With the rapid development of the petrochemical industry in Taiwan significant amount of nitrogenous organic wastewater is generated. Some of this wastewater contains volatile residual monomers, such as the Acrylonitrile-Butadiene-Styrene (ABS) manufacturing wastewater. Because of the high volatility of acrylonitrile monomer, this chemical partly will be removed from the aeration system by the air stripping effect. In this paper an empirical model was developed for evaluating the TOC removal by air stripping and biodegradation when the wastewater was treated in an aerobic submerged membrane bioreactor (ASMBR). The results showed that the removal of BOD from ABS wastewater by air stripping was in a range from 4�X2O %. These results also showed that the estimation of contribution of air stripping and biodegradation in the TOC removal in the MBR is very important in the optimum design of the MBR for the ABS wastewater.