Biological nitrogen and phosphorus removal system for sewage and sewage treatment method

Abstract

The invention provides a biological nitrogen and phosphorus removal system for sewage and a sewage treatment method, 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, 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. All biochemical pools of the system operate at high sludge concentration. According to the system provided by the invention, the organic matter uptake capacity and phosphate release capacity of microorganisms in the anaerobic zone can be improved, synchronous nitrification and denitrification and denitrification phosphorus removal reaction can be promoted in the denitrification anoxic tank to remove nitrogen and phosphorus, and synchronous nitrification and denitrification and phosphorus accumulation reaction can be carried out in the low dissolved oxygen aeration tank; organic matter removal is achieved, no additional carbon source needs to be added, the aeration intensity is small, the operation energy consumption is low, and the treatment effect is good.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a sewage biological denitrification and dephosphorization system and a sewage treatment method. Background Art

[0002] Wastewater treatment is a key link in the field of environmental protection, especially in the context of rapid social and economic development and increasing requirements for water environment protection. The eutrophication problem caused by excessive nitrogen and phosphorus discharge has become one of the most severe challenges in current water pollution control. At present, the sewage treatment industry has ushered in a new era with carbon reduction and emission reduction as the key strategic direction. Strict emission standards have made the research and innovation of sewage treatment technology a hot topic in the industry.

[0003] At present, the processes commonly used in urban sewage treatment plants include A2 / O process, oxidation ditch process and SBR process. These processes play an important role in sewage treatment, but they also have some limitations. First, the energy consumption of treatment is high, especially in the traditional activated sludge method. In order to maintain a high dissolved oxygen content in the aeration tank, a large amount of energy is required for aeration. Secondly, the treatment effect of the effluent is not stable. When the carbon source in the influent is insufficient, the microbial denitrification process lacks the necessary electron donors, resulting in the difficulty of meeting the total nitrogen standard in the effluent. This not only requires additional carbon source addition, but may also require the addition of subsequent deep treatment processes, thereby increasing operating costs and project investment. Finally, the existing process produces a large amount of sludge, and the cost of sludge treatment and disposal is high, which brings considerable challenges to the operation of the sewage plant.

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

[0005] Low dissolved oxygen aeration and high sludge concentration operation are two effective methods for improving sewage treatment efficiency found in recent years. Under low dissolved oxygen conditions, the diversity of activated sludge microbial communities is increased, which helps to improve the shock load resistance of sewage treatment. High sludge concentration operation can improve the degradation efficiency of organic pollutants by microorganisms and achieve efficient synergy of multiple metabolic pathways, such as simultaneous nitrification and denitrification and denitrification phosphorus removal, thereby improving the removal of nitrogen and phosphorus. At the same time, high sludge concentration can also prolong the sludge age, promote the death of microorganisms and further decomposition of metabolites, reduce the output of residual sludge, and reduce the cost of sludge treatment and disposal.

[0006] Although these research findings provide new ideas for sewage treatment technology, there is an urgent need to develop a sewage treatment process that combines low dissolved oxygen aeration and high sludge concentration to solve the problems of unstable treatment effect, high operating energy consumption and cost under the condition of limited influent carbon source. This new process should be able to meet the sewage treatment industry's demand for synergistic efficiency in reducing pollution and carbon emissions, and promote the development of sewage treatment technology towards a more efficient, energy-saving and environmentally friendly direction. Summary of the invention

[0007] The first purpose of the present invention is to provide a sewage biological denitrification and phosphorus removal system and a sewage treatment method. The sewage biological denitrification and phosphorus removal system has the advantages of low operating energy consumption and good treatment effect.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] In a first aspect, the present invention provides a sewage biological denitrification 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 sequentially connected along the sewage flow direction;

[0011] The anaerobic zone is provided with anaerobic activated sludge; the denitrification anoxic zone is provided with anoxic activated sludge; 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 are all operated with high sludge concentration;

[0013] The anaerobic zone is an environment without dissolved oxygen and is connected to a water inlet pipe for placing sewage;

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

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

[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 through an overflow hole, so that the first anoxic tank receives 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 pool is connected to the second anoxic pool;

[0021] The second aerobic tank is connected to the solid-liquid separation zone through 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 embodiment, the equipment area further includes a frequency conversion control device;

[0024] 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 within the range of 0.8mg / L to 1.2mg / L, and the dissolved oxygen concentration of the second aerobic tank within the range of 0.4mg / L to 0.6mg / L.

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

[0026] In an optional embodiment, 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 reflux pump is arranged on the first reflux pipeline so as to return the concentrated sludge in the solid-liquid separation zone to the anaerobic zone.

[0029] In an optional embodiment, 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;

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

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

[0032] 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;

[0033] The second reflux pump is arranged on the second reflux pipeline so as to return the sewage in 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 sewage treatment method, based on the sewage biological denitrification and phosphorus removal system as described in any one of the aforementioned embodiments, the sewage treatment method comprises:

[0036] S1, putting anaerobic activated sludge into the anaerobic zone of the sewage biological denitrification and phosphorus removal system, putting anoxic activated sludge into the denitrification anoxic zone of the sewage biological denitrification and phosphorus removal system, and putting aerobic activated sludge into the low dissolved oxygen aeration zone of the sewage biological denitrification and phosphorus removal system;

[0037] S2, controls the water inlet pipe to release sewage into the anaerobic zone;

[0038] S3, controlling the dissolved oxygen supply device in the low dissolved oxygen aeration zone to provide dissolved oxygen through the equipment zone, and controlling the stirring device in the equipment zone to stir in the anaerobic zone and the denitrification anoxic zone;

[0039] After passing through the anaerobic zone, the sewage enters the denitrification anoxic zone for denitrification and denitrification, and then enters the low dissolved oxygen aeration zone for nitrification and phosphorus accumulation, and then enters the solid-liquid separation zone for solid-liquid separation. The treated supernatant is discharged through a drain pipe.

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

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

[0042] In an optional embodiment, the frequency conversion control device of the equipment area controls the dissolved oxygen supply device to make the dissolved oxygen concentration of the first aerobic tank within the range of 0.8 mg / L to 1.2 mg / L and the dissolved oxygen concentration of the second aerobic tank within the range of 0.4 mg / L to 0.6 mg / L based on the detection data of the dissolved oxygen meters in the first aerobic tank and the second aerobic tank provided in the low dissolved oxygen aeration zone;

[0043] In an optional embodiment, the sewage in the second aerobic tank is returned to the first anoxic tank in the denitrification anoxic zone through a second return pipe by a second return pump in the equipment area;

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

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

[0046] Compared with the prior art, the sewage biological denitrification and phosphorus removal system provided by the present invention can enhance the ability of microorganisms in the anaerobic zone to absorb organic matter and release phosphate, can promote simultaneous nitrification and denitrification and denitrification and phosphorus removal reactions in the denitrification anoxic tank to remove nitrogen and phosphorus, can carry out nitrification and polyphosphate reactions in the low dissolved oxygen aeration zone, and realize organic matter removal, does not require additional carbon source addition, has low aeration intensity, low operating energy consumption, and good treatment effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 This is a schematic diagram of the structure of the sewage biological nitrogen and phosphorus removal system in the embodiment of the present application;

[0049] Figure 2 This is a graph showing changes in inlet and outlet water quality indicators of the sewage biological denitrification and phosphorus removal system in the embodiment of the present application;

[0050] Figure 3 This is a graph showing the changes in concentrations of various pollutants and internal carbon source components in the sewage biological denitrification and phosphorus removal system in the embodiment of the present application.

[0051] Reference numerals:

[0052] 100, biological nitrogen and phosphorus removal system for sewage; 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, stirring equipment; 52, dissolved oxygen supply equipment; 521, blower; 522, flow meter; 53, dissolved oxygen meter; 54, frequency conversion control equipment; 55, second return pump; 56, second return pipeline; 57, first return pump; 58, first return pipeline; 6, water inlet pipe; 7, drainage pipe. DETAILED DESCRIPTION

[0053] As used herein:

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

[0055] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0056] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described in this article, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0057] In these examples, parts and percentages are by mass unless otherwise indicated.

[0058] "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, it means 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 should not be misunderstood that, unlike the mass parts, the sum of the mass of all components is not limited to 100 parts.

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

[0060] refer to Figure 1 In an embodiment of the present application, a sewage biological denitrification and phosphorus removal system 100 is provided, comprising:

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

[0062] 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;

[0063] The anaerobic zone 1 , the denitrification anoxic zone 2 and the low dissolved oxygen aeration zone 3 are all operated with high sludge concentration.

[0064] The anaerobic zone 1 is an environment without dissolved oxygen and is connected to a water inlet pipe 6 for placing sewage;

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

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

[0067] As mentioned above, 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 ingest organic matter in sewage under the condition of no oxygen.

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

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

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

[0071] Enhanced system stability: Pretreatment in anaerobic tanks can improve the overall wastewater treatment system's ability to withstand shock loads from fluctuations in influent quality.

[0072] Reduce sludge production: High sludge concentration operation helps to extend the sludge age (SRT), promote 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 the aerobic tank and the anoxic tank to form a complete sewage treatment process. In the system of this embodiment, the anaerobic tank is sequentially connected with other tanks to achieve efficient nitrogen and phosphorus removal.

[0074] As mentioned above, the denitrification anoxic zone 2 is mainly used to carry out denitrification and denitrification in the system, and can also carry out denitrification and dephosphorization. Nitrates and nitrites (nitrogen oxides) are reduced to nitrogen gas under anoxic conditions, thereby removing nitrogen from sewage. These pools also help to decompose the internal carbon source in the microorganisms and further remove phosphorus from sewage.

[0075] In the above-mentioned low dissolved oxygen aeration zone 3, the concentration of dissolved oxygen in this zone is relatively high, and nitrification reaction is mainly carried out to convert ammonia nitrogen into nitrate. At the same time, under aerobic conditions, polyphosphate bacteria can absorb phosphate and store it as polyphosphate, which helps to remove phosphorus from sewage in the subsequent sedimentation and reflow process.

[0076] As mentioned above, the second aerobic tank 32 has a lower dissolved oxygen concentration. While ensuring that sufficient nitrate enters the first anoxic tank 21, the dissolved oxygen content in the second return pipe is reduced as much as possible to keep the anoxic condition stable.

[0077] The biological denitrification and phosphorus removal system 100 for sewage also includes activated sludge in various zones, specifically, 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 .

[0078] Anaerobic activated sludge, under anaerobic conditions, is mainly composed of anaerobic microorganisms, such as anaerobic bacteria, hydrolytic bacteria, glycogen-accumulating bacteria, phosphate-accumulating bacteria, etc. Its main function is to perform anaerobic decomposition and uptake of organic matter, while releasing phosphorus.

[0079] Anoxic activated sludge, under anoxic conditions, is mainly composed of microorganisms capable of denitrification, such as denitrifying denitrification bacteria and denitrifying dephosphorization bacteria. Its main function is to denitrify and reduce nitrates to nitrogen gas, thereby removing nitrogen from sewage.

[0080] Aerobic activated sludge, under aerobic conditions, is mainly composed of aerobic microorganisms, such as nitrifying bacteria, polyphosphate bacteria, etc. The main functions are to carry out the oxidative decomposition of organic matter, the nitrification of ammonia nitrogen (converted into nitrate), and the absorption of phosphorus by polyphosphate bacteria (absorption and storage of phosphate).

[0081] Although the activated sludge in each zone is different in microbial composition and function, they are interconnected and interdependent in the whole sewage treatment process. For example, the nitrate produced by nitrification in the low dissolved oxygen aeration zone 3 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 accumulation in the aerobic tank.

[0082] In addition, the microbial community of activated sludge will adapt and evolve according to changes in environmental conditions. In actual sewage treatment systems, operations such as returning sludge and adjusting dissolved oxygen concentration can further promote the formation and development of different microbial communities, thereby optimizing the treatment efficiency of the entire system.

[0083] As mentioned above, the solid-liquid separation zone 4 is used to separate the sludge from the water. The solid-liquid separation zone 4 can adopt sedimentation technology, centrifugal technology, ultrafiltration technology and the like.

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

[0085] As mentioned above, the equipment area 5 may include a stirring device 51 and a dissolved oxygen providing device 52 .

[0086] The equipment area 5 is responsible for controlling the operation of the entire system, such as continuously, regularly or in real time stirring the sewage sludge in the anaerobic zone 1 and the denitrification anoxic zone 2 through the stirring device 51, providing the required dissolved oxygen through the dissolved oxygen providing device 52, and monitoring the dissolved oxygen concentration to ensure efficient and stable operation of the system.

[0087] As mentioned above, the stirring device 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 sewage through the stirring paddle.

[0088] As mentioned above, the dissolved oxygen providing device may be, for example, a blower 521, through which the sludge and sewage are aerated to provide dissolved oxygen molecules.

[0089] As mentioned above, the water inlet pipe 6 is used to introduce sewage, and the drain pipe 7 is used to lead out the supernatant in the solid-liquid separation area 4 to complete sewage treatment.

[0090] The sewage biological denitrification and phosphorus removal system 100 provided in the embodiment of the present application is a sewage biological denitrification and phosphorus removal system 100 with low dissolved oxygen and high sludge concentration, which can enhance the ability of microorganisms in the anaerobic zone 1 to absorb 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, perform nitrification and polyphosphate reactions in the low dissolved oxygen aeration zone 3, and achieve organic matter removal, without the need for additional carbon source addition, with low aeration intensity, low operating energy consumption, and good treatment effect.

[0091] Furthermore, the denitrification anoxic zone 2 includes a first anoxic pool 21 and a second anoxic pool 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 receives 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 mentioned above, the denitrification anoxic zone 2 can be set to two partitions, namely: a first anoxic pool 21 and a second anoxic pool 22. The two partitions are connected in sequence to form the anaerobic zone 1, the first anoxic pool 21, the second anoxic pool 22, and the low dissolved oxygen aeration zone 3.

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

[0096] Further, 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 pool 31 is connected to the second anoxic pool 22;

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

[0099] As mentioned above, 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 mentioned above, the second anoxic tank 22 receives the muddy-water mixture from the first anoxic tank 21, and inputs the treated muddy-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 sewage mixture therein 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] As mentioned above, the dissolved oxygen meter 53 is an instrument for measuring the concentration of dissolved oxygen (DO) in water. Dissolved oxygen is the form of oxygen in water in a molecular state, and is an important water quality parameter for the survival of aquatic organisms and many water treatment processes.

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

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

[0105] The frequency conversion control device 54 is electrically connected to the dissolved oxygen meter 53 and the dissolved oxygen supply device, and the frequency conversion control device 54, based on the detection data of the dissolved oxygen meter 53, controls the dissolved oxygen supply device to make the dissolved oxygen concentration of the first aerobic tank 31 between 0.8 mg / L and 1.2 mg / L, and the dissolved oxygen concentration of the second aerobic tank 32 between 0.4 mg / L and 0.6 mg / L.

[0106] As mentioned above, the frequency conversion control device 54 is an electrical device for controlling the rotation speed of the motor, and it adjusts the running speed of the motor by changing the frequency of the power supplied to the motor.

[0107] In the sewage biological denitrification and phosphorus removal system 100 provided in the embodiment of the present application, the frequency conversion control device 54 is used to:

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

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

[0110] In the low dissolved oxygen and 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. On the premise of monitoring data, the dissolved oxygen concentration can be accurately controlled by cooperating with the frequency conversion control device 54 and the blower 521 to optimize the sewage treatment efficiency and reduce energy consumption.

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

[0112] As mentioned above, the flow meter 522 is an instrument for measuring fluid flow, which can measure the volume or mass of fluid flowing through a pipe or channel within a certain period of 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:

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

[0114] Return Flow: Measuring the sludge flow rate from the settling tanks back to the anaerobic tanks is critical to maintaining sludge concentration and microbial activity in the system.

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

[0116] Discharge flow: Monitor the flow rate discharged from treated water to comply with the discharge standards and requirements of the sewage treatment plant.

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

[0118] Precise control: Ensure the stability and efficiency of the sewage treatment process by monitoring and adjusting flow in real time.

[0119] Optimize operation: adjust the equipment operation status according to the actual flow rate to achieve energy saving and reduce operating costs. Process monitoring: flow data can be used to monitor the entire sewage treatment process and promptly identify and solve possible problems.

[0120] Data logging: Record flow changes to provide historical data support for system operation, which helps analyze and improve treatment processes.

[0121] Safety assurance: Prevent processing efficiency from decreasing or equipment from being damaged due to excessive or insufficient flow.

[0122] In a sewage treatment system with low dissolved oxygen and high sludge concentration, the blower 521 increases the dissolved oxygen level in the aerobic tank by providing air, while the flow meter 522 accurately controls and displays the air flow rate. The two are used together to achieve accurate control of the dissolved oxygen level, thereby optimizing the sewage treatment effect and reducing energy consumption.

[0123] In addition, further, the dissolved oxygen providing equipment can be two groups, namely: the blower 521 in the first aerobic tank 31 and the flow meter 522 connected to the blower 521, and the blower 521 in the second aerobic tank 32 and the flow meter 522 connected to the blower 521, and then, the frequency conversion control device 54 can be electrically connected to the two blowers 521 and the flow meter 522 respectively through lines.

[0124] Furthermore, the equipment area 5 also includes a first reflux pump 57 and a first reflux 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 disposed on the first reflux pipeline 58 so as to return the concentrated sludge in the solid-liquid separation zone 4 to the anaerobic zone 1 .

[0127] As mentioned above, in the sewage biological phosphorus removal system, the first reflux pump 57 and the first reflux pipeline 58 are provided, which play an important role in improving the treatment efficiency and stability of the system.

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

[0129] The sludge concentration of the entire biological reaction system can be maintained by returning the concentrated sludge in the solid-liquid separation zone 4 (usually a sedimentation tank) to the anaerobic zone 1. This is crucial to maintaining the activity and quantity of microorganisms in the system.

[0130] The return sludge increases the concentration of microorganisms in the reactor, thereby increasing the rates 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 to achieve denitrification.

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

[0133] Backflow operation helps stabilize system operation and reduce the impact of water inlet load fluctuations on the system.

[0134] By controlling the reflow ratio, the residence time of sludge in the system, namely the sludge age (SRT), can be adjusted to meet different treatment requirements.

[0135] Operation at high sludge concentration helps to extend the sludge age, promote the death of microorganisms and further decomposition of metabolites, thereby reducing the production of excess sludge.

[0136] In the low dissolved oxygen and high sludge concentration sewage biological denitrification and phosphorus removal system 100 of the embodiment of the present application, the first reflux pump 57 and the first reflux pipeline 58 are provided to achieve the above-mentioned purpose. By returning 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 costs are reduced.

[0137] Furthermore, 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 to 10000 mg / L through the first reflux pump 57 and the first reflux pipeline 58;

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

[0139] As mentioned above, the reflux ratio of the first reflux pump 57 can ensure that the sludge concentration in the system is kept within the optimal range to support an efficient biological treatment process. The activity of the sludge and the diversity of the microbial community are maintained, and the processing capacity and shock load resistance of the system are improved. By adjusting the reflux ratio, the residence time (sludge age) of the sludge in the system can be controlled, thereby affecting the processing efficiency and the dynamics of the microbial population.

[0140] As mentioned above, 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 and nitrogen and phosphorus removal. High sludge concentration can improve the treatment capacity of the bioreactor because more microorganisms participate in the reaction. Sludge concentration also affects sedimentation performance. Appropriate sludge concentration helps to form a good sludge layer in the sedimentation tank and improve the solid-liquid separation efficiency.

[0141] In the sewage biological denitrification and phosphorus removal system 100, the sludge concentration is controlled to be maintained at 8000 mg / L to 10000 mg / L by the first reflux pump 57 and the first reflux pipeline 58. Such a high sludge concentration helps to: improve the biodegradability and nitrogen and phosphorus removal efficiency of the system. Reduce the output of excess sludge and reduce the cost of sludge treatment and disposal. Enhance the system's adaptability to fluctuations in influent water quality and improve its ability to resist shock loads.

[0142] The return ratio of the first return pump 57 is 100%, which means that the amount of sludge returned from the sedimentation tank to the anaerobic zone 1 is equal to the amount of sludge entering the sedimentation tank. This full return strategy helps maintain the uniformity and stability of the sludge concentration in the entire system and ensures efficient operation of the system.

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

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

[0145] The second reflux pump 55 is disposed on the second reflux pipeline 56 so as to return the sewage 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 reflux pump 55 returns the muddy water mixture (containing a large amount of nitrate) in the second aerobic tank 32 to the first anoxic tank 21 through the second reflux pipeline 56. This internal reflux is a key step in achieving denitrification, because under anoxic conditions, nitrate can be reduced to nitrogen gas and thus removed from the sewage.

[0148] By returning the nitrate-rich mixed liquor to the anoxic tank, the nitrate concentration in the anoxic tank is increased, providing more electron acceptors for denitrifying bacteria, thereby improving the denitrification efficiency.

[0149] In the anoxic tank, the recirculated nitrate reacts with the organic matter in the sewage and is converted into nitrogen gas. This process is called simultaneous nitrification and denitrification (SND) or denitrification and phosphorus removal, which helps to improve the nitrogen removal rate. The provision of the second reflux pump 55 helps to maintain the fluidity of the mixed liquor in the entire biological treatment system and ensure the effective connection and material transfer between the various treatment units. By adjusting the flow rate of the second reflux pump 55, the nitrate load entering the anoxic tank can be adjusted to adapt to different treatment requirements and inlet conditions. Increasing the number of sludge circulations in the system helps to improve the activity of the sludge and the efficiency of biological treatment. Internal reflow helps to balance the sludge distribution in the system and reduce the impact of load fluctuations or changes in operating conditions on system stability.

[0150] In the sewage biological denitrification and phosphorus removal system 100, the second reflux pump 55 and the second reflux pipeline 56 are provided to achieve a more efficient denitrification effect while maintaining efficient operation and stability of the system. By accurately controlling the reflux ratio and reflux flow rate, the entire biological denitrification process can be optimized and the overall performance of sewage treatment can be improved.

[0151] In addition, a sewage treatment method is also provided in an embodiment of the present application. Based on the sewage biological denitrification and phosphorus removal system 100 as described in any of the above embodiments, the sewage treatment method includes:

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

[0153] Activated sludge contains a large number of microorganisms, which are essential for the degradation of organic matter, removal of nitrogen and phosphorus, etc. Activated sludge is added to quickly start and maintain the biological treatment capacity in the sewage treatment system.

[0154] S2, controlling the water inlet pipe 6 to release sewage into the anaerobic zone 1;

[0155] The sewage first enters the anaerobic zone 1, where, due to the lack of dissolved oxygen, the anaerobic decomposition of organic matter and the release of phosphorus by polyphosphate bacteria are mainly carried out. This step is very important for the subsequent phosphorus removal process.

[0156] S3, controlling the dissolved oxygen providing device 52 in the low dissolved oxygen aeration zone 3 to provide dissolved oxygen through the device zone 5, and controlling the stirring device 51 in the device zone 5 to stir in the anaerobic zone 1 and the denitrification anoxic zone 2;

[0157] After passing through the anaerobic zone 1, the sewage enters the denitrification anoxic zone 2 for denitrification and dephosphorization, and after the reaction, enters the low dissolved oxygen aeration zone 3 for nitrification and phosphorus accumulation, and enters the solid-liquid separation zone 4 for solid-liquid separation treatment, and the treated supernatant is discharged through the drain pipe 7;

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

[0159] 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 are fully in contact with the pollutants in the sewage, thereby improving the treatment efficiency.

[0160] As mentioned above, after the sewage flows out of the anaerobic zone 1, it enters the denitrification anoxic zone 2, where denitrification and denitrification and phosphorus removal reactions are carried out to convert nitrate into nitrogen gas to achieve denitrification, and at the same time, the carbon source in the microorganisms is used to convert phosphorus into polyphosphate for absorption.

[0161] As mentioned above, the sewage after denitrification treatment then enters the low dissolved oxygen aeration zone 3 to undergo nitrification reaction to convert ammonia nitrogen into nitrate.

[0162] As described above, the mixed liquor after biological treatment enters the solid-liquid separation zone 4 (such as a sedimentation tank) to separate the sludge and the treated supernatant by gravity sedimentation.

[0163] As mentioned above, the separated supernatant, i.e. the treated water, is discharged from the system through the drain pipe 7 to meet the discharge standards.

[0164] The sewage treatment method provided by the present application achieves efficient removal of organic matter, nitrogen and phosphorus in sewage by precisely controlling the dissolved oxygen concentration and stirring conditions through orderly 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, aeration energy consumption is reduced and energy efficiency is improved, which meets the requirements of modern sewage treatment for high efficiency, energy saving and environmental protection. The entire treatment process runs continuously to ensure the continuity and stability of sewage treatment. At the same time, through the precise control of equipment area 5, the treatment effect is optimized and strict emission standards are met.

[0165] Furthermore, 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 to 10000 mg / L by the first reflux pump 57 and the first reflux pipeline 58;

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

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

[0168] Furthermore, the sewage in the second aerobic tank 32 is refluxed to the first anoxic tank 21 of the denitrification anoxic zone 2 through the second reflux pipeline 56 by the second reflux pump 55 in the equipment zone 5;

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

[0170] Furthermore, the concentrated sludge in the solid-liquid separation zone 4 is refluxed into the anaerobic zone 1 through the first reflux pump 57 in the equipment zone 5 .

[0171] The above arrangement can enhance the ability of microorganisms in the first anaerobic tank to absorb organic matter and release phosphate, promote simultaneous nitrification and denitrification and denitrification and phosphorus removal reactions in the first anoxic tank 21 and the second anoxic tank 22 to remove nitrogen and phosphorus, and perform nitrification and polyphosphate reactions in the first aerobic tank 31 and the second aerobic tank 32, and achieve organic matter removal without the need for additional carbon source addition, low aeration intensity, low operating energy consumption, and good treatment effect.

[0172] The present invention is further described below by means of specific examples, but it should be understood that these examples are only used for more detailed description and should not be construed as limiting the present invention in any form.

[0173] Example 1: Long-term test

[0174] In this embodiment, a sewage biological denitrification and phosphorus removal system was used for a long-term test. The sewage biological denitrification 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] Among them, the anaerobic tank is equipped with anaerobic activated sludge; the first anoxic tank and the second anoxic tank are equipped with anoxic activated sludge; the first aerobic tank and the second aerobic tank are equipped with aerobic activated sludge;

[0177] The first aerobic pool and the second aerobic pool are both provided with dissolved oxygen meters.

[0178] The equipment area also includes frequency conversion 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 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 within the range of 0.8mg / L to 1.2mg / L, and the dissolved oxygen concentration of the second aerobic tank within the range of 0.4mg / L to 0.6mg / 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 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.

[0181] In the sewage biological denitrification and phosphorus removal system, the concentration of sludge therein is controlled to be maintained at 8000 mg / L to 10000 mg / L through the first reflux pump and the first reflux pipeline;

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

[0183] 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 arranged on the second reflux pipeline to return the sewage in the second aerobic tank to the first anoxic tank. The reflux ratio of the second reflux pump is 300%.

[0184] Experimental findings:

[0185] like Figure 2 As shown, from the 0th day to the 15th day of the experiment, the conventional sewage treatment process was adopted, wherein the sludge concentration in the system was 3000 mg / L, the dissolved oxygen concentration in the aerobic pool was controlled at above 2.0 mg / L, the average removal rate of the system for organic matter COD in the influent was 89.7%, and the average COD in the effluent was 36.1 mg / L; the average removal rate of total nitrogen was 68.1%, and the average total nitrogen in the effluent was 10.07 mg / L. It should be noted that the operating conditions of the sewage biological denitrification and phosphorus removal system were not adopted in this stage, and there was sufficient carbon source in the influent for denitrification (the carbon-nitrogen ratio of the influent C / N=13.0 from the 0th day to the 15th day), but the orthophosphate content in the effluent was relatively high in this stage, and the average orthophosphate content in the effluent was 3.91 mg / L, which was much higher than the 0.5 mg / L of the first-level A standard specified in the Pollutant Discharge Standard for Urban Sewage Treatment Plants GB 18918-2002.

[0186] To achieve efficient nitrogen and phosphorus removal, from the 16th day to the 45th day, the sewage biological nitrogen and phosphorus removal system described in this embodiment is used. The dissolved oxygen concentration of the first aerobic tank is controlled at 0.8-1.2 mg / L through the equipment area, and the dissolved oxygen of 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 carbon-nitrogen ratio of the inlet water is reduced to C / N=4.0.

[0187] In this stage, the sewage biological denitrification and phosphorus removal system has an average removal rate of 90.4% for organic matter COD in the influent, and an average COD of 24.1 mg / L in the effluent; an average removal rate of 77.9% for total nitrogen, and an average total nitrogen of 13.68 mg / L in the effluent; an average removal rate of 52.1% for orthophosphate, and an average total nitrogen of 1.41 mg / L in the effluent. By comparison, it can be found that after adopting the sewage biological denitrification and phosphorus removal system, the removal efficiency of the system for organic matter, total nitrogen and orthophosphate has been greatly improved.

[0188] From the 46th to the 75th day, the pollution load of organic matter and nitrogen source in the influent was further reduced by using the sewage biological denitrification and phosphorus removal system, while keeping the low carbon-nitrogen ratio unchanged, so as to better meet the actual conditions of the urban sewage treatment plant. Under the long-term operation of the sewage biological denitrification and phosphorus removal system, the average COD of the system effluent during this stage was 28.3mg / L, the average total nitrogen of the effluent was 9.17mg / L, and the average orthophosphate of the effluent was 0.15mg / L. That is, through the sewage biological denitrification and phosphorus removal system, efficient purification treatment of low carbon-nitrogen ratio municipal sewage can be achieved, and synchronous denitrification and phosphorus removal can be completed without additional addition of carbon source and other agents. Under the premise of ensuring the removal effect, the sewage biological denitrification and phosphorus removal system can reduce the aeration energy consumption by about 55% compared with the traditional treatment system and method.

[0189] Example 2: Experiment along the way

[0190] In this example, in order to further illustrate the material transformation process in the sewage biological denitrification and phosphorus removal system, a monitoring experiment of various pollutants and internal carbon source components along the process was also carried out. Figure 3 As shown. For the theoretical conversion rate of the internal carbon source in the system in Example 1, COD and the measured COD conversion rate along the process σ COD The calculation formula is as follows:

[0191]

[0192]

[0193] Calculating the internal carbon source conversion rate can evaluate the metabolic activities of microorganisms in the anaerobic zone, especially the activities of glycogen accumulating microorganisms GAOs and phosphate accumulating bacteria PAOs. These microorganisms decompose the endogenous carbon source in the first anoxic zone and the second anoxic zone to provide carbon source support for the denitrification process. Combined with the changes in COD and nitrogen source concentration in each area of ​​the system, φ COD =75.91%,σ COD =72.40%. The calculation results show that in the sewage biological denitrification and phosphorus removal system, microorganisms have high metabolic activity and can effectively utilize the carbon source in the influent, proving that the sewage biological denitrification and phosphorus removal system has strong application value in treating low carbon-nitrogen ratio municipal sewage with limited carbon source.

[0194] In the sewage biological denitrification and phosphorus removal system, assimilation accounts for 86.46% of the ammonia nitrogen removal mechanism in the system, 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. Nitrification accounts for only 13.54% of the ammonia nitrogen removal. This means that when using the sewage biological denitrification and phosphorus removal system, a lower dissolution intensity may be used in the aerobic tank to meet the ammonia nitrogen removal requirements, that is, the sewage biological denitrification and phosphorus removal system is more suitable for the stable operation of the low dissolved oxygen aeration system.

[0195] The corresponding calculation formula is as follows:

[0196] (1) Contribution rate of assimilation in the anaerobic pool to remove ammonia nitrogen:

[0197]

[0198] (2) Contribution rate of assimilation in the anoxic pool to remove ammonia nitrogen:

[0199]

[0200] (3) Contribution rate of nitrification in the aerobic pool to remove ammonia nitrogen:

[0201]

[0202] (4) Contribution rate of assimilation in the sedimentation tank to remove ammonia nitrogen:

[0203]

[0204] According to the material conservation equation, in the sewage biological denitrification and phosphorus removal system, the nitrate concentrations in the anaerobic tank and the anoxic tank were reduced by 10.64 mg / L and 17.19 mg / L respectively, and subsequently, under the action of ammonia oxidizing bacteria AOB and NOB, ammonia nitrogen and nitrite were oxidized to nitrate. The denitrification contribution rates of the denitrification reaction in the anaerobic tank and the anoxic zone accounted for 38.23% and 61.77% respectively.

[0205] The nitrate removal rate in the first anoxic pool is 57.02%, and the COD content required for denitrification in this area can be calculated as ΔCOD de =9.84 mg / L. Combined with the COD content changes measured along the way, the COD consumption in the first anoxic tank is ΔCOD 第一缺氧池 =4.64mg / L, indicating that microorganisms other than traditional denitrifying bacteria are involved in the denitrification process. According to the changes in phosphate content and polyhydroxyalkanoate PHA content, the phosphate concentration after the polyphosphate bacteria in the anaerobic tank releases phosphorus is 33.36mg / L, while the phosphate concentration in the mixed liquid returned from the second aerobic tank to the first anoxic tank is 0.15mg / L. If it is assumed that no reaction related to phosphorus removal occurs in the anoxic tank, the theoretical phosphate content in the first anoxic tank can be obtained from the material conservation equation as 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 denitrification and phosphorus removal process in the first anoxic tank.

[0206] In the first anoxic pool, the glycogen content increased to 18.75 mg / gSS and reached a peak in the second anoxic pool. This may be due to the fact that the denitrifying phosphate-accumulating bacteria DPAOs used part of the PHA to convert into glycogen for their growth under anoxic conditions. In the first aerobic pool, the phosphate-accumulating bacteria provided energy by degrading PHA under aerobic conditions and absorbed phosphate PO4 in the in vitro environment. 3- And converted into polyphosphate Poly-P, and consume glycogen for its growth and reproduction. This is consistent with the experiment in the first aerobic pool PO4 3- In the biological denitrification and phosphorus removal system for sewage, the denitrification contribution rate of the denitrification process accounts for 52.85% of the denitrification, that is, the biological denitrification and phosphorus removal system for sewage still has the technical advantage of efficient simultaneous denitrification and phosphorus removal under the condition of insufficient carbon source.

[0207] The relevant calculation formula is as follows:

[0208] (1) Nitrate reduction concentration in the anaerobic zone:

[0209]

[0210] (2) Nitrate reduction concentration in the first anoxic pool:

[0211]

[0212] (3) Contribution rate of denitrification in the anaerobic tank:

[0213]

[0214] (4) Contribution rate of denitrification in the first anoxic pool:

[0215]

[0216] (5) Nitrate removal rate of the first anoxic tank:

[0217]

[0218] (6) Theoretical COD consumption value of the denitrification process in the first anoxic tank:

[0219]

[0220] (7) Actual COD consumption value of the denitrification process in the first anoxic tank:

[0221]

[0222] (8) Denitrification contribution rate of the denitrification and phosphorus removal process in the first anoxic tank:

[0223]

[0224] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, 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 invention.

[0225] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and to form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present invention and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A sewage biological denitrification and phosphorus removal system, characterized in that: include: The anaerobic zone, denitrification anoxic zone, low dissolved oxygen aeration zone, solid-liquid separation zone and equipment zone are sequentially connected along the sewage flow direction; The anaerobic zone is provided with anaerobic activated sludge; The denitrification anoxic zone is provided with anoxic activated sludge; the low dissolved oxygen aeration zone is provided with aerobic activated sludge; The anaerobic zone, the denitrification anoxic zone and the low dissolved oxygen aeration zone are all operated with high sludge concentration; The anaerobic zone is an environment without dissolved oxygen and is connected to a water inlet pipe for placing sewage; The solid-liquid separation zone is provided with a drain pipe; The equipment area includes stirring equipment arranged in the anaerobic area and the denitrification anoxic area and dissolved oxygen supply equipment arranged in the low dissolved oxygen aeration area.

2. The sewage biological denitrification and phosphorus removal system as claimed in claim 1, characterized in that: The denitrification anoxic zone includes a first anoxic pool and a second anoxic pool; The anaerobic zone is connected to the first anoxic tank through an overflow hole, so that the first anoxic tank receives 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.

3. The sewage biological denitrification and phosphorus removal system as claimed in claim 2, characterized in that: The low dissolved oxygen aeration zone includes a first aerobic tank and a second aerobic tank connected in sequence; The first aerobic pool is connected to the second anoxic pool; The second aerobic tank is connected to the solid-liquid separation zone through an overflow pipe.

4. The sewage biological denitrification and phosphorus removal system as claimed in claim 3, characterized in that: The equipment area also includes dissolved oxygen meters arranged in the first aerobic tank and the second aerobic tank.

5. The sewage biological denitrification and phosphorus removal system as claimed in claim 4, characterized in that: The equipment area also includes frequency conversion control equipment; 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 within the range of 0.8mg / L to 1.2mg / L, and the dissolved oxygen concentration of the second aerobic tank within the range of 0.4mg / L to 0.6mg / L.

6. The sewage biological denitrification and phosphorus removal system as claimed in claim 5, characterized in that: The dissolved oxygen supplying device comprises a blower and a flow meter connected to the blower.

7. The sewage biological denitrification and phosphorus removal system as claimed in claim 4, characterized in that: 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 arranged on the first reflux 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 as claimed in claim 7, characterized in that: In the sewage biological denitrification and phosphorus removal system, the concentration of sludge therein is controlled to be maintained at 8000 mg / L to 10000 mg / L through the first reflux pump and the first reflux pipeline; The reflux ratio of the first reflux pump is 100%.

9. The sewage biological denitrification and phosphorus removal system as claimed in claim 4, characterized in that: 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 arranged on the second reflux pipeline so as to return the sewage in the second aerobic tank to the first anoxic tank; Preferably, the reflux ratio of the second reflux pump is 300%.

10. A method for treating sewage, characterized in that: Based on the sewage biological denitrification and phosphorus removal system according to any one of claims 1 to 9, the sewage treatment method comprises: S1, putting anaerobic activated sludge into the anaerobic zone of the sewage biological denitrification and phosphorus removal system, putting anoxic activated sludge into the denitrification anoxic zone of the sewage biological denitrification and phosphorus removal system, and putting aerobic activated sludge into the low dissolved oxygen aeration zone of the sewage biological denitrification and phosphorus removal system; S2, controls the water inlet pipe to release sewage into the anaerobic zone; S3, controlling the dissolved oxygen supply device in the low dissolved oxygen aeration zone to provide dissolved oxygen through the equipment zone, and controlling the stirring device in the equipment zone to stir in the anaerobic zone and the denitrification anoxic zone; After passing through the anaerobic zone, the sewage enters the denitrification anoxic zone for denitrification and denitrification, and then enters the low dissolved oxygen aeration zone for nitrification and phosphorus accumulation, and then enters the solid-liquid separation zone for solid-liquid separation. The treated supernatant is discharged through a drain pipe. Preferably, in the sewage biological denitrification and phosphorus removal system, the concentration of the sludge therein is controlled to be maintained at 8000 mg / L-10000 mg / L by the first reflux pump and the first reflux pipeline; Preferably, the reflux ratio of the first reflux pump is 100%; Preferably, the frequency conversion control device in the equipment area controls the dissolved oxygen supply device to make the dissolved oxygen concentration of the first aerobic tank within the range of 0.8mg / L to 1.2mg / L and the dissolved oxygen concentration of the second aerobic tank within the range of 0.4mg / L to 0.6mg / L based on the detection data of the dissolved oxygen meters in the first aerobic tank and the second aerobic tank in the low dissolved oxygen aeration zone; Preferably, the sewage in the second aerobic tank is returned to the first anoxic tank in the denitrification anoxic zone through a second return pipeline by a second return pump in the equipment zone; Preferably, the reflux ratio of the second reflux pump is 300%; Preferably, the concentrated sludge in the solid-liquid separation zone is returned to the anaerobic zone through the first reflux pump in the equipment zone.

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