An evaluation of the relationship between time of sample collection and the performance of the biosand filter

TitleAn evaluation of the relationship between time of sample collection and the performance of the biosand filter
Publication TypeUnpublished
Year of Publication2008
Authors,
Series TitleWater and Watershed Research Institute
InstitutionUniversity of Victoria
CityVictoria
AbstractThe biosand intermittent slow sand filter has been shown to be an effective and inexpensive household water treatment system for reducing microbial pathogens and lowering turbidity. Many tens of thousands have been installed in households in developing countries around the world. However, the parameters of optimal performance for the biosand filter and its limits of tolerance related to source water turbidity and patterns of use are still not well-defined. In this study, the filter's performance in terms of reducing E. coli and turbidity were measured at four different time intervals after the filter's reservoir had been filled with 20 L of source water. The six biosand filters used in the study were divided into two groups, one group processing source water with low turbidity (µ = 1.29) and the other processing water with high turbidity (µ = 28.19). For each time interval, the initial and final turbidities and the E. coli removal efficiencies were recorded for each filter for five consecutive days. The results indicate that there is a decrease in the filter's E. coli removal efficiency and turbidity reduction over time during the course of processing a 20 L aliquot of source water. Increased source water turbidity resulted in only slight increases in filtered water turbidity, but in two of the three filters processing highly turbid source water, the E. coli removal efficiency decreased markedly at the 20-minute and 30-minute intervals.
One Liner: 
E. coli removal was higher in the initial filter effluent (corresponding to water which had remained in the filter during the residence period) than filter effluent later in the filter run.