BTEX (benzene, toluene, ethylbenzene and xylenes) are the most frequently encountered subsurface contaminants among the various petroleum hydrocarbons. Soils and groundwater contaminated with BTEX may pose serious threat to human health and environment. Spreading of these compounds in unsaturated zone as liquid or gas fasecausees groundwater and air contaminant. The main aim of this study is the biodegradation of BTEX contaminated unsaturated zone in batch and column experiment. A new strain (Pseudomonas sp. TR03) degrading BTEX compounds was isolated from oil contaminated groundwater in Tehran Oil Refinery site. A series of batch experiments was performed to investigate the BTEX degradation ability of the new strain using single and mixed substrate. We first used the response surface methodology to optimize the effective parameters (e.g., pH, temperature, humidity, and inorganic nutrients as percent of BTEX concentration) on the degradation of BTEX compounds. Unsaturated soil column was installed horizontally based on optimized effective parameters. Biodegradation of toluene in vapor fase with considering diffusion as a dominnent transport was evaluated.Results showed that the strain is able to completely degrade benzene, toluene, and ethylbenzene in the single substrate batch experiments while m-xylene remains non-degradable if it is an only carbon source in the ambient. Results showed that all BTEX compounds can be degraded within the mixed substrate batch experiments. Concentration of toluene in column decreased exponentially through the column length. Also, the concentration of toluene in sampling ports was decreased exponentially with time until 14ht day. This study shows that establishing a permeable reactive bio-barrier in unsaturated zone can degrad volatile organic carbon and prevent spreading the pollution through soil and air. In this study a computer code was developed to simulate multiphase groundwater contamination.

Achievement

Bacteria isolation, identification and screening from Tehran refinery area

Obtaining the bioremediation technical knowledge for oil pollution (BTEX) in the groundwater