COMPARATIVE EVALUATION OF STERILE AND UNSTERILIZED COW DUNG AS NUTRIENT SOURCE IN THE BIOREMEDIATION OF HYDROCARBON CONTAMINATED SOIL.

This study evaluates the effectiveness of sterile and unsterilized cow dung as a nutrient source in the amendment of soil contaminated with petroleum sludge. Petroleum sludge is a complex and hazardous semi-solid waste generated from crude oil exploration, transportation, and refining processes. It is characterized by high concentrations of recalcitrant total petroleum hydrocarbons (TPH), heavy metals, and other pollutants that pose significant risks to soil ecosystems and human health. The methodology involved amending contaminated soil samples with both sterile and fresh cow dung at a standardized ratio, alongside an unamended control, while monitoring key parameters over a 28-day period. The results demonstrated a notable difference in treatment performance. The unsterilized cow dung treatment achieved a TPH reduction of 92%, accompanied by improved soil conditions and a significant increase in hydrocarbon-degrading bacterial populations. In contrast, the sterilized cow dung amendment, which provided nutrients but lacked viable microorganisms, resulted in a TPH reduction of 37% and a comparatively modest increase in microbial activity. These findings indicate that the remediation process cannot be attributed 100% to nutrient-driven biostimulation alone, as the presence of active microbial communities in unsterilized cow dung significantly enhances hydrocarbon degradation. However, nutrient availability still plays an important supportive role, and the effectiveness of the process may also be influenced by environmental conditions and the potential inhibitory effects of pollutants on microbial populations. The study concludes that fresh cow dung has strong potential as a sustainable and cost-effective amendment for the bioremediation of petroleum sludge-contaminated soils, with both bioaugmentation and biostimulation contributing to the overall remediation process.