Sulfur autotrophic denitrification nitrogen removal composite filler and preparation method thereof

Abstract

The preparation method comprises the following steps: (1) dissolving a binding agent and a toughening agent in a glycerol solution, stirring and reacting, and drying at low temperature to obtain solid powder; (2) heating sulfur to a molten state, and adding EDTA ferric ammonia, slightly soluble or insoluble carbonate and the solid powder in the step (1) while stirring to obtain a mixture; and (3) stirring and cooling the mixture to 110-115 DEG C, and then quenching and molding to obtain the sulfur autotrophic denitrification nitrogen removal composite filler. The composite filler prepared by the invention is easy for efficient enrichment and rapid proliferation of sulfur autotrophic denitrification bacteria, shortens the starting time, and ensures efficient and stable operation of the sulfur autotrophic denitrification nitrogen removal process.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution control, and particularly relates to a sulfur autotrophic denitrification composite filler and a preparation method thereof. Background Art

[0002] In recent years, the state has imposed stricter requirements on the total nitrogen emissions of wastewater. In order to meet the emission requirements, enterprises have successively added traditional denitrification filters at the end of the sewage treatment process. Although the denitrification filter has solved the problem of total nitrogen in the drainage to a certain extent, organic carbon sources need to be added during the treatment process, which increases the operating cost and there is also a hidden danger of exceeding the COD standard in the effluent. After the "dual-carbon goal" was put forward, the high carbon source consumption and high carbon emissions of traditional heterotrophic denitrification can no longer meet the current requirements for green and high-quality development. Autotrophic denitrifying bacteria can use reduced substrates such as sulfur, iron powder or pyrite to reduce nitrate nitrogen to nitrogen gas, and there is no participation of organic carbon sources throughout the process. The operating cost of autotrophic denitrification is greatly reduced compared with the heterotrophic denitrification process, and there is no greenhouse gas emission during the autotrophic denitrification process. Therefore, autotrophic denitrification has become one of the main technologies for low-carbon and low-energy wastewater biological denitrification. In particular, the sulfur autotrophic denitrification technology has been widely used in the deep denitrification of low-carbon-nitrogen ratio wastewater such as groundwater, industrial wastewater, and aquaculture tail water.

[0003] However, the growth of sulfur autotrophic denitrifying bacteria is slow and the start-up period of the reactor is long, which limits the wide application of the sulfur autotrophic denitrification technology. In addition, the current autotrophic denitrification fillers on the market are brittle, have poor toughness, and their strength is not stable enough. During operation, the fillers are easily broken, resulting in problems such as turbid effluent and clogging of the filter tank. Therefore, there is an urgent need to develop an efficient and stable sulfur autotrophic denitrification composite filler carrier to promote the popularization and application of the autotrophic denitrification technology.

[0004] CN107487840A discloses a biological filter media for treating nitrate nitrogen in water, which is used to treat nitrate nitrogen pollutants in domestic and industrial wastewater. The sulfur element and slow-release carbon source in the biological filter media are combined through autotrophic denitrification and heterotrophic denitrification processes, enabling both sulfur autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria to grow abundantly on the surface of the biological filter media, forming a biofilm on the surface, and synergistically treating nitrate nitrogen in water through the denitrification process; the mass percentage range of the sulfur element is 40%-80%, the mass percentage range of the carbonate is 10%-40%, and the mass percentage range of the slow-release carbon source is 1%-20%; the sulfur element in the biological filter media provides electrons for sulfur autotrophic denitrifying bacteria during the denitrification process, and the slow-release carbon source provides electrons for heterotrophic denitrifying bacteria during the denitrification process, enabling sulfur autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria to be enriched on the surface of the biological filter media; the biological filter media also includes metal oxides, and the mass percentage range of the metal oxides is 5%-10%; the metal oxides improve the charge property of the surface of the biological filter media during the denitrification process, which is conducive to attracting the enrichment of denitrifying bacteria; the consumption process of the slow-release carbon source in the biological filter media forms a porous structure on the surface of the fiber bundle, increasing the specific surface area of the biological filter media, which is conducive to the large-scale enrichment of denitrifying bacteria. However, the combined use of autotrophic denitrification and heterotrophic denitrification processes in this filter media enables both sulfur autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria to grow abundantly on the surface of the biological filter media, but still cannot completely avoid the problems of carbon source supplementation and carbon emissions existing in heterotrophic denitrification. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a sulfur autotrophic denitrification nitrogen removal composite filler and a preparation method thereof. The composite filler prepared by the present invention is easy for the efficient enrichment and rapid proliferation of sulfur autotrophic denitrifying bacteria, shortens the startup time, and ensures the efficient and stable operation of the sulfur autotrophic denitrification nitrogen removal process.

[0006] A preparation method of a sulfur autotrophic denitrification nitrogen removal composite filler provided by the present invention includes the following steps:

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

[0008] (2) Heat sulfur to a molten state, add ferric ammonium EDTA, slightly soluble or insoluble carbonate, and the solid powder obtained in step (1) while stirring, and obtain a mixture after adding;

[0009] (3) Stir and cool the above mixture to 110-115°C, and then perform rapid cooling and shaping to obtain a sulfur autotrophic denitrification nitrogen removal composite filler.

[0010] In the preparation method of the present invention, the binder in step (1) is one or a mixture of polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, xanthan gum, etc., and the particle size is 200-300 mesh.

[0011] In the preparation method of the present invention, the toughening agent in step (1) is one or a mixture of polylactic acid (PLA), poly-3-hydroxyalkanoate (PHA), polycaprolactone (PCL), polybutylene succinate (PBS), etc., and the particle size is 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 the glycerol solution used in step (1) to the total amount of the binder and the 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 °C, and it is dried until the moisture content is lower than 1%.

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

[0017] In the preparation method of the present invention, the particle size of the sulfur in step (2) is 100-200 mesh. The particle size of ferric ammonium EDTA is 200-300 mesh.

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

[0019] In the preparation method of the present invention, the mass ratio of the binder, toughening agent, sulfur, ferric ammonium EDTA, 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, in step (3), the mixture is stirred and cooled, the stirring reaction rate is 50-100 rpm, and it is preferably cooled to 112-113 °C for rapid cooling and shaping. The shape is generally granular, with a particle size of 3-5 mm, to obtain a composite filler.

[0021] The sulfur autotrophic denitrification composite filler provided by the present invention is prepared by the method of the present invention described above. The specific gravity of the prepared composite filler is generally 1.5-2.0 g / cm 3 , and the Mohs hardness is 1.0-4.0.

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

[0023] (1) According to the adsorption and growth characteristics of sulfur autotrophic denitrifying bacteria, the composite filler is prepared by combining a specific preparation method on the basis of selecting specific components. It can not only ensure the full play of the functions of each component, but also achieve the firm combination between each component. The active substances are not easily broken and lost, and the use effect attenuation is not obvious within the validity period.

[0024] (2) The composite filler of the present invention is mainly prepared by compounding sulfur, ferric ammonium EDTA, slightly soluble or insoluble carbonate, binder and toughening agent. The selected components act synergistically, which is more conducive to the efficient enrichment and rapid proliferation of sulfur autotrophic denitrifying bacteria, and shortens the startup time.

[0025] (3) The sulfur autotrophic denitrification composite filler prepared by the present invention has the advantages of high strength, strong toughness, no disintegration during operation, no hardening phenomenon, complete biodegradability, no residue, etc., and is suitable for industrial applications. Specific Embodiments

[0026] The technical solution and its effects of the present invention will be further described in detail below through examples. The examples are implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0027] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, can all be obtained from biochemical reagent stores.

[0028] In the examples of the present invention, the detection method of nitrate nitrogen is determined by GB / T 11894-2015 "Determination of Nitrate Nitrogen in Water - Colorimetric Method", and the alkalinity is determined by GB / T 9736-2008 "General Method for the 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 glycerol solution with a mass concentration of 65%, stir and react at 25°C and 80 rpm for 1 h. The mass ratio of the amount of glycerol solution used to the total amount of binder and toughening agent is 50:1, and obtain a solid powder after drying at 50°C;

[0031] (2) Heat 150-mesh sulfur to the molten state, and add 200-mesh ferric ammonium EDTA, 200-mesh calcium carbonate, and the solid powder from step (1) while stirring (60 rpm) at 138 °C. After adding, a mixture is obtained. The mass ratio of the binder, toughening agent, sulfur, ferric ammonium EDTA, 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 and mold it. The particle size is about 3 mm to obtain the sulfur autotrophic denitrification composite filler 1#.

[0033] Example 2

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

[0035] (2) Heat 150-mesh sulfur to the molten state, and add 200-mesh ferric ammonium EDTA, 200-mesh magnesium carbonate, and the solid powder from step (1) while stirring (60 rpm) at 145 °C. After adding, a mixture is obtained. The mass ratio of the binder, toughening agent, sulfur, ferric ammonium EDTA, 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 mold it. The particle size is about 3 mm to obtain the sulfur autotrophic denitrification composite filler 2#.

[0037] Example 3

[0038] (1) Dissolve 300-mesh hydroxyethylcellulose and 100-mesh poly-3-hydroxyalkanoate in a 70% mass concentration glycerol solution, and stir and react at 23 °C and 80 rpm for 1 h. The mass ratio of the amount of glycerol solution used to the total amount of the binder and toughening agent is 70:1. After drying at 60 °C, a solid powder is obtained.

[0039] (2) Heat 150-mesh sulfur to the molten state, and add 200-mesh ferric ammonium EDTA, 200-mesh calcium carbonate, and the solid powder from step (1) while stirring (70 rpm) at 150 °C. After adding, a mixture is obtained. The mass ratio of the binder, toughening agent, sulfur, ferric ammonium EDTA, 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 and mold it. The particle size is about 3 mm to obtain the sulfur autotrophic denitrification composite filler 3#.

[0041] Example 4

[0042] Same as Example 2, except that: the binder used is carboxymethyl cellulose and the toughening agent used is PBS. Sulfur autotrophic denitrification composite filler 4# is obtained.

[0043] Example 5

[0044] Same as Example 2, except that: the carbonate used is ferrous carbonate and the binder used is xanthan gum. Sulfur autotrophic denitrification composite filler 5# is obtained.

[0045] Comparative Example 1

[0046] Same as Example 2, except that: step (1) is cancelled, and methyl cellulose and polycaprolactone are used to replace the solid powder in step (1) and directly added to obtain a mixture. Sulfur autotrophic denitrification composite filler 6# is obtained.

[0047] Comparative Example 2

[0048] Same as Example 2, except that: water is used instead of glycerol solution in the preparation process. Sulfur autotrophic denitrification composite filler 7# is obtained.

[0049] Comparative Example 3

[0050] Same as Example 2, except that: in step (3), it is not stirred and cooled, but directly quenched and granulated. Sulfur autotrophic denitrification composite filler 8# is obtained.

[0051] Comparative Example 4

[0052] Same as Example 2, except that: sulfur autotrophic denitrification composite fillers 9# - 13# are prepared according to the weight ratio shown in Table 1.

[0053] Table 1

[0054]

[0055] Test Example

[0056] The composite fillers prepared in the examples and comparative examples are used in the sulfur autotrophic denitrification process.

[0057] The above fillers are filled into the denitrification filter at a filling ratio of 50%, inoculated with activated sludge containing sulfur autotrophic denitrifying bacteria, and the sludge concentration is about 3000 mg / L. The influent nitrate nitrogen concentration is 50 mg / L, and the alkalinity (calculated as calcium carbonate) is about 100 mg / L. The bottom-up flow form is adopted, and the hydraulic retention time is controlled at about 24 h. The operation effect and filler performance are shown in Table 2 below.

[0058] Table 2

[0059]

[0060]

Claims

1. A preparation method of a sulfur autotrophic denitrification composite filler, characterized in that it includes the following steps: (1) Dissolve the binder and toughening agent in a glycerol solution, stir and react, and obtain a solid powder after low-temperature drying; (2) Heat sulfur to a molten state, add ferric ammonium EDTA, slightly soluble or insoluble carbonate, and the solid powder from step (1) while stirring, and obtain a mixture after adding; (3) Stir and cool the above mixture to 110-115 °C, and then perform rapid cooling and shaping to obtain the sulfur autotrophic denitrification composite filler.

2. The method according to claim 1, characterized in that: The binder described in step (1) is one or a mixture of several of polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, xanthan gum, and the particle size is 200-300 mesh.

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

4. The method according to claim 1, characterized in that: The mass concentration of the glycerol solution described in step (1) is 60%-70%.

5. The method according to claim 1 or 4, characterized in that: The ratio of the dosage of the glycerol solution described in step (1) to the total amount of the binder and toughening agent is 50-100:

1.

6. The method according to claim 1, characterized in that: 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.

7. The method according to claim 1, characterized in that: The drying temperature in step (1) is 50-70 °C, and it is dried until the moisture content is lower than 1%.

8. The method according to claim 1, characterized in that: In step (2), sulfur is heated to a molten state, the temperature is controlled at 130-160 °C, and the stirring reaction rate is 50-100 rpm.

9. The method according to claim 1, characterized in that: The particle size of the sulfur described in step (2) is 100-200 mesh, and the particle size of ferric ammonium EDTA is 200-300 mesh.

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

11. The method according to claim 1, 2, 3 or 10, characterized in that: The mass ratio of the binder, toughening agent, sulfur, ferric ammonium EDTA, and slightly soluble or insoluble carbonate is: 10-20:5-10: 40-60:0.5-5:10-30.

12. The method according to claim 1, characterized in that: In step (3), the mixture is stirred and cooled, the stirring reaction rate is 50-100 rpm, cooled to 112-113 °C for rapid cooling and shaping, and the shape is granular with a particle size of 3-5 mm to obtain the composite filler.

13. A sulfur autotrophic denitrification composite filler, characterized in that It is prepared by using the method described in any one of claims 1-12.

Images