Thesis (M.Sc.)--Chulalongkorn University, 2007

Car washing activity has been generating large amount of oil-contaminated wastewater from petrol station that will be released to the environment. Bioremediation is alternative method used to treat oil-contaminated wastewater due to its less expense and public acceptance. In this work, biodegradation potential of oil-contaminated wastewater was investigated using lubricating oil (PTT V-120) as a model contaminant. In order to use in microcosms, 2 oil-degrading bacteria, Tr1 and R2, isolated from oil-contaminated wastewater. Both isolates could be classified as Acinetobacter sp. based on 16S rDNA sequence analysis. Oil biodegradation activity of each isolate was determined as well. As a result, the strain R2 showed the higher degradation activity of 78.01% removed oil in culture medium after 18 hrs compared to abiotic control (initial oil was 200 ppm in emulsion form). In addition, alkM gene which involved in oil degradation could be detected in strain R2. For microcosms experiment, wastewater collected from petrol station in Bangkok was used. Biostimulation, bioaugmentation I, bioaugmentation II and natural attenuation treatment were conducted with 50 ml of wastewater with initial oil concentration of 39.80 mg/L and spiked with lubricating oil to make the final concentration of 5%(v/v) in 250 ml flasks. Isolate R2 was added to bioaugmentation I and II (approx. 10⁷ CFU/ml). Nitrogen and phosphorus were added to give final C:N:P equal to 100:5:1 in both biostimulations and bioaugmentation II. After 12-day cultivation, bioaugmentation II showed the highest degradation efficiency with the value of remaining oil at 14.47 %. This might be due to the presence of both exogenous degrader and appropriate amount of necessary nutrient provided. PCR-DGGE exhibited slightly change in microcosms and strain R2 was detected in treatments that strain was introduced. Moreover, alkM gene was detected in all treatments except abiotic control. These findings indicate that there was bioremediation potential of wastewater from petrol station.