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Household Water Treatment and Safe Storage
Factsheet: Source Protection
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x Local contamination of the
Not Effective For:
x Naturally occurring
water source
contamination
x Contaminants introduced
upstream of the water source
What is Source Protection?
Source Protection Practices
There are many pollution problems which
may threaten drinking water quality at the
source, point of collection, or during
transport. Source protection can reduce or
eliminate the risk of contamination, resulting
in improved water quality and reduced risk
of disease. Source protection should always
be practiced as the first step in the multibarrier approach to safe drinking water.
The following provides suggestions on
several things that can be done to protect
different water sources from contamination
and improve the quality.
What Causes Contamination?
The main risk factors for contamination at
the water source, collection point and during
transport are:
x
Poor site selection of the water source
x
Poor protection of the water source against
pollution
(e.g.
agricultural
runoff
contaminated with manure and fertilizers)
x
Poor structure design or construction (e.g.
lack of a well lining and/or cover, tank
sealing, poor pipe connections)
x
Deterioration or damage to structures (e.g.
cracks can be entry points for
contaminants)
x
Lack of hygiene and sanitation knowledge
and practice in the community
For all Water Sources and Points of Use
(where the water is stored or used):
x
Locate latrines down hill and at least 30
meters away from water sources.
x
Keep animals away by using fences
around the water source
x
Maintain separate area for washing clothes
and watering animals
x
Keep the general environment around the
water source and points of use clean and
free from excreta and garbage
x
Plant trees along creeks and rivers and
maintain a well forested area above your
water source, to trap contaminants and
prevent erosion
x
Provide adequate drainage to prevent
wastewater from pooling and becoming
stagnant, which provides an ideal breeding
ground for insect vectors
Household Water Treatment and Safe Storage
Fact Sheet: Source Protection
x
Maintain and repair all constructed
elements and ensure water source and
structures are physically sealed from
contaminant inflow (e.g. surface run-off)
x
Ensure watershed use is non-polluting
x
Dig a surface water diversion channel,
ditch or bund above and around the spring
development
x
Seal the top of the source with a sanitary
cap when possible to prevent infiltration of
surface run-off
x
Plant vegetation around the catchment
area but ensure roots will not crack the any
structures
x
Fence off the spring and the catchment
area directly above it to prevent
contamination from livestock or people
x
For gravity fed systems, protect and
maintain collection and storage tanks, lay
piping 50cm below ground or deeper were
possible
Rivers and Lakes:
x
Mark separate zones for washing and
watering animals downstream and away
from water collection areas
Rainwater Harvesting:
Maintain separation distances between
source/collection points and latrines, washing and
animal watering points
Wells, Tubewells and Boreholes:
x
Cut back any trees or vegetation
overhanging the catchment surface
x
Collect and store rainwater in covered
tanks which are periodically cleaned
x
Clean catchment surface, gutters and
screens prior to first rain of the season
x
Divert and do not consume water from the
first rain
x
Use a first-flush system to divert first few
millimetres of each rainfall event as it
contains dust accumulated on the roof or
catchment area
x
Line wells and boreholes (provide a
sanitary seal in the top 2 to 3 meters)
x
Keep protected and covered, and
construct a parapet wall around open wells
Water Collection and Transport
x
Use a separately designated, clean rope
and bucket, a windlass or a hand pump to
pull water out of the well. Store the bucket
in its own covered clean platform.
x
Build a platform with adequate drainage at
the collection point to prevent mud and
wastewater from pooling
It is vital that people collect water in clean
containers and keep them covered while
transporting water from the source to the
point of use, to prevent contamination of the
water after collection.
Springs and Gravity Fed Piped Systems:
x
Stabilize springs by building retaining walls
and collector boxes with screened intakes
Household Water Treatment and Safe Storage
Fact Sheet: Source Protection
Further Information
Davison et al. (2005) Water Safety Plans: Managing Drinking-water Quality from Catchment to
Consumer. World Health Organization, Geneva, Switzerland. Available at:
www.who.int/water_sanitation_health/dwq/wsp0506/en/index.html
CAWST (Centre for Affordable Water and Sanitation Technology)
Wellness through Water.... Empowering People Globally
Calgary, Alberta, Canada
Website: www.cawst.org
Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Settling
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Turbidity
x Protozoa
x Helminths
x Bacteria
x Suspended particles (e.g. iron)
x Taste, odour, colour
x Viruses
x Dissolved chemicals
What is Settling?
Settling has been a traditional practice
throughout history using small vessels or
larger basins, cisterns and storage tanks.
Water quality can sometimes be improved
by allowing it to stand undisturbed long
enough for larger suspended particles to
settle out by gravity, including those that
cause turbidity (e.g. sand and silt) and
certain pathogens (e.g. protozoa and
helminths) Fine clay particles and other
pathogens like bacteria and viruses are
generally too small to settle by gravity.
How Does It Remove Contamination?
Although viruses, bacteria and smaller
protozoa are too small to settle by gravity,
some of these pathogens can attach
themselves to larger suspended particles
that can settle.
Storing water for at least one day will also
promote the natural die-off of some bacteria.
Operation
At least two containers are needed: one to
act as the settling container and another to
put the clean water into after the settling
period. Water can be settled for a few hours
and up to days depending on its quality. The
settled water is then carefully removed by
decanting, ladling or other gentle methods
that do not disturb the sedimented particles.
It is important to clean the containers
between each use.
The three pot settling method ensures water
is settled for a minimum of 2 days to
maximize settling and pathogen die-off. As
shown in the following illustration:
(a) After 24 hours, slowly pour water from
Pot 2 into a clean Pot 3. Clean Pot 2.
(b) Slowly pour water from Pot 1 into Pot 2.
(c) Pour source water (Bucket 4) into Pot 1.
Wait 24 hours before repeating step (a).
Household Water Treatment and Safe Storage
Factsheet: Settling
Key Data
Inlet Water Quality
x
No specific limits
Treatment Efficiency
Bacteria
Laboratory
2
x
x
Up to 90%
Not available
Field
1
Up to 90%
Viruses
1
Protozoa
1
Not available
> 90%
1
Not available
Helminths
> 90%
Not available
Efficiency varies from one water source to another
Longer storage times of 1-2 days can improve efficiency
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Unlimited
Unlimited
Robustness
Simple and easy to perform
Estimated Lifespan
x
Containers may need to be replaced over time if they develop leaks
Manufacturing Requirements
Worldwide Producers:
x Not applicable
Local Production:
x Not applicable
Materials:
x Containers
Fabrication Facilities:
x Not applicable
Labour:
x Traditional practice done in the household
Maintenance
x
Turbidity
2
Varies
2
Varies
Sobsey. M. (2002), effective removal of protozoa and helminths may require longer storage times of 1-2 days
Depends on the size of the suspended particles in the water - the larger the suspended particles, the more efficient.
Operating Criteria
x
1
Need to wash container after decanting the clear water
Household Water Treatment and Safe Storage
Factsheet: Settling
Key Data
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$0
US$0
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
References
Sobsey, M. (2002). Managing Water in the Home: Accelerated Health Gains from Improved
Water Supply. Water, Sanitation and Health, Department of Protection of the Human
Environment, World Health Organization, Geneva, Switzerland.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org Email: [email protected]
Wellness through Water.... Empowering People Globally
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Natural Coagulants
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x Turbidity
x
x
x
x
x
Bacteria
Viruses
Protozoa
Helminths
Taste, odour, colour
What are Natural Coagulants?
The sedimentation process can be
quickened by adding coagulants to the
water.
Coagulation with extracts from natural and
renewable vegetation has been widely
practiced since recorded time. There is a
variety of natural coagulants used around
the world, depending on the availability.
Extracts from the seeds of Moringa oleifera
can be used, the trees of which are widely
present in Africa, the Middle East and the
Indian subcontinent. Strychnos potatorum,
also known as clearing nuts or the nirmali
tree, is found in India to treat water. Prickly
pear cactus is prevalent and traditionally
used in Latin America. There are also
reports of other natural coagulants being
used, such as fava beans.
Not Effective For:
x Dissolved chemicals
Coagulation happens when the positively
and negatively charged particles are
chemically attracted together. They can then
accumulate (flocculation) to form larger and
heavier particles (flocs). The flocs can be
settled out or removed by filtration.
Bacteria and viruses can attach themselves
to the suspended particles in water that
cause turbidity. Therefore, reducing turbidity
levels through coagulation may also improve
the microbiological quality of water.
How Does it Remove Contamination?
Coagulants contain significant quantities of
water-soluble proteins which carry an overall
positive charge when in solution. The
proteins bind to the predominantly
negatively charged particles that cause
turbidity (e.g. sand, silt, clay).
Moringa seed pods (Credit: www.moringanews.org)
Household Water Treatment and Safe Storage
Fact Sheet: Natural Coagulants
Operation
Little research has been done to optimize
and standardize the use of natural
coagulants. Their use is usually passed
through traditional knowledge in the
community.
Generally, natural coagulants are not
available in a usable form and need to be
prepared. This is usually done just
beforehand to keep the coagulant fresh. For
example, prickly pear cactus needs to be
peeled and cut and moringa seeds need to
be dried and crushed into a powder.
Users add the prepared dose of coagulant to
the water. The water is then stirred for a few
minutes to help create flocs. The flocs can
be settled out and the clear water is
decanted, or removed by filtration.
Moringa seeds in a pod (Credit: www.hear.org)
Dried clearing nuts (Credit: www.farmwealthgroup.com)
Prickly pear cactus (Credit: Tennant, R., www.freelargephotos.com)
Household Water Treatment and Safe Storage
Fact Sheet: Natural Coagulants
Key Data
Inlet Water Quality
x
No specific limits
Treatment Efficiency
Bacteria
Laboratory
90-99.99%
3
>96.0%
50%
Field
Viruses
Protozoa
Helminths
Turbidity
Not available
Not available
Not available
80-99.5%
3
83.2-99.8%
Not available
Not available
Not available
95%
1
1
2
1
Madsen et al. (1987). Tests based on Moringa oleifera.
2
Tripathi et al. (1976); Able et al. (1984) cited in Sobsey. M. (2002). Tests based on Strychnos potatorum.
3
Nkurunziza et al. (2009). Tests based on Moringa oleifera.
x
x
2
Little research has been done to evaluate the efficacy of natural coagulants
Effectiveness of natural coagulants varies from one to another
Operating Criteria
x
x
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Unlimited
Unlimited
Little research has been done to optimize and standardize the use of natural coagulants
Generally, natural coagulants need to undergo some processing before use
Preparation, use and dose varies according to the natural coagulant and water source
Robustness
x
Availability depends on local conditions
Estimated Lifespan
x
x
Dried beans and seeds can be stored for a long time
Prickly pear cactus needs to be used before the sap dries
Manufacturing Requirements
Worldwide Producers:
x Not applicable
Local Production:
x Harvested and prepared locally
Materials:
x Natural coagulants (e.g. moringa seeds, prickly pear cactus)
x Miscellaneous tools (e.g. knife)
Fabrication Facilities:
x Prepared in households
Labour:
x Traditional practice, anyone can be taught to prepare and use natural coagulants
Household Water Treatment and Safe Storage
Fact Sheet: Natural Coagulants
Key Data
Maintenance
x
Dried beans and seeds should be stored in a dry location
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$0
US$0
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
Other
x
x
x
Jar testing can be undertaken to optimize effectiveness of particular coagulants with water
sources
Natural coagulants leave organic matter in the water, which may make subsequent chlorine
treatment less effective
Some users complain about the taste that natural coagulants may cause in water
References
Madsen, M., Schlundt, J. and E.F. Omer (1987). Effect of water coagulation by seeds of Moringa
oleifera on bacterial concentrations. Journal of Tropical Medicine and Hygiene; 90(3): 101-109
Sobsey, M. (2002). Managing Water in the Home: Accelerated Health Gains from Improved
Water Supply, Water, Sanitation and Health, Department of Protection of the Human
Environment, World Health Organization, Geneva, Switzerland.
Nkurunziza, T., Nduwayezu, J. B., Banadda E. N. and I. Nhapi (2009). The effect of turbidity
levels and Moringa oleifera concentration on the effectiveness of coagulation in water treatment.
Water Science & Technology, Vol 59, No 8, pp 1551±1558.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org Email: [email protected]
Wellness through Water.... Empowering People Globally
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Chemical Coagulants
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x Turbidity
x
x
x
x
x
x
Bacteria
Viruses
Protozoa
Helminths
Hardness
Taste, odour, colour
What are Chemical Coagulants?
The sedimentation process can be
quickened by adding coagulants to the
water.
Chemical coagulants are commonly used in
community drinking water treatment systems
though some application in household water
treatment occurs.
The main chemicals used for coagulation
are
aluminium
sulphate
(alum),
polyaluminium chloride (also known as PAC
or liquid alum), alum potash, and iron salts
(ferric sulphate or ferric chloride).
Lime (Ca(OH2)), lime soda ash (Na2CO3)
and caustic soda (NaOH) are sometimes
used to "soften" water, usually ground water,
by precipitating calcium, magnesium, iron,
manganese and other minerals that
contribute to hardness.
Not Effective For:
x Dissolved chemicals
then accumulate (flocculation) to form larger
particles (flocs) which settle faster. The flocs
can then be settled out or removed by
filtration.
Some bacteria and viruses can also attach
themselves to the suspended particles in
water that cause turbidity. Therefore,
reducing turbidity levels through coagulation
may also improve the microbiological quality
of water.
Operation
Users IROORZ WKH PDQXIDFWXUHU¶V LQVWUXFWLRQV
and add the prepared dose of coagulant to
the water. The water is then stirred for a few
minutes to help create flocs. The flocs can
be settled out or removed by filtration.
How Does it Remove Contamination?
Particles that cause turbidity (e.g. silt, clay)
are generally negatively charged, making it
difficult for them to clump together because
of electrostatic repulsion. But coagulant
particles are positively charged, and they
chemically attracted to the negative turbidity
SDUWLFOHV QHXWUDOL]LQJ WKH ODWWHU¶V QHJDWLYH
charge. With mixing the neutralized particles
Alum block (Credit: www.cdc.org)
Household Water Treatment and Safe Storage
Fact Sheet: Chemical Coagulants
Key Data
Inlet Water Quality
x No specific limits
Treatment Efficiency
Bacteria
Laboratory
>90 to >99%
< 90%
3
95%
Field
1
Viruses
1
>90 to >99%
Protozoa
1
Helminths
>90 to >99%
1
Turbidity
1
Not available
Not available
Not available
>90 to >99%
2
Not available
Not available
Sproul (1974), Leong (1982), Payment and Armon (1989) cited in Sobsey (2002)
Ongerth (1990) cited in Sobsey (2002)
3
Wrigley (2007)
2
x Maximum effectiveness requires careful control of coagulant dose, pH and consideration of the
quality of the water being treated, as well as mixing
x Effectiveness of chemical coagulants varies from one to another
Operating Criteria
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Unlimited
Unlimited
1HHGWRIROORZPDQXIDFWXUHU¶VLQVWUXFWLRQV
Robustness
x
x
Difficult to optimize without training and equipment
Requires coagulant supply chain and regular purchase
Estimated Lifespan
x
6 months in liquid form and 1 year in solid form
Manufacturing Requirements
Worldwide Producers:
x Many producers around the world
Local Production:
x Most chemical products are difficult and complex to manufacture and local production is not
feasible
Maintenance
x
Chemicals should be stored in a dry location and away from children
Direct Cost
Capital Cost
Operating Cost
US$0
US$9-91/year
1
Replacement Cost
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Sobsey (2002). Assumed 25 litres/household/day.
Household Water Treatment and Safe Storage
Fact Sheet: Chemical Coagulants
Key Data
Other
x
Jar testing can be undertaken to optimize effectiveness of particular coagulants with water
sources
References
Sobsey M. (2002). Managing Water in the Home: Accelerated Health Gains From Improved
Water Supply, Water, Sanitation and Health, Department of Protection of the Human
Environment, World Health Organization, Geneva, Switzerland.
Wrigley. T. (2007) Microbial Counts and Pesticide Concentrations in Drinking Water After Alum
Flocculation of Channel Feed Water at the Household Level, in Vinh Long Province, Vietnam,
Journal of Water and Health; 05:1.
CAWST (Centre for Affordable Water and Sanitation Technology)
Wellness through Water.... Empowering People Globally
Calgary, Alberta, Canada
Website: www.cawst.org
Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Fact Sheet: Straining
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Helminths
x Protozoa
x Turbidity
x Bacteria
x Taste, odour, colour
x Viruses
x Chemicals
What is Straining?
Straining water through a cloth has been
widely used for household water treatment
in many cultures for centuries. A common
sari cloth is usually used for this in South
Asia, for example.
How Does it Remove Contamination?
The pore size range in old (laundered) sari
cloth is 100±ȝPEXWDERXWȝPLIWKH
cloth is folded four to eight times. The holes
allow water to pass but retain particles and
SDWKRJHQV!ȝP
Straining through sari cloth has been shown
to be effective in filtering out the plankton to
which cholera bacteria may attach
themselves, therefore reducing the risk of
cholera. This simple method can also filter
out many helminths and their eggs and
larvae.
Electron micrographs of a single layer of sari cloth
filters (Credit: Colwell et al., 2002)
Operation
Fold a large, clean piece of cloth seven to
eight times. Place the folded cloth over a
clean water container, and secure in place.
Pour water through the cloth into the
container. Wash the cloth in clean water
before using it again.
Old sari cloth made of cotton was found to
be most effective in removing cholera based
on laboratory experiments (Colwell et al.,
2002). After several launderings, threads of
an old sari become soft and loose, reducing
the pore size, compared with new sari cloth.
A woman uses a sari cloth to strain water
Household Water Treatment and Safe Storage
Fact Sheet: Straining
Key Data
Inlet Water Criteria
x
No specific limits
Treatment Efficiency
Bacteria
> 99%
Laboratory
1
Not available
Field
Viruses
Protozoa
Not available
> 100%
Not available
Not available
Helminths
2
> 100%
2
Not available
1
Colwell et al. (2002), Huq et al. (1996), Vibrio cholerae attached to plankton and particlHV!ȝP
2
HHOPLQWKVDQGSURWR]RD!ȝPGRQRWSDVVWKURXJKWKe cloth
3
Suspended particles !ȝPdo not pass through the cloth
x
Efficiency depends on the weave of the cloth and the number of times folded
Operating Criteria
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Unlimited
Unlimited
Robustness
x
x
Simple and easy to perform
Cloth is available around the world, discarded cloth may be used
Estimated Lifespan
x
Cloth may need to be replaced if there are holes
Manufacturing Requirements
Worldwide Producers:
x Not applicable
Local Production:
x Not applicable
Materials:
x Cloth
x Containers
Fabrication Facilities:
x Not applicable
Labour:
x Traditional practice done in the household
Maintenance
x
Cloth needs to be washed in clean water after every use
Turbidity
3
Varies
Not available
Household Water Treatment and Safe Storage
Fact Sheet: Straining
Key Data
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$0
US$0
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
References
Colwell, R., Huq, A., Sirajul Islam, M.S., Aziz, K.M.A., Yunus, M., Huda Khan, N., Mahmud, A.,
Sack, R.B., Nair, G.B., Chakraborty, J., Sack, D.A., and Russek-Cohen, E. (2002), Reduction of
Cholera in Bangladeshi Villages by Simple Filtration. Proc Natl Acad Sci USA. 100(3): 1051±
1055. Available at:
www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=298724#B11
Huq, A., Xu, B., Chowdhury, M.A.R., Islam, M.S., Montilla, R., and Colwell, R.R. (1996), A Simple
Filtration Method to Remove Plankton-Associated Vibrio cholerae in Raw Water Supplies in
Developing Countries. Appl Environ Microbiol. 1996;62:2508±2512. Available at:
www.ncbi.nlm.nih.gov/pubmed/8779590
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Fact Sheet: Biosand Filter
The Treatment Process
Potential Treatment Capacity
Very Effective For:
x
x
x
x
x
Bacteria
Protozoa
Helminths
Turbidity
Taste, odour, colour
Somewhat Effective For:
Not Effective For:
x Viruses
x Iron
x Dissolved chemicals
What is a Biosand Filter?
How Does It Remove Contamination?
The biosand filter (BSF) is an adaptation of
the traditional slow sand filter, which has
been used for community water treatment
for hundreds of years. The BSF is smaller
and adapted for intermittent use, making it
suitable for households.
Pathogens and suspended material are
removed through a combination of biological
and physical processes that take place in
the biolayer and within the sand bed. These
processes include: mechanical trapping,
adsorption, predation and natural death.
Water treatment is carried out by the sand
inside the filter. The filter container can be
made of concrete, plastic or any other waterproof, rust-proof and non-toxic material. The
concrete filter box is cast from a steel mold
or made with pre-fabricated pipe.
The container is filled with layers of sieved
and washed sand and gravel (also referred
to as filter media). There is a standing water
height of 5 cm above the sand layer.
Lid
Diffuser
Outlet Tube
Standing Water
Filtration Sand
As in slow sand filters, a biological layer of
microorganisms (also known as the biolayer
or schmutzedecke) develops at the sand
surface, which contributes to the water
treatment.
A perforated diffuser plate or basin is used
to protect the biolayer from disturbance
when water is poured into the filter.
Separating Gravel
Drainage Gravel
Cross-Section of Concrete Biosand Filter
Household Water Treatment and Safe Storage
Fact Sheet: Biosand Filter
may evaporate quickly in hot climates and
cause the biolayer to dry out.
A pause period is needed between uses to
allow time for the microorganisms in the
biolayer to consume pathogens in the water.
Users should wait at least one hour after all
the water has been filtered before filling the
filter again. It is recommended to use the
filter every day; however users can wait up
to a maximum of 48 hours between batches.
The biosand filter has been designed to
allow for a filter loading rate (flow rate per
square metre of filter area) which has
proven to be effective in laboratory and field
tests. This filter loading rate has been
determined to be not more than 600
litres/hour/square metre.
Cross Section of Plastic Biosand Filter
(Credit: TripleQuest)
Operation
Contaminated water is poured into the top of
the filter on an intermittent basis. The water
slowly passes through the diffuser, and
percolates down through the biolayer, sand
and gravel. Treated water naturally flows
from the outlet pipe.
The biolayer is the key pathogen removing
component of the filter. Without it, the filter is
significantly less effective. It may take up to
30 days to establish the biolayer depending
on inlet water quality and frequency of use.
The water from the filter can be used during
the first few weeks while the biolayer is
being established, but disinfection is
recommended during this time, as during
regular on-going use.
The biolayer requires oxygen to survive.
When water is flowing through the filter,
dissolved oxygen in the water is supplied to
the biolayer. During pause times, when the
water is not flowing, the oxygen is obtained
by diffusion from the air.
Correct installation and operation of the
biosand filter has a water level of
approximately 5 cm above the sand during
the pause period. A water depth of greater
than 5 cm results in lower oxygen diffusion
to the biolayer. A water depth less than 5 cm
The recommended flow rate for the CAWST
Version 10 concrete biosand filter is 0.4
litres/minute measured when the inlet
reservoir is full of water. If the flow rate is
much faster, the filter may become less
efficient at removing pathogens. If the flow
rate is much slower, the user may become
impatient and not use the filter even though
the filter is working well at removing
pathogens. Since the flow rate is controlled
by the size of the sand grains, it is very
important to select, sieve and wash the sand
properly.
The flow rate through the filter will slow
down over time as the biolayer develops and
sediment is trapped in the upper layer of the
sand. For turbidity levels greater than 50
NTU, the water should first be strained
through a cloth or sedimented before using
the BSF.
The biosand filter requires maintenance
when the flow rate drops to a level that is
inadequate for the household use. This is
done by a simple µVZLUODQGGXPS¶SURFHGXUH
performed on the top of the sand, and only
takes a few minutes.
The outlet should also be cleaned regularly
using soap and water or a chlorine solution.
The treated water should be collected by the
user in a safe storage container placed on a
block or stand, so that the container opening
is just under the outlet, minimizing the risk
for recontamination.
Household Water Treatment and Safe Storage
Fact Sheet: Biosand Filter
Key Data
Inlet Water Criteria
x
Turbidity < 50 NTU (Nephelometric Turbidity Units)
Treatment Efficiency
Bacteria
Laboratory
Field
Up to
1,2
96.5%
87.9 to
6,7
98.5%
Viruses
Protozoa
3
Helminths
4
70 to >99%
>99.9%
Not
available
Not
available
Up to 100%
5
Up to 100%
5
Turbidity
Iron
95% to
1
<1 NTU
Not
available
85%
7
8
90-95%
1 Buzunis (1995)
2 Baumgartner (2006)
3 Elliott et al. (2008)
4 Palmateer et al. (1997)
5 Not researched. However, helminths are too large to pass between the sand, up to 100% removal efficiency is assumed
6 Earwaker (2006)
7 Duke & Baker (2005)
8 Ngai et al. (2004) [Note: These tests were done on a plastic version of a biosand filter]
x
x
x
x
x
x
x
Filtration sand selection and preparation are critical to ensure flow rate and effective
treatment5HIHUWR&$:67¶V%LRVDQG)LOWHU0DQXDOIRUGHWDLOHGLQVtructions on how to select
and prepare the filtration sand.
Treatment efficiencies provided in the above table require an established biolayer; it takes up
to 30 days to establish the biolayer depending on inlet water quality and usage
Filter should be used every day to maintain the biological layer
Best performance requires a consistent water source; switching sources may decrease
treatment efficiency
Swirl and dump maintenance will reduce treatment efficiency until the disturbed biolayer is reestablished
Taste, odour and colour of filtered water is generally improved
Treated water temperature is generally cooler from concrete filters
Operating Criteria
Flow Rate
Batch Volume
Daily Water Supply
< 0.4 litres/minute*
12-18 litres
24-72 litres**
Note: Operating criteria is for the concrete biosand filter, plastic biosand filter may have different parameters.
* 0.4 litres/minute is the maximum recommended flow rate for the CAWST Version 10 concrete biosand filter. The actual
flow rate will fluctuate over the filter cleaning cycle and between filters.
** Based on 4 batches per day (i.e. morning, lunch, dinner, before bed).
x
x
Pause period is needed between uses to allow time for the microorganisms in the biolayer to
consume pathogens in the water
Recommended pause period is 6 to 12 hours with a minimum of 1 hour and maximum of 48
hours
Robustness
x
x
No moving or mechanical parts to break
Concrete filters have the outlet pipe embedded in the concrete, protecting it against breaks
and leaks
Household Water Treatment and Safe Storage
Fact Sheet: Biosand Filter
Key Data
x
x
x
x
x
Plastic filters have an external outlet pipe which may be prone to damage and leakage; once
broken repair is difficult or impossible
Plastic filters are lighter (3.5 kg) than concrete filters (70-75 kg for thin wall version and 135
kg for heavy wall version)
Poor transportation of concrete filters can lead to cracking and/or breakage; cracks can
sometimes be repaired
Plastic filters are made from medical grade plastic which is resistant to ultraviolet (UV)
degradation and breakage
Preferably, filters should not be moved after installation
Estimated Lifespan
x
x
x
30+ years for concrete filters; concrete filters are still performing satisfactorily after 10+ years
10+ years for plastic filters
Lids and diffusers may need replacement over time
Manufacturing Requirements
Worldwide Producers:
x Concrete biosand filter designs are freely available from CAWST, Canada
x Plastic biosand filters are patented and licensed to International Aid, USA for manufacturing
and sales
Local Production:
x Concrete biosand filters can be manufactured locally
x Molds can be borrowed, rented, bought or welded locally
x Filters can be constructed at a central production facility, or in the community
x Filter sand and gravel can be prepared (sieved and washed) on-site or nearby
Materials for Concrete Filters:
x Steel mold
x Sand, gravel, and cement
x Filter sand and gravel
x Copper or plastic outlet tubing
x Metal or plastic for the diffuser
x Metal or wood for the lid
x Water for concrete mix and to wash filter sand and gravel
x Miscellaneous tools (e.g. wrench, nuts, bolts)
Fabrication Facilities:
x Workshop space for filter construction
Labour:
x Skilled welder required to fabricate steel mold
x Anyone can be trained to construct and install the filter
Hazards:
x Working with cement and heavy molds is potentially hazardous and adequate safety
precautions should be used
x Concrete filters are heavy and difficult to move and transport
Maintenance
x
Required when the flow rate drops to a level that is insufficient for household use; frequency
depends on turbidity of inlet water
Household Water Treatment and Safe Storage
Fact Sheet: Biosand Filter
Key Data
x
x
Swirl and dump maintenance for the top layer of sand is simple, takes a few minutes and can
be done by household users
Outlet, lid and diffuser should be cleaned on a regular basis
Direct Cost
Filter Type
Capital Cost
Operating Cost
Replacement Cost
Concrete
US$12-50
US$0/year
US$0
US$0/year
US$0
Plastic
US$75
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Prices do not include shipping container, shipping fees, or clearing/related costs.
References
Buzunis, B. (1995). Intermittently Operated Slow Sand Filtration: A New Water Treatment
Process. Department of Civil Engineering, University of Calgary, Canada.
Baumgartner, J. (2006). The Effect of User Behavior on the Performance of Two Household
Water Filtration Systems. Masters of Science thesis. Department of Population and International
Health, Harvard School of Public Health. Boston, Massachusetts, USA.
Duke, W. and D. Baker (2005). The Use and Performance of the Biosand Filter in the Artibonite
Valley of Haiti: A Field Study of 107 Households, University of Victoria, Canada.
Earwaker, P. (2006). Evaluation of Household BioSand Filters in Ethiopia. Master of Science
thesis in Water Management (Community Water Supply). Institute of Water and Environment,
Cranfield University, Silsoe, United Kingdom.
Elliott, M., Stauber, C., Koksal, F., DiGiano, F., and M. Sobsey (2008). Reductions of E. coli,
echovirus type 12 and bacteriophages in an intermittently operated 2 household-scale slow sand
filter.Water Research, Volume 42, Issues 10-11, May 2008, Pages 2662-2670.
Ngai, T., Murcott, S. and R. Shrestha (2004). Kanchan Arsenic Filter (KAF) ± Research and
Implementation of an Appropriate Drinking Water Solution for Rural Nepal. [Note: These tests
were done on a plastic biosand filter]
Palmateer, G., Manz, D., Jurkovic, A., McInnis, R., Unger, S., Kwan, K. K. and B. Dudka (1997).
Toxicant and Parasite Challenge of Manz Intermittent Slow Sand Filter. Environmental
Toxicology, vol. 14, pp. 217- 225.
Stauber, C., Elliot, M., Koksal, F., Ortiz, G., Liang, K., DiGiano, F., and M. Sobsey (2006).
Characterization of the Biosand Filter for Microbial Reductions Under Controlled Laboratory and
Field Use Conditions. Water Science and Technology, Vol 54 No 3 pp 1-7.
Further Information
CAWST (Centre for Affordable Water and Sanitation Technology): www.cawst.org
Triple Quest: www.hydraid.org
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Product Sheet: Concrete Biosand Filter
Treatment Type
Product Name:
Concrete biosand filter
Product Manufacturer:
Designs are freely available from CAWST, Calgary, Canada
Manufacturer Location(s):
Constructed locally
Product Description:
Square concrete filter with diffuser plate and lid. The filter box is
cast from a steel mold. The filter box is filled with layers of sieved
and washed sand and gravel.
Availability:
Robustness:
As of June 2009, CAWST estimates
that over 200,000 concrete biosand
filters have been implemented in
more than 70 countries.
Lid
There are no moving or mechanical
parts to break. Outlet pipe is
embedded in the concrete,
protecting it against breaks and
leaks. Poor transportation can lead
to cracking and/or breakage; cracks
can sometimes be repaired. Filters
should not be moved after
installation.
Outlet Tube
Lifespan:
30+ years, still performing
satisfactorily after 10+ years
Dimensions:
0.9 m tall by 0.3 m
Weight:
70-75 kg for thin wall version and
135 kg for heavy wall version (empty
with no sand)
Costs:
US$12-60, costs will vary depending
on location
Further Information
CAWST (Centre for Affordable Water and Sanitation Technology): www.cawst.org
Diffuser
Standing Water
Filtration Sand
Separating Gravel
Drainage Gravel
Household Water Treatment and Safe Storage
Product Sheet: HydrAidTM BioSand Filter
Treatment Type
TM
Product Name:
HydrAid
BioSand Water Filter
Product Manufacturer:
Triple Quest (venture between Cascade Engineering and
Windquest Group)
Manufacturer Location(s):
Michigan, United States of America
Product Description:
Plastic biosand filter with diffuser plate and lid. The filter is filled
with layers of sieved and washed sand and gravel.
Availability:
Available for bulk purchase to partner organizations.
Robustness:
There are no moving or mechanical parts to break. Uses
ultraviolet (UV) resistant plastic VRLWZRQ¶WEUHDNGRZQLQ
sunlight. Made from US Food and Drug Administration (FDA)
approved materials. The external outlet pipe may be prone to
damage and leakage. Filters should not be moved after
installation.
Lifespan:
10+ years
Approximate Dimensions:
Height ± 0.75 m, Diameter ± 0.4 m
Approximate Weight:
Empty ± 3.5 kg, Filled ± 55 kg
Costs:
Display filter ± US$58, Single filter with sand ± US$75
International retail and wholesale purchase also available. Prices
do not include shipping container, shipping fees, or
clearing/related costs.
Further Information
www.hydraid.org
HydrAid BioSand Filter
(Credit: International Aid)
Household Water Treatment and Safe Storage
Fact Sheet: Ceramic Candle Filter
The Treatment Process
Potential Treatment Capacity
Very Effective For:
x
x
x
x
x
Bacteria
Protozoa
Helminths
Turbidity
Taste, odour, colour
Somewhat Effective For:
Not Effective For:
x Viruses
x Dissolved chemicals
What is a Ceramic Candle Filter?
How Does It Remove Contamination?
Locally produced ceramics have been used
to filter water for hundreds of years. Ceramic
candles are hollow cylindrical forms
fastened into the bottom of a container.
Water seeps through the ceramic candle
and falls into a lower container, which is
fitted with a tap at the bottom. Units often
use more than one candle because the flow
rate through one candle can be slow. A lid is
placed on top of the filter to prevent
contamination. This system both treats the
water and provides safe storage until it is
used.
Pathogens and suspended material are
removed from water through physical
processes such as mechanical trapping and
adsorption.
Ceramic candles are usually made from
local clay mixed with a combustible material
like sawdust, rice husks or coffee husks.
When the candle is fired in a kiln, the
combustible material burns out, leaving a
network of fine pores through which the
water can flow through.
Colloidal silver is sometimes added to the
clay mixture before firing or applied to the
fired ceramic candle. Colloidal silver is an
antibacterial which helps in pathogen
removal, as well as preventing growth of
bacteria within the candle itself.
Ceramic Candle Filter (Credit: USAID, Nepal)
Quality control on the size of the
combustible materials used in the clay mix
ensures that the filter pore size is small
enough to prevent contaminants from
passing through the filter. Colloidal silver
DLGVWUHDWPHQWE\EUHDNLQJGRZQSDWKRJHQV¶
cell membranes, causing them to die.
Household Water Treatment and Safe Storage
Fact Sheet: Ceramic Candle Filter
Operation
Contaminated water is poured into the top
container where the candles are attached.
The water slowly passes through the pores
in the candles and is collected in the lower
container. The treated water is stored in the
container until needed, protecting it from
recontamination. The user simply opens the
tap at the bottom of the container to get
water.
For turbidity levels greater than 50 NTU, the
water should first be strained through a cloth
or sedimented before using the ceramic
candle filter.
The candles should be regularly cleaned
using a cloth or soft brush to remove any
accumulated material. It is recommended
that the candles be replaced every 6 months
to 3 yearsGHSHQGLQJRQWKHPDQXIDFWXUHU¶V
instructions and quality of the candles. This
is in part to protect against fine cracks which
may have developed and are not be visible.
Any cracks will reduce the effectiveness
since water can short-circuit through the
crack without being filtered through the
ceramic pores.
Different types of ceramic candles
Filter with one ceramic candle
Household Water Treatment and Safe Storage
Fact Sheet: Ceramic Candle Filter
Key Data
Inlet Water Quality
x
Turbidity < 50 NTU (Nephelometric Turbidity Units)
Treatment Efficiency
Bacteria
Viruses
1,3,4,5
Laboratory
>99%
Field
>99.95%
>90%
2,3
4,5
Not available
Protozoa
Helminths
5, 6
>100%
6
>100%
>100%
>100%
Turbidity
6
88-97%
3
6
97-99%
3
1 Mattelet (2006)
2 Clasen & Boisson (2006)
3 Franz (2004)
4 Chaudhuri et al. (1994)
5 Horman et al. (2004)
6 Not researched, however helminths and protazoa are too large to pass between the 0.6-3 ȝm pores. Therefore, up to
100% removal efficiency can be assumed.
x
x
x
x
Efficiencies provided in the above table require colloidal silver
Pore size and construction quality are critical to ensure flow rate and effective treatment
Taste, odour and colour of filtered water is generally improved
The system provides safe storage to prevent recontamination
Operating Criteria
x
x
x
Flow Rate
Batch Volume
Daily Water Supply
0.1-1 litres/hour
Depends on size of
upper container
About 10 litres
Flow rate is highest when the upper container is full
Flow rate declines with use and accumulation of contaminants within the filter pores
Flow rate can be improved by using more than one candle in the filter
Robustness
x
x
x
x
x
x
x
x
Lower container is a safe storage container
There are no moving or mechanical parts to break
Small cracks can occur which are not visible to the naked eye, but which allow pathogens to
pass through the candle
Seal between the candle and container is critical; water may pass through untreated if there
is a gap; some locally manufactured candles have a poor seal resulting in lower treatment
efficiencies
Poor transportation of candles can lead to cracking and/or breakage
Plastic taps in the lower container can break, metal taps last longer but increase cost
Requires supply chain and market availability for replacement candles and taps
Recontamination is possible during cleaning; care should be taken to use clean water, not to
touch the ceramic with dirty hands, and not to place the filter on a dirty surface
Estimated Lifespan
x
x
x
Up to 3 years, generally 6 months to 1 year
Candle needs to be replaced if there are visible cracks
Filters must be repaired, resealed or replaced if the seal between the candle and the
container is damaged (e.g., if short-circuiting or dripping is observed)
Manufacturing Requirements
Worldwide Producers:
x Produced by different manufacturers around the world
Household Water Treatment and Safe Storage
Fact Sheet: Ceramic Candle Filter
Key Data
x
Highest quality candles are generally produced by European and North American
manufacturers
Local Production:
x Candles are generally imported, except in a few countries where candles are produced locally
x Filter units can be assembled locally using locally available plastic containers and taps
Materials:
x Ceramic candle
x Plastic container with lid
x Tap
x Sealant
Fabrication Facilities:
x
A small factory with a kiln is required for local production
x
A small workshop is required for local filter assembly
x
Miscellaneous tools
Labour:
x Professional potter with experience in collecting clay, making ceramic articles, semi-industrial
or mass production
x Assistants, preferably potters as well
x Skill and quality control in manufacturing is essential to ensure optimum pore size, flow rate
and effectiveness
Hazards:
x Working with presses and kilns is potentially hazardous and adequate safety precautions
should be used
Maintenance
x
x
x
Filters are cleaned by lightly scrubbing the surface when the flow rate is reduced
Some manufacturers recommend that soap and chlorine should not be used to clean the
candle
Lower container, tap and lid should be cleaned on a regular basis
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$15-30
US$0
~US$4.5/year
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Ceramic candles need to be replaced every 6-12 months
Other
x
Safest design uses clear plastic containers so that candle seal leaks are visible
References
Chaudhuri, M., Verma, S. and A. Gupta (1994). Performance Evaluation of Ceramic Filter
Candles. Journal of Environmental Engineering, Vol 120, No. 6, Nov/Dec 1994, Technical Note #
5432.
Clasen, T and S. Boisson. (2006). Household-based Ceramic Water Filters for the Treatment of
Drinking Water in Disaster Response: An Assessment of a Pilot Programme in the Dominican
Replublic, Water Practice & Technology. Vol 1 No 2. IWA Publishing.
Household Water Treatment and Safe Storage
Fact Sheet: Ceramic Candle Filter
Key Data
Franz, A. (2004). A Performance Study of Ceramic Candle Filters in Kenya Including Tests for
Coliphage Removal. Master of Engineering thesis. Department of Civil and Environmental
Engineering, Massachusetts Institute of Technology. Cambridge, Massachusetts, USA.
Horman, A., Rimhanen-Finne, R., Maunula, L., von Bonsdorff, C., Rapala, J. Lahti, K., and M.
Hanninen (2004). Evaluation of the Purification Capacity of Nine Portable, Small-scale Water
Purification Devices. Water Science and Technology, Vol 50, No. 1, pp 179-183.
Mattelet, C. (2006). Household Ceramic Water Filter Evaluation Using Three Simple Low-cost
Methods: Membrane Filtration, 3M Petrifilm, and Hydrogen Sulfide Bacteria in Northern Region,
Ghana. Master of Engineering thesis. Department of Civil and Environmental Engineering,
Massachusetts Institute of Technology. Cambridge, Massachusetts, USA.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Product Sheet: Siphon Filter
Treatment Type
Product Name:
Siphon Filter
®
®
CrystalPur (India, East Africa, Cambodia) and Tulip (Africa, SouthEast
Asia, India, Central & South America) are the brand names available in
the market.
Manufacturer:
Basic Water Needs India Pvt Ltd, Pondicherry, India
Product Description:
The siphon filter is a ceramic candle-type water filter for household use.
It uses gravity pressure to force water through a high-quality ceramic
filter element impregnated with silver. The product is very compact,
consisting of only a filter element, a plastic hose, and a valve. Some kits
come with 2 water containers, or households can use existing
containers. The siphon action (flow) is started by squeezing the bulb,
and then the water flows by itself.
Availability:
Produced and imported by Basic Water Needs India Pvt Ltd. Filter
element cannot usually be produced locally. Currently implemented
around the globe by EnterpriseWorks/VITA and Connect International.
Robustness:
Ceremic element is quite
fragile; plastic parts are robust.
A washable fabric layer strains
large particles to reduce
clogging of the ceramic
element, but the element may
clog if inlet water contains fine
silt. Ceramic filter element
needs to be replaced if there
are cracks or leaks. Use out of
direct sunlight to avoid
degradation of plastic parts.
Lifespan:
Can treat up to 7,000 litres,
depending on the turbidity of
the water. At 20 L/household
per day, this will last just under 1
year. Plastic parts will last 5 years.
Siphon Filter
(Credit: www.akvo.org)
Household Water Treatment and Safe Storage
Product Sheet: Siphon Filter
Approximate Dimensions: Diameter filter element: 60 mm
®
(Tulip filter)
High filter element: 100 mm
3
Total volume (including package): 2.7 dm
During operation, the ceramic filter element
inside the upper (source water) container
needs to be elevated approximately 70 cm
above the height of the lower (filtered water)
container.
Approximate Weight:
0.45 kg (not including water containers)
Output:
4-6 L/hour
Costs:
US $7-12
Shipping: US $5-6 per filter (depending on quantity)
Replacement ceramic filter element: US $3-4
Maintenance:
Two options for filter cleaning: backwashing and scrubbing the filter
element. Backwashing is done by closing the tap and squeezing the
bulb, which forces the water back through the filter, pushing dirt
particles out.
Tulip Filter
(Credit: www.300in6.org)
Treatment Efficiency
Bacteria
Laboratory
Field
94-100%
96%
1,2
1
Viruses
2,3
50-90%
Protozoa
> 90%
N/A
2
Helminths
> 90%
N/A
N/A
2
Turbidity
96-99.8%
Chemicals
1,2
1
81.2%
N/A
N/A
N/A: Not available.
1
Ziff, 2009
2
Basic Water Needs BV/Pvt.
3
The pore size in the ceramic element may not be small enough to remove all viruses, however some viruses will be
removed due to filtration, adsoption and reaction with the silver in the element.
Further Information
Akvopedia: www.akvo.org/wiki/index.php/Siphon_filter and
www.akvo.org/wiki/index.php/Solution_of_the_week_6
CrystalPur filter (World Health Works): www.enterpriseworks.org/pubs/WHW_onesheet.pdf
Tulip Water Filter: www.tulipwaterfilters.com/
Basic Water Needs: www.basicwaterneeds.com
References
Basic Water Needs BV/Pty. Test results from independent laboratories (2010-2011) and product
information SXEOLVKHGRQILOWHUPDQXIDFWXUHU¶VZHEVLWHZZZEDVLFZDWHUQHHGVFRP
Ziff, S.E. (2009).Siphon filter assessment for Northern Ghana. Thesis (M.Eng.) Massachusetts
Institute of Technology, Dept. of Civil and Environmental Engineering, USA.
Household Water Treatment and Safe Storage
Factsheet: Ceramic Pot Filter
Treatment Type
Potential Treatment Capacity
Very Effective For:
x
x
x
x
x
Bacteria
Protozoa
Helminths
Turbidity
Taste, odour, colour
Somewhat Effective For:
Not Effective For:
x Viruses
x Iron
x Dissolved chemicals
What is a Ceramic Pot Filter?
Locally produced ceramics have been used
to filter water for hundreds of years. Water is
poured into a porous ceramic filter pot, and
is collected in another container after it
passes through the ceramic pot.
Ceramic pot filters usually have a diameter
of about 30 cm by 25 cm deep, with an 8
litre capacity. Two variations of ceramic
filters, flat-bottom and round-bottom, are
currently manufactured.
The ceramic pot typically sits or hangs in the
top of a larger plastic or ceramic container
(20-30 litres), which is fitted with a tap at the
bottom. A lid is placed on top of the filter to
prevent contamination. The system both
treats the water and provides safe storage
until it is used.
Ceramic pots are usually made from local
clay mixed with a combustible material like
sawdust, rice husks or coffee husks. The
clay and combustible material are sieved
through a fine mesh, and then mixed
together with water until it forms a
homogeneous mixture. The mixture is
pressed into shape using a mold. When the
pot is fired in a kiln, the combustible material
burns out, leaving a network of fine pores
through which the water can flow through.
Colloidal silver is sometimes added to the
clay mixture before firing or applied to the
fired ceramic pot. Colloidal silver is an
antibacterial which helps in pathogen
removal, as well as preventing growth of
bacteria within the filter itself.
Some ceramic pot filters also include
activated charcoal in the clay mixture to
improve odour, taste, and colour.
How Does It Remove Contamination?
Pathogens and suspended material are
removed from water through physical
processes such as mechanical trapping and
adsorption. Colloidal silver breaks down the
SDWKRJHQV¶FHOOZDOOVFDXVLQJWKHPWRGLH
Quality control on the size of the
combustible materials used in the clay mix
ensures that the filter pore size is small
enough to prevent contaminants from
passing through the filter. Colloidal silver
aids treatment by breaking down pathogens¶
cell membranes, causing them to die.
Household Water Treatment and Safe Storage
Factsheet: Ceramic Pot Filter
Operation
Contaminated water is poured into the
ceramic pot. The water slowly passes
through the pores and is collected in the
lower container. The treated water is stored
in the container until needed, protecting it
from recontamination. The user simply
opens the tap at the base of the container
when they need water.
For turbidity levels greater than 50 NTU, the
water should first be strained through a cloth
or sedimented before using the ceramic pot
filter.
The filter pot should be regularly cleaned
using a cloth or soft brush to remove any
accumulated material. It is recommended
that the filter pot be replaced every 1-2
years. This is in part to protect against fine
invisible cracks which may have developed
over time. Any cracks will reduce the
effectiveness since water can short-circuit
without being filtered through the ceramic
pores.
Round Bottom Ceramic Pot Filter
(Credit: Filter Pure Inc)
Cross Section of Ceramic Pot Filter
(Credit: Filter Pure Inc)
Flat Bottom Ceramic Pot Filter
(Credit: Potters for Peace)
Household Water Treatment and Safe Storage
Factsheet: Ceramic Pot Filter
Key Data
Inlet Water Quality
x
Turbidity < 50 NTU (Nephelometric Turbidity Units)
Treatment Efficiency
Bacteria
1
Laboratory
Field
>98% 4
100%
2
88% to
3
>95.1%
Viruses
1
Protozoa
19% 6,7
>99%
>100%
Not available
>100%
Helminths
8
>100%
8
>100%
Turbidity
8
83% ±99%
1
8
<5 NTU
Iron
5
Not available
2
>90%
5
1 Lantagne (2001)
2 Smith (2004)
3 Brown and Sobsey (2006)
4 Vinka (2007)
5 Low (2002)
6 Van Halem (2006)
7 Some additives to the clay may increase virus removal
8 Not researched, however helminths and protazoa are too large to pass between the 0.6-3 ȝm pores. Therefore, up to
100% removal efficiency can be assumed.
x
x
x
x
Efficiencies provided in the above table require colloidal silver
Pore size and construction quality are critical to ensure flow rate and effective treatment
Taste, odour and colour of filtered water is generally improved
The system provides safe storage to prevent recontamination
Operating Criteria
x
x
Flow Rate
Batch Volume
Daily Water Supply
1-3 litres/hour
8 litres
20-30 litres
Flow rate is highest when the pot is full
Flow rate declines with use and accumulation of contaminants within the filter pores
Robustness
x
x
x
x
x
x
x
x
Lower container can be used as a safe storage container
There are no moving or mechanical parts to break
Small cracks can occur which are not visible to the naked eye, but which allow pathogens to
pass through the filter
Poor transportation of filters can lead to cracking and/or breakage
Plastic taps in the lower container can break, metal taps last longer but increase cost
Requires supply chain and market availability for replacement filters and taps
Requires construction quality control process to ensure effectiveness
Recontamination is possible during cleaning; care should be taken to use clean water, not to
touch the ceramic with dirty hands, and not to place the filter on a dirty surface
Estimated Lifespan
x
x
Up to 5 years, generally 1-2 years
Filter needs to be replaced if there are visible cracks
Household Water Treatment and Safe Storage
Factsheet: Ceramic Pot Filter
Key Data
Manufacturing Requirements
Worldwide Producers:
x Free press and kiln designs are available from Potters for Peace
Local Production:
x Local production of the filters is common and preferable
x Requires quality control process to ensure filter effectiveness
x The lower container, lid and tap can usually be purchased locally
Materials:
x Clay
x Combustible material (e.g. sawdust, rice husks, coffee husks)
x Colloidal silver (optional)
x Lid
x 20-30 litre ceramic or plastic container with tap
Fabrication Facilities:
x A ceramic factory requires at least 100 square metres of covered area
x 15 to 20 ton hydraulic press (can be fabricated locally)
x Filter molds (can be fabricated locally)
x Mixer for clay and combustible material (can be fabricated locally)
x Hammer mill (can be fabricated locally)
x Kiln with an internal area of at least 1 cubic metre (can be fabricated locally)
x Racks
x Work benches
x Miscellaneous tools (e.g. traditional pottery tools)
Labour:
x Professional potter with experience in collecting clay, making ceramic articles, semi-industrial
or mass production
x Assistants, preferably potters as well
x Skill and quality control in manufacturing is essential to ensure optimum pore size, flow rate
and effectiveness
Hazards:
x Working with presses and kilns is potentially hazardous and adequate safety precautions
should be used
Maintenance
x
x
x
x
Filters are cleaned by lightly scrubbing the surface when the flow rate is reduced
Some manufacturers recommend to boil the filter every three months to ensure effectiveness
Some manufacturers recommend that soap and chlorine should not be used to clean the filter
Lower container, tap and lid should be cleaned on a regular basis
Household Water Treatment and Safe Storage
Factsheet: Ceramic Pot Filter
Key Data
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$12-25
US$0
~US$4
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Filter pots generally need to be replaced every 1-2 years
References
Brown, J. and M. Sobsey (2006). Independent Appraisal of Ceramic Water Filtration Interventions
in Cambodia: Final Report, Department of Environmental Sciences and Engineering, School of
Public Health, University of North Carolina, USA.
Lantagne, D. (2001). Investigation of the Potters for Peace Colloidal Silver Impregnated Ceramic
Filter Report 2: Field Investigations. Alethia Environmental for USAID, USA.
Low, J. (2002). Appropriate Microbial Indicator Tests for Drinking Water in Developing Countries
DQG$VVHVVPHQWRI&HUDPLF:DWHU)LOWHUV¶0DVWHURI(QJLQHHULQJWKHVLV'HSDUWPHQWRI&LYLODQG
Environmental Engineering, Massachusetts Institute of Technology. Cambridge, Massachusetts,
USA.
Napotnik, J., Mayer, A., Lantagne, D. and K. Jellison. Efficacy of Silver-Treated Ceramic Filters
for Household Water Treatment. Department of Civil and Environmental Engineering, Lehigh
University, USA. Available at: www.filterpurefilters.org/files/pdf/silver.pdf
Smith, L. (2004). Ceramic Water Filter Use in Takeo, Cambodia ± Operational Issues and Health
Promotion Recommendations. Submitted in partial fulfilment as a requirement for a Master of
Science in Control of Infectious Diseases, London School of Hygiene and Tropical Medicine,
London, England.
Van Halem, D. (2006). Ceramic silver impregnated pot filters for household drinking water
treatment in developing countries. Masters of Science in Civil Engineering Thesis, Department of
Water Resources, Delft University of Technology, Netherlands.
Vinka, A. et al. (2007). Sustainable Colloidal-Silver-Impregnated Ceramic Filter for Point-of-Use
Water Treatment. Environmental Science & Technology, Vol. 42, No. 3, 927±933
Further Information
Centers for Disease Control and Prevention: www.cdc.gov/safewater/publications_pages/optionsceramic.pdf
Filter Pure, Inc: www.filterpurefilters.org
International Development Enterprises:
www.ideorg.org/OurTechnologies/CeramicWaterPurifier.aspx
Potters for Peace: www.pottersforpeace.org
Resource Development International Cambodia: www.rdic.org/water-ceramic-filtration.html
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Membrane Filters
The Treatment Process
Potential Treatment Capacity
Very Effective For:
x
x
x
x
x
1
2
Somewhat Effective For:
3
Bacteria (UF , NF , RO )
Viruses (UF, RO, NF)
4
Protozoa (MF , UF, NF, RO)
Helminths (MF, UF, NF, RO)
Salt (RO, NF)
x
x
x
x
Colour (UF, RO, NF)
Turbidity (UF, RO, NF)
Iron (UF, RO, NF)
Manganese (UF, RO, NF)
Not Effective For:
x Chemicals, pesticides (UF)
x Heavy metals (UF)
1
Ultrafiltration (see below)
Nanofiltration (see below)
3
Reverse Osmosis (see below)
4
Microfiltration (see below)
2
What Is a Membrane Filter?
A membrane is a thin barrier with holes, or
pores. Some particles, such as water, are
small enough to pass through the membrane
pores, while larger particles cannot pass
through and are retained on the membrane.
Membrane filtration is used as a step in the
multi-barrier approach for water treatment, but
it is also used in other areas such as
desalination and water quality testing.
Membrane filtration can be classified according
to the diameter of the pores in the membrane,
or by the molecular weight of contaminants the
membrane retains.
Filtration Type
Pore Size
(µm / nm)
Microfiltration
(MF)
Ultrafiltration
(UF)
Nanofiltration
(NF)
Reverse
osmosis (RO)
0.1-10 µm
(1-1000 nm)
0.01-0.1 µm
(1-100 nm)
<0.001 µm
(<1 nm)
<0.001 µm
(<1 nm)
(Wagner, 2001 and US EPA, 2005)
Ultrafiltration is the most common membrane
filtration in household drinking water treatment.
How Does It Remove Contamination?
As water passes through the membrane,
pathogens and other contaminants are
removed because they are too big to fit
through the membrane pores. Pressure is
required to force the water through the
membrane.
For
microfiltration
and
ultrafiltration, gravity alone may provide
enough pressure to make the water flow
through the filter.
Molecular
Weight
(Daltons)
10,000500,000
200-1,000
<100
Filter Membrane Illustration
(Credit: www.firstprinciples.com)
Household Water Treatment and Safe Storage
Factsheet: Membrane Filters
Ultrafiltration membranes will remove large
and heavy particles such as sand, bacteria,
protozoa, helminths, and some viruses. They
will not effectively remove most dissolved or
small substances such as salt or smaller
viruses.
Types of Membrane Filtration and Their Contaminant
Removal Capabilities
(Credit: https://netfiles.uiuc.edu/mcheryan/www/memtech.htm)
Sawyer Filter
(Credit: www.sawyerpointonefilters.com)
Microfiltration alone is not as effective as
ultrafiltration for treating drinking water
because the membrane pores are bigger than
most viruses and some bacteria. Microfiltration
is sometimes used as a pre-treatment step in a
multi-barrier treatment system.
Nanofiltration and reverse osmosis are very
effective
at
removing
microbiological
contamination, but these membranes are more
commonly used in water desalination and
industrial processes where the removal of
dissolved contaminants is required.
Lifestraw Family Filter
(Credit: www.vestergaard-frandsen.com/lifestraw)
Operation
There are several HWT products that use
membrane technologies. Operation and
maintenance
procedures
vary between
products. A driving force is required to force
the water through the membrane ± this may be
gravity (microfiltration and ultrafiltration),
pressure or vacuum (nanofiltration and reverse
osmosis). No electricity is required if manual
pumping or gravity are used to force the water
through the membrane. No chemicals are
required, although some household membrane
filter products also include a chemical
disinfection step afterwards.
®
Some examples of such products are Sawyer
®
filters and Lifestraw , which use ultrafiltration,
®
and Nerox filters, which use microfiltration.
Please refer to the individual CAWST
Membrane Filtration Product Sheets for further
information on these technologies.
Nerox-02 Filter
(Credit: www.scan-water.org)
Household Water Treatment and Safe Storage
Fact Sheet: Membrane Filters
Key Data
Inlet Water Criteria
x
x
Some products recommend or incorporate a pre-filtration step such as straining through a
cloth, settling, or sand filtration to reduce inlet water turbidity
Very turbid water will clog membranes, reducing flow rate and requiring more frequent
cleaning
Treatment Efficiency
x
x
Depends on membrane pore size and filter product; see Membrane Filtration Product Sheets
The following illustration shows the different pore sizes of each filtration type in comparison to
the size of various pathogens. It is important to research the pore size and treatment
capability of any filter product before purchase.
3RUH6L]HIRU9DULRXV)LOWUDWLRQ7\SHVDQG5HODWLYH3DWKRJHQ6L]HV³0&)´ Membrane Cartridge Filtration)
(US EPA, 2005)
Operating Criteria
x
Operation depends on product
Membrane Filter Product
®
Sawyer 0.02 filter
1
2
®
Sawyer 0.1 filter
®
Lifestraw Individual
®
3
Lifestraw Family
®
Nerox filter
4
3
Flow Rate
Daily Water Supply
Lifespan Volume
13.6-15 litres/hour
327 litres
3.78 million litres
46.5-54 litres/hour
1117 litres
N/A
N/A
2 litres
700 litres
6-8 litres/hour
144-192 litres
18,000 litres
N/A
15-25 litres
2,500 litres
N/A ± not available
1
www.sawyerpointonefilters.com; based on a 3-foot hose attached to a 5-gallon bucket at sea level. Increasing the hose
length, using a larger container or continuously keeping the bucket full will increase flow rate.
2
www.sawyerpointonefilters.com; based on a 1-foot hose attached to a 5-gallon bucket at sea level. Increasing the hose
length, using a larger container or continuously keeping the bucket full will increase flow rate.
3
www.vestergaard-frandsen.com/lifestraw
4
www.scan-water.com
Household Water Treatment and Safe Storage
Fact Sheet: Membrane Filters
Key Data
Robustness
x
x
Many membrane filter products cannot be used or stored in temperatures below zero
Some products are available for use in emergency contexts
Estimated Lifespan
x
Depends on product
Manufacturing Requirements
Worldwide Producers:
x There is a wide variety of companies that manufacture membrane filter products worldwide
x Compact designs usually allow for easy handling and transport
Local Production:
x It could be difficult to find local producers of membranes or membrane filter products
x Some components for manufacturing or assembling membrane filter products can be found
locally (e.g. tubing, containers)
Materials:
x Membranes are made from a variety of materials such as acrylonitrile, polysulfone,
polypropylene, polyester or polytetrafluoroethylene
Labour:
x Anyone can be trained to construct and install the system
Hazards:
x No specific manufacturing or operational hazards
Maintenance
x
Membranes and other parts of the product may need regular cleaning and/or backwashing
Direct Cost
Capital Cost
Depends on product
1
Operating Cost
1
Not available
Replacement Cost
Depends on product
Operational cost will depend on product chosen, location, local infrastructure, pumping system (manual or electric)
References
Wagner, J. (2001). Membrane Filtration Handbook. Second Edition, Revision 2. Osmonics, Inc.
USA. Available online at: www.ionics.com/content/pdf/1229223-%20Lit%20Membrane%20Filtration%20Handbook.pdf
United States Environmental Protection Agency (US EPA). (2005). Membrane Filtration Guidance
Manual. USA, Nov 2005. Available online at:
www.epa.gov/ogwdw/disinfection/lt2/pdfs/guide_lt2_membranefiltration_final.pdf
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Product Sheet: LifeStraw® Family
Treatment Type
®
Product Name:
LifeStraw Family
Manufacturers:
Vestergaard-Frandsen
Product Description:
LifeStraw Family is a water filtration and disinfection system that
uses gravity to move water through it. The untreated water is
poured into a container at the top. Safe water comes out of the
blue tap at the bottom.
®
The inlet water is treated first by a pre-filter with a pore size of 80
Pm, located in the upper container. This pre-filter removes large
particles and sediment. Water then flows down the hose due to
gravity, and into the purification cartridge. Inside the purification
cartridge, the water is filtered again through a membrane with a
pore size of 0.02 Pm (20 nm). This ultrafiltration step removes
remaining pathogens and turbidity.
Each time the filter is used; the user
must open the red valve at the bottom
of the purification cartridge and let
water flow out for 5 to 30 seconds. This
empties the cartridge of air and allows
maximum treatment. Water from the
red outlet should not be drunk.
Availability:
Must be purchased from Vestergaard
Frandsen (regional offices located in
parts of Africa and Asia) and imported.
Not available on single unit basis, large
quantities must be purchased.
Using Lifestraw Family
(Credit: Vestergaard-Frandsen)
Robustness:
Requires no electricity or spare parts.
There is a chlorine chamber at the
bottom of the upper container which adds a small amount of
active chlorine to the water for the purpose of protecting the
ultrafiltration membrane from fouling, extending the life of the
membrane. The pre-filter and purification cartridge require daily
cleaning to prevent clogging
Lifespan:
18,000 litres (about 2.5 years at 20 litres/day)
Household Water Treatment and Safe Storage
Product Sheet: LifeStraw® Family
Approximate Dimensions:
Upper container capacity: 2 litres
Plastic hose length: 1 metre
Approximate Weight:
Not available
Output:
Average 9 to 10 litres/hour
Cost:
US$25-40; only available in large orders
Maintenance:
Pre-filter should be cleaned daily. Remove pre-filter from
container, wash and replace.
Purification cartridge should be
cleaned daily. Follow
instructions provided to clean
the cartridge by squeezing the
red bulb, waiting 30 seconds,
and repeating twice. Open the
red valve and allow water to
flow out of the red outlet for 30
seconds.
Squeezing the bulb for backwash
(Credit: Vestergaard-Frandsen)
Treatment Efficiency
Bacteria
Laboratory
Viruses
1,2
>99.9999%
Field*
N/A
99.99%
1,2
Protozoa
>99.9%
N/A
N/A
1,2
Helminths
100%
3
N/A
Turbidity
4
Chemicals
2
N/A
0
N/A
N/A
N/A : Not available
1
2
3
Clasen et al., 2009
www.vestergaard-frandsen.com/lifestraw/lifestraw/faq
Due to the pore size (0.02 Pm), it would be expected that helminths will be removed
4
Due to the pore size (0.02 Pm), turbidity removal is expected to be high. Extensive testing has shown it will make turbid
water clear (www.vestergaard-frandsen.com/lifestraw/lifestraw-family/faq).
Lifestraw does not remove salt or chemicals such as arsenic, iron or fluoride.
References
Clasen, T. et al. (2009). Laboratory assessment of a gravity-fed ultrafiltration water treatment
device designed for household use in low-income settings. Am. J. Trop. Med. Hyg., 80(5), 2009,
pp. 819±823.
®
Vestergaard-Frandsen. (no date). Lifestraw . Safe drinking water interventions for home and
outside use. Verstergaard Frandsen Group S.A., Switzerland. Available at: www.lifestraw.com
Household Water Treatment and Safe Storage
Product Sheet: LifeStraw®
Treatment Type
®
Product Name:
LifeStraw
Manufacturers:
Vestergaard-Frandsen
Product Description:
LifeStraw is a portable water filter
that can be carried around with the
user. Water is drunk directly out of
the filter apparatus - the user dips
®
LifeStraw into a water source and
sucks on it like a straw to draw the
water up. The personal filter is
recommended for adults and
children over 3 years old. The filter
is recommended for use when
away from home.
®
®
Drinking with Lifestraw
(www.lifestraw.com)
LifeStraw contains a chamber with
a specially developed halogenated resin (containing iodine) that
kills bacteria and viruses on contact. Micro-filters are also used to
remove all particles larger than 0.2 microns (Pm). Activated
carbon adsorbs residual iodine, improving the taste of water. The
filter will remove some turbidity. More frequent backwashing will
be required if the source water is turbid.
Availability:
Must be purchased from Vestergaard Frandsen (regional offices
located in parts of Africa and Asia) and imported
Robustness:
Requires no electricity or spare parts. The outer shell is
composed of high impact polystyrene plastic. Can be carried
around by the user on a string around their neck. Should be
regularly backwashed by blowing through it to prevent clogging;
will require more frequent backwashing if turbid water is used.
Lifespan:
1,000 litres (about 15 months at 2 litres/day)
Approximate Dimensions:
Not available
Approximate Weight:
Not available
Output:
Maximum 0.6 litres/minute (the actual flow rate will change over
the filter cleaning cycle and the lifespan of the filter)
Household Water Treatment and Safe Storage
Product Sheet: LifeStraw®
Cost:
US$3-$6.50; available retail
and wholesale. Not currently
available on a retail basis in
North America.
Storage:
Can be stored for three years
at a maximum temperature of
30 degrees. Storage at higher
temperatures will results in
lower treatment rates for the
first few millilitres of water
consumed.
Maintenance:
Regularly blow through it after
drinking to keep the filters
clean and to prevent clogging
Backwashing by blowing
(Credit: Vestergaard-Frandsen)
Treatment Efficiency
Bacteria
Laboratory
>99.999%
Field*
N/A
1,2,3
Viruses
99-99.8%
Protozoa
1
>99.9%
N/A
N/A
2,3
Helminths
100%
4
Turbidity
3
Metals
2
99.6%
0
N/A
N/A
N/A
N/A: Not available
1
2
3
4
Sobsey, no date
www.vestergaard-frandsen.com/lifestraw/lifestraw/faq
Naranjo and Gerber, 2010; turbidity removal based on inlet water with turbidity of 104 NTU
due to the pore size (0.2 Pm), it would be expected that helminths will be removed
LifeStraw does not remove salt or chemicals such as arsenic, iron or fluoride.
Inlet water criteria not specified; very turbid water should be pre-filtered or settled first. If turbid
water is to be consumed, only use LifeStraw to drink from the surface (top layer) of the water.
References
Naranjo, J and Gerber, C.P. (2010). Laboratory Test: Evaluation of Vestergaard Frandsen's
®
hollow fiber LifeStraw for the removal of Escherichia Coli and Cryptosporidium according to the
US Environmental Protection Agency guide standard and protocol for evaluation of
microbiological water purifiers. Department of Soil, Water and Environmental Science, University
of Arizona, USA. Available at: www.vestergaard-frandsen.com/lifestraw/lifestraw/longevity-andefficacy
®
Sobsey, M. (no date). LifeStraw Personal: Summary of Test Data Received from the University
of North Carolina, USA.
®
Vestergaard-Frandsen (no date). Lifestraw . Safe drinking water interventions for home and
outside use. Verstergaard Frandsen Group S.A., Switzerland. Available at: www.lifestraw.com
Household Water Treatment and Safe Storage
Product Sheet: Nerox®- 02 Drinking Water Filter
Treatment Type
®
Product Name:
Nerox -02 Drinking Water Filter
Manufacturers:
First Principals Inc., USA
Scan-Water, Norway/Finland
Simpex, Ukraine
Product Description:
®
The Nerox -02 filter is a patented technology. The filter system is
comprised of a chamber containing the membrane, with an outlet
hose and nozzle. The membrane is a thin polymeric film with pore
1
2
3
size of 0.2 , 0.28 or 0.4 microns. The filter operates
mechanically using gravity.
1
Simpex
ScanWater
3
First Principles
2
Availability:
Must be shipped. May also be available as a
kit including water containers or bags with
spigot.
Robustness:
There are no moving or mechanical parts to
break.
Can only be used in above-zero climates.
Warnings:
Do not store in sub-zero temperatures.
Do not clean the membrane with coarse
(Credit: www.filter-systems.com)
material or brush.
Do not expose the filter to direct sunlight or excessive heat.
Do not use the filter if the membrane is in any way damaged.
Lifespan:
Can treat up to 2,500 litres depending on source water turbidity.
Typical use is 15-25 L/day. Lasts up to 10 years when kept in
original packaging and in temperatures between ±10 and +50º C.
Approximate Dimensions:
16 cm x 17.5 cm x 2.5 cm.
The height of the water surface in the inlet water container must
be kept a minimum of 30 cm above the end of the outlet tube.
Approximate Weight:
300 grams (0.66 lb)
Output:
Typically 15 to 25 L/day, turbid water gives lower output
Cost:
US$12-15
Household Water Treatment and Safe Storage
Product Sheet: Nerox®- 02 Drinking Water Filter
Storage:
Dry environment, above 0 ºC.
Maintenance:
The filter membrane must be cleaned with
a sponge when membrane gets clogged.
Treatment Efficiency
(Credit: Scan Water)
Bacteria
Laboratory
94-100 %
Field*
7
N/A
1,2
Viruses
Protozoa
3
100%
3
N/A
N/A
N/A
1,2
6
Helminths
100%
2
6
N/A
Turbidity
90 %
4
Chemicals
60-100 %
6
N/A
5,6
6
N/A
N/A - Not available
1
First Principles Inc., nd
2
www.scan-water.com / www.filter-systems.com / Tullilaboratorio Laboratories, Finland
3
The membrane pore size is too large to retain most viruses
4
www.filter-systems.com
5
Removal of metals and chemicals depends on the quality of the water source. The filter is able to remove some to all
iron, lead, copper, aluminum, manganese, zinc, arsenic and some pesticides. (www.firstprinciples.com, www.filtersystems.com)
6
Arsenic removal efficiency: 90-100% (First Principles Inc., nd)
7
The Nerox filter has been used by international organizations, such as UNICEF, in the field, especially for emergency
situations (see websites below for more information)
References
First Principals Inc. (no date). Nerox Water Filter, No More Bacteria. First Principals Inc.,
Cleveland, USA. Available at: www.firstprincipals.com/3pager_Filter.pdf
Further Information
First Principals: www.firstprincipals.com/Nerox.htm
Information brochure: www.firstprincipals.com/3pager_Filter.pdf
Scan Water: www.scan-water.com
Information brochure: www.scan-water.com/products.php?vareid=103
Simpex/Filter-systems: www.filter-systems.com
Household Water Treatment and Safe Storage
Product Sheet: Sawyer Point OneTM Filter
Treatment Type
TM
Product Name:
Sawyer Point One
filter
Manufacturer:
Sawyer Products Inc., USA
Product Description:
The Sawyer Point One® filter is a gravity membrane
filtration technology that uses hollow fibre membranes to
remove pathogens. It has a pore size of 0.1 microns,
making it effective for removing bacteria, protozoa and
helminths. The Point One® filter does not remove viruses
(see Sawyer Point Zero Two Product Sheet for virus
removal).
The kit includes a filter, hose, compression fitting,
backwash syringe, a hanger for storing the hose, and a
hole cutter for attaching the hose to the inlet water
container. The kit does not include a container to hold the
inlet water or a container to collect the filtered water. The kit
is designed to be used with a plastic container, but other
types may also work; water storage containers should not
be a container that has ever been used to transport
chemicals or toxic materials.
Sawyer PointOneTM Filter Kit
(Credit: www. www.sawyer.com)
The filter membrane is located at the end of the outlet
hose. To stop the flow, the hose and filter are raised up to
the top of the inlet water bucket and hooked on a hanger
(provided) until the next use.
Availability:
Available online. Cannot be exported
internationally through Sawyer Products Inc.
They recommend contacting an international
logistic company for shipping outside of North
America.
Sawyer Filter Operation
(Credit: www.sawyer.com)
Robustness:
7KHPHPEUDQHILOWHUGRHVQ¶WQHHGWREHUHSODFHGEDFNZDVKLQJXVLQJWKHV\ULQJH
when the filter clogs is all that is required to restore the flow rate. Water prefiltration using a cloth and/or settling is recommended for turbid inlet water.
Lifespan:
No field data available yet to estimate how long the filter will remain useable.
Household Water Treatment and Safe Storage
Product Sheet: Sawyer Point OneTM Filter
Approximate Dimensions: Cylindrical filter: length 22 cm, diameter 7 cm.
Plastic tube length: 30 cm (1 foot); other lengths are available.
Approximate Weight:
0.3 kg (0.63 lb)
Output:
46.5-54 litres/hour; 1117 litres/day.
Based on a 1-foot hose attached to
a 5-gallon bucket at sea level.
Increasing the hose length, using a
larger container, continuously
keeping the bucket full will increase
flow rate. Flow rate will be lower at
higher altitudes.
Costs:
Retail US$60
Maintenance:
Need to backwash filter using
syringe provided in the kit when flow
rate slows down. With relatively
clear inlet water, backwashing is
Sawyer PointOneTM Bucket Filter
recommended every 3,800 litres.
(Credit: www.sawyer.com/gallery.htm)
If inlet water is extremely turbid,
backwashing is recommended every 40 litres or less.
Treatment Efficiency
Bacteria**
Laboratory
>99.99999%
Field
5
N/A
Viruses
1
2
Protozoa
N/A
> 99.999%
N/A
N/A
Helminths
3
100%
N/A
4
Turbidity
Chemicals
N/A
N/A
N/A
N/A
N/A: Not available.
1
Hydreion LLC, 2005. Test bacteria: Klebsiella.
2
The Sawyer Point One
3
Hydreion LLC, 2005. Test organisms: Cryptosporidium parvium oocysts and Giardia Lamblia cysts.
4
Helminth removal should be equal to or greater than bacteria and protozoa removal based on pathogen size.
TM
filter does not claim to remove viruses.
5
A field project implementation by Give Clean Water shows its applicability in the field. Available at:
www.sawyerpointonefilters.com . The results from a field study in Bolivia are being analyzed.
References
Hydreion LLC. (2005). Microbiological Testing of the Sawyer 7/6B Filter. USA. Available at:
www.sawyerpointonefilters.com/downloads/MicrobiologicalTest_HydreionLabReport_12-012005_76BFilter.pdf
Sawyer Products Inc (2011). Available at: www.sawyerpointonefilters.com. Accessed May 16,
2011.
Household Water Treatment and Safe Storage
Product Sheet: Sawyer Point Zero TwoTM Purifier
Treatment Type
TM
Product Name:
Sawyer Point Zero Two
Purifier filter
Manufacturer:
Sawyer Products Inc., USA
Product Description:
The Sawyer Point Zero Two® filter is a gravity membrane filtration technology that uses hollow
fibre membranes to remove pathogens from water. It has a pore size of 0.02 microns, making it
effective for removing viruses, bacteria, protozoa and helminths.
The kit includes a filter, hose, compression
fitting, backwash syringe and a hole cutter for
attaching the hose to the inlet water
container. The kit does not include a
container to hold the inlet water or a
container to collect the filtered water. The kit
is designed to be used with a plastic
container, but other types may also work;
water storage containers should not be a
container that has ever been used to
transport chemicals or toxic materials.
The filter membrane is located at the end of
the outlet hose. To stop the flow, the hose
and filter are raised up to the top of the inlet
water bucket and hooked on a hanger
(provided) until the next use.
Sawyer Point Zero Two Filter (Bucket Not Included)
(Credit: www.sawyerdirect.net)
Availability:
Available online. Cannot be exported internationally through Sawyer
Products. They recommend contacting an international logistic company
for shipping outside of North America.
Robustness:
7KHPHPEUDQHILOWHUGRHVQ¶WQHHGWREHUHSODFHGEDFNZDVKLQJXVLQJWKH
syringe when the filter clogs is all that is required to restore the flow rate.
Water pre-filtration using a cloth and/or settling is recommended for
turbid inlet water.
Lifespan:
There is no field data available yet to estimate how long the filter will
remain useable.
Household Water Treatment and Safe Storage
Product Sheet: Sawyer Point Zero TwoTM Purifier
Approximate Dimensions: Cylindrical filter: length 22
cm, diameter 7 cm. Plastic
tube length: 90 cm (3 feet);
other lengths are available.
Approximate Weight:
0.5 kg (1.13 lb)
Output:
13.6-15 litres/hour; 327
litres/day. Based on a 3-foot
hose attached to a 5-gallon
bucket
at
sea
level.
Sawyer Filter Operation
Increasing the hose length, using a
(Credit: www.sawyer.com)
taller container or continuously
keeping the bucket full will increase
flow rate. Flow rate will be lower at higher altitudes.
Cost:
Retail US$145
Maintenance:
Need to backwash filter using syringe provided in the kit when flow
rate slows down. With relatively clear inlet water, backwashing is
recommended every 3,800 litres. If inlet water is extremely turbid,
backwashing is recommended every 40 litres or less.
Treatment Efficiency
Bacteria**
Laboratory
Viruses
1
>99.9999%
Field
5
N/A
>99.999%
Protozoa
2
N/A
> 99.999%
N/A
Helminths
3
100%
4
N/A
Turbidity
Chemicals
N/A
N/A
N/A
N/A
N/A: Not available.
1
Hydreion LLC, 2005. Test bacteria: Klebsiella. Results are for the Point One
have as good or better removal based on pore size.
2
TM
filter; the Point Zero Two
TM
filter should
Hydreion LLC, 2005. Test virus: MS2 coliphage
3
Hydreion LLC, 2005. Test organisms: Cryptosporidium parvium oocysts and Giardia Lamblia cysts. Results are for the
TM
TM
Point One filter; the Point Zero Two filter should have as good or better removal based on pore size.
4
Helminth removal should be equal to or greater than bacteria and protozoa removal based on pathogen size.
5
A field project implementation developed by Give Clean Water shows its applicability in the field. Available at:
www.sawyerpointonefilters.com. The results from a field study in Bolivia are being analyzed.
References
Hydreion LLC. (2005). Microbiological Testing of the Sawyer 7/6B Filter. USA. Available at:
www.sawyerpointonefilters.com/downloads/MicrobiologicalTest_HydreionLabReport_12-012005_76BFilter.pdf
Hydreion LLC. (2005). Virus Removal Test of the Sawyer 7/6BV Filter. USA. Available at:
www.sawyerpointonefilters.com/downloads/PurificationTest_HydreionLabReport_1-62006_76VPurifier.pdf
Sawyer Products Inc (2011). Available at: www.sawyerpointonefilters.com. Accessed May 16,
2011.
Household Water Treatment and Safe Storage
Fact Sheet: Boiling
The Treatment Process
Potential Treatment Capacity
Very Effective For:
x
x
x
x
Somewhat Effective For:
Bacteria
Viruses
Protozoa
Helminths
What is Boiling?
%RLOLQJ LV FRQVLGHUHG WKH ZRUOG¶s oldest,
most common, and one of the most effective
methods for treating water. If done properly,
boiling kills or deactivates all bacteria,
viruses, protozoa (including cysts) and
helminths that cause diarrheal disease.
How Does It Remove Contamination?
Pathogens are killed when the temperature
reaches 100 degrees Celsius.
Operation
Water is heated over a fire or stove until it
boils. Different fuel sources can be used
depending on local availability and cost (e.g.
wood, charcoal, biomass, biogas, kerosene,
propane, solar panels, electricity).
Not Effective For:
x Turbidity
x Chemicals
x Taste, odour, colour
do not stop heating the water before the true
boiling point is reached (CDC, 2009).
CAWST recommends boiling water for 1
minute and adding 1 minute per 1000
metres of elevation.
Recontamination of boiled water is a major
problem. Water is often transferred from the
pot into dirty storage containers which then
make it unsafe to drink. It is recommended
to store boiled water in its pot with a lid to
reduce the risk of recontamination.
Boiled tastes flat to some people. This is
caused by dissolved oxygen escaping from
the water as it boils. The flat taste can be
reduced by vigorously stirring or shaking
cooled water to increase its dissolved
oxygen content.
Water bubbling as it boils provides a visual
indicator does away with the need for a
thermometer.
Recommended boiling times varies among
organizations.
The
World
Health
Organization recommends that water be
heated until it reaches the boiling point
(WHO, nd).
The Centers for Disease
Control and Prevention, recommends a
rolling boil of 1 minute, to ensure that users
Boiling water (Credit: Phitar, 2005)
Household Water Treatment and Safe Storage
Fact Sheet: Boiling
Key Data
Inlet Water Criteria
x
Any water can be boiled
Treatment Efficiency
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Chemicals
100%
100%
100%
100%
0%
0%
Not available
Not available
Not available
0%
0%
Laboratory
1,2
97-99%
Field
1
Clasen, T. et al (2007)
2
Clasen, T. (2007)
3
May precipitate some dissolved chemicals
x
3
Pathogens are killed when the temperature reaches 100 degrees Celsius
Operating Criteria
x
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Depends on container size
Depends on container size and availability of fuel
Boil water for 1 minute and add 1 minute per 1000 metres of elevation
Boiled water should be kept in the pot covered with a lid until it is consumed
Robustness
x
x
x
Almost all households have the equipment required to boil water
Requires fuel supply
Users may not consistently boil water to save fuel and effort
Estimated Lifespan
x
x
On-going requirement for fuel
Pots used for boiling need may need to be replaced over time
Manufacturing Requirements
Worldwide Producers:
x Not applicable
Local Production:
x Not applicable
Materials:
x Fuel (e.g. wood, charcoal, biomass, biogas, kerosene, propane, solar panels, electricity)
x Stove or heater
x Pot and lid
Fabrication Facilities:
x Not applicable
Labour:
x Regular collection of some fuels (e.g. wood, charcoal, other biomass)
Household Water Treatment and Safe Storage
Fact Sheet: Boiling
Key Data
Hazards:
x Potential for burn injuries; caution should be maintained around stoves and fires and when
handling hot water
x Cause of respiratory infections associated with poor indoor air quality; improved stoves can
be used to improve indoor air quality and reduce illness and death
Maintenance
x
Pot and lid should be cleaned on a regular basis
Direct Cost
Capital Cost
US$0
1
Operating Cost
US$0-0.06/10 litres
Replacement Cost
2
US$0
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Households are assumed to already have a pot and fire/stove for cooking
2
Clasen (2007)
Other
x
Boiled water tastes flat to some people. This is caused by dissolved oxygen escaping from
the water as it boils. The flat taste can be reduced by vigorously stirring or shaking cooled
water to increase its dissolved oxygen content.
References
Centers for Disease Control and Prevention (2009). Household Water Treatment Options in
Developing Countries: Boiling. Atlanta, USA.
Clasen, T. (2007). Microbiological Effectiveness and Cost of Boiling to Disinfect Drinking Water:
Case Studies from Vietnam and India. (Presentation) London School of Hygiene and Tropical
Medicine.
Clasen, T., Thao, D., Boisson, S., and O. Shipin (2008). Microbiological Effectiveness and Cost of
Boiling to Disinfect Drinking Water in Rural Vietnam. Environmental Science and Technology;
42(12): 42:55.
World Health Organization (nd). Household Water Treatment and Safe Storage Following
Emergencies and Disasters: South Asia Earthquake and Tsunami. Available at:
www.who.int/household_water/en/
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (NaDCC Tablets)
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Bacteria
x Viruses
x Some protozoa
x Helminths
x
x
x
x
x
Cryptosporidium parvum
Toxoplasma oocysts
Turbidity
Chemicals
Taste, odour, colour
What is NADCC?
How Does It Remove Contamination?
Chlorine began to be widely used as a
GLVLQIHFWDQW LQ WKH HDUO\ ¶V ,W
revolutionized drinking water treatment and
dramatically reduced the incidence of
waterborne diseases. Chlorine remains the
most widely used chemical for water
disinfection in the United States.
When added to water, NaDCC releases
hydrochlorous acid which reacts through
oxidization with microorganisms and kills
them.
NaDCC
also
known
as
sodium
dichloroisocyanurate or sodium troclosene,
is one form of chlorine used for disinfection.
It is often used to treat water in
emergencies, and is now widely available for
household water treatment.
Tablets are available from Medentech Ltd.
with different NaDCC contents (e.g. 2 mg to
5 g) to treat different volumes of water (e.g.
1 to 2,500 litres) at a time. They are usually
effervescent, allowing the smaller tablets to
dissolve in less than 1 minute.
Three things can happen when chlorine is
added to water:
1. Some
chlorine
reacts
through
oxidization with organic matter and the
pathogens in the water and kills them.
This portion is called consumed
chlorine.
2. Some chlorine reacts with other organic
matter, ammonia and iron and forms
new chlorine compounds. This is called
combined chlorine.
3. Excess chlorine that is not consumed or
combined remains in the water. This
portion is called free residual chlorine
(FRC). The FRC is the most effective
form of chlorine for disinfection
(particularly for viruses) and helps
prevent recontamination of the treated
water.
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (NaDCC Tablets)
Operation
Each product should have its own
instructions for correct dosing. In general,
the user adds the correct sized tablet for the
amount of water to be treated, following the
product instructions. Then the water is
agitated, and left for the time instructed,
normally 30 minutes (contact time). The
water is then disinfected and ready to be
used.
The effectiveness of chlorine is affected by
turbidity,
organic
matter,
ammonia,
temperature and pH.
Turbid water should sedimented or filtered
before adding chlorine. These processes
will remove some of the suspended
particles and improve the reaction between
the chlorine and pathogens.
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (NaDCC Tablets)
Key Data
Inlet Water Criteria
x
x
Low turbidity
pH between 5.5 and 7.5; disinfection is unreliable above a pH of 9
Treatment Efficiency
Bacteria
High
Laboratory
Viruses
4
High
Not available
Field
4
Not available
Protozoa
Helminths
Turbidity
5
Low
Ineffective ±
6
Moderate
0%
Not available
Not available
0%
4
1
Bacteria include Burkholderia pseudomallei, Campylobacter jejuni, Escherichia coli, Salmonella typhi, Shigella
dysenteriae, Shigella sonnei, Vibrio cholerae, Yersinia enterocolitica.
2
Viruses include enteroviruses, adenoviruses, noroviruses, rotavirus.
3
Protozoa include Entamoeba histolytica, Giardia lamblia, Toxoplasma gondii, Cryptosporidium parvum.
4
CDC (2007)
5
AWWA (2006) shows that chlorine is ineffective for Ascariasis lumbricoides ova.
6
Mercado-Burgos et al.(1975) show moderate effectiveness for Schistosoma species. Assume moderate effectiveness for
Dracunculus medinensis.
x
Toxoplasma oocysts and Cryptosporidium parvum oocysts are highly resistant to chlorine
disinfection (CDC, 2007). Chlorine alone should not be expected to inactivate these pathogens.
Operating Criteria
x
x
x
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Unlimited
Unlimited
1HHGWRIROORZPDQXIDFWXUHU¶VLQVWUXFWLRQVIRUVSHFLILF1D'&&SURGXFWV
Required dose and contact time varies with turbidity, pH and temperature (Lantagne, 2009)
Very turbid water should be sedimented or filtered prior to chlorination
Use a 30-minute minimum contact time
Robustness
x
x
x
x
Free residual chlorine protects against recontamination
Most users cannot determine the dosing themselves; need to follow manufacturer instructions
Users may use less than the recommended dose to save money
Requires supply chain, market availability and regular purchase
Estimated Lifespan
x
Five year shelf-life in strip packs and a three year shelf-life in tubs (Medentech, 2009)
Manufacturing Requirements
Worldwide Producers:
x Medentech Ltd. manufactures Aquatabs for water disinfection, hospital surface infection
control and general environmental disinfection
Local Production:
x NaDCC tablets cannot be produced locally, but they can be bought in bulk and packaged
locally
Materials:
x Tablets and packaging materials
Fabrication Facilities:
x Workshop space for packaging the tablets
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (NaDCC Tablets)
Key Data
Labour:
x Anyone can be trained for light packaging work
Hazards:
x NaDCC tablets are safe to handle and store
Maintenance
x
x
Products should be protected from exposure to temperature extremes or high humidity
Should be stored away from children
Direct Cost
Capital Cost(s)
US$0
Operating Cost(s)
US$0.03/20 litre tablet
2
US$10.95/year
Replacement Cost
1
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Medentech (2009)
2
Assumed 20 litres/household/day
Other
x
x
x
Some users complain about the taste and odour that chlorine may cause in water, some
NaDCC products claim that at there is no bad odour or taste using the recommended doses
Chlorine reacts with organic matter naturally present in water to form by-products such as
trihalomethanes (THMs), which are potentially cancer-causing
Study results indicate THM levels produced during household chlorination may fall below
WHO guideline values (Lantagne et al., 2008)
References
Clasen, T. and P. Edmondson (2006). Sodium dichloroisocyanurate (NaDCC) tablets as an
alternative to sodium hypochlorite for the routine treatment of drinking water at the household level.
International Journal of Hygiene and Environmental Health Volume 209, Issue 2, pp. 173-181.
Clasen, T., Saed, T., Boisson, S., Edmondson, P., and O. Shipin. (2007). Household Water
Treatment Using Sodium Dichloroisocyanurate (NaDCC) Tablets: A Randomized, Controlled Trial
to Assess Microbiological Effectiveness in Bangladesh. Am. J. Trop. Med. Hyg., 76(1), 2007, pp.
187±192.
Lantagne, D.S., Blount, B. C., Cardinali, F., and R. Quick, R (2008). Disinfection by-product
formation and mitigation strategies in point-of-use chlorination of turbid and non-turbid waters in
western Kenya. Journal of Water and Health, 06.1, 2008.
Lantagne, D. (2009). Summary of Information on Chlorination and pH. Prepared for UNICEF.
Medentech (2009). Personal communication, March 2009.
Molla, N., (2007). Practical Household Use of the Aquatabs Disinfectant for Drinking Water
Treatment in the Low-Income Urban Communities of Dhaka, Bangladesh. Thesis, Asia Institute of
Technology, School of Environment, Resources and Development.
Further Information
Medentech Ltd: www.aquatabs.com or www.medentech.com
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (Sodium Hypochlorite)
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Bacteria
x Viruses
x Some protozoa
x Helminths
x
x
x
x
x
What is Sodium Hypochlorite?
Chlorine began to be widely used as a
disinfectant LQ WKH HDUO\ ¶V. It
revolutionized drinking water treatment and
dramatically reduced the incidence of
waterborne diseases. Chlorine remains the
most widely used chemical for water
disinfection in the United States.
Sodium hypochlorite is one form of chlorine
used for water disinfection. It can be
manufactured in most locations since it can
be obtained through the electrolysis of salt
water.
Bottles can be purchased for household
water treatment from many manufacturers in
various sizes. Chlorine concentrations range
from 0.5 to 10% and each product should
have its own instructions for correct dosing
of contaminated water. Liquid household
bleach also contains sodium hypochlorite,
and is widely available.
Cryptosporidium parvum
Toxoplasma oocysts
Turbidity
Chemicals
Taste, odour, colour
1. Some
chlorine
reacts
through
oxidization with organic matter and the
pathogens in the water to kill them.
This portion is called consumed
chlorine.
2. Some chlorine reacts with other organic
matter, ammonia and iron and forms
new chlorine compounds. This is called
combined chlorine.
3. Excess chlorine that is not consumed or
combined remains in the water. This
portion is called free residual chlorine
(FRC). The FRC is the most effective
form of chlorine for disinfection
(particularly for viruses) and helps
prevent recontamination of the treated
water.
How Does it Remove Contamination?
Chlorine forms hydrochlorous acid when
added to water which reacts through
oxidization with microorganisms and kills
them.
Three things can happen when chlorine is
added to water:
Air Rahmat, Indonesia
(Credit: Tirta/JHUCCP)
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (Sodium Hypochlorite)
Operation
There are several different brands of
chlorine
products
that
have
been
manufactured specifically for household
water treatment. Each product should have
its own instructions for correct dosing and
contact time.
Liquid household bleach products are also
commonly used to disinfect drinking water.
The strength of the product must be known
to calculate how much bleach is needed to
disinfect a given volume of water. See
&$:67¶V Technical Brief on Chlorine
Disinfection
of
Drinking
Water
for
information on how to determine the
chlorine dose and contact time using
household bleach.
The effectiveness of chlorine is affected by
turbidity,
organic
matter,
ammonia,
temperature and pH.
Turbid water should sedimented or filtered
before adding chlorine. These processes
will remove some of the suspended
particles and improve the reaction between
the chlorine and pathogens.
Clorin sold in grocery stores, Zambia
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (Sodium Hypochlorite)
Key Data
Inlet Water Criteria
x
x
Low turbidity
pH between 5.5 and 7.5; disinfection is unreliable above a pH of 9
Treatment Efficiency
Bacteria
High
Laboratory
Viruses
4
High
Not available
Field
4
Not available
Protozoa
Helminths
Turbidity
5
Low
Ineffective ±
6
Moderate
0%
Not available
Not available
0%
4
1
Bacteria include Burkholderia pseudomallei, Campylobacter jejuni, Escherichia coli, Salmonella typhi, Shigella
dysenteriae, Shigella sonnei, Vibrio cholerae, Yersinia enterocolitica.
2
Viruses include enteroviruses, adenoviruses, noroviruses, rotavirus.
3
Protozoa include Entamoeba histolytica, Giardia lamblia, Toxoplasma gondii, Cryptosporidium parvum.
4
CDC (2007)
5
AWWA (2006) shows that chlorine is ineffective for Ascariasis lumbricoides ova.
6
Mercado-Burgos et al.(1975) show moderate effectiveness for Schistosoma species. Assume moderate effectiveness for
Dracunculus medinensis.
x
Toxoplasma oocysts and Cryptosporidium parvum oocysts are highly resistant to chlorine
disinfection (CDC, 2007). Chlorine alone should not be expected to inactivate these
pathogens.
Operating Criteria
x
x
x
x
x
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Unlimited
Unlimited
1HHGWRIROORZPDQXIDFWXUHU¶VLQVWUXFWLRQVIRUVSHFLILFVRGLXPK\SRFKORULWHSURGXFWV
Required dose and contact time varies with water quality (e.g. turbidity, pH, temperature)
Very turbid water should be sedimented or filtered prior to chlorination
Use a 30-minute minimum contact time
For high pH water (>9), the contact time should be increased (Lantagne, 2009)
The contact time should be increased to 1 hour when the temperature is between 10Û and
18ÛC. It should be increased to two or more hours when the temperature falls below 10ÛC.
Robustness
x
x
x
x
x
x
Free residual chlorine protects against recontamination
Most users cannot determine the dosing quantity themselves; proper use requires following
instructions from the manufacturer
Users may use less than the recommended dose to save money
Requires supply chain, market availability and regular purchase
Requires quality control process to ensure product reliability
Sourcing suitable plastic containers to manufacture chlorine solutions can sometimes be a
challenge
Estimated Lifespan
x
x
Chlorine deteriorates over time, especially in liquid form
Liquid chlorine expiry is 6 weeks without pH stabilization and 1 year if the pH of the solution is
above 11.9 (Lantagne et al., 2010)
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (Sodium Hypochlorite)
Key Data
Manufacturing Requirements
Worldwide Producers:
x There are many producers of chlorine solutions all around the world.
Local Production:
x Can be made locally using salt water solution and electrolysis equipment
Materials (in manufacturing chlorine products):
x Generator with electrolysis equipment
x Plastic bottles and labelling equipment
x Salt
x Water
Fabrication Facilities:
x Workshop space required for chlorine production and bottling
x Good ventilation required in the workshop space
Labour:
x Trained workers needed to produce and test the sodium hypochlorite
Hazards (in manufacturing chlorine products):
x Chlorine fumes and contact with skin are hazardous
x Skin and eye protection should be used when handling chlorine solutions
x Work should be conducted in a well ventilated area or in the open air
Maintenance
x
x
Chlorine should be stored in a cool, dark place in a closed container
Should be stored away from children
Direct Cost
Capital Cost
US$0
Operating Cost
US$0.45/1,000 litres
2
US$3.29/year
Replacement Cost
1
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Clasen (2007) based on WaterGuardTM
2
Assumed 20 litres/household/day
Other
x
x
x
Some users complain about the taste and odour that chlorine may cause in water
Chlorine reacts with organic matter naturally present in water to form by-products such as
trihalomethanes (THMs), which are potentially cancer-causing
Lantagne et al. (2008) indicate that THM levels produced during household chlorination may
fall below World Health Organization (WHO) guideline values
Household Water Treatment and Safe Storage
Fact Sheet: Chlorine (Sodium Hypochlorite)
Key Data
References
American Water Works Association (2006). Waterborne Pathogens. American Water Works
Association, USA.
Centers for Disease Control and Prevention (2007). Effect of Chlorination on Inactivating
Selected Pathogens. Available at:www.cdc.gov/safewater/about_pages/chlorinationtable.htm
Clasen, T. (2007). Presentation. London School of Hygiene and Tropical Medicine.
Lantagne, D.S., Blount, B. C., Cardinali, F., and R. Quick (2008). Disinfection by-product
formation and mitigation strategies in point-of-use chlorination of turbid and non-turbid waters in
western Kenya. Journal of Water and Health, 06.1, 2008.
Lantagne, D. (2009). Summary of Information on Chlorination and pH. Prepared for UNICEF.
Lantagne, D., Preston, K., Blanton, E., Kotlarz, N., Gezagehn, H., van Dusen, E., Berens, J. and
K. Jellison (2010). Hypochlorite Solution Expiry and Stability in Household Water Treatment in
Developing Countries. Submitted to Journal of Environmental Engineering.
Luby, S., Agboatwalla, M., Razz, A. and J. Sobel (2001). A Low-Cost Intervention for Cleaner
Drinking Water in Karachi, Pakistan. International Journal of Infectious Diseases; 5(3): 144-150.
Mercado-Burgos, N., Hoehn, R.C. and R.B. Holliman (1975). Effect of Halogens and Ozone on
Schistosoma Ova. Journal Water Pollution Control Federation, Vol. 47, No. 10 (Oct., 1975), pp.
2411-2419.
Further Information
Centers for Disease Control and Prevention:
www.cdc.gov/safewater/publications_pages/pubs_chlorine.htm
Environment and Public Health Organization (ENPHO):
www.enpho.org/product_treatment_piyush.htm
Population Services International (PSI): www.psi.org/child-survival/
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Fact Sheet: P&G Purifier of Water
(formerly known as PUR)
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Bacteria
x Viruses
x Protozoa (including
x Some heavy metals (e.g.
x Salt
x Fluoride
x Nitrate
Cryptosporidium and Giardia)
chromium, lead)
x Some chemicals and pesticides
x Taste, odour, colour
x Helminths
x Arsenic
x Turbidity and some organic
matter
What is P&G Purifier of Water?
How Does it Remove Contamination?
The P&G Purifier of Water (formerly known
as PUR) is a combined flocculentdisinfectant. The Purifier of Water packet
was developed by Procter & Gamble (P&G)
in collaboration with the U.S. Centers for
Disease Control and Prevention (CDC) to
replicate the community water treatment
process at the household level.
Particles that cause turbidity (e.g. silt, clay)
are generally negatively charged, making it
difficult for them to clump together because
of
electrostatic
repulsion.
However,
coagulant particles are positively charged,
and they are chemically attracted to the
negative turbidity particles, neutralizing the
ODWWHU¶V QHJDWLYH FKDUJH :LWK PL[LQJ WKH
neutralized particles then accumulate
(flocculation) to form larger particles (flocs)
which settle faster. The flocs can then be
settled out or removed by filtration.
Purifier of Water is a powder which contains
both coagulants and a timed release form of
chlorine. Purifier of Water is sold in single
packets designed to treat 10 litres of water.
The product uses coagulation and
disinfection to remove turbidity and
pathogens from water at the same time.
When added to water, the coagulant first
helps the suspended particles join together
and form larger clumps, making it easier for
them to settle to the bottom of the container.
Then chlorine is released over time to kill the
remaining pathogens. The treated water
contains residual free chlorine to protect
against recontamination.
P&G Purifier of Water Packet
(Credit: Procter & Gamble, 2012)
Household Water Treatment and Safe Storage
Fact Sheet: P&G Purifier of Water
Some bacteria and viruses can also attach
themselves to the suspended particles in
water that cause turbidity. Therefore,
reducing turbidity levels through coagulation
may also improve the microbiological quality
of water. The flocculent process effectively
removes larger organisms such as parasites
and has been shown to be very effective
even for smaller parasites such as
Cryptosporidium and Giardia.
As well, chlorine forms hydrochloric acid
when added to water which reacts through
oxidization with microorganisms and kills
them.
Contaminated source
water
Formation of
flocculant after
introduction of
Purifier of Water
Operation
The contents of a Purifier of Water packet is
added to 10 litres of water and stirred
vigorously for five minutes. The water is then
left to settle for 5 minutes.
Once the water becomes clear and the flocs
have all settled to the bottom, the water is
decanted and filtered through a cotton cloth.
The water should then be left for 20
additional minutes before it is consumed.
The total of 30 minutes from start of the
process is sufficient for the chlorine to
disinfect pathogens.
Formation of
flocculent after
5 minutes of stirring
Decanting the water
through a clean cotton
cloth
How to Use Purifier of Water (Credit: Population Services International)
Clean water
ready for storage
and use
Household Water Treatment and Safe Storage
Fact Sheet: P&G Purifier of Water
Key Data
Inlet Water Criteria
x
pH between 5.5 and 7.5; disinfection is unreliable above a pH of 9
Treatment Efficiency
Bacteria
Viruses
1,2
Lab
> 100%
Field
> 100%
2
> 99%
1,2
Not available
Protozoa
> 99%
Helminths
1,2
> 99%
Not available
1
Not available
Turbidity
> 100%
87%
5
1
Arsenic
> 98%
1,2,3
2,4
85-99%
1
Allgood (2004)
Souter et al (2003)
3
Shaw Environmental Inc (2006)
4
Norton et al (2003)
5
Norton et al (2003)
2
x
x
x
Can remove small organisms such as Cryptosporidium oocysts and Giardia cysts through the
flocculent process (Souter et al., 2003)
Can remove some organics and some pesticides (Allgood, 2004)
Can remove significant quantities of heavy metals including arsenic (Shaw Environmental
Inc., 2006, Souter et al., 2003), lead and chromium (Allgood, 2004)
Operating Criteria
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
10 L per packet
Unlimited
1HHGWRIROORZPDQXIDFWXUHU¶VLQVWUXFWLRQV
Robustness
x
x
x
Free residual chlorine protects against recontamination
Dosing is predetermined according to a typical water source; proper use requires following
instructions from the manufacturer
Requires supply chain, market availability and regular purchase of the product
Estimated Lifespan
x
Packet needs to be used within 3 years of manufacture
Manufacturing Requirements
Worldwide Producers:
x Procter & Gamble
Local Production:
x Cannot be made locally; must be shipped, distributed and sold locally. No special handling
required; can be shipped as non-hazardous material.
Maintenance
x
Products should be protected from exposure to temperature extremes or high humidity
Household Water Treatment and Safe Storage
Fact Sheet: P&G Purifier of Water
Key Data
Direct Cost
Capital Cost(s)
Operating Cost(s)
1
US$0
Replacement Cost
2
US$0.05 -0.10 /10 L
3
US$36.50-$73/year
US$0
Note: Program, transportation and education costs are not included. Costs may vary depending on location.
1
Allgood, G., personal communication, 2011, 2 Clasen (2007), 3 Assumed 20 litres/household/day
Other
x
x
x
Approved by the United States Environmental Protection Agency (US EPA) as a
microbiological purifier of water indicating that independent studies have demonstrated
>99.9999% removal of pathogenic bacteria, >99.99% kill of viruses, and >99.9% removal of
parasites including Giardia and Cryptosporidium.
Some users complain about the taste and odour that chlorine may cause in water. However,
the level of chlorine in Purifier of Water is lower than chlorine only products.
Lantagne et al. (2008) indicate that possibly produced carcinogenic trihalomethane (THM)
levels during typical household chlorination processes (including sodium chloride and Purifier
of Water) may fall below World Health Organization (WHO) guideline values. THM levels
after using Purifier of Water were shown to be lower than after using chlorine only.
References
Allgood, G. (2004). Evidence from the Field for the Effectiveness of Integrated CoagulationFlocculation-Disinfection. IWA World Water Congress 2004. Marrakech, Morocco. Workshop 33.
Clasen, T. (2007). Presentation. London School of Hygiene and Tropical Medicine.
Lantagne, D.S. et al. (2008). Disinfection by-product formation and mitigation strategies in pointof-use chlorination of turbid and non-turbid waters in western Kenya. Journal of Water and
Health, 06.1, 67-82.
Norton, D.M et al. (2003). A Combined Flocculent-Disinfectant Point-of-Use Water Treatment
Strategy for Reducing Arsenic Exposure in Rural Bangladesh. 10th Asian Conference on
Diarrhoeal Diseases and Nutrition , Dhaka, Bangladesh.
Norton, D. M. et al. (2003). Field Trial of a Flocculent-Disinfectant Point-of-Use Water Treatment
for Improving the Quality and Microbial Safety of Surface Pond Water in Bangladesh. 10th Asian
Conference on Diarrhoeal Diseases and Nutrition Dhaka, Bangladesh.
Shaw Environmental Inc (2006). Evaluation of Grainger Challenge Arsenic Treatment Systems,
PuR System #1. Prepared for the US Environmental Protection Agency and the National
Academy of Engineering. Cincinnati, USA.
Souter et al. (2003). Evaluation of a New Water Treatment for Point-of-Use Household
Applications to Remove Microorganisms and Arsenic from Drinking Water. Journal of Water and
Health, 01.2, 73-84.
Further Information
Proctor & Gamble: www.csdw.org/csdw/pur_packet.shtml
http://news.pg.com/press-release/pg-corporate-announcements/pg-underlines-commitment-itschildrens-safe-drinking-waterCAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: January 2012
Household Water Treatment and Safe Storage
Fact Sheet: Solar Disinfection (SODIS)
The Treatment Process
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x
x
x
x
x Cryptosporidium parvum
x Turbidity
x Chemicals
x Taste, odour, colour
Bacteria
Viruses
Some Protozoa
Helminths
What is SODIS?
The idea of solar water disinfection (SODIS)
was presented by Professor Aftim Acra for
the first time in a booklet published by
UNICEF in 1984.
SODIS has been promoted worldwide since
1991 when an interdisciplinary research
team at EAWAG/SANDEC began laboratory
and field tests to assess the potential of
SODIS and to develop an effective,
sustainable and low cost water treatment
method.
SODIS uses sunlight to destroy pathogens.
It can be used to disinfect small quantities of
water with low turbidity. Most commonly,
contaminated water is put into transparent
plastic bottles and exposed to full sunlight.
The pathogens are destroyed after a period
during the exposure to the sun. Users
determine the length of exposure based on
the weather conditions.
How Does It Remove Contamination?
EAWAG/SANDEC (2002) describes how
pathogens are vulnerable to two effects of
sunlight:
x
Ultraviolet-A (UV-A) radiation which
damages DNA and kills living cells
x
Infrared radiation which heats the water
and is known as pasteurization when the
temperature is raised to 70-75 degrees
Celsius
Many pathogens are not able to resist
increased temperatures, nor do they have
any protection mechanisms against UV
radiation (EAWAG/SANDEC, 2002).
More pathogens are destroyed when they
are exposed to both temperature and UV-A
light at the same time. A synergy of these
two effects occurs at a water temperature of
50 degrees Celsius (Wegelin et al, 1994).
As well, SODIS is more efficient in water
with high levels of oxygen. Sunlight
produces highly reactive forms of oxygen in
the water. These reactive molecules also
react with cell structures and kill pathogens
(Kehoe et al, 2001).
Operation
Use a transparent, non-coloured plastic
bottle made from polyethylene terephthalate
(PET). Do not use plastic bottles made from
polyvinyl chloride (PVC) since it contains
additives that may leach into the water.
Some types of glass bottles (i.e. those with a
higher content of iron oxide, like window
glass) should also not be used since they do
not transmit as much UV-A light.
Household Water Treatment and Safe Storage
Factsheet: Solar Disinfection (SODIS)
UV radiation is reduced at increasing water
depth. Bottles used for SODIS should not
exceed 10 cm in water depth, such as 1-2
litre volume PET bottles placed on their
sides in the sunlight (EAWAG/SANDEC,
2002).
Heavily scratched and old bottles should be
replaced since they reduce the amount of
UV light that can pass through (Wegelin et
al. 2000).
The source water should first be sedimented
and/or filtered if turbidity levels are greater
than 30 NTU, (Sommer et al, 1997).
Fill the plastic bottle ¾ full of low turbidity
water. Shake the bottle for about 20
seconds and then fill the bottle completely.
Place the bottles horizontally on a roof or
rack in the sun for the following times:
x
6 hours if the sky is cloudless or up to
50% cloudy
x
2 consecutive days if the sky is more
than 50% cloudy
x
Do not use SODIS during days of
continuous rainfall.
The efficiency of SODIS is dependent on the
amount of sunlight available. The bottles
must NOT be placed so that they are in
shade for part of the day. The most
favourable geographical regions for SODIS
o
are located between latitudes 15 N and
o
o
o
35 N (as well as 15 S and 35 S). The
majority of developing countries are located
o
o
between
latitudes
35 N
and
35 S
(EAWAG/SANDEC, 2002).
The treatment efficiency can be improved if
the plastic bottles are placed on sunlight
reflecting surfaces, such as corrugated
aluminum or zinc roofs. This can increase
the water temperature by about 5°C. This
has been found to be especially beneficial in
low sunlight conditions when the disinfection
process is the slowest (Mani et al., 2006).
The treated water should preferably be used
directly from the bottle to minimize the
possibility
of
recontamination.
Nonpathogenic organisms, such as algae, may
grow in the conditions created in a SODIS
bottle (EAWAG/SANDEC, 2002).
(Credit: EAWAG/SANDEC)
Household Water Treatment and Safe Storage
Fact Sheet: Solar Disinfection (SODIS) Key Data
Inlet Water Criteria
x
Turbidity < 30 NTU (Nephelometric Turbidity Units)
Treatment Efficiency
Laboratory
Field
Bacteria
Viruses
99.90
99.99%
90-99.9%
0
91.3-99.4%
Protozoa
0
Not available
90-99.99%
Helminths
3
Not available
> 100%
3
Not available
Turbidity
Chemicals
0%
0%
0%
0%
1
Wegelin et al (1994)
2
Saladin (2002)
3
Dependent on reaching a water temperature of 50°C
x
SODIS can reduce the potential viability of Cryptosporidum parvum oocysts, although longer
exposure periods appear to be required than those established for bacteria (Méndez-Hermida
et al., 2007; Gómez-Couso et al., 2009). SODIS alone should not be expected to inactivate all
Cryptosporidum parvum oocysts.
Operating Criteria
x
x
x
x
x
x
x
Flow Rate
Batch Volume
Daily Water Supply
1-2 litres/bottle per
6-48 hours
1-2 litres/bottle
Dependent on the number of bottles and weather
Use a transparent, non-coloured plastic bottle made from polyethylene terephthalate (PET)
Do not use plastic bottles made from polyvinyl chloride (PVC) since it contains additives that
may leach into the water
Some types of glass bottles (i.e. those with a higher content of iron oxide, like window glass)
should not be used since they do not transmit as much UV-A light
Bottles should be filled to ¾ of their capacity, capped and shaken for 20 seconds, and then
filled to the top
Requires 6 hours in full sun or up to 50% cloudy sky; or 2 consecutive days for more than
50% cloudy sky
Placing bottles on surfaces that reflect sunlight increases the treatment efficiency
Treated water should be kept in the same bottle until it is consumed
Robustness
x
x
x
x
x
x
Bottle can be used as a safe storage container
Requires suitable climate and weather conditions; most favourable location: between
latitudes 15° and 35° north/south; next most favourable location: between latitudes 15°
north/south and the equator
PET bottles are abundant in urban areas, but may be less so in rural areas
Not useful for treating large volumes of water, several bottles needed for a large family
Bottles will soften and deform if the temperature reaches 65°C
Users are unable to determine by their senses when sufficient disinfection has taken place,
and so need to keep track of them to know which bottles have been treated and ensure that
they always have treated water
Estimated Lifespan
x
Bottles become scratched or aged by sunlight and must be replaced periodically
Household Water Treatment and Safe Storage
Fact Sheet: Solar Disinfection (SODIS) Key Data
Manufacturing Requirements
Worldwide Producers:
x Not applicable
Local Production:
x Not applicable
Materials:
x 1 or 2 L clear plastic bottles (2 sets of 2 bottles per person, one set of bottles must be filled
and placed on the roof each day, while the water in the other set is consumed)
x Accessible surface that receives full sunlight (e.g. roof, rack)
Maintenance
x
Bottles and caps should be cleaned on a regular basis
Direct Cost
Capital Cost
US$0-5
1
Operating Cost
Replacement Cost
US$0
US$0-5
2
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
PET bottles may be free or cost less than US$0.50/bottle. Assumed 10 bottles required per household.
2
Bottles become scratched or aged by sunlight and must be replaced periodically
Other
x
Studies have shown that PET plastic does not leach chemical additives into water
References
EAWAG/SANDEC (2002). Solar Water Disinfection: A Guide for the Application of SODIS.
SANDEC Report No 06/02.
Gómez-Couso, H., Fontán-Saínz, M., Sichel, C., Fernández-Ibáñez, P. and E. Ares-Mazás
(2009). Efficacy of the solar water disinfection method in turbid waters experimentally
contaminated with Cryptosporidium parvum oocysts under real field conditions. Tropical Medicine
& International Health, Volume 14, Number 6, June 2009, pp. 620-627(8)
Mani, S., Kanjur, R., Singh, I. and R. Reed (2006). Comparative effectiveness of solar disinfection
using small-scale batch reactors with reflective, absorptive and transmissive rear surfaces. Water
Research, Volume 40, Issue 4, February 2006, pp 721-727.
Méndez-Hermida, F., Ares-Mazás, E., McGuigan, K., Boyle, M., Sichel, C. and P. FernándezIbáñez (2007). Disinfection of drinking water contaminated with Cryptosporidium parvum oocysts
under natural sunlight and using the photocatalyst TiO2. Journal of Photochemistry and
Photobiology B: Biology. Volume 88, Issues 2-3, 25 September 2007, pp 105-111.
Saladin, M. (2002). SODIS in Nepal ± Technical Aspects. EAWAG/SANDEC and ENPHO.
Sommer, B., Marino, A., Solarte, Y., Salas, M.L., Dierolf, C., Valiente, C., Mora, D. Rechsteiner,
R., Setter, P., Wirojanagud, W., Ajarmeh, H., Al-Hassan, A. And M. Wegelin. (1997). SODIS ± An
Emerging Water Treatment Process. J. Wat. Sci. Res. Technol. AQUA 46, pp 127-137.
Wegelin, M., Canonica, S., Mechsner, K., Fleischmann, T., Pesaro, F. and A. Metzler (1994).
Solar Water Disinfection: Scope of the Process and Analysis of Radiation Experiments, J Water
SRT, Aqua Vol. 43, No. 4, pp 154-169.
Household Water Treatment and Safe Storage
Fact Sheet: Solar Disinfection (SODIS) Key Data
Wegelin, M., Canonica, S., Alder, A., Marazuela, D, Suter, M., Bucheli, T., Haefliger, O., Zenobi,
R., McGuigan, K., Kelly, M., Ibrahim, P. and M. Larroque. (2000) Does sunlight change the
material and content of polyethylene terephthalate (PET) bottles? IWA Publishing, Journal of
Water Supply: Research and Technology, Aqua No. 1.
Further Information
Centers for Disease Control and Prevention:
www.cdc.gov/safewater/publications_pages/options-sodis.pdf
EAWAG (The Swiss Federal Institute of Aquatic Science and Technology) and SANDEC
(EAWAG's Department of Water and Sanitation in Developing Countries): www.sodis.ch
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Solar Distillation
Potential Treatment Capacity
Very Effective For:
x
x
x
x
x
x
x
x
Somewhat Effective For:
Not Effective For:
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Chemicals
Salt and hardness
Taste, odour, colour
What Is Solar Distillation?
How Does it Remove Contamination?
Solar distillation is an ancient method of
XVLQJ WKH VXQ¶V HQHUJ\ WR WUHDW GULQNLQJ
water. Distillation is the process of
evaporating water into vapour, and then
capturing and cooling the vapour so it
condenses back into a liquid. Any
contaminants in the water are left behind
when the water is evaporated.
As the radiation from the sun heats the
water, it evaporates leaving behind any
contaminants,
including
pathogens,
chemicals and minerals. The contaminants
collect in the bottom of the still and are
periodically flushed or cleaned out.
There are many different designs for solar
distillation units (also known as stills). The
simplest are a piece of plastic stretched over
a container with the source water in the
bottom. The plastic is weighted down in the
middle so that the condensate can drip into
a smaller collection container inside the
bucket.
A simple design requiring some basic
construction, but yielding more water, is that
of a flat bed, basin or box solar still. It
consists of a shallow reservoir containing
water covered with an angled piece of clear
glass or transparent plastic sheet. The
sunlight heats the water through the glass or
plastic, and the water vapour collects and
condenses on it, drips down, and flows into
the collection channel.
Container Still (Credit: www.ehow.com)
Another simple still uses a removable plastic
cone rimmed on the inside edge with a
collection channel. The condensed water
flows down the sides of the cone into the
channel. Water is removed by opening a cap
at the apex of the cone, and turning the still
upside down into a container.
Box Still (Credit: Smith, 2005)
Household Water Treatment and Safe Storage
Factsheet: Solar Distillation
Operation
Flat Bed/Box Still:
The still is filled daily with two to three times
as much water as will be produced. This is
so that the excess, using the built-in
overflow outlets, will flush the unit clean
each day (to remove accumulated salts and
other contaminants). Treated water is
collected in a safe storage container placed
under the outlet.
If systems are not designed to be self
cleaning and flush out accumulated
contaminants, the reservoirs should be
regularly cleaned using soap and clean
water.
Flat Bed Still
(Credit: www.planetkerala.org)
Cone Still:
How to Use the WaterCone® (Credit: www.watercone.com)
Household Water Treatment and Safe Storage
Fact Sheet: Solar Distillation
Key Data
Inlet Water Criteria
x
No specific limits
Treatment Efficiency
Bacteria
Laboratory
> 99.9%
Viruses
1
Not available
Field
Protozoa
1
Not available
> 100%
Not available
Not available
Helminths
> 100%
Turbidity
2
Not available
> 100%
2
Not available
Chemicals
> 99.9%
1
Not available
1
Smith (2005). The pilot project showed the stills to be effective in removing salts and minerals (Na, Ca, As, Fl, Fe, Mn);
bacteria (E coli, cholera, botulinus); protozoa (giardia, cryptosporidium) and heavy metals (Pb, Cd, Hg). Theoretically
should remove arsenic, although no data available at this time.
2
Not tested, but theoretically distillation should remove helminths and turbidity.
Operating Criteria
Flow Rate
Batch Volume
2
Not applicable
1
4±8 litres per m (box)
4
1-1.7 L for cone
Daily Water Supply
2,3
Variable
5
1
Solar still sizes can vary from 0.5 m2 for household use up to around 600 m 2 for community use
Foster (2005)
3
Planet Kerala (2006)
4
Watercone®
5
Daily water supply depends on number sunshine hours and temperature, as well as still size
2
Robustness
x
x
x
No moving or mechanical parts to break
Requires suitable climate and weather conditions
Requires airtight seals and smoothly stretched plastic during construction and operation; poor
handling can break seals
Estimated Lifespan
x
x
Box still: 10+ years, depending on materials and construction quality
Watercone®: ~5 years
Manufacturing Requirements
Worldwide Producers:
x There are many worldwide producers (e.g. Solaqua, Solar Water Distillation Products,
Watercone®, Waterpyramid®)
x Simple designs are available at no cost on the internet
Local Production:
x Can be built with locally available materials
Materials:
x See design details (on internet)
Fabrication Facilities:
x Workshop space for filter construction
Labour:
x Anyone can be trained to construct solar distillation units
Household Water Treatment and Safe Storage
Fact Sheet: Solar Distillation
Key Data
Hazards:
x No specific manufacturing hazards.
Maintenance
x
x
x
Some systems are designed to be self cleaning to flush out accumulated contaminants
Systems without a flushing function should be regularly cleaned using soap and clean water
Very turbid water can be sedimented or filtered prior to distillation to reduce cleaning the
reservoir
Direct Cost
Capital Cost
2
US$10-400/m (box still)
2
~US$32 (cone still)
Operating Cost
Replacement Cost
US$0/year
US$0
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
A square meter for a single basin solar still costs about $400 in Mexico (Foster et al., 2005)
2
Watercone®
Other
x
2
About 0.5 m of solar box still is needed per person to meet potable water needs consistently
throughout the year (Foster et al., 2005)
References
Foster, R., Amos, W. and S. Eby (2005). Ten Years of Solar Distillation Application Along the
U.S.-Mexico Border. Solar World Congress, International Solar Energy Society, Orlando, Florida,
August 11, 2005. Available at: http://solar.nmsu.edu/publications/1437ISESpaper05.pdf
Planet Kerala (2006). Solar Distillation: A Natural Solution for Drinking Water, Now Practical.
Available at: www.planetkerala.org/downloads/SolarDistillation.pdf
Smith, K. (2005). Still Distilled! Water Conditioning & Purification Magazine. Available at:
www.wcponline.com/pdf/0705%20distilled.pdf
Further Information
Planet Kerala, Participatory Learning and Action Network, India:
www.planetkerala.org/downloads/SolarDistillation.pdf
Solaqua, Solar Water Distillation Products, USA: www.solaqua.com/solstilbas.html
TM
AquaCone : www.solarsolutions.info/main.html
Watercone®, Germany: www.watercone.com
Waterpyramid®, The Netherlands: www.waterpyramid.nl
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Solar Pasteurization
The Treatment Process
Potential Treatment Capacity
Very Effective For:
x
x
x
x
Somewhat Effective For:
Not Effective For:
x Turbidity
x Chemicals
x Taste/odour/colour
Bacteria
Viruses
Protozoa
Helminths
What is Solar Pasteurization?
Operation
Pasteurization is the process of disinfecting
water by heat or radiation, short of boiling.
Typical water pasteurization achieves the
same effect as boiling, but at a lower
temperature (usually 65-75°C), over a longer
period of time.
Water is put into a black container, which is
placed in a solar cooker that reflects sunlight
onto the container. The box cooker should
be frequently repositioned to ensure it is
catching all available sunlight (and never in
shade) until the indicator device shows the
water has reached the required temperature.
Water may take 1 to 4 hours or more to heat
to temperature.
A simple method of pasteurizing water is to
put blackened containers of water in a solar
cooker. The cooker may be an insulated box
made of wood, cardboard, plastic, or woven
straw, with reflective panels to concentrate
sunlight onto the water container. It may
also be an arrangement of reflective panels,
RU D UHIOHFWLYH ³VDWHOOLWH GLVK´ RQ ZKLFK WKH
water pot sits.
A thermometer or indicator is needed to tell
when sufficient temperature is reached for
pasteurization.
Common
devices
for
monitoring the water temperature use either
beeswax, which melts at 62°C, or soya bean
fat, which melts at 69°C. A simple device
known as the Water Pasteurization Indicator
(WAPI) has been developed at the
University of California.
How Does It Remove Contamination?
As the water heats due to radiation from the
sun, the increased temperature will kill or
inactivate pathogens at 65°C.
Box Cooker and Water Pasteurization Indicator (WAPI)
(Credit: Solar Cooker International)
Household Water Treatment and Safe Storage
Fact Sheet: Solar Pasteurization
Key Data
Inlet Water Criteria
x
No specific limits
Treatment Efficiency
Bacteria
Laboratory
> 100%
1,2
Not available
Field
Viruses
> 100%
3
Not available
Protozoa
> 100%
Helminths
4
Not available
> 100%
Turbidity
Chemicals
0%
0%
0%
0%
4
Not available
1
100% E. coli in 1.5 hours at 60°C (Ciochetti & Metcalf 1984, Safapour & Metcalf 1998)
2
100% E. coli, Salmonella, S. dysenteriae, and V. cholerae at 70°C (Iijima et al., 2001)
3
100% in 1.5 hours at 70°C (Safapour & Metcalf 1998)
4
Not tested, but other research suggests that many helminths and protozoa will be killed at a temperature of 70°C if
maintained for 45 seconds
Operating Criteria
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
Depends on container size
Depends on container size
Robustness
x
x
x
x
x
x
x
Does not work during continuous rainfall or in very cloudy days
Users require a thermometer or pasteurization indicator device
Users need to keep track of containers to know which ones have been treated and ensure
that they always have treated water
Users may need to wait for water to cool prior to use
Cookers are made from lightweight and easily breakable materials
Recontamination is possible after the water has cooled; safe storage is essential
The system requires no additional inputs after installation
Estimated Lifespan
x
5+ years
Manufacturing Requirements
Worldwide Producers:
x There are many worldwide producers
x Simple designs are available at no cost on the internet
Local Production:
x This device may be built with parts available throughout most countries.
Materials:
x Cardboard
x Straw
x Aluminium foil
x Glass or plastic sheet
x Silver/metallic reflective spray paint
x Dark paint or mud
x Glass or plastic water containers to be painted; or dark/black metal pots
x Water Pasteurization Indicators (WAPI) or thermometers
Household Water Treatment and Safe Storage
Fact Sheet: Solar Pasteurization
Key Data
Fabrication Facilities:
x Workshop space to manufacture solar cookers
Labour:
x Anyone can be trained to construct a solar cooker
Hazards:
x No specific manufacturing hazards
Maintenance
x
Cleaned on a regular basis
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$20-25
US$0/year
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location
Other
x
x
Solar pasteurization boxes can also be used as solar cookers for cooking meals
Boiling is sometime preferred because it provides a visual measure of when the water has
reached sufficient temperature without requiring a thermometer
References
Andreatta, D. (1994). A Summary of Water Pasteurization Techniques. S.E.A. Inc
http://solarcooking.org/pasteurization/solarwat.htm
Ciochetti, D. A., and R. H. Metcalf (1984). Pasteurization of Naturally Contaminated Water with
Solar Energy. California State University, USA.
Iijima Y., Karama M., Oundo, J. O., and T. Honda (2001). Prevention of Bacterial Diarrhea by
Pasteurization of Drinking Water in Kenya. Microbiological Immunology, 45(6), 413-416.
Safapour, N. and R. H. Metcalf (1999). Enhancement of Solar Water Pasteurization with
Reflectors. Applied and Environmental Microbiology, Feb. 1999, p. 859±861.
Further Information
Solar Cookers International: http://solarcookers.org
Safe Water Systems: www.safewatersystems.com
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Factsheet: Ultraviolet (UV) Disinfection
The Treatment Process
Potential Treatment Capacity
Very Effective For:
x
x
x
x
Somewhat Effective For:
Not Effective For:
Bacteria
Viruses
Protozoa
Helminths
x Turbidity
x Chemicals
x Taste, odour, colour
What is UV Disinfection?
How Does It Remove Contamination?
Ultraviolet (UV) disinfection has been used
for more that 100 years in commercial and
community water treatment systems. With
the recent development of the UV tube using
local components, UV is now a viable
household water treatment method.
The UV bulb emits UV-C light, which
inactivates microorganisms by damaging
their genetic material (DNA), rendering them
unable to replicate. UV is effective in
inactivating most pathogens, including
bacteria, viruses, and cyst forming protozoa,
such as cryptosporidium.
The household design uses a UV bulb
suspended inside a larger tube or covered
trough. The water enters the tube at one
end, flows through the tube under the UV
bulb, and through the outlet at the other end
of the tube. The height of the outlet point
determines the depth of water in the tube.
This height also helps regulate the hydraulic
retention time within the tube which is part of
determining the UV dose for the water.
It is common for a UV treatment system to
incorporate a pre-filter to remove turbidity
since it can interfere with UV light
penetration through the water.
The UV tube does not require water
pressure to operate. As such, it may be
adapted to fit a variety of water supply
schemes, including piped water, rainwater
catchment systems, wells, or springs.
Operation
Once the user has installed the equipment
they only need to plug it in and make sure
the water flows though the system at the
prescribed rate. Water should be collected in
a safe storage container and protected from
recontamination.
Users may need to regularly clean the bulb if
it becomes dirty. The UV bulbs should be
replaced every 12 months.
Inlet
Outlet
Germicidal Bulb
Water level
set by height
of outlet
UV Tube Design Concept
(Credit: Fundacion Cantaro Azul)
Household Water Treatment and Safe Storage
Factsheet: Ultraviolet (UV) Disinfection Key Data
Inlet Water Criteria
x
x
Turbidity < 5 NTU (Nephelometric Turbidity Units)
Iron < 1 ppm (parts per million)
Treatment Efficiency
Bacteria
Laboratory
> 99.99%
97% to
0,3
100%
Field
1
0
Viruses
> 99.99%
Protozoa
0
Not available
> 99.99%
0
Not available
Helminths
> 99.9%
Turbidity
Chemicals
0%
0%
0%
0%
0
Not available
Cohn (2002)
Lang et al. (2006)
3
Gadgil et al. (1998)
2
x
x
Effectiveness depends on UV dose; these numbers are for NSF Standard 40 mW-s/cm
Required UV dose varies with water quality (e.g. turbidity, organic matter, pH)
2
Operating Criteria
Flow Rate
5 litres/minute
1
x
x
1
Batch Volume
Daily Water Supply
Not applicable
2,000 litres
1
Depends on the UV tube/apparatus design
Flow and volume depend on system design
Very turbid water should be sedimented or filtered prior to UV treatment
Robustness
x
x
x
x
Requires regular source of electricity, either through a grid or solar panels
Requires supply chain, market availability and regular purchase of UV bulbs
The design flow rate must be maintained by the user to ensure adequate UV dosing
If electricity is intermittent, water can be treated when electricity is available and stored
Estimated Lifespan
x
x
10+ years
UV bulbs should be replaced every 12 months (dirty or scratched bulbs reduce performance)
Manufacturing Requirements
Worldwide Producers:
x Some companies make UV tubes for household water treatment (e.g. UV Waterworks, USA)
x UV bulbs are available in various sizes from most major lamp manufacturers (e.g. General
Electric, Sylvania, Phillips)
Local Production:
x Household UV treatment units can be manufactured from local materials provided adequate
knowledge and UV bulbs are available
x Design will vary depending on local materials available
Materials:
x Feed container
x PVC tubing, or metal, pottery or cement channel
x Stainless steel sheet metal
Household Water Treatment and Safe Storage
Factsheet: Ultraviolet (UV) Disinfection Key Data
x
x
x
Various tubing connectors, valves and taps
Electrical wires and connectors
Miscellaneous tools for construction and installation
Fabrication Facilities:
x Workshop space for construction of UV units
Labour:
x Skilled workers with basic construction and electrical expertise can be taught to manufacture
UV units
Hazards:
x Water and electricity in combination are potentially dangerous
x Necessary safety precautions should be taken both during manufacture and in the home
x Precautions should be taken to prevent the UV bulb and electrical components from getting
wet if it is not enclosed with a protective quartz sleeve
Maintenance
x
x
Clean the bulb if it gets dirty (frequency depends on source water quality)
Replace the bulb every 12 months
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
US$60-150
Depends on cost of electricity
US$10-25/year
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
UV bulbs need to be replaced every 12 months, bulb price varies
References
Cohn, A. (2002). The UV Tube as an Appropriate Water Disinfection Technology: An Assessment
of Technical Performance and Potential for Dissemination. Masters Project for Energy and
Resource Group, University of California, Berkeley.
Lang, M., Kaser, F., Reygadas, F., Nelson, K., and D. Kammen (2006). Meeting the Need for
Safe Drinking Water in Rural Mexico through Point-of-Use Treatment. Center for Latin American
Studies. University of California, Berkeley.
Gadgil, A., Greene, D., Drescher, A., Miller, P. and N. Kibata (1998). Low Cost UV Disinfection
System For Developing Countries: Field Tests In South Africa. Water Health International, Napa,
CA, USA.
Further Information
University of California Berkeley: http://uvtube.berkeley.edu/home
WaterHealth International: http://waterhealth.com
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment and Safe Storage
Product Sheet: Guardian Solid Form Biocide
(SFB) Rope
Treatment Type
Product Name:
Guardian Solid Form Biocide (SFB) Rope
Manufacturer:
H2O, Inc.
Product Description:
The Guardian SFB Rope uses silver to kill pathogens on contact.
SFB strands are covered with water permeable synthetic fabric
with a string attached to one end and used to pull the rope from
the container. Users put the Guardian SFB Rope into a 20 litre
collection container at the water source point, allowing it to be
treated on the way to the household. This technology was
especially designed for transporting source water. Virus and
bacteria removal is accelerated by the motion caused by carrying
the water. The Guardian SFB Rope also prevents water from
recontamination.
Availability:
Can be purchased from the manufacturer upon request.
Robustness:
There are no moving or mechanical parts to break. Inlet water
needs to have low turbidity, total dissolved solids and hardness.
The Guardian SFB Rope has been laboratory tested by the
manufacturer and tested in the field.
Warnings:
If turbidity is higher than 30 NTU, filter the water and shake it
vigorously for 1 minute before using the Guardian Rope. If water
hardness is over 500 ppm, allow 50% more time for treatment.
The treatment effectiveness will be significantly reduced if the
Guardian SFB Rope comes into contact with chlorine products
(such as bleach).
The Guardian SFB Rope may corrode if placed in a metal
container with saline water. The Guardian SFB Rope should be
cleaned if this occurs.
Lifespan:
Up to 2 years, or after processing 12,500 litres of water
Approximate Dimensions:
1.5 metres (5 feet) in length
Approximate Weight:
70 grams when dry
Output:
20 litres/day
Cost:
US$12-15 plus shipping (minimum order of 100)
Household Water Treatment and Safe Storage
Product Sheet: Guardian Solid Form Biocide
(SFB) Rope
Storage:
Cleaning is recommended if the Guardian SFB Rope is stored
for more than a year without use.
Maintenance:
Clean every 4 months if the water source has low turbidity, total
dissolved solids (TDS) and hardness. However, when hardness
is higher than 400 ppm and TDS is higher than 600 ppm, it is
recommended to clean every 3 months. If turbidity is higher than
30 NTU, the Guardian SFB Rope needs to be cleaned every 2
months.
To clean, soak the Guardian SFB Rope in cleaning solution for 1
hour. To make the cleaning solution, use the juice of 1 lemon or
3 grams vitamin C powder or 4 tablespoons vinegar per 1 litre of
water. Then rinse the Guardian SFB Rope with non-turbid water,
and return to use.
Treatment Efficiency*
Bacteria
Laboratory
Field
Viruses
99.9999%
1
99.9999%
99.9999%
2
N/A
3
Protozoa
Helminths
Turbidity
Chemicals
0%
0%
0%
0%
0%
0%
0%
0%
*
Efficiency depends on contact time and water conditions. These results are after 90 minutes and the initial water
conditions were: pH= 6.3, Turbidity= 0.4 NTU, hardness= 284mg/L TDS= 360 mg/L and fluoride= 0.35 mg/L. Data
provided by H2O, Inc.
1
E.coli removal. Tested by EMS Lab in India, reported by H2O, Inc.
2
Tested in the field by Oxfam, reported by H20 Inc. These results are after 120-360 minutes contact time for three
different water sources and stirring every 30 minutes.
3
Colipaghe-MS2 removal. Tested by EMS Lab in India, reported by H2O, Inc.
N/A: Not available
Further Information
H2O Water Solutions Inc.
760 Hobart Street
Menlo Park, CA 94025 USA
Tel: 1.650.325.5321
Website: www.htwentyinc.com
(Credit: www.htwentyinc.com)
CAWST (Centre for Affordable Water and Sanitation Technology)
Wellness through Water.... Empowering People Globally
Calgary, Alberta, Canada
Website: www.cawst.org
Email: [email protected]
Last Update: April 2011
Household Water Treatment and Safe Storage
Fact Sheet: Safe Storage and Handling
Treatment Type
Potential Protection Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Preventing recontamination of
x Keeping water cool
x Preventing algae growth
x Removing existing
safe water
contaminants
What is Safe Storage and Handling?
Safe Storage and Handling Practices
Households do a lot of work to collect,
transport and treat their drinking water. Safe
water must be handled and stored properly
to protect it from becoming recontaminated.
Promoting safe storage and handling of
water in the home is a critical component for
safe drinking water. Recontamination of safe
drinking water is a common issue around
the world and has been documented in
several cases.
Safe storage means keeping treated water
away from sources of contamination. There are
many designs for water containers around the
world. A safe water storage container should
be:
x With a strong and tightly-sealing lid or
cover
x With a tap or narrow opening at the
outlet
x With a stable base so it does not tip over
x Durable and strong
x Not transparent or see-through
x Easy to clean
What Causes Recontamination?
Water can become recontaminated through
several different mechanisms, such as:
x
Using the same container for water
collection and storage
x
Dipping a dirty cup or hand into the
container
x
Drinking directly from the container
x
Children, animals or insects accessing
the container
x
Poor cleaning and hygiene practices
Recontamination is more likely to occur in
uncovered containers that have wide
openings (e.g. buckets, pots). Using chlorine
can provide residual protection against
recontamination, however, proper storage
and handling are still essential for keeping
water safe to drink.
Safe storage containers should also have
pictorial
and/or
written
instructions
describing how to properly use and clean
the container. Ideally the instructions are
permanently affixed to the container, or they
can be provided as a separate document to
the household.
Sometimes it is difficult for rural and poor
households to find or buy good storage
containers. The most important things are to
make sure that they are covered and only
used to store treated water.
Safe water handling practices include:
x
Using a separate container to collect
source water
Household Water Treatment and Safe Storage
Fact Sheet: Safe Storage and Handling
x
Using a proper safe storage container
for treated water, and never use this
container for untreated water
x
Cleaning the safe storage container
frequently with safe water and soap or
chlorine
x
Storing treated water off the ground in a
shady place in the home
x
Storing treated water away from small
children, animals and insects
x
Pouring water from the safe storage
container of using the tap when needed
instead of dipping or scooping water
from it
x
Oxfam Bucket Used Mainly in Emergencies (Credit: Oxfam)
Using the treated water as soon as
possible, preferably on the same day
Examples of Safe Storage Containers
A number of internationally manufactured
containers, locally produced containers, and
locally adapted traditional containers can be
used to store water safely.
Safe storage containers should always be
evaluated in-country for their cost,
availability,
robustness
and
user
acceptability.
CDC Safe Water System (Credit: Centers for Disease Control)
Ceramic Filter Container (Credit: Potters for Peace)
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Arsenic Removal
Fact Sheet: Adsorption
Magc-Alcan Filter
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Arsenic
x Turbidity
x Taste, odour, colour
What Is a Magc-Alcan Filter?
The Magc-Alcan is a two bucket arsenic filter. The
buckets are in series (water flows from one bucket
into the other). Both buckets are filled with an
activated alumina media made in the United States.
The media was developed by MAGC Technologies
and Alcan of the USA; it is produced by thermal
dehydration of an aluminium hydroxide at 250ÛC.
How Does It Remove Arsenic?
The Magc-Alcan filter removes arsenic by
adsorption (adhesion or sticking together) of the
arsenic to the media, which is porous and has a
large surface area.
The arsenic removal rate can be sensitive to pH
level, so additional equipment may be required to
control pH levels.
Operation
x
x
x
Place two buckets in a stand so that one
empties into the other. Each bucket should
have a tap at the bottom and be filled with
activated alumina media
Place a clean container at the outlet of the
second bucket for collecting treated water
Pour arsenic contaminated water into the top
bucket with all of the taps open, and collect
arsenic-free water in the container at the bottom
Similar Technology: Nirmal Filter
A similar filter called the ³1LUPDO )LOWHU´ H[LVWV LQ
India. Arsenic is adsorbed using an Indian-made
activated alumina media. Water is then filtered
through a ceramic candle. The filter needs to be
regenerated every 6 months.
Magc-Alcan Filter
Nirmal Filter
(Credit: T. Ngai)
Key Information:
Treatment
Output
Efficiency
MAGC-ALCAN FILTER
80-85%
arsenic
100
removal
litres/hour
NIRMAL FILTER
80-90%
arsenic
Not Available
removal
Cost
$35-50
capital cost
$10-15
capital cost
Lifespan
6 months to 1
year
Not Available
Household Water Treatment for Arsenic Removal
Fact Sheet: Adsorption
Shapla Filter
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Arsenic
x Turbidity
What Is a Shapla Filter?
The Shapla filter is an earthen household arsenic
removal technology developed by International
Development Enterprises (IDE), Bangladesh. It is
based on adsorption of the arsenic to the iron on
brick chips inside the filter. The brick chips are
coated using a ferrous sulphate solution. The filter
can hold up to 30 litres of inlet water.
How Does It Remove Arsenic?
As water passes through the filter, arsenic from the
water is rapidly adsorbed by the iron on the brick
chips. The filter will reduce arsenic concentrations
to undetectable levels.
Operation
Pour the water into the filter and allow it to pass
through the filter and out the outlet. Collect treated
water in a clean container for drinking.
Each filter has 20 kg of media (brick chips), which
will treat 4,000 litres of arsenic-contaminated water.
The filter can supply 25-32 litres of treated drinking
water per day. The brick chips must be replaced
every 3 to 6 months.
The used brick chips are non-toxic and can be
disposed of safely without danger to the
environment or human health as the arsenic is
attached strongly to the iron. The earthen filter
container is re-useable and easily maintained.
Shapla Filter
(Credit: T. Ngai)
Key Information
Treatment
Efficiency
80-90%
arsenic
removal
Output
25-32
litres/day
Cost
Lifespan
$10 capital
cost
Short media
$10-15
lifespan (3-6
media
months)
replacement
cost/year
Household Water Treatment for Arsenic Removal
Fact Sheet: Adsorption
References
Ontario Centre for Environmental Technology Advancement (OCETA). (no date.) Assessment of five
technologies for mitigating arsenic in Bangladesh well water. Environmental Technology Verification-Arsenic
Mitigation, Arsenic Mitigation Based on an Agreement between the Governments of Canada and Bangladesh.
Available at:
www.physics.harvard.edu/~wilson/arsenic/remediation/ETVAM%20Poster.ppt
Sutherland, D., M. Woolgar, Dr. Nuruzzaman, T. Claydon. (2001). Rapid assessment of household level arsenic
removal technologies: Phase II Executive Summary. WS Atkins International Ltd., Bangladesh Arsenic
Mitigation Water Supply Project and Water Aid Bangladesh. Bangladesh and United Kingdom.
Available at: www.wateraid.org/documents/phs2execsum.pdf
Full Phase I Report available at: www.wateraid.org/documents/phs1report.pdf
Full Phase II Report available at: www.wateraid.org/documents/phs2fullrpt.pdf
World Bank Water and Sanitation Program (2005). Towards a more effective operational response: Arsenic
contamination of groundwater in South and East Asia countries, Volumes I & II. Available at:
http://web.worldbank.org/WBSITE/EXTERNAL/COUNTRIES/SOUTHASIAEXT/0,,contentMDK:22392781~page
PK:146736~piPK:146830~theSitePK:223547,00.html
Further Information
Summary poster of several arsenic mitigation technologies (MIT):
http://web.mit.edu/watsan/Docs/Posters/Ghana%20HWTS%20meeting%20%20arsenic%20tech%20poster%20May08%20FINAL2.ppt
Magc-Alcan Filter:
Water Safety Plan for MAGC-ALCAN arsenic removal technology (2007):
www.buet.ac.bd/itn/pages/outcomes/ALCAN%20WSP%20Jul%2001_2007%20v1.pdf
An Overview of Arsenic Issues and Mitigation Initiatives in Bangladesh (2003), by NGOs Arsenic Information &
Support Unit (NAISU), NGO Forum for Drinking Water Supply & Sanitation and WaterAid:
www.wateraid.org/documents/plugin_documents/arsenicweb.pdf
Shapla Filter:
Website for Shapla and Surokka Aresnic Filters:
https://sites.google.com/site/shaplasurokkaarsenicfilter/
Arsenic Crisis Newsletter and Discussion Group:
http://tech.groups.yahoo.com/group/arsenic-crisis/
6HDUFKIRU³6KDSOD´WRYLHZPHVVDJHVUHODWHGWRWKH6KDSODILOWHU
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Arsenic Removal
Fact Sheet: Coagulation-Flocculation
Bucket Treatment Unit (BTU)
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Most pathogens
x Turbidity
x Taste, odour, colour
x Arsenic
x Chemicals
What Is Bucket Treatment Unit (BTU)?
The Bucket Treatment Unit is a two bucket filter
developed within the DPHE-Danida project in
Bangladesh.
It
uses
oxidation,
coagulation/flocculation and filtration to remove
arsenic. The BTU can be constructed from locally
available materials.
The mixture is then allowed to settle for 1 to 4 hours
or longer VHH PDQXIDFWXUHU¶V recommendation).
Then the upper tap is turned on so that the water
can pass through a cloth filter and a sand filter in
the lower bucket.
The effectiveness of the DPHE-Danida Bucket
Treatment Unit decreases if inlet water arsenic
concentrations are above 0.12 mg/L (Sutherland et
al., 2001).
How Does It Remove Arsenic?
Arsenic is removed by:
x
x
x
x
x
x
Oxidation (loss of electrons) of the arsenic to
change its form from As(III) to As(V), by
applying an oxidizing agent (e.g. potassium
permanganate*)
Coagulation and flocculation using alum or
aluminum sulphate, forming flocs (large
combined particles)
Adsorption (sticking) of arsenic onto flocs
Sedimentation
Straining through a cloth
Sand filtration
*Coagulation/flocculation can also be achieved by using
iron chloride or iron sulfate.
Operation
The upper bucket is filled with inlet water, with the
tap closed. The required chemicals are added and
the water is stirred with a wooden spoon (provided
with the unit).
Recommended chemical doses are (Tanhura et al.,
no date):
x
x
200 mg/L aluminum sulphate
2 mg/L of potassium permanganate
Bucket Treatment Unit
(Credit: T. Ngai)
Key Information
Treatment
Efficiency
~ 60% arsenic
removal
Output
20 litres/hour
Cost
$10 capital cost
$15-25 chemical
cost/year
Household Water Treatment for Arsenic Removal
Fact Sheet: Coagulation-Flocculation
2-Kolshi Filter
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x Arsenic
x Pathogens
x Taste, odour, colour
Not Effective For:
x Chemicals
What Is 2-Kolshi?
2-Kolshi is an arsenic removal method using two
buckets, developed by ENPHO in Nepal. The first
step is a coagulation process, followed by a
filtration through a ceramic filter.
How Does It Remove Arsenic?
Coagulation/flocculation is a traditional treatment
process in which the user adds a chemical
coagulant (typically iron sulphate or iron chloride) to
contaminated water. The coagulant helps
precipitate dissolved and suspended contaminants
so that they will settle out by gravity or can be
removed by filtration. Using this process, arsenic is
co-precipitated with iron.
In the 2-Kolshi system, iron sulphate is used as a
coagulant. The iron sulphate, sodium hypochlorite
and ash are added to the water and stirred. During
this process, the arsenic in the water changes form
(As(III) oxidizes to As(V)). The new form of arsenic
can co-precipitate with iron, forming flocs or large
particles. The water is then filtered to remove the
flocs. Ceramic filtration also removes pathogens.
Operation
x
x
x
x
Add chemicals (e.g. iron sulphate, sodium
hypochlorite and ash) to a bucket of water
Stir water for a few minutes
Let settle for one hour or more
Pass the water through a ceramic filter in the
bottom bucket
2-Kolshi System
(Credit: T. Ngai)
Key Information
Treatment
Output
1
Efficiency
90% arsenic removal
99% microbial
3-5 litres/hour
removal
1
(Hwang, 2002)
Cost
$10 capital cost
$10-20 chemical
cost/year
Household Water Treatment for Arsenic Removal
Fact Sheet: Coagulation-Flocculation
References
Hwang, S.K. (2002). Point-of-use arsenic removal from drinking water in Nepal using coagulation and filtration.
MIT Master of Engineering Thesis, Massachusetts Institute of Technology. USA. Available online at:
http://web.mit.edu/watsan/Docs/Student%20Theses/Nepal/Hwang2002.pdf
Sutherland, D., M. Woolgar, Dr. Nuruzzaman, T. Claydon. (2001). Rapid assessment of household level arsenic
removal technologies: Phase II Executive Summary. WS Atkins International Ltd., Bangladesh Arsenic
Mitigation Water Supply Project and Water Aid Bangladesh. Bangladesh and United Kingdom.
Available at: www.wateraid.org/documents/phs2execsum.pdf
Full Phase I Report available at: www.wateraid.org/documents/phs1report.pdf
Full Phase II Report available at: www.wateraid.org/documents/phs2fullrpt.pdf
Tahura, S., Shahidullah, S.M., Rahman, T., Milton, A. H. and Bhuitan, R.H. (no date.) Evaluation of An Arsenic
Removal Household Device: Bucket Treatment Unit (BTU). NGO Forum for Drinking Water Supply and
Sanitation and Department of Geography and Environment, Dhaka University. Bangladesh. Available at:
www.bvsde.ops-oms.org/bvsacd/arsenico/technologies/tahura.pdf
Further Information
Summary poster of several arsenic mitigation technologies (MIT):
http://web.mit.edu/watsan/Docs/Posters/Ghana%20HWTS%20meeting%20%20arsenic%20tech%20poster%20May08%20FINAL2.ppt
Bucket Treatment Unit (BTU):
The Danish Association for Sustainable Development Arsenic Project (2004-2007)
www.ubu.dk/old/Arsenic%20project/arsenicpage.htm
www.ubu.dk/old/Arsenic%20project/household_treatment.htm#bucket%20treatment%20unit
World Bank (2005). Towards a More Effective Operational Response ± Arsenic Contamination of Groundwater
in South and East Asian Countries. Vol. II. Technical Report. Washington, USA:
http://siteresources.worldbank.org/INTSAREGTOPWATRES/Resources/ArsenicVolII_WholeReport.pdf
2-Kolshi Filter:
Presentation by MIT/CAWST/ENPHO:
http://verification-unit.org/documents/nepal_workshop/presentations/11TNgai_FindingsonArsenicMitigationTechnologiesTestingandEvaluationinNepal.pdf
The Danish Association for Sustainable Development Arsenic Project (2004-2007)
www.ubu.dk/old/Arsenic%20project/arsenicpage.htm
www.ubu.dk/old/Arsenic%20project/household_treatment.htm#bucket%20treatment%20unit
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
Sono (3-Kolshi) Filter
Potential Treatment Capacity
Very Effective For:
x
x
x
x
Arsenic
Bacteria
Turbidity
Taste/odour/colour
Somewhat Effective For:
Not Effective For:
x Chemicals
What is a Sono Filter?
The Sono Filter is a three bucket system
developed in Bangladesh. It uses a
composite iron matrix (CIM) from zero valent
iron filings (cast iron turnings) to remove
arsenic.
composite iron matrix (CIM). Then it flows
into a second bucket where it is filtered
through another layer of coarse sand, wood
charcoal to remove organics, fine sand and
brick chips to remove fine particles and
stabilize water flow. The unit should be
replaced every 3-5 years.
The filter is manufactured from indigenous
materials and it works without chemical
treatment, without regeneration, and without
producing toxic waste. It removes arsenic,
22 other heavy metals, and bacteria.
How Does It Remove Arsenic?
The primary active material is the composite
iron matrix (CIM), made of cast iron.
Manganese in the CIM catalyzes oxidation
of As(III) to As(V). Arsenic (V) is removed by
a surface-complexation reaction (strong
adsoption) between the hydrated iron
(FeOH) molecules in the CIM and Arsenic
(V). FeOH is also known to remove many
other toxic species.
Each of the three buckets contains different
media:
x Top bucket: 3 kg cast iron filings from a
local machine shop, 2 kg coarse sand
x Middle bucket: 2 kg sand, 1 kg of wood
charcoal and 2 kg of brick chips
x Bottom
bucket:
water
collection
container
Operation
The inlet water is poured into the first bucket
containing coarse river sand and the
Sono Filter
(Credit: www.robrasa.com)
Key Information
Treatment
Efficiency
90-95%
arsenic removal
Output
Cost
20-30 litres
per hour
$40-50 capital
cost
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
References
Munir, A.K., S.B. Rasul, M. Habibuddowla, M. Alauddin, A. Hussam and A.H. Khan. (2001.)
Evaluation of performance of Sono 3-Kolshi Filter for arsenic removal from groundwater using
zero valent iron through laboratory and field studies. Bangladesh University of Engineering and
Technology, Dhaka and The United Nations University, Tokyo. Pages 171-189.
Ngai, T., Shrestha, R., Dangol, B., Maharjan, M. and S. Murcott (2007). Design for Sustainable
Development ± Household Drinking Water Filter for Arsenic and Pathogen Treatment in Nepal.
Journal of Environmental Science and Health, Part A. Vol A42 No 12 pp 1879-1888
Ontario Centre for Environmental Technology Advancement. (no date.) Assessment of five
technologies for mitigating arsenic in Bangladesh well water. Environmental Technology
Verification-Arsenic Mitigation, Arsenic Mitigation Based on an Agreement between the
Governments of Canada and Bangladesh. Available at:
www.physics.harvard.edu/~wilson/arsenic/remediation/ETVAM%20Poster.ppt
Sutherland, D., M. Woolgar, Dr. Nuruzzaman, T. Claydon. (2001). Rapid assessment of
household level arsenic removal technologies: Phase II Executive Summary. WS Atkins
International Ltd., Bangladesh Arsenic Mitigation Water Supply Project and Water Aid
Bangladesh. Bangladesh and United Kingdom.
Available at: www.wateraid.org/documents/phs2execsum.pdf
Full Phase I Report available at: www.wateraid.org/documents/phs1report.pdf
Full Phase II Report available at: www.wateraid.org/documents/phs2fullrpt.pdf
Further Information
Summary poster of several arsenic mitigation technologies (MIT):
http://web.mit.edu/watsan/Docs/Posters/Ghana%20HWTS%20meeting%20%20arsenic%20tech%20poster%20May08%20FINAL2.ppt
Sono (3-Kolshi) Filter:
Narrative on the innovation of the Sono Filter by Abul Hussam (2005):
www.physics.harvard.edu/~wilson/arsenic/remediation/SONO/Narrative_Grainger_AH.pdf
World Bank (2005). Towards a More Effective Operational Response ± Arsenic Contamination of
Groundwater in South and East Asian Countries. Vol. II. Technical Report. Washington, USA:
http://siteresources.worldbank.org/INTSAREGTOPWATRES/Resources/ArsenicVolII_WholeRepo
rt.pdf
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
KanchanTM Arsenic Filter
Potential Treatment Capacity
Very Effective For:
x
x
x
x
x
x
Arsenic
Bacteria
Protozoa
Helminths
Turbidity
Taste/odour/colour
Somewhat Effective For:
x Viruses
x Iron
What is a KanchanTM Arsenic Filter?
TM
The Kanchan Arsenic Filter (KAF) is an
adaptation of the biosand filter. The KAF has
been designed to remove arsenic from
drinking water, in addition to providing
microbiological water treatment. Arsenic
removal is achieved by incorporating a layer
of rusty nails in the diffuser basin of the filter.
Not Effective For:
x Chemicals
How Does it Remove Contamination?
Arsenic from the water is rapidly adsorbed
onto the rust on the iron nails. The rust and
arsenic flake off the nails, and are caught in
the sand filter and retained. This is a very
tight bond; re-suspension of arsenic into the
water, or re-mobilization of the arsenic from
the waste produced from cleaning the filter
has shown to be negligible.
The filter container can be constructed out of
concrete or plastic. The container is about
0.9 m tall and either 0.3 m square or 0.3 m
in diameter.
The container is filled with layers of sieved
and washed sand and gravel (also referred
to as filter media). There is a standing water
height of 5 cm above the sand layer.
Similar to slow sand filters, a biological layer
of microorganisms (also known as the
biolayer or schmutzedecke) develops at the
sand surface, which contributes to the
microbiological water treatment.
The diffuser basin is filled with 5 to 6 kg of
non-galvanized iron nails (that will rust) for
arsenic removal. A layer of bricks on top of
the nails prevents displacement of the nails
when water is poured into the filter.
Cross-Section of KanchanTM Arsenic Filter
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
In addition, pathogens, iron and suspended
material are removed from water through a
combination of biological and physical
processes. These occur both in both the
biolayer and within the sand bed. These
processes include: mechanical trapping,
adsorption/attraction, predation and natural
death.
Operation
Contaminated water is poured into the top of
the filter on an intermittent basis. The water
slowly passes through the diffuser, and
percolates down through the biolayer, sand
and gravel. Treated water flows by gravity
out of the outlet tube.
The rusted iron nails are essential for
removing arsenic. The nails need to be
evenly distributed to avoid the water from
short-circuiting. A layer of bricks on top of
the nails prevents displacement of the nails
when water is poured into the filter. As well,
users should pour the water slowly and
carefully into the filter to prevent the nails
from moving around.
The biolayer is the key pathogen removing
component of the filter. Without it, the filter is
significantly less effective. It may take up to
30 days to establish the biolayer depending
on inlet water quality and frequency of use.
The water from the filter can be used during
the first few weeks while the biolayer is
being established, but disinfection is
recommended during this time, as during
regular on-going use.
The biolayer requires oxygen to survive.
When water is flowing through the filter,
dissolved oxygen in the water is supplied to
the biolayer. During pause times, when the
water is not flowing, the oxygen is obtained
by diffusion from the air.
Correct installation and operation of the
biosand filter has a water level of
approximately 5 cm above the sand during
the pause period. A water depth of greater
than 5 cm results in lower oxygen diffusion
to the biolayer. A water depth less than 5 cm
may evaporate quickly in hot climates and
cause the biolayer to dry out.
A pause period is needed between uses to
allow time for the microorganisms in the
biolayer to consume pathogens in the water.
Users should wait at least one hour after all
the water has been filtered before filling the
filter again. It is recommended to use the
filter every day; however users can wait up
to a maximum of 48 hours between batches.
The KAF has been designed to allow for a
filter loading rate (flow rate per square metre
of filter area) which has proven to be
effective in laboratory and field tests. This
filter loading rate has been determined to be
not more than 600 litres/hour/square metre.
The recommended flow rate for the CAWST
Version 10 concrete KAF is 0.4 L/minute
measured when the inlet reservoir is full of
water. If the flow rate is much faster, the
filter may become less efficient at removing
pathogens. If the flow rate is much slower,
the user may become impatient and not use
the filter even though the filter is working
well at removing pathogens. Since the flow
rate is controlled by the size of the sand
grains, it is very important to select, sieve
and wash the sand properly.
The KAF requires maintenance when the
flow rate drops to a level that is inadequate
for the household use. This is done by a
VLPSOH µVZLUO DQG GXPS¶ SURFHGXUH
performed on the top of the sand, and only
takes a few minutes.
The outlet should also be cleaned regularly
using soap and water or a chlorine solution.
The treated water should be collected by the
user in a safe storage container placed on a
block or stand, so that the container opening
is just under the outlet, minimizing the risk
for recontamination.
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
Inlet Water Criteria
x Turbidity < 50 NTU
Treatment Efficiency
Bacteria
Lab
Field
Up to
1,2
96.5%
87.9 to
6,7,8
98.5%
Viruses
Protozoa
70 to
3
>99%
4
>99.9%
Helminths
Turbidity
Iron
Up to
5
100%
Up to
5
100%
95% to
1
<1 NTU
80 to
7,9,10,11
95%
90 to
9,10,11
99%
Arsenic
85 to
9,10,11
95%
1 Buzunis (1995)
2 Baumgartner (2006)
3 Stauber et al. (2006)
4 Palmateer et al. (1997)
5 Not esearched. However, helminths are too large to pass between the sand, up to 100% removal efficiency is assumed
6 Earwaker (2006)
7 Duke & Baker (2005)
8 Sharma (2005)
9 Ngai et al. (2004)
10 Ngai et al., (2007)
11 Uy et al., (2008)
x Treatment efficiencies provided in the above table require an established biolayer; it takes up
to 30 days to establish the biolayer and 2 weeks to establish rust on the nails depending on
inlet water quality and usage
x Filter must be used almost every day to maintain the biological layer (maximum pause period
is 48 hours)
x Best performance requires a consistent water source; switching sources may decrease
treatment efficiency
x Normal cleaning will reduce filter efficiency until the disturbed biolayer re-establishes itself
x Appearance and odour of treated water is generally improved
x Cannot remove pesticides or fertilizers (organic chemicals)
x Cannot remove salt, hardness, and scale (dissolved compounds)
x Does not provide residual protection to minimize recontamination
Operating Criteria
Flow Rate
Batch Volume
Daily Water Supply
< 0.4 litres/minute*
12-18 litres
24-36 litres**
Note: Operating criteria is for the concrete biosand filter, plastic biosand filter may have different parameters.
* 0.4 litres/minute is the maximum recommended flow rate for the CAWST Version 10 concrete biosand filter. The actual
flow rate will fluctuate over the filter cleaning cycle and between filters.
** Based on 2 batches per day to ensure effective arsenic removal
x Pause period is needed between uses to allow time for the microorganisms in the biolayer to
consume pathogens in the water, and to allow time for the nails to rust properly
x The recommended pause period is 6 to 12 hours with a minimum of 1 hour and maximum of
48 hours
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
Robustness
x
x
x
x
x
x
x
There are no moving or mechanical parts to break
In concrete models, piping is embedded in concrete, protecting it against breaks and leaks
Concrete has been shown to last in excess of 30 years
Concrete filters are heavy (70 ± 75 kg for thin wall version and 135 kg for heavy wall version)
Poor transportation of concrete filters can lead to cracking and/or breakage
Filters should not be moved after installation
Cracks can be sometimes be repaired
Estimated Lifespan
x Unlimited; biosand filters are still performing satisfactorily after 10+ years
x Lids and diffusers may need replacement
x Nails need to be replaced every 2-3 years to ensure effective arsenic removal
Manufacturing Requirements
Worldwide Producers:
x Free mold designs are available from CAWST
Local Production (for concrete KAF):
x Local production of concrete filters is common
x Molds for concrete filters can be borrowed, rented, bought or constructed locally
x Concrete filters can be cast at a central production facility, or in the community
x Filter sand and gravel can be prepared (sieved and washed) on-site or nearby
Materials (for concrete KAF):
x Steel mold
x Sand, gravel, and cement
x Filter sand and gravel
x Copper or plastic outlet tubing
x Metal or plastic for the diffuser basin
x 5 to 6 kg of non-galvanized iron nails
x Metal or wood for the lid
x Water is needed during for cement mix and to wash filter sand and gravel
x Miscellaneous tools for construction and installation (e.g. wrench, nuts, bolts)
Fabrication Facilities (for concrete KAF):
x Workshop space required for filter construction
Labour (for concrete KAF):
x Skilled welder required to fabricate molds
x Anyone can be trained to construct and install the filter
x Individual householders can assist in constructing their own filters
Hazards (for concrete KAF):
x Working with cement and heavy molds is potentially hazardous and adequate safety
precautions should be used
x Concrete filters are heavy and difficult to move and transport
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
Maintenance Requirements
x Required when the flow rate drops to a level that is inadequate for the household use
x Swirl and dump maintenance for the top layer of sand is simple, takes a few minutes and can
be done by household users
x Frequency of swirl and dump depends on turbidity of inlet water
x Outlet, lid and diffuser should be cleaned on a regular basis
Direct Cost
Filter Type
Capital Cost
Operating Cost
Replacement Cost
Concrete
US$12-40
US$0/year
US$0
US$0/year
US$0
Plastic
US$75
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Prices do not include shipping container, shipping fees, or clearing/related costs.
Other
x
x
Sand and iron nail selection and preparation are critical to ensure flow rate and treatment
Filters should not be moved after installation
References
Buzunis, B. (1995). Intermittently Operated Slow Sand Filtration: A New Water Treatment
3URFHVV¶'HSDUWPHQWRI&LYLO(QJLQHHULQJ8QLYHUVLW\RI&DOJDU\, Canada.
Baumgartner, J. (2006). The Effect of User Behavior on the Performance of Two Household
Water Filtration Systems. Masters of Science thesis. Department of Population and International
Health, Harvard School of Public Health. Boston, Massachusetts, USA.
Duke, W. and D. Baker (2005). The Use and Performance of the Biosand Filter in the Artibonite
Valley of Haiti: A Field Study of 107 Households, University of Victoria, Canada.
Earwaker, P. (2006). Evaluation of Household BioSand Filters in Ethiopia. Master of Science
thesis in Water Management (Community Water Supply). Institute of Water and Environment,
Cranfield University, Silsoe, United Kingdom.
Elliott, M., Stauber, C., Koksal, F., DiGiano, F., and M. Sobsey (2008). Reductions of E. coli,
echovirus type 12 and bacteriophages in an intermittently operated 2 household-scale slow sand
filter.Water Research, Volume 42, Issues 10-11, May 2008, Pages 2662-2670.
Ngai, T., Murcott, S. and R. Shrestha (2004). Kanchan Arsenic Filter (KAF) ± Research and
Implementation of an Appropriate Drinking Water Solution for Rural Nepal. [Note: These tests
were done on a plastic biosand filter]
Ngai, T., Shrestha, R., Dangol, B., Maharjan, M. and S. Murcott (2007). Design for Sustainable
Development ± Household Drinking Water Filter for Arsenic and Pathogen Treatment in Nepal.
Journal of Environmental Science and Health, Part A. Vol A42 No 12 pp 1879-1888
Household Water Treatment for Arsenic Removal
Fact Sheet: Surface Complexation
Palmateer, G., Manz, D., Jurkovic, A., McInnis, R., Unger, S., Kwan, K. K. and B. Dudka (1997).
Toxicant and Parasite Challenge of Manz Intermittent Slow Sand Filter. Environmental
Toxicology, vol. 14, pp. 217- 225
Sharma, D. (nd) Kanchan Arsenic Filter: Removal of Total Coliform of Gem505 model, 4 weeks
daily study. Bachelor of Science Thesis, Environmental Science, Kathmandu University, Nepal.
Stauber, C., Elliot, M., Koksal, F., Ortiz, G., Liang, K., DiGiano, F., and M. Sobsey (2006).
Characterization of the Biosand Filter for Microbial Reductions Under Controlled Laboratory and
Field Use Conditions. Water Science and Technology, Vol 54 No 3 pp 1-7.
Uy, D., Chea, S., Mao, S., Ngai, T. and T. Mahin (2008). Kanchan Arsenic Filter - Evaluation of
Applicability to Cambodia - Phase I Technical Report. Cambodian Ministry of Rural Development
and the Institute of Technology of Cambodia.
Further Information
CAWST (Centre for Affordable Water and Sanitation Technology): www.cawst.org
AKVOpedia: www.akvo.org/wiki/index.php/Kanchan_Arsenic_Filter
Massachusetts Institute of Technology (MIT):
http://web.mit.edu/watsan/tech_hwts_chemical_kanchanarsenicfilter.html
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Arsenic Removal
Fact Sheet: Oxidation
Passive Oxidation
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x
x
x
x
Not Effective For:
Arsenic
Turbidity
Pathogens
Taste, odour, colour
x Chemicals
What Is Passive Oxidation?
Operation
Passive oxidation uses iron compounds that
naturally reduce
the
arsenic
content
of
groundwater. When groundwater that naturally
contains dissolved Fe(OH)2 is left to stand in
containers, the iron undergoes a natural chemical
process called oxidation (when an element loses
electrons). It changes form into Fe(OH)3 and
precipitates out (or becomes solid). Arsenic adsorbs
or sticks to the iron precipitate. The combined iron
and arsenic particles then settle to the bottom of the
container, thereby removing the arsenic from the
water. This technology does not require chemicals;
it relies only on natural oxidation, adsorption and
sedimentation that take place when both iron and
arsenic are present in the water. Generally, the
higher the level of iron in the groundwater, the
better the arsenic removal.
x
x
Passive oxidation is seen as an easy technology for
users in some areas to adopt because of the
natural habits of some rural people to store their
water in containers before they drink it. However,
its performance at removing arsenic to safe levels
has not been proven.
How Does It Remove Arsenic?
Naturally occurring iron precipitates of Fe(OH)3,
produced from the oxidation of dissolved iron
Fe(OH)2 present in groundwater, is a good
adsorbent for arsenic. The method is based on coprecipitation with iron and sedimentation. It does
not require the use of chemicals, but requires
aeration (oxygen), settling and iron rich water.
The amount of arsenic removal depends on the
concentration of iron in water.
Stir the water for 2 minutes
Leave water overnight in an open container
Passive Oxidation in locally available water jars
(Credit: T. Ngai)
Key Information
Treatment
Efficiency
Typically 30 - 50%
arsenic removal
Output
No limit
Cost
Minimal cost
Household Water Treatment for Arsenic Removal
Fact Sheet: Oxidation
Solar Oxidation
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x
x
x
x Arsenic
x Pathogens
Turbidity
Chemicals
Taste, odour, colour
What Is SORAS?
The SORAS (Solar Oxidation and Removal of
Arsenic) method is similar to the SODIS method of
water treatment, but also requires the addition of
lemon juice. Ultraviolet (UV) rays from the sun
cause the oxidation (loss of electrons) of As(III),
changing it into As(V). The As(V) is strongly
attracted to iron hydroxide particles naturally
present in the water, and adsorbs (sticks) to these
particles.
The
As(V)/Fe(OH)3
co-precipitate
(become solid particles) which settle to the bottom
of the container.
How Does It Remove Arsenic?
SORAS removes
procedure:
x
x
arsenic
using
a
two-step
First step: As(III), which only weakly adsorbs to
iron hydroxide, is oxidized by the sun to the
As(V), which strongly adsorbs to iron hydroxide
Second step: the iron hydroxide precipitates
with the adsorbed arsenic settle to the bottom
of the container
Instead of adding chemical oxidants such as
chlorine or permanganate, reactive oxidants are
produced photo chemically using sunlight.
Operation
x
x
x
x
x
Fill PET (or other UV±A) transparent bottles
with water
Add lemon juice to bottles
Place the bottled in the sunlight for 1-2 days
During the night, place the bottles in vertical
position so particles can settle
Decant clear water into a clean container, it
may be filtered through a cloth or a ceramic
filter
SORAS process
(Credit: T. Ngai)
Key Information
Treatment
Efficiency
If iron > 8 ppm, 7590% arsenic
removal
If iron < 5 ppm,
<50 % arsenic
removal
Excellent microbial
removal (99+%)
Output
Cost
No limit
Minimal
Household Water Treatment for Arsenic Removal
Fact Sheet: Oxidation
Asia Arsenic Network Filter
Potential Treatment Capacity
Very Effective For:
x
x
x
x
Somewhat Effective For:
Arsenic
Most pathogens
Turbidity
Taste, odour, colour
Not Effective For:
x Viruses
x Chemicals
What Is Asia Arsenic Network Filter?
The Asia Arsenic Network Filter consists of an
upper plastic bucket with a lid and tap, and two clay
pitchers (or plastic buckets) that are positioned so
water flows from one container to the next. The
process consists of manual aeration, oxidation of
iron naturally present in the water, and the coprecipitation of the arsenic and the iron. Arsenic
removal depends on iron concentrations in water.
The process is completed by filtering the water
through sand in the second bucket. Treated water is
collected from the bottom bucket.
How Does It Remove Arsenic?
Water added to the upper bucket is stirred and then
allowed to stand. The dissolved iron compound
Fe(OH)2 naturally present in the groundwater
undergoes a natural chemical process called
oxidation (when an element loses electrons). It
becomes Fe(OH)3, which precipitates out or
becomes solid. Arsenic strongly adsorbs (sticks to)
Fe(OH)3. The combined iron and arsenic particles
settle to the bottom of the container, thereby
removing the arsenic from the water. The water is
then filtered through sand, which retains any
particles of iron and arsenic.
Operation
x
x
x
x
Pour raw water into the top bucket and
manually stir for 2 minutes
Let water settle for 6 hours
Open the tap in the top bucket and let the water
flow through the middle bucket, which contains
2 kg of coarse sand
Collect treated water from the bottom bucket
Asia Arsenic Network Filter
(Credit: Asia Arsenic Network, 2001)
Key Information
Treatment
Efficiency
Typically 7080% arsenic
removal
Production
20 litres/6 hours
Cost
$15-20 capital
cost
Household Water Treatment for Arsenic Removal
Fact Sheet: Oxidation
References
Roberts, L.C., S.J. Hug, T. Ruettimann, MD.M. Billah, A.W. Khan, and M.T. Rahman, (2003). Arsenic removal
with iron(II) and iron(III) in waters with high silicate and phosphate concentrations (2003). Environmental
Science & Technology, Web Published November 18, 2003, VOL 38 NO.1, 2004
Available at: http://pubs.acs.org/doi/abs/10.1021/es0343205
Sutherland, D., M. Woolgar, Dr. Nuruzzaman, T. Claydon. (2001). Rapid assessment of household level arsenic
removal technologies: Phase II Executive Summary. WS Atkins International Ltd., Bangladesh Arsenic
Mitigation Water Supply Project and Water Aid Bangladesh. Bangladesh and United Kingdom.
Available at: www.wateraid.org/documents/phs2execsum.pdf
Full Phase I Report available at: www.wateraid.org/documents/phs1report.pdf
Full Phase II Report available at: www.wateraid.org/documents/phs2fullrpt.pdf
World Bank Water and Sanitation Program (2005). Towards a more effective operational response: Arsenic
contamination of groundwater in South and East Asia countries, Volumes I & II. Available at:
http://web.worldbank.org/WBSITE/EXTERNAL/COUNTRIES/SOUTHASIAEXT/0,,contentMDK:22392781~page
PK:146736~piPK:146830~theSitePK:223547,00.html
Further Information
Solar Oxidation and Removal of Arsenic (SORAS):
SORAS Paper. By: Martin Wegelin, Daniel Gechter, Stephan Hug, Abdullah Mahmud, Abdul Motaleb. No Date.
Available at:
http://phys4.harvard.edu/~wilson/arsenic/remediation/sodis/SORAS_Paper.html
Presentation: Arsenic Removal by Solar Oxidation in Groundwater of Los Pereyra Tucumán Province,
Argentina. By: J. d´Hiriart, M.V. Hidalgo, National University of Tucumán, M.G. García, National University of
Córdoba, and M.I. Litter, M.A. Blesa National Atomic Commission Argentina. No Date. Available at:
www.cnea.gov.ar/xxi/ambiental/iberoarsen/docs/presentationAs2006litter.pdf
Presentation: Innovative and Sustainable Technologies to Address the Global Arsenic Crisis. By: Susan Murcott
and Tommy Ngai, Civil and Environmental Engineering Department, Massachusetts Institute of Technology.
(2005.) Available at:
www.sandia.gov/water/Arsenic2005/2005tech_session/Murcott_pres.pdf
Asia Arsenic Network Filter:
Delawar, H.K.M. et al. (2006). A Comparative Study of Household Groundwater Arsenic Removal Technologies
and Their Water Quality Parameters. Journal of Applied Sciences 6(10):2193-2200. Available at:
www.scialert.net/pdfs/jas/2006/21932200.pdf?sess=jJghHkjfd76K8JKHgh76JG7FHGDredhgJgh7GkjH7Gkjg57KJhT&userid=jhfgJKH78Jgh7GkjH7G
kjg57KJhT68JKHgh76JG7Ff
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Fluoride Removal
Factsheet: Activated Alumina Filter
Potential Treatment Capacity
Very Effective For:
x
x
x
x
Somewhat Effective For:
Fluoride
Arsenic
Turbidity
Taste, odour, colour
Not Effective For:
x
x
x
x
x
Bacteria
Viruses
Protozoa
Helminths
Hardness
What Is Activated Alumina Filter?
Activated alumina, also called aluminium oxide
(Al2O3) granular, is one of the most widely
used materials for the removal of chemicals
from water. This highly porous material is
prepared by low temperature (300-600°C)
dehydration of aluminium hydroxides.
Activated alumina grains are packed in a filter
like sand. When water passes through it,
certain contaminants in the water adsorb
(stick) to the activated alumina. Activated
alumina removes fluoride from water, and can
also be used for arsenic removal (see the
corresponding Arsenic Removal by Adsorption
factsheet).
How Does It Remove Contamination?
Fluoride is removed from water through an
exchange reaction at the surface of the
activated alumina. Fluoride adsorbs to the
alumina more easily than other molecules in
water. This results in high defluoridation
capacity.
According to laboratory tests, the fluoride
removal capacity of alumina is between 4 and
15mg of fluoride per gram alumina (Hao and
Huang, 1986). However, field experience
shows that the removal capacity is often about
1mg/g (COWI, 1998). The treatment capacity
also depends on the specific grade (quality) of
activated alumina, the particle size and the
water chemistry (pH, alkalinity and fluoride
concentrations).
The optimum dosage of activated alumina for a
particular source water needs to be
determined by conducting a jar test
experiment.
Activated Alumina-based Household Defluoridation
(Credit: Lyengar, 2002)
Operation
There are different kinds of activated alumina
filters. One of them consists of two containers
(see above diagram). The upper container
holds the activated alumina (3 kg, depth of 17
cm, Lyengar 2002). The top of this container
can be covered with a perforated stainless
steel disc to avoid disturbing the media when
water is poured in. It should also be covered
by a lid. The lower container can be any kind
of bucket or pot with tap, used for storing the
treated water.
Household Water Treatment for Fluoride Removal
Factsheet: Activated Alumina Filter
Activated alumina filters can also consist of a
domestic candle water filter with an additional
middle chamber holding a bag of activated
alumina. The filter could also simply be an
bucket, drum or column with a tap and
drainage pipe that is filled with activated
alumina (see illustration below).
Note: When 4% caustic soda (NaOH) is used
for regeneration it needs to be followed by a
neutralization step to remove residual NaOH
from the filter.
The contact time of the filter is the amount of
time the fluoride contaminated water is in
contact with the activated alumina. Bulusu and
Nawlakhe
(1988)
conducted
jar
test
experiments to determine the effect of contact
time on fluoride removal. It was observed that
the optimum contact time to reduce the fluoride
level from 4.8 mg/L to 1 mg/L is 30 minutes.
This can be used as a recommendation, but as
of yet there is no formal recommendation for
contact time.
When the activated alumina media becomes
saturated, meaning there are no more places
for fluoride to adsorb to the media, the media
can be regenerated using HCl, H2SO4, alum or
NaOH. The wastewater created from this
process should be disposed of in an
appropriate manner away from water sources
and human contact.
Three Common Household Units for Sorption Defluoridation
(Credit: WHO, 2006)
Household Water Treatment for Fluoride Removal
Fact Sheet: Activated Alumina
Key Data
Inlet Water Criteria
x
The pH of the water should preferably be between 5 and 6; at a pH > 7 silicate and hydroxyl
ions become stronger competitors against fluoride ions for adsorption preference (Renu,
Singh and Maheswari, 2001)
Treatment Efficiency
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Fluoride
Laboratory
Not
available
Not
available
Not
available
Not
available
Not
available
90% in batch
up to 98% in
2
column
Field
Not
available
Not
available
Not
available
Not
available
Not
available
Not available
1
1
An initial fluoride concentration of 5 mg/L reduced to down to 1.4 mg/L before regeneration and to 0.5 mg/L on
regeneration with 2N HCl (Savinelli, 1958).
2
(Nakkeeran and Sitaramamurthy, 2007)
Operating Criteria
Flow Rate
Batch Volume
1
Not available
1
x
1
Not available
Daily Water Supply
1
Not available
Depending on filter type (WHO, 2006)
The flow rate, batch volume and daily water supply depend on the kind of filter used
Robustness
x
x
x
Taps can be broken and may need replacement
Activated alumina needs to be replaced or regenerated once saturated
It is necessary to measure the fluoride concentration in the outlet water to know when to
replace or regenerate media
Estimated Lifespan
x
x
Media regeneration every 6 months to 1 year
Estimation of the filter lifespan can be made based on the fluoride concentration of the raw
water, the daily volume through the filter and the adsorption capacity of the activated alumina
Manufacturing Requirements
Worldwide Producers:
x Many producers around the world
Local Production:
x Difficult and complex to manufacture, local production is not feasible
Maintenance
x
x
The regeneration cannot be left to the users: skilled labour is required to test the filtered water
and recharge activated alumina
The effluent from regeneration is high in fluoride and must be disposed of carefully to avoid
recontamination of nearby groundwater
Household Water Treatment for Fluoride Removal
Fact Sheet: Activated Alumina
Key Data
Direct Cost
Capital Cost
US$35-50
1
Operating Cost
Replacement Cost
US$0/year
US$1.3-2/kg media
1
Note: Program, transportation and education costs are not included. Costs will vary depending on location and filter type.
1
x
India, WHO 2006
Activated alumina has become less costly and more easily available, especially in locations
near to where it is manufactured.
References
Banuchandra, C. and P. Selvapathy (2005). A household defluorodation technique. TWAD
Technical Newsletter.
Cavill, S. (2007). Appropriate treatment options for high levels of fluoride in groundwater, Naiva
sha, Kenya. Dew Point.
World Health Organization (2006). Fluoride in drinking-water: Chapter 5, Removal of excessive
fluoride. World Health Organization.
Lyengar L. (2002). Technologies for fluoride removal. Small Community Water Supplies:
Technology, people and partnership, TP 40, Chapter 22.
Miller, K. (2007). Defluoridation of drinking water using appropriate sorption technologies.
Proceedings of the Water Environment Federation, no. 8: 9245±9254.
Nagendra, R. (2003). Fluoride and environment ± A review. Proceedings of the Third International
Conference on Environment and Health, Chennai, India: Pages 386 ± 399.
Nakkeeran, E. and D. V. Sitaramamurthy (2007). Removal of fluoride from groundwater.
Canadian Journal of Pure and Applied Sciences: 79.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org Email: [email protected]
Last Update: June 2011
Household Water Treatment for Fluoride Removal
Factsheet: Bone Char Filter
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Fluoride
x Taste, odour, colour
x Turbidity
x Other Chemicals
x
x
x
x
x
Bacteria
Viruses
Protozoa
Helminths
Hardness
What Is a Bone Char Filter?
How Does It Remove Contamination?
Bone was one of the earliest media suggested
for fluoride removal from water. It was not
widely implemented due to the bad taste of
treated water, the high cost and unavailability.
But in 1988, the WHO claimed it to be an
applicable technology for developing countries.
Major components of bone char are calcium
phosphate, activated carbon and calcium
carbonate. Fluoride is removed from water
through a process based on ion exchange.
When raw water containing fluoride comes into
contact with bone char, the fluoride ion
changes places with the carbonate ion in the
ERQHFKDUDQGWKHIOXRULGHEHFRPHV³VWXFN´ to
the bone char.
Bone char is a blackish porous granular media
capable of absorbing a range of contaminants.
The bone char grains are packed in a filter
(bucket, drum or column) and water flows
through.
Bone char is made from animal bones that are
charred (burnt) and crushed. Correct
preparation of the bone char is essential to
ensure good fluoride removal and to avoid
unattractive taste, colour and odour in the
treated water. Decades ago, bone char was
industrially produced and widely available, but
now the supply is limited. However, bone char
grains can
be
produced locally by
communities.
Bone char has high fluoride removal efficiency,
and can also absorb a wide range of other
contaminants. The fluoride adsorption capacity
is 2mg fluoride per gram of bone char
(Albertus, 2000).
Operation
Bone Char Production
The steps for preparing bone char are:
charring, crushing, sieving and washing/drying.
The colour of the charred bone is a simple way
to determine its quality (Jacobsen and Dahi,
1997):
x
Grey-brownish: Highest fluoride removal
x
Black: Still contains organic impurities
causing odour and colour
x
White: Reduced fluoride removal capacity
Bone char from any animal needs to be
carbonized at a temperature of 400 to 500 ºC
with a controlled air supply. Then the charred
bones can be crushed manually or by using a
crushing machine. Particles between 0.5 mm
and 4 mm can be used as media.
Three Common Households Units for Sorption
Defluoridation (Credit: WHO, 2006)
Household Water Treatment for Fluoride Removal
Factsheet: Bone Char Filter
If bone char is not prepared properly, it may
result in low defluoridation capacity and/or
lower water quality.
Filter Examples
Bone char media can be use in different kinds
of filters. One example is a 20 litre bucket with
a tap fixed at the bottom connected to an outlet
pipe. A perforated plate can be placed on the
surface of the media to avoid disturbance
during addition of raw water. The use of bone
char alone is efficient with a flowing system,
but is not effective in a batch method (Larsen,
1993).
The water level in the filter should never drop
below the top of the bone char. If the bone
char is left dry, its adsorption capacity will
decrease. The water should be in contact with
the bone char for a minimum of 20 minutes.
The filter can be combined with a ceramic
candle
to
remove
microbiological
contamination as well (see picture). For new
filters or after changing the media, the first few
containers of treated water should be
discarded due to high turbidity and colour
(CDN, 2006).
Single and Combined Bone Char Filter
(Credit: Eawag, 2006)
Media Regeneration
Bone char media needs to be renewed or
regenerated periodically. Regeneration can be
done using caustic soda (NaOH). The fluoride
concentration in the treated water needs to be
measured periodically to know when to replace
or regenerate the media. However, an
estimation of the lifespan of the media can be
made based on the fluoride concentration of
the source water, the volume of water filtered
each day and the adsorption capacity of the
bone char.
Acceptance
The use of bones in water treatment might not
be consistent with local customs and beliefs.
Depending on the community, it may be
important to consider the implications of
religious beliefs, etc. on acceptance of using
bone char for water treatment.
Bone Char Domestic Defluoridator Developed by
ICOH-Thailand (Credit: Lyengar, 2002)
Household Water Treatment for Fluoride Removal
Factsheet: Bone Char Filter
Key Data
Inlet Water Criteria
x
No specific limits
Treatment Efficiency
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Fluoride
1
Laboratory
Not
available
N/A
N/A
N/A
N/A
65% in batch
99% in flowing
2
system
N/A
N/A
N/A
N/A
N/A
90%
Field
3
1
Watanesk and Watanesk, 2000
Mavura et al., 2002
3
CDN, 2006
2
Operating Criteria
Flow Rate
Not available
1
Batch Volume
1.6 to 6.5 litres
Daily Water Supply
1
Not available
Depending on filter type (WHO, 2006)
x
The flow rate, batch volume and daily water supply depend on the kind of filter used
Robustness
x
x
x
Taps can be broken and may need replacement
Bone char needs to be replaced or regenerated when saturated
It is necessary to measure the fluoride concentration in the outlet water to know when to
replace or regenerate media
Estimated Lifespan
x
x
Estimating the lifespan can be made based on the fluoride concentration of the source water,
the water volume filtered each day, and the adsorption capacity of the bone char
According to Catholic Diocese of Nakuru Water QXDOLW\¶V laboratory research, the filter can be
filled 200 times with water (using an inlet concentration of 6 mg fluoride/litre) before the
fluoride concentration in the outlet water exceeds 1.5 mg fluoride/litre
Manufacturing Requirements
Worldwide Producers:
x Bone char is still produced in several countries as it is used in food industries such as sugar
production
Local Production:
x Bone char can be produced locally in any country
Materials:
x Bones from animals
x Furnace or kiln
x Crushing machine or tools for manual crushing
x Sieves to obtain correct grain size for bone char media
Fabrication Facilities:
x Storage place with roof to keep bones dry
Household Water Treatment for Fluoride Removal
Factsheet: Bone Char Filter
Key Data
Labour:
x Anyone can be trained to produce bone char
Hazards:
x Safety precautions are needed when charring the bones
Maintenance
x
x
Replacement or regeneration of bone char (skilled labour required)
Cleaned on a regular basis
Direct Cost
Capital Cost
US$17-23
1
Operating Cost
US$1.8/1000 litres
Replacement Cost
2
US$1.8/1000 litres
2
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
CDN, 2006 for the whole defluoridation unit and depending on tap type, Kenya
2
For bone char media replacement (CDN, 2006)
References
Albertus, J. (2000). Bone char quality and defluoridation capacity in contact precipitation. 3rd
International Workshop on Fluorosis Prevention and Defluoridation of Water Session 1
Epidemiology: 57.
Cavill, S. (2007). Appropriate treatment options for high levels of fluoride in groundwater, Naiva
sha, Kenya. Dew Point.
Catholic Diocese of Nakuru, Water Quality (CDN) and K. Müller (2007). CDN's experiences in
producing bone char. Kenya.
Catholic Diocese of Nakuru, Water Quality (CDN) and K. Müller (2006). CDN's defluoridation
experiences on a household scale. Kenya. Available at:
www.eawag.ch/forschung/qp/wrq/publications/pdfs/household_filters
Fawell, J. Kirtley, K. Bailey, and World Health Organization (2006). Fluoride in drinking-water:
Chapter 5, Removal of excessive fluoride. World Health Organization
Korir H., K. Mueller, L. Korir, J. Kubai, E. Wanja, N. Wanjiku, J. Waweru, M.J. Mattle, L.
Osterwatder and C.A. Johnson (2009). The Development of Bone Char-Based Filters For the
Removal of Fluoride From Drinking Water. 34th WEDC International Conference, Addis Ababa,
Ethiopia.
Lyengar L. (2002). Technologies for fluoride removal. Small Community Water Supplies:
Technology, people and partnership, TP 40, Chapter 22.
Miller, K. (2007). Defluoridation of drinking water using appropriate sorption technologies.
Proceedings of the Water Environment Federation, No. 8: 9245±9254.
Nagendra, R. (2003). Fluoride and environment ± A review. Proceedings of the Third International
Conference on Environment and Health, Chennai, India: Pages 386 ± 399.
Watanesk, S. and R. Watanesk (2000). Sorption study for defluoridation by bone Char. Session 1
Epidemiology: 80.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Fluoride Removal
Factsheet: Clay
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x Fluoride
x Turbidity
x
x
x
x
Bacteria
Protozoa
Helminths
Viruses
What Is Clay?
Clay is a very fine textured earthy material. It is
composed mainly of very small particles of
hydrous aluminium silicates, other minerals
and may include other materials. It is used for
making pottery (ceramics), brick and tile. Both
clay powder and fired (baked) clay are capable
of removing fluoride and other contaminants
from water. The ability of clay to clarify turbid
water is well known and it is believed to have
been used in households in ancient Egypt
(WHO, 2006).
Clay can be used in powder form in a bucket
system, or freshly fired clay/brick chips can be
used in column filters. The use of clay powder
in column filters is possible, but it is
troublesome because of difficulties in packing
the columns and controlling the flow.
How Does It Remove Contamination?
Clay is a good flocculent and absorbent for
removing fluoride, because of its relatively high
density (the particles are heavy).So once the
fluoride attaches to the clay particles, it settles
out well.
The best clay for fluoride removal has high
levels of iron oxide and aluminium (e.g.
bauxites, goethite/ hematite). The removal
process is an ion exchange between fluoride
and iron or aluminium.
Operation
Domestic clay column filters are normally
packed using fired (burnt) clay chips. The fired
clay chips can be found as waste from the
manufacturing of brick, pottery or tile.
The Clay Column Defluoridator (pictured) is an
example of a burnt clay filter used in Sri Lanka.
Not Effective For:
x Chemicals
It is a layered column of
freshly fired brick chips,
pebbles
and
crushed
coconut shells. Water is
passed through the unit
upwards (from the bottom
to the top). The filters can
be made out PVC pipe or
cement. In the columns,
brick
chip
sizes
are
generally between 15 and
20 mm.
The firing/burning of the
clay is important because it
activates the aluminium
oxide which reacts with the
fluoride. Once the clay is
fired it is also easier to
break into clay chips.
Column filter used in
Sri Lanka
(Credit: WHO, 2006)
In the bucket system, clay powder is added at
large dosages to water, stirred and left to settle
for several hours. The clean water is scooped
or decanted off the top. The sludge in the
bottom of the bucket must be disposed of
appropriately away from water sources. This
method cannot be used for source water with
high concentrations of fluoride (above 3 mg/L,
WHO 2006).
Clay pottery can also be used if the water is
allowed to drip through the clay. Since water is
often stored in clay pots in many cultures this
method may be quite feasible in communities
where the aluminum oxide concentration in the
soil (and therefore in the clay pots) is high. The
storage time in the pots varies depending on
the aluminum oxide level in the clay.
Household Water Treatment and Safe Storage
Fact Sheet: Clay
Key Data
Inlet Water Criteria
x
x
The treatment capacity of clay is optimum when water pH is about 5.6 (Jinadasa et al. 1988)
Bucket system is only good for low fluoride concentration (<3 mg/L, WHO 2006)
Treatment Efficiency
1
x
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Fluoride
Laboratory
Not
available
Not
available
Not
available
Not
available
Not
available
>93.8%
Field
Not
available
Not
available
Not
available
Not
available
Not
available
Not available
1
Using bauxite from Malawi (Sajidu et al. 2008)
Treatment efficiency depends on the quality of the clay and kind of filter used
Operating Criteria
x
Flow Rate
Batch Volume
Daily Water Supply
Not available
Not available
Not available
The flow rate, batch volume and daily water supply depend on the technique and kind of filter
used
Robustness
x
x
The clay used in filters needs to be replaced or regenerated (very costly) when saturated
It is necessary to measure the fluoride concentration in the outlet water to know when to
replace or regenerate media
Estimated Lifespan
x
Clay media needs to be replaced every 25-40 days typically
Manufacturing Requirements
Worldwide Producers:
x Bricks are produced everywhere
Local Production:
x Clay can be burnt in a kiln locally
Materials:
x Clay
x Kiln
Labour:
x Anyone can be trained to produce burnt clay chips
Maintenance
x
x
Frequent replacement or regeneration of clay
Clean filter on a regular basis
Household Water Treatment and Safe Storage
Fact Sheet: Clay
Key Data
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
Not available
Not available
Not available
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
x
Clay treatment for fluoride may only be cost effective if good quality, freshly burnt broken
bricks are available on site or near to the users, and if the filter is prepared using low cost,
locally available materials (WHO 2006)
References
Bjorvatn K. and A. Bardsen (1995). Use of activated clay for defluoridation of water. Ngurdoto,
Tanzania.
Bjorvatn K. and A. Bardsen (1995). Fluoride sorption isotherm on fired clay.Workshop on fluorosis
and defluoridation of water. Publ. Int. Soc. Fluoride Res, 46±49.
Cavill, S. (2007). Appropriate treatment options for high levels of fluoride in groundwater, Naiva
sha, Kenya. Dew Point.
Chidambaram S., A. L. Ramanathan, and S. Vasudevan (2004). Fluoride removal studies in
water using natural materials: technical note. Water SA 29, no. 3: 339.
Fawell, J.Kirtley, K. Bailey, and World Health Organization (2006). Fluoride in drinking-water:
Chapter 5, Removal of excessive fluoride. World Health Organization.
Lyengar L. (2002). Technologies for fluoride removal. Small Community Water Supplies:
Technology, people and partnership, TP 40, Chapter 22.
Miller, K. (2007). Defluoridation of drinking water using appropriate sorption technologies.
Proceedings of the Water Environment Federation, no. 8: 9245±9254.
Nagendra, R. (2003). Fluoride and environement ± A review. Proceedings of the Third
International Conference on Environment and Health, Chennai, India: Pages 386 ± 399.
Sajidu et al. (2008). Groundwater fluoride levels in villages of Southern Malawi and removal
studies using bauxite, International Journal of Physical Sciences 3, no. 1: 001±011
Wijesundara T. (2004). Low-cost defluoridation of water using broken bricks. in 30th WEDC
International Conference.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Fluoride Removal
Factsheet: Contact Precipitation
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
Not Effective For:
x Fluoride
x Taste, odour, colour
x Other chemicals
x Turbidity
x
x
x
x
x
What Is Contact Precipitation?
Contact precipitation is a technique in which
fluoride is removed from water through the
addition
of
calcium
and
phosphate
compounds, which leads to precipitation of
fluoride. The water is then filtered through
bone char that has been pre-saturated with
fluoride.
The process uses buckets, column filters or a
combination. Different kinds of contact
precipitation filters exist.
Bacteria
Viruses
Protozoa
Helminths
Hardness
before treatment to avoid the precipitation of
calcium phosphate. It is advisable to check the
bulk density as it may vary for different brands.
The most common calcium compounds used
to react with the fluoride are either lime or
calcium chloride (CC). This reacts with fluoride
to form a precipitate (solid form) of calcium
fluoride. A common phosphate compound
used is sodium dihydrogenphosphate, also
called monosodium phosphate or MSP.
How Does It Remove Contamination?
The precipitation of fluoride from water
containing calcium
and phosphate is
theoretically possible, but in reality it is not
feasible because the reactions are so slow.
The addition of a compound like bone char is
necessary to allow the precipitation of fluoride
within a reasonable time. The saturated bone
char helps with the removal of fluoride, and
filters out the precipitate. The contact time of
the water in the filter with the compounds
needs to be long enough to allow sufficient
fluoride removal; however, if the contact time is
too long, calcium ions may precipitate in the
filter and fluoride removal efficiency will
decrease. A 20 to 30 minute contact time is
recommended.
Operation
Water is first treated with calcium and
phosphate compounds. Any calcium and
phosphate compounds can be used, but it is
important to dissolve the chemicals prior to
mixing them with the water. The chemicals are
preferably prepared as two separate stock
solutions and can be prepared once every
month, but should not be mixed together
Contact Precipitation Filter for Household Use
(Credit: WHO, 2006)
Long term operation of the contact
precipitation technique in Tanzania has shown
that the process functions effectively when the
Household Water Treatment and Safe Storage
Factsheet: Contact Precipitation
dosage ratios are 30 and 15 for CC and MSP
respectively, with a raw water fluoride
concentration of about 10 mg/L. This dosage
ensures at least 65% precipitation of
fluorapatite (fluoride compound) and a surplus
of calcium for precipitation of the residual
fluoride as calcium fluoride (WHO 2006).
Water is then passed through a column filter
filled with gravel or coarse grained bone char.
It is important to take into account that the use
of bone char may not be culturally acceptable.
The steps for preparing bone char include:
charring, crushing, sieving and washing/drying.
The colour of the charred bone char is a
simple way to determine its quality (Jacobsen
and Dahi, 1997):
x
Grey-brownish: highest fluoride removal
x
Black: still contains organic impurities
causing odour and colour
x
White: reduced fluoride removal capacity
Bone char from any animal needs to be
carbonized (burnt) at a temperature of 400 to
500ºC with a controlled air supply. Then the
charred bones can be crushed manually or by
machine. Particles between 0.5 mm and 4 mm
can be used as media.
The bone char used in contact precipitation
needs to be pre-saturated with fluoride through
contact with water containing a high
concentration of fluoride (up to 100 mg/L).
Household Water Treatment and Safe Storage
Fact Sheet: Contact Precipitation
Key Data
Inlet Water Criteria
x
No specific limits
Treatment Efficiency
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Fluoride
Laboratory
Not
available
Not
available
Not
available
Not
available
Not
available
>90%
Field
Not
available
Not
available
Not
available
Not
available
Not
available
>95 %
1
Depending on dose (Albertus et al., 2000)
2
WHO, 2006
x
1
2
High fluoride removal efficiency, even the fluoride concentration in inlet water is high
Operating Criteria
x
Flow Rate
Batch Volume
Daily Water Supply
Not available
20 litres (typical)
Not available
The flow rate, batch volume and daily water supply depend on the kind of filter used
Robustness
x
x
x
Taps can be broken and may need replacement
Difficult to optimize without training and equipment
Requires supply chain, market availability and regular purchase of chemical compounds
Estimated Lifespan
x
Chemical solutions must be prepared every month
Manufacturing Requirements
Worldwide Producers:
x Bone char is still produced in several countries as it is used in food industries such as sugar
production
x Calcium and phosphate compounds: many producers around the world
Local Production:
x The chemical products involved are difficult and complex to manufacture and local production
is not always feasible
x Bone char can be produced locally in any country
Materials:
x For saturated bone char: bones from animals, furnace or kiln, sieves, crushing machine
(facultative), fluoride solution for saturation
Fabrication Facilities:
x For bone char: Storage place with roof to keep bones dry
Household Water Treatment and Safe Storage
Fact Sheet: Contact Precipitation
Key Data
Labour:
x Anyone can be trained to produce bone char
Hazards:
x Safety precautions are needed when charring the bones
Maintenance
x
x
x
x
Daily operation is easy; experience from Tanzania has shown that a young student can easily
operate the system
No health risk in the case of misuse or over-dosage of chemicals
The two stock solutions can be prepared once every month
Clean filter on a regular basis
Direct Cost
Capital Cost
Operating Cost
Replacement Cost
Not available
Not available
Not available
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
.
References
Albertus, J. (2000). Bone char quality and defluoridation capacity in contact precipitation. 3rd
International Workshop on Fluorosis Prevention and Defluoridation of Water Session 1
Epidemiology: 57.
Cavill, S. (2007). Appropriate treatment options for high levels of fluoride in groundwater, Naiva
sha, Kenya. Dew Point.
Fawell, J.Kirtley, K. Bailey, and World Health Organization (2006). Fluoride in drinking-water:
Chapter 5, Removal of excessive fluoride. World Health Organization.
Lyengar L. (2002). Technologies for fluoride removal. Small Community Water Supplies:
Technology, people and partnership, TP 40, Chapter 22.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
Household Water Treatment for Fluoride Removal
Factsheet: Nalgonda Technique
Potential Treatment Capacity
Very Effective For:
Somewhat Effective For:
x Turbidity
x
x
x
x
x
x
x
Fluoride
Bacteria
Viruses
Protozoa
Helminths
Hardness
Taste, odour, colour
What Is the Nalgonda Technique?
The Nalgonda technique was first developed
by the National Environmental Engineering
Research Institute (NEERI) in Nalgonda, India.
It involves adding alum (aluminum sulphate,
.
(Al2(SO4)3 16H2O))
and
lime
(calcium
carbonate) to the raw water to precipitate the
fluoride.
Compared
with
normal
drinking-water
flocculation processes, a much larger dose of
alum is required in the defluoridation process.
Because the alum solution is acidic, addition of
lime is needed at the same time to maintain a
neutral pH in the treated water and to complete
precipitation of aluminum.
Calcium hydroxide may be added instead of
lime. Chlorine or bleaching powder can also be
added to the raw water to disinfect it against
microbiological contamination.
After treatment with the chemicals, the treated
water can be decanted or poured into another
Not Effective For:
x Other chemicals
container. The water may be passed through a
filter or cloth while decanting to ensure that no
sludge particles escape with the treated water.
How Does It Remove Contamination?
Aluminum salt is responsible for removal of the
fluoride from the water. During the flocculation
process (creation of large particles in the water
which stick together) many kinds of microparticles and negatively charged ions
(including fluoride) are partially removed by
electrostatic attachment to the flocs.
In this technique, up to a third of the fluoride is
precipitated, while up to 82% reacts with the
alum to make a soluble and toxic aluminum
fluoride complex (Miller, 2007) which will settle
to the bottom as sludge. This should be
disposed of away from water sources.
The process can produce treated water with
fluoride concentrations of 1 to 1.5 mg/L.
Household Defluoridation Using Nalgonda Technology (Credit: Lyengar, 2002)
Household Water Treatment and Safe Storage
Factsheet: Nalgonda Technique
Operation
The Nalgonda Technique is a bucket system
designed to be used on a household scale. It
consists of a 40 litre plastic bucket with a tap
located 5 cm above the bottom of the bucket.
Lime is added to maintain the neutral pH in the
treated water. Excess lime is used to help
sludge settling as it helps form denser
(heavier) flocs, which speeds up settling.
The process involves adding aluminum sulfate,
lime and bleaching powder (optional) to the
water in the bucket, followed by rapid mixing
for 10 minutes. The water is then left to stand
for 1 hour. After coagulation/flocculation and
settling are complete, the treated water is
poured out through the tap, and stored for the
day's drinking in a clean bucket or safe storage
container.
This technique produces large quantities of
sludge. The environmental impact of the
hazardous sludge disposal should be
considered.
The dose of alum to be added depends on the
fluoride concentration and the alkalinity of the
raw water (see table below from Lyengar,
2002). The dose of lime to be added is 5% of
the amount of alum (Lyengar, 2002).
Moreover, care has to be taken to avoid the
presence of aluminum in the treated water, as
this may have adverse health effects. With this
technique, the free residual aluminum content
in the treated water can be as high as 2.01 to
6.86 mg/L (Kailash et al., 1999). The maximum
limit is 0.2 mg/L aluminum.
Alum and Lime Dosage for the Nalgonda Technique
(Credit: Lyengar, 2002)
Household Water Treatment and Safe Storage
Fact Sheet: Nalgonda Technique
Key Data
Inlet Water Criteria
x
x
Total dissolved solids (TDS) must be less than 1500 mg/L
The process cannot be used in cases of fluoride concentration above 20 mg/L
Treatment Efficiency
Laboratory
Field
1
Bacteria
Viruses
Protozoa
Helminths
Turbidity
Fluoride
>90 to
1
>99%
2
< 90%
3
95%
>90 to
1
>99%
>90 to
1
>99%
>90 to
1
>99%
Not available
Up to 70%
Not available
Not available
Not available
Not available
Not available
4
Sproul (1974), Leong (1982), Payment and Armon (1989) as cited in Sobsey, 2002
Ongerth (1990) as cited in Sobsey, 2002
3
Wrigley, 2007
4
Fawell et al., 2006
2
x
Maximum effectiveness requires careful control of coagulant dose, pH and consideration of
the quality of the water being treated, as well as mixing
Operating Criteria
x
x
Flow Rate
Batch Volume
Daily Water Supply
Not applicable
40 litres
Unlimited
Need to follow instructions
Discarding the sludge from the Nalgonda process is considered to be an environmental
health issue. The sludge is quite toxic because it contains the removed fluoride in a
concentrated form. The sludge should be properly disposed (e.g. buried and covered in a pit).
Robustness
x
x
Difficult to optimize without training and equipment
Requires supply chain, market availability and regular purchase
Estimated Lifespan
x
6 months in liquid form and 1 year in solid form
Manufacturing Requirements
Worldwide Producers:
x Many producers around the world
Local Production:
x The chemical products involved are difficult and complex to manufacture and local production
is not always feasible
Maintenance
x
Chemicals should be stored in a dry location and away from children
Household Water Treatment and Safe Storage
Fact Sheet: Nalgonda Technique
Key Data
Direct Cost
Capital Cost
US$0
Operating Cost
US$12/year
1
Replacement Cost
US$0
Note: Program, transportation and education costs are not included. Costs will vary depending on location.
1
Cavill, 2007. Assumed 20 litres/household/day.
References
Agarwal, K.C., S. K. Gupta, and A. B. Gupta (1999). Development of new low cost defluoridation
technology (Krass). Water science and technology: 167±173.
Banuchandra, C. and P. Selvapathy (2205). A household defluorodation technique. TWAD
Technical Newsletter.
Cavill, S. (2007). Appropriate treatment options for high levels of fluoride in groundwater, Naiva
sha, Kenya. Dew Point.
Fawell, J.Kirtley, K. Bailey, and World Health Organization (2006). Fluoride in drinking-water:
Chapter 5, Removal of excessive fluoride. World Health Organization.
Miller, K. (2007). Defluoridation of drinking water using appropriate sorption technologies.
Proceedings of the Water Environment Federation, no. 8: 9245±9254.
Lyengar L. (2002). Technologies for fluoride removal. Small Community Water Supplies:
Technology, people and partnership, TP 40, Chapter 22.
CAWST (Centre for Affordable Water and Sanitation Technology)
Calgary, Alberta, Canada
Website: www.cawst.org, Email: [email protected]
Last Update: June 2011
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