Bacterial removal in flow-through columns packed with iron-manganese bimetallic oxide-coated sand

Abstract

The objective of this study was to investigate the performance of iron-manganese bimetallic oxide-coated sand (IMCS) in the removal of bacteria (Escherichia coli ATCC 11105) using small-scale (length = 20 cm, inner diameter = 2.5 cm) and 30-day long-term (length = 50 cm, inner diameter = 2.5 cm) column experiments. Results indicated that the bacterial removal capacity of IMCS (qeq = 0.66 g/g) was slightly lower than that of iron oxide-coated sand (ICS) (qeq = 0.69 g/g) but about two times greater than those of manganese oxide-coated sand (MCS, qeq = 0.30 g/g) and dual media containing ICS and MCS (qeq = 0.35 g/g). In IMCS, increasing the flow rate from 0.5 to 3.0 mL/min decreased the removal capacity from 1.14 to 0.64 g/g. Nitrate showed an enhancement effect on the removal capacity of IMCS at 1 and 10 mM, while phosphate and bicarbonate had both hindrance (1 mM) and enhancement (10 mM) effects, depending on their concentrations. The long-term column experiment (bacterial injection conc. = 4.2 × 106 CFU/mL) showed that IMCS could remove more than 99.9 % of bacteria within 13 days (effluent conc. = 1.6 × 102 CFU/mL). This study demonstrated that IMCS could be used as an adsorptive filter medium for bacterial removal in water treatment.