Sulfur autotrophic denitrification nitrogen removal composite filler and preparation method thereof

Abstract

The present application relates to a kind of sulfur autotrophic denitrification denitrification composite filling and its preparation method, comprising (1) binder and toughening agent are dissolved in glycerol solution and stirred to react, low-temperature drying is obtained after solid powder;(2) sulfur is heated to melt state, while stirring, iron ammonia of EDTA is added, slightly soluble or insoluble carbonate, the solid powder of step (1) is added, and after being added, mixture is obtained;(3) the above-mentioned mixture is stirred and cooled to 110-115 DEG C, again, obtain sulfur autotrophic denitrification denitrification composite filling by quenching molding.The composite filling prepared in the present application is easy to be efficiently enriched and rapidly proliferated by sulfur autotrophic denitrification bacteria, shorten the start-up time, ensure the efficient, stable operation of sulfur autotrophic denitrification denitrification process.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control technology, specifically relating to a sulfur autotrophic denitrification composite packing and its preparation method. Background Technology

[0002] In recent years, the national requirements for total nitrogen discharge in wastewater have become increasingly stringent. To meet these requirements, enterprises have been adding traditional denitrification filters at the end of their wastewater treatment processes. While denitrification filters have addressed the total nitrogen problem in wastewater to some extent, the process requires the addition of organic carbon sources, increasing operating costs and posing a risk of excessive COD in the effluent. Following the introduction of the "dual carbon target," the high carbon consumption and emissions of traditional heterotrophic denitrification can no longer meet the current demands for green and high-quality development. Autotrophic denitrifying bacteria can utilize reducing substrates such as sulfur, iron powder, or pyrite to reduce nitrate nitrogen to nitrogen gas, without the involvement of organic carbon sources. The operating cost of autotrophic denitrification is significantly lower than that of heterotrophic denitrification, and there are no greenhouse gas emissions. Therefore, autotrophic denitrification has become one of the main technologies for low-carbon, low-energy biological denitrification of wastewater. In particular, sulfur-based autotrophic denitrification technology is widely used for deep denitrification of low-carbon-to-nitrogen ratio wastewater such as groundwater, industrial wastewater, and aquaculture tailwater.

[0003] However, the slow proliferation of sulfur-autotrophic denitrifying bacteria and the long reactor start-up period limit the widespread application of sulfur-autotrophic denitrification technology. Furthermore, currently available autotrophic denitrification packing materials are brittle, lack toughness, and have unstable strength, making them prone to breakage during operation, leading to problems such as turbid effluent and filter bed clogging. Therefore, there is an urgent need to develop a highly efficient and stable sulfur-autotrophic denitrification composite packing carrier to promote the widespread application of autotrophic denitrification technology.

[0004] CN107487840A discloses a biological filter media for treating nitrate nitrogen in water, used to treat nitrate nitrogen pollutants in domestic and industrial wastewater. The biological filter media combines elemental sulfur and a slow-release carbon source through autotrophic and heterotrophic denitrification processes, allowing both sulfur-autotrophic and heterotrophic denitrifying bacteria to grow abundantly on the surface of the filter media, forming a biofilm. This biofilm synergistically treats nitrate nitrogen in the water through denitrification. The mass percentage of elemental sulfur ranges from 40% to 80%, carbonate from 10% to 40%, and the slow-release carbon source from 1% to 20%. The elemental sulfur in the biological filter media provides electrons to the sulfur-autotrophic denitrifying bacteria during the denitrification process. The slow-release carbon source provides electrons to heterotrophic denitrifying bacteria during denitrification, leading to the enrichment of both sulfur-autotrophic and heterotrophic denitrifying bacteria on the surface of the biofilter media. The biofilter media also includes metal oxides, with a mass percentage ranging from 5% to 10%. These metal oxides improve the surface charge properties of the biofilter media during denitrification, which is beneficial for attracting and enriching denitrifying bacteria. The consumption of the slow-release carbon source in the biofilter media creates a porous structure on the fiber bundle surface, increasing the specific surface area of ​​the biofilter media and facilitating the large-scale enrichment of denitrifying bacteria. However, even though this filter media combines autotrophic and heterotrophic denitrification processes, resulting in the abundant growth of both sulfur-autotrophic and heterotrophic denitrifying bacteria on the biofilter media surface, it still cannot completely avoid the problems of needing to replenish carbon sources and carbon emissions associated with heterotrophic denitrification. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a sulfur autotrophic denitrification composite packing material and its preparation method. The composite packing material prepared by this invention facilitates the efficient enrichment and rapid proliferation of sulfur autotrophic denitrifying bacteria, shortens start-up time, and ensures the efficient and stable operation of the sulfur autotrophic denitrification process.

[0006] The present invention provides a method for preparing a sulfur autotrophic denitrification composite packing, comprising the following steps:

[0007] (1) Dissolve the binder and toughening agent in a glycerol solution, stir and react, and dry at low temperature to obtain a solid powder;

[0008] (2) Heat the sulfur to a molten state, and add EDTA iron ammonia, slightly soluble or insoluble carbonate, and solid powder from step (1) while stirring. After adding all the ingredients, a mixture is obtained.

[0009] (3) Stir and cool the above mixture to 110-115℃, then rapidly cool and shape it to obtain sulfur autotrophic denitrification denitrification composite packing.

[0010] In the preparation method of the present invention, the binder in step (1) is one or a mixture of several of polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, xanthan gum, etc., with a particle size of 200-300 mesh.

[0011] In the preparation method of the present invention, the toughening agent mentioned in step (1) is one or a mixture of several of polylactic acid (PLA), poly(3-hydroxyalkanoate) (PHA), polycaprolactone (PCL), polybutylene succinate (PBS), etc., with a particle size of 100-200 mesh.

[0012] In the preparation method of the present invention, the mass concentration of the glycerol solution in step (1) is 60%-70%.

[0013] In the preparation method of the present invention, the ratio of the amount of glycerol solution used in step (1) to the total amount of binder and toughening agent is 50-100:1.

[0014] In the preparation method of the present invention, the stirring reaction rate in step (1) is 50-100 rpm, the reaction temperature is room temperature, and the reaction time is 1-5 h.

[0015] In the preparation method of the present invention, the drying temperature in step (1) is 50-70℃, and the moisture content is dried to less than 1%.

[0016] In the preparation method of this invention, step (2) involves heating sulfur to a molten state at a temperature controlled at 130-160°C. The stirring reaction rate is 50-100 rpm.

[0017] In the preparation method of this invention, the sulfur in step (2) has a particle size of 100-200 mesh. The EDTA iron ammonia has a particle size of 200-300 mesh.

[0018] In this invention, the slightly soluble or water-insoluble carbonate mentioned in step (2) is at least one of calcium carbonate, magnesium carbonate, ferrous carbonate, etc., with a particle size of 200-300 mesh.

[0019] In the preparation method of this invention, the mass ratio of the binder, toughening agent, sulfur, EDTA iron ammonia, and slightly soluble or insoluble carbonate is: 10-20:5-10:40-60:0.5-5:10-30.

[0020] In the preparation method of the present invention, step (3) involves stirring and cooling the mixture at a stirring rate of 50-100 rpm, preferably cooling it to 112-113°C for rapid cooling and shaping. The shape is generally granular with a particle size of 3-5 mm, thus obtaining a composite filler.

[0021] The sulfur-autotrophic denitrification composite packing provided by this invention is prepared using the method described above. The specific gravity of the obtained composite packing is generally 1.5-2.0 g / cm³. 3 Its Mohs hardness is between 1.0 and 4.0.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Based on the adsorption and growth characteristics of sulfur autotrophic denitrifying bacteria, this invention prepares a composite filler by selecting specific components and combining them with specific preparation methods. This not only ensures the full play of the role of each component, but also achieves a strong bond between the components. The active substances are not easily broken or lost, and the effect of use within the effective period is not significantly reduced.

[0024] (2) The composite filler of the present invention is mainly made of sulfur, EDTA iron ammonia, slightly soluble or insoluble carbonate, binder and toughening agent. The selected components work synergistically, making it easier for sulfur autotrophic denitrifying bacteria to be efficiently enriched and rapidly proliferated, thus shortening the start-up time.

[0025] (3) The sulfur autotrophic denitrification composite packing prepared by the present invention has the advantages of high strength, high toughness, no disintegration during operation, no caking, complete biodegradability and no residue, and is suitable for industrial application. Detailed Implementation

[0026] The technical solution and its effects of the present invention will be further described in detail below through embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples can be purchased from biochemical reagent stores.

[0028] In this embodiment of the invention, the nitrate nitrogen was determined using GB / T 11894-2015 "Determination of Nitrate Nitrogen in Water - Colorimetric Method", and the alkalinity was determined using GB / T 9736-2008 "General Method for Determination of Acidity and Alkalinity of Chemical Reagents".

[0029] Example 1

[0030] (1) Dissolve 300 mesh polyvinyl alcohol and 100 mesh polylactic acid in a 65% glycerol solution and stir at 25°C and 80 rpm for 1 hour. The mass ratio of the amount of glycerol solution to the total amount of binder and toughening agent is 50:1. After drying at 50°C, a solid powder is obtained.

[0031] (2) Heat 150 mesh sulfur to a molten state, and add 200 mesh EDTA iron ammonia, 200 mesh calcium carbonate and the solid powder from step (1) while stirring (60 rpm) at 138°C. After the addition is complete, a mixture is obtained. The mass ratio of binder, toughening agent, sulfur, EDTA iron ammonia and slightly soluble or insoluble carbonate is 10:8:50:2:30.

[0032] (3) Stir the above mixture at 100 rpm and cool it to 113°C. Then, rapidly cool it to shape it into particles with a diameter of about 3 mm to obtain sulfur autotrophic denitrification composite packing No. 1.

[0033] Example 2

[0034] (1) Dissolve 300 mesh methylcellulose and 100 mesh polycaprolactone in a 60% glycerol solution and stir at 20°C and 100 rpm for 1 hour. The mass ratio of the amount of glycerol solution to the total amount of binder and toughening agent is 100:1. After drying at 70°C, a solid powder is obtained.

[0035] (2) Heat 150 mesh sulfur to a molten state, and add 200 mesh EDTA iron ammonia, 200 mesh magnesium carbonate and the solid powder from step (1) while stirring (60 rpm) at 145°C. After the addition is complete, a mixture is obtained. The mass ratio of binder, toughening agent, sulfur, EDTA iron ammonia and slightly soluble or insoluble carbonate is 20:5:40:5:20.

[0036] (3) Cool the above mixture to 113°C at 50 rpm, then rapidly cool and shape it to obtain sulfur autotrophic denitrification composite packing No. 2 with a particle size of about 3 mm.

[0037] Example 3

[0038] (1) Dissolve 300 mesh hydroxyethyl cellulose and 100 mesh poly3-hydroxyalkanoate in a 70% glycerol solution and stir at 23°C and 80 rpm for 1 h. The mass ratio of the amount of glycerol solution to the total amount of binder and toughening agent is 70:1. After drying at 60°C, a solid powder is obtained.

[0039] (2) Heat 150 mesh sulfur to a molten state, and add 200 mesh EDTA iron ammonia, 200 mesh calcium carbonate and the solid powder from step (1) while stirring (70 rpm) at 150°C. After the addition is complete, a mixture is obtained. The mass ratio of binder, toughening agent, sulfur, EDTA iron ammonia and slightly soluble or insoluble carbonate is 15:10:60:0.5:14.5.

[0040] (3) Stir the above mixture at 80 rpm and cool it to 113°C, then rapidly cool it to shape it into particles with a diameter of about 3 mm, to obtain sulfur autotrophic denitrification composite packing No. 3.

[0041] Example 4

[0042] Same as Example 2, except that the binder used is carboxymethyl cellulose and the toughening agent is PBS. This yields sulfur autotrophic denitrification composite packing material #4.

[0043] Example 5

[0044] Same as Example 2, except that: the carbonate used is ferrous carbonate and the binder is xanthan gum. A sulfur-autotrophic denitrification composite packing material #5 was obtained.

[0045] Comparative Example 1

[0046] Same as Example 2, except that step (1) is omitted, and methylcellulose and polycaprolactone are added directly to the mixture instead of the solid powder in step (1). This yields sulfur autotrophic denitrification composite packing #6.

[0047] Comparative Example 2

[0048] Same as Example 2, except that water was used instead of glycerol solution in the preparation process. This yielded sulfur autotrophic denitrification composite packing material #7.

[0049] Comparative Example 3

[0050] Same as Example 2, except that step (3) was not stirred and cooled, but directly quenched and granulated. This yielded sulfur autotrophic denitrification composite packing #8.

[0051] Comparative Example 4

[0052] Same as Example 2, except that: sulfur autotrophic denitrification composite packing material 9#-13# was prepared according to the weight ratios described in Table 1.

[0053] Table 1

[0054]

[0055] Test case

[0056] The composite packing materials prepared in the examples and comparative examples were used in the sulfur autotrophic denitrification process.

[0057] The aforementioned packing material was filled into the denitrification filter at a 50% filling ratio, and inoculated with activated sludge containing sulfur-containing autotrophic denitrifying bacteria at a concentration of approximately 3000 mg / L. The influent nitrate concentration was 50 mg / L, and the alkalinity (calculated as calcium carbonate) was approximately 100 mg / L. A bottom-in, top-out flow pattern was adopted, and the hydraulic retention time was controlled at approximately 24 hours. The operational results and packing material performance are shown in Table 2 below.

[0058] Table 2

[0059]

[0060]

Claims

1. A method for preparing a sulfur-autotrophic denitrification composite packing, characterized in that... Includes the following steps: (1) Dissolve the binder and toughening agent in a glycerol solution and stir to react. Dry at low temperature to obtain a solid powder. The mass concentration of the glycerol solution is 60%-70%. The ratio of the amount of glycerol solution to the total amount of binder and toughening agent is 50-100:

1. The binder is one or a mixture of polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and xanthan gum. (2) Heat the sulfur to a molten state, and control the temperature at 130-160℃. While stirring, add EDTA iron ammonia, slightly soluble or insoluble carbonate, and the solid powder from step (1). After adding all the ingredients, a mixture is obtained. The mass ratio of the binder, toughening agent, sulfur, EDTA iron ammonia, and slightly soluble or insoluble carbonate is: 10-20:5-10:40-60:0.5-5:10-30. (3) Stir and cool the above mixture to 110-115℃, then rapidly cool and shape it to obtain sulfur autotrophic denitrification denitrification composite packing.

2. The method according to claim 1, characterized in that: The particle size of the adhesive described in step (1) is 200-300 mesh.

3. The method according to claim 1, characterized in that: The toughening agent mentioned in step (1) is one or a mixture of several of polylactic acid, poly-3-hydroxyalkanoate, polycaprolactone, and polybutylene succinate, with a particle size of 100-200 mesh.

4. The method according to claim 1, characterized in that: The stirring rate in step (1) is 50-100 rpm, the reaction temperature is room temperature, and the reaction time is 1-5 h.

5. The method according to claim 1, characterized in that: The drying temperature in step (1) is 50-70℃, and the moisture content is dried to less than 1%.

6. The method according to claim 1, characterized in that: Step (2) Heat the sulfur to a molten state and stir the reaction at a rate of 50-100 rpm.

7. The method according to claim 1, characterized in that: The sulfur in step (2) has a particle size of 100-200 mesh, and the EDTA iron ammonia has a particle size of 200-300 mesh.

8. The method according to claim 1, characterized in that: The slightly soluble or water-insoluble carbonate mentioned in step (2) is at least one of calcium carbonate, magnesium carbonate, and ferrous carbonate, with a particle size of 200-300 mesh.

9. The method according to claim 1, characterized in that: Step (3) The mixture is stirred and cooled at a stirring rate of 50-100 rpm and cooled to 112-113℃ for rapid cooling and molding. The molding is in the form of granules with a particle size of 3-5 mm to obtain composite filler.

10. A sulfur-autotrophic denitrification composite packing material, characterized in that... It is prepared using the method described in any one of claims 1-9.

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