MABR membrane assembly, MABR reactor, MABR reactor operation method and MABR biofilm optimization control method

Abstract

The present invention proposes a MABR membrane assembly, a MABR reactor, a MABR reactor operation method and a MABR biofilm optimization control method, which adopts a cross-flow working mode between horizontal membrane filaments and water flow to improve the mass transfer efficiency of the matrix and metabolites in the MABR biofilm; the composite structure membrane assembly is used to promote the complementarity and symbiosis of various microorganisms such as carbon removal aerobic bacteria, nitrifying bacteria, denitrifying bacteria and anaerobic ammonia oxidizing bacteria; different areas such as MABR membrane reaction area, pre-reaction area and water distribution and gas distribution area are constructed in the same reactor to complete short-range nitrification or partial short-range nitrification reaction, short-range denitrification reaction and anaerobic ammonia oxidation reaction respectively, so as to achieve efficient biological denitrification of sewage with low carbon-nitrogen ratio in a single-stage MABR reactor. At the same time, the optimization control method of the MABR biofilm solves the problems that the overly thick biofilm in the MABR reactor is not easy to be effectively washed, and the fixed gas washing frequency and intensity are difficult to simultaneously adapt to the biofilm washing and film removal requirements of membrane filaments in different parts.

Description

Technical Field

[0001] The present invention relates to the technical field of biological sewage treatment, and in particular to an MABR membrane assembly, a MABR reactor, a MABR reactor operation method and a MABR biofilm optimization control method. Background Art

[0002] Membrane aerated biofilm reactor (MABR) is a new type of sewage treatment process. It organically integrates the traditional biofilm method with the gas separation membrane technology. It uses an oxygen-permeable membrane to supply oxygen to the bioreactor. At the same time, microorganisms can easily attach and grow on the membrane surface to form a biofilm, thereby efficiently degrading pollutants in the water. In recent years, MABR technology has received more and more attention and applications, especially in sewage denitrification. In 2013, commercial hollow fiber membranes for MABR appeared, and then many environmental protection companies successively launched membrane components and complete sewage treatment solutions based on MABR technology. At present, MABR technology has a lot of applications in upgrading and upgrading municipal sewage treatment plants, energy saving and consumption reduction, and its application in industrial wastewater treatment and river water purification has also developed rapidly.

[0003] The core of MABR technology is the oxygen permeable membrane, which not only provides dissolved oxygen for biochemical reactions, but also serves as a carrier for microorganisms to attach and form biofilms. This requires it to have good oxygen transfer performance and surface properties that are conducive to microbial attachment, as well as sufficient chemical stability, mechanical strength and resistance to microbial contamination. At present, the oxygen permeable membrane materials that have been industrially applied mainly include hydrophobic microporous membranes, non-porous dense membranes and composite membranes composed of the two. Microporous membranes have low mass transfer resistance and large membrane flux, but poor selectivity for oxygen, low bubble point pressure and easy to be blocked by microbial contamination; dense membranes have high mechanical strength, good chemical stability and strong selectivity for oxygen, but poor microbial attachment and growth performance, and it is difficult to form biofilms; composite membranes have the advantages of the first two, but are difficult to produce and costly, and the uniformity and stability of the surface modification layer directly affect the performance and life of the membrane. If the membrane material or structure is not properly selected, the oxygen solubility may be limited, liquid may penetrate into the membrane cavity, and excessive biofilm may accumulate on the membrane surface, affecting the oxygen transfer rate and thus reducing the treatment efficiency. Membrane fouling is difficult to avoid, especially for hydrophilic microporous membranes and composite membranes with hydrophilic surfaces. The membrane pores are easily blocked by microorganisms and their extracellular polymers, increasing the oxygen transfer resistance and reducing the efficiency and stability of the long-term operation of the membrane assembly. Compared with traditional activated sludge and biofilm methods, the MABR process has higher technical requirements in membrane assembly design, installation and maintenance.

[0004] The arrangement of membrane fibers in the MABR membrane assembly and its relationship with the water flow direction will significantly affect the mass transfer rate of the biofilm on the surface of the membrane fibers, and also affect the magnitude of the hydraulic shear force on the outer surface of the membrane, thereby affecting the density of the attached biofilm and the efficiency of removing and flushing excessively thick biofilms.

[0005] The thickness of the MABR biofilm is one of the key factors for the stable and efficient denitrification treatment of the MABR reactor. The biofilm thickness should not be too thin or too thick. The existing methods for controlling the thickness of biological denitrification in MABR reactors mainly include: water circulation to increase shear force, intermittent aeration to flush the biofilm, adding chemical agents, limiting oxygen utilization, and native operation predation method. The biofilm attached to the surface of the MABR membrane has a complex structure and diverse functions. It is the main place for the degradation of pollutants such as organic matter and ammonia nitrogen. The mass transfer directions of oxygen, reaction metabolites and the matrix in the biofilm are opposite, which belongs to the heterogeneous mass transfer process. Therefore, there is a significant correlation between the apparent reaction rate of pollutants and the thickness of the biofilm, especially in MABR reactors with biological denitrification function. On the one hand, the biofilm thickness on the surface of the MABR membrane needs to reach at least 450μm to 600μm to give full play to the advantages of biofilm stratification and promote the smooth progress of nitrification and denitrification reactions; on the other hand, if the biofilm proliferates too thick, especially when its thickness exceeds 1200μm to 1500μm, the mass transfer resistance of the matrix and metabolites in the biofilm will increase significantly, which will continuously reduce the biological denitrification performance of the MABR. At the same time, it is easy for the biofilm to fall off abnormally, affecting the performance of the reactor. Therefore, the thickness of the biofilm on the MABR membrane should not be too thin or too thick, but in the actual operation of the MABR reactor, it is still difficult to accurately control the thickness of the biofilm. How to maintain the optimal thickness of the biofilm through parameters such as the water circulation flow rate, gas flushing intensity and frequency, and pollutant load in the reactor is the key to stable and efficient denitrification treatment of the MABR reactor. The existing MABR reactor still has great difficulty in accurately controlling the thickness of the biofilm, and the in-situ online monitoring technology of the biofilm thickness is not mature, which also increases the difficulty of optimizing the control of the biofilm.

[0006] The shortcomings of existing composite or combined MABR membrane components: ① The alternating arrangement of MABR membrane silk sheets and traditional biofilm fillers helps to increase the amount of attached microorganisms, but the two have not been organically integrated, and have not been able to solve the problems of easy balling and clogging of biofilm fillers and the difficulty in optimizing the control of microbial mass on MABR membrane silk. If forced de-filming is performed by increasing the airflow and backwashing intensity, the biofilm on the surface of the MABR membrane will fall off in pieces, reducing the treatment efficiency of the reactor. ② The membrane silk in the MABR membrane component is arranged in parallel with the water flow, and the mass transfer rate of the matrix and metabolites through the membrane cannot be effectively improved, which is not conducive to the efficient degradation of pollutants. ③ Directly applying porous materials or fiber fillers on the surface of MABR membrane silk will affect the mass transfer area of ​​oxygen to a certain extent, reduce the oxygen transfer flux, affect the working efficiency of the MABR membrane component, and the processing and manufacturing are complex and the cost is high.

[0007] The shortcomings of existing biological denitrification reactors based on MABR technology are as follows: ① The MABR membrane components and the biofilm filter, contact oxidation and other modules are arranged in the same reactor in a simple up-and-down manner. There is a risk of overlapping shortcomings of the two types of treatment modules during long-term operation. The problems of biofilm blockage or membrane filament contamination are still serious, and the membrane components are very inconvenient to backwash, maintain and overhaul. ② Multiple MABR reactors are connected in series as a multi-stage treatment process, which has a more complicated structure, increased infrastructure investment, and more complicated operation and management. The process parameters of each stage of the reactor need to be controlled separately, especially the first stage reactor requires a higher alkalinity for buffering during nitrification or nitrite, which reduces the stability of operation.

[0008] The disadvantages of the existing biofilm control methods in MABR reactors are as follows: ① The biofilm thickness is monitored by microelectrode technology, optical image analysis, radiation signal analysis and other methods, which have only been studied in small-scale laboratories and are not yet mature for application in actual projects; ② Increasing the circulation flow rate and increasing the hydraulic shear force can improve the density and stability of the biofilm to a certain extent, but there are problems such as excessive shearing and shedding of local biofilms or blockage caused by insufficient shear force of local biofilms due to uneven water flow distribution in the reactor; ③ The intermittent aeration and flushing method usually adopts a fixed frequency and flushing intensity, and the control of biofilm thickness in different areas varies greatly, which easily leads to excessive flushing and shedding of the lower biofilm, while the upper biofilm cannot be effectively flushed; ④ Adding chemical agents (such as urea, surfactants, EDTA, etc.) to control the biofilm thickness may destroy the biofilm structure and cause abnormal shedding of the membrane; ⑤ The method of controlling the biofilm thickness by predation of protozoa attached to the membrane has harsh operating conditions and is not easy to operate and control. Summary of the invention

[0009] In order to solve the above technical problems, the present invention proposes a MABR membrane assembly, a MABR reactor, a MABR reactor operation method and a MABR biofilm optimization control method. The MABR reactor adopts a cross-flow working mode between horizontal membrane filaments and water flow, which improves the mass transfer efficiency of the matrix and metabolites in the MABR biofilm; the composite structure membrane assembly promotes the complementarity and symbiosis of various microorganisms such as carbon removal aerobic bacteria, nitrifying bacteria, denitrifying bacteria and anaerobic ammonia oxidizing bacteria; in the same reactor, different areas such as MABR membrane reaction area, pre-reaction area and water distribution and gas distribution area are constructed to complete short-range nitrification or partial short-range nitrification reaction, short-range denitrification reaction and anaerobic ammonia oxidation reaction respectively, so as to achieve efficient biological denitrification of sewage with low carbon-nitrogen ratio in a single-stage reactor. At the same time, the optimization control method of the MABR biofilm solves the problems that the overly thick biofilm in the MABR reactor is not easy to be effectively washed, and the fixed gas washing frequency and intensity are difficult to adapt to the biofilm washing and film removal requirements of membrane filaments in different parts at the same time.

[0010] The present invention provides a MABR membrane assembly, comprising: membrane elements, which are symmetrically arranged in two groups with a gap between the two groups of membrane elements, the membrane elements having a sheet-like support layer and a plurality of horizontal membrane filaments arranged transversely from top to bottom on one side wall of the support layer, the membrane filaments are fixedly spaced from the support layer and the membrane filaments between two adjacent fixed points are in a suspended cable shape, and the membrane filaments are arranged on opposite side walls of the two groups of support layers; and an air pipe, which is vertically arranged on both sides of the support layer and is sealed and connected to the two ends of the plurality of membrane filaments.

[0011] Furthermore, it also includes fixed clamping plates, which are arranged on both sides of the membrane element. The facing sides of the two fixed clamping plates are provided with air pipe clamping slots corresponding to the number of the air pipes, and the opposite sides are provided with support clamping slots.

[0012] Furthermore, the support layer is made of sandwich mesh cloth, and the membrane filament is made of transparent silicone rubber tube.

[0013] Furthermore, the plurality of membrane filaments are evenly distributed longitudinally, and the fixing points on each membrane filament are distributed in a rectangular array.

[0014] Furthermore, a plurality of membrane assembly fixing sleeves parallel to the air pipe are provided between the support layers of the two groups of membrane elements.

[0015] The present invention also provides a MABR reactor, comprising: a reaction tank, a water distribution plate arranged at the bottom of the reaction tank and a central tube with a lower end passing through the water distribution plate, a gas-water distribution area is below the water distribution plate, a membrane reaction area is outside the central tube, and a pre-reaction area is inside the central tube, a water inlet pipe and a water outlet pipe are arranged on the reaction tank, the water inlet pipe is connected to the pre-reaction area, the water outlet pipe is connected to the membrane reaction area, a guide tube is arranged in the pre-reaction area, a gas stripping circulation device for circulating the mixed liquid inside and outside the guide tube is arranged in the guide tube, and multiple layers are arranged from top to bottom in the membrane reaction area. The annular module composed of the MABR membrane components described above, the multi-layer annular membrane group is divided into an inner membrane group area, a middle membrane group area and an outer membrane group area from the inside to the outside, and the extension direction of the membrane fibers of the membrane assembly is staggered with the water flow direction; the air flushing system is used to perform air flushing on the biofilm generated on the annular membrane group; the aeration system is used to aerate the membrane fibers on each layer of the annular membrane group, and the aeration system is provided with an oxygen concentration detection component; the mixed liquor reflux system is used to reflux the mixed liquor in the membrane reaction zone to the pre-reaction zone; the sludge reflux system is used to reflux the sludge in the reaction tank to the pre-reaction zone.

[0016] Furthermore, a plurality of membrane assembly pillars for fixing the MABR membrane assembly are provided in the reaction tank, the membrane assembly pillars cooperate with the membrane assembly fixing sleeve or the pillar slot, and the membrane assembly pillars are in the shape of a plurality of concentric circles and are evenly distributed in the radial direction.

[0017] Furthermore, each of the annular membrane groups includes two symmetrically arranged semi-annular membrane groups, and the semi-annular membrane groups are formed by connecting a plurality of the MABR membrane components in series. The air pipes on both sides of the semi-annular module are respectively an inlet pipe and an outlet pipe. The inlet pipes of the two semi-annular modules are located on the same side of the reaction tank, and each of the inlet pipes is connected to the aeration pipe of the aeration system, and each of the outlet pipes is connected to the exhaust pipe of the aeration system.

[0018] Furthermore, the oxygen concentration detection component includes a membrane air intake sampling tube arranged on the aeration pipe, a membrane exhaust sampling tube arranged on the exhaust pipe, a detection flow slot and a high-precision oxygen concentration analyzer. The membrane air intake sampling tube and the membrane exhaust sampling tube are both connected to the detection flow slot, and the measuring probe of the high-precision oxygen concentration analyzer extends into the detection flow slot.

[0019] Furthermore, the air flushing system includes a plurality of groups of air flushing perforated pipes arranged in the air-water distribution area corresponding to each layer of the annular membrane group, and the air flushing perforated pipes in the same layer of membrane group area are connected to an air flushing branch pipe.

[0020] Furthermore, the mixed liquor reflux system includes a mixed liquor reflux pipe arranged at the top of the reaction tank, and the sludge reflux system includes a sludge reflux pipe arranged at the bottom of the reaction tank. The mixed liquor reflux pipe and the sludge reflux pipe are connected to the pre-reaction zone through a mixed liquor reflux main pipe, and a sludge discharge valve is also provided on the sludge reflux pipe.

[0021] Furthermore, the air lift circulation device includes an air lift assembly with an opening at the bottom end and an air lift fan, the air lift duct of the air lift fan is connected to the top of the central tube, the air lift exhaust duct is connected to the top of the air lift assembly, and the central tube is also provided with a central tube automatic exhaust valve and a central tube vent valve.

[0022] The present invention also provides a method for optimizing and controlling a MABR biofilm, using the above-mentioned MABR reactor:

[0023] S001. According to the operation mode of the MABR reactor, a corresponding composite biofilm is formed on the MABR membrane components in each membrane group area, and the MABR reactor is operated stably;

[0024] S002. Evaluate the biofilm thickness: Use the oxygen concentration detection component to regularly detect the oxygen concentration in the aeration pipe and exhaust pipe in the corresponding membrane group area, calculate the oxygen concentration attenuation coefficient per unit length of membrane filament, and draw a curve of the coefficient changing with time;

[0025] S003. When the change curve in the corresponding membrane group area in step S002 shows a downward trend, the biofilm is too thick, and the aeration of the MABR membrane assembly in the membrane group area is stopped and maintained for a period of time, and then the biofilm in the membrane group area is washed and removed by air through the air flushing system;

[0026] S004. After the biofilm falls off, it grows again, and the change curve shows an upward trend until the change amplitude of the change curve is small, and the biofilm thickness is stable.

[0027] Furthermore, the calculation formula of the oxygen concentration attenuation coefficient per unit length of the membrane fiber in step S002 is:

[0028]

[0029] In formula (1), LOAT is the oxygen concentration attenuation coefficient per unit length of membrane fiber, gO2 / (m·h); W in is the oxygen flow rate in the aeration of MABR membrane module, gO2 / h; W out is the oxygen flow rate in the exhaust gas of the MABR membrane module, gO2 / h; n m is the number of membrane fibers contained in the MABR membrane module, root; l m is the length of a single membrane filament in the MABR membrane module;

[0030] In formula (2), P in is the aeration pressure of MABR membrane module, Pa; Q in is the flow rate of the aeration pipe, m 3 / h; C in is the oxygen content in the aeration pipe, %; 32 is the molar mass of oxygen, g / mol; n n is the number of membrane modules connected to the aeration pipe for measuring flow rate, R is the gas constant, 8.314 J / (mol·K); T in is the intake air temperature, K;

[0031] In formula (3), P out is the exhaust pressure of MABR membrane module, Pa; Q out is the flow rate of the exhaust pipe, m 3 / h; C out is the oxygen content in the exhaust pipe, %; T out is the exhaust temperature, K.

[0032] Furthermore, in step S003, when the MABR reactor is operated in the short-range nitrification and denitrification operation mode, the operating parameters of the membrane flushing and stripping are: after stopping aeration of the MABR membrane components in the membrane group area for 16h to 24h, the corresponding air flushing branch pipe is opened for air flushing, and the air flushing flow rate per unit membrane reaction area effective volume is 8 to 10L / (m 3 有效容积 ·min), air flushing time is 30~60s, with an interval of 5min;

[0033] When the MABR reactor operates in the short-range nitrification-anaerobic ammonium oxidation mode, the operating parameters for flushing and stripping are: after stopping aeration of the MABR membrane components in the membrane group area for 12h to 16h, open the corresponding air flushing branch for air flushing, and the air flushing flow rate per unit membrane reaction area effective volume is 3~6L / (m 3 有效容积 ·min), the air flushing time is 20 to 40 seconds, with an interval of 10 minutes.

[0034] Furthermore, the biofilm forming method of the composite biofilm in step S001 is:

[0035] S0011, Nitrification and denitrification biofilm stage:

[0036] (1) Inoculate sludge through the water inlet pipe, continuously open the sludge return system, aeration system and air stripping circulation device, indirectly open the air flushing system, close the mixed liquid return system, adjust the water inlet to 1 / 3 of the design flow rate, and continuously inlet and outlet water;

[0037] (2) After the biofilm is formed on the membrane surface, gradually increase the water flow rate, intermittently open the mixed liquid reflux system, and gradually increase the interval time of opening the air flushing system;

[0038] (3) After the influent flow rate reaches the design flow rate, the mixed liquor return system is changed to be continuously opened, the sludge return system is continuously opened and the air flushing system is opened intermittently and operated stably for a period of time until the effluent ammonia nitrogen removal rate is higher than 90%, the total nitrogen removal rate exceeds 50%, the nitrite nitrogen accumulation rate is lower than 10%, and a nitrifying biofilm is formed on the surface of the membrane filaments (903) of the MABR membrane assembly, and an anaerobic nitrifying biofilm is formed on the support layer (907);

[0039] S0012, Short-cut nitrification and denitrification biofilm stage: the aeration system is changed to intermittent opening, and it is continuously operated for a period of time until the effluent ammonia nitrogen removal rate exceeds 80%, the total nitrogen removal rate exceeds 60%, and the nitrite nitrogen accumulation rate exceeds 60%, and a biofilm dominated by short-cut nitrification and denitrification is formed in the MABR reactor;

[0040] S0013, short-range nitrification anaerobic ammonium oxidation biofilm stage: add granular anaerobic ammonium oxidation sludge into the central tube, change the sludge return system to intermittent opening, and form a composite biofilm in the MABR reactor after running for a period of time.

[0041] Furthermore, the inoculated sludge is nitrification sludge in an aerobic tank and denitrification sludge in an anoxic tank, and the volume ratio of nitrification sludge to denitrification sludge is 2:1 to 5:1.

[0042] The present invention also provides an operation method of a MABR reactor, using the above-mentioned MABR reactor:

[0043] S001. Set the mixed liquor return ratio, sludge return ratio, gas-liquid volume ratio of the air stripping circulation device and air flow rate in the air stripping assembly according to the operation mode of the MABR reactor; control the aeration pressure, aeration flow rate and intermittent aeration time of the MABR membrane assembly in each membrane group area through the aeration system, and then control the biofilm in each membrane group area to present different working states; regularly flush the biofilm on the MABR membrane assembly in each membrane group area through the air flushing system to maintain the stable operation of the MABR reactor;

[0044] S002. Sewage is injected into the pre-reaction zone from the water inlet pipe, mixed with the return mixed liquor and return sludge, and circulated inside and outside the guide tube under the action of the air stripping circulation device, and denitrification reaction and / or anaerobic ammonium oxidation reaction occurs;

[0045] S003, the effluent from the pre-reaction zone flows from the bottom of the central tube into the gas-water distribution area to undergo heterotrophic denitrification and / or anaerobic ammonia oxidation reactions;

[0046] S004. The effluent from the gas-water distribution area passes through the water distribution plate and enters the membrane reaction area to complete the nitrite reaction, and then continues to undergo anoxic denitrification reaction and / or anaerobic ammonia oxidation reaction, and is then discharged through the outlet pipe.

[0047] Furthermore, in step S001, the mixed liquor reflux ratio is 100% to 300%, the sludge reflux ratio is 50% to 150%, the gas-liquid volume ratio of the air stripping circulation device is 2 to 6, and the air flow rate in the air stripping assembly is 4 to 6 m / s; the aeration pressure of the MABR membrane assembly is 5 KPa to 50 KPa, and the aeration flow rate per unit membrane length is 3 to 10 L / (h·m 膜丝 ); The air flushing flow rate per effective volume of the membrane reaction zone during stable operation is 3 to 8 L / (m 3 有效容积 ·min), and the air flushing frequency is 10 to 20 seconds every 15 to 30 minutes.

[0048] Furthermore, when the MABR reactor operates in the short-cut nitrification and denitrification mode:

[0049] In step S001, the mixed liquor reflux ratio is 150-200%, the sludge reflux ratio is 50%, the gas-liquid volume ratio of the air stripping circulation device is 2-3, and the air flow rate in the air stripping assembly is 4-5 m / s;

[0050] The aeration pressure of the MABR membrane module is 5KPa~10KPa. The gap aeration time of the MABR membrane module in the outer membrane group area is 30 minutes of aeration and 60 minutes of stop. The aeration flow rate is 3~4L / (h·m 膜丝 ), the intermittent aeration time of the MABR membrane module in the middle membrane group area is 30 minutes of aeration and 30 minutes of stop, and the aeration flow rate is 4-6L / (h·m 膜丝 ); The MABR membrane components in the inner membrane group area are continuously aerated, with an aeration flow rate of 6 to 8 L / (h·m 膜丝 ).

[0051] Furthermore, when the MABR reactor operates in the short-cut nitrification-anaerobic ammonium oxidation mode:

[0052] In step S001, the mixed liquor reflux ratio is 200-300%, the sludge reflux ratio is 75%-100%, the gas-liquid volume ratio of the air stripping circulation device is 4-6, and the air flow rate in the air stripping assembly is 8-10 m / s;

[0053] The aeration pressure of the MABR membrane module is 5KPa~10KPa. The gap aeration time of the MABR membrane module in the outer membrane group area is 30 minutes of aeration and 90 minutes of stop. The aeration flow rate is 3~4L / (h·m 膜丝), the intermittent aeration time of the MABR membrane modules in the middle membrane group area and the inner membrane group area is 30 minutes of aeration and 60 minutes of stop, and the aeration flow rate is 3-4L / (h·m 膜丝 ).

[0054] The beneficial effects of the present invention are as follows:

[0055] The present invention proposes an MABR membrane assembly, which is composed of two groups of symmetrically arranged membrane elements. The surface of each membrane element adopts a dense surface silica gel capillary as an oxygen permeable membrane. A single membrane filament is horizontally axial, and a plurality of membrane filaments are evenly distributed longitudinally on a sandwich mesh cloth. The sandwich mesh cloth serves as a carrier for fixing the membrane filaments and retaining and attaching suspended microorganisms. The two are integrated in the membrane assembly, giving full play to the advantages of the two types of processes, MABR and biofilm method, and realizing the synergistic symbiosis of various types of denitrification microorganisms in the MABR heterogeneous mass transfer biofilm and the homogeneous mass transfer biofilm on the carrier. Ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) are rich in the biofilm on the surface of the membrane filament, and denitrifying bacteria, anaerobic ammonia oxidizing bacteria and other facultative aerobic bacteria and anaerobic bacteria are enriched in the biofilm attached to the sandwich mesh cloth, which is conducive to completing synchronous nitrification and denitrification on the MABR membrane assembly.

[0056] In the composite MABR membrane assembly proposed by the present invention, the membrane filaments are arranged horizontally, staggered with the inlet flow direction or even perpendicular to each other to form a cross-flow pattern, which helps to increase the mass transfer rate of the matrix and metabolites in the biofilm on the surface of the membrane filaments, thereby improving the treatment efficiency. In addition, the fixed points of the membrane filaments are in a suspended cable shape, maintaining a relatively large relaxation state, and can swing with the water flow and air flow, which not only helps to form a uniform and dense biofilm, but also is not easy to cause clogging of the membrane assembly, and can have a larger contact area with the sewage to be treated. The biofilm thereon can treat a large area of ​​sewage, further improving the denitrification efficiency of sewage.

[0057] The MABR reactor proposed in the present invention includes three areas: a pre-reaction area, a gas-water distribution area and a membrane reaction area. By dividing a plurality of different functional areas, the coordination and coupling of multiple biological denitrification reactions are achieved, the biological denitrification efficiency of the reactor is improved, and the process flow is simplified. In the pre-reaction zone and the gas-water distribution zone, suspended sludge and granular sludge are mainly present, which are rich in anaerobic ammonia oxidizing bacteria and denitrifying bacteria. Through the internal carbon source, short-term denitrification and anaerobic ammonia oxidation reactions can be completed. In the membrane reaction zone, the microorganisms are attached to the MABR membrane components in the form of attached biofilms. Aerobic and facultative nitrification biofilms are attached to the surface of the membrane fibers, which mainly complete short-term nitrification and denitrification reactions. Facultative anaerobic and anaerobic denitrification biofilms attached to the sandwich mesh cloth can carry out heterotrophic denitrification and denitrification reactions as well as a small amount of anaerobic ammonia oxidation reactions. Therefore, the infrastructure investment is reduced and the operation and management are simple. In a single-stage MABR reactor, multiple functional types of denitrifying microorganisms coexist symbiotically, thereby realizing the combination of short-term nitrification and denitrification, synchronous nitrification and denitrification, and short-term nitrification anaerobic ammonia oxidation and other processes and biological denitrification functions, thereby improving the efficient denitrification treatment effect of low carbon-nitrogen ratio sewage.

[0058] In the pre-reaction zone of the MABR reactor proposed in the present invention, the setting of the mixed liquor return system and the sludge return system can maintain the types and quantity of denitrifying microorganisms therein and improve the denitrification efficiency. At the same time, the air lift circulation device arranged inside it increases the substrate transfer rate and hydraulic shear force, which helps to form fine and dense anaerobic granular sludge and improve the retention performance of autotrophic denitrifying bacteria in the reactor.

[0059] In the MABR reactor proposed in the present invention, the MABR membrane components in the membrane reaction zone are layered into three relatively independent membrane group areas: outer, middle and inner layers. By adjusting different intermittent aeration durations, the biofilms attached to the MABR membrane components in the membrane group areas of different layers can be controlled in different states such as aerobic, aerobic / anaerobic and anaerobic, so that the functions of organic matter removal, ammonia nitrogen oxidation and simultaneous nitrification and denitrification are strengthened respectively to meet the denitrification treatment of sewage with different carbon-nitrogen ratios.

[0060] The present invention proposes an optimization control method for the MABR biofilm in the aforementioned MABR reactor. By regularly performing high-precision and close detection of the oxygen concentration in the inlet and exhaust of the membrane assembly and drawing a curve of the oxygen concentration attenuation coefficient per unit length of the membrane filament, it is possible to indirectly characterize whether the biofilm growth is too thick, so as to perform flushing and denitrification operations on the overly thick biofilm. When the biofilm is over, the inlet and exhaust of the membrane group area where the biofilm is too thick is closed, so that the biofilm is converted into an anaerobic state, the extracellular polymers in the biofilm are gradually metabolized and decomposed, and the adhesion of the biofilm is reduced. Then, a smaller air flushing intensity and hydraulic shear force can be used to achieve uniform and controllable shedding of the MABR biofilm, thereby achieving optimized control of the biofilm thickness.

[0061] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 A top plan view of the MABR membrane assembly of the present invention;

[0063] Figure 2 for Figure 1 Schematic diagram of K-direction structure;

[0064] Figure 3 It is a schematic structural diagram of the MABR reactor of the present invention;

[0065] Figure 4 It is a schematic diagram of the top view of the MABR reactor of the present invention;

[0066] Figure 5 It is a schematic diagram of the structure of the MABR reactor of the present invention when viewed from above.

[0067] Figure numerals: 900—membrane assembly; 901—air inlet pipe; 902—air outlet pipe; 903—membrane wire; 904—membrane wire bonding point; 905—membrane assembly fixing sleeve; 906—fixing point; 907—support layer; 908—outer membrane element; 909—inner membrane element; 910—fixing clamp; 9101—pillar clamp slot; 9102—air pipe clamp slot; 911—embedded plug.

[0068] 1—reaction tank; 2—membrane reaction zone; 3—membrane module support; 4—water outlet tank; 5—gas-water distribution zone; 6—water distribution plate; 7—outer membrane group zone; 8—middle membrane group zone; 9—inner membrane group zone; 10—center tube; 11—pre-reaction zone; 12—flow guide tube; 13—flow guide tube bracket; 14—center tube support column; 15—center tube bell mouth; 16—reflection cone; 17—center tube bracket; 18—air flushing fan; 19—air flushing main pipe valve; 20—air flushing main pipe; 21—air flushing pressure sensor; 22—air flushing branch pipe electric valve; 23—air Air flushing branch pipe flowmeter; 24—air flushing branch pipe; 25—outer layer air flushing perforated pipe; 26—middle layer air flushing perforated pipe; 27—inner layer air flushing perforated pipe; 28—aeration fan; 29—aeration main pipe valve (pressure reducing valve); 30—air filter assembly; 31—aeration main pipe; 32—aeration main pipe pressure sensor; 33—aeration main pipe sampling valve; 34—aeration main pipe electric valve; 35—aeration main pipe flowmeter; 36—aeration main pipe; 37—aeration branch pipe valve; 38—aeration branch pipe; 39—exhaust branch pipe sampling valve; 40—exhaust branch pipe; 41—exhaust branch pipe valve; 42—gas flowmeter for exhaust branch pipe; 43—exhaust main pipe; 44—exhaust exhaust pipe; 45—water inlet pipe; 46—water outlet pipe; 47—water inlet pipe valve for reflux pump; 48—mixed liquor reflux pump; 49—water outlet pipe valve for reflux pump; 50—reflux flowmeter; 51—mixed liquor reflux pipe; 52—reactor mud outlet valve; 53—sludge reflux pump; 54—sludge reflux valve; 55—sludge reflux flowmeter; 56—sludge reflux pipe; 57—sludge discharge valve; 58—residual sludge discharge pipe; 59—mixed liquor reflux main pipe; 60—membrane air inlet sampling pipe; 61—intake of detection flow tank Tube; 62—intake valve of oxygen concentration analyzer; 63—exhaust sampling tube collector; 64—membrane exhaust sampling tube; 65—detection flow slot; 66—high-precision oxygen concentration analyzer; 67—exhaust valve of oxygen concentration analyzer; 68—exhaust pipe of oxygen concentration analyzer; 69—online water quality analysis instrument group; 70—air lift fan; 71—air lift induced draft pipe; 72—air lift exhaust pipe; 73—air lift exhaust flowmeter; 74—center tube vent valve; 75—center tube automatic exhaust valve; 76—air lift assembly; 77—membrane assembly serial pipe; 78—gas state sensor. DETAILED DESCRIPTION

[0069] Specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0070] Reference Figure 1 to Figure 2 , the present invention provides an embodiment of a MABR membrane assembly.

[0071] A MABR membrane assembly includes: membrane elements, two groups of which are symmetrically arranged with a gap between the two groups of membrane elements, namely an outer membrane element 908 and an inner membrane element 909. The MABR membrane assembly 900 is installed vertically and presents a flat curtain-like shape as a whole.

[0072] The outer membrane element 908 has the same structural form as the inner membrane element 909. The membrane element has a sheet-like support layer 907 and a plurality of horizontal membrane threads 903 arranged horizontally from top to bottom on one side wall of the support layer 907. The membrane threads 903 are fixedly spaced from the support layer 907 and the membrane threads 903 between two adjacent fixed points 906 are in the shape of suspension cables. The membrane threads 903 are arranged on the opposite side walls of the two groups of support layers 907; the air pipe is vertically arranged on both sides of the support layer 907 and is sealed and connected to the two ends of the plurality of membrane threads 903. The fixed points of the membrane filament 903 are in a suspended cable shape, and the arc length of the entire membrane filament 903 is relatively long, which can provide a larger film-forming area. The membrane filament maintains a relatively large relaxation state and can swing with the water flow and air flow, which not only helps to form a uniform and dense biofilm, but also is not easy to cause clogging of the MABR membrane component. The position of the membrane filament changes greatly, and it can have a larger contact area with the sewage to be treated. The biofilm thereon can treat sewage over a large area, further improving the denitrification efficiency of the sewage. At the same time, since the membrane filament 903 can swing with the water flow, its swinging position changes, and the flushing water flow can flush various ranges of the membrane filament, and the surface of the membrane filament is easier to clean. Furthermore, at this time, the membrane filament 903 is in a suspended lock shape, and a section of the membrane filament in the form of a cable extends toward the outside and downward of the support layer due to the action of gravity, so that the membrane filament at one end of the cable can deviate from the support layer, and then extend to a deeper position in the flow channel between adjacent MABR membrane components, with a larger reaction area, thereby increasing the reaction area.

[0073] Exemplarily, the MABR membrane assembly 900 is mainly composed of two composite membrane elements, an outer membrane element 908 and an inner membrane element 909, and also includes inlet and outlet pipes and other accessories. The membrane assembly 900 is installed vertically and presents a flat curtain shape. The length and height of the membrane assembly can be customized according to the size of the MABR reactor 1, and the length is generally 1.5m to 3m, and the height is generally 3.0m to 5.0m.

[0074] The outer membrane element 908 and the inner membrane element 909 have the same structural form and size, and are installed symmetrically relative to the horizontal axis at the top of the MABR membrane assembly 900 in the MABR membrane assembly. The membrane filaments 903 in the membrane elements are all located outside the membrane element 900, and the sheet-like support layers 907 in the membrane elements are all located inside the membrane element 900.

[0075] The air pipes at both ends of the membrane element are the air inlet pipe 901 and the air outlet pipe 902. Between the two air pipes is a complex composed of multiple horizontal membrane filaments 903 that are parallel to each other and evenly distributed longitudinally and a whole piece of sandwich mesh cloth as a membrane filament support layer 907. The membrane filament 903 is made of dense transparent silicone rubber tube. The material is polydimethylsiloxane or methylphenyl silicone rubber, with an inner diameter of 0.5mm to 1.2mm and a wall thickness of 0.25mm to 0.5mm. It has good selective permeability to oxygen molecules, stable properties, and a wide range of pressure tolerance; the thickness of the sandwich mesh cloth is 5 to 10mm, and the unit mass is 200 to 600g / m 2 It is made of polyester and consists of three layers: upper fabric, bottom fabric and middle layer. The upper and bottom layers are hexagonal meshes with a pore size of 5 to 9 mm. The middle layer is a connecting layer with a multi-filament structure. The overall structure is light in texture, presents a three-dimensional mesh, has a certain elongation and is not easy to deform, making it suitable for the attachment and growth of microorganisms.

[0076] Each membrane thread 903 is fixed to the sandwich mesh cloth at a fixed point 906, and the fixed point 906 is an anchoring point. The fixed points on each membrane thread 903 are distributed in a rectangular array, that is, each membrane thread anchoring point is in a vertically parallel state and evenly distributed in the horizontal direction. The membrane thread anchoring point is perpendicular to the membrane thread 903, and the anchoring is discontinuous, and the spacing between adjacent anchoring points is 20cm to 30cm. Each membrane thread 903 is arranged horizontally, and maintains an appropriate relaxation state between two adjacent membrane thread anchoring points. Its length is 1.3 times to 1.5 times the spacing between adjacent anchoring points, and it naturally droops in an arc shape, that is, the membrane thread 903 between two adjacent membrane thread anchoring points is in a suspended cable shape, so that each membrane thread 903 appears wavy on the mesh support layer 907.

[0077] The two ends of each membrane thread 903 are effectively connected with the air inlet pipe 901 and the air outlet pipe 902 of the membrane element respectively. The connection method is to open a small hole at the membrane thread connection point 904 on the air inlet pipe 901 or the air outlet pipe 902, and insert the end of the membrane thread 903 into the air pipe. The end of the membrane thread 903 is inserted into the air pipe 3mm to 5mm, so that the inner cavity is well connected with the air pipe, and then the membrane thread 903 is well sealed with the membrane thread connection point 904 on the air pipe by gluing or welding, and ensure that the membrane element is under the maximum working pressure (0 to 150Kpa) without leakage. The left and right ends of the sandwich mesh cloth are respectively bonded to the air inlet pipe 901 and the air outlet pipe 902 of the membrane element.

[0078] Furthermore, the bottom ends of the air inlet pipe 901 and the air outlet pipe 902 on the membrane element are bonded and sealed with an embedded plug 911, and the upper ends are connected to the aeration pipe and the exhaust pipe of the membrane MABR reactor 1 respectively.

[0079] Furthermore, a plurality of membrane assembly fixing sleeves 905 parallel to the air pipe are provided between the supporting layer 907 of the outer membrane element 908 and the inner membrane element 909. There are usually 3 to 9 of them, which are used to install and fix the MABR membrane assembly 900 on the membrane assembly pillar 3 in the MABR reactor 1, and each membrane assembly fixing sleeve 905 is evenly distributed in the horizontal direction. The membrane assembly fixing sleeve 905 is made of ABS material or UPVC material, with a pipe diameter of DN10 to DN25, and is slightly larger than the membrane assembly pillar 3, and the length is 30 cm to 50 cm longer than the height of the MABR membrane assembly. Inside the MABR membrane assembly 900, the outer membrane element 908 and the inner membrane element 909 are separated by the membrane assembly fixing sleeve 905, and the sandwich mesh cloth of the MABR membrane element is firmly bonded to the membrane assembly fixing sleeve 905 at this location.

[0080] Furthermore, it also includes a fixed card plate 910, which is arranged on both sides of the membrane element, and the opposite sides of the two fixed card plates 910 are provided with air pipe card slots 9102 corresponding to the number of air pipes, and the opposite sides are provided with support card slots 9101. Specifically, the MABR membrane assembly 900 is also equipped with a plurality of membrane assembly fixed card plates 910, each of which includes two inlet and outlet air pipe card slots 9102 and one support card slot 9101, which are respectively used to fix the inlet and outlet air pipes at both ends of the MABR membrane assembly 900 and the membrane assembly support 3 in the MABR reactor 1. The membrane component fixing clamp 910 is made of ABS or PP material. The diameter of the inlet and outlet pipe clamping slot 9102 is 5mm to 10mm larger than the outer diameter of the membrane element inlet and outlet pipe. The gap length of the pipe clamping slot is 0.5 to 0.7 times the outer diameter of the membrane element inlet and outlet pipe to ensure that the membrane wire and the sandwich mesh cloth can pass through the gap smoothly. The diameter of the support clamping slot 9101 is slightly larger than the outer diameter of the membrane component support 3 by 5mm to 10mm, and the gap length of the support clamping slot is 0.5 times the outer diameter of the membrane component support 3.

[0081] See also Figures 3 to 5 The present invention also provides an embodiment of a MABR reactor.

[0082] A MABR reactor comprises: a reaction pool 1, which is a circular water pool and can be made of reinforced concrete or steel structure. In this embodiment, a reinforced concrete structure is used, and the ratio of diameter to pool depth is 1:1 to 4:1. A water distribution plate 6 is provided at the lower part of the reaction pool of the MABR reactor 1, which has a thickness of 10 mm to 20 mm and is made of 304 stainless steel. Circular holes with diameters of 5 mm to 15 mm are uniformly opened on the water distribution plate, and the opening rate is 20% to 40%.

[0083] The central tube 10 passes through the water distribution plate 6 at the lower end. The central tube 10 is located in the center of the reaction tank and is installed vertically along the axis of the water tank. The wall thickness is 5mm to 10mm and the material is 304 stainless steel. The ratio of the diameter of the central tube 10 to the diameter of the reaction tank is 2:10 to 3:10. The top of the central tube 10 is 1m higher than the top of the MABR reactor 1 and is sealed with a flange blind plate. A central tube vent valve 74 and a central tube automatic exhaust valve 75 are provided on the central tube 10.

[0084] After the bottom end of the central tube 10 passes through the water distribution plate 6 downward, it is connected to the central tube bell mouth 15. The diameter of the central tube bell mouth 15 is 1.2 to 1.4 times the diameter of the central tube 10. The angle of the central tube bell mouth 15 is 45° to 55°. Its bottom edge is 30cm to 50cm higher than the bottom of the reaction tank 1, which is convenient for the mixed liquid in the central tube 10 to flow out evenly to the bottom of the tank. The central tube 10 is connected and fixed to the reaction tank 1 through the central tube support column 14 and the central tube bracket 17. The support column is a 304 stainless steel pipe, which is evenly arranged at a spacing of 30cm to 50cm; the central tube bracket 15 is respectively arranged at the top of the reaction tank 1 and the water distribution plate 6, and 304 stainless steel channel steel is used. Further, a reflection cone 16 is set at the center of the bottom of the reactor 1, with a cone height of 0.5 to 1.0m and a cone angle of 90° to 110°, which is used for the uniform dispersion of the mixed liquid flowing out of the central tube 10 at the bottom of the reaction tank 1.

[0085] The lower end of the central tube 10 passes through the water distribution plate 6, dividing the reaction pool 1 into three areas. The gas-water distribution area 5 is below the water distribution plate, the upper middle part of the reaction pool 1 outside the central tube 10 is the membrane reaction area 2, and the inner side of the central tube 10 is the pre-reaction area 11. The effective volume ratio of the three areas is 1: (1-2): (3-5). The reaction pool 1 is provided with an inlet pipe 45 and an outlet pipe 46. The inlet pipe 45 is connected to the pre-reaction area 11, and the outlet pipe 46 is connected to the membrane reaction area 2. Furthermore, an annular water outlet trough 4 is provided at the top of the reaction pool 1, and the outlet pipe 46 is connected to the annular water outlet trough 4 for discharging treated water. The outlet water is discharged to subsequent facilities through the outlet pipe 46.

[0086] A guide tube 12 is provided in the pre-reaction zone 11, and a gas stripping circulation device for circulating the mixed liquid inside and outside the guide tube 12 is provided in the guide tube 12. Exemplarily, a cylindrical guide tube 12 is provided in the central tube 10, with a wall thickness of 4mm to 6mm and a material of 304 stainless steel. Its axis coincides with the axis of the central tube 10, and the ratio of the diameter of the guide tube 12 to the diameter of the central tube 10 is 1:2 to 1:3. Both ends of the guide tube 12 are open, and are connected and fixed to the central tube 10 through a guide tube bracket 13. The guide tube bracket 13 is made of 304 stainless steel angle steel, with three groups of upper, middle and lower, and each group is arranged in a cross shape.

[0087] The air stripping circulation device includes an air stripping assembly 76 and an air stripping fan 70 which are arranged at the bottom opening of the guide tube 12. The air stripping assembly 76 is made of 304 stainless steel. The gas-liquid volume ratio of the air stripping circulation device is 2-6, and the air flow rate in the air stripping assembly is 4-6 m / s. The air stripping duct 71 of the air stripping fan 70 is connected to the top of the central tube 10, and the air stripping exhaust duct 72 is connected to the top of the air stripping assembly 76. Under the action of the air stripping circulation device, the mixed liquid in the central tube 10 can circulate from bottom to top inside and outside the guide tube 12. The gas above the liquid surface in the central tube 10 is mainly connected to the air inlet of the air stripping fan 70 through the air stripping duct 71, and the pressurized air is transported to the central tube 10 through the air stripping exhaust duct 72. The air stripping duct 71 is provided with an air stripping exhaust flowmeter 73; the air stripping duct 71 and the air stripping exhaust duct 72 are both provided with valves for adjusting the air volume. The gas used in the gas stripping assembly is mainly nitrogen and other gases produced by the denitrification reaction, which are circulated in the gas stripping assembly 76 and the central tube 10, avoiding the adverse effect of oxygen on the anoxic environment required for the denitrification reaction or anaerobic ammonia oxidation reaction in the pre-reaction zone 11.

[0088] The membrane reaction zone is provided with multiple layers of annular modules composed of the above-mentioned MABR membrane components from the inside to the outside, and each annular module is formed by a plurality of MABR membrane components 900 connected in series. For example, when there are two groups of MABR membrane components, the second air pipe on the first MABR membrane component in the annular module and the first air pipe on the second MABR membrane component are connected to each other by a membrane component series pipe 77, the first air pipe on the first MABR membrane component is connected to the aeration pipe as an inlet pipe 901, and the second air pipe on the second MABR membrane component is connected to the exhaust pipe as an outlet pipe 902. The multiple layers of the annular membrane group are divided into an inner membrane group area 9, a middle membrane group area 8 and an outer membrane group area 7 from the inside to the outside, and the extension direction of the membrane filaments 903 of the membrane component is staggered with the water flow direction; at this time, the membrane filaments 903 and the inlet water flow direction are perpendicular to each other to form a cross-flow mode, which helps to improve the mass transfer rate of the matrix and metabolites in the biofilm on the surface of the membrane filaments 903, thereby improving the treatment efficiency.

[0089] An online water quality analysis instrument group 69 is arranged below the upper liquid surface of the membrane reaction zone 2 for online detection of dissolved oxygen, redox potential, ammonia nitrogen concentration and nitrite nitrogen concentration of the MABR reactor 1 .

[0090] By setting up the MABR membrane components in the membrane reaction area in different zones, the MABR membrane components in each membrane group area can be controlled separately. By adjusting the gap aeration market and aeration flow of the MABR membrane components in different zones, the biofilms in different zones can be controlled in aerobic state, aerobic + anaerobic state and anaerobic state, respectively, so as to strengthen the functions of organic matter removal, ammonia nitrogen oxidation and simultaneous nitrification and denitrification, so as to meet the efficient denitrification treatment of sewage with different carbon-nitrogen ratios. And the inlet and outlet of the MABR membrane components in different membrane groups can be controlled separately, so that the biofilm on them is converted into an anaerobic state, the extracellular polymers in the biofilm are gradually metabolized and decomposed, and the adhesion of the biofilm is reduced, and then a smaller air flushing intensity and hydraulic shear force can be used to achieve uniform and controllable shedding of the MABR biofilm, so as to achieve the optimization control of the biofilm thickness. In this way, each membrane group area can be controlled separately, and other membrane groups can operate normally, so the overall operation of the MABR reactor is not greatly affected, which is conducive to maintaining a stable operation effect.

[0091] In some embodiments, the reaction pool 1 is provided with a plurality of membrane component pillars 3 for fixing the MABR membrane component 900. The membrane component pillars 3 are perpendicular to the bottom of the reaction pool 1, and the top is slightly lower than the top of the reaction pool 1, and are distributed in a ring shape relative to the center of the reaction pool 1. The membrane component pillars 3 extend upward from the bottom of the reaction pool 1 through the water distribution plate 6, and are firmly fixed at two points of the water distribution plate 6 and the bottom of the reaction pool 1, and are used to fix the MABR membrane component 900. The mold component pillars 3 cooperate with the mold component fixing sleeve 905 or the pillar card slot 9101. The membrane component pillars 3 are in the shape of multiple concentric circles in the reaction pool 1 and are evenly distributed in the radial direction. They are divided into three areas, inner, middle, and outer, according to the radius of the concentric circles, corresponding to the installation of the MABR membrane components in the inner membrane group area, the middle membrane group area, and the outer membrane group area, respectively. The polar angles of the two adjacent membrane component pillars 3 in the inner circle and the middle circle relative to the center of the ring are 22.50°, and the polar angle of the outer circle is 11.25°. A plurality of MABR membrane assemblies 900 are vertically installed in the membrane reaction zone 2. When installing the MABR membrane assemblies 900, the membrane assembly fixing sleeves 905 are inserted into the membrane assembly pillars 3. Each membrane assembly fixing sleeve 905 corresponds to a membrane assembly pillar 3 one by one. Both sides of the MABR membrane assembly 900 are fixed to the adjacent membrane assembly pillars 3 by membrane assembly fixing clamps 910.

[0092] In some embodiments, each of the annular membrane groups includes two symmetrically arranged semi-annular membrane groups, and the semi-annular membrane groups are formed by connecting a plurality of the MABR membrane components in series. The two semi-annular modules are symmetrically arranged with respect to the horizontal diameter of the reaction tank 1. The air pipes on both sides of the semi-annular modules are respectively an inlet pipe and an outlet pipe. The inlet pipes of the two semi-annular modules are located on the same side of the reaction tank. In this embodiment, the left end of the semi-ring is an inlet pipe 901, and the right end is an outlet pipe 902. Each of the inlet pipes 901 is connected to the aeration pipe of the aeration system, and each of the outlet pipes 902 is connected to the exhaust pipe of the aeration system. Exemplarily, multiple MABR membrane components in the same half-ring module are connected together in an end-to-end series manner, the second air pipe of the first MABR membrane component and the first air pipe of the second MABR membrane component are interconnected through the membrane component series pipe 77, and the second air pipe of the second MABR membrane component and the first air pipe of the third MABR membrane component are interconnected through the membrane component series pipe 77. At this time, the first air pipe of the first MABR membrane component is located at the left end of the reaction tank as the air inlet pipe 901, and the second air pipe of the third MABR membrane component is located at the right end of the reaction tank 1 as the air outlet pipe.

[0093] In some embodiments, an aeration system is provided to aerate the membrane filaments 903 on each layer of the annular module. The aeration pressure of the MABR membrane assembly is 5KPa to 50KPa, and the aeration flow rate per unit membrane filament length is 3 to 10L / (h·m 膜丝 ). In order to prevent the air in the MABR membrane from generating condensed water, electric heating is installed on the exhaust branch pipe 40 and the discharge main pipe 43 where condensed water is easily generated. The temperature is controlled at 30-40°C, which can effectively reduce the problem of condensed water accumulation.

[0094] Specifically, the aeration system includes an aeration branch pipe 38 connected to two air inlet pipes 901 on one end of each half ring module, and an aeration branch pipe valve 37 is arranged on each aeration branch pipe 38; the two aeration branch pipes 38 are converged to an aeration main pipe 36, and the aeration branch pipes 38 in the same layer of membrane group area (outer layer, middle layer and inner layer) are converged to the aeration main pipe 36 of this layer; each aeration main pipe 36 is provided with an aeration main pipe electric valve 34 and an aeration main pipe flowmeter 35; each aeration main pipe 36 is then converged to the aeration main pipe 31, the aeration main pipe 31 is connected to the aeration fan 28, and an aeration main pipe valve 29, a set of air filter components 30 and an aeration main pipe pressure regulator 32 are arranged on the aeration main pipe 31.

[0095] The aeration system also includes an exhaust branch pipe connected to two outlet pipes 902 on one end of each half ring module, and an exhaust branch pipe valve 41 is provided on each exhaust branch pipe 40; the two exhaust branch pipes 40 on each half ring module are collected and connected to the exhaust main pipe 43 through an exhaust branch pipe gas flow meter 42, and finally converge to the exhaust pipe 40.

[0096] Furthermore, the aeration system is also provided with an oxygen concentration detection component for indirectly evaluating the thickness, density and other properties of the biofilm on the surface of the MABR membrane fibers, thereby determining the biofilm thickness optimization control strategy. The oxygen concentration detection component includes a membrane air intake sampling tube 60, a detection flow slot 65 and a high-precision oxygen concentration analyzer 66 arranged on the aeration tube. The membrane air intake sampling tube 60 and the membrane exhaust sampling tube 64 are both connected to the detection flow slot 65, and the measurement probe of the high-precision oxygen concentration analyzer 66 extends into the detection flow slot 65.

[0097] Among them, the membrane air intake sampling tube 60 is arranged on the aeration main pipe 31, and the membrane air intake sampling tube 60 is provided with an aeration main pipe sampling valve 33; the membrane exhaust sampling tube 64 is connected to the exhaust branch pipe 40 on each half ring module, and the exhaust branch pipe 40 is provided with an exhaust branch pipe sampling valve 39, and each membrane exhaust sampling tube 64 is collected into an exhaust sampling tube collector 63, and then connected with the detection flow slot 65, and the detection flow slot air intake tube 61 is provided with three oxygen concentration analyzer air intake valves 62, which are used to control the membrane air intake sampling, membrane exhaust sampling and detection flow slot air intake respectively. The detection flow slot is provided with an oxygen concentration analyzer tail gas exhaust pipe 68, and the oxygen concentration analyzer tail gas exhaust pipe 68 is provided with an oxygen concentration analyzer exhaust valve 67.

[0098] The gas to be detected enters the detection flow slot 65 from the membrane inlet sampling tube 60 or the membrane exhaust sampling tube 64 through the corresponding oxygen concentration analyzer inlet pipe valve 62, and the measuring probe of the high-precision oxygen concentration analyzer 66 extends into the detection flow slot 65 to detect the oxygen concentration of the gas therein. The detected gas is discharged from the detection flow slot 65 through the oxygen concentration analyzer exhaust valve 67 on the oxygen concentration analyzer exhaust pipe 68.

[0099] In some embodiments, an air flushing system is provided for flushing the biofilm formed on the annular membrane group with air. The air flushing flow rate per effective volume of the membrane reaction zone during steady-state operation is 3 to 8 L / (m 3 有效容积 ·min), and the air flushing frequency is 10 to 20 seconds every 15 to 30 minutes.

[0100] Specifically, the air flushing system includes a plurality of groups of air washing perforated tubes arranged in the air-water distribution area 5 and corresponding to each layer of the annular membrane group. The plurality of air washing perforated tubes are arranged in concentric rings, corresponding to the annular modules in the outer membrane group area 7, the middle membrane group area 8 and the inner membrane group area 9, respectively, and are divided into an outer layer air washing perforated tube 25, a middle layer air washing perforated tube 26 and an inner layer air washing perforated tube 27. The perforated tubes are made of 304 stainless steel or ABS material, and each perforated tube is evenly provided with air outlet holes that are obliquely downward and open at 45 degrees, with a hole diameter of 5mm to 10mm. The air flushing perforated pipes in the same membrane group area are connected to an air flushing branch pipe 24; each air flushing branch pipe 24 is connected to the air flushing main pipe 20, and is connected to the air flushing compressor 18 through an air flushing pressure sensor 21 and an air flushing main pipe valve 19; each air flushing branch pipe 24 is provided with an air flushing branch pipe electric valve 22 and an air flushing branch pipe flow meter 23.

[0101] In some embodiments, a mixed liquor reflux system is provided for reflux the mixed liquor from the membrane reaction zone to the pre-reaction zone and a sludge reflux system is provided for reflux the sludge in the reaction tank to the pre-reaction zone. Usually, the ratio of the mixed liquor reflux to the water inlet is 100% to 300%, and the ratio of the sludge reflux to the water inlet is 50% to 150%.

[0102] Among them, the mixed liquor reflux system includes a mixed liquor reflux pipe 51 arranged at the upper part of the reaction tank 1, and the sludge reflux system includes a sludge reflux pipe 56 arranged at the bottom of the reaction tank 1. The mixed liquor reflux pipe 51 and the sludge reflux pipe 56 are connected to the pre-reaction zone 11 through a mixed liquor reflux main pipe 59, and the sludge reflux pipe 56 is also provided with a sludge discharge valve 57.

[0103] Specifically, the mixed liquid reflux pipe 51 is arranged below the liquid surface, and a mixed liquid reflux pump 48 is arranged on the mixed liquid reflux pipe 51. A reflux pump inlet pipe valve 47 and a reflux pump outlet pipe valve 49 are respectively arranged on the inlet and outlet pipes of the mixed liquid reflux pump 48 to adjust the reflux amount of the mixed liquid. A reflux flow meter 50 is also arranged on the pipe between the reflux pump outlet valve 49 and the mixed reflux main pipe 59.

[0104] The sludge return pipe 56 is arranged at the lower part of the gas-water distribution area 5. A sludge return pump 53 is arranged on the sludge return pipe 56 to lift the return sludge to the mixed liquor return main pipe 59. A reactor mud outlet valve 52 is arranged at the water inlet of the sludge return pump 53. The water outlet pipeline of the sludge return pump 53 is connected to the mixed liquor return main pipe 59 through the sludge return valve 54 and the sludge return flowmeter 55. A residual sludge discharge pipe 58 is arranged on the sludge return pipe 56 between the sludge return pump 53 and the sludge return valve 54, and the sludge discharge amount is controlled by the mud discharge valve 57.

[0105] Based on the above MABR reactor, the present invention also provides an operation method of a MABR reactor.

[0106] A method for operating a MABR reactor, using the above-mentioned MABR reactor:

[0107] S001. Set the mixed liquor return ratio, sludge return ratio, gas-liquid volume ratio of the air stripping circulation device and air flow rate in the air stripping assembly according to the operation mode of the MABR reactor; control the aeration pressure, aeration flow rate and intermittent aeration time of the MABR membrane assembly in each membrane group area through the aeration system, and then control the biofilm in each membrane group area to present different working states; regularly flush the biofilm on the MABR membrane assembly in each membrane group area through the air flushing system to maintain the stable operation of the MABR reactor;

[0108] S002. Sewage is injected into the pre-reaction zone from the water inlet pipe, mixed with the return mixed liquor and return sludge, and circulated inside and outside the guide tube under the action of the air stripping circulation device, and denitrification reaction and / or anaerobic ammonium oxidation reaction occurs;

[0109] S003, the effluent from the pre-reaction zone flows from the bottom of the central tube into the gas-water distribution area to undergo heterotrophic denitrification and / or anaerobic ammonia oxidation reactions;

[0110] S004. The effluent from the gas-water distribution area passes through the water distribution plate and enters the membrane reaction area to complete the nitrite reaction, and then continues to undergo anoxic denitrification reaction and / or anaerobic ammonia oxidation reaction, and is then discharged through the outlet pipe.

[0111] Furthermore, in step S001, the mixed liquor reflux ratio is 100% to 300%, the sludge reflux ratio is 50% to 150%, the gas-liquid volume ratio of the air stripping circulation device is 2 to 6, and the air flow rate in the air stripping assembly is 4 to 6 m / s; the aeration pressure of the MABR membrane assembly is 5 KPa to 50 KPa, and the aeration flow rate per unit membrane length is 3 to 10 L / (h·m 膜丝 ); The air flushing flow rate per effective volume of the membrane reaction zone during stable operation is 3 to 8 L / (m 3 有效容积 ·min), and the air flushing frequency is 10 to 20 seconds every 15 to 30 minutes.

[0112] Illustratively, a first embodiment of a method for operating a MABR reactor is provided.

[0113] When the MABR reactor operates in the short-cut nitrification and denitrification mode:

[0114] Sewage with low carbon-nitrogen ratio, COD = 100 ~ 150 mg / L, NH4 + -N = 70 ~ 100 mg / L. After water quality and quantity adjustment and pre-treatment such as primary sedimentation, it enters the pre-reaction zone 11 of the MABR reactor through the water inlet pipe 45 and is fully mixed with the return mixed liquor and sludge. Denitrifying bacteria are enriched in the suspended sludge and return sludge in the pre-reaction zone 11, and the influent organic matter is used as a carbon source to produce heterotrophic short-range denitrification reaction, reducing nitrite nitrogen and a small amount of nitrate nitrogen in the return mixed liquor to nitrogen gas. The mixed liquor return ratio of the MABR reactor is 150 ~ 200%, and the sludge return ratio is 50%.

[0115] The gas stripping assembly 76 in the pre-reaction zone 11 is continuously opened, and the gas above the liquid in the central tube 10 is used for circulating gas stripping operation. The gas stripping circulation intensity is controlled at a relatively low state. The gas-liquid volume ratio of the gas stripping circulation device is 2 to 3, and the air flow rate in the gas stripping assembly is 4 to 5 m / s.

[0116] The effluent from the pre-reaction zone 11 flows out from the bottom of the central tube 10 and is evenly dispersed to the gas-water distribution zone 5 at the bottom of the pool. There are various forms of sludge in the gas-water distribution zone 5, including suspended denitrification sludge and aged and detached MABR biofilm, which are rich in anaerobic bacteria and denitrifying bacteria. The ammonia nitrogen in the influent, nitrite nitrogen and nitrate nitrogen in the reflux liquid that are not removed in the pre-reaction zone 11 continue to undergo heterotrophic denitrification reaction in the gas-water distribution zone 5. This reaction mainly uses the dead bacteria in the reflux sludge and the organic matter in the metabolites as the internal carbon source, without the need for an external carbon source.

[0117] The outlet water of the gas-water distribution area 5 passes upward through the water distribution plate 6 and is evenly distributed into the membrane reaction area 2. The composite MABR membrane components are evenly arranged in the membrane reaction area 2. The composite structure of the oxygen-permeable membrane filaments 903 and the sandwich mesh cloth is conducive to the attachment and growth of multi-layer structures and various types of denitrification biofilms thereon, thereby completing the removal of organic matter and nitrogen. A biofilm with heterogeneous mass transfer grows on the surface of the membrane filaments 903, that is, the inside of the biofilm close to the surface of the membrane filaments is an aerobic layer, rich in aerobic ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB); the outside of the biofilm is an anaerobic layer, rich in denitrifying bacteria. A biofilm with unidirectional mass transfer grows on the surface and in the mesh of the sandwich mesh cloth 907, that is, a biofilm grown on the surface of the carrier in the traditional biofilm process, with an anaerobic layer on the outside and an anaerobic layer on the inside, rich in denitrifying bacteria and anaerobic bacteria. By controlling the intermittent aeration of the MABR membrane assembly, adjusting the aeration main valve 29 (pressure reducing valve) to control a lower air supply pressure, and adjusting the aeration main electric valve 34 to control an appropriate air supply flow, the growth of nitrite oxidizing bacteria in the MABR biofilm can be inhibited to a certain extent, so that most of the ammonia nitrogen is converted into nitrite nitrogen, that is, the nitrite reaction is completed in the MABR biofilm, and only a small amount of ammonia nitrogen is oxidized to nitrate nitrogen. Part of the generated nitrite nitrogen and nitrate nitrogen can undergo denitrification reaction in the aerobic biofilm on the sandwich mesh cloth nearby to produce nitrogen; the other nitrite nitrogen and nitrate nitrogen can be mixed and refluxed to the pre-reaction zone 11 to undergo a short-range denitrification reaction.

[0118] The membrane components in the MABR reactor are divided into the outer membrane group area 7, the middle membrane group area 8 and the inner membrane group area 9, which are divided into three different areas: outer, middle and inner. By adjusting the intermittent aeration time and air flow of each area separately, the MABR biofilm in different areas can be controlled in different working states such as aerobic or anaerobic. If the aeration time in a certain area is long and the air flow is large, the proportion of aerobic layer in the MABR biofilm increases, which helps to increase the nitrite ratio and enhance the removal efficiency of organic matter; on the contrary, if the aeration time in a certain area is short and the air flow is small, the proportion of anaerobic layer in the MABR biofilm increases, the proportion of aerobic layer decreases, and an anaerobic layer may appear on the outside, which helps to carry out simultaneous nitrification and denitrification reactions on it, while increasing the inhibitory effect on the activity of nitrite oxidizing bacteria.

[0119] In this embodiment, the aeration pressure of the MABR membrane module is adjusted to 5KPa-10KPa, and the hydraulic retention time is 4-6h. The intermittent aeration time of the outer membrane group area 7 is controlled to be aerated for 30min and stopped for 60min, and the aeration flow rate is 3-4L / (h·m 膜丝 ); The intermittent aeration time of the middle membrane group zone 8 is 30 minutes of aeration and 30 minutes of stop, and the aeration flow rate is 4 to 6 L / (h·m 膜丝 ); The inner membrane group zone 9 is continuously aerated, and the aeration flow rate is 6 to 8 L / (h·m 膜丝). As a result, the MABR biofilm in the outer and middle membrane groups is mainly aerobic in the inner layer and facultative in the outer layer, the activity of nitrite oxidizing bacteria is inhibited, and a short-range nitrification reaction occurs; the MABR biofilm in the inner membrane group is aerobic, which is conducive to the aerobic degradation of organic matter that is not easily utilized by denitrifying bacteria in the pre-reaction zone 11, thereby controlling the effluent organic matter concentration at a low level.

[0120] The air flushing system at the bottom of the MABR reactor is used to regularly flush the biofilm that grows too thick on the surface of the MABR membrane assembly, control the normal renewal rate of the MABR biofilm, and maintain the stable operation of the MABR reactor. The air flushing system is also divided into three layers: outer, middle, and inner. Corresponding to the membrane group areas of different layers of the MABR membrane assembly, different air flushing controls can be implemented for the outer, middle, and inner membrane group areas, thereby realizing the optimization control strategy of the MABR biofilm in different areas.

[0121] In this embodiment, conventional air flushing can meet the stable operation of the MABR biofilm, which is conducive to maintaining the biofilm thickness and density of the outer, middle and inner membrane groups in a relatively stable state. The conventional air flushing operation control parameters are: the air flushing frequency of the outer layer air washing perforated pipe 25 is 5 seconds every 60 minutes; the air flushing frequency of the middle layer air washing perforated pipe 26 is 10 seconds every 45 minutes; the air flushing frequency of the inner layer air washing perforated pipe 27 is 15 seconds every 30 minutes.

[0122] Through the indirect evaluation of the MABR biofilm thickness at regular intervals, it is necessary to perform air flushing and film removal operations on the biofilm that has grown too thick. The operation method can be carried out using the MABR biofilm optimization control method proposed in the present invention.

[0123] An online water quality analysis instrument group 69 is arranged on the upper part of the MABR reactor, including an online dissolved oxygen meter, an online ORP meter, online ammonia nitrogen, online nitrite nitrogen and online nitrate nitrogen, etc., for monitoring the working conditions in the reactor, so as to adjust the process parameters and optimize the operation of the reactor. In this embodiment, the dissolved oxygen concentration is controlled at 0.2mg / L-0.5mg / L, and the ORP value is 100mV-300mV; the nitrite rate (the ratio of nitrite nitrogen to the sum of nitrite nitrogen and nitrate nitrogen) of the reactor is controlled at 80%-90%.

[0124] When the MABR reactor is running stably, the effluent COD is less than 30 mg / L, the ammonia nitrogen is less than 1.0 mg / L, the ammonia nitrogen removal rate is greater than 99%, and the total nitrogen removal rate is greater than 90%.

[0125] A second embodiment of a method for operating a MABR reactor is provided.

[0126] When the MABR reactor operates in the short-cut nitrification-anaerobic ammonium oxidation mode:

[0127] The effluent of a high-concentration organic wastewater after pretreatment and anaerobic biological treatment is COD = 100-200 mg / L, NH4 + -N=

[0128] 150-250 mg / L, becoming a typical low carbon-nitrogen ratio sewage. The sewage enters the pre-reaction zone 11 and is fully mixed with the return mixed liquor and the return sludge. The suspended sludge and return sludge in the pre-reaction zone 11 contain anaerobic ammonia-oxidizing bacteria, which use the ammonia nitrogen in the influent as an electron donor and the nitrite nitrogen in the return mixed liquor as an electron acceptor to undergo autotrophic anaerobic ammonia oxidation reaction, converting ammonia nitrogen and nitrite nitrogen into nitrogen gas. The sludge in the pre-reaction zone 11 also contains denitrifying bacteria, which can use the organic matter in the influent as a carbon source and the dead bacteria or metabolites in the return sludge as an internal carbon source to heterotrophically denitrify part of the nitrate nitrogen produced by the anaerobic ammonia-nitrification reaction and the nitrate nitrogen in the mixed liquor return into nitrogen gas. The mixed liquor return ratio of the reactor is 200-300%, and the sludge return ratio is 75%-100%.

[0129] The gas stripping assembly 76 in the pre-reaction zone 11 is continuously opened, and the gas above the liquid in the central tube 10 is used for circulating gas stripping operation. The gas stripping cycle is controlled in a relatively high intensity range to promote the full mixing of sewage, return mixed liquor and return sludge, and improve the substrate mass transfer rate and denitrification reaction rate. At the same time, the gas stripping action drives the rapid circulation of suspended sludge, and the water flow shear force is large, which helps to form a relatively dense granular sludge in which denitrifying bacteria and anaerobic ammonia oxidizing bacteria coexist, improves the sedimentation rate of sludge, and also enhances the retention performance of autotrophic denitrifying microorganisms with a long generation cycle in the reactor. The gas-liquid volume ratio of the gas stripping circulation device is 4-6, and the air flow rate in the gas stripping assembly is 8-10m / s.

[0130] The effluent from the pre-reaction zone 11 flows evenly into the gas-water distribution zone 5, where a large amount of granular anaerobic sludge with good settling performance exists at the bottom, containing anaerobic bacteria and facultative anoxic zones with high abundance of anaerobic ammonia-oxidizing bacteria and denitrifying bacteria; the upper part is mainly composed of suspended sludge, aged and detached MABR biofilm, and granular sludge with low density. The ammonia nitrogen in the influent that is not removed in the pre-reaction zone, and the nitrate nitrogen and nitrite nitrogen in the reflux liquid continue to undergo anaerobic ammonia-oxidation autotrophic denitrification reaction and a small amount of heterotrophic denitrification reaction in the gas-water distribution zone 5.

[0131] The outlet water of the gas-water distribution area 5 flows upward through the water distribution plate 6 and evenly enters the membrane reaction area 2. The composite MABR membrane components are evenly arranged in the membrane reaction area 2. The composite structure of the oxygen-permeable membrane filament 903 and the sandwich mesh cloth is conducive to the attachment and growth of multi-layer structures and various types of denitrification biofilms thereon, completing the removal function of organic matter, ammonia nitrogen and total nitrogen. A biofilm with heterogeneous mass transfer grows on the surface of the membrane filament 903, that is, the inside of the biofilm close to the surface of the membrane filament 903 is an aerobic layer, rich in aerobic ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB); the outside of the biofilm is an anaerobic layer, rich in denitrifying bacteria. An ordinary biofilm with unidirectional mass transfer grows on the surface and mesh of the sandwich mesh cloth, with anaerobic denitrifying bacteria on the outside and anaerobic layers rich in anaerobic ammonia oxidizing bacteria on the inside. Ammonia nitrogen in sewage diffuses into the interior of the MABR biofilm under the action of concentration difference. By controlling the intermittent aeration of the MABR membrane components, the activity of nitrite oxidizing bacteria (NOB) in the MABR biofilm can be inhibited to a certain extent, so that most of the ammonia nitrogen is converted into nitrite nitrogen, that is, the nitrite reaction or partial nitrite reaction is completed in the MABR biofilm. The generated nitrite nitrogen undergoes heterotrophic denitrification in the biofilm on the sandwich mesh cloth to produce nitrogen; or it undergoes anaerobic ammonia oxidation reaction with the ammonia nitrogen in the sewage by the anaerobic ammonia oxidizing bacteria in the inner layer of the biofilm to produce nitrogen.

[0132] In this embodiment, the gas supply pressure of the MABR membrane module is adjusted to 5KPa-10KPa, and the hydraulic retention time is 4-6h. The intermittent aeration time of the outer membrane group area 7 is controlled to be aerated for 30min and stopped for 90min, and the aeration flow rate is 3-4L / (h·m 膜丝 ); Control the intermittent aeration time of the middle membrane group area 8 and the inner membrane group area 9 to be 30 minutes of aeration and 60 minutes of rest, and the aeration flow rate is 3-4L / (h·m 膜丝 ); the nitrite rate (the ratio of nitrite nitrogen to the sum of nitrite nitrogen and nitrate nitrogen) in the membrane reaction zone is controlled at 90% to 95%, and the nitrite reaction degree (the ratio of nitrite nitrogen to ammonia nitrogen in the influent) is controlled at 55% to 65%.

[0133] In this embodiment, conventional air flushing can meet the stable operation of the MABR biofilm, which is conducive to maintaining the biofilm thickness and density of each layer of the membrane assembly in the optimal state. The conventional air flushing operation control parameters are: the air flushing frequency of the outer layer air washing perforated pipe 25 is 10 seconds every 60 minutes; the air flushing frequency of the middle and inner layer air washing perforated pipes is 10 seconds every 30 minutes. Through the indirect assessment of the thickness of the MABR biofilm on a regular basis, it is necessary to perform air flushing and film removal operations on the biofilm that has grown too thick. The operation method can be carried out using the MABR biofilm optimization control method proposed in the present invention.

[0134] An online water quality analysis instrument group 69 is arranged on the upper part of the MABR reactor 1, and the dissolved oxygen concentration is controlled at 0 mg / L to 0.2 mg / L, and the ORP value is -100 mV to 100 mV.

[0135] When the MABR reactor is running stably, the effluent COD is less than 50 mg / L, the ammonia nitrogen is less than 2.0 mg / L, the ammonia nitrogen removal rate is greater than 99%, and the total nitrogen removal rate is 90-95%.

[0136] MABR biofilm will gradually thicken with the operation of the reactor, especially the degradation of organic matter and heterotrophic denitrification process will aggravate the condition of biofilm thickening, so it is necessary to detect and evaluate the thickness of biofilm so as to take measures such as hydraulic shearing and air flushing to control the thickness of biofilm. In view of the current in-situ online monitoring technology of biofilm thickness is not mature.

[0137] The present invention also provides a method for optimizing and controlling a MABR biofilm, using the above-mentioned MABR reactor:

[0138] S001. According to the operation mode of the MABR reactor, a corresponding composite biofilm is formed on the MABR membrane components in each membrane group area, and the MABR reactor is operated stably;

[0139] S002. Evaluate the biofilm thickness: Use the oxygen concentration detection component to regularly detect the oxygen concentration in the aeration pipe and exhaust pipe in the corresponding membrane group area, calculate the oxygen concentration attenuation coefficient per unit length of membrane filament, and draw a curve of the coefficient changing with time;

[0140] S003. When the change curve in the corresponding membrane group area in step S002 shows a downward trend, the biofilm is too thick, and the aeration of the MABR membrane assembly in the membrane group area is stopped and maintained for a period of time, and then the biofilm in the membrane group area is washed and removed by air through the air flushing system;

[0141] S004. After the biofilm falls off, it grows again and the change curve shows an upward trend until the change amplitude of the change curve is small. The biofilm thickness is stable and the air flushing system is operated according to the normal flushing operation parameters.

[0142] The oxygen concentration of the air supply in the aeration main pipe 31 of the MABR membrane assembly and the exhaust in the exhaust branch pipe 40 are regularly detected and analyzed by a high-precision oxygen concentration analyzer 66, and then the oxygen concentration attenuation coefficient of the membrane wire per unit length is calculated according to the number of membrane assemblies and the length of the membrane wire in the semi-ring membrane group where the exhaust branch pipe 40 is located, and the change curve of the coefficient over time is drawn. When the biofilm is too thick, the curve shows a downward trend, and the greater the thickness of the biofilm, the greater the slope of the curve; the curve shows an upward trend during the re-growth process after the biofilm falls off; and during steady-state operation, the biofilm thickness is relatively stable and the curve changes less. For specific influent water quality and specific specifications of MABR reactors, data can be accumulated and corresponding change curves can be drawn, thereby indirectly characterizing the thickness, density and other properties of the MABR biofilm; at the same time, the membrane wires in the reactor can be regularly cut, the biofilm thickness can be measured offline, and the oxygen concentration attenuation curve of the membrane wire per unit length can be corrected to improve the accuracy of indirect evaluation of the biofilm thickness.

[0143] The membrane filaments in the outer, middle and inner membrane assemblies in the MABR reactor 1 are of different lengths, and the number of membrane assemblies in series is also different. Therefore, it is necessary to detect and analyze the half rings of membrane assemblies in different layers and draw the oxygen concentration attenuation curve of the unit length of the membrane filaments in this layer to evaluate the biofilm thickness of this layer.

[0144] Furthermore, the biofilm forming method of the composite biofilm in step S001 is:

[0145] S0011, Nitrification and denitrification biofilm stage:

[0146] (1) Sludge inoculation is carried out through the water inlet pipe. Nitrification sludge in the aerobic tank and denitrification sludge in the anoxic tank of the well-functioning AO or AAO process wastewater treatment facility are taken. After settling for 60 minutes, the supernatant is removed and mixed evenly. The two sludges are used as the inoculation sludge of the MABR reactor 1. The volume ratio of the two sludges is 2:1 to 5:1. The inoculation sludge is added to the central tube 10 of the MABR reactor 1 from the pipeline of the reactor water inlet 45. The sludge return system, aeration system and air lift circulation device are continuously opened, the air flushing system is indirectly opened, the mixed liquor return system is closed, the water inlet is adjusted to 1 / 3 of the design flow rate, and the water is continuously discharged;

[0147] In the MABR reactor, sludge is formed and circulated between the pre-reaction zone and the air-water distribution zone; at the same time, due to intermittent air flushing, the suspended sludge rises with the airflow and is partially retained in the mesh by the sandwich mesh cloth in the membrane assembly, forming a relatively uniform retained sludge layer. Due to the low influent load and the failure to open the mixed liquid backflow, the hydraulic shear force on the surface of the membrane assembly is small, which is conducive to the microorganisms in the retained sludge layer to attach and grow on the membrane fiber surface to form MABR biofilm.

[0148] (2) After the biofilm is formed on the surface of the membrane fibers, the water flow rate is gradually increased, and the mixed liquid reflux system is intermittently opened, and the interval time for opening the air flushing system is gradually increased. The increased hydraulic shear force helps to increase the density of the MABR biofilm;

[0149] (3) After the inlet flow rate reaches the design flow rate, the mixed liquor return system is changed to be continuously opened, and the sludge return system is continuously opened and the air flushing system is opened intermittently and operated stably for a period of time; a nitrifying biofilm is formed on the membrane fiber surface of the MABR membrane assembly, which is rich in ammonia oxidizing bacteria and nitrite oxidizing bacteria, and an aerobic nitrifying biofilm is formed on the sandwich mesh cloth, completing the first stage of the MABR membrane assembly. At this time, the ammonia nitrogen removal rate of the reactor effluent is higher than 90%, the total nitrogen removal rate exceeds 50%, and the nitrite nitrogen accumulation rate is less than 10%.

[0150] S0012. Short-term nitrification and denitrification biofilm stage: Change the aeration system to intermittent opening and run it continuously for a period of time until the effluent ammonia nitrogen removal rate exceeds 80%, the total nitrogen removal rate exceeds 60%, and the nitrite nitrogen accumulation rate exceeds 60%. A biofilm dominated by short-term nitrification and denitrification is formed in the MABR reactor.

[0151] The continuous aeration of the MABR reactor was changed to intermittent aeration, and the mixed liquor reflux, air stripping device and sludge reflux were continuously opened to maintain intermittent air flushing. The activity of ammonia oxidizing bacteria (AOB) in the MABR biofilm continued to increase, while the activity of nitrite oxidizing bacteria (NOB) was gradually suppressed, and its proportion in the biofilm remained at a low level; the thickness of the biofilm on the sandwich mesh cloth gradually increased, forming an external aerobic and internal anaerobic biofilm, in which the proportion of denitrifying bacteria continued to increase. After continuous operation for a period of time, when the effluent ammonia nitrogen removal rate exceeded 80%, the total nitrogen removal rate exceeded 60%, and the nitrite nitrogen accumulation rate exceeded 60%, a biofilm dominated by short-range nitrification and denitrification was formed in the MABR reactor.

[0152] S0013, Short-range nitrification anaerobic ammonium oxidation biofilm stage: Add granular anaerobic ammonium oxidation sludge into the central tube 10, change the sludge return system to intermittent opening, maintain intermittent aeration and intermittent air flushing, continuous mixed liquid return and air stripping device, and run for a period of time; some anaerobic ammonium oxidation granular sludge disintegrate. After the disintegration, the anaerobic ammonium oxidizing bacteria in the granular sludge grow in the form of suspended sludge in the air-water distribution area 5. The suspended sludge enters the central tube 10 with the intermittently returned sludge, and circulates inside and outside the guide tube 12 under the action of the air stripping circulation device. The high hydraulic shear force causes the suspended sludge to gradually form small and dense granular sludge. Some suspended anaerobic ammonium oxidizing bacteria enter the MABR membrane module with the water flow and grow on the sandwich mesh cloth. As a result, a composite biofilm is formed on the MABR membrane assembly, that is, a biofilm dominated by ammonia oxidizing bacteria on the membrane surface and a biofilm dominated by denitrifying bacteria and anaerobic ammonia oxidizing bacteria on the sandwich mesh cloth. In the gas-water distribution area and pre-reaction area of ​​the reactor, fine and dense anaerobic ammonia oxidizing granular sludge and suspended sludge dominated by denitrifying bacteria are gradually formed. At this time, a biological denitrification system with symbiotic heterotrophic denitrification and autotrophic denitrification is formed in the reactor.

[0153] Furthermore, the calculation formula of the oxygen concentration attenuation coefficient per unit length of the membrane fiber in step S002 is:

[0154]

[0155] In formula (1), LOAT is the oxygen concentration attenuation coefficient per unit length of membrane filament, that is, the attenuation value of the oxygen concentration when air flows through a unit length of membrane filament in a MABR membrane module at a specific position, gO2 / (m·h); W in is the oxygen flow rate in the aeration of MABR membrane module, gO2 / h; W out is the oxygen flow rate in the exhaust gas of the MABR membrane module, gO2 / h; n m is the number of membrane fibers contained in the MABR membrane module, root; l m is the length of a single membrane filament in the MABR membrane module;

[0156] In formula (2), P in is the aeration pressure of MABR membrane module, Pa; Q in is the flow rate of the aeration pipe, corresponding to the flow rate of the aeration main pipe on a certain membrane group area, m 3 / h; C in is the oxygen content in the aeration pipe, %; 32 is the molar mass of oxygen, g / mol; n n The number of membrane modules connected to the aeration pipe for measuring flow rate, usually each aeration main pipe will be connected to all aeration branches in the outer, middle and inner membrane module areas of the semi-ring module in the reactor; R is the gas constant, 8.314 J / (mol·K); Tin is the intake air temperature, K; wherein the aeration pressure value comes from the aeration main pipe pressure sensor 32, the aeration main pipe flow value comes from the aeration main pipe flow meter 35, and the aeration oxygen content value comes from the detection value of the high-precision oxygen concentration analyzer;

[0157] In formula (3), P out is the exhaust pressure of MABR membrane module, Pa; Q out is the flow rate of the exhaust pipe, corresponding to the flow rate of the exhaust branch pipe given by a certain membrane group area, m 3 / h; C out is the oxygen content in the exhaust pipe, %; T out is the exhaust temperature, K. The pressure, flow and temperature of the exhaust branch pipe 40 can be measured by the gas state sensor 78 provided on the detection flow slot 65. At this time, the exhaust branch pipe valve 41 to be measured should be closed to allow all exhaust gases to pass through the detection flow slot 65; the exhaust oxygen content value comes from the detection value of the high-precision oxygen concentration analyzer 66.

[0158] In step S003, when the change curve in the corresponding membrane group area in step S002 shows a downward trend, when the biofilm is too thick, first, close the aeration main pipe electric valve 34 and the exhaust branch pipe valve 41 of the membrane group area, and close the air flushing branch pipe electric valve 22 of the corresponding air washing perforated pipe under the membrane area; other membrane groups and the supporting reflux system and air flushing system are working normally, and the MABR reactor continuously enters and exits water. Secondly, after a period of no ventilation, the MABR biofilm in the membrane group area gradually transforms into anoxic or anaerobic state, and anaerobic bacteria rapidly proliferate inside the biofilm on the surface of the membrane filament 903. The anaerobic bacteria decompose the extracellular polymers (ESP) produced by aerobic bacteria in the MABR biofilm, which reduces the adhesion of the biofilm to the surface of the membrane filament 903, and also reduces the contamination of the membrane surface by extracellular polymers and aerobic metabolic intermediates. At the same time, the gaseous metabolites produced by anaerobic bacteria escape from the inside of the biofilm, which also has a certain loosening effect on the biofilm. Finally, the previously closed air flushing electric valve 22 is reopened, and the MABR biofilm is washed off under the action of shearing caused by the rising bubbles and agitation of the water flow.

[0159] For example, when the MABR reactor is operated in the short-range nitrification and denitrification operation mode, the operating parameters for flushing and removing the over-thick biofilm in the corresponding membrane group area are: after stopping aeration of the MABR membrane components in the membrane group area for 16h to 24h, open the corresponding air flushing branch pipe 24 for air flushing, and the air flushing flow rate per unit membrane reaction area effective volume is 8 to 10L / (m 3 有效容积·min), the air flushing time is 30-60s, and the flushing is carried out again after an interval of 5min. During the biofilm shedding and flushing process, the air flushing of the non-flushing area is suspended, and the normal working state is restored after the flushing is completed.

[0160] When the MABR reactor operates in the short-range nitrification-anaerobic ammonium oxidation mode, the operating parameters for flushing and removing the over-thick biofilm in the corresponding membrane group area are as follows: after stopping aeration of the MABR membrane components in the membrane group area for 12h to 16h, open the corresponding air flushing branch pipe 24 for air flushing, and the air flushing flow rate per unit membrane reaction area effective volume is 3 to 6L / (m 3 有效容积 ·min), the air flushing time is 20-40s, and the flushing is performed again after an interval of 10min; during the biofilm shedding and flushing process, the air flushing in the non-flushing area is suspended, and all membrane components return to normal working state after the flushing is completed.

[0161] In this way, during the flushing and shedding operation of the biofilm, aeration and air flushing are stopped for one of the outer, middle and inner membrane groups respectively, and the other membrane groups operate normally, so the overall operation of the MABR reactor is not greatly affected, which is conducive to maintaining a stable operation effect. At the same time, the anaerobic period before flushing reduces the adhesion of the biofilm to the membrane filaments, so that the flushing and shedding of the biofilm can be completed with a lower air flushing intensity, and the biofilm in different parts of the entire membrane assembly is relatively uniform, avoiding the existing MABR reactor. In order to meet the flushing effect of the upper layer of the membrane assembly, a larger air flushing intensity is used, so that the lower part of the membrane assembly is over-flushed, and the biofilm falls off in pieces, which is not conducive to the stable operation of the MABR reactor.

[0162] The air flushing of the overly thick biofilm on the outer, middle and inner membrane groups is carried out in turn, and the flushing area occupies a smaller proportion, which can maintain the overall stable operation of the MABR reactor.

[0163] Since the air flushing method proposed in the present invention requires a relatively low flushing intensity, the biofilm on the surface of the MABR membrane fibers in the flushing area falls off more evenly, and the fallen parts are mainly the middle and outer layers of the overly thick biofilm, while the inner layer of the biofilm is still attached to the surface of the membrane fibers. At the same time, a large number of facultative oxobacteria are still retained in the pores of the adjacent sandwich mesh cloth, which is conducive to the re-formation and activity recovery of the biofilm on the surface of the membrane fibers. The regeneration of the MABR biofilm can usually be basically completed within 12h to 24h, and the biological denitrification activity is basically restored, so that the MABR biofilm is quickly renewed and the good biological denitrification performance of the MABR reactor is maintained.

[0164] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0165] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing and controlling a MABR biofilm, characterized in that: A MABR reactor is used, the MABR reactor comprising a reaction pool (1), a water distribution plate (6) arranged at the bottom of the reaction pool (1) and a central tube (10) whose lower end passes through the water distribution plate (6), a gas-water distribution area (5) is located below the water distribution plate (6), the outer side of the central tube (10) is a membrane reaction area (2), and the inner side is a pre-reaction area (11), the reaction pool (1) is provided with a water inlet pipe (45) and a water outlet pipe (46), the water inlet pipe (45) is connected to the pre-reaction area (11), and the water outlet pipe (46) is connected to the membrane reaction area (2), The pre-reaction zone (11) is provided with a guide tube (12), and the guide tube (12) is provided with an air stripping circulation device for circulating the mixed liquid inside and outside the guide tube (12); the membrane reaction zone (2) is provided with multiple layers of annular membrane groups composed of MABR membrane modules (900) from inside to outside, and the multiple layers of the annular membrane groups are divided into an inner membrane module area (9), a middle membrane module area (8) and an outer membrane module area (7) from inside to outside, and the extension direction of the membrane fibers (903) of the MABR membrane module (900) is staggered with the water flow direction; The air flushing system is used to flush the biofilm generated on the annular membrane group with air; the aeration system is used to aerate the membrane filaments (903) on each layer of the annular membrane group, and the aeration system is provided with an oxygen concentration detection component; the mixed liquid return system is used to return the mixed liquid in the membrane reaction zone (2) to the pre-reaction zone (11); the sludge return system is used to return the sludge in the reaction tank (1) to the pre-reaction zone (11); The MABR membrane assembly (900) comprises: membrane elements, two groups of which are symmetrically arranged with a gap between the two groups of membrane elements, the membrane elements having a sheet-like support layer (907) and a plurality of horizontal membrane filaments (903) arranged on a side wall of the support layer (907) and arranged transversely from top to bottom, the membrane filaments (903) and the support layer (907) are fixedly spaced and the membrane filaments between two adjacent fixed points (906) are in the shape of a suspension cable, and the membrane filaments (903) are arranged on opposite side walls of the two groups of support layers (907); An air pipe, vertically arranged on both sides of the support layer (907) and sealedly connected to both ends of a plurality of the membrane threads (903); The steps of the optimized control method of MABR biofilm are: S001. According to the operation mode of the MABR reactor, a corresponding composite biofilm is formed on the MABR membrane assembly (900) in each membrane group area, and the MABR reactor is operated stably; S002. Evaluate the biofilm thickness: Use the oxygen concentration detection component to regularly detect the oxygen concentration in the aeration pipe and exhaust pipe in the corresponding membrane group area, calculate the oxygen concentration attenuation coefficient per unit length of membrane filament, and draw a curve of the coefficient changing with time; Among them, the calculation formula of the oxygen concentration attenuation coefficient per unit length of membrane fiber is: （1） （2） （3） In formula (1), LOAT is the oxygen concentration attenuation coefficient per unit length of membrane fiber, gO2 / (m·h); W in is the oxygen flow rate in the aeration of MABR membrane module, gO2 / h; W out is the oxygen flow rate in the exhaust gas of the MABR membrane module, gO2 / h; n m is the number of membrane fibers contained in the MABR membrane module, root; l m is the length of a single membrane filament in the MABR membrane module; In formula (2), P in is the aeration pressure of MABR membrane module, Pa; Q in is the flow rate of the aeration pipe, m 3 / h; C in is the oxygen content in the aeration pipe, %; 32 is the molar mass of oxygen, g / mol; n n is the number of MABR membrane modules connected to the aeration pipe for measuring flow rate, R is the gas constant, 8.314 J / (mol·K); T in is the intake air temperature, K; In formula (3), P out is the exhaust pressure of MABR membrane module, Pa; Q out is the flow rate of the exhaust pipe, m 3 / h; C out is the oxygen content in the exhaust pipe, %; T out is the exhaust temperature, K; S003. When the change curve in the corresponding membrane group area in step S002 shows a downward trend, the biofilm is too thick, and the aeration of the MABR membrane assembly (900) in the membrane group area is stopped and maintained for a period of time, and then the biofilm in the membrane group area is washed and removed by air through the air flushing system; S004. After the biofilm falls off, it grows again, and the change curve shows an upward trend until the change amplitude of the change curve is small, and the biofilm thickness is stable.

2. The optimization control method of MABR biofilm according to claim 1, characterized in that: The MABR membrane assembly (900) further comprises a fixing clamp (910) disposed on both sides of the membrane element, and air pipe clamping grooves (9102) corresponding to the number of air pipes are disposed on the facing sides of the two fixing clamps (910), and support clamping grooves (9101) are disposed on the opposite sides, and a plurality of membrane assembly fixing sleeves (905) parallel to the air pipes are disposed between the supporting layers (907) of the two groups of membrane elements.

3. The optimization control method of MABR biofilm according to claim 1, characterized in that: The plurality of membrane filaments (903) of the MABR membrane assembly (900) are evenly distributed longitudinally, and the fixing points (906) on the support layer (907) are distributed in a rectangular array; the support layer (907) is made of sandwich mesh cloth, and the membrane filaments (903) are made of transparent silicone rubber tubes.

4. The optimization control method of MABR biofilm according to claim 1, characterized in that: The reaction tank (1) is provided with a plurality of membrane assembly pillars (3) for fixing the MABR membrane assembly (900), the membrane assembly pillars (3) being matched with the membrane assembly fixing sleeve (905) or the pillar clamping groove (9101), and the membrane assembly pillars (3) are in the shape of a plurality of concentric circles and are evenly distributed in the radial direction.

5. The optimization control method of MABR biofilm according to claim 1, characterized in that, Each of the annular membrane groups comprises two symmetrically arranged semi-annular membrane groups, wherein the semi-annular membrane groups are formed by connecting a plurality of the MABR membrane modules (900) in series, and the air pipes on both sides of the semi-annular membrane groups are respectively an air inlet pipe (901) and an air outlet pipe (902), and the air inlet pipes (901) of the two semi-annular membrane groups are located on the same side of the reaction tank (1), and each of the air inlet pipes (901) is connected to an aeration pipe of an aeration system, and each of the air outlet pipes (902) is connected to an exhaust pipe of the aeration system; The oxygen concentration detection assembly comprises a membrane air intake sampling tube (60) arranged on the aeration tube, a membrane air exhaust sampling tube (64) arranged on the exhaust pipe, a detection flow slot (65) and a high-precision oxygen concentration analyzer (66); the membrane air intake sampling tube (60) and the membrane air exhaust sampling tube (64) are both connected to the detection flow slot (65); and a measuring probe of the high-precision oxygen concentration analyzer (66) extends into the detection flow slot (65).

6. The optimization control method of MABR biofilm according to claim 1, characterized in that: The air flushing system comprises a plurality of groups of air flushing perforated pipes arranged in the air-water distribution area (5) corresponding to each layer of the annular membrane group, and the air flushing perforated pipes in the same layer of the membrane group area are connected to an air flushing branch pipe (24); the mixed liquor return system comprises a mixed liquor return pipe (51) arranged at the upper part of the reaction tank (1), and the sludge return system comprises a sludge return pipe (56) arranged at the bottom of the reaction tank (1), the mixed liquor return pipe (51) and the sludge return pipe (56) are connected to the pre-reaction zone (11) through a mixed liquor return main pipe (59), and the sludge return pipe (56) is also provided with a sludge discharge valve (57).

7. The optimization control method of MABR biofilm according to claim 1, characterized in that: The air lift circulation device comprises an air lift assembly (76) with an opening at the bottom end and an air lift fan (70); an air lift duct (71) of the air lift fan (70) is connected to the top of the central tube (10); an air lift exhaust duct (72) is connected to the top of the air lift assembly (76); and the central tube (10) is also provided with a central tube automatic exhaust valve (75) and a central tube vent valve (74).

8. The optimization control method of MABR biofilm according to claim 1, characterized in that: Method for forming composite biofilm in step S001: S0011, Nitrification and denitrification biofilm stage: (1) Inoculate sludge through the water inlet pipe (45), continuously open the sludge return system, aeration system and air stripping circulation device, indirectly open the air flushing system, close the mixed liquid return system, adjust the water inlet to 1 / 3 of the design flow rate, and continuously fill and discharge water; (2) After the biofilm is formed on the membrane surface, gradually increase the water flow rate, intermittently open the mixed liquid reflux system, and gradually increase the interval time for opening the air flushing system; (3) After the influent flow rate reaches the design flow rate, the mixed liquor return system is changed to be continuously opened, and the sludge return system is continuously opened and the air flushing system is opened intermittently and operated stably for a period of time until the effluent ammonia nitrogen removal rate is higher than 90%, the total nitrogen removal rate exceeds 50%, the nitrite nitrogen accumulation rate is lower than 10%, and a nitrifying biofilm is formed on the surface of the membrane filaments (903) of the MABR membrane assembly, and an anaerobic nitrifying biofilm is formed on the support layer (907); S0012, Short-cut nitrification and denitrification biofilm stage: the aeration system is changed to intermittent opening, and it is continuously operated for a period of time until the effluent ammonia nitrogen removal rate exceeds 80%, the total nitrogen removal rate exceeds 60%, and the nitrite nitrogen accumulation rate exceeds 60%, and a biofilm dominated by short-cut nitrification and denitrification is formed in the MABR reactor; S0013, short-range nitrification anaerobic ammonium oxidation biofilm stage: add granular anaerobic ammonium oxidation sludge into the central tube (10), change the sludge return system to intermittent opening, and form a composite biofilm after running for a period of time.

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