Laboratory investigation into the effect of silver application on the bacterial removal efficacy of filter material for use on locally produced ceramic water filters for household drinking water treatment

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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+-CaCl 2, 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. © 2013 American Chemical Society.

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ACS Sustainable Chemistry and Engineering