Concurrent degradation of petroleum sludge and simultaneous rhamnolipid biosurfactant production: An aesthetic bioremediation approach

Abstract

Petroleum sludge is uncontrollably released in oil field and refineries which can lead to deleterious effect on the environment, as it consists of components of emerging concern such as PAHs, BTEX components, heavy metals, asphaltenes etc. In the present study, a novel bacterium Enterobacter cloacae AR-IASST (01), that have the potential to produce biosurfactant (surface tension reduced to 26.4 mN/m) was utilized to degrade petroleum sludge. A degradation of 86.9% was achieved after 5 days of culture incubation and biosurfactant production was also observed during the degradation process of sludge. In the GC-MS analysis, the peaks numbers reduce from 184 to 13 in the treated sample and complete degradation of PAHs present in the sludge was observed. The biosurfactant was characterized to be rhamnolipid in nature. The biosurfactant exhibited attractive emulsification towards several oils and an E24 of 100% was achieved against crude oil. The biosurfactant was found to be stable over a wide range of temperature, and salt concentration, although it showed sensitivity in high acidic condition. Furthermore, it was found that the bacterial treatment also led to the removal of heavy metals (Ni), zinc (Zn), lead (Pb), iron (Fe), chromium (Cr), copper (Cu), present in the sludge sample. Thus, the present study reveals that the novel bacterium is very potential and can be widely used for restoration of petroleum sludge contaminated sites in future.