Dynamic performance of biosand filters.

Biosand filters (BSFs) are point-of-use water treatment systems that can provide safe and affordable potable water to households in developing countries. However, little information is available on the dynamic performance of BSFs or for selecting local materials to use as filter media. In this study, water quality dynamics, biofilm characteristics, and hydraulic performance were investigated in two full-scale BSFs. During four months of operation with sewage-contaminated surface water, average log₁₀ removals of 1.7, 1.2, and 0.6 were observed for Escherichia coli, total coliforms, and total heterotrophs, respectively. Average removal efficiencies for turbidity, ultraviolet absorbance at 254 nm, and total organic carbon were 86, 36, and 27%, respectively. Dynamic analysis showed that significant removal of indicator organisms and total organic carbon occurred during the pause period between charging the BSFs. Biofilm characterization revealed that more particle-associated biomass exists within the BSF column compared with the schmutzdecke layer. [ABSTRACT FROM AUTHOR]