Ceramic Filters Impregnated with Silver Nanoparticles for Point-of-Use Water Treatment in Rural Guatemala

Abstract

The technological performance and social acceptance of ceramic water filters impregnated with silver nanoparticles for point-of-use water treatment were investigated in the laboratory and in the field in the Guatemalan highland community of San Mateo Ixtatán. In the laboratory, filters were constructed with clay and sawdust collected from the Guatemalan community and were tested to determine the effects of percent sawdust and silver nanoparticle treatment on the transport and removal of E. coli. For ceramic filters without silver treatment, size-exclusion and/or sorption is the mechanism of removal and a lower mass-percent sawdust corresponds to greater bacteria removal. The addition of silver nanoparticles to the ceramic filters improved the performance for all mass percentages of sawdust relative to filter media without nanoparticle treatment. Filters with higher porosity achieved higher bacteria removal than those with lower porosity, suggesting an increase in burnable material percentage is advantageous, assuming structural integrity is not compromised. Subsequent to laboratory testing, ceramic filters were manufactured with local materials and labor in San Mateo Ixtatán, Guatemala, and distributed to 62 households in this peri-urban community. The study participants were randomly divided into two groups, and filters were tested periodically over 23 months or 12 months. Filtered effluent samples were tested for turbidity reduction, bacteria removal, and silver leaching. Over the course of the study, the average percent reduction in total coliforms and E. coli was 87% and 92%, respectively. The average effluent turbidity was 0.18 nephelometric turbidity units (NTUs) and average effluent concentration of ionic silver was 0.02 mg/L (below the U.S. EPA standard of 0.1 mg/L). Filters distributed to the second study group consistently performed better than the first study group as manufacturing techniques improved and contact with researchers increased. Overall, users were satisfied with the filters, citing them as easy to use and maintain while improving water quality. The findings of this study suggest that locally manufactured ceramic filters can significantly improve the microbiological quality of water when used as a point-of-use water-treatment technology.