Electro-chemical arsenic remediation: Field trials in West Bengal

Abstract

Millions of people in rural South Asia are exposed to high levels of arsenic through groundwater used for drinking. Many deployed arsenic remediation technologies quickly fail because they are not maintained, repaired, accepted, or affordable. It is therefore imperative that arsenic remediation technologies be evaluated for their ability to perform within a sustainable and scalable business model that addresses these challenges. We present field trial results of a 600 L Electro-Chemical Arsenic Remediation (ECAR) reactor operating over 3.5 months in West Bengal. These results are evaluated through the lens of a community scale micro-utility business model as a potential sustainable and scalable safe water solution for rural communities in South Asia. We demonstrate ECAR's ability to consistently reduce arsenic concentrations of ~266 μg/L to <5 μg/L in real groundwater, simultaneously meeting the international standards for iron and aluminum in drinking water. ECAR operating costs (amortized capital plus consumables) are estimated as $0.83-$1.04/m(3) under realistic conditions. We discuss the implications of these results against the constraints of a sustainable and scalable business model to argue that ECAR is a promising technology to help provide a clean water solution in arsenic-affected areas of South Asia.

Evaluation of a Point-of-Use Electrocoagulation System for Arsenic Removal

“…These investigations have reported that arsenic adsorption onto HFO particles is fairly independent of pH up to a pH of 8. Limited available field data suggest that groundwaters in the Southern Asia area have pH levels in the near-neutral pH range 6,14 and, as seen herein, would provide a suitable aqueous environment for the application of EC technology. These groundwaters also appear to have an ionic composition (and electrical conductivity) that would also support EC-based arsenic removal systems.…”

“…A few HFO particles apparently were able to pass through the granular media filter bed. Alum has been used to help improve HFO particle removal in a larger scale EC system arsenic removal systems 14 . The sub-10 µg/L arsenic levels achieved after membrane filtration offer hope that an enhanced granular media filter or another size-appropriate solids separation technology can be used to meet global standards.…”

“…Arsenic removal from groundwater using an electrocoagulation (EC)-based process technology has been recently demonstrated as a viable approach to potable water production as it appears to provide effective treatment over a wide range of conditions while minimizing many of the limitations and water chemistry-based site-specific issues associated with other technologies 10,11 . The EC technology has been shown capable of providing treatment either at laboratory scale 12,13 or in small communal systems 14 . The goal of this project was to design and operationally evaluate a small point-of-use arsenic removal system providing arsenic removal based on EC technology.…”

Factors affecting the Faradaic efficiency of Fe(0) electrocoagulation

“…This technology is particularly applicable in decentralized and rural areas because of its low infrastructure requirements, ease of use and potential for scalability [1,2]. While EC systems are often accompanied by supplementary treatment steps, including settling tanks and filters [3], the technology centers on applying an electric current to Fe(0) electrodes in contact with an electrolyte solution to promote the oxidative release of soluble Fe(II) ions [4,5]. The Fe(II) ions migrate from the Fe(0) anode surface to the bulk solution, where contaminant removal occurs by several possible pathways.…”

“…To this end, we investigated the interdependent effects of i, E A and solution composition by combining time dependent measurements of E A and total Fe released from the Fe(0) anode as a function of i and solution chemistry. To encompass the range of current densities likely applied in Fe(0) EC field treatment [3], the i of EC experiments was adjusted over two orders of magnitude (0.25-50 mA/cm 2 ). The impact on the Faradaic efficiency of a variety of dissolved species common in natural waters was studied by systematically varying the ionic composition and pH of the solution, building in complexity from single and binary anion systems to synthetic groundwater matrices.…”