Assessment of Industrial Effluent Impacts on the Vaigai River (Madurai, India) Using Physicochemical Indicators, Water Quality Index, and Bench-Scale Carbon Adsorption

Abstract

Industrial wastewater discharges severely alter receiving surface water ecosystems,
creating localized zones of extreme ecological degradation. This study evaluated
spatial variations in physicochemical quality along an industrially influenced stretch
of the Vaigai River in Madurai District, Tamil Nadu, India. Five strategic sites
representing an upstream control location and zones receiving tyre-manufacturing
and powder-coating effluents were monitored for pH, turbidity, total dissolved solids
(TDS), total hardness, biochemical oxygen demand (BOD5), and chemical oxygen
demand (COD). While pH remained near-neutral (7.2–7.7), industrial outfalls
induced severe spikes in turbidity (up to 221 NTU), BOD5 (up to 36 mg/L), and COD
(up to 120 mg/L). Application of the weighted arithmetic Water Quality Index (WQI)
yielded site-specific scores ranging from 1,137.70 to 13,409.18, categorizing all sites
as unsuitable for human consumption without multi-stage treatment. Turbidity and
organic load accounted for over 96% of the aggregated index severity. Bench-scale
activated carbon adsorption demonstrated 100% apparent removal of COD (reducing
levels below detection limits) but only a 9.25% reduction in TDS (335 to 304 mg/L).
These results demonstrate that while adsorption effectively mitigates organic
pollutants, comprehensive river remediation requires integrated treatment trains
combining adsorption with membrane processes to reduce dissolved inorganic salts.