Biofilm process for high-efficiency nitrogen removal

Abstract

The present invention relates to the technical field of water treatment. Disclosed is a biofilm process for high-efficiency nitrogen removal. A system comprises, successively connected to each other, a first reaction tank to a sixth reaction tank. The process comprises: during the process of starting anaerobic ammonia oxidation, enriching a first reaction tank, a second reaction tank and a fifth reaction tank with anaerobic ammonia oxidation bacteria, and controlling the C / N ratio and using a short HRT so as to accumulate nitrite, thus inducing the occurrence of an anaerobic ammonia oxidation process; and, in a stable operation stage of the system, keeping the anaerobic ammonia oxidation process stable and reducing the dosage of an external carbon source. Controlling in the first reaction tank and the second reaction tank the C / N ratio and the short retention time rapidly accumulates nitrite, and accelerates the enrichment of the anaerobic ammonium oxidation bacteria by means of a biofilm; adding to the fifth reaction tank the external carbon source achieves a more precise C / N ratio; inoculating microorganisms that penetrate to the fifth reaction tank from the first and second reaction tanks accelerates the start of the anaerobic ammonia oxidation process. The present invention achieves the rapid and stable start of anaerobic ammonia oxidation, a great microorganism enrichment capacity, and high-efficiency nitrogen removal.

Description

A highly efficient denitrification biofilm process Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to a high-efficiency denitrification biofilm process. Background Art

[0002] Traditional sewage denitrification is mainly based on nitrification-denitrification. The nitrification process requires oxygen supply through aeration, and the denitrification process requires the addition of carbon sources to supplement nutrients. With the continuous improvement of sewage treatment plant discharge standards, the energy consumption and drug consumption caused by nitrification-denitrification denitrification are also forced to continue to increase, which is contrary to the concept of "both green mountains and clear waters and gold and silver mountains". Anaerobic ammonia oxidation is a new, high-efficiency and low-consumption sewage denitrification process. Compared with traditional nitrification-denitrification denitrification, it can save 60% of aeration energy consumption and 100% of external drug costs. It has been successfully applied to the treatment of high-ammonia nitrogen wastewater. However, municipal sewage treatment systems with broader market prospects rarely have anaerobic ammonia oxidation processes. The main reasons are as follows:

[0003] First, my country's municipal sewage is mainly based on the activated sludge process, and it is difficult for suspended microorganisms to achieve efficient enrichment of long-sludge-age anaerobic ammonium oxidizing bacteria, which makes it difficult for the anaerobic ammonium oxidation process to occur; second, the mainstream municipal sewage is mostly 20-70 mg / L, and its FA is low, making it difficult to achieve a stable short-range nitrification process. The NO2 required for the mainstream anaerobic ammonium oxidation process is - The difficulty in effectively generating NH3-N makes the anaerobic ammonium oxidation process difficult to occur. Third, the anaerobic ammonium oxidation process has strict requirements for water quality and control parameters. Municipal sewage influent has complex water quality, containing ammonia nitrogen, organic matter, and other substances. The removal pathways and control requirements for each substance vary, and competition between bacterial species makes it difficult for the entire system to achieve effective coordination.

[0004] At present, the research reports on the denitrification process of the existing technology are as follows:

[0005] CN114477420A discloses a method and device for achieving deep denitrification of sewage by dual-coupling anaerobic ammonium oxidation with continuous flow AOA short-range nitrification and endogenous short-range denitrification. The device includes a raw water tank for urban domestic sewage, a continuous flow AOA reactor, and a sedimentation tank. The method is that after the urban domestic sewage is pumped into the continuous flow reactor, it is operated in anaerobic, aerobic, and anoxic modes. The anaerobic zone stores the internal carbon source and releases phosphorus. The aerobic zone undergoes short-range nitrification anaerobic ammonium oxidation and absorbs phosphorus. The anoxic zone undergoes endogenous short-range denitrification anaerobic ammonium oxidation. Suspended and fixed biological carriers are added to the aerobic and anoxic zones respectively to retain and enrich anaerobic ammonium oxidizing bacteria. Finally, dual coupling of anaerobic ammonium oxidation is achieved in the aerobic and anoxic zones, respectively, to improve the efficiency of denitrification and phosphorus removal. The main technical problems still exist in this denitrification process are: First, it uses two processes of short-range nitrification anaerobic ammonium oxidation in the aerobic zone and short-range denitrification anaerobic ammonium oxidation in the anoxic zone to achieve synergistic denitrification. In response to the difficulties of short-term nitrification of mainstream sewage, the application documents did not provide clear control measures, making it difficult to ensure a stable source of nitrous oxide, and the anaerobic ammonium oxidation process is difficult to stabilize denitrification. Second, in addition to considering the source of nitrous oxide, the anaerobic ammonium oxidation process in the anoxic zone also needs to ensure the supply of substrates for ammonia nitrogen. This is because the aerobic zone can easily achieve a complete nitrification process, but the application did not take this into account and did not limit the concentration of ammonia nitrogen entering the anoxic zone. Short-term denitrification and anaerobic ammonium oxidation denitrification in the anoxic zone are difficult to stabilize. Third, there is a great operational risk in relying solely on the anaerobic ammonium oxidation process in the anoxic zone to ensure that the effluent ammonia nitrogen meets the standard. Affected by the anaerobic ammonium oxidation process, there is a risk of exceeding the effluent ammonia nitrogen concentration standard.

[0006] CN112811719A discloses an autotrophic denitrification treatment system for municipal sewage and its treatment method. The system includes a raw water storage unit, a CEPT reactor, a sedimentation tank, a sludge concentration tank, a side stream short-cut nitrification reactor, a main stream short-cut denitrification reactor, and an anaerobic ammonium oxidation reactor. Municipal sewage first enters the CEPT reactor to remove phosphorus and some organic matter. Then, ammonia nitrogen in the side stream sludge digestion liquid is used for short-cut nitrification. The generated nitrite nitrogen enters the main stream for autotrophic anaerobic ammonium oxidation denitrification. The effluent from the anaerobic ammonium oxidation reactor is then returned to the main stream short-cut denitrification reactor. The carbon source in the raw water is used to perform short-cut denitrification on the small amount of nitrate nitrogen generated by the anaerobic ammonium oxidation reactor, generating nitrite nitrogen to supplement the main stream anaerobic ammonium oxidation process. This existing technology has a clear process flow and effectively addresses the source of nitrous oxide in the mainstream anaerobic ammonium oxidation (ANAMMOX) process. However, it is difficult to implement in actual projects for the following reasons: First, it does not restrict water quality parameters. The ideal ratio of ammonia nitrogen to nitrous oxide in the ANAMMOX process is 1:1.32. However, calculations based on existing sewage treatment plants that operate anaerobic sludge digestion show that the nitrous oxide concentration in the mixed wastewater is low, with the ratio of ammonia nitrogen to nitrous oxide approaching 2:1. Second, it does not have a safety unit, relying solely on the ANAMMOX unit as the final reaction unit. Based on the Class A standard commonly used for municipal wastewater in my country, this patented system poses a high risk of exceeding the effluent standards for ammonia nitrogen and TN.

[0007] CN116573765A discloses a segmented water inlet and multi-point reflux system for enhancing the autotrophic denitrification of municipal sewage and a method thereof. The system includes a biochemical tank, a sedimentation tank, an inlet pipe or an inlet gallery, a connecting pipe, an outlet pipe, a nitrification liquid reflux pipe, a sludge reflux pipe, a supernatant reflux pipe, and a sludge discharge pipe. The system combines various microbial aggregation forms such as pure biofilm, coexistence of biofilm and flocculent sludge, and pure flocculent sludge in the biochemical tank to give full play to their respective advantages, and regulates the distribution of organic matter, ammonia nitrogen, and nitrate nitrogen in each section by means of segmented water inlet and multi-point reflux to enhance the operating effect of the system through anaerobic ammonia oxidation autotrophic denitrification. In this application, fixed fillers are used in the short-range denitrification anaerobic ammonia oxidation area. During actual operation, due to the lack of sufficient hydraulic shear of the fixed bed biofilm, the biofilm is prone to thickening, which leads to limited mass transfer and thus affects the treatment load.

[0008] This shows that the prior art needs to be further improved. Summary of the Invention

[0009] The purpose of the present invention is to provide a high-efficiency denitrification biofilm process, which adopts a short-range denitrification-anaerobic ammonium oxidation coupled with a traditional denitrification process to achieve synergistic denitrification, without nitrous oxide accumulation during stable operation, and can achieve high-efficiency denitrification.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A highly efficient denitrification biofilm process comprises the following steps:

[0012] Step 1: Build the required system

[0013] The system includes reaction tanks, which include a first reaction tank, a second reaction tank, a third reaction tank, a fourth reaction tank, a fifth reaction tank, and a sixth reaction tank arranged in sequence from front to back;

[0014] A first water inlet pipeline is provided at the water inlet end of the first reaction tank, a second water inlet pipeline and a carbon source addition pipeline are provided at the water inlet end of the fifth reaction tank, a nitration liquid reflux pipeline is provided at the water outlet end of the fourth reaction tank, and the other end of the nitration liquid reflux pipeline is connected to the water inlet end of the first reaction tank;

[0015] The first reaction tank, the second reaction tank, the third reaction tank, and the fifth reaction tank are respectively equipped with a stirring device, and the fourth reaction tank and the sixth reaction tank are respectively equipped with an aeration device;

[0016] The first, second and fifth reaction tanks are added with suspended carriers for anaerobic ammonium oxidation, the third reaction tank is added with suspended carriers for denitrification, and the fourth and sixth reaction tanks are added with suspended carriers for aerobic zones; the suspended sludge concentration in each reaction tank is less than 500 mg / L;

[0017] Step 2: Anaerobic ammonium oxidation start-up

[0018] Through relevant control, the anaerobic ammonia oxidation process in the first and second reaction tanks is successfully started;

[0019] The ammonia nitrogen concentration in the effluent of the fourth reaction tank was controlled between 3 and 5 mg / L. The C / N ratio of the influent of the fifth reaction tank was controlled at 2.5 to 3.0 by adding an external carbon source. The anaerobic ammonia oxidation process in the fifth reaction tank was started by utilizing suitable anaerobic ammonia oxidation reaction conditions and superimposing the anaerobic ammonia oxidation bacteria carried by the effluents of the first and second reaction tanks. The anaerobic ammonia oxidation process in the fifth reaction tank was successfully started until the ammonia nitrogen removal and nitrous oxide production in the fifth reaction tank reached 3 mg / L and 2 mg / L, respectively.

[0020] Step 3: Stable system operation

[0021] Maintain the stability of the anaerobic ammonium oxidation process, improve the denitrification efficiency, and gradually reduce the amount of carbon source added;

[0022] During stable operation of the system, the residence time in the first reaction tank and the second reaction tank is 1.0 to 1.2 hours; the residence time in the third reaction tank is 1.5 to 2.0 times that of the first reaction tank; the residence time in the fourth reaction tank is 3.0 to 4.0 times that of the first reaction tank, and the actual residence time in the fourth reaction tank does not exceed 1.5 hours; the residence time in the fifth reaction tank and the sixth reaction tank is 1.0 to 1.5 times that of the first reaction tank;

[0023] After the system is started up, the biofilm thickness of the first to sixth reaction tanks are 150-200μm, 100-150μm, 100-150μm, 200-300μm, 150-200μm, and 150-200μm respectively; the effluent ammonia nitrogen is <0.5mg / L, TN is <5mg / L, and COD is <30mg / L.

[0024] In the above-mentioned high-efficiency denitrification biofilm process, the density of the suspended carrier for anaerobic ammonia oxidation is 0.98-1.00 g / cm 3 The average gap spacing of the suspended carrier is ≥5mm; the density of the suspended carrier for denitrification is 0.98~1.00g / cm 3 The average gap spacing of the suspended carrier is ≥3mm; the density of the suspended carrier in the aerobic zone is 0.94~0.97g / cm 3 The average gap spacing of the suspended carrier is ≥5mm; the effective specific surface area of ​​each type of suspended carrier is ≥800m2 / m 3 The suspended carrier filling rate of each reaction tank is >45%.

[0025] In the above-mentioned efficient denitrification biofilm process, interception screens are provided between adjacent reaction pools, the suspended carriers in each reaction pool are enriched in a specific area, and the reflux point of the fourth reaction pool is located behind the interception screen of the fourth reaction pool.

[0026] In the above-mentioned high-efficiency denitrification biofilm process, the reflux ratio of the nitrification liquid reflux pipeline is 200-400%; after the system is started up, the biofilm thicknesses of the first to sixth reaction tanks are 150-200μm, 100-150μm, 100-150μm, 200-300μm, 150-200μm, and 150-200μm, respectively; the effluent ammonia nitrogen is <0.5mg / L, TN is <5mg / L, and COD is <30mg / L.

[0027] In the second step of the above-mentioned high-efficiency denitrification biofilm process, the relevant controls specifically refer to: controlling the first water inlet pipeline to operate at full load, closing the second water inlet pipeline, controlling the C / N ratio in the first reaction tank to 3.0~3.5, and the nitrate nitrogen in the effluent of the third reaction tank to <1mg / L, until the ammonia nitrogen removal amount in the first reaction tank and the second reaction tank is greater than 2mg / L and 3mg / L respectively, and the nitrous oxide generation amount is greater than 2mg / L and 1mg / L respectively, the anaerobic ammonia oxidation process in the first reaction tank and the second reaction tank is successfully started.

[0028] In the above-mentioned high-efficiency denitrification biofilm process, the carbon source is sodium acetate, glucose, sodium formate, sodium propionate or methanol.

[0029] In the above-mentioned high-efficiency denitrification biofilm process, the carbon source is sodium acetate.

[0030] In the above-mentioned high-efficiency denitrification biofilm process, the specific steps of the third step are: controlling the inflow of water into the first water inlet pipe and the second water inlet pipe respectively, causing short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification denitrification in the first reaction tank and the second reaction tank, the relative abundance of denitrifying bacteria Denitratisoma is greater than 0.5% and 1.0% respectively, the relative abundance of anaerobic ammonia oxidizing bacteria Candiditaous Brocadia is greater than 1.0% and 1.5% respectively, the cumulative TN removal rate of the first reaction tank and the second reaction tank is greater than 60%, the TN removal rate after anaerobic ammonia oxidation is greater than 30% or the cumulative ammonia nitrogen removal amount is greater than 5 mg / L;

[0031] Anoxic denitrification occurs in the third reaction tank to ensure the anoxic TN removal effect, the relative abundance of denitrifying bacteria is >30%, and the effluent nitrate nitrogen concentration is controlled to <1mg / L or COD concentration is <50mg / L;

[0032] The fourth reaction tank undergoes nitrification and is coupled with an aerobic decarbonization process. The relative abundance of heterotrophic bacteria is >20%, the relative abundance of nitrifying bacteria is >15%, and the effluent ammonia nitrogen is controlled to <0.5 mg / L.

[0033] The fifth reaction tank undergoes short-cut denitrification-anaerobic ammonium oxidation coupled with heterotrophic denitrification, controlling the C / N ratio between 2.5 and 3.0, achieving a TN removal rate greater than 10% or ammonia nitrogen removal greater than 2 mg / L via the anaerobic ammonium oxidation pathway, and a relative abundance of biofilm denitrifying bacteria greater than 10%, while the relative abundances of anaerobic ammonium oxidizing bacteria Candiditaous Brocadia and denitrifying bacteria Denitratisoma are both greater than 0.5%.

[0034] The nitrification process in the sixth reaction tank is coupled with the aerobic decarbonization process to ensure that the total effluent COD and ammonia nitrogen meet the standards, the relative abundance of biofilm heterotrophic bacteria is >30%, the relative abundance of nitrifying bacteria is >10%, and the effluent COD and ammonia nitrogen are less than 30 mg / L and 0.5 mg / L, respectively.

[0035] In the above-mentioned high-efficiency denitrification biofilm process, when the third step system is running stably, the stirring device needs to be turned on, and the stirring power density of the stirring device in the first reaction tank and the second reaction tank is greater than 7.5W / m 3 , the stirring power density in the third reaction tank is >10W / m 3 , the stirring power density in the fifth reaction cell is >7.5W / m 3 The aeration intensity in the fourth and sixth reaction tanks is greater than 12-16 m 3 / m 2 / h, 10~14 m 3 / m 2 / h.

[0036] In the above-mentioned high-efficiency denitrification biofilm process, the system influent ammonia nitrogen concentration is greater than 20 mg / L, C / N is less than 4, and the proportion of carboxylic acids in the influent organic matter is greater than 20%.

[0037] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0038] 1) Energy saving and consumption reduction. The TN removal rate of the present invention through the anaerobic ammonium oxidation process is greater than 40%. On the basis of meeting the TN of the effluent <5mg / L, it reduces the aeration energy consumption by 20% and reduces the external carbon source dosage by 40%.

[0039] 2) No environmental harm. The core denitrification of this invention is to couple the traditional denitrification process with short-range denitrification-anaerobic ammonium oxidation. The two achieve synergistic denitrification. During stable operation, there is no nitrous oxide accumulation and no environmental harm to the effluent.

[0040] 3) Wide range of applications. The minimum influent ammonia nitrogen concentration of this invention is 20 mg / L, and the minimum treatment temperature is 10°C. It has a wide range of applications and can be applied to the treatment of municipal sewage and higher concentrations of high ammonia nitrogen wastewater, such as industrial wastewater.

[0041] 4) Simple operation and control. This invention utilizes a fluidized bed biofilm process, eliminating the need for a sludge return system. The suspended sludge concentration within the system is less than 500 mg / L, eliminating concerns about suspended microbial operation, such as sludge aging and difficulty in separation. The biofilm achieves dynamic microbial renewal during the fluidization process, and the long sludge age system improves impact resistance.

[0042] 5) Rapid and stable ANAMMOX startup. The first and second reaction zones of the present invention rapidly accumulate nitrous oxide by controlling the C / N ratio and shortening the residence time, while simultaneously accelerating the enrichment of ANAMMOX bacteria through the biofilm. The fifth reaction zone achieves a more precise C / N ratio by injecting an external carbon source. Simultaneously, microorganisms are inoculated from the first and second reaction zones and penetrate into the fifth reaction zone, accelerating the startup of the ANAMMOX process and maintaining the long-term stability of the ANAMMOX process within the fifth reaction zone.

[0043] 6) Strong microbial enrichment capacity. The relative abundance of anaerobic ammonia-oxidizing bacteria in the present invention is >1.5%, the relative abundance of denitrifying bacteria is >30%, and the relative abundance of nitrifying bacteria is >15%, achieving efficient synergistic denitrification.

[0044] 7) Land Conservation. Based on the municipal sewage treatment system, the entire system has a maximum HRT of 12.6 hours, saving 50% of land. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention will be further described below with reference to the accompanying drawings:

[0046] FIG1 is a schematic structural diagram of the system of the present invention;

[0047] FIG2 is a diagram showing the effect of the ammonia nitrogen concentration in the effluent from the fourth reaction tank on the effluents from the fifth reaction tank and the sixth reaction tank;

[0048] Figure 3 shows the relative abundance of functional bacteria and their macroscopic effects;

[0049] In the picture:

[0050] I, first reaction tank, II, second reaction tank, III, third reaction tank, IV, fourth reaction tank, V, fifth reaction tank, VI, sixth reaction tank, I1, first water inlet pipeline, I2, second water inlet pipeline, I3, total water outlet pipeline, C1, carbon source addition pipeline, R, nitrification liquid reflux pipeline. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0052] In the description of this application, words such as "first" and "second" are used only to distinguish different objects and do not limit the quantity or execution order. In addition, words such as "first" and "second" do not necessarily mean different. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0053] The structures and use methods of the stirring device and aeration device described in the present invention can be realized by referring to the existing technology.

[0054] The denitrifying bacteria Denitratisoma and anaerobic ammonia oxidizing bacteria Candiditaous Brocadia described in the present invention can be purchased through commercial channels.

[0055] The following explanations are given for the specific terms used in the present invention:

[0056] TN removal rate: refers to the ratio of TN removal in the area to the total nitrogen in the influent;

[0057] Anaerobic ammonium oxidation TN removal rate: refers to the ratio of TN removed by the anaerobic ammonium oxidation process to the total nitrogen in the influent;

[0058] Void spacing: the average diameter of the circumscribed circle formed by the pores of the suspended carrier;

[0059] Nitrous acid accumulation rate: Nitrite nitrogen (NO2 - -N) concentration and nitrite nitrogen (NO2 - -N) concentration and nitrate nitrogen (NO3 - -N) concentration ratio;

[0060] Nitrate nitrogen: refers to inorganic nitrogen in the system in the form of +3 and +5 valence, including NO2 - -N and NO3 - -N;

[0061] C / N: For the anoxic zone, it refers to the difference between the influent COD minus 30 and NO x - -N concentration ratio; for the post-anoxic zone, it refers to the externally injected COD and NO x - -Ratio of N concentration.

[0062] The technical solution of the present application is further described in detail below with reference to the accompanying drawings.

[0063] As shown in Figure 1, the system of the present invention includes a first reaction tank I, a second reaction tank II, a third reaction tank III, a fourth reaction tank IV, a fifth reaction tank V and a sixth reaction tank VI connected in sequence. The denitrification treatment effect is improved by arranging the reaction tanks and combining the control of each reaction tank.

[0064] A first water inlet pipe I1 is provided at the water inlet of the first reaction tank, a second water inlet pipe I2 and a carbon source addition pipe C1 are provided at the water inlet of the fifth reaction tank, a nitrification liquid return pipe R is provided at the water outlet of the fourth reaction tank, the other end of the nitrification liquid return pipe is connected to the water inlet of the first reaction tank, and the water outlet of the sixth reaction tank is connected to the total water outlet pipe I3. A stirring device is installed in the first, second, third, and fifth reaction tanks, and an aeration device is installed in the fourth and sixth reaction tanks. The stirring device may include stirring blades and a motor, and the stirring blades are driven to rotate by the motor. The main structure and working principle of the stirring device and aeration device can be realized by those skilled in the art by referring to the existing technology.

[0065] Anaerobic ammonium oxidation suspended carriers are added to the first, second, and fifth reaction tanks, denitrification suspended carriers are added to the third reaction tank, and aerobic zone suspended carriers are added to the fourth and sixth reaction tanks. The entire system is a pure membrane system, without any mud-water separation unit or sludge return unit. The suspended sludge concentration in each reaction tank is less than 500 mg / L.

[0066] The residence time of the first and second reaction tanks is 1.0 to 1.2 hours; the residence time of the third reaction tank is 1.5 to 2.0 times that of the first reaction tank; the residence time of the fourth reaction tank is 3.0 to 4.0 times that of the first reaction tank, and when internal reflux is comprehensively considered, the actual residence time of the fourth reaction tank does not exceed 1.5 hours; the residence time of the fifth and sixth reaction tanks is 1.0 to 1.5 times that of the first reaction tank. The limitation of the residence time further clarifies that the ingenious concept of the present invention lies in that the residence time of the first and second reaction tanks is short, and the residence time of the third reaction tank is long, which is conducive to the accumulation of nitrous oxide. Short-range denitrification-anaerobic ammonia oxidation coupled with heterotrophic denitrification denitrification occurs in the first reaction tank and the second reaction tank, anoxic denitrification occurs in the third reaction tank to ensure the removal effect of anoxic TN, and the limitation of the residence time in the fourth reaction tank reserves a guarantee for the subsequent inoculation of the fifth reaction tank. In other words, the first reaction tank, the second reaction tank, the third reaction tank, the fourth reaction tank, the fifth reaction tank and the sixth reaction tank of the present invention are interdependent and closely related, and the residence time of the former reaction tank provides a guarantee for the inoculation of the latter reaction tank.

[0067] After system startup, the biofilm thicknesses in the first to sixth reaction tanks reached 150-200μm, 100-150μm, 100-150μm, 200-300μm, 150-200μm, and 150-200μm, respectively. Ammonia nitrogen in the effluent was <0.5mg / L, TN <5mg / L, and COD <30mg / L.

[0068] The specific system process of the system of the present invention is described below.

[0069] Step 1: Anaerobic ammonium oxidation start-up process

[0070] The goal of this process is to enrich anaerobic ammonium-oxidizing bacteria in the first, second and fifth reaction tanks, and to achieve the accumulation of nitrous oxide by controlling C / N and superimposing a short HRT, thereby inducing the occurrence of the anaerobic ammonium oxidation process.

[0071] The first water inlet pipe was controlled to operate at full capacity, and the second water inlet pipe was closed. The C / N ratio of the first reaction tank was controlled to be between 3.0 and 3.5, and the nitrate nitrogen in the effluent of the third reaction tank was controlled to be less than 1 mg / L. The anaerobic ammonia oxidation process in the first and second reaction tanks was successfully initiated until the ammonia nitrogen removal in the first and second reaction tanks exceeded 2 mg / L and 3 mg / L, respectively, and the nitrous oxide production exceeded 2 mg / L and 1 mg / L, respectively. The C / N ratio of the influent of the second reaction tank was lower than that of the first reaction tank by default, and the influent of the second reaction tank would also contain nitrous oxide accumulated in the first reaction tank, so the performance of the second reaction tank was better than that of the first reaction tank.

[0072] The ammonia nitrogen concentration in the effluent of the fourth reaction tank was controlled between 3 and 5 mg / L. The C / N ratio of the influent of the fifth reaction tank was controlled at 2.5 to 3.0 by adding a high-quality carbon source. The anaerobic ammonium oxidation process in the fifth reaction tank was initiated using suitable anaerobic ammonium oxidation (ANAMMXO) reaction conditions and the addition of detached ANAMMXO bacteria from the effluent of the first and second reaction tanks. The ANAMMXO process in the fifth reaction tank was successfully initiated when the ammonia nitrogen removal and nitrous oxide production in the fifth reaction tank reached approximately 3 mg / L and 2 mg / L, respectively. The first and second reaction tanks played an important role in maintaining the stability of ANAMMXO in the fifth reaction tank.

[0073] Step 2: System stable operation

[0074] The goal of this process is to maintain the stability of the anaerobic ammonium oxidation process, improve the denitrification efficiency, and reduce the amount of external carbon source added.

[0075] Control the first water inlet pipeline and the second water inlet pipeline to respectively inlet water.

[0076] Short-cut denitrification-anaerobic ammonium oxidation coupled with heterotrophic denitrification occurred in the first reaction tank and the second reaction tank. The relative abundance of denitrifying bacteria Denitratisoma was >0.5% and 1.0%, respectively; the relative abundance of anaerobic ammonium oxidizing bacteria Candiditaous Brocadia was >1.0% and 1.5%, respectively; the cumulative TN removal rate of the first reaction tank and the second reaction tank was >60%, and the TN removal rate after anaerobic ammonium oxidation was >30% or the cumulative ammonia nitrogen removal was greater than 5 mg / L.

[0077] Anoxic denitrification occurs in the third reactor to ensure effective TN removal. Denitrifying bacteria are present at a relative abundance >30%, and the effluent nitrate concentration is controlled to <1 mg / L or COD concentration <50 mg / L. Considering the reduction in COD usage due to ANAMMOX, COD excess may occur, with nitrate concentrations below 1 mg / L. If COD is already low, COD concentrations below 50 mg / L are more likely.

[0078] The fourth reaction tank undergoes nitrification and is coupled with an aerobic decarbonization process. The relative abundance of heterotrophic bacteria is >20%, and the relative abundance of nitrifying bacteria is >15%. The ammonia nitrogen content in the effluent is controlled to be <0.5 mg / L.

[0079] The fifth reaction tank undergoes short-cut denitrification-anaerobic ammonium oxidation coupled with heterotrophic denitrification denitrification, controlling the C / N ratio at 2.5-3.0. The TN removal rate through the anaerobic ammonium oxidation pathway is greater than 10%, or the ammonia nitrogen removal amount is greater than 2 mg / L. The relative abundance of biofilm denitrifying bacteria is greater than 10%, and the relative abundance of anaerobic ammonium oxidizing bacteria Candiditaous Brocadia and denitrifying bacteria Denitratisoma are both greater than 0.5%.

[0080] The nitrification process in the sixth reaction tank is coupled with the aerobic decarbonization process to ensure that the total effluent COD and ammonia nitrogen meet the standards, the relative abundance of biofilm heterotrophic bacteria is >30%, the relative abundance of nitrifying bacteria is >10%, and the effluent COD and ammonia nitrogen are less than 30 mg / L and 0.5 mg / L, respectively.

[0081] The thickness of the biofilm maintained in the first to sixth reaction tanks are 150-200 μm, 100-200 μm, 100-200 μm, 300-400 μm, 150-200 μm, and 300-400 μm, respectively.

[0082] Preferably, the density of the suspended carrier for anaerobic ammonium oxidation is 0.98-1.00 g / cm 3 The average gap spacing of the suspended carrier is ≥5mm; the density of the suspended carrier for denitrification is 0.98~1.00g / cm 3 The average gap spacing of the suspended carrier is ≥3mm; the density of the suspended carrier in the aerobic zone is 0.94~0.97g / cm 3The average gap spacing of the suspended carrier is ≥5mm. The effective specific surface area of ​​each type of suspended carrier is ≥800m 2 / m 3 The suspended carrier filling rate of each reaction tank is >45%.

[0083] Preferably, when the system is in a stable operating state, the stirring power density of the first reaction tank and the second reaction tank is greater than 7.5W / m 3 , stirring power density of the third reaction tank>10W / m 3 With this design, the denitrification load of the third reaction tank is lower than that of the first and second reaction tanks, the gas production is less, and the corresponding fluidization power is improved. The stirring power density of the fifth reaction tank is >7.5W / m 3 The aeration intensity of the fourth and sixth reaction tanks is respectively>12~16 m 3 / m 2 / h, 10~14 m 3 / m 2 / h.

[0084] Preferably, adjacent reaction pools are separated by intercepting screens, which can ensure that the suspended carriers are enriched in specific areas and do not flow between them.

[0085] The ammonia nitrogen concentration of the system influent is greater than 20 mg / L, C / N is less than 4, and the proportion of carboxylic acid substances in the influent organic matter is greater than 20%; the internal reflux ratio (nitration liquid reflux pipeline from the fourth reaction tank to the first reaction tank) is controlled at 200-400%.

[0086] By comparing carbon sources such as sodium acetate, glucose, sodium formate, sodium propionate and methanol, the present invention preferably adds sodium acetate as the carbon source in the fifth reaction tank.

[0087] The present invention will be further described below with reference to specific embodiments. Example

[0088] A sewage treatment plant with a designed water volume of 10,000 m 3 / d, designed influent COD, BOD5, NH4 + -N and TN are 580mg / L, 260mg / L, 50mg / L and 70mg / L respectively. The AOAO process based on fluidized bed biofilm method is adopted, and a total of 6 reaction tanks are set up, of which the first and second reaction tanks have a residence time of 1h, the third reaction tank has a residence time of 1.5h, the fourth reaction tank has a residence time of 4h, the fifth reaction tank has a residence time of 1.2h, and the sixth reaction tank has a residence time of 1.5h. The system MLSS is less than 300mg / L. The effective surface area of ​​the suspended carrier added to each reaction tank is 800m 2 / m 3, the filling rate is 55%. The water inflow of the first reaction tank is 95% of the actual water inflow, and the water inflow of the fifth reaction tank is 5% of the actual water inflow. According to the detection and calculation along the process, the TN removal rate of the first and second reaction tanks after the anaerobic ammonium oxidation process reaches 35%, and the TN removal rate of the fifth reaction tank after the anaerobic ammonium oxidation process reaches 12%. The overall TN removal rate of the system is 93%, and the effluent NH4 + -N <0.5mg / L, TN <5mg / L. Example

[0089] A sewage treatment plant with a designed water volume of 20,000 m 3 / d, designed influent COD, BOD5, NH4 + -N and TN are 500mg / L, 200mg / L, 60mg / L and 72mg / L respectively. The AOAO process based on fluidized bed biofilm method is adopted, and a total of 6 reaction tanks are set up. The residence time of the first to sixth reaction tanks are 1.2h, 1.2h, 1.5h, 4.5h, 1.2h and 1.2h respectively. The system MLSS is <300mg / L. The effective surface area of ​​the suspended carrier added to each reaction tank is 800m 2 / m 3 The filling rates of the first, second, third, and fifth reaction tanks were all 58%, while the filling rates of the fourth and sixth reaction tanks were 66%. In the initial stage of operation, the project adopted a single-point water inlet model, with all sewage entering the first reaction tank. During operation, by controlling the C / N ratio of the influent, it was observed that a stable anaerobic ammonium oxidation process occurred in the first and second reaction tanks, with a TN removal rate of 40%. High-throughput sequencing revealed that the biofilms were enriched with anaerobic ammonium-oxidizing bacteria, Candiditaous Brocadia, with relative abundances of >1.5% and 2.0%, respectively. During operation, by controlling the DO of the fourth reaction tank, a portion of ammonia nitrogen was released into the fifth reaction tank, with an ammonia nitrogen concentration of 3-4 mg / L. By reducing the amount of external carbon source added to the fifth reaction tank and controlling the C / N ratio to 2.8, a short-term denitrification process was induced to produce nitrous oxide, thereby promoting the occurrence of the ANAMMOX process. After 10 days of operation, the ammonia nitrogen loss in the fifth reaction tank reached nearly 2 mg / L.

[0090] Subsequently, a new inlet pipeline was added to the fifth reactor, diverting 8% of the influent water to provide a stable source of ammonia nitrogen. After 20 days of operation, high-throughput sequencing revealed that the dominant anaerobic ammonium-oxidizing bacteria in the fifth reactor's biofilm were Candiditaous Brocadia, with a relative abundance of 1.0%. Measurements along the process also showed that the TN removal rate during the anaerobic ammonium oxidation process reached 15%, demonstrating significant energy savings.

[0091] Comparative Example 1:

[0092] Pilot system processing scale 100m 3 During startup, the effluent from the fourth reactor was controlled to maintain a certain ammonia nitrogen concentration in the fifth reactor. As shown in Figure 2, when the ammonia nitrogen concentration in the effluent from the fourth reactor was 1 or 2 mg / L, the fifth reactor struggled to achieve stable ammonia nitrogen removal over the long term, hindering the enrichment of anaerobic ammonium-oxidizing bacteria and the subsequent anaerobic ammonium oxidation process. When the effluent from the fourth reactor was 3-5 mg / L, the fifth reactor demonstrated significant ammonia nitrogen removal, exceeding 1 mg / L. Furthermore, the sixth reactor further nitrified the ammonia nitrogen in the post-anoxic zone effluent, ensuring a final effluent concentration below 0.5 mg / L. When the ammonia nitrogen concentration in the effluent from the fourth reactor was 6-7 mg / L, the anaerobic ammonium oxidation efficiency of the fifth reactor continued to improve. However, this also led to a gradual increase in the ammonia nitrogen concentration in the effluent from the fifth reactor. Due to the high ammonia nitrogen concentration in the influent from the sixth reactor and the impact of post-A organic matter penetration, the effluent from the fifth reactor struggled to maintain a stable ammonia nitrogen concentration below 0.5 mg / L. Therefore, during startup, controlling the ammonia nitrogen effluent from the main aerobic tank to 3-5 mg / L was the optimal value.

[0093] Comparative Example 2:

[0094] A pilot system with a processing capacity of 100m 3 / d, using an AOAO process system based on a fluidized bed biofilm method. The first and fifth reaction tanks were fed with water at inflow ratios of 95% and 5%, respectively. The removal of suspended carrier biofilms in the anoxic zone and its various functional zones was tracked over a long period of time, with the results shown in Figure 3. The biofilm method offers a natural advantage in enriching ANAMMOX bacteria. A certain amount of ANAMMOX bacteria can be detected in the anoxic biofilm during the initial stages of operation through high-throughput processes. However, macroscopic results show that when the relative abundance of ANAMMOX bacteria is only 0.1% to 0.3%, although bacteria are present, no ANAMMOX process occurs at the macroscopic level. However, when the relative abundance of ANAMMOX bacteria reaches 0.5 or above, ANAMMOX becomes evident. Experimental results show a positive correlation between macroscopic denitrification capacity and microscopic enrichment.

[0095] Comparative Example 3:

[0096] An anoxic pilot system, water treatment capacity 100m 3 / d, influent NO3 - The -N content was 10 mg / L, the relative abundance of denitrification in the system filler was >10%, there were no anaerobic ammonium oxidizing bacteria, and the HRT was 1 h. Five carbon sources—sodium acetate, glucose, sodium formate, sodium propionate, and methanol—were added, controlling the C / N ratio to 3 to verify nitrous oxide accumulation in the system. As shown in Table 1, sodium acetate had the highest nitrous oxide accumulation, followed by sodium formate and sodium propionate. Glucose and methanol showed no nitrous oxide accumulation.

[0097] Table 1 Nitrous acid accumulation of different carbon source types

[0098] Comparative Example 4:

[0099] An anoxic pilot system, water treatment capacity 100m 3 / d, influent NO3 - -N content is 15 mg / L, ammonia nitrogen content is 15 mg / L, the relative abundance of denitrification in the system filler is 10%, the relative abundance of anaerobic ammonium oxidizing bacteria is 1%, and the HRT is 1h. The carbon source type is sodium acetate, and the control C / N is 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0, respectively. As can be seen from Table 2, the lower the C / N, the higher the load of anaerobic ammonium oxidation denitrification membrane and the greater the denitrification contribution rate. However, low C / N also leads to a decrease in the overall denitrification load. When the C / N is controlled at 2.5~3.5, the overall denitrification membrane load is greater than 0.7 g / m 2 ·d -1 , and the contribution rate of anaerobic ammonium oxidation to denitrification is greater than 40%.

[0100] Table 2 Effect of C / N on TN removal

[0101] Comparative Example 5:

[0102] An anoxic pilot system, water treatment capacity 100m 3 d, treating actual domestic sewage with a COD of 200 mg / L and an influent ammonia nitrogen of 50 mg / L. An anoxic system was established with a HRT of 1.2 h. Nitrate nitrogen was artificially supplemented to 40 mg / L to study the effectiveness of anoxic denitrification. Microbial relative abundance and macroscopic nitrogen removal were also tracked. The experimental results are shown in Table 3. With increased operation time, suspended carriers gradually formed biofilm, leading to a gradual increase in the relative abundance of denitrifying bacteria and nitrate nitrogen removal efficiency. By day 14, the relative abundance of denitrifying bacteria had reached 10%, but the percentage of Denitrifying bacteria was only 0.1%, indicating no nitrous oxide accumulation in the system. Only after the percentage of Denitrifying bacteria reached 0.5% did nitrous oxide accumulation of 2 mg / L occur, and the nitrate nitrogen removal efficiency reached 90%. By day 40, the relative abundance of Denitrifying bacteria reached 1.0%. At this point, the accumulation of nitrous oxide triggered anaerobic ammonium oxidation (ANAMMOX), which also began to remove ammonia nitrogen, indicating successful initiation of ANAMMOX. Therefore, it can be seen that in order to realize the anaerobic ammonium oxidation process, there must be enrichment of Denitratisoma, which provides a source of nitrous oxide for anaerobic ammonium oxidation through a short-range denitrification process.

[0103] Table 3 Effects of Denitratisoma on the anaerobic ammonium oxidation process of the system

[0104] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. An efficient denitrification biofilm process, characterized in that, It includes the following steps: Step 1: Assemble the required system The system includes a reaction tank, which includes a first reaction tank, a second reaction tank, a third reaction tank, a fourth reaction tank, a fifth reaction tank, and a sixth reaction tank arranged in sequence from front to back; A first water inlet pipeline is provided at the water inlet end of the first reaction tank, a second water inlet pipeline and a carbon source dosing pipeline are provided at the water inlet end of the fifth reaction tank, and a nitrification liquid reflux pipeline is provided at the water outlet end of the fourth reaction tank. The other end of the nitrification liquid reflux pipeline is connected to the water inlet end of the first reaction tank; Stirring devices are respectively installed in the first reaction tank, the second reaction tank, the third reaction tank, and the fifth reaction tank, and aeration devices are respectively installed in the fourth reaction tank and the sixth reaction tank; Suspended carriers for anaerobic ammonium oxidation are added to the first reaction tank, the second reaction tank, and the fifth reaction tank, suspended carriers for denitrification are added to the third reaction tank, and suspended carriers for the aerobic zone are added to the fourth reaction tank and the sixth reaction tank; the suspended sludge concentration in each reaction tank is <500 mg / L; Step 2: Start anaerobic ammonium oxidation First, make the anaerobic ammonium oxidation process in the first reaction tank and the second reaction tank start successfully through relevant controls; Control the ammonia nitrogen concentration at the water outlet of the fourth reaction tank to be between 3 and 5 mg / L, control the C / N ratio at the water inlet of the fifth reaction tank to be 2.5 - 3.0 by externally dosing carbon source, and utilize suitable anaerobic ammonium oxidation reaction conditions and the anaerobic ammonium oxidation bacteria carried by the effluent from the first reaction tank and the second reaction tank to start the anaerobic ammonium oxidation process in the fifth reaction tank. When the ammonia nitrogen removal amount and nitrite production amount in the fifth reaction tank reach 3 mg / L and 2 mg / L respectively, the anaerobic ammonium oxidation in the fifth reaction tank starts successfully; Step 3: Stable operation of the system Maintain the stability of the anaerobic ammonium oxidation process, improve the nitrogen removal efficiency, and gradually reduce the dosage of carbon source; During the stable operation of the system, the residence time in the first reaction tank and the second reaction tank is 1.0 - 1.2 h; the residence time in the third reaction tank is 1.5 - 2.0 times that of the first reaction tank; the residence time in the fourth reaction tank is 3.0 - 4.0 times that of the first reaction tank, and the actual residence time in the fourth reaction tank does not exceed 1.5 h; the residence time in the fifth reaction tank and the sixth reaction tank is 1.0 - 1.5 times that of the first reaction tank.

2. The high-efficiency denitrification biofilm process according to claim 1, characterized in that: The density of the suspended carrier for anaerobic ammonium oxidation is 0.98 - 1.00 g / cm 3 , and the average void spacing of the suspended carrier is ≥ 5 mm; the density of the suspended carrier for denitrification is 0.98 - 1.00 g / cm 3 , and the average void spacing of the suspended carrier is ≥ 3 mm; the density of the suspended carrier for the aerobic zone is 0.94 - 0.97 g / cm 3 , and the average void spacing of the suspended carrier is ≥ 5 mm; the effective specific surface area of each type of suspended carrier is ≥ 800 m 2 / m 3 , and the filling rate of the suspended carrier in each reaction tank is > 45%.

3. An efficient denitrification biofilm process according to claim 1, characterized in that: Intercepting screens are provided between adjacent reaction tanks, and the suspended carriers in each reaction tank are enriched in specific areas. The reflux point of the nitrification liquid reflux pipeline is located behind the intercepting screen of the fourth reaction tank.

4. An efficient denitrification biofilm process according to claim 1, characterized in that: The reflux ratio of the nitrification liquid reflux pipeline is 200 - 400%; after the system starts up, the biofilm thicknesses of the first reaction tank to the sixth reaction tank are 150 - 200 μm, 100 - 150 μm, 100 - 150 μm, 200 - 300 μm, 150 - 200 μm, and 150 - 200 μm respectively; the effluent ammonia nitrogen <0.5 mg / L, TN <5 mg / L, and COD <30 mg / L.

5. An efficient denitrification biofilm process according to claim 1, characterized in that: In the second step, the relevant control specifically refers to: controlling the first water inlet pipeline to operate at full load, closing the second water inlet pipeline, controlling the C / N ratio in the first reaction tank to be 3.0 - 3.5, and the nitrate nitrogen in the effluent of the third reaction tank to be < 1 mg / L. Until the ammonia nitrogen removal amounts in the first reaction tank and the second reaction tank are respectively greater than 2 mg / L and 3 mg / L, and the nitrite nitrogen generation amounts are respectively greater than 2 mg / L and 1 mg / L, the anaerobic ammonium oxidation processes in the first reaction tank and the second reaction tank are successfully started.

6. An efficient denitrification biofilm process according to claim 1, characterized in that: The carbon source is sodium acetate, glucose, sodium formate, sodium propionate or methanol.

7. An efficient denitrification biofilm process according to claim 6, characterized in that: The carbon source is sodium acetate.

8. An efficient denitrification biofilm process according to claim 1, characterized in that The specific steps of the third step are: controlling the first water inlet pipeline and the second water inlet pipeline to feed water respectively, and short-cut denitrification-anaerobic ammonium oxidation coupled with heterotrophic denitrification for nitrogen removal occurs in the first reaction tank - the second reaction tank. The relative abundances of the denitrifying bacteria Denitratisoma are respectively > 0.5% and 1.0%, and the relative abundances of the anaerobic ammonium oxidation bacteria Candiditaous Brocadia are respectively > 1.0% and 1.5%. The cumulative TN removal rate of the first reaction tank and the second reaction tank is > 60%, and the TN removal rate through anaerobic ammonium oxidation is > 30% or the cumulative ammonia nitrogen removal amount is greater than 5 mg / L; Anoxic denitrification occurs in the third reaction tank to ensure the TN removal effect of the front anoxic zone. The relative abundance of denitrifying bacteria is > 30%, and the nitrate nitrogen concentration in the effluent is controlled to be < 1 mg / L or the COD concentration is < 50 mg / L; Nitrification process and coupled aerobic carbon removal process occur in the fourth reaction tank. The relative abundance of heterotrophic bacteria is > 20%, and the relative abundance of nitrifying bacteria is > 15%. The ammonia nitrogen in the effluent is controlled to be < 0.5 mg / L; Short-cut denitrification-anaerobic ammonium oxidation coupled with heterotrophic denitrification for nitrogen removal occurs in the fifth reaction tank. The C / N is controlled to be 2.5 - 3.

0. The TN removal rate through the anaerobic ammonium oxidation pathway is > 10% or the ammonia nitrogen removal amount is greater than 2 mg / L. The relative abundance of the biofilm denitrifying bacteria genus is > 10%, and the relative abundances of the anaerobic ammonium oxidation bacteria Candiditaous Brocadia and the denitrifying bacteria Denitratisoma are both > 0.5%; Nitrification process and coupled aerobic carbon removal process occur in the sixth reaction tank to ensure that the total effluent COD and ammonia nitrogen meet the standards. The relative abundance of biofilm heterotrophic bacteria is > 30%, and the relative abundance of nitrifying bacteria is > 10%. The effluent COD and ammonia nitrogen are respectively less than 30 mg / L and 0.5 mg / L.

9. The high-efficiency denitrification biofilm process according to claim 1, characterized in that: When the third-step system operates stably, the stirring device needs to be turned on, and the stirring power density of the stirring devices in the first reaction tank and the second reaction tank > 7.5 W / m 3 , and the stirring power density in the third reaction tank > 10 W / m 3 , and the stirring power density in the fifth reaction tank > 7.5 W / m 3 , and the aeration intensities in the fourth reaction tank and the sixth reaction tank are greater than 12 - 16 m 3 / m 2 / h and 10 - 14 m 3 / m 2 / h, respectively.

10. An efficient denitrification biofilm process according to claim 1, characterized in that: The ammonia nitrogen concentration in the system inlet is > 20 mg / L, C / N < 4, the proportion of carboxylic acid substances in the inlet organic matter is > 20%, and the minimum temperature of the system inlet is 10 °C.

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