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 nano-filtration 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.