Point of Use Biosand Filters of the Rural Dominican Republic

Abstract

The point of use biosand filter (BSF) is used globally as a drinking water treatment solution. In this research, point of use BSFs were inoculated with active biosand from the Linnwood Drinking Water Treatment plant slow sand filter beds (Milwaukee, Wisconsin) and with sands collected from point of use filters operating in the Dominican Republic. These filters were maintained with varying source waters (surface water, groundwater, or tap water to simulate chlorination encountered in the field). The microbial community of filters with varied influents and biosand inoculum were analyzed quantitatively by sequencing and qPCR. Filter efficacy and microbial community were found to be largely a function of source water and pretreatment conditions. Filters were intermittently challenged with E. coli as a fecal indicator bacteria and bacteriophage MS2 as a surrogate for pathogenic virus to evaluate filtration efficiency. This research suggests that the point of use BSF should not be used in conjunction with chlorinated source waters. Chlorination may inhibit biofilm colonization and allow for interstitial survival or growth of pathogenic bacteria. Based on the non-dimensional scaling analysis of genome sequencing data, the interstitial microbial community of the BSF could be grouped into four categories as a function of source waters: biosand filters in the Dominican Republic, laboratory filters maintained with tap water, groundwater, or with Lake Michigan water as influent. The microbial community within active biosand collected in the field was not retained under laboratory conditions.