Efficient removal of nitrate and arsenic using a two‐stage biotic‐abiotic treatment system

Abstract

AbstractNitrate and arsenic often co‐exist in groundwater sources. Reverse osmosis, electrodialysis, and ion exchange are the commonly implemented technologies for nitrate removal. Compared to these technologies that generate high‐strength waste streams, biological treatment converts nitrate to innocuous nitrogen gas without producing a concentrated waste. When nitrate and arsenic co‐exist in a water source, combining a biotic process for nitrate removal with an abiotic process (i.e., chemical–physical process such as coagulation/flocculation) for arsenic removal may provide an effective approach for simultaneous removal of these contaminants. A 12‐month pilot study was conducted with a two‐stage, fixed‐bed biotreatment system, originally developed for nitrate removal, for simultaneous removal of nitrate and arsenic. With an empty bed contact time as low as 10 min in the bioreactor, nitrate was consistently lowered from ~35 mg/L N to <0.1 mg/L N (treatment target was <1 mg/L N), whereas arsenic was effectively lowered from ~14 μg/L to <5 μg/L. Overall, the results demonstrated efficient and resilient simultaneous removal of nitrate and arsenic using a two‐stage biotic‐abiotic treatment system.