Sewage treatment system control method

Abstract

The application provides a sewage treatment system control method, which is applied to an AOA sewage treatment system. The AOA sewage treatment system comprises a denitrifying microorganism directional screening device and a biochemical tank and a secondary sedimentation tank connected in sequence. The control method comprises the following steps: obtaining the current total nitrogen concentration of effluent from the secondary sedimentation tank, obtaining the effluent total nitrogen concentration, and controlling the running state of the denitrifying microorganism directional screening device by using the effluent total nitrogen concentration. The sewage treatment system control method provided by the application can further improve the system running efficiency and reduce the running cost on the basis of promoting the denitrification, reducing the effluent total nitrogen concentration and improving the effluent water quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, and particularly relates to a sewage treatment system control method. BACKGROUND

[0002] The AOA sewage treatment system is a system for treating sewage through an anaerobic-aerobic-anoxic process (AOA process), and is widely applied to various fields such as municipal domestic sewage and industrial wastewater. In the AOA process, the anoxic section mainly realizes denitrification, that is, through the action of denitrifying microorganisms, nitrate or nitrite is reduced to nitrogen, so as to realize the denitrification treatment of sewage, and is one of the core processes in sewage treatment. However, in the actual application process, the denitrification capacity is often reduced, thereby affecting the denitrification effect of the system, increasing the difficulty and cost of subsequent treatment, and causing problems such as an increase in the total nitrogen concentration of effluent and non-compliance of effluent quality. SUMMARY

[0003] Therefore, the purpose of the present application is to provide 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, and the AOA sewage treatment system comprises a denitrifying microbial 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 with the biochemical tank through a reflux pipeline;

[0006] The denitrifying microbial directional screening device is connected with the reflux pipeline and the biochemical tank, so as to screen part of sludge in the reflux pipeline to obtain target sludge and external sludge, and return the target sludge to the biochemical tank, and the external sludge is discharged to the outside of the system; wherein the number of denitrifying microorganisms in the target sludge is higher than that in the external sludge;

[0007] The control method comprises:

[0008] Obtaining the current total nitrogen concentration of effluent of the secondary sedimentation tank to obtain the total nitrogen concentration of effluent, and using the total nitrogen concentration of effluent to control the running state of the denitrifying microbial directional screening device.

[0009] Further, the using the total nitrogen concentration of effluent to control the running state of the denitrifying microbial directional screening device comprises:

[0010] In response to the total nitrogen concentration of effluent being greater than or equal to a total nitrogen concentration standard value of effluent, the denitrifying microbial directional screening device is controlled to run 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, obtaining a current denitrification rate of the biochemical tank and performing a denitrification rate judgment step to determine the operating state of the denitrifying microbial directional screening device using the current denitrification rate.

[0012] Further, the denitrification rate judgment step includes:

[0013] in response to the current denitrification rate being less than a second threshold value, controlling the denitrifying microbial directional screening device to operate at 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 value, controlling the denitrifying microbial directional screening device to operate at a third parameter;

[0015] wherein the number of denitrifying microorganisms screened by the denitrifying microbial directional screening device under the first parameter, the second parameter and the third parameter decreases in turn.

[0016] Further, the denitrifying microbial directional screening device is a hydrocyclone;

[0017] wherein the first parameter, the second parameter and the third parameter each include a ratio of underflow overflow cross-sectional area, and the ratio of underflow overflow cross-sectional area corresponding to the first parameter, the second parameter and the third parameter decreases in turn.

[0018] Further, the first parameter, the second parameter and the third parameter also include feed flow rate, and the feed flow rate corresponding to the first parameter, the second parameter and the third parameter decreases in turn.

[0019] Further, the biochemical tank includes an anaerobic tank, a first conversion zone, an aerobic tank and an anoxic tank connected in turn; the control method further includes:

[0020] in response to determining to start the denitrifying microbial directional screening device, calculating the actual volume of the anoxic tank required for the effluent water quality of the AOA sewage treatment system to meet the standard, and determining the operating state of the first conversion zone using the actual volume of the anoxic tank.

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

[0022] in response to determining to start the denitrifying microbial directional screening device, calculating the actual volume of the aerobic tank required for the effluent water quality of the AOA sewage treatment system to meet the standard, and determining the operating state of the second conversion zone using the actual volume of the aerobic tank.

[0023] Further, the operation state of the first conversion zone is determined by the actual volume of the anoxic tank, including:

[0024] in response to the actual volume of the anoxic tank being less than the design volume of the anoxic tank, the first conversion zone is controlled to be in an anaerobic state;

[0025] in response to the actual volume of the anoxic tank being greater than or equal to the design volume of the anoxic tank, the first conversion zone is controlled to be in an anoxic state;

[0026] the operation state of the second conversion zone is determined by the actual volume of the aerobic tank, including:

[0027] in response to the actual volume of the aerobic tank being less than the design volume of the aerobic tank, the second conversion zone is controlled to be in an anoxic state;

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

[0029] Further, the actual volume of the anoxic tank is calculated by the following steps:

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

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

[0032] the actual volume of the aerobic tank is calculated by the influent flow rate, the influent COD concentration, the standard value of the effluent COD concentration, the sludge age, the sludge yield coefficient, and the current sludge concentration of the second conversion zone of the AOA sewage treatment system.

[0033] Further, the AOA sewage treatment system further comprises an influent pipeline and a segmented influent branch line;

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

[0035] one end of the segmented influent branch line is connected to the influent pipeline, and the other end is connected to the anoxic tank;

[0036] the control method further comprises:

[0037] a ratio coefficient is calculated according to the ratio of the COD concentration difference and the total nitrogen concentration difference of the influent and effluent of the AOA sewage treatment system;

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

[0039] Further, the anoxic tank and the secondary sedimentation tank are also provided with a gas supplement area;

[0040] And / or, the upper part of the secondary sedimentation tank is provided with a water outlet, and the bottom part is provided with a sludge outlet communicated with the reflux pipeline, and the water outlet is connected with a water outlet pipeline to guide the treated sewage to the next stage;

[0041] And / or, the reflux pipeline is connected with the anaerobic tank, and the target sludge is refluxed to the first conversion area.

[0042] From the above, it can be seen that the present application provides a sewage treatment system control method, which is applied to an AOA sewage treatment system. First, a denitrifying microbial directional screening device is arranged on the sludge reflux path (and the reflux pipeline) of the AOA sewage treatment system to effectively screen the sludge in the system, separate the target sludge with high denitrifying microbial quantity from the external sludge with low denitrifying microbial quantity, and reflux the target sludge to the biochemical tank to improve the denitrifying microbial quantity and activity in the biochemical tank, promote the denitrification, and thus effectively improve the denitrification efficiency. Second, the effect of denitrification directly affects the concentration of total nitrogen in the effluent. When the denitrification is reduced, the concentration of total nitrogen in the effluent will be obviously increased. When the denitrification capacity is improved, the concentration of total nitrogen in the effluent will be reduced. Therefore, the running state of the denitrifying microbial directional screening device is regulated by using the concentration of total nitrogen in the effluent of the system, so that the running of the denitrifying microbial directional screening device 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 water quality of the effluent, the system operation efficiency can be further improved, and the operation cost can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the present application or related art, the following will briefly introduce the drawings needed to be used in the embodiments or related art descriptions. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating labor.

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

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

[0046] Figure 3Fig. 2 is a schematic view of another wastewater treatment system in the embodiments of the present application.

[0047] 100 - biochemical tank; 101 - anaerobic tank; 102 - first conversion zone; 103 - oxic tank; 104 - second conversion zone; 105 - anoxic tank; 106 - air supply zone; 200 - secondary sedimentation tank; 300 - device for directional screening of denitrifying microorganisms; 400 - reflux pipeline; 500 - feed pipeline; 600 - underflow pipeline; 700 - overflow pipeline; 800 - influent pipeline; 810 - subsection influent branch pipeline; 900 - effluent pipeline. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the embodiments and 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 understood as the common meanings understood by those with ordinary skills in the art to which the present application belongs. The terms "first", "second" and similar terms used in the embodiments of the present application do not represent any order, number or importance, but are only used to distinguish different components. The terms "comprise", "include" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, without excluding other elements or objects. The terms "connect" or "connected" and similar terms do not mean physical or mechanical connection, but can include electrical connection, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like only represent relative positional relationships, which can change when the absolute positions of the described objects change.

[0050] The AOA process is an anaerobic-oxic-anoxic process, including an anaerobic stage, an oxic stage and an anoxic stage, and is a post-anoxic denitrification operation mode, which is conducive to the enrichment of phosphorus accumulating organisms and glycogen accumulating organisms, promotes the storage and utilization of internal carbon sources, and greatly reduces the concentration of organic matter entering the oxic stage. In the anaerobic stage, phosphorus release by phosphorus accumulating organisms and organic matter degradation are mainly performed. Under anaerobic conditions, the phosphorus accumulating organisms decompose the stored polyphosphorus and release it into the water in the form of phosphate, creating conditions for phosphorus uptake in the oxic stage. At the same time, the phosphorus accumulating organisms or glycogen accumulating organisms can convert the easily degradable organic matter in the wastewater into internal carbon sources, which can be stored by microorganisms to provide carbon sources for subsequent denitrification and activity of the phosphorus accumulating organisms. In the oxic stage, nitrification, phosphorus removal and organic matter degradation are mainly performed. Under sufficient oxygen conditions, the oxic microorganisms (such as nitrifying bacteria) oxidize ammonia nitrogen (NH4 + ) to nitrite (NO2 - ) or nitrate (NO3 -), to provide nitrate for denitrification in the anoxic stage; in the aerobic environment, the phosphorus accumulating organisms use the phosphate released in the anaerobic stage to store as polyphosphate through biological metabolism, achieving phosphorus removal; and under the activity of aerobic heterotrophic bacteria, the organic matter in the wastewater is decomposed, reducing the COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) of the wastewater. In the anoxic stage, denitrification mainly occurs, and the denitrifying microorganisms use the nitrate or nitrite generated in the aerobic stage as an electron acceptor and use organic matter as a carbon source to reduce it to nitrogen, which eventually escapes from the water, thereby achieving total nitrogen removal and further reducing the concentration of organic matter in the wastewater. In the AOA process, the reduction of denitrification will directly affect the nitrogen removal effect, leading to a decrease in total nitrogen (TN) removal efficiency, thereby causing problems such as an increase in the total nitrogen concentration of the effluent, non-compliance of the effluent quality, and an increase in the difficulty and cost of subsequent advanced treatment.

[0051] Therefore, the present application provides a wastewater treatment system control method, which is applied to an AOA wastewater treatment system, as shown in Figure 1 The AOA wastewater treatment system includes a denitrifying microorganism directional screening device 300 and a biochemical tank 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 through a reflux pipeline 400.

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

[0054] The control method includes:

[0055] The current total nitrogen concentration of the effluent of the secondary sedimentation tank 200 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 300.

[0056] In the AOA sewage treatment system, the biochemical tank 100 is used to realize the AOA process, i.e., the anaerobic-aerobic-anoxic process. The water treated by the biochemical tank 100 is introduced into the secondary sedimentation tank 200 for sedimentation to realize mud-water separation. The upper clear liquid is the treated sewage which is discharged to the subsequent process, such as the advanced treatment section, etc. The lower layer is sludge which is rich in microorganisms required for biochemical treatment and is returned to the biochemical tank 100 through the reflux pipeline 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 quantity and activity will directly affect the denitrification capacity of the system.

[0057] It is found through research that the microorganisms in the activated sludge flocs usually present a hierarchical structure, which is a complex ecosystem composed of various microorganisms. The microorganisms are distributed and arranged in a specific way in the flocs to form a functionally differentiated hierarchical structure. On the outer layer, i.e., the surface of the flocs, the oxygen and organic matter concentrations are high due to direct contact with water, and the flocs are directly affected by the external dissolved oxygen, so the area is dominated by aerobic conditions, and therefore mainly distributes aerobic microorganisms (such as nitrifying bacteria, heterotrophic bacteria, etc.), aerobic phosphorus accumulating organisms, etc. In the interior of the flocs, the oxygen supply is limited (low DO environment), close to anoxic or micro-aerobic state, which is conducive to the growth of facultative microorganisms (such as denitrifying bacteria) and the like. When the sludge flocs are large and have a certain tightness, a low-oxygen or anoxic environment can be formed in the inner layer, which is conducive to the growth of denitrifying microorganisms. At the same time, since denitrifying microorganisms can inhibit the excessive proliferation of filamentous bacteria, the sludge is not prone to bulking and has good settling performance. Therefore, sludge with a large number of denitrifying microorganisms and high activity usually presents a good floc shape and has good settling performance, and the floc diameter is large. In contrast, sludge with poor settling performance and loose structure contains fewer denitrifying microorganisms. Therefore, sludge screening can be realized by taking advantage of the different characteristics of sludge with a large number of denitrifying microorganisms and high activity and sludge with a small number of denitrifying microorganisms and low activity, and the sludge with a large number of denitrifying microorganisms and high activity (i.e., target sludge) and the sludge with a small number of denitrifying microorganisms and low activity (i.e., external sludge) can be effectively separated.

[0058] In the present application, the denitrifying microbial directional screening device 300 is arranged on the sludge return path (i.e. the return pipeline 400) of the AOA sewage treatment system, which effectively screens the sludge in the system, separates the target sludge with high number of denitrifying microorganisms from the external sludge with low number of denitrifying microorganisms, and returns the target sludge to the biochemical tank 100, so as to improve the number and activity of denitrifying microorganisms in the biochemical tank 100, promote denitrification, and effectively improve the denitrification efficiency. The effect of denitrification directly affects the concentration of total nitrogen in the effluent. When the denitrification is reduced, the concentration of total nitrogen in the effluent will increase significantly. When the denitrification capacity is improved, the concentration of total nitrogen in the effluent will decrease. Therefore, the running state of the denitrifying microbial directional screening device 300 is regulated by using the concentration of total nitrogen in the effluent of the system, so that the running of the denitrifying microbial 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 water quality of the effluent, 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 by the combination of multiple factors including the number and activity of denitrifying microorganisms, the concentration of dissolved oxygen (DO), the concentration of carbon source, the concentration of nitrate, temperature, and the hydraulic retention time in the anoxic zone. The carbon source is the electron donor for the denitrification reaction, and the concentration of nitrate is the electron acceptor for the denitrification reaction, both of which directly participate in the denitrification process and will affect the occurrence of the denitrification reaction. Denitrification needs to be carried out under anoxic conditions, and oxygen will be preferentially used as an electron acceptor, so that a too high concentration of dissolved oxygen will also inhibit the denitrification reaction. Temperature affects the metabolic rate and enzyme activity of denitrifying microorganisms, and denitrification reactions require a certain reaction time, so temperature and hydraulic retention time will also affect the denitrification process. However, in the actual operation process of the AOA wastewater treatment system, the concentrations of carbon source and nitrate are greatly affected by the quality of the influent water and the nitrification reaction, and it is difficult to adjust these two parameters to promote the denitrification process, and the adjustment precision is not high. Improper adjustment can easily cause an excess of carbon source and nitrate, thereby increasing the total nitrogen and COD concentrations in the effluent. If the temperature is adjusted to promote denitrification, on the one hand, the reaction in the system is complex, and there are many types and quantities of microorganisms, so frequent temperature adjustment can easily cause an imbalance in microbial competition, and the adjustment precision is limited. On the other hand, the cost of adjustment is also high, and the effect of promoting denitrification by adjusting the temperature is also limited. If the hydraulic retention time is changed to promote denitrification, the treatment efficiency of the OA wastewater treatment system will be reduced first, and the amount of wastewater that can be treated per unit time will be reduced, which does not meet the actual needs of the wastewater treatment plant. Secondly, wastewater needs to go through a very long process from entering the wastewater treatment plant to the final water quality representation and discharge. For example, before entering the AOA wastewater treatment system, it needs to go through a pretreatment stage, and after being treated by the AOA wastewater treatment system, it needs to be further treated by deep treatment. Therefore, changes in the treatment capacity of the AOA wastewater treatment system will affect the efficiency of the entire wastewater treatment process, and will have a certain impact on the treatment capacity and efficiency of the preceding and subsequent processes. Finally, the effect of promoting denitrification by adjusting the hydraulic retention time is also limited. Therefore, considering the treatment efficiency, cost input, practicality, precision, and other factors of the wastewater treatment, the present application screens the sludge and returns the target sludge with a large number of denitrifying microorganisms and good activity to the system, which can quickly improve the denitrification capacity, has low operation difficulty and high control precision, is easy to apply and popularize in wastewater treatment plants, and can further improve the wastewater treatment capacity and efficiency of the wastewater treatment plant.

[0060] In some embodiments, the use of the total nitrogen concentration of the effluent to control the operating state of the denitrifying microorganism directional screening device 300 includes:

[0061] in response to the effluent total nitrogen concentration being greater than or equal to the effluent total nitrogen concentration standard value, the denitrifying microorganism directional screening device 300 is controlled to run 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 tank 100 is obtained and a denitrification rate judgment step is performed to determine the running state of the denitrifying microorganism directional screening device 300 by 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 effluent total nitrogen concentration of the system, improve the effluent water quality and ensure that the effluent water quality can meet the standard, the first parameter with the highest load is run at this time, that is, the denitrifying microorganism directional screening device 300 runs at full load under the first parameter, more denitrifying microorganisms are screened and returned to the biochemical tank 100, so as to quickly improve the number and activity of denitrifying microorganisms in the biochemical tank 100, thereby promoting denitrification and strengthening the denitrification effect of the system to reduce 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 effluent total nitrogen concentration standard value, it indicates that the current effluent total nitrogen concentration is in a standard state. However, the effluent total nitrogen concentration meeting the standard does not mean that the current denitrification is in a standard or efficient state, and the denitrification rate may still be low. For example, when the water retention time in the anoxic stage is long enough, the denitrification reaction is slow, but eventually the total nitrogen can be removed through long-time reaction, but the overall denitrification efficiency of the system is not high, and the cost is increased. At the same time, when the denitrification rate in the system is low for a long time, the processing capacity and stability of the system are low, especially in the case of high influent load or water fluctuation, which may lead to unstable or even excessive effluent total nitrogen concentration; 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 flora, making it difficult for denitrifying microorganisms to compete with other microorganisms, further reducing the number and activity of denitrifying microorganisms, and further reducing the denitrification efficiency of the system. Therefore, in order to ensure that the system can run stably and efficiently for a long time and 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 running state of the denitrifying microorganism directional screening device 300 is further determined by using the current denitrification rate of the biochemical tank 100, so as to understand the denitrification of the system in time, so as to start the denitrifying microorganism directional screening device 300 to screen the sludge in time, obtain the target sludge containing a large number of denitrifying microorganisms, and thus promote the denitrification in the system in time, and ensure that the system runs stably and efficiently for a long time.

[0065] The effluent total nitrogen concentration standard value can be determined according to the emission standard requirements of different places and different scenes. For example, according to the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002), the total nitrogen control requirements of the effluent of the municipal wastewater treatment plant are divided into first level A, first level B and second level standards. The first level A standard is ≤15 mg / L, which is strictly required for sensitive water bodies or ecological protection areas; the second level B standard is ≤20 mg / L, which is generally applicable to ordinary discharge requirements; and the second level standard has no explicit TN requirement. For example, for rural domestic sewage treatment or decentralized small sewage treatment facilities, the total nitrogen requirement of the effluent is 15-25 mg / L; the total nitrogen emission standard of industrial wastewater can be further subdivided according to specific industries. Some industries (such as chemical industry, pharmaceutical industry, etc.) have more stringent requirements, usually ≤10-20 mg / L. Therefore, the effluent total nitrogen concentration standard value 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 circumstances, or other values can also be set, and the specific limitation is not limited. The first threshold value can be determined according to the effluent total nitrogen concentration standard value, for example, it can be set to 70% of the effluent total nitrogen concentration standard value, or other percentages such as 65%, 68%, 72%, 75%, 78%, 80% of the effluent total nitrogen concentration standard value, and the specific limitation is not limited.

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

[0067] The current denitrification rate of the biochemical tank 100 can be calculated by recording the change of the concentration of nitrate (or nitrite) over time to calculate the denitrification rate. For example, it can be calculated by monitoring the anoxic stage of the biochemical tank 100, first recording the sludge concentration of the anoxic stage, recording the change value of the initial nitrate concentration and the interval time, and then calculating according to the change of the nitrate concentration and the sludge concentration. For example, it can be calculated by the difference of the nitrate concentration of the influent and effluent of the anoxic stage, combined with the hydraulic retention time and volume of the anoxic stage. For example, it can be calculated by an experimental method, that is, sampling from the anoxic stage of the biochemical tank 100 to obtain a mixture of sludge and water containing denitrifying microorganisms, maintaining the mixture under anoxic conditions, adjusting the initial concentration of nitrate in the mixture to a certain level, and adding an appropriate amount of carbon source (such as acetic acid or glucose, etc.), ensuring that the C / N ratio is appropriate (such as 4-6), collecting a certain amount of sample every certain time, and then measuring the nitrate concentration in the sample by ion chromatography, ultraviolet spectrophotometry or kit method, etc. to draw the curve of the change of the nitrate concentration over time, and then calculate the denitrification rate. According to the actual situation, the current denitrification rate of the biochemical tank 100 can be calculated in different ways, or it can be directly monitored and calculated by some intelligent online monitoring system, which is not limited. Specifically, the current denitrification rate of the biochemical tank 100 can be detected once a day, or multiple times a day, or the average value of multiple times, etc., which is not limited.

[0068] In some embodiments, the control method further comprises: in response to the total nitrogen concentration of the effluent being less than the first threshold value, controlling the denitrifying microorganism directional screening device 300 to be closed. When the total nitrogen concentration of the effluent is less than the first threshold value, it indicates that the current total nitrogen concentration of the effluent is much lower than the standard value of the total nitrogen concentration of the effluent, which reflects that the AOA sewage treatment system is running stably and well. 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 determining step comprises:

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

[0072] wherein the number of denitrifying microorganisms screened by the denitrifying microorganism directional screening device 300 under the first parameter, the second parameter and the third parameter decreases in turn.

[0073] As Figure 2 shown, when the current denitrification rate is less than the denitrification rate target value and greater than or equal to the second threshold value, it indicates that the current denitrification rate of the biochemical tank 100 is slightly lower than the denitrification rate target value, at this time, although the total nitrogen in the effluent meets the standard, but long-term operation may lead to low system efficiency, reduced denitrification efficiency and other risks, therefore the denitrifying microbial directional screening device 300 is controlled to operate at the third parameter; when the current denitrification rate is less than the second threshold value, it indicates that the current denitrification rate is significantly lower than the denitrification rate target value. The load capacity of the denitrifying microbial directional screening device 300 under 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 that in the external sludge, under the first parameter and the second parameter, more denitrifying microorganisms can be returned to the biochemical tank 100, thereby increasing the number and activity of denitrifying microorganisms in the system, and further improving the denitrification efficiency. In the case that the total nitrogen in the effluent meets the standard, further determining the state of the denitrifying microbial directional screening device 300 according to the current denitrification rate can effectively improve the stability of long-term operation of the system, and ensure that the denitrification reaction is in a high-efficiency state for a long time to ensure that the effluent quality meets the standard stably; at the same time, the 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 third parameter with the lowest load capacity is operated, which can effectively reduce the system operation cost and is more beneficial to practical application and promotion.

[0074] The denitrification rate target value can be set according to different application scenarios and actual conditions. For example, the denitrification rate target value of the ordinary sewage treatment process can be in the range of 1.0-5.0 mg NO3 - -N / (L·h), specifically, it can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5.0 mg NO3 - -N / (L·h), or other values within 1.0-5.0 mg NO3 - -N / (L·h), specifically, it can be 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10.0 mg NO3 - -N / (L·h), or other values within 6.0-10.0 mg NO3 - -N / (L·h), specifically, it can be 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10.0 mg NO3 - -N / (L·h), or other values within 6.0-10.0 mg NO3 -- N / (L h), specifically can be 1, 1.5, 2, 2.5, 3 mg NO3 - - N / (L h), also can be 1.0-3.0 mg NO3 - - other values within N / (L h), specifically not limited; the value range of the denitrification rate target value of industrial wastewater treatment can be 4.0-6.0 mg NO3 - - N / (L h), specifically can be 4, 4.5, 5, 5.5, 6 mg NO3 - - N / (L h), also can be 4.0-6.0 mg NO3 - - other values within N / (L h), specifically not limited.

[0075] The second threshold value can be determined according to the denitrification rate target value, for example, can be set to 50% of the denitrification rate target value, or can be set to other percentages, for example, 40%, 45%, 55%, 60%, 65%, 70% of the denitrification rate target value, specifically not limited.

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

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

[0078] The first parameter, the second parameter and the third parameter all include the ratio of underflow overflow cross-sectional area, and the ratio of underflow overflow cross-sectional area corresponding to the first parameter, the second parameter and the third parameter decreases in turn.

[0079] A hydrocyclone is a highly efficient separation device that utilizes centrifugal force for solid-liquid separation, particle classification, impurity removal, and sludge screening. The hydrocyclone uses centrifugal separation to separate the sludge in the feed into different parts within a high-speed rotating flow field. Heavy sludge (high-density particles or larger flocs) moves towards the periphery of the hydrocyclone under centrifugal force and is discharged through the lower outlet; light particles (low-density particles or smaller flocs) move towards the center of the hydrocyclone under the action of the inner swirling flow and are discharged through the top outlet. In this application, the target sludge, with better floc structure and settling performance and containing more denitrifying microorganisms, moves towards the lower part of the hydrocyclone under the action of the swirling flow, while the discharge sludge, with poorer floc structure and settling performance and containing fewer denitrifying microorganisms, moves towards the upper part of the hydrocyclone under the action of the swirling flow, thereby achieving the screening of the target sludge and the discharge sludge.

[0080] A hydrocyclone typically includes a main body and an overflow port at the top, a bottom outlet at the bottom, and a feed inlet located between the overflow port and the bottom outlet. Sludge enters the main body, and under the action of the cyclone, the target sludge is separated from the discharged sludge. For example... Figure 1 As shown, the feed inlet is connected to the return pipeline 400 via the feed pipeline 500 to introduce the sludge in the return pipeline 400 into the main body of the hydrocyclone; the underflow outlet is connected to the biological treatment tank 100 via the underflow pipeline 600 to return the target sludge to the biological treatment tank 100; the overflow outlet is connected to the overflow pipeline 700 to discharge the external sludge to the outside of the system. Optionally, the underflow-overflow cross-sectional area ratio is the ratio of the cross-sectional area of ​​the underflow outlet to the cross-sectional area of ​​the overflow outlet.

[0081] During the operation of the hydrocyclone, a larger diameter ratio between the underflow outlet and the overflow outlet allows more heavy sludge to be discharged smoothly from the underflow, reducing the likelihood of heavy sludge entering the overflow outlet. When heavy sludge is the screening target, a larger diameter ratio between the underflow outlet and the overflow outlet generally improves separation efficiency. Therefore, by setting the underflow and overflow cross-sectional area ratios corresponding to the third, second, and first parameters to increase sequentially, the target sludge containing a large number of denitrifying microorganisms can be smoothly discharged through the underflow outlet, thereby screening out more denitrifying microorganisms and returning them to the biological treatment tank 100 to enhance the denitrification capacity of the biological treatment tank 100.

[0082] In the biological treatment of wastewater, a large number and variety of microorganisms are involved, including aerobic and anaerobic microorganisms, as well as denitrifying bacteria, polyphosphate-accumulating bacteria, nitrifying bacteria, and polysaccharide-producing bacteria. The dynamic balance among these microorganisms is crucial for the long-term stable operation of the system. The dynamic balance of the microbial population means that different types of microorganisms maintain a stable structure through continuous competition, growth, and death, ensuring the normal functioning of organic matter degradation, nitrogen and phosphorus removal, and other treatment functions. However, the dynamic balance among microorganisms is a rather complex process, and excessive adjustments can easily lead to an imbalance in competition, thus negatively impacting system operation. The total nitrogen concentration in the effluent is the most critical performance indicator for wastewater treatment.

[0083] Therefore, as Figure 2 As shown, in this scheme, the total nitrogen concentration of the effluent is first used to determine the system's operating status. When the total nitrogen concentration of the effluent is less than the first threshold, it indicates 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. At this time, the denitrifying microorganism directional screening device 300 is not activated. 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 indicates that the competition among the current microorganisms has become significantly unbalanced. The system is then operated with the highest underflow-overflow cross-sectional area ratio (i.e., the first parameter) to discharge sludge of poor quality and low denitrifying microorganism content (i.e., external sludge) from the system, thereby increasing the proportion of denitrifying microorganisms and thus quickly correcting the competitive state among various microorganisms in the system, promoting a new balance. When the total nitrogen concentration in the effluent is greater than or equal to the first threshold but less than the standard value, although the effluent quality meets the standards, to ensure the long-term stable operation of the system, the current denitrification rate is used to further evaluate the system's operation. When the current denitrification rate is less than the second threshold, it indicates that the competition among microorganisms is very unfavorable to 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 that of the first parameter. Operating with this parameter allows for the return of more denitrifying microorganisms without causing excessive fluctuations in the effluent quality. When the current denitrification rate is less than the target value but greater than or equal to the second threshold, it indicates that the water quality meets the standards but is not conducive to the long-term operation of the system. In this case, the system is operated with the lowest underflow overflow cross-sectional area ratio. This can appropriately increase the proportion of denitrifying microorganisms in the system, gradually improve the system's denitrification capacity, and avoid causing new problems due to the imbalance of competition among the microorganisms in the system caused by adding too many denitrifying microorganisms in the short term.

[0084] The activated sludge usually contains high concentration of organic matter and colloids, and has problems of large viscosity, poor fluidity, small density difference, poor classification accuracy, etc. compared with solid-liquid separation. The sludge in the reflux pipeline also has the above characteristics, so when the denitrifying microbial directional screening device 300 is used to realize the screening of target sludge and discharged sludge, the above problems also exist. In the scheme, by adjusting the bottom flow overflow cross-sectional area ratio of the denitrifying microbial directional screening device 300, compared with adjusting the cross-sectional area of the overflow port or the bottom flow port alone, the separation accuracy and efficiency can be effectively improved, which is more suitable for sludge screening. The sludge has high viscosity and poor fluidity, and unstable flow state (such as turbulent flow or short circuit flow) is easily formed in the cyclone. Only adjusting the cross-sectional area of the overflow or bottom flow port may cause flow field imbalance and further exacerbate uneven separation. By controlling the bottom flow overflow cross-sectional area ratio, the difference between the bottom flow cross-sectional area and the overflow cross-sectional area can be controlled, avoiding the problem of transition adjustment of overflow or bottom flow, thereby stabilizing the centrifugal force field, reducing the problem of flow field imbalance, ensuring the separation accuracy; at the same time, it can also avoid the long-term high load state of overflow or bottom flow, reduce the risk of blockage, and ensure its long-term stable operation; avoid the internal pressure fluctuation easily caused by single parameter adjustment, reduce the problem of turbulent flow and back mixing, thereby further improving the separation efficiency.

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

[0086] When the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow is too large or too small, some poor-quality sludge may not flow out of the overflow. When the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow is too small, it indicates that the cross-sectional area of the underflow is too small, and large-diameter sludge flocs containing a large number of denitrifying microorganisms may not flow out of the underflow, which may also cause problems such as reduced screening efficiency. Therefore, in order to further ensure the screening efficiency and stability, the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow is kept in a relatively appropriate range, that is, the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow corresponding to the first parameter is greater than or equal to 8 and less than or equal to 10, the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow corresponding to the second parameter is greater than or equal to 6 and less than 8, and the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow corresponding to the third parameter is greater than or equal to 5 and less than 6. Specifically, the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow 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., and can also be other values in the above range, without specific limitation; the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow 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., and can also be other values in the above range, without specific limitation; the ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow 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., and can also be other values in the above 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 ratio of the cross-sectional area of the underflow to the cross-sectional area of the overflow is large, it indicates that the diameter or equivalent diameter of the underflow is large, which is beneficial for large-diameter sludge flocs to pass through, that is, it is beneficial for target sludge containing a large number of denitrifying microorganisms to pass through, so that more denitrifying microorganisms can be screened. In actual application, in order to further ensure the screening effect and efficiency, the cross-sectional area of the underflow 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, the cross-sectional area of the underflow corresponding to the first parameter is not less than the first area, the cross-sectional area of the underflow corresponding to the second parameter is not less than the second area, and the cross-sectional area of the underflow 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 , and the third area is 0.02m 2The sludge containing more denitrifying microorganisms has a larger diameter, so by limiting the minimum cross-sectional area of the underflow port through the first area, the second area, and the third area, the screening of the target sludge can be better achieved. In some embodiments, the first parameter, the second parameter, and the third parameter further include a feed flow rate, and the feed flow rates corresponding to the first parameter, the second parameter, and the third parameter decrease in turn.

[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 as the external sludge out of the system, and the performance of the sludge (i.e., the target sludge) after screening and then flowing back to the biochemical pool 100 is obviously improved, thereby effectively improving the denitrification and nitrogen removal effect of the AOA wastewater treatment system; on the other hand, the flow rate and centrifugal force in the hydrocyclone will also increase, and the larger flow rate and centrifugal force will accelerate the heavy sludge (high-density or large-particle-size particles) to the outer layer, so that the heavy sludge is more easily discharged by underflow. Therefore, while adjusting the underflow overflow cross-sectional area ratio, the feed flow rate is further adjusted, a larger feed flow rate can screen more sludge and improve the quality of the reflux sludge; at the same time, the screening and separation of the target sludge and the external sludge can be improved, and the quality of the reflux sludge can be further improved. Specifically, the feed flow rates corresponding to the first parameter, the second parameter, and the third parameter can be determined by the design feed flow rate of the denitrifying microorganism directional screening device 300, and the feed flow rate corresponding to the first parameter is the design feed flow rate; the feed flow rate corresponding to the second parameter is 60% to 85% of the design feed flow rate, such as 60%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 85%, etc., or other percentages, or other values less than 60% or greater than 85%, which are not limited in particular; the feed flow rate corresponding to the third parameter is 40% to 60% of the design feed flow rate, such as 40%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, etc., or other percentages, or other values less than 40% or greater than 60%, which are not limited in particular.

[0089] In some embodiments, as shown in FIG. 1, 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 turn; and the control method further includes: Figure 1

[0090] In response to determining to start the denitrifying microorganism directional screening device 300, calculating an actual volume of the anoxic pool required for the effluent water quality of the AOA wastewater treatment system to meet the standard, and determining the operating state of the first conversion zone 102 by using the actual volume of the anoxic pool.

[0091] ​The anaerobic tank 101 is used to realize the anaerobic stage of the AOA process, and the phosphorus release of the phosphorus accumulating organisms and the degradation of the organic matter are carried out; the aerobic tank 103 is used to realize the aerobic stage of the AOA process, and the nitrification reaction, the phosphorus removal effect and the degradation of the organic matter are carried out; the anoxic tank 105 is used to realize the anoxic stage of the AOA process, and the denitrification effect is mainly carried out. The mechanical agitator is arranged in the anaerobic tank 101 to improve the reaction efficiency. The sludge concentration in the aerobic tank 103 is controlled to be 3000-5000 mg / L, the carbon source is released by the phosphorus accumulating organisms to carry out the aerobic phosphorus absorption, the ammonia nitrogen is fully oxidized, the internal carbon source consumption is reduced, more carbon source is reserved for the subsequent denitrification. Part of the nitrate nitrogen in the aerobic tank 103 can be removed through the simultaneous nitrification and denitrification, and the aerator is arranged in the aerobic tank 103 to carry out aeration.

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

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

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

[0095] When the above-mentioned cases exist, it indicates that the denitrification effect of the current AOA wastewater treatment system is abnormal, and the denitrifying microbial directional screening device 300 is started to improve the number and activity of the denitrifying microorganisms in the current AOA wastewater treatment system. However, in addition to the denitrifying microorganisms, the concentration of nitrate and the concentration of carbon source also affect the denitrification effect of the system. For example, when the ammonia nitrogen or nitrate nitrogen concentration in the influent is too high or the carbon source is insufficient, the denitrification efficiency will be affected, and then the total nitrogen concentration of the effluent will be increased.

[0096] Therefore, in order to better improve the denitrification effect and improve the effluent quality, the first conversion zone 102 is arranged between the anaerobic tank 101 and the aerobic tank 103, and the operating state of the first conversion zone 102 is an adjustable state, 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 quality of the AOA wastewater 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 it is more suitable for various water qualities, especially for the case that the water quality changes greatly, and at the same time, the denitrification effect can be improved, and the efficient and stable operation of the AOA wastewater treatment system can be ensured.

[0097] In some embodiments, the determining the operation state of the first conversion zone 102 according to the actual volume of the anoxic tank comprises: in response to the actual volume of the anoxic tank being less than the design 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 tank being greater than or equal to the design volume of the anoxic tank 105, controlling the first conversion zone 102 to be in an anoxic state.

[0099] When the calculated actual volume of the anoxic tank is greater than or equal to the design volume of the anoxic tank 105, it indicates that the current design volume of the anoxic tank 105 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 tank 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 tank is less than the design volume of the anoxic tank 105, it indicates that the current design volume of the anoxic tank 105 meets the actual demand. In general, sewage is rich in not only nitrogen but also phosphorus. Therefore, when the design volume of the anoxic tank 105 meets the actual demand, the first conversion zone 102 can be adjusted to the anaerobic state. When the first conversion zone 102 is in the anaerobic state, on the one hand, the phosphorus release efficiency of the phosphorus accumulating bacteria can be enhanced, and on the other hand, the phosphorus release of the phosphorus accumulating bacteria requires the absorption of carbon sources, thereby reducing the competition of organic matter for denitrification in the anoxic zone. Specifically, when the first conversion zone 102 is in the 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 the anaerobic state, no aeration is performed.

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

[0101] In response to determining to start the denitrifying microorganism directional screening device 300, calculating the actual volume of the aerobic tank required for the effluent water quality of the AOA sewage treatment system to meet the standard, and determining the operation state of the second conversion zone 104 according to the actual volume of the aerobic tank.

[0102] Denitrification is a process of reducing nitrate or nitrite to nitrogen gas using organic matter as a carbon source. Nitrate or nitrite is an important participant, which is mainly produced in the aerobic tank 103, i.e., under sufficient oxygen conditions, aerobic microorganisms (such as nitrifying bacteria) oxidize ammonia nitrogen to nitrite or nitrate. Therefore, the operation of the aerobic tank 103 also affects the subsequent denitrification effect.

[0103] In order to better improve the denitrification effect and improve the effluent quality, a second conversion zone 104 is arranged between the aerobic tank 103 and the anoxic tank 105, and the operating state of the second conversion zone 104 is an adjustable state, 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 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 better adapt to various water qualities, especially for the case that the water quality changes greatly, the denitrification effect can be improved, and the efficient and stable operation of the AOA sewage treatment system can be ensured. Specifically, the first conversion zone 102 and the second conversion zone 104 are both provided with aerators to realize aeration, and are both provided with mechanical mixers to promote system reaction.

[0104] In some embodiments, the operating state of the second conversion zone 104 is determined by the actual volume of the aerobic tank, including:

[0105] In response to the actual volume of the aerobic tank being less than the design volume of the aerobic tank 103, the second conversion zone 104 is controlled to be in an anoxic state;

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

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

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

[0109] The actual volume of the anoxic tank is calculated by using the influent flow rate, influent total nitrogen concentration, daily sludge discharge amount, standard value of effluent total nitrogen concentration, current denitrification rate, and 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 of the AOA sewage treatment system to meet the standard can be calculated by using the current water quality and quantity information (i.e., influent flow rate and influent total nitrogen concentration) of the AOA sewage treatment system, actual operation conditions (daily sludge discharge amount, current denitrification rate, and current sludge concentration of the first conversion zone 102), and effluent standard (i.e., standard value of effluent total nitrogen concentration). When the influent water quality and quantity and the actual operation conditions fluctuate, the changes can be captured in time, and a new actual volume of the anoxic tank required for the effluent to meet the standard can be calculated. Thus, the operation state of the first conversion zone 102 can be adjusted according to the new actual volume of the anoxic tank, so that the AOA sewage treatment system can effectively respond to fluctuations in water quality and quantity, thereby improving the stability of system operation, effectively improving the denitrification effect, and ensuring that the effluent meets the standard.

[0111] Specifically, the actual volume V of the anoxic tank is calculated by the following formula: n The actual volume V of the anoxic tank can be calculated by the following formula:

[0112]

[0113] wherein Q0 is the influent flow rate, TN0 is the influent total nitrogen concentration, TN is the standard value of effluent total nitrogen concentration, ΔX is the daily sludge discharge amount, k is the current denitrification rate, and X1 is the current sludge concentration of the first conversion zone 102. e v The actual volume of the anoxic tank is calculated by using the influent flow rate, influent total nitrogen concentration, daily sludge discharge amount, standard value of effluent total nitrogen concentration, current denitrification rate, and current sludge concentration of the first conversion zone 102 of the AOA sewage treatment system.

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

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

[0116] ​In the AOA wastewater 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 metabolic action, achieving 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, the current water quality and quantity information of the AOA wastewater treatment system (i.e. influent flow rate, influent COD concentration), the actual operation of the system (sludge age, sludge yield coefficient, current sludge concentration of the second conversion zone 104) and the effluent standard (effluent COD concentration standard value) can be used to calculate the actual volume of the aerobic tank required for the effluent water quality to meet the standard. When the influent water quality and quantity fluctuate, the above changes can be captured in time, and the new actual volume of the aerobic tank 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 adjusted according to the new actual volume of the aerobic tank, so that the AOA wastewater treatment system can effectively respond to water quality and quantity fluctuations, thereby improving the stability of the system operation. Not only can the effective removal of organic matter be achieved, but also enough nitrate or nitrite can be provided for subsequent 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 tank V a can be calculated by the following formula:

[0118]

[0119] wherein, COD o is the influent COD concentration of the AOA wastewater treatment system, COD e is the effluent COD concentration standard value of the AOA wastewater treatment system, θ co is the sludge age of the AOA wastewater treatment system, Y t is the sludge yield coefficient of the AOA wastewater treatment system, and X2 is the current sludge concentration of the second conversion zone 104.

[0120] In some embodiments, the AOA wastewater treatment system further comprises an influent pipeline 800 and a segmented influent branch line 810;

[0121] The influent pipeline 800 is connected with the anaerobic tank 101, so as to pass the wastewater to be treated into the anaerobic tank 101;

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

[0123] The control method further comprises:

[0124] A ratio coefficient is calculated according to the ratio of the COD concentration difference and the total nitrogen concentration difference of the influent and effluent of the AOA wastewater treatment system;

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

[0126] In the denitrification process, the lack of carbon source will also affect the efficiency of denitrification. Therefore, the segmented water inlet branch 810 is connected between the water inlet pipeline 800 and the anoxic tank 105, and when the carbon source in the anoxic tank 105 is insufficient, part of the water inlet is directly introduced into the anoxic tank 105 to use the organic matter in the water inlet as a carbon source to promote the denitrification process and ensure the denitrification and nitrogen removal effect. The opening of the segmented water inlet branch 810 can be determined by using the ratio coefficient calculated by the difference between the chemical oxygen demand concentration and the total nitrogen concentration of the influent and effluent of the AOA sewage treatment system. Specifically, the ratio coefficient N can be calculated by the following formula:

[0127]

[0128] COD0-TN0COD1-TN1 o COD0 is the influent COD concentration of the AOA sewage treatment system, COD1 is the effluent COD concentration of the AOA sewage treatment system, TN0 is the influent total nitrogen concentration of the AOA sewage treatment system, and TN1 is the effluent total nitrogen concentration of the AOA sewage treatment system.

[0129] The reaction equation of denitrification is: NO3 - + organic matter (COD) → N2+ CO2+ H2O+ OH - In the denitrification process, 1g of NO3 - -N (calculated as nitrogen) requires the consumption of COD, which can be calculated to be about 2.86g COD. Therefore, in actual operation, the ideal COD / N is 2.86. However, in actual operation, part of the COD needs to be used for microbial growth and maintenance metabolism, and there may be non-biodegradable part in the influent COD, so the ratio of COD / N needs to be controlled to be slightly higher than the ideal value 2.86. If the COD / N ratio is too high, it is easy to cause the COD concentration in the effluent to be too high, resulting in the effluent water quality not meeting the standard. Therefore, considering the smooth progress of the denitrification process and the requirements of the effluent water quality, the third threshold value in the present scheme is in the range of 3-4, 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, which is not limited. 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, so part of the water inlet is introduced into the anoxic tank 105 through the segmented water inlet branch 810. The organic matter concentration in the water inlet is usually high, which can avoid consumption in the front-end anaerobic tank 101, aerobic tank 103 and other processes, quickly supplement the carbon source required for denitrification, and ensure the efficient progress of the denitrification process.

[0130] Specifically, the flow rate Q1 of the segmented influent branch 810 is calculated by the following formula:

[0131]

[0132] wherein Q1 is the flow rate of the segmented influent branch 810, Q0 is the influent flow rate of the AOA sewage treatment system (i.e. the influent flow rate of the influent pipeline 800), A0 is the NH3 concentration of the influent of the AOA sewage treatment system, A1 is the NH3 concentration of the aerobic tank 103, and A2 is the NH3 concentration of the aeration zone 106.

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

[0134] In some embodiments, the anoxic tank 105 and the secondary sedimentation tank 200 are further provided with an aeration zone 106. The dissolved oxygen concentration of the effluent of the anoxic tank 105 is low, which is not conducive to the solid-liquid separation of the secondary sedimentation tank 200. Therefore, the aeration zone 106 is provided to further improve the sludge settling property. The aeration zone 106 is provided with an aerator, and the dissolved oxygen concentration is controlled to be about 0.5-1.5 mg / L.

[0135] Specifically, the sludge age θ of the AOA sewage treatment system is calculated by the following formula: co

[0136]

[0137] wherein X0, X1, X2, X3, X4 and X5 respectively correspond to the current sludge concentration 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, V0, V1, V2, V3, V4 and V5 respectively correspond to the sludge volume 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, ΔX is the sludge concentration of the sludge discharged per day, and ΔV is the sludge volume of the sludge discharged per day. a b c d a b c d

[0138] In some embodiments, the upper portion of the secondary sedimentation tank 200 is provided with a drainage port, and the bottom portion is provided with a sludge discharge port in communication with the reflux pipeline 400. The drainage port is connected with a drainage pipeline 900, which is used to guide the treated sewage to the next stage.

[0139] ​​​​​​​​​In some embodiments, the return pipeline 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 anaerobic state and anoxic state, and when switched to anoxic state, a denitrification reaction can be performed to remove nitrogen in the sewage. Therefore, the target sludge rich in denitrification microorganisms is directly introduced into the first conversion zone 102, which is beneficial to maintaining the activity of the denitrification microorganisms and can also quickly improve the denitrification rate and rapidly strengthen the nitrogen removal effect of the system.

[0140] Based on the same inventive concept, the present application also provides an electronic device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the control method of the sewage treatment system according to any one of the embodiments when executing the program.

[0141] Figure 3 A more specific hardware structure of an electronic device is shown in the embodiment, which can 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 for communication within the device.

[0142] The processor 1010 can be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits, and is used to execute related programs to implement the technical solutions provided by the embodiments of the present application.

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

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

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

[0146] The bus 1050 includes a channel to transmit information between various components (such as the processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040) of the device.

[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 can also include other components necessary for normal operation. In addition, those skilled in the art can understand that the above device can also only include 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 embodiments is used to implement the sewage treatment system control method of any one of the above embodiments, and has the beneficial effects of the corresponding method embodiments, which are not described here.

[0149] Based on the same inventive concept, corresponding to the method of any of the above embodiments, the present application also provides a non-transitory computer readable storage medium storing computer instructions for causing the computer to execute a sewage treatment system control method according to any one of the above embodiments.

[0150] The computer readable media of the embodiments can include permanent and non-permanent, removable and non-removable media, which can be implemented by any method or technology to store information. The information can be computer readable instructions, data structures, program modules 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, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic tape disk storage or other magnetic storage device, or any other non-transmission medium that can be used to store information accessible by a computing device.

[0151] The storage medium of the above embodiments stores computer instructions for causing the computer to perform a sewage treatment system control method as described in any of the above embodiments, and has the beneficial effects of the corresponding method embodiments, which are not described here.

[0152] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present application (including claims) is limited to these examples; the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of the different aspects of the embodiments of the present application as described above. In order to be brief, they are not provided in detail. In addition, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these details or with changes in these details, even if specific details are described to describe the exemplary embodiments of the present application. Therefore, these descriptions should be considered illustrative rather than limiting.

[0153] In order to simplify the description and discussion, and so as not to make the embodiments of the present application difficult to understand, the known power supply / ground connections with other components can or can not be shown in the provided drawings. In addition, the devices can be shown in the form of block diagrams in order to avoid making the embodiments of the present application difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform to be implemented the embodiments of the present application (i.e. these details should be fully within the understanding of those skilled in the art). In the case of describing specific details to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than limiting.

[0154] While the present application has been described in connection with certain embodiments thereof, many modifications, substitutions, and alterations, thereof will be readily apparent to those of ordinary skill in the art, given the benefit of this disclosure. For example, other memory architectures (e.g., dynamic RAM (DRAM)) can use the embodiments discussed.

[0155] It is intended that the embodiments of the present application encompass all such substitutions, modifications, and alterations as fall within the broad scope of the appended claims. Accordingly, any and all such modifications, substitutions, and alterations as come within the spirit and scope of the embodiments of the present application are intended to be encompassed by the claims.

Claims

1. A sewage treatment system control method applied to an AOA sewage treatment system, characterized in that, The AOA sewage treatment system comprises a denitrifying microbial directional screening device and a biochemical tank and a secondary sedimentation tank connected in sequence; The bottom of the secondary sedimentation tank is connected with the biochemical tank through a reflux pipeline; The denitrifying microbial directional screening device is connected with the reflux pipeline and the biochemical tank, and is used to screen part of sludge in the reflux pipeline to obtain target sludge and external discharge sludge, and to reflux the target sludge to the biochemical tank, and to discharge the external discharge sludge to the outside of the system; wherein the number of denitrifying microorganisms in the target sludge is higher than that in the external discharge sludge; The control method comprises: obtaining the current total nitrogen concentration of the effluent of the secondary sedimentation tank to obtain the effluent total nitrogen concentration, and using the effluent total nitrogen concentration to control the operating state of the denitrifying microbial directional screening device; wherein, using the effluent total nitrogen concentration to control the operating state of the denitrifying microbial directional screening device comprises: in response to the effluent total nitrogen concentration being greater than or equal to the effluent total nitrogen concentration standard value, controlling the denitrifying microbial 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, obtaining the current denitrification rate of the biochemical tank and performing a denitrification rate judgment step to determine the operating state of the denitrifying microbial directional screening device using the current denitrification rate; the denitrification rate judgment step comprises: in response to the current denitrification rate being less than a second threshold value, controlling the denitrifying microbial directional screening device to operate at a second parameter; in response to the current denitrification rate being less than a denitrification rate target value and greater than or equal to the second threshold value, controlling the denitrifying microbial directional screening device to operate at a third parameter; wherein, the number of denitrifying microorganisms screened by the denitrifying microbial directional screening device under the first parameter, the second parameter and the third parameter decreases in turn; the denitrifying microbial directional screening device is a hydrocyclone; wherein, the first parameter, the second parameter and the third parameter all include the ratio of underflow overflow cross-sectional area of the hydrocyclone, and the ratio of underflow overflow cross-sectional area corresponding to the first parameter, the second parameter and the third parameter decreases in turn; the first parameter, the second parameter and the third parameter also include the feed flow rate of the hydrocyclone, and the feed flow rate corresponding to the first parameter, the second parameter and the third parameter decreases in turn; By setting a denitrifying microbial directional screening device on the sludge reflux path of the AOA sewage treatment system, the sludge in the system is effectively screened, the target sludge with a high number of denitrifying microorganisms is separated from the external discharge sludge with a low number of denitrifying microorganisms, and the target sludge is refluxed to the biochemical tank, so as to increase the number and activity of denitrifying microorganisms in the biochemical tank, promote denitrification, and effectively improve the denitrification efficiency.

2. The method of claim 1, wherein The biochemical tank comprises an anaerobic tank, a first conversion zone, an aerobic tank and an anoxic tank connected in sequence; the control method further comprises: in response to determining to start the denitrifying microbial directional screening device, calculating an actual volume of the anoxic tank required for the effluent water quality of the AOA sewage treatment system to meet the standard, and determining the operation state of the first conversion zone by using the actual volume of the anoxic tank; And / or, a second conversion zone is further arranged between the aerobic tank and the anoxic tank; the control method further comprises: in response to determining to start the denitrifying microbial directional screening device, calculating an actual volume of the aerobic tank required for the effluent water quality of the AOA sewage treatment system to meet the standard, and determining the operation state of the second conversion zone by using the actual volume of the aerobic tank; wherein, the operation state of the first conversion zone is determined by using the actual volume of the anoxic tank, comprising: in response to the actual volume of the anoxic tank being less than the design 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 tank being greater than or equal to the design volume of the anoxic tank, controlling the first conversion zone to be in an anoxic state; the operation state of the second conversion zone is determined by using the actual volume of the aerobic tank, comprising: in response to the actual volume of the aerobic tank being less than the design volume of the aerobic tank, 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 design volume of the aerobic tank, controlling the second conversion zone to be in an aerobic state; the actual volume of the anoxic tank is calculated by the following steps: the actual volume of the anoxic tank is calculated by using the influent flow rate, influent total nitrogen concentration, daily sludge discharge amount, 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 tank is calculated by the following steps: the actual volume of the aerobic tank is calculated by using the influent flow rate, influent COD concentration, effluent COD concentration standard value, sludge age, sludge yield coefficient and current sludge concentration of the second conversion zone of the AOA sewage treatment system.

3. The method of claim 2, wherein the method further comprises: an air supply zone is further arranged between the anoxic tank and the secondary sedimentation tank; And / or, the upper part of the secondary sedimentation tank is provided with a drainage port, and the bottom part is provided with a sludge discharge port communicated with the reflux pipeline, and the drainage port is connected with a drainage pipeline for guiding the treated sewage to the next stage; And / or, the reflux pipeline is connected with the anaerobic tank, and the target sludge is refluxed to the first conversion zone.

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