Sewage treatment system control method

Abstract

The invention provides a sewage treatment system control method which is applied to an AOA sewage treatment system, and the AOA sewage treatment system comprises a denitrifying microorganism directional screening device, and a biochemical pool and a secondary sedimentation tank which are connected in sequence; the control method comprises the following steps: acquiring the current total nitrogen concentration of the effluent of the secondary sedimentation tank to obtain the total nitrogen concentration of the effluent, and controlling the running state of the denitrifying microorganism directional screening device by utilizing the total nitrogen concentration of the effluent. According to the sewage treatment system control method provided by the invention, on the basis of promoting the denitrification effect, reducing the total nitrogen concentration of the effluent and improving the quality of the effluent, the operation efficiency of the system can be further improved, and the operation cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a sewage treatment system control method. Background Art

[0002] The AOA sewage treatment system is a system that treats sewage through the anaerobic-aerobic-anoxic process (AOA process), and is widely used in various fields such as urban domestic sewage and industrial wastewater. In the AOA process, the anoxic stage mainly realizes denitrification, that is, through the action of denitrifying microorganisms, nitrates or nitrites are reduced to nitrogen gas, thereby achieving sewage denitrification treatment, which is one of the core processes in sewage treatment. However, in actual application, there is often a decrease in denitrification capacity, which affects the denitrification effect of the system, resulting in increased total nitrogen concentration in the effluent, substandard effluent water quality, and other problems, increasing the difficulty and cost of subsequent treatment. Summary of the invention

[0003] In view of this, the purpose of this application is to propose a sewage treatment system control method to solve the technical problems of insufficient denitrification capacity and poor denitrification effect.

[0004] The present application provides a sewage treatment system control method, which is applied to an AOA sewage treatment system, wherein the AOA sewage treatment system comprises a denitrifying microorganism directional screening device and a biochemical tank and a secondary sedimentation tank connected in sequence;

[0005] The bottom of the secondary sedimentation tank is connected to the biochemical tank via a reflux pipeline;

[0006] The denitrifying microorganism directional screening device is connected to the return pipeline and the biochemical pool, and is used to screen part of the sludge in the return pipeline to obtain target sludge and external sludge, and return the target sludge to the biochemical pool, and discharge the external sludge to the outside of the system; wherein the number of denitrifying microorganisms in the target sludge is higher than the number of denitrifying microorganisms in the external sludge;

[0007] The control method comprises:

[0008] The current total nitrogen concentration of the effluent from the secondary sedimentation tank is obtained to obtain the effluent total nitrogen concentration, and the effluent total nitrogen concentration is used to control the operating state of the denitrifying microorganism directional screening device.

[0009] Furthermore, the use of the effluent total nitrogen concentration to control the operating state of the denitrifying microorganism directional screening device includes:

[0010] In response to the effluent total nitrogen concentration being greater than or equal to the effluent total nitrogen concentration standard value, controlling the denitrifying microorganism directional screening device to operate at a first parameter with the highest load;

[0011] In response to the effluent total nitrogen concentration being greater than or equal to a first threshold value and less than the effluent total nitrogen concentration standard value, the current denitrification rate of the biochemical pool is obtained and a denitrification rate judgment step is performed to determine the operating status of the denitrifying microorganism directional screening device using the current denitrification rate.

[0012] Furthermore, the denitrification rate determination step includes:

[0013] In response to the current denitrification rate being less than a second threshold, controlling the denitrifying microorganism directional screening device to operate with a second parameter;

[0014] In response to the current denitrification rate being less than the denitrification rate target value and greater than or equal to the second threshold, controlling the denitrifying microorganism directional screening device to operate with a third parameter;

[0015] Wherein, the number of denitrifying microorganisms screened by the denitrifying microorganism directional screening device decreases successively when the first parameter, the second parameter and the third parameter are operated.

[0016] Furthermore, the denitrifying microorganism directional screening device is a hydrocyclone;

[0017] Among them, the first parameter, the second parameter and the third parameter all include an underflow overflow cross-sectional area ratio, and the underflow overflow cross-sectional area ratios corresponding to the first parameter, the second parameter and the third parameter decrease in sequence.

[0018] Furthermore, the first parameter, the second parameter and the third parameter also include a feed flow rate, and the feed flow rates corresponding to the first parameter, the second parameter and the third parameter decrease in sequence.

[0019] Furthermore, the biochemical pool includes an anaerobic pool, a first conversion zone, an aerobic pool and an anoxic pool connected in sequence; the control method also includes:

[0020] In response to determining to start the denitrifying microorganism directional screening device, the actual volume of the anoxic tank required when the effluent water quality of the AOA sewage treatment system meets the standard is calculated, and the operating state of the first conversion zone is determined using the actual volume of the anoxic tank.

[0021] And / or, a second conversion zone is further provided between the aerobic pool and the anoxic pool; the control method further comprises:

[0022] In response to determining to start the denitrifying microorganism directional screening device, the actual volume of the aerobic tank required when the effluent water quality of the AOA sewage treatment system meets the standard is calculated, and the operating state of the second conversion zone is determined using the actual volume of the aerobic tank.

[0023] Further, the determining the operating state of the first conversion zone by using the actual volume of the anoxic pool includes:

[0024] In response to the actual volume of the anoxic tank being smaller than the designed volume of the anoxic tank, controlling the first conversion zone to be in an anaerobic state;

[0025] In response to the actual volume of the anoxic pool being greater than or equal to the designed volume of the anoxic pool, controlling the first conversion zone to be in anoxic state;

[0026] The step of determining the operating state of the second conversion zone by using the actual volume of the aerobic pool includes:

[0027] In response to the actual volume of the aerobic pool being smaller than the designed volume of the aerobic pool, controlling the second conversion zone to be in an anoxic state;

[0028] In response to the actual volume of the aerobic tank being greater than or equal to the designed volume of the aerobic tank, the second conversion zone is controlled to be in an aerobic state.

[0029] Furthermore, the actual volume of the anoxic pool is calculated by the following steps:

[0030] The actual volume of the anoxic tank is calculated using the influent flow rate, influent total nitrogen concentration, daily sludge discharge volume, effluent total nitrogen concentration standard value, current denitrification rate and current sludge concentration of the first conversion zone of the AOA sewage treatment system;

[0031] The actual volume of the aerobic pool is calculated by the following steps:

[0032] The actual volume of the aerobic tank is calculated using the inlet flow, inlet COD concentration, effluent COD concentration standard value, sludge age, sludge production coefficient and current sludge concentration of the second conversion zone of the AOA sewage treatment system.

[0033] Furthermore, the AOA sewage treatment system also includes a water inlet pipeline and a segmented water inlet branch line;

[0034] The water inlet pipeline is connected to the anaerobic tank to pass the sewage to be treated into the anaerobic tank;

[0035] One end of the segmented water inlet branch line is connected to the water inlet pipeline, and the other end is connected to the anoxic tank;

[0036] The control method further comprises:

[0037] The ratio coefficient is calculated based on the ratio of the difference in COD concentration between the inlet and outlet water of the AOA sewage treatment system to the difference in total nitrogen concentration;

[0038] In response to the ratio coefficient being less than a third threshold, the segmented water inlet branch line is controlled to be opened so as to guide part of the water inlet pipeline into the anoxic tank.

[0039] Furthermore, an air supply area is provided between the anoxic tank and the secondary sedimentation tank;

[0040] And / or, a drain outlet is provided at the upper part of the secondary sedimentation tank, and a mud discharge outlet connected to the return pipeline is provided at the bottom, and the drain outlet is connected to a drainage pipeline to guide the treated sewage to the next stage;

[0041] And / or, the return pipeline is connected to the anaerobic tank, and the target sludge is returned to the first conversion zone.

[0042] As can be seen from the above, the present application provides a sewage treatment system control method, which is applied to the AOA sewage treatment system. First, a denitrifying microorganism directional screening device is set on the sludge return path (and return pipeline) of the AOA sewage treatment system to effectively screen the sludge in the system, separate the target sludge with a high number of denitrifying microorganisms from the external sludge with a low number of denitrifying microorganisms, and return the target sludge to the biochemical pool to increase the number and activity of denitrifying microorganisms in the biochemical pool, promote denitrification, and thus effectively improve the denitrification efficiency; secondly, the effect of denitrification directly affects the concentration of total nitrogen in the effluent. When the denitrification effect decreases, the total nitrogen concentration of the effluent will increase significantly. When the denitrification capacity increases, the total nitrogen concentration of the effluent will decrease. Therefore, the total nitrogen concentration of the effluent of the system is used to regulate the operating state of the denitrifying microorganism directional screening device, so that the operation of the denitrifying microorganism directional screening device is more in line with the actual situation of the AOA sewage treatment system. On the basis of promoting denitrification, reducing the total nitrogen concentration of the effluent, and improving the effluent water quality, the system operation efficiency can be further improved and the operation cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 is a schematic diagram of the AOA sewage treatment system in an embodiment of the present application;

[0045] Figure 2 This is a flow chart of a sewage treatment system control method in an embodiment of the present application;

[0046] Figure 3Schematic diagram of another sewage treatment system in an embodiment of the present application.

[0047] Figure numerals: 100-biochemical pool; 101-anaerobic pool; 102-first conversion zone; 103-aerobic pool; 104-second conversion zone; 105-anoxic pool; 106-aeration zone; 200-second sedimentation tank; 300-denitrifying microorganism directional screening device; 400-reflux pipeline; 500-feed pipeline; 600-underflow pipeline; 700-overflow pipeline; 800-water inlet pipeline; 810-segmented water inlet branch line; 900-drainage pipeline. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0049] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should be the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in the embodiments of the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0050] The AOA process is an anaerobic-aerobic-anoxic process, including the anaerobic stage, the aerobic stage and the anoxic stage. It is a post-anoxic denitrification operation mode, which is conducive to the enrichment of polyphosphate and polysaccharide bacteria, promotes the storage and utilization of internal carbon sources, and greatly reduces the concentration of organic matter entering the aerobic stage. In the anaerobic stage, the polyphosphate bacteria mainly release phosphorus and degrade organic matter. Under anaerobic conditions, the polyphosphate bacteria decompose the polyphosphate stored in the body and release it into the water in the form of phosphate, creating conditions for phosphorus absorption in the aerobic stage; at the same time, the polyphosphate bacteria or polysaccharide bacteria can convert the easily degradable organic matter in the sewage into an internal carbon source, which can be stored by microorganisms to provide a carbon source for subsequent denitrification and the activity of polyphosphate bacteria. In the aerobic stage, nitrification, phosphorus removal and organic matter degradation are mainly carried out. Aerobic microorganisms (such as nitrifying bacteria) convert ammonia nitrogen (NH 4 + ) is oxidized to nitrite (NO 2 -) or nitrate (NO 3 - ), providing nitrate for denitrification in the anoxic stage; in an aerobic environment, polyphosphate bacteria use the phosphate released in the anaerobic stage to store polyphosphate through biological metabolism to achieve phosphorus removal; and under the active aerobic heterotrophic bacteria, decompose the organic matter in the sewage to reduce the COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) of the sewage. In the anoxic stage, denitrification mainly occurs. Under anoxic conditions, denitrifying microorganisms use nitrates or nitrites generated in the aerobic stage as electron acceptors and organic matter as a carbon source to reduce them to nitrogen gas, which eventually escapes from the water, thereby achieving total nitrogen removal and further reducing the concentration of organic matter in the sewage. In the AOA process, the reduction of denitrification will directly affect the denitrification effect, resulting in a decrease in the removal efficiency of total nitrogen (TN), which will cause problems such as increased total nitrogen concentration in the effluent and substandard effluent water quality, increasing the difficulty and cost of subsequent deep treatment.

[0051] In view of this, the present application provides a sewage treatment system control method, which is applied to the AOA sewage treatment system, such as Figure 1 As shown, the AOA sewage treatment system includes a denitrifying microorganism directional screening device 300 and a biochemical pool 100 and a secondary sedimentation tank 200 connected in sequence;

[0052] The bottom of the secondary sedimentation tank 200 is connected to the biochemical tank 100 via a return line 400;

[0053] The denitrifying microorganism directional screening device 300 is connected to the return pipeline 400 and the biochemical pool 100, and is used to screen part of the sludge in the return pipeline 400 to obtain target sludge and external sludge, and return the target sludge to the biochemical pool 100, and discharge the external sludge to the outside of the system; wherein the number of denitrifying microorganisms in the target sludge is higher than the number of denitrifying microorganisms in the external sludge;

[0054] The control method comprises:

[0055] The current total nitrogen concentration of the effluent from the secondary sedimentation tank 200 is obtained to obtain the effluent total nitrogen concentration, and the operating state of the denitrifying microorganism directional screening device 300 is controlled by using the effluent total nitrogen concentration.

[0056] In the AOA sewage treatment system, the biochemical pool 100 is used to implement the AOA process, i.e., the anaerobic-aerobic-anoxic process. The water treated by the biochemical pool 100 is passed into the secondary sedimentation tank 200 for sedimentation to achieve mud and water separation. The upper clear liquid is the treated sewage, which is discharged to the subsequent process, such as the deep treatment stage, etc. The lower layer is sludge, which is rich in microorganisms required for biochemical treatment and returns to the biochemical pool 100 through the return line 400 to continue to participate in the reaction. In the AOA sewage treatment system, denitrifying microorganisms are the executors of the denitrification process, and their number and activity will directly affect the denitrification capacity of the system.

[0057] According to research, the distribution of microorganisms in activated sludge flocs usually presents a hierarchical structure. It is a complex ecosystem composed of a variety of microorganisms. Microorganisms are distributed and arranged in a specific way in the flocs, forming a hierarchical structure with functional differentiation. In the outer layer, i.e., the surface of the flocs, due to direct contact with the water phase, the concentration of oxygen and organic matter is high, and it is directly affected by the external dissolved oxygen. It is an area where aerobic conditions are dominant. Therefore, the main distributed microorganisms are aerobic microorganisms (such as nitrifying bacteria, heterotrophic bacteria, etc.) and aerobic polyphosphate bacteria. Inside the flocs, the oxygen supply is limited (low DO environment), close to anoxic or microaerobic state, which is conducive to the growth of anaerobic microorganisms (such as denitrifying bacteria). When the sludge flocs are large and have a certain degree of compactness, the inner layer can form a low oxygen or anoxic environment, which is conducive to the growth of denitrifying microorganisms. At the same time, because denitrifying microorganisms can inhibit the excessive reproduction of filamentous bacteria, the sludge is usually not easy to swell and has good sedimentation performance. Therefore, sludge with a large number of denitrifying microorganisms and good activity usually presents a good flocculent state, has good sedimentation performance, and has a large floc diameter, while sludge with poor sedimentation performance and looseness contains fewer denitrifying microorganisms. Therefore, the different characteristics of sludge with a large number of denitrifying microorganisms and good activity and sludge with a small number of denitrifying microorganisms and low activity can be used to achieve sludge screening, and then the sludge with a large number of denitrifying microorganisms and good activity (i.e., target sludge) and the sludge with a small number of denitrifying microorganisms and low activity (i.e., discharged sludge) can be effectively separated.

[0058] In the present application, a denitrifying microorganism directional screening device 300 is set on the sludge return path (i.e., the return pipeline 400) of the AOA sewage treatment system to effectively screen the sludge in the system, separate the target sludge with a high number of denitrifying microorganisms from the discharged sludge with a low number of denitrifying microorganisms, and return the target sludge to the biochemical pool 100 to increase the number and activity of denitrifying microorganisms in the biochemical pool 100, promote denitrification, and thus effectively improve the denitrification efficiency. The effect of denitrification directly affects the concentration of total nitrogen in the effluent. When the denitrification effect decreases, the concentration of total nitrogen in the effluent will increase significantly. When the denitrification capacity increases, the concentration of total nitrogen in the effluent will decrease. Therefore, the operation state of the denitrifying microorganism directional screening device 300 is regulated by using the total nitrogen concentration in the effluent of the system, so that the operation of the denitrifying microorganism directional screening device 300 can better meet the actual situation of the AOA sewage treatment system. On the basis of promoting denitrification, reducing the concentration of total nitrogen in the effluent and improving the effluent water quality, the system operation efficiency can be further improved and the operation cost can be reduced.

[0059] In addition, the denitrification capacity of the system is affected not only by the number and activity of denitrifying microorganisms, but also by the combined influence of multiple factors such as dissolved oxygen (DO) concentration, carbon source concentration, nitrate concentration, temperature, and hydraulic retention time in the anoxic zone. Carbon source is the electron donor of the denitrification reaction, and nitrate concentration is the electron acceptor of denitrification. Both are directly involved in the denitrification process, and their concentrations will affect the occurrence of the denitrification reaction; denitrification needs to be carried out under anaerobic conditions, and oxygen will preferentially serve as an electron acceptor, so excessive dissolved oxygen concentration will also inhibit the denitrification reaction; temperature affects the metabolic rate and enzyme activity of denitrifying microorganisms, and the denitrification reaction requires a certain reaction time, so temperature, hydraulic retention time, etc. will also affect the denitrification process. However, in the actual operation of the AOA sewage treatment system, the carbon source concentration and nitrate concentration fluctuate greatly due to the influence of the influent water quality, nitrification reaction conditions, etc. It is difficult to promote the denitrification process by adjusting these two parameters, and the control accuracy is not high. Improper adjustment can easily lead to excess carbon source and nitrate, which in turn causes an increase in the total nitrogen and COD concentrations in the effluent. If denitrification is to be promoted by adjusting the temperature, on the one hand, the reactions in the system are complex, and the types and numbers of microorganisms are large. Frequent temperature adjustments can easily cause an imbalance in microbial competition and limit the adjustment accuracy. On the other hand, the cost of adjustment is also high, and the effect of promoting denitrification by temperature is also limited. If the denitrification capacity is promoted by changing the hydraulic retention time, the treatment efficiency of the OA sewage treatment system will be reduced first, and the amount of sewage that can be treated per unit time will be reduced, which does not meet the actual needs of the sewage treatment plant; secondly, the sewage needs to go through a very long process from entering the sewage treatment plant to the final water quality representative after discharge. For example, before entering the AOA sewage treatment system for treatment, it is usually necessary to go through a pretreatment stage. After being treated by the AOA sewage treatment system, it is necessary to enter deep treatment for further treatment. Therefore, the change in the treatment capacity of the AOA sewage treatment system will affect the efficiency of the entire sewage treatment process, and will have a certain impact on the treatment volume and treatment efficiency of the previous and subsequent processes; finally, the effect of promoting denitrification by adjusting the hydraulic retention time is also limited. Therefore, this application takes into account the treatment efficiency, cost investment, practical application difficulty, accuracy and other factors of the comprehensive sewage treatment process. By screening the sludge and returning the target sludge with a large number of denitrifying microorganisms and good activity to the system, it can not only quickly improve the denitrification capacity, but also has a low operating difficulty and high control accuracy, which is easy to promote in actual application of sewage treatment plants, and can also further improve the sewage treatment capacity and efficiency of sewage treatment plants.

[0060] In some embodiments, the method of controlling the operating state of the denitrifying microorganism directional screening device 300 by using the effluent total nitrogen concentration includes:

[0061] In response to the effluent total nitrogen concentration being greater than or equal to the effluent total nitrogen concentration standard value, controlling the denitrifying microorganism directional screening device 300 to operate at the first parameter with the highest load;

[0062] In response to the effluent total nitrogen concentration being greater than or equal to the first threshold value and less than the effluent total nitrogen concentration standard value, the current denitrification rate of the biochemical pool 100 is obtained and a denitrification rate judgment step is performed to determine the operating status of the denitrifying microorganism directional screening device 300 using the current denitrification rate.

[0063] In the present application, when the effluent total nitrogen concentration is greater than or equal to the effluent total nitrogen concentration standard value, it indicates that the current denitrification capacity has decreased significantly. In order to quickly reduce the system effluent total nitrogen concentration, improve the effluent water quality and ensure that the effluent water quality meets the standard, the system operates with the first parameter with the highest load at this time, that is, under the first parameter, the denitrifying microorganism directional screening device 300 operates at full load, and more denitrifying microorganisms are screened and returned to the biochemical pool 100, thereby quickly increasing the number and activity of denitrifying microorganisms in the biochemical pool 100, thereby promoting denitrification, strengthening the system denitrification effect, and reducing the effluent total nitrogen concentration.

[0064] When the effluent total nitrogen concentration is greater than or equal to the first threshold value and less than the standard value of the effluent total nitrogen concentration, it means that the current effluent total nitrogen concentration is up to standard. However, the effluent total nitrogen concentration reaching the standard does not mean that the current denitrification is up to standard or highly efficient, and the denitrification rate may still be low. For example, when the hydraulic retention time in the anoxic stage is long enough, although the denitrification reaction is slow, the total nitrogen removal can still be achieved through a long reaction, but the overall nitrogen removal efficiency of the system is not high, and the cost increases. At the same time, when the denitrification rate in the system is in a low state for a long time, the processing capacity and stability of the system are low, especially in the case of high influent load or water volume fluctuations, which may cause the effluent total nitrogen concentration to be unstable or even exceed the standard; at the same time, the denitrifying microorganisms are in a low number and low activity state for a long time, which will further affect the distribution of the bacterial community, making it difficult for the denitrifying microorganisms to compete with other microorganisms, so that their number and activity are further reduced, and then the system denitrification efficiency is further reduced. Therefore, in order to ensure that the system can operate stably and efficiently for a long time and to ensure that the denitrifying microbial flora always maintains a good state, when the effluent total nitrogen concentration is greater than or equal to the first threshold value and less than the effluent total nitrogen concentration standard value, the current denitrification rate of the biochemical pool 100 is further used to determine the operating state of the denitrifying microorganism directional screening device 300, so as to timely understand the denitrification of the system, so as to timely start the denitrifying microorganism directional screening device 300 to screen the sludge and obtain the target sludge containing a high number of denitrifying microorganisms, thereby timely promoting the denitrification in the system and ensuring the long-term stable and efficient operation of the system.

[0065] The standard value of total nitrogen concentration in effluent can be determined according to the emission standard requirements in different places and scenarios. For example, according to the "Pollutant Discharge Standard for Urban Sewage Treatment Plants" (GB 18918-2002), the total nitrogen control requirements for effluent from urban sewage treatment plants are divided into Level A, Level B and Level II standards. The Level A standard is ≤15mg / L, which is strictly required to be applicable to sensitive water bodies or ecological protection areas; the Level B standard is ≤20mg / L, which is generally applicable to general emission requirements; the Level II standard has no clear TN requirements. For another example, for rural domestic sewage treatment or decentralized small-scale sewage treatment facilities, the total nitrogen requirement for effluent is 15-25mg / L; the total nitrogen emission standard for industrial wastewater can be subdivided according to specific industries, and some industries (such as chemicals, pharmaceuticals, etc.) have stricter requirements, usually ≤10-20mg / L. Therefore, the standard value of the effluent total nitrogen concentration can be set to 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 25 mg / L, etc., according to the specific situation, or it can be set to other values, without specific restrictions. The first threshold value can be determined according to the standard value of the effluent total nitrogen concentration, for example, it can be set to 70% of the standard value of the effluent total nitrogen concentration, or it can be set to other percentages, such as 65%, 68%, 72%, 75%, 78%, 80%, etc. of the standard value of the effluent total nitrogen concentration, without specific restrictions.

[0066] Due to the fluctuation of influent water quality, the effluent water quality parameters usually also fluctuate within a certain range. Therefore, in order to ensure the accuracy of the effluent total nitrogen concentration detection, the effluent total nitrogen concentration detected can truly reflect the actual situation of the effluent water quality, and can be the average value of multiple consecutive measurements. For example, the current total nitrogen concentration of the effluent of the secondary sedimentation tank 200 is tested once an hour, and 4 test results are obtained for 4 consecutive hours, and then the average of the 4 test results is taken as the final effluent total nitrogen concentration.

[0067] The current denitrification rate of the biochemical pool 100 can be calculated by recording the change of the concentration of nitrate (or nitrite) over time. For example, it can be calculated by monitoring the anoxic stage of the biochemical pool 100, first recording the sludge concentration in the anoxic stage, recording the change value of the initial nitrate concentration and the interval time of the reaction, and then calculating according to the change of nitrate concentration and sludge concentration. For example, the denitrification rate can be calculated by the difference of the nitrate concentration of the inlet and outlet water in the anoxic stage, combined with the hydraulic retention time and volume of the anoxic stage. For example, it can be calculated by experimental method, that is, sampling from the anoxic stage of the biochemical pool 100, obtaining a muddy water mixture containing denitrifying microorganisms, maintaining the mixture under anoxic conditions, adjusting the initial nitrate concentration in the mixture to a certain level, and adding an appropriate amount of carbon source (such as acetic acid or glucose, etc.) to ensure that the C / N ratio is appropriate (such as 4 to 6), collecting a certain amount of samples at intervals, and then determining the nitrate concentration in the sample by ion chromatography, ultraviolet spectrophotometry or kit method, and drawing a curve of nitrate concentration over time, and then calculating the denitrification rate. According to actual conditions, the current denitrification rate of the biochemical pool 100 can be calculated in different ways, or it can be directly monitored and calculated by some intelligent online monitoring systems, without specific restrictions. Specifically, the current denitrification rate of the biochemical pool 100 can be detected once a day, multiple times a day, or the average value of multiple times can be taken, etc., without specific restrictions.

[0068] In some embodiments, the control method further includes: in response to the effluent total nitrogen concentration being less than the first threshold, controlling the denitrifying microorganism directional screening device 300 to be closed. When the effluent total nitrogen concentration is less than the first threshold, it means that the current effluent total nitrogen concentration is much lower than the standard value of the effluent total nitrogen concentration, which reflects that the operation of the AOA sewage treatment system is relatively stable and good. Therefore, in order to effectively reduce the operating cost, the denitrifying microorganism directional screening device 300 is controlled to be closed at this time.

[0069] In some embodiments, the denitrification rate determination step comprises:

[0070] In response to the current denitrification rate being less than a second threshold, controlling the denitrifying microorganism directional screening device 300 to operate with a second parameter;

[0071] In response to the current denitrification rate being less than the denitrification rate target value and greater than or equal to the second threshold, controlling the denitrifying microorganism directional screening device 300 to operate with a third parameter;

[0072] Wherein, the number of denitrifying microorganisms screened by the denitrifying microorganism directional screening device 300 decreases successively when the first parameter, the second parameter and the third parameter are operated.

[0073] like Figure 2 As shown, when the current denitrification rate is less than the denitrification rate target value and is greater than or equal to the second threshold value, it means that the current denitrification rate of the biochemical pool 100 is slightly lower than the denitrification rate target value. At this time, although the total nitrogen in the effluent meets the standard, long-term operation may lead to risks such as low system efficiency and reduced denitrification efficiency. Therefore, the denitrifying microorganism directional screening device 300 is controlled to operate with the third parameter; when the current denitrification rate is less than the second threshold value, it means that the current denitrification rate is significantly lower than the denitrification rate target value. The load capacity of the denitrifying microorganism directional screening device 300 under the operation of the first parameter, the second parameter and the third parameter gradually decreases, and the number of denitrifying microorganisms screened also decreases in turn. Since the number of denitrifying microorganisms in the target sludge is higher than the number of denitrifying microorganisms in the discharged sludge, more denitrifying microorganisms can be returned to the biochemical pool 100 under the first parameter and the second parameter, thereby increasing the number and activity of denitrifying microorganisms in the system, thereby improving the denitrification efficiency. When the total nitrogen in the effluent meets the standard, the state of the denitrifying microorganism directional screening device 300 is further determined based on the current denitrification rate, which can effectively improve the stability of the long-term operation of the system and ensure that the denitrification reaction is in a high-efficiency state for a long time, so as to ensure that the effluent water quality is stable and meets the standard; at the same time, a second threshold value lower than the denitrification rate target value is set. When the current denitrification rate is less than the denitrification rate target value and greater than or equal to the second threshold value, the system is operated with the third parameter with the lowest load capacity, which can effectively reduce the system operation cost and is more conducive to practical application and promotion.

[0074] The denitrification rate target value can be set according to different application scenarios, actual conditions, etc. For example, the denitrification rate target value of a common sewage treatment process can range from 1.0 to 5.0 mg NO 3 - -N / (L·h), specifically 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5.0 mg NO 3 - -N / (L·h), can also be 1.0~5.0mg NO 3 - -N / (L·h) is not limited to other values; the denitrification rate target value of the high-efficiency denitrification process can be in the range of 6.0 to 10.0 mg NO 3 - -N / (L·h), specifically 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10.0 mg NO 3 - -N / (L·h), can also be 6.0~10.0mg NO 3 --N / (L·h) are not limited to other values; the denitrification rate target value for urban sewage treatment can range from 1.0 to 3.0 mg NO 3 - -N / (L·h), specifically 1, 1.5, 2, 2.5, 3 mg NO 3 - -N / (L·h), can also be 1.0~3.0mg NO 3 - -N / (L·h) are not limited to other values; the denitrification rate target value for industrial wastewater treatment can range from 4.0 to 6.0 mg NO 3 - -N / (L·h), specifically 4, 4.5, 5, 5.5, 6 mg NO 3 - -N / (L·h), can also be 4.0~6.0mg NO 3 - Other values ​​within -N / (L·h) are not specifically limited.

[0075] The second threshold value can be determined according to the denitrification rate target value, for example, it can be set to 50% of the denitrification rate target value, or it can be set to other percentages, such as 40%, 45%, 55%, 60%, 65%, 70% of the denitrification rate target value, etc., without specific limitation.

[0076] In some embodiments, the control method further includes: in response to the current denitrification rate being greater than or equal to the denitrification rate target value, controlling the denitrifying microorganism directional screening device 300 to be closed. When the current denitrification rate is greater than or equal to the denitrification rate target value, it means that the denitrification efficiency in the biochemical pool 100 can meet the target requirements. At this time, the current denitrification rate and the effluent total nitrogen concentration of the system can meet the target requirements, the reaction system operates well, and the number and activity of denitrifying microorganisms are also good. Therefore, in order to reduce the operating cost, the denitrifying microorganism directional screening device 300 is kept in a closed state at this time, and the return sludge is returned to the biochemical pool 100 through the return pipeline 400.

[0077] In some embodiments, the denitrifying microorganism directional screening device 300 is a hydrocyclone;

[0078] Among them, the first parameter, the second parameter and the third parameter all include an underflow overflow cross-sectional area ratio, and the underflow overflow cross-sectional area ratios corresponding to the first parameter, the second parameter and the third parameter decrease in sequence.

[0079] A hydrocyclone is an efficient separation device that uses the principle of centrifugal force to perform solid-liquid separation, particle classification, impurity removal, and sludge screening. The hydrocyclone uses the principle of centrifugal separation to separate the sludge in the feed into different parts in a high-speed rotating flow field. The heavy sludge (higher density particles or larger flocs) moves toward the periphery of the hydrocyclone under the action of centrifugal force and is discharged through the lower outlet; the light particles (lower density particles or smaller flocs) move toward the center of the hydrocyclone under the action of the internal vortex and are discharged through the top outlet. In the present application, the target sludge with better floc state and better sedimentation performance containing more denitrifying microorganisms moves to the lower part of the hydrocyclone under the action of the vortex, and the externally discharged sludge with poor floc state and sedimentation performance containing fewer denitrifying microorganisms moves to the upper part of the hydrocyclone under the action of the vortex, thereby achieving the screening of the target sludge and the externally discharged sludge.

[0080] The hydrocyclone usually includes a main body and an overflow port at the top of the main body, an underflow port at the bottom of the main body, and a feed port between the overflow port and the underflow port. The sludge enters the main body and is separated from the external sludge by the cyclone. Figure 1 As shown, the feed port is connected to the return line 400 through the feed line 500, so as to introduce the sludge in the return line 400 into the main body of the hydrocyclone; the underflow port is connected to the biochemical pool 100 through the underflow line 600, so as to return the target sludge to the biochemical pool 100; the overflow port is connected to the overflow line 700, so as to discharge the external sludge to the outside of the system. Optionally, the underflow overflow cross-sectional area ratio is the cross-sectional area ratio of the underflow port to the overflow port.

[0081] During the operation of the hydrocyclone, when the diameter ratio of the underflow port to the overflow port is larger, more heavy sludge can be discharged smoothly from the underflow, reducing the possibility of heavy sludge entering the overflow port. When heavy sludge is the screening target, the larger the diameter ratio of the underflow port to the overflow port is, the more separation efficiency is usually improved. Therefore, the underflow overflow cross-sectional area ratio corresponding to the third parameter, the second parameter and the first parameter is set to increase in sequence, so that the target sludge containing a large number of denitrifying microorganisms can flow out smoothly through the underflow port, thereby screening more denitrifying microorganisms and returning them to the biochemical pool 100 to improve the denitrification capacity of the biochemical pool 100.

[0082] In the biochemical treatment of sewage, the number and types of participating microorganisms are large, including aerobic microorganisms, anaerobic microorganisms, denitrifying bacteria, polyphosphate bacteria, nitrifying bacteria, polysaccharide bacteria, etc. The dynamic balance between microorganisms is the key to the long-term stable operation of the system. The dynamic balance of microbial populations means that different types of microorganisms maintain a stable structure in the process of constant competition, growth, and decay to ensure the normal operation of treatment functions such as organic matter degradation, denitrification and phosphorus removal. However, the dynamic balance between microorganisms is a rather complex process, and transitional adjustments can easily cause an imbalance in competition between microorganisms, thereby having a negative impact on the operation of the system. The total nitrogen concentration of the effluent is the most core test indicator for sewage treatment.

[0083] Therefore, if Figure 2 As shown, in this scheme, the total nitrogen concentration of the effluent is first used to determine the operation status of the system, that is, when the total nitrogen concentration of the effluent is less than the first threshold value, it means that the total nitrogen concentration in the effluent is significantly lower than the standard requirement, reflecting that the current microorganisms have reached a good dynamic balance, and the denitrifying microorganism directional screening device 300 is not started at this time; when the total nitrogen concentration of the effluent is greater than or equal to the standard value of the total nitrogen concentration of the effluent, it reflects that the competition between the current microorganisms has been obviously unbalanced, and the system is operated at the highest underflow overflow cross-sectional area ratio (i.e., the first parameter), and sludge with poor quality and low denitrifying microorganism content (i.e., externally discharged sludge) is discharged from the system to increase the proportion of denitrifying microorganisms, thereby quickly correcting the competition status between various microorganisms in the system and promoting them to reach a new balance. When the effluent total nitrogen concentration is greater than or equal to the first threshold value and less than the standard value of the effluent total nitrogen concentration, although the effluent water quality can meet the standard at this time, in order to ensure the long-term stable operation of the system, the current denitrification rate is used to further evaluate the operation of the system. When the current denitrification rate is less than the second threshold value, it reflects that the current competition relationship between microorganisms is very unfavorable for the growth of denitrifying microorganisms. Therefore, the system is operated with the second parameter. The underflow overflow cross-sectional area of ​​the second parameter is smaller than the first parameter. When the system is operated with this parameter, more denitrifying microorganisms can be returned without causing excessive fluctuations in the effluent water quality. When the current denitrification rate is less than the denitrification rate target value and greater than or equal to the second threshold value, it means that the water quality meets the standard but is not conducive to the long-term operation of the system. At this time, the system is operated with the lowest underflow overflow cross-sectional area ratio, which can appropriately increase the proportion of denitrifying microorganisms in the system and gradually improve the denitrification capacity of the system without causing new problems due to the imbalance of competition between the microorganisms in the system due to the addition of too many denitrifying microorganisms in a short period of time.

[0084] Activated sludge usually contains high concentrations of organic matter and colloids. Compared with solid-liquid separation, it has problems such as high viscosity, poor fluidity, small density difference, and poor classification accuracy. The sludge in the return line also has the above characteristics. Therefore, when using the denitrifying microorganism directional screening device 300 to achieve target sludge and external sludge screening, the above problems also exist. In this solution, by adjusting the underflow overflow cross-sectional area ratio of the denitrifying microorganism directional screening device 300, compared with a single adjustment of the cross-sectional area of ​​the overflow port or the underflow port, the separation accuracy and separation efficiency can be effectively improved, which is more suitable for sludge screening. The sludge has high viscosity and poor fluidity, and unstable flow states (such as turbulence or short-circuit flow) are easily formed in the cyclone. Only adjusting the cross-sectional area of ​​the overflow or underflow port may cause flow field imbalance, further aggravating the uneven separation. By controlling the underflow-overflow cross-sectional area ratio, the difference between the underflow cross-sectional area and the overflow cross-sectional area can be controlled, avoiding the problem of overflow or underflow transition adjustment, thereby stabilizing the centrifugal field, reducing flow field imbalance, and ensuring separation accuracy; at the same time, it can also avoid the overflow or underflow being in a high-load state for a long time, reduce the risk of clogging, and ensure its long-term stable operation; avoid internal pressure fluctuations easily caused by single parameter adjustment, reduce turbulence and backmixing problems, and further improve separation efficiency.

[0085] In some embodiments, the range of the bottom flow overflow cross-sectional area ratio corresponding to the first parameter is greater than or equal to 8 and less than or equal to 10, the range of the bottom flow overflow cross-sectional area ratio corresponding to the second parameter is greater than or equal to 6 and less than 8, and the range of the bottom flow overflow cross-sectional area ratio corresponding to the third parameter is greater than or equal to 5 and less than 6.

[0086] When the underflow overflow cross-sectional area ratio is too large or too small, some poor quality sludge may not be able to flow out from the overflow port. When the underflow overflow cross-sectional area ratio is too small, it means that the cross-sectional area of ​​the underflow port is too small, and large-diameter sludge flocs containing more denitrifying microorganisms may not be able to flow out smoothly through the underflow port, which may also lead to problems such as reduced screening efficiency. Therefore, in order to further ensure the screening efficiency and stability, the underflow overflow cross-sectional area ratio is maintained in a more appropriate range, that is, the value range of the underflow overflow cross-sectional area ratio corresponding to the first parameter is greater than or equal to 8 and less than or equal to 10, the value range of the underflow overflow cross-sectional area ratio corresponding to the second parameter is greater than or equal to 6 and less than 8, and the value range of the underflow overflow cross-sectional area ratio corresponding to the third parameter is greater than or equal to 5 and less than 6. Specifically, the underflow overflow cross-sectional area ratio corresponding to the first parameter can be 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 9.95, etc., or other values ​​within the aforementioned range, without specific limitation; the underflow overflow cross-sectional area ratio corresponding to the second parameter can be 6, 6.1, 6.2, 6.3, 6.4, 6.5 , 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 7.95, etc., or other values ​​in the aforementioned range, without specific limitation; the underflow overflow cross-sectional area ratio corresponding to the second parameter can be 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 5.95, etc., or other values ​​in the aforementioned range, without specific limitation.

[0087] The larger the cross-sectional area of ​​the opening, the larger the diameter or equivalent diameter of the opening. Therefore, when the cross-sectional area of ​​the underflow overflow is relatively large, it means that the diameter or equivalent diameter of the underflow port is larger, which is conducive to the passage of large-diameter sludge flocs, that is, it is conducive to the passage of target sludge containing more denitrifying microorganisms, thereby screening more denitrifying microorganisms. In the actual application process, in order to further ensure the screening effect and efficiency, the cross-sectional area range of the underflow port can be further limited, that is, the first parameter, the second parameter and the third parameter all include the cross-sectional area of ​​the underflow port, the cross-sectional area of ​​the underflow port corresponding to the first parameter is not less than the first area, the cross-sectional area of ​​the underflow port corresponding to the second parameter is not less than the second area, and the cross-sectional area of ​​the underflow port corresponding to the third parameter is not less than the third area, wherein the first area, the second area and the third area gradually decrease. Specifically, the first area is 0.06m 2 , the second area is 0.04m 2 , the third area is 0.02m 2The diameter of sludge containing more denitrifying microorganisms is larger, so the minimum cross-sectional area of ​​the underflow port is limited by the first area, the second area, and the third area, so as to better achieve the screening of the target sludge. In some embodiments, the first parameter, the second parameter, and the third parameter also include a feed flow rate, and the feed flow rates corresponding to the first parameter, the second parameter, and the third parameter decrease in sequence.

[0088] When the feed flow rate of the denitrifying microorganism directional screening device 300 is larger, on the one hand, more sludge can be screened, and the sludge with low density and poor performance is discharged from the system as external sludge. After screening, the sludge (i.e., the target sludge) that flows back to the biochemical pool 100 has significantly improved performance, which can effectively improve the denitrification and denitrification effect of the AOA sewage treatment system. On the other hand, the flow rate and centrifugal force in the hydrocyclone will also increase accordingly, and a larger flow rate and centrifugal force will accelerate the heavy sludge (high density or large particle size particles) to gather in the outer layer, making it easier to be discharged by the bottom flow. Therefore, while adjusting the cross-sectional area ratio of the underflow overflow, the feed flow rate is further adjusted. A larger feed flow rate can screen more sludge and improve the quality of the returned sludge; at the same time, the screening separation of the target sludge and the external sludge can be improved, further improving the quality of the returned sludge. Specifically, the feed flow rate corresponding to the first parameter, the second parameter and the third parameter can be determined by the designed feed flow rate of the denitrifying microorganism directional screening device 300, and the feed flow rate corresponding to the first parameter is the designed feed flow rate; the feed flow rate corresponding to the second parameter is 60% to 85% of the designed feed flow rate, such as 60%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 85%, etc., and can also be other percentages, or other values ​​less than 60% or greater than 85% can be set, without specific limitation; the feed flow rate corresponding to the third parameter is 40% to 60% of the designed feed flow rate, such as 40%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, etc., and can also be other percentages, or other values ​​less than 40% or greater than 60% can be set, without specific limitation.

[0089] In some embodiments, Figure 1 As shown, the biochemical pool 100 includes an anaerobic pool 101, a first conversion zone 102, an aerobic pool 103 and an anoxic pool 105 connected in sequence; the control method also includes:

[0090] In response to determining to start the denitrifying microorganism directional screening device 300, the actual volume of the anoxic tank required when the effluent water quality of the AOA sewage treatment system meets the standard is calculated, and the operating state of the first conversion zone 102 is determined using the actual volume of the anoxic tank.

[0091] The anaerobic tank 101 is used to realize the anaerobic stage of the AOA process, and the polyphosphate bacteria release phosphorus and degrade organic matter; the aerobic tank 103 is used to realize the aerobic stage of the AOA process, and nitrification reaction, phosphorus removal and organic matter degradation are carried out; the anoxic tank 105 is used to realize the anoxic stage of the AOA process, mainly for denitrification. A mechanical agitator is set in the anaerobic tank 101 to improve the reaction efficiency. The sludge concentration in the aerobic tank 103 is controlled at 3000-5000 mg / L to promote the polyphosphate bacteria to release carbon source for aerobic phosphorus absorption, reduce the internal carbon source consumption while fully oxidizing ammonia nitrogen, and reserve more carbon source for subsequent denitrification. In the aerobic tank 103, part of the nitrate nitrogen can be removed by simultaneous nitrification and denitrification, and an aerator is set in the aerobic tank 103 for aeration.

[0092] The starting conditions of the denitrifying microorganism directional screening device 300 include the following situations:

[0093] (1) The effluent total nitrogen concentration does not meet the standard, that is, the effluent total nitrogen concentration is greater than or equal to the standard value of the effluent total nitrogen concentration;

[0094] (2) The effluent total nitrogen concentration slightly meets the standard, but the denitrification rate does not meet the standard, which includes the following two situations: ① The effluent total nitrogen concentration is greater than or equal to the first threshold and less than the standard value of the effluent total nitrogen concentration, and the current denitrification rate is less than the second threshold; ② The effluent total nitrogen concentration is greater than or equal to the first threshold and less than the standard value of the effluent total nitrogen concentration, and the current denitrification rate is less than the denitrification rate target value and greater than or equal to the second threshold.

[0095] When the above situation exists, it means that the denitrification of the current AOA sewage treatment system is abnormal, and the denitrification microorganism directional screening device 300 is started to increase the number and activity of denitrification microorganisms in the current AOA sewage treatment system. However, in addition to denitrification microorganisms, the concentration of nitrates, the concentration of carbon sources, etc. will also affect the denitrification effect of the system. For example, when the concentration of ammonia nitrogen or nitrate nitrogen in the influent is too high or the carbon source is insufficient, the denitrification efficiency will be affected, thereby increasing the total nitrogen concentration of the effluent.

[0096] Therefore, in order to better improve the denitrification effect and improve the effluent water quality, a first conversion zone 102 is set between the anaerobic tank 101 and the aerobic tank 103. The operating state of the first conversion zone 102 is adjustable, so that the specific operating state of the first conversion zone 102 can be determined according to the actual volume of the anoxic tank required when the effluent water quality of the AOA sewage treatment system meets the standard, so that the operating state of the first conversion zone 102 can be adjusted according to the actual situation of the influent, and can better adapt to a variety of water qualities, especially for situations where the water quality changes greatly. At the same time, it can improve the denitrification effect and ensure the efficient and stable operation of the AOA sewage treatment system.

[0097] In some embodiments, the determining the operating state of the first conversion zone 102 by using the actual volume of the anoxic tank includes: in response to the actual volume of the anoxic tank being smaller than the designed volume of the anoxic tank 105, controlling the first conversion zone 102 to be in an anaerobic state;

[0098] In response to the actual volume of the anoxic pool being greater than or equal to the designed volume of the anoxic pool 105 , the first conversion zone 102 is controlled to be in an anoxic state.

[0099] When the calculated actual volume of the anoxic pool is greater than or equal to the design volume of the anoxic pool 105, it means that the design volume of the current anoxic pool 105 of the system cannot meet the actual demand, and the operation state of the first conversion zone 102 is adjusted to the anoxic state to increase the volume of the anoxic pool 105 in the system, enhance the denitrification capacity of the system, and improve the nitrogen removal effect. When the calculated actual volume of the anoxic pool is less than the design volume of the anoxic pool 105, it means that the current design volume of the anoxic pool 105 meets the actual demand. Generally, sewage is not only rich in nitrogen, but also in phosphorus. Therefore, when the design volume of the anoxic pool 105 meets the actual demand, the first conversion zone 102 can be adjusted to an anaerobic state. When the first conversion zone 102 is in an anaerobic state, on the one hand, the efficiency of phosphorus release by polyphosphate bacteria can be enhanced, and on the other hand, the polyphosphate bacteria need to absorb carbon sources when releasing phosphorus, reducing the competition of organic matter for denitrification in the anoxic zone. Specifically, when the first conversion zone 102 is in anoxic state, the dissolved oxygen concentration of aeration is controlled to be between 0 and 0.5 mg / L, and when the first conversion zone 102 is in anaerobic state, no aeration is performed thereon.

[0100] In some embodiments, a second conversion zone 104 is further provided between the aerobic pool 103 and the anoxic pool 105; the control method further comprises:

[0101] In response to determining to start the denitrifying microorganism directional screening device 300 , the actual volume of the aerobic tank required when the effluent water quality of the AOA sewage treatment system meets the standard is calculated, and the operating state of the second conversion zone 104 is determined using the actual volume of the aerobic tank.

[0102] Denitrification is a process in which nitrate or nitrite is used as an electron acceptor and organic matter is used as a carbon source to reduce it to nitrogen gas. Nitrate or nitrite is an important participating substance, which is mainly produced in the aerobic tank 103, that is, aerobic microorganisms (such as nitrifying bacteria) oxidize ammonia nitrogen into nitrite or nitrate under the condition of sufficient oxygen. Therefore, the operation of the aerobic tank 103 will also affect the denitrification effect of subsequent denitrification.

[0103] In order to better improve the denitrification effect and improve the effluent water quality, a second conversion zone 104 is set between the aerobic tank 103 and the anoxic tank 105. The operating state of the second conversion zone 104 is adjustable, so that the specific operating state of the second conversion zone 104 can be determined according to the actual volume of the aerobic tank required when the effluent water quality of the AOA sewage treatment system meets the standard, so that the operating state of the second conversion zone 104 can be adjusted according to the actual situation of the influent, and can be more adaptable to a variety of water qualities, especially for situations where the water quality changes greatly, the denitrification effect can be improved to ensure the efficient and stable operation of the AOA sewage treatment system. Specifically, the first conversion zone 102 and the second conversion zone 104 are both provided with aerators to achieve aeration, and are both provided with mechanical agitators to promote system reactions.

[0104] In some embodiments, the determining the operating state of the second conversion zone 104 using the actual volume of the aerobic pool includes:

[0105] In response to the actual volume of the aerobic pool being smaller than the designed volume of the aerobic pool 103, controlling the second conversion zone 104 to be in an anoxic state;

[0106] In response to the actual volume of the aerobic pool being greater than or equal to the designed volume of the aerobic pool 103 , the second conversion zone 104 is controlled to be in an aerobic state.

[0107] When the calculated required actual volume of the aerobic pool is greater than or equal to the design volume of the aerobic pool 103, it means that the current design volume of the aerobic pool 103 of the system cannot meet the actual demand, and the operating state of the second conversion zone 104 is adjusted to the anoxic state to increase the volume of the aerobic pool 103, promote the generation of more nitrite or nitrate, and provide a basis for the subsequent denitrification of the anoxic pool 105, thereby enhancing the denitrification capacity of the system and improving the nitrogen removal effect. When the calculated actual volume of the aerobic pool is less than the design volume of the aerobic pool 103, it means that the current design volume of the aerobic pool 103 meets the actual demand. The denitrification process is an important link in achieving nitrogen removal in sewage, which is crucial for reducing the total nitrogen content. The denitrification process occurs in the anoxic pool 105. When the actual volume of the aerobic pool meets the demand, it means that the production of nitrite or nitrate can meet the current denitrification demand. At this time, in order to ensure the efficient occurrence of the denitrification process, the second conversion zone 104 is switched to the anoxic state to provide more sufficient conditions for the occurrence of denitrification and strengthen the denitrification effect of the system. Specifically, when the second transition zone 104 is in anoxic state, the dissolved oxygen concentration of aeration is controlled to be between 0 and 0.5 mg / L; when the second transition zone 104 is in aerobic state, the dissolved oxygen concentration of aeration is controlled to be between 0.5 and 2 mg / L.

[0108] In some embodiments, the actual volume of the anoxic pool is calculated by the following steps:

[0109] The actual volume of the anoxic tank is calculated using the influent flow rate, influent total nitrogen concentration, daily sludge discharge, the standard value of effluent total nitrogen concentration, the current denitrification rate and the current sludge concentration of the first conversion zone 102 of the AOA sewage treatment system.

[0110] The actual volume of the anoxic tank required for the effluent water quality of the AOA sewage treatment system to meet the standard can be calculated using the current water quality and quantity information of the AOA sewage treatment system (i.e., influent flow rate, influent total nitrogen concentration), the actual operation of the system (daily sludge discharge, current denitrification rate, current sludge concentration of the first conversion zone 102) and the effluent standard (i.e., the standard value of the effluent total nitrogen concentration). When the influent water quality and quantity and the actual operation of the system fluctuate, the above changes can be captured in time, and the new actual volume of the anoxic tank required for the effluent water quality to meet the standard can be recalculated, so as to readjust the operation status of the first conversion zone 102 according to the new actual volume of the anoxic tank, so that the AOA sewage treatment system can effectively cope with fluctuations in water quality and quantity, thereby improving the system operation stability, effectively improving the effect of denitrification and denitrification, and ensuring that the effluent water quality meets the standard.

[0111] Specifically, the actual volume of the anoxic pool V n It can be calculated by the following formula:

[0112]

[0113] Among them, Q 0 is the water inlet flow rate, TN 0 is the total nitrogen concentration in the influent, TN e is the standard value of total nitrogen concentration in effluent, ΔX v is the daily sludge discharge, k is the current denitrification rate, X 1 is the current sludge concentration in the first conversion zone 102.

[0114] In some embodiments, the actual volume of the aerobic pool is calculated by the following steps:

[0115] The actual volume of the aerobic tank is calculated using the inlet flow, inlet COD concentration, effluent COD concentration standard value, sludge age, sludge production coefficient and current sludge concentration of the second conversion zone 104 of the AOA sewage treatment system.

[0116] In the AOA sewage treatment system, the removal of organic matter is mainly in the aerobic stage. Under sufficient dissolved oxygen conditions, aerobic microorganisms decompose organic matter into carbon dioxide and water through metabolism to achieve the removal of organic matter. COD (i.e., chemical oxygen demand) is an important indicator for measuring the content of organic matter in water. Therefore, it can be calculated using the current water quality and quantity information of the AOA sewage treatment system (i.e., influent flow rate, influent COD concentration), the actual operation of the system (sludge age, sludge production coefficient, current sludge concentration of the second conversion zone 104), and the effluent standard (standard value of effluent COD concentration). When the influent water quality and quantity and the actual operation of the system fluctuate, the above changes can be captured in time, and the new actual volume of the aerobic pool required for the effluent water quality to meet the standard can be recalculated, so that the operating state of the second conversion zone 104 can be readjusted according to the new actual volume of the aerobic pool, so that the AOA sewage treatment system can effectively cope with fluctuations in water quality and quantity, thereby improving the stability of system operation, not only realizing the effective removal of organic matter, but also providing sufficient nitrate or nitrite for subsequent denitrification and denitrification, further strengthening the denitrification effect of the system, and ensuring that the effluent water quality meets the standard.

[0117] Specifically, the actual volume of the aerobic pool V a It can be calculated by the following formula:

[0118]

[0119] Among them, COD o is the influent COD concentration of AOA sewage treatment system, COD e is the standard value of effluent COD concentration of AOA sewage treatment system, θ co is the sludge age of the AOA sewage treatment system, Y t is the sludge generation coefficient of the AOA sewage treatment system, X 2 is the current sludge concentration in the second conversion zone 104.

[0120] In some embodiments, the AOA sewage treatment system further includes an inlet pipeline 800 and a segmented inlet branch line 810;

[0121] The water inlet pipeline 800 is connected to the anaerobic tank 101 to pass the sewage to be treated into the anaerobic tank 101;

[0122] One end of the segmented water inlet branch line 810 is connected to the water inlet pipeline 800, and the other end is connected to the anoxic tank 105;

[0123] The control method further comprises:

[0124] The ratio coefficient is calculated based on the ratio of the difference in COD concentration between the inlet and outlet water of the AOA sewage treatment system to the difference in total nitrogen concentration;

[0125] In response to the ratio coefficient being less than the third threshold, the segmented water inlet branch line 810 is controlled to be opened so as to guide part of the water inlet of the water inlet pipeline 800 into the anoxic tank 105 .

[0126] In the process of denitrification, insufficient carbon source will also affect the efficiency of denitrification. Therefore, the present application connects a segmented water inlet branch line 810 between the water inlet pipeline 800 and the anoxic tank 105. When the carbon source in the anoxic tank 105 is insufficient, a portion of the inlet water is directly passed into the anoxic tank 105, and the organic matter in the inlet water is used as a carbon source to promote the denitrification process and ensure the denitrification effect. The ratio coefficient can be calculated by using the ratio of the difference in chemical oxygen demand concentration of the inlet and outlet water of the AOA sewage treatment system to the difference in total nitrogen concentration to determine the opening of the segmented water inlet branch line 810. Specifically, the ratio coefficient N can be calculated by the following formula:

[0127]

[0128] Among them, COD o is the influent COD concentration of AOA sewage treatment system, COD 1 is the effluent COD concentration of the AOA sewage treatment system, TN 0 is the total nitrogen concentration in the influent of the AOA sewage treatment system, TN 1 is the total nitrogen concentration in the effluent of the AOA wastewater treatment system.

[0129] The reaction equation for denitrification is: NO 3 - + organic matter (COD) → N 2 +CO 2 +H 2 O+OH - During the denitrification process, 1g of NO is removed 3 --N (in terms of nitrogen) The COD that needs to be consumed can be calculated, which is about 2.86gCOD. Therefore, in actual operation, the ideal COD / N is 2.86. However, in the actual operation process, part of the COD needs to be used for microbial growth and maintenance of metabolism, and there may also be non-biodegradable parts in the influent COD, so it is necessary to control the COD / N ratio to be slightly higher than the ideal value of 2.86. If the COD / N ratio is too high, it is easy to cause the COD concentration in the effluent to be high, resulting in substandard effluent water quality. Therefore, taking into account the smooth progress of the denitrification process and the requirements of the effluent water quality, the third threshold value in this scheme ranges from 3 to 4, specifically, it can be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, or other values ​​in this range, without specific limitation. When the ratio coefficient N is less than the third threshold value, it indicates that the current carbon source in the system is insufficient to support the denitrification reaction. Therefore, part of the influent is directly introduced into the anoxic tank 105 through the segmented influent branch line 810. The organic matter concentration in the influent is usually high. Directly entering the anoxic tank 105 can avoid consumption in the front-end anaerobic tank 101, aerobic tank 103 and other processes, quickly replenish the carbon source required for denitrification, and ensure the efficient progress of the denitrification process.

[0130] Specifically, the flow rate Q of the segmented water inlet branch line 810 is 1 Calculated by the following formula:

[0131]

[0132] Among them, Q 1 is the flow rate of the segmented water inlet branch line 810, Q 0 is the inlet flow rate of the AOA sewage treatment system (i.e. the inlet flow rate of the inlet pipeline 800), A 0 NH for the influent of AOA sewage treatment system 3 Concentration, A 1 NH for aerobic pool 103 3 Concentration, A 2 NH 3 concentration.

[0133] In some embodiments, in response to the ratio coefficient being not less than a third threshold, the segmented water inlet branch line 810 is controlled to be closed.

[0134] In some embodiments, an aeration zone 106 is provided between the anoxic tank 105 and the secondary sedimentation tank 200. The effluent from the anoxic tank 105 has a low dissolved oxygen concentration, which is not conducive to the solid-liquid separation in the secondary sedimentation tank 200. Therefore, the aeration zone 106 is provided to further improve the sludge settling performance. An aerator is provided in the aeration zone 106 to control the dissolved oxygen concentration to be about 0.5-1.5 mg / L.

[0135] Specifically, the sludge age θ of the AOA wastewater treatment system co It can be calculated by the following formula:

[0136]

[0137] Among them, X a , X 1 , X b , X 2 , X c , X d The current sludge concentrations of the anaerobic tank 101, the first conversion zone 102, the aerobic tank 103, the second conversion zone 104, the anoxic tank 105 and the aeration zone 106 are respectively corresponding to V a 、V 1 、V b 、V 2 、V c 、V d They correspond to the sludge volumes of the anaerobic tank 101, the first conversion zone 102, the aerobic tank 103, the second conversion zone 104, the anoxic tank 105 and the aeration zone 106 respectively, ΔX is the sludge concentration of the sludge discharged every day, and △V is the sludge volume of the sludge discharged every day.

[0138] In some embodiments, a drain outlet is provided at the top of the secondary sedimentation tank 200, and a mud outlet connected to the return pipeline 400 is provided at the bottom. The drain outlet is connected to a drainage pipeline 900 to guide the treated sewage to the next stage.

[0139] In some embodiments, the return line 400 is connected to the anaerobic tank 101, and the target sludge is returned to the first conversion zone 102. The first conversion zone 102 switches between the anaerobic state and the anoxic state. When switched to the anoxic state, denitrification reaction can be performed to remove nitrogen in the sewage. Therefore, the target sludge rich in denitrifying microorganisms is directly introduced into the first conversion zone 102, which is conducive to maintaining the activity of denitrifying microorganisms, while faster improving the denitrification rate and quickly strengthening the denitrification effect of the system.

[0140] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments and methods, the present application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, a sewage treatment system control method described in any of the above embodiments is implemented.

[0141] Figure 3A more specific schematic diagram of the hardware structure of an electronic device provided in this embodiment is shown, and the device may include: a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. The processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040 are connected to each other through the bus 1050 in the device.

[0142] The processor 1010 can be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0143] The memory 1020 may be implemented in the form of ROM (Read Only Memory), RAM (Random Access Memory), static storage device, dynamic storage device, etc. The memory 1020 may store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program codes are stored in the memory 1020 and are called and executed by the processor 1010.

[0144] The input / output interface 1030 is used to connect the input / output module to realize information input and output. The input / output module can be configured in the device as a component (not shown in the figure), or it can be externally connected to the device to provide corresponding functions. The input device may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output device may include a display, a speaker, a vibrator, an indicator light, etc.

[0145] The communication interface 1040 is used to connect a communication module (not shown) to realize communication interaction between the device and other devices. The communication module can realize communication through a wired mode (such as USB, network cable, etc.) or a wireless mode (such as mobile network, WIFI, Bluetooth, etc.).

[0146] The bus 1050 includes a path that transmits information between the various components of the device (eg, the processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040).

[0147] It should be noted that, although the above device only shows the processor 1010, the memory 1020, the input / output interface 1030, the communication interface 1040 and the bus 1050, in the specific implementation process, the device may also include other components necessary for normal operation. In addition, it can be understood by those skilled in the art that the above device may also only include the components necessary for implementing the embodiments of the present specification, and does not necessarily include all the components shown in the figure.

[0148] The electronic device of the above embodiment is used to implement a corresponding sewage treatment system control method in any of the above embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be repeated here.

[0149] Based on the same inventive concept, corresponding to any of the above-mentioned embodiment methods, the present application also provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute a sewage treatment system control method as described in any of the above embodiments.

[0150] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0151] The computer instructions stored in the storage medium of the above embodiment are used to enable the computer to execute a sewage treatment system control method as described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0152] It should be understood by those skilled in the art that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the present application (including the claims) is limited to these examples; under the concept of the present application, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other variations of different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of simplicity. In addition, in the case of elaborating details to describe exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application may be implemented without these details or with changes in these details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0153] For simplifying explanation and discussion, and in order not to make the embodiment of the present application difficult to understand, the known power supply / ground connection with other parts may or may not be shown in the provided drawings. In addition, the device can be shown in the form of a block diagram to avoid making the embodiment of the present application difficult to understand, and this also takes into account the following fact, that is, the details of the implementation method of these block diagram devices are highly dependent on the platform to be implemented in the embodiment of the present application (that is, these details should be completely within the scope of understanding of those skilled in the art). In the case of elaborating specific details to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiment of the present application can be implemented without these specific details or when these specific details are changed. Therefore, these descriptions should be considered to be illustrative rather than restrictive.

[0154] Although the present application has been described in conjunction with specific embodiments of the present application, many replacements, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed.

[0155] The embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A sewage treatment system control method, applied to the AOA sewage treatment system, characterized in that: The AOA sewage treatment system includes a denitrifying microorganism directional screening device and a biochemical tank and a secondary sedimentation tank connected in sequence; The bottom of the secondary sedimentation tank is connected to the biochemical tank via a reflux pipeline; The denitrifying microorganism directional screening device is connected to the return pipeline and the biochemical pool, and is used to screen part of the sludge in the return pipeline to obtain target sludge and external sludge, and return the target sludge to the biochemical pool, and discharge the external sludge to the outside of the system; wherein the number of denitrifying microorganisms in the target sludge is higher than the number of denitrifying microorganisms in the external sludge; The control method comprises: The current total nitrogen concentration of the effluent from the secondary sedimentation tank is obtained to obtain the effluent total nitrogen concentration, and the effluent total nitrogen concentration is used to control the operating state of the denitrifying microorganism directional screening device.

2. A sewage treatment system control method according to claim 1, characterized in that: The method of controlling the operating state of the denitrifying microorganism directional screening device by using the effluent total nitrogen concentration includes: In response to the effluent total nitrogen concentration being greater than or equal to the effluent total nitrogen concentration standard value, controlling the denitrifying microorganism directional screening device to operate at a first parameter with the highest load; In response to the effluent total nitrogen concentration being greater than or equal to a first threshold value and less than the effluent total nitrogen concentration standard value, the current denitrification rate of the biochemical pool is obtained and a denitrification rate judgment step is performed to determine the operating status of the denitrifying microorganism directional screening device using the current denitrification rate.

3. A sewage treatment system control method according to claim 2, characterized in that: The denitrification rate determination step comprises: In response to the current denitrification rate being less than a second threshold, controlling the denitrifying microorganism directional screening device to operate with a second parameter; In response to the current denitrification rate being less than the denitrification rate target value and greater than or equal to the second threshold, controlling the denitrifying microorganism directional screening device to operate with a third parameter; Wherein, the number of denitrifying microorganisms screened by the denitrifying microorganism directional screening device decreases successively when the first parameter, the second parameter and the third parameter are operated.

4. A sewage treatment system control method according to claim 3, characterized in that: The denitrifying microorganism directional screening device is a hydrocyclone; Among them, the first parameter, the second parameter and the third parameter all include an underflow overflow cross-sectional area ratio, and the underflow overflow cross-sectional area ratios corresponding to the first parameter, the second parameter and the third parameter decrease in sequence.

5. A sewage treatment system control method according to claim 3, characterized in that: The first parameter, the second parameter and the third parameter also include a feed flow rate, and the feed flow rates corresponding to the first parameter, the second parameter and the third parameter decrease in sequence.

6. A sewage treatment system control method according to claim 3, characterized in that: The biochemical pool includes an anaerobic pool, a first conversion zone, an aerobic pool and an anoxic pool connected in sequence; the control method also includes: In response to determining to start the denitrifying microorganism directional screening device, calculating the actual volume of the anoxic tank required when the effluent water quality of the AOA sewage treatment system meets the standard, and determining the operating state of the first conversion zone using the actual volume of the anoxic tank; And / or, a second conversion zone is further provided between the aerobic pool and the anoxic pool; the control method further comprises: In response to determining to start the denitrifying microorganism directional screening device, the actual volume of the aerobic tank required when the effluent water quality of the AOA sewage treatment system meets the standard is calculated, and the operating state of the second conversion zone is determined using the actual volume of the aerobic tank.

7. A sewage treatment system control method according to claim 6, characterized in that: The determining the operating state of the first conversion zone by using the actual volume of the anoxic pool includes: In response to the actual volume of the anoxic tank being smaller than the designed volume of the anoxic tank, controlling the first conversion zone to be in an anaerobic state; In response to the actual volume of the anoxic pool being greater than or equal to the designed volume of the anoxic pool, controlling the first conversion zone to be in anoxic state; The step of determining the operating state of the second conversion zone by using the actual volume of the aerobic pool includes: In response to the actual volume of the aerobic pool being smaller than the designed volume of the aerobic pool, controlling the second conversion zone to be in an anoxic state; In response to the actual volume of the aerobic tank being greater than or equal to the designed volume of the aerobic tank, the second conversion zone is controlled to be in an aerobic state.

8. A sewage treatment system control method according to claim 6, characterized in that: The actual volume of the anoxic pool is calculated by the following steps: The actual volume of the anoxic tank is calculated using the influent flow rate, influent total nitrogen concentration, daily sludge discharge volume, effluent total nitrogen concentration standard value, current denitrification rate and current sludge concentration of the first conversion zone of the AOA sewage treatment system; The actual volume of the aerobic pool is calculated by the following steps: The actual volume of the aerobic tank is calculated using the inlet flow, inlet COD concentration, effluent COD concentration standard value, sludge age, sludge production coefficient and current sludge concentration of the second conversion zone of the AOA sewage treatment system.

9. A sewage treatment system control method according to claim 6, characterized in that: The AOA sewage treatment system also includes a water inlet pipeline and a segmented water inlet branch line; The water inlet pipeline is connected to the anaerobic tank to pass the sewage to be treated into the anaerobic tank; One end of the segmented water inlet branch line is connected to the water inlet pipeline, and the other end is connected to the anoxic tank; The control method further comprises: The ratio coefficient is calculated based on the ratio of the difference in COD concentration between the inlet and outlet water of the AOA sewage treatment system to the difference in total nitrogen concentration; In response to the ratio coefficient being less than a third threshold, the segmented water inlet branch line is controlled to be opened so as to guide part of the water inlet pipeline into the anoxic tank.

10. A sewage treatment system control method according to claim 6, characterized in that: A gas replenishment area is also provided between the anoxic tank and the secondary sedimentation tank; And / or, a drain outlet is provided at the upper part of the secondary sedimentation tank, and a mud discharge outlet connected to the return pipeline is provided at the bottom, and the drain outlet is connected to a drainage pipeline to guide the treated sewage to the next stage; And / or, the return pipeline is connected to the anaerobic tank, and the target sludge is returned to the first conversion zone.

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