Remediation of Petroleum - Sludge Contaminated Soil Enhanced with Organic Wastes (Sterilized Cow Dung and Plantain Peel Biochar)

Abstract

Petroleum sludge contamination remains a pressing challenge in oil-producing regions, posing risks to soil health, ecosystem and public safety due to the high concentrations of hydrocarbons such as Total Petroleum Hydrocarbons (TPH) and Polycyclic Aromatic Hydrocarbons (PAHs). This study investigated the remediation potential of two organic waste materials, Plantain Peel Biochar (PPB) and Sterilized Cow Dung (SCD), applied individually and in combination to stimulate indigenous microbial communities for enhanced biodegradation of the contaminated soil. A 120-day ex-situ treatment experiment was conducted to assess efficacy at varying dosage (100g and 200g) and monitored at 30-day intervals, with physicochemical parameters and microbial population dynamics used to evaluate remediation performance. The results showed that the combined treatment of PPB and SCD (200g) achieved 99.5% reduction in TPH (from 12,306.57mg/kg to 41.18 mg/kg) and 99.8% reduction in PAHs (from 443.04 mg/kg to 0.69 mg/kg), complying with Nigerian Upstream Petroleum Regulatory Commission (NUPRC) target values of 50mg/kg for TPH and 1mg/kg for PAHs. Metagenomic profiling of contaminated soil revealed a diverse microbial community such as Pseudomonas, Bacillus, Acinetobacter, and Rhodococcus as major hydrocarbon degraders. These findings demonstrate that the synergistic application of agro-waste-derived biochar and animal manure can significantly accelerate the degradation of petroleum pollutants, restore soil quality, and support sustainable waste management.