Recycling comprehensive utilization method of long-chain diacid microbial fermentation wastewater

Abstract

The invention discloses a resource comprehensive utilization method of long-chain diacid microbial fermentation wastewater, and belongs to the field of wastewater treatment and utilization of resources and environments. The method comprises the following steps in sequence: adjusting, neutralizing, coagulating and precipitating, hydrolytic acidification, A / O (Anaerobic / Oxic) process treatment, immersed MBR (Membrane Bioreactor) process treatment, reverse osmosis treatment, hardness removal treatment, nanofiltration treatment, mechanical vapor recompression treatment and the like. By adopting the combination of a chemical treatment process, a biochemical treatment process, a physical membrane separation process and an evaporation process and reasonable arrangement of the steps, the quality of wastewater reuse water and the purity of anhydrous sodium sulphate are improved, the risk of scaling of a membrane system and an evaporation system is reduced, the stability and efficiency of system operation are enhanced, and the production cost is reduced. The comprehensive resource utilization of the long-chain dicarboxylic acid microbial fermentation wastewater is realized.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment and utilization of resources and environment, and more specifically, relates to a comprehensive resource utilization of wastewater produced by long-chain dibasic acid microbial fermentation. Background Art

[0002] Long-chain dibasic acids refer to straight-chain aromatic saturated dibasic acids containing ten or more carbon atoms. Long-chain dibasic acids can not only be used as monomers to synthesize high-performance polyamides, but are also important raw materials for musk fragrances, paints, coatings, lubricants, plasticizers, new medicines and pesticides.

[0003] There are two production methods for long-chain dibasic acids: chemical synthesis and biological fermentation. The biological fermentation method has a simple production process, mild production conditions, and the entire production process is carried out at room temperature and pressure. The production cost is lower than that of the chemical synthesis method. However, a large amount of wastewater will be generated during the entire production process. Specifically, about 50-60 tons of wastewater will be discharged for every ton of long-chain dibasic acid product produced.

[0004] The wastewater from the long-chain dibasic acid biofermentation process contains residual sulfuric acid, dibasic acid salts, and culture medium components, so it is highly acidic (pH value is about 2-3) and contains high concentrations of total phosphorus (H2PO4). 4- , contributed by excess inorganic culture medium), COD (contributed by dibasic acid ions and unconsumed organic culture medium) and sulfate (contributed by sulfuric acid added during the acidification process), as well as medium concentrations of total nitrogen (urea and ammonia nitrogen, urea is contributed by excess inorganic culture medium, and ammonia nitrogen comes from the conversion of urea during the fermentation process). Among them, the total phosphorus concentration is 200-400 mg / L, and COD (chemical oxygen demand, indicating the degree of water pollution by organic matter) is about 7000-10000 mg / L. The concentration is relatively high and cannot be directly discharged to the downstream sewage treatment plant; high concentrations of sulfate ions have a great toxic effect on microorganisms and cannot effectively exert the biochemical energy efficiency of the A / O process. At the same time, it will be accompanied by the escape of hydrogen sulfide, which increases the difficulty of odor pollution control. Therefore, in order to reduce environmental pollution, reduce resource waste, and reduce operating costs, it is imperative to treat and recycle this type of wastewater.

[0005] At present, there have been studies on the treatment and resource utilization of wastewater from long-chain dibasic acid microbial fermentation. For example, CN110776136A discloses a pretreatment method for wastewater from a long-chain dibasic acid preparation process using a biological fermentation method, which includes: sending the wastewater from the filter press section discharged intermittently in the long-chain dibasic acid preparation process into a regulating tank for storage and then mixing it with wastewater discharged from other sections for homogenization; mixing the homogenized mixed wastewater with an excess of calcium salt dephosphorizing agent and / or calcium hydroxide for phosphorus removal to obtain a first suspension; mixing the first suspension with an aluminum salt treatment agent for sulfate removal to obtain a second suspension; mixing the second suspension with a flocculant and subjecting it to sedimentation separation, sending the supernatant to a monitoring tank, and collecting concentrated flocs at the same time; mechanically dehydrating the concentrated flocs, collecting solid residues, and sending the filtrate to a monitoring tank; using a degradable organic acid to adjust the pH value of the water in the monitoring tank to a weak alkalinity of less than 9, and then discharging it to a comprehensive sewage treatment plant.

[0006] This method removes total phosphorus and sulfate ions from wastewater by adding a large amount of chemicals, which will lead to a significant increase in chemical costs. At the same time, a large amount of physicochemical sludge will be produced, leading to an increase in solid waste disposal costs. The large amount of sodium sulfate in the wastewater cannot be recycled, resulting in a waste of resources.

[0007] CN101333047 B discloses a method for deep treatment of wastewater from a fermentation process for producing long-chain dibasic acids. The method uses acid to adjust the pH value of the discharged wastewater, adds an appropriate amount of oxidant to the supernatant after static precipitation, and precipitates the solution again. Then, the oxidant is added to the separated supernatant for deep chemical oxidation until the COD of the treated aqueous solution meets the requirements. After that, the aqueous solution is neutralized with alkali to neutrality, and the water after the iron mud is separated can be discharged into the secondary pipe network. The method can recover about 80% of the organic dibasic acid by controlling the amount of oxidant added, the wastewater treatment time is short, the amount of oxidant used is small, and the amount of CO2 waste gas released is small. The recovered dibasic acid can be used to prepare fine chemicals such as cold-resistant plasticizers, high-grade lubricating oils, high-temperature dielectrics, high-grade hot melt adhesives and high-grade coatings: the generated iron mud can be used for the production of iron series pigments.

[0008] Although this method can recover dibasic acid in wastewater, it adds a large amount of oxidants, iron salts, concentrated sulfuric acid and sodium hydroxide, and the cost of reagents is high. After the wastewater is treated, the salt content in the wastewater is high, and the COD, ammonia nitrogen, total nitrogen, etc. cannot meet the standards for process water or discharge. The wastewater is not fully reused, and the main sodium sulfate salt in it cannot be recycled as a resource.

[0009] CN115259542 A discloses a method for recycling long-chain dibasic acid high-salt wastewater, comprising the following steps: step 1: adding liquid alkali to high-salt wastewater to adjust pH value, acidic substances such as long-chain dibasic acid and fatty acid in wastewater react with liquid alkali to generate sodium salt, solubility is improved, and it is easier to be intercepted by nanofiltration membrane. By using nanofiltration membrane to preferentially intercept divalent and multivalent anions, high-salt wastewater is pre-concentrated to increase the sodium sulfate content to 15-18%, and the water produced by the nanofiltration membrane is filtered through secondary reverse osmosis to obtain recycled water that meets the needs of process production. The concentrated high-salt wastewater enters an evaporator for concentration to further increase its concentration to the saturated concentration of sodium sulfate, so that sodium sulfate is precipitated in the form of crystals to form slurry, and harmless disposal of high-salt wastewater and sodium sulfate is achieved. At the same time, the cost of the existing recycling method is significantly reduced by selling industrial-grade sodium sulfate, condensed water, and filtered water instead of tap water.

[0010] This method first uses nanofiltration concentration and then reverse osmosis separation. The nanofiltration concentrate enters a two-stage evaporation crystallization. The reverse osmosis fresh water and evaporation condensate are used as recycled water, and the reverse osmosis concentrate returns to the regulating tank. This causes the monovalent ions to accumulate and increase in the entire system, and finally causes the operating pressure of the reverse osmosis to increase and cannot work stably. At the same time, the COD concentration in the nanofiltration influent is high. Although nanofiltration can intercept part of it, it will cause organic pollution of the membrane system and poor color quality of the salt in the evaporation crystallization. After dissolving the crystalline crude salt, the organic matter is oxidized with high concentration ozone, and then further evaporated and concentrated, which leads to an increase in equipment investment and operating costs.

[0011] Research on the treatment process of long-chain dibasic acid microbial fermentation wastewater needs to focus on recycling water resources and sodium sulfate as much as possible while controlling operating costs, thereby reducing resource waste. Summary of the invention

[0012] 1. Problem to be solved

[0013] Based on the fact that in the prior art, when treating the crystallization plate frame mother liquor and initial washing water in the long-chain dibasic acid microbial fermentation process, a large amount of reagents need to be added, and no resource recycling is carried out, or the cost-effectiveness of resource recycling is low, resulting in high wastewater treatment costs and serious waste of resources. The purpose of the present invention is to provide a method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater, which enhances the stability and efficiency of system operation through the reasonable setting of process steps, realizes effective control of operating costs, and can save 10% to 20%; further, the process realizes the recycling of sodium sulfate, obtains economic benefits by selling sodium sulfate (sodium sulfate) and using recycled water instead of tap water, reduces operating costs, and improves the degree of resource utilization.

[0014] On the basis of the above purpose, the present invention also provides a system for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater, which is used for recovering sodium sulfate from long-chain dibasic acid microbial fermentation wastewater and preparing recycled water.

[0015] 2. Technical solution

[0016] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0017] The first aspect of the present invention provides a method for comprehensive resource utilization of wastewater from long-chain dibasic acid microbial fermentation, comprising treating the crystallization plate frame mother liquor and initial washing water in the long-chain dibasic acid microbial fermentation process through a regulation step, a neutralization step, a coagulation and precipitation step, and a hydrolysis and acidification step in sequence; and further comprising the following steps:

[0018] Anoxic / aerobic (A / O) treatment step: the effluent after hydrolysis and acidification treatment enters the A / O process tank;

[0019] Submerged membrane bioreactor (MBR) treatment: the effluent from the A / O process pool enters the submerged MBR process pool for treatment; the activated sludge produced in the membrane bioreactor (MBR) process is regulated to flow back to the A / O process pool;

[0020] Reverse Osmosis (RO) Treatment Steps: The effluent from the submerged MBR pool enters the reverse osmosis (RO) system;

[0021] Hardness removal treatment steps: The concentrate from the reverse osmosis system enters the hardness removal system to reduce the hardness of the concentrate;

[0022] Nanofiltration (NF) treatment steps: The effluent from the hardness removal system enters the NF system and the sulfate is intercepted by the NF membrane;

[0023] Mechanical vapor recompression (MVR) treatment steps: The nanofiltration concentrate first enters the horizontal tube falling film MVR evaporation concentration device, and after reaching the set concentration, it enters the forced circulation MVR evaporation crystallization device. After the precipitated solid slurry is separated from the solid and liquid, sodium sulfate crystals are obtained.

[0024] Compared with the prior art that first performs nanofiltration concentration and then performs reverse osmosis separation, the present invention first performs reverse osmosis concentration and then performs nanofiltration separation. In the prior art, in the order of first entering the NF system for treatment and then entering the RO system for treatment, NF treatment is used as a pretreatment process for RO treatment to ensure that the wastewater meets the water inlet conditions of the RO system. In the present invention, the wastewater undergoes a combined process of the A / O process and the MBR process, and the water quality has been greatly improved relative to the untreated raw water, and has met the water inlet conditions of the RO system. It can directly enter the reverse osmosis RO system for membrane separation without the need for pretreatment of the nanofiltration NF system, thereby shortening the process and reducing investment costs. The NF system behind the RO system is used to treat the concentrated liquid of the RO system, and its function is to reduce the impurity ions on one side of the concentrated liquid and improve the purity of the sodium sulfate, so as to facilitate the subsequent sale of sodium sulfate as a product.

[0025] As a preferred embodiment of any one of the first aspects of the present invention, the method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater specifically comprises the following steps:

[0026] (1) Adjustment step: The crystallization plate and frame mother liquor, initial washing water and other wastewater (such as equipment washing water, concentrated water after RO membrane deionized water production, etc.) are discharged into the adjustment tank to form comprehensive wastewater, adjust the water quality and quantity, and reduce the TDS concentration in the wastewater;

[0027] (2) Neutralization step: The comprehensive wastewater from the regulating tank is pumped to the neutralization tank, and liquid alkali (liquid sodium hydroxide) is added to adjust the pH;

[0028] (3) Coagulation and sedimentation step: wastewater flows from the neutralization tank to the coagulation and sedimentation tank, precipitation reagents are added, and the lower sludge in the coagulation and sedimentation tank is transported to the sludge tank;

[0029] (4) Hydrolysis and acidification step: The supernatant of the coagulation and sedimentation tank enters the hydrolysis and acidification tank, and sludge containing cultured and domesticated microorganisms is added. Through the action of microorganisms, long-chain organic matter is converted into short-chain organic matter that is easily biodegradable, and some organic pollutants are removed at the same time. The lower sludge of the hydrolysis and acidification tank is transported to the sludge tank;

[0030] (5) Anoxic / aerobic (A / O) treatment: The effluent from the hydrolysis acidification tank enters the A / O process tank. In the A / O process tank, the added aerobic bacteria and anoxic bacteria are used to achieve simultaneous nitrogen removal and carbon removal. The lower sludge of the A / O process tank is transported to the sludge tank.

[0031] (6) Submerged membrane bioreactor (MBR) treatment: The effluent from the A / O process pool enters the submerged MBR process pool. The MBR membrane can effectively intercept activated sludge, suspended solids and other substances to achieve efficient and stable sludge-water separation. The activated sludge produced in the membrane bioreactor (MBR) process is regulated to flow back to the A / O process pool, so that the activity of microorganisms in the aerobic and anoxic activated sludge is maintained at the optimal stage. The sludge that flows back to the A / O process pool is removed, and the remaining sludge is transported to the sludge pool.

[0032] (7) Reverse osmosis (RO) treatment: The effluent from the submerged MBR pool enters the reverse osmosis (RO) system. After the monovalent ions, organic matter and inorganic matter are intercepted by the reverse osmosis membrane, the reverse osmosis produced water is reused as the feed water of the circulating cooling tower;

[0033] (8) Hardness removal treatment: The concentrate from the reverse osmosis system enters the hardness removal system to reduce the hardness in the concentrate and the risk of scaling in the subsequent nanofiltration (NF) system. The sludge in the hardness removal system is transported to the sludge pool.

[0034] (9) Nanofiltration (NF) treatment: The effluent from the hardness removal system enters the nanofiltration system, where sulfate is intercepted by the nanofiltration membrane to increase the sulfate concentration. The concentrated nanofiltration concentrate enters the evaporation system for treatment; the nanofiltration produced water enters the discharge pool.

[0035] (10) Mechanical vapor recompression (MVR) treatment: The MVR process adopts falling film and forced circulation evaporation. The concentrated sodium sulfate first enters the horizontal tube falling film MVR evaporation concentration device, and then enters the forced circulation MVR evaporation crystallization device after reaching the set concentration. The material is continuously concentrated until the salt in the material exceeds the solubility saturation point and precipitates. The precipitated solid crystal slurry is sent to the centrifuge for solid-liquid separation. The obtained sodium sulfate crystals meet the industrial grade sodium sulfate purity index requirements and are sold externally. The evaporated condensate is discharged into the effluent discharge pool.

[0036] As a preferred embodiment of any embodiment of the first aspect of the present invention, after the mechanical vapor recompression (MVR) treatment step, it also includes:

[0037] (11) Tail liquid / material treatment: A fixed amount of concentrated mother liquor is continuously discharged from the MVR system to the dryer for drying. The daily discharge of mother liquor is 5% of the nanofiltration concentrate entering the MVR system. The miscellaneous salts generated by drying are entrusted to external manufacturers for disposal as hazardous solid waste. The mixed water in the discharge pool can be discharged to the downstream sewage treatment plant, or used as toilet flushing water or landscaping water. The sludge in the sludge pool is dehydrated and transported to external manufacturers for disposal.

[0038] The purpose of discharging mother liquor from the MVR system is to prevent the continuous enrichment of impurities in the MVR system, thereby affecting the evaporation efficiency of the MVR system.

[0039] As a preferred embodiment of any embodiment of the first aspect of the present invention, the CODcr of the crystallization plate frame mother liquor and the initial washing water is 7000-12000 mg / L, BOD5 is 3000-4000 mg / L, NH3-N is 100-300 mg / L, total phosphorus is 200-400 mg / L, pH is 4-5, TDS is 30000-40000 mg / L, wherein SO4 2- It is 18000~22000mg / L.

[0040] As a preferred embodiment of any embodiment of the first aspect of the present invention, the CODcr of the comprehensive wastewater discharged in the adjustment step is 4000-6000 mg / L, BOD5 is 1500-3000 mg / L, NH3-N is 80-110 mg / L, total phosphorus is 110-160 mg / L, TDS is 15000-16500 mg / L, and SO4 2- It is 9000~12000mg / L.

[0041] As a preferred embodiment of any embodiment of the first aspect of the present invention, the MBR membrane in the MBR treatment is made of polyvinylidene fluoride; further, the pore size of the MBR membrane is 0.02 μm, so that the MBR treatment step has the advantages of high sludge concentration, high organic load, long biosolids retention time (SRT) and short hydraulic retention time (HRT).

[0042] As a preferred embodiment of any embodiment of the first aspect of the present invention, the volume ratio of the mud-water mixture containing activated sludge returned to the A / O process tank in the MBR treatment to the wastewater introduced into the A / O process tank is (4.5-5):1, and by controlling the process parameters, it is ensured that the microorganisms effectively degrade organic matter and ammonia nitrogen in different periods such as the logarithmic growth period, the decelerated growth period, and the endogenous respiration period.

[0043] As a preferred embodiment of any one of the first aspects of the present invention, the effluent COD of the MBR process pool is controlled within 100 mg / L to reduce organic pollution to the RO membrane and the NF membrane.

[0044] As a preferred embodiment of any one of the first aspects of the present invention, in the hydrolysis and acidification step, sludge is inoculated in the hydrolysis and acidification tank, and the sludge is obtained by culturing and domesticating sludge from a sewage treatment plant through long-chain dibasic acid microbial fermentation wastewater.

[0045] Specifically, by cultivating the action of microorganisms in the domesticated sludge, long-chain organic matter is converted into short-chain organic matter that is easily biodegradable, such as acetic acid, propionic acid, ethanol, butyric acid and lactic acid, thereby further improving the biodegradability of the wastewater. At the same time, about 20% of organic pollutants are removed, reducing the organic load for subsequent aerobic degradation.

[0046] As a preferred embodiment of any embodiment of the first aspect of the present invention, the concentration set in the horizontal tube falling film MVR evaporation concentration device in the mechanical vapor recompression (MVR) system is not less than 30wt%, and the moisture content of the sodium sulfate crystals finally obtained is within 5%.

[0047] As a preferred embodiment of any one of the first aspects of the present invention, in the adjustment step, the TDS concentration is reduced to 20000 mg / L to avoid inhibiting microbial activity.

[0048] Specifically, the method of reducing the TDS concentration is to mix the three wastewaters of crystallization plate and frame mother liquor and initial washing water, various equipment washing water, and concentrated water after RO membrane makes deionized water, and use various equipment washing water with low TDS concentration and concentrated water after RO membrane makes deionized water to dilute the crystallization plate and frame mother liquor and initial washing water with high TDS concentration, so as to achieve the purpose of reducing TDS concentration, while making full use of waste water and saving water resources.

[0049] As a preferred embodiment of any one of the first aspects of the present invention, in the neutralization step, the pH of the comprehensive wastewater is adjusted to 6 to 8; preferably adjusted to 6.5 to 7.5, most preferably 7.0.

[0050] This is because the best phosphorus removal effect of ferric sulfate occurs in a neutral or slightly acidic environment, that is, the pH value is between 6 and 8. At this pH, ferric sulfate can maintain good solubility and activity, and effectively react with phosphates in the water to form insoluble iron phosphate precipitation, and then remove phosphorus from the water through flocculation and precipitation. In particular, when the pH value is between 6.5 and 7.5, the phosphorus removal effect is most ideal.

[0051] As a preferred embodiment of any one of the first aspects of the present invention, in the coagulation sedimentation tank step, a precipitation reagent is added to perform coagulation sedimentation, and the precipitation reagent is ferric sulfate, polyaluminium chloride and polyacrylamide;

[0052] The daily treatment capacity of comprehensive wastewater is 750m 3 For example, 1000-1500ppm, i.e. 750-1125kg, of iron sulfate is first added to the coagulation sedimentation tank, and the iron ions and phosphates in the wastewater form iron phosphate precipitates. Then, 50-100ppm, i.e. 37.5-75kg, of polyaluminium chloride (PAC) and 2-5ppm, i.e. 1.5-3.75kg, of polyacrylamide (PAM) are added to improve the effect of coagulation and sedimentation, while removing suspended matter and some organic pollutants in the wastewater.

[0053] As a preferred embodiment of any one of the first aspects of the present invention, in the aerobic / anoxic treatment step, the aerobic bacteria and anoxic bacteria added to the A / O process pool are heterotrophic carbonizing bacteria, nitrifying bacteria and denitrifying bacteria;

[0054] Specifically, the A / O process can effectively remove pollutants such as organic matter and ammonia nitrogen in sewage with a high removal efficiency; under anaerobic conditions, denitrifying bacteria use organic carbon in sewage for denitrification, thereby improving the degradation efficiency of pollutants; since enhanced biochemistry is used in the nitrification stage and high-concentration sludge membrane technology is used in the denitrification stage, the sludge concentration of nitrification and denitrification is effectively increased; this step has a simple process, does not require an external carbon source and a post-aeration tank, uses raw sewage as a carbon source, and has low construction and operation costs; further, since the activated sludge produced in the MBR process is returned to the A / O process pool, the microorganisms in this part of the activated sludge can significantly improve the degradation rate of difficult-to-degrade substances in the A / O process.

[0055] As a preferred embodiment of any embodiment of the first aspect of the present invention, in the reverse osmosis treatment step, the pore size of the reverse osmosis membrane is less than or equal to 1 nm, the reverse osmosis recovery rate in the reverse osmosis system is set to 60% to 65%, and the daily treatment capacity of the comprehensive wastewater is 750m 3 For example, the output of reverse osmosis fresh water is 450m 3 ~487.5m 3 The TDS of the reverse osmosis concentrate can reach about 40800-46600 mg / L, and the volume of the reverse osmosis concentrate is 262.5-300m 3 .

[0056] As a preferred embodiment of any embodiment of the first aspect of the present invention, in the hardness removal treatment step, the hardness of the reverse osmosis concentrate is reduced to below 100 mg / L in the hardness removal system, effectively reducing the risk of scaling in the subsequent nanofiltration (NF) system.

[0057] As a preferred embodiment of any embodiment of the first aspect of the present invention, in the hardness removal treatment step, sodium hydroxide and / or sodium carbonate are added to the hardness removal system to reduce the hardness of the reverse osmosis concentrate to 90-100 mg / L.

[0058] Specifically, the sewage hardness in any embodiment of the first aspect of the present invention refers to the content of calcium and magnesium ions in the water.

[0059] The addition of a hardness removal system is to reduce the scaling risk of NF membranes in NF systems. Adding a hardness removal system requires consideration of the hardness of wastewater. In existing processes, the concentration of hardness in wastewater is relatively low, and hardness cannot be effectively removed. However, in this process, after being concentrated by the reverse osmosis system, the hardness in the RO system concentrate increases by 2-3 times. At this time, the chemical precipitation method is used to remove hardness, and the effect is significant. Because it is relatively easy to reduce hardness from high concentration to low concentration, but it is relatively difficult to reduce hardness from low concentration to ultra-low concentration. The method of hardness removal is chemical precipitation, which involves chemical reactions between molecules. From the efficiency point of view, the lower the concentration, the lower the rate of chemical reaction, and the more reagents need to be added, which increases the cost of reagents. Choosing not to remove hardness will lead to serious scaling on the concentrated water side of the NF system, which will lead to frequent chemical cleaning of the NF membrane. Frequent chemical cleaning will shorten the life of the membrane, and at the same time affect the normal and continuous operation of the membrane system, increasing the cost of wastewater treatment.

[0060] As a preferred embodiment of any embodiment of the first aspect of the present invention, in the nanofiltration treatment step, the pore size of the nanofiltration membrane is 1 to 10 nm, the recovery rate of nanofiltration is set to 55% to 60%, and the daily treatment capacity of the comprehensive wastewater is 750m 3 For example, the water output of nanofiltration fresh water is 157.5~165m 3 The TDS of the nanofiltration concentrate can reach about 111800-87300 mg / L, and the amount of nanofiltration concentrate is 105.0-135m 3 .

[0061] Specifically, the recovery rate range set by the nanofiltration system is conducive to reducing the processing scale of the MVR system equipment, thereby reducing investment and operating costs.

[0062] The second aspect of the present invention provides a system for the comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater, comprising a regulating tank, a neutralization tank, a coagulation sedimentation tank, a hydrolysis acidification tank, an anaerobic / aerobic tank, an submerged membrane bioreactor, a reverse osmosis system, a nanofiltration system and a mechanical vapor recompression system connected in sequence; the submerged membrane bioreactor is provided with a sludge return pipe for returning the sludge to the anoxic / aerobic tank.

[0063] As a preferred embodiment of any embodiment of the second aspect of the present invention, the system further comprises a sludge tank; the coagulation sedimentation tank, hydrolysis acidification tank, anoxic / aerobic tank, submerged membrane bioreactor and hardness removal system are respectively connected to the sludge tank via pipelines.

[0064] 3. Beneficial effects

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) The sulfate content in the wastewater of long-chain dibasic acid microbial fermentation is relatively high. Acidic substances such as long-chain dibasic acids react with liquid alkali to form sodium salts, and the solubility is improved. Since sulfate ions, long-chain dibasic acid ions and divalent and multivalent anions are more easily retained by nanofiltration membranes, and in order to reduce the filtration pressure of reverse osmosis membranes, for such wastewater, the prior art needs to adopt the sequence of first entering the NF system for treatment and then passing through the RO system for treatment twice, wherein NF treatment is a pretreatment process for RO treatment to ensure that the wastewater meets the water inlet conditions of the RO system, and the double RO system is to obtain recycled water that meets the process production use. In the present invention, reverse osmosis separation is first performed, and then nanofiltration concentration is performed. The wastewater undergoes a combined process of A / O process and MBR process, and the water quality has been greatly improved relative to the untreated raw water, and the water inlet conditions of the RO system have been met. It can directly enter the reverse osmosis RO system for membrane separation without the need for pretreatment of the nanofiltration NF system, thereby shortening the process and reducing the investment cost. The NF system behind the RO system is used to process the concentrated liquid of the RO system. Its function is to reduce the impurity ions on one side of the concentrated liquid and improve the purity of the alum, so as to facilitate the subsequent sale of the alum as a product.

[0067] (2) The sludge is returned to the A / O process pool, so that the A / O process pool has a sludge return system. The microorganisms in the sludge returned to the A / O process pool can significantly improve the degradation rate of difficult-to-degrade substances in the A / O process.

[0068] (3) Adjust the inoculum sludge in the acidification tank and use the cultivated microorganisms in the inoculum sludge to convert long-chain organic matter into short-chain organic matter that is easily biodegradable, such as acetic acid, propionic acid, ethanol, butyric acid and lactic acid, so as to further improve the biodegradability of the wastewater. At the same time, it can also remove some organic pollutants and reduce the organic load for degradation in the aerobic stage in the subsequent A / O process tank.

[0069] (4) The water content of the recovered sodium sulfate crystals is less than 5%, and the purity meets the requirements of Class III qualified products of "Industrial Anhydrous Sodium Sulfate (GB / T6009-2014)", and can be directly sold. Compared with the prior art, which requires dissolving the crystalline crude salt and then using high-concentration ozone to oxidize organic matter, and then further evaporating and concentrating, the present invention reduces equipment investment and operating costs. Moreover, the amount of sodium sulfate recovered by the present invention is also much higher than that of the prior art, mainly because the concentration of sulfate by the nanofiltration system is beneficial to the output of evaporation crystallization of the MVR system.

[0070] (5) Through the entire process, the output and standard of wastewater reuse water are improved in a hierarchical manner, thereby reducing the cost of wastewater treatment; the output and purity of alum are increased, and the cost of wastewater treatment is partially offset by selling alum; the amount of chemicals added in the overall process is small, the cost of chemicals is reduced, and the cost of wastewater treatment is further reduced; the risk of scaling of the membrane system and the evaporation system is reduced, thereby enhancing the stability and efficiency of the system operation.

[0071] Specifically, the water produced by the reverse osmosis system meets the reuse standards for cooling circulating water and can be used as make-up water for cooling towers; the water produced by the nanofiltration system and the condensate of the MVR system can meet the pipe standards of downstream sewage treatment plants and be discharged to downstream sewage treatment plants. They can also be used as toilet flushing water or landscaping water within the factory area, thereby making full use of water resources and reducing the cost of wastewater treatment.

[0072] Specifically, by adopting the neutralization step and the coagulation and sedimentation step, by adding a small amount of chemical agents, the suspended solids and total phosphorus in the wastewater can be effectively removed; by adopting the hydrolysis acidification step, the A / O process treatment step and the submerged MBR process treatment step, the COD, ammonia nitrogen and total nitrogen in the wastewater can be effectively removed through biochemical methods, thereby reducing the cost of wastewater treatment.

[0073] In summary, the method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater of the present invention can effectively reduce the cost of wastewater treatment and utilize the water resources and sodium sulfate salt in the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 Schematic diagram of the process for resource utilization of wastewater from long-chain dibasic acid microbial fermentation in the embodiment; DETAILED DESCRIPTION

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0076] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0077] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement or value. The degree of flexibility for a particular variable can be easily determined by one skilled in the art.

[0078] Concentration, amount and other numerical data can be presented in range format herein.It should be understood that such range format is only used for convenience and simplicity, and should be flexibly interpreted as not only including the numerical value clearly described as range limit, but also including all single numerical values ​​or sub-ranges contained in the range, just as each numerical value and sub-range are clearly described.For example, the numerical range of about 1 to about 4.5 should be interpreted as not only including the limit value of 1 to about 4.5 clearly described, but also including single numerals (such as 2,3,4) and sub-ranges (such as 1 to 3,2 to 4, etc.).The same principle is applicable to the scope of only narrating a numerical value, such as "less than about 4.5", which should be interpreted as including all the above-mentioned values ​​and ranges.In addition, no matter how the breadth of the described range or feature is, this explanation should be applicable.

[0079] The present invention is further described below in conjunction with specific embodiments.

[0080] Example 1

[0081] The treatment in this example is the wastewater from the long-chain dibasic acid microbial fermentation production process of a certain company, with a water volume of 750m 3 / d, the specific water quality is as follows:

[0082] Table 1 Water quality of three wastewater streams in a company's long-chain dibasic acid microbial fermentation process

[0083]

[0084] Note: The crystallization plate and frame mother liquor and initial washing water, various equipment cleaning water, and concentrated water after RO membrane deionization are all wastewaters in the long-chain dibasic acid microbial fermentation production process. The RO membrane here is the RO membrane in the long-chain dibasic acid microbial fermentation production process, not the RO membrane in this wastewater resource comprehensive utilization method.

[0085] CODcr: dichromate index, indicating the degree of organic pollution in wastewater;

[0086] BOD5: Biochemical oxygen demand in five days, is an important indicator that indirectly indicates the degree of organic pollution in water by the amount of dissolved oxygen consumed by microbial metabolism;

[0087] SS: It is the insoluble solid matter in water, usually used to assess the content of suspended solids in water quality;

[0088] NH3-N: Ammonia nitrogen, often used as a wastewater indicator;

[0089] TDS: It is the total amount of solids dissolved in water, usually used to measure the purity of water quality. It includes the sum of inorganic and organic salts in water. The main components are calcium, magnesium, sodium, potassium ions, and also some heavy metal dissolved substances;

[0090] It can be seen from the data in Table 1 that the wastewater is acidic, contains a large amount of organic matter and suspended solids, high concentrations of total phosphorus, organic salts and inorganic salts, and medium concentrations of ammonia nitrogen.

[0091] The process flow of the method of the present invention for comprehensive resource utilization of wastewater from long-chain dibasic acid microbial fermentation is as follows: Figure 1 , the specific process of Example 1 is as follows:

[0092] (1) Regulating tank: The wastewaters shown in Table 1 are mixed to form a comprehensive wastewater and then enter the regulating tank to adjust the water quality and quantity and reduce the TDS concentration in the wastewater to less than 20,000 mg / L to avoid inhibiting the activity of microorganisms.

[0093] (2) Neutralization tank: The wastewater from the regulating tank is pumped to the neutralization tank, and liquid alkali (liquid sodium hydroxide) is added to adjust the pH to about 7.0.

[0094] (3) Coagulation and sedimentation tank: Wastewater flows from the neutralization tank to the coagulation and sedimentation tank by gravity. 750 kg / d of iron sulfate is added. The iron ions and phosphates in the wastewater form iron phosphate precipitates. 37.5 kg / d of polyaluminium chloride (PAC) and 1.5 kg / d of polyacrylamide (PAM) are added to remove suspended solids and some organic pollutants in the wastewater. The lower layer of sludge in the coagulation and sedimentation tank is transported to the sludge tank.

[0095] (4) Hydrolysis and acidification tank: The supernatant of the coagulation and sedimentation tank enters the hydrolysis and acidification tank, where sludge is inoculated. Through the action of microorganisms in the sludge, long-chain organic matter is converted into short-chain organic matter that is easily biodegradable, thereby improving the biodegradability of the wastewater and removing about 20% of organic pollutants. The lower layer of sludge in the hydrolysis and acidification tank is transported to the sludge tank.

[0096] (5) Anoxic / aerobic (A / O) process pool: The effluent from the hydrolysis acidification pool enters the A / O process pool, where heterotrophic carbonizing bacteria, nitrifying bacteria, and denitrifying bacteria are added to achieve simultaneous denitrification and carbon removal. The lower sludge of the A / O process pool is transported to the sludge pool.

[0097] (6) Submerged membrane bioreactor (MBR) process pool: The effluent from the A / O process pool enters the submerged MBR process pool. The MBR membrane is made of polyvinylidene fluoride (PVDF) with a pore size of 0.02μm, which intercepts activated sludge, suspended solids and other substances, so that the effluent COD of the MBR process can reach less than 100mg / L. At the same time, the volume ratio of the mud-water mixture containing activated sludge returned from the MBR process pool to the A / O process pool and the wastewater entering the A / O process pool is 4.5:1; the sludge returned to the A / O process pool is removed, and the remaining sludge is transported to the sludge pool.

[0098] The effluent quality after MBR process treatment is shown in Table 2. SO4 2- and Na + The ion concentration of Mg is much higher than that of other ions, which is beneficial to the crystallization and separation of sodium sulfate and also to improve the purity of sodium sulfate; it can effectively reduce COD to 100 mg / L and reduce organic pollution to RO membrane and NF membrane; 2+ and Ca 2+ The ion concentration is very low, no hardness removal operation is required, and no inorganic pollution will be caused to the RO membrane and NF membrane.

[0099] Table 2 Water quality of a company's long-chain dibasic acid microbial fermentation production process comprehensive wastewater after it flows out of the MBR process and before entering the RO system

[0100] Serial number ion unit concentration 1 <![CDATA[K + ]]> mg / L 250 2 <![CDATA[Ca 2+ ]]> mg / L 40 3 <![CDATA[Mg 2+ ]]> mg / L 9 4 <![CDATA[Na + ]]> mg / L 4900 5 <![CDATA[Cl - ]]> mg / L 100 6 <![CDATA[SO4 2- ]]> mg / L 10000 7 <![CDATA[CO3 2- ]]> mg / L 800 8 TDS mg / L 16500 9 COD mg / L 100 10 <![CDATA[NH3-N]]> mg / L 5 11 SS mg / L 5

[0101] (7) Reverse Osmosis (RO) System: The effluent from the submerged MBR pool enters the reverse osmosis (RO) system. After the monovalent ions, organic matter, and inorganic matter are intercepted by the reverse osmosis membrane with a pore size of less than or equal to 1 nm, the reverse osmosis water is reused as the feed water of the circulating cooling tower. The reverse osmosis recovery rate is set at 60%, and the reverse osmosis fresh water output is 450m3. 3 / d, the TDS of the reverse osmosis concentrate can reach about 40800mg / L, and the reverse osmosis concentrate volume is 300m 3 / d.

[0102] (8) Hardness removal system: The concentrated liquid from the reverse osmosis system enters the hardness removal system, where sodium hydroxide and sodium carbonate are added to reduce the hardness of the concentrated liquid to 100 mg / L; the lower layer of sludge in the hardness removal system is transported to the sludge pool.

[0103] (9) Nanofiltration (NF) system: The effluent from the hardness removal system enters the nanofiltration system, where sulfate is intercepted by a nanofiltration membrane with a pore size of 1 to 10 nm to increase the concentration of sodium sulfate. The concentrated nanofiltration concentrate enters the evaporation system for treatment, and the nanofiltration water enters the discharge pool. The recovery rate of the nanofiltration is set to 55%, and the output of the nanofiltration fresh water is 165m 3 / d, the TDS of the nanofiltration concentrate can reach about 87300mg / L, and the amount of nanofiltration concentrate is 135m 3 / d.

[0104] (10) Mechanical vapor recompression (MVR) system: The MVR process adopts falling film and forced circulation evaporation. The nanofiltration concentrate first enters the horizontal tube falling film MVR evaporation concentration device, and after reaching a concentration of 30wt%, it enters the forced circulation MVR evaporation crystallization device. The material is continuously concentrated until the salt in the material exceeds the solubility saturation point and precipitates. The precipitated solid slurry is sent to the centrifuge. After solid-liquid separation, the water content of the sodium sulfate crystals obtained is reduced to less than 5%, which meets the purity index requirements of industrial-grade sodium sulfate that can be directly sold. The evaporated condensate is discharged into the effluent discharge pool.

[0105] (11) Tail liquid / material treatment: A fixed amount of mother liquor is continuously discharged from the MVR system to the dryer for drying. The daily discharge of mother liquor is 5% of the nanofiltration concentrate entering the MVR system. The miscellaneous salts generated by drying are entrusted to external manufacturers for disposal as hazardous solid waste. The mixed water in the discharge pool can be discharged to the downstream sewage treatment plant, or used as toilet flushing water or landscaping water. The sludge in the sludge pool can be dehydrated and transported to external manufacturers for disposal.

[0106] Example 2

[0107] The process flow of the method of this embodiment for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater is as follows: Figure 1 , the specific process of Example 2 is as follows:

[0108] (1) Regulating tank: The wastewaters shown in Table 1 are mixed to form a comprehensive wastewater and then enter the regulating tank to adjust the water quality and quantity and reduce the TDS concentration in the wastewater to less than 20,000 mg / L to avoid inhibiting the activity of microorganisms.

[0109] (2) Neutralization tank: The wastewater from the regulating tank is pumped to the neutralization tank, and liquid alkali (liquid sodium hydroxide) is added to adjust the pH to about 7.0.

[0110] (3) Coagulation and sedimentation tank: Wastewater flows from the neutralization tank to the coagulation and sedimentation tank by gravity. 900 kg / d of iron sulfate is added, and the iron ions and phosphates in the wastewater form iron phosphate precipitates. 55 kg / d of polyaluminium chloride (PAC) and 2.5 kg / d of polyacrylamide (PAM) are added to remove suspended solids and some organic pollutants in the wastewater. The lower layer of sludge in the coagulation and sedimentation tank is transported to the sludge tank.

[0111] (4) Hydrolysis and acidification tank: The supernatant of the coagulation and sedimentation tank enters the hydrolysis and acidification tank, where sludge is inoculated. Through the action of microorganisms in the sludge, long-chain organic matter is converted into short-chain organic matter that is easily biodegradable, thereby improving the biodegradability of the wastewater and removing about 20% of organic pollutants. The lower layer of sludge in the hydrolysis and acidification tank is transported to the sludge tank.

[0112] (5) Anoxic / aerobic (A / O) process pool: The effluent from the hydrolysis acidification pool enters the A / O process pool, where heterotrophic carbonizing bacteria, nitrifying bacteria, and denitrifying bacteria are added to achieve simultaneous denitrification and carbon removal. The lower sludge of the A / O process pool is transported to the sludge pool.

[0113] (6) Submerged membrane bioreactor (MBR) process pool: The effluent from the A / O process pool enters the submerged MBR process pool. The MBR membrane is made of polyvinylidene fluoride (PVDF) with a pore size of 0.02μm, which intercepts activated sludge, suspended solids and other substances, so that the effluent COD of the MBR process can reach less than 100mg / L. At the same time, the volume ratio of the mud-water mixture containing activated sludge returned from the MBR process pool to the A / O process pool and the wastewater entering the A / O process pool is 5:1; the sludge returned to the A / O process pool is removed, and the remaining sludge is transported to the sludge pool.

[0114] (7) Reverse Osmosis (RO) System: The effluent from the submerged MBR pool enters the reverse osmosis (RO) system. After the monovalent ions, organic matter and inorganic matter are intercepted by the reverse osmosis membrane with a pore size of less than or equal to 1 nm, the reverse osmosis water is reused as the feed water of the circulating cooling tower. The reverse osmosis recovery rate is set at 65%, the reverse osmosis fresh water output is 487.5 m3 / d, the reverse osmosis concentrate TDS can reach about 46600 mg / L, and the reverse osmosis concentrate volume is 262.5 m3 / d.

[0115] (8) Hardness removal system: The concentrated liquid from the reverse osmosis system enters the hardness removal system, where sodium hydroxide and sodium carbonate are added to reduce the hardness of the concentrated liquid to 100 mg / L; the lower layer of sludge in the hardness removal system is transported to the sludge pool.

[0116] (9) Nanofiltration (NF) system: The effluent from the hardness removal system enters the nanofiltration system, where sulfate is intercepted by a nanofiltration membrane with a pore size of 1 to 10 nm to increase the concentration of sodium sulfate. The concentrated nanofiltration concentrate enters the evaporation system for treatment, and the nanofiltration water enters the discharge pool. The recovery rate of the nanofiltration is set at 55%, and the output of the nanofiltration fresh water is 144.4 m 3 / d, the TDS of the Nafil concentrate can reach about 99700mg / L, and the volume of the Nafil concentrate is 118.1m 3 / d.

[0117] (10) Mechanical vapor recompression (MVR) system: The MVR process adopts falling film and forced circulation evaporation. The concentrated sodium sulfate solution first enters the horizontal tube falling film MVR evaporation concentration device, and after reaching a concentration of 30 wt%, it enters the forced circulation MVR evaporation crystallization device. The material is continuously concentrated until the salt in the material exceeds the solubility saturation point and precipitates. The precipitated solid slurry is sent to the centrifuge. After solid-liquid separation, the water content of the sodium sulfate crystals obtained is reduced to less than 5%, which meets the purity index requirements of industrial grade sodium sulfate that can be directly sold. The evaporated condensate is discharged into the effluent discharge pool;

[0118] (11) Tail liquid / material treatment: A fixed amount of mother liquor is continuously discharged from the MVR system to the dryer for drying. The daily discharge of mother liquor is 5% of the nanofiltration concentrate entering the MVR system. The miscellaneous salts generated by drying are entrusted to external manufacturers for disposal as hazardous solid waste. The mixed water in the discharge pool can be discharged to the downstream sewage treatment plant, or used as toilet flushing water or landscaping water. The sludge in the sludge pool can be dehydrated and transported to external manufacturers for disposal.

[0119] Example 3

[0120] The process flow of the method of the present invention for comprehensive resource utilization of wastewater from long-chain dibasic acid microbial fermentation is as follows: Figure 1 , the specific process of Example 3 is as follows:

[0121] (1) Regulating tank: The wastewaters shown in Table 1 are mixed to form a comprehensive wastewater and then enter the regulating tank to adjust the water quality and quantity and reduce the TDS concentration in the wastewater to less than 20,000 mg / L to avoid inhibiting the activity of microorganisms.

[0122] (2) Neutralization tank: The wastewater from the regulating tank is pumped to the neutralization tank, and liquid alkali (liquid sodium hydroxide) is added to adjust the pH to about 7.0.

[0123] (3) Coagulation and sedimentation tank: Wastewater flows from the neutralization tank to the coagulation and sedimentation tank by gravity. 1125 kg / d of iron sulfate is added, and the iron ions and phosphates in the wastewater form iron phosphate precipitates. 75 kg / d of polyaluminium chloride (PAC) and 3.75 kg / d of polyacrylamide (PAM) are added to remove suspended solids and some organic pollutants in the wastewater. The lower layer of sludge in the coagulation and sedimentation tank is transported to the sludge tank.

[0124] (4) Hydrolysis and acidification tank: The supernatant of the coagulation and sedimentation tank enters the hydrolysis and acidification tank, where sludge is inoculated. Through the action of microorganisms in the sludge, long-chain organic matter is converted into short-chain organic matter that is easily biodegradable, thereby improving the biodegradability of the wastewater and removing about 20% of organic pollutants. The lower layer of sludge in the hydrolysis and acidification tank is transported to the sludge tank.

[0125] (5) Anoxic / aerobic (A / O) process pool: The effluent from the hydrolysis acidification pool enters the A / O process pool, where heterotrophic carbonizing bacteria, nitrifying bacteria, and denitrifying bacteria are added to achieve simultaneous denitrification and carbon removal. The lower sludge of the A / O process pool is transported to the sludge pool.

[0126] (6) Submerged membrane bioreactor (MBR) process pool: The effluent from the A / O process pool enters the submerged MBR process pool. The MBR membrane is made of polyvinylidene fluoride (PVDF) with a pore size of 0.02μm, which intercepts activated sludge, suspended solids and other substances, so that the effluent COD of the MBR process can reach less than 100mg / L. At the same time, the volume ratio of the mud-water mixture containing activated sludge returned from the MBR process pool to the A / O process pool and the wastewater entering the A / O process pool is 5:1; the sludge returned to the A / O process pool is removed, and the remaining sludge is transported to the sludge pool.

[0127] (7) Reverse Osmosis (RO) System: The effluent from the submerged MBR pool enters the reverse osmosis (RO) system. After the monovalent ions, organic matter and inorganic matter are intercepted by the reverse osmosis membrane with a pore size of less than or equal to 1 nm, the reverse osmosis water is reused as the feed water of the circulating cooling tower. The reverse osmosis recovery rate is set at 65%, the reverse osmosis fresh water output is 487.5 m3 / d, the reverse osmosis concentrate TDS can reach about 46600 mg / L, and the reverse osmosis concentrate volume is 262.5 m3 / d.

[0128] (8) Hardness removal system: The concentrated liquid from the reverse osmosis system enters the hardness removal system, where sodium hydroxide and sodium carbonate are added to reduce the hardness of the concentrated liquid to 90 mg / L; the lower layer of sludge in the hardness removal system is transported to the sludge pool.

[0129] (9) Nanofiltration (NF) system: The effluent from the hardness removal system enters the nanofiltration system, and the sulfate is intercepted by the nanofiltration membrane with a pore size of 1 to 10 nm to increase the concentration of sodium sulfate. The concentrated nanofiltration concentrate enters the evaporation system for treatment, and the nanofiltration water enters the discharge pool. The recovery rate of nanofiltration is set to 60%, the water output of nanofiltration fresh water is 157.5m3 / d, the TDS of the nanofiltration concentrate can reach about 111800mg / L, and the amount of nanofiltration concentrate is 105.0m3 / d.

[0130] (10) Mechanical vapor recompression (MVR) system: The MVR process adopts falling film and forced circulation evaporation. The concentrated sodium sulfate solution first enters the horizontal tube falling film MVR evaporation concentration device, and after reaching a concentration of 30 wt%, it enters the forced circulation MVR evaporation crystallization device. The material is continuously concentrated until the salt in the material exceeds the solubility saturation point and precipitates. The precipitated solid slurry is sent to the centrifuge. After solid-liquid separation, the water content of the sodium sulfate crystals obtained is reduced to less than 5%, which meets the purity index requirements of industrial grade sodium sulfate that can be directly sold. The evaporated condensate is discharged into the effluent discharge pool;

[0131] (11) Tail liquid / material treatment: A fixed amount of mother liquor is continuously discharged from the MVR system to the dryer for drying. The daily discharge of mother liquor is 5% of the nanofiltration concentrate entering the MVR system. The miscellaneous salts generated by drying are entrusted to external manufacturers for disposal as hazardous solid waste. The mixed water in the discharge pool can be discharged to the downstream sewage treatment plant, or used as toilet flushing water or landscaping water. The sludge in the sludge pool can be dehydrated and transported to external manufacturers for disposal.

[0132] The above content is a schematic description of the present invention and its implementation methods, which is not restrictive. What is shown in the embodiment is only one of the implementation methods of the present invention, and the actual implementation method is not limited thereto. Therefore, if a person of ordinary skill in the art is inspired by it and designs implementation methods and embodiments similar to the technical solution without creative design without departing from the purpose of the invention, they should all fall within the scope of protection of the present invention.

Claims

1. A method for comprehensive resource utilization of wastewater from long-chain dibasic acid microbial fermentation, comprising treating the crystallization plate frame mother liquor and initial washing water in the long-chain dibasic acid microbial fermentation process through a conditioning step, a neutralization step, a coagulation and precipitation step, and a hydrolysis and acidification step in sequence; characterized in that The following steps are also included: Anoxic / aerobic treatment step: the effluent after hydrolysis and acidification treatment enters the anoxic / aerobic process tank; Submerged membrane bioreactor treatment steps: the effluent from the anoxic / aerobic process pool enters the submerged membrane bioreactor process pool for treatment; Regulate the return of activated sludge produced in the membrane bioreactor process to the anoxic / aerobic process tank; Reverse osmosis treatment steps: the effluent from the submerged membrane bioreactor process tank enters the reverse osmosis system; Hardness removal treatment steps: The concentrate from the reverse osmosis system enters the hardness removal system to reduce the hardness of the concentrate; Nanofiltration treatment steps: The effluent from the hardness removal system enters the nanofiltration system and the sulfate is intercepted by the nanofiltration membrane; Mechanical vapor recompression treatment steps: The nanofiltration concentrated liquid first enters the horizontal tube falling film mechanical vapor recompression evaporation concentration device, and after reaching the set concentration, it enters the forced circulation mechanical vapor recompression evaporation crystallization device, and the precipitated solid crystal slurry is separated into solid and liquid to obtain sodium sulfate crystals.

2. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 1, characterized in that: The crystallization plate frame mother liquor and initial washing water have CODcr of 7000-12000mg / L, BOD5 of 3000-4000mg / L, NH3-N of 100-300mg / L, total phosphorus of 200-400mg / L, pH of 4-5, TDS of 30000-40000mg / L, and SO4 2- It is 18000~22000mg / L.

3. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 2, characterized in that: The comprehensive wastewater discharged after the adjustment step of the crystallization plate frame mother liquor and the initial washing water has a CODcr of 4000-6000 mg / L, a BOD5 of 1500-3000 mg / L, an NH3-N of 80-110 mg / L, a total phosphorus of 110-160 mg / L, a TDS of 15000-16500 mg / L, and SO4 2- It is 9000~12000mg / L.

4. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 1, characterized in that: In the submerged membrane bioreactor treatment, the submerged membrane bioreactor membrane is made of polyvinylidene fluoride; The volume ratio of the sludge-water mixture containing activated sludge returned to the anoxic / aerobic process tank during the treatment in the submerged membrane bioreactor to the wastewater introduced into the anoxic / aerobic process tank is (4.5-5):1; The effluent COD of the submerged membrane bioreactor process pool is controlled within 100 mg / L.

5. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 1, characterized in that: The concentration set in the horizontal tube falling film mechanical vapor recompression evaporation concentration device in the mechanical vapor recompression system is not less than 30wt%, and the moisture content of the sodium sulfate crystals finally obtained is within 5%.

6. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 1, characterized in that: In the neutralization step, the pH of the comprehensive wastewater is adjusted to 6 to 8; In the coagulation sedimentation tank step, a precipitation reagent is added for coagulation sedimentation, wherein the precipitation reagent is 1000-1500 ppm of ferric sulfate, 50-100 ppm of polyaluminium chloride and 2-5 ppm of polyacrylamide; In the anoxic / aerobic process pool, the aerobic bacteria added are heterotrophic carbonizing bacteria and nitrifying bacteria, and the anoxic bacteria added are denitrifying bacteria.

7. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 1, characterized in that: In the reverse osmosis treatment step, the pore size of the reverse osmosis membrane is less than or equal to 1 nm, and the recovery rate is set to 60% to 65%; In the hardness removal step, sodium hydroxide and / or sodium carbonate are added to reduce the hardness of the reverse osmosis concentrate to less than 100 mg / L; The pore size of the nanofiltration membrane in the nanofiltration system is 1-10 nm, and the recovery rate of the nanofiltration is set to 55%-60%.

8. The method for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 1, characterized in that: The step of treating tail liquid is further included, wherein the tail liquid treating step is to discharge the mother liquid in the mechanical vapor recompression treating step to a drying machine for drying; The amount of the mother liquor discharged from the mechanical vapor recompression treatment step does not exceed 5% of the nanofiltration concentrate entering the mechanical vapor recompression treatment step.

9. A system for comprehensive resource utilization of wastewater from long-chain dibasic acid microbial fermentation, characterized in that: It includes a regulating tank, a neutralization tank, a coagulation sedimentation tank, a hydrolysis acidification tank, an anoxic / aerobic tank, an immersed membrane bioreactor, a reverse osmosis system, a nanofiltration system and a mechanical vapor recompression system which are connected in sequence; the immersed membrane bioreactor is provided with a sludge return pipe for returning the sludge to the anoxic / aerobic tank.

10. The system for comprehensive resource utilization of long-chain dibasic acid microbial fermentation wastewater according to claim 9, characterized in that: The system also comprises a sludge tank; the coagulation sedimentation tank, the hydrolysis acidification tank, the anoxic / aerobic tank, the submerged membrane bioreactor and the hardness removal system are respectively connected to the sludge tank through pipelines.

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