Performance of modified design pond sand filters

Two pond sand filters (PSFs) with modified design were constructed in Pathorghata Upazila of Barguna District located in southern Bangladesh. Performance assessment of the PSFs was done after commissioning in terms of quality of filtered water, ease of operation and maintenance, monthly check-up of production capacity/efficiency of the filters, users' participation and acceptability of the modified PSFs. Some important parameters such as total coliform, fecal coliform, turbidity, colour, total suspended solids (TSS), chemical oxygen demand (COD) and pH were measured for the raw water and at the various stages of treatment in order to determine the effectiveness of different units of the PSFs. Close observations were made to assess the removal of turbidity in the roughing/pre-filtration chamber to ensure trouble-free operation of the main filter bed. In combination with roughing filters, the average turbidity and fecal coliform removal efficiency of the sand filters were found to be 76 and 98%, respectively. Filter run of the modified PSFs was also found higher (about 3 months) than the existing PSFs.