Small-scale membrane-based arsenic removal for decentralized applications–Developing a conceptual approach for future utilization

Various technologies are used for the treatment of arsenic (As) contaminated water, but only a few seem to be suitable for small-scale applications; these are mostly used in rural communities where the access to potable water is the most vulnerable. In this review paper, the salient advantages and most notable challenges of membrane-based technologies for the removal of arsenate As(V) and arsenite As(III) are evaluated and systematically compared to alternative technologies such as e.g. adsorption. A comparison of different scientific papers, case studies and pilot trials is used to discuss the most important aspects when evaluating As mitigation technologies, including the ability to comply with the stringent WHO drinking water guideline limit value of 10 µg/L As and the safe disposal of produced As-laden waste. The use of renewable energies such as solar power in small-scale (<10 m³/day) membrane applications is evaluated. Finally, a conceptual approach for holistic As mitigation is proposed as an important approach to prevent exposure to As by providing a safe water supply

Iron-based subsurface arsenic removal (SAR): Results of a long-term pilot-scale test in Vietnam

The principle of subsurface arsenic removal (SAR) from groundwater is based on oxidation and adsorption reactions by infiltrating oxygen into the anoxic aquifer and the immobilization of arsenic (As) onto freshly formed iron (Fe)-(hydr)oxides. In this study, a pilot-scale plant for SAR has been subject to long term testing in the Mekong Delta, Vietnam. Initial concentrations of Fe (8.4 ± 1.3 mg L−1) and As (81 ± 8 μg L−1) in the exploited groundwater were successfully lowered to below the WHO guideline value limits for drinking water of 0.3 mg L−1 and 10 μg L−1, respectively. Adsorption and co-precipitation of As with Fe-(hydr)oxides could be identified as the principal mechanism responsible for the As removal from groundwater, demonstrating the feasibility of SAR as a low-cost and zero-waste solution over a period of two years. However, naturally occurring geochemical reducing conditions and high ammonium levels in the groundwater delayed the removal of manganese (Mn). An additional post-treatment filtration for Mn-removal was temporarily used to comply with the Vietnamese drinking water standard until a Mn-mitigation was achieved by the SAR process. In contrast to most As-remediation technologies, SAR appears to be a long-term, sustainable treatment option with the salient advantage of negligible production of toxic waste, which with ex-situ processes require additionally management costs