Crude oil contamination of soils remains a persistent environmental challenge in oil-producing regions, particularly in the Niger Delta of Nigeria, where artisanal refining and pipeline failures are prevalent. This study evaluated and compared the effectiveness of phytoremediation and amendment-based strategies using water hyacinth–compost combinations and Oclansorb in restoring crude oil–contaminated soils from Obi-Ayagha Community, Ughelli South Local Government Area, Delta State. A repeated-measures experimental design was employed over a nine-week remediation period, involving six treatment regimes (three combination treatments and three Oclansorb-only treatments) alongside an uncontaminated control. Key parameters assessed included total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), pH, total organic carbon (TOC), nutrient levels, and microbial populations, particularly hydrocarbon-degrading bacteria (HDB).Results revealed substantial reductions in TPH across all amended treatments, with the 100% compost–water hyacinth combination achieving the highest reduction (94.01%) by Week 9. PAHs were completely eliminated (100% reduction) in all treated samples within three weeks, demonstrating rapid remediation of persistent aromatic compounds. Soil pH shifted toward neutral to mildly alkaline conditions, enhancing microbial activity and soil health. TOC levels declined significantly, indicating effective mineralization of hydrocarbon carbon. Increases in hydrocarbon-degrading bacterial populations further confirmed biologically driven degradation processes. Overall, combination treatments consistently outperformed Oclansorb-only applications, suggesting synergistic benefits of organic amendments and phytoremediation. The findings underscore the potential of integrated, low-cost, and environmentally sustainable remediation strategies for restoring oil-impacted soils in resource-limited settings of the Niger Delta.
