Evaluation of a submerged membrane bioreactor (SMBR) coupled with chlorine disinfection for municipal wastewater treatment and reuse

In this study, municipal wastewater was treated by a SMBR system and further disinfected with chlorine to produce reclaimed water. The primary objective was to examine the water quality with a focus on trihalomethanes (THMs). As disinfection conditions are important aspects in controlling the formation of THMs, influences of chlorine dose and contact time on THM formation and speciation were also investigated. High quality reclaimed water was generated though the SMBR system with regard to five-day biological oxygen demand (BOD5), suspend solid (SS) and turbidity. However the concentration of total trihalomethanes (TTHM) in the chlorinated SMBR effluent was up to 160 μg/L, demonstrating that the SMBR was insufficient in the removal of THM precursors. TTHM levels increased with chlorine dose and contact time. As chlorine dose increased, the yields of trichloromethane (CHCl3) and bromodichloromethane (CHBrCl2) increased, whereas both tribromomethane (CHBr3) and dibromochloromethane (CHBr2Cl) decreased due to the rise of Cl2/Br− ratio. In order to reduce health risks of reclaimed water, efficient removal of disinfection by-product precursor and opportune chlorine disinfection conditions are recommended.

► SMBR with post-chlorination was used for municipal wastewater reuse.
► Evaluation of the reused water quality was focused on trihalomethanes (THMs) level.
► Single SMBR process was proved insufficient in THM precursor removal.
► Higher chlorine dose and contact time were found to create more THMs formation