A high-salt food processing wastewater treatment system and method

Abstract

The application discloses a high-salt food processing wastewater treatment system and method. The system comprises a grid pool, an adjusting and homogenizing pool, an aeration activated sludge pool, a membrane bioreactor and a micro-nano aeration system; the membrane bioreactor is divided into an anoxic pool and an immersed membrane filtration pool, the anoxic pool is located at the front end of the immersed membrane filtration pool, and the anoxic pool and the immersed membrane filtration pool are connected through pipelines; the immersed membrane filtration pool is provided with a membrane filtration component system, a sludge outlet and a water outlet; the grid pool is provided with a wastewater inlet, the grid pool, the adjusting and homogenizing pool and the aeration activated sludge pool are sequentially connected through pipelines, and the water outlet pipe of the aeration activated sludge pool is connected with the anoxic pool. The system does not need to use high-efficiency anaerobic process devices such as IC towers and UASB, etc.; in addition, the system process flow is short, the efficiency is high, the maintenance is convenient, the operation cost is low, the process can realize standard drainage, and the odor and the residual sludge can be eliminated and accommodated.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control technology, specifically relating to a high-salt food processing wastewater treatment system and method. Background Technology

[0002] Wastewater from pickled vegetable factories is a common type of high-salt food processing wastewater. It mainly originates from wastewater generated during the washing and pickling processes of raw materials such as vegetable leaves, stems, and seasonings, as well as wastewater from cleaning and disinfection processes. The main pollutants in this wastewater include: 1) Organic matter: During the production process, vegetables release large amounts of organic matter, including proteins, fats, and carbohydrates, during washing and pickling. This organic matter consumes oxygen, reducing the dissolved oxygen concentration in the water and harming aquatic life. 2) Ammonia nitrogen: Vegetable leaves and stems release large amounts of ammonia nitrogen during pickling. Excessive ammonia nitrogen levels can severely harm aquatic life and cause eutrophication. 3) Total phosphorus: The chemicals and seasonings used in the production process contain large amounts of phosphorus, and the vegetables themselves are also rich in phosphorus. Therefore, the total phosphorus content in the wastewater is high. Direct discharge without treatment will cause eutrophication. 4) Other impurities: The wastewater also contains small amounts of suspended solids, sediments, and other impurities, which need to be removed through pretreatment. If these pollutants are discharged directly into the environment without treatment, they will cause significant pollution to the surrounding environment and harm the surrounding ecosystem.

[0003] In the existing technology, for example: [1] Yu Yubin, Lin Xing, Jia Yun. Engineering case of MBR process for treating typical pickled vegetable wastewater[J]. Environmental Science and Technology, 2019, 32(1):40-43. A three-stage treatment process of modified equalization tank-hydrolysis acidification tank-A2 / O-MBR membrane system was adopted to treat pickled vegetable wastewater in an industrial park, and the effluent could meet the GB18918-2002 Class A standard; [2] Liu Jiangguo. Study on treatment of pickled vegetable wastewater by coagulation-anaerobic-electrode SBBR method[D]. Chongqing: Southwest University, 2011. However, the traditional biological method disclosed in the above literature is not ideal for treating high-salt organic wastewater in the pickled vegetable industry, while the physicochemical method has high energy consumption and high operating cost. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a high-salt food processing wastewater treatment system that features a short process flow, high efficiency, and low energy consumption.

[0005] Another objective of this invention is to provide a method for treating high-salt food processing wastewater.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A high-salt food processing wastewater treatment system includes a bar screen, a regulating tank, an aerated activated sludge tank, a membrane bioreactor, and a micro-nano aeration system. The membrane bioreactor is divided into an anoxic tank and a submerged membrane filter. The anoxic tank is located upstream of the submerged membrane filter, and the anoxic tank and the submerged membrane filter are connected by a pipeline. The submerged membrane filter is equipped with a membrane filtration module system, a sludge outlet, and a effluent outlet.

[0008] The screen tank is equipped with a wastewater inlet. The screen tank, the equalization tank and the aerated activated sludge tank are connected in sequence by pipes. The effluent pipe of the aerated activated sludge tank is connected to the facultative tank.

[0009] The effluent pipe of the anoxic tank is divided into two channels. One channel is connected to the submerged membrane filter tank, and the other channel is connected to the mixed liquor return pipe. The effluent end of the mixed liquor return pipe is connected to the equalization tank and the aerated activated sludge tank respectively, so that a portion of the effluent from the anoxic tank is returned to the equalization tank and the aerated activated sludge tank.

[0010] The sludge outlet of the submerged membrane filter is connected to the aerated activated sludge tank and the equalization tank respectively through a sludge return pipe, so as to return the sludge separated by the submerged membrane filter to the equalization tank and the aerated activated sludge tank for decomposition and digestion.

[0011] The micro-nano aeration system includes several micro-nano jet aeration devices, several gas-liquid mixers, an inlet pipe, an air pipe, and a submersible pump. The micro-nano jet aeration devices are respectively installed in the equalization tank, the aerated activated sludge tank, and the submerged membrane filter tank. The number of gas-liquid mixers is the same as the number of micro-nano jet aeration devices. The submersible pump pumps water into the inlet pipe. The air introduced from the air pipe and the water introduced from the inlet pipe are mixed by the gas-liquid mixer and then enter the micro-nano jet aeration devices to provide aeration for the equalization tank, the aerated activated sludge tank, and the submerged membrane filter tank.

[0012] Furthermore, J-shaped water distribution pipes are installed on both sides of the anoxic tank, with an installation height of 20-30cm from the bottom of the tank; the outlet of the J-shaped water distribution pipe adopts a trumpet-shaped mushroom-head shower head water distributor; the anoxic tank adopts a central water inlet, so that the J-shaped water distribution pipes on both sides of the tank distribute water evenly; an overflow trough is provided at the tail end of the anoxic tank, and the wastewater treated in the anoxic tank overflows from the overflow trough to the outlet pipe and is divided into two parts, one part enters the submerged membrane filter tank, and the other part flows back to the equalization tank and the aerated activated sludge tank.

[0013] Furthermore, the trumpet-shaped mushroom-head shower head water distributor has evenly spaced holes with a diameter of 2-4mm; the overflow groove has a 1 / 4 arc design, which makes it easier to overflow water to the outlet pipe.

[0014] Furthermore, the membrane filtration system uses a corrugated flat sheet membrane as the filter membrane. It is commercially available, easy to install and disassemble, modularly designed, and exhibits good compatibility as sludge and pollutants do not easily adhere to it.

[0015] Furthermore, the corrugated flat sheet membrane has a salt tolerance of ≥10000 mg / L and a pore size of 0.1μm~0.5μm.

[0016] Furthermore, the submersible pump is a portable submersible pump.

[0017] Furthermore, the bubble particle size generated by the micro-nano jet aeration device is 60nm~200nm, and the air intake method of the micro-nano jet aeration device is autonomous air intake; the air-liquid volume ratio of air to water mixed in the gas-liquid mixer is 1:2~4.

[0018] Furthermore, the micro-nano jet aeration device can be installed at the top or bottom of the equalization tank, aerated activated sludge tank, or submerged membrane filter tank, with flexible selection; the micro-nano jet aeration device is suitable for water depths of 1~5m. Installation at the top is preferred for ease of maintenance.

[0019] Furthermore, the regulating homogenizing tank is a narrow and elongated tank with a water depth of 3-4m and a length-to-width ratio of (6-12):2. The length L of a single tank is between 6m and 12m, and the minimum width is 2m. The number of micro-nano jet aeration devices in the regulating homogenizing tank is set according to the tank volume. They are arranged at uniform intervals in the same direction as the water flow and installed on the same axis, either in a single row or in parallel, with an installation spacing of 2m or 3m.

[0020] Furthermore, the aerated activated sludge tank is a narrow and elongated tank type with a water depth of 1~5m and a length-to-width ratio of (6~12):2. The length L of a single tank is between 6m≤L≤12m, and the minimum width is 2m. The number of micro-nano jet aeration devices in the aerated activated sludge tank is set according to the tank volume. They are arranged at uniform intervals in the same direction as the water flow and installed on the same axis, either in a single row or in parallel, with an installation spacing of 2m or 3m.

[0021] Furthermore, the number of micro-nano jet aeration devices installed in the regulating homogenization tank and the aerated activated sludge tank is two or more.

[0022] This invention provides a method for treating high-salt food processing wastewater, comprising the following steps:

[0023] (1) The high-salt food processing wastewater to be treated is pretreated by a grit chamber to remove suspended solids and large particulate impurities before entering the equalization tank.

[0024] (2) In the equalization tank, the wastewater is pre-aerated by a micro-nano jet aeration device, and the aeration-generated thrust is used to stir the wastewater so that the wastewater is evenly mixed.

[0025] (3) The wastewater homogenized in step (2) enters the aerated activated sludge tank for aerobic decomposition. The aerated activated sludge tank is filled with aerobic activated sludge. The wastewater is aerated in the aerated activated sludge tank by a micro-nano jet aeration device, and the aeration is used to stir the wastewater, so that the aerobic activated sludge and wastewater are fully and evenly mixed and contacted. The aerobic microorganisms in the aerobic activated sludge decompose the organic macromolecular compounds in the wastewater into small molecules.

[0026] (4) Wastewater treated aerobically in the aerated activated sludge tank enters the facultative tank, where facultative bacteria are added. These bacteria, possessing both aerobic and facultative properties, degrade the salinity of the wastewater and adjust the Cl- concentration in the wastewater. - SO4 2- Na + Ca 2+ The concentration of plasma provides a guarantee for subsequent membrane filtration;

[0027] (5) The wastewater after treatment in the facultative anoxic tank is divided into two parts. One part is returned to the equalization tank and the aerated activated sludge tank; the other part enters the submerged membrane filter tank. In the submerged membrane filter tank, aeration and power are provided by the micro-nano jet aeration device, so that the wastewater passes through the membrane filter component system. The filter membrane in the system further decomposes the organic matter in the wastewater and separates the sludge in the wastewater to obtain qualified effluent and sludge.

[0028] The sludge is returned to the equalization tank and the aerated activated sludge tank for decomposition and digestion, and the qualified effluent is discharged directly, achieving odorless and residue-free sludge treatment of high-salt food processing wastewater.

[0029] Preferably, the dissolved oxygen content (DO value) in the equalization tank is 1-3 mg / L, and the hydraulic retention time (HRT) is 8-24 h. This step utilizes aeration and stirring to ensure uniform mixing of the influent, while simultaneously achieving pre-aeration.

[0030] Preferably, the oxygen utilization rate of the equalization tank is ≥60%; and the oxygen utilization rate of the aerated activated sludge tank is ≥80%.

[0031] Preferably, the dissolved oxygen content (DO value) of the aerated activated sludge tank is 4-8 mg / L; the sludge concentration (MLSS) of the aerated activated sludge tank is controlled at 3000 mg / L-7000 mg / L, and the hydraulic retention time (HRT) is 12h-48h.

[0032] Preferably, the aerobic activated sludge is made from food wastewater sludge of the same type as the wastewater to be treated, or municipal sludge with added aerobic engineered bacteria.

[0033] More preferably, the acclimation method of the aerobic activated sludge is carried out in accordance with conventional methods in the art, wherein the main process parameters are as follows: aerobic activated sludge is added according to the sludge concentration MLSS≥3000mg / L; the influent is added in stages at 10% or 20% increments, and the influent is continuously aerated for 10 days or 5 days; the dissolved oxygen content (DO value) is 6mg / L, and the mixed liquor is returned to the equalization tank at 100%~200%.

[0034] The aerobic engineered bacteria include at least one of Bacillus subtilis, Bacillus spheroidosa, and Bacillus licheniformis; the dosage of the aerobic engineered bacteria is 0.01% to 0.03% of the tank volume (g / m³). 3 ).

[0035] Preferably, the dissolved oxygen content (DO value) of the anaerobic tank is 0.5-2 mg / L, the sludge concentration (MLSS) is controlled at 5000-7000 mg / L, and the hydraulic retention time (HRT) is 4-8 h.

[0036] The wastewater treated by the anoxic tank mixed liquor is partially fed directly into the submerged membrane filter, partially returned to the equalization tank with a return ratio of 100% to 300%, and partially returned to the aerated activated sludge tank with a return ratio of 100% to 200%.

[0037] Preferably, the facultative anaerobic bacteria are salt-tolerant bacteria that thrive in both aerobic and facultative anaerobic environments, such as halophilic Bacillus. The dosage of the facultative anaerobic bacteria is one to five ten-thousandths of the facultative anaerobic tank volume (g / m³). 3 ).

[0038] Preferably, the wastewater to be treated has a COD of 3000 mg / L to 20000 mg / L and a salt content of 1% to 2% (equivalent to 10000 to 20000 mg / L), and is preferably wastewater from a pickling and salting vegetable factory.

[0039] Preferably, the qualified effluent has a COD value ≤100mg / L and a chloride content ≤600mg / L.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] 1. The system described in this invention is an aerobic treatment process that is easy to operate throughout, and does not require the use of efficient anaerobic process devices, such as IC towers, UASB, etc.

[0042] 2. The system described in this invention uses micro-nano jet aeration devices with large thrust in the equalization tank, aerated activated sludge tank, and submerged membrane filter tank. The aeration can fully mix the sludge and water, and no stirring device is required throughout the process. The separate aeration devices also facilitate the control of dissolved oxygen (DO value).

[0043] 3. The system described in this invention has an anoxic tank at the front end of the membrane bioreactor. Wastewater treated by the aerated activated sludge tank first enters the anoxic tank for treatment. No additional oxygen is supplied to this part (i.e., no aeration device is installed in this part). The anoxic bacteria effectively buffer water quality fluctuations by utilizing their resistance to load shocks. Furthermore, it can degrade part of the COD in the wastewater, further stabilizing the sludge concentration and influent water quality of the membrane bioreactor.

[0044] 4. The system described in this invention has a short process flow, high efficiency, convenient maintenance, and low operating costs; the process can achieve compliant drainage, while eliminating odor and disposing of excess sludge.

[0045] 5. The system described in this invention is suitable for small-scale light industrial and food processing enterprises (wastewater output Q≤1000 m³). 3 / d). Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the high-salt food processing wastewater treatment system of the present invention; 1-grid tank, 2-regulating and homogenizing tank, 3-aerated activated sludge tank, 4-membrane bioreactor, 4-A is an anaerobic tank, 4-B is a submerged membrane filter, 5-mixed liquor return pipe, 6-sludge pipe, 7-micro-nano jet aeration device, 8-gas-liquid mixer, 9-submersible pump.

[0047] Figure 2 This is a schematic diagram of the anoxic tank in the high-salt food processing wastewater treatment system of the present invention; 4-1 is the inlet pipe, 4-2 is the J-shaped distribution pipe, 4-3 is the outlet nozzle, 4-4 is the overflow trough, and 4-5 is the outlet pipe. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0049] like Figure 1As shown, this invention provides a high-salt food processing wastewater treatment system, including a bar screen tank 1, a regulating and homogenizing tank 2, an aerated activated sludge tank 3, a membrane bioreactor 4, and a micro-nano aeration system; the membrane bioreactor 4 is divided into an anoxic tank 4-A and a submerged membrane filter tank 4-B, which are connected by pipes; the submerged membrane filter tank 4-B is equipped with a membrane filtration component system, a sludge outlet, and a effluent outlet; the bar screen tank 1 is equipped with a wastewater inlet, and the bar screen tank 1, the regulating and homogenizing tank 2, and the aerated activated sludge tank 3 are connected sequentially by pipes; the effluent pipe of the aerated activated sludge tank 3 is connected to the anoxic tank 4-A;

[0050] The effluent pipe of the anoxic tank 4-A is divided into two channels. One channel is connected to the submerged membrane filter tank 4-B, and the other channel is connected to the mixed liquor return pipe 5. The effluent end of the mixed liquor return pipe 5 is connected to the equalization tank 2 and the aerated activated sludge tank 3 respectively, so that a portion of the effluent from the anoxic tank 4-A is returned to the equalization tank 2 and the aerated activated sludge tank 3.

[0051] The sludge outlet of the submerged membrane filter 4-B is connected to the aerated activated sludge tank 3 and the equalization tank 2 respectively through the sludge return pipe 6, so as to return the sludge separated from the submerged membrane filter 4-B to the equalization tank 2 and the aerated activated sludge tank 3 for decomposition and digestion.

[0052] The micro-nano aeration system includes several micro-nano jet aeration devices 7, several gas-liquid mixers 8, an inlet pipe, an air pipe, and a submersible pump 9. The micro-nano jet aeration devices 7 are respectively installed in the equalization tank 2, the aerated activated sludge tank 3, and the submerged membrane filter tank 4-B. The number of gas-liquid mixers 8 is the same as the number of micro-nano jet aeration devices 7. The submersible pump 9 pumps water into the inlet pipe. The air introduced from the air pipe and the water introduced from the inlet pipe are mixed by the gas-liquid mixers 8 and then enter the micro-nano jet aeration devices 7 to provide aeration for the equalization tank 2, the aerated activated sludge tank 3, and the submerged membrane filter tank 4-B.

[0053] The membrane filtration system uses a corrugated flat sheet membrane as the filter membrane, the corrugated flat sheet membrane has a salt tolerance ≥10000 mg / L and a membrane pore size of 0.1μm~0.5μm; the submersible pump is a portable submersible pump.

[0054] like Figure 2As shown, J-shaped water distribution pipes 4-2 are installed on both sides of the anoxic tank, with an installation height of 20-30cm from the bottom of the tank. The outlet nozzles 4-3 of the J-shaped water distribution pipes adopt a trumpet-shaped mushroom-head sprinkler-type water distributor. The anoxic tank adopts a central water inlet, with the inlet pipe 4-1 installed in the middle, so that the J-shaped water distribution pipes 4-2 on both sides of the tank distribute water evenly. An overflow trough 4-4 is set at the tail end of the anoxic tank. The wastewater treated in the anoxic tank overflows from the overflow trough 4-4 to the outlet pipe 4-5 and is divided into two parts. One part enters the submerged membrane filter tank, and the other part flows back to the equalization tank and the aerated activated sludge tank. The trumpet-shaped mushroom-head sprinkler-type water distributor has evenly distributed openings with a diameter of 2-4mm. The overflow trough has a 1 / 4 arc design, which makes it easier for the effluent to overflow to the outlet pipe.

[0055] Example 1

[0056] This embodiment adopts Figure 1 and 2 The high-salt food processing wastewater treatment system shown treats pickled vegetable wastewater from a certain enterprise. The wastewater output is 40m³. 3 / day, the wastewater quality of pickled vegetables is: COD 4000mg / L~7000mg / L, BOD 2500mg / L~3000mg / L.

[0057] In the system described in this embodiment, the homogenization tank is a long and narrow tank, 2m wide × 6m long × 3m deep, and is equipped with four 1.5kW units with an air intake capacity of 3.6m³ / h. 3 The device features a micro-nano jet aeration system with a capacity of [number] h; the aerated activated sludge tank is a long and narrow design, measuring 2m wide × 8m long × 5m deep, with a volume of 80 m³. 3 It is equipped with four 3.7kw units with an air intake of 15m³ / h. 3 A micro-nano jet aeration device with a volume ratio of / h; the bubbles generated by the micro-nano jet aeration device have a particle size of about 70% of 100 nm and a gas-liquid volume ratio of 1:3.

[0058] The system debugging and operation control parameters described in this embodiment are as follows: the water inflow is increased sequentially by 10%, 30%, 50%, 70%, and 100% of the total water inflow. When the COD of the effluent meets the discharge requirements, the water inflow is increased.

[0059] The wastewater treatment process for pickled vegetables is as follows:

[0060] (1) Pickled vegetable wastewater is pretreated by a grid tank to remove suspended solids and large particulate impurities before entering a regulating and homogenizing tank.

[0061] (2) The wastewater is pre-aerated by the micro-nano jet aeration device in the equalization tank, and the wastewater is stirred by the aeration thrust to make the wastewater uniformly mixed; the dissolved oxygen content in the equalization tank is 1-3 mg / L, and the hydraulic retention time is 8-16 h.

[0062] (3) The homogenized wastewater from step (2) enters the aerated activated sludge tank for aerobic decomposition. The aerated activated sludge tank contains aerobic activated sludge. Aeration is carried out in the aerated activated sludge tank using a micro-nano jet aeration device, and the aeration is stirred by the thrust of the aeration to ensure that the aerobic activated sludge and wastewater are fully and evenly mixed and contacted. The aerobic microorganisms in the aerobic activated sludge decompose the organic macromolecular compounds in the wastewater into small molecules. The MLSS sludge concentration in the aerated activated sludge tank is controlled at ≥3000mg / L, the hydraulic retention time is 12-24h, the dissolved oxygen content is 4-8mg / L, and the sludge settling volume ratio is SV30≈30%.

[0063] (4) The wastewater after aerobic treatment in the aerated activated sludge tank enters the facultative tank at the front end of the membrane bioreactor. The facultative bacteria, salt-tolerant Bacillus, which have both aerobic and facultative advantages, degrade the salinity of the wastewater and adjust the ion concentration of the wastewater, thus providing a guarantee for subsequent membrane filtration.

[0064] The dissolved oxygen content (DO value) in the anoxic tank is 0.5-2 mg / L, the sludge concentration (MLSS) is controlled at 5000-7000 mg / L, and the hydraulic retention time (HRT) is 4-8 h.

[0065] The dosage of the salt-tolerant Bacillus is three ten-thousandths of the facultative anaerobic tank volume (g / m³). 3 );

[0066] (5) The wastewater after treatment in the anoxic tank is divided into two parts. One part is returned to the equalization tank (return ratio of 100%~200%) and the aerated activated sludge tank (return ratio of 200%). The other part enters the submerged membrane filter tank. In the submerged membrane filter tank, aeration and power are provided by the micro-nano jet aeration device, so that the wastewater passes through the membrane filter component system. The filter membrane in the system further decomposes the organic matter in the wastewater and separates the sludge in the wastewater to obtain effluent and sludge. The COD of the effluent is 20~30mg / L and the BOD is 5mg / L. The sludge is returned to the equalization tank and the aerated activated sludge tank for decomposition and digestion. The qualified effluent is directly discharged, realizing the odorless and residue-free treatment of high-salt food processing wastewater.

[0067] In the submerged membrane filter, the dissolved oxygen content (DO value) is ≥2mg / L, and the sludge concentration (MLSS) is controlled at ≥3000mg / L.

[0068] In this embodiment, the acclimation method for aerobic activated sludge is carried out in accordance with conventional methods in the field. The main process parameters are as follows: municipal dewatered sludge (80% moisture content) + aerobic engineered bacteria (Bacillus subtilis, Bacillus spheroidis, and Bacillus licheniformis) are added based on a sludge concentration MLSS ≥ 3000 mg / L; the influent is increased in stages at 10% increments, and continuous influent is aerated for 10 days; the dissolved oxygen content is 6 mg / L, and 200% of the mixed liquor is returned to the equalization tank; the dosage of aerobic engineered bacteria is 0.02% (g / m³) of the tank volume. 3 ).

[0069] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A high-salt food processing wastewater treatment system, characterized in that, It includes a bar screen, a regulating tank, an aerated activated sludge tank, a membrane bioreactor, and a micro-nano aeration system; the membrane bioreactor is divided into an anoxic tank and a submerged membrane filter, with the anoxic tank located at the front end of the submerged membrane filter, and the anoxic tank and the submerged membrane filter connected by a pipeline; the submerged membrane filter is equipped with a membrane filtration module system, a sludge outlet, and an effluent outlet. The screen tank is equipped with a wastewater inlet. The screen tank, the equalization tank and the aerated activated sludge tank are connected in sequence by pipes. The effluent pipe of the aerated activated sludge tank is connected to the facultative tank. The effluent pipe of the anoxic tank is divided into two channels. One channel is connected to the submerged membrane filter tank, and the other channel is connected to the mixed liquor return pipe. The effluent end of the mixed liquor return pipe is connected to the equalization tank and the aerated activated sludge tank respectively, so that a portion of the effluent from the anoxic tank is returned to the equalization tank and the aerated activated sludge tank. The sludge outlet of the submerged membrane filter is connected to the aerated activated sludge tank and the equalization tank respectively through a sludge return pipe, so as to return the sludge separated by the submerged membrane filter to the equalization tank and the aerated activated sludge tank for decomposition and digestion. The micro-nano aeration system includes several micro-nano jet aeration devices, several gas-liquid mixers, an inlet pipe, an air pipe, and a submersible pump. The micro-nano jet aeration devices are respectively installed in the equalization tank, the aerated activated sludge tank, and the submerged membrane filter tank. The number of gas-liquid mixers is the same as the number of micro-nano jet aeration devices. The submersible pump pumps water into the inlet pipe. The air introduced from the air pipe and the water introduced from the inlet pipe are mixed by the gas-liquid mixer and then enter the micro-nano jet aeration devices to provide aeration for the equalization tank, the aerated activated sludge tank, and the submerged membrane filter tank. The micro-nano jet aeration device produces bubbles with a particle size of 60nm~200nm, and the air intake method of the micro-nano jet aeration device is autonomous air intake; the air-liquid volume ratio of air to water mixed in the gas-liquid mixer is 1:2~4.

2. The high-salt food processing wastewater treatment system according to claim 1, characterized in that, J-shaped water distribution pipes are installed on both sides of the anoxic tank, with an installation height of 20-30cm from the bottom of the tank. The outlet of the J-shaped water distribution pipes adopts a trumpet-shaped mushroom-head shower head water distributor. The anoxic tank adopts a central water inlet, so that the J-shaped water distribution pipes on both sides of the tank distribute water evenly. An overflow trough is set at the tail end of the anoxic tank. The wastewater treated in the anoxic tank overflows from the overflow trough to the outlet pipe and is divided into two parts. One part enters the submerged membrane filter tank, and the other part flows back to the equalization tank and the aerated activated sludge tank.

3. The high-salt food processing wastewater treatment system according to claim 2, characterized in that, The trumpet-shaped mushroom-head shower head water distributor has evenly spaced holes with a diameter of 2-4 mm; the overflow groove has a 1 / 4 arc-shaped design.

4. The high-salt food processing wastewater treatment system according to claim 1, characterized in that, The membrane filtration assembly system uses a corrugated flat sheet membrane as the filter membrane. The corrugated flat sheet membrane has a salt tolerance of ≥10000 mg / L and a pore size of 0.1μm~0.5μm.

5. The high-salt food processing wastewater treatment system according to claim 1, characterized in that, The regulating and homogenizing tank is a narrow and elongated tank with a water depth of 3-4m and a length-to-width ratio of (6-12):

2. The length L of a single tank is between 6m and 12m, and the minimum width is 2m. The aerated activated sludge tank is a narrow and elongated tank with a water depth of 1-5m and a length-to-width ratio of (6-12):

2. The length L of a single tank is between 6m and 12m, and the minimum width is 2m.

6. A method for treating high-salt food processing wastewater based on the system described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) The high-salt food processing wastewater to be treated is pretreated by a grit chamber to remove suspended solids and large particulate impurities before entering the equalization tank. (2) In the equalization tank, the wastewater is pre-aerated by a micro-nano jet aeration device, and the aeration-generated thrust is used to stir the wastewater so that the wastewater is evenly mixed. (3) The wastewater homogenized in step (2) enters the aerated activated sludge tank for aerobic decomposition. The aerated activated sludge tank is filled with aerobic activated sludge. The wastewater is aerated in the aerated activated sludge tank by a micro-nano jet aeration device, and the aeration is used to stir the wastewater, so that the aerobic activated sludge and wastewater are fully and evenly mixed and in contact. The aerobic microorganisms in the aerobic activated sludge decompose the organic macromolecular compounds in the wastewater into small molecules. (4) The wastewater after aerobic treatment in the aerated activated sludge tank enters the facultative tank, where facultative bacteria are added. In the facultative tank, the advantages of facultative bacteria, which have both aerobic and facultative properties, are utilized to degrade the salinity of the wastewater and adjust the concentration of ions in the wastewater. (5) The wastewater after treatment in the facultative anoxic tank is divided into two parts. One part is returned to the equalization tank and the aerated activated sludge tank; the other part enters the submerged membrane filter tank. In the submerged membrane filter tank, aeration and power are provided by the micro-nano jet aeration device, so that the wastewater passes through the membrane filter component system. The filter membrane in the system further decomposes the organic matter in the wastewater and separates the sludge in the wastewater to obtain qualified effluent and sludge. The sludge is returned to the equalization tank and the aerated activated sludge tank for decomposition and digestion, and the qualified effluent is directly discharged, achieving odorless and residue-free sludge treatment of high-salt food processing wastewater. The oxygen utilization rate of the equalization tank is ≥60%; the oxygen utilization rate of the aerated activated sludge tank is ≥80%.

7. The method according to claim 6, characterized in that, The dissolved oxygen content in the equalization tank is 1-3 mg / L, and the hydraulic retention time is 8-24 h.

8. The method according to claim 6, characterized in that, The dissolved oxygen content of the aerated activated sludge tank is 4-8 mg / L, the sludge concentration is controlled at 3000 mg / L-7000 mg / L, and the hydraulic retention time is 12-48 h.

9. The method according to claim 6, characterized in that, The dissolved oxygen content in the facultative anaerobic tank is 0.5–2 mg / L, the sludge concentration is controlled at 5000–7000 mg / L, and the hydraulic retention time is 4–8 h. The wastewater treated in the anoxic tank is partially fed directly into the submerged membrane filter, partially returned to the equalization tank with a return ratio of 100% to 300%, and partially returned to the aerated activated sludge tank with a return ratio of 100% to 200%.

10. The method according to claim 6, characterized in that, The COD of the high-salt food processing wastewater to be treated is 3000 mg / L to 20000 mg / L, and the salt content is 10000 to 20000 mg / L. The effluent meeting the standards has a COD value ≤100mg / L and a chloride value ≤600mg / L.

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