Small-scale performance of a novel arsenic sorbent from contaminated groundwater

Abstract

Several arsenic (As) treatment technologies exist for arsenic-contaminated groundwater, but the majority of them are cost-prohibitive for rural communities and small municipalities around the world. Our proposed technology relies on a packed bed reactor (PBR) system, utilizing a novel, low-cost, As filter medium, i.e., the drinking-water treatment residuals (WTRs). The drinking-water treatment process generates a by-product, the WTRs, which are available, free of charge from the drinking water treatment facilities in the U.S. Earlier batch experiments have shown the tremendous affinity of WTRs for soluble As(V) and As(III). A small-scale (30 x 5 cm) PBR system containing the WTRs were tested for its effectiveness in treating As-contaminated, synthetic groundwater. Influent groundwater composition was 150 µgL-1 As added either as As(V) or As(III) mixed with 2 mg Fe++ at a pH of 6.5. Influent solution was constantly purged with N2 to simulate typical anaerobic conditions in groundwater, and it was delivered to the PBR filter medium consisted of either an Al-, or Fe-based WTRs (<1-mm). The total bed volumes processed varied between the WTR type (Fe-, or Al-based), and the As oxidation state (III vs. V). The AlWTR was superior to the Fe-WTR effectiveness in treating both As(V) and As(III)- contaminated groundwater, processing > 18,000 bed volumes before exceeding the current MCL value for As in the U.S. and Europe (10 µgL-1) for As in India and other developing countries that are being poisoned by their drinking water. Continuous monitoring of several metals (Al, Fe, Cr, Cu, Zn, Pb, and Mn) did not show that WTRs leached metals to the effluent solution to any measure of significance.