Bimetallic oxide-coated sand filter for simultaneous removal of bacteria, Fe(II), and Mn(II) in small- and pilot-scale column experiments

Abstract

The aim of this study was to examine the simultaneous removal of bacteria, Fe(II), and Mn(II) by iron-manganese bimetallic oxide-coated sand (IMCS) using small-scale (length = 20 cm, inner diameter = 2.5 cm) and pilot-scale (length = 140 cm, height of filter media = 100 cm, inner diameter = 20 cm) column experiments. Small-scale column experiments showed that the Mn(II) removal capacity of IMCS (qeq = 0.027 mg g−1) was greater than that of iron oxide-coated sand (ICS) (qeq = 0.020g g−1), manganese oxide-coated sand (MCS, qeq = 0.012 mg g−1), and dual media containing ICS and MCS (qeq = 0.015 mg g−1). The Fe(II) removal capacity of IMCS (qeq = 0.034 mg g−1) was similar to that of ICS (qeq = 0.035 mg g−1), MCS (qeq = 0.035 mg g−1), and ICS/MCS (qeq = 0.034 mg g−1). Simultaneous removal experiments in small columns indicated that the bacterial removal capacity of IMCS (qeq = 7.158 mg g−1) in solution containing Fe(II) and bacteria was greater than that in solution with Mn(II) and bacteria (qeq = 4.031 mg g−1). For solutions with Fe(II), Mn(II), and bacteria, the bacterial removal capacity of IMCS was 6.636 mg g−1, which was greater than that in samples with Mn(II) and bacteria. These results indicated that bacterial removal capacity was improved in the presence of Fe(II). Pilot-scale column experiments (46-day operation) showed that the removal capacities of IMCS for Fe(II), Mn(II), and bacteria were 0.059, 0.068, and 1.187 mg g−1, respectively. The long-term experiments demonstrated that IMCS was effective as an adsorptive filter medium for the simultaneous removal of Fe(II) and bacteria. However, chemical additions might be necessary for Mn(II) removal to meet the water quality limit.