Biochar from invasive weeds for enhanced removal of organic pollutants and pathogens from municipal wastewater

Agro-waste management and waste water treatment is one of the major global issues. The present study investigated biochars derived from invasive weeds Calotropis gigantea, Crotalaria burhia, and Tephrosia purpurea for municipal wastewater treatment in Jodhpur, India. Biochars produced at 450 °C yielded 31% (C. gigantea), 33.23% (C. burhia), and 30.18% (T. purpurea). Untreated wastewater showed high pollutant loads, including COD (369 mg/L), BOD (58 mg/L), turbidity (66 NTU), color (175 Hazen), SAR (13.07), and coliform count (177.5 ± 4.86 MPN/100 mL). Treatment with biochar improved water quality within 4 h of residence time. C. burhia exhibited the highest efficiency which reduced COD and BOD by 89% and 88.27%, respectively, followed by C. gigantea (65.85%, 63.41%) and T. purpurea (66.39%, 60.34%). Dissolved oxygen increased by 51.35% with C. burhia, 37.83% with C. gigantea, and 32.43% with T. purpurea. Turbidity and color removal efficiencies were highest for C. gigantea (77.71%) and C. burhia (75.43%), while SAR declined by 38.79%, 29.84%, and 25.78%, respectively, enhancing irrigation suitability. Total coliform counts decreased by up to 73.33% with C. burhia. Overall, invasive weed-derived biochars with high fixed carbon (64-81%) proved sustainable, low-cost alternatives for wastewater remediation while addressing invasive species management.