BIODEGRADABILITY AND TOXICITY STUDIES OF BTEX CONTAINING WASTEWATER USING ANAROBIC BIOMASS

摘要

The BTEX compounds (Benzene, Toluene, Ethylbenzene and Xylene) are the mostrnsoluble components of gasoline and are common ground water contaminants. Thesernhydrocarbons are also used as raw materials for the manufacture of pesticides,rnplastics, and synthetic fibers. The objective of this research was to investigate therntoxic effects and biotransformation of BTEX compounds in acclimated andrnnonacclimated methanogenic cultures. The microbial acclimation potential of fiverndifferent anaerobic cultures, namely methanogenic enrichment culture (MEC),rnbenzene-acclimated methanogenic enrichment culture (BAMEC), toluene-acclimatedrnmethanogenic enrichment culture (TAMEC), xylene-acclimated methanogenicrnenrichment culture (XAMEC), and ethylbenzene-acclimated methanogenicrnenrichment culture (EAMEC), were examined. The integrated Monod equation wasrnused to determine the methanogenic transformation rate coefficients from the sourcernreactor. The kinetic coefficients in the source reactor were k = 0.87 day-1 and Ks =rn90 mg/l. The results with batch culture assays indicated that BTEX compounds wererntoxic to anaerobic biomass. However, the methanogens showed the potential forrnrecovery after a certain period of time, with BTEX concentration between 50-2000rnmg/l. The SMA (Specific Methanogenic Activity) value of MEC and XAMEC werernrelated to the concentration of the BTEX compound, but the values for TAMEC,rnBAMEC, and EAMEC did not appear to be related to the concentration of BTEXrncompounds. For MEC (nonacclimated culture), benzene concentration above 500rnmg/l reduced the gas production by nearly 50%; moderate inhibition was found withrn500 mg/l toluene (30% gas reduction); 90% gas reduction was observed with 500 mg/lrnxylene; no gas production was observed with 500 mg/l ethylbenzene. Higher tolerancernwas observed with acclimated methanogenic cultures. Xylene and ethylbenzenernexhibited the strongest inhibition, but at higher concentrations with acclimatedrncultures. The results indicated that anaerobic biomass from digesters of municipalrnwastewater treatment processes could be used for treatment of wastewater containingrnBTEX compounds, with controlled application of microbial acclimation.