A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management, School of Enviromnent, Resources and Development.

Thesis (M.Sc.) - Asian Institute of Technology - Chulabhorn Research Institute - Mahidol University, 2006

BTEX is the abbreviation of four compounds; Benzene, Toluene, Ethylbenzene and Xylenes found in petroleum products. BTEX vapors are emitted into the atmosphere during its manufacture, transportation, use, and disposal every year. BTEX vapors are corrosive and toxic substances. BTEX compounds can also pose a drinking water hazard when they accumulate in ground water. Petroleum refinery industry can be a source of BTEX that contributes volatile organic compounds including BTEX through manufacture, transportation and disposal of petrochemicals. The study was conducted in a petroleum refinery industry. The objectives of this study were, to determine the level of BTEX inside and outside of the petroleum refinery industry and to assess possible risk from exposure to BTEX in these refinery industrial areas. The study was carried out taking air, water and soil samples from both inside and outside environments of the industry. Firstly, the measurement of BTEX inside the industry was conducted in different locations such as storage tank site, refinery plant site, stack, and wastewater treatment plant site. The highest level of BTEX (among other sites) was found in wastewater treatment plant (oily water pond location); benzene 178.43 ppb, toluene 342.07 ppb, ethylbenzene 68.96 ppb, xylenes 564.36 ppb. The level of benzene (359.78 ppb) in desalter unit of refinery plant was highest among other sites. In water, the level of BTEX was high in refinery plant site; benzene 44740 ppb, toluene 40435 ppb, ethylbenzene 2872.88 ppb, and xylenes 34165.09 ppb but the level of BTEX in polishing pond was below the detection limit. In soil, the levels of BTEX in most samples were below the detection limit. Only in crude oil storage tank location near the outlet point the soil contained low level of ethylbenzene, and xylenes. In the vicinity area of the industry, study was conducted in four sides such as canal 1 site, river site, canal 2 site and village site. In the river site, the level of BTEX was higher than other sites; benzene (15.16±1.68) ppb, toluene (26.3±2.53) ppb, ethylbenzene (3.89±0.39) ppb, xylenes (16.01±1.49) ppb. In water of the vicinity area of the industry, the level of benzene was (13.1±6.18) ppb and toluene was (5.18±1.75) ppb but the other compounds were below the detection limit in the river site. In the canal 1 site, the level of BTEX in water was below the detection limit and in canal 2 site, toluene (54.18 ppb) was found only at one point. The level of BTEX in soil samples that were collected from canal 2 site of the vicinity area of the industry was below the detection limit. The current study showed that the water and soil environments of the vicinity of the industry might not contaminated by BTEX by the industry but the air environment could be affected by the emission of BTEX from the industry as well as other factors such as road traffic.