Preparation method of light filter material for deeply removing total nitrogen and total phosphorus

Abstract

According to the preparation method of the light filter material for deeply removing the total nitrogen and the total phosphorus, the foaming porous filter material is prepared by taking the steel slag, the zeolite, the lime and the like as main components, and the sludge is cultivated in the starting period, so that the tolerance of microorganisms to sulfide toxicity is improved; sulfur and cultured strains of autotrophic thiobacillus denitrificans and sulfate reducing bacteria are solidified on the porous filter material through a biological embedding technical means, so that autotrophic denitrification of elemental sulfur and reduction of sulfate radicals are realized. The porous structure of the light filter material is beneficial to transmission of substances such as nitrogen and phosphorus, the surface of the filter material can provide conditions for attachment and growth of microorganisms such as phosphorus-accumulating bacteria, nitrifying bacteria, thiobacillus denitrificans and sulfate reducing bacteria, the high porosity and large specific surface area of the filter material can bring a large microorganism attachment amount, and the huge specific surface area is beneficial to growth of a biological membrane, so that the biological membrane can be effectively degraded. The filter material is subjected to combined treatment through a solid physicochemical adsorption method and a microbiological method, the pollutant removal capacity is high, and the effect is remarkable.

Description

Technical Field

[0001] This invention belongs to the field of granular filter media preparation technology, specifically relating to a method for preparing lightweight filter media for deep removal of total nitrogen and total phosphorus. Background Technology

[0002] The excessive use of nitrogen and phosphorus fertilizers and the continuous discharge of domestic sewage and industrial wastewater have introduced large amounts of nitrogen and phosphorus into natural water bodies, which is the main cause of eutrophication. Eutrophication leads to the proliferation of algae on the water surface, reducing dissolved oxygen levels and hindering the growth and reproduction of aquatic plants and animals. Furthermore, excessive nitrogen can also threaten human health, as it increases nitrate levels (NO3) in drinking water. - When NO3- (N-N) levels exceed the standard and are ingested by the human body, NO3- - -N can be converted into nitrite (NO2) by the action of organs such as the stomach and intestines. - -N), NO2 - -N may cause mutations in human cells, increasing the risk of cancer. Furthermore, NO3... - -N and NO2 - High levels of -N may also increase the risk of developing chronic diseases such as diabetes and hypertension.

[0003] Currently, phosphorus treatment methods include chemical precipitation, biological methods, physical adsorption, constructed wetlands, and membrane treatment. Among these, chemical precipitation and biological methods have good treatment effects and are widely used. Chemical precipitation requires the addition of flocculants such as polyaluminum chloride (PAC), which results in higher costs. Biological treatment is affected by volatile fatty acids (VFA), dissolved oxygen in the aerobic tank, and sludge return from the secondary sedimentation tank, requiring process optimization.

[0004] And NO3 - Methods for treating nitrogen oxides (NOx) include ion exchange, reverse osmosis, chemical reduction, adsorption, and biological methods. Ion exchange and chemical reduction are relatively expensive and unsuitable for large-scale application. Wastewater treatment plants primarily use heterotrophic denitrification (HDD) to remove nitrogen from wastewater. Traditional HDD requires the addition of large amounts of organic carbon sources. While biological denitrification processes have low operating costs and do not cause secondary pollution, making them one of the most efficient and feasible nitrate removal processes, the COD concentration in the water after secondary biological treatment is low. If heterotrophic denitrification is used, an external carbon source is required to ensure denitrification efficiency. This not only increases treatment costs but also makes it difficult to control the amount of carbon source added, and it easily leads to the risk of BOD5 exceeding the standard in the effluent.

[0005] Sulfur autotrophic denitrification is a process in which autotrophic denitrifying bacteria utilize reducing sulfur sources (such as sulfur) under anaerobic or hypoxic conditions. 0 S 2- S2O3 2-As electron donors, CO2 and HCO3 - Using inorganic carbon sources, NO3 - -N or NO2 - The technique for reducing -N to N2. The specific reaction equations for using sulfur sources with different valence states as electron donors are shown below: When S0 is used as the sulfur source: 1.10S+NO 3 - +0.76H 2 0+0.40CO 2 +0.08NH 4 + → 1.10SO 4 2- +0.50N 2 +0.08C 5 H 7 O 2 N+1.28H + (1-1) With S 2- When the sulfur source is: 0.421H 2 S+0.421HS - +NO 3 - +0.346CO 2 +0.086HCO 3 - +0.086NH 4 + → 0.842SO 4 2- +0.500N 2 +0.086C 5 H 7 O 2 N+0.434H 2 0+0.262H + (1-2) With S2O3 2- When the sulfur source is: 0.844S 2 0 3 2- +NO 3 - +0.347CO 2 +0.086HCO 3 - +0.086NH 4 + +0.434 H 2 0→ 1.689SO 4 2- +0.500N 2 +0.086C 5 H 7 O 2 N+0.679H + (1-3) Although the advanced treatment process based on autotrophic denitrification technology using denitrifying thiobacilli eliminates the need for organic carbon sources, avoiding the risk of excessive BOD5 in the effluent, and features high denitrification efficiency, low sludge production, low cost, resource conservation, and simple and safe operation, it also has certain drawbacks and the following problems: 1. Filter media caking problem: Biofilms are prone to clogging filter media, which reduces nitrogen removal efficiency, requires frequent backwashing, and also increases the cost of filter media. 2. Under high load conditions, a large amount of SO4 will inevitably be present in the effluent. 2- In the presence of sulfate-reducing bacteria (SRB), H2S gas is released, which not only causes corrosion of drainage pipes, but its odor and toxicity will also cause secondary pollution problems. 3. In autotrophic denitrification processes that utilize sulfides as electron donors, the microorganisms in the system may be inhibited by the toxicity of sulfides, resulting in low treatment efficiency and reduced treatment capacity. Summary of the Invention

[0006] This invention provides a method for preparing lightweight filter media for deep removal of total nitrogen and total phosphorus, overcoming the problems of existing filter media based on autotrophic denitrification technology of denitrifying thiobacilli that are prone to clogging, resulting in reduced denitrification efficiency, release of H2S gas causing corrosion and secondary pollution of drainage pipes, and low treatment efficiency due to the toxic inhibitory effect of sulfides on microorganisms.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing a lightweight filter media for deep removal of total nitrogen and total phosphorus includes the following steps: S1. Weigh water and raw materials separately at a weight ratio of 0.45-0.49:1. The raw materials consist of cementing materials and additives. The cementing materials include, by weight percentage: 30-40% steel slag, 20-30% zeolite, 6-10% lime, 2-6% desulfurized gypsum, 20-30% cement, and 0.01-0.1% sodium bicarbonate. The additives include 2-4% sodium sulfate, 0.03-0.1% foam stabilizer, 0.5-1% water glass, 0.5-1% sodium hydroxide, 0.5-0.9% curing agent, 0.5-1.5% water-reducing agent, and 0.5-1.0% surfactant. S2. The gel material, additives and water weighed in step S1 are mixed, stirred, poured and molded, dried, demolded, cured, cut into pieces, crushed and screened to obtain porous filter material. S3. Collect activated sludge from the bottom of the fishpond or modular aquaculture equipment, store it in a container, control the temperature at around 30℃, add an appropriate amount of culture medium for sludge cultivation, and periodically measure the NO3 content in the culture medium. - The concentration of -N, when NO3 - When the -N removal rate reaches 90.00%, the culture medium is replaced to complete the sludge cultivation. S4. Wash the cultivated bacterial sludge with deionized water 2-3 times to remove impurities, and centrifuge at 5000 rpm / min for 10 min to obtain wet bacterial cells; S5. Mix the wet bacterial cells obtained in step S4 and the porous filter media prepared in step S2 at a mass ratio of 1:20, adsorb for 30 min, and add a small amount of deionized water to prevent the bacterial cells from dehydrating and dying, and obtain the embedded body. S6. Add polyvinyl alcohol, sodium alginate and water in a mass ratio of 10%:2%:88% to a beaker, heat in a water bath at 95°C to form a uniform viscous liquid, and cool to room temperature to obtain a PVA-SA solution. S7. The embedded body, sulfur powder electron donor, and PVA-SA solution were mixed evenly at a mass ratio of 1:1:1.2 to prepare irregular embedded particles. The embedded particles were then crosslinked and fixed in a saturated boric acid solution with pH 7.0 and 2% calcium chloride solution for 16 h. The fixed embedded particles were then refrigerated at 4℃ for 6 h to enhance the strength of the lightweight filter media. Finally, the lightweight filter media with deep removal of total nitrogen and total phosphorus was obtained at room temperature.

[0008] The aforementioned gel material comprises, by weight percentage, 35% steel slag, 24% zeolite, 7% lime, 3% desulfurized gypsum, 24% cement, and 0.06% sodium bicarbonate; the additives comprise 3.4% sodium sulfate, 0.04% foam stabilizer, 0.7% water glass, 0.8% sodium hydroxide, 0.7% curing agent, 0.6% water-reducing agent, and 0.7% surfactant.

[0009] In step S1 above, the cement is composed of silicate cement and calcium aluminate cement in a mass ratio of 9:1, the foam stabilizer is sodium α-alkenyl sulfonate, the modulus of the water glass is 1.2, and the curing agent is triethanolamine.

[0010] The surfactant in step S1 above is one or more of fatty alcohol polyoxyethylene ether (AEO-20), sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and dodecylphenol polyoxyethylene ether (OP-10).

[0011] The specific process of step S2 above includes the following: (1) Mix and stir the cementitious materials, dry mix for 1-2 minutes to make a mixture; (2) Take 5% of the total water weight, add sodium bicarbonate and foam stabilizer to the water to make a suspension with sodium bicarbonate content of 1-3%, and the water temperature is 40-70℃; (3) Dissolve the water glass in the remaining 95% of the water at a temperature of 40-70℃ and stir well; (4) After cooling the solution obtained in step (3) to 45-50°C at room temperature, pour it into the mixture obtained in step (1) and stir to obtain a slurry; (5) Add the suspension obtained in step (2) to the slurry obtained in step (4) and stir to obtain a slurry with uniform consistency; (6) Pour the slurry prepared in step (5) into the mold and cast it into shape; (7) Place the mold after pouring the slurry in step (6) in a 60℃ hot and humid curing box for gas generation and pre-curing for 12 to 24 hours, then put it in an 80℃ oven for drying for 4 to 6 hours, and then demold it. (8) The demolded blanks are cured in a 60℃ hot and humid curing box for 7 to 28 days to obtain finished blocks; (9) Demolding and cleaning, cutting into blocks of appropriate size as needed, and finally crushing by a box crusher and then sorting by particle size through a multi-stage linear vibrating screen to obtain porous filter material.

[0012] The above steps (1), (4) and (5) are all carried out by stirring with a stirring device that rotates at 135-150 r / min and revolves at 55-70 r / min. The stirring time in step (4) is 3-5 min, and the stirring time in step (5) is 15-50 s.

[0013] The culture medium in step S3 above consists of the following components: 4.96 g / L Na2S2O3·5H2O, 2.52 g / L NaHCO3, 2.02 g / L KNO3, 2.00 g / L KH2PO4, 1.00 g / L NH4Cl, 0.80 g / L MgSO4·7H2O, 0.06 g / L FeSO4·7H2O, and 0.01 g / L CaCl2·2H2O.

[0014] NO3 in the sludge of step S3 above - The NO3- removal rate was determined by taking 10 mL of the supernatant from the reactor, filtering it through a 0.45 μm filter membrane, and measuring the NO3- content in the sample. - -N and NO2 - Changes in -N can be used to determine the sludge cultivation status.

[0015] Based on the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are as follows: 1. The lightweight filter media of this invention can buffer the acidity generated during sulfur autotrophic denitrification and provide an inorganic carbon source for the biochemical reactions of microorganisms. Simultaneously, the formation of calcium sulfate precipitate can slightly reduce sulfate production, facilitating the consumption of reducing sulfur sources (such as sulfur dioxide) by denitrifying thiobacteria. 0 S 2- S2O3 2- ) and generate sulfate (SO4) 2- Simultaneously, sulfate-reducing bacteria can consume sulfate and generate reducing sulfur sources, thus achieving a complete sulfur cycle. The porous structure of this lightweight filter media is conducive to the transport of substances such as nitrogen and phosphorus. The surface of the filter media provides conditions for the attachment and growth of microorganisms such as polyphosphate-accumulating bacteria, nitrifying bacteria, denitrifying thiobacilli, and sulfate-reducing bacteria. The high porosity and large specific surface area of ​​the filter media can lead to a large amount of microbial attachment. The huge specific surface area is conducive to the growth of biofilm, which greatly improves the efficiency of phosphorus removal, nitrification, and denitrification. The filter media, through the combined treatment of solid physicochemical adsorption and microbial methods, has a strong pollutant removal capacity and significant effect.

[0016] 2. The method for preparing the lightweight filter media of this invention involves cultivating sludge during the start-up phase to continuously improve the microbial tolerance to sulfide toxicity and ensure stable system operation. Immobilizing sulfur along with cultivated autotrophic denitrifying thiobacilli and sulfate-reducing bacteria onto the porous filter media further enables elemental sulfur autotrophic denitrification and sulfate reduction, thereby achieving resource recycling.

[0017] 3. The lightweight filter media of this invention is a foamed porous filter media prepared with steel slag and zeolite as the main components. Utilizing steel slag not only turns waste into treasure but also protects the environment. Zeolite contains a certain amount of active silica and alumina. These active components can participate in the hydration and coagulation process of the cementitious material, fully utilizing their pozzolanic activity. They react with Ca(OH)2 precipitated during the hydration of the cementitious material to generate C-S-H and C-Al-H gels, promoting the hydration reaction, increasing the amount of hydration products, and improving the pore structure, thereby increasing the density of the filter media. Simultaneously, due to the special lattice-like internal structure of zeolite powder, filled with cavities and channels of varying pore sizes, it has strong hydrophilicity, which can increase the consistency of the mixture, reduce bleeding, reduce micro-cracks in the hardened filter media, and improve the bonding interface between the aggregate and the cementitious material. Furthermore, since various zeolites are rock-forming minerals of the Earth's crust, they possess extremely high stability. Therefore, incorporating zeolite-based cementitious substances into filter media will greatly improve the strength, durability, ion exchange capacity, and acid resistance of the filter media. Detailed Implementation

[0018] The specific embodiments of the present invention are described below. Many details are described below to provide a comprehensive understanding of the invention; however, those skilled in the art can implement the invention without these details.

[0019] Example 1 This embodiment provides a method for preparing lightweight filter media for deep removal of total nitrogen and total phosphorus, including the following steps: Step 1: Weigh water and raw materials separately at a weight ratio of 0.45:1. The raw materials consist of cementitious materials and additives. In this embodiment, the cementitious materials include 35% steel slag, 24% zeolite, 7% lime, 3% desulfurized gypsum, 24% cement, and 0.06% sodium bicarbonate; the additives include 3.4% sodium sulfate, 0.04% foam stabilizer, 0.7% water glass, 0.8% sodium hydroxide, 0.7% curing agent, 0.6% water-reducing agent, and 0.7% surfactant. The cement is composed of silicate cement and calcium aluminate cement in a mass ratio of 9:1. The foam stabilizer is sodium α-alkenyl sulfonate, the water glass has a modulus of 1.2, and the curing agent is triethanolamine.

[0020] Step 2: Mix the cementitious materials (rotation 130-150 r / min, revolution 55-70 r / min), dry mix for 1.5 min, and make a mixture.

[0021] Step 3: Take 5% of the total water weight, add sodium bicarbonate and foam stabilizer to the water to make a suspension with a sodium bicarbonate content of 2%, and the water temperature is about 50℃.

[0022] Step 4: Dissolve the water glass in the remaining 95% of the water at a temperature of 50°C and stir until there is no sodium hydroxide solid residue.

[0023] Step 5: After cooling the solution obtained in Step 4 to 48°C at room temperature, pour it into the mixture obtained in Step 2 and stir for 3.8 min (rotation 135-150 r / min, revolution 55-70 r / min) to obtain the slurry.

[0024] Step 6: Add the suspension obtained in Step 3 to the slurry obtained in Step 5, stir for 32 seconds (rotation 135-150 r / min, revolution 55-70 r / min) to obtain a slurry with uniform consistency.

[0025] Step 7: Pour the slurry prepared in step 6 into the mold and cast it into shape.

[0026] Step 8: Place the mold after pouring the slurry in Step 7 in a 60℃ hot and humid curing chamber for gas generation and pre-curing for 18 hours, then put it in an 80℃ oven for drying for 4.8 hours, and then demold.

[0027] Step 9: After demolding, the green body is subjected to hot and humid curing in a 60℃ hot and humid curing chamber for 15 days to obtain the finished blocks.

[0028] Step 10: Demolding and cleaning, cutting into blocks of appropriate size as needed, and finally crushing by a box crusher and then sorting by particle size through a multi-stage linear vibrating screen to obtain porous filter media.

[0029] Step 11: Take activated sludge from the bottom of the fishpond or modular aquaculture equipment, store it in a container, and control the temperature at around 30℃. Add an appropriate amount of culture medium for sludge cultivation. The culture medium consists of the following components: 4.96 g / L Na₂S₂O₃·5H₂O, 2.52 g / L NaHCO₃, 2.02 g / L KNO₃, 2.00 g / L KH₂PO₄, 1.00 g / L NH₄Cl, 0.80 g / L MgSO₄·7H₂O, 0.06 g / L FeSO₄·7H₂O, and 0.01 g / L CaCl₂·2H₂O. Periodically measure the NO₃⁻ content in the culture medium. - The concentration of NO3- was determined by taking 10 mL of the supernatant from the reactor each time, filtering it through a 0.45 μm filter membrane, and measuring the NO3- concentration in the sample promptly. - -N and NO2 -Changes in NO3- were used to assess the sludge cultivation progress. After 14 days of enrichment cultivation, when NO3-... - Replace the culture medium when the -N removal rate reaches 90.00% to complete sludge cultivation.

[0030] Step 12: Wash the cultivated bacterial sludge with deionized water 2-3 times to remove impurities, and centrifuge at 5000 rpm / min for 10 min to obtain wet bacterial cells.

[0031] Step 13: Mix the wet bacterial cells obtained in Step 12 and the porous filter media prepared in Step 10 at a mass ratio of 1:20, adsorb for 30 min, and add a small amount of deionized water to prevent the bacterial cells from dehydrating and dying, thus obtaining the embedded body.

[0032] Step 14: Add polyvinyl alcohol (PVA), sodium alginate (SA) and water in a mass ratio of 10%:2%:88% to a beaker, heat in a water bath at 95°C to form a uniform viscous liquid, and cool to room temperature to obtain a PVA-SA solution.

[0033] Step 15: Mix the embedded body, sulfur powder electron donor, and PVA-SA solution at a mass ratio of 1:1:1.2 to form irregular embedded particles; then fix the embedded particles by crosslinking in a saturated boric acid solution with pH 7.0 and 2% calcium chloride solution for 16 h; then refrigerate the fixed embedded particles at 4℃ for 6 h to enhance the strength of the lightweight filter media; finally, place them at room temperature to obtain a lightweight filter media that deeply removes total nitrogen and total phosphorus.

[0034] The lightweight filter media prepared in this embodiment has a porosity of 73.5% and a specific surface area of ​​15.6 m². 2 / g.

[0035] Example 2 This embodiment provides a method for preparing lightweight filter media for deep removal of total nitrogen and total phosphorus, including the following steps: Step 1: Weigh water and raw materials separately at a weight ratio of 0.48:1. The raw materials consist of cementitious materials and additives. In this embodiment, the cementitious materials include 32% steel slag, 26% zeolite, 6% lime, 4% desulfurized gypsum, 25% cement, and 0.04% sodium bicarbonate; the additives include 3.2% sodium sulfate, 0.06% foam stabilizer, 0.6% water glass, 0.7% sodium hydroxide, 0.5% curing agent, 1.1% water-reducing agent, and 0.8% surfactant. The cement is composed of silicate cement and calcium aluminate cement in a mass ratio of 9:1. The foam stabilizer is sodium α-alkenyl sulfonate, the water glass has a modulus of 1.2, and the curing agent is triethanolamine.

[0036] Step 2: Mix the cementitious materials (rotation 130-150 r / min, revolution 55-70 r / min), dry mix for 1.2 min, and make a mixture.

[0037] Step 3: Take 5% of the total water weight and add sodium bicarbonate and foam stabilizer to the water to make a suspension with a sodium bicarbonate content of 1.5% at a water temperature of about 55℃.

[0038] Step 4: Dissolve the water glass in the remaining 95% of the water at a temperature of 55°C and stir until there is no sodium hydroxide solid residue.

[0039] Step 5: After cooling the solution obtained in Step 4 to 46°C at room temperature, pour it into the mixture obtained in Step 2 and stir for 4 minutes (rotation 135-150 r / min, revolution 55-70 r / min) to obtain the slurry.

[0040] Step 6: Add the suspension obtained in Step 3 to the slurry obtained in Step 5, stir for 25 seconds (rotation 135-150 r / min, revolution 55-70 r / min) to obtain a slurry with uniform consistency.

[0041] Step 7: Pour the slurry prepared in step 6 into the mold and cast it into shape.

[0042] Step 8: Place the mold after pouring the slurry in Step 7 in a 60℃ hot and humid curing chamber for gas generation and pre-curing for 18 hours, then put it in an 80℃ oven for drying for 5 hours, and then demold.

[0043] Step 9: After demolding, the green body is cured in a 60℃ hot and humid curing chamber for 20 days to obtain the finished blocks.

[0044] Step 10: Demolding and cleaning, cutting into blocks of appropriate size as needed, and finally crushing by a box crusher and then sorting by particle size through a multi-stage linear vibrating screen to obtain porous filter media.

[0045] Step 11: Take activated sludge from the bottom of the fishpond or modular aquaculture equipment, store it in a container, and control the temperature at around 30℃. Add an appropriate amount of culture medium for sludge cultivation. The culture medium consists of the following components: 4.96 g / L Na₂S₂O₃·5H₂O, 2.52 g / L NaHCO₃, 2.02 g / L KNO₃, 2.00 g / L KH₂PO₄, 1.00 g / L NH₄Cl, 0.80 g / L MgSO₄·7H₂O, 0.06 g / L FeSO₄·7H₂O, and 0.01 g / L CaCl₂·2H₂O. Periodically measure the NO₃⁻ content in the culture medium. -The concentration of NO3- was determined by taking 10 mL of the supernatant from the reactor each time, filtering it through a 0.45 μm filter membrane, and measuring the NO3- concentration in the sample promptly. - -N and NO2 - Changes in NO3- were used to assess the sludge cultivation progress. After 14 days of enrichment cultivation, when NO3-... - Replace the culture medium when the -N removal rate reaches 90.00% to complete sludge cultivation.

[0046] Step 12: Wash the cultivated bacterial sludge with deionized water 2-3 times to remove impurities, and centrifuge at 5000 rpm / min for 10 min to obtain wet bacterial cells.

[0047] Step 13: Mix the wet bacterial cells obtained in Step 12 and the porous filter media prepared in Step 10 at a mass ratio of 1:20, adsorb for 30 min, and add a small amount of deionized water to prevent the bacterial cells from dehydrating and dying, thus obtaining the embedded body.

[0048] Step 14: Add polyvinyl alcohol (PVA), sodium alginate (SA) and water in a mass ratio of 10%:2%:88% to a beaker, heat in a water bath at 95°C to form a uniform viscous liquid, and cool to room temperature to obtain a PVA-SA solution.

[0049] Step 15: Mix the embedded body, sulfur powder electron donor, and PVA-SA solution at a mass ratio of 1:1:1.2 to form irregular embedded particles; then fix the embedded particles by crosslinking in a saturated boric acid solution with pH 7.0 and 2% calcium chloride solution for 16 h; then refrigerate the fixed embedded particles at 4℃ for 6 h to enhance the strength of the lightweight filter media; finally, place them at room temperature to obtain a lightweight filter media that deeply removes total nitrogen and total phosphorus.

[0050] The lightweight filter media prepared in this embodiment has a porosity of 73.5% and a specific surface area of ​​15.6 m². 2 / g.

[0051] Example 3 This embodiment provides a method for preparing lightweight filter media for deep removal of total nitrogen and total phosphorus, including the following steps: Step 1: Weigh water and raw materials separately at a weight ratio of 0.49:1. The raw materials consist of cementitious materials and additives. In this embodiment, the cementitious materials include 30% steel slag, 23% zeolite, 8% lime, 2% desulfurized gypsum, 29% cement, and 0.08% sodium bicarbonate; the additives include 3.8% sodium sulfate, 0.07% foam stabilizer, 0.55% water glass, 0.6% sodium hydroxide, 0.6% curing agent, 1.4% water-reducing agent, and 0.9% surfactant. The cement is composed of silicate cement and calcium aluminate cement in a mass ratio of 9:1. The foam stabilizer is sodium α-alkenyl sulfonate, the water glass has a modulus of 1.2, and the curing agent is triethanolamine.

[0052] Step 2: Mix the cementitious materials (rotation 130-150 r / min, revolution 55-70 r / min), dry mix for 1.8 min, and make a mixture.

[0053] Step 3: Take 5% of the total water weight and add sodium bicarbonate and foam stabilizer to the water to make a suspension with a sodium bicarbonate content of 1.5% at a water temperature of about 62℃.

[0054] Step 4: Dissolve the water glass in the remaining 95% of the water at a temperature of 52°C and stir until there is no sodium hydroxide solid residue.

[0055] Step 5: After cooling the solution obtained in Step 4 to 48°C at room temperature, pour it into the mixture obtained in Step 2 and stir for 5 minutes (rotation 135-150 r / min, revolution 55-70 r / min) to obtain the slurry.

[0056] Step 6: Add the suspension obtained in Step 3 to the slurry obtained in Step 5, stir for 40 seconds (rotation 135-150 r / min, revolution 55-70 r / min) to obtain a slurry with uniform consistency.

[0057] Step 7: Pour the slurry prepared in step 6 into the mold and cast it into shape.

[0058] Step 8: Place the mold after pouring the slurry in Step 7 in a 60℃ hot and humid curing chamber for gas generation and pre-curing for 22 hours, then put it in an 80℃ oven for drying for 5.5 hours, and then demold it.

[0059] Step 9: After demolding, the green body is subjected to hot and humid curing in a 60℃ hot and humid curing chamber for 24 days to obtain the finished blocks.

[0060] Step 10: Demolding and cleaning, cutting into blocks of appropriate size as needed, and finally crushing by a box crusher and then sorting by particle size through a multi-stage linear vibrating screen to obtain porous filter media.

[0061] Step 11: Take activated sludge from the bottom of the fishpond or modular aquaculture equipment, store it in a container, and control the temperature at around 30℃. Add an appropriate amount of culture medium for sludge cultivation. The culture medium consists of the following components: 4.96 g / L Na₂S₂O₃·5H₂O, 2.52 g / L NaHCO₃, 2.02 g / L KNO₃, 2.00 g / L KH₂PO₄, 1.00 g / L NH₄Cl, 0.80 g / L MgSO₄·7H₂O, 0.06 g / L FeSO₄·7H₂O, and 0.01 g / L CaCl₂·2H₂O. Periodically measure the NO₃⁻ content in the culture medium. - The concentration of NO3- was determined by taking 10 mL of the supernatant from the reactor each time, filtering it through a 0.45 μm filter membrane, and measuring the NO3- concentration in the sample promptly. - -N and NO2 - Changes in NO3- were used to assess the sludge cultivation progress. After 15 days of enrichment cultivation, when NO3-... - Replace the culture medium when the -N removal rate reaches 90.00% to complete sludge cultivation.

[0062] Step 12: Wash the cultivated bacterial sludge with deionized water 2-3 times to remove impurities, and centrifuge at 5000 rpm / min for 10 min to obtain wet bacterial cells.

[0063] Step 13: Mix the wet bacterial cells obtained in Step 12 and the porous filter media prepared in Step 10 at a mass ratio of 1:20, adsorb for 30 min, and add a small amount of deionized water to prevent the bacterial cells from dehydrating and dying, thus obtaining the embedded body.

[0064] Step 14: Add polyvinyl alcohol (PVA), sodium alginate (SA) and water in a mass ratio of 10%:2%:88% to a beaker, heat in a water bath at 95°C to form a uniform viscous liquid, and cool to room temperature to obtain a PVA-SA solution.

[0065] Step 15: Mix the embedded body, sulfur powder electron donor, and PVA-SA solution at a mass ratio of 1:1:1.2 to form irregular embedded particles; then fix the embedded particles by crosslinking in a saturated boric acid solution with pH 7.0 and 2% calcium chloride solution for 16 h; then refrigerate the fixed embedded particles at 4℃ for 6 h to enhance the strength of the lightweight filter media; finally, place them at room temperature to obtain a lightweight filter media that deeply removes total nitrogen and total phosphorus.

[0066] The lightweight filter media prepared in this embodiment has a porosity of 73.5% and a specific surface area of ​​15.6 m². 2 / g.

[0067] The following table shows the results of domestic sewage treatment using existing volcanic rock and the lightweight filter media of this invention.

[0068] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A method for preparing a lightweight filter media for deep removal of total nitrogen and total phosphorus, characterized in that, S1. Weigh water and raw materials separately at a weight ratio of 0.45-0.49:

1. The raw materials consist of cementing materials and additives. The cementing materials include, by weight percentage: 30-40% steel slag, 20-30% zeolite, 6-10% lime, 2-6% desulfurized gypsum, 20-30% cement, and 0.01-0.1% sodium bicarbonate. The additives include 2-4% sodium sulfate, 0.03-0.1% foam stabilizer, 0.5-1% water glass, 0.5-1% sodium hydroxide, 0.5-0.9% curing agent, 0.5-1.5% water-reducing agent, and 0.5-1.0% surfactant. S2. The gel material, additives and water weighed in step S1 are mixed, stirred, poured and molded, dried, demolded, cured, cut into pieces, crushed and screened to obtain porous filter material. S3. Collect activated sludge from the bottom of the fishpond or modular aquaculture equipment, store it in a container, control the temperature at 30℃, add an appropriate amount of culture medium for sludge cultivation, and periodically measure the NO3 content in the culture medium. - The concentration of -N, when NO3 - When the -N removal rate reaches 90.00%, the culture medium is replaced to complete the sludge cultivation. S4. Wash the cultivated bacterial sludge with deionized water 2-3 times to remove impurities, and centrifuge at 5000 rpm / min for 10 min to obtain wet bacterial cells; S5. Mix the wet bacterial cells obtained in step S4 and the porous filter media prepared in step S2 at a mass ratio of 1:20, adsorb for 30 minutes, and add a small amount of deionized water to prevent the bacterial cells from dehydrating and dying, thus obtaining the embedded body. S6. Add polyvinyl alcohol, sodium alginate and water in a mass ratio of 10%:2%:88% to a beaker, heat in a water bath at 95°C to form a uniform viscous liquid, and cool to room temperature to obtain a PVA-SA solution. S7. The embedded body, sulfur powder electron donor, and PVA-SA solution were mixed evenly at a mass ratio of 1:1:1.2 to prepare irregular embedded particles. The embedded particles were then crosslinked and fixed in a saturated boric acid solution with pH 7.0 and 2% calcium chloride solution for 16 h. The fixed embedded particles were then refrigerated at 4℃ for 6 h to enhance the strength of the lightweight filter media. Finally, the lightweight filter media with deep removal of total nitrogen and total phosphorus was obtained at room temperature.

2. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 1, characterized in that: The gel material comprises, by weight percentage, 35% steel slag, 24% zeolite, 7% lime, 3% desulfurized gypsum, 24% cement, and 0.06% sodium bicarbonate; the additives comprise 3.4% sodium sulfate, 0.04% foam stabilizer, 0.7% water glass, 0.8% sodium hydroxide, 0.7% curing agent, 0.6% water-reducing agent, and 0.7% surfactant.

3. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 1, characterized in that: The cement in step S1 is composed of silicate cement and calcium aluminate cement in a mass ratio of 9:

1. The foam stabilizer is sodium α-alkenyl sulfonate, the modulus of the water glass is 1.2, and the curing agent is triethanolamine.

4. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 1, characterized in that: The surfactant in step S1 is one or more of fatty alcohol polyoxyethylene ether (AEO-20), sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, and dodecylphenol polyoxyethylene ether (OP-10).

5. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 1, characterized in that, The specific process of step S2 above is as follows: (1) Mix and stir the cementitious materials, dry mix for 1-2 minutes to make a mixture; (2) Take 5% of the total water weight, add sodium bicarbonate and foam stabilizer to the water to make a suspension with sodium bicarbonate content of 1-3%, and the water temperature is 40-70℃; (3) Dissolve the water glass in the remaining 95% of the water at a temperature of 40-70℃ and stir well; (4) After cooling the solution obtained in step (3) to 45-50°C at room temperature, pour it into the mixture obtained in step (1) and stir to obtain a slurry; (5) Add the suspension obtained in step (2) to the slurry obtained in step (4) and stir to obtain a slurry with uniform consistency; (6) Pour the slurry prepared in step (5) into the mold and cast it into shape; (7) Place the mold after pouring the slurry in step (6) in a 60℃ hot and humid curing box for gas generation and pre-curing for 12 to 24 hours, then put it in an 80℃ oven for drying for 4 to 6 hours, and then demold it. (8) The demolded blanks are cured in a 60℃ hot and humid curing box for 7 to 28 days to obtain finished blocks; (9) Demolding and cleaning, cutting into blocks of appropriate size as needed, and finally crushing by a box crusher and then sorting by particle size through a multi-stage linear vibrating screen to obtain porous filter material.

6. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 5, characterized in that: Steps (1), (4) and (5) are all carried out by stirring with a stirring device that rotates at 135-150 r / min and revolves at 55-70 r / min. The stirring time in step (4) is 3-5 min, and the stirring time in step (5) is 15-50 s.

7. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 1, characterized in that: The culture medium in step S3 consists of the following components: 4.96 g / L Na2S2O3·5H2O, 2.52 g / L NaHCO3, 2.02 g / L KNO3, 2.00 g / L KH2PO4, 1.00 g / L NH4Cl, 0.80 g / L MgSO4·7H2O, 0.06 g / L FeSO4·7H2O, and 0.01 g / L CaCl2·2H2O.

8. The method for preparing a lightweight filter material for deep removal of total nitrogen and total phosphorus as described in claim 1, characterized in that: NO3 in the sludge during step S3 - The NO3- removal rate was determined by taking 10 mL of the supernatant from the reactor, filtering it through a 0.45 μm filter membrane, and measuring the NO3- content in the sample. - -N and NO2 - Changes in -N can be used to determine the sludge cultivation status.

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