Transcript The Efficacy of a Low-technology, Low

The Effectiveness and Sustainability of a
Low-cost Water Filter in Removing
Pathogens during Long-term Household Use
KATHERINE WESTPHAL
MPH CANDIDATE, 2008
EARL WALL, M.S.,
KELLOGG SCHWAB, PHD., M.S.
Ceramic Water Filter (CWF)
 Technology developed in
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Guatemala in 1981
Potters for Peace promotes CWF
Filters are produced by local
organizations
Manufactured in 23 factories
throughout 20 countries
Worldwide over 300,000 sold
Organizations promoting CWF
include Save the Children,
UNICEF and Oxfam
CWF production
 Made from locally available clay,
screened combustible material
(sawdust or rice husks) and water
 Pressed into bucket shape with a
hydraulic press
 Fired for 8-12 hours in Mani Kiln
 Filtration flow rate (1-2.5 Ltr/hr)
 Painted with colloidal silver
 Sold with plastic receptacle and
spigot for $15 (small) and $20 (large)
Background
 Research to date 
Non-peer reviewed studies have found:
 CWF removes between 98-100% bacteria
 effective in removing protozoa although the virus removal is
minimal
 Concerns –
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Effectiveness of the filter to remove water-borne pathogens
Possible quality control issues within and between
manufacturing facilities
Research objectives
 Quantify the effectiveness of the
CWF to remove water-borne
pathogens in the laboratory and in
the field
 Evaluate the long-term
sustainability of the CWF
 Determine if the CWF should be
promoted by organizations as a
POU water treatment system
Study design
3 Parts:
Laboratory –
1.
o
tested bacteria, virus and
protozoa removal of 24 CWFs
from Honduras
Field survey -
2.
o
a cross-sectional survey of
households in Nicaragua that
received a CWF
Field assessment –
3.
o
in-situ tests of CWF
effectiveness to remove bacteria
Research findings
Laboratory
(15 CWFs with silver) –
L og 10 R educ tion Values
B acteria
Virus
P rotozoa
C W F L aboratory
3.22 - 6.06
0.27 - 1.85
2.47 - 2.97
US E P A
S tandards
6.0
4.0
3.0
Field –
 53% (23/43) of filters removed 100% of E. coli
 78% (34/43) of filters removed > 95% E. coli
 9.3% (4/43) of households had more E. coli in filtered water than
pre-filtered water
Research findings
Cross-sectional survey (167 households) –
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48.5% of households had stopped using filter daily
Among households not using the CWF, the primary reasons were :
broken spigot ( 58.0%)
 broken ceramic filter (40.7%)
 broken receptacle (30.9%)
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Even among households using the CWF, 31.4% had a broken spigot
Only 26.3% of households knew where to purchase CWF spare parts
86% of households reported that the CWF provided enough water
for their family to drink
All households surveyed liked the taste of the filtered water
The majority of households reported that they liked the CWF because
it cleaned the water and kept their family healthy
Sustainability
 Social/Cultural
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People like the taste of the filtered water and appearance of the filter
Households consider the CWF beneficial enough to pay for it
 Economic
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Provides employment for local potters
A one-time cost if unit does not break
 Technical
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Effectiveness –
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Significantly reduces bacteria and protozoa in water
Does not effectively remove viruses and there is no residual protection
Durability –
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The ceramic filter, spigot and receptacle are fragile and break easily
Spare parts are not readily available
 Environmental
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Uses locally available materials and fuel efficient kilns for firing filters
Conclusions
 Laboratory 
CWF improves the quality of water but it does not consistently
remove water-borne pathogens to meet USEPA standards
 Field 
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In general, the CWF improves household water quality
Without modifications to the spigot and receptacle, long-term
sustainability will not be achieved
 Overall 
Necessary to consider the social, economic and environmental
constraints of a country before defining water quality standards
Recommendations
 CWF 
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Adaptations to the spigot and/or receptacle of the CWF
Increase availability of CWF replacement parts
 Research 
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Compare effectiveness of filters across production sites
Longitudinal study of diarrheal prevalence comparing
households with a CWF to those without
 Quality assurance 
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Establish QA protocols for CWF production
Develop a certification process for locally-produced CWFs
Acknowledgements
 The Johns Hopkins Center for a
Livable Future
 Ron Rivera, Potters for Peace
 Save the Children Canada,
Nicaragua
 Earl Wall, Kellogg Schwab,
Kristen Gibson, Stephanie Guo,
Casey Branchini and Jimmy
Schissler
 Joan Kub and Sara Groves