Semi-permanent filamentous sulfur autotrophic filler for micro-plastic end treatment as well as preparation method and application of semi-permanent filamentous sulfur autotrophic filler

Abstract

The invention belongs to the technical field of environmental functional materials and sewage treatment, and particularly relates to a semi-permanent filamentous sulfur autotrophic filler for micro-plastic end treatment as well as a preparation method and application of the semi-permanent filamentous sulfur autotrophic filler. The invention provides a semi-permanent filamentous sulfur autotrophic filler. The semi-permanent filamentous sulfur autotrophic filler is prepared from the following raw materials: sodium sulfide, humic acid, Portland cement, slaked lime, pyrite, municipal sewage plant sludge, chitosan, aluminum powder and water. The semi-permanent filamentous sulfur autotrophic filler has the characteristic of light weight, also retains enough strength, and overcomes the problem of insufficient strength of the existing filler. Besides, the semi-permanent filamentous sulfur autotrophic filler can further accelerate the domestication speed and enrichment speed of sludge and promote rapid growth of filamentous sulfur autotrophic bacteria, so that the interception capacity of the filamentous sulfur autotrophic bacteria on micro-plastics is improved, the denitrification capacity of microorganisms is further improved, a large amount of residual fine micro-plastics in municipal sewage plants can be effectively removed, and the service life of the filamentous sulfur autotrophic filler is prolonged. The application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental functional materials and sewage treatment, and specifically relates to a semi-permanent filamentous sulfur autotrophic filler for microplastic terminal treatment, and a preparation method and application thereof. Background Art

[0002] Microplastics (MPs) generally refer to plastics with an equivalent diameter of less than 5 mm, which come from a wide range of sources and are of various types. Generally speaking, for larger microplastic particles, most of them tend to settle with the sludge during sewage treatment, thus leaving the water cycle. However, for smaller microplastic particles, such as fine microplastic particles (or filamentous plastics) less than 50 microns, it is difficult to remove them from the water.

[0003] At present, microplastics have been found in the human body and various water bodies, and have entered various cycles related to the biosphere. For example, in the food chain, microplastics accumulate and circulate continuously as animals eat and drink water. At the same time, microplastics can also circulate continuously in the human blood system, and then accumulate in certain tissues or small blood vessels. Generally speaking, microplastics do not directly cause chemical damage to the human body. It is usually due to large-scale accumulation that causes blockage of certain tissues or blood vessels of animals, resulting in terrible consequences. Microplastics that can enter the blood system are often small microplastics that are difficult to see with the naked eye.

[0004] There are many reasons why microplastics enter water bodies. Compared with large natural water bodies, humans can better control the water quality safety of sewage treatment plants and water plants. As for the water cycle, the vast majority of microplastics produced in people's production and life start from water pollution. In addition to direct pollution of water waste, some of them are plastics in the soil that are degraded and washed into the water body with groundwater or rainwater, thus entering the water cycle. Therefore, for effective control methods of microplastics in water, perhaps more appropriate control methods can be found in sewage treatment plants and water treatment plants.

[0005] Sulfur autotrophic denitrification is an autotrophic denitrification process technology with the advantage of not requiring the addition of a carbon source. Currently, the sulfur autotrophic technology used in the market is mainly carried out by preparing sulfur-containing fillers, with different characteristics. But in general, there are still shortcomings such as the lack of ability to screen special bacteria; the inability to deal with special pollutants such as microplastics; low water permeability; the material is easily broken and falls off after use, resulting in uneven hydraulic distribution, and then the phenomenon of "hydraulic short flow"; re-adding materials requires re-mounting microorganisms, etc.

[0006] There are a large number of tiny microplastics in municipal sewage that are difficult to remove from the water, and the chemical oxygen demand: total nitrogen (C / N) is low, requiring additional addition of a large amount of carbon source. Moreover, for municipal sewage treatment plants, the main functions are nitrogen and phosphorus removal, and the removal of microplastics is only a byproduct, resulting in most municipal sewage treatment plants still discharging a large amount of microplastics into natural water bodies every year. In addition, the current methods for treating microplastics are mainly physical interception and physicochemical precipitation, which are costly and require the independent construction of new structures, occupying more land area. Therefore, there is still a lack of process technology that can simultaneously remove the two major problems of microplastics and total nitrogen. There are many types of sulfur autotrophic bacteria. In the same anaerobic system, under the condition of high sulfide concentration, the sulfur cycle can be integrated on a small scale in a reactor, so the microbial system in a single anaerobic sulfur reactor is very complex. The microbial community abundance of the sludge domesticated with sulfur is often high in the genus Thiobacillus, which cannot quickly form a relatively good biofilm and bacterial floc, and cannot perform deep filtration for tiny microplastics. Sulfur filamentous bacteria can form better and more stable biofilms and bacterial flocs, naturally forming a permeable and filtration biofilm layer, which is expected to achieve the purpose of intercepting tiny microplastic particles. Therefore, it is necessary to develop a filamentous sulfur autotrophic filler for the terminal treatment of microplastics. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a semi-permanent filamentous sulfur autotrophic filler for the terminal treatment of microplastics (MPs), which can effectively remove a large amount of fine microplastics remaining in municipal sewage treatment plants and further improve the denitrification ability of microorganisms, and has important application value.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

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

[0010] Preferably, the mass ratio of the silicate cement, slaked lime, 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, slaked lime, 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 silicate cement is 32.5R-52.5R.

[0014] Preferably, the pyrite and slaked lime are of a size of 200-400 mesh.

[0015] Preferably, the water content of municipal sewage plant sludge is between 20% and 50%.

[0016] The second aspect of the present invention provides a method for preparing the semi-permanent filamentous sulfur autotrophic filler according to the first aspect, comprising the following steps:

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

[0018] S2, adding silicate cement, slaked lime and pyrite powder into water, stirring and mixing, then adding aluminum powder suspension, continuing to stir until uniform, and finally pouring into a multi-ball mold to encapsulate and fix the shape;

[0019] S3, placing the prepared mold in a constant temperature and humidity chamber and leaving it to stand for 3-6 hours to obtain a biofiller embryo with a fixed shape;

[0020] S4, placing the embryo body into an autoclave and continuing to stand to obtain a biofiller matrix;

[0021] S5, after chitosan is prepared into a uniform mucus, sludge from a municipal sewage plant and humic acid are added, and after fully stirring, slaked lime is added, and further stirring is continued to be fully stirred to obtain a biofiller middle layer mucus;

[0022] S6, taking out the biological filler matrix of S4, breaking the matrix into spherical fillers according to the mold shaping, and then evenly applying the biological filler middle layer mucus of S5 on the rough spherical filler matrix;

[0023] S7, while the middle layer of mucus has not yet solidified and lost water, the spherical filler substrate coated with the middle layer of mucus is quickly coated with a thin layer of slaked lime powder, so that the mucus seeps out and infiltrates the lime powder, and finally stands for 1-3 hours to ensure that the middle layer of mucus seeps out and infiltrates the lime powder, and then dries to obtain a semi-finished biological filler;

[0024] S8. Sodium sulfide is prepared into an 8-12% sodium sulfide solution, and the sodium sulfide solution is attached to the semi-finished biological filler in a relatively uniform and small amount by multiple atomization spraying, spraying once every 4 hours, a total of 5 sprayings, and a total spraying period of 24 hours. After the surface filler is modified with the sodium sulfide solution, it is left to stand for 2-5 days, and then the surface impurities are washed with water, and finally dried to obtain a semi-permanent filamentous sulfur autotrophic 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°C-60°C, the humidity is above 95%, and the time is 3-6 hours.

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

[0028] Preferably, S6 applies the biofiller intermediate layer mucus on the spherical filler matrix to a thickness of 2-4 mm.

[0029] Preferably, the process of making the slaked lime powder coating in S7 is repeated 2-5 times until the thickness of the lime powder coating is 2-4 mm.

[0030] The second aspect of the present invention provides an application of the semi-permanent filamentous sulfur autotrophic filler described in the first aspect in the terminal treatment of microplastics, specifically: the semi-permanent filamentous sulfur autotrophic filler described in the first aspect is placed in an anaerobic bioreactor, and after the reactor forms a relatively uniform water distribution condition through internal reflux, anaerobic tank sludge from a municipal sewage treatment plant is added, and then in-situ domestication is carried out. After the domestication is completed, it can be used to treat microplastics.

[0031] The present invention mainly adopts the combination of microorganisms and fillers to effectively intercept tiny microplastics. The main bacterial genera used are Beggiatoa and Thiothrix. These two genera are screened by semi-directional screening, thereby achieving the effect of effectively filtering microplastics and denitrifying.

[0032] The filler prepared by the present invention belongs to a semi-permanent filler. Under reasonable use and maintenance conditions, the replacement time can be as long as 3-5 years, and the filler belongs to a light modified filler, which is simple to replace and not easy to age and corrode. At the same time, the filler prepared by the present invention is mainly for microplastics that cannot be treated by general precipitation and physicochemical treatment, so the front end needs to add removal equipment for larger microplastics. In addition, the filler prepared by the present invention is mainly to create good sulfur circulation conditions. Under the condition of good combination of filler and microorganism, a microplastic fixed filter bed is formed at the bottom of the pool body, and sulfur autotrophic microorganisms can be similar to riverbed mud, using various sulfur element substances for sulfur circulation. When used in the stable period, generally only a small amount of sulfate needs to be supplemented. Under low dissolved oxygen and low nitrate nitrogen conditions, sulfate-reducing bacteria will generate sulfur or sulfur ions for sulfur oxidizing bacteria, and sulfur oxidizing bacteria can produce sulfate when oxygen or nitrate nitrogen is used as an electron acceptor, thereby achieving circulation. It has a good adaptation effect on the low C / N ratio and low nitrate nitrogen wastewater of municipal sewage treatment plants, and can effectively remove a large number of fine microplastics remaining in municipal sewage treatment plants.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) Aluminum powder is used in the semi-permanent filamentous sulfur autotrophic filler provided by the present invention. The added aluminum powder can play a role in reinforcing the filler and increasing the stability of the filler. It can also foam during the heating process. The small bubbles generated can make the filler lighter. The aluminum hydroxide formed can serve as a hidden alkalinity reserve required by sulfur autotrophic microorganisms.

[0035] (2) Different from the existing sulfur autotrophic denitrification fillers, the semi-permanent filamentous sulfur autotrophic filler of the present invention has the characteristics of being lighter and retaining sufficient strength, thus overcoming the problem of insufficient strength of the existing fillers. For example, the fillers made of sulfur as the main material are bonded with polyvinyl alcohol or sodium alginate or other hydrophilic adhesives, which have the prominent problem of being difficult to bear pressure. In order to prevent the fillers from being crushed and collapsed, the only option is to use a high-strength frame to fill the pool body, which brings a lot of inconvenience to the use of the fillers;

[0036] (3) The semi-permanent filamentous sulfur autotrophic filler provided by the present invention uses pyrite powder mixed with silicate cement and slaked lime, wherein the pyrite powder has the characteristics of relatively stable physical and chemical properties and high hardness. While reducing the silicon content, it also makes the filler have a stronger affinity for filamentous sulfur autotrophic bacteria, thereby accelerating the acclimation and enrichment speed of sludge, improving the interception ability of filamentous sulfur autotrophic bacteria for microplastics, and further improving the denitrification ability of microorganisms.

[0037] (4) The semi-permanent filamentous sulfur autotrophic filler provided by the present invention uses a combination of municipal sewage plant sludge and humic acid, wherein the municipal sludge is destroyed by strong alkalinity or dehydrated during the preparation process, causing the sludge to die. Humic acid has certain colloidal properties and strong ion exchange activity, which can improve the mass transfer capacity, promote electron and proton mass transfer, and is beneficial to microorganisms, especially chemoautotrophic microbial reactions. The dead sludge will break off a large amount of protein, amino acids and inorganic salt ions, and the combination with humic acid can retain the beneficial components therein to a large extent. After adding 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, and the rapid growth of filamentous sulfur autotrophic bacteria can further improve the removal capacity of microplastics and the nitrate nitrogen effect.

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

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

[0040] Figure 2 is the nitric nitrogen removal effect of reactor R2;

[0041] Figure 3 is the microplastic removal effect of reactor R2;

[0042] Figure 4 The nitric nitrogen removal effect of reactor R3;

[0043] Figure 5 is the microplastic removal effect of reactor R3;

[0044] Figure 6 is the nitric nitrogen removal effect of reactor R4;

[0045] Figure 7 is the microplastic removal effect of reactor R4;

[0046] Figure 8 is the nitric nitrogen removal effect of reactor R5;

[0047] Fig. 9 is the microplastic removal effect of reactor R5;

[0048] Fig.10 It is a special distribution of sludge microbial communities before and after domestication. DETAILED DESCRIPTION

[0049] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

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

[0052] The preparation method of the filler comprises the following steps:

[0053] (1) Take 100g of aluminum powder and add it to 200mL of clean water. After sufficient stirring, prepare an aluminum powder suspension of about 33% (calculated by solute: solution = mass fraction);

[0054] (2) 10000g of silicate cement (strength grade 42.5R), 9000g of slaked lime (size 200-400 mesh) and 5000g of pyrite powder (size 200-400 mesh, purity greater than 90%, sulfur accounting for 48.06%, iron accounting for 41.94%) are added to a blender and stirred. After being basically mixed, 24000mL of clean water is added. After being fully stirred, the aluminum powder suspension prepared in step (1) is added, and the mixture is further fully stirred until uniform. Finally, the mixture is poured into a multi-spherical mold (symmetrical half-open, spherical, equivalent diameter 10mm) and packaged into a fixed shape;

[0055] (3) placing the prepared mold in a constant temperature and humidity chamber and leaving it to stand for 5 hours at a temperature of 50° C. and a humidity of 95% or more to obtain a biofiller embryo with a fixed shape;

[0056] (4) placing the embryos in an autoclave and allowing to stand for 7 hours at 185° C. to obtain a biofiller matrix;

[0057] (5) Use pure water to prepare 50g of chitosan into a uniform mucus with a concentration of 1%, then add 20,000g of municipal sewage plant sludge (sludge from a municipal sewage plant in Shenzhen, the sludge is obtained after concentration in the secondary sedimentation tank, and the water content is 35%) and 1,000g of humic acid (molecular weight range is 1,000-4,000), stir well and then add 4,000g of slaked lime, continue to stir well to obtain the biofiller middle layer mucus.

[0058] (6) The matrix of step (4) is taken out, and the matrix is ​​disassembled into spherical fillers according to the mold shaping, and then the biological filler intermediate layer mucus of step (5) is evenly applied on the rough spherical filler matrix, so that the thickness of the mucus coating is about 2-4 mm.

[0059] (7) While the middle layer of mucus has not yet solidified and lost water, the spherical filler coated with the middle layer of mucus is quickly coated with a thin layer of slaked lime powder (spread a 3 mm thick layer of lime powder on a flat plate, then place the spherical filler matrix on it, put on gloves, and use hands to rub and roll it evenly) to allow the mucus to seep out and soak the lime powder. This treatment is repeated 3 times. The final thickness of the lime powder coating is about 2-4 mm. Finally, let it stand for 1 hour to make sure that the middle layer of mucus seeps out and soaks the lime powder. Then put it in a 60°C oven and let it stand for 2 hours (the light baking process needs to make sure that the surface lime powder is naturally diffused and soaked by water before putting it in the oven). After the end, take it out to obtain a semi-finished biological filler.

[0060] (8) Prepare a sodium sulfide solution with a mass concentration of 10%, and use multiple atomization spraying methods to make the sodium sulfide solution evenly and in small amounts adhere to the semi-finished biological filler. Repeat once every 4 hours, repeat 5 times in total, and the total treatment period is 24 hours. After the filler surface is modified with the sodium sulfide solution, wait for three days, then use clean water to wash away the surface impurities, and finally dry to obtain the finished biological filler.

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

[0062] (1) 5000 g of the biological filler prepared in Example 1 was taken and placed in an ascending anaerobic bioreactor (UASB reactor) 1 (R1) with an effective volume of 20 L. The filler was fixed to the middle of the reactor 1 (R1) using two flanges. A peristaltic pump was used to perform internal reflux at 2 L / day from the upper part to the lower part. The reflux pipe and the water inlet pipe were connected by a tee and merged into the water distribution pipe at the lower part of the reactor to achieve a relatively uniform water distribution condition for the entire reactor.

[0063] (2) Take the anaerobic tank sludge of a municipal sewage plant (anaerobic tank sludge of a municipal sewage 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 special water inlet bucket 1 is used for domestication water, and a mechanical stirring device is installed in the bucket to ensure that the suspended matter in the water inlet bucket 1 is evenly distributed and the amount of microplastics added per unit time remains relatively stable. A metering pump is used to quantitatively inlet water, and the hydraulic retention time is set to 24-48 hours. Only one bucket of water is introduced per day, and the water distribution is changed daily to reduce data errors. The water quality of the inlet water distribution is: the inlet water is prepared with tap water, the nitrate nitrogen concentration is 500 mg / L, the ammonia nitrogen concentration is 5 mg / L, the CODCr is 40-60 mg / L, the phosphate is 1 mg / L, the pH is controlled at about 8.0, the sodium bicarbonate concentration is 0.6 g / L, and the sodium sulfide concentration is 20 mg / L. The domestication time is 30 days to complete the cultivation of filamentous sulfur autotrophic bacteria. During the domestication period, samples are taken and tested once a day. The nitrate nitrogen removal effect is as follows: Figure 1 shown.

[0065] from Figure 1From the data, it can be found that the denitrification effect of reactor 1 was not good in the early stage of domestication. Under the dilution of the initial sludge mixture, the initial nitrate nitrogen was 329.6 mg / L. However, since the sludge in reactor 1 had not yet adapted to the water quality, the denitrification effect was not good. In the first few days, the maximum cumulative value of nitrate nitrogen in reactor 1 exceeded 400 mg / L. Subsequently, the sludge in reactor 1 gradually began to adapt to the water quality, the denitrification denitrification effect began to appear, and the effluent nitrate nitrogen began to decrease. At this time, reactor 1 began to denitrify, but it still took a longer time of domestication to enter the promotion period and sludge growth period. Due to domestication at a higher nitrate nitrogen concentration and the excellent living environment provided by the filler, the microorganisms began to grow rapidly, and the result was that the denitrification effect was enhanced and the effluent nitrate nitrogen continued to decrease until 30 days. The effluent nitrate nitrogen was lower than 10 mg / L for 5 consecutive days, indicating that the growth abundance of its filamentous sulfur autotrophic microorganisms has reached the conditions for full biofilm load and is ready to enter the second stage.

[0066] (4) After 30 days of acclimatization, the reactor 1 has basically started up and the filler biofilm has formed well. Then the filler and the mixed liquid in the reactor 1 are evenly divided into four parts, and one quarter is added to the ascending anaerobic bioreactor 2 (R2), reactor 3 (R3), reactor 4 (R4), and reactor 5 (R5). Then, under the condition of unchanged influent conditions, 20-40um microplastics are added to each influent to make it into a concentration of about 2500 / L [the actual concentration of influent microplastics needs to be determined by microplastic detection, where the microplastics added to R2, R3, R4, and R5 are polyethylene plastic (PE), polypropylene plastic (PP), polystyrene plastic (PS), and polyvinyl chloride plastic (PVC) respectively]. After the preparation is completed, ultrasonic vibration is performed for 20 minutes to ensure that the microplastics are evenly distributed. The particle size of microplastics is determined by a stainless steel sieve. In the microplastic experiment, try to use and touch plastic products as little as possible, prevent the reactor from being placed in a corner sheltered place, and reduce the microplastic particles raised by people walking and affecting the experimental results.

[0067] Microplastic detection: a. Take 100mL of daily inlet and outlet water samples and filter them using a 10um stainless steel filter membrane; b. Use (1+1) hydrochloric acid for further filtration after filtration; c. Place the filter membrane in 50mL of anhydrous ethanol after filtration and perform ultrasonic treatment for 30 minutes so that the filtered particles can be fully dispersed in the anhydrous ethanol. After testing, 30 minutes of ultrasonic treatment is sufficient to fully separate the particles from the filter membrane, and there is almost no residue on the filter membrane; d. Remove the filter membrane after shaking and rinse it with 20mL of anhydrous ethanol to wash off the trace microplastics adhering to the surface of the filter membrane; e. Add 180mL of hydrogen peroxide solution (30%) to digest some sticky organic matter for 30 minutes; f. After digestion, use a 0.45um glass fiber filter membrane for filtration; g. Finally, dry at room temperature, read the reading under a microscope, and convert the calculated results into concentration units. Among them, the detection results of 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 of reactor 4 (R4) are as follows Figure 6 , Figure 7 As shown, the detection results of reactor 5 (R5) are as follows Figure 8 , Fig. 9 shown.

[0068] It should be noted that the R2, R3, R4, and R5 reactors are the results of different types of microplastics being exposed to the fillers that have been successfully domesticated in reactor 1, and they serve as control groups for each other.

[0069] according to Figure 2 , Figure 4 , Figure 6 and Figure 8 It can be found that the fillers tamed by reactor 1 were divided into 4 reactors. Compared with reactor 1, the denitrification effect of the 4 reactors was slightly reduced at the initial start-up. This is because although the integrity of the fillers was maintained as much as possible during the transfer process, the stable structure of the fillers and microorganisms was still damaged to a certain extent, and it took a certain amount of time to re-adapt to the new reactor so that the biofilm became rich enough. As the reaction time increased day by day, it can be found that the subsequent total nitrogen removal rate was close to 100%, indicating that the filler had a good denitrification effect and the growth of sulfur autotrophic bacteria was in a relatively advantageous position.

[0070] according to Figure 3 , Figure 5 , Figure 7 and Fig. 9From the results, it can be seen that the filler of the present invention has a significant removal effect on ultramicroplastics after the biofilm is fully restored (the denitrification effect can be used as an indicator). For different types of microplastics, the removal effect of polyethylene microplastics is slightly lower than that of 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 Figure 2-Figure 9 The test results show that by transferring the semi-permanent filamentous filler (biofilmed microorganisms) and mixed liquid of reactor R1 to reactors R2, R3, R4 and R5, four types of common microplastics (ultra-microplastics, 20-40um) were efficiently removed. Although the nitrate nitrogen and microplastics in the effluent were high at the beginning of the startup of the last four reactors due to the incomplete recovery of the biofilm of the sludge filler, as time went on, the semi-permanent filamentous sulfur autotrophic filler gradually restored the biofilm and finally achieved efficient removal of nitrate nitrogen and microplastics, indicating that the filler has a significant removal effect on the four common ultra-microplastics.

[0072] In addition, the initial sludge and the sludge after acclimation for 30 days were used for high-throughput microbial detection and analysis to determine the distribution characteristics of microbial communities. The results are as follows: Fig.10 As shown. It can be found from the above figure that after thirty days of domestication, the dominant genus of microorganisms gradually turned into filamentous sulfur-oxidizing bacteria (Thiothrix). Thiothrix is ​​a filamentous, sulfur-oxidizing bacterium belonging to the Gammaproteobacteria class, Thiotrichales order, and Thiotrichaceae family. It is related to sulfur autotrophy and has the characteristics of long filaments. Secondly, the genus Beggiatoa also showed a significant increase. Beggiatoa is a colorless sulfur bacterium with a long and large body. It can form filamentous aggregates visible to the naked eye in wastewater. Bacteria of the genus Beggiatoa have diverse morphologies and metabolic modes. They can be cylindrical or disc-shaped, with a width between 1-200 microns and a length between 2-10 microns, and can form filaments up to hundreds of cells. The present invention utilizes this feature to assemble a more dense mesh biofilm to intercept microplastics while processing nitrate nitrogen. Finally, Sulfurimonas also appeared, indicating that the microbial system in the reactor is more inclined to the overall sulfur cycle and gradually becomes a more stable biochemical system, indicating that the semi-permanent filamentous sulfur autotrophic filler of the present invention has an obvious effect on promoting microbial removal of nitrate and microplastics in the terminal treatment of microplastics.

[0073] In summary, the semi-permanent filamentous sulfur autotrophic filler provided by the present invention has the characteristics of light weight while retaining sufficient strength, overcoming the problem of insufficient strength of existing fillers. In addition, it can also accelerate the acclimation and enrichment speed of sludge, promote the rapid growth of filamentous sulfur autotrophic bacteria, thereby improving the interception ability of filamentous sulfur autotrophic bacteria for microplastics, and further improve the denitrification ability of microorganisms, which can effectively remove a large amount of fine microplastics remaining in municipal sewage treatment plants.

[0074] The embodiments of the present invention are 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 of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A semi-permanent filamentous sulfur autotrophic filler, characterized in that: The raw materials for preparing the semi-permanent filamentous sulfur autotrophic filler include sodium sulfide, humic acid, silicate cement, slaked lime, pyrite, municipal sewage plant sludge, chitosan, aluminum powder and water.

2. A semi-permanent filamentous sulfur autotrophic filler according to claim 1, characterized in that: The mass ratio of silicate cement, slaked lime, pyrite, municipal sewage plant sludge, humic acid, aluminum powder and chitosan is 100-150: 100-150: 50-100: 300-500: 10-20: 1-3: 0.5-1.

3. The semi-permanent filamentous sulfur autotrophic filler according to claim 1, characterized in that: The amount of water used is 0.6-0.8 of the total mass of silicate cement, slaked lime, pyrite, municipal sewage plant sludge, humic acid, aluminum powder and chitosan.

4. The semi-permanent filamentous sulfur autotrophic filler according to claim 1, characterized in that: The molecular weight of humic acid ranges from 1000-4000, the strength grade of Portland cement is 32.5R-52.5R, the size of pyrite and slaked lime is 200-400 mesh, and the moisture content of municipal sewage plant sludge is between 20%-50%.

5. The method for preparing the semi-permanent filamentous sulfur autotrophic filler according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Prepare aluminum powder suspension by using water; S2, adding silicate cement, slaked lime and pyrite powder into water, stirring and mixing, then adding aluminum powder suspension, continuing to stir until uniform, and finally pouring into a multi-ball mold to encapsulate and fix the shape; S3, placing the prepared mold in a constant temperature and humidity chamber and leaving it to stand for 3-6 hours to obtain a biofiller embryo with a fixed shape; S4, placing the embryo body into an autoclave reactor and continuing to stand to obtain a biofiller matrix; S5, after chitosan is prepared into a uniform mucus, sludge from a municipal sewage plant and humic acid are added, and after fully stirring, slaked lime is added, and further stirring is continued to be fully stirred to obtain a biofiller middle layer mucus; S6, taking out the biological filler matrix of S4, breaking the matrix into spherical fillers according to the mold shaping, and then evenly applying the biological filler middle layer mucus of S5 on the rough spherical filler matrix; S7, while the middle layer of mucus has not yet solidified and lost water, the spherical filler substrate coated with the middle layer of mucus is quickly coated with a thin layer of slaked lime powder, so that the mucus seeps out and infiltrates the lime powder, and finally stands for 1-3 hours to ensure that the middle layer of mucus seeps out and infiltrates the lime powder, and then dries to obtain a semi-finished biological filler; S8. Sodium sulfide is prepared into an 8-12% sodium sulfide solution, and the sodium sulfide solution is attached to the semi-finished biological filler in a relatively uniform and small amount by multiple atomization spraying, spraying once every 4 hours, a total of 5 sprayings, and a total spraying period of 24 hours. After the surface filler is modified with the sodium sulfide solution, it is left to stand for 2-5 days, and then the surface impurities are washed with water, and finally dried to obtain a semi-permanent filamentous sulfur autotrophic filler.

6. The method for preparing the semi-permanent filamentous sulfur autotrophic filler according to claim 5, characterized in that: In S1, the mass concentration of the aluminum powder suspension is 20%-50%.

7. The method for preparing the semi-permanent filamentous sulfur autotrophic filler according to claim 5, characterized in that: In S3, the temperature in the constant temperature and humidity chamber is 40°C-60°C, the humidity is above 95%, and the time is 3-6 hours.

8. The method for preparing the semi-permanent filamentous sulfur autotrophic filler according to claim 5, characterized in that: In S4, the temperature of the autoclave is 180° C.-190° C., and the time is 6-8 hours.

9. The method for preparing the semi-permanent filamentous sulfur autotrophic filler according to claim 5, characterized in that: S6 applies the biofiller middle layer mucus on the spherical filler substrate to a thickness of 2-4 mm, and S7 repeats the process of making the slaked lime powder coating 2-5 times until the thickness of the lime powder coating is 2-4 mm.

10. Use of the semi-permanent filamentous sulfur autotrophic filler according to any one of claims 1 to 4 in the terminal treatment of microplastics, characterized in that: The semi-permanent filamentous sulfur autotrophic filler described in any one of claims 1 to 4 is placed in an anaerobic bioreactor, and after the reactor is formed with relatively uniform water distribution conditions by internal reflux, anaerobic tank sludge from a municipal sewage plant is added, and then in-situ domestication is carried out. After the domestication is completed, it can be used to treat microplastics.

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