Modification of a biosand filter in the northern region of Ghana

Abstract

Four local plastic design (LPD) BSFs were constructed in Northern Region, Ghana, to test and evaluate an experimental modification of the LPD BSF for treatment of highly turbid water. Modifications of the LPD BSFs were made in order to provide an additional "biolayer," the core layer of a BSF where most removal and degradation of pathogens occur. This adjustment was carried out by providing an additional diffuser basin, with an additional layer of sand in it. Along with two unmodified LPD BSFs, two modified LPD BSFs were built: one with an additional 5-cm sand layer, one with an additional 10-cm sand layer. Filter ripening was confirmed through an increase in turbidity removal after 13 days. All four LPD BSFs removed turbidity by an average of 92-95 % after Day 13, with average effluents of 10 - 16 TU (14 - 22 NTU). The modified BSFs showed slightly higher removal of turbidity after 27 days of operation. This could be an indication that the modified BSFs potentially withstand greater operational variation, or that the modified BSFs require less frequent cleaning. The average total coliform removal after 11 days was 87 % with an average effluent concentration of 430 cfu/100 ml from an influent concentration of 15,000 cfu/100 ml. Concurrently, 30 BSFs (HydrAidTM BioSand Water Filter) that were installed in a local village were tested for flow rate, turbidity, and E. coli/total coliform bacteria. These HydrAid BSFs showed an average turbidity removal of 87 %, and an average total coliform removal of 95 %, with average effluents of 2.9 NTU for turbidity and 710 cfu/100 ml of total coliform. Further research, such as testing the BSFs with influent of higher turbidity, which is typical in Northern Region, Ghana, is recommended to evaluate the effectiveness of the HydrAid BSF.