Assessment and Remediation of Two Most Polluted Urban Sites of Yamuna River, India: An Algal-Based Approach

Water pollution is a criticalw environmental issue affecting rivers and water bodies worldwide. River Yamuna particularly its 22 km stretch through Delhi, is one of the most polluted areas, often referred to as the "dead stretch," contributing 80% of the river's total pollution. The present study investigates the physicochemical parameters and heavy metal content in water samples from two highly polluted sites, Geeta Colony and Sonia Vihar, and compares them with pond water. It also evaluates the effectiveness of phycoremediation using various microalgae strains, including Scenedesmus sp., Chlorella sp., Chlorococcum sp., Klebsormidium sp., and a Blue-Green Algae (BGA) consortium (Phormidium sp., Spirulina sp., Cladophora sp. Gloeocapsa sp.). The results show significantly higher pollution and heavy metal levels in the Yamuna River compared to pond water. At Sonia Vihar, the highest recorded pH was 8.7 ± 1.04, BOD was 5.6 ± 0.24 mg/L, nitrate (NO₃⁻) and chloride (Cl⁻) levels as 966.56 ± 19.51 mg/L and 872.22 ± 17.35 mg/L respectively. Geeta Colony had the highest salinity at 967 ± 18.56 PPM, conductivity at 2000 ± 46.7 µs/cm, COD at 13.6 ± 3.21 mg/L, and phosphate (PO₄³⁻) at 21.86 ± 2.01 mg/L. Heavy metals like zinc (129.81 ± 5.4 µg/L at Sonia Vihar) and lead (39.96 ± 3.21 µg/L at Geeta Colony) were significantly higher. Phycoremediation showed substantial pollutant removal potential, with the Blue Green Algae (BGA) consortium achieving the highest removal efficiency: 91.01% of NO₃⁻, 78.9% of PO₄³⁻, 87.45% of sulfate (SO₄²⁻), and 80.44% of Cl⁻. Scenedesmus sp. effectively reduced biological oxygen demand (BOD) and chemical oxygen demand (COD), removing 83.08% of NO₃⁻, 69.03% of PO₄³⁻, 53.88% of SO₄²⁻, and 65.25% of Cl⁻. Chlorella sp. showed the highest Cl⁻ removal. The study underscores the severe pollution in the Yamuna River and the potential of algae-based remediation techniques to improve water quality.