Paper No. 281-5
Presentation Time: 2:40 PM
ARSENITE REMOVAL IN GROUNDWATER TREATMENT PLANTS BY SEQUENTIAL PERMANGANATE―FERRIC TREATMENT
The Dutch drinking water sector is actively investigating methods to reduce arsenic (As) to <1 µg/L in drinking water supply. We investigated (1) the effectiveness of sequential permanganate (MnO4)—ferric (Fe(III)) dosing during aeration—rapid sand filtration to achieve <1 µg/L As (2) the influence of MnO4—Fe(III) dosing on pre-established removal patterns of As(III), Fe(II), Mn(II) and NH4+ in rapid sand filters and (3) the influence of MnO4—Fe(III) dosing on the settling and molecular-scale structural properties of the filter backwash solids. We report that MnO4—Fe(III) dosing is an effective technique to improve arsenite [As(III)] removal at groundwater treatment plants. At a typical aeration—rapid sand filtration facility in the Netherlands effluent As concentrations of <1 µg/L were achieved with 1.2 mg/L MnO4 and 1.8 mg/L Fe(III). The optimized combination of MnO4 and Fe(III) doses did not affect the removal efficiency of Fe(II), Mn(II) and NH4+ in rapid sand filters, however, the removal patterns of Fe(II) and Mn(II) in rapid sand filter were altered, as well as the settling behaviour of backwash solids. The characterization of backwash solids by Fe K-edge X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) showed that the altered settling behaviour of backwash solids was not due to changes in the molecular-scale structure of Fe-precipitates that formed during treatment.
Key words
Arsenic removal; Arsenite oxidation; Drinking water; Groundwater treatment; Permanganate; Rapid sand filtration