Seven-year performance of biosand filters in rural Rwanda

Waterborne diseases remain a significant public health problem, and biosand filters (BSFs) are a common household water filtration method for improving drinking water quality to prevent diseases. The purpose of this study was to evaluate the effectiveness of BSFs over time in a rural Rwandan community. Sixteen BSFs were installed – eight in 2015 and eight in 2018. Influent and effluent samples were tested with Colilert Presence/Absence kits in 2015, 2017, 2018, 2019, and 2022. About 92.9% of filters were still in use in July 2022, but only 64.3% were functioning well, and 50% of effluent samples tested positive for fecal coliforms. A Kruskal–Wallis H test showed no statistically significant difference in effluent percent positive for fecal coliforms by filter age [χ2 (1) = 4.00, p = 0.41]. Recorded observations about each filter, such as rusted diffuser plates, may be useful for understanding the need for maintenance over time.