Assessment of groundwater quality for drinking purposes near the industrial area of Bharatpur, Chitwan, Nepal: Physicochemical, microbiological, and statistical approaches

Groundwater quality in rapidly urbanizing Bharatpur areas with unregulated industries remains a critical, understudied challenge. This study addresses this knowledge gap by comprehensively assessing the physicochemical and microbiological contamination of drinking water near the Bharatpur industrial area, Nepal, using a statistical approach. Twelve physicochemical and microbiological parameters were analyzed based on the Nepal Drinking Water Quality Standard (NDWQS) and the World Health Organization (WHO) guidelines. Statistical methods (correlation and regression) and an index-based assessment (water quality index [WQI]) were used to interpret contamination patterns. The results showed that the mean values of pH, conductivity, total dissolved solids, hardness, alkalinity, and Cl− were within the WHO/NDWQS guidelines. However, NO3−, PO43− (4.3–9.8 mg/L), NH3 (7–19.5 mg/L), free Carbon dioxide (CO2), and Escherichia coli (0–9 colony-forming unit/100 mL) exceeded the limits, indicating industrial and fecal contamination. The WQI values ranged from 560 to 663, indicating that all groundwater samples were unsuitable for drinking without treatment. Statistical analysis revealed strong positive correlations among key parameters. Conductivity was strongly associated with total dissolved solid, hardness, alkalinity, CO2, NH3, Cl−, PO43−, and E. coli. Hardness, alkalinity, and CO2 showed near-perfect intercorrelations, while additional strong associations were observed between Cl− and E. coli, PO43− and NO3−, and pH and NO3−. Further validation was performed using regression analysis with a first-degree linear equation. The findings indicate that groundwater near Bharatpur’s industrial zone is critically contaminated, necessitating the urgent need for policy interventions, such as wastewater treatment to safeguard public health.