In the evolution of life on earth, the membrane was essential in that it allowed the formation of cells, and later the compartmentalization of processes in cells. As humans have learned how to produce more complicated and efficient synthetic membranes, so too have we developed the ability to compartmentalize processes. In the way. Membranes can be used to filter cells from for example wastewater. If the filtered cells play a role in breaking down additional waste flowing through the membranes, a membrane bioreactor has been created. A membrane bioreactor consists of some biological item or items in association with a membrane. A membrane is a surface that has the ability to let some things through it and will block others.
Membrane bioreactors (MBRs) combine the use of biological processes and membrane technology to treat wastewater. Within one process unit, a high standard of treatment is achieved, replacing the conventional arrangement of aeration tank, settling tank and filtration that generally produces what is termed as a tertiary standard affluent.
The dependence on disinfection is also reduced, since the membranes with pore openings, generally in the 0.1-0.5mm range, trap a significant proportion of pathogenic organisms. The more common MBR configuration is to have the membrane immersed in the wastewater, although a side stream configuration is also possible, with the wastewater pumped through the membrane module and then returned to the bioreactor. Operating at a mixed liquor suspended solids (MLSS) concentration of up to 20,000mg/L and a sludge age of 30-60 days, MBRs offer additional advantages over conventional activated sludge plants, including a smaller footprint.