Remediation of Heavy Metals from Petroleum Sludge Impacted Soils using Organic Waste

Soil infectivity caused by heavy metals has increasingly received worldwide attention due to their high toxicity, thus its remediation is a priority. Petroleum sludge impacted soil samples around Warri Refinery and Petrochemical Company (WRPC), Delta State, Nigeria, were subjected to bioremediation of heavy metals (Cr, Cd, Pb, Ni, Cu, Co, Mn, Fe and Zn) using agro-waste from Moringa Oleifera seed (3:1) and monitored for contaminants reduction for 90 days at 30 days interval. Results obtained were compared with that of the control soil sample collected 8.5 km away from WRPC. At the end of 90 days, the percentage removal of all the heavy metals was between 65.00 % and 88.32 % which showed a successful bioremediation. Metal indicators like Enrichment Factor (EF) and Geoaccumulation Index (Igeo) were employed to assess the intensity of contamination. At the end of the study, EF revealed no to minor enrichment except for Cr and Pb. The computed Igeo further confirmed that all the studied sites were decontaminated except for Cr and Pb. When the portion of soil to biostimulant was varied (3:2) and observed for another 30 days, the EF and Igeo revealed that addition of higher mix ratio did not produce a corresponding increase in the removal of residual metals as expected. From the results, the applied organic fertilization treatment has proven to be effective to accelerate bioremediation of petroleum sludge impacted soils