High-ammonia-nitrogen organic wastewater treatment process and device based on gas-liquid circulation

Abstract

The invention discloses a high-ammonia-nitrogen organic wastewater treatment process and device based on gas-liquid circulation, and relates to the technical field of municipal wastewater treatment.The high-ammonia-nitrogen organic wastewater treatment process comprises the following steps that pretreated high-ammonia-nitrogen high-concentration organic wastewater is introduced into an anaerobic circulation tower to generate anaerobic gas; effluent of the anaerobic circulating tower is discharged after being treated by a denitrification tank, a nitrification tank and an ultrafiltration membrane in sequence, denitrification liquid generated by the denitrification tank flows back to the anaerobic circulating tower, and nitrification liquid generated by the nitrification tank flows back to the denitrification tank; sequentially introducing the anaerobic gas into a biogas desulfurization tower and an ammonia absorption tower for treatment; wherein one part of the gas deaminated by the ammonia absorption tower flows back to the anaerobic circulating tower, and the other part of the gas flows back to the biogas desulfurization tower; treating the solution generated by the ammonia absorption tower by adopting a struvite crystallization method, dehydrating, and introducing the filtrate generated by dehydration into a denitrification tank; the method has the characteristics of high anaerobic efficiency, high denitrification efficiency, no need of additional carbon source supplementation, low cost, ammonia resource recovery, high purity of discharged biogas and the like.

Description

Technical Field

[0001] This invention relates to the field of municipal wastewater treatment technology, specifically to a process and apparatus for treating high-ammonia-nitrogen organic wastewater based on gas-liquid circulation. Background Technology

[0002] High-ammonia nitrogen and high-concentration organic wastewater refers to wastewater containing both high concentrations of ammonia nitrogen (NH3-N) and organic pollutants (such as COD and BOD). It is commonly found in industries such as aquaculture wastewater, landfill leachate, and municipal sludge dewatering. For example, the ammonia nitrogen in sludge dewatering can reach as high as 800 mg / L, the COD in landfill leachate can reach tens of thousands of mg / L, the ammonia nitrogen can reach more than 1000 mg / L, and the TN can reach more than 1500 mg / L. Therefore, this type of wastewater is difficult to treat.

[0003] The current common treatment process is "pretreatment + UASB anaerobic digestion + two-stage nitrification and denitrification (first-stage denitrification + first-stage nitrification + second-stage denitrification + second-stage nitrification) + ultrafiltration + advanced treatment (NF + RO)", and the final effluent meets the discharge standards or is reused. However, there are many defects in the operation of the process: on the one hand, the anaerobic treatment efficiency of organic matter is low, the COD concentration of anaerobic effluent is high, the total nitrogen load in the biological stage is high, and a large amount of carbon source needs to be added externally, which increases the COD load of the secondary system, and increases the land area and civil engineering investment costs; on the other hand, the direct emission of anaerobic biogas not only produces secondary pollution, but also cannot recover and utilize the ammonia, CH4 and other substances produced by anaerobic digestion, which wastes resources.

[0004] Based on this, a process and apparatus for treating high ammonia nitrogen organic wastewater based on gas-liquid circulation is provided. Summary of the Invention

[0005] This invention addresses the technical problems of existing high-ammonia-nitrogen organic wastewater treatment, including low anaerobic treatment efficiency, high total nitrogen load in the biochemical stage, high cost of external carbon sources, untreated anaerobic biogas, and waste of ammonia resources. The aim is to provide a gas-liquid cycle-based high-ammonia-nitrogen organic wastewater treatment process and apparatus. This process utilizes denitrification of ammonia nitrogen by the denitrification return liquid and the stripping of deammonia-removed biogas to improve anaerobic degradation efficiency, effectively reducing the total nitrogen load in the biochemical stage. The membrane concentrate is returned to the denitrification tank, eliminating the need for additional carbon sources and recovering ammonia resources from the anaerobic gas. It features good anaerobic degradation of organic matter, high denitrification efficiency, low operating costs, and high purity of emitted biogas.

[0006] The present invention is achieved through the following technical solution.

[0007] The first objective of this invention is to provide a gas-liquid circulation-based process for treating high-ammonia-nitrogen organic wastewater, comprising the following steps: Pretreated high-ammonia-nitrogen, high-concentration organic wastewater is fed into an anaerobic circulation tower to generate anaerobic gas. The effluent from the anaerobic circulation tower is sequentially treated by a denitrification tank, a nitrification tank, and an ultrafiltration membrane before being discharged. Specifically, the denitrified liquid produced by the denitrification tank is recycled back to the anaerobic circulation tower for denitrification to reduce the total nitrogen load in the biological stage. The nitrified liquid produced by the nitrification tank is recycled back to the denitrification tank to provide nitrate nitrogen for the denitrification reaction. The concentrated liquid produced by the ultrafiltration membrane treatment is recycled back to the denitrification tank to supplement the carbon source. Anaerobic gas is sequentially fed into a biogas desulfurization tower and an ammonia absorption tower for treatment. Part of the gas after ammonia removal from the ammonia absorption tower is returned to the anaerobic circulation tower to strip the ammonia in the tower and to stir the dead zone in the anaerobic circulation tower. The other part is returned to the biogas desulfurization tower to stir the introduced anaerobic gas. The solution produced by the ammonia absorption tower is treated by struvite crystallization and then dehydrated. The filtrate produced by dehydration is then fed into the denitrification tank to dilute the effluent from the anaerobic circulation tower and reduce the pollution load.

[0008] In the process of this invention: By recirculating the denitrified liquid from the denitrification tank to the anaerobic circulation tower for denitrification, some ammonia nitrogen is converted into nitrogen gas, increasing the pH and alkalinity of the liquid phase in the anaerobic circulation tower. Due to the increased pH in the upper part of the anaerobic circulation tower, free ammonia is converted from the liquid phase to the gaseous phase, reducing the total nitrogen value in the liquid phase and thus reducing the total nitrogen load in the biological treatment stage. Furthermore, a portion of the gas after ammonia removal from the ammonia absorption tower is recirculated back to the anaerobic circulation tower for ammonia stripping, further reducing the total nitrogen concentration. This effectively reduces the total nitrogen load in the subsequent biological treatment stage and improves the treatment efficiency of the biological treatment stage. The nitrified liquid produced in the nitrification tank is recycled to the denitrification tank to provide nitrate nitrogen for the denitrification reaction. The concentrated liquid produced by the ultrafiltration membrane treatment is recycled to the denitrification tank to provide a carbon source for the denitrification process, eliminating the need for additional carbon source replenishment. The struvite dewatering filtrate is recycled to the denitrification tank to dilute the effluent from the anaerobic circulating tower and reduce the pollution load. By recirculating a portion of the gas after ammonia removal from the ammonia absorption tower back into the anaerobic circulation tower to agitate the dead zone within the tower, the mass transfer effect is increased, thus improving the degradation efficiency of organic matter. Another portion is recirculated back into the biogas desulfurization tower to agitate the incoming anaerobic gas. The recirculated gas and the biogas entering the desulfurization tower form air agitation, increasing the contact area and time between the incoming gas and the packing material, thereby improving the desulfurization efficiency.

[0009] In summary, this invention first removes impurities such as oil, colloids, and suspended solids from the water, then utilizes an anaerobic recirculation tower to decompose high-concentration organic matter as a carbon source, rapidly reducing the COD value. Simultaneously, within the anaerobic recirculation tower, nitrate nitrogen and ammonia nitrogen undergo denitrification using the denitrification reflux liquid. Combined with the biogas returned after ammonia removal to the anaerobic recirculation tower for stripping and denitrification, this significantly reduces the total nitrogen load in subsequent biological treatment stages. Then, the effluent from the anaerobic recirculation tower undergoes subsequent biological denitrification, nitrification, and ultrafiltration membrane treatment to meet discharge standards. Furthermore, the denitrification tank utilizes the concentrated ultrafiltration membrane reflux liquid as a carbon source supplement, eliminating the need for... To avoid the problem of increased COD load and cost caused by the need for additional carbon sources in existing technologies, the gas produced by the anaerobic cycle tower is recycled and treated by the biogas desulfurization tower and the ammonia absorption tower for desulfurization and denitrification. After ammonia removal, part of the biogas is returned to the anaerobic cycle tower for stripping, denitrification and stirring, and part is returned to the biogas desulfurization tower for stirring. The biogas reflux improves the denitrification and organic matter degradation efficiency of the anaerobic cycle tower and the desulfurization efficiency of the biogas desulfurization tower. The remaining biogas can meet the emission standards. The removed ammonia is recycled using the struvite crystallization method, realizing the recovery of ammonia and phosphorus resources.

[0010] Furthermore, the reflux ratio of the denitrification reflux liquid is 10%~30%. The denitrification reflux liquid is refluxed to the bottom and middle of the anaerobic circulation tower for denitrification reaction. The pH value of the bottom and middle of the anaerobic circulation tower is controlled at 6.5~7.5, and some ammonia nitrogen is converted into nitrogen gas, so that the pH of the liquid phase in the upper part of the anaerobic circulation tower is raised to 9~10.

[0011] Furthermore, the reflux ratio of the nitrification tank reflux liquid is 50%~100%.

[0012] Furthermore, the concentrate produced after ultrafiltration membrane treatment is returned to the denitrification tank.

[0013] Furthermore, a portion of the gas after ammonia removal is returned to the biogas desulfurization tower at a return gas volume ratio of 20% to 60%, and another portion is returned to the anaerobic circulation tower at a return gas volume ratio of 40% to 80%.

[0014] A second objective of this invention is to provide a high-ammonia-nitrogen organic wastewater treatment device based on gas-liquid circulation, comprising: Pretreatment tank; The anaerobic circulation tower is connected to the outlet of the pretreatment tank and is used to decompose organic matter in wastewater and generate anaerobic gas. The denitrification tank is connected to the outlet of the anaerobic circulation tower, and the return outlet of the denitrification tank is connected to the inlet of the anaerobic circulation tower. The nitrification tank is connected to the outlet of the denitrification tank, and the return port of the nitrification tank is connected to the inlet of the denitrification tank. An ultrafiltration membrane is connected to the outlet of the nitrification tank, and the concentrate outlet of the ultrafiltration membrane is connected to the inlet of the denitrification tank. The biogas desulfurization tower is connected to the outlet of the anaerobic circulation tower and is used for desulfurization treatment of anaerobic gas. An ammonia absorption tower is connected to the outlet of a biogas desulfurization tower and is used to treat anaerobic gas for ammonia removal. The outlet of the ammonia absorption tower is connected to the inlet of the anaerobic circulation tower and the inlet of the biogas desulfurization tower. The struvite crystallization tank is connected to the bottom outlet of the ammonia absorption tower and is used to crystallize and recover the solution produced by the ammonia absorption tower. A centrifuge device is used to dewater the sediment produced by the struvite crystallization tank, and the outlet of the centrifuge device is connected to the inlet of the denitrification tank.

[0015] Furthermore, the bottom of the anaerobic circulation tower is provided with a water distribution pipe and an aeration pipe, the return port of the denitrification tank is connected to the water distribution pipe of the anaerobic circulation tower, and the air outlet of the ammonia absorption tower is connected to the aeration pipe of the anaerobic circulation tower.

[0016] Furthermore, the upper part of the anaerobic circulation tower is equipped with a three-phase separator, an exhaust pipe, and a desulfurization tower inlet pipe. The three-phase separator is used to separate the gas into three phases. The exhaust pipe and the desulfurization tower inlet pipe are located above the three-phase separator. The exhaust pipe is used to discharge biogas. The desulfurization tower inlet pipe is connected to the inlet of the biogas desulfurization tower.

[0017] Furthermore, the biogas desulfurization tower is equipped with a spray pipe assembly at the top, a packing layer in the middle, and a sedimentation tank at the bottom. The spray pipe assembly is used to spray sodium hydroxide solution into the biogas desulfurization tower to react with the rising gas and achieve desulfurization. The supernatant of the sedimentation tank is connected to the spray pipe assembly through a return pipeline for recycling.

[0018] Furthermore, the ammonia absorption tower is equipped with a second spray pipe assembly at the top and a solution collection area at the bottom. The second spray pipe assembly is used to spray phosphoric acid solution into the ammonia absorption tower to react with the rising gas and achieve ammonia removal. The bottom of the solution collection area is connected to the inlet of the struvite crystallizer, and the upper part of the solution collection area is connected to the ammonia removal membrane assembly through a return pipeline. After being processed by the ammonia removal membrane assembly, the solution is returned to the second spray pipe assembly for recycling.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention improves wastewater purification by using an anaerobic circulating tower for anaerobic oxidation, denitrification, and stripping, followed by further reduction of total nitrogen in the effluent through a denitrification and nitrification tank. Anaerobic biogas is purified by desulfurization and denitrification through a biogas desulfurization tower and an ammonia absorption tower, recovering ammonia products from the circulating gas and achieving the recycling of ammonia absorption liquid. It features good anaerobic degradation of organic matter, high denitrification efficiency, no need for additional carbon source, low operating cost, and high purity of emitted biogas. It effectively reduces the denitrification load in the biochemical section, saves more than 20% of land area, and achieves ammonia resource recovery. It is highly effective in treating high-ammonia-nitrogen, high-concentration organic wastewater. 2. This invention utilizes the denitrification process of nitrate nitrogen and ammonia nitrogen in the denitrification reflux liquid within the anaerobic circulation tower to remove nitrogen, and combines this with the return of biogas after ammonia removal to the anaerobic circulation tower for stripping and denitrification, thereby greatly reducing the total nitrogen load in the subsequent biochemical stages; 3. The denitrification tank of the present invention uses the concentrate from the returned ultrafiltration membrane as a carbon source supplement, eliminating the need for additional carbon source supplementation and avoiding the problems of increased COD load and increased cost caused by the need for a large amount of external carbon source in the prior art; 4. This invention improves the denitrification and organic matter degradation efficiency of the anaerobic circulation tower and the desulfurization efficiency of the biogas desulfurization tower by biogas reflux; 5. This invention utilizes the struvite crystallization method for resource utilization, achieving the recovery of ammonia and phosphorus resources. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0021] The attached diagram shows the markings and corresponding component names: 1-Pretreatment tank, 2-Anaerobic circulation tower, 201-Water distribution pipe, 202-Aeration pipe, 203-First pH meter, 204-Three-phase separator, 205-Exhaust pipe, 206-Exhaust valve, 207-Ammonia concentration detector, 208-Desulfurization tower inlet pipe, 3-Biogas desulfurization tower, 301-Sedimentation tank, 302-Sludge concentration meter, 303-Lower packing layer, 304-Perforated baffle, 305-Upper packing layer, 306-Spray pipe assembly one, 4-Ammonia absorption tower, 401-Solution collection area, 402-Ammonium hydrogen phosphate concentration meter, 403-Spray pipe assembly two, 5-Ammonia removal membrane assembly, 6-Exhaust fan, 7-Strombite crystallization tank, 701-Agitation assembly, 702-Second pH meter, 8-Centrifuge device, 9-Denitrification tank, 10-Nitrification tank, 11-Ultrafiltration membrane. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0023] The following detailed description of an embodiment of a high-ammonia-nitrogen organic wastewater treatment process and apparatus based on gas-liquid circulation according to the present invention is provided with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art.

[0024] The "scope" disclosed in this invention is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way can include or exclude end values, and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope.

[0025] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0026] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0027] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0028] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0029] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0030] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0031] Example 1

[0032] A process for treating high-ammonia-nitrogen organic wastewater based on gas-liquid circulation includes the following steps: (1) Pretreatment High-ammonia nitrogen and high-concentration organic wastewater is fed into a pretreatment tank, where impurities such as oil, colloids, and suspended solids are removed through sedimentation.

[0033] (2) Anaerobic treatment The pretreated wastewater is fed into an anaerobic circulation tower, where high-concentration organic matter is anaerobicly decomposed, causing the COD value of the wastewater to drop rapidly and producing anaerobic gases such as CH4 and H2S. During the anaerobic treatment process, the flow rate of biogas discharged from the anaerobic circulation tower is controlled to maintain the gas pressure balance inside the anaerobic tower and keep the pressure in the upper part of the anaerobic tower at 0.05-0.1 kPa.

[0034] In this process, denitrification reflux liquid is also introduced into the anaerobic circulation tower. The denitrification reflux liquid, which is rich in nitrate nitrogen, is refluxed to the bottom and middle of the anaerobic circulation tower to carry out denitrification reaction. The organic matter and nitrate nitrogen decomposed by anaerobic decomposition react with ammonia nitrogen to increase the alkalinity in the liquid phase of the anaerobic circulation tower. By controlling the reflux ratio to 10%~30%, the pH of the liquid in the upper part of the anaerobic circulation tower is increased to 9~10. Due to the increase in pH value in the upper part of the anaerobic circulation tower, free ammonia is converted from the liquid phase to the gas phase, which reduces the total nitrogen value in the liquid phase. The total nitrogen value of the effluent from the anaerobic circulation tower is about 200~300 mg / L.

[0035] The bottom of the anaerobic circulation tower is also circulated with deammoniation reflux gas treated by the ammonia absorption tower. The circulation speed of the reflux gas is controlled at 1~2m / s to strip ammonia from the anaerobic circulation tower, further reducing the total nitrogen concentration. The deammoniation reflux gas is agitated by air through the aeration pipe at the bottom of the anaerobic circulation tower. The upward flow velocity of the mud-water mixture is controlled at 3.2~4.8m / h to agitate the dead zone of the anaerobic tower, increase the mass transfer effect of the anaerobic tower, and accelerate the degradation rate of pollutants such as nitrate nitrogen and COD. The COD value of the effluent from the anaerobic circulation tower is 400~500mg / L.

[0036] (3) Denitrification-nitrification treatment The effluent from the anaerobic circulation tower enters the denitrification tank, where it undergoes nitrification and denitrification together with the nitrification tank to reduce the total nitrogen in the effluent.

[0037] The nitrification liquor is recycled (recycled at a rate of 50% to 100%) to the denitrification tank to provide nitrate nitrogen for the denitrification reaction; the concentrate produced by the ultrafiltration membrane treatment is recycled to the denitrification tank to provide a carbon source for the denitrification process.

[0038] (4) Ultrafiltration membrane treatment The effluent from the nitrification tank is treated by an ultrafiltration membrane and discharged after meeting the standards. The concentrated liquid produced by filtration is returned to the denitrification tank.

[0039] (5) Desulfurization treatment The biogas mixture produced in the anaerobic tower is separated from the top of the anaerobic tower by a three-phase separator and then enters the biogas desulfurization tower.

[0040] The deammonia-removing gas (with a return gas volume ratio of 20% to 60%) introduced into the lower part of the biogas desulfurization tower from the ammonia absorption tower can stir the gas entering the desulfurization tower and control the upward flow velocity of the gas in the biogas desulfurization tower at 8 to 12 m / h. This can increase the contact area and time between the gas inlet and the packing material, thereby improving the desulfurization efficiency.

[0041] The biogas desulfurization tower has a tower structure with the feed inlet located at the bottom and a spray pipe installed at the top. The spray pipe is a perforated pipe with a hole diameter of 6-8 mm, and the spray liquid is sodium hydroxide.

[0042] The biogas desulfurization tower is internally packed with packing material, consisting of upper and lower layers separated by perforated baffles. These baffles have unevenly distributed small holes (8-20 mm in diameter). The lower layer is a complexed iron catalyst packing material, specifically a sintered mixture of Fe, Fe₂O₃, and Mn, with a mass ratio of Fe:Fe₂O₃:Mn of 1:2:1. The packing material is 30-50 mm wide, approximately 10-20 mm long, and 1-2 mm thick, with a porosity of 0.5-0.7. The upper layer is a special packing material for immobilized wood chips, using wood chips as a carrier and cross-linking to immobilize microorganisms. Immobilized microorganisms such as *Acidithiobacillus ferrooxidans* are prepared by using sawdust as a crosslinking agent with a concentration of 3%–8% silane KH550. The reaction conditions are atmospheric pressure, a temperature of 60–80℃, and a catalyst mixture of potassium persulfate and H2O2 (concentration 2%–5%). The reaction time is 10–12 hours. The sawdust-immobilized microbial packing material is 2–3 cm wide, 1–5 mm thick, and 10–20 cm long. This special packing material exhibits excellent desulfurization performance, achieving over 95%–98% desulfurization efficiency at low concentrations and over 90% at high concentrations. After biogas passes through the upper and lower packing layers, the H2S gas concentration at the biogas desulfurization tower outlet is reduced to below 10 ppm, demonstrating high desulfurization efficiency.

[0043] The bottom of the biogas desulfurization tower is equipped with a sedimentation zone. The gas reacts in the biogas desulfurization tower to generate sulfur precipitate. After the sludge concentration reaches the set concentration, the sludge is discharged. The supernatant in the sedimentation zone is pumped to the spray pipe for circulation, with a circulation ratio of 30% to 50%.

[0044] (6) Deammoniation treatment The gas exiting the biogas desulfurization tower enters from the bottom of the ammonia absorption tower. Phosphoric acid absorbent (pH=2~5) is sprayed from the top of the ammonia absorption tower, reacting with ammonia to form ammonium phosphate. The precipitate is discharged from the bottom outlet of the ammonia absorption tower. After ammonia removal, the free ammonia in the biogas is reduced from 3000-5000ppm to less than 5ppm, and the ammonia removal efficiency can reach more than 98%, realizing the recovery of ammonia resources.

[0045] The gas after ammonia removal is used for reflux. Part of it is refluxed to the anaerobic circulation tower, with a reflux gas volume ratio of 40% to 80%, and the other part is refluxed to the biogas desulfurization tower, with a reflux gas volume ratio of 20% to 60%.

[0046] The ammonia absorption tower is equipped with a spray pipe assembly at the top, with a main pipe diameter of 32mm and spray holes of 4-8mm in diameter. The spray pipes are spaced 100mm apart. At the bottom of the ammonia absorption tower is a solution collection zone, whose main component is ammonium hydrogen phosphate solution. A portion of this solution is refluxed (approximately 10%-20%) to the ammonia removal membrane module for ammonia removal treatment. The ammonia in the solution is recovered and converted into gas, which is then reintroduced into the ammonia absorption tower for further treatment. The deammoniated solution is mixed with the phosphoric acid absorbent for recycling. The ammonia removal membrane module does not require the introduction of new ions; it is recycled and only requires water replenishment. The ammonia removal membrane module enables the regeneration and recycling of the phosphoric acid absorbent. The module achieves internal water balance through internal circulation, improving the stability of ammonia recovery in the system. The ammonium hydrogen phosphate concentration in the solution collection zone is approximately 500-2000 mg / L, and an ammonium hydrogen phosphate concentration meter is installed. Once the set concentration is reached, the solution is discharged to a struvite crystallization tank for crystallization treatment.

[0047] (6) Struvite crystals The ammonium phosphate produced by the ammonia absorption tower is introduced into the struvite crystallization tank. Magnesium hydroxide is added to adjust the pH to 9-10. The dosage is based on the molar ratio of magnesium:nitrogen:phosphorus of (1-1.3):1:(1-1.3). The mixture is stirred for 30-90 minutes to generate magnesium ammonium phosphate precipitate. The ammonia nitrogen concentration of the supernatant after precipitation is less than 5 mg / L, and it is discharged to the nitrification tank for further treatment.

[0048] (7) Dehydration treatment The magnesium ammonium phosphate precipitate was dehydrated using a centrifuge, and the resulting filtrate was discharged into the denitrification tank to dilute the concentration of pollutants in the influent.

[0049] Example 2

[0050] A high-ammonia-nitrogen organic wastewater treatment device based on gas-liquid circulation, such as Figure 1 As shown, it includes: Pretreatment pool 1; Anaerobic circulation tower 2 is connected to the outlet of pretreatment tank 1 and is used to decompose organic matter in wastewater and generate anaerobic gas. The denitrification tank 109 is connected to the outlet of the anaerobic circulation tower 2, and the return port of the denitrification tank 109 is connected to the inlet of the anaerobic circulation tower 2. The nitrification tank 10 is connected to the outlet of the denitrification tank 109, and the return port of the nitrification tank 10 is connected to the inlet of the denitrification tank 109. Ultrafiltration membrane 11 is connected to the outlet of nitrification tank 10, and the concentrate outlet of ultrafiltration membrane 11 is connected to the inlet of denitrification tank 109. The biogas desulfurization tower 3 is connected to the gas outlet of the anaerobic circulation tower 2 and is used for desulfurization treatment of anaerobic gas. Ammonia absorption tower 4 is connected to the outlet of biogas desulfurization tower 3 and is used to treat anaerobic gas for ammonia removal. The outlet of ammonia absorption tower 4 is connected to the inlet of anaerobic circulation tower 2 and the inlet of biogas desulfurization tower 3 for the reflux of biogas after ammonia removal. The struvite crystallization tank 7 is connected to the bottom outlet of the ammonia absorption tower 4 and is used to recover the ammonium phosphate produced by the ammonia absorption tower 4. Centrifuge device 8 is used for dewatering the sediment produced by the struvite crystallization tank 7. The outlet of centrifuge device 8 is connected to the inlet of denitrification tank 109.

[0051] This invention not only anaerobicly decomposes organic matter by setting up an anaerobic circulation tower 2, but also connects to a denitrification tank 109 to use the nitrates and ammonia in the denitrification reflux liquid for denitrification and nitrogen removal reaction, thereby reducing the total nitrogen load of subsequent biochemical processes, achieving simultaneous nitrogen removal and carbon removal, and reducing the biochemical process flow and floor space. This invention utilizes anaerobic circulation tower 2 for anaerobic oxidation, denitrification, and stripping to remove nitrogen, followed by further reduction of total nitrogen in the effluent through denitrification tank 109 and nitrification tank 10, thus improving wastewater purification efficiency. Anaerobic biogas undergoes desulfurization and denitrification purification through biogas desulfurization tower 3 and ammonia absorption tower 4, recovering ammonia products from the circulating gas and achieving the recycling and regeneration of ammonia absorption liquid. It features good anaerobic degradation of organic matter, high denitrification efficiency, no need for additional carbon source replenishment, low operating cost, and high purity of emitted biogas. It effectively reduces the denitrification load in the biochemical section, saves more than 20% of land area, and achieves ammonia resource recovery, demonstrating significant benefits in the treatment of high-ammonia-nitrogen, high-concentration organic wastewater.

[0052] It should be noted that the various devices are connected by pipelines, and pumps are installed on the pipelines to transport the fluid. For the return gas, an induced draft fan 6 is also installed on the pipeline.

[0053] In one specific embodiment, the bottom of the anaerobic circulation tower 2 is provided with a water distribution pipe 201 and an aeration pipe 202. The return port of the denitrification tank 109 is connected to the water distribution pipe 201 at the bottom of the anaerobic circulation tower 2 through a pipe. The denitrification return liquid is introduced into the middle and bottom space of the anaerobic circulation tower 2 through the water distribution pipe 201. The gas outlet of the ammonia absorption tower 4 is connected to the aeration pipe 202 at the bottom of the anaerobic circulation tower 2 to introduce the returned biogas into the anaerobic circulation tower 2.

[0054] The anaerobic circulation tower 2 is equipped with a three-phase separator 204, an exhaust pipe 205, and a desulfurization tower inlet pipe 208 at its upper part. The three-phase separator 204 is used for three-phase separation of the gas. The exhaust pipe 205 and the desulfurization tower inlet pipe 208 are located above the three-phase separator 204. The exhaust pipe 205 is located below the desulfurization tower inlet pipe 208. The exhaust pipe 205 has a small hole with a diameter of 3-4 mm. The exhaust pipe 205 is equipped with an ammonia concentration detector 207. When the ammonia concentration is lower than the discharge standard, the exhaust valve 206 is opened to discharge biogas. The flow rate of biogas discharged from the anaerobic circulation tower 2 can be controlled by adjusting the opening of the exhaust valve 206 to control the gas pressure balance inside the anaerobic circulation tower 2 and maintain the internal pressure of the anaerobic circulation tower 2 at 0.05-0.1 kPa. The desulfurization tower inlet pipe 208 is connected to the inlet of the biogas desulfurization tower 3 for further purification of the anaerobic gas.

[0055] The anaerobic circulation tower 2 is also equipped with a first pH meter 203 for detecting the internal pH.

[0056] Anaerobic circulation tower 2 can not only anaerobic decompose organic matter, but also use the nitrates and ammonia in the denitrification reflux liquid for denitrification and nitrogen removal. After ammonia removal, the biogas is refluxed for stripping and nitrogen removal, reducing the total nitrogen load of subsequent biochemical processes, achieving simultaneous nitrogen removal and carbon removal, and reducing the biochemical process flow and floor space.

[0057] In one specific embodiment, the biogas desulfurization tower 3 is provided with a spray pipe assembly 306 at the top, a packing layer in the middle, and a sedimentation tank 301 at the bottom. The spray pipe assembly 306 is used to spray sodium hydroxide solution into the biogas desulfurization tower 3 to react with the rising gas to achieve desulfurization. The supernatant of the sedimentation tank 301 is connected to the spray pipe assembly 306 through a return pipeline for recycling.

[0058] The sedimentation tank 301 is equipped with a sludge concentration meter 302. The sludge is discharged after the set concentration is reached by detecting the sludge concentration. The packing layer includes a lower packing layer 303, a perforated baffle 304 and an upper packing layer 305. The perforated baffle 304 has unevenly distributed small holes of 8-20 mm. The lower packing is a spiral packing, which is a complexed iron-manganese catalyst packing. The upper packing is a special packing for wood chip immobilized microorganisms, which uses wood chips as a carrier to immobilize ferrooxidizobacterium and other microorganisms in a cross-linking manner.

[0059] The biogas desulfurization tower 3 of the present invention uses high-efficiency desulfurization and purification packing. The complexed iron-manganese catalyst packing and the special packing for immobilized wood chips can greatly reduce the sulfur content in biogas. After desulfurization, the H2S gas concentration in biogas is reduced to below 10ppm, with high removal efficiency.

[0060] In one specific embodiment, the ammonia absorption tower 4 is provided with a second spray pipe assembly 403 at the top and a solution collection area 401 at the bottom. The second spray pipe assembly 403 is used to spray phosphoric acid solution into the ammonia absorption tower 4 to react with the rising gas and achieve ammonia removal. The bottom of the solution collection area 401 is connected to the inlet of the struvite crystallizer 7. The upper part of the solution collection area 401 is connected to the ammonia removal membrane assembly 5 through a return pipeline, and after being processed by the ammonia removal membrane assembly 5, it is returned to the second spray pipe assembly 403 for recycling.

[0061] The spray pipe assembly 403 has a main pipe diameter of 32mm and spray holes with a diameter of 4-8mm. The spray pipes are spaced 100mm apart. The solution collection area 401 is equipped with an ammonium hydrogen phosphate concentration meter 402. After the set concentration is reached, sludge is discharged. The supernatant from the sedimentation tank enters the ammonia removal membrane assembly 5 to recover ammonia from the supernatant and form gas. The solution is returned to the phosphoric acid absorption liquid for recycling.

[0062] Ammonia in anaerobic biogas is recovered by spraying through ammonia absorption tower 4, reducing the concentration of free ammonia in the liquid phase to less than 5 ppm with an efficiency of over 98%, thus achieving effective recovery of ammonia resources. Furthermore, the phosphoric acid absorbent can be regenerated and recycled through the ammonia removal membrane module 5. The module achieves internal water balance through internal circulation, improving the stability of ammonia recovery in the system.

[0063] Among them, the struvite crystallization tank 7 is equipped with a pH meter, a stirring component 701, and a second pH meter 702. By adding magnesium hydroxide, the pH is adjusted to 9-10 to generate magnesium ammonium phosphate precipitate. The magnesium ammonium phosphate precipitate enters the centrifugation device 8, such as a centrifuge, for dehydration treatment. The resulting filtrate is discharged into the denitrification tank 109 to dilute the concentration of pollutants in the influent.

[0064] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A high ammonia-nitrogen organic wastewater treatment process based on gas-liquid circulation, characterized in that, The method comprises the following steps: The pretreated high-ammonia-nitrogen and high-concentration organic wastewater is introduced into an anaerobic circulation tower to produce anaerobic gas; The effluent of the anaerobic circulation tower is sequentially treated by a denitrification tank, a nitrification tank and an ultrafiltration membrane, and then discharged, wherein the denitrification liquid produced by the denitrification tank is returned to the anaerobic circulation tower, and the nitrification liquid produced by the nitrification tank is returned to the denitrification tank; The anaerobic gas is sequentially introduced into a biogas desulfurization tower and an ammonia absorption tower for treatment; wherein part of the gas after ammonia removal in the ammonia absorption tower is returned to the anaerobic circulation tower, and part of the gas is returned to the biogas desulfurization tower; The solution produced by the ammonia absorption tower is treated by a struvite crystallization method and then dehydrated, and the filtrate produced by the dehydration is introduced into the denitrification tank.

2. The high ammonia-nitrogen organic wastewater treatment process based on gas-liquid circulation according to claim 1, characterized in that, The return ratio of the denitrification return liquid is 10% to 30%, the denitrification return liquid is returned to the bottom and middle part of the anaerobic circulation tower for denitrification reaction, the pH value of the bottom and middle part of the anaerobic circulation tower is controlled to be 6.5 to 7.5, part of the ammonia nitrogen is converted into nitrogen, and the pH value of the liquid phase in the upper part of the anaerobic circulation tower is increased to 9 to 10.

3. The high ammonia-nitrogen organic wastewater treatment process based on gas-liquid circulation according to claim 1, characterized in that, The return ratio of the nitrification tank return liquid is 50% to 100%.

4. The high-ammonia-nitrogen organic wastewater treatment process based on gas-liquid circulation according to claim 1, characterized in that, The concentrated liquid produced after the ultrafiltration membrane treatment is returned to the denitrification tank.

5. The high ammonia-nitrogen organic wastewater treatment process based on gas-liquid circulation according to claim 1, characterized in that, The return ratio of the gas after ammonia removal to the biogas desulfurization tower is 20% to 60%, and the return ratio of the gas to the anaerobic circulation tower is 40% to 80%.

6. A device for treating high-ammonia-nitrogen organic wastewater based on gas-liquid circulation, characterized in that, It comprises: a pretreatment tank; an anaerobic circulation tower connected with the effluent port of the pretreatment tank, used for decomposing organic matters in the wastewater and producing anaerobic gas; a denitrification tank connected with the effluent port of the anaerobic circulation tower, wherein the return port of the denitrification tank is connected with the water inlet port of the anaerobic circulation tower; a nitrification tank connected with the effluent port of the denitrification tank, wherein the return port of the nitrification tank is connected with the water inlet port of the denitrification tank; an ultrafiltration membrane connected with the effluent port of the nitrification tank, wherein the concentrated liquid outlet of the ultrafiltration membrane is connected with the water inlet port of the denitrification tank; a biogas desulfurization tower connected with the gas outlet port of the anaerobic circulation tower, used for desulfurization treatment of the anaerobic gas; an ammonia absorption tower connected with the gas outlet port of the biogas desulfurization tower, used for ammonia removal treatment of the anaerobic gas, wherein the gas outlet port of the ammonia absorption tower is connected with the gas inlet port of the anaerobic circulation tower and the gas inlet port of the biogas desulfurization tower; a struvite crystallization tank connected with the bottom outlet port of the ammonia absorption tower, used for crystallization recovery of the solution produced by the ammonia absorption tower treatment; a centrifugal device used for dehydration treatment of the precipitate produced by the struvite crystallization tank, wherein the water outlet port of the centrifugal device is connected with the water inlet port of the denitrification tank.

7. The device for treating high-ammonia-nitrogen organic wastewater based on gas-liquid circulation according to claim 6, characterized in that, The bottom of the anaerobic circulation tower is provided with a water distribution pipe and an aeration pipe, the return port of the denitrification tank is connected with the water distribution pipe of the anaerobic circulation tower, and the gas outlet port of the ammonia absorption tower is connected with the aeration pipe of the anaerobic circulation tower. 8.The high-ammonia-nitrogen organic wastewater treatment device based on gas-liquid circulation according to claim 7, characterized in that, The upper part of the anaerobic circulation tower is provided with a three-phase separator, an exhaust pipe and a desulfurization tower gas inlet pipe, the three-phase separator is used for three-phase separation of the gas, the exhaust pipe and the desulfurization tower gas inlet pipe are arranged above the three-phase separator, the exhaust pipe is used for external discharge of biogas, and the desulfurization tower gas inlet pipe is connected with the gas inlet port of the biogas desulfurization tower.

9. The high ammonia-nitrogen organic wastewater treatment device based on gas-liquid circulation according to claim 6, characterized in that, The biogas desulfurization tower is provided with a spraying pipe assembly one at the upper portion, a filler layer at the middle portion and a sedimentation tank at the bottom portion, the spraying pipe assembly one is used for spraying sodium hydroxide solution into the biogas desulfurization tower to react with the ascending gas to realize desulfurization, and the supernatant of the sedimentation tank is connected with the spraying pipe assembly one through a reflux pipeline to realize recycling.

10. The high ammonia-nitrogen organic wastewater treatment device based on gas-liquid circulation according to claim 6, characterized in that, The ammonia absorption tower is provided with a spraying pipe assembly two at the upper portion and a solution collecting area at the bottom portion, the spraying pipe assembly two is used for spraying phosphoric acid solution into the ammonia absorption tower to react with the ascending gas to realize ammonia removal, the bottom portion of the solution collecting area is connected with the inlet of the struvite crystallization tank, the upper portion of the solution collecting area is connected with the ammonia removal membrane assembly through a reflux pipeline, and the solution is returned to the spraying pipe assembly two after being treated by the ammonia removal membrane assembly to realize recycling.

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