Upstream–downstream assessment of physicochemical and microbiological water quality of the Nagavali River influenced by a paper industry discharge
Abstract
Sustainable management of freshwater resources requires continuous environmental monitoring of rivers receiving industrial effluents. Pulp and paper industries are known to generate wastewater containing organic matter and microbial contaminants, which may influence receiving water bodies even after treatment. In this context, the present study evaluates the impact of a paper industry discharge on the water quality of the Nagavali River using an upstream–downstream assessment approach, with emphasis on environmental and public health implications.
Monthly river water samples were collected during 2025 from one upstream reference station and two downstream stations located near and beyond the industrial discharge zone. Physicochemical parameters such as temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were analysed following standard analytical methods. Microbiological indicators including total coliform (TC), fecal coliform (FC), and fecal streptococci (FS) were also assessed. Water Quality Index (WQI) was employed to integrate individual parameters and evaluate overall water quality status.
The results indicated that pH remained within neutral to mildly alkaline range, DO concentrations consistently exceeded 5 mg/L, and BOD values remained below 2 mg/L at all monitoring stations, suggesting satisfactory physicochemical conditions. However, downstream locations exhibited elevated TC and FC counts compared to the upstream site, indicating localized anthropogenic influence. Although WQI classified the river water as satisfactory throughout the study period, microbiological indicators revealed subtle downstream deterioration.
The study highlights the importance of integrating microbiological parameters with index-based environmental assessment for realistic evaluation of river water quality and supports sustainable monitoring and management of industrial effluent–receiving river systems.