Anti-fouling autotrophic denitrification denitrogenation filter material and preparation method and application thereof

Abstract

This invention provides a self-trophic denitrification filter media with anti-scaling function and its preparation method. The filter media uses sulfur, magnesite, and a microporous carrier as its main components, supplemented with soluble salts for continuous pore formation, forming a highly efficient self-trophic denitrification filter media with anti-scaling function. This filter media overcomes the problem of scale formation and reduced efficiency when treating high-concentration nitrate wastewater, which is often caused by conventional methods using calcium carbonate as a neutralizing agent. It also overcomes the problems of slow reaction rates and poor filter media activity caused by the inability of filter media prepared using magnesite or siderite to neutralize the generated acid in a timely manner.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an anti-scaling, self-trophic denitrification filter media, its preparation method, and its application. Background Technology

[0002] Autotrophic denitrification, as a novel denitrification method, has advantages such as low sludge production and no need for external carbon sources. Currently, most autotrophic denitrification carriers or filter media are obtained by melting liquid sulfur or chemical sulfur at high temperature, mixing it with calcium carbonate, cooling it, crushing and screening it, or by direct underwater granulation. For example, the patent with publication number CN105621609B uses a carrier prepared by melting sulfur and calcium carbonate. However, calcium sulfate scaling is prone to occur during operation, making it unsuitable for denitrification treatment of wastewater with nitrate concentrations higher than 100 mg / L. Therefore, when treating high concentrations of nitrate, this method produces a large amount of calcium sulfate adhering to the surface of the filter media, causing scaling and blockage of the packing.

[0003] To address the scaling and clogging problem of calcium sulfate, researchers both domestically and internationally have proposed using siderite powder or magnesite powder as pH adjusters, based on the high solubility of magnesium sulfate and ferric sulfate. This is achieved by granulating the powder with liquid sulfur to obtain autotrophic denitrification filter media. For example, patent application CN109879415A uses a carrier prepared by melting sulfur and siderite. However, because the pH neutralization capacity of magnesite and siderite is significantly lower than that of calcium carbonate, they cannot promptly eliminate the hydrogen ions and carbon dioxide produced during denitrification, causing the autotrophic denitrifying bacteria to cease functioning. Although the apparent pH does not decrease, its total nitrogen removal efficiency is significantly lower than that of filter media using calcium carbonate as the inorganic carbon source. In addition, there are methods for granulating magnetite powder, sulfur powder, and siderite / magnesite powder together with a binder to obtain a denitrification carrier. For example, patent application CN115304159A uses sulfur powder, magnesite powder, and an organic emulsion as a binder, or partially sintered sulfur powder as a binder, to prepare columnar denitrification carriers for high-concentration wastewater denitrification treatment. Because this method uses a partial sintering process, the strength of the prepared carrier is usually less than 150 N / particle, which is significantly lower than that of carriers prepared by complete melting. Furthermore, the price of sulfur powder is usually higher than that of liquid sulfur, which also results in a low cost-effectiveness of the carrier prepared by this process.

[0004] Furthermore, in the aforementioned methods, neither siderite powder nor magnesite powder reacts in cold hydrochloric acid, exhibiting poor neutralization ability against weak acids and slow pH adjustment. Therefore, when using siderite or magnesite to prepare filter media, whether through melt granulation or powder bonding granulation, the inability to promptly regulate the hydrogen ions produced by denitrifying thiobacilli during denitrification leads to the cessation of denitrification activity, thus affecting the material's denitrification rate.

[0005] In addition, there are other methods for producing denitrification filter media, such as the patent with publication number CN110104760B, which uses sodium bicarbonate as a foaming agent and melts sulfur and calcium / magnesium carbonate to prepare a denitrification carrier. Due to its large and uneven pore size, this method often leads to a significant decrease in filter media strength. Furthermore, the foaming process produces uneven large pores (pore diameter greater than 100 micrometers), resulting in a minimal improvement in denitrification efficiency. If chemically synthesized or artificially synthesized basic magnesium carbonate or magnesium oxide is used in the preparation of the filter media, its strong alkalinity (typically pH > 8.5) results in an excessively high pH in the aqueous solution after immersion, which denitrifying thiobacteria cannot adapt to. Simultaneously, artificially synthesized basic magnesium carbonate typically has a low bulk density, leading to low hardness and strength in the prepared filter media.

[0006] Therefore, there is an urgent need to develop a denitrification filter media with high denitrification activity, capable of handling high nitrate concentrations, and able to overcome the problem of filter media scaling and clogging. Summary of the Invention

[0007] To address the problems of existing autotrophic denitrification filter media being prone to scaling and clogging during use, which hinders the operation of autotrophic denitrifying bacteria, this invention provides a denitrification filter media with high denitrification activity, capable of handling high nitrate concentrations, and overcoming the scaling and clogging problem, as well as its preparation method. The invention also provides the application environment for this filter media.

[0008] The technical solution is as follows: an anti-scaling, self-nourishing, denitrifying filter material, characterized in that it comprises the following components in weight proportions: 100-500 parts sulfur, 50-200 parts hydromagnesia, 5-50 parts porous carrier, and 5-50 parts soluble inorganic salt.

[0009] Furthermore, the hydromagnesite in the filter media can react rapidly with dilute acid (sulfuric acid) at room temperature, and the pH value of the hydromagnesite mixed with water can meet the pH value required for the normal operation of autotrophic denitrifying bacteria.

[0010] Furthermore, the magnesium oxide content in the hydromagnesite is greater than 35.0% (by weight), and the calcium oxide content is less than 5.0% (by weight).

[0011] Furthermore, the magnesite is natural magnesite or magnesite powder, with a particle size of 60-600 mesh and a bulk density of 0.3-1.2 g / cm³. 3 .

[0012] Furthermore, the porous carrier includes one or more of activated carbon, bamboo charcoal, diatomaceous earth, and zeolite powder, and the particle size of the porous carrier is 100-750 mesh.

[0013] The soluble inorganic salt is one or more of ferrous sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, sodium chloride, potassium chloride, magnesium chloride, and ferrous chloride, and the particle size of the soluble inorganic salt is 50-600 mesh.

[0014] Furthermore, the filter material also includes 0.8-4.0% by weight of ultrafine fiber powder, which includes one or more of sepiolite fiber, rock wool fiber, carbon fiber, lignin fiber, and cellulose fiber. The diameter of the fibers in the ultrafine fiber powder is 10-100 micrometers and the length is less than 1000 micrometers.

[0015] A method for preparing the above-mentioned anti-scaling, self-nutritive denitrification filter material is characterized by comprising the following steps: (1) adding liquid sulfur to the magnesite, the porous carrier, the soluble inorganic salt and the ultrafine fiber powder at a temperature of 125-180 degrees Celsius, stirring thoroughly to obtain a mixed slurry, wherein the order of addition of the magnesite, the porous carrier, the soluble inorganic salt and the ultrafine fiber powder is not limited;

[0016] (2) The mixed slurry is granulated by wet or dry granulation to obtain spherical particles or irregular crushed stone filter media with a diameter of 2-30 mm.

[0017] Furthermore, the bulk density of the mixture, excluding sulfur, is 0.3-1.2 g / cm³. 3 The true density of the filter media is 1.8-2.8 g / cm³. 3 The bulk density of the granulated filter media is 0.8-1.5 g / cm³. 3 .

[0018] An application method of an anti-scaling, self-nutritive denitrification filter media is characterized by: using the filter media prepared by the above-mentioned method for anti-scaling, self-nutritive denitrification filter media for autotrophic denitrification in wastewater containing nitrate nitrogen or nitrite nitrogen at a concentration of 20-2000 mg / L.

[0019] Furthermore, when the total alkalinity of the wastewater and the alkalinity released by the filter media cannot meet the alkalinity requirements for denitrification by sulfur autotrophic denitrifying bacteria, 5-50% of the total mass of the packing material is added to the denitrification filter as an alkalinity slow-release agent; the maximum directional dimension of the hydrated magnesium pebbles is 1-50 mm, and the calcium oxide content in the hydrated magnesium pebbles is less than 5% (by weight).

[0020] The beneficial effects of this invention are as follows: Because magnesite is used in the filter media, magnesite can quickly react with cold dilute hydrochloric acid at room temperature and is sparingly soluble in water. When its powder is mixed with water, the pH is around 8.0, so that the filter media prepared does not produce excessive alkalinity that would inhibit the growth of autotrophic denitrifying bacteria. Therefore, by using magnesite, the problems of high pH and low strength of filter media after soaking in water caused by using basic magnesium carbonate can be solved.

[0021] In addition, the addition of soluble salts can gradually dissolve in water, providing certain pores on the surface of the filter media, which is conducive to the attachment and growth of autotrophic denitrifying bacteria. Furthermore, the addition of a small amount of ultrafine fibers, such as carbon fiber, rock wool fiber, and cellulose fiber, can enhance the compressive strength of the carrier. And the addition of porous carriers, such as powdered activated carbon, can improve the strength of the filter media and provide attachment sites for free autotrophic denitrifying bacteria, thus shortening the start-up time. Attached Figure Description

[0022] Figure 1 This is a picture of the actual filter media. Detailed Implementation

[0023] A scale-resistant, self-nourishing, denitrifying filter media, characterized in that it comprises the following components in weight proportions: 100-500 parts sulfur, 50-200 parts magnesite, 5-50 parts porous carrier, and 5-50 parts soluble inorganic salt.

[0024] The sulfur mentioned above is natural sulfur or by-product sulfur from petrochemical, coking, and coal industries, and the sulfur content in the sulfur is not less than 90%. It can be produced by melting liquid sulfur or solid sulfur at high temperature to form liquid sulfur.

[0025] The aforementioned hydromagnesite contains more than 35.0% (by weight) magnesium oxide and less than 5.0% (by weight) calcium oxide. It is natural hydromagnesite or hydromagnesite powder, with a particle size of 60-600 mesh and a bulk density of 0.3-1.2 g / cm³. 3 This is beneficial for the mixture to have good fluidity after being added to liquid sulfur.

[0026] The aforementioned porous carriers are microporous carriers and include one or more of activated carbon, bamboo charcoal, diatomaceous earth, and zeolite powder. The particle size of the porous carriers is 100-750 mesh. It is necessary to ensure that more than 95% of the porous carriers can pass through a 50-mesh standard sieve.

[0027] The aforementioned soluble inorganic salts are one or more selected from ferrous sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, sodium chloride, potassium chloride, magnesium chloride, and ferrous chloride, accounting for 2.0-20.0% of the total filter media by mass. The particle size of the soluble inorganic salts is 50-600 mesh. The soluble inorganic salts selected are reducing iron salts such as ferrous sulfate and ferrous chloride, which can remove some dissolved oxygen and lower the redox potential. Simultaneously, ferrous iron can serve as an electron donor for iron-autotrophic denitrifying bacteria, which is beneficial for promoting iron-autotrophic denitrification.

[0028] The filter media also includes 0.8-4.0% by weight of ultrafine fiber powder, which includes one or more of sepiolite fiber, rock wool fiber, carbon fiber, lignin fiber, and cellulose fiber, accounting for 0.8-4.0% of the total filter media by weight. The diameter of the fibers in the ultrafine fiber powder is 10-100 micrometers and the length is less than 1000 micrometers.

[0029] The steps for preparing the above filter material are as follows: (1) Melt solid sulfur at 125-180 degrees Celsius to form liquid sulfur, add magnesite, microporous carrier, soluble salt and ultrafine fiber powder, stir thoroughly to obtain a mixed slurry; or directly purchase commercial liquid sulfur, maintain 125-180 degrees Celsius, the order of adding magnesite, microporous carrier, soluble salt and ultrafine fiber powder is not limited, stir thoroughly to obtain a mixed slurry; or mix magnesite, microporous carrier, soluble salt and ultrafine fiber powder evenly to prepare a mixture, then add the mixture to liquid sulfur, and then mix thoroughly to obtain a mixed slurry.

[0030] (2) The mixed slurry is granulated to obtain spherical or irregularly shaped particles of 2-20 mm. When the granulation method is underwater wet granulation, the mixed slurry is continuously dripped into cooling water through a distributor with an aperture of 2-10 mm. After dehydration through a filter screen, spherical or spherical particles with a diameter of 2-20 mm are formed. The temperature of the circulating cooling water is below 55 degrees Celsius, and the pH value is maintained in the range of 6.0-8.0. When the granulation method is casting mold granulation, the mixed slurry is poured into the mold and naturally cooled before being crushed and screened to obtain irregular particles of 2-30 mm. When the granulation method is molten steel strip granulation, hemispherical particles of 2-30 mm are formed on a molten granulator.

[0031] The bulk density of the mixture of the above-mentioned additives, excluding sulfur, is 0.3-1.2 g / cm³. 3 The true density of the filter media is 1.8-2.8 g / cm³. 3 The bulk density of the granulated filter media is 0.8-1.5 g / cm³. 3 .

[0032] The filter media prepared by the above-mentioned method for anti-scaling autotrophic denitrification filter media is used for autotrophic denitrification in wastewater containing nitrate nitrogen or nitrite nitrogen at a concentration of 20-2000 mg / L. It is suitable for denitrification aerated biological filters and denitrification deep-bed filters. When the total alkalinity of the wastewater and the alkalinity released by the filter media cannot meet the alkalinity requirements for denitrification by sulfur-autotrophic denitrifying bacteria, 5-50% (by weight) of hydromagnesia pulveratum particles are added to the denitrification filter as an alkalinity slow-release agent. The maximum axial dimension of the hydromagnesia pulveratum particles is 1-50 mm, and the calcium oxide content in the hydromagnesia pulveratum particles is less than 5% (by weight).

[0033] Commonly found magnesium carbonates (magnesite, magnesite) and iron carbonates (such as siderite powder) react slowly with dilute acids at room temperature, failing to provide timely neutralization and release of inorganic carbon sources. Synthetic magnesium carbonates, such as basic magnesium carbonate and light magnesium carbonate, react rapidly with dilute acids at room temperature; however, they cause an alkaline reaction in water, resulting in a pH above 8.5 after immersion. Excessively high pH can inhibit the activity of autotrophic denitrifying bacteria. Furthermore, synthetic magnesium carbonate and ferrous carbonate have a loose structure and low hardness, which, as major additives in filter media preparation, can easily lead to low filter media strength. During long-term immersion use, there is a risk of filter media disintegration.

[0034] The hydromagnesia in this filter media can react rapidly with dilute hydrochloric acid (e.g., 1 mol / L) at room temperature (around 20°C) during the denitrification process. It is also poorly soluble in water. Furthermore, the pH value of the hydromagnesia mixed with water is approximately 8.0, which is lower than that of chemically synthesized magnesium carbonate. This pH value meets the normal working requirements of autotrophic denitrifying bacteria, ensuring that the filter media prepared does not produce excessive alkalinity that would inhibit the growth of autotrophic denitrifying bacteria (e.g., denitrifying thiobacillus).

[0035] By selecting hydromagnesite, which forms a neutral to slightly alkaline solution in water (pH 7.0-8.0), as the main neutralizing component in the autotrophic denitrification filter media, the problems of high pH and low strength of the filter media after soaking in water caused by using basic magnesium carbonate are solved. Hydromagnesite is a rare type of naturally hydrated basic magnesium carbonate in the world. It is white in color, has medium hardness (Mohs hardness 3.5-4.0), which is higher than that of limestone. Using hydromagnesite as a substitute for calcium carbonate results in autotrophic denitrification filter media with good strength.

[0036] In addition, the addition of soluble salts allows for gradual dissolution in water, providing pores on the filter media surface, which is beneficial for the attachment and growth of denitrifying thiobacteria. Furthermore, the addition of small amounts of ultrafine fibers, such as carbon fiber, rock wool fiber, and cellulose fiber, enhances the compressive strength of the carrier. The addition of porous carriers, such as powdered activated carbon, improves the strength of the filter media and provides attachment sites for free denitrifying thiobacteria, shortening the start-up time.

[0037] The present invention will be further described below with reference to embodiments:

[0038] Example 1

[0039] The process involves melting granular sulfur at 120-160 degrees Celsius to form liquid sulfur. Then, the weighed powder (according to the formula in Table 1) is added to the liquid sulfur in sequence, and after thorough mixing and stirring, it is poured into a stainless steel mold. Finally, the mixture is crushed and sieved to obtain 3-10 mm particles, which are then used as the test samples for this experiment.

[0040] The sulfur in question is industrial sulfur sold by petrochemical companies, with a content of over 98%.

[0041] Hydromagnesite: Purchased from Tibet Dade New Materials, 325 mesh, magnesium oxide content >45%;

[0042] Magnesite powder: purchased from Liaoning Haicheng Xinhe Magnesium Products Co., Ltd., 325 mesh, magnesium carbonate content >95%;

[0043] Bruxite powder: purchased from Liaoning Haicheng Xinhe Magnesium Products Co., Ltd., 325 mesh, magnesium hydroxide content >95%.

[0044] Siderite powder: purchased from Changsha Weichuang Chemical Co., Ltd., ferrous carbonate, 325 mesh, iron content >38%;

[0045] Hydrated basic magnesium carbonate: purchased from Hebei Ximei Biotechnology, 325 mesh, magnesium oxide content >40%;

[0046] Potassium chloride: analytical grade reagent, dried, pulverized, and passed through a 200-mesh sieve;

[0047] Powdered activated carbon: Purchased from Jiangsu Zhuxi Activated Carbon Co., Ltd., 200 mesh, wood-based.

[0048] Lignin fiber: Purchased from Yixing Zhenbang Building Materials Co., Ltd., model MC-HB200, with a bulk density of about 210g / L, an average length of 200um, an appearance color of grayish-white, a fiber content of about 98%, a heat resistance of 225 degrees Celsius, and a pH value of 7.0.

[0049]

[0050] The filter media AF in the above experimental group was broken into 3-10mm pieces, and the average hardness and leaching pH of the packing were tested as shown in Table 2.

[0051]

[0052] Experimental methods:

[0053] Hardness test method: Randomly select small pieces with a particle size of 5-10mm and measure their compressive strength after crushing on a grain hardness tester.

[0054] Method for pH test of supernatant after soaking: Weigh 100g of each group of filter media, wash 3 times with tap water, then add 200ml of tap water, soak for 8 hours and then measure the pH of the supernatant.

[0055] pH restoration after acidification: Dilute hydrochloric acid was added to the soaked filter media-tap water solution to adjust the pH of the supernatant to 4.0. After standing for 3 hours, the pH of the supernatant was measured. During this period, the mixture was manually stirred 3 times.

[0056] Comparative analysis:

[0057] As shown in Table 2, the filter media prepared using magnesite, magnesite powder, brucite powder, siderite, and limestone exhibits good hardness, with a hardness greater than 170 N / particle using a grain hardness tester. In contrast, the filter media prepared using synthetically produced basic magnesium carbonate has an average hardness lower than 140 N / particle. This difference may be due to the relatively loose structure and low bulk density of synthetic basic magnesium carbonate, resulting in more hollow components in the prepared carrier and a decrease in the hardness of the filler.

[0058] As shown in Table 2, the filter media prepared using magnesite, magnesite powder, siderite powder, and limestone exhibits moderate alkalinity, with a supernatant pH less than 8.2 after soaking in water. However, when using magnesite and chemically synthesized basic magnesium carbonate, a large amount of hydroxide ions are released after soaking, causing the pH to exceed 8.5. When the filter media releases alkalinity too quickly and strongly, it leads to poor growth of denitrifying thiobacilli. According to literature reports, denitrifying thiobacilli generally thrive at pH levels between 7.0 and 8.3. Furthermore, the comparative data shows that filter media B (magnesite) and filter media D (siderite) have weaker pH-regulating capabilities, possibly due to the slow reaction of magnesite and siderite with cold, dilute hydrochloric acid.

[0059] Therefore, based solely on the hardness of the prepared denitrification packing material, the pH after soaking, and its buffering capacity against acid, the filter media prepared from magnesite and limestone have better overall performance, while the filter media prepared from magnesite and siderite have weaker neutralization capacity against dilute acids; and the filter media prepared from synthetic basic magnesium carbonate releases alkalinity too quickly after soaking, resulting in a rapid increase in pH, while the material hardness is also poor.

[0060] Example 1: The performance of the AF group in denitrification of artificially prepared wastewater was investigated.

[0061] The autotrophic denitrification sludge acclimation method used in the experiment:

[0062] (1) Source of sludge: sludge from the anoxic pool of Ningxia Nuanquan Sewage Treatment Plant;

[0063] (2) Acclimation method: Take 1L of sludge, add 1L of acclimation culture medium, place it in a 3L Erlenmeyer flask, and seal it with sealing film; place it in a constant temperature incubator at 30°C, change the water every 2 days, pour out the supernatant, and add acclimation culture medium.

[0064] (3) Formula for acclimatization culture medium: 5.0g sodium thiosulfate, 1.4g potassium nitrate, 0.1g potassium dihydrogen phosphate, 0.1g ammonium chloride, and 1000ml tap water.

[0065] Experimental conditions:

[0066] First, soak the denitrification filter media AF in tap water for 48 hours, then change the tap water and soak it again. Repeat this process 5 times. After washing, it can be used in the experiment.

[0067] Add 500g of each of the denitrification composite denitrification filter material AF prepared in the example to a 1L wide-mouth glass bottle.

[0068] Add 100ml of acclimated autotrophic denitrifying sludge and 50ml of acclimated sulfur-autotrophic denitrifying bacterial solution. Add 500ml of artificially prepared wastewater and let it stand at room temperature (20-30 degrees Celsius) to monitor the total nitrogen degradation in the supernatant. To eliminate the influence of sludge, discard the supernatant every 48 hours, repeating this process 5 times before starting the experiment. After starting the experiment, add 400ml of artificially prepared wastewater again.

[0069] Artificial water preparation formula 1 (estimated total nitrogen TN = 100 mg / L): potassium nitrate 0.7 g, potassium dihydrogen phosphate 0.1 g, ammonium chloride 0.1 g, tap water 1000 ml.

[0070] Artificial water preparation formula 2 (estimated total nitrogen TN = 500 mg / L): potassium nitrate 3.5 g, potassium dihydrogen phosphate 0.1 g, ammonium chloride 0.1 g, sodium bicarbonate 1.0 g, tap water 1000 ml.

[0071] When treating wastewater from simulated water formulation 1, 500ml of water is replaced each time, with an interval of 48 hours.

[0072] When treating wastewater from simulated water distribution formula 2, 500ml of water is replaced each time, with an interval of 96 hours.

[0073] Total nitrogen was determined using an LH-380 total nitrogen analyzer manufactured by Beijing Lianhua Technology Co., Ltd., and the measurement results are shown in Tables 3 and 4.

[0074]

[0075] As can be seen from the comparative experimental results in Table 3, formulation group A (using magnesite as a neutralizing agent) and formulation group F (using calcite as a neutralizing agent) showed better treatment effects on the simulated wastewater than the other four groups. This may be related to the ability of magnesite and calcite (whose main component is heavy calcium carbonate) to rapidly neutralize weak acids.

[0076]

[0077] As shown in Table 4, when treating simulated high-concentration nitrate wastewater, formulation group A (using magnesite as a neutralizing agent) was significantly better than other experimental groups. This is related to the appropriate dissolution rate and good acid buffering capacity of magnesite. Magnesite and siderite react slowly with dilute acid, resulting in insufficient time to neutralize the acid produced by autotrophic denitrification, and also failing to provide sufficient carbonate ions. The calcite group showed good results in the early stages, but the effect dropped sharply in the later stages. This may be due to the calcium sulfate precipitation, which caused scaling on the filter media surface, affecting the contact between denitrifying thiobacilli and the sulfur matrix.

[0078] Example 2

[0079] The preparation method is a melt method. Particle sulfur is heated to 120-160 degrees Celsius and melted into liquid sulfur. Then, the weighed powder (according to the formula in Table 1) is added to the liquid sulfur in sequence. After being thoroughly mixed and stirred, it is poured into a stainless steel mold and then crushed and screened to obtain particles of 3-20 mm as the test samples for this experiment. In this embodiment, the magnesite group and the calcite group are used as comparative experiments.

[0080] Experimental setup parameters:

[0081] It uses a 5L acrylic glass column, filled with 3.0kg of 3-20mm gravel filter media, with a peristaltic pump for continuous water intake at the bottom and water outlet at the top.

[0082] First-stage formula (estimated total nitrogen TN = 200 mg / L): potassium nitrate 1.4 g, potassium dihydrogen phosphate 0.1 g, ammonium chloride 0.1 g, sodium bicarbonate 1.0 g, tap water 1000 ml.

[0083] Second stage formula (estimated total nitrogen TN = 50 mg / L): potassium nitrate 0.35 g, potassium dihydrogen phosphate 0.1 g, ammonium chloride 0.1 g, sodium bicarbonate 0.1 g, tap water 1000 ml.

[0084] The influent flow rate for the first stage is 10 L / d, and the unit packing load is 0.66 g NO3-N / kg▪d; the influent flow rate for the second stage is 40 L / d, and the unit packing load is 0.66 g NO3-N / kg▪d.

[0085]

[0086] As can be seen from the comparative experiments in Table 5, when treating wastewater with a nitrate nitrogen concentration of about 200 mg / L, the stability of the MgO-hydrate formulation is better than that of the calcite formulation. Especially in the later stage, the calcite formulation shows a significant increase, while the MgO-hydrate formulation is relatively stable, with the total nitrogen in the effluent basically maintained below 50 mg / L.

[0087]

[0088] Water is supplied continuously every day, and testing is conducted irregularly based on actual conditions.

[0089] As can be seen from the comparative experiments in Table 6, the treatment effect of the calcite group decreased sharply after operating on high-concentration nitrate wastewater in the first stage. In the second stage, the total nitrogen in the influent was reduced to 50 mg / L, and the effluent from the magnesia group decreased accordingly, showing good treatment effect. However, the calcite group containing calcium carbonate did not recover its denitrification function when treating low-concentration nitrate wastewater. This may be because when treating high-concentration wastewater, a large amount of calcium sulfate was generated, forming a large amount of scale on the surface of the packing material, which blocked the micropores formed by soluble salts, resulting in poor treatment effect.

[0090] Example 3

[0091] The sample was prepared by a melt method. Granular sulfur was heated to 120-160 degrees Celsius and melted into liquid sulfur. Then, the weighed powder (according to the formula in Table 1) was added to the liquid sulfur in sequence. After being thoroughly mixed and stirred, the mixture was poured into a stainless steel mold and then crushed and sieved to obtain particles of 3-20 mm as the test samples for this experiment. In this example, a comparative experiment was conducted using magnesia hydrate. One group was supplemented with 10% magnesia hydrate particles as an alkalinity supplement, while the other group was a blank. The particle size of the magnesia hydrate particles was 3-6 mm.

[0092] Artificial water preparation formula (estimated total nitrogen TN = 300 mg / L): potassium nitrate 2.1 g, potassium dihydrogen phosphate 0.1 g, ammonium chloride 0.1 g, tap water 1000 ml.

[0093] The experimental materials and methods are the same as in Example 1.

[0094]

[0095] Artificial water preparation was used, as shown in Table 7. 500g of hydromagnesia-sulfur filter media was added to a 1L wide-mouth bottle with a lid. The experimental group was further supplemented with 50g of hydromagnesia granules (3-6mm), while the control group was supplemented with only 500g of filter media without adding a neutralizing agent.

[0096]

[0097] As can be seen from the total nitrogen values ​​measured in Table 8, adding hydromagnesite particles with slow-release carbonate to the denitrification filter media helps to improve the nitrate removal efficiency when treating high-concentration nitrate wastewater.

[0098] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An anti-fouling autotrophic denitrifying denitrification filter material, characterized by, It comprises the following ingredients by weight: 100-500 parts of sulfur, 50-200 parts of hydromagnesite, 5-50 parts of porous carrier, and 5-50 parts of soluble inorganic salt; the hydromagnesite in the filter material can rapidly react with hydrogen ions generated in the autotrophic denitrification process at normal temperature during the denitrification process, and the pH value of the mixture of the hydromagnesite and water can meet the pH value required for the normal operation of the autotrophic denitrification bacteria; the content of magnesium oxide in the hydromagnesite is greater than 35.0% by weight, and the content of calcium oxide is less than 5.0% by weight; the hydromagnesite is natural hydromagnesite or hydromagnesite powder, the particle size of the hydromagnesite is 60-600 mesh, and the bulk density is 0.3-1.2 g / cm 3 .

2. The anti-fouling autotrophic denitrifying nitrogen removal filter material according to claim 1, characterized in that: The porous carrier includes one or more of activated carbon, bamboo charcoal, diatomite, and zeolite powder, and the particle size of the porous carrier is 100-750 mesh. The soluble inorganic salt is one or more of ferrous sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, sodium chloride, potassium chloride, magnesium chloride, and ferrous chloride, and the particle size of the soluble inorganic salt is 50-600 mesh.

3. The anti-fouling autotrophic denitrifying nitrogen removal filter material according to any one of claims 1-2, characterized in that: The filter material further includes 0.8-4.0% of superfine fiber powder by total weight, and the superfine fiber powder includes one or more of sepiolite fiber, rock wool fiber, carbon fiber, lignin fiber, and cellulose fiber, and the diameter of the fiber in the superfine fiber powder is 10-100 microns and the length is less than 1000 microns.

4. A process for the preparation of the anti-fouling autotrophic denitrifying denitrification media as claimed in claim 3, wherein, It includes the following steps: (1) adding liquid sulfur to the hydromagnesite, the porous carrier, the soluble inorganic salt, and the superfine fiber powder under the condition of a temperature of 125-180 degrees Celsius, and fully stirring to obtain a mixed slurry, and the order of adding the hydromagnesite, the porous carrier, the soluble inorganic salt, and the superfine fiber powder is not limited; (2) obtaining 2-30 mm spherical granules or irregular gravel-shaped filter material by wet or dry granulation.

5. The method according to claim 4, wherein the method is characterized by: The bulk density of the mixture of other additives except sulfur is 0.3-1.2 g / cm 3 The true density of the filter material is 1.8-2.8 g / cm 3 The bulk density of the granulated filter material is 0.8-1.5 g / cm 3 .

6. The application mode of anti-fouling autotrophic denitrification denitrogenation filter material, characterized in that: The filter material prepared by the method for preparing the anti-fouling autotrophic denitrification filter material of claim 4 or 5 is used for autotrophic denitrification in wastewater containing nitrate nitrogen or nitrite nitrogen and having a concentration of 20-2000 mg / L.

7. The application mode of the anti-fouling autotrophic denitrification denitrogenation filter material according to claim 6, characterized in that: When the total alkalinity of the wastewater and the alkalinity released by the filter material cannot meet the alkalinity requirement of the sulfur autotrophic denitrification bacteria, 5-50% of hydromagnesite particles by weight of the total filter material are added to the denitrification filter tank as an alkalinity release agent, the maximum dimension of the hydromagnesite particles is 1-50 mm, and the calcium oxide content in the hydromagnesite particles is less than 5% by weight.

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