The Influence of Differing Sand Media On the Performance of the Biosand Intermittent Slow Sand Filter

The biosand filter is an affordable household water treatment system appropriate for use in many developing countries. Sand derived from crushed rock is recommended for the filter, but it is not always locally available. This study compares the performance of twelve biosand filters, four each using sand media from three different sources: ocean beach, river beach, and rock quarry. Twenty liters of contaminated pond water was put through each filter for twenty consecutive days. The filters were challenged with source water with low turbidity (1.68±0.31 NTU) and with high turbidity (16.79±6.56 NTU). Turbidity and E. coli counts for source and filtered water samples were recorded.All nine “mature” filters functioned well in lowering turbidity and removing E. coli, and no significant difference in performance based on sand type was identified using source water with both high and low turbidity (P=0.917, one-way ANOVA). Of the three more recently installed filters, the quarry sand performed better than the other two. The ‘mature’ filters were slightly more effective at removing E. coli than the more recently installed filters. Sedimentation before filtration improved performance and decreased maintenance of the filters.