MBR is the abbreviation of MembraneBio-Reactor. It is a brand-new efficient sewage treatment process produced by the organic combination of modern membrane separation technology and traditional biological treatment technology. MBR process not only eliminates the construction of secondary sedimentation tank, but also greatly improves the efficiency of solid-liquid separation by organically combining membrane separation technology in separation engineering with traditional wastewater biological treatment technology. Due to the increase in the mass concentration of activated sludge in the aeration tank and the emergence of special bacteria (especially the dominant flora) in the sludge, the biochemical reaction rate is increased. At the same time, by reducing the F/M ratio to reduce the amount of surplus sludge produced (or even zero), it basically solves many prominent problems existing in the traditional activated sludge process.
The basic structure of MBR includes four links: water intake system, biological reaction tank, membrane module, automatic control system. MBR has different classifications due to the diversity of the individual components. According to the relative position of the membrane module and the bioreactor, MBR can be divided into three types: integrated membrane bio reactor, separate membrane bioreactor and composite membrane bioreactor. Separate membrane bioreactors operate by staggered flow of material and liquid circulation. It is characterized by easy operation and management, easy cleaning, replacement and addition of membranes. The integrated membrane bioreactor is the simplest combination. The membrane module is directly placed in the bioreactor and pumped by a vacuum pump or other types of pumps to obtain the filtrate. In order to reduce the membrane surface pollution and extend the operation cycle, the suction of the general pump is operated intermittently. Compared with the split type, the most important feature of the integrated type is the low energy consumption for operation. The composite membrane bioreactor is also an integrated membrane bioreactor in form, but the difference is that fillers are added to the bioreactor to form a composite membrane bioreactor, which changes some characteristics of the membrane bioreactor.
Since the MBR membrane can trap almost all biomass in the reactor, obtain long sludge age and high suspended solids concentration, and maintain a low F/M, it has the following main advantages over the conventional activated sludge process.
1. Water treatment chemical products can make the hydraulic retention time and sludge age completely separate, which makes the operation control more flexible and stable.
2. The effluent BOD5, hydrogen, phosphorus and suspended solids concentration is very low and does not contain bacteria, viruses, parasitic eggs, etc. The effluent meets the tertiary treatment standards and can be directly reused or supplemented with groundwater.
3. MBR sludge load is generally around 0.1~0.2kgCOD/(kgvSS-d), while the volumetric load can be around several kilograms
4. The sludge concentration is high, and the oxygen transfer efficiency is as high as about 26% to 60%, which saves energy.
5. MBR, as a kind of water treatment disinfectant, can ensure the effluent quality at the peak of organic load by using its high MLSS, and the sludge can digest itself (endogenous respiration) at the low peak, resulting in 50%~80% less residual sludge than conventional activated sludge treatment, which can reduce the residual sludge disposal cost.
6. Conducive to the proliferation of nitrifying bacteria with a long generation time, thereby improving the nitrification efficiency.
7. Due to the high concentration of MLSS in the MBR, nitrification and denitrification exist at the same time, which has a high denitrification effect, so the denitrification ability is strong.