Arsenic and Salinity Affected Groundwater in South-Western Bangladesh: An Assessment of Managed Aquifer Recharge and Sub-Surface Arsenic Removal as Mitigation Techniques

Abstract

Naturally occurring groundwater arsenic contamination is a major problem in Narail, Bangladesh. Analyses of 32 groundwater samples showed arsenic concentrations ranged 20.33–158.90 µg/L. Relatively deeper aquifer (>45 m depth) in addition to arsenic, is contaminated with substantial amount of salinity. Electrical conductivity (EC) ranged 1.01–7.90 mS/cm indicating the enormity of salinity. The groundwater is mainly Na–Cl to Na–HCO3 type, and is SO4 limited. This research demonstrates the effectiveness of two mitigation techniques (i) managed aquifer recharge (MAR) and (ii) sub-surface arsenic removal (SAR) for in-situ salinity and arsenic treatment of contaminated groundwater. A two-year long experiment revealed that the MAR system was effective in reducing both salinity and arsenic. Groundwater EC reduced 72–81% from an initial value of 3.4 mS/cm to less than 1 mS/cm. Arsenic concentration dropped below 50 µg/L from an initial concentration of 100 µg/L. The SAR system reduced arsenic concentration below 50 µg/L from an initial concentration of 100 µg/L. The system was capable of yielding 1500 liters of arsenic safe water when injected volume of oxygen saturated water was 2000 liters indicating 70–80% recovery. Both systems can provide 1000 liters of safe drinking water at a cost of $2.00.