ABSTRACT
This study was carried out to investigate the microbial load and degradability of petroleum hydrocarbons in soil contaminated with petroleum hydrocarbons, treated with cassava mill effluent (CME). Ten buckets were filled with 5kg of uncontaminated soil labeled CG, TN, TM, TW, TD, CP, PTN, PTM, PTW, and PTD. CG served as the general control, being uncontaminated and untreated. TN to TD were treated at different time intervals (once, monthly, weekly and daily), acting as treatment controls. CP to PTD were polluted with 500ml of waste engine oil, with CP being pollution control. PTN to PTD were treated alongside the treatment controls for three months. At the end of the treatment, microbial (bacterial and fungal) load analysis was conducted to assess the impact of CME on indigenous microbes, while petroleum hydrocarbon degradation was assessed using GC FID. Results indicated positive growth in TN compared to CG, while excessive treatment in TD and TW reduced microbial load. Polluted samples showed increased microbial load compared to treated sample as TN (8.1X104 cfu/g) increased in PTN (9.1X104 cfu/g) which experienced similar treatment. Polluted samples also showed varied increase from PTN (9.1x104 cfu/g) – PTD (4.6x104 cfu/g) compared to untreated CP(4.8x104 cfu/g). This increase was also observed in the fungi microbial load. Overall, CME promoted the growth of indigenous microbes and decreased total petroleum hydrocarbon levels as CP (5673.7 µg/kg) decreases across all treatment range PTN (5565.7 µg/kg), PTM (2299 µg/kg), PTW (3629.3 µg/kg), PTD (2596.8 µg/kg), suggesting its potential as a bioremediation agent.
