Effect of Linear Alkylbenzene Sulphonate on Bacterial Population and Hydrocarbon Degradation in Crude-oil Polluted Soil

Abstract

Aim: The aim of this study was to determine the concentrations of linear alkyl benzene sulphonate (LAS) that are non-toxic to bacteria in crude-oil polluted soil, and also effective in enhancing biodegradation of the hydrocarbons. Methodology: Seven concentrations (4, 8, 16, 32, 64, 128, and 256 mg/L) of LAS were prepared, and 50 ml of each were added to 500 g soils artificially polluted with crude-oil. Based on the quantity of soil used and the volume of LAS solutions added, the in-soil LAS concentrations were calculated to be 0.4 – 25.6 mg/Kg. A control was also set up were 50 ml sterile distilled water was used. The setups were maintained for seven days; on day 1, 3, and 7, the population of total heterotrophic bacteria (THB) were determined. Total hydrocarbon concentrations (THC) were determined on day 1 and 7. Results: The results obtained showed that the extent of hydrocarbon degradation increased with increase in LAS concentration from 35.9 to 61.4%, with the control having 10.9%. The THB population strength in all the setups increased from 106 to 107; in the setup treated with the highest concentration of LAS, the increase was from 106 to 108. Bacteria isolated from the setups included Bacillus, Micrococcus, Acinetobacter, Staphylococcus, and Pseudomonas sp, which are known hydrocarbon degraders. Conclusion: LAS concentration of up to 25.6 mg/Kg can lead to significant hydrocarbon biodegradation in crude-oil polluted soil with no adverse effect on bacteria present in the soil.