A high-efficiency denitrification biofilm process

Abstract

This invention discloses a highly efficient denitrification biofilm process, relating to the field of water treatment technology. The system includes a first to a sixth reaction tank connected sequentially. During the anaerobic ammonia oxidation (AAO) start-up process, anaerobic ammonia-oxidizing bacteria are enriched in the first, second, and fifth reaction tanks. Nitrous oxide accumulation is achieved by controlling the C / N ratio and superimposing a short residence time (HRT), inducing the AAO process. During the stable operation phase, the AAO process is kept stable, and the amount of external carbon source added is reduced. Nitrous oxide accumulation is rapidly achieved in the first and second reaction tanks by controlling the C / N ratio and short residence time, while the biofilm accelerates the enrichment of anaerobic ammonia-oxidizing bacteria. In the fifth reaction tank, a more precise C / N ratio is achieved by adding an external carbon source, and microorganisms that have penetrated from the first and second reaction tanks into the fifth reaction tank are inoculated, accelerating the start-up of the AAO process. This invention provides rapid and stable AAO start-up, strong microbial enrichment capacity, and achieves highly efficient denitrification.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and more specifically to a highly efficient denitrification biofilm process. Background Technology

[0002] Traditional wastewater denitrification primarily relies on nitrification-denitrification. Nitrification requires aeration to supply oxygen, while denitrification requires the addition of carbon sources to replenish nutrients. With increasingly stringent wastewater discharge standards, the energy and chemical consumption associated with nitrification-denitrification denitrification is constantly rising. Anaerobic ammonia oxidation (AAO) is a novel, highly efficient, and low-cost wastewater denitrification process. Compared to traditional nitrification-denitrification, it can save 60% of aeration energy and 100% of external chemical costs. It has been successfully applied to the treatment of high-ammonia nitrogen wastewater; however, it is rarely used in municipal wastewater treatment systems, which have a broader market potential. The main reasons for this are as follows:

[0003] First, municipal wastewater in my country is mostly treated using the activated sludge process, but suspended microorganisms make it difficult to efficiently enrich long-aged anaerobic ammonia-oxidizing bacteria, thus hindering the occurrence of anaerobic ammonia oxidation. Second, mainstream municipal wastewater typically has a concentration of 20–70 mg / L, resulting in low fatty acid (FA) levels, making it difficult to achieve a stable short-cut nitrification process. The mainstream anaerobic ammonia oxidation process requires NO2... - -N is difficult to generate effectively, making the anaerobic ammonia oxidation process difficult to occur; third, the anaerobic ammonia oxidation process has strict requirements on water quality and control parameters. The influent water quality of municipal sewage is complex, containing ammonia nitrogen, organic matter, etc. The removal pathways and control requirements of each substance are different, and there is competition between bacterial species, making it difficult for the entire system to achieve effective synergy.

[0004] Current research reports on denitrification processes include:

[0005] CN114477420A discloses a method and apparatus for deep nitrogen removal from wastewater through continuous flow AOA short-cut nitrification and endogenous short-cut denitrification coupled anaerobic ammonium oxidation. The apparatus includes a raw wastewater tank for municipal domestic sewage, a continuous flow AOA reactor, and a sedimentation tank. The method involves pumping municipal domestic sewage into the continuous flow reactor and operating it in anaerobic, aerobic, and anoxic modes. In the anaerobic zone, internal carbon sources are stored and phosphorus is released; in the aerobic zone, short-cut nitrification and anaerobic ammonium oxidation occur and phosphorus is absorbed; in the anoxic zone, endogenous short-cut denitrification and anaerobic ammonium oxidation occur. Suspended and fixed biological carriers are added to the aerobic and anoxic zones respectively to retain and enrich anaerobic ammonium-oxidizing bacteria. Ultimately, the dual coupling of anaerobic ammonium oxidation is achieved in both the aerobic and anoxic zones, improving nitrogen and phosphorus removal efficiency. The main technical problem with this nitrogen removal process is that it employs two processes—aerobic short-cut nitrification and anaerobic ammonium oxidation—to achieve synergistic nitrogen removal. Regarding the difficulties of short-cut nitrification in mainstream wastewater, the application document does not provide clear control measures, making it difficult to guarantee a stable source of nitrite, and thus hindering stable nitrogen removal during anaerobic ammonia oxidation. Secondly, in addition to considering the source of nitrite, the anaerobic ammonia oxidation process in the anoxic zone also requires ensuring a sufficient substrate supply for ammonia nitrogen, as complete nitrification can be easily achieved in the aerobic zone. However, this application does not consider this aspect and does not limit the concentration of ammonia nitrogen entering the anoxic zone, making stable short-cut denitrification and anaerobic ammonia oxidation in the anoxic zone difficult. Thirdly, relying solely on the anaerobic ammonia oxidation process in the anoxic zone to ensure effluent ammonia nitrogen compliance carries significant operational risks, as the effluent ammonia nitrogen concentration is prone to exceeding the standard due to the influence of the anaerobic ammonia oxidation process.

[0006] CN112811719A discloses an autotrophic denitrification system and method for urban wastewater. The device includes a raw water storage unit, a CEPT reactor, a sedimentation tank, a sludge thickening tank, a side-flow short-cut nitrification reactor, a main-flow short-cut denitrification reactor, and an anaerobic ammonium oxidation reactor. First, urban wastewater enters the CEPT reactor to remove phosphorus and some organic matter. Then, ammonia nitrogen from the side-flow sludge digestion liquid is used for short-cut nitrification, and the resulting nitrite nitrogen enters the main flow for autotrophic denitrification via anaerobic ammonium oxidation. The effluent from the anaerobic ammonium oxidation reactor is also returned to the main flow short-cut denitrification reactor, where carbon sources from the raw water are used to perform short-cut denitrification on the small amount of nitrate nitrogen produced in the anaerobic ammonium oxidation reactor, generating nitrite nitrogen to supplement the main flow anaerobic ammonium oxidation process. The existing technology has a clear process and effectively solves the problem of nitrite source in the mainstream anaerobic ammonia oxidation process. However, it is difficult to implement in actual engineering, mainly due to the following reasons: First, it does not limit water quality parameters. The ideal ratio of ammonia nitrogen to nitrite in the anaerobic ammonia oxidation process is 1:1.32. According to calculations based on existing wastewater treatment plants that include sludge anaerobic digestion, the nitrite concentration in the mixed wastewater is low, and the ratio of ammonia nitrogen to nitrite is close to 2:1. Second, it does not include a backup unit, using only the anaerobic ammonia oxidation unit as the final reaction unit. Considering the Class A standard commonly implemented for municipal wastewater in my country, this patented system has an extremely high risk of exceeding the standards for ammonia nitrogen and total nitrogen (TN) in the effluent.

[0007] CN116573765A discloses a segmented influent multi-point recirculation enhanced municipal wastewater autotrophic denitrification system and method. The system includes a biological treatment tank, a sedimentation tank, an influent pipe or influent corridor, connecting pipes, an effluent pipe, a nitrified liquid recirculation pipe, a sludge recirculation pipe, a supernatant recirculation pipe, and a sludge discharge pipe. This system combines various microbial aggregation forms in the biological treatment tank, such as pure biofilm, coexistence of biofilm and flocculent sludge, and pure flocculent sludge, leveraging their respective advantages. The distribution of organic matter, ammonia nitrogen, and nitrate nitrogen in each section is regulated through segmented influent and multi-point recirculation to enhance the system's autotrophic denitrification effect through anaerobic ammonia oxidation. In this application, the short-cut denitrification anaerobic ammonia oxidation zone uses fixed packing. In actual operation, the fixed-bed biofilm lacks sufficient hydraulic shear, leading to biofilm thickening, which restricts mass transfer and affects the treatment load.

[0008] This shows that the existing technology needs further improvement. Summary of the Invention

[0009] The purpose of this invention is to provide a highly efficient denitrification biofilm process, which adopts a short-cut denitrification-anaerobic ammonia oxidation coupled with a traditional denitrification process to achieve synergistic denitrification. During stable operation, there is no accumulation of nitrogen oxides, thus achieving highly efficient denitrification.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A highly efficient denitrification biofilm process includes 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 sequentially from front to back.

[0014] A first inlet pipe is provided at the inlet end of the first reaction tank, a second inlet pipe and a carbon source addition pipe are provided at the inlet end of the fifth reaction tank, and a nitrification liquid return pipe is provided at the outlet end of the fourth reaction tank. The other end of the nitrification liquid return pipe is connected to the 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 each equipped with a stirring device, and the fourth reaction tank and the sixth reaction tank are each equipped with an aeration device.

[0016] Suspended carriers for anaerobic ammonia oxidation were added to the first, second, and fifth reaction tanks; suspended carriers for denitrification were added to the third reaction tank; and suspended carriers for the aerobic zone were added to the fourth and sixth reaction tanks. The concentration of suspended sludge in each reaction tank was <500 mg / L.

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

[0018] Through relevant controls, the anaerobic ammonia oxidation process in the first and second reaction tanks was successfully started.

[0019] The ammonia nitrogen concentration in the effluent of the fourth reaction tank is controlled between 3 and 5 mg / L. The C / N ratio in the influent of the fifth reaction tank is controlled between 2.5 and 3.0 by external carbon source. With suitable anaerobic ammonia oxidation reaction conditions and the superposition of anaerobic ammonia oxidizing bacteria carried by the effluent of the first and second reaction tanks, the anaerobic ammonia oxidation process in the fifth reaction tank is started. The anaerobic ammonia oxidation in the fifth reaction tank is successfully started when the ammonia nitrogen removal and nitrous oxide generation in the fifth reaction tank are 3 mg / L and 2 mg / L, respectively.

[0020] Step 3: Stable System Operation

[0021] To maintain the stability of the anaerobic ammonium oxidation process, improve nitrogen removal efficiency, and gradually reduce the amount of carbon source added;

[0022] During stable operation of the system, the residence time in the first and second reaction tanks 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 and sixth reaction tanks is 1.0 to 1.5 times that of the first reaction tank.

[0023] After the system is started, the biofilm thicknesses in the first to sixth reaction tanks 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 is <0.5 mg / L, TN is <5 mg / L, and COD is <30 mg / L.

[0024] In the aforementioned high-efficiency nitrogen removal biofilm process, the density of the suspended carrier used for anaerobic ammonia oxidation is 0.98–1.00 g / cm³. 3 The average porosity of the suspended carrier is ≥5mm; the density of the suspended carrier for denitrification is 0.98~1.00g / cm³. 3 The average porosity of the suspended carrier is ≥3mm; the density of the suspended carrier used in the aerobic zone is 0.94~0.97g / cm³. 3 The average void spacing of the suspended carrier is ≥5mm; the effective specific surface area of ​​each type of suspended carrier is ≥800m².2 / m 3 The suspended carrier filling rate in each reaction tank was >45%.

[0025] In the aforementioned efficient denitrification biofilm process, an intercepting screen is installed between adjacent reaction tanks, and the suspended carriers in each reaction tank are enriched in specific regions. The reflux point of the fourth reaction tank is located after the intercepting screen of the fourth reaction tank.

[0026] In the aforementioned high-efficiency denitrification biofilm process, the reflux ratio of the nitrification liquor return 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 aforementioned high-efficiency denitrification biofilm process, the relevant control measures specifically refer to: controlling the first inlet pipeline to operate at full load, closing the second inlet pipeline, controlling the C / N ratio in the first reaction tank to be 3.0–3.5, and controlling the nitrate nitrogen in the effluent of the third reaction tank to be <1 mg / L, until the ammonia nitrogen removal in the first and second reaction tanks is greater than 2 mg / L and 3 mg / L respectively, and the nitrous oxide generation is greater than 2 mg / L and 1 mg / L respectively, at which point the anaerobic ammonia oxidation process in the first and second reaction tanks is successfully started.

[0028] The carbon source for the aforementioned efficient denitrification biofilm process is sodium acetate, glucose, sodium formate, sodium propionate, or methanol.

[0029] In the aforementioned efficient denitrification biofilm process, the carbon source is sodium acetate.

[0030] The third step of the above-mentioned efficient denitrification biofilm process is as follows: control the first inlet pipe and the second inlet pipe to receive water respectively, and short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification occurs in the first reaction tank-second reaction tank. The relative abundance of denitrifying bacteria Denitrosoma is >0.5% and 1.0% respectively, and the relative abundance of anaerobic ammonia oxidizing bacteria Candiditaous Brocadia is >1.0% and 1.5% respectively. The cumulative TN removal rate of the first reaction tank and the second reaction tank is >60%, and the TN removal rate after anaerobic ammonia oxidation is >30% or the cumulative ammonia nitrogen removal is greater than 5 mg / L.

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

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

[0033] In the fifth reaction tank, short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification was carried out, with the C / N ratio controlled at 2.5-3.0. The TN removal rate via anaerobic ammonia oxidation was >10% or the ammonia nitrogen removal was >2 mg / L. The relative abundance of denitrifying bacteria in the biofilm was >10%, and the relative abundance of anaerobic ammonia oxidizing bacteria Candiditaous Brocadia and denitrifying bacteria Denitratisoma were both >0.5%.

[0034] The nitrification process in the sixth reaction tank is coupled with an aerobic decarbonization process to ensure that the total effluent COD and ammonia nitrogen meet the standards, the relative abundance of heterotrophic bacteria in the biofilm 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 aforementioned efficient nitrogen removal biofilm process, during the third step of stable system operation, the stirring device needs to be activated. The stirring power density of the stirring device in the first and second reaction tanks should be >7.5 W / m³. 3 The stirring power density in the third reaction tank is >10W / m³ 3 The stirring power density in the fifth reaction tank is >7.5 W / m³. 3 The aeration intensities in the fourth and sixth reaction tanks are greater than 12–16 m³ / s, respectively. 3 / m 2 / h, 10~14m 3 / m 2 / h.

[0036] The above-mentioned efficient denitrification biofilm process has an influent ammonia nitrogen concentration >20mg / L, C / N <4, and a carboxylic acid content >20% in the influent organic matter.

[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 this invention through anaerobic ammonia oxidation process is >40%, which reduces aeration energy consumption by 20% and external carbon source addition by 40% while meeting the requirement of effluent TN <5mg / L.

[0039] 2) No environmental hazards. The core nitrogen removal process of this invention uses short-cut denitrification-anaerobic ammonia oxidation coupled with the traditional denitrification process. The two processes achieve synergistic nitrogen removal, and there is no accumulation of nitrogen nitrite during stable operation, resulting in no environmental hazards 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℃, making it widely applicable; it can be used for municipal sewage treatment as well as high-ammonia nitrogen wastewater treatment such as industrial wastewater with higher concentrations.

[0041] 4) Simple operation and control. This invention adopts a fluidized bed biofilm method, eliminating the need for a sludge return system. The suspended sludge concentration in the system is <500mg / L, thus avoiding issues such as sludge aging and difficulty in separation that can occur with suspended microorganisms. The biofilm achieves dynamic microbial renewal during fluidization, and the long sludge age system improves its shock resistance.

[0042] 5) Rapid and stable initiation of anaerobic ammonia oxidation. In this invention, the first and second reaction zones rapidly accumulate nitrous oxide by controlling the C / N ratio and short residence time, while simultaneously accelerating the enrichment of anaerobic ammonia-oxidizing bacteria through a biofilm. The fifth reaction zone achieves a more precise C / N ratio through external carbon source input, and is inoculated with microorganisms that penetrate from the first and second reaction zones into the fifth reaction zone, accelerating the initiation of the anaerobic ammonia oxidation process and maintaining its stability over a long period.

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

[0044] 7) Land-saving design. Based on the municipal sewage treatment system, the maximum HRT of the entire system is 12.6 hours, which can save 50% of the land occupation. Attached Figure Description

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

[0046] Figure 1 This is a schematic diagram of the system of the present invention;

[0047] Figure 2 The graph shows the effect of ammonia nitrogen concentration in the effluent from the fourth reaction tank on the effluent from the fifth and sixth reaction tanks.

[0048] Figure 3 A graph showing 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 inlet water pipe, I2. Second inlet water pipe, I3. Main outlet water pipe, C1. Carbon source addition pipe, R. Nitrification liquid return pipe. Detailed Implementation

[0051] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0052] In the description of this application, the words "first," "second," etc., are used only to distinguish different objects and do not limit the quantity or order of execution, nor do they imply that they must be different. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0053] The structure and usage of the stirring device and aeration device mentioned in this invention can be achieved by referring to existing technologies.

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

[0055] The following is an explanation of the technical terms used in this invention:

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

[0057] Anaerobic ammonia oxidation TN removal rate: refers to the proportion of TN removed by the anaerobic ammonia oxidation process in the total nitrogen in the influent in this area;

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

[0059] Nitrite accumulation rate: Nitrite nitrogen (NO2) in the system - -N) concentration and nitrite nitrogen (NO2) - -N) concentration and nitrate nitrogen (NO3) - The ratio of the sum of -N concentrations;

[0060] Nitrate nitrogen: refers to inorganic nitrogen existing in the system in the +3 and +5 oxidation states, including NO2. - -N and NO3 - -N;

[0061] C / N: For pre-anoxic zones, this refers to the difference between the influent COD minus 30 and the NO... x - The ratio of -N concentration; for the post-hypoxic zone, this refers to the externally administered COD and NO concentration. x - The proportion of -N concentration.

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

[0063] like Figure 1As shown, 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. By arranging the reaction tanks and controlling each reaction tank, the denitrification effect is improved.

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

[0065] Suspended carriers for anaerobic ammonia oxidation are added to the first, second, and fifth reaction tanks; suspended carriers for denitrification are added to the third reaction tank; and suspended carriers for the aerobic zone are added to the fourth and sixth reaction tanks. The entire system does not have any sludge-water separation units or sludge return units; it is a pure membrane system, and the suspended sludge concentration in each reaction tank is <500 mg / L.

[0066] The residence time in the first and second reaction tanks is 1.0–1.2 hours; 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 considering internal reflux, the actual residence time in the fourth reaction tank does not exceed 1.5 hours; the residence time in the fifth and sixth reaction tanks is 1.0–1.5 times that of the first reaction tank. These limitations on residence time further clarify the ingenious aspect of this invention: the short residence times in the first and second reaction tanks and the long residence time in the third reaction tank facilitate the accumulation of nitrous oxide. The first and second reaction tanks undergo short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification for nitrogen removal. The third reaction tank undergoes anoxic denitrification to ensure the TN removal effect before anoxic conditions. The fourth reaction tank's limited residence time provides a guarantee for the inoculation of the subsequent fifth reaction tank. In other words, the first, second, third, fourth, fifth, and sixth reaction tanks of this invention are interdependent and closely related, with the residence time of the former reaction tanks ensuring the inoculation of the latter reaction tanks.

[0067] After the system is started, the biofilm thickness in the first to sixth reaction tanks reaches 150–200 μm, 100–150 μm, 100–150 μm, 200–300 μm, 150–200 μm, and 150–200 μm, respectively. The effluent ammonia nitrogen is <0.5 mg / L, TN is <5 mg / L, and COD is <30 mg / L.

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

[0069] Step 1: Anaerobic Ammonium Oxidation Start-up Process

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

[0071] Control the first inlet pipeline to operate at full load and shut down the second inlet pipeline. Control the C / N ratio of the first reaction tank to 3.0-3.5, and the nitrate nitrogen in the effluent of the third reaction tank to <1 mg / L. When the ammonia nitrogen removal in the first and second reaction tanks is greater than 2 mg / L and 3 mg / L respectively, and the nitrous oxide generation is greater than 2 mg / L and 1 mg / L respectively, the anaerobic ammonia oxidation process in the first and second reaction tanks is successfully started. The C / N ratio of the influent to the second reaction tank is lower than that of the first reaction tank by default, and the influent to the second reaction tank will also contain nitrous oxide accumulated in the first reaction tank. Therefore, the effect of the second reaction tank is 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. A high-quality external carbon source was used to control the C / N ratio of the influent to the fifth reaction tank to 2.5–3.0. Utilizing suitable anaerobic ammonia oxidation (ANAMMXO) conditions and superimposed with detached ANAMMXO bacteria carried from the effluents of the first and second reaction tanks, the ANAMMXO process in the fifth reaction tank was initiated. The process continued until the ammonia nitrogen removal and nitrite formation in the fifth reaction tank reached approximately 3 mg / L and 2 mg / L, respectively, indicating successful ANAMMXO initiation. The first and second reaction tanks play a crucial role in maintaining the stability of ANAMMXO in the fifth reaction tank.

[0073] Step 2: Stable System Operation

[0074] The goal of this process is to maintain the stability of the anaerobic ammonia oxidation process, improve nitrogen removal efficiency, and reduce the amount of external carbon source required.

[0075] Control the first and second water inlet pipes to allow water to enter separately.

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

[0077] In the third reaction tank, anoxic denitrification is required to ensure effective TN removal before anoxic conditions. The relative abundance of denitrifying bacteria should be >30%, and the effluent nitrate nitrogen concentration should be controlled to <1 mg / L or COD concentration to <50 mg / L. Considering that ANAMMOX reduced COD usage, an excess COD problem may occur, resulting in a nitrate nitrogen concentration less than 1 mg / L. If the initial COD level is low, a COD concentration less than 50 mg / L is more likely.

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

[0079] In the fifth reaction tank, short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification was carried out, with the C / N ratio controlled at 2.5-3.0. The TN removal rate via anaerobic ammonia oxidation was >10% or the ammonia nitrogen removal was >2 mg / L. The relative abundance of denitrifying bacteria in the biofilm was >10%, and the relative abundance of anaerobic ammonia oxidizing bacteria Candiditaous Brocadia and denitrifying bacteria Denitratisoma were both >0.5%.

[0080] The nitrification process in the sixth reaction tank is coupled with an aerobic decarbonization process to ensure that the total effluent COD and ammonia nitrogen meet the standards, the relative abundance of heterotrophic bacteria in the biofilm 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 biofilm thicknesses 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 used for anaerobic ammonium oxidation is 0.98–1.00 g / cm³. 3 The average porosity of the suspended carrier is ≥5mm; the density of the suspended carrier for denitrification is 0.98~1.00g / cm³. 3 The average porosity of the suspended carrier is ≥3mm; the density of the suspended carrier used in the aerobic zone is 0.94~0.97g / cm³. 3The average void spacing of the suspended carrier is ≥5mm. The effective specific surface area of ​​all types of suspended carriers is ≥800m². 2 / m 3 The suspended carrier filling rate in each reaction tank was >45%.

[0083] Preferably, under stable system operation, the stirring power density of the first and second reaction tanks is >7.5W / m³. 3 The stirring power density of the third reaction tank is >10W / m³ 3 With this design, the denitrification load in the third reaction tank is lower than that in the first and second reaction tanks, resulting in less gas production and a corresponding increase in fluidization motive force. The stirring power density in the fifth reaction tank is >7.5W / m³. 3 The aeration intensities of the fourth and sixth reaction tanks are >12-16 m³ / s, respectively. 3 / m 2 / h, 10~14m 3 / m 2 / h.

[0084] Preferably, adjacent reaction tanks are separated by intercepting screens, which ensures that the suspended carrier is enriched in specific areas and does not flow into each other.

[0085] The system influent ammonia nitrogen concentration is >20mg / L, C / N <4, and the proportion of carboxylic acid substances in the influent organic matter is >20%; the internal reflux ratio (the nitrification 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, this invention preferably uses sodium acetate as the carbon source added to the fifth reaction tank.

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

[0088] Example 1:

[0089] A wastewater treatment plant has a designed flow rate of 10,000 m³. 3 / d, designed influent COD, BOD5, NH4 + -N and TN were 580 mg / L, 260 mg / L, 50 mg / L, and 70 mg / L, respectively. An AOAO process based on fluidized bed biofilm technology was employed, comprising six reaction tanks. The residence times for the first and second reaction tanks were both 1 h, for the third reaction tank 1.5 h, for the fourth reaction tank 4 h, for the fifth reaction tank 1.2 h, and for the sixth reaction tank 1.5 h. The system MLSS was <300 mg / L. The effective surface area of ​​the suspended carrier added to each reaction tank was 800 m². 2 / m 3The filling rate of both reactors was 55%. The influent volume of the first reactor was 95% of the actual influent volume, and the influent volume of the fifth reactor was 5% of the actual influent volume. According to the flow monitoring, the TN removal rate of the first and second reactors after the anaerobic ammonia oxidation process reached 35%, and the TN removal rate of the fifth reactor after the anaerobic ammonia oxidation process reached 12%. The overall TN removal rate of the system was 93%, and the effluent NH4 content was [not specified]. + -N<0.5mg / L, TN<5mg / L.

[0090] Example 2:

[0091] A wastewater treatment plant has a designed flow rate of 20,000 m³. 3 / d, designed influent COD, BOD5, NH4 + -N and TN were 500 mg / L, 200 mg / L, 60 mg / L, and 72 mg / L, respectively. An AOAO process based on fluidized bed biofilm was employed, consisting of six reaction tanks. The residence times in the first to sixth reaction tanks were 1.2 h, 1.2 h, 1.5 h, 4.5 h, 1.2 h, and 1.2 h, respectively. The system MLSS was <300 mg / L. The effective surface area of ​​the suspended carrier added to each reaction tank was 800 m². 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%. Initially, the project adopted a single-point influent mode, with all wastewater entering the first reaction tank. During operation, stable anaerobic ammonia oxidation processes were observed in the first and second reaction tanks by controlling the influent C / N ratio, achieving a TN removal rate of 40%. High-throughput sequencing revealed that the biofilm was enriched with anaerobic ammonia oxidizing bacteria *Candiditaous Brocadia*, with relative abundances >1.5% and 2.0%, respectively. During operation, by controlling the DO (dissolved oxygen) in the fourth reaction tank, some ammonia nitrogen was released into the fifth reaction tank, with an ammonia nitrogen concentration of 3–4 mg / L. By reducing the external carbon source input in the fifth reaction tank and controlling the C / N ratio to 2.8, a short-cut denitrification process was induced, producing nitrous oxide and promoting the ANAMMOX process. After 10 days of operation, the ammonia nitrogen loss in the fifth reaction tank reached nearly 2 mg / L.

[0092] Subsequently, an additional inlet pipeline was added to the fifth reactor, diverting 8% of the inlet water to provide a stable source of ammonia nitrogen for the fifth reactor. After 20 days of operation, high-throughput sequencing revealed that the dominant anaerobic ammonia oxidation bacteria in the biofilm of the fifth reactor was Candiditaous Brocadia, with a relative abundance of 1.0%. According to measurements along the process, the TN removal rate after anaerobic ammonia oxidation reached 15%, demonstrating significant energy-saving effects.

[0093] Comparative Example 1:

[0094] Pilot-scale system with a processing capacity of 100m³ 3 / d, during startup and operation, the effluent from the fourth reaction tank was controlled, and a certain ammonia nitrogen concentration was introduced into the fifth reaction tank. Experimental results Figure 2 As shown, when the ammonia nitrogen in the effluent from the fourth reaction tank is 1 or 2 mg / L, the fifth reaction tank struggles to achieve a stable ammonia nitrogen removal process over long-term operation, making it difficult to enrich anaerobic ammonia-oxidizing bacteria for anaerobic ammonia oxidation. When the effluent from the fourth reaction tank is 3–5 mg / L, the fifth reaction tank exhibits a significant ammonia nitrogen removal process, with a removal rate exceeding 1 mg / L. Furthermore, the sixth reaction tank can further nitrify the ammonia nitrogen in the effluent from the post-anoxic zone, ensuring the final effluent concentration is below 0.5 mg / L. When the ammonia nitrogen in the effluent from the fourth reaction tank is 6–7 mg / L, the anaerobic ammonia oxidation effect in the fifth reaction tank continues to improve, but this also leads to a gradual increase in the ammonia nitrogen concentration in the effluent from the fifth reaction tank. Combined with the high influent ammonia nitrogen concentration in the sixth reaction tank and the impact of subsequent organic matter penetration, it is difficult for the ammonia nitrogen in the effluent from the fifth reaction tank to consistently achieve the target of below 0.5 mg / L. Therefore, controlling the ammonia nitrogen effluent from the main aerobic tank to 3–5 mg / L is the optimal value during the startup phase.

[0095] Comparative Example 2:

[0096] A pilot-scale system has a processing capacity of 100m³. 3 / d, an AOAO process system based on fluidized bed biofilm was adopted, with water fed into the first and fifth reaction tanks at proportions of 95% and 5%, respectively. The removal efficiency of the suspended biofilm in the anoxic zone and its various functional zones was monitored over a long period, and the results are as follows: Figure 3 As shown, the biofilm method has a natural advantage in enriching anaerobic ammonia-oxidizing bacteria. In the initial stages of operation, a certain amount of anaerobic ammonia-oxidizing bacteria can be detected on the biofilm in the anoxic zone through high-throughput processing. However, from a macroscopic perspective, when the relative abundance of anaerobic ammonia-oxidizing bacteria is only 0.1%–0.3%, although the bacteria are present, no macroscopic anaerobic ammonia oxidation process occurs. But when the relative abundance of anaerobic ammonia-oxidizing bacteria reaches 0.5 or higher, the anaerobic ammonia oxidation process is significant, and according to the experimental results, the macroscopic denitrification capacity is positively correlated with the microscopic enrichment amount.

[0097] Comparative Example 3:

[0098] A pilot-scale anoxic system with a water treatment capacity of 100m³ 3 / d, NO3 inlet water - The nitrogen content was 10 mg / L, the relative abundance of denitrification in the system packing was >10%, there were no anaerobic ammonia-oxidizing bacteria, and the heating time was 1 h. Five types of carbon sources—sodium acetate, glucose, sodium formate, sodium propionate, and methanol—were added respectively, with the C / N ratio controlled at 3, to verify the nitrogen accumulation in the system. The result of 0 indicates that sodium acetate had a high nitrogen accumulation effect, followed by sodium formate and sodium propionate; glucose and methanol showed no nitrogen accumulation.

[0099] Table 1 Nitrous oxide accumulation by different carbon source types

[0100] Carbon source type Sodium acetate glucose Sodium formate Sodium propionate methanol Nitrous oxide production (mg / L) 6 0 3 2 0

[0101] Comparative Example 4:

[0102] A pilot-scale anoxic system with a water treatment capacity of 100m³ 3 / d, NO3 inlet water - -N content 15 mg / L, ammonia nitrogen content 15 mg / L, system packing denitrification relative abundance 10%, anaerobic ammonia oxidizing bacteria relative abundance 1%, HRT 1h. Carbon source type is sodium acetate, C / N controlled at 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 respectively. As can be seen from 0, the lower the C / N, the higher the anaerobic ammonia oxidation denitrification membrane load and the greater the denitrification contribution. However, a low C / N also leads to a decrease in overall denitrification load. When the C / N is controlled between 2.5 and 3.5, the overall denitrification membrane load is greater than 0.7 g / m³. 2 ·d -1 Furthermore, the contribution rate of anaerobic ammonia oxidation to nitrogen removal is greater than 40%.

[0103] Table 2. Effect of C / N ratio on TN removal

[0104] C / N 1.5 2.0 2.5 3.0 3.5 4.0 <![CDATA[System TN removal membrane loading (g / m 2 ·d -1 )]]> 0.51 0.65 0.70 0.75 0.80 0.90 <![CDATA[Anaerobic ammonia denitrification membrane loading (g / m 2 ·d -1 )]]> 0.44 0.45 0.38 0.35 0.32 0.20 Contribution rate of anaerobic ammonia oxidation for nitrogen removal 86％ 69％ 54％ 47％ 40％ 22％

[0105] Comparative Example 5:

[0106] A pilot-scale anoxic system with a water treatment capacity of 100m³ 3 / d, treating actual domestic wastewater with COD 200 mg / L and influent ammonia nitrogen 50 mg / L, an anoxic system was established with an HRT of 1.2 h. Nitrate nitrogen was artificially supplemented to 40 mg / L to study the anoxic denitrification effect. Simultaneously, the relative abundance of microorganisms and the macroscopic nitrogen removal effect were monitored. The experimental results are shown in Table 3. With the extension of operating time, suspended carriers gradually formed biofilms, and the relative abundance of denitrifying bacteria and the nitrate removal rate gradually increased accordingly. By day 14, the relative abundance of denitrifying bacteria had reached 10%, but Denitrosoma was only 0.1%, and there was no accumulation of nitrous oxide in the system. Only when Denitrosoma reached 0.5% did nitrous oxide accumulate at 2 mg / L, at which point the nitrate removal rate reached 90%. Further operation for day 40 resulted in a Denitrosoma relative abundance of 1.0%. At this point, due to the accumulation of nitrous oxide, an anaerobic ammonia oxidation process was induced, and ammonia nitrogen removal also occurred, indicating successful initiation of the anaerobic ammonia oxidation process. Therefore, it can be seen that in order to achieve the anaerobic ammonium oxidation process, there must be an enrichment of denitrosoma, which provides a source of nitrite for anaerobic ammonium oxidation through a short-cut denitrification process.

[0107] Table 3. Effects of Denitrosoma on the Systemic Anaerobic Ammonium Oxidation Process

[0108] Runtime (d) 0 7 14 21 30 40 Relative abundance of denitrifying bacteria (%) 0 5％ 10％ 15％ 20％ 30％ Relative abundance of Denitratisoma (%) 0 0 0.1％ 0.2％ 0.5％ 1.0％ Nitrogen removal rate (%) 0 20％ 40％ 60％ 90％ 92％ Nitrite formation (mg / L) 0 0 0.1 0.5 2 3 Ammonia nitrogen removal rate (mg / L) 0 0 0 0 0 3

[0109] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A high rate nitrogen removal biofilm process characterized by, The method comprises the following steps: First, assemble the required system The system comprises a reaction tank, which comprises 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 arranged at the water inlet end of the first reaction tank, a second water inlet pipeline and a carbon source adding pipeline are arranged at the water inlet end of the fifth reaction tank, and a nitrification liquid reflux pipeline is arranged at the water outlet end of the fourth reaction tank, with the other end of the nitrification liquid reflux pipeline being connected to the water inlet end of the first reaction tank; Stirring devices are respectively arranged in the first reaction tank, the second reaction tank, the third reaction tank and the fifth reaction tank, and aeration devices are respectively arranged in the fourth reaction tank and the sixth reaction tank; The first reaction tank, the second reaction tank and the fifth reaction tank are provided with suspended carriers for anaerobic ammonia oxidation, the third reaction tank is provided with suspended carriers for denitrification, the fourth reaction tank and the sixth reaction tank are provided with suspended carriers for aerobic zones, and the concentration of suspended sludge in each reaction tank is less than 500 mg / L; Second, start anaerobic ammonia oxidation The first reaction tank and the second reaction tank are first started successfully through relevant control; The ammonia nitrogen concentration of the effluent of the fourth reaction tank is controlled to be between 3 and 5 mg / L, the C / N ratio of the influent of the fifth reaction tank is controlled to be between 2.5 and 3.0 by adding carbon source externally, the anaerobic ammonia oxidation process of the fifth reaction tank is started by using suitable anaerobic ammonia oxidation reaction conditions and superimposing the shedded anaerobic ammonia oxidation bacteria carried by the effluent of the first reaction tank and the second reaction tank, and the anaerobic ammonia oxidation process of the fifth reaction tank is started successfully when the ammonia nitrogen removal amount and the nitrite nitrogen generation amount of the fifth reaction tank are 3 mg / L and 2 mg / L respectively; Third, stable operation of the system The anaerobic ammonia oxidation process is maintained stable, the denitrification efficiency is improved, and the amount of carbon source added is gradually reduced; In the stable operation of the system, the residence time of the first reaction tank and the second reaction tank is 1.0-1.2 h, the residence time of the third reaction tank is 1.5-2.0 times that of the first reaction tank, the residence time of the fourth reaction tank is 3.0-4.0 times that of the first reaction tank, and the actual residence time of the fourth reaction tank is not more than 1.5 h, and the residence time of the fifth reaction tank and the sixth reaction tank is 1.0-1.5 times that of the first reaction tank; The density of the suspended carrier for anaerobic ammonia oxidation is 0.98-1.00 g / cm 3 , 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 , the average void spacing of the suspended carrier is ≥3 mm; the density of the suspended carrier for aerobic zone is 0.94-0.97 g / cm 3 , 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 , the filling rate of the suspended carrier in each reaction tank is >45%; the reflux ratio of the nitrated liquid reflux pipeline is 200-400%; after the system is started, the biological membrane thickness of the first reaction tank to the sixth reaction tank is 150-200 μm, 100-150 μm, 100-150 μm, 200-300 μm, 150-200 μm, 150-200 μm respectively; the effluent ammonia nitrogen is <0.5 mg / L, TN is <5 mg / L, and COD is <30 mg / L; In the second step, the relevant control specifically means that the first water inlet pipeline is controlled to run at full load, the second water inlet pipeline is closed, the C / N ratio in the first reaction tank is controlled to be between 3.0 and 3.5, the nitrate nitrogen concentration of the effluent of the third reaction tank is less than 1 mg / L, and the anaerobic ammonia oxidation process of the first reaction tank and the second reaction tank is started successfully when the ammonia nitrogen removal amount of the first reaction tank and the second reaction tank is greater than 2 mg / L and 3 mg / L respectively, and the nitrite nitrogen generation amount is greater than 2 mg / L and 1 mg / L respectively. The ammonia nitrogen concentration of the influent of the system is greater than 20 mg / L, the C / N ratio is less than 4, the proportion of carboxylic acid substances in the organic matter of the influent is greater than 20%, and the minimum temperature of the influent of the system is 10℃.

2. The high efficiency denitrification biofilm process according to claim 1, characterized in that: Intercepting screens are arranged between adjacent reaction tanks, the specific areas of the suspended carriers in each reaction tank are enriched, and the reflux point of the fourth reaction tank is located after the intercepting screen of the fourth reaction tank.

3. The high efficiency denitrification biofilm process of claim 1, wherein: The carbon source is sodium acetate, glucose, sodium formate, sodium propionate or methanol.

4. The high efficiency denitrification biofilm process of claim 3, wherein: The carbon source is sodium acetate.

5. The high efficiency denitrification biofilm process of claim 1, wherein, The specific steps of the third step are: controlling the first water inlet pipeline and the second water inlet pipeline to respectively input water, short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification denitrification in the first reaction tank-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 oxidation 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 through anaerobic ammonia oxidation is greater than 30% or the cumulative ammonia nitrogen removal amount is greater than 5mg / L; The third reaction tank occurs anoxic denitrification to ensure the effect of TN removal in the front anoxic zone, and the relative abundance of denitrifying bacteria is greater than 30%, the concentration of nitrate nitrogen in the effluent is controlled to be less than 1mg / L or the concentration of COD is controlled to be less than 50mg / L; The fourth reaction tank occurs nitrification process and coupled aerobic decarburization process, the relative abundance of heterotrophic bacteria is greater than 20%, the relative abundance of nitrifying bacteria is greater than 15%, and the ammonia nitrogen in the effluent is controlled to be less than 0.5mg / L; The fifth reaction tank occurs short-cut denitrification-anaerobic ammonia oxidation coupled heterotrophic denitrification denitrification, the C / N is controlled to be 2.5-3.0, the TN removal rate through anaerobic ammonia oxidation is greater than 10% or the ammonia nitrogen removal amount is greater than 2mg / L, the relative abundance of biofilm denitrifying bacteria is greater than 10%, the relative abundance of anaerobic ammonia oxidation bacteria Candiditaous Brocadia and denitrifying bacteria Denitratisoma is greater than 0.5%; The sixth reaction tank occurs nitrification process and coupled aerobic decarburization process, ensuring that the total effluent COD and ammonia nitrogen meet the standards, the relative abundance of biofilm heterotrophic bacteria is greater than 30%, the relative abundance of nitrifying bacteria is greater than 10%, and the effluent COD and ammonia nitrogen are less than 30mg / L and 0.5mg / L respectively.

6. The high efficiency denitrification biofilm process of claim 1, wherein: The third step system is stable, the stirring device needs to be started, the stirring power density of the first reaction tank and the second reaction tank is greater than 7.5 W / m 3 , the stirring power density in the third reaction tank is greater than 10 W / m 3 , the stirring power density in the fifth reaction tank is greater than 7.5 W / m 3 , the aeration intensity in the fourth reaction tank and the sixth reaction tank is greater than 12-16 m 3 / m 2 / h, 10-14 m 3 / m 2 / h respectively.

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