Removal of micropollutants in a ceramic membrane bioreactor for the post-treatment of municipal wastewater

Abstract

Micropollutants, such as pharmaceuticals, endocrine disrupting compounds, and personal care products, have become an emerging environmental issue. In general, they are only partially removed by conventional wastewater treatment plants (WWTPs), and their presence in surface waters may have harmful effects on aquatic organisms and human health. In this study, a pilot-scale ceramic membrane bioreactor (cMBR) was employed as a polishing step in a WWTP to further treat the effluent of the WWTP for 15 months. The removal of chemical oxygen demand (COD) and 29 micropollutants, the process stability, and the development of activated sludge in the cMBR system were investigated. After about 300 days of operation, the cMBR system established stable operating conditions with suspended solids (SS) concentrations and volatile suspended solids (VSS) concentrations at (0.045 ± 0.004) g/L and (0.028 ± 0.005) g/L, respectively. Under these conditions, the cMBR provided stable removal of organic matter and micropollutants. The removal of chemical oxygen demand (COD) was (37.4 ± 3.8)%, and the removal of 29 micropollutants was substance specific and ranged from (−3.6 ± 5.9)% to (42.4 ± 3.0)%. Although the sludge concentration developed in the cMBR was much lower than that in the WWTP aeration tank (SS at 2.3 g/L), the activity of sludge in the cMBR for oxygen consumption and micropollutants removal was more than 10 times higher than that in the WWTP aeration tank. Moreover, as a complement to the cMBR system, an osmosis membrane system was investigated that could completely remove the micropollutants (below detection limits) in the cMBR effluent and achieve high water quality.