Seasonal Assessment of Physico-Chemical Water Quality of the Kharun River and Constructed-Wetland Treatment of Gray Water in Chhattisgarh, India

Abstract

Sustainable approaches for the treatment of river water pollution and domestic wastewater should have efficient pollutant removal and low energy and operational requirements. The present study assesses the seasonal variation in the physico-chemical quality of the Kharun River and explores the possible complementary roles of natural biofilm formation and phytoremediation in improving water quality. In summer, rainy and winter seasons, six parameters namely temperature, turbidity, pH, BOD₅, COD and Fe were evaluated with 49 observations per season. Significant seasonal variations were observed for BOD₅, COD, pH, turbidity and temperature, but Fe did not show any significant seasonal variation. The BOD5 mean concentrations were 17.41, 16.20 and 16.67 mg/L and the concentrations of COD were 18.55, 17.60 and 17.68 mg/L in summer, rainy and winter respectively. Turbidity showed marked seasonal variation with means of 38.67, 7.43 and 15.82 NTU. The results suggest that natural biofilms may have a direct role in organic matter degradation by microbial activity and that vegetation and associated rhizospheres serve complementary functions, including particle retention, sediment stabilization, nutrient uptake and pollutant immobilization. Moreover, the treatment potential was evaluated by a proposed constructed wetland for gray water treatment at Atora village, Durg district, Chhattisgarh. Each parameter was tested for ten inlet and outlet observations. The turbidity, BOD₅, COD and Fe decreased from 72.50 to 21.27 NTU (70.66 %), 44.00 to 13.24 mg/L (69.91 %), 105.94 to 41.59 mg/L (60.74 %) and 0.214 to 0.089 mg/L (58.41 %), respectively. Temperature was comparatively stable and pH showed a slight increase from 7.21 to 7.31. These results demonstrate the potential of constructed wetlands to enhance gray-water quality through integrated physical, microbial and plant-mediated processes. In general, biofilm formation and phytoremediation should be regarded as complementary mechanisms of treatment. But seasonal observations alone do not allow us to quantify the removal contribution of individual species; controlled or paired inlet–outlet experiments are necessary to assess mechanisms.