A biological nitrogen and phosphorus removal system and wastewater treatment method

Abstract

This invention provides a biological nitrogen and phosphorus removal system and method for wastewater treatment, relating to the field of wastewater treatment technology. The system includes: an anaerobic zone, a denitrification-anoxic zone, a low dissolved oxygen aeration zone, a solid-liquid separation zone, and an equipment zone, sequentially connected along the wastewater flow direction; the anaerobic zone is connected to an inlet pipe; the solid-liquid separation zone is equipped with a drain pipe; the equipment zone includes stirring equipment and dissolved oxygen supply equipment. Each biological tank in the system operates with a high sludge concentration. The system provided by this invention can enhance the ability of microorganisms in the anaerobic zone to absorb organic matter and release phosphates. It can promote simultaneous nitrification-denitrification and denitrification-phosphorus removal reactions in the denitrification-anoxic tank for nitrogen and phosphorus removal. Simultaneous nitrification-denitrification and polyphosphate accumulation reactions can be carried out in the low dissolved oxygen aeration tank, achieving organic matter removal without the need for additional carbon sources, with low aeration intensity, low operating energy consumption, and good treatment effect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and more specifically, to a biological nitrogen and phosphorus removal system and wastewater treatment method. Background Technology

[0002] Wastewater treatment is a crucial link in environmental protection, especially against the backdrop of rapid socio-economic development and increasingly stringent water environment protection requirements. Eutrophication caused by excessive nitrogen and phosphorus emissions has become one of the most serious challenges in current water pollution control. Currently, the wastewater treatment industry has entered a new era with carbon reduction and emission reduction as its key strategic directions. Stringent emission standards have made research and innovation in wastewater treatment technologies a hot topic within the industry.

[0003] Currently, commonly used processes in urban wastewater treatment plants include the A2 / O process, oxidation ditch process, and SBR process. These processes play a vital role in wastewater treatment, but they also have some limitations. First, they consume a lot of energy, especially in the traditional activated sludge process, where maintaining a high dissolved oxygen content in the aeration tank requires significant energy for aeration. Second, the effluent treatment effect is not stable. When the carbon source in the influent is insufficient, the microbial denitrification process lacks the necessary electron donor, making it difficult to meet the total nitrogen standards in the effluent. This not only requires the addition of additional carbon sources but may also necessitate the addition of subsequent advanced treatment processes, thus increasing operating costs and engineering investment. Finally, existing processes generate a large amount of sludge, and the cost of sludge treatment and disposal is high, posing a significant challenge to the operation of wastewater treatment plants.

[0004] Biological wastewater treatment technology relies on activated sludge microorganisms participating in various reactions under different conditions to achieve nitrogen and phosphorus removal in wastewater treatment. However, existing technologies still have some shortcomings in practical applications. For example, the energy-intensive aeration process, the instability of effluent quality, and the high sludge production not only increase operating costs but also restrict the further development and application of wastewater treatment technologies.

[0005] Low dissolved oxygen aeration and high sludge concentration operation are two effective methods for improving wastewater treatment efficiency discovered in recent years. Under low dissolved oxygen conditions, the diversity of activated sludge microbial communities increases, which helps improve the wastewater treatment's resistance to shock loads. High sludge concentration operation can improve the degradation efficiency of organic pollutants by microorganisms, achieving efficient synergy of multiple metabolic pathways, such as simultaneous nitrification / denitrification and denitrification for phosphorus removal, thereby enhancing nitrogen and phosphorus removal. Simultaneously, high sludge concentration can extend sludge age, promote microbial death and further decomposition of metabolic products, reduce excess sludge production, and lower sludge treatment and disposal costs.

[0006] While these findings offer new insights into wastewater treatment technology, there is an urgent need to develop a wastewater treatment process that combines low dissolved oxygen aeration with high sludge concentration operation. This is crucial to address the challenges posed by existing technologies, such as unstable treatment performance, high energy consumption, and high costs under conditions of limited influent carbon sources. Such a new process should meet the wastewater treatment industry's demand for synergistic efficiency in pollution and carbon reduction, driving the development of wastewater treatment technology towards greater efficiency, energy conservation, and environmental friendliness. Summary of the Invention

[0007] The primary objective of this invention is to provide a biological nitrogen and phosphorus removal system and a wastewater treatment method, wherein the biological nitrogen and phosphorus removal system has advantages such as low operating energy consumption and good treatment effect.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] In a first aspect, the present invention provides a wastewater biological nitrogen and phosphorus removal system, comprising:

[0010] The anaerobic zone, denitrification anoxic zone, low dissolved oxygen aeration zone, solid-liquid separation zone and equipment zone are connected sequentially along the direction of sewage flow.

[0011] The anaerobic zone contains anaerobic activated sludge; the denitrification anoxic zone contains anoxic activated sludge; and the low dissolved oxygen aeration zone contains aerobic activated sludge.

[0012] The anaerobic zone, the denitrification anoxic zone, and the low dissolved oxygen aeration zone all maintain high sludge concentrations during operation.

[0013] The anaerobic zone is an environment without dissolved oxygen and is connected to an inlet pipe for discharging wastewater.

[0014] The solid-liquid separation zone is equipped with a drainage pipe;

[0015] The equipment area includes stirring equipment located in the anaerobic zone and the denitrification anoxic zone, and dissolved oxygen supply equipment located in the low dissolved oxygen aeration zone.

[0016] In an optional embodiment, the denitrification anoxic zone includes a first anoxic tank and a second anoxic tank;

[0017] The anaerobic zone is connected to the first anoxic tank via an overflow hole, so that the first anoxic tank can receive the sewage flowing out of the anaerobic zone.

[0018] One end of the second anoxic tank is connected to the first anoxic tank, and the other end is connected to the low dissolved oxygen aeration zone.

[0019] In an optional embodiment, the low dissolved oxygen aeration zone includes a first aerobic tank and a second aerobic tank connected in sequence.

[0020] The first aerobic tank is connected to the second anoxic tank;

[0021] The second aerobic tank is connected to the solid-liquid separation zone via an overflow pipe.

[0022] In an optional embodiment, the equipment area further includes a dissolved oxygen meter disposed in the first aerobic tank and the second aerobic tank.

[0023] In an optional implementation, the equipment area further includes frequency converter control equipment;

[0024] The frequency converter control device is electrically connected to both the dissolved oxygen meter and the dissolved oxygen supply device. Based on the detection data from the dissolved oxygen meter, the frequency converter control device controls the dissolved oxygen supply device to maintain the dissolved oxygen concentration in the first aerobic tank at 0.8 mg / L to 1.2 mg / L and the dissolved oxygen concentration in the second aerobic tank at 0.4 mg / L to 0.6 mg / L.

[0025] In an optional embodiment, the dissolved oxygen supply device includes a blower and a flow meter connected to the blower.

[0026] In an optional implementation, the equipment area further includes a first reflux pump and a first reflux pipeline;

[0027] One end of the first reflux pipeline is connected to the solid-liquid separation zone, and the other end is connected to the anaerobic zone;

[0028] The first return pump is installed on the first return pipeline to facilitate the return of concentrated sludge from the solid-liquid separation zone to the anaerobic zone.

[0029] In an optional embodiment, in the wastewater biological nitrogen and phosphorus removal system, the concentration of sludge therein is controlled to be maintained at 8000mg / L-10000mg / L by the first return pump and the first return pipeline;

[0030] The reflux ratio of the first reflux pump is 100%.

[0031] In an optional implementation, the equipment area further includes a second reflux pump and a second reflux pipeline;

[0032] One end of the second return pipeline is connected to the first anoxic tank, and the other end is connected to the second aerobic tank;

[0033] The second return pump is installed on the second return pipeline to facilitate the return of wastewater from the second aerobic tank to the first anoxic tank.

[0034] In an optional embodiment, the reflux ratio of the second reflux pump is 300%;

[0035] In a second aspect, the present invention provides a wastewater treatment method based on a biological nitrogen and phosphorus removal system for wastewater as described in any of the foregoing embodiments, the wastewater treatment method comprising:

[0036] S1, add anaerobic activated sludge to the anaerobic zone of the biological nitrogen and phosphorus removal system for wastewater, add anoxic activated sludge to the denitrification anoxic zone of the biological nitrogen and phosphorus removal system for wastewater, and add aerobic activated sludge to the low dissolved oxygen aeration zone of the biological nitrogen and phosphorus removal system for wastewater.

[0037] S2 controls the discharge of wastewater into the anaerobic zone through the inlet pipe;

[0038] S3, the dissolved oxygen supply equipment in the low dissolved oxygen aeration zone is provided by the equipment area control, and the stirring equipment in the equipment area is controlled to stir in the anaerobic zone and the denitrification anoxic zone;

[0039] After passing through the anaerobic zone, the wastewater enters the denitrification anoxic zone for denitrification and phosphorus removal. After the reaction, it enters the low dissolved oxygen aeration zone for nitrification and polyphosphate reaction. Then, it enters the solid-liquid separation zone for solid-liquid separation treatment. The supernatant after treatment is discharged through the drain pipe.

[0040] In an optional embodiment, in the wastewater biological nitrogen and phosphorus removal system, the concentration of sludge therein is controlled to be maintained at 8000 mg / L to 10000 mg / L by a first return pump and a first return pipeline;

[0041] In an optional implementation, the reflux ratio of the first reflux pump is 100%;

[0042] In an optional embodiment, the frequency converter control device in the equipment area controls the dissolved oxygen supply device based on the detection data of the dissolved oxygen meter in the first aerobic tank and the second aerobic tank in the low dissolved oxygen aeration zone, so that the dissolved oxygen concentration in the first aerobic tank is between 0.8 mg / L and 1.2 mg / L, and the dissolved oxygen concentration in the second aerobic tank is between 0.4 mg / L and 0.6 mg / L.

[0043] In an optional embodiment, the wastewater in the second aerobic tank is returned to the first anoxic tank of the denitrification anoxic zone via the second return pump in the equipment area through the second return pipeline.

[0044] In an optional embodiment, the reflux ratio of the second reflux pump is 300%;

[0045] In an optional implementation, the concentrated sludge in the solid-liquid separation zone is returned to the anaerobic zone by the first return pump in the equipment area.

[0046] Compared with existing technologies, the wastewater biological nitrogen and phosphorus removal system provided by this invention can enhance the ability of microorganisms in the anaerobic zone to take up organic matter and release phosphate. It can promote simultaneous nitrification and denitrification and phosphorus removal reactions in the denitrification anoxic tank to remove nitrogen and phosphorus. It can carry out nitrification and polyphosphate reaction in the low dissolved oxygen aeration zone and achieve organic matter removal. It does not require the addition of an extra carbon source, has low aeration intensity, low operating energy consumption, and good treatment effect. Attached Figure Description

[0047] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the wastewater biological nitrogen and phosphorus removal system in the embodiments of this application;

[0049] Figure 2 This is a graph showing the changes in influent and effluent water quality indicators of the wastewater biological nitrogen and phosphorus removal system in the embodiments of this application;

[0050] Figure 3 This is a graph showing the concentration changes of various pollutants and internal carbon source components in the wastewater biological nitrogen and phosphorus removal system in the embodiments of this application.

[0051] Figure label:

[0052] 100. Wastewater biological nitrogen and phosphorus removal system; 1. Anaerobic zone; 2. Denitrification anoxic zone; 21. First anoxic tank; 22. Second anoxic tank; 3. Low dissolved oxygen aeration zone; 31. First aerobic tank; 32. Second aerobic tank; 4. Solid-liquid separation zone; 5. Equipment area; 51. Mixing equipment; 52. Dissolved oxygen supply equipment; 521. Blower; 522. Flow meter; 53. Dissolved oxygen meter; 54. Variable frequency control equipment; 55. Second return pump; 56. Second return pipeline; 57. First return pump; 58. First return pipeline; 6. Inlet pipe; 7. Drainage pipe. Detailed Implementation

[0053] As used in this article:

[0054] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0055] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0056] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0057] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0058] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0059] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0060] refer to Figure 1 This application provides a wastewater biological nitrogen and phosphorus removal system 100, comprising:

[0061] The anaerobic zone 1, denitrification anoxic zone 2, low dissolved oxygen aeration zone 3, solid-liquid separation zone 4, and equipment zone 5 are connected sequentially along the direction of sewage flow.

[0062] The anaerobic zone 1 contains anaerobic activated sludge; the denitrification anoxic zone 2 contains anoxic activated sludge; and the low dissolved oxygen aeration zone 3 contains aerobic activated sludge.

[0063] The anaerobic zone 1, the denitrification anoxic zone 2, and the low dissolved oxygen aeration zone 3 all maintain high sludge concentrations.

[0064] The anaerobic zone 1 is an environment without dissolved oxygen and is connected to an inlet pipe 6 for discharging wastewater.

[0065] The solid-liquid separation zone 4 is equipped with a drain pipe 7;

[0066] The equipment area 5 includes a stirring device 51 located in the anaerobic zone 1 and the denitrification anoxic zone 2, and a dissolved oxygen supply device 52 located in the low dissolved oxygen aeration zone 3.

[0067] As described above, in the field of wastewater treatment technology, anaerobic zone 1 (such as an anaerobic tank) is a biological treatment unit that operates in an environment without oxygen or with extremely low oxygen concentration. The main function of the anaerobic tank is to promote the growth and activity of anaerobic microorganisms, which can absorb organic matter in wastewater under oxygen-free conditions.

[0068] In this embodiment, the anaerobic tank is a key component of the biological nitrogen and phosphorus removal system 100 for wastewater with low dissolved oxygen and high sludge concentration, and its main functions include:

[0069] Organic matter uptake and phosphate release: In anaerobic tanks, microorganisms take up organic matter in wastewater through anaerobic decomposition, synthesizing it into an internal carbon source and releasing phosphate in the process. This step is crucial for subsequent phosphorus removal.

[0070] Improving nitrogen removal efficiency: Anaerobic conditions help enhance the metabolic activity of certain microorganisms, which can use organic matter as electron donors to carry out denitrification, thereby removing nitrogen from wastewater.

[0071] Enhanced system stability: Pretreatment in the anaerobic tank can improve the overall wastewater treatment system's resistance to shock loads caused by fluctuations in influent water quality.

[0072] Reduce sludge production: High sludge concentration operation helps extend sludge time (SRT), promotes the death of microorganisms and further decomposition of metabolites, thereby reducing the production of excess sludge.

[0073] The anaerobic tank is combined with other treatment units such as aerobic and anoxic tanks to form a complete wastewater treatment process. In the system of this embodiment, the anaerobic tank is connected to other tanks in sequence to achieve efficient nitrogen and phosphorus removal.

[0074] The aforementioned denitrification anoxic zone 2 is primarily used for denitrification in the system, and can also perform denitrification for phosphorus removal. Nitrates and nitrites (nitrogen oxides) are reduced to nitrogen gas under anoxic conditions, thus removing nitrogen from the wastewater. These tanks also help decompose internal carbon sources within microorganisms, further removing phosphorus from the wastewater.

[0075] The aforementioned low dissolved oxygen aeration zone 3 has a high concentration of dissolved oxygen and primarily undergoes nitrification, converting ammonia nitrogen into nitrate. Simultaneously, under aerobic conditions, polyphosphate-accumulating bacteria can absorb phosphate and store it as polyphosphate. These bacteria contribute to phosphorus removal from wastewater during subsequent sedimentation and recirculation processes.

[0076] The second aerobic tank 32 has a low dissolved oxygen concentration. While ensuring that enough nitrate enters the first anoxic tank 21, the dissolved oxygen content in the second return pipeline should be minimized as much as possible to maintain stable anoxic conditions.

[0077] The wastewater biological nitrogen and phosphorus removal system 100 also includes activated sludge located in various zones, specifically: anaerobic activated sludge in anaerobic zone 1; anoxic activated sludge in denitrification anoxic zone 2; and aerobic activated sludge in low dissolved oxygen aeration zone 3.

[0078] Anaerobic activated sludge, under anaerobic conditions, is mainly composed of anaerobic microorganisms, such as anaerobic bacteria, hydrolytic bacteria, polysaccharide-accumulating bacteria, and polyphosphate-accumulating bacteria. Its main function is to anaerobic decompose and absorb organic matter, while releasing phosphorus.

[0079] Anaerobic activated sludge, under anaerobic conditions, is mainly composed of denitrifying microorganisms, such as denitrifying denitrifying bacteria and denitrifying phosphorus-removing bacteria. Its main function is to perform denitrification, reducing nitrates to nitrogen gas, thereby removing nitrogen from wastewater.

[0080] Aerobic activated sludge, under aerobic conditions, is mainly composed of aerobic microorganisms, such as nitrifying bacteria and polyphosphate-accumulating bacteria. Its main functions are the oxidative decomposition of organic matter, the nitrification of ammonia nitrogen (converting it into nitrate), and the phosphorus uptake by polyphosphate-accumulating bacteria (absorbing and storing phosphate).

[0081] Although the activated sludge in each zone differs in microbial composition and function, they are interconnected and interdependent throughout the wastewater treatment process. For example, nitrates produced by nitrification in the low dissolved oxygen aeration zone 3 can serve as electron acceptors for denitrification in the anoxic tank, while phosphorus release in the anaerobic tank provides conditions for phosphorus accumulation in the aerobic tank.

[0082] Furthermore, the microbial community of activated sludge adapts and evolves according to changes in environmental conditions. In actual wastewater treatment systems, operations such as sludge recirculation and dissolved oxygen concentration adjustment can further promote the formation and development of different microbial communities, thereby optimizing the overall system's treatment efficiency.

[0083] The solid-liquid separation zone 4 described above is used to separate sludge from water. Solid-liquid separation zone 4 can employ sedimentation technology, centrifugation technology, ultrafiltration technology, etc.

[0084] For example, solid-liquid separation zone 4 is a settling tank, which separates sludge from treated water through gravity. The settling tank allows sludge particles in the biologically treated mixed liquor to settle to the bottom, the supernatant (treated water) is discharged from the system, while part of the concentrated sludge at the bottom is returned to the anaerobic tank, and the remainder is discharged as excess sludge.

[0085] The aforementioned equipment area 5 may include a stirring device 51 and a dissolved oxygen supply device 52.

[0086] Equipment area 5 is responsible for controlling the operation of the entire system. For example, it uses stirring equipment 51 to continuously, periodically or in real time stir the sewage and sludge in anaerobic zone 1 and denitrification anoxic zone 2, provides the required dissolved oxygen through dissolved oxygen supply equipment 52, and can monitor the dissolved oxygen concentration to ensure the efficient and stable operation of the system.

[0087] As described above, the stirring device 51 can use a stirring paddle to enable the high-concentration activated sludge microorganisms in the anaerobic zone 1 and the anoxic zone to fully react with organic matter, nitrogen, phosphorus and other substances in the wastewater.

[0088] The dissolved oxygen supply equipment mentioned above can be, for example, a blower 521, which aerates the sludge and wastewater to provide dissolved oxygen molecules.

[0089] As described above, inlet pipe 6 is used to introduce sewage. Drain pipe 7 is used to drain the supernatant from solid-liquid separation zone 4 to complete sewage treatment.

[0090] The wastewater biological nitrogen and phosphorus removal system 100 provided in this embodiment is a wastewater biological nitrogen and phosphorus removal system with low dissolved oxygen and high sludge concentration. It can enhance the ability of microorganisms in the anaerobic zone 1 to take up organic matter and release phosphate. It can promote simultaneous nitrification and denitrification and denitrification phosphorus removal reactions in the denitrification anoxic tank to remove nitrogen and phosphorus. It can carry out nitrification and polyphosphate reaction in the low dissolved oxygen aeration zone 3 and achieve organic matter removal. It does not require the addition of an additional carbon source, has low aeration intensity, low operating energy consumption, and good treatment effect.

[0091] Furthermore, the denitrification anoxic zone 2 includes a first anoxic tank 21 and a second anoxic tank 22;

[0092] The anaerobic zone 1 is connected to the first anoxic tank 21 through an overflow hole so that the first anoxic tank 21 can receive the sewage flowing out of the anaerobic zone 1.

[0093] One end of the second anoxic tank 22 is connected to the first anoxic tank 21, and the other end is connected to the low dissolved oxygen aeration zone 3.

[0094] As described above, the denitrification anoxic zone 2 can be divided into two sections: a first anoxic tank 21 and a second anoxic tank 22. The two sections are connected in sequence to form the anaerobic zone 1, the first anoxic tank 21, the second anoxic tank 22, and the low dissolved oxygen aeration zone 3.

[0095] As described above, the first anoxic tank 21 is connected to the anaerobic zone 1 through an overflow hole, so that the sewage in the anaerobic zone 1, after being treated in the anaerobic zone 1, overflows upward and can enter the first anoxic tank 21 through the overflow hole.

[0096] Furthermore, the low dissolved oxygen aeration zone 3 includes a first aerobic tank 31 and a second aerobic tank 32 connected in sequence.

[0097] The first aerobic tank 31 is connected to the second anoxic tank 22;

[0098] The second aerobic tank 32 is connected to the solid-liquid separation zone 4 via an overflow pipe.

[0099] The second anoxic tank 22, the first aerobic tank 31, the second aerobic tank 32, and the solid-liquid separation zone 4 are connected in sequence.

[0100] As described above, the second anoxic tank 22 receives the mud-water mixture from the first anoxic tank 21, and inputs the treated mud-water mixture into the first aerobic tank 31 and the second aerobic tank 32. The second aerobic tank 32 is equipped with an overflow pipe, in which the sewage and sewage mixture overflow upward and are input into the solid-liquid separation zone 4.

[0101] In an optional embodiment, the equipment area 5 further includes a dissolved oxygen meter 53 disposed in the first aerobic tank 31 and the second aerobic tank 32.

[0102] The dissolved oxygen meter 53 described above is an instrument used to measure the concentration of dissolved oxygen (DO) in water. Dissolved oxygen is the form in which oxygen exists in water in a molecular state, and it is an important water quality parameter for the survival of aquatic organisms and in many water treatment processes.

[0103] In wastewater treatment, dissolved oxygen meter 53 is used to monitor and control the dissolved oxygen level in the aerobic treatment unit to ensure that microorganisms have enough oxygen to degrade organic matter.

[0104] Furthermore, the equipment area 5 also includes a frequency converter control device 54;

[0105] The frequency converter control device 54 is electrically connected to both the dissolved oxygen meter 53 and the dissolved oxygen supply device. Based on the detection data from the dissolved oxygen meter 53, the frequency converter control device 54 controls the dissolved oxygen supply device to maintain the dissolved oxygen concentration in the first aerobic tank 31 at 0.8 mg / L to 1.2 mg / L and the dissolved oxygen concentration in the second aerobic tank 32 at 0.4 mg / L to 0.6 mg / L.

[0106] The aforementioned frequency converter 54 is an electrical device used to control the speed of a motor. It adjusts the operating speed of the motor by changing the frequency of the power supply to the motor.

[0107] In the wastewater biological nitrogen and phosphorus removal system 100 provided in this embodiment, the frequency converter control device 54 is used for:

[0108] The operating speed of the dissolved oxygen supply device 52 is controlled to regulate the dissolved oxygen level in the aeration system.

[0109] In addition, the operation of water pumps in the pumping station can be controlled to adapt to different water flow requirements.

[0110] In the biological nitrogen and phosphorus removal system 100 for wastewater with low dissolved oxygen and high sludge concentration in this embodiment of the application, the dissolved oxygen meter 53 is used to monitor the dissolved oxygen concentration in the first aerobic tank 31 and the second aerobic tank 32. Based on the monitoring data, the dissolved oxygen concentration can be precisely controlled by cooperating with the frequency converter 54 and the blower 521 to optimize wastewater treatment efficiency and reduce energy consumption.

[0111] Furthermore, the dissolved oxygen supply device includes a blower 521 and a flow meter 522 connected to the blower 521.

[0112] As described above, the flow meter 522 is an instrument used to measure the flow rate of fluids. It can measure the volume or mass of fluid flowing through a pipe or channel within a certain time. In wastewater treatment systems, the flow meter 522 is used to ensure accurate control and monitoring of the flow of various fluids, including but not limited to:

[0113] Influent flow rate: Monitor the flow rate of sewage entering the sewage treatment system to ensure the uniformity and continuity of the treatment process.

[0114] Return flow rate: This measures the flow rate of sludge returned from the settling tank to the anaerobic tank, which is crucial for maintaining sludge concentration and microbial activity in the system.

[0115] Aeration flow rate: In this invention, the flow meter 522 is connected to the blower 521 to measure the air flow rate in the aeration system, ensuring that the dissolved oxygen level in the aerobic tank is properly regulated.

[0116] Discharge flow rate: The flow rate of treated water discharged into the body is monitored to ensure compliance with the discharge standards and requirements of the wastewater treatment plant.

[0117] The effects of flow meter 522 in the overall wastewater treatment system include:

[0118] Precise control: By monitoring and adjusting the flow rate in real time, the stability and efficiency of the wastewater treatment process are ensured.

[0119] Optimized operation: Adjust equipment operating status based on actual flow rate to achieve energy savings and reduce operating costs. Process monitoring: Flow data can be used to monitor the entire wastewater treatment process, enabling timely detection and resolution of potential problems.

[0120] Data logging: Records flow rate changes, providing historical data support for system operation and helping to analyze and improve processing technology.

[0121] Safety safeguards: Preventing decreased processing efficiency or equipment damage due to excessively high or low flow rates.

[0122] In wastewater treatment systems with low dissolved oxygen and high sludge concentration, blower 521 increases the dissolved oxygen level in the aerobic tank by supplying air, while flow meter 522 precisely controls and displays the air flow. The two work together to achieve precise control of dissolved oxygen levels, thereby optimizing wastewater treatment performance and reducing energy consumption.

[0123] Furthermore, the dissolved oxygen supply equipment can be in two sets: a blower 521 in the first aerobic tank 31 and a flow meter 522 connected to the blower 521, and a blower 521 in the second aerobic tank 32 and a flow meter 522 connected to the blower 521. Then, the frequency converter control device 54 can be electrically connected to the two blowers 521 and the flow meter 522 respectively via lines.

[0124] Furthermore, the equipment area 5 also includes a first return pump 57 and a first return pipeline 58;

[0125] One end of the first reflux pipeline 58 is connected to the solid-liquid separation zone 4, and the other end is connected to the anaerobic zone 1;

[0126] The first reflux pump 57 is installed on the first reflux pipeline 58 to facilitate the return of concentrated sludge in the solid-liquid separation zone 4 to the anaerobic zone 1.

[0127] As mentioned above, the wastewater biological phosphorus removal system is equipped with a first reflux pump 57 and a first reflux pipeline 58, which play an important role in improving the system's treatment efficiency and system stability.

[0128] Specifically, the purpose and effects of reflux include:

[0129] By returning the concentrated sludge from solid-liquid separation zone 4 (typically a settling tank) to anaerobic zone 1, the sludge concentration throughout the bioreactor system can be maintained. This is crucial for maintaining the activity and quantity of microorganisms in the system.

[0130] Returning sludge increases the concentration of microorganisms in the reactor, thereby improving the rate of reactions such as organic matter degradation and nitrogen and phosphorus removal.

[0131] During the denitrification process, the return sludge helps to provide sufficient nitrates, which are reduced to nitrogen gas under anoxic or anaerobic conditions, thus achieving denitrification.

[0132] The return sludge increases the amount of sludge in anaerobic zone 1, which is beneficial for polyphosphate-accumulating bacteria to release phosphorus under anaerobic conditions and then absorb excess phosphorus under aerobic conditions, thereby achieving phosphorus removal.

[0133] Recirculation helps stabilize system operation and reduces the impact of influent load fluctuations on the system.

[0134] By controlling the reflux ratio, the sludge residence time (SRT) in the system can be adjusted to meet different treatment needs.

[0135] High sludge concentration operation helps extend sludge age, promotes the death of microorganisms and further decomposition of metabolic products, thereby reducing the production of excess sludge.

[0136] In the low dissolved oxygen, high sludge concentration wastewater biological nitrogen and phosphorus removal system 100 of this application embodiment, the first return pump 57 and the first return pipeline 58 are set up to achieve the above-mentioned purpose. By returning the concentrated sludge in the sedimentation tank to the anaerobic zone 1, the entire wastewater treatment process is optimized, the nitrogen and phosphorus removal efficiency is improved, and energy consumption and operating costs are reduced.

[0137] Furthermore, in the wastewater biological nitrogen and phosphorus removal system 100, the concentration of sludge therein is controlled to be maintained at 8000mg / L to 10000mg / L by the first return pump 57 and the first return pipeline 58.

[0138] The reflux ratio of the first reflux pump 57 is 100%.

[0139] The aforementioned recirculation ratio of the first recirculation pump 57 ensures that the sludge concentration in the system remains within the optimal range to support a highly efficient biological treatment process. This maintains sludge activity and microbial community diversity, improving the system's treatment capacity and resistance to shock loads. By adjusting the recirculation ratio, the sludge retention time (sludge age) in the system can be controlled, thereby affecting treatment efficiency and the dynamics of the microbial community.

[0140] As mentioned above, sludge concentration directly affects the efficiency of biological treatment because microorganisms in sludge are the main participants in reactions such as organic matter degradation and nitrogen and phosphorus removal. High sludge concentration can increase the treatment capacity of a bioreactor because more microorganisms are involved in the reaction. Sludge concentration also affects settling performance; an appropriate sludge concentration helps form a good sludge layer in the settling tank, improving solid-liquid separation efficiency.

[0141] In the wastewater biological nitrogen and phosphorus removal system 100, the sludge concentration is controlled at 8000 mg / L to 10000 mg / L by the first return pump 57 and the first return pipeline 58. Such a high sludge concentration helps to: improve the system's biodegradation capacity and nitrogen and phosphorus removal efficiency; reduce the production of excess sludge and lower the cost of sludge treatment and disposal; and enhance the system's adaptability to fluctuations in influent water quality and improve its resistance to shock loads.

[0142] The first return pump 57 has a return ratio of 100%, meaning that the amount of sludge returned from the settling tank to the anaerobic zone 1 is equal to the amount of sludge entering the settling tank. This full return strategy helps maintain the uniformity and stability of sludge concentration throughout the system, ensuring efficient system operation.

[0143] Furthermore, the equipment area 5 also includes a second return pump 55 and a second return pipeline 56;

[0144] One end of the second return pipeline 56 is connected to the first anoxic tank 21, and the other end is connected to the second aerobic tank 32;

[0145] The second return pump 55 is installed on the second return pipeline 56 to facilitate the return of wastewater in the second aerobic tank 32 to the first anoxic tank 21.

[0146] Furthermore, the reflux ratio of the second reflux pump 55 is 300%.

[0147] The second return pump 55 returns the sludge-water mixture (containing a large amount of nitrate) in the second aerobic tank 32 to the first anoxic tank 21 through the second return pipeline 56. This internal return is a key step in achieving denitrification, because under anoxic conditions, nitrate can be reduced to nitrogen gas, thereby being removed from the wastewater.

[0148] By recirculating the nitrate-rich mixed liquor back into the anoxic tank, the concentration of nitrate in the anoxic tank is increased, providing more electron acceptors for denitrifying bacteria and thus improving nitrogen removal efficiency.

[0149] In the anoxic tank, the returned nitrates react with organic matter in the wastewater to form nitrogen gas. This process, known as simultaneous nitrification-denitrification (SND) or denitrification for phosphorus removal, helps improve nitrogen removal efficiency. The second return pump 55 helps maintain the flowability of the mixed liquor throughout the biological treatment system, ensuring effective connection and mass transfer between treatment units. By adjusting the flow rate of the second return pump 55, the nitrate load entering the anoxic tank can be regulated to adapt to different treatment needs and influent conditions. Increasing the number of sludge cycles within the system helps improve sludge activity and biological treatment efficiency. Internal recirculation helps balance sludge distribution within the system, reducing the impact of load fluctuations or changes in operating conditions on system stability.

[0150] In the wastewater biological nitrogen and phosphorus removal system 100, the second return pump 55 and the second return pipeline 56 are installed to achieve a more efficient nitrogen removal effect while maintaining the system's high-efficiency operation and stability. By precisely controlling the return ratio and return flow rate, the entire biological nitrogen removal process can be optimized, improving the overall performance of wastewater treatment.

[0151] Furthermore, this application embodiment also provides a wastewater treatment method based on the wastewater biological nitrogen and phosphorus removal system 100 as described in any of the foregoing embodiments, the wastewater treatment method comprising:

[0152] S1, anaerobic activated sludge is added to the anaerobic zone 1 of the biological nitrogen and phosphorus removal system 100, anoxic activated sludge is added to the denitrification anoxic zone 2 of the biological nitrogen and phosphorus removal system 100, and aerobic activated sludge is added to the low dissolved oxygen aeration zone 3 of the biological nitrogen and phosphorus removal system 100.

[0153] Activated sludge contains a large number of microorganisms, which are crucial for processes such as the degradation of organic matter and the removal of nitrogen and phosphorus. Adding activated sludge is to quickly start up and maintain the biological treatment capacity of the wastewater treatment system.

[0154] S2, control the inlet pipe 6 to discharge sewage into anaerobic zone 1;

[0155] Wastewater first enters anaerobic zone 1, where, due to the lack of dissolved oxygen, the main processes involve the anaerobic decomposition of organic matter and the release of phosphorus by polyphosphate-accumulating bacteria. This step is crucial for the subsequent phosphorus removal process.

[0156] S3, dissolved oxygen is provided by dissolved oxygen supply device 52 in low dissolved oxygen aeration zone 3 through device area 5, and stirring device 51 in device area 5 is controlled to stir in anaerobic zone 1 and denitrification anoxic zone 2.

[0157] After passing through the anaerobic zone 1, the wastewater enters the denitrification anoxic zone 2 for denitrification and dephosphorization reactions. After the reaction, it enters the low dissolved oxygen aeration zone 3 for nitrification and polyphosphate reaction, and then enters the solid-liquid separation zone 4 for solid-liquid separation treatment. The supernatant after treatment is discharged through the drain pipe 7.

[0158] As described above, in the low dissolved oxygen aeration zone 3, the concentration of dissolved oxygen is precisely controlled by dissolved oxygen supply equipment 52 (such as blower 521) and flow meter 522 to support the metabolic activities of aerobic microorganisms.

[0159] Meanwhile, the mixing equipment 51 mixes the wastewater in the anaerobic zone 1 and the denitrification anoxic zone 2 to ensure that the microorganisms are in full contact with the pollutants in the wastewater and improve the treatment efficiency.

[0160] As described above, after the wastewater flows out of the anaerobic zone 1, it enters the denitrification anoxic zone 2, where denitrification and dephosphorization reactions take place. Nitrates are converted into nitrogen gas to achieve denitrification, while phosphorus is converted into polyphosphate and absorbed by the carbon source in the microorganisms.

[0161] The wastewater that has undergone denitrification treatment then enters the low dissolved oxygen aeration zone 3 to carry out nitrification, converting ammonia nitrogen into nitrate.

[0162] The above-mentioned biologically treated mixed liquid enters the solid-liquid separation zone 4 (such as a sedimentation tank), where the sludge and the treated supernatant are separated by gravity sedimentation.

[0163] The supernatant after separation, i.e. the treated water, is discharged from the system through drain pipe 7, meeting the discharge standards.

[0164] The wastewater treatment method provided in this application achieves highly efficient removal of organic matter, nitrogen, and phosphorus from wastewater through an orderly, multi-stage biological treatment process and precise control of dissolved oxygen concentration and mixing conditions. This method combines anaerobic, anoxic, and aerobic environments, promoting the degradation of organic matter and the effective removal of nitrogen and phosphorus. The design with low dissolved oxygen and high sludge concentration reduces aeration energy consumption and improves energy efficiency, meeting the requirements of modern wastewater treatment for high efficiency, energy saving, and environmental protection. The entire treatment process operates continuously, ensuring the continuity and stability of wastewater treatment. Furthermore, precise control of equipment zone 5 optimizes the treatment effect, meeting stringent discharge standards.

[0165] Furthermore, in the wastewater biological nitrogen and phosphorus removal system 100, the concentration of sludge is controlled to be maintained at 8000 mg / L to 10000 mg / L by the first return pump 57 and the first return pipeline 58.

[0166] Furthermore, the reflux ratio of the first reflux pump 57 is 100%;

[0167] Furthermore, the frequency conversion control device 54 of the equipment area 5, based on the detection data of the dissolved oxygen meter 53 installed in the first aerobic tank 31 and the second aerobic tank 32 in the low dissolved oxygen aeration zone 3, controls the dissolved oxygen supply device to make the dissolved oxygen concentration in the first aerobic tank 31 between 0.8 mg / L and 1.2 mg / L, and the dissolved oxygen concentration in the second aerobic tank 32 between 0.4 mg / L and 0.6 mg / L, respectively.

[0168] Furthermore, the wastewater in the second aerobic tank 32 is returned to the first anoxic tank 21 of the denitrification anoxic zone 2 via the second return pump 55 in the equipment area 5 through the second return pipeline 56.

[0169] Furthermore, the reflux ratio of the second reflux pump 55 is 300%;

[0170] Furthermore, the concentrated sludge in the solid-liquid separation zone 4 is returned to the anaerobic zone 1 by the first return pump 57 in the equipment zone 5.

[0171] The above settings can enhance the ability of microorganisms in the first anaerobic tank to take up organic matter and release phosphate. They can promote simultaneous nitrification and denitrification phosphorus removal reactions in the first anoxic tank 21 and the second anoxic tank 22 to remove nitrogen and phosphorus. They can also carry out nitrification and polyphosphate reaction in the first aerobic tank 31 and the second aerobic tank 32 to remove organic matter. No additional carbon source is required, the aeration intensity is low, the operating energy consumption is low, and the treatment effect is good.

[0172] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0173] Example 1: Long-term test

[0174] In this embodiment, the wastewater biological nitrogen and phosphorus removal system has undergone long-term testing. The wastewater biological nitrogen and phosphorus removal system includes:

[0175] The anaerobic tank (anaerobic zone), the first anoxic tank, the second anoxic tank, the first aerobic tank, the second aerobic tank, the sedimentation tank (solid-liquid separation zone), and the equipment area are connected in sequence.

[0176] The anaerobic tank contains anaerobic activated sludge; both the first and second anoxic tanks contain anoxic activated sludge; and both the first and second aerobic tanks contain aerobic activated sludge.

[0177] Both the first aerobic tank and the second aerobic tank are equipped with dissolved oxygen meters.

[0178] The equipment area also includes frequency converter control equipment and dissolved oxygen supply equipment; the dissolved oxygen supply equipment includes a blower and a flow meter connected to the blower.

[0179] The frequency converter control device is electrically connected to both the dissolved oxygen meter and the dissolved oxygen supply device. Based on the detection data from the dissolved oxygen meter, the frequency converter control device controls the dissolved oxygen supply device to maintain the dissolved oxygen concentration in the first aerobic tank at 0.8 mg / L to 1.2 mg / L and the dissolved oxygen concentration in the second aerobic tank at 0.4 mg / L to 0.6 mg / L.

[0180] The equipment area also includes a first reflux pump and a first reflux pipeline; one end of the first reflux pipeline is connected to the solid-liquid separation zone and the other end is connected to the anaerobic zone; the first reflux pump is located on the first reflux pipeline to facilitate the return of concentrated sludge from the solid-liquid separation zone to the anaerobic zone.

[0181] In the biological nitrogen and phosphorus removal system for wastewater, the concentration of sludge is controlled to be maintained at 8000 mg / L to 10000 mg / L by the first return pump and the first return pipeline.

[0182] The reflux ratio of the first reflux pump is 100%.

[0183] The equipment area also includes a second return pump and a second return pipeline; one end of the second return pipeline is connected to the first anoxic tank, and the other end is connected to the second aerobic tank; the second return pump is installed on the second return pipeline to facilitate the return of wastewater from the second aerobic tank to the first anoxic tank. The return ratio of the second return pump is 300%.

[0184] Experiments have shown that:

[0185] like Figure 2 As shown, from day 0 to day 15 of the experiment, a traditional wastewater treatment process was used, with a sludge concentration of 3000 mg / L in the system and dissolved oxygen concentration in the aerobic tank controlled above 2.0 mg / L. The system achieved an average removal rate of 89.7% for influent organic matter COD and an average effluent COD of 36.1 mg / L; an average removal rate of 68.1% for total nitrogen and an average effluent total nitrogen of 10.07 mg / L. It should be noted that the operating conditions of the biological nitrogen and phosphorus removal system were not adopted during this stage, and the influent had sufficient carbon source for denitrification (influent C / N ratio = 13.0 from day 0 to day 15). However, the orthophosphate content in the effluent was high during this stage, with an average orthophosphate content of 3.91 mg / L, far exceeding the Class A standard of 0.5 mg / L specified in GB 18918-2002, the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants".

[0186] To achieve efficient nitrogen and phosphorus removal, the wastewater biological nitrogen and phosphorus removal system described in this embodiment is used from day 16 to day 45. The dissolved oxygen concentration in the first aerobic tank is controlled at 0.8–1.2 mg / L, the dissolved oxygen concentration in the second aerobic tank is controlled at 0.4–0.6 mg / L, the sludge concentration in each tank of the system is controlled at 8000–10000 mg / L, and the influent carbon-nitrogen ratio is reduced to C / N = 4.0.

[0187] During this phase, the wastewater biological nitrogen and phosphorus removal system achieved an average removal rate of 90.4% for influent organic matter (COD) and an average effluent COD of 24.1 mg / L; an average removal rate of 77.9% for total nitrogen and an average effluent total nitrogen of 13.68 mg / L; and an average removal rate of 52.1% for orthophosphate and an average effluent total nitrogen of 1.41 mg / L. Comparisons show that the wastewater biological nitrogen and phosphorus removal system significantly improved the removal efficiency of organic matter, total nitrogen, and orthophosphate.

[0188] From day 46 to day 75, the biological nitrogen and phosphorus removal system further reduced the pollution load of organic matter and nitrogen sources in the influent while maintaining a low carbon-to-nitrogen ratio, better meeting the actual operating conditions of the municipal wastewater treatment plant. During the long-term operation of the biological nitrogen and phosphorus removal system, the average effluent COD was 28.3 mg / L, the average total nitrogen was 9.17 mg / L, and the average orthophosphate was 0.15 mg / L. This demonstrates that the biological nitrogen and phosphorus removal system can achieve highly efficient purification of municipal wastewater with a low carbon-to-nitrogen ratio, completing simultaneous nitrogen and phosphorus removal without the addition of additional carbon sources or other reagents. Furthermore, while ensuring removal efficiency, the biological nitrogen and phosphorus removal system reduces aeration energy consumption by approximately 55% compared to traditional treatment systems and methods.

[0189] Example 2: Along-the-path experiment

[0190] In this embodiment, to further elucidate the material transformation process within the wastewater biological nitrogen and phosphorus removal system, monitoring experiments were also conducted on various pollutants along the process and internal carbon source components, such as... Figure 3 As shown. Regarding the theoretical conversion rate φ of the internal carbon source in the system described in Example 1. COD and measured COD conversion rate σ along the process COD The calculation formula is as follows:

[0191]

[0192] Calculating the internal carbon source conversion rate can assess the metabolic activity of microorganisms in the anaerobic zone, particularly the activity of glycogen-accumulating microorganisms (GAOs) and polyphosphate-accumulating bacteria (PAOs). These microorganisms decompose endogenous carbon sources in the first and second anoxic zones, providing carbon source support for the denitrification process. Combining the changes in COD and nitrogen source concentration in each region of the system, φ can be obtained respectively. COD =75.91%, σ COD =72.40%. The calculation results show that in the biological nitrogen and phosphorus removal system for wastewater, the microorganisms have high metabolic activity and can effectively utilize the carbon source in the influent, proving that the biological nitrogen and phosphorus removal system for wastewater has strong application value for treating municipal wastewater with low carbon-to-nitrogen ratio and limited carbon sources.

[0193] In biological nitrogen and phosphorus removal systems for wastewater, assimilation accounts for 86.46% of ammonia nitrogen removal. Specifically, assimilation in the anaerobic, anoxic, and sedimentation tanks accounts for 17.52%, 68.07%, and 0.87% of ammonia nitrogen removal, respectively. Nitrification accounts for only 13.54% of ammonia nitrogen removal. This means that even with lower dissolved oxygen levels in the aerobic tank, ammonia nitrogen removal requirements can be met using biological nitrogen and phosphorus removal systems for wastewater. Therefore, biological nitrogen and phosphorus removal systems for wastewater are more suitable for the stable operation of low dissolved oxygen aeration systems.

[0194] The corresponding calculation formula is as follows:

[0195] (1) The contribution rate of ammonia nitrogen removal by assimilation in the anaerobic tank:

[0196]

[0197] (2) The contribution rate of ammonia nitrogen removal by assimilation in the anoxic tank:

[0198]

[0199] (3) The contribution rate of nitrification in the aerobic tank to the removal of ammonia nitrogen:

[0200]

[0201] (4) The assimilation effect of the sedimentation tank contributes to the removal of ammonia nitrogen:

[0202]

[0203] According to the law of conservation of mass, in the biological nitrogen and phosphorus removal system for wastewater, the nitrate concentrations in the anaerobic and anoxic tanks decreased by 10.64 mg / L and 17.19 mg / L, respectively. Subsequently, under the action of ammonia-oxidizing bacteria (AOB and NOB), ammonia nitrogen and nitrite were oxidized to nitrate. The denitrification reaction occurring in the anaerobic tank and the anoxic zone contributed 38.23% and 61.77% of the nitrogen removal, respectively.

[0204] The nitrate removal rate in the first anoxic tank was 57.02%, and the COD content required for denitrification in this area can be calculated as ΔCOD. de = 9.84 mg / L. Based on the COD content changes measured along the process, the COD consumption in the first anoxic tank is ΔCOD. 第一缺氧池 =4.64 mg / L, indicating that microorganisms other than traditional denitrifying bacteria participated in the denitrification process. Based on the changes in phosphate and polyhydroxyalkanoates (PHA) content, the phosphate concentration after phosphorus release by polyphosphate-accumulating bacteria in the anaerobic tank was 33.36 mg / L, while the phosphate concentration in the mixed liquor returned from the second aerobic tank to the first anoxic tank was 0.15 mg / L. Assuming that no phosphorus removal-related reactions occurred in the anoxic tank, the theoretical phosphate content in the first anoxic tank can be calculated using the material conservation equation as PO42-. 3- =13.44 mg / L, which is 65.63% different from the measured phosphate concentration of 4.62 mg / L in the first anoxic tank, indicating that a denitrification phosphorus removal process exists in the first anoxic tank.

[0205] In the first anoxic tank, the glycogen content increased to 18.75 mg / gSS, and peaked in the second anoxic tank. This is likely due to the denitrifying polyphosphate-accumulating bacteria (DPAOs) utilizing some of the phosphorus phosphate (PHA) to convert into glycogen for their growth under anoxic conditions. In the first aerobic tank, the polyphosphate-accumulating bacteria obtained energy by degrading PHA and taking up phosphate PO4 from the external environment under aerobic conditions. 3- It is then converted into polyphosphate (Poly-P) and consumes glycogen for its growth and reproduction. This aligns with the experimental result of PO4 in the first aerobic tank. 3- The content decreased by 85.15%, and the glycogen content decreased by 27.34%. In the biological nitrogen and phosphorus removal system for wastewater, the nitrogen removal contribution rate of the denitrification phosphorus removal process accounts for 52.85% of the denitrification nitrogen removal, which means that the biological nitrogen and phosphorus removal system for wastewater still has the technical advantage of efficient simultaneous nitrogen and phosphorus removal under the condition of insufficient carbon source.

[0206] The relevant calculation formulas are as follows:

[0207] (1) The nitrate concentration in the anaerobic zone decreased:

[0208]

[0209] (2) The nitrate concentration in the first anoxic tank decreased:

[0210]

[0211] (3) The contribution rate of denitrification to nitrogen removal in the anaerobic tank:

[0212]

[0213] (4) The contribution rate of denitrification in the first anoxic tank:

[0214]

[0215] (5) Nitrate removal rate in the first anoxic tank:

[0216]

[0217] (6) Theoretical COD consumption value of the denitrification process in the first anoxic tank:

[0218]

[0219] (7) Actual COD consumption during the denitrification process in the first anoxic tank:

[0220]

[0221] (8) The nitrogen removal contribution rate of the denitrification and phosphorus removal process in the first anoxic tank:

[0222]

[0223] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0224] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A wastewater treatment method, characterized in that, Wastewater biological nitrogen and phosphorus removal systems include: The anaerobic zone, denitrification anoxic zone, low dissolved oxygen aeration zone, solid-liquid separation zone and equipment zone are connected sequentially along the direction of sewage flow. The anaerobic zone contains anaerobic activated sludge; the denitrification anoxic zone contains anoxic activated sludge; and the low dissolved oxygen aeration zone contains aerobic activated sludge. The anaerobic zone, the denitrification anoxic zone, and the low dissolved oxygen aeration zone all maintain high sludge concentrations during operation. The anaerobic zone is an environment without dissolved oxygen and is connected to an inlet pipe for discharging wastewater. The solid-liquid separation zone is equipped with a drainage pipe; The equipment area includes stirring equipment located in the anaerobic zone and the denitrification anoxic zone, as well as dissolved oxygen supply equipment located in the low dissolved oxygen aeration zone; The denitrification anoxic zone includes a first anoxic tank and a second anoxic tank. The anaerobic zone is connected to the first anoxic tank via an overflow hole, so that the first anoxic tank can receive the sewage flowing out of the anaerobic zone. One end of the second anoxic tank is connected to the first anoxic tank, and the other end is connected to the low dissolved oxygen aeration zone; The low dissolved oxygen aeration zone includes a first aerobic tank and a second aerobic tank connected in sequence. The first aerobic tank is connected to the second anoxic tank; The second aerobic tank is connected to the solid-liquid separation zone via an overflow pipe; The equipment area also includes dissolved oxygen meters installed in the first aerobic tank and the second aerobic tank; The equipment area also includes frequency converter control equipment; The frequency converter control device is electrically connected to both the dissolved oxygen meter and the dissolved oxygen supply device. Based on the detection data from the dissolved oxygen meter, the frequency converter control device controls the dissolved oxygen supply device to maintain the dissolved oxygen concentration in the first aerobic tank at 0.8 mg / L to 1.2 mg / L and the dissolved oxygen concentration in the second aerobic tank at 0.4 mg / L to 0.6 mg / L. The equipment area also includes a first reflux pump and a first reflux pipeline; One end of the first reflux pipeline is connected to the solid-liquid separation zone, and the other end is connected to the anaerobic zone; The first return pump is installed on the first return pipeline to facilitate the return of concentrated sludge from the solid-liquid separation zone to the anaerobic zone; In the biological nitrogen and phosphorus removal system for wastewater, the concentration of sludge is controlled to be maintained at 8000 mg / L~10000 mg / L by the first return pump and the first return pipeline. The reflux ratio of the first reflux pump is 100%; The equipment area also includes a second reflux pump and a second reflux pipeline; One end of the second return pipeline is connected to the first anoxic tank, and the other end is connected to the second aerobic tank; The second return pump is installed on the second return pipeline to facilitate the return of wastewater from the second aerobic tank to the first anoxic tank. The wastewater treatment method includes: S1, anaerobic activated sludge is added to the anaerobic zone of the biological nitrogen and phosphorus removal system for wastewater, anoxic activated sludge is added to the denitrification anoxic zone of the biological nitrogen and phosphorus removal system for wastewater, and aerobic activated sludge is added to the low dissolved oxygen aeration zone of the biological nitrogen and phosphorus removal system for wastewater. S2, control the inlet pipe to discharge wastewater into the anaerobic zone; S3, through the equipment area, the dissolved oxygen supply equipment in the low dissolved oxygen aeration zone is controlled to provide dissolved oxygen, and the stirring equipment in the equipment area is controlled to stir in the anaerobic zone and the denitrification anoxic zone; After passing through the anaerobic zone, the wastewater enters the denitrification-anoxic zone for simultaneous nitrification-denitrification nitrogen removal and denitrification phosphorus removal reactions. After the reaction, it enters the low dissolved oxygen aeration zone for nitrification and polyphosphate reaction, and then enters the solid-liquid separation zone for solid-liquid separation treatment. The treated supernatant is discharged through the drain pipe.

2. The wastewater treatment method as described in claim 1, characterized in that, The reflux ratio of the second reflux pump is 300%.

3. The wastewater treatment method as described in claim 1, characterized in that, The dissolved oxygen supply equipment includes a blower and a flow meter connected to the blower.

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