Kitchen slurry anaerobic fermentation combined with ozone high-efficiency membrane separation method and system

Abstract

The present application relates to the field of environmental protection and sewage treatment technology, and discloses a kind of kitchen slurry anaerobic fermentation combined ozone high-efficiency membrane separation method and system.The method comprises the following steps: (1) the kitchen slurry is subjected to anaerobic fermentation in an anaerobic fermentation unit, and then introduced into a filter press unit for pretreatment to remove filter residue, obtaining a mixture I; (2) the mixture I is subjected to primary ozone oxidation, obtaining a mixture II; (3) the mixture II is introduced into a membrane separation unit for separation and concentration, obtaining clean water and concentrated water; (4) the clean water is subjected to secondary ozone oxidation, obtaining effluent.The method provided by the present application can realize stable operation of a high-efficiency anaerobic reactor by selecting a membrane, controlling the operation mode of a membrane assembly, and coupling with an anaerobic fermentation process and a two-stage ozone oxidation process, effectively removing pollutants while reducing membrane fouling problems and sludge digestion problems.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and wastewater treatment technology, and in particular relates to a method and system for anaerobic fermentation of kitchen waste slurry combined with ozone for high-efficiency membrane separation. Background Technology

[0002] Kitchen wastewater is a high-concentration organic wastewater obtained after a series of pretreatment processes, including crushing, sorting, high-temperature cooking, and three-phase centrifugation, of kitchen waste. Although the pretreatment process involves oil extraction from the kitchen waste, it still cannot achieve 100% extraction efficiency. The main problems encountered in the subsequent anaerobic treatment of oily kitchen wastewater are twofold: firstly, its hydrolysis products—long-chain fatty acids (LCFAs)—exhibit toxicity to methanogens and acetogens; secondly, the oil easily adsorbs onto the surface of microorganisms, forming a lipid layer that hinders the supply of substrates and nutrients to the cells, leading to sludge floating and loss.

[0003] High-efficiency anaerobic ozone membrane separation technology has shown great application prospects in the treatment of high-concentration and complex organic wastewater due to its advantages such as high sludge concentration, long sludge age, strong resistance to shock loads, resistance to membrane fouling, and ability to dissolve excess sludge.

[0004] However, membrane fouling remains a bottleneck limiting their widespread application during operation. Membrane fouling is related to various factors, such as substrate composition, reactor operating parameters (temperature, sludge retention time, organic loading, food-to-microbe ratio), shear stress, membrane materials, and sludge characteristics. Compared to aerobic membrane bioreactors, anaerobic membrane systems experience more severe membrane fouling. This is because in anaerobic systems, anaerobic sludge flocs are smaller than aerobic sludge flocs, resulting in a denser filter cake layer on the membrane surface with lower porosity, thus accelerating the rate of membrane fouling. Furthermore, due to the complete retention of anaerobic sludge by the membrane, the system maintains a high density of microorganisms, and the high concentration of sludge can rapidly deposit on the membrane surface, accelerating the formation of the filter cake layer and further exacerbating membrane fouling.

[0005] CN219409505U discloses a treatment system for nanofiltration concentrate of kitchen waste biogas slurry. This system includes an ozone / activated carbon contact oxidation device, a filter press, an MBR (membrane bioreactor), and a DSA (distillation and oxidation-reduction) electrocatalytic oxidation-reduction device connected in sequence. The effluent from the ozone / activated carbon contact oxidation device is fed into the filter press, and the clarified liquid after filtration enters the MBR. Ozone waste gas is collected by a top-mounted collection device in the ozone / activated carbon contact oxidation device, catalytically converted into oxygen, and then used for aeration in the MBR. The effluent from the MBR is pumped into the DSA electrocatalytic oxidation-reduction device. This system can simultaneously remove COD, ammonia nitrogen, total nitrogen, and total phosphorus, and has advantages such as simple process, convenient operation, low cost, high treatment efficiency, and good treatment effect, effectively treating the membrane filtration concentrate. However, its built-in MBR cannot be used for direct anaerobic biogas slurry production, and it does not solve the problems of ozone fouling of external membranes and the dissolution of residual anaerobic sludge.

[0006] CN214400056U discloses a small-scale kitchen waste fermentation machine wastewater treatment system, including a storage tank with an inlet and an outlet. A partition divides the storage tank's interior into a first chamber and a second chamber, with several through holes on the partition. A filter membrane assembly is installed on one side of the partition in the first chamber. A jet pump is connected to the outlet via a circulating liquid pipe, the other end of which is connected to the storage tank. An ozone generator is installed on one side of the storage tank, its outlet connected to the circulating liquid pipe via an inlet pipe and a jet pump. The system also includes an automatic control system. This wastewater treatment system has a reasonable structural design, is easy to control, has low treatment costs, and can form a wastewater treatment loop, achieving automatic circulation and purification of wastewater, improving purification efficiency, and effectively improving the quality of the fermentation machine wastewater, enabling it to meet reuse standards. However, it is only applicable to the liquid obtained by centrifugation after pretreatment and anaerobic fermentation of kitchen waste. Its SS concentration is low (SS < 8000 mg / L), and it cannot promote the dissolution of the remaining sludge or prevent sludge loss.

[0007] Therefore, it is of great practical significance to provide a system that can efficiently and stably treat kitchen waste slurry, effectively degrade the oil and large colloidal substances in biogas slurry, effectively reduce membrane fouling, extend membrane cleaning time, and effectively dissolve residual sludge. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of severe membrane fouling, low efficiency in treating organic matter such as oils and fats, and poor membrane permeability of biogas slurry in the existing technology when treating kitchen waste slurry by membrane separation.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for anaerobic fermentation of kitchen waste slurry combined with ozone high-efficiency membrane separation, the method comprising:

[0010] (1) The kitchen slurry is anaerobic fermented in an anaerobic fermentation unit, and then introduced into a filtration and pressing unit for pretreatment to remove the filter residue and obtain mixture I;

[0011] (2) Mixture I is subjected to primary ozone oxidation to obtain mixture II;

[0012] (3) The mixture II is introduced into a membrane separation unit for separation and concentration to obtain clear water and concentrated water;

[0013] At least a portion of the concentrated water is recycled back to the anaerobic fermentation unit;

[0014] The separation and concentration process uses an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm.

[0015] (4) The water is subjected to secondary ozone oxidation to obtain effluent.

[0016] The second aspect of the present invention provides a high-efficiency membrane separation system for anaerobic fermentation of kitchen waste slurry combined with ozone. The system is used to implement the method described in the first aspect, and includes an anaerobic fermentation unit, a filtration and pressing unit, a primary ozone oxidation unit, a membrane separation unit and a secondary ozone oxidation unit connected in sequence.

[0017] The anaerobic fermentation unit includes an anaerobic tank and a temporary storage tank.

[0018] The membrane separation unit includes a membrane separation device and a cleaning device;

[0019] The membrane separation device is equipped with an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm.

[0020] Compared with existing technologies, the method and system provided by this invention have at least the following advantages:

[0021] (1) The method provided by the present invention combines anaerobic fermentation, membrane separation technology and two-stage ozone oxidation. It not only retains many advantages of anaerobic fermentation technology, but also retains microorganisms and suspended solids, so that the quality of effluent can be guaranteed. It is also independent of the settling and particulate properties of sludge, and achieves effective separation of sludge retention time and hydraulic retention time.

[0022] (2) The two-stage ozone oxidation method provided by the present invention has a cell wall breaking effect on bacteria and effectively utilizes the highly reactive free radical intermediates generated by ozone molecules on the catalyst surface, especially hydroxyl radicals, to oxidize and remove the difficult-to-biodegrade organic matter in wastewater, further effectively degrade the grease and large colloidal substances in the kitchen slurry, effectively reduce membrane fouling, extend the membrane cleaning time, and at the same time effectively remove odors and reduce color.

[0023] (3) The system provided by the present invention can achieve stable operation of a high-efficiency anaerobic reactor by selecting membranes, controlling the operation mode of membrane modules and linking with anaerobic fermentation process and two-stage ozone oxidation process, thereby effectively removing pollutants and reducing membrane fouling. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a preferred method for anaerobic fermentation of kitchen waste combined with ozone high-efficiency membrane separation, provided by the present invention.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1. Feed pump; 2. Anaerobic digester;

[0027] 3. Filtering and pressing unit; 4. Return pump;

[0028] 5. Temporary storage tank; 6. Booster pump;

[0029] 7. Primary glass reactor; 8. Basket filter;

[0030] 9. Membrane separation unit; 10. Cleaning system;

[0031] 11. Ozone generator; 12. Safety valve;

[0032] 13. Flow meter; 14. Secondary glass reactor. Detailed Implementation

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] As mentioned above, this invention provides a method for anaerobic fermentation of kitchen waste slurry combined with ozone high-efficiency membrane separation, the method comprising:

[0035] (1) The kitchen slurry is anaerobic fermented in an anaerobic fermentation unit, and then introduced into a filtration and pressing unit for pretreatment to remove the filter residue and obtain mixture I;

[0036] (2) Mixture I is subjected to primary ozone oxidation to obtain mixture II;

[0037] (3) The mixture II is introduced into a membrane separation unit for separation and concentration to obtain clear water and concentrated water;

[0038] At least a portion of the concentrated water is recycled back to the anaerobic fermentation unit;

[0039] The separation and concentration process uses an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm.

[0040] (4) The water is subjected to secondary ozone oxidation to obtain effluent.

[0041] Preferably, in step (3), the SS of the clean water is not greater than 1000 mg / L and the COD is not greater than 1000 mg / L.

[0042] According to a preferred embodiment, the ratio of ozone concentration in the primary ozone oxidation to ozone concentration in the secondary ozone oxidation is 1-3:1.

[0043] Preferably, in step (2), the ozone concentration in the primary ozone oxidation is 50-100 mg / L.

[0044] Preferably, in step (4), the ozone concentration in the secondary ozone oxidation is 20-50 mg / L.

[0045] Preferably, the primary ozone oxidation and / or the secondary ozone oxidation are carried out in a glass reactor.

[0046] Preferably, the method of the present invention further includes, in step (3), filtering the mixture II through a basket filter before performing the separation and concentration.

[0047] Preferably, the epoxy resin membrane is an ANA-AER400 epoxy resin membrane manufactured by Wuxi Aina Environmental Protection Technology Co., Ltd. Studies have found that this preferred configuration is more conducive to reducing the load on the deep treatment of the effluent.

[0048] Preferably, the separation and concentration conditions at least satisfy the following: temperature of 25-45℃ and pH of 7.5-8.5.

[0049] In a preferred embodiment, in step (1), the SS concentration of the mixture I is 10-40 g / L.

[0050] It should be noted that, in this invention, the SS concentration represents the mass of suspended solids in a unit volume of wastewater.

[0051] In a preferred embodiment, the pretreatment operation includes filtering and pressing the product of the anaerobic fermentation.

[0052] In a preferred embodiment, in step (1), the pretreatment uses a filter with a precision of 600-800 μm.

[0053] Preferably, the method of the present invention further includes, in step (2), introducing the mixture I into a temporary storage tank first, and then drawing it out from the temporary storage tank for the first-stage ozone oxidation.

[0054] In a preferred embodiment, the reflux ratio of the concentrated water is 5-10. Studies have found that this preferred embodiment can effectively compensate for sludge loss during anaerobic fermentation, ultimately resulting in separation of hydraulic retention time and sludge retention time, leading to better anaerobic fermentation.

[0055] It should be noted that, in this invention, the reflux ratio is the ratio of the flow rate of the refluxed concentrated water to the flow rate of the kitchen slurry entering the anaerobic fermentation unit in step (1).

[0056] More preferably, the method of the present invention further includes, in step (3), at least a portion of the concentrated water is returned to the temporary storage tank and mixed with the mixture I, and then returned from the temporary storage tank to the anaerobic fermentation unit via a variable frequency anaerobic reflux pump, and the reflux ratio of the concentrated water is 5-10.

[0057] The following combination Figure 1 A preferred embodiment of a method for anaerobic fermentation of kitchen waste combined with ozone high-efficiency membrane separation is provided, comprising:

[0058] (1) The kitchen slurry is introduced into the anaerobic tank 2 in the anaerobic fermentation unit by the feed pump 1 and the flow meter 13 for anaerobic fermentation, and then introduced into the filtration and pressing unit 3 for pretreatment to remove the filter residue and obtain mixture I;

[0059] (2) The mixture I is first introduced into the temporary storage tank 5, and then drawn out from the temporary storage tank 5 through the booster pump 6 and the flow meter 13 into the first-stage glass reactor 7 for first-stage ozone oxidation to obtain mixture II; wherein, the ozone is introduced into the first-stage glass reactor 7 from the ozone generator 11 through the safety valve 12.

[0060] (3) The mixture II is filtered through a basket filter 8 and then introduced into the membrane separation unit 9 for separation and concentration to obtain clear water and concentrated water; wherein, the membrane separation unit 9 is cleaned by a cleaning system 10; at least a portion of the concentrated water is returned to the temporary storage tank 5, and then returned to the anaerobic tank 2 by the temporary storage tank 5 through the variable frequency anaerobic reflux pump 4 and the flow meter 13, and the reflux ratio of the concentrated water is 5-10;

[0061] (4) The clean water is introduced into the secondary glass reactor 14 for secondary ozone oxidation, and the effluent is drawn out through the flow meter 13.

[0062] As mentioned above, the second aspect of the present invention provides a high-efficiency membrane separation system for anaerobic fermentation of kitchen waste slurry combined with ozone. The system is used to implement the method described in the first aspect, and includes an anaerobic fermentation unit, a filtration and pressing unit, a primary ozone oxidation unit, a membrane separation unit and a secondary ozone oxidation unit connected in sequence.

[0063] The anaerobic fermentation unit includes an anaerobic tank and a temporary storage tank.

[0064] The membrane separation unit includes a membrane separation device and a cleaning device;

[0065] The membrane separation device is equipped with an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm.

[0066] Preferably, a basket filter is provided upstream of the membrane separation unit.

[0067] Preferably, the epoxy resin film is an ANA-AER400 epoxy resin film manufactured by Wuxi Aina Environmental Protection Technology Co., Ltd.

[0068] In a preferred embodiment, the filtration and pressing unit includes a drum, a drum drive, a backwashing high-pressure blower, a screw extrusion drive, and a flushing water pump, and a filter screen with a precision of 600-800μm is provided in the drum.

[0069] Preferably, a concentrate outlet is provided on the membrane separation device, and the concentrate outlet is connected to the temporary storage tank for introducing at least a portion of the concentrate from the membrane separation device into the temporary storage tank; and

[0070] An outlet is provided on the temporary storage tank and the outlet is connected to the anaerobic tank for introducing at least a portion of the mud-water mixture in the temporary storage tank into the anaerobic tank to achieve reflux.

[0071] In a preferred embodiment, the membrane separation device is provided with an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm.

[0072] Preferably, the membrane separation device is an external tubular membrane module.

[0073] In a preferred embodiment, the primary ozone oxidation unit includes a primary ozone generator and a primary glass reactor, wherein the primary glass reactor is used to perform primary ozone oxidation on the liquid material obtained from the filtration and pressing unit.

[0074] In a preferred embodiment, the secondary ozone oxidation unit includes a secondary ozone generator and a secondary glass reactor, wherein the secondary glass reactor is used to perform secondary ozone oxidation on the liquid phase material obtained from the membrane separation unit.

[0075] Preferably, the system of the present invention further includes a safety valve, a flow meter, and an instrument monitoring and control system.

[0076] It should be noted that the present invention does not have special requirements for the parameters of the pump and the ozone generator, and conventional technical parameters in the field can be selected.

[0077] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products.

[0078] Kitchen waste slurry: This is the slurry of kitchen waste after pretreatment (including crushing and sorting, high-temperature cooking, and three-phase centrifugation). Its physicochemical parameters are: COD of 100,000 mg / L, TS concentration of 80 g / L, pH of 3-4, and oil content of 5,000 mg / L.

[0079] Epoxy resin film:

[0080] Epoxy resin membrane I: Purchased from Wuxi Aina Environmental Protection Technology Co., Ltd., model ANA-AER400, with a molecular weight cutoff of 100kDa, a circulation flow rate of 300m / h, and a membrane fiber diameter of 8mm;

[0081] Epoxy resin membrane II: purchased from Tianjin Haipaite Environmental Protection Technology Co., Ltd., model HPT-WY-65, with a molecular weight cutoff of 100kDa, a circulation flow rate of 200m / h, and a membrane fiber diameter of 1.3mm;

[0082] Filter screen: 800μm precision.

[0083] Example 1

[0084] This embodiment illustrates the high-efficiency membrane separation method for anaerobic fermentation combined with ozone in kitchen waste slurry provided by the present invention. (Refer to...) Figure 1The process shown is to be followed and the steps included are as follows:

[0085] (1) The kitchen slurry is introduced into the anaerobic tank 2 in the anaerobic fermentation unit by the feed pump 1 and the flow meter 13 for anaerobic fermentation to obtain mixture III. Then, mixture III is introduced into the filter pressing unit 3 for pretreatment by filter screen, including filtration and pressing, and then the filter residue is removed to obtain mixture I with SS concentration of 20g / L.

[0086] (2) The mixture I is first introduced into the temporary storage tank 5, and then drawn out from the temporary storage tank 5 through the booster pump 6 and the flow meter 13 into the first-stage glass reactor 7 for first-stage ozone oxidation (ozone concentration is 50mg / L) to obtain mixture II; wherein, the ozone is introduced into the first-stage glass reactor 7 from the ozone generator 11 through the safety valve 12.

[0087] (3) The mixture II is filtered through a basket filter 8 and then introduced into the membrane separation unit 9 (an external tubular membrane module) for separation and concentration using an epoxy resin membrane I at a temperature of 35°C and a pH of 8, to obtain concentrated water and purified water (SS 100 mg / L, COD 500 mg / L), with an instantaneous permeate flow rate of not less than 15 m³ / L. 3 / h; wherein, the membrane separation device 9 is cleaned by the cleaning system 10; a portion of the concentrated water is returned to the temporary storage tank 5, and then returned to the anaerobic tank 2 by the temporary storage tank 5 via the variable frequency anaerobic reflux pump 4 and the flow meter 13, and the reflux ratio of the concentrated water is 5;

[0088] (4) The clean water is introduced into the secondary glass reactor 14 for secondary ozone oxidation (ozone concentration is 20mg / L), and the effluent is drawn out through the flow meter 13.

[0089] The results show that the system operates stably and the sludge production rate is less than 1 wt%. Please refer to Table 1 for the effluent quality.

[0090] Example 2

[0091] This embodiment uses a method similar to that of Example 1, except that the ozone concentration for the first-stage ozone oxidation is 1 mg / L and the ozone concentration for the second-stage ozone oxidation is 20 mg / L.

[0092] The results showed that the system operated stably, but the instantaneous water production of the purified water was less than 12m³. 3 The yield is 1.8 wt%, and the effluent quality is shown in Table 1.

[0093] Comparative Example 1

[0094] This comparative example uses a method similar to that of Example 1, except that step (4) is not performed, and the clean water from step (3) is directly drawn out as the effluent.

[0095] The results showed that the system operated stably, but the instantaneous water production of the purified water was less than 10m³. 3 / h, with a sludge production rate as high as 2wt%. Please see Table 1 for specific effluent quality.

[0096] Comparative Example 2

[0097] This comparative example uses a method similar to that of Example 1, except that the first-stage ozone oxidation in step (2) is performed first, followed by pretreatment using a filter screen in the filtration and pressing unit. Specifically, this includes:

[0098] (1) The kitchen slurry is introduced into the first-stage glass reactor by a feed pump and a flow meter (ozone concentration is 50 mg / L) to obtain mixture IV; wherein, ozone is introduced into the first-stage glass reactor by an ozone generator through a safety valve;

[0099] (2) The mixture IV is introduced into the anaerobic tank in the anaerobic fermentation unit for anaerobic fermentation, and then introduced into the filtration and pressing unit for pretreatment with a filter screen, including filtration and pressing, and then the filter residue is removed to obtain the mixture V;

[0100] Then, replace mixture II with mixture V and perform the operations in steps (3) and (4) of Example 1; finally, effluent is obtained.

[0101] The results showed that the system operated stably, and the instantaneous water production of the purified water was less than 12m³. 3 The sludge production rate is as high as 3% per hour. Please refer to Table 1 for the effluent quality.

[0102] Comparative Example 3

[0103] This comparative example was carried out using a method similar to that of Example 1, except that in step (3), epoxy resin membrane II was used instead of epoxy resin membrane I for separation and concentration.

[0104] Finally, water was released.

[0105] The results showed that the system produced low water quality, consumed a lot of electricity, suffered severe membrane fouling, and produced poor effluent quality. Please refer to Table 1 for the effluent quality.

[0106] Comparative Example 4

[0107] This comparative example was conducted using a method similar to that of Example 1, except that in step (3), the concentrate was not refluxed. The specific operations of step (3) include:

[0108] (3) The mixture II is filtered through a basket filter 8 and then introduced into the membrane separation unit 9 (an external tubular membrane module) for separation and concentration using an epoxy resin membrane I at a temperature of 35°C and a pH of 8. After 10 cycles, concentrated water and clear water are obtained. The membrane separation unit 9 is cleaned using a cleaning system 10.

[0109] Finally, water was released.

[0110] The results showed that the water production of the system decreased significantly over time, with the instantaneous production of clean water falling below 5 m³. 3 / h, membrane fouling intensifies, material concentration in the intermediate storage tank increases, sludge cannot be effectively returned and the digestion rate increases. Please see Table 1 for specific effluent quality.

[0111] Table 1

[0112]

[0113]

[0114] The results above show that the method provided by this invention, through the selection of membranes, control of membrane module operation, and linkage with anaerobic fermentation and two-stage ozone oxidation processes, can achieve stable operation of a high-efficiency anaerobic reactor, effectively removing pollutants while mitigating problems such as membrane fouling and poor membrane permeability of biogas slurry.

[0115] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for anaerobic fermentation combined with ozone high-efficiency membrane separation of kitchen waste slurry, characterized in that, The method includes: (1) The kitchen slurry is anaerobic fermented in an anaerobic fermentation unit, and then introduced into a filtration and pressing unit for pretreatment to remove the filter residue and obtain mixture I; (2) The mixture I is subjected to primary ozone oxidation to obtain mixture II; (3) The mixture II is introduced into a membrane separation unit for separation and concentration to obtain clear water and concentrated water; At least a portion of the concentrated water is recycled back to the anaerobic fermentation unit; The separation and concentration process uses an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm. (4) The purified water is subjected to secondary ozone oxidation to obtain effluent; The ratio of ozone concentration in the primary ozone oxidation to that in the secondary ozone oxidation is 1-3:1; The reflux ratio of the concentrate is 5-10.

2. The method according to claim 1, characterized in that, In step (1), the SS concentration of mixture I is 10-40 g / L.

3. The method according to claim 1 or 2, characterized in that, In step (1), the pretreatment uses a filter with a precision of 600-800 μm.

4. A high-efficiency membrane separation system for anaerobic fermentation combined with ozone in kitchen waste slurry, characterized in that, The system is used to implement the method according to any one of claims 1-3, comprising an anaerobic fermentation unit, a filtration and pressing unit, a primary ozone oxidation unit, a membrane separation unit, and a secondary ozone oxidation unit connected in sequence; The anaerobic fermentation unit includes an anaerobic tank and a temporary storage tank. The membrane separation unit includes a membrane separation device and a cleaning device; The membrane separation device is equipped with an epoxy resin membrane, and the epoxy resin membrane has a molecular weight cutoff of 100-200 kDa, a circulation flow rate of 300-400 m / h, and a membrane fiber diameter of 6-12 mm.

5. The system according to claim 4, characterized in that, The filtration and pressing unit includes a drum, a drum drive, a backwashing high-pressure blower, a screw extrusion drive, and a rinsing water pump, and a filter screen with a precision of 600-800μm is installed in the drum.

6. The system according to claim 4 or 5, characterized in that, A concentrate outlet is provided on the membrane separation device, and the concentrate outlet is connected to the temporary storage tank for introducing at least a portion of the concentrate from the membrane separation device into the temporary storage tank. as well as An outlet is provided on the temporary storage tank and the outlet is connected to the anaerobic tank for introducing at least a portion of the mud-water mixture in the temporary storage tank into the anaerobic tank to achieve reflux.

7. The system according to claim 4 or 5, characterized in that, The epoxy resin film is an ANA-AER400 epoxy resin film manufactured by Wuxi Aina Environmental Protection Technology Co., Ltd.

8. The system according to claim 4 or 5, characterized in that, The primary ozone oxidation unit includes a primary ozone generator and a primary glass reactor. The primary glass reactor is used to perform primary ozone oxidation on the liquid material obtained from the filtration and pressing unit; and / or The secondary ozone oxidation unit includes a secondary ozone generator and a secondary glass reactor. The secondary glass reactor is used to perform secondary ozone oxidation on the liquid phase material obtained from the membrane separation unit.

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