Comparison of Two Treatments for the Removal of Organic Micro-Pollutants: Conventional Activated Sludge (CAS) Followed by Ultrafiltration (UF) vs. Membrane Bioreactor (MBR)

Abstract

The potential of MBR systems to remove organic micro-pollutants was investigated at different scales, operational conditions, and locations. MBR effluent quality was compared with that of a conventional activated sludge (CAS) plant, followed by ultrafiltration (UF), operated and tested in parallel. A MBR pilot plant in Israel was operated for over a year at an MLSS range of 2.8–10.6 g/L. The MBR achieved removal rates comparable to those of a CASUF plant at the Tel-Aviv WWTP for macrolide antibiotics such as roxythromycin, clarithromycin and erythromycin and slightly higher removal rates than the CAS-UF for sulfonamides. A laboratory scale MBR unit in Berlin – at an MLSS of 6–9 g/L – showed better removal rates for macrolide antibiotics, trimethoprim and 5-tolyltriazole compared to the CAS process of the Berlin WWTP Ruhleben at identical raw wastewater quality. Sulfamethoxazole and 4-tolyltriazole were removed slightly better in the CAS while the benzotriazole removal was more significant. In pilot MBR tests at an MLSS of 12 g/L in Aachen, Germany, operating flux significantly affected the resulting membrane fouling rate, but the removal rate of dissolved organic matter and of bisphenol-A was not affected.