Continuous flow AOA whole-course anaerobic ammonia oxidation self-enrichment enhanced denitrification system and method

Abstract

The invention relates to a continuous flow AOA whole-course anaerobic ammonia oxidation self-enrichment enhanced denitrification system and method, and the system comprises a front anoxic tank, an aerobic tank and a rear anoxic tank which are connected in series, and is filled with a biological filler; the monitoring aeration device comprises an ammonia nitrogen detector and an aeration unit which are connected with the aerobic tank; the reflux device is used for communicating a reflux outlet of the rear anoxic tank with water distribution of the front anoxic tank; and the PID control unit is connected with the monitoring aeration device, the backwashing control valve and the reflux device. The method comprises the following steps: sewage flows into the front anoxic tank, the aerobic tank and the rear anoxic tank; regulating and controlling the reflux ratio to domesticate the biological membrane of the aerobic tank; the ammonia nitrogen concentration of effluent of the aerobic tank is detected in real time through an ammonia nitrogen detector, and the PI D control unit dynamically adjusts the aeration rate of the aerobic tank according to the ammonia nitrogen concentration value and a preset target value, so that the aerobic tank and the rear anoxic tank form an anaerobic ammonium oxidation bacteria self-enrichment environment; the backflow device is used for enabling effluent of the rear anoxic tank to flow back to the front anoxic tank according to a preset proportion, so as to form a whole-process anaerobic ammonia oxidation self-enrichment environment.

Description

Technical Field

[0001] The present invention relates to the field of urban sewage treatment and regeneration, and in particular to a continuous-flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification system and method. Background Art

[0002] The construction and upgrading of sewage treatment plants has always received widespread attention. As the core unit of a sewage treatment plant, the biochemical treatment system is both an asset-heavy component in terms of energy and chemical consumption, and occupies a significant portion of land resources. However, the traditional decontamination processes that biochemical treatment systems rely on are no longer able to meet the complex demands of accelerated urbanization, necessitating new breakthroughs in sewage treatment technology.

[0003] For example, patent CN115321683A discloses a switchable zone and sludge return control system and method for a sludge double-return AOA process. The system includes two parts: switchable zone regulation and sludge return regulation. The switchable zone is set at the end of the anaerobic, aerobic and anoxic ends. The volume of the anaerobic, aerobic and anoxic zones, that is, the residence time, can be flexibly regulated by adjusting the switchable zone. Similarly, by real-time monitoring of the influent flow rate, the sludge return volume can be accurately regulated to ensure the constancy of the sludge return ratio. However, the design and application of this patent in actual engineering projects will inevitably design the volume of each functional zone according to the maximum load of nitrogen concentration. Therefore, the switchable zone may be in a long-term open or closed state. In addition, it has not achieved an effective replacement for the sedimentation tank, which has caused a great deal of waste in the tank capacity and is not conducive to alleviating the problem of tight urban construction land.

[0004] Patent CN118026389A discloses a two-stage AO-ABFT process aeration control system, comprising: an anoxic-aerobic tank and an aerated biological fluidized bed tank connected in sequence; an aeration pipeline with branches extending into the aerobic tank and the aerated biological fluidized bed tank to input air; a PLC control system that receives monitoring data from sensors installed in the anoxic-aerobic tank and the aerated biological fluidized bed tank and calculates the required air intake; the PLC control system receives the status of the electric regulating valve installed in the aeration pipeline and adjusts the opening of the electric regulating valve according to the calculated required air intake. Based on multiple feedback adjustments of COD, ammonia nitrogen and dissolved oxygen, the stability of the sewage treatment system is improved, and energy conservation and consumption reduction in the sewage treatment process are achieved. However, due to the fact that the patent mainly relies on traditional nitrification and denitrification processes, it neglects to pay attention to the specific control parameters of anaerobic ammonia oxidation, and thus cannot achieve the ideal decontamination effect.

[0005] Therefore, how to provide a sewage treatment system with intelligent automatic control, small footprint and high anaerobic ammonia oxidation self-enrichment has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0006] In response to the defects in the above-mentioned prior art, the purpose of the present invention is to provide a continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment and enhanced denitrification system and method. By simplifying the structural design and the coordinated cooperation between devices, and setting a control unit to receive feedback results from ammonia nitrogen detectors, DO detectors, etc. and regulate the reflux and aeration volume, the technical problems of traditional systems such as large footprint, high degree of manual intervention, low degree of anaerobic ammonia oxidation self-enrichment, and low denitrification efficiency are solved.

[0007] In a first aspect, the present invention provides a continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification system, comprising:

[0008] The front anoxic tank, aerobic tank and rear anoxic tank are connected in series, and each tank is filled with biological fillers;

[0009] Monitoring aeration equipment, including ammonia nitrogen detector and aeration unit connected to the aerobic tank;

[0010] A reflux device connects the reflux outlet of the rear anoxic tank with the reflux inlet of the front anoxic tank;

[0011] Backwashing device, connected to the front anoxic tank and the rear anoxic tank respectively;

[0012] The PID control unit is connected to monitor the aeration device, the reflux device and the backwash device respectively.

[0013] Through the mutual coordination of devices and intelligent automatic regulation, a variety of denitrification environments are formed, achieving short-term nitrification, nitrite accumulation and precise control of ammonia nitrogen.

[0014] Furthermore, the monitoring aeration device also includes but is not limited to a nitrite detector connected to the aerobic tank, a DO detector connected to the aerobic tank and the post-anoxic tank, and a COD detector connected to the pre-anoxic tank.

[0015] Furthermore, the volume ratio of the pre-anoxic tank, aerobic tank, and post-anoxic tank is (1-3):(1-2):1, and the filling ratio of the biofiller is 50%-70%. Each tank adopts a pure biofilm process. The biofilm on the biofiller in the aerobic tank has a dissolved oxygen mass transfer gradient, including an aerobic layer, a microaerobic layer, and anoxic layer from the outside to the inside. The biofilm thickness is 200-500 μm, preferably 200-400 μm. However, the biofilm thickness can be adjusted according to different aerobic tanks or other application environmental factors. Too thin or too thick a biofilm thickness will have adverse effects.

[0016] Furthermore, the biological filler is any type of filler that can be selected, such as polyethylene filler or other porous filler.

[0017] By optimizing the pool volume ratio and filler filling rate, controlling the hydraulic retention time, increasing the pollutant degradation rate, and synergistically regulating the biofilm thickness, the DO gradient mass transfer efficiency is ensured.

[0018] Furthermore, the backwash device includes a first backwash pipe and a backwash drain valve provided in the front anoxic tank, a second backwash pipe provided in the rear anoxic tank, and a backwash fan for controllably supplying air to the first backwash pipe and the second backwash pipe;

[0019] The front anoxic tank is connected to the aerobic tank through the aerobic tank water inlet valve, and the installation position of the aerobic tank water inlet valve is lower than the backwash drain valve;

[0020] The PID control unit is respectively connected to and controls the aerobic pool water inlet valve, backwash drain valve and backwash fan.

[0021] Furthermore, the front anoxic tank and the rear anoxic tank are fixed bed structures.

[0022] The fixed bed structure is used to intercept the required bacteria and suspended solids, and periodic aeration backwashing is used to remove blockages on the filler surface, thereby maintaining the activity of the biofilm and extending the stable operation period of the system.

[0023] The backwash device of the present invention is comprehensively designed based on the structure and volume of the front anoxic tank, the aerobic tank and the rear anoxic tank, as well as the corresponding treatment process and other factors. Under the control of the PID control unit, it cooperates with the monitoring aeration device, the reflux device, etc. to operate. For example, when the rear anoxic tank is backwashed, the reflux device is closed during the initial aeration and film formation stage, and the backwash water of the rear anoxic tank is switched to flow into the concentration tank via the biochemical outlet; in the later normal operation, in order to return the growing bacteria to the front anoxic tank during backwashing, the reflux device will be regulated to open according to the normal reflux ratio. In addition, when the front anoxic tank is backwashed, the aerobic tank water inlet valve is closed, and the backwash water will not flow from the front anoxic tank into the aerobic tank, but into the concentration tank via the backwash drain valve. Therefore, in the vertical direction, the installation position of the aerobic tank water inlet valve is set to be lower than the backwash drain valve, which is more suitable for the setting method of normal treatment water volume and backwash water volume.

[0024] Furthermore, the aeration unit includes an aeration pipe arranged at the bottom of the aerobic tank, and an automatic variable frequency blower connected to the aeration pipe.

[0025] The aeration volume is dynamically adjusted by the variable frequency blower to accurately control the DO value of the aerobic pool, thereby balancing the needs of short-range nitrification and ammonia nitrogen removal.

[0026] On the other hand, based on the above system, the present invention also provides a continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification method, comprising the following steps:

[0027] Step 1: Make the sewage flow into the front anoxic tank, aerobic tank and rear anoxic tank in sequence;

[0028] Step 2: The ammonia nitrogen concentration value Q1 of the effluent from the aerobic tank is detected in real time by an ammonia nitrogen detector. The PID control unit controls the aeration unit to dynamically adjust the aeration volume of the aerobic tank based on the analysis of the received ammonia nitrogen concentration value Q1 and the preset target value Q0, so that the aerobic tank and the post-anoxic tank form an anaerobic ammonia-oxidizing bacteria self-enrichment environment;

[0029] Step 3: The effluent from the rear anoxic tank is returned to the front anoxic tank at a preset ratio through a reflux device to form a full-process anaerobic ammonia oxidation self-enrichment environment.

[0030] Furthermore, before step 1, a film forming step is performed, including:

[0031] Add blank fillers into the pre-anoxic tank, aerobic tank and post-anoxic tank according to the filling ratio, inject sewage into each tank and inoculate 1000-2000 mg / L activated sludge;

[0032] Controlling the aeration unit (6.2) to aerate the aerobic tank (3);

[0033] Controlling the backwash device to perform periodic aeration backwashing on the front anoxic tank and the rear anoxic tank;

[0034] In addition, the reflux device is closed during the film forming step.

[0035] Furthermore, the backwash device's periodic aeration backwashing includes intermittent aeration backwashing of the front anoxic tank and the rear anoxic tank, with the backwash water entering the concentrating tank separately. For example, the front anoxic tank can be aerated backwashed every 1-2 days, with each aeration lasting 20-40 minutes; the rear anoxic tank can also be aerated backwashed every 1-2 days, with each aeration lasting 5-10 minutes. Before the anaerobic ammonium oxidation (AAM) enrichment of the biofilm in the rear anoxic tank is achieved, all the aeration backwash water enters the concentrating tank. Once the AAM enrichment of the biofilm in the rear anoxic tank is achieved, the backwash water is returned to the front anoxic tank at a preset ratio, with the remaining backwash water still entering the concentrating tank.

[0036] Furthermore, after the film forming step, the reflux device is started to perform the reflux regulation and acclimation step, including:

[0037] S1 initial reflow:

[0038] Returning the effluent from the rear anoxic tank to the front anoxic tank at a return ratio of 100%-250%;

[0039] Regulate the chemical oxygen demand (COD) of the effluent from the pre-anoxic tank to be higher than 50 mg / L;

[0040] Increase the aeration volume of the aerobic pool to promote the thickening of the biofilm of the biological filler in the aerobic pool;

[0041] S2 enhanced recirculation: Increase the recirculation ratio to above 250%, and reduce the chemical oxygen demand (COD) of the effluent from the pre-anoxic tank to below 50 mg / L.

[0042] Furthermore, during the initial reflow of S1, the dissolved oxygen in the effluent of the aerobic tank is regulated to be above 5 mg / L, and the thickness of the biofilm of the biological filler in the aerobic tank is promoted to increase to 200-500 μm, preferably 200-400 μm. The biofilm forms a dissolved oxygen mass transfer gradient, including an aerobic layer, a microaerobic layer and an anoxic layer from the outside to the inside.

[0043] Furthermore, the PID control unit dynamically adjusts the aeration rate of the aerobic tank so that the ammonia nitrogen concentration value Q1 of the effluent from the aerobic tank is dynamically adjusted within the range of (0.5-2)×Q0, and controls the ammonia nitrogen concentration value Q2≤Q0 of the post-anoxic tank, wherein the preset target value Q0 of the ammonia nitrogen concentration of the effluent from the aerobic tank is 1-3 mg / L, preferably 1.5-2.5 mg / L.

[0044] Furthermore, the PID control unit dynamically adjusts the aeration rate of the aerobic tank so that the dissolved oxygen DO1 of the effluent from the aerobic tank is below 5.5 mg / L, and the dissolved oxygen DO2 of the post-anoxic tank (4) is ≤ (0.08-0.1)×DO1; and short-range nitrification and nitrite accumulation are achieved inside the biofilm so that the nitrite concentration of the effluent from the aerobic tank is not less than 0.5 mg / L, preferably 0.5-3 mg / L.

[0045] Furthermore, the ratio of aeration volume to water inlet volume (gas-water ratio) of the aerobic pool is dynamically adjusted between 2 and 15 to meet the aeration volume required for different water volumes, where:

[0046] When the ammonia nitrogen concentration value Q1 of the effluent from the aerobic pool is less than the preset target value Q0, the aeration rate of the aerobic pool is gradually reduced. For example, the dissolved oxygen DO1 of the effluent from the aerobic pool can be reduced by 15%-35%.

[0047] When the ammonia nitrogen concentration value Q1 of the effluent from the aerobic pool is greater than the preset target value Q0, the aeration rate of the aerobic pool is gradually increased. For example, the dissolved oxygen DO1 of the effluent from the aerobic pool can be increased by 20%-50%.

[0048] The beneficial effects of the technical solution of the present invention include at least:

[0049] 1. For the continuous flow process of urban sewage, the present invention adopts a pure biofilm process to replace the traditional activated sludge process by optimizing the system structure and the coordination between devices. It only relies on simple aeration PID control and the regulation of the residual ammonia nitrogen threshold (1.5-2.5 mg / L) of the aerobic tank effluent, avoiding overaeration of the aerobic tank while providing ammonia nitrogen substrate for anaerobic ammonia oxidation self-enrichment in the aerobic tank and the post-anoxic tank. By dynamically adjusting the aeration volume, the aeration volume can be saved by more than 20%, reducing aeration energy consumption, significantly reducing the floor space, and saving operating costs.

[0050] 2. This invention overcomes the stringent low dissolved oxygen requirement (0.1-2 mg / L) required for short-term nitrification and anaerobic ammonium oxidation (ANAMMOX) in municipal sewage and the limited ammonia nitrogen nitrification rate by regulating the recirculation ratio, cultivating the biofilm thickness (200-500 μm) in the aerobic tank, and controlling aeration through a PID control unit. At 4-5 mg / L dissolved oxygen in the aerobic tank, partial short-term nitrification (nitrite accumulation of 0.5-2.5 mg / L) is achieved, providing nitrite substrate for ANAMMOX self-enrichment in the aerobic tank and the subsequent anoxic tank.

[0051] 3. The post-anoxic tank of the present invention utilizes the residual ammonia nitrogen from the aerobic tank to effectively reduce the residual DO in the aerobic tank effluent to below 0.5 mg / L, providing a low-oxygen or anoxic environment for anaerobic ammonia oxidation self-enrichment in the post-anoxic tank. This also reduces the adverse effects of high DO (4-5 mg / L) carried over from the aerobic zone effluent and caused by nitrification solution backflow into the anoxic tank.

[0052] 4. The present invention relies on short-range nitrification regulated by the residual ammonia nitrogen in the effluent of the aerobic pool, without the need to pursue excessive nitrite accumulation. The self-enrichment of anaerobic ammonia-oxidizing bacteria in the entire process of the continuous flow biochemical pool is achieved through plug flow, nitrification liquid reflux and post-anoxic backwashing. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic structural diagram of the continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification system of the present invention;

[0054] Figure 2 It is a control logic diagram of the monitoring aeration device of the present invention;

[0055] Figure 3 1 is a graph showing changes in ammonia nitrogen excess and aeration rate in an aerobic tank aeration PID control according to an embodiment of the present invention;

[0056] Figure 4 This is a graph showing changes in dissolved oxygen concentration in the effluent of an aerobic pool according to an embodiment of the present invention;

[0057] Figure 5 This is a diagram showing the effect of aeration PID control of short-range nitrification in the aerobic tank (O1) according to an embodiment of the present invention;

[0058] Figure 62. It is a diagram showing the anaerobic ammonium oxidation enrichment effect of biofilms in different biochemical pools according to the embodiments of the present invention.

[0059] Explanation of the accompanying symbols: 1-sewage inlet pipe; 2-pre-anoxic tank, 2.1-pre-anoxic tank inlet pipe, 2.2-first backwash pipe, 2.3-aerobic tank inlet valve, 2.4-backwash drain valve; 3-aerobic tank, 3.1 aerobic tank inlet pipe, 3.2-aeration pipe; 4-post-anoxic tank, 4.1-post-anoxic tank inlet pipe, 4.2-second backwash pipe, 4.3-biochemical outlet, 4.4-reflux device; 5-backwash device, 5.1-first backwash valve, 5.2-second backwash valve; 6.1-ammonia nitrogen detector, 6.2-automatic variable frequency blower. DETAILED DESCRIPTION

[0060] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0061] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0062] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0063] like Figure 1 As shown in the figure, the continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification system includes:

[0064] (1) The pre-anoxic tank 2, aerobic tank 3, and post-anoxic tank 4 are connected in sequence. The sewage to be treated flows from the sewage inlet pipe 1 through the inlet pipe extending into the bottom of the pre-anoxic tank 2 into the pre-anoxic tank 2. The treated water flows from the aerobic tank inlet valve 2.3 through the aerobic tank inlet pipe 3.1 extending into the bottom of the aerobic tank 3 into the aerobic tank 3. The treated water in the aerobic tank 3 flows into the post-anoxic tank 4 through the post-anoxic tank inlet pipe 4.1 extending into the bottom of the post-anoxic tank 4. Finally, part of the biochemical effluent flows out of the system through the biochemical outlet 4.3, and part of the biochemical effluent flows back to the pre-anoxic tank 2 in a predetermined ratio. Among them, the reflux ratio of the biochemical system is expressed as the following formula, and different reflux ratios can be used for water circulation during different treatment periods:

[0065]

[0066] (2) Monitoring of aeration devices, including:

[0067] A series of sensors for detecting corresponding parameters include but are not limited to an ammonia nitrogen detector 6.1 connected to the aerobic tank 3, a nitrite detector and a DO detector, a DO detector connected to the post-anoxic tank, and a COD detector connected to the pre-anoxic tank.

[0068] The aeration unit includes an aeration pipe 3.2 provided at the bottom of the aerobic tank 3 and an automatic variable frequency blower 6.2 having the same air path as the aeration pipe. The frequency of the automatic variable frequency blower 6.2 is automatically adjusted between 20-50 Hz, and can provide, for example, 10-35 m³ of air to the aerobic tank 3 according to the search results. 3 / h aeration volume.

[0069] (3) The reflux device 4.4 uses a reflux pipeline and a reflux pump to connect the reflux outlet of the rear anoxic tank 4 with the reflux inlet of the front anoxic tank 2. The effluent of the rear anoxic tank 4 is refluxed to the front anoxic tank 2 at a preset ratio, thereby forming a full-process anaerobic ammonia oxidation self-enrichment environment.

[0070] (4) A backwash device 5, comprising a first backwash pipe 2.2 disposed at the bottom of the pre-anoxic tank 2, with a first backwash valve 5.1 controlling the opening and closing and flow rate of the first backwash pipe 2.2; a second backwash pipe 4.2 disposed at the bottom of the post-anoxic tank 4, with a second backwash valve 5.2 controlling the opening and closing and flow rate of the second backwash pipe 4.2; and a backwash fan 5 for controllably supplying air to the first backwash pipe 2.2 and the second backwash pipe 4.1. Furthermore, a backwash drain valve 2.4 is provided at a position higher than the aerobic tank inlet valve 2.3 of the pre-anoxic tank 2, connected to the concentrating tank, for discharging the flushing water from the aeration backwash of the pre-anoxic tank 2 into the concentrating tank.

[0071] (5) PID control unit, which is connected to and controls the monitoring aeration device, backwash device 5 and reflux device 4.4 respectively. The control logic of the monitoring aeration device can be found in Figure 2 .

[0072] The present invention employs a pure biofilm AOA process in a biochemical tank. The effective volume ratio of the sequentially connected pre-anoxic tank 2, aerobic tank 3, and post-anoxic tank 4 is (1-3):(1-2):1. The biofiller filling ratio is 50-70%. Biofilm formation on the filler is initiated by suffocation. The biofilm thickness of the biofiller in each tank ranges from 200 to 500 μm, preferably 200 to 400 μm. The biofilm on the biofiller in the aerobic tank 3 has a dissolved oxygen mass transfer gradient, comprising an aerobic layer, a microaerobic layer, and an anoxic layer from the outside to the inside.

[0073] The front anoxic tank 2 and the rear anoxic tank 4 are fixed beds. The front anoxic tank 2 uses the first backwash pipe 2.2 of the backwash device 5 for aeration backwashing, with an interval of 1-2 days and a backwashing time of 20-40 minutes each time. The flushing water enters the concentration tank through the backwash drain valve 2.4. At this time, the aerobic tank inlet valve 2.3 is closed to prevent the flushing water from entering the aerobic tank 3; the rear anoxic tank 4 also uses the second backwash pipe 4.2 of the backwash device 5 for aeration backwashing, with an interval of 1-2 days and a backwashing time of 5-10 minutes each time. When the rear anoxic tank 4 is aerated backwashed, the opening and closing state of the reflux device is determined according to the process stage of the system.

[0074] The continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment and enhanced denitrification method of the present invention comprises the following steps:

[0075] Step 1: Exposure and film forming step, including:

[0076] Add blank fillers into the pre-anoxic tank 2, aerobic tank 3 and post-anoxic tank 4 according to the filling ratio, inject sewage into each tank and inoculate 1000-2000 mg / L activated sludge;

[0077] Start the automatic variable frequency blower 6.2 of the aeration unit to aerate the aerobic tank 3;

[0078] The front anoxic tank 2 and the rear anoxic tank 4 are subjected to periodic aeration backwashing. During the flushing, the reflux device 4.4 is closed, and the flushing water of the front anoxic tank 2 enters the concentration tank through the backwash drain valve 2.4, and the flushing water of the rear anoxic tank 4 is switched to the concentration tank through the biochemical water outlet 4.3.

[0079] Step 2: Reflux regulation and acclimation step, including:

[0080] S2.1 Initial Reflux:

[0081] The effluent from the rear anoxic tank 4 is returned to the front anoxic tank 2 at a return ratio of 100%-250%;

[0082] Regulating the chemical oxygen demand (COD) of the effluent from the pre-anoxic tank 2 to be higher than 50 mg / L, for example, 50-90 mg / L;

[0083] Under the action of a small amount of organic matter, the aeration volume of the aerobic tank 3 is increased through the aeration pipe 3.2 and the automatic variable frequency blower 6.2, and the dissolved oxygen in the effluent of the aerobic tank 3 is regulated to be above 5 mg / L, preferably 6-7 mg / L. While ensuring the removal of ammonia nitrogen, the filler of the aerobic tank 3 uses the organic matter to promote the growth of the biofilm thickness to 200-500 μm, and the biofilm forms a dissolved oxygen mass transfer gradient, including an aerobic layer, a microaerobic layer and an anoxic layer from the outside to the inside, and short-range nitrification and nitrite accumulation is achieved within the biofilm, so that the nitrite concentration in the effluent of the aerobic tank 3 is 0.5-2.5 mg / L;

[0084] S2.2 Enhanced reflow: Increase the reflow ratio to above 250%, for example, increase the reflow ratio to 300%-400%, reduce the chemical oxygen demand (COD) of the effluent of the pre-anoxic tank 2 to below 50 mg / L, and avoid excessive growth of the biofilm thickness of the aerobic tank 3.

[0085] Step 3: Make the sewage flow into the front anoxic tank 2, the aerobic tank 3 and the rear anoxic tank 4 in sequence;

[0086] Step 4: The ammonia nitrogen detector 6.1 installed at the outlet of the aerobic tank 3 transmits the real-time detected ammonia nitrogen concentration value Q1 to the PID control unit (the detection results of other detectors are also transmitted to the PID control unit). The PID control unit is connected to the automatic variable frequency blower 6.2. The PID control unit controls the automatic variable frequency blower 6.2 based on the comparison result of the received ammonia nitrogen concentration value Q1 and the preset target value Q0 to dynamically adjust the aeration rate of the aerobic tank 3, so that the aerobic tank 3 and the post-anoxic tank 4 form an environment for self-enrichment of anaerobic ammonia-oxidizing bacteria;

[0087] Specifically, the aeration rate of the aerobic tank 3 is dynamically adjusted through the PID control unit so that the ammonia nitrogen concentration Q1 of the effluent from the aerobic tank 3 is dynamically adjusted within the range of (0.5-2)×Q0, and the ammonia nitrogen concentration Q2 of the post-anoxic tank 4 is controlled to be ≤Q0. The preset target value Q0 for the ammonia nitrogen concentration in the effluent from the aerobic tank 3 is 1-3 mg / L, preferably 1.5-2.5 mg / L; accordingly, Q1 is preferably 1-3 mg / L, and Q2 is preferably below 1.5 mg / L. Furthermore, the dissolved oxygen DO1 of the effluent from the aerobic tank 3 is set below 5.5 mg / L, and the dissolved oxygen DO2 of the post-anoxic tank 4 is set to be ≤(0.08-0.1)×DO1; accordingly, DO2 is preferably below 0.5 mg / L.

[0088] Preferably, the ratio of the aeration volume of the aerobic pool to the water inlet (gas-water ratio) is 2-15, and the PID control unit controls the aeration volume of the aerobic pool 3 to be dynamically adjusted according to different water volume scales, wherein:

[0089] S4.1 When the ammonia nitrogen concentration Q1 of the effluent from aerobic tank 3 is less than or equal to the preset target value Q0, gradually reduce the aeration rate of aerobic tank 3, and the dissolved oxygen DO1 of the effluent from aerobic tank 3 can be reduced by 15%-35%;

[0090] S4.2 When the ammonia nitrogen concentration value Q1 of the effluent from the aerobic pool 3 is greater than the preset target value Q0, the aeration volume of the aerobic pool 3 is gradually increased, and the dissolved oxygen DO1 of the effluent from the aerobic pool 3 can be increased by 20%-50%.

[0091] Step 5: After the aerobic tank 3 and the post-anoxic tank 4 achieve self-enrichment of anaerobic ammonium oxidizing bacteria, the post-anoxic tank 4, under the action of a fixed bed, intercepts the detached biofilm and SS containing anaerobic ammonium oxidizing bacteria. The aeration backwash frequency of the post-anoxic tank 4 is used, that is, once a day or once every two days, with a backwash time of 5-10 minutes. However, the return pump is no longer turned off during the flushing. The effluent of the post-anoxic tank 4 is returned to the pre-anoxic tank 2 through the return device 4.4 at a return ratio of more than 250%. The return water carries some of the detached biofilm and SS back to the pre-anoxic tank 2, and some of the flushing water still enters the concentration tank. Under the action of the fixed bed, the pre-anoxic tank 2 intercepts SS to achieve self-enrichment of anaerobic ammonium oxidizing bacteria. Under long-term action, the pre-anoxic tank 2, aerobic tank 3 and post-anoxic tank 4 of the pure biofilm AOA process form a full-process anaerobic ammonia oxidation self-enrichment environment, achieving partial anaerobic ammonia oxidation enhanced denitrification.

[0092] To further illustrate the present invention, a continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification system and method provided by the present invention is described in detail below with reference to the examples:

[0093] Example:

[0094] This embodiment constructs a 50-ton / day urban sewage continuous flow device, which adopts the continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment and enhanced denitrification system of the present invention, including:

[0095] The volume ratio of the biofilm pre-anoxic tank 2, biofilm aerobic tank 3, and biofilm post-anoxic tank 4 was 1:1:1. The average influent COD concentration of municipal sewage was 138.1 mg / L, the average ammonia nitrogen concentration was 40.3 mg / L, and the average influent total nitrogen was 42.8 mg / L. The fill ratios of the biofilm pre-anoxic tank 2, biofilm aerobic tank 3, and biofilm post-anoxic tank 4 were 60%, 60%, and 60% blank filler, respectively. The tanks were inoculated with 1500 mg / L of excess sludge and aerated for startup. On the seventh day, a small amount of biofilm was observed attached to the filler surfaces of all three biochemical tanks, demonstrating the biofilm's excellent nitrification and denitrification activity.

[0096] The pilot plant operated normally, with an overall recirculation ratio of 150-400% in recirculation unit 4.4. Initially, the recirculation ratio was controlled at 150-250%. The effluent from the pre-anoxic tank 2 contained residual nitrate-nitrogen levels of 2-3 mg / L, and an average COD of 74 mg / L. The average biofilm thickness in the aerobic biofilm tank 3 increased to 276 μm. Subsequently, the recirculation ratio of recirculation unit 4.4 was increased to 300-350%, and the effluent nitrate-nitrogen and COD concentrations from the pre-anoxic biofilm tank 2 decreased to 1.3-1.5 mg / L and 48 mg / L, respectively.

[0097] When the system runs stably, the residual ammonia nitrogen control of the effluent from the biofilm aerobic tank 3 is turned on, the preset target value Q0 of the effluent ammonia nitrogen concentration from the biofilm aerobic tank 3 is set to 2.5 mg / L, and the aeration volume is controlled by the automatic variable frequency blower 6.2 through the PID control unit instruction. Figure 3-4 The relationship between the aeration rate of the biofilm pilot plant and the effluent ammonia nitrogen in the biofilm aerobic tank 3 from 12:00 to 17:00 on a typical day is shown. This embodiment controls the effluent ammonia nitrogen to meet the standard while strengthening anaerobic ammonia oxidation for the remaining ammonia nitrogen in the post-anoxic tank 4.

[0098] In this embodiment, the preset target value Q0 for the ammonia nitrogen concentration in the effluent of aerobic tank 3 is set to 2.5 mg / L. Even if anaerobic ammonia oxidation does not occur, based on the theoretical oxygen demand for complete nitrification of 4.57 mg / L, the effluent of biofilm aerobic tank 3 still contains 4-5 mg / L of dissolved oxygen, which can remove approximately 1 mg / L of ammonia nitrogen. The ammonia nitrogen detector 6.1 monitors the ammonia nitrogen concentration Q1 in the effluent of aerobic tank 3, and the detected value is fed back to the intelligent control system in real time, which performs PID control by the control unit algorithm, including:

[0099] (1) When the ammonia nitrogen concentration value Q1 of the effluent is less than or equal to the preset target value Q0 (2.5 mg / L), the PID control unit calculates and adjusts the operating frequency of the automatic variable frequency blower 6.2 according to the concentration difference, and the aeration volume of the aerobic tank 3 is reduced from about 29m 3 / h gradually decreases to about 13m 3 / h, the corresponding DO of the effluent from aerobic pool 3 gradually decreased from 5.2 mg / L to 4.1 mg / L (a decrease of about 21.2%);

[0100] (2) When the effluent ammonia nitrogen concentration value Q1 is greater than the preset target value Q0 (2.5 mg / L), the PID control unit calculates and increases the operating frequency of the automatic variable frequency blower 6.2 according to the concentration difference, and the aeration volume of the aerobic pool 3 increases from about 13m 3 / h gradually increases to about 25m 3 / h, the DO of the effluent from aerobic pool 3 gradually increased from 4.1 mg / L to 5.2 mg / L (an increase of about 26.8%).

[0101] During the control period of the PID control unit, the ammonia nitrogen concentration value Q1 was 2.5mg / L±0.5mg / L, achieving stable control of ammonia nitrogen in the effluent of aerobic pool 3. Figure 5-6 As shown in Figure 3, this precise control provides suitable environmental conditions for short-range nitrification and anaerobic ammonium oxidation.

[0102] The above introduces the preferred embodiments of the present invention, which is intended to make the spirit of the present invention clearer and easier to understand, and is not intended to limit the present invention. Any modifications, replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A continuous flow AOA full-process anaerobic ammonium oxidation self-enrichment and enhanced denitrification system, characterized in that: include: A pre-anoxic tank (2), an aerobic tank (3) and a post-anoxic tank (4) are connected in series, each tank being filled with biological fillers; A monitoring aeration device, including an ammonia nitrogen detector (6.1) and an aeration unit (6.2) connected to the aerobic tank (3); A reflux device (4.4) connects the reflux outlet of the rear anoxic tank (4) with the reflux inlet of the front anoxic tank (2); A backwash device is connected to the front anoxic tank (2) and the rear anoxic tank (4) respectively; The PID control unit (6) is connected to and controls the monitoring aeration device, the reflux device (4.4) and the backwash device.

2. The system according to claim 1, characterized in that The volume ratio of the front anoxic tank (2), the aerobic tank (3) and the rear anoxic tank (4) is (1-3):(1-2):1, the filling ratio of the biological filler is 50%-70%, and each tank adopts a pure biofilm process. The biofilm on the biological filler in the aerobic tank (3) has a dissolved oxygen mass transfer gradient, which includes an aerobic layer, a microaerobic layer and an anoxic layer from the outside to the inside.

3. The system according to claim 1 or 2, characterized in that: The backwash device comprises a first backwash pipe (2.2) and a backwash drain valve (2.4) arranged in the front anoxic tank (2), a second backwash pipe (4.1) arranged in the rear anoxic tank (4), and a backwash fan (5) for controllably supplying air to the first backwash pipe (2.2) and the second backwash pipe (4.1); The pre-anoxic tank (2) is connected to the aerobic tank (3) through the aerobic tank water inlet valve (2.3), and the installation position of the aerobic tank water inlet valve (2.3) is lower than the backwash drain valve (2.4); The PID control unit (6) is respectively connected to and controls the aerobic pool water inlet valve (2.3), the backwash drain valve (2.4) and the backwash fan (5).

4. A continuous flow AOA full-process anaerobic ammonia oxidation self-enrichment enhanced denitrification method based on the system according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: The sewage flows into the pre-anoxic tank (2), the aerobic tank (3) and the post-anoxic tank (4) in sequence; Step 2: The ammonia nitrogen concentration value Q1 of the effluent from the aerobic tank (3) is detected in real time by an ammonia nitrogen detector (6.1). The PID control unit controls the aeration unit (6.2) based on the analysis of the received ammonia nitrogen concentration value Q1 and the preset target value Q0 to dynamically adjust the aeration volume of the aerobic tank (3), so that the aerobic tank (3) and the post-anoxic tank (4) form an anaerobic ammonia-oxidizing bacteria self-enrichment environment; Step 3: The effluent from the post-anoxic tank (4) is returned to the pre-anoxic tank (2) at a preset ratio through the reflux device (4.4), forming a full-process anaerobic ammonia oxidation self-enrichment environment.

5. The method according to claim 4, wherein Before step 1, a film forming step is performed, including: Add blank fillers to the pre-anoxic tank (2), the aerobic tank (3) and the post-anoxic tank (4) according to the filling ratio, inject sewage into each tank and inoculate 1000-2000 mg / L of activated sludge; Controlling the aeration unit (6.2) to aerate the aerobic tank (3); Controlling the backwashing device to perform periodic aeration backwashing on the front anoxic tank (2) and the rear anoxic tank (4); In addition, the reflux device (4.4) is closed during the film formation step.

6. The method according to claim 5, wherein After the film forming step, the reflux device (4.4) is started to perform the reflux regulation and acclimation step, including: S1 initial reflow: Returning the effluent from the post-anoxic tank (4) to the pre-anoxic tank (2) at a return ratio of 100%-250%; Regulate the chemical oxygen demand (COD) of the effluent from the pre-anoxic tank (2) to be higher than 50 mg / L; Increasing the aeration rate of the aerobic pool (2) to promote the thickening of the biofilm of the biological filler in the aerobic pool (2); S2 enhanced recirculation: increase the recirculation ratio to more than 250%, and reduce the chemical oxygen demand (COD) of the effluent from the pre-anoxic tank (2) to less than 50 mg / L.

7. The method according to claim 6, wherein During the initial reflow of S1, the dissolved oxygen in the effluent of the aerobic tank (2) is regulated to be above 5 mg / L, and the thickness of the biofilm of the biological filler in the aerobic tank (2) is promoted to increase to 200-500 μm. The biofilm forms a dissolved oxygen mass transfer gradient, which includes an aerobic layer, a microaerobic layer and an anoxic layer from the outside to the inside.

8. The method according to any one of claims 4 to 7, wherein: The PID control unit dynamically adjusts the aeration volume of the aerobic tank (3) so that the ammonia nitrogen concentration value Q1 of the effluent from the aerobic tank (3) is dynamically adjusted within the range of (0.5-2)×Q0, and controls the ammonia nitrogen concentration value Q2≤Q0 of the post-anoxic tank (4), wherein the preset target value Q0 of the ammonia nitrogen concentration of the effluent from the aerobic tank (3) is 1-3 mg / L.

9. The method according to claim 8, wherein The PID control unit dynamically adjusts the aeration rate of the aerobic tank (3) so that the dissolved oxygen DO1 of the effluent of the aerobic tank (3) is below 5.5 mg / L, and the dissolved oxygen DO2 of the post-anoxic tank (4) is ≤ (0.08-0.1)×DO1; And short-range nitrification and nitrite accumulation are achieved inside the biofilm, so that the nitrite concentration of the effluent from the aerobic tank (3) is 0.5-2.5 mg / L.

10. The method according to claim 9, wherein The ratio of aeration volume to water inlet of the aerobic tank (3) is dynamically adjusted between 2 and 15, wherein: When the ammonia nitrogen concentration value Q1 of the effluent from the aerobic tank (3) is less than the preset target value Q0, the aeration rate of the aerobic tank (3) is gradually reduced; When the ammonia nitrogen concentration value Q1 of the effluent from the aerobic tank (3) is greater than the preset target value Q0, the aeration volume of the aerobic tank (3) is gradually increased.

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