Removal of selected microorganisms using silver-impregnated and coated, low-cost, micro-porous, ceramic water filters

Abstract

There is great need to purify the contaminated water which the poor people in Africa have access to, and make it safe for drinking in a way that is affordable and effective. A particular challenge is the removal of pathogenic bacteria and viruses, which traditionally are eliminated by expensive nanofiltration or reverse osmosis. An added requirement is satisfying the recent recommendation of the WHO for household water-treatment systems to eliminate 99.99% of microbial contamination, which is proving exceptionally difficult to achieve in poor countries at a cost they can afford. We report on the successful testing of a low-cost, locally produced ceramic filter that has the potential to meet the WHO criterion at a cost of US$10 per year. In one version the filter consisted of a silver-impregnated, highly porous ceramic; in another modification silver nano particles were incorporated on the ceramic surface. The silver-impregnated filter was tested on water samples contaminated with selected Gram negative bacteria: Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa, for its oligodynamic effect and for its effective reduction of bacteriophages. The ceramic filters reduced the viral count by 94-99% and we believe that, with further development, our prototype is easily capable of achieving the WHO criterion. © IWA Publishing 2014.