Sewage treatment system and method for MABR coupled subsurface flow constructed wetland

Abstract

The invention discloses a sewage treatment system and method for an MABR (Membrane Aerated Baffled Reactor) coupled subsurface flow constructed wetland, the system comprises a raw water tank, a sewage lift pump and a water inlet flow distribution valve which are connected in sequence, the water inlet flow distribution valve is connected with a bio-membrane reactor water inlet pipe and a wetland water inlet pipe, and the bio-membrane reactor water inlet pipe is connected with a membrane aeration bio-membrane reactor. The wetland water inlet pipe is connected with the subsurface flow constructed wetland reactor; the membrane aeration bio-membrane reactor comprises a lower bio-membrane reaction area and an upper three-phase separation area, the subsurface flow constructed wetland reactor comprises a water distribution channel, a wetland unit and a water outlet channel which are connected in sequence, the three-phase separation area is connected with the water distribution channel, and the water outlet channel is connected with the bottom of the bio-membrane reaction area. After pollutants such as COD (Chemical Oxygen Demand), N, P and the like in sewage are efficiently removed through the membrane aeration bio-membrane reactor, the sewage enters the subsurface flow constructed wetland reactor to realize deep purification of water, the sewage reaches the discharge standard, and the economical efficiency and the adaptability are excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment system and method of a MABR coupled subsurface flow artificial wetland. Background Art

[0002] With the rapid development of urbanization and the continuous gathering of population, the total amount of domestic sewage discharge is on the rise, water bodies are eutrophicated, and algal blooms occur frequently. Under the low-carbon concept, efficient treatment technology is urgently needed. At present, the mainstream domestic sewage treatment technologies, whether traditional processes such as activated sludge method and biofilm method, or emerging technologies such as membrane bioreactors, have the disadvantages of poor stability and excessive energy consumption to varying degrees for the fluctuations in water quantity and quality in small and medium-sized sewage treatment processes. In terms of stability, the traditional activated sludge method has a poor tolerance for fluctuations in water quality and water quantity. Once the influent water quality changes significantly, the activated sludge on which microorganisms depend for survival will have problems such as swelling and disintegration, the treatment effect is poor, and the effluent water quality is difficult to stably meet the standards. Although the biofilm method has a slightly stronger impact resistance, under extreme conditions such as low temperature and high load, the biofilm will also fall off, seriously affecting the treatment efficiency. In terms of energy consumption, the aeration system of the activated sludge method operates at high power for a long time to meet the aerobic needs of microorganisms, consuming a lot of energy. In the membrane filtration process, the membrane bioreactor needs to be pressurized by a pump to maintain the flux. The energy consumption is even greater after the membrane is contaminated, which runs counter to the concept of green development. Therefore, it is particularly urgent and necessary to develop and promote a new domestic sewage treatment technology system that is both stable, efficient and low-consumption, in order to enhance the removal capacity of nutrients such as nitrogen and phosphorus in the receiving water body and reduce the risk of eutrophication. Summary of the invention

[0003] The present invention aims to solve the problems existing in the prior art and provides a sewage treatment system and method of a MABR coupled subsurface flow artificial wetland, so that after the sewage passes through a membrane aeration biofilm reactor to efficiently remove pollutants such as COD, N, and P, it enters a subsurface flow artificial wetland reactor to achieve deep water purification, thereby meeting the emission standards and having excellent economy and adaptability.

[0004] The technical solution of the present invention is: a sewage treatment system of MABR coupled subsurface flow artificial wetland, comprising a raw water pool, a sewage lifting pump, and an inlet flow distribution valve connected in sequence, wherein the outlet of the inlet flow distribution valve is respectively connected to a biofilm reactor inlet pipe and a wetland inlet pipe, wherein the biofilm reactor inlet pipe is connected to a membrane aeration biofilm reactor, and the wetland inlet pipe is connected to a subsurface flow artificial wetland reactor;

[0005] The membrane aerated biofilm reactor comprises a biofilm reaction zone at a lower part and a three-phase separation zone at an upper part, a membrane assembly is arranged in the biofilm reaction zone, the membrane assembly comprises two hollow aeration rings spaced apart from each other, and membrane filaments arranged between the two hollow aeration rings, an air inlet and an air outlet are respectively arranged on the biofilm reaction zone below and above the membrane assembly, and a mud return pipe is arranged at the bottom of the biofilm reaction zone; the three-phase separation zone is connected to the biofilm reaction zone by a flange, and the three-phase separation zone is connected to the biofilm reaction zone by a liquid guide pipe and a mud guide pipe, a three-phase separator is arranged in the three-phase separation zone, a reflux pipe is arranged in the middle of the three-phase separator, a top exhaust port is arranged at the top of the three-phase separator, a mud discharge port is arranged at the bottom of the three-phase separation zone, an overflow trough is arranged at the top of the three-phase separation zone, and a water outlet of the biofilm reactor is arranged on the overflow trough;

[0006] The submerged flow artificial wetland reactor includes a water distribution channel, a wetland unit, and a water outlet channel which are connected in sequence; the wetland water inlet pipe is connected to the water distribution channel through a first conical filter, the water outlet of the biofilm reactor is connected to the water distribution channel through a connecting pipe, and an emptying port is provided at the bottom of the water distribution channel; a bottom porous filter plate is provided between the wetland unit and the water distribution channel, the wetland unit includes a traditional filling area, wetland plants are planted in the traditional filling area, a porous filter column is also provided in the traditional filling area, and functional fillers are provided in the porous filter column; the water outlet channel is connected to the wetland water outlet pipe through an outlet flow distribution valve, and the outlet flow distribution valve is also connected to a return pipe through a second conical filter, a return pump is provided on the return pipe, and the other end of the return pipe is connected to the bottom of the biofilm reaction area of ​​the membrane aerated biofilm reactor.

[0007] Furthermore, the water inlet flow distribution valve in the present invention has a water inlet, a first water outlet, and a second water outlet. The water inlet is connected to the sewage lift pump, the first water outlet is connected to the biofilm reactor water inlet pipe, and the second water outlet is connected to the wetland water inlet pipe; the membrane aerated biofilm reactor and the submerged flow artificial wetland reactor control the water inlet amount through the water inlet flow distribution valve, and the water inlet flow distribution valve is composed of a reducing tee and an electromagnetic flowmeter, which is used to adjust the water inlet distribution ratio.

[0008] Furthermore, the coupling mode of the membrane aerated biofilm reactor and the submerged flow artificial wetland reactor in the present invention is series coupling, and the coupling part includes the three-phase separator, the overflow tank, the water outlet of the biofilm reactor, the connecting pipe, and the water distribution channel.

[0009] Furthermore, the porous filter columns of the present invention are arranged in a plurality of intervals along the direction of water flow, and the spacing between two adjacent porous filter columns is 35-40% of the total length of the wetland unit; the porous filter column is vertically arranged in the traditional filler area, and the diameter of the porous filter column is 20-25% of the total width of the wetland unit; the surface of the porous filter column is provided with a plurality of circular holes with a diameter of 6-8 mm, and the spacing between two adjacent circular holes in the upper and lower parts or in the left and right parts is 8-10 mm, and the plurality of circular holes are evenly distributed on the surface of the porous filter column.

[0010] Furthermore, the traditional filling area in the present invention is composed of a pebble layer, a gravel layer and a fine sand layer from bottom to top.

[0011] Furthermore, the wetland plants described in the present invention are planted in a plurality of equal intervals in the traditional filling area, and the roots of the wetland plants are fixed at a depth of 20 to 30 mm in the fine sand layer.

[0012] The present invention also provides a sewage treatment method, which comprises: the raw water after the grid treatment is lifted by a sewage lifting pump and then enters a membrane aeration biofilm reactor and a submerged flow artificial wetland reactor respectively through a water inlet flow distribution valve;

[0013] Process 1: The sewage directly enters the membrane aeration biofilm reactor through the biofilm reactor inlet pipe from the bottom of the biofilm reaction zone into the membrane aeration biofilm reactor, fully contacts the membrane filaments and passes through the biofilm attached to the membrane filaments. The inside of the biofilm is in an aerobic state, and the outside of the biofilm is in an anoxic / anaerobic state. The biofilm reaction zone is aerated through the air inlet, and the gas is dispersed through the hollow aeration ring. The aeration pressure and aeration time are adjusted to accurately supply oxygen to ensure the realization of nitrification / denitrification reaction in the membrane aeration biofilm reactor; the sewage enters the three-phase separation zone from the biofilm reaction zone through the liquid guide pipe for gas, liquid and solid three-phase separation, and the sludge is discharged from the sludge outlet. The gas The effluent is discharged from the top exhaust port, and then the effluent is discharged from the water outlet of the biofilm reactor through the connecting pipe into the water distribution channel of the submerged flow artificial wetland reactor after passing through the overflow tank; the sewage directly entering the submerged flow artificial wetland reactor from the water inlet flow distribution valve enters the water distribution channel after being filtered through the first cone filter from the wetland water inlet pipe; the water distribution channel collects the water from the membrane aeration biofilm reactor and the raw water directly entering the submerged flow artificial wetland reactor. The water in the water distribution channel first enters the wetland unit through the bottom porous filter plate. During the operation, the matrix, plants and microorganisms remove pollutants in the water body through the combined action of physical, chemical and biological degradation, and the effluent overflows to the outlet channel and is discharged from the wetland outlet pipe;

[0014] Process 2: When the water quality fluctuates greatly, adjust the outlet flow distribution valve, start the reflux pump, and the reflux liquid is filtered by the second conical filter and then flows back to the bottom of the membrane aerated biofilm reactor through the reflux pipe, and the cycle process is repeated.

[0015] Furthermore, in the present invention, under typical sewage water quality conditions, the water inlet distribution ratio is adjusted by the water inlet flow distribution valve, and the ratio of the water inlet volume of the membrane aerated biofilm reactor to the submerged flow artificial wetland reactor is 4:1, and part of the sewage directly enters the submerged flow artificial wetland reactor through the wetland inlet pipe.

[0016] Furthermore, in the present invention, when the inlet water quality fluctuates greatly, the outlet flow distribution valve is adjusted, the reflux pump is turned on, and the reflux ratio is set to 0-60%. The reflux liquid is filtered by the second conical filter and then refluxed to the bottom of the membrane aerated biofilm reactor through the reflux pipe.

[0017] Furthermore, in the present invention, the ratio of the hydraulic retention time of the membrane aerated biofilm reactor to that of the submerged flow constructed wetland reactor is 1:5-7, and the volume ratio of the membrane aerated biofilm reactor to that of the submerged flow constructed wetland reactor is 1:6-9.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1) In the present invention, the water inlet distribution is controlled by the water inlet flow distribution valve, and part of the sewage can directly enter the submerged flow artificial wetland reactor without passing through the membrane aerated biofilm reactor. The strong impact resistance of the wetland is utilized to reduce the load of the membrane aerated biofilm reactor, thereby facilitating the stability of the entire system;

[0020] 2) In the present invention, the membrane aeration biofilm reactor and the submerged flow artificial wetland reactor are directly coupled in series. Under the action of the three-phase separator and the conical filter, no intermediate processing unit (precipitation or filtration equipment) is added to the coupling part, and the structure is simple and the operation is stable;

[0021] 3) In the present invention, by providing a reflux assembly consisting of a second conical filter, a reflux pipe, and a reflux pump for reflux, it is possible to cope with the load impact caused by fluctuations in water quality and quantity, and achieve long-term stable operation of the system; in low temperature seasons, the reflux assembly slows down heat loss through water circulation, thereby improving the system's resistance to stress;

[0022] 4) In the present invention, the membrane aeration biofilm reactor uses hollow fiber membrane filaments to supply oxygen to the biofilm in the form of molecules. This oxygen supply method enables oxygen to be efficiently transferred within the biofilm, avoiding the complex mass transfer process of bubbles from the liquid phase to the biofilm in the traditional aeration method, significantly improving the oxygen utilization efficiency and mass transfer rate, and greatly reducing energy consumption;

[0023] 5) In the present invention, the matrix and vegetation in the subsurface flow artificial wetland reactor have a loose and porous surface structure and a developed root structure, which can play a physical buffering role in the treatment of sewage; at the same time, the complex ecosystem composed of microorganisms, plants and matrix in the wetland has a high biodiversity and a certain self-regulation and repair ability, which can synergistically treat sewage through multiple effects such as physical, chemical and biological effects, greatly improving the system's impact resistance and treatment effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a sewage treatment system of a MABR coupled with a subsurface flow artificial wetland of the present invention (wherein the arrow indicates the direction of water flow);

[0025] Figure 2 Schematic diagram of the structure of the water inlet flow distribution valve in the present invention (wherein the arrow indicates the direction of water flow);

[0026] Figure 3 It is a schematic diagram of the structure of the wetland unit described in the present invention.

[0027] Among them: 1. Sewage lifting pump; 2. Inlet flow distribution valve; 2a. Inlet; 2b. First outlet; 2c. Second outlet; 3. Biofilm reactor inlet pipe; 4. Wetland inlet pipe; 5. Hollow aeration ring; 6. Membrane wire; 7. Air inlet; 8. Air outlet; 9. Mud return pipe; 10. Liquid guide pipe; 11. Mud guide pipe; 12. Mud discharge port; 13. Overflow tank; 14. Biofilm reactor outlet; 15. Top exhaust port; 16. Three-phase separation separator; 17, return pipe; 18, connecting pipe; 19, first conical filter; 20, water distribution channel; 21, drain port; 22, bottom porous filter plate; 23, traditional filler area; 24, wetland plants; 25, porous filter column; 26, functional filler; 27, outlet channel; 28, outlet flow distribution valve; 29, wetland outlet pipe; 30, second conical filter; 31, return pipe; 32, return pump; A, biofilm reaction zone; B, three-phase separation zone. DETAILED DESCRIPTION

[0028] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0029] Example:

[0030] The attached drawings show a specific embodiment of a sewage treatment system and method of a MABR coupled subsurface flow artificial wetland of the present invention, referring to Figure 1The sewage treatment system includes a raw water pool, a sewage lifting pump 1, and an inlet flow distribution valve 2 connected in sequence. The outlet of the inlet flow distribution valve 2 is respectively connected to a biofilm reactor inlet pipe 3 and a wetland inlet pipe 4. The biofilm reactor inlet pipe 3 is connected to a membrane aeration biofilm reactor, and the wetland inlet pipe 4 is connected to a submerged flow artificial wetland reactor.

[0031] Combination Figure 2 The water inlet flow distribution valve 2 has a water inlet 2a, a first water outlet 2b, and a second water outlet 2c. The water inlet 2a is connected to the sewage lifting pump 1, the first water outlet 2b is connected to the biofilm reactor water inlet pipe 3, and the second water outlet 2c is connected to the wetland water inlet pipe 4. The membrane aerated biofilm reactor and the submerged flow artificial wetland reactor control the water inflow through the water inlet flow distribution valve 2. The water inlet flow distribution valve 2 is composed of a reducing tee and an electromagnetic flowmeter. In the case of fluctuations in water quality and water quantity, the water inlet distribution ratio can be accurately adjusted according to actual conditions.

[0032] Specifically, the membrane aeration biofilm reactor includes a biofilm reaction zone A at the bottom and a three-phase separation zone B at the top. A membrane assembly is arranged in the biofilm reaction zone A. The membrane assembly includes two hollow aeration rings 5 ​​arranged at intervals from top to bottom, and a membrane filament 6 arranged between the two hollow aeration rings 5. The hollow aeration rings 5 ​​are in a circular ring structure, and a plurality of circular holes are opened on the hollow aeration rings 5, so that gas can be dispersed when passing through. An air inlet 7 and an air outlet 8 are respectively arranged on the biofilm reaction zone A below and above the membrane assembly, and a mud return pipe 9 is arranged at the bottom of the biofilm reaction zone A.

[0033] The three-phase separation zone B is connected to the biofilm reaction zone A through a flange, and a perforated horizontal plate is provided between the three-phase separation zone B and the biofilm reaction zone A. A liquid guide pipe 10 and a mud guide pipe 11 are provided on the perforated horizontal plate, and the three-phase separation zone B is connected to the biofilm reaction zone A through the liquid guide pipe 10 and the mud guide pipe 11. A three-phase separator 16 is provided in the three-phase separation zone B, and a reflux pipe 17 is provided in the middle of the three-phase separator 16. The reflux pipe 17 passes through the three-phase separation zone B to the outside, and a top exhaust port 15 is provided at the top of the three-phase separator 16, and a mud discharge port 12 is provided at the bottom of the three-phase separation zone B. An overflow trough 13 is provided at the upper part of the three-phase separation zone B, and a water outlet 14 of the biofilm reactor is provided on the overflow trough 13.

[0034] Combination Figure 1 , Figure 3 The submerged flow artificial wetland reactor includes a water distribution channel 20, a wetland unit, and a water outlet channel 27 which are connected in sequence. The wetland water inlet pipe 4 is connected to the water distribution channel 20 through a first conical filter 19, and the water outlet 14 of the biofilm reactor is connected to the water distribution channel 20 through a connecting pipe 18. The bottom of the water distribution channel 20 is provided with an emptying port 21.

[0035] A bottom porous filter plate 22 is provided between the wetland unit and the water distribution channel 20. The wetland unit includes a traditional filling area 23, which is composed of a pebble layer, a gravel layer, and a fine sand layer from bottom to top. Wetland plants 24 are planted in the traditional filling area 23. Several wetland plants 24 are planted at equal intervals in the traditional filling area 23, and the roots of the wetland plants 24 are fixed at a depth of 20 to 30 mm in the fine sand layer. A porous filter column 25 is provided in the traditional filling area 23. Multiple porous filter columns 25 are arranged in intervals along the direction of the inlet water flow, and the spacing between two adjacent porous filter columns 25 is 35-40% of the total length of the wetland unit; the porous filter column 25 is vertically arranged in the traditional filling area 23, and the diameter of the porous filter column 25 is 20-25% of the total width of the wetland unit; the surface of the porous filter column 25 is provided with a plurality of circular holes with a diameter of 6-8 mm, and the spacing between two adjacent circular holes in the upper and lower or left and right directions is 8-10 mm, and the plurality of circular holes are evenly distributed on the surface of the porous filter column 25. Each porous filter column 25 is provided with a functional filler 26. The functional filler 26 is flexibly configured according to the characteristics of the water quality, and various functional fillers such as the calamus-based composite solid carbon source filler, the calamus-based biochar composite solid antibiotic adsorption filler, and the modified steel slag-based composite functional filler are used to deeply remove nitrogen, phosphorus, antibiotics and other components in the water, and the fillers can be replaced regularly according to the performance of various fillers.

[0036] The outlet channel 27 is connected to a wetland outlet pipe 29 via an outlet flow distribution valve 28. The outlet flow distribution valve 28 is also connected to a return pipe 31 via a second conical filter 30. A return pump 32 is provided on the return pipe 31. The other end of the return pipe 31 is connected to the bottom of the biofilm reaction zone A of the membrane aerated biofilm reactor.

[0037] The coupling mode of the membrane aerated biofilm reactor and the submerged flow artificial wetland reactor is series coupling, and the coupling part includes a three-phase separator 16, an overflow tank 13, a water outlet 14 of the biofilm reactor, a connecting pipe 18, and a water distribution channel 20. The three-phase separator 16 realizes the separation of solid, liquid and gas, and no intermediate sedimentation or filtration equipment is added to the coupling part.

[0038] In this embodiment, the membrane aeration biofilm reactor and the submerged flow artificial wetland reactor are both constructed of organic glass and steel plates.

[0039] The sewage treatment method of the sewage treatment system of this embodiment includes: the raw water after the grid treatment is lifted by the sewage lifting pump 1 and enters the membrane aeration biofilm reactor and the submerged flow artificial wetland reactor respectively through the water inlet flow distribution valve 2;

[0040] Process 1: The sewage directly enters the membrane aeration biofilm reactor from the bottom of the biofilm reaction zone A through the biofilm reactor inlet pipe 3, fully contacts with the membrane filaments 6 of the hollow fiber membrane and passes through the biofilm attached to the membrane filaments. The inside of the biofilm is in an aerobic state, and the outside of the biofilm is in an anoxic / anaerobic state. The biofilm reaction zone A is aerated through the air inlet 7, and the gas is dispersed through the hollow aeration ring 5. The aeration pressure and aeration time are adjusted to accurately supply oxygen to ensure the realization of nitrification / denitrification reaction in the membrane aeration biofilm reactor; the sewage enters the three-phase separation zone B from the biofilm reaction zone A through the liquid guide pipe 10 for gas, liquid and solid three-phase separation, and the sludge is discharged from the sludge outlet 12, and the gas is discharged from the top The effluent is discharged from the air outlet 15, and then the effluent is discharged from the water outlet 14 of the biofilm reactor through the connecting pipe 18 into the water distribution channel 20 of the submerged flow artificial wetland reactor after passing through the overflow tank 13; the sewage directly entering the submerged flow artificial wetland reactor from the water inlet flow distribution valve 2 enters the water distribution channel 20 after being filtered from the wetland water inlet pipe 4 through the first cone filter 19; the water distribution channel 20 collects the water from the membrane aeration biofilm reactor and the raw water directly entering the submerged flow artificial wetland reactor. The water in the water distribution channel 20 first enters the wetland unit through the bottom porous filter plate 22. During the operation, the matrix-plant-microorganism removes pollutants in the water body through the combined action of physical, chemical and biological degradation, and the effluent overflows to the outlet channel 27 and is discharged from the wetland outlet pipe 29;

[0041] Process 2: When the water quality fluctuates greatly, adjust the outlet flow distribution valve 28, start the reflux pump 32, and the reflux liquid is filtered by the second conical filter 30 and then flows back to the bottom of the membrane aerated biofilm reactor through the reflux pipe 31, and the cycle process 1 operation process is repeated.

[0042] Furthermore, under typical sewage quality conditions, the inlet distribution ratio is adjusted by the inlet flow distribution valve 2, and the ratio of the inlet water volume of the membrane aerated biofilm reactor to the submerged flow artificial wetland reactor is 4:1, and part of the sewage directly enters the submerged flow artificial wetland reactor through the wetland inlet pipe 4. The ratio of the hydraulic retention time of the membrane aerated biofilm reactor to the submerged flow artificial wetland reactor is 1:5-7, and the volume ratio of the membrane aerated biofilm reactor to the submerged flow artificial wetland reactor is 1:6-9.

[0043] In addition, when the inlet water quality fluctuates greatly, the outlet flow distribution valve 28 is adjusted, the reflux pump 32 is turned on, and the reflux ratio is set to 0-60%. The reflux liquid is filtered by the second conical filter 30 and then refluxed to the bottom of the membrane aerated biofilm reactor through the reflux pipe 31 for circulation treatment.

[0044] The present invention is implemented with typical rural domestic sewage as a specific scenario: rural sewage has the characteristics of relatively dispersed production, small treatment scale, low management and operation level, and large changes in water quality and water volume over time. The system includes an inlet component (including a sewage lift pump 1 and an inlet flow distribution valve 2), a membrane aerated biofilm reactor (MABR), a constructed wetland (CW), and a reflux component (including a second conical filter 30, a reflux pipe 31, and a reflux pump 32). The MABR reactor uses a hollow fiber membrane to supply oxygen to the biofilm in the form of molecules, avoiding the complex mass transfer process of bubbles from the liquid phase to the biofilm in the traditional aeration method, significantly improving the oxygen utilization efficiency and treatment effect, and greatly reducing energy consumption. The matrix and vegetation in the CW reactor have a loose and porous surface structure and a developed root structure, which can play a physical buffering role in the treatment of rural domestic sewage; at the same time, the complex ecosystem composed of microorganisms, plants and matrices in the wetland has a high biodiversity and a certain self-regulation and repair ability, and can synergistically treat sewage through multiple effects such as physical, chemical and biological effects to extend the equipment maintenance cycle and greatly improve the impact resistance and treatment effect of the wetland. The water inlet component controls the water distribution through the water inlet flow distribution valve 2. Part of the sewage can directly enter the CW reactor without passing through the MABR reactor. The strong impact resistance of the wetland is used to reduce the load of the MABR reactor and improve the stability of the entire system. The backflow component can cope with the load shock caused by fluctuations in water quality and quantity, and achieve long-term stable operation of the system. The temperature difference between day and night in rural areas is large. During low temperature periods, the backflow component slows down heat loss through water circulation and improves the system's resistance to stress.

[0045] Scenario 1: During holidays or gatherings in rural areas, the amount of domestic sewage increases significantly, and the concentration of pollutants in the sewage also increases significantly. Specific treatment process: The influent water volume is twice the daily average flow rate, and the influent water quality parameters are COD concentration of 300mg / L, NH4-N concentration of 60mg / L, and TP concentration of 5mg / L. Due to the large influent water volume and high pollutant concentration, the system is working under high load and the treatment effect is poor. Adjust the influent flow distribution valve 2 so that the ratio of the influent water volume of the membrane aerated biofilm reactor and the submerged flow artificial wetland reactor is 4:1. After the treatment of process one, adjust the effluent flow distribution valve 28, set the reflux ratio to 40%, and the reflux liquid flows back to the bottom of the membrane aerated biofilm reactor through the reflux pipe 31 to repeat the process one operation. Alleviate the load impact of water quality and water quantity fluctuations on the system and achieve long-term stable operation of the system. After treatment, the COD removal rate is 96%, the NH4-N removal rate is 99%, and the P removal rate is 83%. The main indicators of effluent water quality can stably meet the Class A standard in the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB 18918-2002).

[0046] Scenario 2: During the rainy season, a large amount of rainwater flows into the sewage system, causing the concentration of pollutants in the sewage to be diluted. At the same time, the hydraulic load on the system also increases significantly. Specific treatment process: The influent water volume is 4 times the daily average flow rate, and the influent water quality parameters are COD concentration of 100 mg / L, NH4-N concentration of 20 mg / L, and TP concentration of 1 mg / L. Due to the large influent water volume and low pollutant concentration, directly entering the MABR reactor for treatment will cause the reactor to work in a low-load state for a long time, affecting the treatment effect. Therefore, the influent flow distribution valve 2 is adjusted to make the ratio of the influent water volume of the membrane aerated biofilm reactor to the subsurface flow artificial wetland reactor 3:1, reducing the hydraulic load of the MABR reactor. The artificial wetland buffers the water flow, regulates the flow rate, maintains the activity of microorganisms through the synergistic effect of the matrix, plants and microorganisms, enhances the stability of the system, and effectively removes low-concentration pollutants. After treatment, the COD removal rate is 92%, the NH4-N removal rate is 99%, and the P removal rate is 78%. The main indicators of effluent water quality can stably meet the Level A standard in the "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB 18918-2002).

[0047] Of course, the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any modifications made according to the spirit of the main technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A sewage treatment system of MABR coupled with subsurface artificial wetland, characterized by: It comprises a raw water pool, a sewage lifting pump (1), and an inlet flow distribution valve (2) which are connected in sequence, wherein the outlet of the inlet flow distribution valve (2) is respectively connected to a biofilm reactor inlet pipe (3) and a wetland inlet pipe (4), wherein the biofilm reactor inlet pipe (3) is connected to a membrane aeration biofilm reactor, and the wetland inlet pipe (4) is connected to a submerged flow artificial wetland reactor; The membrane aeration biofilm reactor comprises a biofilm reaction zone (A) at the bottom and a three-phase separation zone (B) at the top. A membrane assembly is arranged in the biofilm reaction zone (A). The membrane assembly comprises two hollow aeration rings (5) arranged at an interval up and down, and a membrane filament (6) arranged between the two hollow aeration rings (5). An air inlet (7) and an air outlet (8) are respectively arranged on the biofilm reaction zone (A) below and above the membrane assembly. A mud return pipe (9) is arranged at the bottom of the biofilm reaction zone (A); a gas pipe (10) is connected between the three-phase separation zone (B) and the biofilm reaction zone (A). The three-phase separation zone (B) and the biofilm reaction zone (A) are connected by flange connection, and are connected by a liquid guide tube (10) and a mud guide tube (11). A three-phase separator (16) is provided in the three-phase separation zone (B), a reflux pipe (17) is provided in the middle of the three-phase separator (16), a top exhaust port (15) is provided at the top of the three-phase separator (16), a mud discharge port (12) is provided at the bottom of the three-phase separation zone (B), an overflow trough (13) is provided at the top of the three-phase separation zone (B), and a water outlet (14) of the biofilm reactor is provided on the overflow trough (13); The submerged flow artificial wetland reactor comprises a water distribution channel (20), a wetland unit, and a water outlet channel (27) which are connected in sequence; the wetland water inlet pipe (4) is connected to the water distribution channel (20) via a first conical filter (19); the water outlet (14) of the biofilm reactor is connected to the water distribution channel (20) via a connecting pipe (18); a drain port (21) is provided at the bottom of the water distribution channel (20); a bottom porous filter plate (22) is provided between the wetland unit and the water distribution channel (20); the wetland unit comprises a traditional filler area (23); the traditional filler area (23) ) is planted with wetland plants (24), a porous filter column (25) is also provided in the traditional filler area (23), and a functional filler (26) is provided in the porous filter column (25); the outlet channel (27) is connected to a wetland outlet pipe (29) via an outlet flow distribution valve (28), and the outlet flow distribution valve (28) is also connected to a return pipe (31) via a second conical filter (30), and a return pump (32) is provided on the return pipe (31), and the other end of the return pipe (31) is connected to the bottom of the biofilm reaction zone (A) of the membrane aerated biofilm reactor.

2. A MABR coupled subsurface flow constructed wetland sewage treatment system according to claim 1, characterized in that: The water inlet flow distribution valve (2) comprises a water inlet (2a), a first water outlet (2b), and a second water outlet (2c); the water inlet (2a) is connected to the sewage lifting pump (1), the first water outlet (2b) is connected to the biofilm reactor water inlet pipe (3), and the second water outlet (2c) is connected to the wetland water inlet pipe (4); the membrane aerated biofilm reactor and the submerged flow artificial wetland reactor control the water inlet amount through the water inlet flow distribution valve (2); the water inlet flow distribution valve (2) is composed of a reducing tee and an electromagnetic flowmeter, and is used to adjust the water inlet distribution ratio.

3. A sewage treatment system of a MABR coupled with a subsurface flow constructed wetland according to claim 1, characterized in that: The coupling mode of the membrane aerated biofilm reactor and the submerged flow artificial wetland reactor is series coupling, and the coupling part includes the three-phase separator (16), the overflow tank (13), the biofilm reactor water outlet (14), the connecting pipe (18), and the water distribution channel (20).

4. A sewage treatment system of a MABR coupled with a subsurface flow constructed wetland according to claim 1, characterized in that: A plurality of the porous filter columns (25) are arranged in an interval arrangement along the direction of the incoming water flow, and the spacing between two adjacent porous filter columns (25) is 35-40% of the total length of the wetland unit; the porous filter column (25) is vertically arranged in the traditional filler area (23), and the diameter of the porous filter column (25) is 20-25% of the total width of the wetland unit; a plurality of circular holes with a diameter of 6-8 mm are provided on the surface of the porous filter column (25), and the spacing between two adjacent circular holes in the upper and lower parts or in the left and right parts is 8-10 mm, and the plurality of circular holes are evenly distributed on the surface of the porous filter column (25).

5. A sewage treatment system of a MABR coupled with a subsurface flow constructed wetland according to claim 1, characterized in that: The traditional filling area (23) comprises, from bottom to top, a pebble layer, a gravel layer, and a fine sand layer.

6. A MABR coupled subsurface flow constructed wetland sewage treatment system according to claim 5, characterized in that: A plurality of wetland plants (24) are planted at equal intervals in the traditional filling area (23), and the roots of the wetland plants (24) are fixed at a depth of 20 to 30 mm in the fine sand layer.

7. A sewage treatment method according to any one of claims 1 to 6, characterized in that: The method comprises: raw water treated by the grid is lifted by a sewage lifting pump (1), and then enters a membrane aeration biofilm reactor and a submerged flow artificial wetland reactor respectively through a water inlet flow distribution valve (2); Process 1: The sewage directly enters the membrane aeration biofilm reactor from the bottom of the biofilm reaction zone (A) through the biofilm reactor water inlet pipe (3), enters the membrane aeration biofilm reactor, fully contacts the membrane filaments (6) and passes through the biofilm attached to the membrane filaments. The inner side of the biofilm is in an aerobic state, and the outer side of the biofilm is in an anoxic / anaerobic state. The biofilm reaction zone (A) is aerated through the air inlet (7), and the gas is dispersed through the hollow aeration ring (5). The aeration pressure and aeration time are adjusted to accurately supply oxygen to ensure the realization of nitrification / denitrification reaction in the membrane aeration biofilm reactor; the sewage enters the three-phase separation zone (B) from the biofilm reaction zone (A) through the liquid guide tube (10) for gas, liquid and solid three-phase separation, and the sludge is discharged from the sludge discharge port (12), and the gas is discharged from the top exhaust port (15). The effluent is discharged from the overflow trough (13) through the biofilm reactor outlet (14) through the connecting pipe (18) into the water distribution channel (20) of the submerged flow artificial wetland reactor; the sewage directly entering the submerged flow artificial wetland reactor from the water inlet flow distribution valve (2) is filtered through the first cone filter (19) from the wetland water inlet pipe (4) and then enters the water distribution channel (20); the water distribution channel (20) collects the water from the membrane aeration biofilm reactor and the raw water directly entering the submerged flow artificial wetland reactor, and the water in the water distribution channel (20) first enters the wetland unit through the bottom porous filter plate (22). During the operation, the matrix, plant and microorganism remove pollutants in the water body through the combined action of physical, chemical and biological degradation, and the effluent overflows to the outlet channel (27) and is discharged from the wetland outlet pipe (29); Process 2: When the water quality fluctuates greatly, the outlet flow distribution valve (28) is adjusted, the reflux pump (32) is turned on, and the reflux liquid is filtered by the second conical filter (30) and then refluxed to the bottom of the membrane aerated biofilm reactor through the reflux pipe (31), and the operation process of the cyclic process 1 is repeated.

8. The sewage treatment method according to claim 7, characterized in that: Under typical sewage quality conditions, the water inlet distribution ratio is adjusted by the water inlet flow distribution valve (2), and the ratio of the water inlet volume of the membrane aerated biofilm reactor to that of the submerged flow artificial wetland reactor is 4:1, and part of the sewage directly enters the submerged flow artificial wetland reactor through the wetland water inlet pipe (4).

9. The sewage treatment method according to claim 7, characterized in that: When the inlet water quality fluctuates greatly, the outlet flow distribution valve (28) is adjusted, the reflux pump (32) is turned on, and the reflux ratio is set to 0-60%. The reflux liquid is filtered by the second conical filter (30) and then refluxed to the bottom of the membrane aerated biofilm reactor through the reflux pipe (31).

10. The sewage treatment method according to claim 7, characterized in that: The ratio of the hydraulic retention time of the membrane aerated biofilm reactor to that of the submerged flow artificial wetland reactor is 1:5-7, and the ratio of the volume of the membrane aerated biofilm reactor to that of the submerged flow artificial wetland reactor is 1:6-9.

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