Sorting-immobilized microbial degradation reaction system and method for removing micro-plastics in seawater

Abstract

The invention provides a sorting-immobilized microbial degradation reaction system and a method for removing microplastics in seawater, and belongs to the technical field of mariculture wastewater treatment. The sorting-immobilized microbial degradation reaction system comprises a water inlet unit, a sorting and filtering unit 3 and a permeable reactive barrier 9 which are sequentially communicated, a filter screen 13 is arranged in the sorting and filtering unit 3, the aperture of the filter screen 13 is designed to be 2-2.5 mm, and the permeable reactive barrier 9 is arranged in the direction from water inlet to water outlet. A modified zeolite filler layer, an immobilized microorganism filler combination layer and an adsorption filler layer which are laid in the longitudinal direction are sequentially arranged in the permeable reactive barrier 9. By adopting the sorting-immobilized microbial degradation reaction system provided by the invention, efficient removal of micro-plastics in seawater can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of marine aquaculture wastewater treatment, and in particular to a sorting-immobilized microbial degradation reaction system and a method for removing microplastics in seawater. Background Art

[0002] Microplastics (MP) are new pollutants, broadly referring to plastic particles, fragments or fibers with a diameter of less than 5mm. Microplastics are highly mobile and difficult to degrade, and have now invaded almost every corner of the earth, even the Arctic. Microplastics continue to migrate through surface runoff and gradually spread to most rivers, lakes and seas.

[0003] Microplastic pollutants can interfere with the endocrine system of organisms in aquaculture environments, causing various physiological diseases, and thus posing potential risks to human health. Moreover, because they are difficult to be metabolized and absorbed by passive objects and the human body, the part that cannot be excreted continues to accumulate in the body, causing cell damage, triggering local inflammation, and ultimately destroying the immune system. Compared with plastics visible to the naked eye, microplastics have a larger specific surface area, so they can serve as carriers of pollutants such as heavy metals and persistent organic matter, causing stronger synergistic toxicity to the aquatic environment. Therefore, the problem of microplastic governance is becoming increasingly prominent.

[0004] At present, the treatment technologies for microplastic pollution in water environments mainly include physical and chemical methods (such as flocculation precipitation and multiple filtration), biosorbent adsorption and artificial wetland collaborative removal methods, etc. The safest and most effective way is to degrade microplastics through specific microbial metabolism, and no secondary pollution will be caused to the water environment during the treatment process. However, the efficiency of using only microbial degradation is not high. At present, the relevant technologies are mainly aimed at the removal of microplastics in aquaculture ponds or groundwater. The salt content in marine aquaculture wastewater is relatively high. How to achieve efficient removal of microplastics in marine aquaculture wastewater is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a sorting-immobilized microbial degradation reaction system and a method for removing microplastics in seawater. The sorting-immobilized microbial degradation reaction system provided by the present invention can achieve efficient removal of microplastics in seawater.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a sorting-immobilized microbial degradation reaction system, comprising a water inlet unit, a sorting and filtering unit 3 and a permeation reaction wall 9 which are connected in sequence;

[0008] The sorting and filtering unit 3 includes a water inlet 10, a shell 12 and a water outlet 11. A filter screen 13 is arranged inside the shell 12. The aperture size of the filter screen 13 is designed to be 2 to 2.5 mm. An ultrasonic vibrator 14 is arranged inside the cavity formed by the filter screen 13. The channel between the inner wall of the shell 12 and the filter screen 13 is connected to the water inlet 10, and the water inlet 10 is connected to the water inlet unit; the channel between the filter screen 13 and the ultrasonic vibrator 14 is connected to the water outlet 11, and the water outlet 11 is connected to the osmotic reaction wall 9 through the liquid outlet pipe 5; a valve 15 is arranged at the bottom of the shell 12, and a storage box 4 is arranged at the outlet of the valve 15;

[0009] From the direction of water inlet to water outlet, the infiltration reaction wall 9 is sequentially provided with a modified zeolite filler layer, an immobilized microbial filler combination layer and an adsorption filler layer laid longitudinally;

[0010] The modified zeolite filler layer is filled with modified zeolite, which is natural zeolite soaked in KMnO 4 The solution is modified to obtain the KMnO 4 The concentration of the solution is 0.1-0.2 mol / L;

[0011] The immobilized microbial filler combination layer includes a plurality of groups of immobilized microbial filler layers arranged at intervals and a group of carbon-releasing material layers inserted between two adjacent groups of immobilized microbial filler layers; the immobilized microbial filler layer is filled with immobilized microbial fillers, and the immobilized microbial fillers are prepared by adsorption-embedding-crosslinking method from a first biochar, microbial sludge and a polyvinyl alcohol-sodium alginate composite melt, the mass ratio of the first biochar, microbial sludge and the polyvinyl alcohol-sodium alginate composite melt is 20-30:25-35:45-55, and the microbial sludge is a mixture of Bacillus licheniformis sludge, Bacillus pumilus sludge, Bacillus marinus sludge and Alkanophaga diesel sludge; the carbon-releasing material layer is filled with a carbon-releasing material, and the carbon-releasing material includes a polyvinyl alcohol carrier and starch and α-amylase loaded on the polyvinyl alcohol carrier;

[0012] The adsorption filler layer is filled with modified kaolin-biochar filler, and the modified kaolin-biochar filler is obtained by mixing kaolin and a second biochar and then calcining;

[0013] The first biochar and the second biochar are obtained by carbonization treatment of coastal wetland plants.

[0014] Preferably, the water inlet unit comprises a water pump 1 and a flow meter 2 , and the flow meter 2 is arranged on a pipeline between the water pump 1 and the sorting and filtering unit 3 .

[0015] Preferably, the sorting and filtering unit 3 also includes a backwashing device arranged between the liquid outlet pipe 5 and the osmotic reaction wall 9, and the backwashing device includes a one-way valve 6, a booster pump 7 and a backwashing liquid bottle 8 connected in sequence, and the one-way valve 6 is connected to the pipeline between the liquid outlet pipe 5 and the osmotic reaction wall 9.

[0016] Preferably, the thickness of the modified zeolite packing layer is 0.2-0.3 m, and the particle size of the modified zeolite is 1-2 mm; the modification treatment comprises: heating in a water bath at 30-40° C. for 2-3 h, discarding the supernatant, and rinsing the obtained solid material with deionized water until it is neutral.

[0017] Preferably, the number of immobilized microbial filler layers in the immobilized microbial filler combination layer is 3 to 4 groups, the thickness of each immobilized microbial filler layer is 0.3 to 0.5 m, and the particle size of the immobilized microbial filler is 2 to 3 mm;

[0018] The mass ratio of Bacillus licheniformis sludge, Bacillus pumilus sludge, Marinobacterium sludge and Diesel Alkanophage sludge in the microbial sludge is 20-30:30-40:20-30:10-20, and the total number of colonies of each sludge is ≥10 8 CFU / mL.

[0019] Preferably, the thickness of each group of the carbon-releasing material layer in the immobilized microbial filler combination layer is 0.2-0.3 m, and the particle size of the carbon-releasing material is 3-4 mm.

[0020] Preferably, the thickness of the adsorption filler layer is 0.6 to 0.8 m, and the particle size of the modified kaolin-biochar filler is 3 to 5 mm; when preparing the modified kaolin-biochar filler, the mass ratio of kaolin to the second biochar is 1:0.8 to 1.2, the calcination treatment temperature is 250 to 350°C, the insulation time is 60 to 150 min, and the calcination treatment is carried out in a nitrogen or argon protective atmosphere.

[0021] Preferably, the coastal wetland plants include yellow calamus and / or reed; the temperature of the carbonization treatment is 150-200° C., the insulation time is 60-90 min, and the carbonization treatment is carried out in a nitrogen or argon protective atmosphere.

[0022] The present invention provides a method for removing microplastics in seawater using the sorting-immobilized microbial degradation reaction system described in the above technical solution, comprising the following steps:

[0023] S1, transporting the seawater to be treated to the sorting and filtering unit 3 through the water inlet unit for sorting and processing, and obtaining seawater containing small particles of microplastics and large particles of microplastics, respectively, and the large particles of microplastics are collected in the storage box 4;

[0024] S2. The seawater containing small particles of microplastics is transported to the infiltration reaction wall 9 to sequentially undergo the processes of reducing the salinity and alkalinity of the seawater, undergoing degradation reactions, and adsorbing degradation products, and the purified water is discharged from the sorting-immobilized microbial degradation reaction system.

[0025] Preferably, the seawater to be treated is seawater aquaculture wastewater; the operation mode of the sorting-immobilized microbial degradation reaction system adopts a continuous water inlet method or an intermittent water inlet method; when the operation mode is the intermittent water inlet method, each operation cycle includes three days, of which the sorting-immobilized microbial degradation reaction system is in a full water stage for two days, and the sorting-immobilized microbial degradation reaction system is in an emptying stage on the other day, and the full water stage and the emptying stage are periodically alternated.

[0026] Beneficial effects: The principle of the sorting-immobilized microbial degradation reaction system provided by the present invention is to first use the sorting and filtering unit 3 to sort out large-particle microplastics from small-particle microplastics and then remove them in a targeted manner, which can effectively improve the microplastic removal efficiency. The modified zeolite filler layer in the permeable reaction wall 9 of the present invention has the first function that the modified zeolite has a strong ion exchange capacity, which can effectively reduce the salinity and alkalinity of seawater to an appropriate level, which is conducive to maintaining the activity of microbial mud. The second function is that the modified zeolite releases highly oxidizing primary ecological oxygen when it meets water, which can continuously supplement the dissolved oxygen required for microbial growth, so that the active microbial mud remains in an aerobic state, which is conducive to the efficient and long-term degradation reaction; the immobilized microbial filler layer has good sedimentation performance, and the microbial flora in the immobilized microbial filler layer can still remain fixed even under high hydraulic load operating conditions, thereby improving the efficiency of microplastic degradation; the carbon-releasing material layer can supply carbon sources for microbial growth, which helps the continuous reproduction and growth of microorganisms, so that the degradation reaction can continue; the adsorption filler layer can fully adsorb the degradation products and aging biofilms produced after the microplastics are degraded by the microbial mud, thereby promoting the forward progress of the degradation reaction and improving the degradation efficiency. Therefore, the sorting-immobilized microbial degradation reaction system provided by the present invention can achieve efficient removal of microplastics in seawater. The sorting-immobilization microbial degradation reaction system provided by the present invention has the advantages of rapid structural construction, reasonable cost, simple maintenance and management, and low energy consumption, which is conducive to practical promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the structure of the sorting-immobilized microbial degradation reaction system in an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the cross-sectional structure of the sorting and filtering unit;

[0029] 1 is a water pump, 2 is a flow meter, 3 is a sorting and filtering unit, 4 is a storage box, 5 is a liquid outlet pipe, 6 is a one-way valve, 7 is a booster pump, 8 is a backwash liquid bottle, 9 is an osmotic reaction wall, 10 is a water inlet, 11 is a water outlet, 12 is a shell, 13 is a filter screen, 14 is an ultrasonic vibrator, and 15 is a valve;

[0030] Figure 3 It is a schematic diagram of the cross-sectional structure of the infiltration reaction wall;

[0031] Figure 4 It is a comparison chart of the removal rate of small-particle microplastics with a particle size of <2 mm in each embodiment and comparative example. DETAILED DESCRIPTION

[0032] The present invention provides a sorting-immobilized microbial degradation reaction system, comprising a water inlet unit, a sorting and filtering unit 3 and a permeation reaction wall 9 which are connected in sequence;

[0033] The sorting and filtering unit 3 includes a water inlet 10, a shell 12 and a water outlet 11. A filter screen 13 is arranged inside the shell 12. The aperture size of the filter screen 13 is designed to be 2 to 2.5 mm. An ultrasonic vibrator 14 is arranged inside the cavity formed by the filter screen 13. The channel between the inner wall of the shell 12 and the filter screen 13 is connected to the water inlet 10, and the water inlet 10 is connected to the water inlet unit; the channel between the filter screen 13 and the ultrasonic vibrator 14 is connected to the water outlet 11, and the water outlet 11 is connected to the osmotic reaction wall 9 through the liquid outlet pipe 5; a valve 15 is arranged at the bottom of the shell 12, and a storage box 4 is arranged at the outlet of the valve 15;

[0034] From the direction of water inlet to water outlet, the infiltration reaction wall 9 is sequentially provided with a modified zeolite filler layer, an immobilized microbial filler combination layer and an adsorption filler layer laid longitudinally;

[0035] The modified zeolite filler layer is filled with modified zeolite, which is natural zeolite soaked in KMnO 4 The solution is modified to obtain the KMnO 4 The concentration of the solution is 0.1-0.2 mol / L;

[0036] The immobilized microbial filler combination layer includes a plurality of groups of immobilized microbial filler layers arranged at intervals and a group of carbon-releasing material layers inserted between two adjacent groups of immobilized microbial filler layers; the immobilized microbial filler layer is filled with immobilized microbial fillers, and the immobilized microbial fillers are prepared by adsorption-embedding-crosslinking method from a first biochar, microbial sludge and a polyvinyl alcohol-sodium alginate composite melt, the mass ratio of the first biochar, microbial sludge and the polyvinyl alcohol-sodium alginate composite melt is 20-30:25-35:45-55, and the microbial sludge is a mixture of Bacillus licheniformis sludge, Bacillus pumilus sludge, Bacillus marinus sludge and Alkanophaga diesel sludge; the carbon-releasing material layer is filled with a carbon-releasing material, and the carbon-releasing material includes a polyvinyl alcohol carrier and starch and α-amylase loaded on the polyvinyl alcohol carrier;

[0037] The adsorption filler layer is filled with modified kaolin-biochar filler, and the modified kaolin-biochar filler is obtained by mixing kaolin and a second biochar and then calcining;

[0038] The first biochar and the second biochar are obtained by carbonization treatment of coastal wetland plants.

[0039] The sorting-immobilized microbial degradation reaction system of the present invention includes a water inlet unit. As an embodiment of the present invention, the water inlet unit includes a water pump 1 and a flow meter 2, and the flow meter 2 is arranged on the pipeline between the water pump 1 and the sorting and filtering unit 3, so as to adjust the water inlet speed at any time.

[0040] The sorting-immobilized microbial degradation reaction system of the present invention comprises a sorting filtration unit 3 and a permeation reaction wall 9 which are sequentially connected to a water inlet unit, and are described in detail below.

[0041] In the present invention, the sorting and filtering unit 3 includes a water inlet 10, a shell 12 and a water outlet 11. A filter screen 13 is arranged inside the shell 12. The pore size of the filter screen 13 is designed to be 2 to 2.5 mm. An ultrasonic vibrator 14 is arranged inside the cavity formed by the filter screen 13; the channel between the inner wall of the shell 12 and the filter screen 13 is connected to the water inlet 10, and the water inlet 10 is connected to the water inlet unit; the channel between the filter screen 13 and the ultrasonic vibrator 14 is connected to the water outlet 11, and the water outlet 11 is connected to the osmotic reaction wall 9 through the liquid outlet pipe 5; a valve 15 is arranged at the bottom of the shell 12, and a storage box 4 is arranged at the outlet of the valve 15.

[0042] The pore size of the filter 13 described in the present invention is designed to be 2-2.5 mm, which can sort microplastics into large-particle microplastics and small-particle microplastics. For example, when the pore size of the filter 13 is set to 2 mm, when the seawater to be treated flows through the filter 13, large-particle microplastics with a particle size of 2-5 mm and small-particle microplastics with a particle size of <2 mm are sorted out; the ultrasonic vibrator 14 is used to assist in separating the particles attached to the filter 13; the valve 15 is opened and closed to regulate the connection state with the storage box 14; the storage box 4 is used to collect the sorted large-particle microplastics.

[0043] As an embodiment of the present invention, the sorting and filtering unit 3 may further include a backwashing device disposed between the liquid outlet pipe 5 and the osmotic reaction wall 9, the backwashing device including a one-way valve 6, a booster pump 7 and a backwashing liquid bottle 8 connected in sequence, the one-way valve 6 being connected to the pipeline between the liquid outlet pipe 5 and the osmotic reaction wall 9. The backwashing device of the present invention is used to automatically backwash the filter screen 13, which not only effectively prevents the clogging of the filter screen 13, but also improves the filtration efficiency, simplifies the operation process, and significantly reduces the frequency of manual cleaning of the filter screen 13; the one-way valve 6 is closed during the normal operation of the sorting-immobilized microbial degradation reaction system, and the one-way valve 6 is opened when the filtration efficiency is reduced to realize backwashing the filter screen 13.

[0044] As an embodiment of the present invention, the filter 13 is a detachable accessory, which is arranged between the housing 12 and the ultrasonic vibrator 14 for easy maintenance and replacement.

[0045] As an embodiment of the present invention, the filter screen 13 may be made of corrosion-resistant stainless steel; the housing 12 and the backwash liquid bottle 8 may be made of transparent quartz glass; the valve 15 and the booster pump 7 may be made of corrosion-resistant stainless steel. The present invention uses components made of stainless steel or quartz glass to avoid interference of the chemical composition of the material itself on the sorting of microplastics and the determination of the removal rate.

[0046] In the present invention, from the direction of water inlet to water outlet, the infiltration reaction wall 9 is sequentially provided with a modified zeolite filler layer, an immobilized microorganism filler combination layer and an adsorption filler layer laid longitudinally, corresponding to three functional areas respectively.

[0047] The modified zeolite packing layer of the present invention is filled with modified zeolite. As an embodiment of the present invention, the thickness of the modified zeolite packing layer can be 0.2-0.3m; the particle size of the modified zeolite can be 1-2mm, and the porosity can be 50-55%, specifically 52.2%. The modified zeolite of the present invention is natural zeolite soaked in KMnO 4 The solution is modified to obtain the KMnO 4The concentration of the solution is 0.1-0.2 mol / L. As an embodiment of the present invention, the modification treatment may include: heating in a water bath at 30-40°C for 2-3 hours, discarding the supernatant, and rinsing the obtained solid material with deionized water until neutral. As an embodiment of the present invention, the heating may include first-stage heating and second-stage heating; the temperature of the first-stage heating may be 38-40°C, the time may be 1.5-2 hours, and the first-stage heating may be carried out under stirring conditions; the temperature of the second-stage heating may be 30-32°C, the time may be 0.5-1 hour, and the second-stage heating may be carried out under shaking conditions. As an embodiment of the present invention, the deionized water rinsing to neutrality may also include a drying treatment. The present invention adopts KMnO 4 The solution modifies the zeolite so that the obtained modified zeolite has a strong ion exchange capacity, which can effectively reduce the salinity and alkalinity of seawater to an appropriate level, which is beneficial to maintaining the activity of the microbial sludge; and the modified zeolite releases highly oxidizing primary ecological oxygen when it comes into contact with water, which can continuously replenish the dissolved oxygen required for microbial growth, so that the active microbial sludge remains in an aerobic state, which is beneficial to the efficient and long-term progress of the degradation reaction.

[0048] The immobilized microorganism filler combination layer of the present invention comprises a plurality of groups of immobilized microorganism filler layers arranged at intervals and a group of carbon-releasing material layers inserted between two adjacent groups of immobilized microorganism filler layers. The present invention combines the immobilized microorganism filler layer with the carbon-releasing material layer, and the carbon-releasing material layer can continuously supply carbon sources for the growth of microorganisms. The two functional layers are described in detail below.

[0049] As an embodiment of the present invention, the number of immobilized microbial filler layers in the immobilized microbial filler combination layer is set to 3 to 4 groups, and the thickness of each group of immobilized microbial filler layers can be 0.3 to 0.5 m, specifically 0.4 m. The immobilized microbial filler layer of the present invention is filled with immobilized microbial fillers, and the particle size of the immobilized microbial fillers can be 2 to 3 mm.

[0050] The immobilized microbial filler of the present invention is prepared by an adsorption-embedding-crosslinking method from a first biochar, microbial sludge and a polyvinyl alcohol-sodium alginate composite melt. The mass ratio of the first biochar, microbial sludge and the polyvinyl alcohol-sodium alginate composite melt is 20-30:25-35:45-55, and can be specifically 25:30:50.

[0051] As an embodiment of the present invention, the first biochar is obtained by carbonization treatment of coastal wetland plants, and the coastal wetland plants may include calamus and / or reeds, specifically calamus or reeds. The present invention adopts coastal wetland plants, which not only realizes the local acquisition of raw materials, but also significantly reduces the cost of raw material procurement and transportation. As an embodiment of the present invention, the coastal wetland plants are washed, air-dried, crushed and dried in sequence before carbonization. As an embodiment of the present invention, the temperature of the carbonization treatment can be 150-200°C, further can be 170-190°C, specifically can be 180°C; the heating rate to the temperature required for the carbonization treatment can be 4-6°C / min, specifically can be 5°C / min; the insulation time of the carbonization treatment can be 60-90min, specifically can be 60-70min; the carbonization treatment can be carried out in a nitrogen or argon protective atmosphere. As an embodiment of the present invention, the carbonization treatment may further include cooling, grinding and screening in sequence, the mesh size of the sieve used for screening may be 100 meshes, and the material under the sieve is collected as the first biochar. In the embodiment of the present invention, the first biochar is prepared by a slow pyrolysis method, the preparation process is simple, the raw material source is wide, the cost is low, and it is more environmentally friendly.

[0052] In the present invention, the microbial sludge is a mixture of Bacillus licheniformis sludge, Bacillus pumilus sludge, Marinobacter saline xigens sludge and Alcanivorax dieselolei sludge; the mass ratio of Bacillus licheniformis sludge, Bacillus pumilus sludge, Marinobacter saline xigens sludge and Alcanivorax dieselolei sludge in the microbial sludge can be 20-30:30-40:20-30:10-20, specifically 25:35:25:15; the total colony count of each sludge is ≥10 8CFU / mL. As an embodiment of the present invention, the method for obtaining the Bacillus licheniformis sludge, Bacillus pumilus sludge, Bacillus marinus sludge and diesel alkane sludge may include: continuously in situ domestication of indigenous microorganisms (specifically Bacillus licheniformis, Bacillus pumilus, Bacillus marinus or diesel alkane sludge) for 4 to 5 weeks, and then continuously passage and enrich for more than three times, and then undergo two rounds of screening to obtain a bacterial culture solution; the bacterial culture solution is centrifuged and the supernatant is discarded to obtain the corresponding type of bacterial mud. In an embodiment of the present invention, specifically, a plastic film (for example, a polyethylene film) is placed in the natural habitat corresponding to the above four microbial strains, and the indigenous microorganisms are continuously domesticated in situ for 4 to 5 weeks, and the plastic film and the coated root mud sample are taken as an inoculum; under aseptic operation conditions, 10% inoculation amount is added to the culture medium to complete continuous passage and enrichment for more than three times, and then two rounds of screening are performed to obtain a bacterial culture solution; the bacterial culture solution is centrifuged and the supernatant is discarded, and each type of microbial mud is retained for standby use. The microorganisms in the microbial sludge obtained by the above method of the present invention can attach to the surface of microplastics, produce extracellular enzymes such as esterase, lipase, lignin peroxide and cutinase, etc., and can convert polymers into oligomers, dimers or monomers, thereby achieving effective degradation of microplastics.

[0053] As an embodiment of the present invention, the mass ratio of polyvinyl alcohol to sodium alginate in the polyvinyl alcohol-sodium alginate composite melt can be 8 to 10:1, specifically 9:1. As an embodiment of the present invention, the preparation method of the polyvinyl alcohol-sodium alginate composite melt can include the following steps: mixing polyvinyl alcohol and sodium alginate, heating and melting them, and then cooling them to obtain the polyvinyl alcohol-sodium alginate composite melt.

[0054] As an embodiment of the present invention, the preparation method of the immobilized microbial filler may include the following steps: mixing an emulsifier, a first cross-linking agent and water to obtain a mixed solution; mixing the first biochar, microbial sludge and the polyvinyl alcohol-sodium alginate composite melt, adding the obtained mixed raw materials to the mixed solution using a setting device, and then adjusting the pH value of the obtained system to 7 to obtain the immobilized microbial filler. As an embodiment of the present invention, the emulsifier may be an OP emulsifier, and the first cross-linking agent may be CaCl 2 With H 3 BO 3 The concentration of the OP emulsifier in the mixed solution may be 45 to 55 mol / L, specifically 50 mol / L; CaCl 2 The concentration of H may be 0.8-1.2 wt%, specifically 1 wt%; 3 BO 3 Specifically, it can be a saturated concentration; in the embodiment of the present invention, specifically, OP emulsifier and CaCl2 Add to H 3 BO 3 In one embodiment of the present invention, the reagent used to adjust the pH value may be Na 2 CO 3 solution, the Na 2 CO 3 The concentration of the solution can be 8 to 12 wt%, specifically 10 wt%. As an embodiment of the present invention, after the pH value of the obtained system is adjusted to 7, gel particles appear in the system, and then preferably filtered, the gel particles are collected and washed with water to obtain the immobilized microbial filler. The present invention adopts an adsorption-embedding-crosslinking method to prepare the immobilized microbial filler, wherein the first biochar serves as a skeleton carrier of the immobilized microbial filler, which plays an adsorption and supporting role; the microbial mud serves as a key active substance, which can produce extracellular enzymes that degrade microplastics; the polyvinyl alcohol-sodium alginate composite melt serves as a cross-linking molding liquid to promote the embedding to form an immobilized microbial filler with high impact strength.

[0055] As an embodiment of the present invention, the thickness of each group of carbon-releasing material layers in the immobilized microbial filler combination layer can be 0.2 to 0.3 m. In the present invention, the carbon-releasing material layer is filled with carbon-releasing material, and the particle size of the carbon-releasing material can be 3 to 4 mm. In the present invention, the carbon-releasing material includes a polyvinyl alcohol carrier and starch and α-amylase loaded on the polyvinyl alcohol carrier; the starch can be corn starch.

[0056] As an embodiment of the present invention, the preparation method of the carbon-releasing material may include the following steps: mixing starch, polyvinyl alcohol, sodium alginate, α-amylase and water to obtain a mixed raw material liquid; mixing a second cross-linking agent with water to obtain a cross-linking agent solution; adding the mixed raw material liquid dropwise to the cross-linking agent solution, performing a cross-linking treatment, and obtaining the carbon-releasing material. As an embodiment of the present invention, the mass ratio of starch, polyvinyl alcohol and sodium alginate may be 18-22:16-20:8-12, specifically 20:18:10. As an embodiment of the present invention, the amount ratio of starch to water in the mixed raw material liquid may be 18-22g:350-450mL, specifically 20g:400mL; in the embodiment of the present invention, starch, polyvinyl alcohol, sodium alginate and water may be mixed, heated to 40-50°C (specifically 45°C) under stirring conditions, then cooled to room temperature, and α-amylase is added to the obtained mixture to obtain the mixed raw material liquid. As an embodiment of the present invention, the second cross-linking agent may be CaCl 2; The dosage ratio of the second cross-linking agent to water in the cross-linking agent solution can be 14-18g:450-550mL, specifically 16g:500mL. As an embodiment of the present invention, the dripping rate can be 1 drop / s; the temperature of the cross-linking treatment can be 4-6°C, specifically 5°C; the time can be 25-30h, specifically 28h. As an embodiment of the present invention, after the cross-linking treatment, it is preferred to further include filtration, collect the solid material and wash it with water to obtain the carbon-releasing material. The carbon-releasing material of the present invention uses starch as raw material and polyvinyl alcohol as a skeleton carrier, and obtains a solid slow-release carbon source through low-temperature freezing technology; the present invention inserts a group of carbon-releasing material layers between two adjacent groups of immobilized microbial filler layers, which can supply carbon sources for microbial growth, help the continuous reproduction and growth of microorganisms, and enable the degradation reaction to continue.

[0057] The adsorption filler layer of the present invention is filled with modified kaolin-biochar filler. As an embodiment of the present invention, the thickness of the adsorption filler layer can be 0.6-0.8m; the particle size of the modified kaolin-biochar filler can be 3-5mm. The modified kaolin-biochar filler of the present invention is obtained by mixing kaolin and the second biochar and then calcining. As an embodiment of the present invention, the preparation method of the second biochar can be consistent with the preparation method of the first biochar, which is not repeated here. As an embodiment of the present invention, when preparing the modified kaolin-biochar filler, the mass ratio of kaolin to the second biochar can be 1:0.8-1.2, specifically 1:1. As an embodiment of the present invention, the temperature of the calcination treatment can be 250-350°C, further 280-320°C, specifically 300°C; the insulation time can be 60-150min, further 80-120min, specifically 90-100min; the calcination treatment can be carried out in a nitrogen or argon protective atmosphere. As an embodiment of the present invention, the kaolin is preferably crushed and sieved before calcination, and the undersize is collected and mixed with the second biochar before calcination; the mesh size of the sieve used for sieving can be 100 mesh. The modified kaolin-biochar filler in the present invention can fully absorb the degradation products and aged biofilm produced after the microbial mud degrades microplastics, thereby promoting the forward progress of the degradation reaction and improving the degradation efficiency.

[0058] The present invention provides a method for removing microplastics in seawater using the sorting-immobilized microbial degradation reaction system described in the above technical solution, comprising the following steps:

[0059] S1, transporting the seawater to be treated to the sorting and filtering unit 3 through the water inlet unit for sorting and processing, and obtaining seawater containing small particles of microplastics and large particles of microplastics, respectively, and the large particles of microplastics are collected in the storage box 4;

[0060] S2. The seawater containing small particles of microplastics is transported to the infiltration reaction wall 9 to sequentially undergo the processes of reducing the salinity and alkalinity of the seawater, undergoing degradation reactions, and adsorbing degradation products, and the purified water is discharged from the sorting-immobilized microbial degradation reaction system.

[0061] In the present invention, specifically, the water inlet unit is first started to transport the seawater to be treated to the sorting and filtering unit 3. When the seawater to be treated flows through the filter screen 13, large-particle microplastics and small-particle microplastics are sorted to obtain large-particle microplastics and seawater containing small-particle microplastics; the valve 15 at the bottom of the sorting and filtering unit 3 is opened, and the large-particle microplastics are collected in the storage box 4, regularly transferred and dried for recycling or reasonable landfill disposal; the seawater containing small-particle microplastics flows into the infiltration reaction wall 9, and flows through the three functional areas of the modified zeolite filler layer, the immobilized microbial filler combination layer and the adsorption filler layer in sequence, so as to reduce the salinity and alkalinity of the seawater, fully cause the degradation reaction and the adsorption of the degradation products, obtain the purified water body and then discharge it from the outlet pipe.

[0062] As an embodiment of the present invention, the seawater to be treated can be seawater aquaculture wastewater. As an embodiment of the present invention, the operation mode of the sorting-immobilized microbial degradation reaction system can adopt a continuous water inlet method or an intermittent water inlet method; when the operation mode is the intermittent water inlet method, each operation cycle includes three days, of which the sorting-immobilized microbial degradation reaction system is in a full water stage (or wet stage) for two days, and the sorting-immobilized microbial degradation reaction system is in an emptying stage (or oxygen-rich stage) on the other day, and the full water stage and the emptying stage are periodically alternating. In the embodiment of the present invention, the intermittent water inlet method is adopted, in which the oxygen-rich stage can provide sufficient oxygen for the microorganisms, thereby improving the degradation efficiency of microplastics.

[0063] As an embodiment of the present invention, during the sorting process, the valve 15 is preferably in a closed state, which can ensure that the seawater to be processed entering the housing 12 is screened by the filter 13 and then discharged from the water outlet 11, so that large particles of microplastics are enriched in the housing 12, and then the valve 15 is opened to collect the large particles of microplastics into the storage box 4. As an embodiment of the present invention, when it is observed that the water flow speed in the housing 12 is significantly slowed down, the one-way valve 6 and the booster pump 7 connected to the side of the water outlet 11 can be opened, and the booster pump 7 can promote the backwashing liquid to be poured into the housing 12 through the water outlet 11, backwashing the particles deposited on the filter 13, and the ultrasonic vibrator 14 located inside the housing 12 can also assist the deposited particles to be efficiently separated from the filter 13, thereby improving the degradation efficiency.

[0064] Figure 1 This is a schematic diagram of the structure of the sorting-immobilized microbial degradation reaction system in an embodiment of the present invention. Figure 2 It is a schematic diagram of the cross-sectional structure of the sorting and filtering unit. Figure 3 It is a schematic diagram of the cross-sectional structure of the permeable reaction wall. The technical scheme of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] The specific conditions not specified in the following experiments of the present invention were carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer were all conventional products that can be purchased commercially.

[0066] The Bacillus licheniformis BL-2 (Bacillus licheniformis) used in the following experiments of the present invention was purchased from the China Type Culture Collection Center of Wuhan University, with a preservation number of CCTCC No. M2012458; the Bacillus pumilus DS-3 (Bacillus pumilus) was purchased from the China Type Culture Collection Center of Wuhan University, with a preservation number of CCTCC No: M20221849; the Marinobacter saline xigens was purchased from the General Microbiological Center of the China Microbiological Culture Collection Administration, with a preservation number of CGMCC No. 25242; the Alcanivorax dieselolei was purchased from the General Microbiological Center of the China Microbiological Culture Collection Administration, with a preservation number of CGMCC No. 26017.

[0067] Preparation Example 1

[0068] The preparation of modified zeolite comprises the following steps:

[0069] Weigh natural zeolite and soak it in KMnO with a concentration of 0.2 mol / L. 4 The solution was heated in a 40°C water bath for 2 h under stirring conditions, and then oscillated in a 30°C constant temperature oscillator at an oscillation rate of 200 r / min for 30 min. After the oscillation, the solid material was filtered and rinsed with deionized water until neutral, and then dried to obtain the modified zeolite (particle size of 1 to 2 mm), which was sealed and stored for later use.

[0070] Preparation Example 2

[0071] The preparation of the immobilized microbial filler comprises the following steps:

[0072] (1) polyvinyl alcohol (PVA) and sodium alginate (SA) are uniformly mixed in a mass ratio of 9:1, heated to melt into a viscous liquid, and then cooled to room temperature to obtain a polyvinyl alcohol-sodium alginate composite melt;

[0073] (2) washing the reeds, air-drying, crushing and drying them in sequence, heating the obtained dried reeds to 180°C at a heating rate of 5°C / min in a nitrogen atmosphere, keeping the temperature for carbonization treatment for 60 min, then cooling to room temperature, grinding and sieving with a 100-mesh sieve, and collecting the sieved material to obtain biochar particles;

[0074] (3) placing polyethylene (PE) plastic films in the natural habitats corresponding to Bacillus licheniformis, Bacillus pumilus, Bacillus marinus and Alcanovar diesel fuel respectively, acclimating the indigenous microorganisms in situ for 4 weeks, taking the plastic films and the coated root mud samples as inoculants; under aseptic operation conditions, adding the inoculants to the enrichment medium at a 10% inoculum amount for continuous subculture enrichment 4 times, and then successively undergoing primary screening and rescreening to obtain bacterial culture fluid; centrifuging the bacterial culture fluid, discarding the supernatant, and obtaining Bacillus licheniformis mud, Bacillus pumilus mud, Bacillus marinus mud and Alcanovar diesel fuel respectively; uniformly mixing the Bacillus licheniformis mud, Bacillus pumilus mud, Bacillus marinus mud and Alcanovar diesel fuel mud in a mass ratio of 25:35:25:15 to obtain a mixed mud;

[0075] (4) CaCl 2 OP emulsifier and H 3 BO 3 The saturated solutions are uniformly mixed to obtain a mixed solution, wherein CaCl 2The concentration of the biochar particles, the mixed bacterial mud and the polyvinyl alcohol-sodium alginate composite melt were uniformly mixed in a mass ratio of 25:30:50, and the obtained mixed raw materials were added to the mixed solution using a setting device at room temperature. The concentration of the OP emulsifier was 1wt%, and the concentration of the OP emulsifier was 50mol / L. The biochar particles, the mixed bacterial mud and the polyvinyl alcohol-sodium alginate composite melt were uniformly mixed in a mass ratio of 25:30:50. At room temperature, the obtained mixed raw materials were added to the mixed solution using a setting device. 2 CO 3 The solution was adjusted to obtain a system with a pH value of 7, and gel particles appeared in the system. The system was then filtered, and the gel particles were collected and washed with deionized water to obtain the immobilized microbial filler (particle size of 2 to 3 mm).

[0076] Preparation Example 3

[0077] The preparation of the carbon-releasing material comprises the following steps:

[0078] (1) Weighing 18 g of polyvinyl alcohol, 10 g of sodium alginate, and 20 g of corn starch and uniformly mixing with 400 mL of deionized water to obtain a viscous mixed liquid, heating the mixture to 45° C. in a water bath at a stirring speed of 280 r / min, then cooling the mixture to room temperature, and adding α-amylase to the obtained mixed liquid to obtain a mixed raw material liquid;

[0079] (2) Add 16 g of CaCl into 500 mL of deionized water. 2 , obtaining a cross-linking agent solution; dropping the mixed raw material liquid into the cross-linking agent solution at a rate of 1 drop / s, and performing a cross-linking treatment at 5°C for 28 hours. During the cross-linking treatment, spherical particles appear in the system. After the cross-linking treatment is completed, the spherical particles are filtered, collected, and washed with deionized water to obtain the carbon-releasing material (particle size is 3 to 4 mm).

[0080] Preparation Example 4

[0081] The preparation of modified kaolin-biochar filler comprises the following steps:

[0082] The kaolin was crushed and sieved with a 100-mesh sieve, and the sieve was collected to obtain kaolin particles; the kaolin particles and biochar particles (prepared according to the method of Preparation Example 2) were uniformly mixed in a mass ratio of 1:1 to obtain a mixed raw material; in a nitrogen atmosphere, the mixed raw material was calcined at 300° C. for 90 minutes, and then cooled to room temperature to obtain the modified kaolin-biochar filler (particle size of 3 to 5 mm).

[0083] Example 1

[0084] use Figure 1The sorting-immobilized microorganism degradation reaction system shown in the figure treats water. From the direction of water inlet to water outlet, the permeation reaction wall 9 of the sorting-immobilized microorganism degradation reaction system is sequentially provided with a modified zeolite filler layer, an immobilized microorganism filler combination layer and an adsorption filler layer laid along the longitudinal direction. The fillers used in each layer are prepared by referring to the method in Preparation Examples 1 to 4, as follows:

[0085] The modified zeolite filler layer is filled with modified zeolite, and the thickness of the modified zeolite filler layer is 0.3 m;

[0086] The immobilized microorganism filler combination layer includes 3 groups of immobilized microorganism filler layers laid in the longitudinal direction and a carbon-releasing material layer laid between two adjacent groups of immobilized microorganism filler layers (i.e., a total of two groups of carbon-releasing material layers are provided); wherein the immobilized microorganism filler layers are filled with immobilized microorganism fillers, and the thickness of each group of the immobilized microorganism filler layers is 0.4 m; the carbon-releasing material layer is filled with carbon-releasing materials, and the thickness of each group of the carbon-releasing material layers is 0.2 m;

[0087] The adsorption filler layer is filled with modified kaolin-biochar filler, and the thickness of the adsorption filler layer is 0.6m.

[0088] In this embodiment, the method for removing microplastics in seawater using the sorting-immobilized microbial degradation reaction system includes the following steps:

[0089] The test water source is the local large-scale marine aquaculture wastewater. The sorting-immobilized microbial degradation reaction system is turned on, and the water is transported to the sorting and filtering unit 3 through the water inlet unit (water pump 1 and flow meter 2). The valve 15 at the bottom of the sorting and filtering unit 3 is opened, and the large-particle microplastics with a particle size of 2 to 5 mm and the small-particle microplastics with a particle size of <2 mm in the water are sorted. The large-particle microplastics with a particle size of 2 to 5 mm are collected in the storage box 4, regularly transferred and dried, and are recycled or reasonably landfilled; the water containing small-particle microplastics with a particle size of <2 mm is transported to the osmotic reaction wall 9 through the outlet pipe 5 to complete the reduction of seawater salinity and alkalinity, degradation reaction and adsorption of degradation products, and the effluent is discharged through the outlet pipe of the osmotic reaction wall 9; the system operation mode adopts the continuous water inlet method, and the water inlet load is adjusted to 0.15m through the flow meter 2 3 / m 2 / day~0.4m 3 / m 2 / day, and the stable operation time is 30 days.

[0090] Example 2

[0091] Refer to the method steps of Example 1, the difference is that the system operation mode adopts the intermittent water inflow method, each operation cycle includes three days (two days are full of water and one day is empty), and the system runs reciprocatingly for 10 cycles.

[0092] Comparative Example 1

[0093] Referring to the method steps of Example 2, the difference is that the modified zeolite filler in the permeation reaction wall 9 is replaced by a natural zeolite filler that has not been specially treated. Specifically, the natural zeolite is crushed and sieved in sequence to obtain a natural zeolite with a particle size range of 1 to 2 mm as the filler.

[0094] Comparative Example 2

[0095] The method steps of Example 2 are referred to, except that the adsorption filler layer in the permeation reaction wall 9 is omitted, that is, only a modified zeolite filler layer and an immobilized microorganism filler combined layer are provided.

[0096] Comparative Example 3

[0097] Referring to the method steps of Example 2, the difference is that the immobilized microbial filler layer is replaced by a microbial sludge filler layer. The preparation method of the microbial sludge filler includes the following steps: Bacillus licheniformis sludge, Bacillus pumilus sludge, Bacillus sludge and Bacillus oxysporum sludge are uniformly mixed in a mass ratio of 25:35:25:15 to obtain a mixed sludge; and then the biochar particles and the above-mentioned mixed sludge are uniformly mixed in a mass ratio of 25:30 to obtain the microbial sludge filler.

[0098] Comparative Example 4

[0099] Refer to the method steps of Example 2, except that only Bacillus licheniformis bacterial sludge is used in preparing the immobilized microbial filler (ie, a single type of bacterial sludge is used, and the other three types of bacterial sludge are omitted).

[0100] Comparative Example 5

[0101] The method operation steps of Example 2 are referred to, except that only Marinobacterium sludge is used in preparing the immobilized microbial filler (i.e., a single type of sludge is used, and the other three types of sludge are omitted).

[0102] Test Example 1

[0103] On the initial day of system startup and the 30th day of stable operation, effluent samples of the embodiment and comparative example were collected, and the chemical composition of microplastics was identified and the abundance of microplastics was counted using Fourier transform micro-infrared spectroscopy. Each group of experiments in the embodiment or comparative example included two parallel groups to ensure that there was no accidental result in the system operation and the removal rate data was calculated more accurately.

[0104] Figure 4The figure is a comparison chart of the removal rate of small microplastic particles with a particle size of <2 mm in each embodiment and comparative example. Figure 4 It can be seen that after 30 days of operation, the removal rate of small-particle microplastics with a particle size of <2 mm in the influent water was 91.2% using the continuous water inflow method in Example 1; and the removal rate of small-particle microplastics with a particle size of <2 mm in the influent water was improved to 95.6% using the intermittent water inflow method in Example 2.

[0105] At the same time by Figure 4 It can be seen that in Comparative Example 1, a natural zeolite filler layer is used. Since natural zeolite cannot release oxygen when it comes into contact with water, the removal rate of the small-particle microplastics is low (76.3%); in Comparative Example 2, due to the lack of an adsorption filler layer, the degradation products in the seawater are difficult to be completely adsorbed, so the removal rate of the small-particle microplastics is low (74.6%); in Comparative Example 3, since the microbial mud filler in the infiltration reaction wall is not embedded and fixed by the polyvinyl alcohol-sodium alginate composite melt, the microbial mud filler is unstable in shape and easily washed away by water flow and lost in large quantities, so the removal rate of the small-particle microplastics is low (71.5%); in Comparative Examples 4 and 5, since the immobilized microbial filler layer only uses a single type of mud, the removal rates of the small-particle microplastics are low, which are 84.6% and 79.2% respectively.

[0106] In summary, the present invention has at least the following beneficial effects:

[0107] (1) The design idea of ​​the present invention to separate large and small microplastic particles and then remove them in a targeted manner can, on the one hand, greatly improve the treatment efficiency of the infiltration reaction wall 9, and on the other hand, avoid clogging of each layer of filler when water continues to flow in.

[0108] (2) The filter screen 13 in the sorting and filtering unit 3 of the present invention is configured as a detachable accessory, which is convenient for cleaning and maintenance to maintain the filtering efficiency. At the same time, when the efficiency of the reaction system decreases, it is only necessary to update the filter screen accessory without replacing the entire sorting and filtering unit, thereby reducing the long-term operating cost of the system.

[0109] (3) The one-way valve 6, the booster pump 7 and the backwashing liquid bottle 8 of the present invention are matched to realize the automatic backwashing function of the filter 13 through the liquid outlet pipe 5, which can not only effectively prevent the filter 13 from being blocked, but also significantly reduce the replacement frequency of the filter 13.

[0110] (4) Compared with the common untreated natural fillers such as gravel and zeolite in the prior art, KMnO 4 The modified zeolite releases highly oxidizing primary oxygen when it meets water, which promotes the continuous replenishment of dissolved oxygen, thereby providing a high-quality physical and chemical environment for the growth and reproduction of microbial flora. In addition, the modified zeolite in the present invention also has the effect of adsorbing nitrogen and phosphorus to improve the bottom soil.

[0111] (5) The present invention realizes effective fixation of microbial sludge through the adsorption-embedding-crosslinking method, and its structure has good sedimentation performance. Even under high hydraulic load operating conditions, the morphology of the microbial sludge remains stable, avoiding the problem of flocculent microorganisms exposed in the prior art being washed to the outside of the system as inoculum; experiments have confirmed that the immobilized microbial filler layer still exhibits relatively stable degradation performance after secondary and tertiary recycling, thereby saving a lot of costs.

[0112] (6) The present invention uses a combination of bacterial sludge of Bacillus licheniformis, Bacillus brevis, Bacillus marinus and Alkanobacterium dieselgenophylum to produce a synergistic effect. Compared with the bacterial sludge using a single bacterial species, the degradation efficiency is higher.

[0113] (7) The present invention inserts a carbon-releasing material layer between each two adjacent groups of immobilized microbial filler layers, which can provide a slow-release carbon source for the growth of microorganisms, is beneficial to the self-reproduction and metabolism of microorganisms, and thus improves the degradation efficiency.

[0114] (8) The raw materials for preparing the biochar in the present invention are widely available and easy to obtain, and the preparation process is simple, which can achieve the recycling of waste, for example, solving the problem of local disposal of large-scale harvested wetland plants such as reeds and yellow irises in autumn and winter, and there is no risk of secondary pollution of aquaculture water by biochar.

[0115] (9) The modified kaolin-biochar filler prepared by the special process of the present invention can be combined with the product of the degradation reaction through the action of cationic bridge bonds, and the adsorption efficiency is greatly improved. In addition, this preparation method can realize the repeated utilization of the biochar raw materials.

[0116] (10) When the water inlet control system of the present invention is operated in an intermittent water inlet method, the periodic water inlet mode of alternating between the "filling / wetting" stage and the "drainage / drying" stage can improve the reoxidation efficiency, thereby effectively improving the microplastic removal rate.

[0117] (11) Compared with wastewater purification technologies such as coagulation sedimentation, membrane separation, and advanced oxidation, the structure of the sorting-immobilized microbial degradation reaction system of the present invention is fast to construct, cost-effective, simple to maintain and manage, and has extremely low energy consumption, which is conducive to practical promotion.

[0118] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A sorting-immobilized microbial degradation reaction system, comprising a water inlet unit, a sorting and filtering unit (3) and a permeation reaction wall (9) connected in sequence; The sorting and filtering unit (3) comprises a water inlet (10), a shell (12) and a water outlet (11); a filter screen (13) is arranged inside the shell (12); the pore size of the filter screen (13) is designed to be 2 to 2.5 mm; an ultrasonic vibrator (14) is arranged inside the cavity formed by the filter screen (13); a channel between the inner wall of the shell (12) and the filter screen (13) is connected to the water inlet (10); the water inlet (10) is connected to the water inlet unit; the channel between the filter screen (13) and the ultrasonic vibrator (14) is connected to the water outlet (11); the water outlet (11) is connected to the osmotic reaction wall (9) via a liquid outlet pipe (5); a valve (15) is arranged at the bottom of the shell (12); a storage box (4) is arranged at the outlet of the valve (15); In the direction from water inlet to water outlet, the infiltration reaction wall (9) is sequentially provided with a modified zeolite filler layer, an immobilized microbial filler combination layer and an adsorption filler layer laid longitudinally; The modified zeolite filler layer is filled with modified zeolite, and the modified zeolite is obtained by immersing natural zeolite in a KMnO4 solution for modification, and the concentration of the KMnO4 solution is 0.1-0.2 mol / L; The immobilized microbial filler combination layer includes a plurality of groups of immobilized microbial filler layers arranged at intervals and a group of carbon-releasing material layers inserted between two adjacent groups of immobilized microbial filler layers; the immobilized microbial filler layer is filled with immobilized microbial fillers, and the immobilized microbial fillers are prepared by adsorption-embedding-crosslinking method from a first biochar, microbial sludge and a polyvinyl alcohol-sodium alginate composite melt, the mass ratio of the first biochar, microbial sludge and the polyvinyl alcohol-sodium alginate composite melt is 20-30:25-35:45-55, and the microbial sludge is a mixture of Bacillus licheniformis sludge, Bacillus pumilus sludge, Bacillus marinus sludge and Alkanophaga diesel sludge; the carbon-releasing material layer is filled with a carbon-releasing material, and the carbon-releasing material includes a polyvinyl alcohol carrier and starch and α-amylase loaded on the polyvinyl alcohol carrier; The adsorption filler layer is filled with modified kaolin-biochar filler, and the modified kaolin-biochar filler is obtained by mixing kaolin and a second biochar and then calcining; The first biochar and the second biochar are obtained by carbonization treatment of coastal wetland plants.

2. The sorting-immobilized microbial degradation reaction system according to claim 1, characterized in that: The water inlet unit comprises a water pump (1) and a flow meter (2), wherein the flow meter (2) is arranged on a pipeline between the water pump (1) and the sorting and filtering unit (3).

3. The sorting-immobilized microbial degradation reaction system according to claim 1 or 2, characterized in that: The sorting and filtering unit (3) further comprises a backwashing device arranged between the liquid outlet pipe (5) and the osmotic reaction wall (9), the backwashing device comprising a one-way valve (6), a booster pump (7) and a backwashing liquid bottle (8) which are connected in sequence, and the one-way valve (6) is connected to the pipeline between the liquid outlet pipe (5) and the osmotic reaction wall (9).

4. The sorting-immobilized microbial degradation reaction system according to claim 1, characterized in that: The thickness of the modified zeolite filler layer is 0.2-0.3 m, and the particle size of the modified zeolite is 1-2 mm; The modification treatment comprises: heating in a water bath at 30-40° C. for 2-3 hours, discarding the supernatant, and washing the obtained solid material with deionized water until it becomes neutral.

5. The sorting-immobilized microbial degradation reaction system according to claim 1, characterized in that: The number of immobilized microorganism filler layers in the immobilized microorganism filler combination layer is set to 3 to 4 groups, the thickness of each group of immobilized microorganism filler layers is 0.3 to 0.5 m, and the particle size of the immobilized microorganism filler is 2 to 3 mm; The mass ratio of Bacillus licheniformis sludge, Bacillus pumilus sludge, Marinobacterium sludge and Diesel Alkanophage sludge in the microbial sludge is 20-30:30-40:20-30:10-20, and the total number of colonies of each sludge is ≥10 8 CFU / mL.

6. The sorting-immobilized microbial degradation reaction system according to claim 1 or 5, characterized in that: The thickness of each group of carbon-releasing material layers in the immobilized microbial filler combination layer is 0.2-0.3 m, and the particle size of the carbon-releasing material is 3-4 mm.

7. The sorting-immobilized microbial degradation reaction system according to claim 1, characterized in that: The thickness of the adsorption filler layer is 0.6 to 0.8 m, and the particle size of the modified kaolin-biochar filler is 3 to 5 mm; when preparing the modified kaolin-biochar filler, the mass ratio of the kaolin to the second biochar is 1:0.8 to 1.2, the calcination temperature is 250 to 350° C., the insulation time is 60 to 150 min, and the calcination is carried out in a nitrogen or argon protective atmosphere.

8. The sorting-immobilized microbial degradation reaction system according to claim 1, characterized in that: The coastal wetland plants include yellow calamus and / or reed; the temperature of the carbonization treatment is 150-200° C., the insulation time is 60-90 minutes, and the carbonization treatment is carried out in a nitrogen or argon protective atmosphere.

9. A method for removing microplastics from seawater using the sorting-immobilized microbial degradation reaction system according to any one of claims 1 to 8, comprising the following steps: S1, transporting the seawater to be treated to the sorting and filtering unit (3) through the water inlet unit for sorting and treatment, and obtaining seawater containing small particles of microplastics and large particles of microplastics, respectively, and the large particles of microplastics are collected in a storage box (4); S2. The seawater containing small particles of microplastics is transported to the infiltration reaction wall (9) to sequentially undergo a process of reducing the salinity and alkalinity of the seawater, undergoing a degradation reaction, and adsorbing the degradation products, and the purified water is discharged from the sorting-immobilized microbial degradation reaction system.

10. The method according to claim 9, characterized in that The seawater to be treated is seawater aquaculture wastewater; the operation mode of the sorting-immobilized microbial degradation reaction system adopts a continuous water inlet method or an intermittent water inlet method; when the operation mode is the intermittent water inlet method, each operation cycle includes three days, of which the sorting-immobilized microbial degradation reaction system is in a full water stage for two days, and the sorting-immobilized microbial degradation reaction system is in an emptying stage on the other day, and the full water stage and the emptying stage are operated periodically alternately.

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