Understanding Arsenic removal processes: passive treatment systems as proxies for natural environments

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Groundwater in many regions of the world, including parts of the UK, contains high Arsenic (As) concentrations. Arsenic is toxic also at low concentrations and, unfortunately, groundwater is a major route for intake of As either via drinking or via irrigation and subsequent uptake into plant-based foodstuff such as rice (soil-plant-human pathway). This situation may worsen in coming years as climate change may lead to increasing water stress and thus increasing irrigation around the world. In contrast to the attention that As-contaminated drinking water and its treatment have received over the past decades, removing As from large quantities of irrigation water via treatment or natural attenuation processes has been less extensively studied and is a currently unsolved challenge. The aim of this study is to investigate the fundamental processes of As removal in composed passive treatment systems, as case studies for natural attenuation processes. The choice of this treatment system is based that it is potentially low-cost and operating on zero-energy, still very efficient in metal(oid) removal which mitigates exposure to receptor (water or soil). Specific questions to be addressed include: Which biotic or abiotic processes (or both) are removing As in the treatment systems? How is the removed As bound and what are the consequences for its future release (e.g., due to changes in biogeochemical parameters, waste management practices)? Can we manage these processes in natural environments, particularly soils, to attenuate As contamination and bioavailability? The outcome of the study will help in addressing the challenge of managing arsenic-contaminated irrigation water for food security and public health.