Fluoride mapping and removal using rice husk ash in Bathinda groundwater

Fluoride contamination in groundwater poses a significant threat to the safety of drinking water, particularly in resource-constrained regions. This study evaluates rice husk ash (RHA), an agricultural byproduct, as a low-cost adsorbent for fluoride removal using a continuous-flow column system. A total of 113 groundwater samples from Bathinda, Punjab, showed that 26.55% exceeded the permissible fluoride limit, with concentrations up to 9.6 ppm. A GIS-based hotspot map, generated using the Inverse Distance Weighting method, identified high-risk zones for targeted intervention. Fixed-bed column experiments tested RHA performance under varying bed heights (4–8 cm), flow rates (0.5–1.5 mL/min), and an influent fluoride concentration of 20 ppm. Optimum removal occurred at higher bed height and lower flow rate, achieving a maximum adsorption capacity of 26.39 mg/cm³. Breakthrough curves and kinetic modelling validated column efficiency. The findings demonstrate RHA as a sustainable solution contributing to SDG 6 (Clean Water and Sanitation).