Design and field performance of an integrated horizontal flow treatment managed aquifer recharge system for groundwater rehabilitation in Bangladesh

Abstract The Barind tract in northwest Bangladesh faces severe groundwater challenges due to excessive extraction and limited recharge capacity, primarily caused by its thick top clay layer and intensive agricultural water demand. This study develops and evaluates an innovative horizontal flow treatment unit integrated with Managed Aquifer Recharge (MAR) to address severe groundwater challenges in the Barind tract of northwest Bangladesh. The developed system demonstrated exceptional treatment efficiency, achieving 97.06% turbidity reduction (from 68 to 2 NTU), 87.31% removal of total suspended solids, and significant bacterial contamination reduction of 81.82% (TC) and 93.75% (FC), while maintaining all chemical parameters within ECR 2023 drinking water standards. The system's recharge performance was evaluated under both controlled and natural conditions. Under controlled conditions, the initial recharge rate achieved 168.06 lpm, while during monsoon flooding, natural condition recharge ranged from 154.11 to 167.38 lpm. The system demonstrated remarkable sustainability, with 96% recovery of the original recharge rate possible through backwashing and maintenance, showing only a minimal annual decline rate of 3.43 lpm/year due to minor clogging. Long-term monitoring revealed significant groundwater improvement, with a 2.01 m water table rise over seven years (2015–2021), while maintaining groundwater quality within drinking water standards. The innovative aspects of the system include its novel horizontal flow design that reduces clogging potential, integrated pre-treatment for suspended solids removal, and an efficient self-cleaning mechanism through backwashing. The design's cost-effectiveness and local maintainability make it particularly suitable for widespread implementation. This study demonstrates that the integrated MAR-treatment system provides a sustainable solution for groundwater management in water-stressed regions, effectively addressing both water quantity and quality challenges while ensuring long-term operational viability.