Ceramic Pot Filters: Current Research, Future Directions and Defining Next Steps

Transcription

1 Ceramic Pot Filters: Current Research, Future Directions and Defining Next Steps Justine Rayner 1, Kristen Jellison 2, Vinka Craver 3, Kaira Wagoner 4, Daniele Lantagne 5 1 Consultant; 2 Dept. of Civil & Environmental Engineering, Lehigh University, Bethlehem, PA; 3 Dept. of Civil & Environmental Engineering, University of Rhode Island, Kingston, RI; 4 Potters for Peace ; 5 Dept. of Civil & Environmental Engineering, Tufts University, Medford, MA

2 Outline Introduction Current Practices, Best Practices & Quality Control in Manufacturing Recent research: -Manufacturing Variables -Silver research Scaling up of filter factories Discussion & Questions

3 Introduction History of the ceramic pot filter International Ceramic Pot Workshop Disinfection 2009, February Independent workshop organized by Delft University 74 attendees Ceramic Manufacturing Working Group (CMWG) Goal: To provide guidance to assist filter factories in producing the most effective ceramic filters possible at the lowest cost.

4 Filter Efficacy Effective at removing: > 99% of protozoa 90-99% of bacteria Associated with reduction in diarrheal disease High user acceptability & potential for long-term use

5 Materials processing Production process Water, Clay, Burn-out Material, Additional Materials (Grog, Sand, Laterite) Mixing & Pressing Drying & Firing Quality Assurance & Quality Control Silver Application Package for Sale

6 Prototype filters Filter mixture ratio various filter mixture ratios specific flow rate microbiological testing Flow rate minimum filtration rate production consistency contact time with silver With consistent materials and production, filters that pass flow rate testing should be representative of prototype filters.

7 Variables that influence flow rate: Clay characteristics Burn-out material type particle size Mixture ratio Firing conditions location in kiln & heat distribution firing profile & peak temperature atmosphere

8 Survey: Current Practices in Manufacturing 35 Factories in 18 countries identified (July 2009) 18 Factories participated in the survey - considers 8 Myanmar factories as 1 (25 total)

9 Materials Poor quality clay can result in a failure rate of over 20% Sawdust from different woods have different effects on filters: some pass on color and odor to the filters Most factories get clay from the same source, 17% (3 of 18) do not. source location in the mine Sawdust The type of wood varies at 45% of the factories that use sawdust (5 of the 11) Rice husks inner rice husks (bran) outer rice husks

10 Filter Mixture Ratio 80% (13 of 16) of factories adjust their formula regularly or as needed depending on: location in clay mine clay source burn-out characteristics experience the weather & humidity of materials to achieve the desired flow rate quality control issue

11 Firing Success depends on the person firing the kiln Factories monitor firings with: a pyrometer (50%) pyrometric cones (28%) both (22%) only one factory uses the 3 cone method

12 Factory Established Flow Rates 6 Factory established flow rate ranges Factory Benin Cam-1 Cam-2 Colombia DR Guate-1 Guate-2 Indo-1 Indo-2 MM-All Nica-1 Nica-2 Nigeria SL-1 SL-2 Tanz-1 Tanz-2 Yemen Flow rate (L/hr) L n/r n/r cm n/r n/r n/r n/r n/r n/r n/r Factory, filter capacity (L), filter depth (cm) n/r: no response

13 Silver Application 15 factories use colloidal silver 3 factories use silver nitrate Silver is applied by: dipping (33%) brushing (56%) fired into the filters (11%). Only nine of the 16 factories (56%) that use colloidal silver provided dilution information concentrations range from parts per million (ppm) - excluding the two extremes as possible errors, the silver concentration applied to filters ranges from 107 to 288 ppm.

14 Microbiological Testing 72% (13 of 18) report carrying out microbiological testing regularly 61% test between 0.2%-15% of filters at a laboratory, at the factory or both

15 Failure Rates Number one reason for filter rejection at 60% (9 of 15) of the factories: Flow rate Filter Failure Rates 27% 27% 3% 16% 10% 20% 2% 8% 13% 15% 10% 10% 5% 17% 4% Benin Cam-1 Cam-2 Colombia DR Guate-1 Indo-1 Indo-2 MM-All Nica-1 Nigeria SL-1 SL-2 Tanz-1 Tanz-2 72% (13 of 18) always maintain production logs, the information recorded varies.

16 Best Practice Recommendations Consistent manufacturing Materials & process Monitor and control firing profile & peak temperature Colloidal silver dilution & application Documentation of production Quality control materials, production, evaluation Microbiological testing Photo credit: D. Lantagne

17 Quality Control Protocol Development Objective: to develop guidelines for use at a factory level to establish QA/QC protocol; 1. Draft QA/QC guidelines & develop factory visit plan 2. Review & feedback from CMWG 3. Implement/evaluate at three factories 4. Develop & disseminate quality control program development guidelines

18 Further Research Input variables on filter characteristics, flow rate, porosity & microbiological efficacy clay, burn-out characteristics (type, size) Firing temperature & profile Filter characteristics, strength, flow rate, microbiological efficacy Variables that affect filter strength filter shape, pressure, firing profile, processing, ratio & materials characteristics Silver optimum concentration & quantity, longevity, application methods, effects of water characteristics, effects of chlorine Filter lifespan Additional low-cost quality control tests