Comparative Study of Degradation Kinetics of Crude oil Contaminated Mangrove and Clay Soils

Abstract

A comparative study of the potential of bioremediation in the removal of hydrocarbon contaminants from a mangrove and clay soils, powered by indigenous microbes as bioremediators was evaluated and compared in a 35-days laboratory scale experiment by fitting the bioremediation data obtained for each soil to a first order kinetic model. The research aim was a comparative evaluation of the rates of degradation of crude oil contaminant in mangrove and clay soils when biostimulated with inorganic fertilizer. The experimental pots containing mangrove and clay soils were contaminated with the 7% w/w of Bonny light crude oil and biostimulated with 100g inorganic fertilizer (NPK) per kilogram of soil and was maintained at a pH of 6.5 and 50% of the soil’s
Water Holding Capacity (WHC). Remediation was done in the open laboratory for 35days under atmospheric conditions. The percentage decrease in Total Petroleum Hydrocarbon (TPH) was the response parameter and the crude contaminated soils showed a decrease in TPH over time. The soil nutrient, moisture content and soil pH were the important soil factors known to affect the rate of contaminants degradation were considered. Results show a regular trend in pH and moisture changes in the soils. The degradation rate of crude oil contaminant in each soil varied, but all soils were able to achieve over 70% crude oil removal within 21days of experimentation. There seems to be a correlation between soil texture and the rate of biodegradation. The results also showed that first-order kinetics could be used describe biodegradation of crude oil in soil and kinetic constants for the two soils were 0.0511/day for the mangrove soil an 0.0337/day for the clay soil. The total petroleum hydrocarbon in the experimental pots decreased to 1.9% and 0.93% in the clayey and mangrove soils respectively.