In the field of wastewater treatment and water reuse, MBR, also known as Membrane Bio-Reactor, is a new type of water treatment technology that combines membrane separation units with biological treatment units. According to the structure of the membrane can be divided into flat membrane, tubular membrane and hollow fibre membrane, etc., according to the membrane pore size can be divided into ultrafiltration membrane, microfiltration membrane, nanofiltration membrane, reverse osmosis membrane, etc..
According to the combination of membrane modules and bioreactors, membrane - bioreactors can be divided into three basic types: discrete, integrated and composite. (The following are all solid-liquid separation type membrane - bioreactors)
The membrane module and the bioreactor are set up separately. The mixture in the bioreactor is pressurised by a circulation pump and then pumped to the filter end of the membrane module. The liquid in the mixture passes through the membrane under pressure and becomes the treated water of the system; solids and macromolecules are retained by the membrane and flow back into the bioreactor with the concentrate.
Separate membrane - bioreactors are characterised by stable and reliable operation, easy cleaning, replacement and addition of membranes; and generally larger membrane fluxes. However, to reduce the deposition of contaminants on the membrane surface and to prolong the cleaning cycle of the membrane under normal conditions, a circulation pump is required to provide a high mis-flow rate at the membrane surface, which results in high water circulation and high power costs (Yamamoto, 1989), and the shear forces generated by the high speed rotation of the pump can inactivate some microbial organisms (Brockmann and Seyfried, 1997). ).
The membrane module is placed inside the bioreactor. The influent water enters the membrane bioreactor, where most of the contaminants are removed by the activated sludge in the mix, and the water is then filtered out by the membrane under external pressure.
This form of membrane - bioreactor has received particular attention in the water treatment field due to the elimination of the mixing fluid circulation system and the relatively low energy consumption due to the pumping of the water. However, the general membrane flux is relatively low, and membrane contamination can easily occur, and the membrane cannot be easily cleaned and replaced after contamination.
It is also a one-piece membrane - bioreactor in form, but the difference is the addition of filler in the bioreactor, thus forming a composite membrane - bioreactor, which changes certain traits of the reactor.