High-efficiency sulfur-iron-based nitrogen and phosphorus removal composite filler by autotrophic denitrification and preparation method of high-efficiency sulfur-iron-based nitrogen and phosphorus removal composite filler

Abstract

The invention discloses a high-efficiency sulfur-iron-based nitrogen and phosphorus removal and autotrophic denitrification composite filler and a preparation method thereof. The high-efficiency sulfur-iron-based nitrogen and phosphorus removal and autotrophic denitrification composite filler is characterized by comprising the following raw material components in percentage by mass: 1-60% of activated pyrite powder, 30-95% of sulfur, 1-10% of trivalent iron salt and 1-10% of limestone powder. And forming through a thermal compounding process. The preparation method comprises the following specific steps: firstly, activating the pyrite and the magnetic pyrite at high temperature under the protection of protective gas; sulfur is heated to be in a molten state; uniformly mixing the activated pyrite powder, trivalent iron salt and limestone powder to obtain a powdery mixed material; adding the powdery mixed material into molten sulfur, raising the temperature to 125-145 DEG C, and fully and uniformly mixing; and finally, cooling and curing the obtained material to obtain the autotrophic denitrification composite filler. According to the high-efficiency sulfur-iron-based autotrophic denitrification nitrogen and phosphorus removal composite filler prepared by the preparation method, pyrite is calcined and activated, ferric iron salt is used as an oxidizing agent to promote decomposition of the activated pyrite, and the electron donor release capability of the pyrite is improved, so that the high-efficiency nitrogen and phosphorus removal effect of the filler is realized.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a high-efficiency ferrous sulfide-based autotrophic denitrification and dephosphorization composite filler and a preparation method thereof. Technical Background

[0002] With the continuous improvement of urbanization and industrialization levels, the intensity of pollutant emissions has also been increasing. After secondary biochemical treatment, most pollutants will be degraded, but TN and TP are still difficult to remove, which affects the effluent discharge standards. A large amount of nitrogen and phosphorus-containing tailwater discharged into the receiving water body will weaken the self-purification capacity of the receiving water body and greatly increase the risk of eutrophication of the water body. Therefore, in order for the tailwater of the sewage treatment plant to meet the discharge standards, the tailwater must be deeply denitrified and dephosphorized. At present, deep denitrification and phosphorus removal of tailwater usually adopts deep bed denitrification filter process. During operation, it is usually necessary to add organic carbon sources such as sodium acetate and glucose to increase the C / N ratio and enhance denitrification. However, the addition of external carbon sources increases the cost of sewage treatment and sludge production, and it is difficult to accurately add carbon sources, which may cause carbon source leakage and lead to the risk of effluent COD exceeding the standard.

[0003] Sulfur autotrophic denitrification technology can be a good alternative to traditional deep bed denitrification filters. Sulfur autotrophic denitrification technology relies on sulfur autotrophic denitrifying bacteria to use inorganic carbon sources in an anaerobic state, using reduced sulfide as an electron donor to reduce nitrogen oxides in the water body as an electron acceptor to nitrogen gas to achieve the purpose of removing total nitrogen. However, sulfur is used as an electron donor, but sulfur has the disadvantages of high price and no phosphorus removal function. Pyrite is a cheap ore containing sulfur and iron elements, and its price is much lower than sulfur, which greatly reduces the cost of sulfur autotrophic denitrification fillers.

[0004] The Chinese patent application document with the application number CN202210223420.0 and the application date of July 1, 2022 discloses a method for preparing a sulfur-pyrite composite denitrification filler, which is a mixture of sulfur powder, pyrite powder, gelatinized starch and water. The sulfur powder and pyrite powder are used as electron donors and gelatinized starch is used as a binder. The sulfur powder and pyrite powder are fused together by extrusion granulation, achieving in-situ acid-base neutralization and reducing the sulfate production in the system. However, due to the special physical and chemical structure of pyrite, directly adding pyrite to the filler results in the slow decomposition and release of pyrite, resulting in poor denitrification efficiency and failure to fully exert its effectiveness.

[0005] Chinese patent application number CN201911055687.8, with an application date of January 17, 2020, discloses a wastewater treatment method and device for simultaneously removing ammonia nitrogen, nitric nitrogen and phosphate. The method uses sulfur, calcined pyrite and quinone mediator modified activated carbon fiber felt as fillers. After calcination, the pyrite has a porous loose structure, which is conducive to the attachment of microorganisms, increases the contact area, promotes the dissolution of pyrite, and releases iron ions to neutralize the acid produced by sulfur oxidation. However, although the release efficiency of pyrite after calcination is higher than that of uncalcined pyrite, the release efficiency is still very low. On the other hand, it has not been made into an efficient treatment composite filler, which is very inconvenient to use.

[0006] Therefore, in order to solve the problems of denitrification and dephosphorization of sewage and wastewater in the field of water treatment, a filler for efficient denitrification and dephosphorization with high autotrophic denitrification efficiency, phosphorus removal function, low price and easy use is needed. Summary of the invention

[0007] The purpose of the present invention is to improve the problems existing in the prior art and to provide a high-efficiency sulfide-iron-based autotrophic denitrification and phosphorus removal composite filler. Another purpose of the present invention is to provide a method for preparing the above-mentioned high-efficiency sulfide-iron-based autotrophic denitrification and phosphorus removal composite filler.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a high-efficiency pyrite-based autotrophic denitrification and phosphorus removal composite filler, characterized in that its raw material components and the mass percentage of each component are: activated pyrite powder 1% to 60%, sulfur 30% to 95%, trivalent iron salt 1% to 10%, and limestone powder 1% to 10%.

[0009] Preferably, the activated pyrite powder is obtained by using pyrite or pyrite as raw material and undergoing high temperature activation at 400° C. to 800° C. for 10 min to 180 min under a protective atmosphere.

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

[0011] The present invention also provides a method for preparing the above-mentioned high-efficiency ferrous sulfur-based autotrophic denitrification and dephosphorization composite filler, which is formed by cooling and solidifying through a thermal composite process, and the specific steps are as follows:

[0012] 1) Heat the pyrite or magnetic pyrite raw material at 400℃~800℃ for 10min~

[0013] Activate at high temperature for 180 minutes and grind to obtain activated pyrite powder;

[0014] 2) stirring and mixing the activated pyrite powder, iron salt and limestone powder to obtain a powdery mixed material;

[0015] 3) heating sulfur to a molten state;

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

[0017] 5) After uniform mixing, the mixture is dripped into cooling water with a distributor to be cooled into spherical particles, or is naturally cooled and crushed into particles to obtain a highly efficient sulfur-iron based autotrophic denitrification and dephosphorization composite filler.

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

[0019] In step 5, the obtained solid matter is screened through a 3-5 mm sieve to obtain a high-efficiency ferrous-sulfur-based autotrophic denitrification and dephosphorization composite filler.

[0020] In the present invention, a high-efficiency ferrous sulfide-based autotrophic denitrification and denitrification and phosphorus removal composite filler is applied to deep denitrification and phosphorus removal in sewage, rainwater and other water treatments, and its working principle is as follows: pyrite is activated to increase its specific surface area and weaken the iron-sulfur bonding energy; trivalent iron salt is added to promote the oxidation of divalent iron salt and sulfur, thereby promoting the decomposition of pyrite iron sulfide; activated pyrite, sulfur and other reducing ferrous sulfides are used as electron donors for denitrification by autotrophic denitrifying bacteria; the trivalent iron salt produced at the same time combines with phosphate to form a precipitate that also takes into account the phosphorus removal function; limestone and the like provide inorganic carbon as the carbon required for autotrophic denitrification; and finally the purpose of high-efficiency ferrous sulfide autotrophic denitrification and phosphorus removal is achieved.

[0021] Beneficial effects:

[0022] The invention uses activated pyrite powder, sulfur, iron salt and limestone powder to prepare a high-efficiency pyrite-based autotrophic denitrification and denitrification and phosphorus removal composite filler with high denitrification and phosphorus removal efficiency, cheap and readily available raw materials, simple preparation method, convenient loading, transportation and storage. It can be used to treat various sewage and wastewater contaminated by nitrogen and phosphorus to achieve the purpose of efficiently and safely removing TN and TP in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The denitrification and phosphorus removal efficiencies and comparison diagram of the highly efficient sulfur-iron-based autotrophic denitrification and phosphorus removal composite filler of Example 1 and the commercially available sulfur autotrophic denitrification filler A;

[0024] Figure 2 The denitrification and phosphorus removal efficiencies and comparison diagram of the highly efficient sulfur-iron-based autotrophic denitrification and phosphorus removal composite filler of Example 2 and the commercially available sulfur autotrophic denitrification filler B;

[0025] Figure 3The denitrification and phosphorus removal efficiencies and comparison diagram of the highly efficient sulfur-iron-based autotrophic denitrification and phosphorus removal composite filler of Example 3 and the commercially available sulfur autotrophic denitrification filler C are shown. DETAILED DESCRIPTION

[0026] The technical solution and implementation effects of the present invention are further described below in conjunction with specific implementation cases.

[0027] Example 1

[0028] The pyrite particles are heated to 400°C in a tubular furnace under nitrogen protection and maintained for 180 minutes to obtain activated pyrite, which is then ground to 200 mesh after cooling to obtain activated pyrite powder. Weigh 30g of sulfur, 1g of ferric chloride, 60g of activated pyrite powder and 9g of limestone powder; mix the activated pyrite powder, ferric chloride and limestone powder evenly. Put the sulfur in a steel container and heat it to 110°C in an oil bath to melt it; then add the mixture of activated pyrite powder, ferric chloride and limestone powder, raise the temperature to 125°C; stir to mix evenly. Finally, use a distributor to drop it into water to cool it down to form spherical particles of 3 to 5 mm.

[0029] Take 4kg of composite filler (about 2L volume) and appropriate amount of anaerobic sludge and add them into a simulated denitrification filter with a volume of 4L to treat simulated domestic sewage with TN of 15.0mg / L and TP of 1.0mg / L. The hydraulic retention time is 30min. The removal effect of composite filler on TN and TP prepared by this method is as follows Figure 1 After 7 days, the TN of the filter effluent was stable at 1.6-2.1 mg / L, with an average removal rate of 86.7%; TP was stable at 0.11-0.18 mg / L, with an average removal rate of 83%. Similarly, 4 kg of commercially available sulfur autotrophic denitrification filler A was tested under the same conditions. The results are as follows Figure 1 As shown. After 7 days, the TN of the effluent was 4.6-7.9 mg / L, with an average removal rate of 58.3%; the TP was 0.95-1.0 mg / L, with an average removal rate of 2.6%. It can be seen that the filler of the present invention is significantly better than the commercially available sulfur autotrophic denitrification filler in terms of denitrification and denitrification performance, and also has a good phosphorus removal effect.

[0030] Example 2

[0031] Place an appropriate amount of magnetite particles in a tube furnace and heat to 800℃ under argon protection for 10 minutes to obtain activated magnetite powder. After cooling, grind to 600 mesh to obtain activated magnetite powder. Weigh 95g sulfur, 3g ferric chloride, 1g activated magnetite powder, and 1g limestone powder in proportion; mix the activated magnetite powder, ferric chloride and limestone powder evenly. Place sulfur in a steel container and heat the sulfur to 125℃ in an oil bath to melt the sulfur; then add the mixture of activated magnetite powder, ferric chloride and limestone powder, raise the temperature to 145℃; stir to mix evenly. Then pour it into a tray and cool it naturally and break it to form block particles with different particle sizes, and screen out particles with a particle size of 3 to 5mm.

[0032] Same as Example 1, 4 kg of the composite filler prepared above and an appropriate amount of anaerobic sludge were added to a simulated denitrification filter with a volume of 4 L to treat simulated domestic sewage with a TN content of 15.0 mg / L and a TP content of 1.0 mg / L. The hydraulic retention time was 30 min. The removal effect of the composite filler prepared by this method on TN and TP was as follows: Figure 2 After 7 days, the TN of the filter effluent was stable at 2.3-4.6 mg / L, with an average removal rate of 77.0%; TP was stable at 0.09-0.16 mg / L, with an average removal rate of 87.0%. Similarly, 4 kg of commercially available sulfur autotrophic denitrification filler B was tested under the same conditions. The results are as follows Figure 2 As shown. 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 can be seen that the filler is also superior to the commercially available sulfur autotrophic denitrification filler in terms of denitrification and nitrogen removal performance, and also has a good phosphorus removal effect.

[0033] Example 3

[0034] Heat an appropriate amount of pyrite particles to 500°C in a tubular furnace under nitrogen protection and keep it for 120 minutes to obtain activated pyrite. After cooling, grind it to 800 mesh to obtain activated pyrite powder. Weigh 40g sulfur, 10g ferric sulfate, 40g activated pyrite powder, and 10g limestone powder in proportion; mix the activated pyrite powder, ferric sulfate, and limestone powder evenly. Put the sulfur in a steel container and heat it to 120°C in an oil bath to melt the sulfur; then add the mixture of activated pyrite powder, ferric sulfate, and limestone powder, raise the temperature to 140°C; stir to mix it evenly. Then pour it into a tray and cool it naturally and break it to obtain particles with a particle size of 3 to 5 mm.

[0035] 4 kg of the composite filler prepared by the above method and an appropriate amount of anaerobic sludge were added to a simulated denitrification filter with a volume of 4 L to treat simulated domestic sewage with a TN content of 15.0 mg / L and a TP content of 1.0 mg / L. The hydraulic retention time was 30 min. The removal effect of the composite filler prepared by this method on TN and TP was as follows: Figure 3 After 7 days, the TN of the filter effluent was stable at 2.1-5.1 mg / L, with an average removal rate of 76.0%; TP was stable at 0.05-0.11 mg / L, with an average removal rate of 91.0%. Similarly, 4 kg of commercially available sulfur autotrophic denitrification filler C was tested under the same conditions. The results are as follows Figure 3 As shown. 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 can be seen that the filler in Experiment 3 is also better than the commercially available sulfur autotrophic denitrification filler in terms of denitrification and nitrogen removal performance, and also has a good phosphorus removal effect.

[0036] Pyrite, which is cheaper than sulfur, is added to the filler of the present invention, thereby reducing the production cost of the autotrophic denitrification filler.

Claims

1. A highly efficient sulfur-iron-based autotrophic denitrification and dephosphorization composite filler, characterized in that The raw material components and the mass percentage of each component are: 1% to 60% of activated pyrite powder, 30% to 95% of sulfur, 1% to 10% of trivalent iron salt, and 1% to 10% of limestone powder.

2. The high-efficiency iron-sulfur-based autotrophic denitrification and dephosphorization composite filler according to claim 1, characterized in that The activated pyrite powder is obtained by taking pyrite or magnetic pyrite as raw material and undergoing high temperature activation at 400° C. to 800° C. for 10 min to 180 min under a protective atmosphere.

3. The high-efficiency ferrous sulfur-based autotrophic denitrification and dephosphorization composite filler according to claim 1, characterized in that The trivalent iron salt is ferric chloride or ferric sulfate.

4. A method for preparing the high-efficiency ferrous sulfur-based autotrophic denitrification and dephosphorization composite filler as claimed in claim 1, wherein the specific steps are as follows: 1) Activate the pyrite or magnetic pyrite raw material at 400° C. to 800° C. for 10 min to 180 min under a protective atmosphere, and grind to obtain activated pyrite powder; 2) stirring and mixing the activated pyrite powder, iron salt and limestone powder to obtain a powdery mixed material; 3) heating sulfur to a molten state; 4) Add the powdered mixture into the molten sulfur, raise the temperature to 125°C to 145°C, and continue stirring until fully mixed; 5) After uniform mixing, the mixture is dripped into cooling water with a distributor to be cooled into spherical particles, or is naturally cooled and crushed into particles to obtain a highly efficient sulfur-iron based autotrophic denitrification and dephosphorization composite filler.

5. The method according to claim 4, characterized in that In step 1), the powder is ground to 200-800 mesh.

6. The method according to claim 4, characterized in that In step 1), the protective atmosphere is nitrogen or argon.

7. The method according to claim 4, characterized in that In step 3), the mixture is heated to 110°C to 125°C.

Images