Determining the operational limits of the biosand filter

Worldwide, access to clean drinking water is not available for more than 800 million people. The biosand filter (BSF), an intermittently operated slow sand filter, was developed to address this problem. The BSF is used in homes to improve water quality. Three main objectives were examined in this research: (1) investigate initial startup and recovery performance after cleaning BSF, (2) examine the number of people the BSF may effectively serve, and (3) determine effects of an extended pause period on BSF performance. Laboratory experiments examined the BSF's ability to reduce fecal coliforms (FC) and turbidity for the various objectives. Results indicate that during the startup period, 27 days were needed to achieve 1 log reduction, while only 17 days were needed after cleaning the BSF to achieve 1 log reduction. A maximum of six people can be effectively served by a single BSF based upon the results of the experiment. A 7-day extended pause period determined that the bacterial layer will begin to go dormant or die off when the filter is not used for an extended period.