Slow-release composite sulfur autotrophic denitrification filler, preparation method and application

Abstract

The application belongs to the technical field of sewage treatment and specifically relates to a slow-release type composite sulfur autotrophic denitrification filler, a preparation method and application, which comprises the following components in parts by weight: 4-6 parts of sulfur powder, 1-3 parts of ferrous sulfide, 1-3 parts of a pH buffer, 0.5-1.5 parts of bentonite, 0.5-1.5 parts of starch and 0.5-1.5 parts of an adhesive. The application improves the denitrification effect, makes the pH value of effluent water more neutral, reduces the filler loss and reduces the cost.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a slow-release composite sulfur autotrophic denitrification packing, its preparation method, and its application. Background Technology

[0002] With increasingly stringent national environmental protection policies, stricter standards for municipal wastewater discharge are inevitable, leading to a growing demand for advanced nitrogen removal in effluent. In biological denitrification, heterotrophic denitrification requires a large amount of carbon source to achieve optimal nitrogen removal. However, typical municipal wastewater treatment plants have limited carbon sources available for denitrification in their secondary effluent, necessitating the addition of large amounts of carbon to meet reaction conditions, resulting in excessively high operating costs. This necessitates the use of sulfur autotrophic denitrification processes to treat total nitrogen. However, commercially available sulfur autotrophic denitrification packing materials suffer from poor nitrogen removal efficiency, severe packing material loss, poor system pH buffering capacity, and high costs.

[0003] Patent application publication number CN115028261A discloses a sulfur autotrophic denitrification packing and its preparation method. The sulfur autotrophic denitrification packing comprises the following components in parts by weight: 50-100 parts of sulfur powder, 1-10 parts of alkaline reducing agent, 10-40 parts of pH buffer, 10-50 parts of kaolin, and 10-20 parts of binder; wherein the alkaline reducing agent is sulfite or bisulfite. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a slow-release composite sulfur autotrophic denitrification packing, its preparation method and application, which improves the denitrification effect, makes the pH value of the effluent more neutral, reduces packing loss and lowers costs.

[0005] This invention provides a slow-release composite sulfur autotrophic denitrification packing material, comprising the following components in parts by weight: 4-6 parts sulfur powder, 1-3 parts ferrous sulfide, 1-3 parts pH buffer, 0.5-1.5 parts bentonite, 0.5-1.5 parts starch, and 0.5-1.5 parts adhesive.

[0006] Preferably, the composition includes the following components in parts by weight: 4 parts sulfur powder, 1 part ferrous sulfide, 2 parts pH buffer, 1 part bentonite, 1 part starch, and 1 part adhesive.

[0007] Preferably, the sulfur powder has a particle size of 150-200 mesh.

[0008] Preferably, the pH buffer is a composite calcium carbonate, which comprises the following components by weight percentage: 45-55% light calcium carbonate, 35-45% nano calcium carbonate, and 5-15% sodium chlorate (preferably 50% light calcium carbonate, 40% nano calcium carbonate, and 10% sodium chlorate). The composite calcium carbonate effectively solves the problem of significant pH drop in the system during sulfur autotrophic denitrification.

[0009] Preferably, the bentonite is one or more of sodium-based bentonite, calcium-based bentonite, and magnesium-based bentonite. Bentonite can regulate the pH of the system during sulfur autotrophic denitrification and simultaneously improve the strength of the packing material.

[0010] Preferably, the starch is corn starch.

[0011] Preferably, the adhesive is one or more of styrene and butyl acrylate.

[0012] Preferably, the slow-release composite sulfur autotrophic denitrification packing has a particle size of 8-10 mm and a bulk density of 1.13~1.28 g / cm³. 3 .

[0013] This invention provides a method for preparing the slow-release composite sulfur autotrophic denitrification packing material. Sulfur powder, ferrous sulfide, pH buffer, bentonite and starch are mixed and granulated. During the granulation process, an adhesive is sprayed. After granulation, the mixture is dried, cooled and sieved to obtain the slow-release composite sulfur autotrophic denitrification packing material.

[0014] The specific preparation method is as follows: sulfur powder, ferrous sulfide, pH buffer, bentonite, and starch are sieved. The sieved raw materials are mixed in proportion using a mixer for 20 minutes. The mixed raw materials are then slowly added to a disc granulator. Adhesive and water are mixed at a volume ratio of 1:2~4. The mixture is then evenly sprayed into the disc granulator while feeding the material and spraying adhesive dilution. After granulation, the spraying of adhesive dilution is stopped, and the packing continues to roll in the disc granulator for 5~10 minutes. After rolling, the packing is heated and dried at a temperature of 70~95℃. After drying, the packing is cooled and sieved to obtain the slow-release composite sulfur autotrophic denitrification packing.

[0015] This invention provides an application of the slow-release composite sulfur autotrophic denitrification packing material, which is used for wastewater treatment.

[0016] The beneficial effects of this invention are as follows: It uses composite calcium carbonate as a buffer, which effectively solves the problem of significant pH drop in the system during sulfur autotrophic denitrification. It uses one or more of sodium-based bentonite, calcium-based bentonite, and magnesium-based bentonite, which can regulate the pH of the system during sulfur autotrophic denitrification and improve the strength of the packing material. In this invention, the adhesive and water are mixed at a volume ratio of 1:2-4, which prevents clogging of the disc granulator spraying device and promotes higher packing strength and better slow-release effect. This invention uses a disc granulator for granulation, which does not produce toxic or harmful gases during the granulation process, is easy to operate, easy to form, and has low production costs.

[0017] The sulfur-autotrophic denitrification packing material prepared in this invention is a slow-release denitrification packing material. It uses sulfur in the packing material as an electron donor to reduce nitrate nitrogen in the water to N2, thereby achieving the purpose of water purification. This packing material has a high nitrate nitrogen removal efficiency, reaching over 96%, excellent slow-release effect, requires no additional carbon source or pH adjustment, has high packing strength, and requires infrequent replenishment, greatly saving wastewater treatment costs.

[0018] This invention uses ferrous sulfide as a reducing agent and composite calcium carbonate as a pH buffer. It also includes corn starch and styrene, which significantly improves the removal rate of nitrate nitrogen, keeps the pH of the effluent closer to neutral, and increases the strength of the packing material, resulting in less packing material loss. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments:

[0020] This invention provides a deep denitrification packing material and its preparation method to solve the problems of poor denitrification effect, severe packing material loss, poor system pH buffering effect, and high cost. The technical solutions in the embodiments of this invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Example 1

[0022] A method for preparing a slow-release composite sulfur autotrophic denitrification packing includes the following steps:

[0023] First, sulfur powder with a particle size of 200 mesh, ferrous sulfide, composite calcium carbonate (including the following components by weight percentage: 50% light calcium carbonate, 40% nano calcium carbonate, and 10% sodium chlorate), sodium bentonite powder, and corn starch are screened and filtered. The filtered raw materials are mixed in a mixer at a mass ratio of 4:1:2:1:1 for 20 minutes. The mixed raw materials are then slowly added to a disc granulator. Styrene (styrene and corn starch by weight ratio of 1:1) and water are mixed at a volume ratio of 1:4. The mixture is then evenly sprayed into the disc granulator while feeding the material and spraying adhesive diluent for granulation. After granulation, the spraying of adhesive diluent is stopped, and the filler continues to roll in the disc granulator for 10 minutes. After rolling, the material is heated and dried at 75°C. After drying, the material is cooled and screened to obtain the final product.

[0024] Example 2

[0025] A method for preparing a slow-release composite sulfur autotrophic denitrification packing includes the following steps:

[0026] First, sulfur powder with a particle size of 200 mesh, ferrous sulfide, composite calcium carbonate (including the following components by weight percentage: 50% light calcium carbonate, 40% nano calcium carbonate, and 10% sodium chlorate), calcium-based bentonite powder, and corn starch are screened and filtered. The filtered raw materials are mixed in a mass ratio of 5:3:1:1.5:0.5 using a mixer for 30 minutes. The mixed raw materials are then slowly added to a disc granulator. Butyl acrylate (butyl acrylate and corn starch by weight ratio of 1:1) and water are mixed in a volume ratio of 1:4. The mixture is then evenly sprayed into the disc granulator while feeding the material and spraying adhesive diluent for granulation. After granulation, the spraying of adhesive diluent is stopped, and the filler continues to roll in the disc granulator for 10 minutes. After rolling, the material is heated and dried at 90°C. After drying, the material is cooled and screened to obtain the final product.

[0027] Comparative Example 1

[0028] Compared with Example 1, the difference is that ferrous sulfide is replaced with sodium sulfite, and everything else is the same as Example 1.

[0029] Comparative Example 2

[0030] Compared with Example 1, the difference is that the compound calcium carbonate is replaced with sodium carbonate, and everything else is the same as Example 1.

[0031] Comparative Example 3

[0032] Compared with Example 1, the difference is that corn starch is replaced with kaolin, otherwise it is the same as Example 1.

[0033] Comparative Example 4

[0034] Compared with Example 1, the difference is that styrene is replaced with carboxymethyl cellulose, otherwise it is the same as Example 1.

[0035] Example 3

[0036] One kg of each of the slow-release composite sulfur autotrophic denitrification packing prepared in Examples 1-2 and Comparative Examples 1-4 was used to conduct a comparative experiment on sulfur autotrophic denitrification, and the denitrification effect, pH buffering effect, and packing strength change were compared and analyzed.

[0037] Experimental content: The experimental water sample was the effluent from the secondary sedimentation tank of a municipal sewage treatment plant, with a nitrate nitrogen concentration of 10~15 mg / L and a pH of 6.85~7.0.

[0038] One kg of the prepared slow-release composite sulfur autotrophic denitrification packing material from each example was placed in a denitrification column as the experimental group, and one kg of the prepared slow-release composite sulfur autotrophic denitrification packing material from each comparative example was placed in a denitrification column as the control group. 20 mL of activated sludge from the aeration tank was added to each denitrification column, and then wastewater from the secondary sedimentation tank was introduced for circulating biofilm cultivation. The water temperature was controlled at 25℃. After three days, a continuous influent and effluent experiment was started, with a hRT of 0.5 h. After three days of biofilm cultivation, the nitrate nitrogen concentration was measured daily. The results of the continuous influent and effluent experiment are shown in Tables 1-3.

[0039] Table 1. Nitrate removal status

[0040]

[0041] Table 2. pH changes of influent and effluent

[0042]

[0043] Table 3. Changes in the compressive strength of the packing cylinder

[0044]

[0045] Experimental results showed that the average removal rates of nitrate nitrogen in Examples 1 and 2 were 96% and 97%, respectively, while in the control group, the average removal rates of nitrate nitrogen in Comparative Examples 1-4 were 67%, 77%, 72%, and 81%, respectively.

[0046] The average nitrate removal rate is calculated as the average nitrate removal rate over days 1-5. The nitrate removal rate is calculated as: nitrate removed / influent nitrate on that day. For example, the nitrate removal rate on the first day is (13.4-0.6) / 13.4*100%=96%.

[0047] The pH of the effluent from the experimental group remained stable at around 6.8, while the pH of the effluent from the control group fluctuated significantly. The average pH of the effluent from the control groups (1-4) was between 6.1 and 6.7.

[0048] After the experiment, the strength of the two packing materials was tested. Five packing particles were randomly selected from each group for strength testing, and the test results were calculated as the average value. The test results showed that the average cylinder compressive strength of Examples 1 and 2 was 6.97 MPa, respectively. In the control group, the average cylinder compressive strength of Comparative Examples 1-4 were 6.97 MPa, 6.87 MPa, 6.66 MPa, 5.49 MPa, and 4.51 MPa, respectively. It can be seen that the prepared slow-release composite sulfur autotrophic denitrification packing material has significantly better denitrification effect, pH buffering capacity, and packing strength than the comparative sulfur autotrophic denitrification packing material.

[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0050] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A slow-release composite sulfur autotrophic denitrification packing material, characterized in that it comprises: The following components are in parts by weight: 4-6 parts sulfur powder, 1-3 parts ferrous sulfide, 1-3 parts pH buffer, 0.5-1.5 parts bentonite, 0.5-1.5 parts starch, and 0.5-1.5 parts adhesive. The pH buffer is a composite calcium carbonate, which comprises the following components by weight percentage: 45-55% light calcium carbonate, 35-45% nano calcium carbonate, and 5-15% sodium chlorate. The adhesive is one or more of styrene and butyl acrylate.

2. The slow-release composite sulfur autotrophic denitrification packing material as described in claim 1, characterized in that it comprises: The following components are in parts by weight: 4 parts sulfur powder, 1 part ferrous sulfide, 2 parts pH buffer, 1 part bentonite, 1 part starch, and 1 part adhesive.

3. The slow-release composite sulfur autotrophic denitrification packing material as described in claim 1 or 2, characterized in that, The sulfur powder has a particle size of 150-200 mesh.

4. The slow-release composite sulfur autotrophic denitrification packing material as described in claim 1 or 2, characterized in that, The bentonite is one or more of sodium-based bentonite, calcium-based bentonite, and magnesium-based bentonite.

5. The slow-release composite sulfur autotrophic denitrification packing material as described in claim 1 or 2, characterized in that, The starch is corn starch.

6. The slow-release composite sulfur autotrophic denitrification packing material as described in claim 1 or 2, characterized in that, The slow-release composite sulfur autotrophic denitrification packing has a particle size of 8-10 mm and a bulk density of 1.13~1.28 g / cm³. 3 .

7. A method for preparing a slow-release composite sulfur autotrophic denitrification packing material as described in any one of claims 1-6, characterized in that, Sulfur powder, ferrous sulfide, pH buffer, bentonite and starch are mixed and granulated. Adhesive is sprayed during the granulation process. After granulation, the mixture is dried, cooled and sieved to obtain a slow-release composite sulfur autotrophic denitrification packing.

8. The application of a slow-release composite sulfur autotrophic denitrification packing material as described in any one of claims 1-6, characterized in that, The slow-release composite sulfur autotrophic denitrification packing is used for wastewater treatment.

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