Household slow sand filter to treat groundwater with microbiological risks in rural communities

•HSSFs reached ≥ 3 log of E. coli in 100 operation days without a ripening agent.•HSSFs reduced ≥ 3 log of E. coli in only 20 operation days with a ripening agent.•Continuous-HSSF was superior to intermittent-HSSF in reducing microbiological risk•10 cysts and 20 oocysts passed through the HSSFs even with a ripe schmutzdecke•Exposure to chlorine may have altered the protozoa membrane permeability Household slow sand filters (HSSFs) improve the quality of life in rural communities as they provide safe water. However, HSSFs require time for the growth of the biological layer (schmutzdecke) to achieve maximum performance, especially when groundwater is used as it normally has few nutrients. In this ripening period, pathogenic microorganisms can pass through the filter. In this context, this study reports the performance of two HSSF settings, intermittent (I-HSSF) and continuous (C-HSSF) flows followed by disinfection with sodium hypochlorite to treat groundwater with Escherichia coli, Giardia muris cysts and Cryptosporidium parvum oocysts. The weekly introduction of river water was tested as a filter-ripening agent and this procedure reduced the ripening time in approximately 80 days. Filtered water disinfection improved the water quality and inactivated protozoa. The costs and operational challenges addressed in this study can provide support to HSSF technology transfer in rural communities worldwide. [Display omitted]