A new combined suspended ball filler for simultaneous nitrogen and phosphorus removal in biochemical aerobic section

Abstract

The application discloses a novel combined suspended ball filler for simultaneous nitrogen and phosphorus removal in a biochemical aerobic section, which is filled into a porous suspended ball by a mixed material composed of a composite sulfur component filler and a porous sponge. The novel combined suspended ball filler can be used in the biochemical aerobic section, can enrich the microbial biofilm on one hand, and can successfully remove nitrate nitrogen by increasing the composite sulfur component filler on the other hand, so that simultaneous nitrification and denitrification is achieved, nitrate nitrogen and ammonia nitrogen are removed at the same time, the nitrogen and phosphorus removal effect is improved, and the proportion of the composite sulfur component filler and the porous sponge can be flexibly adjusted according to different water quality conditions, so that efficient nitrogen and phosphorus removal can be realized in different wastewaters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a novel combined suspended ball filler for simultaneous nitrogen and phosphorus removal in biochemical aerobic section. BACKGROUND

[0002] Water eutrophication is a water pollution phenomenon caused by excessive discharge of nitrogen, phosphorus and other nutrients in water bodies, and is a global water quality problem. Water eutrophication is mainly caused by the discharge of exogenous nutrients, and nitrogen and phosphorus are one of the main limiting factors of water eutrophication. Therefore, the control of nitrogen and phosphorus is crucial for the restoration of water eutrophication.

[0003] Biological simultaneous nitrogen and phosphorus removal has been widely valued and applied due to its low cost and no secondary pollution. Biological nitrogen removal mainly includes two stages of aerobic nitrification and anoxic denitrification. In the aerobic state, ammonia nitrogen is converted into nitrate nitrogen, and in the anoxic state, nitrate nitrogen is converted into nitrogen gas. Biological phosphorus removal mainly includes two stages of anaerobic release of phosphorus and aerobic absorption of phosphorus. The widely used A2 / O process is composed of multiple reaction tanks, and the nitrification, denitrification and phosphorus removal processes are carried out in different reaction tanks. The aerobic section is mainly for nitrification, in which ammonia nitrogen is converted into nitrate nitrogen or nitrite nitrogen under the action of microorganisms, and the polyphosphorus bacteria complete the phosphorus accumulation. The whole process has high investment cost and complex operation and management, and it is difficult to meet the increasingly stringent emission standards. In addition, a large amount of excess sludge is produced, and the harmless treatment investment is high. In contrast, the biofilm method has fast microbial film formation speed and more stable and abundant biological phase due to the addition of fillers, and has higher treatment efficiency. Therefore, more and more researchers combine the two processes to treat wastewater, that is, adding suspended fillers in the anoxic or aerobic section of the A2 / O process to form a comprehensive microbial treatment system with suspended activated sludge and attached biofilm.

[0004] The existing A2 / O process often carries out nitrification, denitrification and phosphorus removal processes in different reaction tanks, which has high investment cost, complex operation and management, and is difficult to meet the increasingly stringent nitrogen emission standards. In the biochemical aerobic section, nitrification is mainly carried out to convert ammonia nitrogen into nitrate nitrogen and nitrite nitrogen and to absorb phosphorus. In order to strengthen the effect of simultaneous nitrogen and phosphorus removal, fillers are added in the anoxic or aerobic section, which can increase the number and species of microorganisms and strengthen the nitrification and denitrification capacity. However, the filler often has a relatively long film formation time, and a large amount of organic carbon source needs to be added to improve the efficiency of nitrogen and phosphorus removal, which requires high additional investment. SUMMARY

[0005] To solve the above technical problems, the present application provides a novel combined suspended ball filler for simultaneous nitrogen and phosphorus removal in biochemical aerobic section.

[0006] The technical scheme of the present application is: a new combined suspended ball filler for simultaneous nitrogen and phosphorus removal in biochemical aerobic section, which is filled with mixed material composed of composite sulfur component filler and porous sponge into porous suspended ball, wherein the volume ratio of the mixed material filled in the porous suspended ball is 20%-80%, and the volume ratio of the composite sulfur component filler to the porous sponge is 0.2-2:1.

[0007] Description: The biological filter constructed by taking sulfur and pyrite as electron donors can convert nitrate nitrogen or nitrite nitrogen into nitrogen gas, and at the same time, the pyrite and phosphate can generate precipitate, achieving the effect of simultaneous nitrogen and phosphorus removal. The existing patent discloses a composite sulfur component carbon-free simultaneous nitrogen and phosphorus removal filler and its preparation method and application. The filler has small specific gravity, large effective component loading ratio on the surface of the filler, increases the adhesion of microorganisms and reaction points, and effectively improves the nitrogen and phosphorus removal efficiency. Compared with other fillers, the filler greatly saves the addition of carbon source and phosphorus removal agent, and is more convenient to fill in engineering application. Since a large amount of sulfur and pyrite is added in the preparation process of the filler, the density of the filler is much greater than the density of water, and the filler is often used in fixed bed reactors. Moreover, the filler is mainly applied to the denitrification process under anoxic condition, and the removal effect of nitrate nitrogen and phosphorus is strengthened.

[0008] Considering that the biochemical aerobic section mainly converts ammonia nitrogen into nitrate nitrogen and nitrite nitrogen through aeration, the ammonia nitrogen removal efficiency is high, the nitrate nitrogen removal efficiency is low, and a large amount of organic carbon source needs to be added to achieve the denitrification effect, and the removal of phosphorus mainly depends on the discharge of excess sludge, it is considered to add composite sulfur component filler to strengthen the removal efficiency of nitrate nitrogen and phosphorus, and then improve the simultaneous nitrogen and phosphorus removal effect. However, since the density of the composite sulfur component filler is greater than that of water, it is in a fixed state, and the mass transfer effect is poor under aeration condition, the composite sulfur component filler is modified to prepare a new combined suspended ball filler, so that its density is slightly less than that of water, and it can be in a fluid state under slight aeration or stirring. This kind of filler can better contact with the activated sludge in suspended growth, has high mass transfer efficiency, accelerates the biofilm formation of microorganisms and enriches the types of microorganisms, and improves the simultaneous nitrogen and phosphorus removal effect in the biochemical aerobic section. At the same time, the particularity of the composite sulfur component filler can strengthen the removal effect of nitrate nitrogen and phosphorus under aerobic conditions, and greatly improve the treatment efficiency of the system.

[0009] Further, based on the amount of porous sponge used, when the total nitrogen in wastewater is less than 50 mg / L, the volume ratio of the composite sulfur component filler to the porous sponge is 0.2-0.7:1, and when the total nitrogen in wastewater is higher than 50 mg / L, the volume ratio of the composite sulfur component filler to the porous sponge is 0.7-2:1.

[0010] Description: By flexibly controlling the ratio of the composite sulfur component filler to the porous sponge according to different water qualities, the new combined suspended ball filler can meet the removal requirements of different ammonia nitrogen and nitrate nitrogen, so that the new combined suspended ball filler can maintain high denitrification treatment efficiency under the treatment of different wastewaters.

[0011] Furthermore, the composite sulfur component filler is composed of pyrite, sulfur, and nitrile rubber, and the mass ratio of pyrite, sulfur, and nitrile rubber is 5-30:50-80:10-20.

[0012] Explanation: The composite sulfur component packing material composed of pyrite, sulfur, and nitrile rubber can achieve good denitrification without the need for an external carbon source, while also enhancing phosphorus removal. The addition of nitrile rubber can also serve as a skeleton and slow-release sulfur components. After the addition of the composite sulfur component packing material, the new combined suspended ball packing material can not only remove ammonia nitrogen but also remove nitrate nitrogen at the same time, thereby significantly improving the denitrification effect of the aerobic biological treatment section.

[0013] Furthermore, the preparation method of the novel combined suspended ball packing includes the following steps:

[0014] 1) Mix pyrite, sulfur, and nitrile rubber in the mass ratio described above, then knead and granulate to form a composite sulfur component filler;

[0015] 2) Cut the porous sponge into blocks or sheets of a certain volume;

[0016] 3) After the composite sulfur component packing and porous sponge are filled into the porous suspended ball packing according to the volume ratio, the porous suspended ball is sealed with a cap to produce a new type of combined suspended ball packing.

[0017] Note: By filling the porous suspended ball packing with composite sulfur component packing and porous sponge in proportion and filling rate, the proportion and filling rate can be flexibly controlled according to various wastewaters, and the operation is simple; by cutting the porous sponge into blocks or sheets, more good attachment surfaces can be provided for microorganisms, enriching the amount of microbial biofilm, accelerating the degradation process of organic matter, and improving the denitrification and phosphorus removal effect.

[0018] Furthermore, the granulation involves extruding the rubber compound into a precast mold, then heating the precast mold to 80-90°C and holding it for 15-30 seconds, then cooling the precast mold to room temperature. After the mold blank is formed, the precast mold is disassembled, and each columnar part of the mold blank is cut off to obtain the composite sulfur component filler.

[0019] Explanation: By forming the composite sulfur component packing into columnar materials, the contact area between the composite sulfur component packing and water can be increased, and the possibility of the composite sulfur component packing slipping out of the pores of the porous suspended balls can be further prevented. At the same time, by raising the temperature of the prefabricated template to the above-mentioned range, the phenomenon of rapid surface temperature drop while the internal temperature remains high can be avoided, which would cause rapid surface shrinkage while the internal shrinkage is slow, resulting in cracking, warping or deformation. It can also prevent cracks from forming on the surface of the composite sulfur component packing, which would affect the slow-release performance and structural strength of the composite sulfur component packing.

[0020] Furthermore, the precast template has multiple cylindrical mold grooves, and each mold groove has several hollow protrusions distributed on its inner sidewall. The hollow protrusions have several air holes and are filled with gas-generating powder. The gas-generating powder is sodium bicarbonate, which cools the precast template to room temperature at a rate of 1-5°C / min.

[0021] Explanation: The cylindrical mold groove with hollow protrusions enables the composite sulfur component packing to have several countersunk holes. Furthermore, by utilizing the gas-generating powder and the pores of the hollow protrusions, the countersunk holes of the composite sulfur component packing also have multiple channels and pores, thereby significantly increasing the contact area between the composite sulfur component packing and water. Without affecting the slow-release performance and structural strength of the composite sulfur component packing, the release effect of sulfur components is enhanced, and the denitrification and phosphorus removal effect of the aerobic biological treatment section is improved.

[0022] Meanwhile, taking sodium bicarbonate as an example, heating the prefabricated template to 80-90℃ serves two purposes: firstly, to avoid defects such as cracking, warping, or deformation of the composite sulfur component filler caused by excessively rapid cooling of the adhesive; and secondly, to ensure that the gas-generating powder maintains a high gas-generating effect under the dual action of the adhesive and template temperatures during the initial cooling of the adhesive. Subsequently, the template temperature is gradually slowed down by a cooling rate of 1-5℃ / min to avoid excessive pores that could affect the slow-release performance and structural strength of the composite sulfur component filler. By controlling the temperature changes, the hollow protrusions and gas-generating powder can work together to give the composite sulfur component filler an appropriate number of countersunk holes and pores, thereby improving the sulfur release effect of the composite sulfur component filler without affecting its slow-release performance and structural strength.

[0023] Furthermore, the diameter of the cylindrical mold groove is denoted as d1, the diameter of the hollow protrusion is denoted as d2, the length of the hollow protrusion is denoted as l1, and the adjacent spacing of the hollow protrusions is denoted as l2, which satisfies the following formula:

[0024] d1 / 8≤d2≤d1 / 6

[0025] d1 / 5≤l1≤d1 / 4

[0026] l2=(l1+d2) / 2

[0027] Explanation: The above formula can control the diameter, length, and spacing of the hollow protrusions, avoiding overly dense arrangement of the hollow protrusions which would affect the slow-release performance and structural strength of the composite sulfur component packing, and avoiding overly sparse arrangement of the hollow protrusions which would fail to significantly improve the release effect. After optimizing the diameter, length, and spacing of the hollow protrusions, combined with the composite sulfur component packing prepared by this invention, it can effectively remove nitrogen and phosphorus from the aerobic biological section.

[0028] Furthermore, the porous sponge is made of hydrophilic polyurethane sponge with a porosity greater than 98%; the porous suspended ball filler has a three-dimensional spherical structure with hidden fasteners and loose porous structure, and the porous suspended ball filler is made of organic polymer.

[0029] Note: Due to its high elasticity and softness, polyurethane sponge can be easily filled into porous suspended ball packings of various specifications in proportion. In addition, the large specific surface area of ​​polyurethane sponge packing provides more space for microorganisms to inhabit, thereby enabling a large number of microorganisms to attach and grow. This helps maintain a high concentration of biomass in the biological contact oxidation tank, thereby improving the nitrogen and phosphorus removal effect of the biochemical aerobic section.

[0030] Porous suspended balls facilitate the filling and use of porous sponges and composite sulfur-containing fillers. During use, microorganisms can easily attach and detach, which helps maintain the activity of the biofilm and improve the nitrogen and phosphorus removal efficiency of the aerobic biological stage. At the same time, the fully three-dimensional structure made of organic polymer is not easy to clog, making it suitable for a variety of complex water quality environments. It is also anti-aging and has a long service life.

[0031] Furthermore, the pore size of the porous suspended ball packing is smaller than the particle size of the composite sulfur component packing, and the density of the novel combined suspended ball packing is less than the density of water.

[0032] Note: The pore size of the porous suspended ball packing should be smaller than that of the composite sulfur component packing and porous sponge to prevent the composite sulfur component packing and porous sponge from sliding out of the pores of the porous suspended ball packing after the new combined suspended ball packing is added. By making the density of the new combined suspended ball packing less than that of water, fluidization can be achieved under slight aeration or stirring, improving mass transfer efficiency, accelerating the biofilm formation rate of microorganisms, and thus increasing the biofilm formation rate of microorganisms.

[0033] The beneficial effects of this invention are:

[0034] (1) The novel combined suspended ball packing of the present invention can be used in the biochemical aerobic section, which can enrich the biofilm of microorganisms, remove nitrate nitrogen and ammonia nitrogen at the same time, and can flexibly adjust the ratio of composite sulfur component packing and porous sponge according to different water quality conditions, and can carry out efficient nitrogen and phosphorus removal in different wastewaters.

[0035] (2) The present invention uses a composite sulfur component packing composed of pyrite, sulfur and nitrile rubber, which can achieve good denitrification effect without the need for an external carbon source. By using the composite sulfur component packing, not only ammonia nitrogen can be removed, but also nitrate nitrogen can be removed at the same time, thereby significantly improving the denitrification effect of the biochemical aerobic section, and also playing a certain slow release role. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the novel combined suspended ball packing of the present invention.

[0037] Figure 2 These are simulation diagrams of the composite sulfur component filler structure of Examples 1-7 of the present invention.

[0038] Figure 3 These are simulation diagrams of the composite sulfur component filler structure of Examples 8-12 of the present invention. Detailed Implementation

[0039] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0040] Example 1: A novel combined suspended ball packing material for simultaneous nitrogen and phosphorus removal in the aerobic stage of biochemical processes, such as... Figure 1 As shown, a mixture of composite sulfur-containing filler and porous sponge is filled into porous suspended balls. Based on the amount of porous sponge used, when the total nitrogen in the wastewater is below 50 mg / L, the volume ratio of composite sulfur-containing filler to porous sponge is 1:2; when the total nitrogen in the wastewater is above 50 mg / L, the volume ratio is 3:2, resulting in a density of 0.94 for the novel combined suspended ball filler. It is understandable that the principle of reducing the amount of composite sulfur-containing filler when the total nitrogen in the wastewater decreases and increasing the amount when the total nitrogen in the wastewater increases can be followed. However, because porous sponge is the main carrier of microorganisms, its proportion cannot be too small and needs to be adjusted relative to the above range.

[0041] The porous sponge is made of hydrophilic polyurethane sponge with a porosity of ≥98%; the porous suspended ball filler is a porous three-dimensional spherical structure made of polypropylene with a hidden buckle, with a diameter of 80mm and a pore size of 7mm.

[0042] The preparation method of the novel combined suspended ball packing includes the following steps:

[0043] 1) Mix pyrite, sulfur, and nitrile rubber in a mass ratio of 2:7:1, and then internally mix and granulate the mixture in a mixer at 150°C to obtain the following... Figure 2 The shown is a rod-shaped composite sulfur component filler with a particle size of 8 mm and a length of not less than 10 mm.

[0044] 2) Cut the porous sponge into pieces of 4cm×3cm×1cm;

[0045] 3) After the composite sulfur component packing and porous sponge are filled into the porous suspended ball packing at a ratio of 50%, the porous suspended ball is sealed with a cap to produce a new type of combined suspended ball packing.

[0046] Application Experiment Example 1: The novel combined suspended ball packing material from Example 1 was directly added to the reaction tank, with a filling rate of 50%. Activated sludge was taken from a wastewater treatment plant, and the activated sludge addition ratio was 5%. The influent of the aerobic stage of the biochemical treatment plant was simulated, and the influent indicators are shown in Table 1 below:

[0047] Table 1. Indicators of ammonia nitrogen, total nitrogen, and total phosphorus content in influent

[0048] Item Influent ammonia nitrogen Influent total nitrogen Influent total phosphorus Content index 32 mg / L 45 mg / L 5 mg / L

[0049] With a hydraulic retention time of 1 hour and a 2-week start-up period, the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent are shown in Table 2 below:

[0050] Table 2 Removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in effluent

[0051] Item Effluent ammonia nitrogen Effluent total nitrogen Effluent total phosphorus Removal rate 87％ 72％ 30％

[0052] As shown in Table 2 above, even with a short hydraulic retention time, the novel combined suspended ball packing material of this invention can still remove nitrogen and phosphorus from the wastewater in the aerobic stage of the biological treatment process. To further verify this, a control group was set up. Based on Example 1, the novel combined suspended ball packing material was used without the addition of composite sulfur components. After a hydraulic retention time of 1 hour and a 2-week start-up period, the total nitrogen removal rate of the effluent decreased to 10.7%. This indicates that when composite sulfur components are added, sulfur and pyrite can act as electron donors to construct a biological filter that can convert nitrate or nitrite nitrogen into nitrogen gas. At the same time, pyrite and phosphate can form precipitates, achieving the effect of simultaneous nitrogen and phosphorus removal.

[0053] Example 2: The difference between this example and Example 1 is that the preparation method of the novel combined suspended ball packing is as follows: Step 1) Specifically, 1) Pyrite: sulfur: nitrile rubber are mixed in a mass ratio of 1:10:2.

[0054] Example 3: The difference between this example and Example 1 is that the preparation method of the novel combined suspended ball packing is as follows: Step 1) Specifically, 1) Pyrite: sulfur: nitrile rubber are mixed in a mass ratio of 3:8:2.

[0055] Example 4: The difference between this example and Example 1 is the proportion of composite sulfur component packing and porous sponge placed inside the porous suspended ball packing. Specifically, the composite sulfur component packing and porous sponge are filled into the porous suspended ball packing at a proportion of 20%.

[0056] Example 5: The difference between this example and Example 1 is the proportion of composite sulfur component packing and porous sponge placed inside the porous suspended ball packing. Specifically, the composite sulfur component packing and porous sponge are filled into the porous suspended ball packing at a proportion of 80%.

[0057] Example 6: The difference between this example and Example 1 is that when the total nitrogen in the wastewater is below 50 mg / L, the volume ratio of the composite sulfur component packing to the porous sponge is 0.2:1, and when the total nitrogen in the wastewater is above 50 mg / L, the volume ratio of the composite sulfur component packing to the porous sponge is 0.7:1.

[0058] Example 7: The difference between this example and Example 1 is that when the total nitrogen in the wastewater is below 50 mg / L, the volume ratio of the composite sulfur component packing to the porous sponge is 0.7:1, and when the total nitrogen in the wastewater is above 50 mg / L, the volume ratio of the composite sulfur component packing to the porous sponge is 2:1.

[0059] Application Experiment Example 2: The novel combined suspended ball packing materials from Examples 2-7 were directly added to the reaction tank, with a filling rate of 50%. Activated sludge was taken from a wastewater treatment plant, with an activated sludge addition ratio of 5%. The influent of the aerobic stage of the urban wastewater treatment plant was simulated, and the influent indicators were as shown in Table 1. The hydraulic retention time was 1 hour. After a 2-week start-up period, the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent were shown in Table 3 below.

[0060] Table 3 Removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in effluent

[0061]

[0062]

[0063] As shown in Table 3 above, adjusting the ratio of pyrite, sulfur, and nitrile rubber in the composite sulfur component packing has a certain impact on the removal rate of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent. This may be because the proportion of pyrite and sulfur in Examples 2 and 3 decreased to a certain extent, which reduced the amount of sulfur and pyrite in the mixed system, thus reducing the efficiency of using them as electron donors to construct a biological filter to convert nitrate nitrogen or nitrite nitrogen into nitrogen gas.

[0064] The filling amount of the composite sulfur component packing and porous sponge in the porous suspended ball packing has a certain impact on the removal rate of ammonia nitrogen, total nitrogen and total phosphorus in the effluent. However, under the influent index in Table 1, increasing the filling amount from 50% to 80% does not significantly improve the removal rate of ammonia nitrogen, total nitrogen and total phosphorus in the effluent. This may be because the effect of the composite sulfur component packing and porous sponge has reached the threshold. Therefore, from the perspective of economics, under the influent index in Table 1, the treatment effect and economy are best when the filling amount is 50%.

[0065] The combination ratio of the composite sulfur component packing material to the porous sponge has a certain impact on the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent. The influent index in Table 1 meets the requirement of "total nitrogen in wastewater is less than 50 mg / L". Example 6 is based on Example 1, but the proportion of the composite sulfur component packing material is reduced. It can be found that the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent all decrease to a certain extent. This may be because the amount of sulfur and pyrite in the mixed system is reduced, which reduces the efficiency of the biological filter that can act as an electron donor to convert nitrate nitrogen or nitrite nitrogen into nitrogen gas. Example 7 is based on Example 1, but the proportion of the composite sulfur component is increased. It can be found that the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent do not improve significantly. This may be because the effect of the composite sulfur component packing material and the porous sponge has reached the threshold. Therefore, under the influent index in Table 1, the treatment effect and economy are best when the volume ratio of the composite sulfur component packing material to the porous sponge is 1:2.

[0066] Example 8: This example differs from Example 1 in that the granulation involves extruding the rubber compound into a precast mold, then heating the precast mold to 87°C and holding it for 21 seconds, followed by cooling the precast mold to room temperature (25°C). After the mold blank is formed, the precast mold is disassembled, and the cylindrical portions of the mold blank are cut off to obtain the following... Figure 3 The shown is a rod-shaped composite sulfur component filler with a particle size of 8 mm and a length of 15 mm;

[0067] The precast template has multiple cylindrical mold grooves with a diameter of 8mm and a depth of 15mm. Each mold groove has several hollow protrusions distributed on its inner sidewall. Each hollow protrusion has two downward-sloping vents with a diameter of 0.1mm at -15° and +15°. It can be understood that the vents are located at the tip of the hollow protrusions. The downward-sloping design can reduce the pressure of the adhesive blocking the vents and prevent the gas from being unable to push the adhesive out through the vents. The hollow protrusions are filled with gas-generating powder, which is sodium bicarbonate powder with a particle size of not less than 0.1mm. The precast template is cooled to room temperature, i.e., 25°C, at a rate of 3°C / min.

[0068] Wherein, the diameter of the cylindrical mold groove is denoted as d1, the diameter of the hollow protrusion is denoted as d2, the length of the hollow protrusion is denoted as l1, and the spacing between adjacent hollow protrusions is denoted as l2, which satisfies the following formula:

[0069] d1 / 8≤d2≤d1 / 6

[0070] d1 / 5≤l1≤d1 / 4

[0071] l2=(l1+d2) / 2

[0072] The calculations show that d2 is 1.2mm, l1 is 1.7mm, and l2 is 1.45mm. Therefore, the precast template's columnar mold groove is manufactured with d1 of 8mm and a depth of 15mm, and the hollow protrusion is manufactured with d2 of 1.2mm, l1 of 1.7mm, and l2 of 1.45mm. The wall thickness of the hollow protrusion is set to 0.2mm by default.

[0073] Understandably, to facilitate demolding of the cylindrical mold groove, it is composed of two semi-cylindrical modules that slide and splice together. To facilitate the replenishment of gas-generating powder, the outer end of the hollow protrusion passes through the cylindrical mold groove and communicates with the outside. At the same time, based on a cylindrical mold groove wall thickness of 1mm, the cylindrical mold groove is equipped with a sealing heat-conducting sleeve with an inner diameter of 10mm to prevent the gas-generating powder from leaking out and to fix the two semi-cylindrical modules. The sealing heat-conducting sleeve is preferably made of copper, and the end edge is equipped with a commercially available high-temperature sealing ring with a diameter of 10mm. Heating and cooling the precast template mainly refers to heating and cooling the sealing heat-conducting sleeve.

[0074] Example 9: The difference between this example and Example 8 is that the precast template is heated to 80°C and held for 15 seconds.

[0075] Example 10: This example differs from Example 8 in that the precast template is heated to 90°C and held for 30 seconds.

[0076] Example 11: The difference between this example and Example 8 is that the prefabricated template is cooled to room temperature, i.e., 25°C, at a rate of 1°C / min.

[0077] Example 12: The difference between this example and Example 8 is that the precast template is cooled to room temperature, i.e., 25°C, at a rate of 5°C / min.

[0078] Application Experiment Example 3: The novel combined suspended ball packing materials from Examples 8-12 were directly added to the reaction tank, with a filling rate of 50%. Activated sludge was taken from a wastewater treatment plant, with an activated sludge addition ratio of 5%. The influent of the aerobic stage of the urban wastewater treatment plant was simulated, and the influent indicators were as shown in Table 1. The hydraulic retention time was 1 hour. After a 2-week start-up period, the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent were shown in Table 4 below.

[0079] Table 4 Removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in effluent

[0080]

[0081] As shown in Table 4 above, the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent were all improved after the structure of the composite sulfur component packing was optimized. This may be because the release effect of sulfur components in the composite sulfur component packing was improved without changing the proportion of porous sponge, which improved the efficiency of converting nitrate nitrogen or nitrite nitrogen into nitrogen gas in the biological filter as an electron donor. At the same time, the composite sulfur component packing also has a porous structure, which can provide a larger attachment area for microorganisms to a certain extent.

[0082] Adjusting the initial heating temperature and holding time of the prefabricated template had a certain impact on the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent. Example 9, based on Example 8, reduced the temperature and time of the prefabricated template, resulting in a certain decrease in the gas production rate. At the same time, the cooling rate of the composite sulfur component packing was relatively faster. It can be found that its performance was somewhat lower than that of Example 8, but still better than that of Example 1. Example 10, based on Example 8, increased the temperature and time of the prefabricated template, resulting in a certain increase in the gas production rate. At the same time, the cooling rate of the composite sulfur component packing was relatively slower. It can be found that its performance was also somewhat lower than that of Example 8. This may be because although the cooling rate of the composite sulfur component packing was slowed down, the excessive pores caused a significant reduction in the slow-release performance and structural strength of the composite sulfur component packing, thus reducing the removal rate.

[0083] Adjusting the cooling rate of the precast template had a certain impact on the removal rates of ammonia nitrogen, total nitrogen, and total phosphorus in the effluent. Example 11, based on Example 8, reduced the cooling rate of the precast template. It was found that its performance was not much different from that of Example 8, but its preparation time was longer. Therefore, Example 8 was more economical for mass production. Example 12, based on Example 8, increased the cooling rate of the precast template. It was found that its performance was reduced to a certain extent compared to Example 8. This may be due to the presence of pores and the rapid cooling of the adhesive, which greatly reduced the slow-release performance and structural strength of the composite sulfur component filler, thus reducing the removal rate.

[0084] To further verify this, Control 1 (Dense Type) was set up, based on Example 8. The cylindrical mold groove of the composite sulfur component filler was manufactured with d1 of 8 mm and a depth of 15 mm, and hollow protrusions were manufactured with d2 of 0.8 mm, l1 of 1.2 mm, and l2 of 1.2 mm. The wall thickness of the hollow protrusions was set to 0.3 mm by default. Control 2 (Sparse Type) was set up, based on Example 8. The cylindrical mold groove of the composite sulfur component filler was manufactured with d1 of 8 mm and a depth of 15 mm, and hollow protrusions were manufactured with d2 of 2 mm, l1 of 2.2 mm, and l2 of 2.2 mm. The wall thickness of the hollow protrusions was set to 0.3 mm by default.

[0085] After a hydraulic retention time of 1 hour and a 2-week start-up period, the total nitrogen removal rate of the effluent from Control 1 (dense type) decreased to 75.3%, a decrease of 1.4 percentage points compared to the 76.7% effluent total nitrogen removal rate of Example 8. The total nitrogen removal rate of the effluent from Control 2 (sparse type) decreased to 76.2%, a decrease of 0.5 percentage points compared to the 76.7% effluent total nitrogen removal rate of Example 8. It can be seen that setting the hollow protrusions too sparsely or too densely has a certain impact on the treatment effect.

Claims

1. A combined suspended ball packing material for simultaneous nitrogen and phosphorus removal in the aerobic stage of a biochemical process, characterized in that, The combined suspended ball packing consists of a mixture of composite sulfur component packing and porous sponge, which is filled into porous suspended balls. The volume ratio of the mixture in the porous suspended balls is 20% to 80%, and the volume ratio of composite sulfur component packing to porous sponge is 0.2 to 2:

1. The preparation method of the combined suspended ball packing includes the following steps: 1) Mix pyrite, sulfur, and nitrile rubber, then knead and granulate them to form a composite sulfur-based filler; 2) Cut the porous sponge into blocks or sheets; 3) After filling the porous suspended ball packing with the composite sulfur component packing and porous sponge according to the volume ratio, the porous suspended ball packing is sealed with a cap to form a combined suspended ball packing. The granulation process involves extruding the rubber compound into a precast mold, then heating the precast mold to 80-90°C and holding it for 15-30 seconds, then cooling the precast mold to room temperature. After the mold blank is formed, the precast mold is disassembled, and each columnar part of the mold blank is cut off to obtain the composite sulfur component filler. The precast template has multiple cylindrical mold grooves, and each mold groove has several hollow protrusions distributed on its inner sidewall. Each hollow protrusion has several air holes and is filled with gas-generating powder; wherein, the gas-generating powder is sodium bicarbonate. The precast template is cooled to room temperature at a rate of 1~5℃ / min. The diameter of the cylindrical mold groove is denoted as... d 1 The diameter of the hollow protrusion is denoted as d 2 The length of the hollow protrusion is denoted as l 1 The spacing between adjacent hollow protrusions is denoted as l 2 It satisfies the following formula: d 1 / 8≤ d 2 ≤ d 1 / 6 d 1 / 5≤ l 1 ≤ d 1 / 4 l 2 =（ l 1 ＋ d 2 ） / 2。 2. The combined suspended ball packing material for simultaneous nitrogen and phosphorus removal in the aerobic stage of biochemical treatment as described in claim 1, characterized in that, Based on the amount of porous sponge used, when the total nitrogen in the wastewater is less than 50 mg / L, the volume ratio of composite sulfur component filler to porous sponge is 0.2~0.7:1; when the total nitrogen in the wastewater is greater than 50 mg / L, the volume ratio of composite sulfur component filler to porous sponge is 0.7~2:

1.

3. The combined suspended ball packing material for simultaneous nitrogen and phosphorus removal in the aerobic stage of biochemical treatment as described in claim 1, characterized in that, The composite sulfur component filler is composed of pyrite, sulfur, and nitrile rubber, and the mass ratio of pyrite, sulfur, and nitrile rubber is 5-30:50-80:10-20.

4. The combined suspended ball packing material for simultaneous nitrogen and phosphorus removal in the aerobic stage of biochemical treatment as described in claim 1, characterized in that, The porous sponge is made of hydrophilic polyurethane sponge with a porosity greater than 98%; the porous suspended ball filler has a three-dimensional spherical structure with hidden fasteners and loose porous structure, and the porous suspended ball filler is made of organic polymer.

5. The combined suspended ball packing material for simultaneous nitrogen and phosphorus removal in the aerobic stage of biochemical treatment as described in claim 1, characterized in that, The pore size of the porous suspended ball packing is smaller than that of the composite sulfur component packing. The porous sponge is a hydrophilic polyurethane sponge with a porosity greater than 98%, and the density of the combined suspended ball packing is less than that of water.

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