Bioremediation of Artisanal Refinery Contaminated Soils Enhanced with Biostimulant
D. Oluwabunmi Olafusi
Integrated Institute of Environment and Development, (IIED) Federal University of Petroleum Resources Effurun, Delta State, PMB 1221, Nigeria.
Tudararo-Aherobo, Laurelta
Department of Microbiology, Federal University of Petroleum Resources, P.M.B. 1221, Effurun, Delta State, Nigeria.
F. B. Okorhi-Damisa *
Department of Microbiology, Federal University of Petroleum Resources, P.M.B. 1221, Effurun, Delta State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background: Artisanal petroleum refining contaminates soils and may constrain their ecological recovery.
Aim: This study assessed the effectiveness of composted agricultural waste and NPK fertiliser in reducing hydrocarbon contamination in soils affected by artisanal refining activities in Obi-Ayagha community, Delta State, Nigeria.
Study Design: An experimental study was conducted to evaluate the effects of organic and inorganic amendments on the remediation of hydrocarbon-contaminated soils, using untreated soil as the control.
Place and Duration of Study: The study was conducted in Obi Ayagha community, Ughelli South Local Government Area, Delta State, Nigeria, over a period of nine weeks (63 days).
Methodology: Contaminated soil samples were treated with composted agricultural waste and NPK fertiliser at different amendment levels, while untreated soil served as the control. Soil pH, moisture content, electrical conductivity (EC), nitrate concentration, nutrient composition, and microbial populations were monitored at three-week intervals. Total petroleum hydrocarbon (TPH) concentrations were also measured throughout the study to determine the effectiveness of the treatments.
Results: The amended soils showed greater reductions in TPH concentrations than the untreated control. The 25% contaminated soil plus compost treatment recorded the lowest final TPH concentration of 128.10 ± 10.09 mg/kg, while the 25% contaminated soil plus NPK treatment recorded 182.00 ± 25.06 mg/kg at Week 9. Other amended treatments also showed considerable reductions, whereas TPH concentrations remained relatively high in the control. Soil pH gradually increased towards neutral or slightly alkaline conditions, while electrical conductivity rose sharply by Week 3. Nitrate concentrations generally increased across treatments, suggesting changes in nutrient availability that may have supported microbial activity.
Conclusion: The findings show that composted agricultural waste and NPK fertiliser can improve the remediation of hydrocarbon-contaminated soils, with compost alone producing the best result among the reported treatments. This approach offers a potentially affordable and environmentally friendly means of restoring contaminated land. Further research is needed to assess its long-term effectiveness under field conditions.
Keywords: Bioremediation, hydrocarbon contamination, organic amendments, total petroleum hydrocarbons (TPH)