Sustainable restoration of low-quality groundwater through aquifer storage and recovery

The escalating challenges in urban water supply, driven by rapid urbanization, climate change, and water resources pollution, necessitate innovative solutions for sustainable water management. Urban areas frequently encounter spatial constraints for the installation of new production wells, thereby intensifying water scarcity. Shifting climate conditions lead to increased occurrences of extreme weather events, aggravating global water scarcity and impeding sustainable development, particularly impacting human health and exacerbating societal inequalities. To address this issue, our study explores the retrofitting of inactive production wells for aquifer storage and recovery (ASR) in low-quality aquifers, providing a systematic framework. The evaluation focuses on the suitability of inactive wells for ASR operations and utilizes the FEFLOW 8.1 groundwater model to assess the impact of hydrogeological conditions on ASR system recovery efficiency (RE). To validate this framework, we concentrate on the northwest region of the Hamburg metropolitan area, utilizing generalized hydrogeological conditions to yield universally applicable results. This region is characterized by high sulphate concentrations in groundwater, limiting the utility of production wells. Our findings demonstrate that ASR in a low-quality aquifer can constitute a viable strategy to address water scarcity. Under ideal aquifer conditions, ASR can achieve recovery efficiencies exceeding 100%. Our proposed framework emphasizes the necessity of a meticulous assessment of well design, considering construction materials and geological factors to prevent clogging. Key efficiency factors include the hydraulic gradient, injection and ambient concentrations, proximity to production wells, and dispersivity. Furthermore, ASR contributes to cost reduction by enhancing water management infrastructure and optimizing capacity utilization. This research provides a comprehensive perspective, offering valuable insights applicable to diverse locations grappling with water scarcity challenges.