Mapping drinking water contamination in Gazipur City restaurants using WQI and multivariate analysis.

Groundwater is a primary drinking water source in many regions of Bangladesh, necessitating continuous monitoring to ensure safety. This study evaluates groundwater quality in Gazipur City by analyzing 173 water samples collected in 2019 from restaurants across 18 zones. Fourteen physicochemical parameters, including pH, turbidity, total dissolved solids (TDS), electrical conductivity (EC), and major ions, were assessed. Hierarchical cluster analysis grouped the zones into three clusters based on water quality similarities. Three water quality index (WQI) models - integrated WQI (IWQI), assigned weight WQI (AWWQI), and weighted arithmetic WQI (WAWQI) - were applied to assess drinking water suitability. The results showed that 31% (IWQI) and 49% (WAWQI) of samples were unsuitable for drinking. Pearson correlation analysis revealed strong positive correlations among TDS, EC, and color, while negative correlations were observed between pH and color, and fluoride and nitrate. Factor analysis identified industrial effluents, agricultural runoff, and rock-water interactions as major contamination sources. Additionally, microbial analysis confirmed bacterial contamination, with 47% of samples contaminated by and 64% by total coliform. With rapid urbanization and increasing population density, groundwater pollution is likely to worsen. Therefore, effective monitoring and management strategies are essential to ensure the provision of safe drinking water in Gazipur City restaurants.