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What are some of the misconceptions about the MBR process?

Author: Site Editor     Publish Time: 2023-01-12      Origin: Site


In recent years, the MBR process has been widely used, with water reuse going on, upgrading and renovation going on, and decentralised treatment also going on... As we all know, this is mainly due to its high load, long sludge age, high efficiency interception, occupying less land and other outstanding advantages.

However, there are also some misconceptions in the application process, these misconceptions have caused adverse effects in the application.

Misconception 1: The higher the MBR membrane flux design, the better

The flux of a membrane is determined by the membrane material and structure, and there is an upper limit to the porosity and flux of a particular membrane treatment unit. Filtration is essentially a physical process and membrane materials must reduce pore size at the expense of throughput, while at the same time balancing strength and long term operation, which results in a constant flux.

Therefore, the design and application process should be based on the membrane manufacturer's recommended parameters.

Misconception 2: Using MBR guarantees effluent quality

The MBR process is essentially a combination of activated sludge and membrane filtration, replacing the secondary sedimentation tank with membrane filtration on the basis of the traditional activated sludge process, which brings the advantages of good retention and high sludge concentration, but this does not mean that the MBR process is a cure for all diseases. For the removal of pollutants, membrane filtration has a very obvious effect on SS, while the removal of organic matter still depends on the activated sludge and the biochemical properties of the organic matter, and the MBR is of limited use for poorly biochemical wastewater or wastewater that has undergone adequate biochemical treatment in the previous section.

Misconception 3: MBR processes do not require sludge discharge

Due to the excellent retention effect of membrane filtration, the activated sludge in the MBR process can reach high concentrations, achieving a separation of hydraulic retention time and sludge age, which allows the impact of sludge concentration on the effluent to be disregarded. However, this advantage only enhances the scope for biochemical play, and the fact that it does not affect the effluent does not justify the absence of sludge discharge; the question of whether to discharge sludge or not still comes back to the activated sludge. If sludge is not drained, the activated sludge will age, which in turn will affect the biochemical performance and will have an impact on the aeration. It is true that the MBR process can reduce sludge discharge in engineering, but not without it.

water treatment

Misconception 4: Reduce sludge concentration as much as possible to avoid membrane clogging

Membrane clogging is a common problem in MBR applications, and it is the sludge that clogs the membrane, especially if the sludge concentration is too high, so there is a misconception that the sludge concentration can be reduced to avoid clogging, which is another misconception. Both too low and too high a concentration of sludge can quickly clog the membrane and the correct approach is to keep the concentration in the right range. In addition, aeration has the effect of scouring the membrane surface and should also be kept at the appropriate holding level.

Misconception 5: Membranes are responsible for the effluent

The principle of membrane itself is filtration, a physical process, on the removal of pollutants mainly SS, its significance for MBR is to improve the biochemical performance, but does not filter soluble organic matter, so can not be responsible for COD and other indicators, the removal of organic matter or rely on the entire process chain design and operational management.

Misconception 6: MBR is only applicable to domestic wastewater

The MBR process is a combination of activated sludge and membrane filtration, off the traditional combination of activated sludge plus secondary sedimentation tanks, in this sense, the scenario of using activated sludge is applicable to the MBR process; however, for some wastewater that is likely to cause blockage of the membrane, the pretreatment should meet the requirements.

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