Biochemical treatment process for high-salinity wastewater

Abstract

The invention relates to the technical field of wastewater treatment, and discloses a biochemical treatment process for high-salinity wastewater. According to the process, a composite flocculation pretreatment and anoxic, aerobic and precipitation synergistic technology is adopted, pollutants are deeply captured through a composite flocculant, and a salt-tolerant biochemical system is constructed by utilizing a modified carbon source and enzyme sustained-release microspheres. According to the composite flocculant, the pollutant adsorption capacity in a high-salt environment is improved through a multi-stage cross-linked structure; in the anoxic section, a slow-release carbon source and a biological woven filler are used for synergistically enhancing denitrification; in the aerobic section, the activity stability of nitroenzyme is guaranteed through triple-coated enzyme microspheres; in the treatment process, the partition plate separation type reaction tank and the gas stripping sludge backflow device are integrated, and efficient circulation and solid-liquid separation of activated sludge are achieved. The process effectively solves the problems of high biochemical inhibition efficiency by high salt, high cost of a traditional physicochemical method and sludge bulking, remarkably improves the COD and nitrogen removal rate, reduces the energy consumption and secondary pollution risk, and is suitable for high-salt wastewater treatment in chemical industry, pharmacy and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more particularly to a biochemical treatment process for high-salt wastewater. Background Art

[0002] High-salt wastewater generated during industrial production processes such as chemical, pharmaceutical, and printing and dyeing processes generally has a salinity of ≥1%. Its high osmotic pressure and strong ionic strength pose significant challenges to traditional biochemical treatment processes. The complex pollutant composition and poor water quality conditions of this type of wastewater can easily lead to dehydration and inactivation of microbial cells and dysfunction of the enzyme system, which in turn causes problems such as decreased metabolic activity of activated sludge, sludge bulking, and biofilm shedding. This results in a significant reduction in chemical oxygen demand and nitrogen removal efficiency, seriously affecting the stable operation of the treatment system. Existing physicochemical pretreatment technologies such as evaporative crystallization and advanced oxidation can alleviate the inhibitory effect of salinity on the biochemical system to a certain extent, but they generally have disadvantages such as excessive energy consumption per ton of water, excessive dosage of chemicals, and the easy generation of toxic byproducts. In addition, the removal effect on dissolved organic nitrogen is limited, making it difficult to meet the water quality requirements of subsequent biochemical treatment.

[0003] Conventional solutions to improve the salt tolerance of biochemical systems mainly rely on halophilic bacteria inoculation or carbon source modification, but these methods have multiple drawbacks: traditional iron and aluminum salt flocculants are affected by the "salting-out effect" in high-salt environments, significantly reducing the colloid destabilization efficiency and the ability to capture pollutants; during the anoxic denitrification stage, common carbon sources such as sodium acetate are easily chelated by salt ions, reducing their bioavailability and making it difficult to match the carbon source release rate with denitrification needs; aerobic nitrifying bacteria are sensitive to salinity changes, and the activity of free nitrifying enzymes decays faster in high-salt environments, significantly reducing the ammonia oxidation rate; improper flow control in the reactor can easily lead to short-circuiting, and the solid-liquid separation efficiency of the sedimentation tank is greatly affected by salinity fluctuations, resulting in poor sludge reflux stability and further exacerbating the uncertainty of the biochemical treatment effect. Therefore, the present invention provides a high-salt wastewater biochemical treatment process to solve the above-mentioned technical problems. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a biochemical treatment process for high-salt wastewater, which effectively solves the problems of high salt inhibiting biochemical efficiency, high cost of traditional physicochemical methods and sludge bulking, significantly improves COD and nitrogen removal rates, reduces energy consumption and secondary pollution risks, and is suitable for the treatment of high-salt wastewater in chemical, pharmaceutical and other industries.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A biochemical treatment process for high-salt wastewater comprises the following steps:

[0007] S1. Adjust the pH of high-salt wastewater to 6.5-7.0, add 150-250 mg / L of composite flocculant, and stir at 140-160 r / min for 30-40 min to obtain pretreated wastewater;

[0008] S2, pre-treated wastewater and return sludge with a return ratio of 75-85% are mixed in the top return tank and then flow into the anoxic tank, filled with 40-45% biological braided rope filler, added with 300-400 mg / L modified carbon source, stirred at 50-60 r / min, controlled water temperature at 25-30 ° C, and hydraulic retention time of 5-7 h;

[0009] S3. The sewage flows into the aerobic tank, which is filled with biological braided rope fillers and 30-50g / m³ of enzyme slow-release microspheres. The dissolved oxygen is controlled at 2.0-4.0mg / L, the hydraulic retention time is 10-14h, and the air-water ratio is (12-18):1;

[0010] S4. Aerobic effluent flows into the sedimentation tank through the triangular channel, and solid-liquid separation is achieved through the inclined tube filler. The activated sludge is returned to the anoxic tank through the bottom sludge return trough and micro-perforated pipe air lift. The clean water flows out through the triangular effluent weir.

[0011] Preferably, the preparation steps of the composite flocculant in step S1 are:

[0012] A1. Dissolve chitosan and sodium 2-acrylamide-2-methylpropanesulfonate in deionized water, add cerium nitrate, and polymerize under magnetic stirring at 58-62°C in a nitrogen atmosphere for 3-5 hours to obtain a copolymer solution.

[0013] A2. Ultrasonic dispersion of ZIF-8 in ethanol, dropwise addition of copolymer solution, addition of glutaraldehyde, cross-linking reaction at 45-55°C for 1-3h, freeze-drying, and pulverization to 15-18μm to obtain a composite flocculant.

[0014] Preferably, in step A1, the components by weight include 8-12 parts of chitosan, 13-17 parts of sodium 2-acrylamide-2-methylpropanesulfonate, 90-100 parts of deionized water, and 0.7-0.8 parts of cerium nitrate; and in step A2, the components by weight include 4-6 parts of ZIF-8, 35-40 parts of ethanol, and 4-6 parts of glutaraldehyde.

[0015] Preferably, the preparation steps of the modified carbon source in step S2 are as follows: by weight, 28-32 parts of γ-polyglutamic acid and 9-11 parts of trehalose are dissolved in 100-110 parts of deionized water, 2-4 parts of salt-tolerant denitrifying bacteria freeze-dried powder are added, ultrasonic dispersion is performed, and then spray-dried to obtain 40-60 μm particles; 18-22 parts of dimethylaminoethyl methacrylate, 9-11 parts of butyl methacrylate and 0.4-0.6 parts of azobisisobutyronitrile are mixed, polymerized in a water bath at 55-60° C. for 3-5 hours, added to the particles, stirred and coated, and sieved after cooling to obtain a 24-30 μm modified carbon source.

[0016] Preferably, the preparation steps of the enzyme-activated sustained-release microspheres in step S3 are:

[0017] (1) Dissolve salt-tolerant protease and trehalose in deionized water, add 4-6 wt% sodium silicate solution, add 0.2-0.25 M CaCl2 solution dropwise, adjust the pH to 8-10, react at room temperature for 1-3 h, and then centrifuge and wash to obtain a composite core;

[0018] (2) Dispersing N-isopropylacrylamide and acrylic acid in deionized water, adding potassium persulfate, composite core and sodium lignin sulfonate, polymerizing at a constant temperature of 55-60°C for 1-2 hours under nitrogen protection, and then centrifuging and washing to obtain microspheres;

[0019] (3) The microspheres were immersed in a mixed aqueous solution containing 1-3 wt% sodium alginate and 0.9-1.2 wt% polyethyleneimine for 9-11 min, and evenly sprayed with 0.4-0.6 M magnesium chloride solution. The microspheres were dried at room temperature to obtain enzyme-released microspheres.

[0020] Preferably, in step (1), the components by weight are 9-11 parts of salt-tolerant protease, 18-22 parts of trehalose, 95-100 parts of deionized water, 48-52 parts of sodium silicate solution and 95-100 parts of CaCl2 solution.

[0021] Preferably, in step (2), the components by weight are 6-10 parts of N-isopropylacrylamide, 1-3 parts of acrylic acid, 90-100 parts of deionized water, 0.2-0.4 parts of potassium persulfate, 18-22 parts of composite core and 9-11 parts of sodium lignin sulfonate.

[0022] Preferably, in step (3), the components are 20-25 parts by weight of microspheres, 70-80 parts by weight of a mixed aqueous solution of sodium alginate and polyethyleneimine, and 8-12 parts by weight of a magnesium chloride solution.

[0023] Preferably, the anoxic tank, aerobic tank, sludge return tank and sedimentation tank in the high-salt wastewater biochemical treatment process are separated by partitions, a sewage flow channel is provided at the bottom of the partition between the anoxic tank and the aerobic tank, and the aerobic tank is connected to the sedimentation tank through a triangular channel.

[0024] Preferably, in the high-salt wastewater biochemical treatment process, inclined plate fillers are provided in the sedimentation tank for sludge sedimentation, and the sludge return tank is equipped with micro-perforated tubes for air stripping and reflowing activated sludge, and the air source of the air stripping method is provided by a blower.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The multi-stage cross-linked flocculant constructed based on chitosan, sulfonate copolymer and metal organic framework utilizes the synergistic effects of cationic bridging, coordination bonding and porous adsorption to effectively overcome the "salting out effect" in high-salt environments, enhance the ability of colloid destabilization and pollutant capture, reduce the toxic load of subsequent biochemical stages from the source, and completely solve the problem of attenuation of the bridging ability of traditional flocculants in high-salt environments.

[0027] 2. The present invention utilizes a synergistic mechanism of slow-release carbon sources and bio-woven fillers in the anoxic zone to enhance denitrification. The modified carbon source uses γ-polyglutamic acid and trehalose to encapsulate salt-tolerant denitrifying bacteria, and the outer layer is copolymerized with methacrylate monomers to form a pH-responsive slow-release shell. This core-shell structure isolates the direct toxicity of salt ions on microorganisms and precisely regulates the kinetics of carbon source release. Combined with the micro-aerobic biofilm microenvironment created by the bio-woven filler, it significantly enhances the metabolic activity and denitrification efficiency of denitrifying bacteria under high-salt conditions, fundamentally overcoming the bioavailability limitations of conventional carbon sources caused by salt ion chelation.

[0028] 3. The present invention ensures nitrification stability through a triple protection system of enzyme slow-release microspheres in the aerobic section. The inorganic protective core of the salt-tolerant protease is formed by the gelation reaction of sodium silicate and calcium chloride, and then the enzyme molecules are flexibly encapsulated by thermosensitive hydrogel, and finally coated with sodium alginate and polyethyleneimine polyelectrolyte membrane. This slow-release structure effectively prolongs the activity maintenance time of nitrification enzyme in a salinity fluctuation environment, avoids the rapid inactivation and frequent addition of free enzymes, ensures the efficient and stable operation of the ammonia nitrogen oxidation process, and significantly improves the nitrification reaction efficiency; the optimized design of the reactor configuration serves as an auxiliary link in the process integration, and the synergistic effect of the baffle flow channel and the air stripping reflux device realizes the efficient circulation of activated sludge, providing a guarantee for the stable operation of each treatment unit. The whole process synergizes chemical pretreatment with biological reaction, significantly improves COD and nitrogen removal rate, reduces the dosage of reagents and energy consumption, reduces the risk of secondary pollution, and provides a solution with significant technical advantages for the industrial treatment of high-salt wastewater in chemical, pharmaceutical and other industries. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used are purchased from conventional biochemical reagent stores unless otherwise specified. The quantitative experiments in the following examples were all repeated three times, and the data are the average or mean ± standard deviation of the three repeated experiments.

[0031] Biological braided rope filler, purchased from Yixing Jingtian Environmental Protection Technology Co., Ltd., model JT-009;

[0032] ZIF-8 was purchased from Shanghai Koraman Reagent Co., Ltd., catalog number 095718;

[0033] γ-Polyglutamic acid was purchased from Shenzhen Lefu Biotechnology Co., Ltd.;

[0034] Polyethyleneimine, purchased from Shandong Haizhou Bioengineering Co., Ltd., CAS No. 9002-98-6;

[0035] Salt-tolerant protease was purchased from Shandong Sukehan Bioengineering Co., Ltd.

[0036] Salt-tolerant denitrifying bacteria freeze-dried powder was purchased from Unico (Shanghai) Life Sciences Co., Ltd., product number YLK-jz4573.

[0037] Example 1

[0038] A biochemical treatment process for high-salt wastewater comprises the following steps:

[0039] S1. Take high-salt wastewater and adjust the pH to 6.5, add 150 mg / L of composite flocculant, and stir at 140 r / min for 40 min to obtain pretreated wastewater;

[0040] The preparation steps of the composite flocculant are as follows:

[0041] A1. Weigh 8 parts of chitosan and 13 parts of sodium 2-acrylamide-2-methylpropanesulfonate, dissolve them in 90 parts of deionized water, add 0.7 parts of cerium nitrate, and polymerize them at 58°C under nitrogen protection with magnetic stirring at a stirring speed of 300 r / min for 5 hours to obtain a copolymer solution;

[0042] A2. Disperse 4 parts of ZIF-8 in 35 parts of ethanol and treat with ultrasound at 40 kHz for 30 minutes. Add the dispersion dropwise to the copolymer solution within 25 minutes. Add 4 parts of glutaraldehyde and react at 45°C for 3 hours with stirring. After completion of the reaction, freeze-dry and crush to 18 μm to obtain a composite flocculant.

[0043] S2: The wastewater pretreated in S1 was mixed with 75% of the return sludge in the return tank and then entered the anoxic tank. The tank was filled with 40% of biological braided rope filler and 300 mg / L of modified carbon source was added. The water temperature was controlled at 25°C, the stirring speed was 60 r / min, and the hydraulic retention time was 7 h.

[0044] The preparation steps of the modified carbon source are as follows: 28 parts of γ-polyglutamic acid and 9 parts of trehalose are dissolved in 100 parts of deionized water, 2 parts of salt-tolerant denitrifying bacteria freeze-dried powder are added, and ultrasonic dispersion is performed at 40kHz for 30 minutes. The dispersed mixture is spray-dried to obtain 60μm particles; 18 parts of dimethylaminoethyl methacrylate, 9 parts of butyl methacrylate, and 0.4 parts of azobisisobutyronitrile are mixed, and polymerized at 55°C for 5 hours at a stirring speed of 280rpm to obtain a coating liquid, the above particles are added to the coating liquid for coating, and crushed and sieved to 30μm to obtain a modified carbon source.

[0045] S3: The wastewater treated in S2 is introduced into the aerobic tank, and the tank is filled with biological braided rope filler of the same specifications as S2, and 30g / m³ of enzyme slow-release microspheres are added. The dissolved oxygen is controlled at 2.0mg / L, the air-water ratio is 12:1, and the hydraulic retention time is 14h;

[0046] The preparation steps of enzyme sustained-release microspheres are as follows:

[0047] (1) 9 parts of salt-tolerant protease and 18 parts of trehalose were dissolved in 95 parts of deionized water, 48 parts of 4 wt% sodium silicate solution were added, 95 parts of 0.2 M CaCl2 solution were added dropwise at a rate of 3 mL / min, the pH was adjusted to 8, and the mixture was stirred at 320 rpm at room temperature for 3 h, followed by centrifugation and washing to obtain a composite core;

[0048] (2) 6 parts of N-isopropylacrylamide and 1 part of acrylic acid were dispersed in 90 parts of deionized water, 0.2 parts of potassium persulfate, 18 parts of the above composite core, and 9 parts of sodium lignin sulfonate were added, and the mixture was polymerized at 55°C for 2 hours under nitrogen protection, and then centrifuged and washed to obtain microspheres;

[0049] (3) Take 20 parts of the above microspheres, immerse them in 70 parts of a mixed aqueous solution containing 1 wt% sodium alginate and 0.9 wt% polyethyleneimine for 11 minutes, take them out and evenly spray them with 8 parts of 0.4 M magnesium chloride solution, dry them at room temperature, and then crush and sieve to 25 μm to obtain enzyme sustained-release microspheres.

[0050] S4: The effluent treated by S3 is introduced into the sedimentation tank through a triangular channel. The sludge at the bottom of the sedimentation tank is returned to the return tank of S2 through the sludge return tank by air lift. The clean water flows out through the triangular weir and the sludge concentration is controlled to be maintained at 6000 mg / L.

[0051] Example 2

[0052] A biochemical treatment process for high-salt wastewater comprises the following steps:

[0053] S1. Take high-salt wastewater, adjust the pH to 6.8, add 160 mg / L of composite flocculant, and stir at 150 r / min for 38 min to obtain pretreated wastewater;

[0054] The preparation steps of the composite flocculant are as follows:

[0055] A1. Weigh 9 parts of chitosan and 14 parts of sodium 2-acrylamide-2-methylpropanesulfonate, dissolve them in 95 parts of deionized water, add 0.73 parts of cerium nitrate, and polymerize them at 60°C under nitrogen atmosphere with a stirring speed of 340 r / min for 4.8 h to obtain a copolymer solution;

[0056] A2. Disperse 5 parts of ZIF-8 in 37 parts of ethanol and treat with ultrasound at 45 kHz for 28 minutes. Add the dispersion dropwise to the copolymer solution within 28 minutes. Add 5 parts of glutaraldehyde and react at 48°C for 2.8 hours with stirring. After completion of the reaction, freeze-dry and crush to 17 μm to obtain a composite flocculant.

[0057] S2: The wastewater pretreated in S1 was mixed with 78% return sludge in the return tank and then sent to the anoxic tank. The tank was filled with 42% biological braided rope filler and 320 mg / L modified carbon source was added. The water temperature was controlled at 27°C and the stirring speed was 65 r / min. The hydraulic retention time was 6 h.

[0058] Among them, the preparation steps of the modified carbon source are as follows: 29 parts of γ-polyglutamic acid and 10 parts of trehalose are dissolved in 105 parts of deionized water, 3 parts of salt-tolerant denitrifying bacteria freeze-dried powder are added, and ultrasonic dispersion is performed at 45kHz for 28 minutes. The dispersed mixture is spray-dried to obtain 55μm particles; 19 parts of dimethylaminoethyl methacrylate, 10 parts of butyl methacrylate, and 0.5 parts of azobisisobutyronitrile are mixed, and polymerized at 56°C for 4.8 hours at a stirring speed of 290rpm to obtain a coating liquid, and the above particles are added to the coating liquid for coating, crushed and sieved to 28μm to obtain a modified carbon source.

[0059] S3: The wastewater treated in S2 is introduced into the aerobic tank, which is filled with biological braided rope fillers of the same specifications as S2, and 35g / m³ of enzyme slow-release microspheres are added. The dissolved oxygen is controlled at 2.5mg / L, the air-water ratio is 13:1, and the hydraulic retention time is 13h.

[0060] The preparation steps of enzyme sustained-release microspheres are as follows:

[0061] (1) 10 parts of salt-tolerant protease and 19 parts of trehalose were dissolved in 98 parts of deionized water, 49 parts of 5 wt% sodium silicate solution were added, 98 parts of 0.22 M CaCl2 solution were added dropwise at a rate of 4 mL / min, the pH was adjusted to 9, and the mixture was stirred at 330 rpm at room temperature for 2.8 h, followed by centrifugation and washing to obtain a composite core;

[0062] (2) 7 parts of N-isopropylacrylamide and 2 parts of acrylic acid were dispersed in 95 parts of deionized water, 0.3 parts of potassium persulfate, 19 parts of the above composite core, and 10 parts of sodium lignin sulfonate were added, and the mixture was polymerized at 57°C under nitrogen for 1.8 hours, followed by centrifugation and washing to obtain microspheres;

[0063] (3) Take 23 parts of the above microspheres, immerse them in 73 parts of a mixed aqueous solution containing 2 wt% sodium alginate and 1 wt% polyethyleneimine for 10 min, take them out and evenly spray them with 9 parts of 0.5 M magnesium chloride solution, dry them at room temperature, and then crush and sieve to 23 μm to obtain enzyme sustained-release microspheres.

[0064] S4: The effluent treated by S3 is introduced into the sedimentation tank through a triangular channel. The sludge at the bottom of the sedimentation tank is returned to the return tank of S2 through the sludge return tank by air lift. The clean water flows out through the triangular weir and the sludge concentration is controlled to be maintained at 6300 mg / L.

[0065] Example 3

[0066] A biochemical treatment process for high-salt wastewater comprises the following steps:

[0067] S1. Take high-salt wastewater, adjust the pH to 7.0, add 250 mg / L of composite flocculant, and stir at 160 r / min for 30 min to obtain pretreated wastewater;

[0068] The preparation steps of the composite flocculant are as follows:

[0069] A1. Weigh 12 parts of chitosan and 17 parts of sodium 2-acrylamide-2-methylpropanesulfonate, dissolve them in 100 parts of deionized water, add 0.8 parts of cerium nitrate, and polymerize them at 62°C under nitrogen protection with a stirring speed of 450 r / min for 3h to obtain a copolymer solution;

[0070] A2. Disperse 6 parts of ZIF-8 in 40 parts of ethanol and treat with ultrasound at 55 kHz for 20 minutes. Add the dispersion dropwise to the copolymer solution over 35 minutes. Add 6 parts of glutaraldehyde and react at 55°C for 1 hour with stirring. After completion of the reaction, freeze-dry and crush to 15 μm to obtain a composite flocculant.

[0071] S2: The wastewater pretreated in S1 was mixed with 85% of the return sludge in the return tank and then entered the anoxic tank. The tank was filled with 45% of biological braided rope filler and 400 mg / L of modified carbon source was added. The water temperature was controlled at 30°C, the stirring speed was 75 r / min, and the hydraulic retention time was 5 h.

[0072] Among them, the preparation steps of the modified carbon source are as follows: 32 parts of γ-polyglutamic acid and 11 parts of trehalose are dissolved in 110 parts of deionized water, 4 parts of salt-tolerant denitrifying bacteria freeze-dried powder are added, and ultrasonic dispersion is performed at 60kHz for 20 minutes. The dispersed mixture is spray-dried to obtain 40μm particles; 22 parts of dimethylaminoethyl methacrylate, 11 parts of butyl methacrylate, and 0.6 parts of azobisisobutyronitrile are mixed, and polymerized at 60°C for 3h at a stirring speed of 300rpm to obtain a coating liquid, the above particles are added to the coating liquid for coating, and crushed and sieved to 24μm to obtain a modified carbon source.

[0073] S3: Introduce the wastewater treated in S2 into the aerobic tank, fill the tank with biological braided rope filler of the same specifications as S2, add 50g / m³ enzyme slow-release microspheres, control the dissolved oxygen at 4.0mg / L, the air-water ratio at 18:1, and the hydraulic retention time at 10h;

[0074] The preparation steps of enzyme sustained-release microspheres are as follows:

[0075] (1) 11 parts of salt-tolerant protease and 22 parts of trehalose were dissolved in 100 parts of deionized water, 52 parts of 6 wt% sodium silicate solution were added, 100 parts of 0.25 M CaCl2 solution were added dropwise at a rate of 6 mL / min, the pH was adjusted to 10, and the mixture was stirred at 360 rpm at room temperature for 1 h, followed by centrifugation and washing to obtain a composite core;

[0076] (2) 10 parts of N-isopropylacrylamide and 3 parts of acrylic acid were dispersed in 100 parts of deionized water, 0.4 parts of potassium persulfate, 22 parts of the above composite core, and 11 parts of sodium lignin sulfonate were added, and the mixture was polymerized at 60°C under nitrogen protection for 1 hour, followed by centrifugation and washing to obtain microspheres;

[0077] (3) Take 25 parts of the above microspheres, immerse them in 80 parts of a mixed aqueous solution containing 3 wt% sodium alginate and 1.2 wt% polyethyleneimine for 9 minutes, take them out and evenly spray them with 12 parts of 0.6 M magnesium chloride solution, dry them at room temperature, and then crush and sieve to 20 μm to obtain enzyme sustained-release microspheres.

[0078] S4: The effluent treated by S3 is introduced into the sedimentation tank through a triangular channel. The sludge at the bottom of the sedimentation tank is returned to the return tank of S2 through the sludge return tank by air lift. The clean water flows out through the triangular weir and the sludge concentration is controlled to be maintained at 7000 mg / L.

[0079] Example 4

[0080] A biochemical treatment process for high-salt wastewater comprises the following steps:

[0081] S1. Take high-salt wastewater and adjust the pH to 7.0, add 200 mg / L of composite flocculant, and stir at 160 r / min for 32 min to obtain pretreated wastewater;

[0082] The preparation steps of the composite flocculant are as follows:

[0083] A1. Weigh 10 parts of chitosan and 14 parts of sodium 2-acrylamide-2-methylpropanesulfonate, dissolve them in 100 parts of deionized water, add 0.7 parts of cerium nitrate, and polymerize them at 60 ° C under nitrogen protection with magnetic stirring at a stirring speed of 400 r / min for 3.5h to obtain a copolymer solution;

[0084] A2. Disperse 6 parts of ZIF-8 in 40 parts of ethanol and treat with ultrasound at 50 kHz for 25 minutes. Add the dispersion dropwise to the copolymer solution over 32 minutes. Add 5 parts of glutaraldehyde and react at 50°C for 2 hours with stirring. After completion of the reaction, freeze-dry and crush to 16 μm to obtain a composite flocculant.

[0085] S2: The wastewater pretreated in S1 was mixed with 80% of the return sludge in the return tank and then entered the anoxic tank. The tank was filled with 40% of biological braided rope filler and 350 mg / L of modified carbon source was added. The water temperature was controlled at 28°C, the stirring speed was 70 r / min, and the hydraulic retention time was 6 h.

[0086] Among them, the preparation steps of the modified carbon source are as follows: 32 parts of γ-polyglutamic acid and 10 parts of trehalose are dissolved in 100 parts of deionized water, 3 parts of salt-tolerant denitrifying bacteria freeze-dried powder are added, and ultrasonic dispersion is performed at 55kHz for 25 minutes. The dispersed mixture is spray-dried to obtain 40μm particles; 20 parts of dimethylaminoethyl methacrylate, 9 parts of butyl methacrylate, and 0.5 parts of azobisisobutyronitrile are mixed, and polymerized at 60°C for 3h at a stirring speed of 300rpm to obtain a coating liquid, the above particles are added to the coating liquid for coating, and crushed and sieved to 24μm to obtain a modified carbon source.

[0087] S3: The wastewater treated in S2 is introduced into the aerobic tank, and the tank is filled with biological braided rope filler of the same specifications as S2, and 45g / m³ of enzyme slow-release microspheres are added. The dissolved oxygen is controlled at 3.0mg / L, the air-water ratio is 16:1, and the hydraulic retention time is 10h;

[0088] The preparation steps of enzyme sustained-release microspheres are as follows:

[0089] (1) 10 parts of salt-tolerant protease and 20 parts of trehalose were dissolved in 100 parts of deionized water, 50 parts of 5 wt% sodium silicate solution were added, 100 parts of 0.24 M CaCl2 solution were added dropwise at a rate of 5 mL / min, the pH was adjusted to 9, and the mixture was stirred at 360 rpm at room temperature for 2 h, followed by centrifugation and washing to obtain a composite core;

[0090] (2) 10 parts of N-isopropylacrylamide and 3 parts of acrylic acid were dispersed in 100 parts of deionized water, 0.3 parts of potassium persulfate, 20 parts of the above composite core, and 9 parts of sodium lignin sulfonate were added, and the mixture was polymerized at 60°C under nitrogen protection for 1.5 hours, followed by centrifugation and washing to obtain microspheres;

[0091] (3) Take 25 parts of the above microspheres, immerse them in 80 parts of a mixed aqueous solution containing 2 wt% sodium alginate and 1 wt% polyethyleneimine for 10 min, take them out and evenly spray them with 10 parts of 0.5 M magnesium chloride solution, dry them at room temperature, and then crush and sieve to 20 μm to obtain enzyme sustained-release microspheres.

[0092] S4: The effluent treated by S3 is introduced into the sedimentation tank through a triangular channel. The sludge at the bottom of the sedimentation tank is returned to the return tank of S2 through the sludge return tank by air lift. The clean water flows out through the triangular weir and the sludge concentration is controlled to be maintained at 6500 mg / L.

[0093] Comparative Example 1

[0094] A high-salt wastewater biochemical treatment process differs from Example 4 in that the composite flocculant in step S1 is replaced with polyaluminum chloride. Specifically, 200 mg / L polyaluminum chloride is added in step S1 to replace the composite flocculant. The rest of the high-salt wastewater biochemical treatment process is the same as Example 4.

[0095] Comparative Example 2

[0096] A biochemical treatment process for high-salt wastewater differs from Example 4 in that the composite flocculant does not contain ZIF-8 and the cross-linking step is omitted. Specifically, after Step A1, the copolymer solution is directly freeze-dried and pulverized to 16 μm to produce the flocculant. The remaining steps for preparing the composite flocculant and the biochemical treatment process for high-salt wastewater are the same as those in Example 4.

[0097] Comparative Example 3

[0098] A high-salinity wastewater biochemical treatment process differs from Example 4 in that no modified carbon source is added during the anoxic stage. Specifically, the step of adding the modified carbon source for encapsulating the halotolerant bacteria with γ-polyglutamic acid is omitted in step S2. Specifically, the anoxic reaction stage relies solely on the inherent carbon source of the returned sludge, without the addition of any additional exogenous carbon source. The remaining anoxic tank operating parameters and high-salinity wastewater biochemical treatment process are the same as those in Example 4.

[0099] Comparative Example 4

[0100] A biochemical treatment process for high-salt wastewater differs from Example 4 in that the modified carbon source is not coated. Specifically, in step S2, the modified carbon source preparation retains only the spray-dried particles containing γ-polyglutamic acid and trehalose encapsulating the salt-tolerant denitrifying bacteria, omitting the methacrylate monomer copolymerization and coating step. Specifically, 32 parts of γ-polyglutamic acid and 10 parts of trehalose are dissolved in 100 parts of deionized water, 3 parts of freeze-dried salt-tolerant denitrifying bacteria powder are added, and ultrasonic dispersion is performed at 55 kHz for 25 minutes. The particles are spray-dried to obtain 40 μm particles, which are used directly as a carbon source. The remainder of the high-salt wastewater biochemical treatment process is the same as in Example 4.

[0101] Comparative Example 5

[0102] A biochemical treatment process for high-salt wastewater differs from Example 4 in that the enzyme-release microspheres in step S3 are replaced with free salt-tolerant protease. Specifically, free salt-tolerant protease with the same enzymatic activity as the enzyme-release microspheres is added in step S3 instead of the enzyme-release microspheres. Specifically, 45 g / m³ of free salt-tolerant protease is directly added during the aerobic reaction phase, and a triple-coated slow-release microsphere structure is not used. The remaining aerobic tank operating parameters, filler configuration, and high-salt wastewater biochemical treatment process are the same as those in Example 4.

[0103] Performance Testing

[0104] The company's own high-salt wastewater was selected as the treatment object. After testing, it was found that the salinity of the wastewater was 3.5%, the initial COD was 1850 mg / L, the ammonia nitrogen was 210 mg / L, and the total nitrogen was 320 mg / L. The high-salt wastewater after biochemical treatment of Examples 1-4 and Comparative Examples 1-5 was tested, and the test results are shown in Table 1 below.

[0105] Table 1

[0106] Test items COD removal rate (%) Ammonia nitrogen removal rate (%) Total nitrogen removal rate (%) Example 1 93.79 91.03 92.52 Example 2 94.81 91.87 93.69 Example 3 96.11 93.19 95.18 Example 4 97.91 94.76 96.87 Comparative Example 1 74.15 62.19 74.28 Comparative Example 2 85.85 79.58 86.29 Comparative Example 3 88.37 87.33 63.31 Comparative Example 4 91.35 89.86 85.07 Comparative Example 5 90.17 55.93 80.07

[0107] Examples 1-4 demonstrated significantly superior treatment efficiency compared to the comparative example, with Example 4 achieving COD, ammonia nitrogen, and total nitrogen removal rates of 97.91%, 94.76%, and 96.87%, respectively, the best among all examples. This result is closely related to the coordinated optimization of process parameters, including the adjustment of the chitosan and ZIF-8 ratio in the composite flocculant, the design of the coating structure of the modified carbon source, the triple protection system of the enzyme-release microspheres, and the synergistic effect of the pretreatment and biochemical stages. These optimizations collectively improved the capture and degradation efficiency of pollutants in high-salinity environments, ensuring a stable and efficient denitrification process.

[0108] The treatment effects of Comparative Examples 1-5 are generally lower than those of Example 4. In Comparative Example 1, polyaluminum chloride is used instead of the composite flocculant, which is prone to salting out in a high-salt environment, resulting in a decrease in flocculation capacity and an increase in the subsequent biochemical treatment load. In Comparative Example 2, ZIF-8 is not added to the composite flocculant, and the multi-stage cross-linking structure is lacking, so the adsorption capacity of pollutants is weakened. In Comparative Example 3, no modified carbon source is added, and the denitrification process is limited due to insufficient carbon source, and the total nitrogen removal rate is significantly reduced. The modified carbon source in Comparative Example 4 is not coated, and the carbon source release rate cannot match the denitrification requirements, and the salt-tolerant bacteria are easily directly poisoned by high salt. In Comparative Example 5, free salt-tolerant protease is used, and the enzyme activity decays rapidly in a high-salt environment, and the ammonia nitrogen oxidation efficiency is greatly reduced.

[0109] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A biochemical treatment process for high-salt wastewater, characterized in that: The following steps are involved: S1. Adjust the pH of high-salt wastewater, add a composite flocculant, and stir and flocculate to obtain pretreated wastewater; S2, mixing the pretreated wastewater and the return sludge in the top return tank and then flowing into the anoxic tank for anoxic reaction, wherein the anoxic tank is filled with biological braided rope filler and a modified carbon source is added; S3, the denitrified wastewater is flowed into an aerobic tank for aerobic reaction, wherein the aerobic tank is filled with biological braided rope fillers and enzyme slow-release microspheres are added; S4. The effluent from the aerobic tank is introduced into the sedimentation tank for solid-liquid separation. The activated sludge is returned to the anoxic tank through the sludge return trough by air lift, and the clean water is discharged.

2. The biochemical treatment process for high-salt wastewater according to claim 1, characterized in that: The preparation steps of the composite flocculant in step S1 are: A1. Dissolve chitosan and sodium 2-acrylamide-2-methylpropanesulfonate in deionized water, add cerium nitrate, and polymerize to obtain a copolymer solution; A2. Disperse ZIF-8 in ethanol and then drop the copolymer solution into it. Add glutaraldehyde for cross-linking. After freeze-drying and pulverization, a composite flocculant is obtained.

3. The biochemical treatment process for high-salt wastewater according to claim 2, characterized in that: In step A1, the components by weight include 8-12 parts of chitosan, 13-17 parts of sodium 2-acrylamide-2-methylpropanesulfonate, 90-100 parts of deionized water, and 0.7-0.8 parts of cerium nitrate; and in step A2, the components by weight include 4-6 parts of ZIF-8, 35-40 parts of ethanol, and 4-6 parts of glutaraldehyde.

4. The biochemical treatment process for high-salt wastewater according to claim 1, characterized in that: The preparation steps of the modified carbon source in step S2 are as follows: dissolving 28-32 parts of γ-polyglutamic acid and 9-11 parts of trehalose in 100-110 parts of deionized water, adding 2-4 parts of salt-tolerant denitrifying bacteria freeze-dried powder, ultrasonically dispersing and spray drying to obtain particles; mixing and polymerizing 18-22 parts of dimethylaminoethyl methacrylate, 9-11 parts of butyl methacrylate and 0.4-0.6 parts of azobisisobutyronitrile, adding the particles to the mixture for stirring and coating, cooling and sieving to obtain the modified carbon source.

5. The biochemical treatment process for high-salt wastewater according to claim 1, characterized in that: The preparation steps of the enzyme sustained-release microspheres in step S3 are: (1) Dissolve salt-tolerant protease and trehalose in deionized water, add sodium silicate solution, add calcium chloride solution dropwise and adjust the pH, and centrifuge and wash after the reaction to obtain a composite core; (2) N-isopropylacrylamide and acrylic acid were dispersed in deionized water, potassium persulfate, composite core and sodium lignin sulfonate were added, and microspheres were obtained by constant temperature polymerization under nitrogen protection; (3) The microspheres were immersed in a mixed aqueous solution of sodium alginate and polyethyleneimine, evenly sprayed with magnesium chloride solution and dried to obtain enzyme-activated sustained-release microspheres.

6. The biochemical treatment process for high-salt wastewater according to claim 5, characterized in that: In step (1), the components by weight include 9-11 parts of salt-tolerant protease, 18-22 parts of trehalose, 95-100 parts of deionized water, 48-52 parts of sodium silicate solution and 95-100 parts of CaCl2 solution.

7. The biochemical treatment process for high-salt wastewater according to claim 5, characterized in that: In step (2), the components by weight include 6-10 parts of N-isopropylacrylamide, 1-3 parts of acrylic acid, 90-100 parts of deionized water, 0.2-0.4 parts of potassium persulfate, 18-22 parts of composite core and 9-11 parts of sodium lignin sulfonate.

8. The biochemical treatment process for high-salt wastewater according to claim 5, characterized in that: In step (3), the components by weight include 20-25 parts of microspheres, 70-80 parts of a mixed aqueous solution of sodium alginate and polyethyleneimine, and 8-12 parts of a magnesium chloride solution.

9. The biochemical treatment process for high-salt wastewater according to claim 1, characterized in that: The anoxic tank, aerobic tank, sludge return trough and sedimentation tank are separated by a partition. A sewage flow channel is provided at the bottom of the partition between the anoxic tank and the aerobic tank. The aerobic tank is connected to the sedimentation tank through a triangular channel.

10. The biochemical treatment process for high-salt wastewater according to claim 1, characterized in that: Inclined plate fillers are provided in the sedimentation tank for sludge sedimentation, and micro-perforated pipes are provided in the sludge return tank for air lift return activated sludge, and the air source of the air lift method is provided by a blower.