A composite biomass carbon source and sulfur source denitrifying agent and its preparation and application

Abstract

The present invention discloses a composite biomass carbon source and sulfur source denitrifying agent, as well as its preparation and application. The denitrifying agent comprises a biomass carbon source composed of crude glycerol and growth factors with a COD of 1.1 million to 1.2 million mg / L, and calcium polysulfide, prepared by boiling quicklime, sulfur, and water in a mass ratio of 1:(2-4):(10-12) and a COD of 600,000 to 700,000 mg / L. This denitrifying agent couples heterotrophic denitrification with autotrophic denitrification, combining their respective advantages to achieve efficient denitrification in water pollution control. Under a COD / TN ratio of 1, both the nitrate reduction rate and total nitrogen removal efficiency can reach over 90%. Furthermore, no ammonium nitrogen and nitrite accumulation is observed in the treated water, and sulfate generation is approximately 70 mg / L, both meeting national surface water discharge standards. The composite biomass carbon source and sulfur source denitrifying agent of the present invention is a biodenitrifying material that is non-secondary-pollution, environmentally friendly, low-cost, and easy to prepare.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution prevention and control, and in particular to a composite biomass carbon source and sulfur source denitrifying agent, and a preparation method and application thereof. Background Art

[0002] Nitrate pollution can cause cancer, methemoglobinemia, and malformations, posing significant risks to the ecological environment and biosafety. Therefore, exploring feasible denitrification processes has become an urgent issue in treating nitrogen pollution in water bodies and preventing eutrophication.

[0003] Nowadays, biological denitrification has become the most popular denitrification technology due to its high efficiency and low cost. Depending on the type of electron donor, biological denitrification includes heterotrophic and autotrophic methods. Among them, heterotrophic denitrification requires organic carbon to provide electrons for the reduction of nitrates, and at the same time provide a carbon source for the metabolism of heterotrophic microorganisms. At present, the main carbon sources for enhanced denitrification in sewage and wastewater treatment are small molecule acids, alcohols and low-carbon sugars. Among them, crude glycerol is a by-product of biodiesel production and a high-quality carbon source for denitrification of heterotrophic microorganisms. There are a large number of autotrophic bacteria in the natural environment. If a large amount of carbon source is added, it will lead to the massive reproduction of heterotrophic bacteria and inhibit the denitrification of autotrophic bacteria. If the organic carbon source and inorganic electron donor are combined to strengthen the synergistic effect of autotrophic and heterotrophic bacteria, the remediation cost can be reduced and the denitrification efficiency of sewage can be improved.

[0004] Sulfur-based autotrophic denitrification processes have become the mainstream trend. Currently, the sulfur-based material used is primarily elemental sulfur. However, due to its extremely low water solubility, elemental sulfur has low bioavailability, resulting in low nitrate removal rates, limiting its practical application in denitrification in wastewater treatment plants. Compared to insoluble elemental sulfur, liquid polysulfides have higher COD and bioavailability, making them more readily utilized by autotrophic denitrifying bacteria. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite biomass carbon source and sulfur source denitrifying agent to achieve efficient biological denitrification of wastewater in response to the shortcomings of the above-mentioned technology.

[0006] The denitrifying agent of the present invention is mainly composed of crude glycerol, vitamins, amino acids and polysulfides. Under the condition of low COD / TN, the removal rate of nitrate and total nitrogen is improved to achieve efficient denitrification.

[0007] Specifically, the technical solution of the present invention is as follows: a composite biomass carbon source and sulfur source denitrifier, comprising a biomass carbon source composed of crude glycerol and growth factors with a COD of 1.1 million to 1.2 million mg / L, and calcium polysulfide with a COD of 600,000 to 700,000 mg / L, which is prepared by boiling quicklime, sulfur and water in a mass ratio of 1:(2-4):(10-12), wherein the crude glycerol as the carbon source and the calcium polysulfide as the sulfur source are mixed in a ratio of 1:(1-3) to the COD of the denitrifier.

[0008] Furthermore, the biomass carbon source is composed of 99%-99.5% by mass of crude glycerol and 0.5%-1% by mass of growth factors.

[0009] Preferably, the calcium polysulfide is prepared by boiling quicklime, sulfur and water in a mass ratio of 1:2:10.

[0010] The preparation method of the composite biomass carbon source and sulfur source denitrifying agent of the present invention comprises the following steps:

[0011] 1. Mix 99%-99.5% crude glycerol and 0.5%-1% growth factor to form a biomass carbon source with a COD of 1.1 million to 1.2 million mg / L;

[0012] 2. Add quicklime and sulfur to water in a mass ratio of 1: (2-4): (10-12) to produce calcium polysulfide with a COD of 600,000-700,000 mg / L;

[0013] 3. The crude glycerol as a biomass carbon source and the calcium polysulfide as a sulfur source are mixed in a ratio of 1:(1-3) to the expected COD of the mixed denitrifying agent to prepare a composite biomass carbon source and sulfur source denitrifying agent.

[0014] The growth factors mentioned in step 1 above refer to a class of organic substances that are necessary for regulating the normal growth and metabolism of microorganisms but cannot be synthesized by simple carbon and nitrogen sources, mainly including vitamins, amino acids, purines and pyrimidines, etc. In this article, growth factors mainly refer to amino acids and vitamins.

[0015] The specific operation of step 2 above is as follows: first, add 10-12 parts by weight of water to a crucible, then place 1 part by weight of lime in the crucible and stir until the lime becomes a slurry. Then, dissolve 2-4 parts by weight of sulfur powder in a small amount of water to dilute it into a paste, and slowly pour it into the crucible while stirring. Continue heating and boiling until the color turns dark reddish-brown. After cooling, filter out the residue with gauze to obtain calcium polysulfide.

[0016] Preferably, in step 3, when mixing the biomass carbon source and the calcium polysulfide sulfur source, ultrasonic oscillation at 3 W / mL is used for 20 minutes.

[0017] The beneficial effects of the present invention are as follows: the composite biomass carbon source and sulfur source denitrifying agent of the present invention couples heterotrophic denitrification and autotrophic denitrification, and can achieve efficient denitrification in sewage and wastewater treatment. Under the condition of COD / TN being 1, the nitrate reduction rate and the total nitrogen removal efficiency can both reach more than 90%. In addition, no accumulation of ammonium nitrogen and nitrite was found in the water body, and the sulfate production was about 70 mg / L, both of which have reached the national surface water discharge standard. In addition, compared with other sulfur-based materials, calcium polysulfide has low cost, is easy to prepare, has high bioavailability, and has no secondary pollution to the environment. It is a new type of sulfur-based material that supports autotrophic denitrification. Therefore, the present invention combines a biomass carbon source with a new type of sulfur-based carbon source to form a new type of composite denitrifying material, which is an innovative biological denitrification material. The denitrifying agent is a biological denitrification material that has no secondary pollution, is environmentally friendly, low-cost, and easy to prepare. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The method is to observe the bacterial flocs in the mixed denitrification system driven by the present invention under a microscope.

[0019] Figure 2 This is a bar chart showing the relative abundance of various microbial genus taxonomic levels in different denitrification systems. The horizontal axis represents the sample number, and the vertical axis represents the relative abundance ratio of species. Different fill patterns correspond to the species names at that taxonomic level, and different fill block widths represent the relative abundance ratio of different species. R1 represents a heterotrophic denitrification system driven by a biomass carbon source; R2 represents an autotrophic denitrification system driven by calcium polysulfide; and R3 represents a hybrid denitrification system driven by the present invention. DETAILED DESCRIPTION

[0020] The following is a further detailed description with reference to the embodiments.

[0021] Example 1

[0022] A composite biomass carbon source and sulfur source denitrifier comprises the following components: 0.393 mL of biomass carbon source and 0.687 g of calcium polysulfide. The biomass carbon source is composed of a mixture of 99%-99.5% crude glycerol and 0.5%-1% growth factor. The calcium polysulfide is prepared by first adding 10-12 parts by weight of water to an iron crucible, then adding 1 part by weight of lime to the crucible and stirring until the lime becomes a slurry. Then, a small amount of water is added to dissolve 2 parts by weight of sulfur powder into a paste, which is then slowly poured into the crucible while stirring. Continue heating and boiling until the mixture turns dark reddish-brown. After cooling, filter the residue with gauze to obtain the calcium polysulfide. Finally, the biomass carbon source and calcium polysulfide mixture is placed in a centrifuge tube and homogenized using ultrasonic oscillation at 3 W / mL for 20 minutes.

[0023] Example 2

[0024] A composite biomass carbon source and sulfur source denitrifier comprises the following components: 0.262 mL of biomass carbon source and 0.458 g of calcium polysulfide. The biomass carbon source is composed of a mixture of 99%-99.5% crude glycerol and 0.5%-1% growth factor. The calcium polysulfide is prepared by first adding 10-12 parts by weight of water to an iron crucible, then adding 1 part by weight of lime to the crucible and stirring until the lime becomes a slurry. Then, a small amount of water is added to dissolve 2 parts by weight of sulfur powder into a paste, which is then slowly poured into the crucible while stirring. Continue heating and boiling until the mixture turns dark reddish-brown. After cooling, filter the residue with gauze to obtain the calcium polysulfide. Finally, the biomass carbon source and calcium polysulfide mixture is placed in a centrifuge tube and homogenized using 3W / mL ultrasonic vibration for 20 minutes.

[0025] Example 3

[0026] A composite biomass carbon source and sulfur source denitrifier comprises the following components: 0.131 mL of biomass carbon source and 0.229 g of calcium polysulfide. The biomass carbon source is composed of a mixture of 99%-99.5% crude glycerol and 0.5%-1% growth factor. The calcium polysulfide is prepared by first adding 10-12 parts by weight of water to an iron crucible, then adding 1 part by weight of lime to the crucible and stirring until the lime becomes a slurry. Then, a small amount of water is added to dissolve 2 parts by weight of sulfur powder into a paste, which is then slowly poured into the crucible while stirring. Continue heating and boiling until the mixture turns dark reddish-brown. After cooling, filter the residue with gauze to obtain the calcium polysulfide. Finally, the biomass carbon source and calcium polysulfide mixture is placed in a centrifuge tube and homogenized using ultrasonic oscillation at 3 W / mL for 20 minutes.

[0027] Comparative Example 1

[0028] A calcium polysulfide denitrifier comprises the following components: 1.374 g of calcium polysulfide. The calcium polysulfide preparation process is as follows: First, add 10-12 parts by weight of water to an iron crucible. Then, place 1 part by weight of lime in the crucible and stir until the lime becomes a slurry. Then, dissolve 2 parts by weight of sulfur powder in a small amount of water to dilute it into a paste. Slowly pour the paste into the crucible while stirring. Continue heating and boiling until the color turns dark reddish-brown. After cooling, filter out the residue with gauze to obtain calcium polysulfide.

[0029] Comparative Example 2

[0030] A calcium polysulfide denitrifier comprises the following components: 0.916 g of calcium polysulfide. The calcium polysulfide preparation process is as follows: First, add 10-12 parts by weight of water to an iron crucible. Then, place 1 part by weight of lime in the crucible and stir until the lime becomes a slurry. Then, dissolve 2 parts by weight of sulfur powder in a small amount of water to dilute it into a paste. Slowly pour the paste into the crucible while stirring. Continue heating and boiling until the color turns dark reddish-brown. After cooling, filter out the residue with gauze to obtain calcium polysulfide.

[0031] Comparative Example 3

[0032] A calcium polysulfide denitrifier comprises the following components: 0.458 g of calcium polysulfide. The calcium polysulfide preparation process is as follows: First, add 10-12 parts by weight of water to an iron crucible. Then, place 1 part by weight of lime in the crucible and stir until the lime becomes a slurry. Then, dissolve 2 parts by weight of sulfur powder in a small amount of water to dilute it into a paste. Slowly pour the paste into the crucible while stirring. Continue heating and boiling until the color turns dark reddish-brown. After cooling, filter out the residue with gauze to obtain calcium polysulfide.

[0033] Comparative Example 4

[0034] A biomass carbon source denitrifier comprises the following components: 0.786 mL of a biomass carbon source, wherein the biomass carbon source is a mixture of 99% to 99.5% by mass of crude glycerol and 0.5% to 1% by mass of a growth factor.

[0035] Comparative Example 5

[0036] A biomass carbon source denitrifier comprises the following components: 0.524 mL of a biomass carbon source, wherein the biomass carbon source is a mixture of 99% to 99.5% by mass of crude glycerol and 0.5% to 1% by mass of a growth factor.

[0037] Comparative Example 6

[0038] A biomass carbon source denitrifier comprises the following components: 0.262 mL of a biomass carbon source, wherein the biomass carbon source is a mixture of 99% to 99.5% by mass of crude glycerol and 0.5% to 1% by mass of a growth factor.

[0039] Effect test:

[0040] According to the above examples and comparative examples, various denitrifying agents were prepared and sequentially added into a denitrifying sludge reactor with an effective volume of 5 L. Under the culture conditions of COD / TN of 3, 2, and 1, their nitrate reduction rate and total nitrogen removal rate were tested. The test results are shown in Table 1.

[0041] Table 1

[0042]

[0043] Three reactors, R1, R2, and R3, were set up, wherein R1 was a sludge denitrification reactor using the biomass carbon source as a carbon source; R2 was a sludge denitrification reactor using the calcium polysulfide as a sulfur source; and R3 was a sludge denitrification reactor using the composite biomass carbon source and sulfur-based denitrifying agent of the present invention as a carbon source. As can be seen from the data in Table 1, under the same conditions, the composite biomass carbon source and sulfur-based denitrifying agent of the present invention achieved higher nitrate reduction rates and total nitrogen removal rates, indicating good application prospects.

[0044] Observe the activated sludge in the three reactors, such as Figure 1 shown. Figure 1 A large number of spherical, long rod and irregular shaped flocs can be observed in the liquid. They are very compact and there is a clear boundary between the flocs and the liquid. In addition to the darker aged flocs, a large number of colorless, transparent and compactly structured new flocs can also be observed. They have vigorous growth, strong adsorption and oxidation capabilities, as well as strong regeneration capabilities. It can be seen that the activity of the flocs at this time is better.

[0045] After the experiment, the differences in the sludge microbial communities in the three reactors were analyzed. The results are as follows: Figure 2 shown. Pseudoxanthomonas 、 Thermomonas and Thiobacillus The relative abundances of sulfur-based autotrophic bacteria in reactors R2 and R3 were 6.09%, 6.78%, and 1.84%, and 2.21%, 1.2%, and 0.97%, respectively. These bacteria are autotrophic denitrifiers, indicating that effective autotrophic denitrification occurred in reactors R2 and R3.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art may modify or make equivalent substitutions for the technical solutions of the present invention without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be based on the claims.

Claims

1. A composite biomass carbon source and sulfur source denitrifying agent, comprising a biomass carbon source with a COD of 1.1 million to 1.2 million mg / L composed of crude glycerol and growth factors, and calcium polysulfide with a COD of 600,000 to 700,000 mg / L prepared by boiling quicklime, sulfur, and water in a mass ratio of 1:(2-4):(10-12). The preparation method of the composite biomass carbon source and sulfur source denitrifying agent comprises the following steps: 1) Mixing 99%-99.5% crude glycerol and 0.5%-1% growth factor to form a biomass carbon source with a COD of 1.1 million to 1.2 million mg / L; 2) Boiling quicklime, sulfur, and water in a mass ratio of 1:(2-4):(10-12) to prepare calcium polysulfide with a COD of 600,000 to 700,000 mg / L; 3) Mixing the biomass carbon source and calcium polysulfide, and homogenizing them by ultrasonic oscillation to prepare a composite biomass carbon source and sulfur source denitrifier.

2. The composite biomass carbon source and sulfur source denitrifying agent according to claim 1, characterized in that: The growth factors are amino acids and vitamins.

3. A method for preparing a composite biomass carbon source and sulfur source denitrifying agent, comprising the following steps: 1) Mix 99%-99.5% crude glycerol and 0.5%-1% growth factor to form a biomass carbon source with a COD of 1.1 million to 1.2 million mg / L; 2) Boil quicklime, sulfur and water in a mass ratio of 1:(2-4):(10-12) to produce calcium polysulfide with a COD of 600,000-700,000 mg / L; 3) The biomass carbon source and calcium polysulfide are mixed and homogenized by ultrasonic oscillation to prepare a composite biomass carbon source and sulfur source denitrifying agent.

4. The preparation method according to claim 3, wherein The growth factors in step 1) are amino acids and vitamins.

5. The preparation method according to claim 3, wherein Step 3) When mixing the biomass carbon source and calcium polysulfide, ultrasonic oscillation was performed at 3 W / mL for 20 min.

6. Use of the composite biomass carbon source and sulfur source denitrifying agent according to claim 1 or 2 in wastewater treatment.

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