Method for effectively removing microplastics in sewage and denitrifying in constructed wetland

Abstract

The invention discloses a method for effectively removing microplastics in sewage and denitrifying in a constructed wetland. The method comprises the following steps: introducing sewage into a micro-plastic denitrification system, wherein the micro-plastic denitrification system is provided with an aeration area, a micro-plastic interception area, a nitrification area, a denitrification area and a sulfur autotrophic denitrification area which are communicated in sequence; the micro-plastic interception filler layer is composed of modified volcanic rocks; the method comprises the following steps: immersing volcanic rock in a hydrochloric acid solution, carrying out ultrasonic or oscillation treatment, and washing the volcanic rock until eluate is neutral to obtain pretreated volcanic rock; and immersing the pretreated volcanic rock in a lauryl sodium sulfate solution, carrying out ultrasonic or oscillation treatment, washing and drying the volcanic rock to obtain the modified volcanic rock. According to the method, the pelelith is modified, so that the removal rate of micro-plastics can be greatly increased, the influence on denitrification of the constructed wetland is reduced, and the total nitrogen removal rate of the constructed wetland is further increased in cooperation with the nitrification region, the denitrification region and the sulfur autotrophic denitrification region.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method for effectively removing microplastics and denitrifying sewage using an artificial wetland. Background Art

[0002] Microplastics (MPs) refer to tiny plastic particles with a particle size of less than 5 mm in the environment. They are a new type of pollutant that is widely present in the current environment. The main sources of MPs are the fragmentation of larger plastic products, the shedding of synthetic fibers, the damage of agricultural plastic films, the wear of vehicle tires and personal care products, and direct emissions during industrial production. According to the China Synthetic Resin Association, China's plastic consumption was 80.9784 million tons in 2019 and 90.877 million tons in 2020, a year-on-year increase of 12.2%. China has become the world's largest plastic consumer. MPs are not easily degraded, can continue to accumulate in the environment and migrate over long distances, which in turn has an adverse impact on ecological security and human health. Domestic sewage is an important sink for MPs and an important potential source of MPs entering the ecological environment. Simon et al. found that Danish sewage treatment plants discharge about 3tMPs into the environment each year, and the removal of MPs has become a research hotspot in recent years.

[0003] Sewage treatment is an effective treatment method for MPs. Its main removal mechanism includes precipitation, adsorption and interception at various sewage treatment stages. Most MPs are eventually transferred to sludge. Although sewage treatment plants have a good removal rate for MPs, a large amount of MPs are still discharged into the environment every day. Constructed wetland system refers to a technology formed by human factors, which mainly uses the physical, chemical and biological synergistic effects of soil, artificial media, plants and microorganisms to treat sewage and sludge. However, studies have found that the accumulation of MPs reduces the removal rate of total nitrogen (TN) in constructed wetlands by about 8~16%. The accumulation of MPs causes changes in microbial structure and functional differences. Some important genes in nitrite oxidation, denitrification and electron generation are inhibited, and the species contribution of nitrogen conversion genes is changed, which interferes with nitrogen conversion metabolism and weakens the denitrification performance of CWs. Therefore, a method for effectively removing microplastics and denitrifying in sewage using artificial wetlands is needed, which can not only effectively remove microplastics in sewage, but also does not affect subsequent denitrification treatment and can denitrify efficiently. Summary of the invention

[0004] In view of the above-mentioned prior art, the purpose of the present invention is to provide a method for effectively removing microplastics and denitrifying wastewater using artificial wetlands. The present invention can greatly improve the removal rate of microplastics by modifying volcanic rocks, and reduce the impact on denitrification in artificial wetlands. In combination with nitrification zones, denitrification zones and sulfur autotrophic denitrification zones, the removal rate of total nitrogen in artificial wetlands is further improved.

[0005] To achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for effectively removing microplastics and denitrifying sewage using an artificial wetland, the method comprising: passing sewage into a microplastic removal and denitrification system, the microplastic removal and denitrification system comprising a microplastic retention zone, the microplastic retention zone having a microplastic retention filler layer disposed therein; one end of the microplastic retention zone is connected to an aeration zone, and the other end is connected to a nitrification zone; the nitrification zone is connected to a denitrification zone; the denitrification zone is connected to a sulfur autotrophic denitrification zone; an aeration oxygenator is disposed therein; a water distribution device is disposed at the top of the nitrification zone, and a nitrification filler layer is disposed at the bottom; a denitrification filler layer is disposed therein; a sulfur autotrophic denitrification filler layer is disposed therein; The sewage enters the aeration area for oxidation, then enters the microplastic retention area to remove the microplastics it contains, and then passes through the nitrification area for natural oxygen-enriched nitrification, enters the denitrification area for denitrification, and finally enters the sulfur autotrophic denitrification area to reduce nitrates to nitrogen gas and discharge the treated sewage.

[0006] Preferably, the microplastic is PVC microplastic.

[0007] Preferably, a water inlet is provided at the top of the aeration zone; a water outlet is provided at the bottom of the sulfur autotrophic denitrification zone; drain outlets are provided at the bottoms of the aeration zone and the nitrification zone; the aeration zone is connected to the microplastic retention zone through a first water outlet, the nitrification zone is connected to the denitrification zone through a second water outlet, and the denitrification zone and the sulfur autotrophic denitrification zone are both connected through a third water outlet; the aeration zone is connected to the nitrification zone through a water distribution device.

[0008] Preferably, the first water outlet is located at the bottom of the microplastic retention zone; the second water outlet is located at the bottom of the denitrification zone; and the third water outlet is located at the top of the sulfur autotrophic denitrification zone.

[0009] Preferably, the water distribution device comprises a main pipe with one end open, the main pipe is connected to a plurality of longitudinally connected branch pipes; and a plurality of water spray holes are provided on the main pipe and the branch pipes.

[0010] Preferably, the water distribution device is located above the nitrifying filler layer, and the distance between the water spray hole and the top of the nitrifying filler layer is 20-40 cm; and the nitrifying filler layer is composed of gravel.

[0011] Preferably, the denitrification filler layer is composed of gravels with increasing particle sizes from top to bottom, the upper part of the denitrification filler layer is paved with gravel with a particle size of 5-6 mm, and the lower part of the denitrification filler layer is paved with gravel with a particle size of 8-12 mm.

[0012] Preferably, the microplastics intercepting filler layer is composed of modified volcanic rock; the modified volcanic rock is prepared by the following method: (1) Immersing the volcanic rock in a hydrochloric acid solution, ultrasonically or oscillatingly treating the volcanic rock, and washing the volcanic rock until the washing solution is neutral to obtain the pretreated volcanic rock; (2) The pretreated volcanic rock is immersed in a sodium dodecyl sulfate (SDS) solution, and the volcanic rock is washed and dried by ultrasonic or oscillation treatment to obtain a modified volcanic rock.

[0013] Preferably, the concentration of the hydrochloric acid solution is 5 wt %; the concentration of the sodium dodecyl sulfate solution is 0.1 mol / L; the drying temperature is 105° C. and the drying time is 12 h.

[0014] Preferably, the sulfur autotrophic denitrification filler layer is composed of gravel, sulfur autotrophic denitrification filler and limestone from top to bottom; the volume ratio of the gravel, sulfur autotrophic denitrification filler and limestone is 1:6:2.

[0015] The second aspect of the present invention provides the application of the above method in the simultaneous removal of microplastics and denitrification in artificial wetlands.

[0016] Beneficial effects of the present invention: The invention provides an artificial wetland technology that can effectively remove microplastics and denitrify efficiently. The artificial wetland technology that can effectively remove microplastics and denitrify efficiently has a scientific design, a reasonable structure, convenient construction, and readily available materials. On the basis of traditional artificial wetland technology, the front end of the artificial wetland is filled with fillers to remove MPs, and the domestic sewage is treated with sulfur autotrophic denitrification denitrification technology, which can effectively remove MPs to avoid affecting the subsequent denitrification performance of the artificial wetland. At the same time, compared with traditional artificial wetlands, it can effectively enhance its denitrification performance, avoid secondary pollution, be friendly to the ecological environment, and be suitable for decentralized sewage treatment in rural areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : Schematic diagram of the microplastic removal and denitrification system; Figure 2 : Top view of the microplastic removal and denitrification system; Figure 3 : Front view of the microplastic removal and denitrification system; Among them: 1- aeration zone, 2- microplastic interception zone, 3- nitrification zone, 4- denitrification zone, 5- sulfur autotrophic denitrification zone, 6- aeration oxygenator, 7- microplastic interception filler layer, 8- water distribution device, 9- nitrification filler layer, 10- denitrification filler layer, 11- sulfur autotrophic denitrification filler layer, 12- water inlet, 13- outlet pipe, 14- drain outlet, 15- first water outlet, 16- second water outlet, 17- third water outlet, 18- main pipe, 19- branch pipe, 20- spray hole; Figure 4 : Removal of microplastics by the microplastic removal and denitrification system; Figure 5 : Removal of TN and other pollutants in water by microplastic removal and denitrification system. DETAILED DESCRIPTION

[0018] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0019] As introduced in the background technology section, the accumulation of MPs reduces the removal rate of total nitrogen (TN) in artificial wetlands by about 8~16%. The accumulation of MPs causes changes in the microbial structure and functional differences. Some important genes in nitrite oxidation, denitrification and electron generation processes are inhibited. At the same time, the species contribution of nitrogen conversion genes is changed, which interferes with nitrogen conversion metabolism and causes the weakening of CWs denitrification performance.

[0020] Based on this, the purpose of the present invention is to provide a method for effectively removing microplastics and denitrifying sewage using an artificial wetland. The present invention designs a new artificial wetland system that can be used for removing microplastics and efficiently converting nitrogen, which has the following characteristics: (1) Extremely high MPs interception rate: A large number of studies have proved that artificial wetlands can very effectively intercept MPs in water, and its interception rate reaches more than 98%; (2) Long-term removal of microplastics: The "MPs interception zone" at the front end of the artificial wetland system is designed as an upflow vertical submerged flow structure, and most of the MPs are intercepted at the lower end of the filler, which can be backwashed and regenerated regularly; (3) MPs removal and sewage purification can operate normally at the same time: The artificial wetland system is designed to have multiple independent wetland units, and the "MPs interception zone" at the front end can efficiently remove microplastics, ensuring the normal removal of pollutants such as COD, ammonia nitrogen, TP, and TN in the back-end sewage; (4) Efficient denitrification: The artificial wetland system is equipped with a "nitrification zone" and a "denitrification zone", combined with the back-end "sulfur autotrophic denitrification zone", which can efficiently remove nitrate nitrogen without adding additional carbon sources and reduce effluent TN. The present invention treats volcanic rocks by screening modifiers, and finds that the volcanic rocks treated with SDS after acid washing not only have improved microplastic interception capabilities, but also improve the subsequent ability to remove pollutants such as nitrogen. The method of the present invention not only removes more than 98% of the MPs generated during the operation of the equipment, but also can deeply remove pollutants such as nitrogen and phosphorus in the effluent; the design is simple, the raw materials used are widely available, the cost is low, and it is easy to mass produce and apply in practice. The filler in the microplastic interception unit can be disassembled and rinsed, which is convenient for renewal and utilization, which improves the convenience of operation and the feasibility of implementation, and is in line with the concept of sustainable development.

[0021] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0022] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0023] Example 1: Preparation of modified volcanic rock (1) Pickling stage Weigh 100g of volcanic rock with a particle size of 5-6mm, accurate to 0.001g, and put it into a clean beaker. Add enough 5wt% HCl solution to the beaker to completely immerse the volcanic rock filler. Make sure that the HCl solution is excessive to ensure sufficient reaction. Place the beaker containing the volcanic rock filler and HCl solution in a constant temperature oscillator or ultrasonic cleaner, set the ultrasonic frequency to 30-40KHZ, and ultrasonically treat for 60 minutes at room temperature. After the treatment, rinse the volcanic rock filler repeatedly with deionized water until the washing liquid is neutral (pH value is about 7) to remove residual acidic substances. Place the washed volcanic rock filler in an oven and dry it at 105℃ for 12 hours, then take it out and cool it to room temperature for use.

[0024] (2) SDS processing stage Prepare an SDS solution with a concentration of 0.1mol / L. Put the acid-washed and dried volcanic rock filler back into a clean beaker and add the prepared SDS solution at a solid-liquid ratio of 1:10. Place the mixture in an ultrasonic cleaner, set the ultrasonic frequency to 30-40KHZ, and oscillate or ultrasonicate at room temperature for 30 minutes. After the treatment, let it stand for a while to allow the volcanic rock filler to settle naturally, carefully pour off the supernatant, and retain the solid part. Rinse the SDS-treated volcanic rock filler several times with deionized water, and try to drain the water after each rinse until the washing liquid no longer contains SDS. Finally, put the treated volcanic rock filler back into the oven and dry it at 105°C for 12 hours. After it is completely dry, it can be used for subsequent research. Example 2: Microplastic Removal and Nitrogen Removal System like Figures 1 to 3As shown, the microplastic removal and denitrification system includes a microplastic interception zone 2, wherein a microplastic interception filler layer 7 is provided inside the microplastic interception zone 2; one end of the microplastic interception zone 2 is connected to the aeration zone 1, and the other end is connected to the nitrification zone 3; the nitrification zone 3 is connected to the denitrification zone 4; the denitrification zone 4 is connected to the sulfur autotrophic denitrification zone 5; an aeration oxygenator 6 is provided inside the aeration zone 1; a water distribution device 8 is provided on the top of the nitrification zone 3, and a nitrification filler layer 9 is provided on the bottom; A denitrification filler layer 10 is provided inside the denitrification zone 4; a sulfur autotrophic denitrification filler layer 11 is provided inside the sulfur autotrophic denitrification zone 5; a water inlet 12 is provided at the top of the aeration zone 1; a water outlet 13 is provided at the bottom of the sulfur autotrophic denitrification zone 5; a drainage port 14 is provided at the bottom of the aeration zone 1 and the nitrification zone 3; the aeration zone 1 is connected to the microplastic interception zone 2 through a first water inlet 15, the nitrification zone 3 is connected to the denitrification zone 4 through a second water inlet 16, and the denitrification zone 1 is connected to the microplastic interception zone 2 through a first water inlet 15, and the nitrification zone 3 is connected to the denitrification zone 4 through a second water inlet 16. The aeration zone 4 and the sulfur autotrophic denitrification zone 5 are both connected through the third water inlet 17; the aeration zone 1 is connected to the nitrification zone 3 through the water distribution device 8; the first water inlet 15 is located at the bottom of the microplastic interception zone 2; the second water inlet 16 is located at the bottom of the denitrification zone 4; the third water inlet 17 is located at the top of the sulfur autotrophic denitrification zone 5; the water distribution device 8 includes a main pipe 18 with an opening at one end, and the main pipe is connected to a plurality of longitudinally connected branch pipes 19; the main pipe 18 and the branch pipe 1 9 are provided with a plurality of water spray holes 20; the water distribution device 8 is located above the nitrification filler layer 9, and the distance between the water spray hole 20 and the top of the nitrification filler layer 9 is 20-40 cm; the nitrification filler layer 9 is composed of gravel; the denitrification filler layer 10 is composed of gravel with increasing particle sizes from top to bottom, the upper part of the denitrification filler layer 10 is paved with gravel with a particle size of 5-6 mm, and the lower part of the denitrification filler layer 10 is paved with gravel with a particle size of 8-12 mm. The microplastic interception filler layer is composed of the modified volcanic rock prepared in Example 1. The sulfur autotrophic denitrification filler layer 11 is composed of gravel, sulfur autotrophic denitrification filler and limestone from top to bottom; the volume ratio of the gravel, sulfur autotrophic denitrification filler and limestone is 1:6:2.

[0025] Example 3: Wastewater Treatment Treatment of sewage using the microplastic removal and denitrification system of Example 2: Sewage enters the aeration zone through the water inlet at a rate of 40L / d, and is oxidized with the help of oxygen (5.25 L / min) provided by the aeration oxygenator (Yuting brand ACO-001 oxygenation pump), and then enters the microplastic interception zone to remove the contained microplastics using modified volcanic rocks. After passing through the nitrification zone, the water distribution device sprays the sewage into the nitrification filler layer composed of gravel at the bottom. Natural oxygen enrichment is formed during the spraying process, and natural oxygen enrichment nitrification is carried out. In the nitrification filler layer, microorganisms convert ammonia nitrogen into nitrate. Then it enters the denitrification zone for denitrification. The gravel particle size on the top of the denitrification filler layer is 5~6mm, and the height is about 25cm. The gravel on the bottom gradually increases to 8~12mm, and the height is about 10cm. Under anaerobic conditions, denitrifying bacteria reduce nitrates and nitrites to nitrogen gas. Finally, it enters the sulfur autotrophic denitrification zone, where gravel, sulfur autotrophic denitrification filler (purchased from Shandong Longantai Environmental Protection Technology Co., Ltd., particle size 2-6mm) and limestone are arranged in a volume ratio of 1:6:2, forming the sulfur autotrophic denitrification filler layer from top to bottom. Under anoxic or anaerobic conditions, microorganisms use reduced sulfur as an electron donor to reduce nitrate to nitrogen gas, thereby removing microplastics from sewage and denitrifying it.

[0026] Comparative Example 1: Microplastic Removal and Nitrogen Removal System The difference from Example 2 is that the modified volcanic rock is replaced by an equal amount of volcanic rock.

[0027] Comparative Example 2: Microplastic Removal and Nitrogen Removal System (1) Prepare an SDS solution with a concentration of 0.1 mol / L. Weigh 100 g of volcanic rock with a particle size of 5-6 mm and put it into a clean beaker. Add the prepared SDS solution at a solid-liquid ratio of 1:10. Place the mixture in an ultrasonic cleaner, set the ultrasonic frequency to 30-40 KHZ, and oscillate or ultrasonicate at room temperature for 30 minutes. After the treatment, let it stand for a while to allow the volcanic rock filler to settle naturally, carefully pour off the supernatant, and retain the solid part. Rinse the SDS-treated volcanic rock filler several times with deionized water. After each rinse, drain as much water as possible until the washing liquid no longer contains SDS. Finally, put the treated volcanic rock filler back into the oven and dry it at 105°C for 12 hours to obtain SDS-treated volcanic rock.

[0028] (2) The difference from Example 2 is that the modified volcanic rock is replaced by an equal amount of SDS-treated volcanic rock prepared in step (1).

[0029] Comparative Example 3: Microplastic Removal and Nitrogen Removal System (1) Pickling stage Weigh 100g of volcanic rock with a particle size of 5-6mm, accurate to 0.001g, and put it into a clean beaker. Add enough 5wt% HCl solution to the beaker to completely immerse the volcanic rock filler. Make sure that the HCl solution is excessive to ensure sufficient reaction. Place the beaker containing the volcanic rock filler and HCl solution in a constant temperature oscillator or ultrasonic cleaner, set the ultrasonic frequency to 30-40KHZ, and ultrasonically treat for 60 minutes at room temperature. After the treatment, rinse the volcanic rock filler repeatedly with deionized water until the washing liquid is neutral (pH value is about 7) to remove residual acidic substances. Place the washed volcanic rock filler in an oven and dry it at 105℃ for 12 hours, then take it out and cool it to room temperature for use.

[0030] (2) Hexadecyltrimethylammonium chloride treatment stage Prepare an SDS solution with a concentration of 0.1mol / L. Put the acid-washed and dried volcanic rock filler back into a clean beaker and add the above-prepared hexadecyltrimethylammonium chloride solution at a solid-liquid ratio of 1:10. Place the mixture in an ultrasonic cleaner, set the ultrasonic frequency to 30-40KHZ, and oscillate or ultrasonicate at room temperature for 30 minutes. After the treatment is completed, let it stand for a while to allow the volcanic rock filler to settle naturally, carefully pour off the supernatant, and retain the solid part. Rinse the volcanic rock filler treated with hexadecyltrimethylammonium chloride several times with deionized water, and try to drain the water after each rinse until the washing liquid no longer contains SDS. Finally, put the treated volcanic rock filler back into the oven and dry it at 105℃ for 12 hours. After it is completely dry, it can be used for subsequent research.

[0031] (2) The difference from Example 2 is that the modified volcanic rock is replaced by an equal amount of hexadecyltrimethylammonium chloride modified volcanic rock prepared in step (1).

[0032] Test example The domestic sewage effluent was taken from the sewage treatment plant of Southwest University of Science and Technology, and the concentration of PVC microplastic particles, TN, total phosphorus, chemical oxygen demand, and ammonia nitrogen contained therein were detected by LDIR laser infrared method, alkaline potassium persulfate digestion ultraviolet spectrophotometry, ammonium molybdate spectrophotometry, rapid digestion spectrophotometry, and Nessler reagent spectrophotometry; the concentration of microplastics (PVC) was 226.8 / L, the concentration of TN was 19.17mg / L, the concentration of total phosphorus was 4.03mg / L, the concentration of chemical oxygen demand was 16.39mg / L, and the concentration of ammonia nitrogen was 11.99mg / L. The above sewage was divided into four equal parts, and 40L / d was passed into the four microplastic removal and denitrification systems of Example 2 and Comparative Examples 1 to 3 for sewage treatment according to the method of Example 3. The concentration of microplastics, TN, TP, COD and ammonia nitrogen in the treated wastewater were detected by LDIR laser infrared method, alkaline potassium persulfate digestion ultraviolet spectrophotometry, ammonium molybdate spectrophotometry, rapid digestion spectrophotometry and Nessler reagent spectrophotometry. The results are shown in Figure 4-5 .

[0033] according to Figure 4 It can be seen that in the influent samples, the concentration of PVC microplastics is very high, reaching 226.8 pieces / L. However, after being treated by the microplastic removal and denitrification system in Example 2, the concentration of microplastics in the effluent was significantly reduced to only 3 pieces / L, and the removal rate was as high as 98.68%. This result shows that the system in Example 2 performs well in removing microplastics. In contrast, the treatment effects of the microplastic removal and denitrification systems in Comparative Examples 1 to 3 are slightly inferior. Specifically, the concentrations of microplastics in the effluents of Comparative Examples 1, 2 and 3 were 53.4 pieces / L, 36.1 pieces / L and 24.3 pieces / L, respectively, and the corresponding removal rates were 76.46%, 84.08% and 89.29%, respectively. Although the removal performance of these systems is gradually improving, it still has not reached the level of Example 2. From the perspective of microplastic emissions, the daily water intake of these systems is 40L. According to calculations, the number of microplastics discharged into the environment per month by Example 2 is about 3,600, while the emissions of Comparative Examples 1 to 3 are about 64,080, 43,320, and 29,160, respectively. This shows that the system of Example 2 has obvious advantages in reducing microplastic emissions, and can reduce a large amount of microplastic emissions per month compared with the comparative examples. In summary, the microplastic removal and denitrification system of Example 2 performs well in removing microplastics, and its removal rate and emission reduction effect are significantly better than those of the systems of Comparative Examples 1 to 3. This effectively reduces the pollution of microplastics to the environment.

[0034] according to Figure 5It can be seen that in the influent, the concentrations of total nitrogen (TN), ammonia nitrogen, total phosphorus (TP) and chemical oxygen demand (COD) are 19.17 mg / L, 11.99 mg / L, 4.03 mg / L and 16.39 mg / L, respectively. The four microplastic removal and denitrification systems of Example 2 and Comparative Examples 1-3 can effectively remove these four pollutants. Among them, the removal performance of Example 2 is the most significant, and its removal rates for TN, ammonia nitrogen, TP and COD are 84.92%, 90.66%, 80.65% and 61.93%, respectively. In contrast, although the systems of Comparative Examples 1-3 can also remove these pollutants, their removal rates are relatively low. Specifically, the TN removal rates of Comparative Examples 1-3 were 75.64%, 80.96% and 81.17%, respectively, the ammonia nitrogen removal rates were 80.15%, 84.24% and 85.24%, respectively, the TP removal rates were 74.19%, 76.67% and 77.92%, respectively, and the COD removal rate was between 30% and 42%. This shows that Example 2 has obvious advantages in removing pollutants. Constructed wetland systems are usually used for deep treatment of effluent from sewage treatment plants or equipment. From the above data, the system of Example 2 can more effectively remove these pollutants, especially TN and TP, thereby significantly reducing the discharge of pollutants in the effluent, which is of great significance for reducing the risk of eutrophication of water bodies. In summary, the microplastic removal and denitrification system of Example 2 performs well in removing pollutants such as TN, ammonia nitrogen, TP and COD, and its removal rate is much higher than that of the systems of Comparative Examples 1 to 3. This efficient removal capacity not only improves the cleanliness of water quality, but also effectively reduces the risk of eutrophication of water bodies, and has important environmental significance and application value.

[0035] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for effectively removing microplastics and denitrifying wastewater using artificial wetlands, characterized in that: The method comprises: passing sewage into a microplastic removal and denitrification system, wherein the microplastic removal and denitrification system comprises a microplastic interception zone, wherein a microplastic interception filler layer is provided inside the microplastic interception zone; One end of the microplastic interception zone is connected to the aeration zone, and the other end is connected to the nitrification zone; the nitrification zone is connected to the denitrification zone; the denitrification zone is connected to the sulfur autotrophic denitrification zone; an aeration oxygenator is provided inside the aeration zone; a water distribution device is provided on the top of the nitrification zone, and a nitrification filler layer is provided at the bottom; a denitrification filler layer is provided inside the denitrification zone; a sulfur autotrophic denitrification filler layer is provided inside the sulfur autotrophic denitrification zone; The sewage enters the aeration area for oxidation, then enters the microplastic retention area to remove the microplastics it contains, and then passes through the nitrification area for natural oxygen-enriched nitrification, enters the denitrification area for denitrification, and finally enters the sulfur autotrophic denitrification area to reduce nitrates to nitrogen gas and discharge the treated sewage.

2. The method according to claim 1, characterized in that A water inlet is provided at the top of the aeration zone; a water outlet is provided at the bottom of the sulfur autotrophic denitrification zone; drainage outlets are provided at the bottoms of the aeration zone and the nitrification zone; the aeration zone is connected to the microplastic retention zone through a first water outlet, the nitrification zone is connected to the denitrification zone through a second water outlet, and the denitrification zone and the sulfur autotrophic denitrification zone are both connected through a third water outlet; the aeration zone is connected to the nitrification zone through a water distribution device.

3. The method according to claim 2, characterized in that The first water outlet is located at the bottom of the microplastic retention zone; the second water outlet is located at the bottom of the denitrification zone; and the third water outlet is located at the top of the sulfur autotrophic denitrification zone.

4. The method according to claim 2, characterized in that: The water distribution device comprises a main pipe with an opening at one end, the main pipe is communicated with a plurality of longitudinally connected branch pipes; a plurality of water spray holes are arranged on the main pipe and the branch pipes.

5. The method according to claim 4, characterized in that The water distribution device is located above the nitrification filler layer, and the distance between the water spray hole and the top of the nitrification filler layer is 20-40 cm; the nitrification filler layer is composed of gravel.

6. The method according to claim 1, characterized in that The denitrification filler layer is composed of gravels with increasing particle sizes from top to bottom. The upper part of the denitrification filler layer is paved with gravels with a particle size of 5-6 mm, and the lower part of the denitrification filler layer is paved with gravels with a particle size of 8-12 mm.

7. The method according to claim 1, characterized in that The microplastic interception filler layer is composed of modified volcanic rock; the modified volcanic rock is prepared by the following method: (1) Immersing the volcanic rock in a hydrochloric acid solution, ultrasonically or oscillatingly treating the volcanic rock, and washing the volcanic rock until the washing solution is neutral to obtain the pretreated volcanic rock; (2) The pretreated volcanic rock is immersed in a sodium dodecyl sulfate solution, and the volcanic rock is washed and dried by ultrasonic or oscillation treatment to obtain a modified volcanic rock.

8. The method according to claim 7, characterized in that The concentration of the hydrochloric acid solution is 5wt%; the concentration of the sodium dodecyl sulfate solution is 0.1mol / L; the drying temperature is 105°C and the drying time is 12h.

9. The method according to claim 1, characterized in that: The sulfur autotrophic denitrification filler layer is composed of gravel, sulfur autotrophic denitrification filler and limestone from top to bottom; the volume ratio of the gravel, sulfur autotrophic denitrification filler and limestone is 1:6:

2.

10. Use of the method according to any one of claims 1 to 9 in the simultaneous removal of microplastics and denitrification in artificial wetlands.

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