Biogas slurry resourceful treatment method and biogas slurry resourceful treatment system

Abstract

The invention relates to a biogas slurry resourceful treatment method and a biogas slurry resourceful treatment system. The treatment method comprises the following steps: inputting biogas slurry subjected to anaerobic fermentation into an aeration tank for aeration; preliminarily filtering the biogas slurry subjected to aeration treatment, and then inputting the biogas slurry into a disinfection device for disinfection; the disinfected biogas slurry is subjected to secondary filtration and then input into a forward osmosis assembly, and forward osmosis concentrated liquid and first filtrate are obtained after forward osmosis; the first filtrate is input into a reverse osmosis assembly for reverse osmosis, a reverse osmosis concentrated solution and a second filtrate are obtained after the first filtrate passes through a reverse osmosis membrane, and the reverse osmosis concentrated solution is input into a forward osmosis assembly for cyclic utilization. Compared with the prior art, the forward osmosis concentrated solution is finally obtained by adopting aeration, disinfection, fine filtration, forward osmosis and other technologies, and the concentration efficiency is high; and the cyclic utilization of the forward osmosis filtrate is further realized through a reverse osmosis technology, so that the full-flow utilization of the biogas slurry is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of biogas slurry treatment, and in particular relates to a biogas slurry resource treatment method and a treatment system. Background Art

[0002] Biogas slurry is a byproduct of the fermentation of agricultural organic waste such as livestock and poultry manure and crop straw under anaerobic conditions. It is rich in organic matter and various nutrients and has extremely high resource utilization value. The biogasification of agricultural waste is one of the important ways to recycle agricultural waste. It realizes comprehensive resource utilization while harmlessly treating it, and its pollution reduction and emission reduction effects are widely recognized. my country's agricultural biogas projects have developed rapidly and are distributed in all provinces, autonomous regions, and municipalities directly under the central government. Large and medium-sized biogas projects have become increasingly mature. By the end of 2020, there were 93,481 biogas projects in my country.

[0003] However, the rapid development of biogas projects will inevitably bring about the problem of handling a large amount of biogas slurry. More than 90% of biogas slurry is water, and the nutrient content is low, so its economic transportation distance is short. In addition, most of the nutrients in biogas slurry are fast-acting and easily absorbed by plants, but excessive concentration of biogas slurry will also inhibit plant growth and seed germination. Biogas slurry may contain heavy metals such as copper, zinc, iron, and arsenic. The premise for the safe and efficient use of biogas slurry is to ensure that the heavy metal content in the soil and agricultural and forestry crops does not exceed the standard. The resource utilization of biogas slurry is an important part of agricultural sustainable development and environmental protection. How to use biogas slurry efficiently and safely has become an urgent problem for scientific researchers to solve.

[0004] After searching, CN104058799A discloses the physical membrane concentration of biogas slurry: the biogas slurry is first filtered through precipitation to remove macromolecular substances, then enters the aeration tank for aeration acidification and hydrolysis to decompose the remaining macromolecules, and then enters the ultrafiltration membrane for ultrafiltration after filtration through a 30-mesh security filter. The ultrafiltration clear liquid is subjected to nanofiltration, and the nanofiltration clear liquid is subjected to reverse osmosis. The reverse osmosis clear liquid can meet the discharge standards, and the ultrafiltration concentrate, nanofiltration concentrate, and reverse osmosis concentrate are mixed in different proportions to obtain different concentrated liquid fertilizers. CN106007201A discloses the chemical concentration of biogas slurry: after the biogas slurry is precipitated and filtered, it enters the flocculation tank, and flocculates after adding polyacrylamide flocculants. The liquid is subjected to ultrafiltration, nanofiltration, and reverse osmosis to meet the discharge standards, and the remaining concentrate is used as liquid fertilizer. Although the prior art discloses the membrane concentration technology of biogas slurry, it has the defects of long processing flow, high reverse osmosis energy consumption, high concentration cost, strong corrosiveness of flocculants, toxic monomers, and environmental unfriendliness, and still cannot realize the full process utilization of biogas slurry.

[0005] Therefore, it is urgent to develop a new method for resource processing of biogas slurry to realize the full process utilization of biogas slurry. Summary of the invention

[0006] The purpose of the present invention is to provide a biogas slurry resource processing method and processing system in order to realize the full process utilization of biogas slurry.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The present invention first provides a biogas slurry resource treatment method, comprising the following steps:

[0009] S1: The biogas slurry after anaerobic fermentation is input into the aeration tank for aeration;

[0010] S2: The aerated biogas slurry is initially filtered and then input into the disinfection device for disinfection;

[0011] S3: After the disinfected biogas slurry is filtered twice, it is input into the forward osmosis module to obtain the forward osmosis concentrate and the first filtrate after forward osmosis;

[0012] Wherein, the forward osmosis component comprises a forward osmosis membrane (FO membrane), the two sides of the forward osmosis membrane are the raw liquid side and the drawn liquid side, and the pressure on the raw liquid side is always greater than that on the drawn liquid side;

[0013] S4: The first filtrate is input into a reverse osmosis module for reverse osmosis, and a reverse osmosis concentrate and a second filtrate are obtained after passing through a reverse osmosis membrane, wherein the reverse osmosis concentrate is input into a forward osmosis module for recycling.

[0014] Furthermore, in step S1, the aeration time is 24-48 hours, preferably 48 hours. The biogas slurry after anaerobic fermentation is aerated to promote the continued decomposition of macromolecular substances, reduce odor, and kill residual anaerobic microorganisms.

[0015] Furthermore, in step S2, the preliminary filtration uses a security filter of 80-120 mesh.

[0016] Furthermore, in step S2, the disinfection device is an ultraviolet disinfection device.

[0017] Furthermore, the disinfection device can be connected to an ultrafiltration system to ultrafilter the disinfected biogas slurry to further intercept pollutants in the biogas slurry.

[0018] Furthermore, in step S3, the secondary filtration uses a multi-stage multi-media fine filter, for example, a three-stage multi-media filtration fine filter.

[0019] Furthermore, in step S3, the pressure of the biogas slurry on the raw liquid side is 5-10 bar, the operating pressure difference on both sides of the forward osmosis membrane is 2-4 bar, and there can be no back pressure during operation.

[0020] Furthermore, in step S3, the forward osmosis membrane is operated at a temperature of ≤35°C, and the pH of the raw liquid side and the drawn liquid side are both controlled at 5-7.

[0021] Furthermore, the pH of the stock solution on the stock solution side is adjusted by hydrochloric acid, and the pH of the drawn solution on the drawn solution side is adjusted by sulfuric acid.

[0022] Furthermore, in step S3, the drawn liquid on the drawn liquid side is an 8-15wt% ammonium sulfate solution, preferably a fertilizer-grade 10wt% ammonium sulfate solution.

[0023] Furthermore, in step S3, the organic matter content in the forward osmosis concentrated solution is ≥6000 mg / mL, the humic acid content is ≥3500 mg / mL, the N content is ≥7000 mg / mL, and the P2O5 content is ≥100 mg / mL.

[0024] Furthermore, in step S3, the forward osmosis concentrated solution is used to prepare liquid water-soluble fertilizer, and the liquid water-soluble fertilizer includes any one of humic acid-containing water-soluble fertilizer (macro-element type) or amino acid-containing water-soluble fertilizer (medium-element type).

[0025] Furthermore, the humic acid-containing water-soluble fertilizer contains nitrogen, phosphorus, potassium and humic acid, and the amino acid-containing water-soluble fertilizer uses amino acids prepared by acid hydrolysis process with a total free amino acid content of ≥80%, as well as EDTA-Ca and EDTA-Mg.

[0026] Furthermore, in step S4, the second filtrate is discharged or reused as recycled water after reaching the standard.

[0027] The present invention also provides a treatment system using the biogas slurry resource treatment method, the treatment system comprising: a biogas slurry sedimentation tank, used to receive biogas slurry after anaerobic fermentation; an aeration tank connected to the biogas slurry sedimentation tank, used to decompose macromolecular substances in the biogas slurry and reduce odor; a primary filtering device connected to the aeration tank; a disinfection device connected to the primary filtering device; a secondary filtering device connected to the disinfection device; a forward osmosis component connected to the secondary filtering device, used to perform forward osmosis on the filtered biogas slurry to separate the forward osmosis concentrate and the first filtrate; a reverse osmosis component connected to the forward osmosis component, used to perform reverse osmosis on the first filtrate to separate the reverse osmosis concentrate and the second filtrate.

[0028] Furthermore, the forward osmosis component comprises a raw liquid pump connected to the secondary filtration device and a forward osmosis membrane connected to the raw liquid pump, and a reflux valve is provided between the raw liquid pump and the forward osmosis membrane.

[0029] Furthermore, to ensure the smooth operation of the forward osmosis module, the operation sequence should follow the principle of opening the valve first and then the pump, and closing the pump first and then the valve. When the pump is a power frequency pump, it is necessary to delay for 3-5 seconds before closing the valve.

[0030] Furthermore, the reverse osmosis component includes a draw liquid pump, a reverse osmosis membrane (RO membrane) and a draw liquid tank connected in sequence. The draw liquid pump is connected to the forward osmosis membrane and delivers the first filtrate to the reverse osmosis membrane. The reverse osmosis concentrated liquid after reverse osmosis is input into the draw liquid tank.

[0031] Furthermore, a regulating valve is provided between the draw liquid pump and the forward osmosis membrane. When the pressure on the raw liquid side reaches the requirement, the draw liquid pump is turned on, and the operating pressure difference on both sides of the forward osmosis membrane is made between 2.0-4.0 bar by adjusting the frequency of the valve and the draw liquid pump.

[0032] Furthermore, the forward osmosis membrane may be a polyamide membrane element or a cellulose acetate membrane, preferably a cellulose acetate membrane; the reverse osmosis membrane may be a disc-tube reverse osmosis membrane (DRTO membrane).

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention adopts aeration, disinfection, fine filtration, forward osmosis and other technologies to obtain forward osmosis concentrated liquid with high concentration efficiency according to the characteristics of biogas slurry. The forward osmosis filtrate is further recycled through reverse osmosis technology, thereby realizing the full process utilization of biogas slurry and finding a sustainable development path for biogas slurry utilization.

[0035] (2) In the process of resource recovery of biogas slurry, the present invention does not need to use corrosive and toxic flocculant products. It promotes the decomposition of macromolecular substances in the biogas slurry through aeration, ultraviolet disinfection, etc., reduces odor, and can effectively eliminate residual anaerobic microorganisms and significantly reduce the heavy metal content in the concentrated liquid. It is an environmentally friendly and sustainable treatment method.

[0036] (3) The biogas slurry resource treatment method of the present invention adopts a forward osmosis system, which has low energy consumption for low-pressure operation, almost complete interception of many pollutants, good separation effect, strong anti-pollution ability, and long service life of the forward osmosis membrane.

[0037] (4) The biogas slurry resource treatment method of the present invention realizes high-value resource utilization of biogas slurry products, and can make forward osmosis concentrated liquid into high-value liquid water-soluble fertilizer products, greatly improving the economic benefits of the biogas slurry resource treatment method. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the process of the biogas slurry resource treatment method of the present invention.

[0039] Description of the markings in the figure:

[0040] 1-slurry sedimentation tank, 2-aeration tank, 3-primary filtration device, 4-disinfection device, 5-secondary filtration device, 6-forward osmosis component, 7-reverse osmosis component. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] In the present invention, it should be noted that the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] Unless otherwise specified, the instruments and equipment used in the present invention are conventional instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available. Among them, the forward osmosis membrane uses a cellulose acetate film; the reverse osmosis membrane can use a disc-tube reverse osmosis membrane.

[0044] The biogas slurry resource treatment methods provided in the following embodiments and comparative examples are all implemented based on the following treatment system: the treatment system includes a biogas slurry sedimentation tank 1, for receiving biogas slurry after anaerobic fermentation; an aeration tank 2 connected to the biogas slurry sedimentation tank 1, for decomposing macromolecular substances in the biogas slurry and reducing odor; a primary filtration device 3 connected to the aeration tank 2; a disinfection device 4 connected to the primary filtration device 3; a secondary filtration device 5 connected to the disinfection device 4; a forward osmosis component 6 connected to the secondary filtration device 5, for performing forward osmosis on the filtered biogas slurry to separate the forward osmosis concentrate and the first filtrate; a reverse osmosis component 7 connected to the forward osmosis component 6, for performing reverse osmosis on the first filtrate to separate the reverse osmosis concentrate and the second filtrate.

[0045] Wherein, the forward osmosis component 6 comprises a stock liquid pump connected to the secondary filtration device 5 and a forward osmosis membrane connected to the stock liquid pump, and a reflux valve is provided between the stock liquid pump and the forward osmosis membrane. The reverse osmosis component 7 comprises a draw liquid pump, a reverse osmosis membrane (RO membrane) and a draw liquid tank connected in sequence, the draw liquid pump is connected to the forward osmosis membrane and delivers the first filtrate to the reverse osmosis membrane, and the reverse osmosis concentrated liquid after reverse osmosis is input into the draw liquid tank. A regulating valve is provided between the draw liquid pump and the forward osmosis membrane, and when the pressure on the stock liquid side reaches the requirement, the draw liquid pump is turned on, and the operating pressure difference on both sides of the forward osmosis membrane is made between 2.0-4.0bar by adjusting the frequency of the regulating valve and the draw liquid pump.

[0046] Based on the above treatment system, the present invention provides a biogas slurry resource treatment method, comprising the following steps:

[0047] S1: The biogas slurry after anaerobic fermentation is input into the aeration tank for aeration;

[0048] S2: The aerated biogas slurry is initially filtered and then input into the disinfection device for disinfection;

[0049] S3: After the disinfected biogas slurry is filtered twice, it is input into the forward osmosis module to obtain the forward osmosis concentrate and the first filtrate after forward osmosis;

[0050] Wherein, the forward osmosis component comprises a forward osmosis membrane, the two sides of the forward osmosis membrane are respectively a raw liquid side and an extraction liquid side, and the pressure on the raw liquid side is always greater than that on the extraction liquid side;

[0051] S4: The first filtrate is input into a reverse osmosis module for reverse osmosis, and a reverse osmosis concentrate and a second filtrate are obtained after passing through a reverse osmosis membrane, wherein the reverse osmosis concentrate is input into a forward osmosis module for recycling.

[0052] In some specific embodiments, in step S1, the aeration time is 24-48 hours.

[0053] In some specific implementations, in step S2, the preliminary filtration uses a security filter with a mesh size of 80-120.

[0054] In some specific embodiments, in step S2, the disinfection device is an ultraviolet disinfection device.

[0055] In some specific implementations, in step S3, the secondary filtration uses a multi-stage multi-media fine filter.

[0056] In some specific implementations, in step S3, the pressure of the biogas slurry on the raw liquid side is 5-10 bar, and the operating pressure difference on both sides of the forward osmosis membrane is 2-4 bar.

[0057] In some specific embodiments, the forward osmosis membrane is operated at a temperature of ≤35° C., and the pH of the raw liquid side and the drawn liquid side are both controlled at 5-7.

[0058] In some specific embodiments, in step S3, the draw liquid on the draw liquid side is 8-15 wt % ammonium sulfate solution.

[0059] In some specific embodiments, in step S3, the organic matter content in the forward osmosis concentrate is ≥6000 mg / mL, the humic acid content is ≥3500 mg / mL, the N content is ≥7000 mg / mL, and the P2O5 content is ≥100 mg / mL.

[0060] In some specific embodiments, in step S3, the forward osmosis concentrate is used to prepare a liquid water-soluble fertilizer, and the liquid water-soluble fertilizer includes any one of a humic acid-containing water-soluble fertilizer and an amino acid-containing water-soluble fertilizer. The humic acid-containing water-soluble fertilizer contains nitrogen, phosphorus, potassium and humic acid, and the amino acid-containing water-soluble fertilizer uses amino acids prepared by an acid hydrolysis process with a total free amino acid content of ≥80%, as well as EDTA-Ca and EDTA-Mg.

[0061] In some specific embodiments, in step S4, the second filtrate is discharged or reused as recycled water after reaching the standard.

[0062] The above embodiments can be implemented individually or in any combination of two or more. The above embodiments are described in more detail below with reference to specific examples.

[0063] Embodiment 1:

[0064] This embodiment provides a biogas slurry resource processing method, and the specific steps are as follows:

[0065] (1) The anaerobic fermented biogas slurry is taken from the biogas slurry sedimentation tank and sent to the aeration tank for aeration for 48 hours to promote the continued decomposition of macromolecular substances and kill the residual anaerobic microorganisms;

[0066] (2) The aerated biogas slurry is pumped to the ultraviolet disinfection device through an 80-mesh safety filter;

[0067] (3) passing the biogas slurry pretreated in step (2) through a three-stage multi-media fine filter for fine filtration;

[0068] (4) The filtered biogas slurry of step (3) is pumped to the forward osmosis system (FO), and the frequency of the reflux valve and the raw liquid pump is adjusted so that the raw liquid (biogas slurry) pressure is between 5 bar and 10 bar; when the raw liquid side pressure reaches the requirement, the draw liquid pump is turned on, and the operating pressure difference on both sides of the FO membrane is between 2.0 and 4.0 bar by adjusting the valve and the frequency of the draw liquid pump; fertilizer-grade ammonium sulfate is used as the draw liquid, and the pH of the raw liquid (biogas slurry) entering the forward osmosis system is adjusted to 5-7 with hydrochloric acid, and the draw liquid concentration is adjusted to 10% with sulfuric acid.

[0069] (5) After the treatment in step (4), the forward osmosis concentrate and filtrate are obtained. The filtrate enters the DTRO reverse osmosis system for reverse osmosis, and the reverse osmosis concentrate enters the extraction tank for reuse. The filtrate after reverse osmosis meets the discharge standard and is discharged or reused as recycled water.

[0070] The biogas slurry in this embodiment is produced by garage-type dry anaerobic fermentation of crop straw and livestock and poultry manure.

[0071] In this embodiment, the forward osmosis concentrated solution obtained can be further utilized as a resource. In the forward osmosis concentrated solution obtained by final concentration in this embodiment, the organic matter content is 6282 mg / mL, the humic acid content is 3900 mg / mL, the N content is 7400 mg / mL, the P2O5 content is 133 mg / mL, and the K2O content is 2.36 mg / mL.

[0072] Furthermore, the concentrated solution can be supplemented with nitrogen, phosphorus, potassium and mineral humic acid according to the test results to prepare a water-soluble fertilizer containing humic acid (a large amount of elements); or acid-hydrolyzed amino acids (total free amino acid content ≥ 80wt%), EDTA-Ca and EDTA-Mg can be added to the above concentrated solution to prepare a water-soluble fertilizer containing amino acids (a medium amount of elements).

[0073] Embodiment 2:

[0074] This embodiment provides a biogas slurry resource treatment method, which is different from the embodiment 1 in that an ultrafiltration system is added between the ultraviolet disinfection device and the three-stage multi-media fine filter. The disinfected biogas slurry is pumped into the ultrafiltration system for further filtration.

[0075] Since biogas slurry contains a lot of large particles, adding an ultrafiltration system can further intercept biogas slurry pollutants and reduce the frequency of subsequent fine filter pore cleaning by about 6%-8%. Those skilled in the art can selectively use the ultrafiltration system in actual production based on factors such as product quality and cost.

[0076] Embodiment 3:

[0077] This embodiment provides a biogas slurry resource treatment method. The difference from the embodiment 1 is that the aeration time of this embodiment is 24 hours, which can also promote the continued decomposition of macromolecular substances, reduce odor and kill residual anaerobic microorganisms. In addition, this embodiment uses a 120-mesh security filter to further improve the initial filtration effect of the biogas slurry.

[0078] Comparative Example 1:

[0079] This comparative example provides a method for resource processing of biogas slurry, which is different from Example 1 in that a 6wt% NaCl solution is used as the draw liquid in this example, the pH of the original liquid (biogas slurry) entering the forward osmosis system is adjusted to 5-7 with hydrochloric acid, and the concentration of the draw liquid is maintained at about 6wt% with hydrochloric acid.

[0080] The present invention conducts the following tests on the biogas slurry resource treatment methods of Example 1 and Comparative Example 1:

[0081] (1) Nutrient determination: The determination of organic matter content shall refer to NY / T 525-2021 Organic Fertilizers; the determination of humic acid content shall refer to NY / T 1971-2010 Determination of humic acid content in water-soluble fertilizers; the determination of N, P2O5, and K2O content shall refer to NY / T 1977-2010 Determination of total nitrogen, phosphorus, and potassium content in water-soluble fertilizers.

[0082] (2) Determination of cumulative ammonia nitrogen: With reference to HJ 535-2009 Determination of ammonia nitrogen in water quality, the cumulative ammonia nitrogen in the forward osmosis biogas slurry concentrate was determined using the Nessler reagent spectrophotometric method.

[0083] (3) Conductivity of reverse osmosis product water: refer to GB / T 5750.4-2023 Standard Test Methods for Drinking Water Part 4: Sensory Properties and Physical Indicators 9 Conductivity to measure the conductivity of the filtrate after reverse osmosis.

[0084] The concentration effects of the biogas slurry resource treatment methods of Example 1 and Comparative Example 1 on nutrients in the biogas slurry are shown in Table 1, and the cumulative amount of ammonia nitrogen, the conductivity of the reverse osmosis produced water and the average energy consumption of the system per ton of water treated are shown in Table 2.

[0085] Table 1 Concentration effect of different extraction liquids on nutrients in biogas slurry

[0086]

[0087] Table 2 Ammonia nitrogen accumulation, conductivity and average energy consumption per ton of water treated by the system

[0088]

[0089] As shown in Table 1 and Table 2, using 6% sodium chloride and 10% ammonium sulfate as the draw liquid can achieve better concentration effects compared with raw water. However, when sodium chloride is used as the draw liquid, ammonia nitrogen has obvious accumulation, and the conductivity of the reverse osmosis water also increases significantly; when ammonium sulfate is used as the draw liquid, ammonia nitrogen does not accumulate significantly, and during the stable operation, the conductivity of the reverse osmosis water is maintained at about 300 mg / L. Compared with NaCl as the draw liquid, there is no obvious increase trend and it is relatively stable. When 6% sodium chloride is used as the draw liquid, the average energy consumption of the system for treating a ton of water is 4.51 kWh; when 10% ammonium sulfate is used as the draw liquid, the average energy consumption of the system for treating a ton of water is 4.37 kWh, and the energy consumption is also greatly reduced.

[0090] In addition, the present invention also tests the forward osmosis biogas slurry concentrate obtained by using 10% ammonium sulfate, and the heavy metal content thereof is shown in Table 3.

[0091] Table 3 Heavy metal content test results

[0092]

[0093]

[0094] It can be seen from the above table that the heavy metal content in the forward osmosis biogas slurry concentrate obtained by the biogas slurry resource treatment method of the present invention is much lower than the relevant parameters of the national standard GB / T 40750-2021 on agricultural concentrated biogas slurry fertilizer, and can also meet the Class I standard for non-concentrated biogas slurry fertilizer. The final biogas slurry concentrate is safe and environmentally friendly.

[0095] Therefore, even though ammonium sulfate is more expensive in unit price and its overall extraction effect is slightly weaker than that of sodium chloride, its advantage is that it has little effect on the ammonia nitrogen in the produced water, the replacement cycle of the extraction liquid can be extended by dripping sulfuric acid, and it can be used as a fertilizer solution, which is easy to recycle, environmentally friendly, and does not produce secondary pollution. Therefore, the present invention selects ammonium sulfate as the extraction liquid after comprehensive consideration.

[0096] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A biogas slurry resource processing method, characterized in that: The following steps are involved: S1: The biogas slurry after anaerobic fermentation is input into the aeration tank for aeration; S2: The aerated biogas slurry is initially filtered and then input into the disinfection device for disinfection; S3: After the disinfected biogas slurry is filtered twice, it is input into the forward osmosis module to obtain the forward osmosis concentrate and the first filtrate after forward osmosis; Wherein, the forward osmosis component comprises a forward osmosis membrane, the two sides of the forward osmosis membrane are respectively a raw liquid side and an extraction liquid side, and the pressure on the raw liquid side is always greater than that on the extraction liquid side; S4: The first filtrate is input into a reverse osmosis module for reverse osmosis, and a reverse osmosis concentrate and a second filtrate are obtained after passing through a reverse osmosis membrane, wherein the reverse osmosis concentrate is input into a forward osmosis module for recycling.

2. A biogas slurry resource treatment method according to claim 1, characterized in that: In step S1, the aeration time is 24-48 hours.

3. The biogas slurry resource treatment method according to claim 1, characterized in that: In step S2, the preliminary filtration uses a 80-120 mesh security filter; the disinfection device uses an ultraviolet disinfection device.

4. The biogas slurry resource treatment method according to claim 1, characterized in that: In step S3, the secondary filtration uses a multi-stage multi-media fine filter.

5. The biogas slurry resource treatment method according to claim 1, characterized in that: In step S3, the pressure of the biogas slurry on the raw liquid side is 5-10 bar, and the operating pressure difference on both sides of the forward osmosis membrane is 2-4 bar; The forward osmosis membrane is operated at a temperature of ≤35°C, and the pH values ​​of the raw liquid side and the drawn liquid side are both controlled at 5-7.

6. The biogas slurry resource treatment method according to claim 1, characterized in that: In step S3, the draw liquid on the draw liquid side is 8-15wt% ammonium sulfate solution.

7. The biogas slurry resource treatment method according to claim 1, characterized in that: In step S3, the organic matter content in the forward osmosis concentrate is ≥6000 mg / mL, the humic acid content is ≥3500 mg / mL, the N content is ≥7000 mg / mL, and the P2O5 content is ≥100 mg / mL; The forward osmosis concentrated liquid is used to prepare liquid water-soluble fertilizer, and the liquid water-soluble fertilizer includes any one of a humic acid-containing water-soluble fertilizer and an amino acid-containing water-soluble fertilizer.

8. The biogas slurry resource treatment method according to claim 1, characterized in that: In step S4, the second filtrate is discharged or reused as regenerated water after reaching the standard.

9. A treatment system using the biogas slurry resource treatment method according to any one of claims 1 to 8, characterized in that: The processing system comprises: The biogas slurry sedimentation tank is used to receive the biogas slurry after anaerobic fermentation; An aeration tank connected to the biogas slurry sedimentation tank is used to decompose the macromolecular substances in the biogas slurry and reduce the odor; A preliminary filtration device connected to the aeration tank; A disinfection device connected to the primary filtration device; A secondary filtration device connected to the disinfection device; A forward osmosis component connected to the secondary filtration device is used to perform forward osmosis on the filtered biogas slurry to separate the forward osmosis concentrate and the first filtrate; The reverse osmosis component connected to the forward osmosis component is used to perform reverse osmosis on the first filtrate to separate the reverse osmosis concentrate and the second filtrate.

10. A processing system according to claim 9, characterized in that: The forward osmosis component comprises a raw liquid pump connected to the secondary filtration device and a forward osmosis membrane connected to the raw liquid pump, and a reflux valve is provided between the raw liquid pump and the forward osmosis membrane; The reverse osmosis component comprises a draw liquid pump, a reverse osmosis membrane and a draw liquid tank which are connected in sequence. The draw liquid pump is connected to the forward osmosis membrane and delivers the first filtrate to the reverse osmosis membrane. The reverse osmosis concentrated liquid after reverse osmosis is input into the draw liquid tank.

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