Study of membrane bioreactor system in biological separation of volatile organic components from petrochemical wastewater

In this study, separation of styrene and ethyl benzene from petrochemical wastewater using membrane bioreactor was investigated. The results showed that the removal efficiency of chemical oxygen demand (COD), styrene and ethyl benzene in the hydraulic retention time (HRT) of 20 hours were 98, 99 and 99%, respectively. With reducing HRT to 15 hours, COD removal efficiency did not change and styrene and ethyl benzene removal efficiency through stripping decreased about 0.4%. On the other hand, it was indicated that existing ethylbenzene could have a negative effect on styrene removal. Also, results show that due to decreasing sludge particle size and increasing soluble microbial product (SMP), transmembrane pressure (TMP) changes rate increased at 15 hour compared to 20 hours. Further, changes of EPS for mixed liquor showed that EPS concentration decreased with decreasing HRT.