Device and method for simultaneously removing nitrogen and recovering phosphorus from domestic sewage by enhancing A2N process based on shortcut nitrification-anaerobic ammonium oxidation

Abstract

An apparatus and method for synchronously removing nitrogen and recovering phosphorus from domestic sewage based on enhanced A₂N process by shortcut nitrification-anaerobic ammonium oxidation, belonging to the field of biological sewage treatment. Domestic sewage enters the A₂N-SBR system, undergoes anaerobic reaction in A₂-SBR, and denitrifying phosphorus-accumulating bacteria store extracellular carbon source as intracellular carbon source (PHA) and release phosphorus. After the anaerobic reaction, the supernatant enters N-SBR for shortcut nitrification; the effluent of the previous cycle of N-SBR enters A₂-SBR for anoxic anaerobic ammonium oxidation (Anammox) and denitrifying phosphorus removal (DPR); in N-SBR, nitrifying bacteria convert ammonia nitrogen into nitrite, and a small amount of remaining NH₄⁺-N provides substrates for Anammox and DPR in the anoxic section of A₂-SBR in the next cycle. The supernatant of sludge fermentation is regularly added to the influent of A₂-SBR, and Ca²⁺ is added in the anoxic section to promote the formation of crystals mainly composed of hydroxyapatite, effectively retaining anaerobic ammonium oxidation bacteria. The combination of DPR and biological induced crystallization phosphorus recovery realizes the deep nitrogen and phosphorus removal of domestic sewage while recovering phosphorus resources.

Description

Technical Field

[0001] The present invention relates to a device and method for synchronously removing nitrogen and recovering phosphorus from domestic sewage based on an enhanced A2N process by shortcut nitrification-anaerobic ammonium oxidation, and belongs to the field of sewage biological treatment. Background Technique

[0002] The discharge of urban domestic sewage has increased, and the annual treatment volume of domestic sewage in sewage treatment plants has also increased year by year. Discharging untreated water into natural water bodies will cause the water quality to deteriorate sharply, lead to excessive reproduction of algae, and cause serious water eutrophication. Excessive discharge of nutrients such as nitrogen and phosphorus is the main cause of water eutrophication. There is an urgent need for new sewage nitrogen and phosphorus removal technologies with good nitrogen and phosphorus removal effects and low energy consumption.

[0003] Moreover, the demand for phosphate fertilizer shows a linear upward trend. As a non-renewable and irreplaceable resource, the sustainable utilization of phosphorus has become the focus of global attention. It can be seen that while solving the eutrophication problem, it is of great significance to convert the removal of phosphorus in sewage into recovery, so as to reuse the lost phosphorus resources.

[0004] The A2N-SBR process is a typical dual-sludge system. A2-SBR and N-SBR separate nitrifying bacteria and phosphorus-accumulating bacteria, and the reaction conditions can be controlled so that they are in suitable growth environments respectively, achieving nitrogen and phosphorus removal in different reaction systems. Using the denitrifying phosphorus removal technology, the phosphorus removal effect is good. However, the traditional A2N-SBR process is limited by SVI and the volume exchange ratio. The influent ammonia nitrogen in the A2-SBR process will be trapped in the sludge and enter the anoxic zone, resulting in a high ammonia nitrogen content in the effluent.

[0005] Anaerobic ammonium oxidation (Anammox) is an autotrophic nitrogen removal technology that saves carbon sources, does not require aeration, and has a low sludge yield. It has a high nitrogen removal efficiency and can be used for advanced sewage treatment. It means that under anoxic conditions, anaerobic ammonium oxidizing bacteria use nitrite nitrogen (NO2 - -N) as an electron acceptor to directly convert ammonia nitrogen (NH4 + -N) into nitrogen gas and produce a small amount of nitrate nitrogen. The stable supply of the substrate NO2 - -N and the retention problem of anaerobic ammonium oxidizing bacteria are the key to the practical application of the Anammox process. Shortcut nitrification (Partial Nitrification) can convert NH4 + -N in domestic sewage into NO2 - -N, providing the substrate for Anammox and without the need for a carbon source.

[0006] The biological induced crystallization technology can induce the reaction between phosphate and calcium ions in water through biological reactions that lead to a local increase in pH and utilize the catalytic effect of biological aggregates at nucleation sites, causing local saturation of minerals to form precipitates. This technology can be used to recover phosphorus from wastewater. The anaerobic ammonium oxidation process can lead to an increase in the system pH value, creating conditions for the crystallization of calcium ions and phosphate in water into hydroxyapatite, inducing the formed HAP to combine with Anammox microorganisms, and promoting the attachment and self-immobilization of microorganisms on the particle surface. Therefore, the anaerobic ammonium oxidation coupled with biological induced crystallization technology can provide an attachment carrier for Anammox while recovering phosphorus in the form of hydroxyapatite, which is beneficial to the enrichment growth of Anammox bacteria. Summary of the Invention

[0007] The object of the present invention is to propose a device and method for synchronous nitrogen and phosphorus recovery from domestic sewage based on the short-cut nitrification-anaerobic ammonium oxidation enhanced A2N process. Aiming at the problem of high ammonia nitrogen in the effluent of the A2N-SBR process, the anaerobic ammonium oxidation function is introduced into the A2-SBR. Short-cut nitrification biofilm is added to the N-SBR to provide substrates for anaerobic ammonium oxidation in the anoxic section of the A2-SBR. Anaerobic ammonium oxidation sludge is added to the A2-SBR, and the supernatant of sludge fermentation is regularly added for sufficient phosphorus release. Calcium ions are added in the anoxic stage to promote the formation of calcium phosphate crystals. The calcium phosphate crystals mainly composed of hydroxyapatite serve as crystal nuclei and are coupled with anaerobic ammonium oxidation biomass to quickly form granular sludge, effectively enriching and retaining anaerobic ammonium oxidation bacteria. At the same time, the combination of denitrifying phosphorus removal and biological induced crystallization phosphorus recovery can achieve the removal of phosphorus in sewage, recovering phosphorus resources while achieving deep nitrogen and phosphorus removal from domestic sewage.

[0008] A device for synchronous nitrogen and phosphorus recovery from domestic sewage based on the short-cut nitrification-anaerobic ammonium oxidation enhanced A2N process, the device adopted includes: two SBR reactors, an A2-SBR reactor (4) and an N-SBR reactor (7). As Figure 1As shown in the figure, the influent peristaltic pump Ⅰ (2) pumps domestic sewage from the influent water tank (1) into the A2-SBR reactor (4), and a stirrer (4.1) is set to stir to mix the activated sludge inside the reactor; after the anaerobic stage ends, the sludge settles, and the supernatant enters the N-SBR reactor (7) through the peristaltic pump Ⅱ (5) for shortcut nitrification reaction. The effluent from the previous cycle of shortcut nitrification in the intermediate water tank (8) flows back to the A2-SBR reactor (4) through the peristaltic pump (9) for anoxic anaerobic ammonium oxidation denitrifying phosphorus removal, and a stirrer (4.1) is set to stir; an aeration head (7.6) is arranged inside the N-SBR reactor (7), connected to an aeration pump (7.4), and the aeration volume is controlled by a rotameter (7.5). After the shortcut nitrification ends, the supernatant is discharged to the intermediate tank (8); every 10 - 15 days, the sludge fermentation supernatant (11) is pumped into the A2-SBR reactor through the influent peristaltic pump Ⅲ (12) to provide sufficient organic matter for the anaerobic stage. In this cycle, the CaCl2 solution in the chemical dosing tank (13) is pumped into the anoxic stage through the peristaltic pump (14). Along with the progress of the anaerobic ammonium oxidation reaction, it promotes the formation of hydroxyapatite; after one cycle of reaction ends and after precipitation, the effluent enters the effluent water tank (10) through the drain valve (4.3). The side wall of the A2-SBR reactor (4) is provided with a reflux supernatant influent valve (4.2), a drain valve (4.3), and a sludge discharge valve (4.4); the pH probe (3.1) and the DO probe (3.2) are connected to the WTW mainframe (3) through data lines, which can reflect the sludge properties inside the reactor; the side wall of the N-SBR reactor (7) is provided with a drain valve (7.2) and a sludge discharge valve (7.3); the pH probe (6.1) and the DO probe (6.2) are connected to the WTW mainframe (6) through data lines to monitor the pH value and dissolved oxygen in the reactor.

[0009] A method for realizing synchronous nitrogen and phosphorus recovery from domestic sewage based on a shortcut nitrification - anaerobic ammonium oxidation enhanced A2N process, characterized by comprising the following steps:

[0010] (1) Start the shortcut nitrification biofilm reactor: inoculate shortcut nitrification sludge, control the sludge concentration at 2800 - 3000 mg / L, add polyethylene biofillers for biofilm formation, with a filling ratio of 20%; the shortcut nitrification SBR reactor operates four cycles per day, including 10 min of influent water, 180 min of aerobic aeration, 40 min of sedimentation, 10 min of drainage, and 2 h of idling, with a drainage ratio of 50%, control the dissolved oxygen at the end of aerobic stage to be 0.5 - 1 mg / L, and the remaining ammonia nitrogen to be 8 - 10 mg / L; regularly take out the biofilm fillers for batch tests. Add the fillers in the process of biofilm formation to a 500 ml small test bottle, with a filling ratio of 20%, add ammonia nitrogen at a concentration of 28 - 30 mg / L, conduct the small test for 2 h, take 10 ml of the mud - water mixture every 15 min, filter and then measure the ammonia nitrogen concentration. When the ammonia nitrogen degradation rate in the biofilm ≥ 10 mg N / (gVSS×h), it is considered that the shortcut nitrification biofilm system is successfully started. Drain all the flocs to form a pure biofilm shortcut nitrification system;

[0011] (2) Start - up of the denitrifying phosphorus removal system using NO x - -N as the electron acceptor: Inoculate biological phosphorus - removing sludge in the SBR reactor, control the sludge concentration at 2500 mg / L; In the first stage, enrich the polyphosphate - accumulating organisms (PAOs) using NO3 - -N as the electron acceptor. The reactor operates in the anaerobic / anoxic mode, with three cycles per day, each cycle being 8 h, including 10 min of influent water, 170 min of anaerobic stirring, 240 min of anoxic stirring, 30 min of sedimentation, 10 min of drainage, and 20 min of idling. The influent water is the prepared water, control the influent COD at 60 - 80 mg / L, and the PO4 3- -P concentration at 5 - 7 mg / L. Add NO3 - -N before the anoxic stage to make the NO3 - -N in the reactor 20 - 30 mg / L. Screen the polyphosphate - accumulating organisms using NO3 - -N as the electron acceptor. When the removal rate of PO4 3- -P ≥ 80%, it is considered that the polyphosphate - accumulating organisms using NO3 - -N as the electron acceptor become the dominant bacteria, and the next stage can begin; In the second stage, enrich the polyphosphate - accumulating organisms using NO x - -N as the electron acceptor. Continue to operate in the denitrifying phosphorus removal system using NO3 - -N as the electron acceptor, only change the ratio of NO3 x - -N and NO2 - -N in the NO - -N in the influent of the anoxic stage. Gradually reduce the addition of NO3 - -N in the anoxic stage, and at the same time increase the addition of NO2 -- The dosage of -N is such that the NO in the reactor x - -N is 20 - 30 mg / L until NO3 - -N:NO2 - -N is 1:1 to enrich polyphosphate-accumulating organisms using NO2 - -N and NO3 - -N as the electron acceptor. Similarly, when the removal rate of PO4 3- -P ≥ 80%, it is considered that the denitrifying phosphorus removal system using NO x - -N as the electron acceptor is successfully started. When the removal rate of PO4 3- -P ≥ 80% is maintained for 30 d, it is considered that the reactor operates stably;

[0012] (3) Start-up of the A2N process based on the short-cut nitrification biofilm system and the anaerobic ammonium oxidation denitrifying phosphorus removal system: Anaerobic ammonium oxidation sludge is added to the denitrifying phosphorus removal system using NO x - -N as the electron acceptor to make the sludge concentration of the anaerobic ammonium oxidation denitrifying phosphorus removal system 3800 - 4000 mg / L. Connect the anaerobic ammonium oxidation denitrifying phosphorus removal reactor (A2-SBR) and the short-cut nitrification biofilm reactor (N-SBR) to form an A2N process for treating domestic sewage; The operation mode of A2-SBR is anaerobic / anoxic, running three cycles per day, including 10 min of influent, 140 min of anaerobic stirring, 30 min of sedimentation, 10 min of supernatant drainage and then entering N-SBR for short-cut nitrification. The short-cut nitrification effluent from the previous cycle in the intermediate water tank is pumped back to A2-SBR by the supernatant reflux pump for 10 min, followed by 230 min of anoxic stirring, 20 min of sedimentation, 10 min of drainage, and 20 min of idling; N-SBR runs three cycles per day, including 10 min of influent, 180 - 300 min of aerobic aeration, controlling the dissolved oxygen at the end of aerobic stage to be 0.5 - 1 mg / L and the remaining ammonia nitrogen to be 5 - 7 mg / L. The effluent from the previous cycle is discharged into the intermediate water tank as the influent for the anoxic section of the next cycle of A2-SBR. The drainage ratios of both A2-SBR and N-SBR are set to 70%. Monitor the nitrogen loss every day. When the total nitrogen in the effluent < 10 mg / L and is maintained for more than 15 d, it is considered that the A2N system based on short-cut - anaerobic ammonium oxidation denitrifying phosphorus removal is successfully started; When maintained for 30 - 40 d, it is considered that the system is stable;

[0013] (4) Anaerobic ammonium oxidation coupled with bio-induced crystallization technology realizes sludge granulation and phosphorus recovery: During the long-term operation of the reactor, three cycles are run every day. A2-SBR includes 10 minutes of influent water, 140 minutes of anaerobic stirring, 30 minutes of sedimentation, 10 minutes of supernatant drainage, 10 minutes of supernatant reflux, 230 minutes of anoxic stirring, 20 minutes of sedimentation, 10 minutes of drainage, and 20 minutes of idling; N-SBR includes 10 minutes of influent water, 180 - 300 minutes of aerobic aeration, controlling the dissolved oxygen at the end of aerobic stage to be 0.5 - 1 mg / L, and the remaining ammonia nitrogen to be 5 - 7 mg / L. The effluent of the previous cycle is discharged into the intermediate water tank as the influent water for the anoxic section of the next cycle of A2-SBR; Adequate phosphorus release is carried out every 10 - 15 days. The supernatant of sludge fermentation is added to the domestic sewage to make the influent COD reach 450 - 550 mg / L. After 140 minutes of anaerobic stirring, sedimentation is carried out for 30 minutes. Then, the phosphorus-rich supernatant containing ammonia nitrogen is discharged into N-SBR through a peristaltic pump for short-cut nitrification reaction. The short-cut nitrification effluent pump of the previous cycle is pumped into A2-SBR, and the stirrer is turned on. At the same time, the CaCl2 solution enters A2-SBR through a dosing pump. The mass ratio of Ca to P is 3.0, and hydroxyapatite crystals can be formed as crystal nuclei. Anaerobic ammonium oxidation sludge forms granular sludge with hydroxyapatite as crystal nuclei, which can be used for subsequent phosphorus recovery; After 230 minutes of anoxic stirring and 20 minutes of sedimentation, drainage is carried out.

[0014] The present invention has the following advantages:

[0015] Adopting a dual-sludge system, the sludge ages of polyphosphate-accumulating organisms and nitrifying bacteria are separated, improving the nitrogen removal efficiency. Denitrifying phosphorus removal "utilizes one carbon for two purposes", and nitrogen and phosphorus removal can be achieved using domestic sewage as the carbon source;

[0016] N-SBR adopts a short-cut nitrification biofilm, and anaerobic ammonium oxidation bacteria sludge is added to A2-SBR, solving the problem of high ammonia nitrogen concentration in the effluent of the traditional A2N process, saving energy and carbon sources;

[0017] Sludge fermentation supernatant is regularly added to the influent of A2-SBR for adequate phosphorus release, and CaCl2 is added in the anoxic section to form hydroxyapatite, which is beneficial to the attachment and growth of anaerobic ammonium oxidation bacteria, realizing the effective interception of anaerobic ammonium oxidation bacteria. At the same time, phosphorus recovery can be achieved through sludge discharge. Description of the Drawings

[0018] Figure 1 It is a structural schematic diagram of a device for realizing synchronous nitrogen and phosphorus removal and phosphorus recovery from domestic sewage based on a short-cut nitrification-anaerobic ammonium oxidation enhanced A2N process;

[0019] Figure 2 It is an operating cycle condition diagram of a short-cut nitrification-anaerobic ammonium oxidation enhanced A2N process;

[0020] Figure 1 In the figure: 1 - domestic sewage water tank, 2 - feed pump I, 3 - WTW main unit, 3.1 - pH probe, 3.2 - dissolved oxygen probe, 4 - A2-SBR, 4.1 - agitator, 4.2 - return supernatant water inlet valve, 4.3 - drain valve, 4.4 - sludge discharge valve, 5 - feed pump II, 6 - WTW main unit, 6.1 - pH probe, 6.2 - dissolved oxygen probe, 7 - N-SBR, 7.1 - agitator, 7.2 - drain valve, 7.3 - sludge discharge valve, 7.4 - aeration pump, 7.5 - rotameter, 7.6 - aeration head, 8 - intermediate water tank, 9 - supernatant return pump, 10 - effluent water tank, 11 - sludge fermentation supernatant water tank, 12 - feed pump III, 13 - chemical dosing tank, 14 - chemical dosing pump. Specific implementation mode

[0021] The present invention will be further described below in conjunction with the attached drawings and specific examples. As Figure 1 shown, a device for realizing synchronous nitrogen removal and phosphorus recovery from domestic sewage based on the short-cut nitrification-anaerobic ammonia oxidation enhanced A2N process, characterized in that it includes a domestic sewage water tank (1), a sludge fermentation supernatant water tank (11), a chemical dosing tank (13), an intermediate water tank (8) and an effluent water tank (10) are respectively connected to the A2-SBR through a feed pump I (2), a feed pump III (12), a chemical dosing pump, a supernatant return pump (9) and a drain valve (4.3); the N-SBR is connected to the A2-SBR and the intermediate water tank respectively through a feed pump II (5) and a drain valve (7.2).

[0022] The specific operation and steps are as follows:

[0023] (1) Start the short-cut nitrification biofilm reactor: inoculate short-cut nitrification sludge in the N-SBR (7), control the sludge concentration at 2800 - 3000 mg / L, add polyethylene biofillers for film hanging, and the filling ratio is 20%; the short-cut nitrification SBR reactor operates four cycles per day, including 10 minutes of water inlet, 180 minutes of aerobic aeration, 40 minutes of sedimentation, and 10 minutes of drainage, and the drainage ratio is 50%. Control the dissolved oxygen at the end of aerobic aeration to be 0.5 - 1 mg / L and the remaining ammonia nitrogen to be 8 - 10 mg / L through the rotameter (7.5), and carry out sludge discharge through the sludge discharge valve (4.4), and control the sludge age at 15 days; regularly take out the biofilm fillers for batch tests. Add the fillers being hung with film in a 500 ml small test bottle, with a filling ratio of 20%, and add ammonia nitrogen concentration of 28 - 30 mg / L. The small test is carried out for 2 hours, and 10 ml of the mud-water mixture is taken every 15 minutes. After filtration, measure the ammonia nitrogen concentration. When the ammonia nitrogen degradation rate in the biofilm ≥ 10 mg N / (gVSS×h), it is considered that the short-cut nitrification biofilm system is successfully started, and all the flocs are discharged to form a pure biofilm short-cut nitrification system;

[0024] (2) Using NO x- - Start-up of the denitrifying phosphorus removal system with -N as the electron acceptor: Inoculate biological phosphorus removal sludge into the A2-SBR reactor (4), and control the sludge concentration at 2300 - 2500 mg / L; In the first stage, enrich the polyphosphate-accumulating organisms (PAOs) with NO3 - - -N as the electron acceptor. The reactor operates in the anaerobic / anoxic mode, with three cycles per day, each cycle lasting 8 h. The influent is the prepared water, with the COD controlled at 60 - 80 mg / L and the PO4 3- - -P concentration at 5 - 7 mg / L; The prepared water enters the A2-SBR (4), and the stirrer (4.1) is turned on. After anaerobic stirring for 170 min, the dosing pump (14) pumps the NO3 - - -N from the dosing tank (13) into the A2-SBR (4). Then, anoxic stirring is carried out for 240 min, followed by sedimentation for 30 min. Drainage is performed through the drain valve (4.3), and the sludge age is controlled at 12 - 15 d, with sludge discharged by the sludge discharge valve (4.4); The NO3 - - -N added before anoxia makes the NO3 - - -N in the reactor reach 20 - 30 mg / L, and screen the polyphosphate-accumulating organisms with NO3 - - -N as the electron acceptor. When the removal rate of PO4 3- - -P ≥ 80%, it is considered that the polyphosphate-accumulating organisms with NO3 - - -N as the electron acceptor become the dominant bacteria, and the next stage can begin; In the second stage, enrich the polyphosphate-accumulating organisms with NO x - - -N as the electron acceptor. Continue to operate in the denitrifying phosphorus removal system with NO3 - - -N as the electron acceptor, only changing the proportion of NO x - - -N in the anoxic influent, gradually reducing the NO3 - - -N addition, and at the same time increasing the NO2 - - -N addition amount, so that the NO - - -N in the reactor is 20 - 30 mg / L, until NO3 - - -N:NO2 x - - -N is 1:1, to enrich the polyphosphate-accumulating organisms with NO2 - - -N and NO3 - - -N as the electron acceptor. Similarly, when the removal rate of PO4 - - -N and NO3 - - -N as the electron acceptor. When the removal rate of PO4 3- - -P ≥ 80%, it is considered that the denitrifying phosphorus removal system with NO x - - -N as the electron acceptor is successfully started up. When the removal rate of PO4 3- - -P ≥ 80% is maintained for 30 d, it is considered that the reactor operates stably;

[0025] (3) Start-up of the A2N process based on the short-cut nitrification biofilm system and the anaerobic ammonium oxidation denitrifying phosphorus removal system: Anaerobic ammonium oxidation sludge was added to the denitrifying phosphorus removal A2-SBR (4) with NO x - -N as the electron acceptor, so that the sludge concentration of the anaerobic ammonium oxidation denitrifying phosphorus removal system was 3800-4000 mg / L. The anaerobic ammonium oxidation denitrifying phosphorus removal reactor A2-SBR (4) was connected to the short-cut nitrification biofilm reactor N-SBR (7) to form an A2N process for treating domestic sewage; the operation mode of A2-SBR was anaerobic / anoxic, and it ran three cycles per day. The influent peristaltic pump I (2) pumped domestic sewage from the influent water tank (1) into the A2-SBR reactor (4), and the stirrer (4.1) was turned on for anaerobic stirring for 140 min; after the anaerobic stage ended, the sludge settled for 30 min, and the supernatant passed through the peristaltic pump II (5) into the N-SBR reactor (7) for short-cut nitrification reaction. The short-cut nitrification effluent from the previous cycle in the intermediate water tank (8) was pumped back to A2-SBR (4) by the supernatant reflux pump (9). After anoxic stirring for 230 min, it settled for 20 min, and the effluent was discharged through the drain valve (4.3); N-SBR (7) ran three cycles per day, with aerobic aeration for 180-300 min. The dissolved oxygen at the end of aerobic was controlled at 0.5-1 mg / L by the rotameter (7.5), and the remaining ammonia nitrogen was 5-7 mg / L. The effluent from the previous cycle was discharged into the intermediate water tank (8) as the influent for the anoxic section of A2-SBR (4) in the next cycle. The drainage ratios of A2-SBR and N-SBR were both set at 70%. The nitrogen loss was monitored every day. When the total nitrogen in the effluent < 10 mg / L and it was maintained for more than 15 days, it was considered that the A2N system based on short-cut - anaerobic ammonium oxidation denitrifying phosphorus removal was successfully started; when it was maintained for 30-40 days, it was considered that the system was stable;

[0026] (4) Anaerobic ammonium oxidation coupled with bio-induced crystallization technology realizes sludge granulation and phosphorus recovery: During the long-term operation of the reactor, three cycles are run every day. The A2-SBR includes 10 minutes of influent, 140 minutes of anaerobic stirring, 30 minutes of sedimentation, 10 minutes of supernatant discharge, 10 minutes of supernatant reflux, 230 minutes of anoxic stirring, 20 minutes of sedimentation, 10 minutes of drainage, and 20 minutes of idling; the N-SBR includes 10 minutes of influent, 180 - 300 minutes of aerobic aeration, controlling the dissolved oxygen at the end of aerobic stage to be 0.5 - 1 mg / L, the remaining ammonia nitrogen to be 5 - 7 mg / L, and the effluent of the previous cycle is discharged into the intermediate water tank as the influent of the anoxic stage of the next cycle A2-SBR; Adequate phosphorus release is carried out every 10 - 15 days. The domestic sewage in the domestic sewage tank (1) and the fermentation supernatant in the sludge fermentation supernatant tank (11) enter the A2-SBR (4) through the feed pump Ⅰ (2) and the feed pump Ⅲ (12), so that the mixed influent COD reaches 450 - 550 mg / L. After the stirrer (4.1) stirs anaerobically for 140 minutes, it sediments for 30 minutes. Then, the phosphorus-rich supernatant containing ammonia nitrogen is discharged into the N-SBR through the feed pump Ⅱ (5) for short-term nitrification reaction. The short-term nitrification effluent pump of the previous cycle is pumped into the A2-SBR (4), the stirrer (4.1) is turned on, and at the same time, the CaCl2 solution in the chemical dosing tank (13) enters the A2-SBR through the chemical dosing pump (14). The mass ratio of Ca to P is 3.0 to form hydroxyapatite crystals as crystal nuclei. The anaerobic ammonium oxidation sludge forms granular sludge with hydroxyapatite as crystal nuclei, which can be used for subsequent phosphorus recovery; stir anoxically for 230 minutes and drain after sedimenting for 20 minutes.

Claims

1. A method for synchronously removing nitrogen and recovering phosphorus from domestic sewage based on the enhanced A2N process of shortcut nitrification - anammox. The device used in this method includes two SBR reactors: an anammox denitrifying phosphorus - removing reactor A2 - SBR and a shortcut nitrification biofilm reactor N - SBR, a domestic sewage inlet water tank, an intermediate water tank, an outlet water tank, a supernatant water tank of sludge fermentation, and a chemical dosing tank; The A2 - SBR is equipped with a stirrer, and on its side wall, there are a reflux supernatant inlet valve, a drainage valve, and a sludge discharge valve; a pH probe and a DO probe are connected to a WTW main machine through data lines; the N - SBR is equipped with a stirrer, an aeration head is connected to an aeration pump through a rotameter for aeration, and on its side wall, there are a drainage valve and a sludge discharge valve; a pH probe and a DO probe are connected to a WTW main machine through data lines to monitor the pH value and dissolved oxygen in the reactor; The domestic sewage inlet water tank, the supernatant water tank of sludge fermentation, the chemical dosing tank, the intermediate water tank, and the outlet water tank are respectively connected to the A2 - SBR through a feed pump Ⅰ, a feed pump Ⅲ, a chemical dosing pump, a supernatant reflux pump, and a drainage valve; the N - SBR is connected to the A2 - SBR and the intermediate water tank respectively through a feed pump Ⅱ and a drainage valve; the A2 - SBR and the N - SBR are connected through a feed pump Ⅱ, the intermediate water tank, and the supernatant reflux pump; It is characterized in that The steps are as follows: (1) Start the shortcut nitrification biofilm reactor N - SBR: inoculate shortcut nitrification sludge, control the sludge concentration at 2800 - 3000 mg / L, add polyethylene biological fillers for film formation, and the filling ratio is 20%; the N - SBR operates four cycles per day, including 10 min of water inlet, 180 min of aerobic aeration, 40 min of sedimentation, 10 min of drainage, and 2 h of idling, the drainage ratio is 50%, control the dissolved oxygen at the end of aerobic aeration to be 0.5 - 1 mg / L, and the remaining ammonia nitrogen is 8 - 10 mg / L; regularly take out the biological film fillers for batch tests. Add the fillers being formed into a 500 - ml small test bottle, with a filling ratio of 20%, add ammonia nitrogen at a concentration of 28 - 30 mg / L, conduct the small test for 2 h, take 10 ml of the mud - water mixture every 15 min, filter it and then measure the ammonia nitrogen concentration. When the ammonia nitrogen degradation rate in the biological film ≥ 10 mg N / (gVSS×h), it is considered that the shortcut nitrification biofilm reactor N - SBR is successfully started, and all the flocs are discharged to form a pure biological film shortcut nitrification system; (2) Using NO x - -N as the electron acceptor for denitrifying phosphorus removal in A2-SBR startup: Inoculate biological phosphorus removal sludge in A2-SBR and control the sludge concentration at 2500 mg / L; In the first stage, enrich polyphosphate-accumulating organisms (PAOs) using NO3 - -N as the electron acceptor. The reactor operates in the anaerobic / anoxic mode, with three cycles per day, each cycle lasting 8 h, including 10 min of influent feeding, 170 min of anaerobic stirring, 240 min of anoxic stirring, 30 min of sedimentation, 10 min of drainage, and 20 min of idling. The influent is synthetic wastewater, and the influent COD is controlled at 60 - 80 mg / L, and the PO4 3- -P concentration is controlled at 5 - 7 mg / L. Add NO3 - -N before the anoxic stage to make the NO3 - -N concentration in the reactor 20 - 30 mg / L. Screen PAOs using NO3 - -N as the electron acceptor. When the removal rate of PO4 3- -P ≥ 80%, it is considered that PAOs using NO3 - -N as the electron acceptor become the dominant bacteria, and the next stage can begin; In the second stage, enrich PAOs using NO x - -N as the electron acceptor. Continue to operate in the A2-SBR using NO3 - -N as the electron acceptor, only changing the influent NO x - -N in the anoxic stage. Gradually reduce the addition of NO3 - -N and increase the addition of NO2 - -N to make the NO - -N concentration in the reactor 20 - 30 mg / L until the ratio of NO3 - -N:NO2 x - -N is 1:1 to enrich PAOs using NO2 - -N and NO3 - -N as the electron acceptor. Similarly, when the removal rate of PO4 - -N and NO3 - -N as the electron acceptor. When the removal rate of PO4 3- -P ≥ 80%, it is considered that the startup of A2-SBR for denitrifying phosphorus removal using NO x - -N as the electron acceptor is successful. When the removal rate of PO4 3- -P ≥ 80% is maintained for 30 d, it is considered that the reactor operates stably; (3) Start-up and operation of the A2N system based on the short-cut nitrification biofilm reactor N-SBR and the anaerobic ammonium oxidation and denitrifying phosphorus removal reactor A2-SBR: Anaerobic ammonium oxidation sludge was added to the A2-SBR for denitrifying phosphorus removal with NO x - -N as the electron acceptor, so that the sludge concentration of A2-SBR was 3800-4000 mg / L. A2-SBR was connected to N-SBR to form the A2N process for treating domestic sewage. The operation mode of A2-SBR was anaerobic / anoxic, running three cycles per day, including 10 min of influent, 140 min of anaerobic stirring, 30 min of sedimentation, and 10 min of supernatant discharge into N-SBR for short-cut nitrification. The short-cut nitrification effluent from the previous cycle in the intermediate water tank was pumped back to A2-SBR by the supernatant reflux pump for 10 min, followed by 230 min of anoxic stirring, 20 min of sedimentation, 10 min of drainage, and 20 min of idling. N-SBR ran three cycles per day, including 10 min of influent, 180-300 min of aerobic aeration, controlling the dissolved oxygen at the end of aerobic stage to be 0.5-1 mg / L and the remaining ammonia nitrogen to be 5-7 mg / L. The effluent from the previous cycle was discharged into the intermediate water tank as the influent for the anoxic stage of the next cycle of A2-SBR. The drainage ratios of A2-SBR and N-SBR were both set at 70%. Nitrogen loss was monitored daily. When the total nitrogen in the effluent < 10 mg / L and was maintained for more than 15 days, it was considered that the A2N system based on the short-cut nitrification biofilm reactor N-SBR and the anaerobic ammonium oxidation and denitrifying phosphorus removal reactor A2-SBR was successfully started up. Maintaining for 30-40 days was considered that the system was stable; (4) Anaerobic ammonium oxidation coupled with bio-induced crystallization technology for sludge granulation and phosphorus recovery: During the long-term operation of A2N-SBR, three cycles are run every day. A2-SBR includes 10 minutes of influent water, 140 minutes of anaerobic stirring, 30 minutes of sedimentation, 10 minutes of supernatant discharge, 10 minutes of supernatant reflux, 230 minutes of anoxic stirring, 20 minutes of sedimentation, 10 minutes of drainage, and 20 minutes of idling; N-SBR includes 10 minutes of influent water, 180 - 300 minutes of aerobic aeration, controlling the dissolved oxygen at the end of aerobic stage to be 0.5 - 1 mg / L, the remaining ammonia nitrogen to be 5 - 7 mg / L, and the effluent from the previous cycle is discharged into the intermediate water tank as the influent water for the anoxic stage of the next cycle of A2-SBR; Adequate phosphorus release is carried out every 10 - 15 days. Sludge fermentation supernatant is added to domestic sewage to make the influent COD reach 450 - 550 mg / L. After 140 minutes of anaerobic stirring, sedimentation is carried out for 30 minutes. Then, the phosphorus-rich supernatant containing ammonia nitrogen is pumped into N-SBR through feed pump II for short-term nitrification reaction. The short-term nitrification effluent from the previous cycle is pumped into A2-SBR, and the stirrer is started. At the same time, the CaCl2 solution enters A2-SBR through the dosing pump, with the mass ratio of Ca to P being 3.0, forming hydroxyapatite crystals as crystal nuclei. Anaerobic ammonium oxidation sludge forms granular sludge with hydroxyapatite as crystal nuclei, which can be used for subsequent phosphorus recovery; After 230 minutes of anoxic stirring and 20 minutes of sedimentation, drainage is carried out.

Images