Joe Brown and Mark Sobsey, University of North Carolina School of Public Health, Department of Environmental Sciences and Engineering
Sorya Proum, Department of Chemistry, Royal University of Phnom Penh
Ceramic Filters:
– Locally produced ceramic pot-style filters (flower pot shaped; i.e. “pot-style”) have the advantages of being lightweight, portable, relatively inexpensive, chemical free, low-maintenance, effective, and easy to use. The filters provide for removal of microorganisms from water by gravity filtration through porous ceramics, with typical flow rates of 1-3 liters per hour.
– Porosity of filters ~ 1µm and larger
– Created by mixing burnout material (very fine sawdust, ground rice husks, or some other combustible material) that disintegrates during the firing process to leave behind pore space in the unfired clay.
– Filters may be treated with a silver compound or other agent to inhibit microbial growth in the filter and possibly to enhance microbiological effectiveness.
– Water passes through the porous ceramic filter (capacity approximately 10 liters) at 1-3 liters/hr into the receiving container (10-20 liters) where it is dispensed via a tap to prevent post-filtration contamination of the product through dipping or other contact with soiled hands or vessels.
– Porous ceramic filters vary widely in design, effectiveness, and cost. The model for the CWP is the ICAITI filter developed in Latin America in the early 1980s (AFA Guatemala 1995), promoted widely by the NGO Potters for Peace.
Study and Effectiveness of Use:
Health effect measures reported are:
- The proportion of diarrheal disease in study groups
- The risk ratio (RR = the risk of diarrheal disease among the subjects using the filter / the risk of diarrheal disease experienced by the control group)
“Longitudinal prevalence of diarrheal disease in children has been shown to be a powerful predictor of mortality in children in developing countries” – (Morris et al. 1996)
During the study period (February – April (dry season))
- 243 households (48%) reported using surface water (lake, pond, river, stream, or canal) as a primary drinking water source
- 79 (16%) reported use of a deep well (defined here as ≥10m in depth)
- 152 (30%) used a shallow well
- 39 (8%) used stored rainwater from the previous rainy season
- 9 households (2%) reported using bottled drinking water
Did all these above people use the ceramic filters, or was this before the filters were introduced? How many households used the ceramic filter? Is this “Potters for Peace”? Are they out of Harvard?
Subject Responses:
- Ninety-two percent (92%) of study respondents indicated that diarrhea is a serious illness for children.
- Eighty-one percent (81%) of respondents reported that water is an important route of disease transmission.
- Users reported filling the filter an average of 1.8 times per day and cleaning it 2.3 times per week. 133 (86%) of households reported using the filter for drinking water only.
The ceramic filter surface is regenerated through regular scrubbing to reduce surface deposits which slow filtration rates The useful life of a ceramic filter depends on the frequency of cleaning, the quality of water being treated, and the thickness, since repeated cleaning will eventually wear away the filter surface.
Monetary Concerns:
- 72% of respondents were willing to pay US$2.50
- 29% were willing to pay US$4
- 26% were willing to pay US$5
The cost of replacing a ceramic filter element in Cambodia is currently in the US$2.50-$4 range (avg. Cambodian income ~$0.70-$1.90 / day)
Filters maintain effectiveness when used properly. “Since time in use was not shown to be strongly related to performance, recommendations that users replace the ceramic filter elements every one or two years (as is current practice) may not be necessary.”
Results:
A clear negative association in diarrheal disease prevalence was observed in filter households compared to control households, indicating a strong positive influence. The filter’s demonstrated effectiveness in improving water quality and health, over a wide range of conditions, makes it among the best available options for household water treatment.The filter’s demonstrated effectiveness in improving water quality and health, over a wide range of conditions, makes it an attractive option for household water treatment in Cambodia. ??
Results suggest that ceramic water filters are more likely to be used by households that:
- (i) already have some knowledge of safe water, sanitation, and hygiene practices
- (ii) invest in (purchase) the technology
- (iii) use surface water sources for drinking water
- (iv) do not use deep wells (≥10m) as a primary source of drinking water
Major findings of this study were that:
- (i) The rate of filter disuse was approximately 2% per month after implementation, due largely to breakages and may limit the sustainability of ceramic filter intervention efforts.
- (ii) Controlling for time since implementation, continued filter use over time was most closely positively associated with related water, sanitation, and hygiene practices in the home, cash investment in the technology by the household, and use of surface water as a primary drinking water source I don’t understand this one above.
- (iii) The filters reduced E. coli/100ml counts by a mean 98% in treated versus untreated household water.
- (iv) Microbiological effectiveness of the filters was not observed to be closely related to time in use (i.e. period of contact and flow rate)
- (v) Filters can be highly effective in reducing microbial indicator organisms but may be subject to recontamination, probably during “cleaning” with soiled cloths.
- (vi) The filters were associated with an estimated 46% reduction in diarrhea in filter users versus non users, placing them among the most effective water quality interventions at the household level. You mention some of the facts twice in this entire statement. Please read things over and improve writing. I think you should remove the graph below because it is formatted badly. Also there are only 6 facts represented that you might just put on a table or make a graph yourself that is easier to read.
Author’s Recommendations for Improvement:
- People must be educated in order to have faith in their filter. This study found that 5% of users were not using filters that were otherwise in working condition because they believed the filter to be “expired” according to the manufacturer’s instructions. Furthermore, individuals must be educated on how and when to clean the filters. Unicef advises intervention courses.
- Filter replacement parts must be available and accessible. The high number damaged filters in the sample size, and the low number of purchased replacement filters, suggests that users did not want to or could not access repairs or replacement filters, suggesting either problems of acceptance or of access.
- Further work is needed to substantiate how the filter performs against other microbes over time and for durations of more than 4 years.
- More research is needed on the health impacts of the CWPs.Ceramic Water Philters?
Specifically, randomized, controlled, blinded intervention trials should be performed in order to assess the effectiveness of the CWPs in reducing diarrheal diseases. - More research is needed on the microbiological effectiveness of the CWPs both in the laboratory and in the field. Evidence suggests that filter effectiveness may be improved through systematic testing and optimization of key parameters, such as: pore size, flow rate, base clay, burnout material, and microbicidal surface treatments or additives. Although filters performed well based on two bacterial indicators in this study, the performance of the filters in reducing viruses, protozoan parasites, and potentially important bacterial pathogens has not been adequately characterized.
Source: http://www.unicef.org/eapro/WSP_UNICEF_FN_CWP_Final.pdf
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