Bioremediation of Three Heavy Metals (Cu²⁺, Ni²⁺, and Cr⁶⁺) by Riverine Bacterial Isolates from a Saharanpur-Adjacent Stretch of the Hindon River, India

Abstract

Heavy metal contamination in river systems near industrial belts is a persistent environmental and public health concern. This study evaluated the bioremediation potential of indigenous bacterial isolates recovered from river water and sediment collected near Saharanpur (Western Uttar Pradesh, India). A total of 18 morphologically distinct isolates were obtained on nutrient agar and screened for resistance and remediation capacity against copper (Cu²⁺), nickel (Ni²⁺), and hexavalent chromium (Cr⁶⁺). Three promising isolates (HWR-3, HWS-7, and HSD-2) exhibited high tolerance and removal efficiency and were identified by 16S rRNA sequencing as Pseudomonas putida, Bacillus subtilis, and Stenotrophomonas maltophilia, respectively. Batch biosorption/bioreduction experiments demonstrated significant reduction of metal concentrations under optimized conditions (pH 7–8, 30–37 °C, 24–72 h). The best-performing isolate achieved removal efficiencies of 78–92% for Cu²⁺, 65–88% for Ni²⁺, and 70–90% for Cr⁶⁺ depending on initial concentration (25–100 mg/L). FTIR analysis indicated involvement of hydroxyl, carboxyl, phosphate, and amide functional groups in metal binding. The study supports the use of river-native bacteria as eco-friendly candidates for treating metal-contaminated aquatic environments near Saharanpur.