Bacterial filtration efficiencies and the bacterial communities’ proportions differences between sand size and depths in biosand filters

Abstract

The biosand filter (BSF) is a household sand filter used with pause periods in between uses, but it is not clear if larger sand particles can be used to increase the flow rate while maintaining the same bacterial filtration rate. Smaller scale BSFs were prepared to first measure if larger sand particles can filter water effectively. It was found that after 2 months of ripening BSFs, there was no significant difference in bacterial filtration rate between BSFs of a sand diameter less than 0.7 mm and less than 1.4 mm after 24 h of a pause period. Bacteria were identified by taking 16S rRNA in three layers of the sand in each BSF. Lelliottia sp. Enterobacter aerogenes, Kluyvera sp. Buttiauxellanoackiae, and Pantoea sp. were identified. By examining the band intensities in denaturing gel gradient electrophoresis, it was found that the microbial communities’ proportions differ between the levels of the sand and between the two BSFs of differing sand diameters, indicating differing filtration method priorities between the BSFs of different sand sizes. These findings indicate that, in the case of a 24 h pause period, a BSF with sand sizes 1.4 mm or less is just as viable as the current BSFs, while allowing for easier construction.