A pilot study on the biodegradation of hydrocarbon and its kinetics on kerosene simulated soil

A pilot study was carried out on soil from the Niger Delta region of Southern Nigeria, contaminated with kerosene by 10% artificial simulation to determine the attendant effect associated with the soil physicochemical properties and microbiological composition. Biodegradation of the contaminant using soil microbes biostimulated with a blend of animal wastes and the kinetics of such process was also investigated. Soil parameters such as pH, electrical conductivity, total organic carbon and matter, total nitrogen and phosphorus, texture, heavy metals(Cd, Pb, Ni, V and Cr) and total petroleum hydrocarbon (TPH) were characterized using standard analytical methods. Trend in growth phase of soil heterotrophic and hydrocarbon utilizing microbes were investigated. Kerosene contamination was seen to affect certain soil properties as a reduction in pH, conductivity, total phosphorus and heterotrophic microbial population was observed, while an increase in the concentration of heavy metals such as Nickel, Vanadium and Chromium were recorded. Other soil properties were unaffected by the impact of kerosene. The rate of microbial degradation was found to be dependent on pH and nutrient source. Effective degradation and increased microbial growth occurred between between pH 6.0 and 9.5 but recorded reduced microbial growth and biodegradation rate at much higher pH, thereby defining a suitable pH condition for the process. The method was found to be very effective and efficient as an impressive 82.24% remediation efficiency was achieved on the sixth week. Kinetic evaluation of the biodegradation process shows that the degradation pattern followed first order with a rate constant of 0.034dai^l. A determination of the biodegradation isotherm Kd gave negative value of unity showing the opposing trend between the concentration of the contaminant in the soil (Cs) and the concentration degraded by the microbes (Cd); which explains that as Cs is decreasing with time, Cd is increasing.