Treatment method and application of methionine production wastewater

Abstract

The invention relates to the field of industrial wastewater treatment of environmental engineering, and discloses a treatment method and application of methionine production wastewater, and the treatment method comprises the following steps: (1) pre-conditioning the methionine production wastewater, and then carrying out anaerobic biological treatment; (2) oxygenating the wastewater treated in the step (1), and carrying out aerobic treatment; and (3) carrying out catalytic ozonation on the wastewater treated in the step (2). According to the treatment method of the methionine production wastewater, the methionine production wastewater can be better degraded, and the total amount of discharged pollutants is reduced; the problem of toxicity inhibition by formaldehyde, acrylic acid and the like can be avoided, and the application range is wider; meanwhile, the treatment method of the methionine production wastewater can save a large amount of natural gas consumed by an incineration method and reduce carbon emission; in the preferred embodiment of the invention, the biogas generated by the treatment method for the methionine production wastewater can be used as a combustion aid, so that the energy is further saved.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment in environmental engineering, specifically to a method and application for treating methionine production wastewater. Background Technology

[0002] Methionine is one of the basic building blocks of proteins and is widely used in pharmaceuticals, nutritional products, food additives, and feed additives. The wastewater generated during methionine production contains organic compounds such as acrylic acid, acetic acid, acrolein, formaldehyde, allyl alcohol, and hydroquinone. The COD content of this organic wastewater can reach as high as 100,000–200,000 mg / L, and the formaldehyde content can reach as high as 12,000–24,000 mg / L. Due to the presence of large amounts of acrylic acid and aldehydes, these substances have significant inhibitory and toxic effects on microorganisms; therefore, it is generally considered that biological treatment technologies cannot be used to treat this type of wastewater.

[0003] The current treatment method involves incinerating wastewater, which uses high-pressure nozzles to spray wastewater into an incineration zone to burn off the organic matter. Since the main component of wastewater is water, completely burning the organic matter vaporizes the water, consuming large amounts of natural gas. Furthermore, incineration produces significant amounts of nitrogen oxides. In today's world, with energy shortages and environmental requirements demanding a continuous reduction in total pollutant emissions, incineration, a high-energy-consuming and high-polluting treatment method, is no longer suitable for the needs of modern society.

[0004] Under the above conditions, some companies have proposed methods to recover organic matter from methionine production wastewater to address the problems of high energy consumption and low material utilization in existing incineration methods. The main approach involves extracting the wastewater with an organic solvent. The extracted phase enters an azeotropic distillation column from the top of the extraction tower, while the raffinate phase enters the extractant recovery stage from the bottom. In the azeotropic distillation column, the azeotrope of water and organic solvent is distilled off from the top, condensed, and then separated in a reflux tank. The organic phase is then recycled to the extraction tower after removing light components such as acrolein in a light component removal column. Acrylic acid in the wastewater is collected from the lower side stream of the azeotropic distillation column, cooled, and sent to an acrylic acid product storage tank. The distillation waste liquid from the azeotropic distillation column is sent for incineration. The main problems with this method are: firstly, the distillation wastewater still needs to be incinerated; secondly, because biodegradable acrylic acid is extracted from the wastewater after extraction, the proportion of toxic formaldehyde in the wastewater increases. Therefore, the wastewater after extraction needs to undergo saccharification pretreatment to remove formaldehyde before it can be biochemically treated. However, saccharification introduces calcium hydroxide and sodium hydroxide, increasing the salt content in the system. In summary, the extraction-combined saccharification method cannot fundamentally solve the problems of high energy consumption and high pollutant emissions in methionine production wastewater treatment. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of high concentration, high toxicity, and poor biodegradability of methionine production wastewater in the prior art, and to provide a method and application for treating methionine production wastewater. This method can not only better degrade methionine production wastewater and reduce carbon emissions, but also avoid the problem of inhibition by the toxicity of formaldehyde, acrylic acid, etc. in traditional biochemical treatment methods.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for treating methionine production wastewater, the method comprising: (1) The methionine production wastewater is pre-treated and then subjected to anaerobic biological treatment; wherein, after solid-liquid separation of the effluent after anaerobic biological treatment, the solid phase is completely recycled for anaerobic biological treatment, and the liquid phase is recycled for anaerobic biological treatment at a volume ratio of 1:20-30. (2) The wastewater treated in step (1) is subjected to aerobic treatment; wherein, the mixture after aerobic treatment is settled to obtain supernatant and sludge layer, part of the supernatant is refluxed at a reflux ratio of 100-400 vol% for aerobic treatment, part of the supernatant is refluxed at a reflux ratio of 1:2-15 for methionine production wastewater pretreatment, and the sludge layer is refluxed at a reflux ratio of 50-200 vol% for aerobic treatment; (3) The wastewater treated in step (2) is subjected to ozone catalytic oxidation.

[0007] The second aspect of this invention applies the processing method described in the first aspect to the production of methionine.

[0008] Through the above technical solution, the present invention can achieve at least the following beneficial effects: (1) The method for treating methionine production wastewater of the present invention can better degrade methionine production wastewater and reduce the total amount of pollutants discharged. (2) The method for treating methionine production wastewater of the present invention can avoid the problem of inhibition by the toxicity of formaldehyde, acrylic acid and other substances, and has a wider range of applications; (3) The method for treating methionine production wastewater of the present invention can save a large amount of natural gas consumed by incineration and reduce carbon emissions; (4) In a preferred embodiment of the present invention, the biogas generated by the treatment method of methionine production wastewater can be used as a combustion aid to further save energy. Detailed Implementation

[0009] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0010] The first aspect of this invention provides a method for treating methionine production wastewater, the method comprising: (1) The methionine production wastewater is pre-treated and then subjected to anaerobic biological treatment; wherein, after solid-liquid separation of the effluent after anaerobic biological treatment, the solid phase is completely recycled for anaerobic biological treatment, and the liquid phase is recycled for anaerobic biological treatment at a volume ratio of 1:20-30. (2) The wastewater treated in step (1) is subjected to aerobic treatment; wherein, the mixture after aerobic treatment is settled to obtain a supernatant sludge layer, part of the supernatant is refluxed at a reflux ratio of 100-400 vol% for aerobic treatment, part of the supernatant is refluxed at a reflux ratio of 1:2-15 for methionine production wastewater pretreatment, and the sludge layer is refluxed at a reflux ratio of 50-200 vol% for aerobic treatment; (3) The wastewater treated in step (2) is subjected to ozone catalytic oxidation.

[0011] During their research, the inventors of this invention discovered that the method for treating methionine production wastewater of this invention can better degrade methionine production wastewater and reduce the total amount of pollutants discharged; it can also avoid the problem of inhibition by the toxicity of formaldehyde, acrylic acid, etc., and has a wider range of applications; at the same time, the method for treating methionine production wastewater of this invention can save a large amount of natural gas consumed by incineration, reducing carbon emissions; in a preferred embodiment of this invention, the biogas generated by the method for treating methionine production wastewater can be used as a combustion aid, further saving energy.

[0012] It is understood that the recirculation ratio mentioned in this invention refers to the flow rate ratio, that is, the ratio of the recirculation flow rate to the influent flow rate. The influent flow rate refers to the initial influent flow rate without any recirculation.

[0013] In this invention, preferably, the pre-adjustment method may include: mixing methionine production wastewater with trace elements, nutrients and optional water, and adjusting the pH to 6-9.

[0014] In this invention, preferably, the content of trace elements in the pre-treated methionine production wastewater can be 0.001-0.01 wt% (for example, it can be any two values ​​formed by 0.001 wt%, 0.002 wt%, 0.003 wt%, 0.004 wt%, 0.005 wt%, 0.006 wt%, 0.007 wt%, 0.008 wt%, 0.009 wt%, 0.01 wt%, or values ​​within that range), more preferably 0.003-0.006 wt%; the content of nutrients can be 0.005- 0.02wt% (for example, it can be a range formed by any two values ​​from 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, 0.009wt%, 0.01wt%, 0.011wt%, 0.012wt%, 0.013wt%, 0.014wt%, 0.015wt%, 0.016wt%, 0.017wt%, 0.018wt%, 0.019wt%, 0.02wt%, and values ​​within that range), more preferably 0.008-0.015wt%.

[0015] In this invention, preferably, the trace element may be selected from at least one of nickel, cobalt, molybdenum, zinc, manganese and copper; the nutrient salt may be selected from phosphate salts and / or calcium salts, more preferably from at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, calcium chloride, calcium carbonate and calcium nitrate.

[0016] In this invention, the above-mentioned method is used to pre-treat methionine production wastewater, ensuring stable operation of the treatment system, improving treatment efficiency, and guaranteeing the long-term stable operation of the entire biochemical treatment system. It also optimizes the anaerobic reaction environment, enhances biochemical effects, and achieves a pretreatment process integrating homogenization, temperature control, pH optimization, and nutrient balance. This invention employs a high-proportion reflux treatment of the highly polluted methionine production wastewater, effectively reducing the total amount of pollutants discharged and avoiding the problems of inhibition by the toxicity of formaldehyde, acrylic acid, etc. Compared to existing technologies that only use incineration to treat methionine production wastewater, the method of this invention can save a large amount of natural gas consumed by incineration, reducing carbon emissions.

[0017] In this invention, preferably, the anaerobic biological treatment method may include: mixing pre-treated methionine production wastewater with activated sludge, anaerobic compound bacteria and formaldehyde-degrading bacteria in an anaerobic tank.

[0018] In this invention, the above-mentioned method for anaerobic biological treatment avoids incineration, which involves spraying wastewater into the incineration zone through high-pressure nozzles to burn off the organic matter. Since the main component of the wastewater is water, completely burning the organic matter would vaporize the water, consuming a large amount of natural gas. Furthermore, incineration produces a large amount of nitrogen oxides. The main advantage of anaerobic biological treatment in this invention is that biogas (mainly methane) is produced during the anaerobic degradation of organic matter, which can be reused as a clean energy source, achieving resource recovery and saving production enterprises significant costs, resulting in substantial economic benefits. In addition, anaerobic biological treatment does not emit nitrogen oxides into the atmosphere, reducing pollutant emissions compared to incineration and providing good environmental benefits. Moreover, this invention combines anaerobic compound bacteria and formaldehyde-degrading bacteria in the anaerobic biological treatment process, significantly improving treatment efficiency and enhancing system stability, resulting in a synergistic effect.

[0019] In this invention, preferably, the concentration of the activated sludge in the anaerobic tank can be 5000-40000 mg / L (for example, it can be any two values ​​formed by 5000 mg / L, 6000 mg / L, 7000 mg / L, 8000 mg / L, 9000 mg / L, 10000 mg / L, 11000 mg / L, 12000 mg / L, 13000 mg / L, 14000 mg / L, 15000 mg / L, 20000 mg / L, 25000 mg / L, 30000 mg / L, 35000 mg / L, 40000 mg / L, or any value within that range), more preferably, it can be 9000-12000 mg / L.

[0020] In this invention, preferably, the activated sludge load in the anaerobic tank can be 0.03-0.3 (for example, it can be any two values ​​formed by 0.03, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.23, 0.25, 0.27, 0.3 and the values ​​within the range) kgCOD / (kgVSS•d), more preferably 0.05-0.18 kgCOD / (kgVSS•d).

[0021] In this invention, preferably, the amount of formaldehyde-degrading bacteria can be 1-3 wt‰ of the activated sludge (for example, it can be any two values ​​formed by 1 wt‰, 1.2 wt‰, 1.5 wt‰, 1.8 wt‰, 2 wt‰, 2.3 wt‰, 2.5 wt‰, 2.7 wt‰, 3 wt‰, or any value within that range), and more preferably, it can be 1.5-2.5 wt‰.

[0022] In this invention, preferably, the amount of anaerobic compound bacteria can be 1-3 wt‰ of the activated sludge (for example, it can be any two values ​​formed by 1 wt‰, 1.2 wt‰, 1.5 wt‰, 1.8 wt‰, 2 wt‰, 2.3 wt‰, 2.5 wt‰, 2.7 wt‰, 3 wt‰, or any value within the range), and more preferably, it can be 1.5-2.5 wt‰.

[0023] In this invention, preferably, the conditions for the anaerobic biological treatment may include: a temperature of 30-40℃ (for example, a range formed by any two values ​​from 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, and 40℃, and values ​​within that range), more preferably 35-38℃; and a pH value of 6-9.

[0024] In this invention, preferably, the conditions for the aerobic treatment may include: a temperature of 15-37°C (for example, a range formed by any two values ​​from 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, and values ​​within that range), more preferably 30-35°C; and a pH value of 6-9.

[0025] In this invention, meeting the above-mentioned treatment conditions can effectively improve the system's resistance to shock loads, resulting in stable and efficient treatment effects. Furthermore, under optimal conditions, organic matter is converted into methane (CH4) to the maximum extent, increasing biogas production and methane content (typically reaching 60%-75%).

[0026] In this invention, preferably, in step (2), the aerobic treatment method may include: oxygenating the wastewater and mixing it with activated sludge in an aerobic tank containing suspended packing.

[0027] In this invention, preferably, the oxygenation is performed such that the amount of dissolved oxygen in the aerobic tank in step (2) can be 1.5-4 mg / L (for example, it can be any two values ​​formed by 1.5 mg / L, 2 mg / L, 2.5 mg / L, 3 mg / L, 3.5 mg / L, 4 mg / L and the value within the range), more preferably it can be 2-3 mg / L.

[0028] In this invention, the aerobic biological treatment method described above can efficiently degrade organic matter and ammonia nitrogen, improve effluent quality, and significantly reduce ammonia nitrogen concentration to meet national emission standards. It can also be adapted to the treatment of medium- and low-concentration wastewater, reducing operating costs.

[0029] In this invention, preferably, the volume of the suspended packing material accounts for 20-50 vol% of the total volume of the aerobic tank (for example, it can be any two values ​​formed by 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, and values ​​within the range), more preferably it can be 25-35 vol%.

[0030] In this invention, preferably, the concentration of activated sludge in the aerobic tank can be 2500-5000 mg / L (for example, it can be any two values ​​formed by 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L, 4500 mg / L, and 5000 mg / L, or a value within that range), more preferably, it can be 3000-4000 mg / L.

[0031] In this invention, preferably, the activated sludge load in the aerobic tank can be 0.05-0.3 kgCOD / (kgVSS•d) (for example, it can be any two values ​​formed by 0.05, 0.1, 0.15, 0.2, 0.25, 0.3 and the value within the range), more preferably it can be 0.1-0.2 kgCOD / (kgVSS•d).

[0032] In this invention, meeting the above-mentioned treatment conditions can effectively increase the total amount of microorganisms, thereby making the treatment method for methionine production wastewater of this invention highly resistant to shock loads and with stable and efficient treatment effects.

[0033] In this invention, preferably, the reflux ratio for aerobic treatment of the sludge layer can be 100-150 vol% (for example, it can be any two values ​​formed by 100 vol%, 110 vol%, 120 vol%, 130 vol%, 140 vol%, 150 vol%, and values ​​within that range).

[0034] In this invention, preferably, the reflux volume ratio of the supernatant refluxed for aerobic treatment can be 200-300 vol% (for example, it can be any two values ​​formed by 200 vol%, 210 vol%, 220 vol%, 230 vol%, 240 vol%, 250 vol%, 260 vol%, 270 vol%, 280 vol%, 290 vol%, 300 vol%, and values ​​within that range).

[0035] In this invention, by controlling the sludge return ratio and supernatant return ratio within the aforementioned ranges, a stable activated sludge concentration can be maintained, ensuring a sufficient number of microorganisms to treat pollutants. This guarantees stable treatment efficiency and strong resistance to shock loads caused by fluctuations in influent quality and quantity. Furthermore, it balances the microbial community, keeping the microorganisms in a highly active and stable state, enabling them to efficiently degrade organic matter while forming a good floc structure, inhibiting the excessive proliferation of filamentous bacteria, ensuring the flocculation and settling properties of the activated sludge, and ultimately achieving highly efficient biological denitrification.

[0036] In this invention, preferably, the anaerobic complex bacteria can be at least one of Bacillus circularis, Bacillus cereus, Bacillus subtilis, Bacillus sulfate-reducing syntrophic bacteria, Clostridium beyerii, Methanococcus pastoris, Methanobacterium flexures, and psychrothermic methanogens.

[0037] In this invention, preferably, the formaldehyde-degrading bacteria can be at least one of oligotrophic trophozoites, microbacterium oxidans, and achromobacterium.

[0038] In this invention, preferably, the suspended packing can be selected from multifaceted hollow sphere packing and / or combined suspended sphere packing (e.g., MBBR packing).

[0039] In this invention, preferably, based on the total mass of the anaerobic complex bacteria, the content of *Bacillus circulans* is 3.5-35 wt%, the content of *Bacillus cereus* is 3.5-35 wt%, the content of *Bacillus subtilis* is 3.5-35 wt%, the content of *Symplocos rubrum* is 7-40 wt%, the content of *Clostridium beyere* is 7-40 wt%, the content of *Methanococcus pasteurellii* is 3-25 wt%, the content of *Methanobacterium curvatureum* is 3-25 wt%, and the content of *Methanophora psychrophila* is 3-25 wt%. 5 wt%; more preferably, based on the total mass of the anaerobic complex bacteria, the content of Bacillus circulans is 5-18 wt%, the content of Bacillus cereus is 5-18 wt%, the content of Bacillus subtilis is 5-18 wt%, the content of Bacillus sulfate-reducing bacteria is 15-32 wt%, the content of Clostridium beyerii is 15-32 wt%, the content of Methanococcus pastoris is 5-12 wt%, the content of Methanobacterium curvatureum is 5-12 wt%, and the content of psychrothermic methanogens is 5-12 wt%.

[0040] In this invention, preferably, the formaldehyde-degrading bacteria can be *Oligotrophomonas*, *Microbacterium oxysporum*, and *Achromobacterium*. The mass ratio of *Oligotrophomonas*, *Microbacterium oxysporum*, and *Achromobacterium* can be 1:1-3:1-3, more preferably 1:1-1.5:1-1.5.

[0041] In a preferred embodiment of the present invention, when the formaldehyde-degrading bacteria are oligotrophic trophozoites, microbacteria oxidans, and achromobacteria, and are used in the above proportions, the essence is to construct a highly efficient, stable, and self-regulating ecosystem. This ecosystem can achieve functional complementarity, cover the complete degradation pathway, relieve metabolic inhibition, improve overall efficiency, enhance system stability and resistance to shock loads, and form a stable biological community structure. This results in faster formaldehyde removal rate, higher treatment efficiency, more thorough degradation, better effluent quality, faster system start-up, stronger recovery ability, more stable operation, and enhanced anti-interference ability.

[0042] In this invention, preferably, in step (3), the ozone catalyst for ozone catalytic oxidation can be a supported ozone catalyst.

[0043] In this invention, preferably, the active component of the supported ozone catalyst can be a metal oxide, more preferably at least one of iron oxide, manganese oxide and cerium oxide.

[0044] In this invention, preferably, the molar ratio of iron oxide, manganese oxide and cerium oxide in the supported ozone catalyst, calculated as metal elements, can be 2-6:3-8:1, more preferably 3-5:4-6:1.

[0045] In this invention, preferably, the support for the supported ozone catalyst can be at least one of modified activated carbon, molecular sieve, and alumina, more preferably modified activated carbon. The modified activated carbon can be carboxyl-modified activated carbon.

[0046] In a preferred embodiment of the present invention, the carboxyl-modified activated carbon can be modified with methods commonly used in the art, such as oxidation modification.

[0047] In this invention, preferably, the average pore size of the modified activated carbon can be 1-10 nm, more preferably 2-5 nm.

[0048] In this invention, preferably, the modified activated carbon has a specific surface area ≥ 1000 m². 2 / g, more preferably 1200-2000m 2 / g.

[0049] In this invention, preferably, based on the total mass of the supported ozone catalyst, the loading of the active component of the supported ozone catalyst can be 0.1-2 wt%, more preferably 0.7-1 wt%; the content of the support of the supported ozone catalyst can be 98-99.9 wt%, more preferably 99-99.3 wt%.

[0050] In this invention, preferably, the amount of ozone used is 10-200 mg, more preferably 80-120 mg, for 1 L of wastewater treated in step (2).

[0051] In this invention, preferably, the conditions for ozone catalytic oxidation may include: a temperature of 15-35°C, more preferably 22-27°C; and a time of 0.1-5h, more preferably 0.5-1h.

[0052] In a preferred embodiment of the present invention, using the above-mentioned ozone catalyst for ozone catalytic oxidation can significantly improve ozone utilization efficiency and oxidation capacity, transforming ozone oxidation from selective oxidation (ozone molecules mainly attack unsaturated bonds and specific functional groups) to non-selective oxidation (·OH can almost indiscriminately attack the vast majority of organic matter), increasing oxidation capacity by more than an order of magnitude. This means that with the same ozone dosage, COD removal rate is significantly improved. It can achieve efficient, economical, and selective removal of the most difficult-to-degrade and most stable toxic pollutants in wastewater.

[0053] In this invention, preferably, the anaerobic biological treatment method may further include: collecting the biogas produced after anaerobic biological treatment into a biogas stabilizing cabinet for resource utilization or incineration.

[0054] In this invention, preferably, the waste gas generated from the pre-conditioning and aerobic treatment, after desulfurization, can be co-incinerated with the biogas generated from the anaerobic biological treatment.

[0055] In this invention, preferably, the methionine production wastewater may include a COD content of 10 × 10⁻⁶. 4 -20×10 4 mg / L, more preferably 12×10 mg / L, can be used. 4 -16×10 4 mg / L; TN content can be 400-600 mg / L, more preferably 450-550 mg / L; formaldehyde content can be 12×10 mg / L. 3 -25×10 3 mg / L, more preferably 16×10 mg / L, can be used. 3 -24×10 3 mg / L.

[0056] The methionine production wastewater of this invention has high concentrations of pollutants such as COD and TN, and contains biotoxic compounds such as formaldehyde. The treatment method for methionine production wastewater of this invention can better degrade the methionine production wastewater and reduce the total amount of pollutants discharged.

[0057] In this invention, preferably, the pH of the methionine production wastewater can be 1-2.

[0058] The second aspect of this invention applies the processing method described in the first aspect to the production of methionine.

[0059] The present invention will be described in detail below through embodiments. The following embodiments: *Oligotrophomonas* was purchased from the Shanghai Microbiological Culture Collection Center (SHMCC), strain number D17292; *Microbacterium oxysporum* was purchased from the Shanghai Microbiological Culture Collection Center (SHMCC), strain number D11000; *Achromobacterium* was purchased from the Shanghai Microbiological Culture Collection Center (SHMCC), strain number D50689; *Bacillus circulans* was purchased from Lian Shi Ge (Wuhan) Life Science Technology Co., Ltd., brand name: *Grey Algae Biotechnology*, model number: HZB359715; *Bacillus cereus* was purchased from Shanghai Xuanya Biotechnology Co., Ltd., catalog number: XY-WSW-1007; *Bacillus subtilis* was purchased from Shanghai Gandu Environmental Engineering Co., Ltd., model number: GANDUEW-BAC; *Symplocos sulfadiazine* was purchased from the Shanghai Microbiological Culture Collection Center (SHMCC), catalog number: DSM. 16706; Clostridium beyerridis was purchased from Shanghai Microbiological Culture Collection Center (SHMCC), product number D50340; Methanococcus pastoris was purchased from Shanghai Microbiological Culture Collection Center (SHMCC), product number D25118; Methanobacterium curvatureum was purchased from Ruichu Biotechnology (Jiangsu) Co., Ltd., product specification SHMCC D72265; Psychrothermic methanophobic spirochetes were purchased from Shanghai Microbiological Culture Collection Center (SHMCC), product number D72241.

[0060] COD parameters were measured using the dichromate method (HJ828-2017) for the determination of chemical oxygen demand in water.

[0061] The laboratory pH meter is a commercially available product from METTLER TOLEDO.

[0062] The TN parameter was measured by the method of "Alkaline potassium persulfate ultraviolet spectrophotometry" (HJ 636-2012).

[0063] Formaldehyde parameters were determined using the acetylacetone spectrophotometric method (HJ 601-2011).

[0064] Example 1 For acrylic acid wastewater from a methionine manufacturer, the treatment capacity is 500L / h, the pH is 1-2, the influent COD content is 150000mg / L, the TN content is 465mg / L, and the formaldehyde content is 24000mg / L.

[0065] Phase 1: On-site addition of microbial inoculum and sludge acclimatization (1) On-site application Formaldehyde-degrading bacteria: The mass ratio of Oligotrophozoites, Microbacterium oxysporum, and Achromobacterium was 1:1:1.

[0066] Dosage: Total amount of anaerobic inoculated sludge × (2‰).

[0067] Dosage method: Injected into the bottom of the reactor through a sludge circulation pump, mixed with the returned sludge, and aerated with a trace amount of biogas (CH4≥50%) to promote bacterial colonization.

[0068] Dosing time: Start adding when the COD of the anaerobic reactor influent reaches 50% of the design value, and continue adding for 3 days.

[0069] Anaerobic complex bacteria: Based on the total mass of the anaerobic complex bacteria, the content of Bacillus circulans is 10 wt%, the content of Bacillus cereus is 10 wt%, the content of Bacillus subtilis is 10 wt%, the content of Bacillus sulfate-reducing bacteria is 20 wt%, the content of Clostridium beyerii is 22 wt%, the content of Methanococcus pastoris is 8 wt%, the content of Methanobacter flexuralis is 10 wt%, and the content of psychrothermic methanogens is 10 wt%.

[0070] Dosage: Total amount of anaerobic inoculated sludge × (2‰).

[0071] Dosing method: The water is injected evenly into the reactor through the inlet pipe and the water distribution system.

[0072] Dosing time: 24 hours after the formaldehyde-degrading bacteria are added, add in 3 times within 3 days.

[0073] (2) Sludge acclimatization Anaerobic system: Concentration of activated sludge in the anaerobic system: 10000 mg / L.

[0074] Initial sludge load: 0.05 kg COD / (kg VSS•d).

[0075] Load increase: When the COD and formaldehyde removal rates are stable at over 80% and there is no significant accumulation of VFA (volatile fatty acids), the influent load can be gradually increased (by 20% each time) until the design load (0.15 kg COD / (kg VSS•d)) is reached.

[0076] Source of microbial strain: anaerobic digested sludge from food processing wastewater treatment, with an inoculum concentration of 3000 mg / L.

[0077] Supplementation of microbial inoculum: If VFA accumulation > 1500 mg / L, suspend increasing the load and supplement with 1‰ of the total anaerobic inoculum sludge volume of anaerobic compound bacteria. If formaldehyde removal rate < 80%, supplement with 1‰ of the total anaerobic inoculum sludge volume of formaldehyde-degrading bacteria.

[0078] Aerobic system: Concentration of activated sludge in the aerobic system: 3000 mg / L.

[0079] Source of microbial strain: residual sludge from the aerobic treatment system of an urban wastewater treatment plant, with an inoculum concentration of 1000 mg / L.

[0080] Starting sludge load: The starting activated sludge load in the aerobic tank is 0.05 kg COD / (kg VSS•d).

[0081] Load increase: When the COD removal rate stabilizes at 60% or above, the influent load can be gradually increased (by 20% each time) until the design load (0.2 kg COD / (kg VSS•d)) is reached.

[0082] After the sludge acclimation of the second-stage anaerobic and aerobic systems is completed and all other unit equipment is debugged, the entire system will operate according to the following steps: (1) Acrylic acid wastewater is pumped to the anaerobic preconditioning tank (in case of an accident, acrylic acid wastewater is stored in the accident tank and then slowly sent to the anaerobic preconditioning tank for treatment in small amounts). It is mixed with the supernatant effluent from the secondary sedimentation tank after aerobic treatment and added with trace elements, nutrients and steam (the content of trace elements in acrylic acid wastewater is 0.003wt% and the content of nutrients is 0.015wt%). The pH is adjusted to 7.5 and the water temperature is adjusted to 37℃ to meet the influent conditions of the anaerobic reactor.

[0083] (2) The acrylic acid wastewater with adjusted water quality and temperature is pumped to the anaerobic reactor. Most of the organic matter in the wastewater is degraded by anaerobic microorganisms and converted into biogas, which is collected in the biogas stabilizing cabinet. A small portion of the biogas is used as fuel for incineration of waste gas generated during the wastewater treatment process, and the excess biogas is sent to the plant for utilization. The effluent from the anaerobic reactor flows by gravity into the sedimentation tank. The sedimentation tank can settle the anaerobic particulate sludge carried with the wastewater and return it to the anaerobic reactor (all solid phase is returned, and the liquid phase is returned at a volume ratio of 1:25). The effluent from the sedimentation tank is pumped to the multi-effect aeration tower.

[0084] (3) The wastewater is cooled to about 30°C by the multi-effect aeration tower and undergoes a pre-aerobic reaction in the tower. The filling rate of the packing material (multi-faceted hollow ball packing) in the tower is 25 vol.

[0085] (4) The effluent from the multi-effect aeration tower flows by gravity into the aerobic tank (temperature in the aerobic tank is 30℃, pH is 7.5). Aerators are installed in the aerobic tank for aeration supply (dissolved oxygen in the aerobic tank is 2.5mg / L). MBBR packing is added to the aerobic tank, and the volume of the packing accounts for 35 vol% of the total volume of the aerobic tank. The sludge-water mixture in the aerobic tank flows by gravity into the secondary sedimentation tank for solid-liquid separation. Part of the separated sludge is returned to the aerobic tank at a sludge return ratio of 100 vol%. The remaining sludge is discharged to the sludge treatment system. Part of the supernatant from the secondary sedimentation tank is returned to step (1) (return ratio is 1:8). Part of the supernatant is returned to the aerobic tank at a return ratio of 200 vol%. The remaining supernatant is pumped to the ozone catalytic oxidation device.

[0086] (5) The ozone catalytic oxidation device (temperature 25℃, residence time 0.8h) distributes water from bottom to top. In this device, ozone is used as the oxidant (ozone dosage is 100mg / L). The gas is distributed from bottom to top and flows through the solid catalyst (based on the total mass of the solid catalyst, the loading of the active component is 1wt%, and the content of the support is 99wt%; carboxyl-modified activated carbon is used as the support, and iron tetroxide, manganese dioxide and cerium dioxide are used as the active components in a molar ratio of 4:5:1; the average particle size of the solid catalyst is 4nm and the specific surface area is 1500m²). 2 The hydroxyl radicals (•OH) generated by the hydroxyl radicals ( / g) oxidize and remove organic matter from the water. The concentrations of COD, TN, and formaldehyde in the treated effluent are shown in Table 1.

[0087] Example 2 The methionine production wastewater was treated according to the method in Example 1, except that in step (4) of the second stage, the supernatant was returned to step (1) at a reflux ratio of 1:3, and the supernatant was returned to the aerobic tank at a reflux ratio of 100 vol%.

[0088] Example 3 The methionine production wastewater was treated according to the method in Example 1, except that in step (4) of the second stage, part of the sludge separated from the secondary sedimentation tank was returned to the aerobic tank, and the sludge return ratio was 200 vol.

[0089] Example 4 The methionine production wastewater was treated according to the method in Example 1, except that in step (4) of the second stage, part of the sludge separated from the secondary sedimentation tank was returned to the aerobic tank, and the sludge return ratio was 50 vol.

[0090] Example 5 The method for treating methionine production wastewater according to Example 1 differs in that, in the first stage of on-site addition, formaldehyde-specific degrading bacteria are added in a mass ratio of 1:3:3 for Oligotrophosomes, Microbacterium hydrogenation, and Achromobacterium.

[0091] Example 6 The method for treating methionine production wastewater according to Example 1 differs in that, in the first stage of on-site addition, only Oligotrophozoites and Microbacterium oxysporum are added to the formaldehyde-specific degrading bacteria at a mass ratio of 1:1.

[0092] Example 7 The method for treating methionine production wastewater according to Example 1 differs in that, in the first stage of on-site addition, based on the total mass of the anaerobic complex bacteria, the content of Bacillus circularis is 3.5 wt%, Bacillus cereus is 35 wt%, Bacillus subtilis is 22 wt%, Bacillus sulfate-reducing bacteria is 7 wt%, Clostridium beyerii is 7 wt%, Methanococcus pastoris is 3.5 wt%, Methanobacterium curvatureum is 3 wt%, and Methanophora psychrophila is 19 wt%.

[0093] Example 8 The method for treating methionine production wastewater according to Example 1 differs in that, in the first stage of on-site addition, Clostridium beyerridis, Methanococcus pastoris, Methanobacterium flexures, and Methanophora psychrophila are not added to the anaerobic compound bacteria; specifically, based on the total mass of the anaerobic compound bacteria, the content of Bacillus circulans is 35 wt%, the content of Bacillus cereus is 35 wt%, the content of Bacillus subtilis is 10 wt%, and the content of Bacillus sulfate-reducing synergists is 20 wt%.

[0094] Comparative Example 1 The methionine production wastewater was treated according to the method in Example 1, except that in step (4) of the second stage, the supernatant from the secondary sedimentation tank was not returned to step (1).

[0095] Comparative Example 2 The methionine production wastewater was treated according to the method in Example 1, except that in step (4) of the second stage, the supernatant from the secondary sedimentation tank was not returned to the aerobic tank.

[0096] Comparative Example 3 The methionine production wastewater was treated according to the method in Example 1, except that in step (4) of the second stage, the supernatant was refluxed back to step (1) at a reflux ratio of 1:20.

[0097] Table 1

[0098] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating methionine production wastewater, characterized in that, The processing method includes: (1) The methionine production wastewater is pre-treated and then subjected to anaerobic biological treatment; wherein, after solid-liquid separation of the effluent after anaerobic biological treatment, the solid phase is completely recycled for anaerobic biological treatment, and the liquid phase is recycled for anaerobic biological treatment at a recycling volume ratio of 1:20-30. (2) The wastewater treated in step (1) is subjected to aerobic treatment; wherein, the mixture after aerobic treatment is settled to obtain supernatant and sludge layer, part of the supernatant is refluxed at a reflux ratio of 100-400 vol% for aerobic treatment, part of the supernatant is refluxed at a reflux ratio of 1:2-15 for methionine production wastewater pretreatment, and the sludge layer is refluxed at a reflux ratio of 50-200 vol% for aerobic treatment; (3) The wastewater treated in step (2) is subjected to ozone catalytic oxidation.

2. The processing method according to claim 1, wherein, The pre-adjustment method includes: mixing methionine production wastewater with trace elements, nutrients and optional water, and adjusting the pH to 6-9; Preferably, the content of trace elements in the pre-treated methionine production wastewater is 0.001-0.01 wt%, more preferably 0.003-0.006 wt%; the content of nutrients is 0.005-0.02 wt%, more preferably 0.008-0.015 wt%. Preferably, the trace element is selected from at least one of nickel, cobalt, molybdenum, zinc, manganese, and copper; Preferably, the nutrient salt is selected from phosphate salts and / or calcium salts.

3. The processing method according to claim 1 or 2, wherein, The anaerobic biological treatment method includes: mixing pre-treated methionine production wastewater with activated sludge, anaerobic compound bacteria and formaldehyde-degrading bacteria in an anaerobic tank; Preferably, the concentration of the activated sludge in the anaerobic tank is 5000-40000 mg / L, more preferably 9000-12000 mg / L; Preferably, the activated sludge loading in the anaerobic tank is 0.03-0.3 kg COD / (kg VSS•d), more preferably 0.05-0.18 kg COD / (kg VSS•d); Preferably, the amount of formaldehyde-degrading bacteria is 1-3 wt‰ of the activated sludge, more preferably 1.5-2.5 wt‰; Preferably, the dosage of the anaerobic compound bacteria is 1-3 wt‰ of the activated sludge, more preferably 1.5-2.5 wt‰; And / or, the conditions for the anaerobic biological treatment include: a temperature of 30-40°C, preferably 35-38°C; and a pH value of 6-9.

4. The processing method according to claim 1, wherein, In step (2), the aerobic treatment method includes: oxygenating the wastewater and mixing it with activated sludge in an aerobic tank containing suspended packing material; Preferably, the oxygenation process results in a dissolved oxygen content of 1.5-4 mg / L in the aerobic tank of step (2), more preferably 2-3 mg / L. Preferably, the volume of the suspended packing material accounts for 20-50 vol% of the total volume of the aerobic tank; more preferably, it is 25-35 vol%. Preferably, the concentration of activated sludge in the aerobic tank is 2500-5000 mg / L, more preferably 3000-4000 mg / L; Preferably, the activated sludge loading in the aerobic tank is 0.05-0.3 kgCOD / (kgVSS•d), more preferably 0.1-0.2 kgCOD / (kgVSS•d); And / or, the reflux ratio for aerobic treatment of the sludge layer is 100-150 vol%. And / or, the reflux ratio for aerobic treatment of the supernatant is 200-300 vol%. And / or, the conditions for the aerobic treatment include: a temperature of 15-37°C, preferably 30-35°C; and a pH value of 6-9.

5. The processing method according to claim 3, wherein, The anaerobic complex bacteria are at least one of Bacillus circularis, Bacillus cereus, Bacillus subtilis, Bacillus sulfate-reducing bacteria, Clostridium beyerii, Methanococcus pastoris, Methanobacterium flexuralis, and Methanophora psychrophila. And / or, the formaldehyde-degrading bacteria are at least one of oligotrophic phytotrophs, microbacterium oxidans, and achromobacterium.

6. The processing method according to claim 5, wherein, Based on the total mass of the anaerobic complex bacteria, the content of *Bacillus circulans* is 3.5-35 wt%, *Bacillus cereus* is 3.5-35 wt%, *Bacillus subtilis* is 3.5-35 wt%, *Symplocos rubrum* is 7-40 wt%, *Clostridium beyerridis* is 7-40 wt%, *Methanococcus pastoris* is 3-25 wt%, *Methanobacterium flexures* is 3-25 wt%, and *Methanophora psychrophila* is 3-25 wt%. Preferably, based on the total mass of the anaerobic complex bacteria, the content of *Bacillus circulans* is 5-18 wt%, the content of *Bacillus cereus* is 5-18 wt%, the content of *Bacillus subtilis* is 5-18 wt%, the content of *Symplocos rubrum* is 15-32 wt%, the content of *Clostridium beyerridis* is 15-32 wt%, the content of *Methanococcus pastoris* is 5-12 wt%, the content of *Methanobacterium flexures* is 5-12 wt%, and the content of *Methanococcus pyogenes* is 5-12 wt%. And / or, the mass ratio of the oligotrophic phytospira, microbacterium oxysporum, and achromobacterium is 1:1-3:1-3, more preferably 1:1-1.5:1-1.

5.

7. The processing method according to claim 1, wherein, In step (3), the ozone catalyst for ozone catalytic oxidation is a supported ozone catalyst; Preferably, the active component of the supported ozone catalyst is a metal oxide, more preferably at least one of iron oxide, manganese oxide and cerium oxide; Preferably, the support for the supported ozone catalyst is at least one of modified activated carbon, molecular sieve and alumina, more preferably modified activated carbon; Preferably, based on the total mass of the supported ozone catalyst, the loading of the active component in the supported ozone catalyst is 0.1-2 wt%, more preferably 0.7-1 wt%; and the content of the support in the supported ozone catalyst is 98-99.9 wt%, more preferably 99-99.3 wt%. And / or, equivalent to 1L of wastewater treated in step (2), wherein the amount of ozone used is 10-200mg, preferably 80-120mg; And / or, the conditions for ozone catalytic oxidation include: a temperature of 15-35°C, preferably 22-27°C; and a time of 0.1-5 h, preferably 0.5-1 h.

8. The processing method according to claim 7, wherein, The molar ratio of iron oxide, manganese oxide and cerium oxide in the supported ozone catalyst, calculated as metal elements, is 2-6:3-8:1, more preferably 3-5:4-6:1; Preferably, the modified activated carbon is carboxyl-modified activated carbon. Preferably, the modified activated carbon has an average pore size of 1-10 nm, more preferably 2-5 nm; Preferably, the modified activated carbon has a specific surface area ≥ 1000 m². 2 / g, more preferably 1200-2000m 2 / g.

9. The processing method according to claim 1, wherein, The anaerobic biological treatment method further includes: collecting the biogas produced after anaerobic biological treatment into a biogas pressure stabilizing cabinet for resource utilization or incineration. And / or, the methionine production wastewater includes wastewater with a COD content of 10 × 10⁻⁶. 4 -20×10 4 mg / L, preferably 12×10 mg / L 4 -16×10 4 mg / L; TN content is 400-600 mg / L, preferably 450-550 mg / L; formaldehyde content is 12×10 mg / L. 3 -25×10 3 mg / L, preferably 16×10 mg / L 3 -24×10 3 mg / L.

10. The application of the processing method according to any one of claims 1-9 in the production of methionine.

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