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The Effectiveness and Sustainability of a Low-cost Water Filter in Removing Pathogens during Long-term Household PowerPoint Presentation
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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 Guatemala in 1981

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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
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
cwf production
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
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
research objectives
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
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
research findings
Research findings

Laboratory (15 CWFs with silver) –

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 findings1
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
sustainability
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
conclusions
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
recommendations
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
acknowledgements
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