Improving the efficiency of biosand filters

Access to reliable safe drinking water is a worldwide crisis; millions die every year from waterborne illness. Point of use filtration has been utilized in a half a million homes in developing countries, where other treatments are not available. The focal point of our research is bateyes (housing on cane plantations, occupied by Haitian), where biosand filters were donated to provide a source of filtration. Few studies have focused on efficiency in removing pathogenic bacteria, viruses, and protozoa while considering variables such as chlorination or composition of the biological community. The filters are designed with three layers of rocks with different grain sizes, a diffuser plate on top, and outlet tubes to supply effluent water. Inside this simple design exists an ecosystem, the biofilm and biological area is predominantly on the top 40 cm while at greater depths biochemical activities are at work. A combination of the biological, biochemical, and mechanical processes produce an environment undesirable for human pathogens. Two filters from four bateyes were sampled, both the effluent water and sand from the biofilm; water samples were screened for growth of Escherichia coli (E. Coli) and total coliform colonies present. Chlorine residual testing was done at each site, since Central La Romana Sugar Can Co. (which provides the water to the bateyes) treats only intermittently and this may affect the efficiency of biofilm formation in the filters. Plate counts showed that some filters improved the quality of the water (lower numbers of E.coli in effluent vs. source water), while other filters decreased the quality of the water (higher E.coli in effluent than source). Community sequencing of the bacteria communities present in sand and water samples will allow us to examine differences in the microorganisms associated with good and poor filtration efficiency. Replicating the microorganisms and nutrients present in the bateyes’ filters to analyze and develop a more effective biofilm. Indicator bacteria plate count was different for each filter suggesting performance of biological and biochemical processes that could be explained by user error and chlorination effects