Oil spillage and contaminated effluent are inevitable consequences of oil exploration, production and refining. As a result, the problem of pollution during production and transportation of refinery product had been a major issue during the last few decades. Organic compounds such as alkanes, cycloalkanes, aromatic hydrocarbons, or more complicated chemicals such as asphaltene are the main components of refinery effluents. Among these compounds, mono-aromatic hydrocarbons such as benzene, toluene and phenol are found in huge amounts [4]. These aromatic compound are highly toxic in nature and cause damage to the aquatic biota. Even for human lives, these compounds can cause liver and kidney damage, cardiac toxicity including weak pulse, cardiac depression and reduced blood pressure [1].
The microbiological degradation is a potential biological treatment technique which is based on the ability of microorganism (generally bacteria) to convert organic pollutant into water, carbon dioxide and biomass under aerobic or anaerobic condition. It appears to be the most environment friendly method of removal of oil pollutant, as no undesirable by-products or secondary emissions, such as chemical scrubbing or thermal waste gas treatment, are generated [2, 3]. Aerobic treatment is easier to implement on site than anaerobic process due to its less number of constraints on design parameters.
Thus, our present work is focused on, (a) to isolate and identify a microorganism which is capable of degrading refinery wastewater more efficiently than other reported microorganism [2], (b) to find whether the degradation process produces environment friendly byproducts, (c) to verify whether there are any kind of toxicity present in those byproducts and if yes, whether that can be controlled or manipulated by changing the degradation pathway or by any other means.
In our recent laboratory scale studies, we have isolated O. intermedium from the activated sludge of petroleum refinery. It has been observed that this organism is capable of degrading waste from the refineries and it has the ability to grow on and utilize some toxic compounds like phenol as sole carbon and energy source. The optimum temperature and pH required for maximum degradation are 37 oC and 7.0 respectively at 120 rpm. The microbe is capable of degrading high concentration of phenol (up to 2000mg/L) under aerobic condition. Microbial growth kinetic models shows the best fit for Haldane model with R2=0.9978.
References
1. A., Nuhoglu, B., Yalcin, , Modeling of phenol removal in a batch reactor. Process Biochemistry) 40, 1233-1239, (2005)
2. N. Khoury, W. Dott, P. Kampfer, Anaerobic degradation of phenol in batch and continuous cultures by a denitrifying bacterial consortium. Appl. Microbiol. Biotechnol. 37, 524-528, (1992)
3. Schaefer, M., Juliane, F., The influence of earthworms and organic additives on the biodegradation of oil contaminated soil, Applied soil ecology, 36, 53-62, (2007)
4. Thangaraj, K., Kapley, A., Purohit, H.J., Characterization of diverse Acinetobacter isolates for utilization of multiple aromatic compounds, Bioresource Tech., 99, 2488–2494, (2008)