What are the characteristics of the MBR process?
Compared with traditional biochemical water treatment technology, MBR has the following characteristics:
1) Efficient solid-liquid separation, the separation effect is far better than the traditional sedimentation tank, effluent water quality is good, effluent suspended matter and turbidity close to zero, can be directly reused, realize sewage resources.
2) The efficient interception effect of the membrane enables the microorganisms to be completely trapped in the bioreactor, realizing the complete separation of hydraulic retention time (HRT) and sludge age (SRT) of the reactor, and flexible and stable operation control.
3) Since MBR integrates the aeration tank and secondary sedimentation tank of traditional sewage treatment into one, and replaces all process facilities of tertiary treatment, it can greatly reduce the land area and save civil construction investment.
4) It is conducive to the interception and propagation of nitrifying bacteria, and the system has high nitrification efficiency. Deamination and dephosphorization can also be achieved through the change of operation mode.
5) Because the mud age can be very long, thus greatly improving the degradation efficiency of refractory organic matter.
6) The reactor is operated under high volume load, low sludge load and long sludge age, and the surplus sludge yield is very low. Since the sludge age can be infinite, zero sludge discharge can be realized theoretically.
7) The system realizes PLC control, convenient operation and management.
What are the components of MBR process? The commonly referred to membrane bioreactor is actually a general term for three types of reactors:
① Aeration Membrane Bioreactor (AMBR);
② Extractive Membrane Bioreactor (EMBR);
③ Solid/Liquid Separation membrane-bioreactor (SLSMBR).
1) Aeration membrane: aeration membrane -- biological reactor (AMBR) adopts dense permeable membrane (such as silicone rubber membrane) or microporous membrane (such as hydrophobic polymeric membrane). Plate or hollow fiber components can realize bubble-free aeration to the bioreactor under the condition that the gas component is kept lower than the Bubble Point; The characteristics of this process are that the contact time and oxygen transfer efficiency are improved, which is conducive to the control of aeration process, and it is not affected by the factors of bubble size and residence time in traditional aeration.
2) Extraction Membrane: extraction membrane -- Bioreactor, also known as EMBR (Extractive Membrane Bioreactor). Because of the existence of high pH or toxic substances to organisms, some industrial wastewater should not be treated by direct contact with microorganisms. When the waste water contains volatile toxic substances, if the traditional aerobic biological treatment process is used, the pollutants are easy to volatilize with the aerated air stream, and the phenomenon of gas stripping occurs. The treatment effect is not only very unstable, but also cause air pollution. In order to solve these technical problems, British scholar Livingston research and development of EMB, wastewater and activated sludge is separated by membrane, wastewater flows in the membrane, and activated sludge containing some obligate bacteria flows in the membrane, wastewater and microorganisms do not directly contact, organic pollutants can be selectively through the membrane by the other side of the microbial degradation; Since the bioreactor units and wastewater circulation units on both sides of the extraction membrane are independent, the water flow of each unit has little influence on each other, and the living conditions of nutrients and microorganisms in the bioreactor are not affected by the water quality of the wastewater, so that the water treatment effect is stable. The operating conditions of the system such as HRT and SRT can be controlled within the optimal range, respectively, to maintain the maximum contaminant degradation rate.
3) Solid-liquid separation membrane: solid-liquid separation membrane -- Bioreactor is the most widely and deeply studied membrane -- bioreactor in the field of water treatment. It is a kind of water treatment technology that uses membrane separation process to replace the secondary sedimentation tank in the traditional activated sludge process. It uses membrane components to return solid organic matter to the reactor, and then drains the treated organic water. Membrane separation bioreactor types can be classified according to membrane components and bioreactor location, including integrated membrane bioreactor, separate membrane bioreactor, composite membrane bioreactor.
(1) In the traditional wastewater biological treatment technology, the sludge and water separation in the secondary sedimentation tank is completed by gravity, and its separation efficiency depends on the settling performance of activated sludge. The better the settling performance, the higher the sludge and water separation efficiency. The sedimentation of sludge depends on the operation condition of aeration tank. To improve the sedimentation of sludge, the operation condition of aeration tank must be strictly controlled, which limits the application scope of this method. Due to the requirement of solid-liquid separation in the secondary sedimentation tank, the sludge in the aeration tank cannot maintain a relatively high concentration, generally around 1.5~3.5g/L, thus limiting the biochemical reaction rate. Hydraulic retention time (HRT) and sludge age (SRT) depend on each other, increasing volume load and decreasing sludge load often form a contradiction. A large amount of residual sludge is also generated during the operation of the system, and its disposal cost accounts for 25% ~ 40% of the operation cost of the sewage treatment plant. The traditional activated sludge treatment system is also prone to sludge swelling, the effluent contains suspended solids, and the effluent quality deteriorates.
(2) To solve the above problems, MBR organically combines the membrane separation technology in the separation engineering with the traditional wastewater biological treatment technology, which greatly improves the solid-liquid separation efficiency; The increase of activated sludge concentration in aeration tank and the emergence of specific bacteria (especially dominant bacteria) in sludge improved the biochemical reaction rate. At the same time, by reducing the F/M ratio to reduce the amount of surplus sludge production (even to 0), which basically solves many outstanding problems existing in the traditional activated sludge method.
