Katherine Westphal

1
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.
2
Ceramic Water Filter (CWF)

• Technology developed in 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

3
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)

4
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
• Effectiveness of the filter to remove water-borne
  pathogens
• Possible quality control issues within and
  between manufacturing facilities

5
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

6
Study design

• 3 Parts
• Laboratory
• tested bacteria, virus and protozoa removal of 24
  CWFs from Honduras
• Field survey -
• a cross-sectional survey of households in
  Nicaragua that received a CWF
• Field assessment
• in-situ tests of CWF effectiveness to remove
  bacteria

7
Research findings

• Laboratory (15 CWFs with silver)
• Field
• 53 (23/43) of filters removed 100 of E. coli
• 78 (34/43) of filters removed gt 95 E. coli
• 9.3 (4/43) of households had more E. coli in
  filtered water than pre-filtered water

8
Research findings

• Cross-sectional survey (167 households)
• 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)
• 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

9
Sustainability

• Social/Cultural
• People like the taste of the filtered water and
  appearance of the filter
• Households consider the CWF beneficial enough to
  pay for it
• Economic
• Provides employment for local potters
• A one-time cost if unit does not break
• Technical
• Effectiveness
• Significantly reduces bacteria and protozoa in
  water
• Does not effectively remove viruses and there is
  no residual protection
• Durability
• The ceramic filter, spigot and receptacle are
  fragile and break easily
• Spare parts are not readily available
• Environmental
• Uses locally available materials and fuel
  efficient kilns for firing filters

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Conclusions

• Laboratory -
• CWF improves the quality of water but it does not
  consistently remove water-borne pathogens to meet
  USEPA standards
• Field -
• 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

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Recommendations

• CWF -
• Adaptations to the spigot and/or receptacle of
  the CWF
• Increase availability of CWF replacement parts
• Research -
• Compare effectiveness of filters across
  production sites
• Longitudinal study of diarrheal prevalence
  comparing households with a CWF to those without
• Quality assurance -
• Establish QA protocols for CWF production
• Develop a certification process for
  locally-produced CWFs

12
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