Abstract
Iron (Fe) amended dual unit ceramic filters (DUCF) can be a viable treatment option for arsenic (As) removal from highly contaminated groundwater. The present field study investigated the effect of filter configurations, the separate-unit dual filter (SUDF) and connect-unit dual filter (CUDF), on As removal from groundwater having As concentration of 475 mu g/L. SUDF was configured by placing 1st and 2nd filter units side-by-side, whereas the 1st filter unit was placed on the top of the 2nd filter unit in CUDF configuration. Comparing the two filter configurations, SUDF achieving As concentration in the effluent below 50 mu g/L (standard value) was found more effective due to sufficient Fe2+ in the 2nd filter. Average As concentrations in the final product (effluent of 2nd filter) were 43 mu g/L from SUDF and 111 mu g/L from CUDF. The short hydraulic residence time (3.3 min) in the 2nd filter of CUDF, along with limited contact between water and the iron net, lead to inadequate soluble Fe2+ resulting in poor As removal. Both filter configurations effectively removed Fe, P, and Mn with more than 90% reduction of these parameters by the 1st filter. Analysis of insoluble hydrous ferric oxides flocs through XAFS L3edge spectra confirmed the oxidation of As(III) to As(V) in both the SUDF and CUDF systems resulting in enhanced As removal efficiency. The study results found SUDF as an appropriate configuration for filter design to treat highly contaminated groundwater in rural areas of developing countries.