Urbanization-driven water quality and microplastic pollution in a wastewater-dominated tributary: Evidence from the Kahn River, India

Abstract

Rapid urbanization has transformed many tributary rivers into wastewater-dominated systems, posing serious ecological and public health risks. This study presents the first integrated assessment of physicochemical characteristics, heavy metals, and microplastic contamination along the urban stretch of the Kahn River (Indore, India), a key tributary of the Kshipra River within the Ganga basin. Twenty sampling locations were selected to represent upstream reference conditions, urban discharge zones, major drain confluences, and downstream recovery stretches, enabling assessment of spatial variability influenced by anthropogenic inputs. Results revealed severe spatial deterioration in water quality characterized by high organic pollution, elevated dissolved and suspended solids, nutrient enrichment, and critically depleted dissolved oxygen in wastewater-affected stretches. Peak BOD concentrations reached 786 mg/L at locations receiving major drain discharges, while dissolved oxygen levels at several polluted sites declined below 1.5 mg/L, indicating localized zones of extreme ecological stress. Microplastics were found in all locations, with 475 particles/L recorded. Fibers were the most dominant, followed by fragments and films. Elevated microplastic concentrations were observed in midstream urban reaches receiving major wastewater discharges. Polymer identification by ATR-FTIR spectroscopy revealed polypropylene and polyethylene as the dominant microplastics. The findings provide critical insights for urban wastewater management and tributary restoration strategies. © 2026 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.