and single and multiple water intake points.
4. What are the existing and emerging short-term and long-term problems and risks of
impacts to the quality and quantity of the source water for drinking water in the community, and
also to the watershed including changes in loadings of contaminants, changes in flow rates,
changes in volume, evaporation rates, and changes in ground water directional flow and
gradients and recharge rates?
5. What financial and other resources are available and how much money is the community
willing to spend?
The delineation method for defining source water protection zones should be consistent with
the Source Water Protection Plan goals and objectives of the community and the requirements
for precision and accuracy and timing of the monitoring and surveillance data. It is important to allow a realistic spatial and temporal scale by applying a level-of-concern
approach for risk assessment, such that there should be a sufficient warning system for
operationalizing risk communication and risk management actions, as necessary and
appropriate to the situation, if spills and other situations occur that impact the quality and
supply of safe drinking water.
In this series of courses on Water and Health, the Course entitled "Water-related Impacts on
Health - Principles Methods and Applications provides a comprehensive discussion of risk
assessment risk management and risk communication, including information on key terms
frameworks and resources used in risk assessment management and communications,
including examples relevant to safe drinking water.
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WLC Template
Source Water Protection And Risk Assessment
Precautionary Principle
The precautionary principle should be applied in the development of source water protection
zones and the assessment and management of risks to safe drinking water. The precautionary principle is defined as an approach to risk management that can be applied
in circumstances of scientific uncertainty, reflecting a perceived need to take action in the face
of a potentially serious risk without waiting for definitive results
of scientific research. (Duffus et al., 2007. Glossary of Terms Used in Toxicology IUPAC Pure
and Applied Chemistry 79:1153-1344). A glossary of risk assessment and toxicology
terminology is included in the Resources folder of Course 2 in this series on Water and Health.
Note: The 1992 Rio Declaration on Environment and Development says: “In order to protect the environment, the precautionary
approach shall be widely applied by states according to their capabilities. Where there are threats of serious or irreversible damage,
lack of
full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”
Development of a Source Water Protection Plan for Minimizing Risks to Drinking Water
The development of a Source Water Protection Plan involves the application of the principles of
risk assessment and risk management.
The findings of a risk assessment (RA) of the comunity's source water for its drinking water
supply should document the identification of major and minor hazards and key factors
contributing to risks of harmful effects.
The information in the RA should provide pertinent and essential background information for
risk management decisions on mitigating possible harmful impacts to the safety of the
community's drinking water supply, including the development of risk communications
materials and an implementation strategy.
Note: The previous course (Course 2) in this series on Water and Health entitled "Water Related Impacts on Health - Principles
Methods and Applications" provides a comprehensive overview of environmental and human health risk assessment, risk
management, and risk communication links to resources and examples of their applications. A brief review of the framework for risk
assessment and key terms are provided below.
Questions that might be asked in framing the development of a source water protection plan could
include the following, 1. What are the identified hazards, including sources and contaminants (past, present and
planned in future)? (Identification and inventory of existing and emerging problems)
2. How likely is harmful exposure event to occur?
3. What is the probability that the source water supply could be impacted by the identified
hazards?
3. What is the expected frequency magnitude and severity of impacts on the performance of the
drinking water treatment and of harmful effects in the exposed population and the ecosystem?
4. What are the contributing factors to risk of those harmful effects and their comparative level
of concern and importance?
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WLC Template
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M020C023SWPR.htm[11/3/2014 7:38:07 PM]
WLC Template
Summary
Source water protection involves: i) Knowledge about your water resources.
ii) Developing zones of protection.
iii) Identifying exisiting and emerging problems from known hazards and threats within the
protection zones.
iv) Developing plans to reduce or eliminate those hazards and threats and to protect the
source water supplies and drinking water from significant risks of harmful impacts on water
quality and quantity.
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WLC Template
PoU - Heat and UV Disinfection (boiling, SODIS + 2 products)
Boiling for Disinfection
Treatment
Solar Disinfection
(SODIS)
Boiling for Disinfection
AquaPak – solar disinfection
Solar disinfection is a
simple way of disinfecting
water from pathogenic
bacteria and viruses.
Description
and
Features
It involves the filling of old
water bottles with raw
water, if possible filtered
boiling water is one of the oldest
water, and leaving them in
and most commonly practiced
a sunny area to expose
disinfection methods
the water to the sunlight's
water should be boiled in a clean UV radiation in an effort to
container for at least a minimum of reduce the number of
5 minutes, depending on elevation pathogens.
longer boiling times may be
Bottles should be made of
needed.
PET (polyethylene
major drawback is its dependency terephtalate) or glass that
on fuels which can be costly and is transparent and
colourless. Bottle should
in scarce supply
not be larger than 3 L.
it is estimated that 1 kg of wood or
0.1-0.2 kWh is needed to boil 1 L Water temperature in bottle
should reach 40°C and be
of water
left in the sunlight for a
minimum of 6 h on a
sunny day or 2 consecutive
days if the sky has more
than 50% cloud cover.
AquaPak is a low cost
polyethylene bag intended for
solar disinfection
Naiade
this unit contains two bag
filters (25 µm and 10 µm)
and a 100 L storage tank
for the filtered water which
contains a UV lamp for
added disinfection
modifications to the bag such
as a bubble pack layer help to
increase the temperature up to power to the unit is provided
by photovoltaic panels and
65°C where pasteurization
excess power is stored in a
takes place
batter for 24 hour service
a replaceable glass vial filled
the unit can filter up to
with orange wax is inserted
3.500 L per day with a flow
into the bag. The wax melts
and changes colour once 65°C rate of 5 L per minute
is reached and pasteurization
the estimated lifespan of the
starts
unit is 10 years with UV
bulb replacement after
AquaPak can treat up to 5 L
10000 hours of use
per day
education and training appear
to be needed to improve
peoples willingness to use
it is easily installed with little
technical expertise needed
It is highly effective in
removing pathogens with
additional turbidity removal
Bottles should be replaced
every 4 to 6 months.
Disinfection
and
Contaminant
Removal
Efficiency
boiling is generally 100% effective
against bacteria, viruses, protozoa
and helminths when water boiled
for the required minimum time.
Exceptions are bacterial
endospores, other heat resistant
forms of pathogens.
Sunlight treatment for 6
hours at 40°C can remove
it has been found to reduce
up to 99.999% bacteria,
bacterial pathogens by
99.9 – 99.99% viruses, but
99.999%
it is less effective for
protozoa.
example
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WLC Template
Unit
Treatment
Price
unit treatment price is 17.85 Euro
per cubic metre water filtered
0.87 Euro per cubic metre
water filtered
3.13 Euro per cubic metre
water filtered
0.59 Euro per cubic metre
water filtered
Overall
evaluation
7.8 (good)
7.0 (good)
6.4 (good)
5.8 (medium)
www.who.int www.sodis.ch
More
information
www.cawst.org
www.medapnaiade.com www.solarsolutions.info
www.akvo.org
www.akvo.org
www.cleanwaternow.nl
(Internet Access Required)
(Internet Access
Required)
(Internet Access
Required)
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M030C0015heatuv.htm[11/3/2014 7:38:08 PM]
(Internet Access
Required)
WLC Template
PoU - Chemical Disinfection Treatment (Chlorine + 5 products)
Boiling for Disinfection
Treatment
Description
and
Features
Chlorine - Disinfection
AquaEst Plation® Floats Disinfection
NaDCC for disinfection
this product is composed of
specialized ceramic balls that have
a coating of a high quality colloidal
Chlorine has been used as a
silver
NaDCC are a form of chlorine disinfection
disinfectant since the early
tablets containing sodium
1900’s.
once in the water natural
dichloroisocyanurate also referred to as
processes ionize the silver to
sodium troclosene
Sodium hyperchloride can also release silver ions in to the water
be used and it can be
to inactivate pathogenic bacterial
NaDCC tablets have historically been
manufactured in most locations
used to treat water emergencies, but are
through brine electrolysis.
the main purpose of this product is now starting to become more available to
to prevent bacterial growth in
the general public
Each chlorine disinfection
treated water during long term
product should have its own
storage
they come in different sizes (3.5 mg to 10
instructions that will need to be
g) to treat water volumes between 1 to
consulted to achieve the correct it appears the floats can be used
3000 L
dosage for destruction of
to treat raw drinking water,
pathogens and prevention of
however, the contact time may
the required dose and contact time vary
harmful health effects.
need to be extended – presumable with water quality. Ideal conditions for use
for days
are low turbidity and pH within 5.5-9.0
A minimum contact time of 30
minutes is required and may be they are easy to use and do not
tablets have a shelf life of 5 years if
longer depending on water
require electricity or maintenance protected from high temperatures and high
quality.
humidity
anticipated life expectancy is
Residual chlorine in the water
approx 2 years in stored water, but can provide some protection
if used in chlorinated water the
against recontamination.
effectiveness by be reduced to less
than 2 years
Chlorine is effective against
Disinfection
bacteria and viruses and can
and
achieve upwards of a 2 to 8 log
Contaminant
removal, but it is not as
Removal
effective against protozoa and
Efficiency
helminths.
PUR Purifier of Water™ WATA – chlorine generator
this technology relies on placing
a specially developed probe that
when placed in salt water will
generate active chlorine through
electrolysis
WaterPurifier
this is a self-contained, ready
to use water purification unit
water is first filtered with
ceramic Ultrafiltration
membranes (40 nm pore
size). Solar-powered
electrolysis generates
25 g of salt per L of water are
it is now sold world wide, but placed into a bottle to generate a hypochlorous acid which
cost can still be restrictive to chlorine solution that can be used disinfects the water in the
storage reservoir
some
to disinfect water
this product is both a
flocculant (ferric sulphate)
and a disinfectant (calcium
hypochlorite)
one sachet treats 10 L of raw disinfection is accomplished by
water
adding a known volume of this
chlorine solution to the raw
once added, the water is
drinking water and allowing it to
stirred and allowed to settle
stand for 30 minutes
for 5 minutes. After this the
solids are filtered through a
electrodes need cleaning of
cotton cloth filter into a
calcareous deposits (generally
second container where the
after every 150 h of use)
water is allowed to stand for
the lifespan of the device is
an additional 20 minutes to
approx 20000 hours or 4.5 years
give time for disinfection
shelf life is 3 years
indicator strips provide check
on water quality (presence of
residual chlorine)
estimated lifespan up to 20
years, membranes and
electrodes likely last only 5
years
maintenance consist of
backwashing by hand the
filters with hand powered air
pump
requires electricity for operation,
can be equipped with
can be connected to solar panels
additional carbon filters to
remove chemical
contaminants
PUR removes >99.99%
bacteria, up to 99.99%
viruses and 99.9% protozoa
tablets are highly effective against bacteria
PUR will remove high
and viruses but not effective against
turbidity, heavy metals such
protozoa
as arsenic and some
dissolved chemical
contaminants
example
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M030C0018chemical.htm[11/3/2014 7:38:08 PM]
effectively removes bacteria,
viruses, protozoa, helminths
and turbidity
WLC Template
Unit
Treatment
Price
0.24 Euro per cubic metre
water filtered.
0.75 Euro per cubic metre water
filtered
3.25 Euro per cubic metre water filtered
7.14 Euro per cubic metre
water filtered
0.02 Euro per cubic metre water
filtered
1.21 Euro per cubic metre
water filtered
Overall
evaluation
7.0 (good).
6.6 (good)
6.5 (good)
6.5 (good)
4.9 (medium)
5.4 (medium)
www.cawst.org www.csdw.org www.cdc.gov
www.purpurifierofwater.com
www.antenna.ch
www.mobilewatermaker.nl www.psi.org www.aquatabs.com www.pghsi.com www.jolivert.org
www.who.int
www.who.int
(Internet Access Required)
(Internet Access Required)
(Internet Access Required)
(Internet Access Required)
www.cawst.org More
information
www.cdc.gov
www.aquaesteurope.com
(Internet Access Required)
(Internet Access Required)
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WLC Template
Point of Use Disinfection and Small-Scale Drinking Water Treatment
Access to “improved” water supplies does not always a guarantee that supplies are safe and
reliable.
This is especially true in developing countries and elsewhere, when contamination particularly
microbial and also chemical occurs because of inadequate treatment and recontamination
during transport and storage.
Point of use (PoU) and small-scale treatment is a strategy to improve access to safe drinking
water, particularly where municipal water treatment systems are not available and the safety of
water available for drinking is unknown.
Recent studies have shown PoU can reduce diarrhea morbidity for children under the age of 5
by 29% .
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WLC Template
Disinfection - Point of Use and Small-Scale Treatment of Drinking Water
Disinfection of drinking water to destroy and decrease the amount of bacteria, viruses, protozoa and parasites can
be accomplished by:
Physical destruction (heat/boiling; Ultra Violet light)
Physical filtering: membranes, ceramic filters, slow sand filters, coagulation / precipitation +
sedimentation, bank infiltration
Biological destruction (e.g. Schmutzdeck layer in slow sand filtration)
Chemical destruction and prevention of multiplication (chlorine, chlorine dioxide, monochloramine,
iodine, ozone, hydrogen peroxide, silver or copper)
Baseline log removal by different treatment methods
Source: WHO Guidelines, table 7.6a; adapted from Smart Disinfection Solutions 201
Logunits: 1=10% remaining or 90% removal; 2=1% remaining or 99% removal; 3=0.1% remaining or 99.9% removal; 4=0.01% remaining
or 99.99% removal; 5=10 -5 remaining; 6=10 -6 remaining; 7=10 -7 remaining
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WLC Template
Pre-Treatment for Disinfection of Drinking Water
Pre-treatment factors to consider include the following:
i) When possible it is always best to acquire your water from the cleanest sources possible
such as,
Spring water, or groundwater from depths > 5 m.
High mountain streams with little turbidity.
ii) Pre-treatment might be required to remove turbidity (e.g., sedimentation, coagulation and
filtration).
iii) Chlorination may not be very effective in turbid waters and the final filters used for
treatment may easily clog if not pre-filtered first.
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M030C003pretreatment.htm[11/3/2014 7:38:08 PM]
WLC Template
Point of Use - Evaluation of Drinking Water Treatment Methods
A total of 21 PoU methods have been evaluated based on performance, ease of use, and impact to
the environment.
The 21 PoU technologies can be categorized into four major groupings based on common modes of
action.
The four main categories include:
Filtration Units (6 PoU products)
Disinfection (8 PoU products / techniques)
Filter + Disinfection (6 PoU products)
Other (1 PoU product)
file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M030C004categories.htm[11/3/2014 7:38:08 PM]
WLC Template
PoU – Filter (6 products)
Product
Name
Ceramic Water Purifier
Biosand Filter
Water 4Life Filter
Tulip Siphon Filter
Jal-TARA Water Filter
(SSF)
Kanchan Arsenic Filter
There are many variations of
biosand filters.
the upper portion of the
container is equipped with 1
or 2 ceramic candle filters.
a candle-type filter that uses
The filtered water is stored siphon pressure to force water
There are many variations of
in lower portion
ceramic pot filters.
through a high-quality ceramic
• filled with sieved and washed
filter element
• the outer layer of the
sand and gravel
• the one illustrated below is
candle filter is made with
from Potters for
• the ceramic filter is impregnated
clay and has a fine pore
peace www.pottersforpeace.org • a layer of water should
with silver and also contains a core
always cover the top of the
structure capable of filtering of activated carbon
sand in order to create a bio- out bacteria larger than 0.5
• typically designed for a
layer often called the
capacity of 20 to 30 L with a
µm. The second layer is
• flow rate is 4 to 6 L/hour.
Description flow rate of 0.5 to 2.5 L per
“schmutzdecke” which
impregnated with colloidal
and Features hour
contributes to pathogen
silver to inactivate bacteria. • when filter becomes plugged, flow
removal.
The third layer is filled with rate can be re-established by
• the estimated life span is up
backwashing using the bulb
activated carbon to absorb
• daily production depends on iron, chlorine, ordour and
to five year
• the filter element has been found to
use but is often between 24 to colour.
• in many cases they can be
last between 6 months to 2 years
72 L per day with a flow rate
locally made
of approx 0.3 to 0.6 L/min.
• average flow rate is limited and could produce about 7000 L of
to approx 1 to 2 L per hour filtered water.
• it also provides safe storage • when flow rate drops it can
for filtered water
• the plastic parts have a life
be rejuvenated by a simple
• particles captured by the
expectancy of approx 5 years.
swirl and dump maintenance
clay layer can be carefully
of upper layer
scraped off to improve rate
of filtration.
• some filters are still
performing satisfactory after
10+ years
• outer container can be made
of concrete, plastic or any
other waterproof, rustproof
and non-toxic material
this is a gravity slow
sand filter that treats with
a biofilm (schmutzdecke)
and through physical
(straining) methods to
filter designed to remove arsenic by provide water quality
incorporating a layer of rusty nails comparable to the natural
percolation of water
in the diffuser basin to which the
through soil
arsenic adsorbs
• pathogen removal is through both • tank size is typically
a biological (bio-layer) and physical around 1 m3 and can
provide 2-3 m3 of treated
(straining)
water per day
• typical dimensions are 90x90x30
cm and flow rates are approx 15 to • the SSF has to be
operated under
20 L/hour.
continuous flow to sustain
the biofilm
concern for proper disposal of
arsenic impregnated nails.
• the system is designed
to require little
maintenance
• a typical lifespan is
approx 15 years
Disinfection and
Contaminant
Removal
Efficiency
field experience and clinical
tests have shown filter to
eliminate approx 99.88% of
most waterborne disease
agents
lab tests show >98.5%
removal of bacteria, 70-99%
treatment provides 99.9 to
viruses, >99.9 protozoa, up to
99.99 bacterial removal
100% helminths and 95% of
turbidity to < 1 NTU
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lab tests show bacteria removal up
to 96.5%, viruses 70-99%, protozoa
>99%, helminths up to 100%, iron
and turbidity 90-99% and arsenic
85-95%
removal efficiencies for
suspended solids is up to
99.99%, pathogenic
bacteria up to 99.99%
and viruses range
between 91-99.99%
WLC Template
example
water4life filter
figure - jal tara filter
ceramic pot purifier
biosand filter
Unit
Treatment
Price
0.57 Euro per cubic metre
water filtered
0.11 Euro per cubic metre
water filtered
0.42 Euro per cubic metre
water filtered
0.51 Euro per cubic metre water
filtered
0.11 Euro per cubic
metre water filtered
Overall
evaluation
7.9 (good)
6.4 (good)
6.25 (good)
6.1 (good)
6.1 (good)
0.22 Euro per cubic
metre water filtered
5.2 (medium)
www.basicwaterneeds.com www.akvo.org More
information
www.akvo.org
www.hydraid.org
www.cawst.org
www.cawst.org
www.arrakis.nl
www.waret4life.eu
www.jalmandir.com
www.nulpuntenergie.net www.cawst.org
www.akvo.org
(Internet Access required)
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www.cleanindia.org
WLC Template
PoU - Heat and UV Disinfection (boiling, SODIS + 2 products)
Boiling for Disinfection
Treatment
Boiling for Disinfection
Solar Disinfection (SODIS)
AquaPak – solar disinfection
Solar disinfection is a simple
way of disinfecting water from
pathogenic bacteria and
viruses.
Description
and
Features
It involves the filling of old
water bottles with raw water, if
possible filtered water, and
boiling water is one of the oldest
leaving them in a sunny area
and most commonly practiced
to expose the water to the
disinfection methods
sunlight's UV radiation in an
water should be boiled in a clean effort to reduce the number of
container for at least a minimum of pathogens.
5 minutes, depending on elevation
Bottles should be made of
longer boiling times may be
PET (polyethylene
needed.
terephtalate) or glass that is
major drawback is its dependency transparent and colourless.
on fuels which can be costly and Bottle should not be larger
in scarce supply
than 3 L.
AquaPak is a low cost polyethylene bag
intended for solar disinfection
Naiade
this unit contains two bag filters
(25 µm and 10 µm) and a 100 L
storage tank for the filtered water
which contains a UV lamp for
added disinfection
power to the unit is provided by
modifications to the bag such as a bubble
photovoltaic panels and excess
pack layer help to increase the temperature power is stored in a batter for 24
up to 65°C where pasteurization takes
hour service
place
the unit can filter up to 3.500 L
a replaceable glass vial filled with orange
per day with a flow rate of 5 L
wax is inserted into the bag. The wax melts per minute
and changes colour once 65°C is reached
the estimated lifespan of the unit
and pasteurization starts
is 10 years with UV bulb
AquaPak can treat up to 5 L per day
replacement after 10000 hours of
use
it is estimated that 1 kg of wood or Water temperature in bottle
education and training appear to be needed
0.1-0.2 kWh is needed to boil 1 L should reach 40°C and be left to improve peoples willingness to use
it is easily installed with little
of water
in the sunlight for a minimum
technical expertise needed
of 6 h on a sunny day or 2
consecutive days if the sky
It is highly effective in removing
has more than 50% cloud
pathogens with additional turbidity
cover.
removal
Bottles should be replaced
every 4 to 6 months.
Disinfection
and
Contaminant
Removal
Efficiency
boiling is generally 100% effective
against bacteria, viruses, protozoa
and helminths when water boiled
for the required minimum time.
Exceptions are bacterial
endospores, other heat resistant
forms of pathogens.
Sunlight treatment for 6 hours
at 40°C can remove up to
99.999% bacteria, 99.9 –
99.99% viruses, but it is less
effective for protozoa.
it has been found to reduce bacterial
pathogens by 99.999%
example
Unit
Treatment
Price
unit treatment price is 17.85 Euro
per cubic metre water filtered
0.87 Euro per cubic metre
water filtered
3.13 Euro per cubic metre water filtered
0.59 Euro per cubic metre water
filtered
Overall
evaluation
7.8 (good)
7.0 (good)
6.4 (good)
5.8 (medium)
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WLC Template
More
information
www.who.int ww.cawst.org
www.sodis.ch
www.medapnaiade.com www.solarsolutions.info
www.akvo.org
www.akvo.org
www.cleanwaternow.nl
(Internet Access required)
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WLC Template
PoU - Chemical Disinfection Treatment (Chlorine + 5 products)
Boiling for Disinfection
Treatment
Chlorine - Disinfection
AquaEst Plation® Floats Disinfection
this product is composed of
specialized ceramic balls that
have a coating of a high quality
colloidal silver
Chlorine has been used as a
disinfectant since the early 1900’s.
Sodium hyperchloride can also be
used and it can be manufactured in
most locations through brine
electrolysis.
Description
and
Features
Each chlorine disinfection product
should have its own instructions that
will need to be consulted to achieve
the correct dosage for destruction of
pathogens and prevention of harmful
health effects.
A minimum contact time of 30
minutes is required and may be
longer depending on water quality.
Residual chlorine in the water can
provide some protection against
recontamination.
Disinfection
and
Contaminant
Removal
Efficiency
NaDCC for disinfection
PUR Purifier of Water™ this technology relies on placing
a specially developed probe that
when placed in salt water will
generate active chlorine through
electrolysis
NaDCC are a form of chlorine disinfection
tablets containing sodium
dichloroisocyanurate also referred to as
sodium troclosene
once in the water natural
processes ionize the silver to
release silver ions in to the water
to inactivate pathogenic bacterial NaDCC tablets have historically been
used to treat water emergencies, but are
the main purpose of this product now starting to become more available to
is to prevent bacterial growth in the general public
treated water during long term
storage
they come in different sizes (3.5 mg to 10
g) to treat water volumes between 1 to
it appears the floats can be used 3000 L
to treat raw drinking water,
however, the contact time may
the required dose and contact time vary
need to be extended –
with water quality. Ideal conditions for use
presumable for days
are low turbidity and pH within 5.5-9.0
this product is both a flocculant (ferric sulphate)
and a disinfectant (calcium hypochlorite)
it is now sold world wide, but cost can still be
restrictive to some
one sachet treats 10 L of raw water
once added, the water is stirred and allowed to
settle for 5 minutes. After this the solids are
filtered through a cotton cloth filter into a second
container where the water is allowed to stand for
an additional 20 minutes to give time for
disinfection
they are easy to use and do not tablets have a shelf life of 5 years if
require electricity or maintenance protected from high temperatures and high shelf life is 3 years
humidity
anticipated life expectancy is
approx 2 years in stored water,
but if used in chlorinated water
the effectiveness by be reduced
to less than 2 years
PUR removes >99.99% bacteria, up to 99.99%
tablets are highly effective against bacteria viruses and 99.9% protozoa
and viruses but not effective against
PUR will remove high turbidity, heavy metals such
protozoa
as arsenic and some dissolved chemical
contaminants
Chlorine is effective against bacteria
and viruses and can achieve upwards
of a 2 to 8 log removal, but it is not
as effective against protozoa and
helminths.
WATA – chlorine generator
25 g of salt per L of water are
placed into a bottle to generate
a chlorine solution that can be
used to disinfect water
WaterPerifier ***check
spelling***
this is a self-contained,
ready to use water
purification unit
water is first filtered with
ceramic Ultrafiltration
membranes (40 nm pore
size). Solar-powered
electrolysis generates
hypochlorous acid which
disinfects the water in the
storage reservoir
disinfection is accomplished by
adding a known volume of this
chlorine solution to the raw
drinking water and allowing it to
stand for 30 minutes
indicator strips provide
check on water quality
(presence of residual
chlorine)
electrodes need cleaning of
calcareous deposits (generally
after every 150 h of use)
estimated lifespan up to
20 years, membranes and
electrodes likely last only
5 years
the lifespan of the device is
approx 20000 hours or 4.5
years
maintenance consist of
backwashing by hand the
filters with hand powered
requires electricity for operation, air pump
can be connected to solar
can be equipped with
panels
additional carbon filters to
remove chemical
contaminants
effectively removes
bacteria, viruses,
protozoa, helminths and
turbidity
example
Unit
Treatment
0.24 Euro per cubic metre water
filtered.
0.75 Euro per cubic metre water
3.25 Euro per cubic metre water filtered
filtered
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7.14 Euro per cubic metre water filtered
0.02 Euro per cubic metre water 1.21 Euro per cubic metre
filtered
water filtered
WLC Template
Price
Overall
evaluation
More
information
7.0 (good).
6.6 (good)
www.cawst.org www.cdc.gov
6.5 (good)
6.5 (good)
4.9 (medium)
5.4 (medium)
www.antenna.ch
www.mobilewatermaker.nl www.cawst.org www.cdc.gov www.csdw.org www.purpurifierofwater.com
www.aquaesteurope.com
www.psi.org www.jolivert.org
www.aquatabs.com www.who.int www.pghsi.com www.who.int
(Internet Access required)
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WLC Template
PoU - Combined Chemical and Physical Treatment (4 products)
Treatment
LifeStraw® Personal
LifeStraw® - Family
Perfector-E
Pureit
this is a compact drinking
water treatment unit
a simple hand held personal
water filter
contains a halogenated resin
(iodine) that kills bacterial and
viruses on contact
granular activated carbon (silverimpregnated) absorbs residual
iodine and thereby improves
taste
Description
and
Features
a micro-filter removes all
particles down to 15 microns
this is a point of use instant microbial
water purifier designed for a household
(different than the LifeStraw designed for
personal use)
the 27 µm filter basket removes course
turbidity while a halogen chamber at
bottom of bucket releases minimal chlorine
to prevent membrane fouling from
development of biofilm
this is a self-contained portable water
treatment system designed for water
emergencies
it consists of two Norit X-Flow
ultrafiltration (UF) membranes and UV
disinfection
it has a capacity of 2000 L/h and can
draw from surface waters 25 m away
the purification cartridge (ultrafiltration, pore with a submersible pump
size 20 nm) is gravity fed. It removes
bacteria, viruses, parasites and fine
power requirements are 230 Volts/3.1
particles
kW or a 5kW power generator
can filter up to 700 L of water –
an approx 1 year lifespan based
on consumption of 2 L/d
flow rate is 8 to 10 L per hour. Course pre- membranes need cleaning once every
filter needs to be cleaned every 30 h, while 3 months and lifespan of membranes is
shelf life is 2 years at 25°C or 1
cartridge requires cleaning every 11 hours approx 3-5 years
year at 30°C
by squeezing on red bulb to backwash.
capital cost for purchase is high and
people with thyroid problems or
filters a minimum of 18000 L and has an
around 30,000 Euro however, it may be
allergic to iodine must seek
expected lifespan of 3 years. Complete
possible to rent from manufacture
medical advice.
system requires replacement once
Not suitable for children who can cartridge is exhausted
not produce suction needed to
draw water through straw.
water poured into the top
reservoir is first screened
with a mico-fiber mesh to
remove course particles.
The filtered water drains out of the reservoir through
a compact carbon trap
which removes additional
dirt, parasites and some
pesticide impurities.
the carbon filtered water
enters a battery operated
Germkill processor which
uses a “sustained release
chlorine technology” to kill
bacterial and viruses
lastly the water passes
through the Polisher which
remove odour and improves
water clarity
a battery indicator tells you
when the Germkill battery kit
is working
the unit is designed to filter
1.500 L of water . Shelf life
of battery is approx 2 years.
Disinfection
and
Contaminant
Removal
Efficiency
removes 99.99% of waterborne
bacteria, and more than 98%
viruses. Not effective in
removing parasites (e.g.,
Giardia), high turbidity and
chemicals.
It removes bacteria, viruses, parasites and
fine particles.
highly effective at removal of total
suspended solids, bacteria, protozoa,
helminths and viruses, but not
applicable for chemical contaminants
unless modified
example
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highly effective against
bacteria and viruses but not
effective against parasites.
WLC Template
figure- perfector
figure - pureit
figure lifestraw family
2 figures- lifestraw
Unit
Treatment
Price
4.08 Euro per cubic metre water
0.79 Euro per cubic metre water filtered
filtered
0.69 Euro per cubic metre water
filtered
4.35 Euro per cubic metre
water filtered
Overall
evaluation
6.4 (good)
6.2 (good)
5.1 (medium)
More
information
www.vestergaard-frandsen.com www.vestergaard-frandsen.com
www.noritmt.ml www.atatwork.org
www.vestergaardfrandsen.com
5.3 (medium)
(Internet Access required)
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WLC Template
Multi-Stage Rainwater Treatment Purification System
AquaEst RainPC®
AquaEst RainPC
This is a multi-stage rainwater purification system.
The primary components include a course screen to filter out larger debris from the roof top
collected rainwater.
The filtered rainwater is temporarily collected into short term storage tanks.
Water from the short term storage tanks is passed through a series of 3 filters.
The first is a 80 µm pre-filter.
The second is a 10 µm filter.
And finally through the third which is an activated carbon filter impregnated with silver coated
balls and copper for inactivation of pathogens.
Treated rainwater is then collected into long term storage tanks containing AquaEst Plation Floats
(silver coated ceramic balls) to prevent the growth of bacteria.
The maximum flow rate through the filters is approx 8 L per minute.
The unit treatment price is 2.00 Euro per cubic metre water filtered
The overall evaluation is 5.4 (medium)
More information is available at www.aquaesteurope.com . (Internet Access required)
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WLC Template
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Conventional Treatment Technologies - Drinking Water
Surface Water Treatment
Typical conventional treatment consists of 4 stages of treatment before storage testing and
distribution of treated drinking water.
The purpose of conventional treatment is to remove solids, organics, and other chemical
characteristics that may be present in the raw water.
CWT process
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WLC Template
Water Characterization
Microbiological Factors
Physical Characteristics
–Pathogenic organisms
–Turbidity and particles
–Nuisance organisms
–Colour
–Algae
–Temperature
–Taste & Odour
–Iron bacteria
Radiological Factors
Chemical Characteristics
–Radioactive materials in drinking water
–Organic and inorganic
–pH
–Iron and manganese
–Hardness, alkalinity
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Physical Characteristics
What is the difference between suspended solids, particulates and colloidal matter?
Suspended solids and particulates are organic and mineral particles such as clay, silt,
organisms.
Colloidal matter are very small particles, less than 10 micrometers (does not settle).
Turbidity
‘Cloudiness’ caused by the presence of suspended matter.
Measured by the scattering and absorption of light.
Why is turbidity important?
Pathogens may adhere to particles.
Particles may shield pathogens from disinfection.
Turbidity may create a high chlorine demand.
Turbidity level gives feedback for process control.
Regulated limits.
Turbidity water samples and turbidity testing
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WLC Template
Physical Characteristics
Taste – sweet sour bitter or salty
Odour – the presence of a noticable smell
Why is taste and odour important?
Taste and odour (and colour) are indicators of the purity of water. Safe drinking water does not
smell and taste like sewage.
Taste and odour may indicate treatment effectiveness.
Taste and odour are aesthetic properties of water and influence customer satisfaction.
Temperature
The degree of hotness or coldness measured on a definitive scale.
Why is the temperature of drinking water important?
The temperature of drinking water affects the disinfection process.
Warm water temperatures favour the growth of waterborne pathogens and other biological
contaminants.
The temperature of drinking water also affects the aesthetic properties of taste and odour.
Cold water has higher oxygen content. Warm water can be anaerobic (having little to no
oxygen).
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WLC Template
Chemical Characteristics
Water Hardness Water hardness is caused principally by calcium and magnesium ions in water.
Water hardness is a measure of the capacity of water to react with soap.
Why is water hardness important?
Water hardness can an interfere with chemical reactions.
Hard water can form scale (e.g., a precipitate on the inside of pipes).
Soft water may be corrosive.
Alkalinity
Alkalinity is the concentration of the bicarbonates (HCO3- ), carbonates (CO3 - ), and hydroxyl ions
(OH - ) dossolved in water.
Why is alkalinity of water important?
Alkalinity is a measure of the ‘buffering capacity’ of water, the ability to withstand change in
water pH (e.g., to withstand acidification of water and decrease in water pH).
Alkalinity is needed for coagulation.
Low alkalinity water may require added alkali for effective treatment.
Alkalinity is a measure of corrosivity.
Iron (Fe) and Manganese (Mn)
These naturally occurring minerals are commonly found in groundwater.
Iron and manganese usually occur in groundwater in reduced soluble forms (dissolved).
Soluble forms of iron and manganese oxidize into particulate forms by addition of chlorine to
water and in the presence of air.
Iron reacts quickly forming iron oxides that have a red in colour; manganese reacts much more
slowly forming manganese oxides that have a black colour.
Why are iron and manganese important?
“Dirty” coloured water caused by iron and managanese is often the reason for
complaints about staining of toilet bowls and wash basins and laundry.
The occurrence of iron and manganese in water causes increases in turbidity.
Bacteria often also occur.
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Possibility of harmful health effects, depending on concentrations and exposures.
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Pre-Treatment
Pre-treatment consists of screening of the raw water to remove larger debris and pre-oxidation to
control algae and bacteria, and the arresting of biological growth.
Pretreatment of raw water
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Photo of pretreatment filter
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Coagulation - Flocculation
Ferric chloride and aluminum sulphate are common coagulants used to flocculate out organic
matter.
Coagulation flocculation treatment
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Removal of Flocculated Material
Flocculated material is allowed to settle out of solution. Additional filtration is often added to ensure
a high clarity of the water prior to disinfection.
Removal of flocculated material
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WLC Template
Disinfection
Chlorine has historically been the disinfectant of choice, but other methods such as ozone, UV
irradiation and membrane filtration are used in an attempt to avoid the generation of Chlorine
disinfection byproducts (DBPs).
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Storage Testing and Distribution
Storage testing and distribution
Pumping and Storage of Treated Water
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Treated water is pumped to large storage tanks.
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Testing
Testing laboratory and instrumentation
Water is diligently tested to ensure high quality before consumption.
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Where to Sample - Water Treatment Process and Storage and Distribution
Where to sample in the water treatmetn process
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WLC Template
What to Measure - Sampling and Monitoring - Water Treatment Process, Storage and Distribution
Sampling and monitoring of water treatment process
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Household Water Treatment - Introduction
Diarrheal diseases (such as cholera) kill more children than AIDS, malaria, and measles combined,
making it the second leading cause of death among children under five
Access to safe water and improved hygiene and sanitation has the potential to prevent at least 9.1%
of the global disease burden and 6.3% of all deaths access to safe water and improved hygiene and
sanitation has the potential to prevent at least 9.1% of the global disease burden and 6.3% of all
deaths
Household water treatment has the potential to significantly decrease this global disease burden
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Household Water Treatment - Overview
Two good examples of organizations addressing the issues of household water treatment in a
very organized and systematic way are the Center for Disease Control (CDC) in the USA and
the World Health Organization (WHO)
o The CDC and the Pan American Health Organization (PAHO) developed the Safe Water
System (SWS), which protects communities from contaminated water by promoting
behavior change and providing affordable and sustainable solutions
o The WHO developed the concept of “Household water treatment and safe storage
(HWTS) interventions”
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Household Water Treatment - Options
Water Treatment Options
Household water treatment (treatment that happens at the point of water collection or use, rather
than at a large, centralized location) improves water quality and reduces diarrheal disease in
developing countries .
Five proven treatment options –
chlorination
1.
flocculant/disinfectant
2.
powder (P&G™)
solar
3.
disinfection
ceramic
4.
filtration
slow
5.
sand filtration
– are widely implemented in many developing countries.
A more complete classification of simple low-cost technologies for water treatment is that
of Skinner, B and Shaw, R "Household Water Treatment 1 & 2, technical briefs #58 & #59",
Waterlines, October 1998 and January 1999. It includes methods for removing inorganic chemicals,
odour and taste from water as well as methods to remove pathogenic microorganisms.
Aeration
Coagulation and flocculation
Desalination
Disinfection
Disinfection by boiling
Chemical disinfection
Solar disinfection
Filtration
Storage and settlement
Straining
Selecting the most appropriate treatment method for a community’s specific circumstances is often a
difficult decision. The most appropriate option for a community depends on existing water and
sanitation conditions, water quality, cultural acceptability, implementation feasibility, availability of
technology, and other local conditions.
Household water treatment and safe storage interventions can lead to dramatic improvements in
drinking water quality and reductions in diarrhoeal disease—making an immediate difference to the
lives of those who rely on water from polluted rivers, lakes and, in some cases, unsafe wells or piped
water supplies.
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Household Water Treatment - Aeration
1.
Aeration
Aeration can be accomplished by vigorous shaking in a vessel part full of water or allowing
water to trickle down through one or more perforated trays containing small stones. It can
remove inorganic materials and some taste and odour.
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Household Water Treatment - PUR
2.
Coagulation and flocculation
The Procter & Gamble Company developed the PUR Purifier of Water™ .The sachets are now
centrally produced in Pakistan. The product is a small sachet containing powdered ferric sulfate
(a flocculant) and calcium hypochlorite (a disinfectant) and was designed to reverse-engineer a
water treatment plant
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Household Water Treatment - Desalination
3.
Desalination
Desalination, or desalting, is the separation of fresh water from salt water or brackish water.
There are two basic types of larger-scale desalting techniques: thermal processes and
membrane processes. Both types consume considerable amounts of energy.
For household use, simpler and cheaper systems are required; typical examples use a black
solar panel that distills saline water and deposits the vapor on a surface where it is collected.
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Household Water Treatment - Disinfection
4. Disinfection
4a. Disinfection by Boiling
Boiling is a very simple method of water disinfection. Heating water to a high temperature,
100°C, kills most of the pathogenic organisms, particularly viruses and bacteria causing
waterborne diseases.
4b. Chemical disinfection This treatment method is point-of-use chlorination by consumers with a locally-manufactured
dilute sodium hypochlorite (chlorine bleach) solution. 4c. Solar disinfection
Solar disinfection (SODIS) was developed in the 1980s to inexpensively disinfect water used for
oral rehydration solutions. Users of SODIS fill 0.3-2.0 liter plastic soda bottles with lowturbidity water, shake them to oxygenate, and place the bottles on a roof or rack for 6 hours (if
sunny) or 2 days (if cloudy). The combined effects of UV-induced DNA alteration, thermal
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Household
Water Treatment - Filtration and Storage
5. Filtration
5a. Ceramic Filtration
Locally manufactured ceramic filters have traditionally been used throughout the world to treat
household water. Currently, the most widely implemented ceramic filter is the Potters for Peace
design. The filter is flowerpot shaped, holds about 8-10 liters of water, and sits inside a plastic
or ceramic receptacle.
5b. Slow Sand Filtration
A slow sand filter is a sand filter adapted for household use. Please note that although
commonly referred to as the BioSand Filter, the BioSand Filter terminology is trademarked to
one particular design, and this fact sheet encompasses all slow sand filters. The version most
widely implemented consists of layers of sand and gravel in a concrete or plastic container
approximately 0.9 meters tall and 0.3 meters square. 6.
6. Straining
Pouring water through a clean cotton cloth will remove a certain amount of the suspended
solids or turbidity. Special monofila- ment filter cloths have been developed for use in areas
where Guinea- worm disease is prevalent. The cloths filter out the copepods which are
intermediate hosts for the Guinea-worm larvae
7.
7. Storage and Settlement
It is preferable, especially when using treatment options that do not leave residual protection, to
store treated water in plastic, ceramic, or metal containers.
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Household Water Treatment - Summary of Methods
Summary and Analysis of Household Water Treatment and Safe Storage methods
Household water treatment systems can be evaluated based on their performance in removing
pathogenic organisms, their advantages and their limitations.Together with a microbiological water
quality analysis, an analysis of local environmental and economic factors together with a monitoring
and evaluation program, the choice of technology and process becomes easier. Note that most of
these household water treatment systems do not remove chemical contaminants from drinking
water.
The World Health Organization has developed a Toolkit for Monitoring and Evaluating Household
Water Treatment (WHO/UNICEF, 2012) that gives details on how to carry out such analyses and it
includes a decision tree for selecting good indicators to use in given environments. It is available on
the CD
The most widely used household treatment systems
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Household Water Treatment - Summary
The various methods available for the treatment of water to improve its quality and/or remove
pathogenic microorganisms are quite varied, ranging from simple boiling of the water to household
level solar distillation units.
The choice of which to use in a given situation can become quite complex and has to take into
account many factors - not just the efficacy of the particular method.
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Advanced Treatment Technologies - Drinking Water
Overview
Conventional treatment technologies for raw drinking water have historically been focussed on:
i) Removal of suspended material.
ii) Disinfection of waterborne pathogens
The underlying rationale is that coventional filtration and disinfection methods will provide
adequate protection against exposures to harmful particulates, especially metals and
pathogens.
Since the end of the second world war, the expansion of industry, manufacturing, service
industry, meat and food production & processing, and health care has increased releases of
waste waters into the environment, including releases of organic pesticides, pharmaceuticals,
personal care products, radiolabelled compounds, nanomaterials, and animal and human blood
and biotechnology products.
There is a growing awareness that a wide variety of compounds occur in raw water supplies
used for drinking water.
The human health and ecological implications for many of these compounds remains unknown,
of particular environmental concern is the confirmation of detectable quantities of pesticides,
flame retardents, pharmaceuticals and personal care products and nanomaterials in water and
sediments sampled from lakes rivers and oceans and in tissues of fish other aquatic organisms
and marine life, including mammals and seabirds, and in some human tissues.
Some of those contaminants are persistent organic compounds of comparatively low water
solubilities, whereas others dissolve more easily in water and can be biologically active in even
small exposures, raising concerns whether conventional water treatment processes are capable
of removing all potentially harmful contaminants.
Environmental testing methods involving analytical chemistry techniques and modified
enivironmental monitoring protocols are currently not available for many emerging biological
chemical and physical contaminants of concern (e.g., antiviral drugs, immunosuppressants,
biotechnology products, nanomaterials, viruses and parasites).
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New Treatment Options to Remove Emerging Contaminants of Concern
Improved analytical techniques together with a greater understanding have now shown that
undesirable by-products can be generated from some of the most common treatment options
such as chlorine.
Research over the last two decades has devoted much focus into developing new treatment
options aimed at improving the treatment and hence the quality of drinking water through
enhanced removal of emerging chemicals of concern, the reduction of undesirable disinfection
byproducts and better methods for the removal or inactivation of chlorine resistant pathogens.
The efforts directed at improving water treatment are underscored by a greater global
awareness that high quality raw drinking water supplies are diminishing either through
unsustainable withdrawals, degradation from contaminants or changes in climatic patterns that
threaten the natural recharge mechanisms for these resources, as presented in Course 1 on
Water and Health.
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Advanced Technologies
Advanced treatment technologies have focussed primarily on the use of:
Ozone
Peroxide
UV irradiation
Advanced oxidative processes
Electron beam
Cavitation
Membrane filtration
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Ozone (O3 )
Ozonation is used most often in the treatment of municipal drinking water supplies
The most common applications of ozone are for decreasing problems of: odour; trihalomethane
disinfection by-products; colour; cryptosporidium oocysts; Mn and Fe.
Additional applications for ozone
Ozone is a strong biocide against biofilms.
Ozone can remove exopolysaccharides in the biofilm matrix.
The survival rate for biofilm bacteria has been shown to be reduced to < 1% when exposed to 1
mg O 3 /L for a duration of 5 min.
Ozone can also slow down the fouling of membranes.
Ozone has also been used to reduce the concentrations of natural organic matter (precursors of
THMs) and therefore decrease the overall potential for the production of DBPs.
Ozone can also increase the assailable organic compounds produced by ozonation of NOM and enhance the biological activity in a subsequent activated carbon filtration step.
Ozone has been found to be a powerful oxidant capable of degrading and inactivating: various
pesticides; PPCPs; endocrine disrupting compounds (EDCs).
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Ozone in Combination with Other Treatments
Ozone has been coupled with other treatment options to improve the overall effectiveness of the
process.
For example,
O 3 + UV (decreased the potential formation of brominated DBPs)
O 3 + cavitation (increased disinfection)
O 3 + chlorine (increased disinfection)
O 3 + Peroxide + UV (increased oxidation of TrOCs)
Supplemental Reading
The supplemental reading authored by Balch and Metcalfe (2006) provides additional information
regarding the use of ozonation and reverse osmosis treatment for the removal of micro-contaminants
from domestic wastewater for the purpose of water recycling. The reading materials are discussed in
more depth later on in this course under ozone & membranes. Many of the operational principles for
these techniques are similar whether applied to drinking water or wastewater.
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Decentralized Treatment - On-Site and Decentralized Wastewater Treatment
Definition
Decentralized wastewater treatment (DWWT) systems are different from conventional centralized systems
in the following ways:
1.
Wastewater is treated either on-site or near the site of its generation.
2.
DWWT systems are designed to service smaller localized household, typically less than 20 dwellings.
3.
A common feature is the disposal of treated effluent to soil absorption fields rather than to surface
waters.
With decentralized treatment, wastewater is treated either i) on-site or ii) through a cluster system.
On-site treatment generally refers to the treatment of the waste generated on an individual property and the
disposal of the treated effluent on-site.
Cluster systems collect and treat the wastewater generated from generally between 2 to 10 household
properties.
Centralized
Decentralized
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On-Site Systems
The choice of which on-site technology to use can vary greatly and is often influenced by the
following:
1.
The public’s familiarity and perception.
2.
Financial resources
3.
Existing municipal infrastructure
4.
Regulatory requirements
5.
Public policy
6.
Logistical challenges
7.
Others
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On-Site Systems - Eco-san Technologies
Three fundamental Principals:
1. To prevent pollution rather than attempting to control it after pollution has occurred
2. Sanitize the urine and faeces
3. Develop safe products for agriculture from the treated excreta
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On-Site Systems - Eco-san Technologies
Urine
Contains relatively few disease causing organisms in comparison to faeces.
Storage of undiluted urine for approximately one month will render it safe for use in agriculture.
The undiluted urine produces a harsh environment in which most pathogens can not survive.
Swedish storage guidelines
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On-Site Systems - Eco-san Technologies
Faeces
Faeces contain the greatest and most harmful pathogens from human excreta.
Ecosan treatment provides barriers between faeces, flies, fields and fluids.
This is generally done in two stages, the first stage to provide some preliminary treatment to
make it more easily handled for more through secondary treatment.
Primary Processing
The purpose is to reduce weight in order to facilitate storage, transport and further (secondary)
treatment. Primary processing takes place in the chambers below the toilet.
Secondary Processing
The purpose is to make the faeces safe enough to return to the soil.
Secondary processing can take place on-site or off-site.
It generally includes further treatment by high temperature composting or pH increase by
addition of urea, lime as well as longer storage.
If complete sterilization is desired, then this could be accomplished by carbonization or
incineration.
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On-Site Systems - Eco-san Technologies
There are 3 main eco-san systems that basically accomplish the same results
1.Dehydrating systems
2.Composting systems
3.Soil Composting systems
Dehydrating System
Urine is collected separately to keep faeces dry and the volume small.
Faeces are isolated and held in this chamber for 6 to 12 months.
Ash, lime or urea is added after each defecation to lower moisture content and increase pH to 9
or higher.
The primarily processed matter is then removed and undergoes one of the four secondary
processes.
Composting System
Human faeces and in some cases urine are added to the storage chamber along with organic
household and garden refuse and bulking agents (straw, peat moss, wood shavings, etc.).
A variety of organisms break down the material into humus.
Temperature, airflow, carbon content are all important factors controlling the composting.
After 6-8 months the material is removed and undergoes high temperature composting as the
secondary process.
Soil Composting System
Faeces, and in some cases faeces + urine are added to the chamber with a liberal amount of
soil.
Soil is added after each defecation along with wood ash.
Most pathogenic bacteria are destroyed in 3-4 months.
Composted material is then removed to undergo one of the four secondary processes
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On-Site Systems - Eco-san Technologies
Common features of an Eco-san system
There are a variety of organisations developing and promoting eco-san systems; for more information a list
of references has been provided.
Additonal information is provided in PDFs on eco-san systems, guidance for Eco-San and case studies in
the Resources folder for this course.
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On-site and Cluster Systems - Flush Away Approach
a) On-site systems
Septic tank and drain field
and
b) Cluster systems
Photo of homes connected to cluster system
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On-Site Systems
The most commonly known on-site system is the typical septic system designed for single
residences. Septic systems consist of a septic tank designed to provide primary treatment through the
removal of settleable and floating constituents.
The primary treated effluent is released into a subsurface tiled drain bed.
Typical septic tank and drainfield
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Cluster Systems
Cluster systems are generally used to collect wastewater from a small cluster of homes.
Waste is transported to the site of treatment via alternative sewers.
The transported wastewater is treated at either a conventional treatment system or receives pretreatment prior to soil absorption of the pretreated effluent.
There can be many reasons to install a cluster systems.
Cluster systems are most often installed because the land size of individual properties is not
large enough to accommodate an on-site system, and because construction of a conventional
treatment plant is not feasible given the associated financial costs.
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Alternative Sewer Systems
Systems that typically have small diameter plastic collection pipes (2-4 in diameter).
Three typical forms of alternative sewers systems in use are described below.
a) Small-diameter gravity (SDG) systems Household waste is first deposited to a septic (interceptor) tank on site.The septic tank removes
settleable and floatable solids before wastewater enters the small diameter collection pipe.
This will reduces the potential for sewer clogging and minimizes the need for high flow
velocities to keep solids suspended
b) Vacuum sewers
A vacuum is created by a centralized vacuum source. Sewage is first deposited into a small
holding tank at the home. Once the holding tank is full, a sensor opens a pneumatic valve and
wastewater is sucked into the line and deposited at a common collection point.
Generally there is no need to use a vacuum toilet.
c) Pressure sewers
Line pressure is created by pumping wastewater from the small holding tank at the house into
the collection line. There are generally two styles of pumping systems associated that could be
used:
i) Grinder pump: to ensure all solids are ground into smaller components
ii) Septic pump that pumps effluents out of septic tank while solids are retained in the
tank
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Alternative Sewer Lines Connecting Individual Dwellings to a Decentralized Cluster System
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Pre-treatment Options
Pre-treatment can occur before the wastewater from the initial holding tank is transferred to the
sewer pipes.
Additional treatment often occurs in a cluster system between the point of common collection and
disposal to soil.
This additional treatment step is often added in order to improve the quality of the wastewater in
order to limit the impact to the environment and to decrease the size of the absorption field.
The additional treatment is particularly important in areas where either the water table is high or there
is a significant risk of contamination to groundwater or surface waters.
Pre-treatment before release to soil for absorption
A variety of pre-treatment options exist for improving the quality of the wastewater prior to disposal
to soil.
The choice depends on the soil conditions and the level of pre-treatment desired.
Options for pre-treatment include the following:
Sand filters (open, buried, recirculating)
Lagoons (facultative, aerated, anaerobic)
Constructed wetlands
Trickling filters
Membrane technologies
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Final Disposal Options
Decentralized systems typically dispose of the primary treated wastewater to soil absorption
systems rather than release it to surface waters.
There are several options for disposal of primary treated wasye water to soils, including the
following:
Sandfilters (open, buried, recirculating)
Spray and drip irrigation
Mounded systems
Evaporation systems
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Constructed Wetlands - Wastewater Treatment
What are Treatment Wetlands?
Treatment wetlands come in many sizes and shapes.
Some of the more common designs include the following:
Free Surface Water (FSW) Cells
Horizontal Subsurface Flow (HSSF) Cells
Vertical Subsurface Flow (VSSF) Cells
Floating Islands
Hybrid Systems
Natural Treatment Wetlands
What are the primary purposes of treatment wetlands?
The primary purpose is for the treatment of domestic sewage involving removal of the
following,
waterborne pathogens
ammonia and other nitrogen products
phosphorus
turbidity and associated compounds
biological oxygen demand
chemical oxygen demand
odour
Treatment wetlands can be used to treat a variety of other unwanted constituents related to
agriculture, industry and mining.
Wetlands as an Alternative Treatment Technology
Wetlands were once considered to be primarily in the domain of decentralized wastewater
treatment systems.
In many cases, wetlands are still used for decentralized systems, however, there is a trend to
recognize that larger wetland systems can now be used to treat the waste of larger communities
than once historically thought.
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Waste Water Treatment Strategies
Where do wetlands fit into treatment strategies?
Constructed wetlands can be used as stand alone units or in combination with other treatment
options.
For example, it is common to pre-treat domestic sewage prior to discharge into a wetland and
often wetland effluents can be further treated by discharge to a drain field.
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Constructed Wetlands for Wastewater Treatment
Risk assessment and environmental monitoring of potential impacts from contaminants (biological
chemical and physical) in wastewaters on:
ground water supply
human health
water quality
air quality
soil quality
ecosystem health - including wildlife, animals, birds, fish, insects, and plants, f
These should be addressed in the design, operational and post-operational phases of a constructed
wetland.
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How do Wetlands Work
Treatment wetlands utilize physical, chemical and biological processes naturally found in the
environment.
Treatment wetlands are often designed to enhance one or more of these natural processes.
The greater the complexity of the wastewater constituents, the greater the need for hybrid wetland
systems.
Key operational parameters that govern the performance of any constructed wetland include:
a) Wetland size measured in both surface area and depth
b) Flow volumes and flow rates entering the wetland
c) Loading rates of effluent entering the wetland
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WASTEWATER CONSTITUENT REMOVAL MECHANISM
Key processes that contribute to pollution removal include the following,
• Microbial mediated processes
• Physical processes (filtration, volatilization, sorption / sedimentation / vertical diffusion in
soils& sed / accretion, photodegradation)
• Plant uptake / transpiration flux
• Seasonal cycles
• Chemical network processes
WASTEWATER CONSTITUENT
REMOVAL MECHANISM
• sedimentation
Suspended Solids
• filtration
• aerobic microbial degradation
Soluble Organics • anaerobic microbial degradation
• ammonification followed by microbial
nitrification
Soluble Organics Nitrogen
• denitrification
• plant uptake
• matrix absorption
• ammonia volatilization
• matrix sorption
Phosphorus
• plant uptake
• adsorption and cation exhange
Metals
• complexation
• precipitation
• plant uptake
• microbial oxidation /
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• sedimentation
• filtration
• natural die-off
• predation
• UV irradiation
• exertion of antibiotics from roots of
macrophytes
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Biological Processes Within a Wetland
Many of the biological processes within a wetland are mediated by micoorganisms, primarily
bacteria.
Bacterial are instrumental in key processes such as the degradation and solubilisation of
organic matter, ammonification, nitrification, denitrification, precipitation of ionic compounds,
and others.
Wetland plants also play a role, but to a lesser extent.
Uptake into plants, including symbiotic support for microbial populations.
Major Microbial Groupings participating in the cycling and removal of nutrients trace metals and
other elements and in the breakdown of organic compounds in constructed wetlands include the
following,
Bacteria
Fungi
Actinomycetes
Protozoa
Microbial Mediated Processes involved in the cycling transformation of trace metals and elements
and breakdown of organic compounds.
nitrate reductions – denitrification (Nitrospira)
ammonia oxidations (Nitrosomonas)
sulfate reducers (Desulfovibrio)
iron reducers (Geobacter)
degrade resistant substrates (Streptomyces)
falcultative aerobes (Bacillus)
methanogenesis (Methanobacteria)
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Physical Processes
A number of physical processes are responsible for the removal of unwanted wastewater
constituents. Some of the more common processes include the following:
Filtration and sedimentation
Adsorption, absorption
Accretion
Volatilization
Photo-degradation (UV irradiation)
Volatilization
Wetlands breath
Gas exchange occurs at the interfaces of soil, water, air.
Plant interactions are particularly important to HSSF wetland.
Major gases include:
Carbon dioxide (CO2)*
Nitrous oxide (N2O)* – an stable intermediate in denitrification
Methane (CH4)*
Ammonia (NH3)
Hydrogen Sulfide (H2S)
* indicates a Greenhouse gas.
Photodegradation
Sunlight can degrade or convert many waterborne substances.
Many microorganisms, including pathogenic bacteria, and viruses can be killed by ultraviolet
radiation in sufficent intensity and duration of exposure.
The process of photodegradation often involves photooxidation which results from the
development of free radical molecules.
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Plant uptake - Evapotranspiration fluxes
Uptake rates by plants depend on plant species, time of year (e.g., growth phase), compound being
absorbed.
Some metals are absorbed and translocated – location depends on metal and plant species.
Some organic molecules are also translocated, but once again depends on compound and plant
species.
Typically, plant uptake does not count for a significant portion of metal or nutrient removal.
Seasonal Cycles
Seasonal changes are major influencers on biological and physical removal processes.
Temperature (affects metabolism)
Plant growth phase (growing or senescing)
precipitation (dilution of wastewater, increased flows, lower hydraulic residency times)
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Environmental Fate and Transport - Chemical Transformation and Degradation (Breakdown) of Waste
Water Constituents
Several wetland removal processes involve more than one reaction and more than one chemical
species.
For example,
Organic N ---> ammonia N ---> Oxidized N ---> gaseous N2
Trichloroethylene ----> dichloroethylene ----> vinyl chloride -----> CO2 + H2 O + Cl-
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Environmental Fate and Transport - Carbon
Carbon cycle in wetlands. Source: Kadlec & Wallace 2009
DC = dissolved carbon
PC = particulate carbon
DIC = dissolved inorganic carbon
DOC = dissolved organic carbon
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Process Networks Nitrogen Interactions
Nitrogen cycle. Source: Kadlec & Wallace 2009
Fixation: atmospheric Nitrogen into plant or animal tissues
Ammonificaton: conversion of organic nitrogen to ammonia by decomposers
Nitrification: oxidation of ammonia to nitrate or nitrite (addition of oxygen)
Denitrification: reduction of nitrate to nitrogen gas (removal of oxygen)
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Kadlec & Wallace 2009
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Process Networks Phosphorus Interactions
PP = particulate phosphorus
PO4-P = orthophosphate
PH3 = phosphine
DPO = dissolved organic phosphorus
Image:- phosphorous cycle. Source: Kadlec & Wallace 2009
Forms of Phosphorus in the Wetland Environment
Total Phosphorus (TP): all forms of phosphorus
Dissolved Phosphorus (filtered 0.45 µm)
Orthophosphate (PO 4 -P)
condensed phosphates (pyro-phosphate, meta-phosphate, poly-phosphates)
other forms of phosphorus that are convertible to PO 4 -P upon oxidative digestion such as dissolved
organic phosphate (DOP)
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Phosphorus is contained in the structure of soil and suspended particles or biomass such as,
adsorbed to inorganic minerals or contained in biomass.
usually needs some form of digestion or acid extraction to remove and analyse P.
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Process Networks Sulfur Interactions
Importance of Sulfur in the Wetland Environment
• sulfur in the form of sulfide (e.g., sulfate reduction processes) is of special importance for its
influence on wetland performance and in particular its ability of sediments to immobilize trace
elements
• anaerobic bioreactors is a developing science in the use of wetland technologies for the
treatment of mining wastes
Examples:
S2- + 2Cu + ---> Cu 2 S (insoluble precipitate)
S2- + Cd 2+ ---> CdS (insoluble precipitate)
Reference: Kadlec & Wallace 2009
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Oxidation – Reduction Potential (REDOX)
A chemical reaction in which electrons are transferred from a donor compound to an acceptor compound.
For example,
Donor compound: looses electrons and increases its oxidative state (becoming oxidized)
Acceptor compound: receives electrons (reduces its oxidative state) (becoming reduced)
Fe3+ + e-1 = Fe2+ (Fe3+ is reduced to Fe2+)
Oxygen is one of the dominant oxidizers (can accept electrons) in wetland systems
However, once oxygen is depleted, then NO3- , MnO2 , FeOOH, SO 4 2- and CO2 can serve as electron acceptors (becoming reduced)
Oxidation / Reduction Potential (ORP or the Redox potential)
An environment with a redox potential of -400 mV is strongly reduced (typically anaerobic conditions would prevail); whereas an environment with a redox potential of +700 mV is well
oxidized.
Oxygen Transfer and Plant Interactions
Oxygen transfer by Phragmites (Brix & Schierup 1990, Pergamon Press; Armstrong & Armstrong 1990, Pergamon Press; Brix 1986, IWA Publishing)
Plants affect the redox potential around the roots and thus influence Nitrogen dynamics (Kadlec & Redox conditions in wetlands (Kadlec & Wallace 2008)
Wallace 2009)
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Redox conditions around plant roots and aerobic/anaerobic zomes
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Acidity and Alkalinity in Wetlands
Healthy aquatic systems function within only a narrow pH range near neutrality (6.5 to 7.5); the pH is
a measurement of the hydrogen ion concentration (H+) and of acidity.
The pH influences many chemical reactions (e.g., the ammonium ion NH 4 + converts to ammonia NH 3
(gas) at pH >7).
The pH will affect the solubility of many metals and metalloids (has application for sequestering of
metals from mining wastes).
The simplistic definition of alkalinity is the opposite of acidity in a lake system.
Alkalinity is a measurement of the hydroxyl ion concentration and of the ability to neutralize inputs of
an acid (buffering capacity).
The greatest buffering capacity in aquatic systems comes from HCO 3 - , CO3 2- , OH- , (bicarbonate,
carbonate and hydroxyl ions)
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Sorption, Sedimentation, Accretion
Conservative elements (e.g., P, metals, metalloids) do not volatilize to atmosphere
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Accretion Kadlec & Wallace 2009
In the aquatic environment there are many different sorption or uptake sites for conservative
elements.
Iron & aluminum sorption sites are common in sediment and calcium & magnesium sites are plentiful
in plant tissues (Fe, Al, Mn are oxide formers).
Influential factors on adsorption and absorption processes involve equilibrium dynamics, redox,
temp, microbial, and others.
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Constructed Wetlands - Different Forms
Constructed wetlands can come in many different forms.
Each form is often designed for specific treatment attributes.
Some of the more common forms of wetland (variants) are presented as follows.
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Free Water Surface Wetland (FWS)
FWS diagram
Sunlight (UV irradiation): influences microorganisms, photolytic compounds
Limited microbial and chemical reactions occurs.
Volatilization of some compounds (e.g., ammonia) occurs.
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Floating Island
Floating island
Biofilm forms on roots (e.g., microbial degradation, entrapment of particles).
Limited removal of nutrients and metals and soluble organics (e.g., lower cBOD) occurs.
Removal rates are influenced by the mass of root mats and water flow rates.
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Horizontal Subsurface Flow (HSSF)
HSSF diagram
Sediments are poorly oxygenated making it not good at nitrification, but good for denitrification.
It can be good at filtration and entrapment of particles.
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Vertical Subsurface Flow
VSSF
Ammonification is microbially mediated (heterotrophs) and can occur both aerobically or
anaerobically, but nitrification requires oxygen.
VSSF are good for nitrification, but poor for denitrification.
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Forced Bed Aeration
Water input is at top of wetland with a bottom draw off.
The air hose lies on bottom of the wetland and air is bubbled up to the surface, so that the
wetland is well oxygenated.
Advantage: possibly the best wetland type for removal of cBOD, but also very good for
nitrification.
Disadvantage: requires pumps and electricity = extra cost and maintenance.
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Horizontal Subsurface Flow with steel slag
Diagram HSSF with slag
Wetland media replacement with compounds that are good at removing targeted compounds.
For example, steel slag is high in oxides (like Al2O3, MnO, SiO2) that act as binding sites for phosphorus.
Other materials like aluminum oxide could also be used.
Disadvantages: unwanted problems can occur such as, high pH, release of undesirable and harmful metals
– Vanadium and others.
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Successive alkalinity-producing systems (SAPS)
SAPS
The organic layer can act as filter to remove some precipitated metals. It can also be used to
change Fe3+ (colloidal form) to Fe2+ soluble ionic form.
Limestone removes acidity and with some metals like Aluminum, a higher pH means the metals
precipitate out of solution.
Other metals like soluble ionic iron (Fe2+) require treatment with an oxidation pond at outflow of
SAPS.
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Biochemical Reactor (BCR)
The BCRs facilitate micobially mediated processes, usually involving sulfur reducing bacteria
The presence of organic matter fuels sulfate reduction.
e.g., SO 4 2- + 2CH 2 O + 2H + ---> H2 S + 2H 2 O + 2CO2
and SO 4 2- + 2CH 2 O ---> HS - + H+ + 2HCO 3 When Fe2+ combines with HS - it produces FeS (very insoluble).
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Hybridized Wetland Systems
Researchers and wetland designers and operators are now starting to look more to the use of hybridized systems.
Treatment efficiencies may be improved greatly and can be customized to meet specific treatment objectives for
complex or varied waste water types.
The following figures show how some hybridized systems may be assembled.
VSSF + HSSF Hybrid
Nitrification (VSSF) + denitrification (HSSF)
VSSF + HSSF + Steel Slag Hybrid
nitrification + denitrification + phosphorus removal
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SAPS + BCR Hybrid
SAPS + BCR
Removal of acidic waters plus removal of iron in form of insoluble FeS.
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Case Studies
Case studies provide information about real world wetland installations.
1. Municipal wastewater (hybrid system)
2. Landfill lechate (hybrid system)
3. Airport (forced bed aeration)
4. Storm water (free water surface wetland)
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Municipal wastewater (hybrid system)
CONSTRUCTED WETLANDS TREATMENT PLANT FOR THE TREATMENT OF DICOMANO (FLORENCE PROVINCE) MUNICIPAL WASTEWATER
Total Area = 6080 m2 (0.61 ha)
HSSF + VSSF + HSSF + FWS
Person Equivalents = 3500
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Landfill Leachate (hybrid system)
MULTI-STAGE CONSTRUCTED WETLANDS SYSTEM FOR LANDIFILL LEACHATE TREATMENT: THE “TAGLIETTO” LANDIFILLS PROJECT
leachate line
Each line consists of:
1. SFS-v (e.g.,VSSF) stage with a superficial peat layer to ensure odor remove, leachate pre-oxidation and metals
precipitation.
2. Two stage SFS-v in series for nitrification (add O2) and organic load removal (e.g., BOD).
3. Two stage SFS-h (e.g., HSSF) in series for denitrification (remove O2) and removal of persistent organic compounds.
4. A stage FWS to complete the denitrification and the organic compounds removal and to enhance the
evapotranspiration.
5. A final detention pond to accumulate the effluent and enhance the evapotranspiration.
The system is designed to ensure high removal rates (>90-95% COD and NH3), and a good reduction of the effluent due
to evapotranspiration.
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Airport (forced bed aeration)
Buffalo Niagara International Airport
Higgins et al. 2010 (design and installation)
Wallace & Liner 2011 (evaluation) Case Study: Treatment of glycol contaminated aircraft deicing fluids (ADFs)
Challenge
Complexity of runoff: Treatment volume = 4600 m3/d
• ethylene glycol (200,000 mg/L BOD)
• Propylene glycol (320,000 mg/L BOD)
• snow and melt water (20,000 mg/L BOD)
• many other constituents:
• fuel and lubricant residuals
• oils and greases
• sewage leaks
• washing products
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• fertilizers & decaying vegetation
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Airport (forced bed aeration)
Approach: Forced Bed Aeration
figure - diagram and photo of FBA
A forced bed aeration treatment system generally would occupy 1/10 the size of an equivalent CW. **define CW**
The treatment is generally 5-30x more efficient and typically uses 1/10 the energy of mechanical WWTPs.
A FBA system can handle much greater flow volumes than CW (up to thousands m3/d).
The anticipated life of the FBA system is 50 to 100 years.
Solution:
Construction of 4 cells (FBA) with a cell size of 51 X 91 m.
The areal coverage is 1.9 ha.
The treatment capacity is 4600 m3/d, and a BOD removal rate of approximately 4500 kg/d.
The BOD removal is estimated to be equivalent to a city of 50000 people.
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3 photos of FBA at Buffalo Airport
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Airport (forced bed aeration)
Evaluation (Wallace & Liner, 2011)
By 2009 - 2010 full scale operation had been achieved.
Problems observed included the following,
nutrient-limited conditions had developed; the bacterial community was in poor health.
foaming associated with the formation of polysaccharide slimes.
In 2010 / 2011 a nutrient addition scheme was implemented.
The following observations were made:
BOD5 removal > 20,000 kg/d
BOD5 5X greater than original design
avg BOD5 removal rates 98.3%
BOD5 of effluent remained constant despite high inputs.
BOD5 removal was 5X greater than design specifications.
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Storm Water Treatment (free water surface wetland)
Shepard Wetland in Calgary, Alberta is the largest constructed wetland in Canada.
The areal size is 1 square mile (260 ha) when full and 0.6 square miles when at normal level.
The purpose of the constructed wetland is twofold: i) short-term storm water storage; and ii)
treatment wetland.
The storage capacity is 6.24 million cubic metres.
The maximum inflow rate is 44 m 3 /s and the maximum discharge rate is 6.5 m 3 /s.
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Storm Water Treatment (free water surface wetland)
Shepard Wetland, Calgary, AB
Goal: To treat stormwater before it enters the Bow River.
Calgary wanted to expand on east side of river (approx 24 km2), but existing stormwater
discharges emptied into the Western Irrigation Ditch used to irrigate crop land.
City did not want to degrade water quality of either the ditch or the river.
The first two cells are for sediment retention, last five cells are for treatment.
Shepard Wetland, Calgary, AB
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Dagram Shepard wetland
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Conventional Treatment Technologies - Wastewater
Treatment Stages within Conventional Wastewater Treatment
Conventional water treatment
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Activated Sludge Treatment Process
An overview of the treatment processes that utilize an activated sludge treatment process.
Diagram Activated Sludge Treatment Process
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Activated Sludge Wastewater Treatment Plant Providing Secondary Treatment.
A schematic of a typical Activated Sludge Wastewater Treatment Plant providing Secondary treatment.
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Trickle Filters
• most WWTPs utilize an activated sludge process
• some utilize a trickle filter process where primary effluent is sprayed over crushed stone where the
biofilm provides biological treatment of the effluent
Trickle filters photo and diagram
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Pre-Treatment Waste Water
Pre-Treatment of Raw Sewage
• The raw sewage entering the waste treatment facility will often contain large pieces of debris
that could damage or plug the facilities infrastructure.
• Screens separate the larger material out of the waste stream.
• Grit chambers also remove inert grit and stones.
• Comminutor shred the solids into smaller sizes in preparation for treatment.
• Flow equalization tanks balance out the flow of waste which is often uneven.
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Primary Treatment
The primary clarifier removes remaining light organic material by allowing the solids to settle to the
bottom to form sludge.
The sludge is removed from the primary treatment tank with mechanical scrapers and pumps.
Grease, oil, and other floating substances rise to the top, where they are removed by surface
skimming equipment.
The remaining effluent is transferred to the aeration tank for secondary treatment via biological,
chemical and physical processes.
Photo of a primary clarifier.
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Secondary Treatment: Aeration Tank
Primary effluent contains bacteria, colloidal solids and solubilised organic compounds.
The primary effluent is vigorously aerated to facilitate microbial growth and digestion of organic
constituents.
The mass of the microbial population grows and there is a constant cycle of new bacteria and
dead and dying bacteria that add to this mass.
Bacteria and undigested organic matter begin to clump together into larger particle sizes that
will be allowed to settle out of solution in the secondary clarifier.
Aeration tank – notice the vigorous aeration occurring in the tank closes to the top of this photo.
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Secondary Treatment: Secondary Clarifier
The effluent, or mixed liquor from the aeration tank contains a mixture of bacteria (living and dead),
carrier water and organic compounds (solubilised and particulate).
The lack of flow or turbulence in the clarifier allows the particulates and effluent (liquor) to separate.
The settled material is called activated sludge since it contains living bacteria.
A portion of the activated sludge is returned to the aeration tank to “spike” the incoming primary
effluent with the bacteria.
The clarified secondary effluent is often disinfected at this point.
Diagram secondary treatment
This diagram illustrates the inflow of primary effluent into the aeration tank and the removal of
activated sludge (returned or wasted) from the secondary clarifier.
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Tertiary Treatment
Secondary treatment has the potential to remove over 85% of the BOD, suspended solids and nearly
all pathogens.
However, regulatory requirements may require additional treatment.
Phosphorous and nitrogen compounds have often been common wastewater constituents for which
additional treatment is desired due to the negative impacts they can have on the receiving
environments.
Tertiary Treatment: Filtration
Secondary effluent exiting the secondary clarifier can still contain suspended material even
after the settling period and removal of the activated sludge.
Effluents are often filtered before release to the environment, or before their transfer to tertiary
treatment processes.
Filtration is often accomplished via sand filters, however, there are a variety of filter designs
that could be used.
The intent is to produce a low turbidity effluent that is now more stable since the majority of the
biological organisms have been removed.
Tertiary Treatment: Carbon Adsorption
Biological treatment of municipal wastes targets easily digested organic materials.
Not all wastewater constituents are easily digested microbally.
Some refractory compounds remaining in secondary effluents can be removed by adsorption
onto activated carbon.
Tertiary Treatment: Phosphorus Removal
Phosphorus is considered an essential nutrient for plant growth an often the nutrient that is in
limited supply within natural waters.
Addition of phosphorus to natural waters from wastewater effluents can cause eutrophication
and degradation of the ecosystem.
Phosphorus removal in most conventional treatment plants is accomplished through the
addition of metal salts such as ferric chloride or alum.
Phosphorus will react with these additives to create a precipitate that falls out of solution via
gravitational forces once the effluent is moved to a clarifier.
Tertiary Treatment: Nitrogen Removal
Nitrogen can be removed from the system through either biological or chemical processes.
Microorganisms are involved in the conversion of organic nitrogen into nitrogen dioxide gas
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through the processes of ammonification, nitrification and denitrification.
Chemical processes involve raising the pH to convert the ammonium ion into the more volatile
ammonia which can be stripped with aeration.
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Sludge Digestion
Sludge is further digested in a separate process.
This digestion can take place in the lack of oxygen (anaerobic) or with oxygen (aerobic).
Anaerobic digestion is the most common method used by WWTPs since it creates considerably less
biomass than what is produced via aerobic digestion.
Three Goals of Anaerobic Sludge Digestion
1. To reduce the volume of biosolids.
2. To stabilize the remaining biosolids.
3. To capture and utilize methane (biogas).
Anaerobic Sludge Digestion
Sludge is moved to large digesting tanks.
The environment is kept anaerobic and is heated to approx 37°C to encourage the growth of
anaerobic bacteria.
Different groups of bacteria are present, with each group feeding on a different substrate (e.g., food).
The anaerobic process includes the following four basic steps:
1. Hydrolysis: large polymers are degraded by enzymes
2. Fermentation: acetate is the main end product from acidogenic fermentation. Volatile fatty
acids are produced along with CO2 and hydrogen
3. Acetogenesis: volatile acids are metabolized to acetate and hydrogen
4. Methanogenesis: formaldehyde, acetate, CO2 and hydrogen are converted to methane and
H2O
Aerobic Sludge Digestion
More commonly used in small communities.
Sludge is aerated in an open tank.
The same processes are operative in aerobic sludge digesters as in aeration tanks used for
effluent treatment.
Approximately 30% reduction of suspended solids can be expected over a 20 day treatment
period.
Power consumption from aeration is an added expense that must be considered.
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Resulting biosolids can be suitable for agricultural applications.
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Cost-Risk-Benefit Analysis of Primary Secondary and Tertiary Waste Water Treatment
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Waste Water - Advanced Treatment Technologies
Conventional treatment
Conventional treatment technologies for wastewater have historically been focussed on:
Primary treatment: Removal of large course material & grit.
Secondary treatment: Reduction of BOD and settable solids + disinfection.
Tertiary treatment: Reduction of other unwanted constituents (P, N).
Tertiary treatment is often designed to provide additional removal of phosphorus, nitrogen,
BOD/COD
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Need for Advanced Treatment
Since the end of the second world war, there has been a rapid development in a variety of
synthetic chemicals used in industry, manufacturing, service industries, food production & processing and health care
There is a growing awareness that many of these compounds may not be adequately treated
with conventional wastewater treatment designs.
It is known that some of the compounds more resistant to conventional treatment methods may
be released to the environment during the discharge of treated effluent.
The human health implications for many of these compounds remains unknown, especially
pharmaceuticals and personal care products which have been engineered to be biologically
active at very low exposure levels.
How are advanced treatment processes different from conventional treatment?
Advanced treatment process are designed to either degrade or remove selected recalcitrant
compounds of interest that are not degraded or removed with conventional processes.
Degradation of the recalcitrant compounds does not necessary mean mineralization.
Advanced treatment processes often include the use of different combinations of treatment
processes at different stages in the treatment train.
Advance treatment processes are generally custom designed to address the complexities of
specific waste streams and regulatory requirements.
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Advanced Treatment Options
Advanced treatment options can be grouped into four basic areas:
1.Degradation of the compound
Oxidation
2.Membrane separation
Ultra-, nano-filtration, reverse osmosis
3.Clean-up method
pH adjustment, use of GAC, etc.
4. Soil-Aquifer Treatment
A mixture of microbial, ion exchange, adsorption, etc.
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Oxidation - AOPs
Oxidation is often accomplished by either ozone, peroxide, or UV irradiation.
Advanced Oxidative Processes (AOP) involves the use of two or more oxidants at one time.
In many cases (not all) the combined use of two or more of the above oxidants will enhance
oxidation more than can be achieved when using only one oxidant.
In some cases a catalyst such as titanium dioxide coated on aluminum (TiO2 and Al2O3) is used
to enhance the formation of the hydroxyl radical.
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Comparison of UV, O 3 , H2 O 2
Breakdown of organic chemical contaminants
\Comparison of UV ozone peroxide graphs
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Membrane Separation
Solute parameters:
Molecular weight (W)
Molecular size (length and width)
Acid disassociation constant (pKa)
Hydrophobicity / hydrophilicity (log Kow)
Diffusion coefficient (Dp)
Membrane properties:
Molecular weight cut-off
Pore size
Surface charge (measured as zeta potential)
Hydrophobicity / hydrophilicity (measured as contact angle)
Surface morphology (measured as roughness)
Feed water composition:
pH
Ionic strength
Hardness
Presence of organic matter
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Sequencing of Treatment Processes
The sequencing of advanced treatments depends on the objectives of the advanced treatment.
Oxidation procedures can be added to either pre-treat the primary effluent to enhance microbial
digestion or later in the train to oxidize TrOCs.
Likewise, membrane filtration can be added at different stages in the process, either to remove
TrOCs of secondary effluents or to enhance subsequent treatment methods such as UV
irradiation or ozonation.
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Ozone Treatment of Secondary Effluents (Oneby et al. 2010)
Wastewater treatment ozone
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Example of Advance Wastewater Treatment
El Paso, TX, USA: Fred Hervey Water Reclamation Plant (c.f. Loeb et al. 2012)
Secondary effluent from conventional treatment plant is further treated by:
Lime treatment
Recarbonation
Tertiary filtration
Granular activated carbon adsorption
Ozonation
Gwinnet County, GA, USA (c.f. Loeb et al. 2012)
Secondary effluent from conventional treatment plant is further treated by:
The tertiary treatment train of this plant includes:
Chemical clarification
Granular medium filtration
Pre-ozonation
Granular Activated Carbon
Post ozonation
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Membrane Filtration and Ozonation
Clark County Water Reclamation District, Nevada, USA (c.f. Loeb et al., 2012)
Used ozonation as a treatment option following membrane filtration of wastewater effluent for the
following purposes:
i) Enhanced phosphorus removal.
ii) Improved removal of pathogenic bacteria and viruses.
iii) Removal of PPCPs, EDCs and other micro-contaminants.
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Water Reclamation and Reuse
There is a growing awareness that high quality raw drinking water supplies are diminishing
either through unsustainable withdrawals, degradation from contaminants or changes in
climatic patterns that threaten the natural recharge mechanisms for these resources.
Polishing of Reclaimed Water
The level of polishing or conditioning of reclaimed water depends on the intended use.
Water reclaimed from wastewater effluent is used for a variety of wide ranging purposes.
These purposes can range from the irrigation of non-agricultural lands, to use in cooling towers
to high quality drinking water.
Many of the operational principles for these techniques are similar whether applied to drinking
water or wastewater.
References: additional information regarding the use of ozonation and reverse osmosis treatment for the removal
of micro-contaminants from domestic wastewater for the purpose of water recycling
Rahman et al 2010
Jasim et al 2006
Balch and Metcalfe
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References and Links on Drinking Water Treatment and Wastewater Treatment:
Additional papers are provided in the Resources folder to this course and some have been included as
hyperlinks in some Discussion slides.
A toolkit for monituide: A Participatory Approach for the Control of Diarrhoeal Disease. PHAST - SIDA-UNDP- WHP, 2000
oring and evaluating household water treatment and safe storage programmes - World Health Organization (On CD)
SAFE WATER FOR THE COMMUNITY A Guide for Establishing a Community-Based Safe Water
System Program CDC 2006 (On CD)
CDC Booklet on Safe Water - Ceramic Filters
CDC Booklet on Safe Water - Chlorination
CDC Booklet on Safe Water - Sand Filters
CDC Booklet on Safe Water - Solar
CDC Booklet on Safe Water - Flocculation
CDC Handbook on Safe Water - Implementation
Scaling Up Household Water Treatment Among Low-Income Populations - World Health
Organization 2008 (On CD)
Smart Disinfection Solutions, Netherland Water Partners
Soap Toilets and Taps, A Foundation for Healthy Children. How UNICEF supports water supply
sanitation and hygiene. UNICEF (2009)
Community Approaches to Total Sanitation UNICEF (2009).
Sick Water? The Central Role of Wastewater Management in Sustainable Development UNEP
UNHabitat (2010)
PHAST Step-by-Step G
Water Treatment and Pathogen Control. Process Efficiency in Achieving Safe Drinking Water.
LeChevallier, M.W. and Kwok-Kueng, A. (2004).
Clearing the Waters. A focus on water quality solutions. Meena Palaniappan, Peter H. Gleick, Lucy
Allen, Michael J. Cohen, Juliet Christian-Smith
Courtney Smith, Editor: Nancy Ross. Copyright © 2010, United Nations Environment Programme
Guidance for the safe use of urine and faeces in Ecological Sanitation. Caroline Schönning and Thor
Axel Stenström Swedish Institute for Infectious Disease Control (SMI) SEI 2004
Bibliography of Safe Water, Small Scale and Household Water Treatment (Microsoft Word Document)
Bibliography of Safe Water, Small Scale and Household Water Treatment (HTML Page)
Safe Use of Wastewater, Excreta and Greywater. Volume II. WHO 2006 file:///F|/Dropbox/WaterHealthNewFinal/Course3/concepts/WH30M100C001reference.htm[11/3/2014 7:38:24 PM]
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v. 1. Policy and regulatory aspects
v. 2. Wastewater use in agriculture
v. 3. Wastewater and excreta use in aquaculture —
v. 4. Excreta and greywater use in agriculture.
1. Water supply. 2. Water supply - legislation. 3. Agriculture. 4. Aquaculture. 5. Sewage.
6. Wastewater treatment plants. 7. Guidelines. I. World Health Organization. II. Title:
Safe use of wastewater, excreta and greywater. III. Title: Policy and regulatory aspects. IV.
Title: Wastewater use in agriculture.
V. Title: Wastewater and excreta use in aquaculture. VI. Title: Excreta and greywater use in
agriculture
WHO Guidelines for Drinking Water Quality 4th Edition WHO 2011
Additional Resources and Links
Concerned Municipal Strategies (CMS) a program coordinated by the Municipal Development Partnership (MDP) and
programme Solidarite (pS-Eau). there is a total of six guidance documents in this series.
Women in Europe for a Common Future (WECF) http://www.wecf.eu/english/water-sanitation/
(Internet Access
Required)
Water and Sanitation in Developing Countries Training Tool EAWG
http://www.eawag.ch/forschung/sandec/elearning/trainingtool/index_EN (Internet Access Required)
UNESCO Institute for Water Education Ecological Sanitation - online course http://www.unesco-ihe.org/onlinecourses (Internet Access Required)
http://www.health.gov.bc.ca/protect/pdf/cs2ta-mod7.pdf (Internet Access Required)
Additional papers are provided in the Resources folder to this course and have been included as hyperlinks in some Discussion
slides.
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