J. Int. Environmental Application & Science, Vol. 2 (3&4): 33-39 (2007) 33 Anaerobic removal of volatile organic compounds (VOC) from wastewater using methanol and ethylene glycol as co-substrate Celalettin Ozdemir 1 , Nejdet Sen 2 , Sukru Dursun 1 1 Selcuk University, Department of Environmental Engineering, 42031, Konya, Turkey 2 Selçuk University, Department of Chemistry, 42031, Konya-Turkey Accepted September 17, 2007 Abstract: Low concentration of chlorinated aliphatic compounds may be found in the wastewater, and has been accepted as toxic compounds for biological life. These volatile organic compounds (VOC) could be removed by different methods, but in this study, anaerobic decomposition was studied removal of VOC from the contaminated water. Aim of this work was treatment of VOC’s by up-flow anaerobic blanket reactor (UASB) and to determine effects of different co-substrates (methanol and ethylene glycol) on VOC’s removal at the anaerobic conditions. Furthermore, theoretical and practical investigation on the degradation of chlorinated hydrocarbons has importance in the water pollution. According to our results methanol was better co-substrate for VOC removal at anaerobic condition than ethylene glycol. Removal rates of DCM, CF, PCE and TCE in this investigation were approximately 65, 95, 100 and 90 % respectively with using co-substrate methanol. Key words: Volatile Organic Compounds (VOC), anaerobic treatment, methanol, ethylene glycol. Introduction Chlorine has been used for water disinfection and domestic disinfection which has very strong oxidation effect on many chemicals. Furthermore, this usage gives chlorine and chloramines with a number of substation reactions. Disinfectant formed from substation reaction produces too much chlorine aliphatic components (Johnson & Jensen, 1986).Volatile organic compounds as like dichloromethane (DCM), chloroform (CF) and trichloroethylene (TCE) were the important compounds used widespread in the many industry (Davidson et al., 1982).Toxic effects of VOC’s were found with the most of micro-organisms cultures tested. High concentrations of VOC’s have also toxic effect to kidneys, acute toxicity to respiration systems of human and animals. On the other hand, some scientific findings showed that low concentrations of VOC’s have genetic effect for human which, all known VOC’s have mutagenic, carcinogenic or teratogenic effects (Kokoszka & Flood, 1989; Graham et al., 1998). VOC’s have high ability of chemical oxidation, but have not at the aerobic treatment systems. For this reason anaerobic removal processes of these compounds were mostly preferred. In the present, hybrid processes produced from package column were used, which are rapid anaerobic systems, suitable for the fluctuation regimes. Low level of VOC’s could be removed by adsorption, incineration and bio-filtration methods, but these methods have some disadvantages with low removal efficiency or high operation cost. Freedman and Gossett (1989) and Distefano et al. (1991) produced the biomass at laboratory conditions in the anaerobic incubator. De Bruin et al. (1992) used mixed river sediments and granulated sludge for anaerobic incubation. Freedman and Gossett (1989) used methanol for electron donor and De Bruin et al. (1992) lactate. On the other hand, Hollinger et al., (1993) isolated a specific species from anaerobic mixed culture and showed that this species was electron receiver for PCE and TCE. Removal of PCE efficiency was about 99% in the mixed continuous flow reactor at the study of Vogel and McCarty (1985) but totally removal of vinyl chloride (VC) could never found. Fennell and