Bioremediation of petroleum hydrocarbons contaminated wastewater for baiji thermal power station in Iraq

3 selected yeasts - Yarrowia lipolytica NCAIM Y00591, Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019 and 2 bacteria isolated from Baiji thermal power plant wastewaters - Stenotrophomonas maltophilia and Acromobacter sp., were used in order to investigate the microorganisms' feasibility for petroleum hydrocarbons biodegradation that contaminated wastewater for Baiji Thermal Power Station. The medium is prepared by adding 1 g of petroleum oil and inoculating 4 Mc Farland density of yeast separately while the wastewater is directly used for bacteria. The culture medium was incubated at 30 ºC with shaking speed of 150 rpm/min for two weeks; the bacteria and the yeast were counted once every two days for monitoring and recording the growth of the microorganisms. The experiment was terminated at the end of the second week and the samples were prepared for Gas chromatography analysis. The degraded hydrocarbon compounds were identified by GC-MS (Gas chromatography and mass spectrometry) analysis. The results showed that 80.95 % of the hydrocarbon compounds degraded by mixed indigenous bacteria, 66.6 % by Y. lipolytica, 47.6 % by C. parapsilosis and 38.1 % by C. albicans. This indicates that the bacteria have a better ability to use hydrocarbons than yeasts, and Y. lipolytica is the best among the three yeasts. So the removal of wastewater pollutants for Baiji power plant is possible by creating favorable conditions for the bacteria to carry out the biodegradation.