A method for preparing autotrophic denitrification packing and its application

Abstract

This invention discloses a method for preparing an autotrophic denitrification packing material, specifically: 0.3–1.2 parts by weight of dolomite powder, 90–95 parts by weight of modified sulfur powder, 0.5–1.5 parts by weight of iron powder, 1–2 parts by weight of ferrous carbonate powder, 0.5–2 parts by weight of sodium bicarbonate, 0.5–1.5 parts by weight of kaolin, 0.5–1.2 parts by weight of straw powder, and 0.5–1 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. A liquid bio-enhancing agent is then sprayed into the disc granulator. Upon contact with the liquid, the solid powder in the disc granulator gradually forms spherical particles under the tilting and stirring action of the granulator. This invention also discloses the application of the autotrophic denitrification packing material prepared by the above method in the treatment of wastewater from an electronics industrial park.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of autotrophic denitrification filler, and also relates to the application of the autotrophic denitrification filler prepared by the method in treating tail water of an electronic industrial park. BACKGROUND

[0002] Since the 21st century, with the continuous improvement of the industrial degree in China, the scale and the number of the development of the domestic electronic industrial park have shown a gradual upward trend, and the deep treatment and reuse of the industrial park wastewater have been increasingly valued. At present, the discharge standard of the sewage treatment plant is gradually improved by the country, and more and more industrial park sewage treatment plants and municipal sewage treatment plants have raised the discharge standard to the first A standard or higher standard from the second standard and the first B standard in the “Urban Sewage Treatment Plant Pollutant Discharge Standard” GB18918-2002.

[0003] Taking the first A standard as an example, the effluent TN is required to be lower than 15 mg / L, and the discharge standard of the industrial park and municipal wastewater in some areas has required TN ≤ 10 or 5 mg / L. At present, the biological method mainly using A 2 O + denitrification filter is usually used to remove total nitrogen. Due to the low carbon-nitrogen ratio of the electronic industrial park wastewater, a large amount of organic carbon source such as sodium acetate needs to be added in the traditional heterotrophic denitrification, which not only increases the cost of reagent, but also increases the risk of exceeding the standard of effluent COD due to carbon source breakthrough. Autotrophic denitrification has the advantages of no need to add organic carbon source, low sludge yield and low operation cost, and is widely studied in the field of deep denitrification. Sulfur autotrophic denitrification process is a process of using reducing sulfur substances (such as S, S 2- , S2O3 2- ) as electron donor to convert nitrate nitrogen or nitrite nitrogen into nitrogen gas under anoxic or anaerobic conditions. In the reaction process, no organic carbon source needs to be added, but acid will be produced in the reaction process, which makes the pH of the denitrification filler gradually decrease along the way, causing the inhibition of microbial activity on the surface of the denitrification filler in the later stage, and finally leading to the decrease of denitrification efficiency (1.1S + 1.0NO3 - + 0.76H2O + 0.4CO2 + 0.08NH4 + → 0.08C5H7O2N + 0.5N2 + 1.1SO4 2- + 1.28H + ). In addition, the high content of sulfate in the effluent of the sulfur autotrophic denitrification will cause the pollution of water body by sulfate (secondary pollution). Iron autotrophic denitrification bacteria are also a group of microorganisms that can use nitrate as electron acceptor and elemental iron or various forms of Fe 2+ compound as electron donor, but alkalinity will be produced in the denitrification process. In addition to the high pH of the effluent, the produced Fe 2+ , Fe 3+ will react with OH -Combining, and further making the filler surface scale passivation, affecting the denitrification operation effect (5Fe + 2NO3 - + 6H2O→N2+5Fe 2+ + 12OH - , 10Fe 2+ + 2NO3 - + 6H2O→N2+10Fe 3+ + 12OH - ). Hydrogen autotrophic denitrification does not produce any by-products affecting water quality safety, and is a clean wastewater denitrification method (5H2 + 2NO3 - → N2 + 4H2O + 2OH - ), but exogenous hydrogen has safety hazards and low hydrogen utilization efficiency.

[0004] At present, sulfur autotrophic denitrification can be divided into three categories according to different electron donors, which are sulfur autotrophic denitrification with elemental sulfur as electron donor, sulfur autotrophic denitrification with sulfide as electron donor and sulfur autotrophic denitrification with reducing sulfur compounds as electron donor. Sulfide has certain toxicity to microorganisms, and is easy to be oxidized, so there is a disadvantage that it is difficult to control the dosage of sulfide when it is used as an electron donor. When S2O3 2- as an electron donor, more SO4 2- is produced, which also limits the application of reducing sulfur compounds. The autotrophic denitrification technology with elemental sulfur as electron donor has the characteristics of efficient denitrification, no need of external carbon source, stable process, and less sludge production. Elemental sulfur has many advantages such as stable chemical properties, can be used as electron donor and microbial growth filler, low price, easy to handle and transport, etc., so the application of elemental sulfur as autotrophic denitrification is more widely used, and the technical advantage is more obvious. However, elemental sulfur is difficult to dissolve in water, which limits the mass transfer rate of the system and reduces the biological oxidation rate of denitrification. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of autotrophic denitrification filler. The filler prepared by the method can ensure the stability of pH in the denitrification process, improve the denitrification rate, and reduce the content of sulfate in the effluent. On the other hand, it can effectively reduce the occurrence of iron and calcium scale on the surface of the filler, so that the microorganisms on the surface of the filler always have high reaction activity, thereby greatly improving the denitrification efficiency. Another purpose of the present application is to provide the application of the autotrophic denitrification filler prepared by the above method in treating tail water in an electronic industrial park.

[0006] Technical Solution: The preparation method of the autotrophic denitrification packing material of the present invention is as follows: 0.3-1.2 parts by weight of dolomite powder, 90-95 parts by weight of modified sulfur powder, 0.5-1.5 parts by weight of iron powder, 1-2 parts by weight of ferrous carbonate powder, 0.5-2 parts by weight of sodium bicarbonate, 0.5-1.5 parts by weight of kaolin, 0.5-1.2 parts by weight of straw powder, and 0.5-1 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. Liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator.

[0007] The modified sulfur powder is prepared by the following method:

[0008] (1) Use a ball mill to grind the sulfur powder until it reaches the micron level; the particle size range of the sulfur powder after grinding is 1 to 5 microns. The purpose of ball milling is to grind the large sulfur particles (0.1 to 0.15 cm) into finer particles, which is beneficial for subsequent modification.

[0009] (2) The ground micron-sized sulfur powder is mixed with the surfactant polyoxyethylene fatty acid ester (oily substance) and thoroughly mixed in a ball mill for 30-60 seconds. The mass-volume ratio of the two is 100g:1mL, that is, 1mL of polyoxyethylene fatty acid ester is added to every 100g of micron-sized sulfur powder. The sulfur powder is emulsified by the hydrophilic surfactant polyoxyethylene fatty acid ester. Under the shearing action of the ball mill, the emulsifier is fully and evenly attached to the surface of the micron-sized sulfur powder. The purpose is that when the sulfur comes into contact with water, it can change from "solid" to "semi-solid" emulsion under the action of the emulsifier.

[0010] (3) Place the powder obtained in step (2) in an oven to dry (dry the oily substance polyoxyethylene fatty acid ester on the surface of the sulfur powder) to obtain the initial powder; the drying temperature is 50-60℃ and the drying time is 2-3h;

[0011] (4) Place the dried initial powder on a conical funnel with filter paper, pour dimethyl sulfoxide into the funnel to completely soak the initial powder, and let it flow out of the conical funnel through the filter paper, so that the solubilizer is completely attached to the surface of the initial powder; the purpose of this step is to further increase the solubility of the initial powder, so that it changes from a "semi-solid" state to a "dissolved state".

[0012] (5) Place the powder obtained in step (4) in an oven to dry it to obtain modified sulfur powder; the drying temperature is 50-60℃ and the drying time is 2-3h.

[0013] By modifying elemental sulfur to increase its water solubility, the rate and efficiency of denitrification can be improved. Increased elemental sulfur solubility enhances the mass transfer efficiency of sulfur particles, meaning more sulfur particles act as electron donors per unit time, converting nitrate or nitrite nitrogen into nitrogen gas. This increases the denitrification rate and further reduces the nitrate nitrogen concentration in the effluent, meeting increasingly stringent discharge standards (some regions require <5 mg / L).

[0014] The solid-liquid ratio of the solid powder to the liquid bio-enhancing agent is 50g:2mL.

[0015] The granulator has an inclination angle of 45° to 55° and a stirring speed of 60 to 80 r / min. The particle size of the spherical particles is controlled by the inclination angle and the stirring speed.

[0016] During use, spherical particles are filtered and retained using a 3-5mm sieve. Particles that are too small are directly returned to the disc granulator to continue granulation and growth. Then, particles that are too large are crushed using a 6-8mm sieve and returned to the granulator.

[0017] In this process, spherical particles with a diameter of 3-5 mm are dried at 85-110℃ for 3-4 hours and then cooled to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0018] The liquid bio-enhancing agent is composed of the following components in the indicated mass fractions: 0.05-0.1 parts magnesium sulfate, 0.1-0.3 parts potassium nitrate, 0.05-0.2 parts calcium chloride, 0.2-0.4 parts potassium dihydrogen phosphate, 0.5-1 parts ferrous sulfate, 0.1-0.2 parts EDTA-Na, 0.1-0.2 parts zinc sulfate, and 95-99 parts water.

[0019] Dolomite fine powder, due to its high density and molar hardness, is a hard material and can be used as a carrier for autotrophic denitrification fillers; sulfur (S) acts as an electron donor to convert nitrate nitrogen into nitrogen gas, and produces sulfate and hydrogen ions; 1.1S + 1.0NO3 - +0.76H₂O + 0.4CO₂ + 0.08NH₄ + →0.08C5H7O2N+0.5N2+1.1SO4 2- +1.28H +

[0020] Both zero-valent iron and divalent ferrous iron (ferrous carbonate) act as electron donors to convert nitrate nitrogen into nitrogen gas and generate alkalinity (hydroxyl ions), which can neutralize the hydrogen ions produced by the sulfur autotrophic reaction. In addition, the carbonate ions in ferrous carbonate can also provide alkalinity, thereby ensuring that the pH remains relatively stable along the denitrification process and will not inhibit the activity of microorganisms on the packing surface due to acid production or excessive alkalinity.

[0021] 5Fe + 2NO3 - +6H₂O→N₂+5Fe 2+ +12OH -

[0022] 10Fe 2+ +2NO3 - +6H₂O→N₂+10Fe 3+ +12OH -

[0023] H + +OH - →H2O

[0024] In addition, the purpose of introducing zero-valent iron into the packing is not only to allow zero-valent iron to directly participate in the denitrification reaction, but also to ensure that the ferric iron produced by divalent iron in the denitrification reaction is not lost. The ferric iron will react with zero-valent iron to generate divalent iron, which will continue to carry out the denitrification reaction and improve the utilization rate of iron salts.

[0025] Fe + 2Fe 3+ →3Fe 2+

[0026] The main function of sodium bicarbonate in the packing material is to provide a buffer system, thereby ensuring the stability of the reaction pH and preventing pH fluctuations in the influent or the water during the denitrification process from inhibiting the denitrification reaction. In addition, sodium bicarbonate decomposes under controlled temperature heating to produce tiny CO2 gases, which escape during the drying process of the packing material, forming multiple and uniform pores, increasing the contact area between microorganisms and the packing material, and thus improving the denitrification efficiency. The ferrous iron in ferrous carbonate also acts as an electron donor to convert nitrate nitrogen into nitrogen gas.

[0027] HCO3 - +H + →H2O+CO2

[0028] HCO3 - +OH - →CO3 2- +H2O

[0029] 2HCO3 - →CO3 2- +H₂O + CO₂ (when heated)

[0030] Straw can be used as a raw material for hydrogen-producing bacteria in both anaerobic and aerobic processes. The hydrogen produced by these bacteria can then be used for hydrogen autotrophic denitrification.

[0031] C(straw) + 2H₂O → CO₂ + H₂

[0032] The introduction of sodium hexametaphosphate into the packing material is to prevent fluoride ions and calcium ions in the water from forming scale on the packing material and biofilm surface, which would affect the denitrification efficiency. Sodium hexametaphosphate reacts with calcium ions to form a very stable soluble complex, which dissolves in the water and is discharged directly with the product water, thus avoiding calcium scaling on the packing material surface.

[0033] Na₂(PO₃)₆ + 2Ca 2+ →Na2{Ca2(PO3)6} (soluble complex)

[0034] The autotrophic denitrification packing material of this invention can synergistically complete the autotrophic denitrification reaction of sulfur, iron and hydrogen, and achieve efficient nitrogen removal.

[0035] The application of the autotrophic denitrification packing material prepared by the above method in the treatment of tailwater from an electronics industrial park is as follows: the packing material is filled in an autotrophic denitrification reactor, the reactor having a packing zone filled with the packing particles prepared in this invention, the packing height being 2-4m; a support zone is provided below the packing zone; a cylindrical graphite anode penetrating the packing zone is also provided in the reactor; the stainless steel sidewall of the reactor serves as the cathode, and the cathode and anode are respectively connected to an external power source via wires.

[0036] The inner wall surface of the reactor is provided with spiral rising guide vanes in the corresponding packing area, with an inclination angle of 15-30°. The purpose is to ensure that the water is distributed in a spiral rising manner after entering from the bottom horizontal pipe. The spiral rising water distribution method can not only greatly increase the reaction time of wastewater in contact with the packing in the reactor and improve the denitrification efficiency, but also enhance the stirring effect, making the water quality more uniform. At the same time, it can also smoothly carry out the generated nitrogen gas. The hydraulic residence time of the water in the reactor is 0.5-3 hours.

[0037] Applying the sulfur, iron, and hydrogen synergistic autotrophic denitrification packing material of this invention to an autotrophic denitrification reactor can significantly improve the autotrophic denitrification rate and solve the problems of traditional single sulfur autotrophic, iron autotrophic, and hydrogen autotrophic reactors. Electrolysis is used to provide hydrogen to the system, further enhancing the hydrogen autotrophic denitrification rate. Simultaneously, the electrolysis process raises the water temperature, thereby increasing the activity of functional enzymes within the autotrophic denitrifying bacteria community and enhancing the nitrogen removal effect. The reactor uses a swirling inlet method, increasing the reaction time of wastewater in the packing material. Furthermore, the swirling agitation makes the water quality inside the reactor more uniform, both contributing to improved nitrogen removal efficiency.

[0038] The reactor is equipped with a water inlet and an air inlet at the bottom; and an exhaust outlet, a product water outlet, a return outlet, and a backwash water outlet at the top.

[0039] The treatment system based on the autotrophic denitrification reactor also includes a wastewater collection tank, a pH adjustment tank, a product water tank, and a blower. A quartz sand filter is installed on the connecting pipe between the wastewater collection tank and the pH adjustment tank. The effluent from the pH adjustment tank enters the reactor through the inlet. After treatment in the reactor, the product water enters the product water tank through the product water inlet, and part of the return water flows back to the pH adjustment tank through the return outlet. During the backwashing process, the water from the product water tank enters the reactor through the inlet, and the blower is connected to the reactor air inlet.

[0040] The supporting area uses a porous filter plate as a support layer, and a pebble layer is provided on the support layer.

[0041] A porous filter plate is also provided as a support layer below the packing area.

[0042] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) The packing material prepared by the present invention can simultaneously realize the synergistic autotrophic denitrification reaction of sulfur, iron and hydrogen, and gradually modify elemental sulfur from sparingly soluble to water soluble, so that it can be fully dissolved and dispersed in water, greatly improving the removal effect of nitrate nitrogen in wastewater of electronic industrial parks, and at the same time greatly reducing the sulfate content in the produced water; (2) The packing material of the present invention can provide sufficient alkalinity to the water body, keep the pH of the wastewater stable along the process, and will not inhibit the microbial activity on the surface of the packing material due to acid production or excessive alkalinity; (3) Zero-valent iron and divalent iron in the packing material synergistically In addition to serving as an electron donor, the ferric iron produced in the reaction will react with the ferrous iron to generate ferrous iron, which will continue to carry out the denitrification reaction and improve the utilization rate of iron salts; (4) The packing contains multiple and uniform pores, which increases the contact area between microorganisms and packing, thereby improving the mass transfer performance of the denitrification reaction and thus improving the denitrification efficiency; (5) The wastewater in the electronic industrial park contains a certain concentration of fluoride ions and calcium ions, which are easy to scale on the surface of packing and biofilm. Sodium hexametaphosphate in the packing can react with calcium ions to generate a very stable soluble complex, thereby effectively reducing the occurrence of iron scale and calcium scale on the surface of the packing. Attached Figure Description

[0043] Fig. 1 This is a schematic diagram of the entire denitrification treatment system including the reactor of the present invention;

[0044] Fig. 2 This is a schematic diagram of the reactor structure;

[0045] Fig. 3 This is a schematic diagram of the reactor cylinder structure;

[0046] Fig. 4 This is a schematic diagram of the structure of a porous filter plate;

[0047] Fig. 5 This is a diagram illustrating the modification mechanism of modified sulfur powder. Detailed Implementation

[0048] Example 1

[0049] The method for preparing the autotrophic denitrification packing material of the present invention includes the following steps:

[0050] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of modified sulfur powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50 g: 2 mL. The tilt angle of the granulator is 50° and the stirring speed is 65 r / min.

[0051] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0052] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0053] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0054] like Figs. 1-4As shown, the application of the autotrophic denitrification packing material prepared by the above method in the treatment of tailwater from an electronics industrial park is as follows: the packing material is filled into an autotrophic denitrification reactor 1. The reactor 1 has a packing zone 2, which is filled with the packing particles prepared in this invention. The packing height is 2-4m. A support zone 3 is provided below the packing zone 2. The reactor 1 also has a cylindrical graphite or carbon rod anode 4 that penetrates the packing zone. The stainless steel sidewall of the reactor 1 serves as the cathode. The cathode and anode are connected to an external power source through wires. Under energized conditions (voltage 0.25-0.5V, current 20-50mA), hydrogen gas is generated on the cathode surface, providing a hydrogen source for hydrogen autotrophic denitrifying bacteria. Under the flushing action of the influent, the hydrogen gas is mixed in the water and comes into full contact with the denitrification packing material, further increasing the hydrogen autotrophic denitrification rate. In addition, the energization will heat the water, increasing the water temperature and enhancing the activity of functional enzymes within the autotrophic denitrifying bacteria community, thereby increasing the nitrate nitrogen removal rate. The inner wall surface of reactor 1 is provided with spiral rising guide vanes 17 in the corresponding packing area, and the inclination angle of the guide vanes 17 is 15 to 30°; the bottom of reactor 1 is provided with a water inlet 11 and an air inlet 12; the top of reactor is provided with an exhaust outlet 13, a product water outlet 14, a return outlet 15 and a backwash water outlet 16.

[0055] The entire denitrification system, including the reactor, also includes a wastewater collection tank 5, a pH adjustment tank 6, a product water tank 7, and a blower 8. A quartz sand filter 9 is installed on the connecting pipe between the wastewater collection tank 5 and the pH adjustment tank 6. The effluent from the pH adjustment tank 6 enters the reactor 1 through the inlet 11. After treatment in the reactor 1, the product water enters the product water tank 7 through the product water inlet 14, and some of the return water flows back to the pH adjustment tank 6 through the return outlet 15. During backwashing, water from the product water tank 7 enters the reactor 1 through the inlet 11, and the blower 8 is connected to the reactor's air inlet 12. The backwashing sequence is air washing, combined air-water washing, and water washing. Backwash water and air enter from the inlet 11 and air inlet 12 at the bottom of the reactor 1. The backwash water is the product water from the reactor 1, which is pumped from the product water tank 7 to the bottom of the reactor 1 for backwashing by the backwash water pump. The air for backwashing is provided by the blower 8.

[0056] The support zone 3 uses a porous filter plate 31 as a support layer. The pore diameter of the porous filter plate 31 is 4 mm, the spacing between adjacent pores is 2 mm, and the thickness of the porous filter plate 31 is 100 mm. A pebble layer 32 is provided on the support layer. In the pebble layer 32, the particle sizes of the pebbles from top to bottom are 4-8, 8-16, and 16-32 mm, respectively, and the filling height of the pebble layer 32 is 300-360 mm. The packing material of this invention can maintain a relatively stable pH of the reactor water during the reaction process, preventing excessive acidity or alkalinity from inhibiting the denitrification rate. A packing filling port 21 is provided at the top of the corresponding packing zone of the reactor, which facilitates replenishment when the packing material is consumed.

[0057] The flow rate of wastewater in a certain electronics industrial park is 10,000 m³.3 / d, the influent nitrate nitrogen concentration is 30 mg / L, pH is 6.5-7.5, calcium ion concentration is 400 mg / L, fluoride ion concentration is 15 mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5 mg / L; the packing material of this invention is used to denitrify the above wastewater, specifically as follows:

[0058] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0059] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0060] The pH of the effluent from reactor 1 is 7.9, and the pH deviation between the influent and effluent is controlled within 0.1. The newly added sulfate concentration in the effluent is 138 mg / L (if pure sulfur packing is used, the newly added sulfate concentration in the effluent of the system of this invention is 197 mg / L), the effluent nitrate nitrogen concentration is 4 mg / L, the nitrate nitrogen removal rate reaches 87%, the effluent calcium ion concentration is 400 mg / L, and the fluoride ion concentration is 15 mg / L. The calcium ion and fluoride ion concentrations in the effluent are consistent with those in the influent, indicating that no calcium sulfate or calcium fluoride scaling has occurred on the surface of the packing.

[0061] During system operation, nitrogen gas is generated on the surface of the packing material, gradually preventing the wastewater from contacting and reacting with the packing material, thus reducing the denitrification efficiency. Therefore, the reactor needs to be periodically washed with water to remove nitrogen during operation, with a washing cycle of twice a day, a washing intensity of 20 m³ / h, and a washing time of 4 min. The washing water source is the reactor effluent from the product water tank 7, and the wastewater after washing is discharged into the upstream wastewater collection tank 5. To prevent the system packing material from slowly caking, air washing, combined air-water washing, and water washing are set up sequentially. The blower 8 is turned on and the air washing intensity is adjusted to 15 L / (m³). 2The air washing time was 2 minutes, and the water washing intensity was 6 L / (m). 2 The combined air washing and water washing time is 1 minute, and the water washing time alone is 5 minutes. The water source for the water washing is the reactor effluent in the product water tank 7. The water washing wastewater is discharged into the front wastewater collection tank 5.

[0062] Comparative Example 1

[0063] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0064] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of unmodified elemental sulfur powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50 g: 2 mL. The tilt angle of the granulator is 50° and the stirring speed is 65 r / min.

[0065] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0066] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0067] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0068] The packing material prepared in Comparative Example 1 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0069] The wastewater was treated for denitrification using the packing material from Comparative Example 1, specifically as follows:

[0070] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0071] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0072] The pH of the effluent from reactor 1 is 8.4, the pH difference between the influent and effluent is 0.4, the nitrate nitrogen concentration in the effluent is 11 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate is only 63%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0073] Comparative Example 2

[0074] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0075] (1) 0.5 parts by weight of dolomite powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-fortifier is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-fortifier is 50g:2mL. The tilt angle of the granulator is 50° and the stirring speed is 65r / min.

[0076] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0077] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0078] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0079] The packing material prepared in Comparative Example 2 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0080] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0081] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0082] The pH of the effluent from reactor 1 is 8.5, the pH deviation between the influent and effluent is controlled within 0.5, the nitrate nitrogen concentration in the effluent is 18 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate is only 40%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0083] Comparative Example 3

[0084] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0085] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of modified sulfur powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50g:2mL. The tilt angle of the granulator is 50° and the stirring speed is 65r / min.

[0086] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0087] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0088] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0089] The packing material prepared in Comparative Example 3 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0090] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0091] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0092] The pH of the effluent from reactor 1 is 7.7, the pH deviation between the influent and effluent is 0.3, the nitrate nitrogen concentration in the effluent is 12 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate reaches 60%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0093] Comparative Example 4

[0094] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0095] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of modified sulfur powder, 0.8 parts by weight of iron powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50g:2mL. The tilt angle of the granulator is 50° and the stirring speed is 65r / min.

[0096] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0097] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0098] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0099] The packing material prepared in Comparative Example 4 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0100] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0101] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0102] The pH of the effluent from reactor 1 is 7.4, the pH difference between the influent and effluent is 0.6, the nitrate nitrogen concentration in the effluent is 13 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate reaches 57%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0103] Comparative Example 5

[0104] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0105] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of modified sulfur powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.0 part by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50g:2mL. The tilt angle of the granulator is 50° and the stirring speed is 65r / min.

[0106] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0107] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0108] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0109] The packing material prepared in Comparative Example 5 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0110] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0111] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0112] The pH of the effluent from reactor 1 is 7.1, the pH difference between the influent and effluent is 0.9, the nitrate nitrogen concentration in the effluent is 16 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate is 47%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0113] Comparative Example 6

[0114] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0115] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of modified sulfur powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50 g: 2 mL. The tilt angle of the granulator is 50° and the stirring speed is 65 r / min.

[0116] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0117] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0118] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0119] The packing material prepared in Comparative Example 6 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0120] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0121] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0122] The pH of the effluent from reactor 1 is 7.9, the pH deviation between the influent and effluent is controlled within 0.1, the nitrate nitrogen concentration in the effluent is 9 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate reaches 70%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0123] Comparative Example 7

[0124] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0125] (1) 0.5 parts by weight of dolomite powder, 92.5 parts by weight of modified sulfur powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, and 0.5 parts by weight of straw powder are placed in a disc granulator and mixed evenly. Liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50 g: 2 mL. The tilt angle of the granulator is 50° and the stirring speed is 65 r / min.

[0126] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0127] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0128] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0129] The packing material prepared in Comparative Example 7 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0130] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0131] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0132] The pH of the effluent from reactor 1 was 7.9, and the pH deviation between the influent and effluent was controlled within 0.1. The nitrate nitrogen concentration in the effluent was 11 mg / L, which did not meet the discharge requirements (<5 mg / L). The nitrate nitrogen removal rate reached 63%. The calcium ion concentration in the effluent was 380 mg / L, and the fluoride ion concentration was 8 mg / L. The calcium ion and fluoride ion concentrations in the effluent were lower than those in the influent, indicating that calcium sulfate and calcium fluoride scaling had occurred on the surface of the packing material, resulting in a decrease in the nitrate removal rate.

[0133] Comparative Example 8

[0134] A method for preparing an autotrophic denitrification packing material includes the following steps:

[0135] (1) 0.5 parts by weight of dolomite powder, 80 parts by weight of modified sulfur powder, 0.8 parts by weight of iron powder, 1 part by weight of ferrous carbonate powder, 1.2 parts by weight of sodium bicarbonate, 1.0 parts by weight of kaolin, 0.5 parts by weight of straw powder and 0.5 parts by weight of sodium hexametaphosphate are placed in a disc granulator and mixed evenly. The liquid bio-enhancing agent is sprayed into the disc granulator. After the solid powder in the disc granulator comes into contact with the liquid, it gradually forms spherical particles under the tilting and stirring action of the granulator. The solid-liquid ratio of solid powder to liquid bio-enhancing agent is 50 g: 2 mL. The tilt angle of the granulator is 50° and the stirring speed is 65 r / min.

[0136] (2) Use a 3-5mm sieve to filter and retain spherical particles. Particles that are too small are directly poured back into the disc granulator to continue granulation and growth. Then use a 6-8mm sieve to crush the particles that are too large and pour them back into the granulator.

[0137] (3) Dry spherical particles with a particle size of 3-5 mm at 85-110℃ for 3-4 hours, and then cool them to room temperature to obtain filler particles with large specific surface area and good mechanical strength.

[0138] The liquid bio-enhancing agent is composed of the following components by mass fraction: 0.05 parts magnesium sulfate, 0.2 parts potassium nitrate, 0.15 parts calcium chloride, 0.2 parts potassium dihydrogen phosphate, 0.6 parts ferrous sulfate, 0.1 parts EDTA-Na, 0.2 parts zinc sulfate, and 98.5 parts water.

[0139] The packing material prepared in Comparative Example 8 was used in the autotrophic denitrification system of Example 1 to treat the wastewater from an electronics industrial park. The specific application process was as follows: the flow rate of wastewater from an electronics industrial park was 10,000 m³ / s. 3 / d, the influent nitrate nitrogen concentration is 30mg / L, the pH is 6.5~7.5, the calcium ion concentration is 400mg / L, the fluoride ion concentration is 15mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5mg / L;

[0140] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0141] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The system is continuously run and the nitrate nitrogen concentration in the effluent is monitored. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful. After the system is started, the power supply with the positive and negative terminals is started simultaneously, and the voltage is maintained at 0.3V and the current at 40mA to electrolyze the wastewater to produce hydrogen and increase the water temperature.

[0142] The pH of the effluent from reactor 1 is 7.9, the pH deviation between the influent and effluent is controlled within 0.1, the nitrate nitrogen concentration in the effluent is 12.5 mg / L, which does not meet the discharge requirements (<5 mg / L), the nitrate nitrogen removal rate is 58%, the calcium ion concentration in the effluent is 400 mg / L, and the fluoride ion concentration is 15 mg / L.

[0143] Comparative Example 9

[0144] The packing material in the autotrophic denitrification reactor of Comparative Example 9 was exactly the same as that in Example 1. The only difference between Comparative Example 9 and Example 1 was that the autotrophic denitrification reactor did not have anode and cathode.

[0145] The flow rate of wastewater in a certain electronics industrial park is 10,000 m³. 3 / d, the influent nitrate nitrogen concentration is 30 mg / L, pH is 6.5-7.5, calcium ion concentration is 400 mg / L, fluoride ion concentration is 15 mg / L, and the effluent nitrate nitrogen concentration is required to be less than 5 mg / L; the above wastewater is treated for denitrification based on the packing material of Example 1 and the autotrophic denitrification reactor of Comparative Example 8, specifically as follows:

[0146] (1) Wastewater from the electronic park is pumped from the wastewater collection tank 5 to the quartz sand filter 9 (to remove suspended impurities from the wastewater) by a booster pump. It flows in from the top of the quartz sand filter 9 and flows out from the bottom to the pH adjustment tank 6. Chemical solutions are added to the pH adjustment tank 6 by sulfuric acid and liquid alkali dosing pumps to control the pH of the wastewater to about 8.0. The stirring reaction time is 25 minutes, and then it enters the autotrophic denitrification reactor 1.

[0147] (2) The reactor 1 is filled with pebbles (4-32mm) with a height of 0.3m and autotrophic denitrification packing with a height of 2.6m. Wastewater enters from the bottom horizontal pipe of the reactor 1. Under the action of the spiral guide vanes, the wastewater rises in a spiral and flows out from the top horizontal port of the reactor 1 into the product water tank 7. The hydraulic retention time of the wastewater in the reactor 1 is 3h, and the horizontal angle of the guide vanes is 15°. When running for the first time, the autotrophic denitrification packing needs to be inoculated with activated sludge from the biological system of the electronic industrial park. The nitrate nitrogen concentration in the effluent is monitored during continuous operation. If the nitrate nitrogen removal rate is greater than 60% and a brownish-yellow biofilm covers the surface of the packing, the inoculation and biofilm formation are considered successful.

[0148] The effluent nitrate nitrogen concentration was 10.5 mg / L, which did not meet the discharge requirements (<5 mg / L). The nitrate nitrogen removal rate was 65%. The effluent calcium ion concentration was 400 mg / L, and the fluoride ion concentration was 15 mg / L.

Claims

1. A method for preparing an autotrophic denitrification packing material, characterized by, Specifically, 0.3-1.2 parts by mass of dolomite powder, 90-95 parts by mass of modified sulfur powder, 0.5-1.5 parts by mass of iron powder, 1-2 parts by mass of ferrous carbonate powder, 0.5-2 parts by mass of sodium bicarbonate, 0.5-1.5 parts by mass of kaolin, 0.5-1.2 parts by mass of straw powder and 0.5-1 part by mass of sodium hexametaphosphate are placed in a disc granulator and mixed uniformly, and a liquid biological enhancer is sprayed into the disc granulator, and the solid powder in the disc granulator gradually forms spherical particles under the action of the inclined operation and stirring of the granulator after contacting the liquid. The modified sulfur powder is prepared by the following method: (1) grinding sulfur powder using a ball mill until micron grade is achieved; (2) mixing the micron grade sulfur powder after grinding with a surfactant polyoxyethylene fatty acid ester and fully mixing under the ball mill, the ball milling time is 30-60 s, and the mass-volume ratio of the mixture is 100 g:1-1.5 mL; (3) drying the powder obtained in step (2) in an oven to obtain an initial powder; the drying temperature is 50-60 DEG C, and the drying time is 2-3 h; (4) placing the dried initial powder on a conical funnel with filter paper, pouring dimethyl sulfoxide into the funnel to completely soak the initial powder, and flowing out of the conical funnel from the filter paper, so that the solubilizing agent is attached to the surface of the initial powder; (5) drying the powder obtained in step (4) in an oven to obtain modified sulfur powder; the drying temperature is 50-60 DEG C, and the drying time is 2-3 h; The liquid biological enhancer is composed of the following components by mass fraction: 0.05-0.1 parts of magnesium sulfate, 0.1-0.3 parts of potassium nitrate, 0.05-0.2 parts of calcium chloride, 0.2-0.4 parts of potassium dihydrogen phosphate, 0.5-1 parts of ferrous sulfate, 0.1-0.2 parts of EDTA-Na, 0.1-0.2 parts of zinc sulfate, and 95-99 parts of water; the solid-liquid ratio of the solid powder and the liquid biological enhancer is 50 g:2-3 mL.

2. The process for the preparation of autotrophic denitrification packing according to claim 1, characterized in that: The inclination angle of the granulator is 45-55 DEG; the stirring speed is 60-80 r / min.

3. Use of the autotrophic denitrifying packing produced by the method of claim 1 for treating tail water in an electronic industrial park, characterized in that, Specifically, the filler is filled in the autotrophic denitrification reactor, the reactor is provided with a filler zone, the filler zone is filled with the filler particles prepared in claim 1; a supporting zone is provided below the filler zone; the reactor is also provided with a cylindrical graphite / carbon rod penetrating through the filler zone; the cylindrical graphite / carbon rod serves as an anode, the stainless steel side wall of the reactor serves as a cathode, and the cathode and the anode are respectively connected to an external power source through wires.

4. Use of the autotrophic denitrification packing according to claim 3 for treating tailwater in an electronic industrial park, characterized in that: The reactor inner side wall surface is provided with a spiral upward guide vane corresponding to the filler zone, and the inclination angle is 15-30 DEG.

5. Use of the autotrophic denitrification packing according to claim 4 for treating tailwater in an electronic industrial park, characterized in that: The reactor bottom is provided with a water inlet and an air inlet; the reactor top is provided with an exhaust port, a water production port, a backflow port and a backwash water outlet. The reactor bottom is provided with a water inlet and an air inlet; the reactor top is provided with an exhaust port, a water production port, a backflow port and a backwash water outlet.

6. Use of the autotrophic denitrification packing according to claim 5 for treating tailwater of an electronic industrial park, characterized in that: The reactor-based treatment system further comprises a wastewater collecting tank, a pH adjusting tank, a water producing tank and a fan; a quartz sand filter is arranged on the connecting pipeline of the wastewater collecting tank and the pH adjusting tank; the effluent of the pH adjusting tank enters the reactor through the water inlet, and after being treated in the reactor, the produced water enters the water producing tank through the water outlet, and part of the backflow water flows back to the pH adjusting tank through the backflow port; during the backwashing process, the water in the water producing tank enters the reactor through the water inlet, and the fan is connected with the air inlet of the reactor.

7. Use of the autotrophic denitrification packing according to claim 6 for treating tailwater of an electronic industrial park, characterized in that: The supporting area is supported by a porous filter plate, and a cobblestone layer is arranged on the supporting layer.

8. Use of the autotrophic denitrification packing according to claim 7 for treating tailwater of an electronic industrial park, characterized in that: A porous filter plate is also arranged below the filler area as a supporting layer.

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