Reactive transport impacts on recovered freshwater quality during multiple partially penetrating wells (MPPW-)ASR in a brackish heterogeneous aquifer |
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| Institution: | 1. KWR Watercycle Research Institute, P.O. Box 1072, 3430 BB, Nieuwegein, The Netherlands;2. Technical University Delft, Faculty of Civil Engineering, P.O. Box 5048, 2600 GA, Delft, The Netherlands;3. Utrecht University, Faculty of Geosciences, P.O. Box 80021, 3508 TA, Utrecht, The Netherlands;1. Department of Mechanical and Production Engineering, Sathyabama University, Chennai, India;2. Department of Petroleum Engineering, Vels University, Chennai, India;3. Department of Petroleum Engineering and Earth Sciences, University of Petroleum and Energy Studies, Dehradun, Uttarakhand, India;1. Nuclear Physics and Bio Physics Research Division, Department of Physics, Bandung Institute of Technology Gedung Fisika, Jl. Ganesha 10, Bandung 40132, Indonesia;2. Department of Science and Technology for Nuclear Material Management (STNM), Japan Atomic Energy Agency (JAEA), 2-4 Shirane, Shirakata, Tokai Mura, Naka-gun, Ibaraki 319-1195, Japan;3. Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro-ku, Tokyo 152-8550, Japan;1. Singapore-ETH Centre for Global Environmental Sustainability, Future Cities Laboratory, Singapore;2. Department of Civil and Environmental Engineering, National University of Singapore, Singapore;3. Institute of Environmental Engineering, ETH-Zürich, Switzerland |
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| Abstract: | The use of multiple partially penetrating wells (MPPW) during aquifer storage and recovery (ASR) in brackish aquifers can significantly improve the recovery efficiency (RE) of unmixed injected water. The water quality changes by reactive transport processes in a field MPPW-ASR system and their impact on RE were analyzed. The oxic freshwater injected in the deepest of four wells was continuously enriched with sodium (Na+) and other dominant cations from the brackish groundwater due to cation exchange by repeating cycles of ‘freshening’. During recovery periods, the breakthrough of Na+ was retarded in the deeper and central parts of the aquifer by ‘salinization’. Cation exchange can therefore either increase or decrease the RE of MPPW-ASR compared to the RE based on conservative Cl−, depending on the maximum limits set for Na+, the aquifer’s cation exchange capacity, and the native groundwater and injected water composition. Dissolution of Fe and Mn-containing carbonates was stimulated by acidifying oxidation reactions, involving adsorbed Fe2+ and Mn2+ and pyrite in the pyrite-rich deeper aquifer sections. Fe2+ and Mn2+ remained mobile in anoxic water upon approaching the recovery proximal zone, where Fe2+ precipitated via MnO2 reduction, resulting in a dominating Mn2+ contamination. Recovery of Mn2+ and Fe2+ was counteracted by frequent injections of oxygen-rich water via the recovering well to form Fe and Mn-precipitates and increase sorption. The MPPW-ASR strategy exposes a much larger part of the injected water to the deeper geochemical units first, which may therefore control the mobilization of undesired elements during MPPW-ASR, rather than the average geochemical composition of the target aquifer. |
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| Keywords: | Aquifer storage and recovery ASR Multiple partially penetrating wells MPPW Reactive transport Water quality Cation exchange Arsenic Subsurface iron removal Coastal aquifers |
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