Method for simultaneous enhanced phosphorus and nitrogen removal by anaerobic-aerobic granular sludge reactor

Abstract

The application discloses a method for simultaneously strengthening phosphorus removal and nitrogen removal by using an anaerobic-aerobic granular sludge reactor, and specifically comprises the following steps: adopting an anaerobic-aerobic operation mode to form aerobic granular sludge with biological phosphorus removal capacity in a sequencing batch reactor; sequentially performing an anaerobic water feeding stage, an aerobic stage, a sedimentation stage and a water discharge stage in each operation cycle; wherein the multi-point layered water feeding mode is adopted in the anaerobic water feeding stage; the wastewater to be treated is fed from the bottom and the middle of the granular sludge layer, wherein the water feeding amount at the bottom of the granular sludge layer accounts for 70-90% of the total water feeding amount; the intermittent aeration mode is adopted in the aerobic stage, each intermittent aeration cycle comprises an aeration period and a non-aeration period, and the time ratio of the single aeration period to the single non-aeration period is 2-3:1. By operation regulation, a microenvironment conducive to denitrification and phosphorus precipitation is constructed inside the aerobic granular sludge, carbon source competition can be effectively alleviated, phosphorus removal pathways are expanded, and the synergistic strengthening of the nitrogen removal and phosphorus removal processes is promoted.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to aerobic granular sludge reactors, specifically to a method for simultaneously enhancing phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor. Background Technology

[0002] Aerobic granular sludge (AGS) technology is an advanced biological wastewater treatment process based on self-immobilized microbial aggregates. Compared with the traditional activated sludge process, aerobic granular sludge technology has advantages such as excellent settling performance, high biomass holding capacity, and the ability to create aerobic and anoxic microenvironments within the granules. It can simultaneously achieve nitrification, denitrification, and biological phosphorus removal, making it one of the most promising biological wastewater treatment technologies currently available.

[0003] However, in aerobic granular sludge systems, the anaerobic phosphorus release process of polyphosphate-accumulating bacteria consumes readily degradable organic carbon sources, while denitrification also relies on a large supply of carbon sources. When the influent carbon source is limited, carbon source competition arises between denitrification and biological phosphorus removal, making it difficult for the system to simultaneously achieve efficient nitrogen and phosphorus removal. Furthermore, existing aerobic granular sludge systems mainly rely on the enhanced biological phosphorus removal by polyphosphate-accumulating bacteria, but this enhanced biological phosphorus removal is easily affected by factors such as influent water quality, pH, temperature, and dissolved oxygen, making the phosphorus removal effect extremely unstable.

[0004] In recent years, researchers have observed biologically induced calcium and phosphorus precipitation in aerobic granular sludge. These inorganic precipitates mainly exist in the form of calcium and phosphorus in granular sludge, which can improve particle density and settling performance. However, in existing technologies, the formation of calcium and phosphorus precipitation is mostly sporadic and uncontrollable, making it difficult to utilize as a primary phosphorus removal pathway.

[0005] Therefore, developing a method that can effectively alleviate carbon source competition, expand phosphorus removal pathways, and simultaneously enhance phosphorus and nitrogen removal is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for simultaneously enhancing phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor. Through operational regulation, the present invention constructs a microenvironment conducive to denitrification and phosphorus precipitation within the aerobic granular sludge, effectively alleviating carbon source competition, expanding phosphorus removal pathways, and promoting the synergistic enhancement of nitrogen and phosphorus removal processes.

[0007] The technical solution of this invention is implemented as follows:

[0008] A method for simultaneously enhancing phosphorus and nitrogen removal using an anaerobic-aerobic granular sludge reactor, specifically including the following steps:

[0009] S1: Adopting an anaerobic-aerobic operation mode, aerobic granular sludge with biological phosphorus removal capability is formed in the sequencing batch reactor;

[0010] S2: The wastewater to be treated is introduced into the reactor, and the reactor is operated in a sequential batch reactor manner. Each operating cycle includes an anaerobic influent stage, an aerobic stage, a sedimentation stage, and a effluent stage. During the anaerobic influent stage, a multi-point stratified influent method is adopted: the wastewater to be treated enters from both the bottom and middle of the granular sludge layer. The bottom of the granular sludge layer accounts for 70-90% of the total influent volume, while the remaining wastewater enters from the middle of the granular sludge layer. Here, the middle of the granular sludge layer refers to the midpoint of the granular sludge layer in the vertical direction.

[0011] Intermittent aeration is used in the aerobic stage. Each intermittent aeration cycle includes an aeration period and a stop period, and the time ratio of a single aeration period to a single stop period is 2-3:1.

[0012] Furthermore, the anaerobic influent stage lasts 50-80 minutes, the aerobic stage lasts 150-180 minutes, the sedimentation stage lasts 4-6 minutes, and the drainage stage lasts 4-6 minutes.

[0013] Furthermore, the water exchange ratio of the reactor is 20-50%.

[0014] Furthermore, the COD concentration in the wastewater to be treated is 200-500 mg / L, and the NH4+ concentration is... + -N concentration is 35-45 mg / L, PO4 3- -P concentration is 5-10 mg / L, Ca 2+ Concentration ≥ 60 mg / L, pH ≥ 7.0.

[0015] Furthermore, when Ca in the wastewater to be treated 2+ When the concentration is < 60 mg / L, add soluble calcium salts to the reactor.

[0016] Furthermore, the soluble calcium salt is calcium chloride.

[0017] Furthermore, in step S2, the duration of a single aeration period is 15-30 min, the duration of a single aeration stop period is 5-15 min, and the dissolved oxygen concentration is controlled at 2-4 mg / L during the aeration period.

[0018] Furthermore, the duration of a single aeration period is 15-20 minutes, and the duration of a single aeration stop period is 5-10 minutes.

[0019] Furthermore, during reactor operation, the ratio of volatile suspended solids to volatile suspended solids (MLVSS / MLSS) in the sludge is monitored regularly. When MLVSS / MLSS < 0.4, 2-5% of the bottom high-density granular sludge is discharged from the bottom of the reactor weekly to maintain MLVSS / MLSS above 0.5. At the same time, the sludge age is controlled to 15-30 days by discharging the suspended sludge from the top of the reactor.

[0020] Furthermore, in step S2, when the water is fed into multiple layers, the water volume at the bottom of the granular sludge layer accounts for 80-90% of the total water volume.

[0021] The core of this invention for simultaneously enhancing phosphorus and nitrogen removal lies in: constructing a stable bio-chemical coupled reaction unit within the aerobic granular sludge through operational regulation, enabling anaerobic phosphorus release, calcium-phosphorus precipitation, aerobic phosphorus uptake, and endogenous denitrification alkali production to occur synergistically. A multi-point stratified influent and intermittent aeration strategy matching the reaction process is proposed, and sludge discharge is controlled through a sludge discharge strategy to achieve simultaneous enhancement of phosphorus and nitrogen removal. Specifically: In the anaerobic influent stage, a multi-point stratified influent method is adopted, allowing the wastewater to enter from the bottom and middle of the granular sludge layer; 70-90% of the wastewater enters from the bottom of the granular sludge layer, which is beneficial for providing more carbon sources for polysaccharide-accumulating bacteria in the high-density granular sludge at the bottom, promoting their synthesis and storage of intracellular carbon sources, providing electron donors for subsequent endogenous denitrification; 10-30% of the wastewater enters from the middle of the granular sludge layer, promoting the absorption and conversion of carbon sources into intracellular carbon sources by polyphosphate-accumulating bacteria in the upper low-density granular sludge, and enhancing anaerobic phosphorus release. This anaerobic phosphorus release process is initially characterized by a significant increase in phosphate concentration in the liquid phase. In the presence of calcium ions in the wastewater, calcium phosphate precipitates form in both the upper low-density granular sludge and the bottom high-density granular sludge, achieving phosphorus removal via a chemical pathway. During the aerobic stage, an intermittent aeration strategy is employed. During aeration periods, ammonia-oxidizing bacteria oxidize ammonia nitrogen to nitrite, which is then further oxidized to nitrate by nitrite-oxidizing bacteria, completing the nitrification process. Simultaneously, polyphosphate-accumulating bacteria utilize their stored internal carbon sources to absorb phosphate in the liquid phase and resynthesize polyphosphate within their cells, achieving aerobic phosphorus uptake. Furthermore, nitrate nitrogen formed on the outer layer of the granules during aeration can diffuse into the anoxic zone inside the granules and be denitrified endogenously by polyphosphate-accumulating bacteria using their stored internal carbon sources. During periods of aeration cessation, the anoxic zone inside the granules is further expanded, intensifying the nitrate nitrogen reduction process, promoting the distribution of internal carbon sources to the denitrification pathway, and generating alkalinity. The high-density granular sludge at the bottom maintains a high pH environment due to continuous alkali production from endogenous denitrification, thus inhibiting the dissolution of calcium and phosphorus precipitates formed in the anaerobic stage during the aerobic stage. In other words, the high-density granular sludge at the bottom not only participates in endogenous denitrification but also provides a microenvironmental guarantee for the stable existence of calcium and phosphorus precipitates. The low-density granular sludge at the top, due to its relatively small particle size and relatively less internal carbon source, has a relatively weaker endogenous denitrification effect and a less significant increase in alkalinity, making the calcium and phosphorus precipitates formed in the granules more easily soluble. Furthermore, by controlling the MLVSS / MLSS ratio above 0.5 through a sludge discharge strategy, a sufficient proportion of active biomass is maintained in the granular sludge, preventing excessive accumulation of inorganic components and ensuring the long-term stable operation of the aforementioned bio-chemical coupling reaction unit. Therefore, this invention constructs an enhanced mechanism for the coupling of anaerobic phosphorus release, calcium and phosphorus precipitation, aerobic phosphorus uptake, and endogenous denitrification alkali production through the synergistic effect of "multi-point stratified influent + intermittent aeration + sludge discharge control."Among them, anaerobic phosphorus release and its induced calcium and phosphorus precipitation expand the phosphorus removal pathway, reduce the consumption of organic carbon sources by biological phosphorus removal, and enable more limited carbon sources to be allocated to the endogenous denitrification process; while the endogenous denitrification alkali production in the high-density granular sludge at the bottom not only enhances nitrogen removal, but also promotes the stable existence of calcium and phosphorus precipitation by maintaining local high pH conditions, ultimately achieving simultaneous enhancement of phosphorus and nitrogen removal.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention, through operational mode regulation, establishes a stable coupling relationship between anaerobic phosphorus release, calcium-phosphorus precipitation formation, and aerobic denitrification alkali production processes within the granular sludge, promoting each other. This invention transforms the previously sporadic and uncontrollable calcium-phosphorus precipitation process into a stable and controllable biologically induced phosphorus precipitation process, thereby overcoming the limitation of existing aerobic granular sludge systems that rely heavily on enhanced biological phosphorus removal for phosphorus removal. This helps improve the stability and shock resistance of phosphorus removal, with a phosphate removal rate exceeding 80%.

[0024] 2. The calcium-phosphorus precipitation of this invention achieves partial phosphorus removal via chemical pathways, expanding the phosphorus removal pathway and reducing the consumption of organic carbon sources by polyphosphate-accumulating bacteria in biological phosphorus removal. Simultaneously, the multi-point stratified influent at the bottom provides more carbon sources for polysaccharide bacteria in the high-density granular sludge at the bottom, enhancing the synthesis and storage of internal carbon sources for endogenous denitrification. This synergistic effect allows for the redistribution of limited carbon sources in the system, with more carbon sources allocated to the polysaccharide bacteria-mediated endogenous denitrification process. This effectively alleviates the inherent contradiction in traditional processes where nitrogen and phosphorus removal compete for carbon sources, achieving simultaneous nitrogen and phosphorus removal under low carbon source conditions, with a total nitrogen removal rate exceeding 70%.

[0025] 3. This invention employs intermittent aeration. During the aerobic phase when aeration is stopped, polysaccharide-producing bacteria utilize internal carbon sources for endogenous denitrification. While completing nitrogen removal, they also generate alkalinity, maintaining a locally high-alkaline environment (pH > 7.5) within the granular sludge. This effectively inhibits the dissolution of calcium and phosphorus precipitates, ensuring that the calcium and phosphorus precipitates generated in the anaerobic phase remain stable and do not disintegrate during the aerobic phase. Thus, by spontaneously generating alkalinity through microbial metabolism to maintain precipitate stability, no additional alkalinity adjusters or chemical precipitants are required, which helps reduce operating costs and simplifies operation and management, demonstrating promising engineering application prospects.

[0026] Simultaneously, calcium and phosphorus precipitates adhere to the interior of granular sludge, forming an inorganic mineral framework. This increases the density and settling properties of the granular sludge, enhancing the retention capacity of biomass within the reactor. This allows the system to maintain relatively stable treatment performance even under fluctuations in influent load and changes in water quality, significantly improving the system's shock resistance and long-term operational stability. As a recyclable phosphorus product, calcium and phosphorus precipitates provide an opportunity to combine nutrient removal with resource recovery within the existing AGS framework.

[0027] 4. Furthermore, this invention, through a multi-point stratified water inlet and intermittent aeration operation strategy, can construct a stable and coexisting aerobic and anoxic microenvironment within the granular sludge, providing an adaptive ecological environment for polyphosphate-accumulating bacteria and polysaccharide-accumulating bacteria. Simultaneously, the sludge discharge strategy based on sludge properties maintains the structural stability of the granular sludge while controlling the accumulation of inorganic components, achieving synergistic optimization of granular structural stability and long-term treatment performance. Attached Figure Description

[0028] Figure 1 - Sludge biomass in the reactor in Example 1.

[0029] Figure 2 - Scanning electron microscope image of granular sludge in Example 1.

[0030] Figure 3 - X-ray diffraction (XRD) pattern of inorganic precipitate of granular sludge in Example 1.

[0031] Figure 4 Example 1: pH profile of the high-density granular sludge at the bottom of the aerobic stage.

[0032] Figure 5 - Graph showing the pollutant removal effect during reactor operation in Example 1.

[0033] Figure 6 -In Example 1, the granular sludge at the bottom and top of the reactor has a horizontal microbial community structure.

[0034] Figure 7 - Sludge biomass in the reactor of Comparative Example 3.

[0035] Figure 8 - Scanning electron microscope image of granular sludge in Comparative Example 3.

[0036] Figure 9 - X-ray diffraction (XRD) pattern of inorganic precipitate of granular sludge in Comparative Example 3.

[0037] Figure 10 - Comparative Example 3: pH profile of high-density granular sludge at the bottom of the aerobic stage.

[0038] Figure 11- A diagram showing the pollutant removal effect during reactor operation in Comparative Example 3.

[0039] Figure 12 - In Comparative Example 3, the granular sludge at the bottom and top of the reactor exhibits a horizontal microbial community structure. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0041] Example 1

[0042] An aerobic granular sludge reactor was operated in SBR mode. The reactor had a working volume of 2.5 L, a volume exchange ratio of 50%, and the water temperature was maintained at 25±1℃, with dissolved oxygen controlled at 2-4 mg / L. The reactor operated in an anaerobic-aerobic mode, with each cycle consisting of an 80-minute anaerobic plug flow influent stage, a 150-minute aeration stage (aerobic stage), a 5-minute settling stage, and a 5-minute effluent stage, for a total cycle time of 240 minutes. During operation, the sludge retention time (SRT) was controlled to approximately 20 days by discharging high-density granular sludge from the bottom and suspended sludge from the top.

[0043] The reactor influent was simulated domestic sewage, with the following main water quality indicators: COD concentration of 400 mg / L and NH4+ concentration of... + -N concentration was 40 mg / L, PO4 3- -P concentration is 8 mg / L, Ca 2+ The concentration was 60 mg / L, and the pH of the reactor influent was 7.0.

[0044] A multi-point stratified influent and intermittent aeration operation mode was adopted to regulate calcium and phosphorus precipitation and carbon source distribution. In the anaerobic stage, the influent volume at the bottom of the granular sludge layer was controlled at 80% to promote carbon source absorption by polysaccharide-accumulating bacteria in the high-density granular sludge at the bottom, while the influent volume in the middle of the granular sludge layer was controlled at 20% to enhance the anaerobic phosphorus release by polyphosphate-accumulating bacteria in the upper low-density granular sludge, and to generate calcium and phosphorus precipitates within the granular sludge. In the aerobic stage, intermittent aeration was used, with aeration and shutdown times controlled at 20 min and 10 min respectively, and dissolved oxygen concentration controlled at 2-4 mg / L to complete nitrification and biological phosphorus removal, enhance endogenous denitrification, generate alkalinity, and maintain a relatively high pH value within the granular sludge to ensure the stable existence of the generated calcium and phosphorus precipitates. During this operation, when MLVSS / MLSS < 0.4, approximately 3% of the high-density granular sludge from the bottom of the reactor is manually discharged weekly to maintain MLVSS / MLSS above 0.5.

[0045] During reactor operation, the sludge biomass of the reactor in Example 1 was as follows: Figure 1 As shown, by Figure 1 It can be seen that as the reactor continues to operate, the sludge gradually transforms from an initial flocculent state into a dense granular morphology, and the reactor's MLVSS gradually increases from 2000 mg / L to 6000 mg / L. At this point, calcium and phosphorus precipitation begins to accumulate inside the particles, and the MLVSS / MLSS ratio gradually decreases from 0.8 to 0.5, remaining relatively stable during the stable operation phase. This indicates that the inorganic mineral content within the particles continues to increase without significant dissolution.

[0046] Scanning electron microscope (SEM) images of granular sludge during the stable operation phase in Example 1 are shown below. Figure 2 As shown, by Figure 2 As can be seen, the granular sludge has clear edges, a compact and complete structure, and obvious mineral crystals. Figure 3 As shown, further analysis of the granular sludge during the stable operation phase revealed the presence of calcium phosphate precipitates, primarily composed of hydroxyapatite. Simultaneously, analysis of the pH distribution of the high-density granular sludge at the bottom during the aerobic phase yielded the following results: Figure 4 As can be seen from the figure, the pH inside the high-density granular sludge at the bottom is between 7.5 and 8.0.

[0047] like Figure 5 As shown, after the reactor stabilized, the COD removal rate exceeded 90%, the total nitrogen removal rate exceeded 80%, and the total phosphorus removal rate exceeded 85%, achieving good and stable pollutant removal performance. Figure 6 As shown, the abundance of slow-growing bacteria g__Candidatus_Competibacter (polysaccharide bacteria) in both the bottom and upper layers of granular sludge exceeded 20%, and the abundance of g__Candidatus_Accumulibacter (polyphosphate bacteria) also exceeded 5%.

[0048] Example 2

[0049] This embodiment is the same as Embodiment 1, except that in the anaerobic stage, the bottom water intake of the granular sludge layer is controlled at 70% and the middle water intake of the granular sludge layer is controlled at 30% by using a multi-point stratified water intake method.

[0050] In this embodiment, after the reactor operates stably, the COD removal rate exceeds 90%, the total nitrogen removal rate exceeds 70%, and the total phosphorus removal rate exceeds 90%, achieving good and stable pollutant removal performance.

[0051] Example 3

[0052] This embodiment is the same as Embodiment 1, except that in the anaerobic stage, the bottom water intake of the granular sludge layer is controlled at 90% and the middle water intake of the granular sludge layer is controlled at 10% by using a multi-point stratified water intake method.

[0053] In this embodiment, after the reactor operates stably, the COD removal rate exceeds 90%, the total nitrogen removal rate exceeds 90%, and the total phosphorus removal rate exceeds 80%, achieving good and stable pollutant removal performance.

[0054] Example 4

[0055] This embodiment is the same as Embodiment 1, except that during intermittent aeration, the aeration time and the aeration stop time are controlled at 30 min and 10 min respectively, and the duration of the aerobic phase of each cycle is 160 min.

[0056] In this embodiment, after the reactor operates stably, the COD removal rate exceeds 90%, the total nitrogen removal rate exceeds 75%, and the total phosphorus removal rate exceeds 80%, achieving good and stable pollutant removal performance.

[0057] Example 5

[0058] This embodiment is the same as Embodiment 1, except that during intermittent aeration, the aeration time and the aeration stop time are controlled at 15 min and 5 min respectively, and the duration of the aerobic phase of each cycle is 180 min.

[0059] In this embodiment, after the reactor operates stably, the COD removal rate exceeds 90%, the total nitrogen removal rate exceeds 80%, and the total phosphorus removal rate exceeds 80%, achieving good and stable pollutant removal performance.

[0060] Comparative Example 1

[0061] This comparative example is the same as Example 1, except that the reactor in this comparative example does not adopt a multi-point stratified water inlet method. The water enters only from the bottom of the reactor, and the water inlet accounts for 100% of the total water inlet. There is no water inlet in the middle of the granular sludge layer.

[0062] In this comparative example, after the reactor stabilized, the COD removal rate exceeded 90%, the total nitrogen removal rate was less than 80%, and the total phosphorus removal rate was less than 70%.

[0063] Comparative Example 2

[0064] This comparative example is the same as Example 1, except that the reactor in this comparative example operates in a continuous aeration mode during the aerobic stage without intermittent aeration control, and the dissolved oxygen concentration is controlled at 2-4 mg / L during the aeration process.

[0065] In this comparative example, after the reactor stabilized, the COD removal rate exceeded 90%, the total nitrogen removal rate was less than 70%, and the total phosphorus removal rate was less than 80%.

[0066] Comparative Example 3

[0067] This comparative example is the same as Example 1, except that in the anaerobic stage, the reactor does not use a multi-point stratified influent method; instead, the influent enters only from the bottom of the reactor, accounting for 100% of the total influent volume, and there is no inlet in the middle of the granular sludge layer. In the aerobic stage, the reactor operates with continuous aeration without intermittent aeration control, and the dissolved oxygen concentration is controlled at 2-4 mg / L during aeration. Except for the differences in multi-point stratified influent and intermittent aeration mentioned above, the other operating conditions are consistent with the example.

[0068] Under these operating conditions, the sludge can also gradually transform from flocculent to granular form. Figure 7 It can be seen that the biomass in the reactor continued to increase, and the MLVSS / MLSS ratio rose to approximately 0.8, indicating that the accumulation of inorganic sediment in the sludge was significantly lower than in Example 1. From Figure 8 It can be seen that granular sludge has a loose structure, a flat and irregular shape, and no mineral crystals are formed on it, indicating that the stable enrichment capacity of calcium and phosphorus precipitation inside the granules is limited. Figure 9 It was found that no obvious hydroxyapatite was observed in the inorganic precipitates enriched within the sludge. Simultaneously, the pH distribution of the high-density granular sludge at the bottom was analyzed during the aerobic stage, and the results are as follows: Figure 10 As can be seen from the figure, the pH inside the high-density granular sludge at the bottom is between 7.2 and 7.6. Regarding pollutant removal performance, [the following text appears to be incomplete and requires further context: "from..."] Figure 11 It can be seen that, under the same influent conditions as in Example 1, after the comparative reactor stabilized, the COD removal rate remained stable at approximately 90%, while the system's removal efficiency for phosphorus and nitrogen was low. The total phosphorus concentration in the effluent fluctuated significantly, with a total phosphorus removal rate below 60% and a total nitrogen removal rate below 50%. During operation, the endogenous denitrification of the granular sludge was weak, resulting in insufficient synergistic effect of phosphorus and nitrogen removal. Figure 12 It can be seen that the abundance of slow-growing bacteria g__Candidatus_Competibacter in both the bottom and upper layers of granular sludge is less than 15%, and the abundance of g__Candidatus_Accumulibacter is less than 1%.

[0069] Example 1 observed biologically induced phosphorus precipitation in granular sludge. However, in Comparative Example 3, no obvious and stable calcium-phosphorus precipitation was formed, and the precipitation was low in degree and lacked persistence, failing to form a stable functional effect inside the granules and having limited synergistic effect on the denitrification and phosphorus removal processes of the system. In contrast, Example 1, through operation mode regulation, established a stable coupling relationship between the phosphorus precipitation process and the denitrification reaction inside the granules, and constructed it into a functional reaction unit that can operate sustainably, thereby optimizing the organic carbon distribution pathway and improving the synergistic efficiency of denitrification and phosphorus removal in the system.

[0070] Comparative Example 4

[0071] This comparative example is the same as Example 1, except that in the anaerobic stage, the bottom water intake of the granular sludge layer is controlled at 50% and the middle water intake of the granular sludge layer is controlled at 50% by using a multi-point stratified water intake method.

[0072] In this comparative example, after the reactor stabilized, the COD removal rate exceeded 90%, the total nitrogen removal rate was less than 60%, and the total phosphorus removal rate reached 85%.

[0073] Comparative Example 5

[0074] This comparative example is the same as Example 1, except that during intermittent aeration, the aeration time and the aeration stop time are controlled at 40 min and 20 min respectively, and the duration of the aerobic phase of each cycle is 180 min.

[0075] In this comparative example, after the reactor stabilized, the COD removal rate exceeded 90%, the total nitrogen removal rate was less than 70%, and the total phosphorus removal rate was less than 70%.

[0076] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for simultaneously enhancing phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor, characterized in that, Specifically, the following steps are included: S1: Adopting an anaerobic-aerobic operation mode, aerobic granular sludge with biological phosphorus removal capability is formed in the sequencing batch reactor; S2: The wastewater to be treated is introduced into the reactor and the reactor is operated in a sequential batch process. In each operating cycle, the anaerobic influent stage, aerobic stage, sedimentation stage and drainage stage are carried out in sequence. In the anaerobic influent stage, a multi-point stratified influent method is adopted: the wastewater to be treated enters from the bottom and middle of the granular sludge layer, respectively, with the bottom of the granular sludge layer accounting for 70-90% of the total influent. Intermittent aeration is used in the aerobic stage. Each intermittent aeration cycle includes an aeration period and a stop period, and the time ratio of a single aeration period to a single stop period is 2-3:

1.

2. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 1, characterized in that, The anaerobic influent stage lasts 50-80 minutes, the aerobic stage lasts 150-180 minutes, the sedimentation stage lasts 4-6 minutes, and the drainage stage lasts 4-6 minutes.

3. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 1, characterized in that, The water exchange ratio of the reactor is 20-50%.

4. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 1, characterized in that, The COD concentration in the wastewater to be treated is 200-500 mg / L, and the NH4 concentration is... + -N concentration is 35-45 mg / L, PO4 3- -P concentration is 5-10 mg / L, Ca 2+ Concentration ≥ 60 mg / L, pH ≥ 7.

0.

5. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 4, characterized in that, When Ca in the wastewater to be treated 2+ When the concentration is < 60 mg / L, add soluble calcium salts to the reactor.

6. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 5, characterized in that, The soluble calcium salt is calcium chloride.

7. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 1, characterized in that, In step S2, the duration of a single aeration period is 15-30 min, the duration of a single aeration stop period is 5-15 min, and the dissolved oxygen concentration is controlled at 2-4 mg / L during the aeration period.

8. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 7, characterized in that, The duration of a single aeration period is 15-20 minutes, and the duration of a single aeration stop period is 5-10 minutes.

9. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 1, characterized in that, During reactor operation, the ratio of volatile suspended solids to volatile suspended solids (MLVSS / MLSS) in the sludge is monitored regularly. When MLVSS / MLSS < 0.4, 2-5% of the high-density granular sludge from the bottom of the reactor is discharged weekly to restore and maintain MLVSS / MLSS above 0.

5. At the same time, the sludge age is controlled to 15-30 days by discharging the suspended sludge from the top of the reactor.

10. The method for simultaneous enhanced phosphorus and nitrogen removal in an anaerobic-aerobic granular sludge reactor according to claim 1, characterized in that, In step S2, when multiple-point stratified water inlet is used, the water inlet volume at the bottom of the granular sludge layer accounts for 80-90% of the total water inlet volume.

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