Advanced nitrogen removal and phosphorus resource recovery method for sidestream anaerobic ammonia oxidation effluent

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a lateral flow anaerobic ammonia oxidation effluent deep nitrogen and phosphorus resource recycling method which comprises the following steps: mixing treated anaerobic sludge digestion liquid and untreated anaerobic sludge digestion liquid in an intermediate water tank to form mixed inlet water; adding a magnesium source into the mixed inlet water in the middle water tank to form a middle mixed solution; transferring the intermediate mixed solution into a short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor, adjusting the pH value of the intermediate mixed solution, and adding a carbon source into the pH-adjusted intermediate mixed solution to form a reaction solution; and carrying out solid-liquid separation on a product obtained after the reaction of the reaction liquid, and discharging the separated liquid or systematically recycling the separated liquid. According to the invention, deep nitrogen removal and phosphorus resource recovery under the condition of low carbon source can be realized, and a new way is provided for subsequent deep treatment of a short-cut nitrification-anaerobic ammonia oxidation process.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular relates to a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation. Background Technology

[0002] Anaerobic ammonia oxidation (ANAO) technology has been widely used in the treatment of high ammonia nitrogen wastewater. Among them, the engineered pathway represented by the short-cut nitrification-ANAO process has become an important means of energy-saving operation of wastewater treatment plants due to its advantages such as no need for external organic carbon sources, low oxygen consumption, and low sludge production. However, in actual operation, whether it is traditional ANAO technology or the more mature short-cut nitrification-ANAO process, the reaction process inevitably produces nitrates (NO3⁻–N), which limits the further reduction of total nitrogen (TN) in the effluent. At the same time, existing ANAO technology or short-cut nitrification-ANAO process only serves as nitrogen conversion and does not involve phosphorus removal and recovery mechanisms. It cannot remove phosphates (PO4³⁻–P) in wastewater, nor can it realize phosphorus resource recovery.

[0003] The digestate produced by anaerobic sludge digestion is characterized by high ammonia nitrogen and low carbon-to-nitrogen ratio. Efficient treatment of this effluent is crucial for reducing ammonia load and enhancing nitrogen removal in urban wastewater treatment plants. Anaerobic sludge digesters typically also contain high concentrations of PO4³⁻-P, making it a critical target for synergistic nitrogen and phosphorus control. In practice, short-cut nitrification-anammox processes are often used as pre-treatment to reduce most of the NH4⁺–N. However, residual NO3⁻-N from the short-cut nitrification-anammox reaction remains difficult to remove, and this process cannot treat phosphates in the system. Therefore, relying solely on short-cut nitrification-anammox processes is insufficient to achieve deep nitrogen removal and simultaneous phosphorus removal.

[0004] To address the challenge of further reducing NO3⁻-N in the effluent of short-cut nitrification-anammox processes, the CANDAN process was proposed. This process directionally reduces NO3⁻-N to NO2⁻-N by coupling short-cut denitrification and anammox, providing substrate for anammox and thus improving total nitrogen removal efficiency. However, the CANDAN reaction remains limited to nitrogen conversion processes and is ineffective in removing and recovering PO4³⁻–P.

[0005] Therefore, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation is needed to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonium oxidation, achieving deep denitrification and phosphorus resource recovery under low carbon source conditions, and providing a new approach for subsequent deep treatment of short-cut nitrification-anaerobic ammonium oxidation processes.

[0007] To achieve the above objectives, the present invention provides the following solution: a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation, comprising the following steps:

[0008] The treated anaerobic sludge digestion liquid is mixed with the untreated anaerobic sludge digestion liquid in an intermediate water tank to form mixed influent.

[0009] A magnesium source is added to the mixed water in the intermediate water tank to form an intermediate mixed solution;

[0010] The intermediate mixture was transferred to a short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor and the pH of the intermediate mixture was adjusted. A carbon source was added to the pH-adjusted intermediate mixture to form a reaction solution.

[0011] The products after the reaction of the reaction solution are subjected to solid-liquid separation, and the separated liquid is discharged or reused in the system.

[0012] According to the present invention, in a side-flow anaerobic ammonia oxidation effluent deep denitrification and phosphorus resource recovery method, the NH4⁺-N / NO3⁻-N molar ratio of the mixed influent in the intermediate water tank is 1.4–1.6.

[0013] According to the present invention, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation is provided, wherein the magnesium source is either magnesium chloride or magnesium sulfate, and the molar ratio of Mg / P is 1.10-1.20.

[0014] According to the present invention, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonium oxidation is proposed, wherein the sludge concentration of the reaction liquid in the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor is 10.0 g / L-15.0 g / L.

[0015] According to the present invention, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonium oxidation is proposed, wherein the pH value of the reaction liquid in the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor is 8.5-9.0.

[0016] The present invention provides a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation, wherein the carbon source is sodium acetate.

[0017] According to the present invention, in a side-flow anaerobic ammonia oxidation effluent deep denitrification and phosphorus resource recovery method, the mass concentration ratio of organic matter to nitrate nitrogen in the mixed influent in the intermediate water tank is 1.2-1.6.

[0018] According to the present invention, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation is provided, wherein the NO3⁻-N concentration in the separated liquid is less than 15.0 mg / L.

[0019] According to the present invention, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation is provided, wherein the concentration of NH4⁺-N in the separated liquid is less than 25.0 mg / L and the concentration of NO2⁻-N is less than 15.0 mg / L.

[0020] According to the present invention, a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation is provided, wherein the concentration of dissolved phosphorus in the separated liquid is less than 25.0 mg / L.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] 1. The short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor constructed in this invention efficiently couples short-cut denitrification, anaerobic ammonium oxidation and struvite crystallization. Compared with the traditional two-stage CANDAN system, it further simplifies the structure setup and process configuration, and achieves a total nitrogen removal rate of >90% while simultaneously achieving a phosphorus removal rate of >70%, effectively solving the technical bottleneck of the CANDAN process that cannot simultaneously achieve phosphorus removal and phosphorus recovery.

[0023] 2. This invention fully utilizes the combined influent characteristics of the end effluent and untreated digestate in the short-cut nitrification-anaerobic ammonium oxidation process system. By precisely controlling the carbon-nitrogen ratio of the influent and adding magnesium source, the nitrogen and phosphorus removal processes are synergistically optimized, thereby improving the resource utilization efficiency of the system.

[0024] 3. This invention can avoid the problems of increased hydraulic retention time, high energy consumption and complex control that are common in multi-stage series systems, and provides an efficient solution for municipal or industrial low-carbon wastewater to achieve simultaneous nitrogen and phosphorus removal and resource recovery.

[0025] 4. This invention introduces the struvite crystallization process as a key means for simultaneous phosphorus removal and resource utilization. It utilizes the local alkaline conditions generated by the anaerobic ammonia oxidation reaction to promote the crystallization and precipitation of phosphorus, ammonium and magnesium ions, effectively mitigating the potential inhibition of inorganic salt accumulation on the activity of anaerobic ammonia oxidizing bacteria, while ensuring the stable operation of the reaction system.

[0026] 5. The struvite crystal products formed by this invention can be enriched and recovered periodically through granular sludge discharge, realizing the synchronous transfer and resource utilization of phosphorus from the sewage treatment process, which has good economic and environmental benefits and is in line with the development direction of sewage resource treatment. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0028] Figure 1 This is a process flow diagram of the present invention.

[0029] Figure 2 This is a schematic diagram of the device of the present invention.

[0030] The system comprises: 1. Sludge anaerobic digester; 2. Short-cut nitrification-anaerobic ammonium oxidation coupled reactor; 3. Intermediate water tank; 4. Magnesium reagent tank; 5. Alkalinity reagent tank; 6. Short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor; 7. Carbon source storage tank; 8. Effluent tank; 9. Phosphorus resource recovery tank; 2-1. First inlet pump; 2-2. Rotor flow meter; 2-3. Air pump; 2-4. Agitator; 3-1. Fifth inlet pump; 3-2. First outlet; 3-3. First outlet pump; 5-1. Second inlet pump; 5-2. Third inlet pump; 6-1. Second outlet; 6-2. Second outlet pump; 7-1. Fourth inlet pump; 8-1. Third outlet pump; 9-1. Sludge pump. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] CANDAN refers to the simultaneous removal of ammonium and nitrate through denitrification-anaerobic ammonium oxidation mediated by nitrite.

[0034] Anaerobic digestion effluent from sludge is typically alkaline and contains high concentrations of NH4⁺-N and PO4³⁻-P. After short-cut nitrification-anaerobic ammonium oxidation treatment, a certain amount of NO3⁻-N and PO4³⁻-P still remain in the effluent. When further introduced into the CANDAN system, the anaerobic ammonium oxidation reaction releases alkalinity, causing the system pH to continue to rise. Under these conditions, if an appropriate amount of magnesium ions (Mg²⁺) is added and the pH is appropriately adjusted, NH4⁺-N, PO4³⁻-P, and Mg²⁺ can be induced to form struvite (MAP) precipitate in the CANDAN reaction system. The precipitation of struvite not only efficiently fixes and recovers phosphates but also synergistically reduces some NH4⁺–N through inorganic precipitation, thereby further enhancing the denitrification performance of CANDAN.

[0035] In summary, coupling the CANDAN process with struvite-induced crystallization in the same reactor, i.e., CANDAN-MAP, and arranging it in the post-treatment unit of short-cut nitrification-anaerobic ammonium oxidation, can achieve deep denitrification and phosphorus resource recovery simultaneously on the basis of preliminary denitrification by short-cut nitrification-anaerobic ammonium oxidation. This provides an innovative, efficient, energy-saving, and engineering-feasible technical approach for the synergistic deep removal of nitrogen and phosphorus from high ammonia nitrogen wastewater.

[0036] Reference Figures 1 to 2 As shown, this invention provides a method for deep denitrification and phosphorus resource recovery of effluent from side-flow anaerobic ammonia oxidation, comprising the following steps:

[0037] The anaerobic sludge digestate treated by the short-cut nitrification-anaerobic ammonium oxidation process was mixed with the untreated anaerobic sludge digestate in a certain proportion and then sent to the intermediate water tank 3 for pretreatment. The NH4⁺-N / NO3⁻-N molar ratio was adjusted to 1.4–1.6 to facilitate subsequent reactions.

[0038] A magnesium source is added to the mixed water in intermediate water tank 3 to form an intermediate mixed solution;

[0039] The intermediate mixture was transferred to the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 and the pH value of the intermediate mixture was adjusted. A carbon source was added to the intermediate mixture after the pH value was adjusted to form a reaction solution.

[0040] The products after the reaction of the reaction solution are subjected to solid-liquid separation, and the separated liquid is discharged or reused in the system.

[0041] The intermediate mixed liquor from intermediate tank 3 is introduced into short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6, with a carbon source added simultaneously. Through short-cut denitrification, NO3⁻-N is reduced to NO2⁻-N, and under anaerobic ammonium oxidation, NO2⁻-N and NH4⁺-N are converted to N2, thus achieving a coupled denitrification and anaerobic ammonium oxidation composite reaction system for deep nitrogen removal. Simultaneously, a magnesium source is added to intermediate tank 3. By controlling the molar ratio of Mg²⁺, NH4⁺, and PO4³⁻ to 1.10-1.20, n(NH4):n(P) ≥ 1.0, and the pH value within the range of 8.5-9.0, struvite crystallization is induced inside or on the surface of the granular sludge, causing dissolved phosphorus to react with Mg²⁺ to form struvite precipitate, achieving simultaneous phosphorus removal and recovery.

[0042] Furthermore, the molar ratio of NH4⁺-N / NO3⁻-N in the mixed water in intermediate water tank 3 is 1.4–1.6.

[0043] Furthermore, the magnesium source is either magnesium chloride or magnesium sulfate, and the Mg / P molar ratio is 1.10-1.20.

[0044] Furthermore, the operating sludge concentration of the reaction liquid in the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 is 10.0 g / L-15.0 g / L.

[0045] Furthermore, the pH value of the reaction solution in the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 is 8.5-9.0.

[0046] Furthermore, the carbon source is sodium acetate.

[0047] Furthermore, the mass concentration ratio of organic matter to nitrate nitrogen in the mixed influent of intermediate water tank 3, C / N, is 1.2-1.6.

[0048] Furthermore, the NO3⁻-N concentration in the separated liquid was less than 15.0 mg / L.

[0049] Furthermore, the concentrations of NH4⁺-N in the separated liquid were below 25.0 mg / L and the concentrations of NO2⁻-N were below 15.0 mg / L.

[0050] Furthermore, the concentration of soluble phosphorus in the separated liquid was less than 25.0 mg / L.

[0051] The removal rate of dissolved phosphorus in the separated liquid can be controlled by one or both of the following methods to make it less than 30%: increase the amount of magnesium source added to intermediate water tank 3 to increase the Mg / P molar ratio; adjust the pH value of short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 to 8.5-9.0 to promote complete struvite precipitation reaction.

[0052] When the NO3⁻-N concentration in the effluent of the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 is greater than 15.0 mg / L, the carbon source dosage should be appropriately increased until the effluent NO3⁻-N concentration is lower than 15.0 mg / L; when the NH4⁺-N concentration is greater than 25 mg / L and the NO2⁻-N concentration is greater than 15 mg / L, the wastewater retention time should be extended or the ratio of organic matter to nitrate nitrogen (C / N) should be adjusted; when the phosphorus recovery rate is lower than 70% or the PO4³⁻ concentration in the effluent is higher than 25.0 mg / L, the magnesium source dosage should be adjusted or the reactor pH should be increased to 8.5-9.0 to promote struvite formation.

[0053] The effluent from the short-cut nitrification-anaerobic ammonia oxidation coupled reactor 2 is mixed with a portion of the untreated anaerobic digestate in a predetermined ratio and introduced into the intermediate water tank 3 for mixing and adjustment, ensuring that the NH4⁺-N / NO3⁻-N molar ratio is within the range of 1.4–1.6. This step is used to regulate the hydraulic load and pollutant concentration to ensure stable subsequent reaction conditions.

[0054] The intermediate mixed liquor is pumped into the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6. By precisely controlling the carbon source addition, short-cut denitrification is promoted, reducing NO3⁻-N to NO2⁻-N, which then synergistically undergoes anaerobic ammonium oxidation with NH4⁺-N to remove nitrogen. High-efficiency nitrogen removal is achieved through reasonable control of the reaction load, hydraulic retention time, and sludge concentration. A magnesium reagent tank 4 is set up to add MgSO4, and the alkaline environment formed during the CANDAN reaction and the pH artificially adjusted to 8.5-9.0 promote the struvite crystallization reaction between soluble phosphorus, magnesium, and ammonium within the system.

[0055] Within the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6, sludge communities of varying particle sizes are formed. MAP crystals are primarily enriched in the larger granular sludge particles and deposited at the bottom of the reactor. Regular sludge discharge and sludge-water separation allow for the recovery of phosphorus-rich granular sludge for subsequent resource utilization, such as fertilizer production.

[0056] The system is equipped with online monitoring devices for pH and key water quality parameters (such as NH4⁺-N, NO2⁻-N, NO3⁻-N and PO4³⁻), which provide real-time feedback to regulate the dosage of carbon and magnesium sources, ensuring that the reaction process is precise and controllable.

[0057] The TN removal rate in the treated end-of-process effluent can reach over 90%, and the TP removal rate exceeds 70%, achieving significant reduction of nitrogen and phosphorus in the side stream and resource recovery of phosphorus.

[0058] This invention also provides a side-flow anaerobic ammonium oxidation effluent deep denitrification and phosphorus resource recovery device, including a sludge anaerobic digester 1, a short-cut nitrification-anaerobic ammonium oxidation coupled reactor 2, an intermediate water tank 3, a magnesium reagent tank 4, an alkalinity reagent tank 5, a short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6, a carbon source storage tank 7, an effluent water tank 8, and a phosphorus resource recovery tank 9. The sludge anaerobic digester 1 is connected to the short-cut nitrification-anaerobic ammonium oxidation coupled reactor 2 via a first inlet pump 2-1. A stirrer 2-4 is installed inside the short-cut nitrification-anaerobic ammonium oxidation coupled reactor 2. An air pump 2-3 is connected to the bottom of the short-cut nitrification-anaerobic ammonium oxidation coupled reactor 2. A rotor flow meter 2-2 is installed between the air pump 2-3 and the short-cut nitrification-anaerobic ammonium oxidation coupled reactor 2. The sludge anaerobic digester 1 is connected to the intermediate water tank 3 via a fifth inlet pump 3-1. A first drain outlet 3- is provided on the short-cut nitrification-anaerobic ammonium oxidation coupled reactor 2. 2. The intermediate water tank 3 is connected to the first drain outlet 3-2. A first drain pump 3-3 is installed between the first drain outlet 3-2 and the intermediate water tank 3. The magnesium reagent tank 4 is connected to the intermediate water tank 3 through the second inlet pump 5-1. The intermediate water tank 3 has a second drain outlet 6-1, which is connected to the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6. A second drain pump 6-2 is installed between the second drain outlet 6-1 and the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6. The alkalinity reagent tank 5 is connected to the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 through the third inlet pump 5-2. The carbon source storage tank 7 is connected to the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 through the fourth inlet pump 7-1. The short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 is connected to the effluent tank 8 through the third drain pump 8-1 and to the phosphorus resource recovery tank 9 through the sludge pump 9-1.

[0059] During operation of the short-cut nitrification-anaerobic ammonia oxidation coupled reactor 2, the sludge concentration was 8.0 g / L-15.0 g / L and the temperature was 30℃±2℃.

[0060] Intermediate tank 3 is used to mix the anaerobic digestion liquid of PN / A treated sludge with the original digestion liquid; alkalinity reagent tank 5 is used to adjust the internal pH of short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6; carbon source storage tank 7 is used to provide carbon source for short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 and maintain a stable carbon-nitrogen ratio inside short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6; short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 is a stirred reactor without physical barriers, used to simultaneously carry out short-cut denitrification, anaerobic ammonium oxidation and struvite precipitation reaction, and has a phosphorus-rich granular sludge discharge outlet at the bottom to achieve nitrogen and phosphorus removal.

[0061] The short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 of this invention integrates short-cut denitrification, anaerobic ammonium oxidation, and struvite precipitation processes into a single unit, forming a composite functional unit of "deep nitrogen removal—synergistic phosphorus removal—resource recovery". Utilizing the localized alkaline environment generated by the anaerobic ammonium oxidation reaction and the artificially adjusted pH of the reactor, it achieves efficient removal of NH4⁺-N and NO3⁻-N while simultaneously promoting the in-situ crystallization of residual dissolved phosphorus with NH4⁺-N and soluble magnesium in the raw water within the reactor, forming struvite precipitates coupled with sludge. The phosphorus removal rate reaches over 70%, and the effluent dissolved phosphorus concentration can be stably maintained at 10–25 mg / L.

[0062] Compared to traditional CANDAN or single chemical phosphorus removal processes, this invention achieves a synergistic reaction of nitrogen and phosphorus removal in a granular sludge system, which improves both treatment efficiency and system stability. The formation of struvite not only improves sludge structure and settling properties but also prevents phosphorus resource loss and secondary pollution.

[0063] This invention scientifically combines the effluent from anaerobic sludge digestion liquid treated by the PN / A process with untreated digestion liquid, and achieves simultaneous denitrification and phosphorus removal based on the CANDAN-MAP process. It breaks through the bottlenecks of traditional deep denitrification systems, such as high dependence on carbon sources and low phosphorus removal efficiency, and forms a stable, efficient and resource-based new deep treatment path with broad engineering application prospects.

[0064] Example 1: The wastewater source was a wastewater treatment plant, with NH4⁺-N content of 1564.2 mg / L, PO4³⁻-P content of 126.3 mg / L, and pH value of 8.3. After treatment by the PN / A process, the effluent of this wastewater had an NO3⁻-N concentration of approximately 412.6 mg / L, an NH4⁺-N concentration of approximately 63.2 mg / L, a PO4³⁻-P concentration of approximately 122.4 mg / L, and a pH of 8.1.

[0065] The processing procedure is as follows:

[0066] 1. The anaerobic digester effluent and PN / A process effluent are mixed at a volume ratio of 1:3 to achieve a NH4⁺-N / NO3⁻-N molar ratio of 1.5 in the mixture. This mixture is then pumped into intermediate tank 3, where the NH4⁺-N concentration is 438.5 mg / L and the NO3⁻-N concentration is 309.5 mg / L. Intermediate tank 3 is equipped with an automatic stirring system and an online pH monitoring system to adjust the proportion of the composite wastewater and stabilize the influent quality, ensuring uniform and stable water quality entering the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6.

[0067] 2. The mixed liquor enters the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6. The reactor is inoculated with highly active short-cut denitrifying bacteria and anaerobic ammonium oxidation coupled granular sludge, and the reaction temperature is maintained at 30±2℃. Simultaneously, reagents from the carbon source storage tank are added to the system, and the reactor pH is adjusted to maintain the molar ratio of Mg²⁺ to PO₄³⁻-P within the range of 1.15±0.05. The reactor is equipped with online pH and water quality monitoring devices to achieve precise pH control at 8.7±0.2, which is beneficial for struvite formation. The hydraulic retention time is controlled at 3 hours, and the granular sludge concentration is maintained at approximately 10.2 g / L.

[0068] 3. During operation, the NO3⁻-N concentration in the effluent of the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 decreased to below 14.6 mg / L, NH4⁺-N decreased to 24.2 mg / L, NO2⁻-N remained within the suitable range for anaerobic ammonium oxidation, and PO4³⁻-P concentration decreased to 22.9 mg / L. The total nitrogen removal rate reached over 94.8%, and the phosphorus removal rate reached 81.3%. Compared with the CANDAN system without MAP precipitation, the phosphorus removal rate increased by more than 50 percentage points, and the system's operational stability was significantly enhanced. Struvite crystals formed in the reactor were deposited on the surface of the granular sludge and at the bottom of the reactor. After solid-liquid separation and crystallization, XRD analysis confirmed that the main product was MgNH4PO4·6H2O crystals, verifying the occurrence of the MAP crystallization reaction and effectively realizing the resource recovery of phosphorus.

[0069] 4. In the short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor 6, the granular sludge rich in struvite crystals at the bottom is periodically discharged for concentration and solid-liquid separation. The crystals can be recovered and used as agricultural fertilizer. The remaining mixed liquid enters the solid-liquid separation device for treatment. After testing, the effluent meets the national Class A discharge standard and can be directly discharged or used for ecological greening.

[0070] Example 2: The wastewater source is a livestock and poultry farm. The water quality indicators of the mixture of anaerobic sludge digester and anaerobic sludge digestate treated by the PN / A process before mixing are as follows:

[0071] The anaerobic digestion solution contained approximately 520.5 mg / L of NH4⁺-N, less than 5 mg / L of NO3⁻-N, approximately 102.6 mg / L of PO4³⁻-P, and a pH of approximately 8.2.

[0072] The effluent from the anaerobic sludge digester treated by the PN / A process had NO3⁻-N concentrations of approximately 132.3 mg / L, NH4⁺-N concentrations of approximately 42.3 mg / L, PO4³⁻-P concentrations of approximately 98.4 mg / L, and a pH of 7.9.

[0073] The processing procedure is as follows:

[0074] 1. The anaerobic digestion liquid and the effluent from the anaerobic sludge digester treated by the PN / A process are mixed at an NH4⁺-N / NO3⁻-N molar ratio within the range of 1.4–1.6 and then sent to the intermediate water tank 3, i.e., a volume ratio of 1:2.4-2.7. The water tank is equipped with an automatic stirring and online pH monitoring system to adjust the ratio of the mixed wastewater and stabilize the influent water quality, ensuring that the water quality entering the short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor 6 is uniform and stable.

[0075] 2. The mixed liquor enters the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6. The reactor is inoculated with highly active short-cut denitrifying bacteria and anaerobic ammonium oxidation coupled granular sludge, and the reaction temperature is maintained at 30±2℃. Simultaneously, reagents from the carbon source storage tank are added to the system and the reactor pH is adjusted to promote struvite crystallization. The molar ratio of Mg²⁺ to dissolved phosphorus is controlled within the range of 1.10–1.20, the pH value is controlled at 8.7±0.2, the hydraulic retention time is controlled at 3.5 hours, and the granular sludge concentration is maintained at approximately 10.5 g / L.

[0076] 3. During operation, the NO3⁻-N concentration in the effluent of the short-cut denitrification-anaerobic ammonium oxidation coupled struvite reactor 6 decreased to below 14.7 mg / L, NH4⁺-N decreased to 12.1 mg / L, NO2⁻-N remained within the suitable range for anaerobic ammonium oxidation, and the soluble phosphorus concentration decreased to 21.1 mg / L. The total nitrogen removal rate reached 90.0%, and the phosphorus removal rate exceeded 75.0%, significantly enhancing the system's operational stability. The struvite crystals formed within the reactor deposited on the surface of the granular sludge and at the bottom of the reactor. After solid-liquid separation and crystallization, phosphorus was effectively recovered as a resource.

[0077] 4. The granular sludge rich in struvite crystals at the bottom of the short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor 6 is periodically discharged to the phosphorus resource recovery tank for concentration and solid-liquid separation. The recovered crystals can be used for agricultural fertilizer.

[0078] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0079] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for side-stream anaerobic ammonia oxidation effluent advanced denitrification and phosphorus resource recovery, characterized in that, The method comprises the following steps: mixing the treated anaerobic sludge digestion liquid with untreated anaerobic sludge digestion liquid in an intermediate water tank (3) to form mixed influent; adding a magnesium source to the mixed influent in the intermediate water tank (3) to form intermediate mixed liquid; transferring the intermediate mixed liquid to a short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor (6) and adjusting the pH value of the intermediate mixed liquid, adding a carbon source to the intermediate mixed liquid after the pH value is adjusted to form reaction liquid; performing solid-liquid separation on the product after the reaction liquid is reacted, and discharging or recycling the separated liquid.

2. The method according to claim 1, wherein, The molar ratio of NH4⁺-N / NO3⁻-N of the mixed influent in the intermediate water tank (3) is 1.4-1.

6.

3. The method according to claim 1, wherein, The magnesium source is one of magnesium chloride or magnesium sulfate, and the molar ratio of Mg / P is 1.10-1.

20.

4. The method according to claim 1, wherein, The operation sludge concentration of the reaction liquid in the short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor (6) is 10.0 g / L-15.0 g / L.

5. The method according to claim 1, wherein, The pH value of the reaction liquid in the short-cut denitrification-anaerobic ammonia oxidation coupled struvite reactor (6) is 8.5-9.

0.

6. The method according to claim 1, wherein, The carbon source is sodium acetate.

7. The method according to claim 1, wherein, The mass concentration ratio of organic matter to nitrate nitrogen (C / N) of the mixed influent in the intermediate water tank (3) is 1.2-1.

6.

8. The method according to claim 1, wherein, The concentration of NO3⁻-N in the separated liquid is lower than 15.0 mg / L.

9. The method according to claim 1, wherein, The concentration of NH4⁺-N in the separated liquid is lower than 25.0 mg / L and the concentration of NO2⁻-N is lower than 15.0 mg / L.

10. The method according to claim 1, wherein, The concentration of dissolved phosphorus in the separated liquid is lower than 25.0 mg / L.

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