Assessment of industrial effluent discharges contributing to Ganga water pollution through a multivariate statistical framework: investigating the context of Indian industries

Abstract

The swift industrial expansion has posed significant environmental challenges, particularly in the context of water pollution. Industrial effluents consist of substantial amounts of harmful pollutants that enter the main rivers via various tapped and untapped drains/local water streams, causing alterations in their physical and chemical properties. This study investigated 153 grossly polluting industries (GPIs) that were identified to release their effluents into the main rivers through different drains within multiple sectors in the industrial zone of four northern states of India in 2023. Physicochemical analysis, multivariate statistical analyses, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), and spatial analysis were conducted to evaluate the impact of these discharges. The results show significant variations in mean concentrations, such as pH (6.55–8.42), biochemical oxygen demand (6–707.83 mg/l), chemical oxygen demand (20–1504.25 mg/l), total suspended solids (5–417 mg/l), total dissolved solids (560–9908 mg/l), and chloride (101–4360.7 mg/l) across all the sectors. PCA results indicated that two principal loadings significantly influence the wastewater chemistry. PC1 accounts for 49.85% of the variance, reflecting organic and nutrient pollution, while PC2 contributes 19.128% of the total variance, reflecting the dominance of chloride, dissolved solids, and chemical oxygen demand. HCA classified the GPIs into six clusters for their substantial roles in releasing highly polluted (C3, C4, C5, and C6), moderately polluted (C2), and less polluted (C1) wastewater. Overall findings reveal the alarming magnitude of industrial wastewater discharge into the rivers, emphasizing the urgent need for improved regulatory frameworks, stricter enforcement of environmental laws, and greater corporate responsibility.