Petrol hidrokarbonlarının biyoremediasyonunun incelenmesi
Özet
Monohyrocarbons such as benzene, toluene, ethylbenzene and three isomers xylene (BTEX) are commen groundwather pollutants associated with petroleum product release. BTEX are of particular concern because they are confirmed or suspected carcinogens, even at very low concentrations. In addition, these compounds are classified as environmental priority pollutants by the EPA. Therefore, there is considarable interest in exploiting natural degradative processes (biodegradation) to remove these priority pollutants from contaminated sites (bioremediation). In this study, the biodegradation of BTEX compounds (benzene, toluene, ethylbenzene and xylene) which is monoaraomatic hydrocarbon by a mixed culture obtained from the formation water which was produced from the petroleum wells of Turkey Petroleum Corporation (TPAO) in Adıyaman region (south-eastern Turkey), was investigated. After the mixed culture was grown on brain heart infusion enriched medium at 30°C, it was used for the biodegradation experiments. The first aim of this study was to determine to biodegradation of BTEX compounds with non adapted mixed culture. In the experiments, each of the BTEX compounds was added at a concentration of 20 mg/L to the mineral media. BTEX concentrations in the batch reactors were determined by headspace analysis. As a result, it was found that the mixed culture degradated all BTEX compounds indivually and in a mixture form. Toluen was the fastest biodegradated as a single compenent and ethylbenzene was the fastest biodegradated in a mixture form. Mixed culture was adapted to toluene in order to performing biodegradation in a shorter time. Biodegradation experiments of BTEX was studied with mMixed culture was adapted to toluene in order to performing biodegradation in a shorter time. Biodegradation experiments of BTEX was studied with mixed culture adapted two times to mineral media containing toluene. As result, it was found that the biodegradation rate of BTEX compounds induvidually was increased with toluene adapted mixed culture. Especially, degradation rate of benzene was increased more than that of the other BTEX compounds and it was completely biodegradated. After the biodegradation experiments of BTEX, the effect of the microorganisms dry cell concentration on benzene and toluene biodegradation were investigated. It was found that, biodegradation rate increased when dry cell concentration was increased and the highest rate was obtained at 2.34 g/L of dry cell concentration. Experiments were also performed in order to determine the effect of different initial concentrations on the benzene and toluene biodegradation rate. As a conclusion, it was determined that biodegradation was inhibited with highest substrat concentrations for benzene and toluene. In addition, the effect of hydrogen peroxide with 70 mg/L initial concentration on biodegradation was investigated. It was found that, hydrogen peroxide decreased biodegradation of all BTEX compounds. Finally the substrat interactions were investigated and BTEX was added to mineral media as a binary and four mixtures with was 10 mg/L of each BTEX compounds. As a result, when a BTEX compound was present with one of the other BTEX compound, their biodegradation rate were effected Especially, toluene increased biodegradation rate of the other BTEX compounds. On the other hand, xylene decreased degradation rate of the others. 2001, 92 pages Key words: Biodegradation, BTEX, aromatic hydrocarbon, pollutant, mixed culture. IV