A semi-permanent filamentous sulfur autotrophic filler for microplastic end treatment and a preparation method and application thereof

Abstract

The present application belongs to the field of environmental functional materials and sewage treatment technology, and particularly relates to a semi-permanent filamentous sulfur autotrophic filler for microplastic end treatment and a preparation method and application thereof. The present application provides a semi-permanent filamentous sulfur autotrophic filler, and the preparation raw materials thereof include sodium sulfide, humic acid, silicate cement, slaked lime, pyrite, municipal sewage plant sludge, chitosan, aluminum powder and water. The semi-permanent filamentous sulfur autotrophic filler has the characteristics of light weight while retaining sufficient strength, overcoming the problem of insufficient strength of the existing filler. In addition, the semi-permanent filamentous sulfur autotrophic filler can also accelerate the domestication speed and enrichment speed of sludge, promote the rapid growth of filamentous sulfur autotrophic bacteria, thereby improving the interception capacity of filamentous sulfur autotrophic bacteria on microplastics, and further improving the denitrification capacity of microorganisms, which can effectively remove a large amount of fine microplastics remaining in the municipal sewage plant, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and wastewater treatment technology, specifically relating to a semi-permanent filamentous sulfur self-trophic filler for microplastic end-of-life treatment, its preparation method and application. Background Technology

[0002] Microplastics (MPs) generally refer to plastics with an equivalent diameter of less than 5 millimeters. They are widely sourced and diverse. Generally, larger microplastic particles tend to settle with sludge during wastewater treatment and thus escape the water cycle. However, smaller microplastic particles, such as fine microplastic particles (or filamentous plastics) smaller than 50 micrometers, are difficult to remove from water.

[0003] Currently, microplastics have been found in the human body and various water bodies, entering various biosphere-related cycles. For example, microplastics accumulate in the food chain as animals eat and drink, continuously circulating throughout the body. Simultaneously, microplastics can also circulate in the human bloodstream, accumulating in tissues or small blood vessels. Generally, microplastics do not directly cause chemical harm to the human body; however, their accumulation often leads to blockages in tissues or blood vessels, resulting in serious consequences. Microplastics that can enter the bloodstream are often tiny and invisible to the naked eye.

[0004] There are many reasons why microplastics enter water bodies. Compared to the vast natural water bodies, humans have more control over the water quality safety of wastewater treatment plants and tap water treatment plants. Regarding the water cycle, the vast majority of microplastics generated in daily life and production originate from water pollution. Besides direct pollution from aquatic waste, some microplastics in the soil degrade and are washed into water bodies by groundwater or rainwater, thus entering the water cycle. Therefore, effective control methods for microplastics in water may find more suitable management approaches in wastewater treatment plants and tap water treatment plants.

[0005] Sulfur autotrophic denitrification is an autotrophic nitrogen removal technology with the advantage of not requiring the addition of a carbon source. Currently, sulfur autotrophic processes used in the market are mainly carried out through the preparation of sulfur-containing packing materials, each with its own characteristics. However, in general, it still has disadvantages such as lack of ability to screen for specific bacteria; inability to deal with special pollutants such as microplastics; low water permeability; easy breakage and detachment of materials after use, leading to uneven hydraulic distribution and thus the phenomenon of "hydraulic short-circuiting"; and the need to re-load microorganisms when adding materials again.

[0006] Municipal wastewater contains a large amount of fine microplastics that are difficult to remove from the water, and has a low chemical oxygen demand (COD) to total nitrogen (C / N) ratio, requiring the addition of large amounts of carbon sources. Furthermore, for municipal wastewater treatment plants, nitrogen and phosphorus removal is the primary function, while microplastic removal is only a secondary function, resulting in most municipal wastewater treatment plants still discharging large amounts of microplastics into natural water bodies annually. In addition, current microplastic treatment methods are mainly physical interception and physicochemical precipitation, which are costly and require the construction of new structures, occupying more land area. Therefore, there is currently a lack of technology that can simultaneously remove both microplastics and total nitrogen. There are many types of sulfur autotrophic bacteria. In the same anaerobic system, under high sulfide concentrations, sulfur cycling can be integrated on a small scale in a single reactor. Therefore, the microbial system in a single anaerobic sulfur reactor is very complex. The sludge domesticated with sulfur often has a high abundance of *Thiobacillus* spp., which cannot quickly form a good biofilm and flocs and cannot perform deep filtration of fine microplastics. Sulfur filamentous bacteria can form better and more stable biofilms and flocs, naturally creating a water-permeable filtration biofilm layer that holds promise for intercepting fine microplastic particles. Therefore, it is necessary to develop a filamentous sulfur autotrophic packing material for the end-stage treatment of microplastics. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention proposes a semi-permanent filamentous sulfur autotrophic packing material for end-of-pipe treatment of microplastics (MPs), which can effectively remove a large number of fine microplastics remaining in municipal sewage treatment plants and further improve the denitrification capacity of microorganisms, and has important application value.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a semi-permanent filamentous sulfur self-growth filler, wherein the raw materials for preparing the semi-permanent filamentous sulfur self-growth filler include sodium sulfide, humic acid, silicate cement, quicklime, pyrite, municipal sewage sludge, chitosan, aluminum powder and water.

[0010] Preferably, the mass ratio of silicate cement, quicklime, pyrite, municipal sewage sludge, humic acid, aluminum powder, and chitosan is 100-150:100-150:50-100:300-500:10-20:1-3:0.5-1.

[0011] Preferably, the amount of water used is 0.6-0.8% of the total mass of silicate cement, quicklime, pyrite, municipal sewage sludge, humic acid, aluminum powder and chitosan.

[0012] Preferably, the molecular weight of humic acid is in the range of 1000-4000.

[0013] Preferably, the strength grade of the silicate cement is 32.5R-52.5R.

[0014] Preferably, the size of the pyrite and quicklime is 200-400 mesh.

[0015] Preferably, the moisture content of sludge from municipal wastewater treatment plants is between 20% and 50%.

[0016] The second aspect of this invention provides a method for preparing the semi-permanent filamentous sulfur self-growing filler described in the first aspect, comprising the following steps:

[0017] S1. Prepare an aluminum powder suspension using water;

[0018] S2. Add silicate cement, quicklime and pyrite powder to water, stir and mix well, then add aluminum powder suspension, continue to stir thoroughly until uniform, and finally pour into a multi-spherical mold and seal to fix the shape.

[0019] S3. Place the prepared mold in a constant temperature and humidity chamber and let it stand for 3-6 hours to obtain a biological filler embryo with a fixed shape.

[0020] S4. Place the embryo into an autoclave and let it stand to obtain the biological filler matrix;

[0021] S5. After preparing chitosan into a uniform viscous liquid, add municipal sewage treatment plant sludge and humic acid, stir thoroughly and then add quicklime, continue to stir thoroughly to obtain the intermediate layer viscous liquid of biological packing.

[0022] S6. Take out the biological filler matrix of S4, shape it according to the mold, break the matrix into individual spherical fillers, and then evenly apply the intermediate layer viscous liquid of the biological filler of S5 onto the rough spherical filler matrix.

[0023] S7. While the intermediate layer of mucus has not yet solidified and lost water, quickly coat the spherical filler matrix coated with the intermediate layer of mucus with a thin layer of quicklime powder, so that the mucus seeps out and wets the lime powder. Finally, let it stand for 1-3 hours to confirm that the intermediate layer of mucus has seeped out and wetted the lime powder, and then dry it to obtain the semi-finished biological filler.

[0024] S8. Prepare an 8-12% sodium sulfide solution and apply it evenly and in small amounts to the semi-finished biological filler using multiple atomized spraying methods. Spray once every 4 hours for a total of 5 sprayings, with a total spraying cycle of 24 hours. After modifying the surface filler with sodium sulfide solution, let it stand for 2-5 days, then wash off the surface impurities with water, and finally dry it to obtain a semi-permanent filamentous sulfur self-nourishing filler.

[0025] Preferably, in S1, the mass concentration of the aluminum powder suspension is 20%-50%.

[0026] Preferably, in S3, the temperature in the constant temperature and humidity chamber is 40℃-60℃, the humidity is above 95%, and the time is 3-6 hours.

[0027] Preferably, in step S4, the temperature of the autoclave is 180℃-190℃ and the time is 6-8 hours.

[0028] Preferably, in step S6, the thickness of the intermediate layer of bio-filler mucus applied to the spherical filler matrix is ​​2-4 mm.

[0029] Preferably, the process of preparing the quicklime powder coating in step S7 is repeated 2-5 times until the thickness of the quicklime powder coating is 2-4 mm.

[0030] The second aspect of this invention provides the application of the semi-permanent filamentous sulfur autotrophic packing material described in the first aspect in the end-of-pipe treatment of microplastics. Specifically, the semi-permanent filamentous sulfur autotrophic packing material described in the first aspect is placed in an anaerobic bioreactor. After the reactor is made to form relatively uniform water distribution conditions through internal reflux, sludge from the anaerobic tank of a municipal sewage treatment plant is added, and then in-situ acclimation is carried out. After acclimation, it can be used to treat microplastics.

[0031] This invention mainly uses a combination of microorganisms and packing materials to effectively intercept fine microplastics. The main bacterial genera used are Beggiatoa and Thiothrix. These two genera are screened by semi-directional screening bacteria to achieve effective filtration of microplastics and denitrification.

[0032] The packing material prepared in this invention is a semi-permanent type. Under reasonable use and maintenance conditions, it can be replaced every 3-5 years. Furthermore, the packing material is a lightweight modified packing material, making replacement simple and resistant to aging and corrosion. Simultaneously, the packing material prepared in this invention is primarily designed to target microplastics that cannot be treated by general sedimentation and physicochemical treatments; therefore, upstream equipment for removing larger microplastics is required. In addition, the packing material prepared in this invention is mainly designed to create favorable sulfur cycling conditions. Under conditions of good integration between the packing material and microorganisms, a fixed microplastic filter bed is formed at the bottom of the tank. The sulfur-autotrophic microorganisms, similar to riverbed sediment, utilize various sulfur elements for sulfur cycling. During the stable period, only a small amount of sulfate needs to be added. Under low dissolved oxygen and low nitrate nitrogen conditions, sulfate-reducing bacteria generate sulfur or sulfur ions for use by sulfur-oxidizing bacteria. Sulfate-oxidizing bacteria, using oxygen or nitrate nitrogen as electron acceptors, can produce sulfate, thus achieving cycling. It is well-suited for municipal wastewater treatment plants with low C / N ratios and low nitrate nitrogen, and is particularly effective in removing large amounts of residual fine microplastics.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] (1) The semi-permanent filamentous sulfur autotrophic filler provided by the present invention uses aluminum powder. The added aluminum powder can strengthen the filler and increase its stability. It can also foam during heating. The small bubbles generated can make the filler lighter. The aluminum hydroxide formed can serve as a reserve of latent alkalinity required by sulfur autotrophic microorganisms.

[0035] (2) Unlike existing sulfur autotrophic denitrification packings, the semi-permanent filamentous sulfur autotrophic packings of the present invention are lighter while retaining sufficient strength, overcoming the problem of insufficient strength of existing packings. For example, packings that use polyvinyl alcohol or sodium alginate and other hydrophilic adhesives to bond the main material sulfur have a very prominent problem of being difficult to withstand pressure. In order to prevent the packings from being crushed and collapsed, only high-strength frames can be used to fill the tank, which brings many inconveniences to the use of the packings.

[0036] (3) The semi-permanent filamentous sulfur autotrophic packing provided by the present invention uses a mixture of pyrite powder, silicate cement and quicklime. Pyrite powder has relatively stable physical and chemical properties and high hardness. While reducing the silicon content, it also makes the packing more compatible with filamentous sulfur autotrophic bacteria, thereby accelerating the acclimatization and enrichment of sludge, improving the interception ability of filamentous sulfur autotrophic bacteria on microplastics, and further improving the denitrification ability of microorganisms.

[0037] (4) The semi-permanent filamentous sulfur autotrophic packing material provided by this invention uses a combination of municipal sewage sludge and humic acid. During the preparation process, the municipal sewage sludge is destroyed by strong alkalinity or loses water, causing the sludge to die. Humic acid has certain colloidal properties and strong ion exchange activity, which can improve mass transfer capacity, promote electron and proton mass transfer, and benefit microorganisms, especially chemoautotrophic microorganisms. The dead sludge will decompose into a large amount of protein, amino acids and inorganic salt ions. The combination with humic acid can retain the beneficial components to a large extent. After the addition of calcium ions, the colloidal properties of humic acid can fix it. When used, it can be slowly released in low calcium or high potassium sodium salts and utilized by filamentous sulfur autotrophic bacteria. The rapid growth of filamentous sulfur autotrophic bacteria can further improve the removal capacity of microplastics and the nitrate removal effect.

[0038] (5) In the preparation of semi-permanent filamentous sulfur autotrophic filler, the present invention uses sodium sulfide solution applied in small amounts and multiple times to the surface of the filler semi-finished product, which can modify the surface of the filler. Calcium sulfide is a slightly soluble compound that will slowly dissolve during use. The precipitation of calcium ions can further provide the substances needed for microorganisms to stabilize on the filler, while sulfur ions are the main food source of filamentous sulfur autotrophic bacteria and are one of the main methods for screening filamentous microorganisms. Attached Figure Description

[0039] Figure 1 The effect of nitrate removal during in-situ acclimation of sludge;

[0040] Figure 2 The nitrate removal efficiency of reactor R2;

[0041] Figure 3 The microplastic removal efficiency of reactor R2;

[0042] Figure 4 Nitrate removal efficiency of reactor R3;

[0043] Figure 5 The microplastic removal efficiency of reactor R3;

[0044] Figure 6 The nitrate removal efficiency of reactor R4;

[0045] Figure 7 The microplastic removal efficiency of reactor R4;

[0046] Figure 8 The nitrate removal efficiency of reactor R5;

[0047] Figure 9 The microplastic removal efficiency of reactor R5;

[0048] Figure 10 This is a special feature of the community distribution of sludge microorganisms before and after domestication. Detailed Implementation

[0049] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0051] Example 1: A method for preparing a semi-permanent filamentous sulfur self-nourishing filler

[0052] The method for preparing the filler includes the following steps:

[0053] (1) Take 100g of aluminum powder and add it to 200mL of water. Stir thoroughly to obtain an aluminum powder suspension of about 33% (calculated by solute:solution = mass fraction);

[0054] (2) Take 10,000g of silicate cement (strength grade 42.5R), 9,000g of quicklime (size 200-400 mesh) and 5,000g of pyrite powder (size 200-400 mesh, purity greater than 90%, sulfur content 48.06%, iron content 41.94%) and add them to a mixer and stir. After they are basically mixed, add 24,000mL of clean water and stir thoroughly. Then add the aluminum powder suspension prepared in step (1) and continue to stir thoroughly until uniform. Finally, pour it into a multi-spherical mold (symmetrical semi-open, spherical, equivalent diameter 10mm) and seal it to fix the shape.

[0055] (3) Place the prepared mold in a constant temperature and humidity chamber and let it stand for 5 hours at a temperature of 50℃ and a humidity of 95% or higher to obtain a biological filler embryo with a fixed shape.

[0056] (4) Place the embryo into an autoclave and let it stand at 185°C for 7 hours to obtain the biological filler matrix;

[0057] (5) Prepare a uniform viscous solution with a concentration of 1% by mixing 50g of chitosan with pure water, then add 20000g of municipal sewage sludge (sludge from a municipal sewage plant in Shenzhen, which was obtained after concentration in the secondary sedimentation tank and has a water content of 35%) and 1000g of humic acid (molecular weight range of 1000-4000), stir thoroughly and then add 4000g of quicklime, continue to stir thoroughly to obtain the intermediate layer viscous solution of biological packing.

[0058] (6) Take out the substrate from step (4), shape it according to the mold, break the substrate into spherical fillers, and then evenly apply the biofiller intermediate layer mucus from step (5) onto the rough spherical filler substrate so that the thickness of the mucus coating is about 2-4 mm.

[0059] (7) While the intermediate layer of mucus has not yet solidified and lost water, quickly coat the spherical filler coated with the intermediate layer of mucus with a thin layer of quicklime powder (spread a 3mm thick layer of quicklime powder on a flat plate, then place the spherical filler substrate on it, wear gloves, and use your hands to continuously rub and roll it evenly) so that the mucus seeps out and wets the quicklime powder. This treatment is repeated 3 times. The final thickness of the quicklime powder coating is about 2-4mm. Finally, let it stand for 1 hour to confirm that the intermediate layer of mucus has seeped out and wetted the quicklime powder. Then put it in a 60℃ oven and let it stand for 2 hours (the light drying process requires confirming that the surface quicklime powder is naturally diffused and wetted by water before putting it in the oven). After the process is completed, take it out to obtain the semi-finished biological filler.

[0060] (8) Prepare a 10% sodium sulfide solution and spray it multiple times using atomization to ensure that the sodium sulfide solution adheres evenly and in small amounts to the semi-finished biological packing material. Repeat this process every 4 hours for a total of 5 times, with a total treatment cycle of 24 hours. After modifying the surface of the packing material with the sodium sulfide solution, let it stand for three days, then wash away the surface impurities with clean water, and finally dry it to obtain the finished biological packing material.

[0061] Example 2: Application of semi-permanent filamentous sulfur autotrophic filler in the end-treatment of microplastics (MPs)

[0062] (1) Take 5000g of the biological packing material prepared in Example 1 and put it into the rising anaerobic bioreactor (UASB reactor) 1 (R1) with an effective volume of 20L. Use two flanges to fix the packing material in the middle of the reactor 1 (R1). Use a peristaltic pump to perform internal reflux of 2L / day, from the top to the bottom. The reflux pipe and the inlet pipe are connected by a tee and merge into the water distribution pipe at the bottom of the reactor to achieve a relatively uniform water distribution condition for the entire reactor.

[0063] (2) Take anaerobic sludge from a municipal wastewater treatment plant (anaerobic sludge from a municipal wastewater treatment plant in Shenzhen) and prepare it to a sludge concentration of 3000 mg / L MLVSS as the initial sludge for in-situ acclimatization.

[0064] (3) A dedicated inlet tank 1 was used for acclimatization. The tank contained a mechanical agitator to ensure uniform distribution of suspended solids and a relatively stable microplastic replenishment rate per unit time. A metering pump was used for quantitative water intake, with a hydraulic retention time set to 24-48 hours. Only one tank of water was introduced per day, and the water was changed daily to minimize data errors. The inlet water quality was as follows: tap water was used, with a nitrate concentration of 500 mg / L, ammonia concentration of 5 mg / L, CODcr of 40-60 mg / L, phosphate concentration of 1 mg / L, pH controlled at approximately 8.0, sodium bicarbonate concentration of 0.6 g / L, and sodium sulfide concentration of 20 mg / L. The acclimatization period was 30 days to complete the cultivation of filamentous sulfur-autotrophic bacteria. Samples were taken and tested daily during the acclimatization period. The nitrate removal effect was as follows: Figure 1 As shown.

[0065] from Figure 1The data shows that the denitrification effect of reactor 1 was poor in the initial acclimatization stage. With the initial dilution of the sludge mixed liquor, the initial nitrate nitrogen was 329.6 mg / L. However, because the sludge in reactor 1 had not yet adapted to the water quality, the denitrification effect was poor, and in the first few days, the highest cumulative nitrate nitrogen value in reactor 1 exceeded 400 mg / L. Subsequently, the sludge in reactor 1 gradually began to adapt to the water quality, and the denitrification effect began to appear, with the effluent nitrate nitrogen starting to decrease. At this point, reactor 1 began denitrification, but still needed a longer acclimatization period to enter the enhancement and sludge growth phase. Due to the acclimatization at a higher nitrate nitrogen concentration and the excellent living environment provided by the packing material, the microorganisms began to grow rapidly, resulting in enhanced denitrification and a continuous decrease in effluent nitrate nitrogen. Until day 30, the effluent nitrate nitrogen was below 10 mg / L for five consecutive days, indicating that the abundance of filamentous sulfur-autotrophic microorganisms had reached the conditions for full biofilm loading, and it was ready to enter the second stage.

[0066] (4) After 30 days of acclimatization, reactor 1 was basically started up, and the biofilm in the packing material was well formed. Then, the packing material and mixed liquid in reactor 1 were divided into four equal parts. One-quarter of these parts were added to rising anaerobic bioreactors 2 (R2), 3 (R3), 4 (R4), and 5 (R5), respectively. Under constant influent conditions, 20-40 μm of microplastics were added to the influent each time to prepare a concentration of approximately 2500 particles / L. [The actual concentration of microplastics in the influent needs to be determined by microplastic testing. The microplastics added to R2, R3, R4, and R5 are polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), respectively]. After preparation, the mixture was ultrasonically vibrated for 20 minutes to ensure uniform distribution of the microplastics. The microplastic particle size was determined using a stainless steel sieve. During the microplastic experiment, the use and contact with plastic products should be minimized, and the reactors should be placed in sheltered corners to reduce the impact of microplastic particles stirred up by personnel on the experimental results.

[0067] Microplastic detection: a) Take 100 mL of daily influent and effluent water samples and filter them using a 10 μm stainless steel filter membrane; b) After filtration, further wash with (1+1) hydrochloric acid; c) After filtration, place the filter membrane in 50 mL of anhydrous ethanol and sonicate for 30 minutes to ensure the filtered particles are fully dispersed in the anhydrous ethanol. Experiments showed that 30 minutes of sonication was sufficient to separate the particles from the filter membrane, leaving almost no residue; d) After shaking, remove the filter membrane and rinse thoroughly with 20 mL of anhydrous ethanol to remove any trace microplastics adhering to the filter membrane surface; e) Add 180 mL of hydrogen peroxide solution (30%) to digest some of the sticky organic matter for 30 minutes; f) After digestion, filter using a 0.45 μm glass fiber filter membrane; g) Finally, dry at room temperature, read the values ​​under a microscope, and convert the calculated results to concentration units. The detection results for reactor 2 (R2) are as follows: Figure 2 , Figure 3 As shown, the detection results of reactor 3 (R3) are as follows: Figure 4 , Figure 5 As shown, the detection results for reactor 4 (R4) are as follows: Figure 6 , Figure 7 As shown, the detection results of reactor 5 (R5) are as follows: Figure 8 , Figure 9 As shown.

[0068] It should be noted that reactors R2, R3, R4, and R5 are the results of different types of microplastics under the action of the packing material in reactor 1, which has been successfully acclimatized, and serve as control groups for each other.

[0069] according to Figure 2 , Figure 4 , Figure 6 and Figure 8 It was observed that when the packing material acclimated in reactor 1 was distributed to four reactors, the denitrification efficiency of the four reactors was slightly lower than that of reactor 1 during the initial start-up phase. This is because although the integrity of the packing material was maintained as much as possible during the transfer process, the stable structure of the packing material and microorganisms was still disrupted to some extent, requiring time to readapt to the new reactors and for the biofilm to become sufficiently abundant. As the reaction time increased day by day, it was found that the subsequent total nitrogen removal rate approached 100%, indicating that the packing material had a good denitrification effect and that sulfur autotrophic bacteria were in a dominant position.

[0070] according to Figure 3 , Figure 5 , Figure 7 and Figure 9The results show that the packing material of the present invention has a significant removal effect on microplastics after the biofilm is fully restored (the denitrification effect can be used as an indicator). For different types of microplastics, the removal effect on polyethylene microplastics is slightly lower than that on the other three types of microplastics, but the overall microplastic removal efficiency is good. After the reactor is stabilized, the microplastic removal rate is basically above 80%.

[0071] comprehensive Figures 2-9 The test results show that by transferring the semi-permanent filamentous packing material (with attached microorganisms) and mixed liquor from reactor R1 to reactors R2, R3, R4, and R5, efficient removal of four common microplastics (ultra-microplastics, 20–40 μm) was achieved. Although the effluent nitrate and microplastic levels were relatively high in the initial startup phase of the latter four reactors due to the incomplete recovery of the biofilm from the sludge packing material, efficient removal of nitrate and microplastics was eventually achieved over time as the biofilm gradually recovered through this semi-permanent filamentous sulfur-autotrophic packing material. This indicates that the packing material has a significant removal effect on the four common ultra-microplastics.

[0072] In addition, high-throughput microbial detection and analysis were performed on initial sludge and sludge after 30 days of acclimation to determine the community distribution characteristics of microorganisms. The results are as follows: Figure 10 As shown in the figure above, after thirty days of acclimatization, the dominant microbial genus gradually shifted to *Thiothrix*, a filamentous sulfur-oxidizing bacterium belonging to the class Gammaproteobacteria, order Thiotrichales, family Thiotrichaceae. It is associated with sulfur autotrophy and is characterized by its long filamentous bodies. Secondly, *Beggiatoa* also showed significant growth. *Beggiatoa* is a colorless sulfur bacterium, long and large, capable of forming visible filamentous aggregates in wastewater. Bacteria of the *Beggiatoa* genus exhibit diverse morphologies and metabolic pathways; they can be cylindrical or disc-shaped, with widths ranging from 1-200 micrometers and lengths from 2-10 micrometers, and can form filaments up to hundreds of cells long. This invention utilizes these characteristics to assemble a finer mesh biofilm, treating nitrate nitrogen while intercepting microplastics. Finally, the presence of *Sulfurimonas* indicates that the microbial system within the reactor is more inclined towards overall sulfur recycling, gradually becoming a more stable biochemical system. This demonstrates that the semi-permanent filamentous sulfur autotrophic packing material of this invention has a significant effect on promoting the removal of nitrate nitrogen and microplastics by microorganisms in the end-of-pipe treatment of microplastics.

[0073] In summary, the semi-permanent filamentous sulfur autotrophic packing material provided by this invention possesses lightweight characteristics while retaining sufficient strength, overcoming the problem of insufficient strength in existing packing materials. Furthermore, it can accelerate the acclimatization and enrichment rate of sludge, promote the rapid growth of filamentous sulfur autotrophic bacteria, thereby improving the interception capacity of filamentous sulfur autotrophic bacteria for microplastics, and further enhancing the denitrification capacity of microorganisms, effectively removing a large amount of residual fine microplastics in municipal wastewater treatment plants.

[0074] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. The application of a semi-permanent filamentous sulfur self-growth filler in the end-treatment of microplastics, characterized in that, The semi-permanent filamentous sulfur autotrophic packing material is placed in an anaerobic bioreactor. After the reactor is made to form relatively uniform water distribution conditions through internal reflux, sludge from the anaerobic tank of a municipal sewage treatment plant is added and then in-situ acclimation is carried out. After acclimation, it can be used to treat microplastics. The preparation method of the semi-permanent filamentous sulfur self-growth filler includes the following steps: S1. Prepare an aluminum powder suspension using water; S2. Add silicate cement, quicklime and pyrite powder to water, stir and mix well, then add aluminum powder suspension, continue to stir thoroughly until uniform, and finally pour into a multi-spherical mold and seal to fix the shape. S3. Place the prepared mold in a constant temperature and humidity chamber and let it stand for 3-6 hours to obtain a biological filler embryo with a fixed shape. S4. Place the embryo into an autoclave and let it stand to obtain the biological filler matrix; S5. After preparing chitosan into a uniform viscous liquid, add municipal sewage treatment plant sludge and humic acid, stir thoroughly and then add quicklime, continue to stir thoroughly to obtain the intermediate layer viscous liquid of biological packing. S6. Take out the biological filler matrix of S4, shape it according to the mold, break the matrix into individual spherical fillers, and then evenly apply the intermediate layer viscous liquid of the biological filler of S5 onto the rough spherical filler matrix. S7. While the intermediate layer of mucus has not yet solidified and lost water, quickly coat the spherical filler matrix coated with the intermediate layer of mucus with a thin layer of quicklime powder, so that the mucus seeps out and wets the lime powder. Finally, let it stand for 1-3 hours to confirm that the intermediate layer of mucus has seeped out and wetted the lime powder, and then dry it to obtain the semi-finished biological filler. S8. Prepare an 8-12% sodium sulfide solution and apply it evenly and in small amounts to the semi-finished biological filler using multiple atomized spraying methods. Spray once every 4 hours for a total of 5 sprayings, with a total spraying cycle of 24 hours. After modifying the surface filler with sodium sulfide solution, let it stand for 2-5 days, then wash off the surface impurities with water, and finally dry it to obtain a semi-permanent filamentous sulfur self-nourishing filler.

2. The application according to claim 1, characterized in that, The molecular weight range of humic acid is 1000-4000, the strength grade of silicate cement is 32.5R-52.5R, the size of pyrite and quicklime is 200-400 mesh, and the moisture content of sludge from municipal sewage treatment plants is between 20% and 50%.

3. The application according to claim 1, characterized in that, In S1, the mass concentration of the aluminum powder suspension is 20%-50%.

4. The application according to claim 1, characterized in that, In S3, the temperature in the constant temperature and humidity chamber is 40℃-60℃, the humidity is above 95%, and the time is 3-6 hours.

5. The application according to claim 1, characterized in that, In S4, the temperature in the autoclave is 180℃-190℃ and the time is 6-8 hours.

6. The application according to claim 1, characterized in that, S6 Apply the intermediate layer of bio-filler viscous liquid to the spherical filler matrix to a thickness of 2-4 mm. S7 Repeat the process of making the quicklime powder coating 2-5 times until the thickness of the quicklime powder coating is 2-4 mm.

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