Earthworm-Assisted Bioremediation of Lead-Contaminated Municipal Sludge and Its Impact on Soil Health

Abstract

Lead contamination in soil and municipal sludge poses serious environmental and public health challenges, necessitating sustainable remediation strategies. This study investigated the potential of Eisenia fetida in the bioremediation of lead-contaminated municipal sludge and its subsequent application for soil improvement. Four experimental treatments (A, B, C, and D) were established using different proportions of municipal sludge and cow dung, including positive and negative controls. Key physicochemical parameters, including pH, electrical conductivity (EC), total organic carbon (TOC), total nitrogen (TN), available phosphorus (P), C:N ratio, and lead concentration (mg/kg), were analyzed over a 60-day vermicomposting period.The results revealed a significant reduction in lead concentration across all treatments, with the highest reduction observed in sludge-amended treatments. Vermicomposting also led to a decrease in pH (8.0 to 5.07–7.43), EC, TOC, and C:N ratio, indicating enhanced stabilization and maturity of the compost. In contrast, essential nutrients such as nitrogen and phosphorus increased significantly, improving the overall quality of the vermicompost.