Bioremediation of Surface Water Contaminated with Hydrocarbons in a Non-oil Producing Area

Aim: The study investigated the microbial degradation, kinetic and physicochemical studies of surface water contaminated with hydrocarbons of common interest (domestic purpose kerosene and diesel) by mixed culture of microorganism at ambient temperature (28-32°C).
Methodology: Four experimental set-ups were arranged of which two served as the control experiments. In this work, microbiological analyses were not carried out but organic supplement used have been reported by earlier investigators to contain heterotrophic bacteria, hydrocarbon degraders and fungi that are capable of utilizing hydrocarbons as carbon substrates. Bioremediation was principally monitored using reduction in TPH and the control experiments. Kinetic study and physicochemical analysis were also carried out.
Place and Duration of Study: Experiments were carried out in the Central Science Laboratory Complex, Taraba State University- Jalingo Nigeria. The study was carried out in a period of 4 months.
Study Design: In the first experiment, 37.5 g of the organic supplement that served as a source of nutrients and microorganisms was added to surface water simulated with diesel in a plastic container. In a second experiment, the diesel was replaced with domestic purpose kerosene (DPK). In the third and fourth experimental set-ups, the plastic containers had only DPK and diesel respectively without the organic amendment and served as controls. The four experimental set-ups were allowed to stand for 21 days for possible bioremediation.
Results: The results obtained for the diesel medium showed that the native microorganisms had positive response in utilizing hydrocarbon as diesel. The degradation followed a pseudo-first order kinetic with rate constant of 1×102 mg-1Lhr-1 and remediation efficiency of 59.14%. Only 23.1% of the physicochemical properties examined at the end of remediation were restored to their initial states and found to be within the W.H.O. standard. For the DPK medium, results showed that the microorganisms present had negative response in utilizing domestic purpose kerosene. At the end of the third week (504 hours) very low remediation efficiency of 39.62% was attained with a rate constant of 1×10-3 hr-1. The control experiments showed no appreciable reductions in TPH except for a small decrease by 1.5% for diesel and 2.0% for DKP, this was indicative that bioremediation had occurred in the diesel and DPK microcosms other than the controls.
Conclusion: Bioremediation of surface water contaminated with hydrocarbons using agricultural waste was found not to be very effective as a biological treatment option in a non-oil producing area. The physicochemical properties of the treated surface water samples were grossly impaired and therefore needed post treatments to make them safe for human consumption.