The biofilm membrane bioreactor (BF-MBR)-a review

Membrane bioreactors (MBR) based on the activated sludge process is a relatively new technology, with implementation worldwide increasing over the last 20 y. In parallel to commercial development, a lot of research work has been done in fundamental studies, development and optimization of this technology. Although the main focus has been on activated sludge processes, several research groups have been investigating biofilm based MBR systems. The biofilm processes have several advantages over activated sludge process and can be used as complementary, assisted to activated sludge MBR (aBF-MBR) or self standing, pure biofilm based MBRs (pBF-MBR). This article reviews the status of MBR technology with biofilm implementations for wastewater treatment, excluding membrane aerated/supported biofilm reactors (MABR). Reports published within the last 10 y are reviewed with respect to aBF-MBR and pBF-MBR studies, highlighting advantages proposed of this approach over activated sludge MBRs, identifying performance and operational characteristics given, and taking an outlook of perspectives in further development of this concept.