Biological nitrogen and phosphorus removal system for sewage

Abstract

The utility model provides a biological nitrogen and phosphorus removal system for sewage, and relates to the technical field of sewage treatment. The system comprises an anaerobic zone, a denitrification anoxic zone, a low dissolved oxygen aeration zone, a solid-liquid separation zone and an equipment zone which are sequentially communicated along a sewage flowing direction, all biochemical areas in the system are operated at high sludge concentration; the anaerobic zone is connected with a water inlet pipe; the solid-liquid separation area is provided with a drainage pipe; and the equipment area comprises stirring equipment and dissolved oxygen providing equipment. According to the biological nitrogen and phosphorus removal system for the sewage, provided by the utility model, the organic matter intake capacity and phosphate release capacity of microorganisms in the anaerobic zone can be improved, and synchronous nitrification and denitrification and denitrification phosphorus removal reaction can be promoted in the denitrification anoxic tank to remove nitrogen and phosphorus; synchronous nitrification and denitrification and phosphorus accumulation reaction can be performed in the low-dissolved-oxygen aeration area, organic matter removal is realized, no additional carbon source is needed, the aeration intensity is small, the operation energy consumption is low, and the treatment effect is good.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of sewage treatment, specifically, relate to a sewage biological denitrification and phosphorus removal system. BACKGROUND

[0002] Sewage treatment is a key link in the field of environmental protection, especially under the background of rapid social and economic development and increasing demand for water environment protection. The eutrophication problem caused by excessive discharge of nitrogen and phosphorus has become one of the most severe challenges in current water pollution control.

[0003] Currently, the processes commonly used in municipal wastewater treatment plants include A2 / O process, oxidation ditch process and SBR process, etc. These processes play an important role in wastewater treatment, but also have some limitations. First, the treatment energy consumption is high, especially in the traditional activated sludge process, in order to maintain a high dissolved oxygen content in the aeration tank, a large amount of energy is consumed for aeration. Second, the treatment effluent effect is not stable, when the carbon source in the influent is insufficient, the microbial denitrification process lacks the necessary electron donor, resulting in difficulty in meeting the total nitrogen discharge standard, which not only needs additional carbon source, but also may need to increase the subsequent advanced treatment process, thereby increasing the operation cost and engineering investment. Finally, the sludge produced by the existing process is large, and the cost of sludge treatment and disposal is high, which brings not small challenge to the operation of the wastewater treatment plant.

[0004] Sewage biological treatment technology relies on activated sludge microorganisms to participate in various reactions under different conditions to achieve denitrification and phosphorus removal in wastewater treatment. However, there are still some defects in the actual application of the existing technology. For example, high energy consumption of aeration process, unstable effluent effect and high sludge yield, these problems not only increase the operation cost, but also restrict the further development and application of wastewater treatment technology.

[0005] Low dissolved oxygen aeration and high sludge concentration operation are two effective methods to improve the efficiency of wastewater treatment found in recent research. Under low dissolved oxygen conditions, the diversity of activated sludge microbial community is increased, which helps to improve the impact load resistance of wastewater treatment. High sludge concentration operation can improve the degradation efficiency of microorganisms to organic pollutants, realize efficient cooperation of various metabolic pathways such as simultaneous nitrification and denitrification and denitrification and phosphorus removal, so as to improve the removal effect of nitrogen and phosphorus. At the same time, high sludge concentration can prolong the sludge age, promote the death of microorganisms and further decomposition of metabolic products, reduce the production of excess sludge, and reduce the cost of sludge treatment and disposal.

[0006] Although these research findings provide new ideas for sewage treatment technology, it is urgent to develop a sewage treatment process combining low-dissolved oxygen aeration and high-sludge concentration operation to solve the problems of unstable treatment effect, high energy consumption and high cost of existing technology under the condition of limited carbon source in influent. This new process should be able to meet the synergistic effect demand of sewage treatment industry in pollution reduction and carbon reduction, and promote the development of sewage treatment technology to be more efficient, energy-saving and environmentally friendly. Content of the utility model

[0007] The first purpose of the utility model is to provide a sewage biological denitrification and phosphorus removal system and a sewage treatment method, which has the advantages of low operation energy consumption, good treatment effect and the like.

[0008] In order to achieve the above purpose of the utility model, the following technical scheme is adopted:

[0009] In a first aspect, the utility model provides a sewage biological denitrification and phosphorus removal system, comprising:

[0010] An anaerobic zone, a denitrification anoxic zone, a low-dissolved oxygen aeration zone and a solid-liquid separation zone and a device zone are sequentially communicated along the flow direction of sewage;

[0011] The anaerobic zone is provided with anaerobic activated sludge; the denitrification anoxic zone is provided with anoxic activated sludge; and the low-dissolved oxygen aeration zone is provided with aerobic activated sludge;

[0012] The anaerobic zone, the denitrification anoxic zone and the low-dissolved oxygen aeration zone all maintain high-sludge-concentration operation;

[0013] The anaerobic zone is a dissolved oxygen-free environment and is connected with an influent pipe for feeding sewage;

[0014] The solid-liquid separation zone is provided with a drain pipe;

[0015] The device zone comprises stirring equipment arranged in the anaerobic zone and the denitrification anoxic zone and dissolved oxygen providing equipment arranged in the low-dissolved oxygen aeration zone.

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

[0017] The anaerobic zone is connected with the first anoxic tank through an overflow hole, so that the first anoxic tank receives the sewage flowing out of the anaerobic zone;

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

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

[0020] The first aerobic tank is connected with the second anoxic tank.

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

[0022] In an optional embodiment, the equipment zone further comprises a dissolved oxygen meter arranged in the first aerobic tank and the second aerobic tank.

[0023] In an optional embodiment, the equipment zone further comprises a variable frequency control device.

[0024] The variable frequency control device is electrically connected with the dissolved oxygen meter and the dissolved oxygen providing device, and the variable frequency control device controls the dissolved oxygen providing device to make the dissolved oxygen concentration of the first aerobic tank be 0.8 mg / L-1.2 mg / L and the dissolved oxygen concentration of the second aerobic tank be 0.4 mg / L-0.6 mg / L based on the detection data of the dissolved oxygen meter.

[0025] In an optional embodiment, the dissolved oxygen providing device comprises a blower and a flow meter connected with the blower.

[0026] In an optional embodiment, the equipment zone further comprises a first reflux pump and a first reflux pipeline; one end of the first reflux pipeline is connected with the solid-liquid separation zone, and the other end is connected with the anaerobic zone.

[0027] The first reflux pump is arranged on the first reflux pipeline so as to reflux the concentrated sludge in the solid-liquid separation zone into the anaerobic zone.

[0028] In an optional embodiment, the concentration of the sludge in the sewage biological denitrification and phosphorus removal system is controlled to be 8000 mg / L-10000 mg / L through the first reflux pump and the first reflux pipeline.

[0029] The reflux ratio of the first reflux pump is 100%.

[0030] In an optional embodiment, the equipment zone further comprises a second reflux pump and a second reflux pipeline.

[0031] One end of the second reflux pipeline is connected with the first anoxic tank, and the other end is connected with the second aerobic tank.

[0032] The second reflux pump is arranged on the second reflux pipeline so as to reflux the wastewater in the second aerobic tank into the first anoxic tank.

[0033] In an optional embodiment, the reflux ratio of the second reflux pump is 300%.

[0034] Compared with the prior art, the sewage biological denitrification and phosphorus removal system can improve the organic matter uptake ability and phosphate release ability of microorganisms in the anaerobic zone, promote simultaneous nitrification and denitrification and denitrification phosphorus removal reactions in the denitrification anoxic tank to remove nitrogen and phosphorus, carry out simultaneous nitrification and denitrification and phosphorus accumulation reactions in the low-dissolved oxygen aeration zone, and achieve organic matter removal, without the need of additional carbon source, small aeration intensity, low operation energy consumption, and good treatment effect. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope of the present application.

[0036] Figure 1 It is a structure schematic diagram of the sewage biological denitrification and phosphorus removal system in the embodiments of the present application.

[0037] Figure 2 It is a water quality index change diagram of the sewage biological denitrification and phosphorus removal system in the embodiments of the present application.

[0038] Figure 3 It is a pollutant and internal carbon source component concentration change diagram of the sewage biological denitrification and phosphorus removal system in the embodiments of the present application.

[0039] REFERENCE NUMERALS:

[0040] 100, sewage biological denitrification 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 zone; 51, stirring equipment; 52, dissolved oxygen providing equipment; 521, air blower; 522, flow meter; 53, dissolved oxygen meter; 54, frequency conversion control equipment; 55, second reflux pump; 56, second reflux pipeline; 57, first reflux pump; 58, first reflux pipeline; 6, water inlet pipe; 7, drain pipe. DETAILED DESCRIPTION

[0041] As used herein:

[0042] “Prepared from” is synonymous with “comprising”. The terms “comprising”, “including”, “having” or “with” as used herein, are meant to be non-exhaustive inclusions. For example, a composition, step, method, article, or apparatus that comprises a listed element need not be limited to those elements, but can include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0043] The conjunctive word "comprising" does not exclude other elements or steps than those listed in a claim. The phrase "consisting essentially of" permits the inclusion of additional elements or steps that do not materially affect the basic and novel characteristics of the claimed application. The optional phrases "consisting of" and "consisting only of" exclude any element or step not specified in the claim.

[0044] When expressing a range, a preferred range, or a range of upper and lower preferred values in a series, it is to be understood that the disclosure specifically envisions all ranges formed from any pair of values between the upper and lower limits of the range, whether or not the range is explicitly stated or otherwise disclosed. For example, where a range of "1-5" is disclosed, the disclosure is to be interpreted to include ranges of "1-4," "1-3," "1-2," "1-2 and 4-5," "1-3 and 5," etc. When numerical ranges are disclosed, unless otherwise stated, the range is intended to include both the upper and lower values and all intervening values of the range, including integers within the range, unless the context clearly indicates otherwise.

[0045] In these embodiments, the parts and percentages described are by mass, unless otherwise indicated.

[0046] "Parts by mass" refers to a basic unit of measurement that represents the proportional relationship of the mass of multiple components, 1 part can represent any unit mass, such as 1 g, 2.689 g, etc. If we say that the mass of component A is a parts, and the mass of component B is b parts, it means that the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK, and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It must not be misunderstood that, unlike parts by mass, the sum of the parts by mass of all components is not limited to 100 parts.

[0047] "and / or" is used to indicate that one or both of the described situations can occur, for example, A and / or B includes (A and B) and (A or B).

[0048] Reference Figure 1 In the embodiments of the present application, a sewage biological denitrification and phosphorus removal system 100 is provided, comprising:

[0049] An anaerobic zone 1, a denitrification anoxic zone 2, a low-dissolved oxygen aeration zone 3, a solid-liquid separation zone 4, and an equipment zone 5 are sequentially connected in the flow direction of the sewage.

[0050] The anaerobic zone 1, the denitrification anoxic zone 2, and the low-dissolved oxygen aeration zone 3 are all operated at high sludge concentration.

[0051] The anaerobic zone 1 is provided with anaerobic activated sludge; the denitrification anoxic zone 2 is provided with anoxic activated sludge; the low-dissolved oxygen aeration zone 3 is provided with aerobic activated sludge;

[0052] The anaerobic zone 1 is a dissolved oxygen-free environment, and is connected with a water inlet pipe 6 for feeding sewage;

[0053] The solid-liquid separation zone 4 is provided with a drain pipe 7;

[0054] The equipment zone 5 includes a stirring equipment 51 provided in the anaerobic zone 1 and the denitrification anoxic zone 2, and a dissolved oxygen providing equipment 52 provided in the low-dissolved oxygen aeration zone 3.

[0055] In the field of sewage treatment technology, the 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 uptake organic matter in sewage without oxygen.

[0056] In this embodiment, the anaerobic tank is a key component of the low-dissolved oxygen high-sludge concentration sewage biological denitrification and phosphorus removal system 100, and its main functions include:

[0057] Organic matter uptake and phosphate release: In the anaerobic tank, microorganisms uptake organic matter in sewage and synthesize it into internal carbon sources, and release phosphate in the process. This step is crucial for subsequent phosphorus removal.

[0058] Improving denitrification efficiency: Anaerobic conditions help enhance the metabolic activity of certain microorganisms that can utilize organic matter as an electron donor for denitrification, thereby removing nitrogen in sewage.

[0059] Enhancing system stability: By pretreating in the anaerobic tank, the impact load resistance of the entire sewage treatment system to fluctuations in water quality can be improved.

[0060] Reducing sludge production: High-sludge-concentration operation helps to prolong the sludge age (SRT), promote the death of microorganisms and further decomposition of metabolic products, thereby reducing the production of residual sludge.

[0061] The anaerobic zone is combined with other treatment units such as low-dissolved oxygen aeration zone and anoxic zone to form a complete sewage treatment process. In the system of this embodiment, the anaerobic zone is connected in sequence with other tank bodies to achieve efficient denitrification and phosphorus removal.

[0062] The above-mentioned denitrification anoxic zone 2 is mainly used for denitrification and nitrogen removal in the system, and can also perform denitrification and phosphorus removal. Nitrate and nitrite (nitrogen oxides) are reduced to nitrogen as electron acceptors, thereby removing nitrogen from the wastewater. These tanks also help to decompose internal carbon sources in microorganisms, further removing phosphorus from the wastewater.

[0063] The above-mentioned low-dissolved oxygen aeration zone 3 has a high concentration of dissolved oxygen and mainly performs nitrification to convert ammonia nitrogen into nitrate. At the same time, under aerobic conditions, polyphosphorus bacteria can absorb phosphate and store it as polyphosphate, which helps to remove phosphorus from the wastewater during subsequent settling and reflux.

[0064] The above-mentioned second aerobic tank 32 has a low concentration of dissolved oxygen, which ensures that sufficient nitrate enters the first anoxic tank 21 while minimizing the dissolved oxygen content in the second reflux line to maintain stable anoxic conditions.

[0065] The wastewater biological denitrification and phosphorus removal system 100 also includes activated sludge in each zone, specifically including: anaerobic activated sludge in the anaerobic zone 1; anoxic activated sludge in the denitrification anoxic zone 2; and aerobic activated sludge in the low-dissolved oxygen aeration zone 3.

[0066] The anaerobic activated sludge, under anaerobic conditions, is mainly composed of anaerobic microorganisms such as anaerobic bacteria, hydrolytic bacteria, polysaccharide bacteria, and polyphosphorus bacteria. Its main function is to take up organic matter under anaerobic conditions while releasing phosphorus.

[0067] The anoxic activated sludge, under anoxic conditions, is mainly composed of microorganisms capable of denitrification, such as denitrifying bacteria and denitrifying phosphorus bacteria. Its main function is to perform denitrification to reduce nitrate to nitrogen, thereby removing nitrogen from the wastewater.

[0068] The aerobic activated sludge, under aerobic conditions, is mainly composed of aerobic microorganisms such as nitrifying bacteria and polyphosphorus bacteria. Its main function is to oxidize and decompose organic matter, nitrify ammonia nitrogen (convert it to nitrate), and absorb phosphorus by polyphosphorus bacteria (absorb and store phosphate).

[0069] Although the activated sludge in each zone differs in microbial composition and function, they are interconnected and dependent on each other throughout the wastewater treatment process. For example, the nitrification in the low-dissolved oxygen aeration zone 3 produces nitrate, which can serve as an electron acceptor for denitrification in the anoxic tank, while the phosphorus release in the anaerobic tank provides conditions for the phosphorus absorption in the aerobic tank.

[0070] In addition, the microbial community of activated sludge will adapt and evolve according to the change of environmental conditions. In the actual wastewater treatment system, further by the operation such as return sludge and adjusting the dissolved oxygen concentration, the formation and development of different microbial communities can be promoted, so as to optimize the treatment efficiency of the whole system.

[0071] The solid-liquid separation zone 4 is used to realize the separation of sludge and water. The solid-liquid separation zone 4 can adopt sedimentation technology, centrifugal technology, ultrafiltration technology, etc.

[0072] For example, the solid-liquid separation zone 4 is a sedimentation tank, which realizes the separation of sludge and treated water by gravity. The sedimentation tank makes the sludge particles in the mixed liquid after biological treatment settle at the bottom, and the supernatant (treated water) is discharged from the system, and the concentrated sludge part at the bottom is returned to the anaerobic tank, and the rest is discharged as residual sludge.

[0073] The equipment zone 5 can include a stirring equipment 51 and a dissolved oxygen providing equipment 52.

[0074] The equipment zone 5 is responsible for controlling the operation of the whole system, such as continuously, timing or real-time stirring of wastewater and sludge in the anaerobic zone 1 and the denitrification anoxic zone 2 by the stirring equipment 51, providing the required dissolved oxygen by the dissolved oxygen providing equipment 52, and monitoring the dissolved oxygen concentration to ensure the efficient and stable operation of the system.

[0075] The stirring equipment 51 can make the high-concentration activated sludge microorganisms in the anaerobic zone 1 and the anoxic zone fully react with organic matter, nitrogen, phosphorus and other substances in the wastewater through stirring paddles.

[0076] The dissolved oxygen providing equipment can be a blower 521, which can provide dissolved oxygen molecules by aeration treatment of sludge and wastewater.

[0077] The water inlet pipe 6 is used to introduce wastewater. The water outlet pipe 7 is used to lead the supernatant in the solid-liquid separation zone 4 out, and complete the wastewater treatment.

[0078] The wastewater biological denitrification and phosphorus removal system 100 provided in the embodiment of the application is a low-dissolved-oxygen high-sludge-concentration wastewater biological denitrification and phosphorus removal system 100, which can improve the ability of microorganisms in the anaerobic zone 1 to uptake organic matter and release phosphate, promote simultaneous nitrification and denitrification and denitrification and phosphorus removal reactions in the denitrification anoxic tank to remove nitrogen and phosphorus, and perform simultaneous nitrification and denitrification and phosphorus accumulation reactions in the low-dissolved-oxygen aeration zone 3 to remove organic matter without additional carbon source, with small aeration intensity, low operation energy consumption and good treatment effect.

[0079] Further, the denitrification anoxic zone 2 comprises a first anoxic tank 21 and a second anoxic tank 22; wherein the anaerobic zone 1 is connected with the first anoxic tank 21 through an overflow hole, so that the first anoxic tank 21 receives the sewage flowing out of the anaerobic zone 1.

[0080] One end of the second anoxic tank 22 is connected with the first anoxic tank 21, and the other end is connected with the low-dissolved-oxygen aeration zone 3.

[0081] The above-mentioned denitrification anoxic zone 2 can be divided into two sub-zones, i.e., the first anoxic tank 21 and the second anoxic tank 22. The two sub-zones 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.

[0082] The above-mentioned first anoxic tank 21 is connected with 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, flows upward and enters the first anoxic tank 21 through the overflow hole.

[0083] Further, the low-dissolved-oxygen aeration zone 3 comprises a first aerobic tank 31 and a second aerobic tank 32 connected in sequence;

[0084] The first aerobic tank 31 is connected with the second anoxic tank 22;

[0085] The second aerobic tank 32 is connected with the solid-liquid separation zone 4 through an overflow pipe.

[0086] The above-mentioned second anoxic tank 22, first aerobic tank 31, second aerobic tank 32, and solid-liquid separation zone 4 are connected in sequence.

[0087] The above-mentioned second anoxic tank 22 receives the sludge-water mixture from the first anoxic tank 21, and inputs the treated sludge-water mixture into the first aerobic tank 31 and the second aerobic tank 32. The second aerobic tank 32 is provided with an overflow pipe, and the sewage and sludge-water mixture in the second aerobic tank 32 flow upward and are input into the solid-liquid separation zone 4.

[0088] In an optional embodiment, the equipment zone 5 further comprises a dissolved oxygen meter 53 arranged in the first aerobic tank 31 and the second aerobic tank 32.

[0089] The above-mentioned dissolved oxygen meter 53 is an instrument for measuring the concentration of dissolved oxygen (DO) in water. Dissolved oxygen is the form of oxygen existing in water in a molecular state, and is an important water quality parameter for the survival of aquatic organisms and many water treatment processes.

[0090] In sewage treatment, the 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.

[0091] Further, the equipment area 5 also includes a variable frequency control device 54;

[0092] The variable frequency control device 54 is electrically connected to the dissolved oxygen meter 53 and the dissolved oxygen supply device, and based on the detection data of the dissolved oxygen meter 53, the variable frequency control device 54 respectively controls the dissolved oxygen supply device to make the dissolved oxygen concentration of the first aerobic tank 31 at 0.8mg / L~1.2mg / L, and the dissolved oxygen concentration of the second aerobic tank 32 at 0.4mg / L~0.6mg / L.

[0093] The above-mentioned variable frequency control device 54 is an electrical device for controlling the speed of the motor, which adjusts the running speed of the motor by changing the frequency of the power supply to the motor.

[0094] In the sewage biological denitrification and phosphorus removal system 100 provided in the embodiment of the present application, the variable frequency control device 54 is used to:

[0095] Control the running speed of the dissolved oxygen supply device 52 to adjust the dissolved oxygen level in the aeration system.

[0096] In addition, the operation of the water pump in the pump station can also be controlled to adapt to different water flow requirements.

[0097] In the low-dissolved-oxygen high-sludge-concentration sewage biological denitrification and phosphorus removal system 100 in the embodiment of the present 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, and under the premise of monitoring data, the precise control of the dissolved oxygen concentration can be realized through cooperation with the variable frequency control device 54 and the air blower 521, so as to optimize the sewage treatment efficiency and reduce energy consumption.

[0098] Further, the dissolved oxygen supply device includes an air blower 521 and a flow meter 522 connected to the air blower 521.

[0099] The above-mentioned flow meter 522 is an instrument for measuring the flow of fluid, which can measure the volume or mass of fluid flowing through a pipe or channel within a certain time. In the sewage treatment system, the flow meter 522 is used to ensure accurate control and monitoring of the flow of various fluids, including but not limited to:

[0100] Influent flow: monitoring the flow of sewage entering the sewage treatment system to ensure uniformity and continuity of the treatment process.

[0101] Return flow: measuring the sludge flow from the settling tank back to the anaerobic tank, which is crucial for maintaining sludge concentration and microbial activity in the system.

[0102] Aeration flow rate: In the utility model, flow meter 522 is connected with air blower 521, which is used for measuring the flow rate of air in the aeration system, to ensure that the dissolved oxygen level in the aerobic tank is properly adjusted.

[0103] Discharge flow rate: Monitor the flow rate of the treated water discharged to meet the discharge standards and requirements of the sewage treatment plant.

[0104] The effects of flow meter 522 in the overall sewage treatment system include:

[0105] Precise control: Real-time monitoring and adjustment of flow rate ensure the stability and efficiency of the sewage treatment process.

[0106] Optimized operation: Adjust the equipment operating state according to the actual flow rate to achieve energy saving and reduce operating costs.

[0107] Process monitoring: Flow data can be used to monitor the entire sewage treatment process, and problems that may arise can be found and solved in a timely manner.

[0108] Data recording: Record flow changes to provide historical data support for system operation, which helps to analyze and improve the treatment process.

[0109] Safety guarantee: Prevents the decline in treatment efficiency or equipment damage caused by excessive or insufficient flow rate.

[0110] In a sewage treatment system with low dissolved oxygen and high sludge concentration, air blower 521 provides air to increase the dissolved oxygen level in the aerobic tank, and flow meter 522 precisely controls and displays the air flow rate, both of which are used together to achieve precise control of the dissolved oxygen level, thereby optimizing the sewage treatment effect and reducing energy consumption.

[0111] In addition, further, the dissolved oxygen providing device can be two groups, respectively: the air blower 521 in the first aerobic tank 31 and the flow meter 522 connected with the air blower 521, and the air blower 521 in the second aerobic tank 32 and the flow meter 522 connected with the air blower 521, then the frequency control device 54 can be respectively electrically connected with the two air blowers 521 and flow meters 522 through lines.

[0112] Further, the device area 5 further comprises a first backflow pump 57 and a first backflow pipeline 58;

[0113] One end of the first backflow pipeline 58 is connected with the solid-liquid separation area 4, and the other end is connected with the anaerobic area 1;

[0114] The first backflow pump 57 is arranged on the first backflow pipeline 58, so as to backflow the concentrated sludge in the solid-liquid separation area 4 to the anaerobic area 1.

[0115] The first reflux pump 57 and the first reflux pipeline 58 are provided in the sewage biological denitrification and phosphorus removal system, which plays an important role in improving the treatment efficiency and system stability of the system.

[0116] Specifically, the purposes and effects of reflux include:

[0117] By refluxing the concentrated sludge in the solid-liquid separation zone 4 (usually a sedimentation tank) to the anaerobic zone 1, the sludge concentration of the entire biological reaction system can be maintained. This is crucial for maintaining the activity and quantity of microorganisms in the system.

[0118] The reflux sludge increases the concentration of microorganisms in the reactor, thereby increasing the rates of organic matter degradation, nitrogen and phosphorus removal, etc.

[0119] During the denitrification process, the reflux sludge helps to provide sufficient nitrate, which is reduced to nitrogen gas under anoxic or anaerobic conditions, achieving denitrification.

[0120] The reflux sludge increases the amount of sludge in the anaerobic zone 1, which is beneficial for phosphorus release by phosphorus accumulating organisms under anaerobic conditions, followed by excessive phosphorus uptake under aerobic conditions, thereby achieving phosphorus removal.

[0121] The reflux operation helps to stabilize the system operation and reduce the impact of inflow load fluctuations on the system.

[0122] By controlling the reflux ratio, the sludge retention time (SRT) in the system can be adjusted to meet different treatment needs.

[0123] High sludge concentration operation helps to extend the sludge age, promote the death of microorganisms and further decomposition of metabolic products, thereby reducing the production of excess sludge.

[0124] In the low-dissolved oxygen high-sludge-concentration sewage biological denitrification and phosphorus removal system 100 of the embodiments of the present application, the first reflux pump 57 and the first reflux pipeline 58 are provided to achieve the above purposes. By refluxing the concentrated sludge in the sedimentation tank to the anaerobic zone 1, the entire sewage treatment process is optimized, the denitrification and phosphorus removal efficiency is improved, and the energy consumption and operating cost are reduced.

[0125] Further, in the sewage biological denitrification and phosphorus removal system 100, the concentration of sludge therein is controlled by the first reflux pump 57 and the first reflux pipeline 58 to be maintained at 8000 mg / L to 10000 mg / L.

[0126] The reflux ratio of the first reflux pump 57 is 100%.

[0127] The first return pump 57 controls the sludge concentration in the system to maintain it within the optimal range, which supports efficient biological treatment processes. Maintaining the activity of the sludge and the diversity of the microbial community improves the treatment capacity and resistance to shock loads of the system. By adjusting the return flow, the sludge retention time (SRT) in the system can be controlled, which in turn affects the treatment efficiency and the dynamics of the microbial population.

[0128] The sludge concentration directly affects the efficiency of biological treatment because the microorganisms in the sludge are the main participants in reactions such as organic matter degradation, nitrogen and phosphorus removal. High sludge concentration can increase the treatment capacity of the biological reactor because more microorganisms are involved in the reaction. Sludge concentration also affects the settling performance, and appropriate sludge concentration helps form a good sludge layer in the settling tank, improving the efficiency of solid-liquid separation.

[0129] In the wastewater biological denitrification and phosphorus removal system 100, the sludge concentration is controlled by the first return pump 57 and the first return pipeline 58 to maintain it within the range of 8000 mg / L to 10000 mg / L. Such high sludge concentration helps to: improve the biological degradation capacity and nitrogen and phosphorus removal efficiency of the system, reduce the production of excess sludge, reduce the cost of sludge treatment and disposal, and enhance the adaptability of the system to fluctuations in influent water quality, improving the resistance to shock loads.

[0130] The return flow ratio of the first return pump 57 is 100%, which means 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-quantity return strategy helps maintain the uniformity and stability of the sludge concentration in the entire system, ensuring efficient operation of the system.

[0131] Further, the equipment area 5 also includes a second return pump 55 and a second return pipeline 56;

[0132] The second return pipeline 56 is connected at one end to the first anoxic tank 21 and at the other end to the second aerobic tank 32;

[0133] The second return pump 55 is provided on the second return pipeline 56 to facilitate the return of wastewater from the second aerobic tank 32 to the first anoxic tank 21.

[0134] Further, the return flow of the second return pump 56 is 300%.

[0135] 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 to achieve denitrification, because under anoxic conditions, nitrate can be reduced to nitrogen gas, thereby removing it from the wastewater.

[0136] By recirculating the nitrate-rich mixed liquor back to the anoxic tank, the concentration of nitrate in the anoxic tank is increased, providing more electron acceptors for denitrifying bacteria, thereby improving the efficiency of nitrogen removal.

[0137] In the anoxic tank, the recirculated nitrate reacts with the organic matter in the wastewater, converting into nitrogen gas, a process known as simultaneous nitrification and denitrification (SND) or denitrifying phosphorus removal, which helps to improve the removal rate of nitrogen. The presence of the second recirculation pump 55 helps to maintain the flowability of the mixed liquor within the entire biological treatment system, ensuring effective connection and mass transfer between the various treatment units. By adjusting the flow rate of the second recirculation pump 55, the nitrate load entering the anoxic tank can be adjusted to adapt to different treatment requirements and influent conditions. Increasing the number of sludge cycles in the system helps to improve the activity of the sludge and the efficiency of biological treatment. Internal recirculation helps to balance the sludge distribution in the system, reducing the impact of load fluctuations or changes in operating conditions on system stability.

[0138] In the wastewater biological denitrification and phosphorus removal system 100, the second recirculation pump 55 and the second recirculation pipeline 56 are provided to achieve more efficient nitrogen removal while maintaining the high efficiency and stability of the system. By precisely controlling the recirculation ratio and flow rate, the entire biological denitrification process can be optimized, improving the overall performance of wastewater treatment.

[0139] In addition, the present application also provides a wastewater treatment method based on the wastewater biological denitrification and phosphorus removal system 100 as described in any of the preceding embodiments, which comprises:

[0140] S1, feeding anaerobic activated sludge to the anaerobic zone 1 in the wastewater biological denitrification and phosphorus removal system 100, feeding anoxic activated sludge to the denitrifying anoxic zone 2 in the wastewater biological denitrification and phosphorus removal system 100, and feeding aerobic activated sludge to the low-dissolved oxygen aeration zone 3 in the wastewater biological denitrification and phosphorus removal system 100;

[0141] The activated sludge contains a large number of microorganisms, which are crucial for the degradation of organic matter, removal of nitrogen and phosphorus, etc. Feeding activated sludge is to quickly start and maintain the biological treatment capacity in the wastewater treatment system.

[0142] S2, controlling the wastewater feeding pipe 6 to feed wastewater to the anaerobic zone 1;

[0143] The wastewater first enters the anaerobic zone 1, where due to the lack of dissolved oxygen, anaerobic decomposition of organic matter and phosphorus release by phosphorus accumulating organisms mainly occur. This step is very important for the subsequent phosphorus removal process.

[0144] S3, controlling the dissolved oxygen supply device 52 in the low-dissolved oxygen aeration zone 3 to provide dissolved oxygen, and controlling the stirring device 51 in the equipment zone 5 to stir in the anaerobic zone 1 and the denitrifying anoxic zone 2.

[0145] The sewage after the anaerobic zone 1 enters the denitrification anoxic zone 2 for denitrification reaction, and after the reaction, enters the low-dissolved oxygen aeration zone 3 for nitrification reaction, enters the solid-liquid separation zone 4 for solid-liquid separation treatment, and the supernatant after treatment is discharged through the drain pipe 7;

[0146] In the low-dissolved oxygen aeration zone 3, the dissolved oxygen concentration is accurately controlled by the dissolved oxygen supply device 52 (such as a blower 521) and the flow meter 522 to support the metabolic activity of aerobic microorganisms.

[0147] At the same time, the stirring device 51 stirs in the anaerobic zone 1 and the denitrification anoxic zone 2 to ensure that the microorganisms and the pollutants in the sewage are in full contact, thereby improving the treatment efficiency.

[0148] After the sewage flows out of the anaerobic zone 1, it enters the denitrification anoxic zone 2, where the denitrification reaction is carried out to convert nitrate into nitrogen, thereby achieving denitrification.

[0149] After the denitrification treatment, the sewage enters the low-dissolved oxygen aeration zone 3 for nitrification reaction to convert ammonia nitrogen into nitrate.

[0150] After the biological treatment, the mixed liquid enters the solid-liquid separation zone 4 (such as a sedimentation tank) to separate the sludge and the supernatant after treatment by gravity sedimentation.

[0151] The supernatant after separation, i.e. the treated water, is discharged from the system through the drain pipe 7 to meet the discharge standard.

[0152] The sewage treatment method provided by the application realizes efficient removal of organic matter, nitrogen and phosphorus in the sewage by accurately controlling the dissolved oxygen concentration and the stirring conditions through the ordered multi-stage biological treatment steps. The method combines anaerobic, anoxic and aerobic environments to promote the degradation of organic matter and the effective removal of nitrogen and phosphorus. Through the design of low-dissolved oxygen and high sludge concentration, the aeration energy consumption is reduced, the energy efficiency is improved, and the requirements of modern sewage treatment for high efficiency, energy saving and environmental protection are met. The whole treatment process is continuously operated to ensure the continuity and stability of the sewage treatment, and the treatment effect is optimized through the accurate control of the equipment zone 5 to meet the strict discharge standard.

[0153] Further, in the sewage biological denitrification and phosphorus removal system 100, the concentration of the sludge therein is controlled to be maintained at 8000 mg / L-10000 mg / L by the first reflux pump 57 and the first reflux pipeline 58;

[0154] Further, the reflux amount of the first reflux pump 57 is 100%;

[0155] Further, the frequency conversion control device 54 of the device area 5 controls the dissolved oxygen providing device based on the detection data of the dissolved oxygen meter 53 in the first and second aerobic tanks 31 and 32 of the low-dissolved oxygen aeration area 3, so that the dissolved oxygen concentration of the first aerobic tank 31 is 0.8-1.2 mg / L, and the dissolved oxygen concentration of the second aerobic tank 32 is 0.4-0.6 mg / L.

[0156] Further, the second reflux pump 55 in the device area 5 is used to reflux the sewage in the second aerobic tank 32 to the first anoxic tank 21 of the denitrification anoxic area 2 through the second reflux pipeline 56.

[0157] Further, the reflux amount of the second reflux pump 55 is 300%.

[0158] Further, the first reflux pump 57 in the device area 5 is used to reflux the concentrated sludge in the solid-liquid separation area 4 to the anaerobic area 1.

[0159] The above arrangement can improve the ability of microorganisms in the first anaerobic tank to uptake organic matter and release phosphate, promote the simultaneous nitrification and denitrification and denitrification phosphorus removal reaction in the first and second anoxic tanks 21 and 22, and perform nitrification and phosphorus accumulation reaction in the first and second aerobic tanks 31 and 32, so as to achieve organic matter removal without additional carbon source, small aeration intensity, low operation energy consumption, and good treatment effect.

[0160] The utility model will be further described below through specific embodiments, but it should be understood that these embodiments are only used for more detailed description, and should not be understood as limiting the utility model in any form.

[0161] Example 1: Long-term test

[0162] In this embodiment, the sewage biological denitrification and phosphorus removal system is subjected to long-term test. The sewage biological denitrification and phosphorus removal system comprises:

[0163] The anaerobic tank (anaerobic area), the first anoxic tank, the second anoxic tank, the first aerobic tank, the second aerobic tank, the sedimentation tank (solid-liquid separation area), and the device area are sequentially connected.

[0164] The anaerobic tank is provided with anaerobic activated sludge; the first and second anoxic tanks are provided with anoxic activated sludge; and the first and second aerobic tanks are provided with aerobic activated sludge.

[0165] The first and second aerobic tanks are provided with dissolved oxygen meters.

[0166] The equipment area further includes a frequency conversion control device and a dissolved oxygen supply device; the dissolved oxygen supply device includes a blower and a flow meter connected to the blower.

[0167] The frequency conversion control device is electrically connected to the dissolved oxygen meter and the dissolved oxygen supply device, and the frequency conversion control device, based on the detection data of the dissolved oxygen meter, controls the dissolved oxygen supply device to make the dissolved oxygen concentration of the first aerobic tank between 0.8 mg / L and 1.2 mg / L, and the dissolved oxygen concentration of the second aerobic tank between 0.4 mg / L and 0.6 mg / L.

[0168] 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 area, and the other end is connected to the anaerobic area; the first reflux pump is arranged on the first reflux pipeline to facilitate the return of concentrated sludge in the solid-liquid separation area to the anaerobic area.

[0169] In the sewage biological denitrification and phosphorus removal system, the concentration of sludge therein is controlled to be maintained at 8000 mg / L-10000 mg / L by the first reflux pump and the first reflux pipeline;

[0170] The reflux ratio of the first reflux pump is 100%.

[0171] The equipment area also includes a second reflux pump and a second reflux pipeline. One end of the second reflux pipeline is connected to the first anoxic tank and the other end is connected to the second aerobic tank. The second reflux pump is installed on the second reflux pipeline to return wastewater from the second aerobic tank to the first anoxic tank. The reflux ratio of the second reflux pump is 300%.

[0172] The experiment found that:

[0173] like Figure 2 As shown, from day 0 to day 15 of the experiment, a conventional sewage treatment process was used, wherein the sludge concentration in the system was 3000 mg / L, the dissolved oxygen concentration in the aerobic tank was controlled at above 2.0 mg / L, and the system had an average COD removal rate of 89.7% for the influent, and an average COD value of 36.1 mg / L for the effluent; an average total nitrogen removal rate of 68.1%, and an average total nitrogen value of 10.07 mg / L for the effluent. It should be noted that during this stage, the operating conditions of the sewage biological denitrification and phosphorus removal system were not adopted, and there was sufficient carbon source in the influent for denitrification (the influent carbon-nitrogen ratio C / N=13.0 from day 0 to day 15). However, the orthophosphate content in the effluent was relatively high during this stage, with an average orthophosphate content of 3.91 mg / L, which is much higher than the Class A standard of 0.5 mg / L specified in the "Pollutant Discharge Standard for Municipal Wastewater Treatment Plants" GB 18918-2002.

[0174] To achieve efficient denitrification and phosphorus removal, the dissolved oxygen concentration in the first aerobic tank was controlled at 0.8-1.2 mg / L, the dissolved oxygen concentration in the second aerobic tank was controlled at 0.4-0.6 mg / L, the sludge concentration in each tank of the system was controlled at 8000-10000 mg / L, and the carbon-nitrogen ratio of the influent was reduced to C / N=4.0 by using the sewage biological denitrification and phosphorus removal system described in this embodiment from the 16th day to the 45th day.

[0175] In this stage, the average removal rate of organic matter COD in the influent by the sewage biological denitrification and phosphorus removal system was 90.4%, the average value of effluent COD was 24.1 mg / L; the average removal rate of total nitrogen was 77.9%, the average value of effluent total nitrogen was 13.68 mg / L; the average removal rate of orthophosphate was 52.1%, the average value of effluent total nitrogen was 1.41 mg / L. By comparison, it can be found that after using the sewage biological denitrification and phosphorus removal system, the removal efficiency of organic matter, total nitrogen and orthophosphate by the system is greatly improved.

[0176] From the 46th day to the 75th day, the pollution load of organic matter and nitrogen source in the influent was further reduced while the low carbon-nitrogen ratio was maintained, so as to be more in line with the actual conditions of the municipal wastewater treatment plant. Under the long-term operation of the sewage biological denitrification and phosphorus removal system, the average value of effluent COD in this stage was 28.3 mg / L, the average value of effluent total nitrogen was 9.17 mg / L, and the average value of effluent orthophosphate was 0.15 mg / L. That is, by using the sewage biological denitrification and phosphorus removal system, efficient purification treatment of low carbon-nitrogen ratio municipal wastewater can be achieved, and simultaneous denitrification and phosphorus removal can be completed without additional carbon source and other reagents, and under the premise of ensuring removal effect, the sewage biological denitrification and phosphorus removal system can reduce about 55% of aeration energy consumption compared with traditional treatment systems and methods.

[0177] Example 2: Along-the-way experiment

[0178] In this embodiment, in order to further illustrate the material conversion process in the sewage biological denitrification and phosphorus removal system, along-the-way monitoring experiments of pollutants and internal carbon source components were also conducted, as shown in Table 2. Figure 3 The theoretical conversion rate φ COD of internal carbon source in the system in Example 1 and the measured COD conversion rate σ COD along the way were calculated as follows:

[0179]

[0180] The calculation of the internal carbon source conversion rate can evaluate the metabolic activity of microorganisms in the anaerobic zone, especially the activity of microorganisms such as glycogen-accumulating organisms (GAOs) and phosphorus-accumulating organisms (PAOs). These microorganisms decompose endogenous carbon sources in the first and second anoxic zones to provide carbon source support for the denitrification process. By combining the changes in COD and nitrogen source concentrations in each region of the system, the contribution rates of the anaerobic zone, the first anoxic zone, the second anoxic zone, the aerobic zone, and the sedimentation tank to the removal of ammonia nitrogen can be calculated as follows: COD = 75.91%, σ COD = 72.40%. The calculation results show that in the wastewater biological denitrification and phosphorus removal system, the microorganisms have high metabolic activity and can effectively utilize the carbon source in the influent, proving that the wastewater biological denitrification and phosphorus removal system has strong application value for treating low-carbon-nitrogen-ratio municipal wastewater with limited carbon source.

[0181] In the wastewater biological denitrification and phosphorus removal system, the assimilation accounts for 86.46% of the ammonia nitrogen removal mechanism, of which the assimilation occurring in the anaerobic tank, the anoxic tank, and the sedimentation tank accounts for 17.52%, 68.07%, and 0.87% of the ammonia nitrogen removal, respectively. The nitrification accounts for only 13.54% of the ammonia nitrogen removal. This means that in the wastewater biological denitrification and phosphorus removal system, a lower dissolved intensity can be used in the aerobic tank to meet the requirements of ammonia nitrogen removal, i.e., the wastewater biological denitrification and phosphorus removal system is more suitable for stable operation of a low-dissolved-oxygen aeration system.

[0182] The corresponding calculation formulas are as follows:

[0183] (1) The contribution rate of assimilation in the anaerobic tank to the removal of ammonia nitrogen:

[0184]

[0185] (2) The contribution rate of assimilation in the anoxic tank to the removal of ammonia nitrogen:

[0186]

[0187] (3) The contribution rate of nitrification in the aerobic tank to the removal of ammonia nitrogen:

[0188]

[0189] (4) The contribution rate of assimilation in the sedimentation tank to the removal of ammonia nitrogen:

[0190]

[0191] According to the material balance equation, the nitrate concentration in the anaerobic tank and the anoxic tank is reduced by 10.64 mg / L and 17.19 mg / L respectively, and then under the action of ammonia-oxidizing bacteria AOB and NOB, ammonia nitrogen and nitrite are oxidized to nitrate. The denitrification reaction in the anaerobic tank and the anoxic zone contributes 38.23% and 61.77% respectively.

[0192] The nitrate removal rate in the first anoxic tank is 57.02%, and the required COD content for denitrification in this area is calculated as ΔCOD de = 9.84 mg / L. Combined with the change of COD content along the way, the COD consumption in the first anoxic tank is ΔCOD 第一缺氧池 = 4.64 mg / L, indicating that there are microorganisms other than traditional denitrifying bacteria participating in the denitrification process. According to the change of phosphate content and polyhydroxyalkanoate PHA content, the phosphate concentration after the release of phosphorus by polyphosphorus in the anaerobic tank is 33.36 mg / L, and the phosphate concentration in the mixed liquor returned from the second aerobic tank to the first anoxic tank is 0.15 mg / L. If it is assumed that there is no phosphorus removal related reaction in the anoxic tank, then according to the material balance equation, the theoretical phosphate content in the first anoxic tank is PO4 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 there is a denitrifying phosphorus removal process in the first anoxic tank.

[0193] In the first anoxic tank, the glycogen content increases to 18.75 mg / gSS, and reaches a peak in the second anoxic tank, which may be due to the fact that under anoxic conditions, part of the PHA is converted to glycogen by denitrifying polyphosphorus DPAOs for their growth. In the first aerobic tank, polyphosphorus degrades PHA to provide energy, takes up phosphate PO4 3- from the environment and converts it to polyphosphate Poly-P, and consumes glycogen for growth and reproduction. In the experiment, the PO4 3- content in the first aerobic tank decreased by 85.15%, and the glycogen content decreased by 27.34%. In the wastewater biological denitrification and phosphorus removal system, the denitrification contribution rate of denitrifying phosphorus removal process accounts for 52.85% of the denitrification, that is, the wastewater biological denitrification and phosphorus removal system still has the technical advantage of efficient simultaneous denitrification and phosphorus removal under the condition of insufficient carbon source.

[0194] The relevant calculation formula is as follows:

[0195] (1) The nitrate concentration in the anaerobic zone is reduced:

[0196]

[0197] (2) the nitrate reduction concentration of the first anoxic tank:

[0198]

[0199] (3) the denitrification contribution rate of the anaerobic tank:

[0200]

[0201] (4) the denitrification contribution rate of the first anoxic tank:

[0202]

[0203] (5) the nitrate removal rate of the first anoxic tank:

[0204]

[0205] (6) the COD theoretical consumption value of the denitrification process of the first anoxic tank:

[0206]

[0207] (7) the COD actual consumption value of the denitrification process of the first anoxic tank:

[0208]

[0209] (8) the denitrification contribution rate of the denitrification and phosphorus removal process of the first anoxic tank:

[0210]

[0211] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0212] Furthermore, to the extent that the terms "comprises", "comprising", "includes", "including" and "has" or any variation thereof are used in the following description and / or claims, such terms are intended to include a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, where appropriate to context, the above description and / or claims can refer to aspects of the present application in the singular tense. However, the term, "a" or "an", or "the" used in the context of this patent, are to be read as referring to one or more, unless otherwise indicated. The indefinite article "a" or "an" preceding an element, material, substance, composition, or article, is not to be construed to mean that there is only one of the element, material, substance, composition, or article. The indefinite article "a" or "an" is to be construed to mean "one or more." It is further noted that the claims can be drafted to exclude any elements or steps from the disclosure. Thus, no limitation is implied by such exclusion.

Claims

1. A sewage biological denitrification and dephosphorization system, characterized in that, The system comprises: an anaerobic zone, a denitrification anoxic zone, a low-dissolved oxygen aeration zone, a solid-liquid separation zone and an equipment zone connected in sequence along the direction of sewage flow; the anaerobic zone is provided with anaerobic activated sludge; the denitrification anoxic zone is provided with anoxic activated sludge; and the low-dissolved oxygen aeration zone is provided with aerobic activated sludge; high sludge concentration is maintained in the anaerobic zone, the denitrification anoxic zone and the low-dissolved oxygen aeration zone; the anaerobic zone is a dissolved oxygen-free environment and is connected with a water inlet pipe for feeding sewage; the solid-liquid separation zone is provided with a drain pipe; the equipment zone comprises stirring equipment provided in the anaerobic zone and the denitrification anoxic zone and a dissolved oxygen providing device provided in the low-dissolved oxygen aeration zone.

2. The system for biological removal of nitrogen and phosphorus from sewage water according to claim 1, characterized in that, The denitrification anoxic zone comprises a first anoxic tank and a second anoxic tank; the anaerobic zone is connected with the first anoxic tank through an overflow hole so that the first anoxic tank receives the sewage flowing out of the anaerobic zone; one end of the second anoxic tank is connected with the first anoxic tank and the other end is connected with the low-dissolved oxygen aeration zone.

3. The wastewater biological nitrogen and phosphorus removal system according to claim 2, wherein The low-dissolved oxygen aeration zone comprises a first aerobic tank and a second aerobic tank connected in sequence; the first aerobic tank is connected with the second anoxic tank; the second aerobic tank is connected with the solid-liquid separation zone through an overflow pipe.

4. The system for biological removal of nitrogen and phosphorus from sewage water according to claim 3, characterized in that, The equipment zone further comprises a dissolved oxygen meter provided in the first aerobic tank and the second aerobic tank.

5. The system for biological removal of nitrogen and phosphorus from sewage water according to claim 4, characterized in that, The equipment zone further comprises a variable frequency control device; the variable frequency control device is electrically connected with the dissolved oxygen meter and the dissolved oxygen providing device, and based on the detection data of the dissolved oxygen meter, the variable frequency control device controls the dissolved oxygen providing device to make the dissolved oxygen concentration of the first aerobic tank be 0.8 mg / L-1.2 mg / L and the dissolved oxygen concentration of the second aerobic tank be 0.4 mg / L-0.6 mg / L.

6. The wastewater biological nitrogen and phosphorus removal system as claimed in claim 5, wherein the first and second anoxic zones are connected in series. The dissolved oxygen providing device comprises a blower and a flow meter connected with the blower.

7. The system for biological removal of nitrogen and phosphorus from sewage water according to claim 4, characterized in that, The equipment zone further comprises a first backflow pump and a first backflow pipeline; one end of the first backflow pipeline is connected with the solid-liquid separation zone and the other end is connected with the anaerobic zone; the first backflow pump is arranged on the first backflow pipeline so as to return the concentrated sludge in the solid-liquid separation zone to the anaerobic zone.

8. The sewage biological denitrification and phosphorus removal system according to claim 7, wherein the sludge concentration in the system is controlled by the first backflow pump and the first backflow pipeline to be 8000 mg / L-10000 mg / L; the backflow ratio of the first backflow pump is 100%.

9. The system for biological removal of nitrogen and phosphorus from sewage water according to claim 4, characterized in that, The equipment zone further comprises a second backflow pump and a second backflow pipeline; one end of the second backflow pipeline is connected with the first anoxic tank and the other end is connected with the second aerobic tank; the second backflow pump is arranged on the second backflow pipeline so as to return the sewage in the second aerobic tank to the first anoxic tank.

10. The system for biological removal of nitrogen and phosphorus from sewage water according to claim 9, characterized in that, The backflow ratio of the second backflow pump is 300%.

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