Comparison of Three Household Water Treatment Technologies in San Mateo Ixtatán, Guatemala

Abstract

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 silver-impregnated 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.