Bioremediation of oil sludge using crude biosurfactants

A microbial consortium consisting of two isolates of Pseudomonas aeruginosa and one of rhodococcal from soil contaminated with oily sludge was able to degrade 90% of hydrocarbons in 6 weeks in liquid culture. The ability of the consortium to degrade sludge hydrocarbons was tested in two separate field trials. In addition, the effect of two additives (a nutrient mixture and a crude biosurfactant preparation) on the efficiency of the process was also assessed. The biosurfactant used was produced by a consortium member and was identified as being a mixture of 11 rhamnolipid congeners. The consortium degraded 91% of the hydrocarbon content of soil contaminated with 1% (v/v) Ratnagiri, India, crude oil sludge in 5 weeks. Separate use of any one additive along with the consortium brought about a 91–95% depletion of the hydrocarbon content in 4 weeks, with the crude biosurfactant preparation being a more effective enhancer of degradation. However, more than 98% hydrocarbon depletion was obtained when both additives were added together with the consortium. Similar results were observed with soil contaminated with sludge from IOCL, Faridabad, India. The data substantiate the use of a crude biosurfactant preparation for hydrocarbon remediation.