Membrane bioreactor for wastewater treatment and reuse: virus removal

Membrane bioreactor (MBR) is a unit process consisting of a biological reactor with suspended biomass and a microfiltration/ultrafiltration membrane. In addition to its biological degradation and solid-liquid separation functions, MBR may potentially provide a non-hazardous disinfection means. In this paper, an experimental study on virus removal was carried out in a bench-scale MBR unit, using MS-2 bacteriophage as a viral indicator. The membrane itself without the presence of the mixed liquor and the attached biofilm could achieve only 80% virus removal. With the additional presence of suspended biomass in the MBR unit, the total virus removal was enhanced to 93.7%. When sufficient time was given to allow biofilm accumulation on the membrane surface, the removal further increased to 99.9%. Submerging this biofilmed membrane module into a clear water tank gave evidence that the major contribution to the virus removal in an MBR system was the biofilm.