Modified biosand filters enriched with iron oxide coated gravel to remove chemical, organic and bacteriological contaminants

Modified biosand filters (MBSF) are one of the emerging point-of-use water treatment technologies. In this study, a series of laboratory scale MBSFs enriched with iron oxide-coated gravel (IOCG) with three layers of underdrain were used to remove organic matter (chemical oxygen demand (COD), total organic carbon (TOC), turbidity, total coliforms, Escherichia Coli (E. coli) and different concentrations of metals (nickel, iron, copper, zinc)from source water. The removal efficiencies of contaminants in MBSF control were found to be 92.66%–96.37% for turbidity, 99% - 98.2% for Cu, 99.12% - 99.06% for Zn, 98.17% - 94.03% for Ni, 95.27% - 92.33% for Fe(II) for influent metal concentrations of 2 and 5 mg/L respectively, 45.18% for COD, 48.36% for TOC, 98.07% for E. coli and 94.21% for total coliforms. The removal efficiencies of contaminants in MBSF IOCG were found to be 90.54%–95.84 % for turbidity, 99.27% - 98.52 for Cu, 99.1 - 99% for Zn, 98.61% - 94.52% for Ni, 95.28 - 92.23% for Fe(II) for 2 and 5 mg/L influent metal concentrations respectively, 49.29% for COD, 49.65% for TOC, 99.0% for E. coli and 95.33% for total coliforms. MBSF IOCG produced better bacteria, TOC, COD, Cu and Ni removal rates. Regeneration studies of the filters showed filters’ media reusability effectively. The effluent water quality met drinking water standards for MBSFs in terms of metal concentrations and turbidity.