AWWA JAW69263

A successful arsenic removal technology must be capable of removing both arsenate and arsenite. Research has shown that low-pressure nanofiltration (NF) membranes remove most of the arsenate but only some of the arsenite. To exploit membrane filtration's ability to remove arsenate, several researchers have suggested that a pretreatment step oxidizing arsenite to arsenate would improve the performance of NF membranes. The current study investigated this hypothesis by assessing the effect of the oxidation step on the arsenic removal performance of two NF membranes and a low-energy reverse osmosis membrane. Because of its inert nature, long life, simple operation, and compatibility with oxidant-sensitive membranes, manganese dioxide was chosen as the companion oxidant for membrane filtration. Results indicated that preoxidation with manganese dioxide significantly enhanced arsenic removal. For treatment facilities using membrane filtration to treat hard or brackish water, manganese dioxide may provide a low-maintenance, cost-effective pretreatment alternative if additional arsenic removal is required to meet the regulatory target of 10 µg/L arsenic. Includes 38 references, tables, figures.