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Silver-impregnated ceramic water filters (CWFs) are a simple and sustainable low-cost technology that has shown promise in improving household drinking water quality and reducing incidences of early childhood diarrhea in a variety of settings. Despite this promise, lower reservoir contamination is thought to be a contributing factor to the decline in the effectiveness being seen over time. A novel silverimpregnated ceramic torus that can be placed in the lower reservoir was designed to minimize this contamination. This study uses a one-year randomized trial to compare the relative effectiveness of the CWF + torus design with a standard CWF and point-of-use chlorination. The effectiveness of each technology was measured at project inception and subsequently after six and 12 months. Results indicate that the toruses, as designed, are not able to consistently maintain lower-reservoir silver concentrations above those of the simple CWF design and are hence unable to prevent contamination. Furthermore, after six months, only 65% of households that used point-of-use chlorination maintained sufficient chlorine levels above the 0.2 mg/L needed to be effective. All three technologies showed statistically equivalent log removal efficiencies for total coliform bacteria and all three declined in effectiveness over the first six months. Combined average log removal efficiencies for all three technologies ranged from 2.22 ± 0.21 initially but declined to 1.45 ± 0.35 after six months and to 1.42 ± 0.29 after one year. [ABSTRACT FROM AUTHOR]

Resource-limited communities throughout the developing world face significant environmental health problems related to the myriad of coliform sources within those communities. This study comprehensively investigated contamination sources and the biological and chemical mechanisms sustaining them in two adjacent communities in rural Limpopo, South Africa. An 8-month study was conducted of household () and source water quality, measurements of biofilm layers on the inside of household water storage containers and water transfer devices, and also hand-based coliforms and hand-washing effectiveness. A 7-day water container incubation experiment was also performed to determine the biological and chemical changes that occur in a household water storage container independent of human interference. Results indicate that household drinking water frequently becomes contaminated after collection but before consumption (197 versus 1,046 colony-forming ; ; ). The most important contamination sources include biofilm layers on the inside of storage containers ( colony-forming ; ), hands ( colony-forming ; ), and coliform regrowth resulting from high assimilable organic carbon (AOC) levels during storage. A maximum specific growth rate, , of was determined for total coliform bacteria on AOC, and a high correlation between AOC concentrations and the growth potential of total coliform bacteria was observed. These results support the implementation of point-of-use water treatment and other interventions aimed at maintaining the safe water chain and preventing biological regrowth. [ABSTRACT FROM AUTHOR]