High-salinity wastewater biochemical treatment process

Abstract

The present application relates to wastewater treatment technical field, disclose a kind of high-salinity wastewater biochemical treatment process.The process uses composite flocculation pretreatment and anoxic, aerobic, precipitation synergistic technology, through composite flocculant depth capture pollutant, utilize modified carbon source and enzyme slow-release microsphere to build salt-tolerant biochemical system.The composite flocculant is through multistage crosslinking structure to improve the adsorption capacity of pollutant under high-salinity environment;Anoxic section uses slow-release carbon source and biological braiding filler to synergistically strengthen denitrification;Aerobic section is through triple-coated enzyme microsphere to guarantee the stability of nitrification enzyme activity;During the treatment process, integrated partition type reaction tank and air-lift sludge return device, realize the efficient circulation of activated sludge and solid-liquid separation.The process effectively solves the problems of high-salinity inhibition biochemical efficiency, high cost of traditional physicochemical method and sludge bulking, significantly improves the removal rate of COD and nitrogen, reduces energy consumption and secondary pollution risk, suitable for chemical, pharmaceutical and other high-salinity wastewater treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, more particularly, it relates to a biochemical treatment process for high-salinity wastewater. BACKGROUND

[0002] High-salinity wastewater generated in the production processes of chemical industry, pharmaceutical industry, printing and dyeing industry, etc. has a salinity generally ≥1%, and its high osmotic pressure and strong ion strength pose significant challenges to traditional biochemical treatment processes. The complex pollutant composition and poor water quality conditions of such wastewater easily lead to problems such as deactivation of microbial cells, disorder of enzyme system, metabolic activity decline of activated sludge, sludge bulking and biofilm shedding, etc., thereby significantly reducing the removal efficiency of chemical oxygen demand and nitrogen, and seriously affecting the stable operation of the treatment system. Although existing physical and chemical pretreatment technologies such as evaporation crystallization and advanced oxidation can alleviate the inhibition of salinity on the biochemical system to some extent, they generally have the disadvantages of high energy consumption per ton of water, large amount of reagent addition and easy generation of toxic by-products, and have limited effect on the removal of dissolved organic nitrogen, which is difficult to meet the water quality requirements of subsequent biochemical treatment.

[0003] In view of the improvement of salt tolerance of the biochemical system, the conventional solutions mainly rely on inoculation of halophilic bacteria or modification of carbon source, but have multiple defects: the traditional iron salt and aluminum salt flocculants are affected by the "salting-out effect" in a high-salinity environment, and the colloidal destabilization efficiency is significantly deteriorated, and the pollutant capture capacity is insufficient; in the anoxic denitrification stage, ordinary carbon sources such as sodium acetate are easily chelated by salt ions, and the biological availability is reduced, and the carbon source release rate and nitrogen removal demand are difficult to match; the aerobic nitrifying bacteria are sensitive to changes in salinity, and the activity of free nitrifying enzymes is attenuated in a high-salinity environment, and the ammonia oxidation rate is significantly reduced; improper control of reactor flow regime easily causes short flow phenomenon, and the solid-liquid separation efficiency of the sedimentation tank is greatly affected by salinity fluctuations, which leads to poor stability of sludge return, and further aggravates the uncertainty of biochemical treatment effect. Therefore, the present application provides a biochemical treatment process for high-salinity wastewater to solve the above technical problems. SUMMARY

[0004] In order to solve the above problems, the present application provides a biochemical treatment process for high-salinity wastewater, which effectively solves the problems of high-salinity inhibition of biochemical efficiency, high cost of traditional physical and chemical methods and sludge bulging, significantly improves the removal rates of COD and nitrogen, reduces energy consumption and secondary pollution risk, and is suitable for high-salinity wastewater treatment in chemical industry, pharmaceutical industry, etc.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] A biochemical treatment process for high-salinity wastewater, comprising the following steps:

[0007] S1, adjust the pH of high-salinity 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, mix the pretreated wastewater with reflux sludge at a reflux ratio of 75-85% in the top reflux tank, then flow into the anoxic tank, fill 40-45% of biological woven rope-shaped filler, add 300-400 mg / L of modified carbon source, stir at 50-60 r / min, control the water temperature at 25-30℃, and control the hydraulic retention time at 5-7 h;

[0009] S3, flow the wastewater into the aerobic tank, fill the biological woven rope-shaped filler, add 30-50 g / m³ of enzyme slow-release microspheres, control the dissolved oxygen at 2.0-4.0 mg / L, control the hydraulic retention time at 10-14 h, and control the gas-water ratio at 12-18:1;

[0010] S4, flow the aerobic effluent into the sedimentation tank through the triangular channel, realize solid-liquid separation through the inclined pipe filler, reflux the activated sludge to the anoxic tank through the micro-perforated pipe air-lift reflux through the bottom sludge reflux tank, and flow the clear water out through the triangular effluent weir.

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

[0012] A1, dissolve chitosan and 2-acrylamide-2-methylpropanesulfonic acid sodium in deionized water, add cerium nitrate, magnetically stir and polymerize at 58-62℃ in a nitrogen atmosphere for 3-5 h to prepare a copolymer solution;

[0013] A2, ultrasonically disperse ZIF-8 in ethanol, drop the copolymer solution into the ethanol, add glutaraldehyde, cross-link at 45-55℃ for 1-3 h, freeze-dry, crush to 15-18 μm, and prepare the composite flocculant.

[0014] Preferably, in step A1, the proportions by weight are 8-12 parts of chitosan, 13-17 parts of 2-acrylamide-2-methylpropanesulfonic acid sodium, 90-100 parts of deionized water, and 0.7-0.8 parts of cerium nitrate, and in step A2, the proportions are 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: dissolve 28-32 parts of γ-polyglutamic acid and 9-11 parts of trehalose in 100-110 parts of deionized water, add 2-4 parts of freeze-dried salt-tolerant denitrifying bacteria powder, ultrasonically disperse, and spray dry to obtain 40-60 μm particles; mix 18-22 parts of dimethylaminoethyl methacrylate, 9-11 parts of butyl methacrylate, and 0.4-0.6 parts of azobisisobutyronitrile, polymerize in a water bath at 55-60℃ for 3-5 h, stir and coat with the particles, sieve after cooling to obtain 24-30 μm modified carbon source.

[0016] Preferably, the preparation step of the enzyme-activated slow-release microspheres in step S3 is:

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

[0018] (2) Disperse N-isopropyl acrylamide and acrylic acid in deionized water, add potassium persulfate, composite core and sodium lignosulfonate, polymerize at 55-60℃ under nitrogen protection for 1-2h, then centrifuge and wash to obtain the microspheres;

[0019] (3) Soak the microspheres in a mixed aqueous solution containing 1-3 wt% sodium alginate and 0.9-1.2 wt% polyethyleneimine for 9-11min, uniformly spray 0.4-0.6M magnesium chloride solution, and dry at room temperature to obtain the enzyme slow-release microspheres.

[0020] Preferably, in step (1), the weight parts 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 weight parts are 6-10 parts of N-isopropyl acrylamide, 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 lignosulfonate.

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

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

[0024] Preferably, in the high-salinity wastewater biochemical treatment process, an inclined plate filler is arranged in the sedimentation tank for sludge settling, and a micro perforated pipe is arranged in the sludge return tank for air stripping of activated sludge, and the air source of the air stripping mode is provided by a blower.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1.The present application is based on the construction of a multi-stage cross-linking flocculant of chitosan, sulfonate copolymer and metal organic framework. The synergistic effect of cation bridging, coordination bonding and porous adsorption effectively overcomes the "salting-out effect" in high salt environment, strengthens the colloidal destabilization and pollutant capture capacity, reduces the toxicity load of subsequent biochemical section from the source, and completely solves the problem of bridge capacity attenuation of traditional flocculants in high salt environment.

[0027] 2.The present application uses the synergistic mechanism of slow-release carbon source and biological braided filler in the anoxic section to achieve denitrification enhancement. The modified carbon source uses gamma-polyglutamic acid and trehalose to embed salt-tolerant denitrifying bacteria, and the outer layer is co-polymerized with methacrylate monomers to form a pH-responsive slow-release shell. This core-shell structure isolates the direct toxicity of salt ions to microorganisms and precisely controls the carbon release kinetics; combined with the micro-aerobic biofilm microenvironment constructed by the biological braided filler, the metabolic activity and denitrification efficiency of the denitrifying bacteria under high salt conditions are significantly improved, and the biological availability defect of ordinary carbon source caused by salt ion chelation is fundamentally overcome.

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

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0030] In the following examples, the experimental methods are conventional methods unless otherwise specified, and the test materials used are commercially available from conventional biochemical reagent stores unless otherwise specified. In the following examples, the quantitative test is set up with three repeated experiments, and the data is the average value or average value ± standard deviation of three repeated experiments.

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

[0032] ZIF-8, purchased from Shanghai Kolaman Reagent Co., Ltd., item number 095718;

[0033] Gamma-polyglutamic acid, purchased from Shenzhen Lovefu Biological Technology Co., Ltd.;

[0034] Polyethyleneimine, purchased from Shandong Haizhou Biological Engineering Co., Ltd., CAS number 9002-98-6;

[0035] Salt-tolerant protease, purchased from Shandong Sukuo Han Biological Engineering Co., Ltd.;

[0036] Salt-tolerant denitrifying bacteria freeze-dried powder, purchased from Yuliko (Shanghai) Life Science Co., Ltd., item number YLK-jz4573.

[0037] Example 1

[0038] A high-salinity wastewater biochemical treatment process, comprising the following steps:

[0039] S1, taking high-salinity wastewater and adjusting the pH to 6.5, adding 150 mg / L of a composite flocculant, stirring at 140 r / min for 40 min to obtain pretreated wastewater;

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

[0041] A1. Take 8 parts of chitosan and 13 parts of 2-acrylamide-2-methylpropanesulfonic acid sodium, dissolve in 90 parts of deionized water, add 0.7 parts of cerium nitrate, and magnetically stir at 58°C under nitrogen protection conditions at a stirring speed of 300 r / min for 5 h to obtain a copolymer solution;

[0042] A2. Take 4 parts of ZIF-8 and disperse in 35 parts of ethanol, ultrasonically treat at 40 kHz for 30 min, and drop the dispersion into the above copolymer solution within 25 min, add 4 parts of glutaraldehyde, and react at 45°C for 3 h, while stirring during the reaction. After the reaction is completed, freeze-drying, crushing to 18 μm, to obtain a composite flocculant.

[0043] S2, after mixing the pretreated wastewater of S1 with 75% reflux sludge in a reflux tank, entering an anoxic tank, filling 40% bio-woven rope-shaped filler in the tank, adding 300 mg / L of modified carbon source, controlling water temperature at 25°C, stirring at a stirring speed of 60 r / min, and hydraulic retention time of 7 h;

[0044] The preparation steps of the modified carbon source are as follows: 28 parts of gamma-polyglutamic acid, 9 parts of trehalose are dissolved in 100 parts of deionized water, 2 parts of salt-tolerant denitrifying bacteria freeze-dried powder is added, and ultrasonic dispersion is carried out at 40 kHz for 30 min; the mixed solution after dispersion is subjected to spray drying to obtain 60 μm particles; 18 parts of dimethylaminoethyl methacrylate, 9 parts of butyl methacrylate and 0.4 parts of azobisisobutyronitrile are mixed, and polymerization is carried out at 55°C for 5 h under stirring at a speed of 280 rpm to obtain a coating liquid; the above particles are added into the coating liquid for coating, and are crushed and sieved to 30 μm to obtain the modified carbon source.

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

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

[0047] (1) 9 parts of salt-tolerant protease and 18 parts of trehalose are dissolved in 95 parts of deionized water, 48 parts of 4 wt% sodium silicate solution is added, 95 parts of 0.2M CaCl2 solution is added dropwise at a rate of 3 mL / min, the pH is adjusted to 8, and the reaction is carried out at room temperature for 3 h under stirring at a speed of 320 rpm, and then centrifugal washing is performed to obtain a composite core;

[0048] (2) 6 parts of N-isopropyl acrylamide and 1 part of acrylic acid are dispersed in 90 parts of deionized water, 0.2 parts of potassium persulfate, 18 parts of the above-mentioned composite core and 9 parts of sodium lignosulfonate are added, and polymerization is carried out at 55°C for 2 h under nitrogen protection, and then centrifugal washing is performed to obtain microspheres;

[0049] (3) 20 parts of the above-mentioned microspheres are immersed in 70 parts of a mixed aqueous solution containing 1 wt% sodium alginate and 0.9 wt% polyethyleneimine for 11 min, 8 parts of 0.4M magnesium chloride solution is uniformly sprayed after taking out, and then crushing and sieving to 25 μm are performed to obtain enzyme slow-release microspheres.

[0050] S4, the effluent after S3 treatment is introduced into a sedimentation tank through a triangular channel, the sludge at the bottom of the sedimentation tank is returned to the reflux tank of S2 through air stripping, and the clear water flows out through a triangular weir, and the sludge concentration is controlled to be maintained at 6000 mg / L.

[0051] Example 2

[0052] A high-salinity wastewater biochemical treatment process, comprising the following steps:

[0053] S1, the high-salinity wastewater is adjusted to pH 6.8, 160 mg / L of composite flocculant is added, and stirring is carried out at 150 r / min for 38 min to obtain pretreated wastewater;

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

[0055] A1. 9 parts of chitosan, 14 parts of 2-acrylamide-2-methylpropanesulfonic acid sodium, 95 parts of deionized water, 0.73 parts of cerium nitrate were weighed and dissolved, and then polymerization was carried out at 60°C under nitrogen protection condition with magnetic stirring at a stirring speed of 340 r / min for 4.8 h to obtain a copolymer solution;

[0056] A2. 5 parts of ZIF-8 were taken and dispersed in 37 parts of ethanol, and ultrasonic treatment was carried out at 45 kHz for 28 min, and the dispersion liquid was dropped into the above-mentioned copolymer solution within 28 min, 5 parts of glutaraldehyde was added, and reaction was carried out at 48°C for 2.8 h, and stirring was maintained during the reaction, and after the reaction was completed, freeze-drying and crushing to 17 μm were carried out to obtain a composite flocculant.

[0057] S2, after the wastewater pretreated by S1 was mixed with 78% reflux sludge in a reflux tank, it was introduced into an anoxic tank, the tank was filled with 42% biological braided rope-shaped filler, 320 mg / L of modified carbon source was added, the water temperature was controlled at 27°C, stirring was carried out at a stirring speed of 65 r / min, and the hydraulic retention time was 6 h;

[0058] The preparation steps of the modified carbon source are as follows: 29 parts of γ-polyglutamic acid, 10 parts of trehalose were dissolved in 105 parts of deionized water, 3 parts of salt-tolerant denitrifying bacteria freeze-dried powder was added, ultrasonic dispersion was carried out at 45 kHz for 28 min, and the dispersed mixture was subjected to spray drying to obtain 55 μm particles; 19 parts of dimethylaminoethyl methacrylate, 10 parts of butyl methacrylate, and 0.5 parts of azobisisobutyronitrile were mixed, and polymerization was carried out at 56°C for 4.8 h with stirring at a stirring speed of 290 rpm to obtain a coating liquid, the above-mentioned particles were added to the coating liquid for coating, and crushing and sieving were carried out to 28 μm to obtain a modified carbon source.

[0059] S3, the wastewater treated by S2 was introduced into an aerobic tank, the tank was filled with biological braided rope-shaped filler of the same specification as S2, 35 g / m³ of enzyme slow-release microspheres were added, the dissolved oxygen was controlled at 2.5 mg / L, the gas-water ratio was 13:1, and the hydraulic retention time was 13 h;

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

[0061] (1) 10 parts of salt-tolerant protease, 19 parts of trehalose, 98 parts of deionized water, 49 parts of 5 wt% sodium silicate solution, 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 reaction was carried out at room temperature for 2.8 h with stirring at a stirring speed of 330 rpm, and then centrifugal washing was carried out to obtain a composite core;

[0062] (2) Take 7 parts of N-isopropyl acrylamide, 2 parts of acrylic acid, disperse in 95 parts of deionized water, add 0.3 parts of potassium persulfate, 19 parts of the above composite core, 10 parts of sodium lignosulfonate, and polymerize at 57℃ under nitrogen protection for 1.8h, then centrifuge and wash to obtain microspheres;

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

[0064] S4, the effluent after S3 treatment is introduced into the sedimentation tank through the triangular channel, the sludge at the bottom of the sedimentation tank is returned to the reflux tank of S2 through air stripping, and the clear water flows out through the triangular weir, and the sludge concentration is controlled to maintain at 6300mg / L.

[0065] Example 3

[0066] A high-salinity wastewater biochemical treatment process, comprising the following steps:

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

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

[0069] A1. Take 12 parts of chitosan and 17 parts of 2-acrylamide-2-methylpropane sulfonic acid sodium, dissolve in 100 parts of deionized water, add 0.8 parts of cerium nitrate, and magnetically stir at 450r / min under the condition of 62℃ and nitrogen protection for 3h to obtain a copolymer solution;

[0070] A2. Take 6 parts of ZIF-8, disperse in 40 parts of ethanol, ultrasonic treat at 55kHz for 20min, drop the dispersion into the above copolymer solution within 35min, add 6 parts of glutaraldehyde, react at 55℃ for 1h, keep stirring during the reaction, and after the reaction is completed, freeze-dry, crush to 15μm to obtain the composite flocculant.

[0071] S2, mix the pretreated wastewater of S1 with 85% reflux sludge in the reflux tank, then enter the anoxic tank, fill 45% of the biological braided rope-shaped filler in the tank, add 400mg / L of modified carbon source, control the water temperature at 30℃, stir at a stirring speed of 75r / min, and the hydraulic retention time is 5h;

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

[0073] S3, the wastewater treated in S2 is introduced into an aerobic tank, the tank is filled with biological braided rope-shaped filler of the same specification as S2, 50 g / m3 of enzyme slow-release microspheres are added, the dissolved oxygen is controlled at 4.0 mg / L, the gas-water ratio is 18:1, and the hydraulic retention time is 10 h;

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

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

[0076] (2) 10 parts of N-isopropyl acrylamide and 3 parts of acrylic acid are dispersed in 100 parts of deionized water, 0.4 parts of potassium persulfate, 22 parts of the above-mentioned composite core and 11 parts of sodium lignosulfonate are added, and polymerization is carried out at 60°C for 1 h under nitrogen protection, followed by centrifugal washing to obtain microspheres;

[0077] (3) 25 parts of the above-mentioned microspheres are immersed in 80 parts of a mixed aqueous solution containing 3 wt% sodium alginate and 1.2 wt% polyethyleneimine for 9 min, 12 parts of 0.6 M magnesium chloride solution is uniformly sprayed after taking out, and the enzyme slow-release microspheres are obtained by crushing and sieving to 20 μm after drying at room temperature.

[0078] S4, the effluent after S3 treatment is introduced into a sedimentation tank through a triangular channel, the sludge at the bottom of the sedimentation tank is returned to the reflux tank of S2 through air stripping, and the clear water flows out through a triangular weir, and the sludge concentration is controlled to be maintained at 7000 mg / L.

[0079] Example 4

[0080] A high-salinity wastewater biochemical treatment process, comprising the following steps:

[0081] S1, the high-salinity wastewater is adjusted to pH 7.0, and 200 mg / L of a composite flocculant is added, and the wastewater is stirred at 160 r / min for 32 min to obtain pretreated wastewater;

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

[0083] A1. 10 parts of chitosan, 14 parts of 2-acrylamide-2-methylpropanesulfonic acid sodium, and 100 parts of deionized water were weighed and dissolved, 0.7 parts of cerous nitrate was added, and the mixture was magnetically stirred at 400 r / min under the condition of nitrogen protection at 60°C for 3.5 h to obtain a copolymer solution;

[0084] A2. 6 parts of ZIF-8 were taken and dispersed in 40 parts of ethanol, and ultrasonic treatment was performed at 50 kHz for 25 min. The dispersion was dropped into the copolymer solution in 32 min, 5 parts of glutaraldehyde was added, and the reaction was carried out at 50°C for 2 h. Stirring was maintained during the reaction. After the reaction was completed, freeze-drying and crushing to 16 μm were performed to obtain the composite flocculant.

[0085] S2, after the wastewater pretreated by S1 was mixed with 80% reflux sludge in a reflux tank, it was introduced into an anoxic tank, which was filled with 40% biological braided rope-shaped filler, 350 mg / L of modified carbon source was added, the water temperature was controlled at 28°C, and the stirring speed was 70 r / min, and the hydraulic retention time was 6 h;

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

[0087] S3, the wastewater treated by S2 was introduced into an aerobic tank, which was filled with biological braided rope-shaped filler of the same specification as S2, 45 g / m³ of enzyme slow-release microspheres was added, the dissolved oxygen was controlled at 3.0 mg / L, the gas-water ratio was 16:1, and the hydraulic retention time was 10 h;

[0088] The preparation steps of the enzyme slow-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 was added, 100 parts of 0.24 M CaCl2 solution was added dropwise at a rate of 5 mL / min, the pH was adjusted to 9, and the mixture was reacted at room temperature for 2 h at a stirring speed of 360 rpm, followed by centrifugal washing to obtain a composite core;

[0090] (2) Take 10 parts of N-isopropyl acrylamide, 3 parts of acrylic acid, disperse in 100 parts of deionized water, add 0.3 parts of potassium persulfate, 20 parts of the above composite core, 9 parts of sodium lignosulfonate, and polymerize at 60°C for 1.5 hours under nitrogen protection, then centrifuge and wash to obtain microspheres;

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

[0092] S4, the effluent after S3 treatment is introduced into the sedimentation tank through the triangular channel, the sludge at the bottom of the sedimentation tank is returned to the reflux tank of S2 through air stripping, and the clear water flows out through the triangular weir, and the sludge concentration is controlled to maintain at 6500mg / L.

[0093] Comparative Example 1

[0094] A high-salinity wastewater biochemical treatment process, which is different from Example 4 in that the composite flocculant in step S1 is replaced by polyaluminum chloride. Specifically, 200mg / L of polyaluminum chloride is added in place of the composite flocculant in step S1, and the rest of the high-salinity wastewater biochemical treatment process is the same as Example 4.

[0095] Comparative Example 2

[0096] A high-salinity wastewater biochemical treatment process, which is different from Example 4 in that the composite flocculant does not add ZIF-8 and the cross-linking step, i.e. the ZIF-8 dispersion and glutaraldehyde cross-linking treatment in step A2 is omitted. Specifically, after step A1, the copolymer solution is freeze-dried and crushed to 16μm to prepare the flocculant, and the rest of the composite flocculant preparation steps and the high-salinity wastewater biochemical treatment process are the same as Example 4.

[0097] Comparative Example 3

[0098] A high-salinity wastewater biochemical treatment process, which is different from Example 4 in that the modified carbon source is not added in the anoxic section, i.e. the modified carbon source dosing step of γ-polyglutamic acid embedding salt-tolerant bacteria in step S2 is omitted. Specifically, only the inherent carbon source of the reflux sludge is relied on in the anoxic reaction stage, without additional external carbon source, and the rest of the anoxic tank operating parameters and the high-salinity wastewater biochemical treatment process are the same as Example 4.

[0099] Comparative Example 4

[0100] A high-salinity wastewater biochemical treatment process, which is different from example 4 in that the modified carbon source is not coated, that is, only the spray-dried particles of γ-polyglutamic acid and trehalose embedding salt-tolerant denitrifying bacteria are retained in the preparation of the modified carbon source in step S2, and the step of co-polymer coating with methacrylate monomers is omitted. Specifically, 32 parts of γ-polyglutamic acid, 10 parts of trehalose, and 3 parts of salt-tolerant denitrifying bacteria freeze-dried powder are dissolved in 100 parts of deionized water, and ultrasonic dispersion is performed at 55 kHz for 25 min. The 40 μm particles are obtained by spray drying and directly used as carbon source. The rest of the high-salinity wastewater biochemical treatment process is the same as example 4.

[0101] Comparative example 5

[0102] A high-salinity wastewater biochemical treatment process, which is different from example 4 in that the enzyme slow-release microspheres are replaced by free salt-tolerant protease in step S3, that is, free salt-tolerant protease with the same enzyme activity as the enzyme slow-release microspheres is added instead of enzyme slow-release microspheres in step S3. Specifically, 45 g / m³ of free salt-tolerant protease is directly added in the aerobic reaction stage, and the triple-coated slow-release microsphere structure is not used. The rest of the aerobic tank operating parameters, filler configuration, and high-salinity wastewater biochemical treatment process are the same as example 4.

[0103] Performance test

[0104] The high-salinity wastewater of the company itself is selected as the treatment object. The test shows that the salinity of the wastewater is 3.5%, the initial COD is 1850 mg / L, the ammonia nitrogen is 210 mg / L, and the total nitrogen is 320 mg / L. The high-salinity wastewater after biochemical treatment of examples 1-4 and comparative examples 1-5 is tested, and the test results are shown in Table 1.

[0105] Table 1

[0106] Test item 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 show significantly better treatment performance than comparative examples, among which the COD removal rate, ammonia nitrogen removal rate, and total nitrogen removal rate of example 4 reach 97.91%, 94.76%, and 96.87% respectively, which is the best among all examples. This result is closely related to the synergistic optimization of process parameters, including the adjustment of the ratio of chitosan to ZIF-8 in the composite flocculant, the design of the coating structure of the modified carbon source, the triple protection system of the enzyme slow-release microspheres, and the synergistic effect of pretreatment and biochemical stage. These optimizations collectively improve the capture and degradation efficiency of pollutants in high-salinity environment, ensuring stable and efficient denitrification process.

[0108] The treatment effects of Comparative Examples 1-5 are generally lower than that 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, and the flocculation capacity decreases, resulting in an increased load of subsequent biochemical treatment. In Comparative Example 2, ZIF-8 is not added to the composite flocculant, and the multi-level cross-linking structure is lacking, which weakens the adsorption capacity of pollutants. In Comparative Example 3, the modified carbon source is not added, and the denitrification process is limited due to insufficient carbon source, and the total nitrogen removal rate is significantly reduced. In Comparative Example 4, the modified carbon source is not coated, and the carbon source release rate cannot match the denitrification demand, 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 rapidly decays in a high-salt environment, and the ammonia nitrogen oxidation efficiency is greatly reduced.

[0109] The above is merely an example and description of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the invention or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

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 tank by air stripping, and the clean water is discharged; Wherein, 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, dispersing ZIF-8 in ethanol and then dropping the copolymer solution, adding glutaraldehyde for cross-linking, freeze-drying and pulverizing to obtain a composite flocculant; The preparation steps of the enzyme sustained-release microspheres in step S3 are as follows: (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.

2. The high-salt wastewater biochemical treatment process according to claim 1, 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.

3. The biochemical treatment process for high-salt wastewater according to claim 1, 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.

4. The biochemical treatment process for high-salt wastewater according to claim 1, 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.

5. The biochemical treatment process for high-salt wastewater according to claim 1, 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.

6. 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.

7. 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.