Assessment and phycoremediation of Yamuna river contaminants originating from the Najafgarh Drain, India, using LC-MS

Yamuna River supplies over 70% water to the Indian capital Delhi. It has become one of the most polluted rivers globally, impacting the daily lives of over 57 million people. This study analyzes the changes in the water quality of the Yamuna River resulting from the inflow of wastewater from the Najafgarh Drain (Sahibi River) and investigates the phycoremediation potential of microalga Scenedesmus sp. Water quality parameters were assessed at the points where drains meet with the river, revealing significant degradation in water quality. Results show a 12.33 ± 0.5% decrease in pH and substantial increase in salinity (137 ± 2.2%), conductivity (155.73 ± 2.7%), total dissolved solids (TDS) (135.27 ± 3.4%), chemical oxygen demand (COD) (113.33 ± 3.6%), biochemical oxygen demand (BOD) (150 ± 4.5%), and other chemical contaminants. Heavy metal analysis of Yamuna after merging with drain using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) revealed alarming concentrations, particularly of lead (Pb, 44.33 ± 0.03 µg/L) and mercury (Hg, 1.06 ± 0.02 µg/L), exceeding World Health Organization (WHO) guidelines. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis identified a wide range of pollutants, including herbicides, insecticides, fungicides, plasticizers, xenobiotic compounds, and persistent chemicals like perfluoropentanesulfonic acid (PFBS). Treatment with Scenedesmus sp. significantly reduced pollution in Najafgarh Drain water, with the highest reductions in manganese (Mn) at 95.86 ± 6.92% and cadmium (Cd) at 86.90 ± 2.97%. Scenedesmus sp. reduced magnesium (Mg) by 87.98 ± 7.84%, Pb by 80.12 ± 4.02% in Yamuna water, and effectively lowered nitrate and phosphate levels by 86.62 ± 8.6% and 65.53 ± 4.35%, respectively. The algae also contributed to significant reductions in salinity, conductivity, TDS, COD, and BOD. This study highlights the critical role of the Najafgarh Drain in polluting Yamuna and demonstrates the potential of Scenedesmus sp. for water quality improvement. A comprehensive approach that combines pollution source reduction and bioremediation using Scenedesmus is essential for restoring and enhancing Yamuna's water quality.