Double-layer anaerobic bacteria-algal-bacterial symbiotic immobilized particle as well as preparation method and application thereof

Abstract

The invention relates to the field of sewage treatment, and provides double-layer anaerobic bacteria-algal-bacterial symbiotic immobilized particles as well as a preparation method and application thereof. The double-layer anaerobic bacteria-algal-bacterial symbiotic immobilized particle sequentially comprises a PAN (polyacrylonitrile) fiber particle, an anaerobic bacteria layer, a polymer film, an algal-bacterial symbiotic layer and a calcium alginate gel layer from inside to outside. The preparation method comprises the following steps: modifying PAN fiber particles to enable the PAN fiber particles to carry positive charges, and putting the modified PAN fiber particles into an anaerobic bacteria solution for dipping adsorption; coating a PVDF (Polyvinylidene Fluoride) solution to form a polymer film, so as to obtain PAN (Polyacrylonitrile) fiber particles for immobilizing anaerobic bacteria; soaking in a mixed solution of an algal-bacterial symbiotic suspension and sodium alginate, taking out, putting into a calcium chloride solution, and cross-linking and hardening to form gel. Anaerobic microorganisms and aerobic microorganisms in the immobilized particles are subjected to regional division and immobilization, and the inner-layer anaerobic microorganisms and the outer-layer aerobic microorganisms play a greater role in different regions of a carrier by virtue of a physiological synergistic effect among the microorganisms, so that carbon, nitrogen and phosphorus in sewage are deeply removed.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, and in particular to double-layer anaerobic bacteria-bacteria-algae symbiotic immobilized particles and a preparation method and application thereof. Background Art

[0002] Aquaculture tailwater contains high concentrations of organic matter and nutrients, such as nitrogen compounds such as ammonia, nitrite, nitrate, phosphate, and dissolved organic carbon. With the rapid development of marine aquaculture, the discharge of marine aquaculture tailwater has continued to increase, and the total amount of pollutants in marine aquaculture tailwater has gradually exceeded the water body's receiving capacity, which may lead to eutrophication of water bodies and cause serious environmental impacts on coastal natural ecosystems.

[0003] Biological methods have become a water treatment technology that has developed rapidly in recent years because of their environmental protection, economy, almost no secondary pollution and high removal rate. Microbial immobilization technology has been widely used in water treatment because it can significantly improve the stability of cells and increase microbial activity. The encapsulation technology forms a unique microenvironment by enclosing microorganisms in particles that are relatively isolated from the outside world. For fluctuations in the external environment, the embedded particles can play a buffering role, reduce the impact on the growth and metabolism of internal microorganisms, and maintain the nitrogen and phosphorus removal performance of microorganisms. At present, most encapsulation methods adopt a mode of cross-linking the microorganisms and materials to make gel balls. Only aerobic microorganisms or anaerobic microorganisms can be embedded separately, and aerobic and anaerobic microorganisms cannot be embedded at the same time. For example, patent CN117923698A discloses a microbial embedding immobilization coupled aerobic granular sludge sewage treatment system, and patent CN114133044A discloses an organic sewage treatment agent for embedding anaerobic microorganisms and its preparation method.

[0004] AO, A 2 -O process is a common sewage treatment technology. By combining anaerobic and aerobic processes, ammonia in the water is oxidized and nitrite and nitrate are reduced to nitrogen. Concentrating anaerobic and aerobic processes on different levels of the carrier at the same time helps to build a modular sewage treatment unit and improve the sewage treatment rate. Therefore, it is a problem worthy of attention to explore how to embed and zone anaerobic and aerobic microorganisms at the same time and improve the sewage treatment rate of existing embedded microorganism technology. Summary of the invention

[0005] The present invention provides double-layer anaerobic bacteria-algae symbiotic immobilized particles and a preparation method and application thereof. The anaerobic microorganisms and aerobic microorganisms in the immobilized particles are divided into regions and fixed, and the physiological synergy between the microorganisms is utilized to allow the inner layer anaerobic microorganisms and the outer layer aerobic microorganisms to play a greater role in different regions of the carrier, thereby achieving the purpose of deeply removing carbon, nitrogen, phosphorus, etc. in sewage.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A double-layer anaerobic bacteria-algae symbiotic immobilization particle comprises, from the inside to the outside, PAN (polyacrylonitrile) fiber particles, an anaerobic bacteria layer, a polymer film, a bacteria-algae symbiotic layer and a calcium alginate gel layer.

[0007] The present invention also provides a method for preparing the double-layer anaerobic bacteria-bacteria-algae symbiotic immobilization particles, comprising the following steps: 1) After modifying PAN fiber particles so that they carry positive charges, they are immersed in an anaerobic bacteria solution to obtain PAN fiber particles adsorbed by anaerobic bacteria; 2) coating PAN fiber particles adsorbed with anaerobic bacteria with a PVDF solution, forming a polymer film on the surface of the PAN fiber particles by a phase inversion method, and obtaining PAN fiber particles with fixed anaerobic bacteria; 3) The PAN fiber particles with fixed anaerobic bacteria are immersed in a mixture of bacteria-algae symbiotic suspension and sodium alginate, and then taken out and placed in a calcium chloride solution to cross-link and harden to form a gel, that is, a double-layer anaerobic bacteria-algae symbiotic immobilized particle.

[0008] Preferably, the method for modifying PAN fiber particles to make them positively charged is: the PAN fiber particles are first treated with alkali, and then immersed in a PEI (polyethyleneimine) aqueous solution. Specifically, the dried PAN fiber particles are placed in a NaOH solution for water bath heating, then placed in an HCl aqueous solution to neutralize excess NaOH, taken out and washed with deionized water, and finally immersed in a PEI aqueous solution, taken out, washed and dried to obtain modified PAN fiber particles with positive charges.

[0009] Preferably, the preparation method of PAN fiber particles is: crushing PAN fiber into particles in a grinder, washing with deionized water for several times, and drying to obtain PAN fiber particles. The particle size of PAN fiber particles is preferably 7-8 mm.

[0010] The concentration of NaOH solution is 2-5 mol / L, the water bath heating time is 0.5-3 h, and the water bath temperature is 40-60° C.; the concentration of HCl aqueous solution is 1-4 mol / L; the mass fraction of PEI solution is 1-8%, and the immersion time is 0.5-2 h.

[0011] Preferably, the preparation method of the anaerobic bacteria solution is: using food-grade brown sugar culture medium to culture the anaerobic bacteria under anoxic conditions to the logarithmic growth phase. The composition and concentration of the food-grade brown sugar culture medium are as follows: NaCl 35000mg / L, brown sugar 10-15g / L. The anaerobic bacteria include acetogenic bacteria and methanogenic bacteria.

[0012] Preferably, the mass concentration of the PVDF solution is 10-18%, and the solvent is DMF; the specific method of forming a polymer film on the modified PAN fiber ball by the phase inversion method is as follows: dissolving PVDF in DMF to obtain a casting solution, using tweezers to clamp the modified PAN fiber ball and dip it in the PVDF casting solution, so that the surface of the modified PAN fiber ball is evenly coated with the PVDF casting solution, and finally placing the PVDF casting solution with the surface coated with the modified PAN fiber ball in pure water to form a polymer film on the surface of the modified PAN fiber ball by the phase inversion method.

[0013] Preferably, the preparation method of the bacteria-algae symbiotic suspension is: using algae liquid culture medium and BTB culture medium to culture Chlorella and aerobic denitrifying bacteria to the logarithmic growth phase, respectively, using a centrifuge to separate the algae and aerobic denitrifying bacteria, and then mixing the obtained algae precipitate and aerobic denitrifying bacteria precipitate with equal mass (dry weight), and finally using simulated wastewater to re-suspend the bacteria-algae mixed precipitate to obtain the bacteria-algae symbiotic suspension.

[0014] Preferably, the concentration of the bacteria-algae symbiotic suspension is 2200-2800 mg / L, and the mass concentration of the sodium alginate solution is 1-5%.

[0015] Preferably, the mass concentration of the calcium chloride solution is 1-4%, and the cross-linking time is 8-24 hours.

[0016] The present invention also provides application of the double-layer anaerobic bacteria-bacteria-algae symbiotic immobilization particles in sewage treatment.

[0017] Therefore, the beneficial effects of the present invention are as follows: (1) the modified PAN fiber particles have positive charges and the anaerobic bacteria have negative charges, so more anaerobic bacteria can be loaded.

[0018] (2) From the inside to the outside, there is an anaerobic layer-bacteria-algae mixed layer. The algae in the bacteria-algae mixed layer can produce oxygen and provide it to aerobic denitrifying bacteria. The aerobic denitrifying bacteria use this oxygen to decompose and metabolize organic matter and perform denitrification at the same time. The carbon dioxide produced by metabolism can be provided to the algae while maintaining the anoxic environment of the anaerobic bacteria in the inner core. The acetogenic bacteria in the anaerobic layer can convert organic matter not used by aerobic denitrifying bacteria into acetic acid, and the methanogenic bacteria further converts acetic acid into methane, thereby realizing multi-stage utilization of carbon sources in sewage and achieving the purpose of further reducing COD. The double-layer anaerobic bacteria-bacteria-algae symbiotic immobilization particles can achieve deep removal of carbon, nitrogen and phosphorus in the tail water.

[0019] (3) The double-layer anaerobic bacteria-algae symbiotic immobilization particles divide and immobilize anaerobic microorganisms and aerobic microorganisms into regions, and utilize the physiological synergy between microorganisms to allow the inner layer anaerobic microorganisms and the outer layer aerobic microorganisms to play a greater role in different regions of the carrier, thereby achieving the purpose of deep removal of carbon, nitrogen, phosphorus, etc. in sewage.

[0020] (4) The double-layered anaerobic-bacteria-algae symbiotic immobilization particles adopt a double encapsulation strategy. Compared with the traditional alginate encapsulation method, the construction of the porous polymer layer can effectively prevent the loss of microorganisms and the use of modified PAN fibers can load more microorganisms and improve the material strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The degradation effects of the immobilized particles of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 on the simulated wastewater are shown in FIG. 1-1 is the degradation rate of TP, 1-2 is the degradation rate of TN, 1-3 is the degradation rate of nitrate, and 1-4 is the degradation rate of COD.

[0022] Figure 2 The degradation effects of the immobilized particles of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 on the actual marine aquaculture tail water are shown in Figure 2-1, 2-2, 2-3, 2-4 and 2-5. In the figure, 2-1 is the degradation rate of TP, 2-2 is the degradation rate of TN, 2-3 is the degradation rate of nitrate and 2-4 is the degradation rate of COD. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below through specific embodiments.

[0024] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art. Unless otherwise specified, parts are all weight parts, temperatures are expressed in ° C or at ambient temperature, and pressures are atmospheric pressure or near atmospheric pressure. There are many variations and combinations of reaction conditions (such as component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method, and only reasonable routine experiments will be required to optimize such method conditions.

[0025] Example 1. A double-layer anaerobic bacteria-algae symbiotic immobilization particle From the inside to the outside, it includes PAN (polyacrylonitrile) fiber particles, an anaerobic bacteria layer, a polymer film, a bacteria-algae symbiotic layer and a calcium alginate gel layer. The particle size of the PAN fiber particles is preferably 7-8 mm.

[0026] 2. Preparation method of double-layer anaerobic bacteria-algae symbiotic immobilization particles The following steps are involved: 1) After modifying PAN fiber particles so that they carry positive charges, they are immersed in an anaerobic bacteria solution to obtain PAN fiber particles adsorbed by anaerobic bacteria; The PAN fiber is crushed into particles in a grinder, washed with deionized water several times, and then dried to obtain PAN fiber particles with a particle size of 7-8mm. The dried PAN fiber particles are placed in a 2-5mol / L NaOH solution and heated in a 40-60℃ water bath for 0.5-3h, then soaked in a 1-4mol / L HCl aqueous solution for 1-4h to neutralize the excess NaOH, taken out and washed with deionized water, and finally immersed in a 1-8% PEI (polyethyleneimine) aqueous solution for 0.5-2h, taken out, washed and dried to obtain modified PAN fiber particles with positive charge. The preparation method of the anaerobic solution is: anaerobic bacteria are cultured under anaerobic conditions using food-grade brown sugar culture medium to the logarithmic growth phase. The composition and concentration of the food-grade brown sugar culture medium are as follows: NaCl 35000mg / L, brown sugar 10-15g / L. Anaerobic bacteria include acetogenic bacteria and methanogenic bacteria.

[0027] 2) coating the PAN fiber particles adsorbed with anaerobic bacteria with a PVDF solution to form a polymer film, thereby obtaining PAN fiber particles with fixed anaerobic bacteria; The mass concentration of the PVDF solution is 10-18%, and the solvent is DMF; the specific method of using the phase inversion method to form a polymer film on the modified PAN fiber ball is as follows: dissolving PVDF in DMF to obtain a casting solution, using tweezers to clamp the modified PAN fiber ball and dip it in the PVDF casting solution, so that the surface of the modified PAN fiber ball is evenly coated with the PVDF casting solution, and finally placing the PVDF casting solution coated with the modified PAN fiber ball on the surface in pure water to form a polymer film on the surface of the modified PAN fiber ball through the phase inversion method.

[0028] 3) The PAN fiber particles with fixed anaerobic bacteria are immersed in a mixture of the bacteria-algae symbiotic suspension and sodium alginate, and then taken out and placed in a calcium chloride solution to cross-link and harden to form a gel, which is a double-layer anaerobic bacteria-algae symbiotic immobilized particle; The preparation method of the bacteria-algae symbiotic suspension is as follows: use algae liquid culture medium and BTB culture medium to culture Chlorella and aerobic denitrifying bacteria to the logarithmic growth phase respectively, use a centrifuge to separate the algae and aerobic denitrifying bacteria, and then mix the obtained algae precipitate and aerobic denitrifying bacteria precipitate with equal mass (dry weight), and finally use simulated wastewater to re-suspend the bacteria-algae mixed precipitate to obtain the bacteria-algae symbiotic suspension. The concentration of the bacteria-algae symbiotic suspension is 2200-2800 mg / L, and the mass concentration of the sodium alginate solution is 1-5%. The mass concentration of the calcium chloride solution is 1-4%, and the cross-linking time is 8-24h. The composition and concentration of the algae liquid culture medium are as follows: NaCl 35000 mg / L, NaNO 3 800mg / L, NH 4 Cl 600mg / L, MgSO 4 7H 2O 75mg / L, K 2 HPO 4 40mg / L, CaCl 2 36mg / L, Na 2 CO 3 20mg / L, C 6 H 8 O 7 (Citric acid) 6mg / L, H 3 BO 3 2.86mg / L, MnCl 2 ·H 2 O1.81mg / L, C 10 H 16 N 2 O 8 (ethylenediaminetetraacetic acid) 1mg / L, Na 2 MoO 4 ·2H 2 O 0.39mg / L, ZnSO 4 7H 2 O0.222mg / L, CuSO 4 0.079mg / L, Co(NO 3 ) 2 6H 2 O 0.049mg / L; the composition and concentration of BTB medium are as follows: NaCl 35000mg / L, KNO 3 1000mg / L, C 4 H 4 Na 3 O 2 (Succinic acid) 1000mg / L, KH 2 PO 4 1000mg / L, FeSO 4 7H 2 O 50mg / L, CaCl 2 200mg / L, MgSO 4 7H 2 O 1000mg / L.

[0029] 3. Application of double-layer anaerobic bacteria-algae symbiotic immobilization particles The double-layer anaerobic bacteria-algae symbiotic immobilized particles are applied to sewage treatment to remove carbon, nitrogen, phosphorus, etc. in the sewage.

[0030] Example 1 A method for preparing double-layer anaerobic bacteria-algae symbiotic immobilized particles, the steps are as follows: Step 1: Preparation of modified PAN fiber balls Step 1-1: Preparation of unmodified PAN fiber balls The PAN fibers to be treated are placed in a grinder and crushed into balls; they are first washed with deionized water for several times, and then dried to obtain unmodified PAN fiber balls with a particle size of 7-8 mm.

[0031] Step 1-2: Preparation of modified PAN fiber balls The dried PAN fiber balls were placed in a 3 mol / L NaOH solution and heated in a 45°C water bath, then placed in a 2 mol / L HCl aqueous solution for 2 h to neutralize excess NaOH, taken out and washed with deionized water, and finally immersed in a 1% by mass PEI aqueous solution for 0.5 h. After being taken out, washed and dried, modified PAN fiber balls with positive charge were obtained.

[0032] Step 2: Immobilization of anaerobic bacteria Step 2-1: Adsorption of anaerobic bacteria by modified PAN fiber balls Using an edible brown sugar medium with a composition and concentration of 35000 mg / L NaCl and 10 g / L brown sugar, the antibacterial agent (anaerobic bacteria purchased from Haiyam Environmental Protection Factory) was cultured to the logarithmic growth phase under anoxic conditions to obtain an anaerobic solution. The modified PAN fiber ball was placed in the anaerobic solution, and the positive charge of the modified PAN fiber ball adsorbed the negatively charged anaerobic bacteria to obtain the modified PAN fiber ball adsorbed with anaerobic bacteria.

[0033] Step 2-2: Fixation of anaerobic bacteria Weigh PVDF and dissolve it in N,N-dimethylformamide, place it on a magnetic stirrer and stir until PVDF is completely dissolved to obtain a PVDF casting solution with a mass concentration of 15%. Use tweezers to hold the modified PAN fiber ball and dip it in the PVDF casting solution to evenly coat the surface of the modified PAN fiber ball with the PVDF casting solution. Finally, place the PVDF casting solution coated with the modified PAN fiber ball in pure water to form a polymer film on the surface of the modified PAN fiber ball through a phase inversion method to obtain a fixed anaerobic modified PAN fiber ball.

[0034] Step 3: Preparation of bacteria-algae-sodium alginate mixture Step 3-1: Cultivation of bacterial-algal symbiotic system Chlorella and aerobic denitrifying bacteria were cultured to the logarithmic growth phase using algae liquid culture medium and BTB culture medium, respectively. The algae and aerobic denitrifying bacteria were separated using a centrifuge. The obtained algae precipitate and aerobic denitrifying bacteria precipitate were then mixed at a ratio of 1:1 (dry weight). Finally, the bacteria-algae mixed precipitate was resuspended using simulated wastewater to obtain a bacteria-algae symbiotic suspension with a concentration of 2500 mg / L.

[0035] The composition and concentration of algae liquid culture medium are as follows: NaCl 35000mg / L, NaNO3 800mg / L, NH 4 Cl600mg / L, MgSO 4 7H 2 O 75mg / L, K 2 HPO 4 40mg / L, CaCl 2 36mg / L, Na 2 CO 3 20mg / L, C 6 H 8 O 7 (Citric acid) 6mg / L, H 3 BO 3 2.86mg / L, MnCl 2 ·H 2 O 1.81mg / L, C 10 H 16 N 2 O 8 (ethylenediaminetetraacetic acid) 1mg / L, Na 2 MoO 4 ·2H 2 O 0.39mg / L, ZnSO 4 7H 2 O 0.222mg / L, CuSO 4 0.079mg / L, Co(NO 3 ) 2 6H 2 O0.049mg / L; the composition and concentration of BTB medium are as follows: NaCl 35000mg / L, KNO 3 1000mg / L, C 4 H 4 Na 3 O 2 (Succinic acid) 1000mg / L, KH 2 PO 4 1000mg / L, FeSO 4 7H 2 O 50mg / L, CaCl 2 200mg / L, MgSO 4 7H 2 O 1000mg / L.

[0036] Step 3-2: Preparation of bacteria-algae-sodium alginate mixture A sodium alginate solution with a mass concentration of 3% was prepared, and the sodium alginate solution was evenly mixed with the bacteria-algae symbiotic suspension to obtain a bacteria-algae sodium alginate mixed solution.

[0037] Step 4: Preparation of dual-layered anaerobic bacteria-algae symbiotic immobilization particles The modified PAN fiber balls encapsulated by polymer film and adsorbed with anaerobic bacteria were placed in a mixture of bacteria and algae and sodium alginate to adsorb bacteria and algae. After being taken out, they were placed in a 3% mass concentration of CaCl 2 The cross-linking reaction was carried out in the solution for 10 hours to harden it into a gel; finally, it was cleaned to complete the preparation of the double-layered anaerobic bacteria-algae symbiotic immobilization particles.

[0038] Example 2 A method for preparing double-layer anaerobic bacteria-algae symbiotic immobilized particles, the steps are as follows: Step 1: Preparation of modified PAN fiber balls Step 1-1: Preparation of unmodified PAN fiber balls The PAN fibers to be treated are placed in a grinder and crushed into balls; they are first washed with deionized water for several times, and then dried to obtain unmodified PAN fiber balls with a particle size of 7-8 mm.

[0039] Step 1-2: Preparation of modified PAN fiber balls The dried PAN fiber balls were placed in a 2 mol / L NaOH solution and heated in a 40°C water bath, then placed in a 1 mol / L HCl aqueous solution for 1 hour to neutralize excess NaOH, taken out and washed with deionized water, and finally immersed in a 5% by mass PEI aqueous solution for 1 hour. After being taken out, washed and dried, modified PAN fiber balls with positive charge were obtained.

[0040] Step 2: Immobilization of anaerobic bacteria Step 2-1: Adsorption of anaerobic bacteria by modified PAN fiber balls Using an edible-grade brown sugar medium with a composition and concentration of 35000 mg / L NaCl and 12 g / L brown sugar, the antibacterial agent (anaerobic bacteria purchased from Haiyam Environmental Protection Factory) was cultured to the logarithmic growth phase under anoxic conditions to obtain an anaerobic solution. The modified PAN fiber ball was placed in the anaerobic solution, and the positive charge of the modified PAN fiber ball adsorbed the negatively charged anaerobic bacteria to obtain the modified PAN fiber ball adsorbed with anaerobic bacteria.

[0041] Step 2-2: Fixation of anaerobic bacteria Weigh PVDF and dissolve it in N,N-dimethylformamide, place it on a magnetic stirrer and stir until PVDF is completely dissolved to obtain a PVDF casting solution with a mass concentration of 10%. Use tweezers to hold the modified PAN fiber ball and dip it in the PVDF casting solution to evenly coat the surface of the modified PAN fiber ball with the PVDF casting solution. Finally, place the PVDF casting solution coated with the modified PAN fiber ball in pure water to form a polymer film on the surface of the modified PAN fiber ball through a phase inversion method to obtain a fixed anaerobic modified PAN fiber ball.

[0042] Step 3: Preparation of bacteria-algae-sodium alginate mixture Step 3-1: Cultivation of bacterial-algal symbiotic system Chlorella and aerobic denitrifying bacteria were cultured to the logarithmic growth phase using algae liquid culture medium and BTB culture medium, respectively. The algae and aerobic denitrifying bacteria were separated using a centrifuge. The obtained algae precipitate and aerobic denitrifying bacteria precipitate were then mixed at a ratio of 1:1 (dry weight). Finally, simulated wastewater was used to resuspend the bacteria-algae mixed precipitate to obtain a bacteria-algae symbiotic suspension with a concentration of 2200 mg / L.

[0043] The composition and concentration of algae liquid culture medium are as follows: NaCl 35000mg / L, NaNO 3 800mg / L, NH 4 Cl600mg / L, MgSO 4 7H 2 O 75mg / L, K 2 HPO 4 40mg / L, CaCl 2 36mg / L, Na 2 CO 3 20mg / L, C 6 H 8 O 7 (Citric acid) 6mg / L, H 3 BO 3 2.86mg / L, MnCl 2 ·H 2 O 1.81mg / L, C 10 H 16 N 2 O 8 (ethylenediaminetetraacetic acid) 1mg / L, Na 2 MoO 4 ·2H 2 O 0.39mg / L, ZnSO 4 7H 2 O 0.222mg / L, CuSO 4 0.079mg / L, Co(NO 3 ) 2 6H 2 O0.049mg / L; the composition and concentration of BTB medium are as follows: NaCl 35000mg / L, KNO 3 1000mg / L, C 4 H 4 Na 3 O 2 (Succinic acid) 1000mg / L, KH 2 PO4 1000mg / L, FeSO 4 7H 2 O 50mg / L, CaCl 2 200mg / L, MgSO 4 7H 2 O 1000mg / L.

[0044] Step 3-2: Preparation of bacteria-algae-sodium alginate mixture A sodium alginate solution with a mass concentration of 1% was prepared, and the sodium alginate solution was evenly mixed with the bacteria-algae symbiotic suspension to obtain a bacteria-algae sodium alginate mixed solution.

[0045] Step 4: Preparation of dual-layered anaerobic bacteria-algae symbiotic immobilization particles The modified PAN fiber balls encapsulated by polymer film and adsorbed with anaerobic bacteria were placed in a mixture of bacteria and algae and sodium alginate to adsorb bacteria and algae. After being taken out, they were placed in a 1% mass concentration of CaCl 2 The cross-linking reaction is carried out in the solution for 8 hours to harden it into a gel; finally, it is cleaned to complete the preparation of the double-layered anaerobic bacteria-algae symbiotic immobilization particles.

[0046] Example 3 A method for preparing double-layer anaerobic bacteria-algae symbiotic immobilized particles, the steps are as follows: Step 1: Preparation of modified PAN fiber balls Step 1-1: Preparation of unmodified PAN fiber balls The PAN fibers to be treated are placed in a grinder and crushed into balls; they are first washed with deionized water for several times, and then dried to obtain unmodified PAN fiber balls with a particle size of 7-8 mm.

[0047] Step 1-2: Preparation of modified PAN fiber balls The dried PAN fiber balls were placed in a 5 mol / L NaOH solution and heated in a 60°C water bath, then placed in a 4 mol / L HCl aqueous solution for 4 hours to neutralize excess NaOH, taken out and washed with deionized water, and finally immersed in an 8% by mass PEI aqueous solution for 2 hours. After being taken out, washed and dried, modified PAN fiber balls with positive charge were obtained.

[0048] Step 2: Immobilization of anaerobic bacteria Step 2-1: Adsorption of anaerobic bacteria by modified PAN fiber balls Using an edible-grade brown sugar medium with a composition and concentration of 35000 mg / L NaCl and 15 g / L brown sugar, the antibacterial agent (anaerobic bacteria purchased from Haiyam Environmental Protection Factory) was cultured to the logarithmic growth phase under anoxic conditions to obtain an anaerobic solution. The modified PAN fiber ball was placed in the anaerobic solution, and the positive charge of the modified PAN fiber ball adsorbed the negatively charged anaerobic bacteria to obtain the modified PAN fiber ball adsorbed with anaerobic bacteria.

[0049] Step 2-2: Fixation of anaerobic bacteria Weigh PVDF and dissolve it in N,N-dimethylformamide, place it on a magnetic stirrer and stir until PVDF is completely dissolved to obtain a PVDF casting solution with a mass concentration of 18%. Use tweezers to hold the modified PAN fiber ball and dip it in the PVDF casting solution to evenly coat the surface of the modified PAN fiber ball with the PVDF casting solution. Finally, place the PVDF casting solution coated with the modified PAN fiber ball in pure water to form a polymer film on the surface of the modified PAN fiber ball through a phase inversion method to obtain a fixed anaerobic modified PAN fiber ball.

[0050] Step 3: Preparation of bacteria-algae-sodium alginate mixture Step 3-1: Cultivation of bacterial-algal symbiotic system Chlorella and aerobic denitrifying bacteria were cultured to the logarithmic growth phase using algae liquid culture medium and BTB culture medium, respectively. The algae and aerobic denitrifying bacteria were separated using a centrifuge. The obtained algae precipitate and aerobic denitrifying bacteria precipitate were then mixed at a ratio of 1:1 (dry weight). Finally, simulated wastewater was used to resuspend the bacteria-algae mixed precipitate to obtain a bacteria-algae symbiotic suspension with a concentration of 2200 mg / L.

[0051] The composition and concentration of algae liquid culture medium are as follows: NaCl 35000mg / L, NaNO 3 800mg / L, NH 4 Cl600mg / L, MgSO 4 7H 2 O 75mg / L, K 2 HPO 4 40mg / L, CaCl 2 36mg / L, Na 2 CO 3 20mg / L, C 6 H 8 O 7 (Citric acid) 6mg / L, H 3 BO 3 2.86mg / L, MnCl 2 ·H 2 O 1.81mg / L, C 10 H 16 N2 O 8 (ethylenediaminetetraacetic acid) 1mg / L, Na 2 MoO 4 ·2H 2 O 0.39mg / L, ZnSO 4 7H 2 O 0.222mg / L, CuSO 4 0.079mg / L, Co(NO 3 ) 2 6H 2 O0.049mg / L; the composition and concentration of BTB medium are as follows: NaCl 35000mg / L, KNO 3 1000mg / L, C 4 H 4 Na 3 O 2 (Succinic acid) 1000mg / L, KH 2 PO 4 1000mg / L, FeSO 4 7H 2 O 50mg / L, CaCl 2 200mg / L, MgSO 4 7H 2 O 1000mg / L.

[0052] Step 3-2: Preparation of bacteria-algae-sodium alginate mixture A sodium alginate solution with a mass concentration of 5% was prepared, and the sodium alginate solution was evenly mixed with the bacteria-algae symbiotic suspension to obtain a bacteria-algae sodium alginate mixed solution.

[0053] Step 4: Preparation of dual-layered anaerobic bacteria-algae symbiotic immobilization particles The modified PAN fiber balls encapsulated by polymer film and adsorbed with anaerobic bacteria were placed in a mixture of bacteria and algae and sodium alginate to adsorb bacteria and algae. After being taken out, they were placed in a 4% mass concentration of CaCl 2 The cross-linking reaction is carried out in the solution for 24 hours to harden it into a gel; finally, it is cleaned to complete the preparation of the double-layered anaerobic bacteria-algae symbiotic immobilization particles.

[0054] Comparative Example 1 The difference from Example 1 is that the PAN fiber balls are not modified and carry positive charges. The details are as follows: A method for preparing double-layer anaerobic bacteria-algae symbiotic immobilized particles, the steps are as follows: Step 1: Preparation of PAN fiber balls Take the PAN fiber to be treated, place it in a grinder and grind it into balls; wash it several times with deionized water, and then dry it to obtain PAN fiber balls with a particle size of 7-8mm. Place the dried PAN fiber balls in a 3mol / L NaOH solution and heat them in a 45℃ water bath, then place them in a 2mol / L HCl aqueous solution for 2h to neutralize the excess NaOH, take them out and wash them with deionized water to obtain the treated PAN fiber balls.

[0055] Step 2: Immobilization of anaerobic bacteria Step 2-1: PAN fiber balls adsorb anaerobic bacteria Using an edible brown sugar medium with a composition and concentration of 35000 mg / L NaCl and 10 g / L brown sugar, the antibacterial agent (anaerobic bacteria purchased from Haiyam Environmental Protection Factory) was cultured to the logarithmic growth phase under anoxic conditions to prepare an anaerobic solution. The treated PAN fiber balls were placed in the anaerobic solution to obtain PAN fiber balls adsorbed with anaerobic bacteria.

[0056] Step 2-2: Fixation of anaerobic bacteria Weigh PVDF and dissolve it in N,N-dimethylformamide, place it on a magnetic stirrer and stir until PVDF is completely dissolved to obtain a PVDF casting solution with a mass concentration of 15%. Use tweezers to grab the PAN fiber ball and dip it in the PVDF casting solution to evenly coat the surface of the PAN fiber ball with the PVDF casting solution. Finally, place the PVDF casting solution coated with the PAN fiber ball in pure water to form a polymer film on the surface of the PAN fiber ball through the phase inversion method to obtain the PAN fiber ball with fixed anaerobic bacteria.

[0057] Step 3: Preparation of bacteria-algae-sodium alginate mixture Step 3-1: Cultivation of bacterial-algal symbiotic system Chlorella and aerobic denitrifying bacteria were cultured to the logarithmic growth phase using algae liquid culture medium and BTB culture medium, respectively. The algae and aerobic denitrifying bacteria were separated using a centrifuge. The obtained algae precipitate and aerobic denitrifying bacteria precipitate were then mixed at a ratio of 1:1 (dry weight). Finally, the bacteria-algae mixed precipitate was resuspended using simulated wastewater to obtain a bacteria-algae symbiotic suspension with a concentration of 2500 mg / L.

[0058] The composition and concentration of algae liquid culture medium are as follows: NaCl 35000mg / L, NaNO 3 800mg / L, NH 4 Cl600mg / L, MgSO 4 7H 2 O 75mg / L, K 2 HPO 4 40mg / L, CaCl 2 36mg / L, Na 2 CO3 20mg / L, C 6 H 8 O 7 (Citric acid) 6mg / L, H 3 BO 3 2.86mg / L, MnCl 2 ·H 2 O 1.81mg / L, C 10 H 16 N 2 O 8 (ethylenediaminetetraacetic acid) 1mg / L, Na 2 MoO 4 ·2H 2 O 0.39mg / L, ZnSO 4 7H 2 O 0.222mg / L, CuSO 4 0.079mg / L, Co(NO 3 ) 2 6H 2 O0.049mg / L; the composition and concentration of BTB medium are as follows: NaCl 35000mg / L, KNO 3 1000mg / L, C 4 H 4 Na 3 O 2 (Succinic acid) 1000mg / L, KH 2 PO 4 1000mg / L, FeSO 4 7H 2 O 50mg / L, CaCl 2 200mg / L, MgSO 4 7H 2 O 1000mg / L.

[0059] Step 3-2: Preparation of bacteria-algae-sodium alginate mixture A sodium alginate solution with a mass concentration of 3% was prepared, and the sodium alginate solution was evenly mixed with the bacteria-algae symbiotic suspension to obtain a bacteria-algae sodium alginate mixed solution.

[0060] Step 4: Preparation of dual-layered anaerobic bacteria-algae symbiotic immobilization particles The PAN fiber balls encapsulated by the polymer film and adsorbed with anaerobic bacteria were placed in the mixture of bacteria and algae and sodium alginate to adsorb the bacteria and algae. After taking them out, they were placed in a mixture of 3% CaCl 2 The cross-linking reaction was carried out in the solution for 10 hours to harden it into a gel; finally, it was cleaned to complete the preparation of the double-layered anaerobic bacteria-algae symbiotic immobilization particles.

[0061] Comparative Example 2 The difference from Example 1 is that the PAN fiber balls are replaced by glass fiber balls. The glass fiber balls have a particle size of 5-6 mm and are made from 3 mm chopped glass fibers.

[0062] Comparative Example 3 The difference from Example 1 is that the concentration of the bacteria-algae symbiotic suspension in step 3-1 is 1500 mg / L.

[0063] Performance Testing The sewage treatment performance of the immobilized particles of each embodiment and comparative example was tested.

[0064] (1) Simulated wastewater degradation experiment Based on the concentration of marine aquaculture tail water as a reference, simulated wastewater of marine aquaculture tail water was prepared, and the prepared double-layer structure anaerobic-bacteria-algae symbiotic immobilization particles were placed in the simulated wastewater. Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were selected for experiments. The particles were placed on a shaker and oscillated at a speed of 120 r / min. Three parallel experiments were set up. The concentrations of TP, TN, nitrate, and COD in the wastewater were measured every 12 h, and the degradation rate was calculated. The experimental results are as follows: Figure 1 The initial concentrations of the simulated wastewater were: NaCl 3500 mg / L; TP 1.14 mg / L, TN 7.26 mg / L, nitrate (NO 3 - N) 4.18mg / L, COD 4.88mg / L. The concentrations of TP, TN, nitrate and COD of the four double-layered anaerobic bacteria-algae symbiotic immobilized particles after 48h of degradation of simulated wastewater are shown in Table 1.

[0065] Table 1. TP, TN, nitrate and COD concentrations after 48 h of degradation of simulated wastewater by double-layer anaerobic bacteria-algae symbiotic immobilized particles project TP(mg / L) TN(mg / L) <![CDATA[NO 3 - N(mg / L)]]> COD(mg / L) Example 1 0.14 1.51 0.27 0.67 Comparative Example 1 0.21 1.94 0.41 1.19 Comparative Example 2 0.29 2.19 0.53 1.30 Comparative Example 3 0.32 2.59 0.83 0.86 (2) Degradation experiment of tailwater treatment pool in marine aquaculture farm The prepared double-layer structure anaerobic-bacteria-algae symbiotic immobilized particles were placed in the tail water of a marine aquaculture farm in Zhoushan City. Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were selected for experiments. The aeration was performed, and the concentrations of TP, TN, nitrate, and COD in the tail water were measured every 12 hours and the degradation rate was calculated. The experimental results are shown in FIG. Figure 2 The initial concentrations of marine aquaculture tail water are: NaCl 3500mg / L; TP 1.32mg / L, TN 3.64mg / L, nitrate (NO 3 -N) 1.95 mg / L, COD 11.4 mg / L, the concentrations of TP, TN, nitrate and COD after the four double-level structure anaerobic bacteria-algae symbiotic immobilized particles degraded the simulated wastewater for 48 hours are shown in Table 2.

[0066] Table 2. TP, TN, nitrate and COD concentrations of double-layer anaerobic bacteria-algae symbiotic immobilized particles after degradation of marine aquaculture tail water for 48 hours project TP(mg / L) TN(mg / L) <![CDATA[NO 3 - N(mg / L)]]> COD(mg / L) Example 1 0.23 0.90 0.24 2.21 Comparative Example 1 0.28 1.17 0.33 3.94 Comparative Example 2 0.36 1.30 0.38 4.54 Comparative Example 3 0.45 1.03 0.48 3.16 From the above results, it can be seen that compared with Example 1, the PAN fiber balls in Comparative Example 1 are not modified and are not charged. Because the anaerobic bacteria loaded are negatively charged, the anaerobic bacteria loaded are reduced, which affects the multi-stage utilization of carbon sources in the sewage by acetogenic bacteria and methanogenic bacteria in the anaerobic layer, resulting in a decrease in COD degradation rate, and the corresponding TP, TN, NO 3 - The degradation rate of N also decreased; after the PAN fiber balls in comparative example 2 were changed to glass fiber balls, the adsorption of anaerobic bacteria by glass fiber balls was less than that of unmodified PAN fiber balls, resulting in a decrease in the amount of anaerobic bacteria loaded, a decrease in the COD degradation rate, and a lower degradation rate than that in comparative example 1. The degradation rates of TP, TN, and NO 3 - The degradation rates of N also decreased. In Comparative Example 3, the concentration of the algae symbiotic suspension decreased from 2500 mg / L to 1500 mg / L. The physiological synergy between the microorganisms in the algae mixed layer was weakened due to the decrease in the concentration of the algae symbiotic suspension. Therefore, the degradation rates of TN, TP, and NO 3 - N decreased.

[0067] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. Double-layer anaerobic bacteria-algae symbiotic immobilization particles, characterized in that: From the inside to the outside, it includes PAN fiber particles, anaerobic bacteria layer, polymer film, bacteria-algae symbiotic layer and calcium alginate gel layer.

2. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 1, characterized in that: The following steps are involved: 1) After modifying PAN fiber particles so that they carry positive charges, they are immersed in an anaerobic bacteria solution to obtain PAN fiber particles adsorbed by anaerobic bacteria; 2) coating PAN fiber particles adsorbed with anaerobic bacteria with a PVDF solution, forming a polymer film on the surface of the PAN fiber particles by a phase inversion method, and obtaining PAN fiber particles with fixed anaerobic bacteria; 3) The PAN fiber particles with fixed anaerobic bacteria are immersed in a mixture of bacteria-algae symbiotic suspension and sodium alginate, and then taken out and placed in a calcium chloride solution to cross-link and harden to form a gel, that is, a double-layer anaerobic bacteria-algae symbiotic immobilized particle.

3. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 2, characterized in that: Step 1) The method for modifying PAN fiber particles to make them carry positive charges is: the PAN fiber particles are first treated with alkali and then immersed in a polyethyleneimine aqueous solution.

4. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 3, characterized in that: The PAN fiber particles are first treated in a 2-5 mol / L NaOH solution at 40-60 °C for 0.5-3 h, taken out after neutralization, and immersed in a 1-8% by mass polyethyleneimine aqueous solution for 0.5-2 h.

5. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 2, 3 or 4, characterized in that: Step 1) The method for preparing the anaerobic bacteria solution is as follows: using food-grade brown sugar culture medium to culture the anaerobic bacteria under anoxic conditions to a logarithmic growth phase.

6. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 2, characterized in that: In step 2), the mass concentration of the PVDF solution is 10-18%, and the solvent is DMF.

7. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 2, characterized in that: Step 3) The preparation method of the bacteria-algae symbiotic suspension is as follows: using algae liquid culture medium and BTB culture medium to culture Chlorella and aerobic denitrifying bacteria to the logarithmic growth phase respectively, using a centrifuge to separate the algae and the aerobic denitrifying bacteria, and then mixing the obtained algae precipitate and aerobic denitrifying bacteria precipitate with equal mass (dry weight), and finally using simulated wastewater to re-suspend the bacteria-algae mixed precipitate to obtain the bacteria-algae symbiotic suspension.

8. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 2, characterized in that: Step 3) The concentration of the bacteria-algae symbiotic suspension is 2200-2800 mg / L, and the mass concentration of the sodium alginate solution is 1-5%.

9. The method for preparing the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 2, 7 or 8, characterized in that: Step 3) The mass concentration of the calcium chloride solution is 1-4%, and the cross-linking time is 8-24 h.

10. Use of the double-layer anaerobic bacteria-algae symbiotic immobilized particles according to claim 1 in sewage treatment.

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