A method for treating low-concentration ammonia nitrogen water at the liquid ammonia production terminal

Abstract

The present invention relates to the technical field of ammonia nitrogen wastewater treatment, and specifically discloses a method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal. Specifically, the method effectively combines short-range nitrification and denitrification technology with anaerobic ammonia oxidation technology. By constructing a stable nitrite ammonia environment, the method can effectively reduce sludge production, save the carbon source required for denitrification, and save about 30% of the oxygen supply. In addition, the entire treatment device has high treatment efficiency, strong capacity, and a small footprint.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid ammonia production, and in particular to a method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal. Background Art

[0002] Liquid ammonia is primarily used in the production of nitric acid, urea, and other chemical fertilizers, and can also be used as a raw material for pharmaceuticals and pesticides. The production process generates wastewater containing ammonia nitrogen. The ammonia nitrogen content in the wastewater at the end of liquid ammonia production is approximately 200 mg / L, which is considered low-concentration ammonia nitrogen wastewater. Directly discharging large quantities of this low-concentration ammonia nitrogen wastewater can have serious consequences for water bodies, disrupting water balance and affecting human health.

[0003] The commonly used treatment methods for low-concentration ammonia nitrogen wastewater include breakpoint chlorination, adsorption, and biological methods. Among them, the breakpoint chlorination method can accurately reduce the total ammonia nitrogen content in the wastewater, but it requires high operating costs and also produces secondary pollution byproducts such as chloramines. The selection of adsorption materials and consideration of adsorption capacity for the adsorption method generally cannot play a corresponding role in liquid ammonia. The biological method is to produce N2 through a series of reactions such as nitrification and denitrification by various microorganisms. The advantage is that the effect is stable and no secondary pollution occurs, but the treatment equipment occupies a large area, and the treatment efficiency is easily affected by temperature and toxic substances. In addition, N2O is produced during the denitrification process, which is easily converted into other nitrogen oxides that affect the ozone layer. Denitrification converts valuable substances such as NH4+ into N2 that escapes into the air, causing waste.

[0004] Short-cut nitrification and denitrification biological denitrification can save 25% of oxygen supply, reduce energy consumption, save carbon sources required for denitrification, and reduce sludge production by up to 50%. However, it is greatly affected by temperature, pH value, free ammonia, dissolved oxygen, sludge age, etc. In addition, the full-cut nitrification and denitrification process requires large equipment space and low treatment efficiency. However, both short-cut and full-cut denitrification processes require the addition of additional carbon sources. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned technologies, the purpose of the present invention is to provide a method for treating low-concentration ammonia nitrogen water at the terminal of liquid ammonia production, wherein the method effectively combines short-range nitrification and denitrification technology with anaerobic ammonia oxidation technology. By constructing a stable nitrite ammonia environment, it can effectively reduce sludge production, save the carbon source required for denitrification, and save about 30% of the oxygen supply, and make the entire treatment device high in treatment efficiency, strong in capacity and with a small footprint.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal is characterized by being achieved through the following steps:

[0008] Step 1) constructing a treatment device, which includes a closed shell, an exhaust pipe connected to the top of the closed shell, a one-way valve connected to the exhaust pipe, a hollow transition box and a porous partition fixedly connected in sequence from bottom to top in the closed shell, and the inner cavity of the closed shell is divided into an anaerobic reaction zone at the top, an anoxic reaction zone in the middle, and an aerobic reaction zone at the bottom by the porous partition and the hollow transition box; wherein a wavy water passage is formed in the aerobic reaction zone by a zeolite filler carrier plate, and the water passage is connected to the inner cavity of the hollow transition box; a plurality of water holes penetrating the aerobic reaction zone and the anoxic reaction zone are formed on the hollow transition box; a plurality of carrier columns connected to the inner cavity of the hollow transition box are connected to the top wall of the hollow transition box, and the carrier columns are located in the anoxic reaction zone; a suction port is also fixedly connected to one side of the hollow transition box; a wastewater inlet pipe connected to the water passage is fixedly connected to the bottom of one side of the closed shell, and a drain pipe connected to the anaerobic reaction zone is fixedly connected to the top of one side of the closed shell;

[0009] Step 2), hanging a biofilm on the zeolite filler carrier plate;

[0010] Step 3) Add the collected terminal ammonia nitrogen wastewater to the suspended biological filler under stirring, mix thoroughly, and then send it into the water channel of the treatment device, wherein the volume of the suspended biological filler is 0.4%-0.6% of the volume of the ammonia nitrogen wastewater. During the stirring process, intermittent aeration is performed to make the dissolved oxygen content of the effluent at the end of the water channel less than 1 mg / L; inoculate anaerobic ammonia-oxidizing bacteria into the anaerobic reaction zone;

[0011] Step 4) Regularly suck out the suspended biological filler through the suction port and then re-hang the biofilm.

[0012] Preferably, in the above step 2), the specific operation of hanging the biofilm on the zeolite filler carrier plate is to first close the electric flap valve on the communication channel between the water channel and the hollow transition box, and then discharge the terminal ammonia nitrogen wastewater without the addition of suspended biological filler into the water channel. After the wastewater submerges the zeolite filler carrier plate, a microbial liquid containing nitrifying bacteria and denitrifying bacteria is added through the top opening on one side of the aerobic reaction zone, and is continuously aerated into the aerobic reaction zone through the water channel for 3-5 hours per day until the surface of the zeolite filler carrier plate is covered with a light yellow biofilm.

[0013] Preferably, in the above step 3), the collected terminal ammonia nitrogen wastewater is aerated before adding the suspended biological filler, and the aeration time is 1-2 hours.

[0014] Preferably, in the above step 4), when it is detected that the biofilm thickness on the surface of the suspended biological filler is greater than 80 μm or less than 5 μm, the suspended biological filler is sucked out by introducing water into the water passage while suctioning through the suction port.

[0015] Preferably, the particle size of the zeolite in the zeolite filler carrier plate is 15-25 mm.

[0016] Preferably, an exhaust pipe is fixedly connected to the top of one side of the closed shell and is connected to the inner cavity of the anaerobic reaction zone, and the other end of the exhaust pipe is connected to an exhaust pump; when the ammonia nitrogen wastewater rises to the carrier column, the exhaust pump is started, and when the ammonia nitrogen wastewater rises to more than 2 / 3 of the height of the carrier column, the exhaust is stopped.

[0017] Preferably, a vertical observation window is opened on one side of the closed shell, and a transparent window is fixedly connected to the vertical observation window. This design is used to observe the liquid level in the device.

[0018] Preferably, a circulation pipe is connected to the closed shell, one end of the circulation pipe is connected to the anaerobic reaction zone, and the other end is connected to the wastewater inlet pipe. The circulation pipe is connected to a valve and a water pump.

[0019] Preferably, a suction pipe is fixedly connected to the outer end of the suction port, a bucket-shaped material box is connected and communicated with the bottom of the suction pipe, a valve is connected to the bottom of the bucket-shaped material box, and a suction pump is connected and communicated with the top of the suction pipe.

[0020] In the present invention, since the drain pipe (equivalent to the overflow pipe) is set higher, when the final treated wastewater level is lower than the height of the drain pipe, the water in the treatment equipment is circulated 2-4 times through the circulation pipe (set at the bottom of one side of the anaerobic reaction zone) and finally discharged through the supplementary drain pipe.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention allows ammonia nitrogen wastewater to enter the aerobic reaction zone from the bottom, and then flow into the anoxic reaction zone and anaerobic reaction zone. Compared with the existing technology of reacting from top to bottom, it can effectively delay the reaction time of each zone and optimize the ammonia nitrogen treatment effect;

[0023] 2. The present invention mixes the suspended biological filler with the ammonia nitrogen wastewater first, and then transports them together through the water channel. During the process of transporting the wastewater forward, part of the liquid flows through the zeolite filler through the holes on the zeolite filler carrier plate on the periphery of the water channel, and then enters the cavity outside the zeolite filler carrier plate in the aerobic reaction zone; the other part flows into the hollow transition box through the water channel, while the suspended biological filler can only flow into the hollow transition box through the water channel because it is larger than the pore size of the zeolite filler carrier plate, and then flows into the carrier column; during the whole process, in the aerobic reaction zone, the oxygen content in the water channel is higher than that outside the water channel, and the oxygen content at the water inlet end of the water channel is higher than that at the water outlet end. In the place with high oxygen content, the wastewater undergoes nitrification and nitritation. As the oxygen content decreases, the nitrification reaction weakens, and the nitritation is relatively stable, providing more nitrite ammonia for the subsequent anaerobic ammonia oxidation reaction. In addition, due to the presence of denitrifying bacteria, short-range denitrification can also be achieved;

[0024] 3. The present invention connects the carrier column and the water channel through a hollow transition box, which can selectively inhibit the activity of different bacterial species in the suspended biological filler under different oxygen environments, thereby reducing the filler cost;

[0025] 4. The treatment method of the present invention can create a relatively stable nitrite ammonia environment and optimize the anaerobic ammonium oxidation reaction effect;

[0026] 5. The present invention fills zeolite in the zeolite filler carrier plate, and the filler can be used for a long time without replacement;

[0027] 6. The present invention does not require the addition of an additional carbon source and can also avoid secondary pollution of the effluent. With a relatively small footprint of the treatment equipment, it can effectively reduce the nitrogen concentration of the effluent to below 25 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the external structure of the processing equipment of the present invention;

[0029] Figure 2 This is a schematic diagram of the internal structure of the processing equipment of the present invention;

[0030] Figure 3 This is a top view schematic diagram of the hollow transition box, carrier column and other structures of the present invention;

[0031] Among them, 1. closed shell, 1.1. anaerobic reaction zone, 1.2. anoxic reaction zone, 1.3. aerobic reaction zone, 2. exhaust pipe, 3. one-way valve, 4. hollow transition box, 4.1. water through hole, 5. porous partition, 6. zeolite filler carrier plate, 7. water through channel, 8. carrier column, 9. suction port, 10. wastewater inlet pipe, 11. drain pipe, 12. oxygen content detection head, 13. electric flap valve, 14. bucket-shaped material box, 15. suction pump, 16. transparent window, 17. exhaust pipe, 18. exhaust pump, 19. circulation pipe, 20. water pump, 21. supplementary drain pipe. DETAILED DESCRIPTION

[0032] The present invention will now be further described with reference to specific embodiments.

[0033] The following are only preferred embodiments of the present application and are not intended to limit the scope of protection of the present invention. Any equivalent or similar replacements that do not depart from the concept of the present application should fall within the scope of protection of the present invention.

[0034] The parts not described in detail below are all carried out with reference to the existing technology in the field.

[0035] In the applicant's actual liquid ammonia production, the production wastewater entering the terminal wastewater treatment station mainly includes drainage from the gasification cycle, compressor oil discharge wastewater, concentrated water generated by the soft water treatment system, drainage from the synthesis cycle, flushing water in the joint plant, desulfurization, and condensate discharged from the coke filter. The wastewater quality is pH 8-9.5, COD is 340 mg / L, and the ammonia nitrogen content is approximately 200 mg / L. Example 1

[0036] The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal of this embodiment is implemented by the following steps:

[0037] Step 1) constructing a treatment device, which includes a closed shell 1, an exhaust pipe 2 is connected to the top of the closed shell 1, a one-way valve 3 that only allows air to exit but not enter is connected to the exhaust pipe 2, a hollow transition box 4 and a porous partition 5 are fixedly connected in sequence from bottom to top in the closed shell 1, and the inner cavity of the closed shell 1 is divided into an anaerobic reaction zone 1.1 at the top, an anoxic reaction zone 1.2 in the middle, and an aerobic reaction zone 1.3 at the bottom by the porous partition 5 and the hollow transition box 4; wherein a wave-shaped water passage 7 is formed in the aerobic reaction zone 1.3 by multiple zeolite filler carrier plates 6, and the water passage 7 can be surrounded by only the zeolite filler carrier plates 6 on the upper and lower surfaces and the corresponding positions on the front and back of the shell, or all four surfaces can be zeolite filler carrier plates 6, and Each surface is formed by a plurality of zeolite filler carrier plates 6 fixedly connected end to end. Each zeolite filler carrier plate 6 is formed by a plurality of porous plates surrounding a cavity and then loading zeolite in the cavity. The pore size of the porous plate is smaller than the particle size of the suspended biological filler, and the particle size of the zeolite in the zeolite filler carrier plate is 15-20 mm. The outlet end of the water passage 7 is connected to the inner cavity of the hollow transition box 4. An oxygen content detection head 12 is fixed in the hollow transition box 4 and near the connection between the hollow transition box 4 and the water passage 7. An electric flap valve 13 is connected in a conventional manner in the water passage 7 and near the connection between the hollow transition box 4 and the hollow transition box 4. A plurality of water through holes 4 are formed on the hollow transition box 4, which pass through the aerobic reaction zone 1.3 and the anoxic reaction zone 1.2. .1. A plurality of carrier columns 8 are connected to the top wall of the hollow transition box 4 and are connected to the inner cavity of the hollow transition box 4. The top of the carrier column 8 is closed and hollow. A plurality of water holes are provided on the outer peripheral wall of the carrier column 8 and the aperture of the water holes is smaller than the particle size of the suspended biological filler. The carrier column 8 is located in the anoxic reaction zone 1.2. A suction port 9 is also fixedly connected to one side of the hollow transition box 4. A suction pipe is fixedly connected to the outer end of the suction port. A bucket-shaped material box 14 is connected and communicated with at the bottom of the suction pipe. A valve is connected to the bottom of the bucket-shaped material box 14. A suction pump 15 is connected and communicated with at the top of the suction pipe. A return water pipe 14.1 is connected and communicated with at the bottom of one side of the bucket-shaped material box 14. A blocking net for preventing the suspended biological filler from being discharged is fixedly connected to the port on the recovery pipe 14.1 located inside the bucket-shaped material box 14. Under the operation of the suction pump 15, the suspended biological filler in the hollow transition box 4, carrier column 8, etc. is extracted; a vertical observation window is opened on one side of the closed shell 1, and a transparent window 16 is fixedly connected to the vertical observation window; a wastewater inlet pipe 10 connected to the water passage is fixedly connected to the bottom of one side of the closed shell 1, and a drain pipe 11 connected to the anaerobic reaction zone is fixedly connected to the top of one side of the closed shell 1; an exhaust pipe 17 is fixedly connected to the top of one side of the closed shell 1 and is connected to the inner cavity of the anaerobic reaction zone 1.1. The other end of the exhaust pipe 17 is connected to the exhaust pump 18; a supplementary drain pipe 21 is connected to the bottom of one side of the closed shell 1, and the supplementary drain pipe 21 is connected to the inner cavity of the aerobic reaction zone.

[0038] Step 2) hanging a biofilm on the zeolite filler carrier plate 6. The specific operation is to first close the electric flap valve 13 on the communication channel between the water channel 7 and the hollow transition box 4, and then discharge the terminal ammonia nitrogen wastewater without suspended biological filler into the water channel 7. After the wastewater submerges the zeolite filler carrier plate, stop adding wastewater, and add microbial liquid containing nitrifying bacteria and denitrifying bacteria through the top opening of the aerobic reaction zone. The microbial liquid is continuously aerated into the aerobic reaction zone through the water channel for 3-5 hours a day until the surface of the zeolite filler carrier plate is covered with a light yellow biofilm.

[0039] Step 3), adding the collected terminal ammonia nitrogen wastewater to the suspended biological filler under stirring, and sending it into the water channel 7 of the treatment device after thorough mixing, wherein the volume of the suspended biological filler is 0.4%-0.6% of the volume of the ammonia nitrogen wastewater, and the suspended biological filler is also loaded with nitrifying bacteria and denitrifying bacteria. Intermittent aeration is performed during the stirring process to make the oxygen content of the effluent at the tail end of the water channel less than 1 mg / L; when the ammonia nitrogen wastewater rises to the carrier column 8, the air pump 18 is started, and when the ammonia nitrogen wastewater rises to more than 2 / 3 of the height of the carrier column, the air extraction is stopped. The air extraction is performed after the zeolite filler carrier plate forms a film; when the liquid level (ammonia nitrogen wastewater liquid level) is in the anaerobic reaction zone, anaerobic ammonia-oxidizing bacteria are inoculated into the anaerobic reaction zone;

[0040] Step 4) When it is detected that the biofilm thickness on the surface of the suspended biological filler is greater than 80 μm or less than 5 μm, water is introduced into the water channel while suction is performed through the suction port to suck out the suspended biological filler, and then the biofilm is hung again in the conventional manner.

[0041] After the treatment in this embodiment, the wastewater is finally discharged, and its average ammonia nitrogen concentration is 24.6 mg / L. Example 2

[0042] Except for the following differences, the rest is the same as Example 1:

[0043] In step 3), the collected terminal ammonia nitrogen wastewater is aerated before adding the suspended biological filler, and the aeration time is 102 hours.

[0044] After the treatment in this embodiment, the wastewater is finally discharged, and its average ammonia nitrogen concentration is 23.2 mg / L. Example 3

[0045] The same as in Example 2 except for the following differences: A circulation pipe 19 is also connected to the closed housing 1. One end of the circulation pipe 19 is connected to the anaerobic reaction zone 1.1, and the other end is connected to the wastewater inlet pipe 10 via a tee. A valve and a water pump 20 are connected to the circulation pipe 19. A return pipe 14.1 at the bottom of one side of the bucket-shaped material bin 14 is connected to the circulation pipe 19. By turning on the water pump and opening the corresponding valve, the wastewater from the anaerobic reaction zone is discharged back into the aerobic reaction zone for a recirculation reaction. A single cycle is generally provided. After the cycle is complete, the wastewater is discharged through the drain pipe 11.

[0046] After the treatment in this embodiment, the wastewater is finally discharged, and its average ammonia nitrogen concentration is 20.8 mg / L.

Claims

1. A method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal, characterized in that: This is achieved by the following steps: Step 1) constructing a treatment device, which includes a closed shell, an exhaust pipe connected to the top of the closed shell, a one-way valve connected to the exhaust pipe, a hollow transition box and a porous partition fixedly connected in sequence from bottom to top in the closed shell, and the inner cavity of the closed shell is divided into an anaerobic reaction zone at the top, an anoxic reaction zone in the middle, and an aerobic reaction zone at the bottom by the porous partition and the hollow transition box; wherein a wavy water passage is formed in the aerobic reaction zone by a zeolite filler carrier plate, and the water passage is connected to the inner cavity of the hollow transition box; a plurality of water holes penetrating the aerobic reaction zone and the anoxic reaction zone are formed on the hollow transition box; a plurality of carrier columns connected to the inner cavity of the hollow transition box are connected to the top wall of the hollow transition box, and the carrier columns are located in the anoxic reaction zone; a suction port is also fixedly connected to one side of the hollow transition box; a wastewater inlet pipe connected to the water passage is fixedly connected to the bottom of one side of the closed shell, and a drain pipe connected to the anaerobic reaction zone is fixedly connected to the top of one side of the closed shell; Step 2), hanging a biofilm on the zeolite filler carrier plate; Step 3) Add the collected terminal ammonia nitrogen wastewater to the suspended biological filler under stirring, mix thoroughly, and then send it into the water channel of the treatment device, wherein the volume of the suspended biological filler is 0.4%-0.6% of the volume of the ammonia nitrogen wastewater. During the stirring process, intermittent aeration is performed to make the dissolved oxygen content of the effluent at the end of the water channel less than 1 mg / L; inoculate anaerobic ammonia-oxidizing bacteria into the anaerobic reaction zone; Step 4) Regularly suck out the suspended biological filler through the suction port and then re-hang the biofilm.

2. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 1, characterized in that: In the above step 2), the specific operation of hanging the biofilm on the zeolite filler carrier plate is to first close the electric flap valve on the connecting channel between the water channel and the hollow transition box, and then discharge the terminal ammonia nitrogen wastewater without the addition of suspended biological filler into the water channel. After the wastewater submerges the zeolite filler carrier plate, a microbial liquid containing nitrifying bacteria and denitrifying bacteria is added through the top opening on one side of the aerobic reaction zone, and is continuously aerated into the aerobic reaction zone through the water channel. Aeration is continued for 3-5 hours per day until the surface of the zeolite filler carrier plate is covered with a light yellow biofilm.

3. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 2, wherein: The particle size of the zeolite in the zeolite filler carrier plate is 15-25 mm.

4. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 3, characterized in that: An exhaust pipe is fixedly connected to the top of one side of the closed shell and is connected to the inner cavity of the anaerobic reaction zone. The other end of the exhaust pipe is connected to an exhaust pump. When the ammonia nitrogen wastewater rises to the carrier column, the exhaust pump is started and the exhaust is stopped when the ammonia nitrogen wastewater rises to more than 2 / 3 of the height of the carrier column.

5. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 4, characterized in that: In the above step 4), when it is detected that the biofilm thickness on the surface of the suspended biological filler is greater than 80 μm or less than 5 μm, the suspended biological filler is sucked out by introducing water into the water passage while suctioning through the suction port.

6. A method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 1, 2, 3, 4 or 5, characterized in that: A suction pipe is fixedly connected to the outer end of the suction port, a bucket-shaped material box is connected to and communicated with the bottom of the suction pipe, a valve is connected to the bottom of the bucket-shaped material box, and a suction pump is connected to and communicated with the top of the suction pipe.

7. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 6, characterized in that: In the above step 3), the collected terminal ammonia nitrogen wastewater is aerated before adding the suspended biological filler, and the aeration time is 1-2 hours.

8. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 7, characterized in that: The closed shell is also connected to a circulation pipeline, one end of which is connected to the anaerobic reaction zone and the other end is connected to the wastewater inlet pipe. The circulation pipeline is connected to a valve and a water pump.

9. The method for treating low-concentration ammonia nitrogen water at a liquid ammonia production terminal according to claim 1, characterized in that: A vertical observation window is provided on one side of the closed shell, and a transparent window is fixedly connected to the vertical observation window.

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