Locally produced ceramic water filters (CWF) are an effective technology to treat pathogen-contaminated drinking water at the household level. CWF manufacturers apply silver to filters during production, although the silver type and concentration vary and evidence-based silver application guidelines have not been established. We evaluated the effects of three concentrations of two silver species on effluent silver concentration, E. coli removal, and viable bacteria retained on the surface and contained in the pores of ceramic disks manufactured with clay imported from three CWF factories using sawdust as the burn-out material. Additionally, we evaluated performance using water with three chemistry characteristics (Na+–NaCl, Ca2+–CaCl2, and humic acid as natural organic matter) of disks made from the different clays using either sawdust or rice husk as the burn-out material. Results showed the following: (1) Silver desorption from disks coated with silver nitrate (Ag+) was greater than desorption of silver nanoparticles (nAg) for all disks. (2) Effluent silver concentration, E. coli removal, and viable bacteria retention were dose-dependent on the amount of silver applied. (3) Nither water chemistry conditions (inorganic or organic compounds) nor burn-out material showed an effect on any of the parameters evaluated at the silver concentration tested. The recommendation for filter manufacturers to use only nAg and at a higher concentration than currently recommended is discussed.

Locally manufactured ceramic filters can improve drinking water quality and reduce diarrheal disease burden in developing countries; however, production methods and quality control protocols vary at the >50 factories. We manufactured filter disks with varied clay, burn-out material, burn-out material sieved with different mesh sizes, and burn-out material to clay ratios and calculated filter characteristics, including porosity, density, shrinkage, and flow rate. Water was run through filters daily for 4 weeks, and flow rate and Escherichia coli reduction, as measured by log reduction value (LRV), were tested twice weekly. Our results suggest: (1) the first and last LRV test results do not correlate strongly (R2 = 0.38, p < 0.010); (2) there is not a strong association between flow rate and first, average, or last LRV results (R2 = 0.17, p = 0.090; R2 = 0.30, p = 0.020; R2 = 0.24, p = 0.040); and (3) first and average LRV are associated with burn-out material (R2 = 0.68, p < 0.001; R2 = 0.60, p < 0.001), and last LRV is associated with burn-out material and mesh size (R2 = 0.54, p < 0.050). Recommendations for filter factories, are to: (1) verify filtration efficacy with repeated bacteria reduction tests when materials, processing, or filter characteristics vary; (2) carefully control production variables; and (3) continue flow rate testing each filter to evaluate within and across batch production consistency.

HighlightsEighty-six refrigerators were evaluated for non-performance in Mozambique and Uganda.Communicating equipment failures resulted in actions that addressed failures.Systematic monitoring, failure analysis, and reporting strengthen the cold chain.

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