Efficient sulfur-iron-based autotrophic denitrification and phosphorus removal composite filler and preparation method thereof

Abstract

The application discloses a kind of high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite fillers and its preparation method, its characteristic is that raw material component and the mass percentage of each component are as follows: activated pyrite powder 1%~60%, sulfur 30%~95%, ferric salt 1%~10%, limestone powder 1%~10%.Formed by thermal complex process.The specific steps of preparation are as follows: first, pyrite and magnetic pyrite are activated at high temperature under the protection of protective gas;Sulfur is heated into molten state;Then activated pyrite powder, ferric salt and limestone powder are mixed uniformly to obtain powdery mixture;Then the powdery mixture is added to molten sulfur, the temperature is increased to 125~145 DEG C and mixed uniformly;Finally, the obtained material is cooled and solidified into autotrophic denitrification composite filler.The high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite filler prepared by the application realizes high-efficiency denitrification and phosphorus removal effect by calcining and activating pyrite, using ferric salt as oxidant to promote the decomposition of activated pyrite and improve the release capacity of pyrite electron donor.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing and its preparation method. Technical Background

[0002] With the continuous improvement of urbanization and industrialization, the intensity of pollutant emissions is also constantly increasing. After secondary biological treatment, most pollutants are degraded, but TN and TP are still difficult to remove, affecting the effluent's compliance with discharge standards. Large amounts of nitrogen and phosphorus-containing effluent discharged into receiving water bodies weaken their self-purification capacity, significantly increasing the risk of eutrophication. Therefore, to ensure effluent meets discharge standards, wastewater treatment plants must perform deep nitrogen and phosphorus removal treatment. Currently, deep nitrogen and phosphorus removal of effluent typically employs deep-bed denitrification filters. During operation, organic carbon sources such as sodium acetate and glucose are usually added to increase the C / N ratio and enhance nitrogen removal. However, the addition of external carbon sources increases wastewater treatment costs and sludge production, and precise dosing is difficult, posing a risk of carbon source leakage and excessive COD in the effluent.

[0003] Sulfur autotrophic denitrification technology can effectively replace traditional deep-bed denitrification filters. This technology relies on sulfur autotrophic denitrifying bacteria in an anaerobic environment, utilizing inorganic carbon sources and reduced sulfides as electron donors to reduce nitrogen oxides in the water to nitrogen gas, thus removing total nitrogen. However, using sulfur as an electron donor is problematic because sulfur is expensive and lacks phosphorus removal capabilities. Pyrite, on the other hand, is an inexpensive ore containing sulfur and iron, significantly lower in price than sulfur, greatly reducing the cost of sulfur autotrophic denitrification filter media.

[0004] Chinese patent application CN202210223420.0, filed on July 1, 2022, discloses a method for preparing a sulfur-pyrite composite denitrification packing material. This packing material is composed of sulfur powder, pyrite powder, gelatinized starch, and water. Sulfur powder and pyrite powder serve as electron donors, and gelatinized starch as a binder. The sulfur powder and pyrite powder are fused together through extrusion granulation, achieving in-situ acid-base neutralization and reducing sulfate production in the system. However, due to the unique physicochemical structure of pyrite, directly adding pyrite to this packing material results in slow decomposition and release of pyrite, leading to poor denitrification efficiency and failing to fully realize its effectiveness.

[0005] Chinese patent application CN201911055687.8, filed on January 17, 2020, discloses a wastewater treatment method and apparatus for simultaneously removing ammonia nitrogen, nitrate nitrogen, and phosphate. This method uses sulfur, calcined pyrite, and quinone-modified activated carbon fiber felt as fillers. The calcined pyrite possesses a porous structure, which facilitates microbial attachment, increases the contact area, promotes pyrite dissolution, and releases iron ions to neutralize the acid produced by sulfur oxidation. However, although the release efficiency of calcined pyrite is higher than that of uncalcined pyrite, the overall release efficiency remains low. Furthermore, it is not manufactured into a highly efficient composite filler, making its use inconvenient.

[0006] Therefore, in order to solve the problems of denitrification and phosphorus removal in wastewater treatment, there is a need for a high-efficiency denitrification and phosphorus removal packing material that is self-nutritive, has high denitrification efficiency, also has phosphorus removal function, is inexpensive, and easy to use. Summary of the Invention

[0007] The purpose of this invention is to improve the problems existing in the prior art and to provide a high-efficiency sulfur-iron-based autotrophic denitrification and dephosphorization composite packing. Another purpose of this invention is to provide a method for preparing the above-mentioned high-efficiency sulfur-iron-based autotrophic denitrification and dephosphorization composite packing.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency pyrite-iron-based autotrophic denitrification and dephosphorization composite packing, characterized in that its raw material components and the mass percentage of each component are as follows: activated pyrite powder 1% to 60%, sulfur 30% to 95%, ferric salt 1% to 10%, and limestone powder 1% to 10%.

[0009] The preferred activated pyrite powder is obtained by using pyrite or magnetite as raw material and activating it at a high temperature of 400℃~800℃ for 10min~180min under a protective atmosphere.

[0010] Preferably, the trivalent iron salt is ferric chloride or ferric sulfate.

[0011] This invention also provides a method for preparing the above-mentioned high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite filler, which is formed by cooling and solidification through a thermal composite process. The specific steps are as follows:

[0012] 1) The pyrite or magnetite raw material is subjected to 400℃~800℃ for 10 minutes under a protective atmosphere.

[0013] The pyrite powder was activated at high temperature for 180 minutes and then ground to obtain activated pyrite powder.

[0014] 2) Stir and mix the activated pyrite powder, iron salt and limestone powder evenly to obtain a powdery mixture;

[0015] 3) Heat the sulfur to a molten state;

[0016] 4) Add the powdered mixture to the molten sulfur, raise the temperature to 125℃~145℃, and continue stirring until fully mixed;

[0017] 5) After mixing evenly, use a distributor to drip the mixture into cooling water to cool it into spherical particles, or allow it to cool naturally and then break it into particles to obtain a high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing.

[0018] Preferably, in step 1), the material is ground to 200-800 mesh. The protective atmosphere in step 1) is nitrogen or argon. Preferably, in step 3), the material is heated to 110-125°C.

[0019] In step 5, the obtained solid material is screened through a 3-5 mm sieve to obtain a high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing.

[0020] In this invention, a high-efficiency sulfide-iron-based autotrophic denitrification and phosphorus removal composite packing is applied to the deep denitrification and phosphorus removal of wastewater, rainwater, and other water treatment. Its working principle is as follows: Activation of pyrite increases its specific surface area and weakens the iron-sulfur bond energy; addition of ferric salts promotes the oxidation of ferrous salts and sulfur, thereby promoting the decomposition of pyrite iron sulfide; the activated pyrite and sulfur, among other reducing sulfide, serve as electron donors for autotrophic denitrifying bacteria; simultaneously, the generated ferric salts combine with phosphates to form precipitates, also contributing to phosphorus removal; limestone and other materials provide inorganic carbon as the carbon required for autotrophic denitrification; ultimately achieving the goal of high-efficiency sulfide-iron autotrophic denitrification and phosphorus removal.

[0021] Beneficial effects:

[0022] This invention utilizes activated pyrite powder, sulfur, iron salts, and limestone powder to prepare a highly efficient pyrite-iron-based autotrophic denitrification and phosphorus removal composite packing. It boasts high denitrification and phosphorus removal efficiency, uses readily available and inexpensive raw materials, employs a simple preparation method, and is convenient for filling, transportation, and storage. It can be used for the treatment of various wastewaters contaminated with nitrogen and phosphorus, achieving efficient and safe removal of TN and TP from water. Attached Figure Description

[0023] Figure 1 The denitrification and phosphorus removal efficiencies of Example 1, and the commercially available sulfur-autotrophic denitrification packing A, are compared.

[0024] Figure 2 The denitrification and phosphorus removal efficiencies of Example 2 high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing and commercially available sulfur autotrophic denitrification packing B are compared and contrasted.

[0025] Figure 3The figure shows the denitrification and phosphorus removal efficiencies of the high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing and the commercially available sulfur autotrophic denitrification packing C in Example 3, along with a comparison chart. Detailed Implementation

[0026] The technical solution and implementation effects of the present invention are further described below with reference to specific implementation examples.

[0027] Example 1

[0028] Pyrite particles were heated to 400℃ in a tube furnace under nitrogen protection and held for 180 minutes to obtain activated pyrite. After cooling, the activated pyrite was ground to 200 mesh to obtain activated pyrite powder. 30g of sulfur, 1g of ferric chloride, 60g of activated pyrite powder, and 9g of limestone powder were weighed and mixed evenly. The sulfur was placed in a steel container and heated to 110℃ in an oil bath to melt it. Then, the mixture of activated pyrite powder, ferric chloride, and limestone powder was added, and the temperature was raised to 125℃. The mixture was stirred until homogeneous. Finally, it was dripped into water using a distributor to cool, forming spherical particles of 3–5 mm.

[0029] 4 kg of composite packing material (approximately 2 L in volume) and an appropriate amount of anaerobic sludge were added to a 4 L simulated denitrification filter to treat simulated domestic wastewater with TN (total nitrogen) of 15.0 mg / L and TP (total phosphorus) of 1.0 mg / L. The hydraulic retention time was 30 min. The composite packing material prepared by this method showed the following TN and TP removal efficiency: Figure 1 As shown in the figure. After 7 days, the TN in the filter effluent stabilized at 1.6–2.1 mg / L, with an average removal rate of 86.7%; TP stabilized at 0.11–0.18 mg / L, with an average removal rate of 83%. Similarly, 4 kg of commercially available sulfur-based autotrophic denitrification packing A was tested under the same conditions, and the results are as follows. Figure 1 As shown in the figure, after 7 days, the effluent TN was 4.6–7.9 mg / L, with an average removal rate of 58.3%; TP was 0.95–1.0 mg / L, with an average removal rate of 2.6%. It is evident that the packing material of this invention is significantly superior to commercially available sulfur-autotrophic denitrification packing material in denitrification performance, and also exhibits good phosphorus removal effect.

[0030] Example 2

[0031] An appropriate amount of magnetite particles were placed in a tube furnace and heated to 800℃ under argon protection for 10 minutes to obtain activated magnetite powder. After cooling, the powder was ground to 600 mesh. 95g of sulfur, 3g of ferric chloride, 1g of activated magnetite powder, and 1g of limestone powder were weighed according to the specified ratio. The activated magnetite powder, ferric chloride, and limestone powder were mixed evenly. The sulfur was placed in a steel container and heated to 125℃ in an oil bath to melt it. Then, the mixture of activated magnetite powder, ferric chloride, and limestone powder was added, and the temperature was raised to 145℃. The mixture was stirred and stirred until homogeneous. The mixture was then poured into a tray and allowed to cool naturally before being crushed to form lumps of different sizes. Particles with a diameter of 3–5 mm were screened out.

[0032] Similar to Example 1, 4 kg of the composite packing material prepared above and an appropriate amount of anaerobic sludge were added to a 4 L simulated denitrification filter to treat simulated domestic sewage with TN of 15.0 mg / L and TP of 1.0 mg / L. The hydraulic retention time was 30 min. The composite packing material prepared by this method showed the following TN and TP removal effects: Figure 2 As shown in the figure. After 7 days, the TN in the filter effluent stabilized at 2.3–4.6 mg / L, with an average removal rate of 77.0%; TP stabilized at 0.09–0.16 mg / L, with an average removal rate of 87.0%. Similarly, 4 kg of commercially available sulfur-based autotrophic denitrification packing material B was tested under the same conditions, and the results are as follows. Figure 2 As shown in the figure, after 7 days, the effluent TN was 5.6–8.3 mg / L, with an average removal rate of 51.3%; TP was 0.97–1.0 mg / L, with an average removal rate of 1.7%. It is evident that this packing material is superior to commercially available sulfur-autotrophic denitrification packing material in denitrification performance, and also exhibits good phosphorus removal efficiency.

[0033] Example 3

[0034] Activated pyrite particles were obtained by heating a suitable amount of pyrite granules to 500℃ in a tube furnace under nitrogen protection and holding for 120 minutes. After cooling, the pyrite was ground to 800 mesh to obtain activated pyrite powder. 40g of sulfur, 10g of ferric sulfate, 40g of activated pyrite powder, and 10g of limestone powder were weighed according to the following proportions. The activated pyrite powder, ferric sulfate, and limestone powder were mixed evenly. The sulfur was placed in a steel container and heated to 120℃ in an oil bath to melt it. Then, the mixture of activated pyrite powder, ferric sulfate, and limestone powder was added, and the temperature was raised to 140℃. The mixture was stirred until homogeneous. The mixture was then poured into a tray and allowed to cool naturally before crushing to obtain particles with a diameter of 3–5 mm.

[0035] 4 kg of the composite packing material prepared by the above method and an appropriate amount of anaerobic sludge were added to a 4 L simulated denitrification filter to treat simulated domestic sewage with TN of 15.0 mg / L and TP of 1.0 mg / L. The hydraulic retention time was 30 min. The composite packing material prepared by this method showed the following TN and TP removal efficiency: Figure 3 As shown in the figure. After 7 days, the TN in the filter effluent stabilized at 2.1–5.1 mg / L, with an average removal rate of 76.0%; TP stabilized at 0.05–0.11 mg / L, with an average removal rate of 91.0%. Similarly, 4 kg of commercially available sulfur-based autotrophic denitrification packing material C was tested under the same conditions, and the results are as follows. Figure 3 As shown in the figure, after 7 days, the effluent TN was 6.6–7.1 mg / L, with an average removal rate of 54.2%; TP was 0.96–1.0 mg / L, with an average removal rate of 2.5%. It is evident that the packing material in Experiment 3 is superior to commercially available sulfur-autotrophic denitrification packing material in terms of denitrification performance, and also exhibits good phosphorus removal efficiency.

[0036] The present invention incorporates pyrite, which is cheaper than sulfur, into the packing material, thereby reducing the production cost of autotrophic denitrification packing material.

Claims

1. A high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing, characterized in that... The raw material components and their mass percentages are as follows: activated pyrite powder 1%–60%, sulfur 30%–95%, ferric salt 1%–10%, and limestone powder 1%–10%. It is prepared by the following method, with the specific steps as follows: 1) Pyrite or magnetite raw materials are activated at 400℃~800℃ for 10min~180min under a protective atmosphere and then ground to obtain activated pyrite powder. 2) Stir and mix the activated pyrite powder, ferric salt and limestone powder evenly to obtain a powdery mixture; 3) Heat the sulfur to a molten state; 4) Add the powdered mixture to the molten sulfur, raise the temperature to 125℃~145℃, and continue stirring until fully mixed; 5) After mixing evenly, use a distributor to drip the mixture into cooling water to cool it into spherical particles, or allow it to cool naturally and then break it into particles to obtain a high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing.

2. The high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing material according to claim 1, characterized in that... The ferric salt is ferric chloride or ferric sulfate.

3. The high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing material according to claim 1, characterized in that... Grind to 200-800 mesh in step 1).

4. The high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing material according to claim 1, characterized in that... In step 1), the protective atmosphere is nitrogen or argon.

5. The high-efficiency sulfur-iron-based autotrophic denitrification and phosphorus removal composite packing material according to claim 4, characterized in that... In step 3), heat to 110℃~125℃.

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