Accurate aeration control method and system based on AAO process

Abstract

The invention relates to the technical field of sewage treatment, and aims to solve the problems that an existing mode of manually adjusting the frequency of a fan and the opening degree of a valve is rough and not fine, the aeration rate is easy to excessively increase and the energy consumption is increased, and an existing precise aeration control system adopts a water quality analysis model and a fuzzy neural network controller and is small in application range, complex and high in investment cost. The invention provides a precise aeration control method and system based on an AAO process. The method comprises the steps that S1, water inlet data, water outlet data and process instrument data are monitored and collected; s2, setting an aerobic tank dissolved oxygen target value according to effluent ammonia nitrogen online monitoring data; s3, calculating the corresponding fan frequency or valve opening according to the difference between the actual value of the dissolved oxygen in the aerobic tank and the target value of the dissolved oxygen in the aerobic tank; s4, the fan frequency or the valve opening degree is automatically adjusted according to the fan frequency or the valve opening degree determined in the step S3; and S5, judging whether the adjustment of the fan frequency and the valve opening degree reaches the standard or not according to the effluent ammonia nitrogen data.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a precise aeration control method and system based on AAO process. Background Art

[0002] Electricity consumption accounts for up to 60% of sewage treatment operations, and aeration is the main component of electricity consumption. Extensive aeration treatment methods are no longer suitable for refined production management needs. Seeking methods and ways to save energy and reduce consumption is a severe challenge facing enterprises.

[0003] The main influent pollutants of sewage treatment plants include CODcr, BOD5, ammonia nitrogen, total nitrogen, total phosphorus, SS, pH and other pollutants; when the C / N ratio of the influent water quality meets the process requirements, precise control of dissolved oxygen in the aerobic tank is the main control method to save energy and promote carbon neutrality; when the C / N ratio of the influent water quality is seriously insufficient, external carbon source is required, resulting in a substantial increase in sewage treatment costs. Precise control of dissolved oxygen is the key to reducing the use of carbon sources and ensuring that the total nitrogen in the effluent meets the standards.

[0004] The mechanism of sewage denitrification is to convert ammonia nitrogen into nitrite nitrogen and nitrate nitrogen through nitrification through the action of nitrifying bacteria and denitrifying bacteria, and then convert nitrate nitrogen into nitrogen gas through denitrification and remove it from the water.

[0005] The AAO process is a commonly used biochemical wastewater treatment process that has the function of simultaneous nitrogen and phosphorus removal. The aerobic tank in the AAO process can promote the growth and metabolism of microorganisms and reduce pollutants such as nitrogen and phosphorus in the wastewater through aeration and utilization of organic matter in the wastewater.

[0006] At present, many sewage treatment plants using AAO technology still control the dissolved oxygen in the aerobic tank by manually adjusting the frequency of the aeration fan and the opening of the valve. The manual adjustment method is relatively rough and imprecise, resulting in operators excessively increasing the aeration volume to meet the effluent standards during actual operation, which increases energy consumption. When two sets of processes are run in parallel, manual operation becomes more complicated.

[0007] The existing precise aeration control system uses a water quality analysis model and a fuzzy neural network controller. Although it can achieve precise control, it is only applicable to sewage treatment plants with this water quality model. In addition, the control system is relatively complex and has a high investment cost, so it is only suitable for large sewage treatment plants. Summary of the invention

[0008] The present invention aims to provide a precise aeration control method and system based on AAO process, so as to solve the problems that the existing manual adjustment of fan frequency and valve opening is rough and imprecise, easily increases the aeration volume excessively and increases energy consumption, and the existing precise aeration control system adopts water quality analysis model and fuzzy neural network controller, has a small application range, is complex and has a high investment cost.

[0009] The present invention is achieved by adopting the following technical solutions:

[0010] The present invention provides a precise aeration control method based on the AAO process, comprising the following steps:

[0011] S1: Monitor and collect inlet data, outlet data and process instrument data;

[0012] S2: Set the target value of dissolved oxygen in the aerobic pool according to the online monitoring data of effluent ammonia nitrogen;

[0013] S3: Calculate the corresponding fan frequency or valve opening according to the difference between the actual dissolved oxygen value in the aerobic pool and the target dissolved oxygen value in the aerobic pool;

[0014] S4: Automatically adjusting the fan frequency or valve opening according to the fan frequency or valve opening determined in step S3;

[0015] S5: Determine whether the adjustment of fan frequency and valve opening meets the standards based on the outlet water ammonia nitrogen data.

[0016] As the preferred technical solution:

[0017] In step S1, the inlet and outlet data include inlet and outlet CODcr, inlet and outlet ammonia nitrogen data, inlet and outlet pH values; the process instrument data include inlet and outlet flow meter data, aerobic pool dissolved oxygen data, the frequency of the fan connected to the aerobic pool, the air flow meter data on the aerobic pool inlet pipe, and the valve opening.

[0018] As the preferred technical solution:

[0019] Step S2 also includes: adjusting the target value of dissolved oxygen in the aerobic pool, and the adjustment method includes: preliminarily setting the target value of dissolved oxygen, calculating the corresponding fan frequency or valve opening through the PID algorithm, adjusting the fan frequency or adjusting the valve opening to make the actual value of dissolved oxygen in the aerobic pool reach the target value of dissolved oxygen, monitoring whether the effluent index meets the discharge requirements, and if the effluent still meets the standards, continuing to adjust the target value of dissolved oxygen until the effluent index fluctuates, and then determining the target value of dissolved oxygen at this time as the final target value of dissolved oxygen in the aerobic pool.

[0020] Among them, until the water discharge index fluctuates means that the water discharge index is close to the substandard boundary, and the degree of closeness is set according to the actual situation.

[0021] As the preferred technical solution:

[0022] The effluent indicator is selected as the effluent ammonia nitrogen data.

[0023] As the preferred technical solution:

[0024] Step S3 specifically includes:

[0025] The actual value of dissolved oxygen in the aerobic pool is measured by a dissolved oxygen meter and fed back to the PLC control cabinet. The PLC control system in the PLC control cabinet calculates the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool, and calculates the corresponding fan frequency or valve opening according to the difference through the PID algorithm. When the equipment is running, the actual value of dissolved oxygen in the aerobic pool measured by the dissolved oxygen meter is fed back to the PLC control cabinet at regular intervals.

[0026] As the preferred technical solution:

[0027] The fan frequency calculation method includes:

[0028] According to the target dissolved oxygen value of the aerobic pool and the actual dissolved oxygen value of the aerobic pool collected, the dissolved oxygen deviation value is calculated: ΔXDO=XDOm-XDOs, where XDOm is the target dissolved oxygen value of the aerobic pool, XDOs is the actual dissolved oxygen value of the aerobic pool, and ΔXDO is the dissolved oxygen deviation value;

[0029] The frequency to be adjusted ΔF is confirmed by using ΔF=d[f(XDOm)-f(XDOs)] / d(Δt), wherein f is a function, d is a preset fixed factor, and Δt is a set adjustment cycle time;

[0030] The frequency F of the fan is determined by F=F0+ΔF, where F0 is the original frequency of the fan;

[0031] Valve opening calculation methods include:

[0032] According to the target dissolved oxygen value of the aerobic pool and the actual dissolved oxygen value of the aerobic pool collected, the dissolved oxygen deviation value is calculated: ΔXDO=XDOm-XDOs, where XDOm is the target dissolved oxygen value of the aerobic pool, XDOs is the actual dissolved oxygen value of the aerobic pool, and ΔXDO is the dissolved oxygen deviation value;

[0033] The valve opening change value ΔK is determined by ΔK=ΔXDO×C1, where C1 is a preset fixed coefficient factor, and its specific value is determined by the operator based on experience;

[0034] The valve opening K is determined by K=K0+ΔK, where K0 is the original opening of the valve.

[0035] As the preferred technical solution:

[0036] Step S4 specifically includes:

[0037] According to the fan frequency or valve opening determined in step S3, the direction and speed of the frequency modulation of the fan inverter and the direction and speed of the valve adjustment are judged, and an adjustment instruction is automatically issued through the PLC control system in the PLC control cabinet to adjust the fan frequency or valve opening in a related control manner; after the adjustment, the air flow meter on the air inlet pipe of the aerobic pool displays the air volume and feeds back to the PLC control cabinet.

[0038] As the preferred technical solution:

[0039] When the actual dissolved oxygen value of the aerobic pool measured by the dissolved oxygen meter is less than the target dissolved oxygen value of the aerobic pool, the PLC control cabinet issues an adjustment command to control the fan inverter to increase the frequency or the electric valve on the aerobic pool air inlet pipe to increase the opening degree. After the system state stabilizes, the dissolved oxygen meter measures the dissolved oxygen value of the aerobic pool again and feeds it back to the PLC control cabinet; if the target dissolved oxygen value of the aerobic pool is reached, the status quo is maintained, otherwise, calculation and adjustment are performed again;

[0040] When the actual dissolved oxygen value of the aerobic pool measured by the dissolved oxygen meter is greater than the target dissolved oxygen value of the aerobic pool, the PLC control cabinet issues an adjustment command to control the fan inverter to lower the frequency or reduce the opening degree of the electric valve on the aerobic pool air inlet pipe. After the system state stabilizes, the dissolved oxygen meter measures the dissolved oxygen value of the aerobic pool again and feeds it back to the PLC control cabinet; if the target dissolved oxygen value of the aerobic pool is reached, the status quo is maintained, otherwise further calculation and adjustment are performed.

[0041] The method for determining that the system state is stable includes: when the frequency of the fan inverter and the electric valve on the aerobic pool air inlet pipe are adjusted, it is displayed that the system state is stable.

[0042] As the preferred technical solution:

[0043] When the deviation between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool is too large, the PLC control system will automatically control to speed up the speed regulation process. When the deviation between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool is small, the PLC control system will automatically control to slow down the speed regulation process to fully ensure the response speed and stability of the system. In the system design, the default is that when the actual value of dissolved oxygen in the aerobic pool is lower than the target value of dissolved oxygen in the aerobic pool, the fan frequency should be increased, that is, the fan speed should be increased; when the actual value of dissolved oxygen in the aerobic pool is higher than the target value of dissolved oxygen in the aerobic pool, the fan frequency should be decreased, that is, the fan speed should be reduced.

[0044] As the preferred technical solution:

[0045] Step S5 specifically includes:

[0046] The outlet ammonia nitrogen value is set to NH, and NH is compared with the preset standard value NH0. When NH≤NH0, a compliance signal is generated; when NH>NH0, the adjustment process continues.

[0047] As the preferred technical solution:

[0048] For the case where two groups of AAO processes are run in parallel, steps S3 and S4 are specifically as follows:

[0049] The actual dissolved oxygen values ​​of the two aerobic pools are measured by a dissolved oxygen meter, and the actual dissolved oxygen values ​​of the 1# aerobic pool and the 2# aerobic pool are compared. If the actual dissolved oxygen value DO1 of the 1# aerobic pool is less than the actual dissolved oxygen value DO2 of the 2# aerobic pool, the fan frequency is calculated according to the difference between the actual dissolved oxygen value in the 1# aerobic pool and the target dissolved oxygen value of the aerobic pool by the PID algorithm. When the valve opening on the air inlet pipe of the 1# aerobic pool is 100%, the actual dissolved oxygen value DO1 of the 1# aerobic pool reaches the set target dissolved oxygen value of the aerobic pool; 2. #The valve opening on the aerobic pool air inlet pipe is adjusted to 20% to 30%, so that the actual dissolved oxygen value DO2 of the 2# aerobic pool also reaches the set aerobic pool dissolved oxygen target value; if the actual dissolved oxygen value DO1 of the 1# aerobic pool is greater than the actual dissolved oxygen value DO2 of the 2# aerobic pool, then according to the above method, the actual dissolved oxygen value DO1 of the 2# aerobic pool is first made to reach the set aerobic pool dissolved oxygen target value, and then the actual dissolved oxygen value DO1 of the 1# aerobic pool is made to reach the set aerobic pool dissolved oxygen target value; at this time, the initial state parameters of the fan and valve have been determined;

[0050] When the influent water volume increases or the water quality concentration increases, the dissolved oxygen meter reading becomes smaller and deviates from the target value of dissolved oxygen in the aerobic pool. At this time, the PID adjustment cycle Δt of the dissolved oxygen meter is set, and the actual value of dissolved oxygen in the aerobic pool collected is compared with the target value of dissolved oxygen in the aerobic pool. A basic value is set for the proportion, integral, and differential of the PID adjustment. Through the PID algorithm, the given frequency of the fan is automatically calculated to ensure that the actual value of dissolved oxygen in the 1# aerobic pool reaches the target value of dissolved oxygen in the aerobic pool. Then, the electric valve on the air inlet pipe of the 2# aerobic pool is controlled through the PLC control system. By adjusting the opening of the electric valve, the actual value of dissolved oxygen in the 2# aerobic pool also reaches the target value of dissolved oxygen in the aerobic pool.

[0051] The present invention further provides a precise aeration control system based on the AAO process, comprising a monitoring and acquisition module, a calculation module and a control module; wherein:

[0052] The monitoring and acquisition module is used to monitor and collect water inlet data, water outlet data and process instrument data;

[0053] The calculation module is used to determine the target value of dissolved oxygen in the aerobic pool. When the equipment is running, the actual value of dissolved oxygen in the aerobic pool measured by the dissolved oxygen meter is fed back to the PLC control cabinet at regular intervals. The PID algorithm is used to calculate the corresponding fan frequency or valve opening according to the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool, which is used to control the fluctuation of dissolved oxygen.

[0054] The control module is used to automatically adjust the fan frequency or valve opening according to the determined fan frequency or valve opening. After adjustment, the air flow meter on the air inlet pipe of the aerobic pool displays the air volume and feeds back to the PLC control system. The outlet ammonia nitrogen data is used to determine whether the adjustment of the fan frequency and valve opening meets the standards.

[0055] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0056] 1) The data collection and calculation methods involved in the present invention are relatively simple and easy to implement.

[0057] 2) Power consumption and reagent (carbon source) costs are the main sources of direct costs for the entire sewage treatment. Compared with the traditional aeration method, the present invention has the effect of energy saving and consumption reduction under the premise of stable production, and can reduce energy consumption by 10% to 30%.

[0058] 3) The present invention can adaptively adjust to a stable operating state in a relatively short time for interference caused by the outside world (the adjustment period for water quality interference should be ≤20 minutes, the adjustment period for water volume interference should be ≤15 minutes, the adjustment period for temperature and rainfall interference should be ≤2 minutes, and the adjustment period for other interferences such as manual interference should be ≤10 minutes).

[0059] 4) The present invention can realize on-demand gas supply in the sewage treatment process through precise aeration control, reduce the fluctuation range of dissolved oxygen concentration in the biological reaction tank, and realize the degradation of organic matter in the sewage in multiple alternating anoxic and aerobic conditions, providing good external conditions for nitrogen and phosphorus removal in the treatment system, thereby maximizing the efficiency of nitrogen and phosphorus removal, and ensuring that the effluent water quality meets the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a flow chart of the precise aeration control method based on the AAO process described in the present invention.

[0061] Figure 2 It is a schematic diagram of the principle framework of the present invention.

[0062] Figure 3 It is a structural schematic diagram of the precise aeration control system based on AAO process described in the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] Example 1

[0065] like Figure 1 and Figure 2 As shown, this embodiment proposes a precise aeration control method based on the AAO process, comprising the following steps:

[0066] S1: Monitor and collect inlet water data, outlet water data and process instrument data.

[0067] The inlet and outlet data include inlet and outlet CODcr, inlet and outlet ammonia nitrogen data, and inlet and outlet pH values; the process instrument data include inlet and outlet flow meter data, aerobic pool dissolved oxygen data, the frequency of the fan connected to the aerobic pool, the air flow meter data on the aerobic pool inlet pipe, and the valve opening.

[0068] S2: Set the target value of dissolved oxygen in the aerobic pool based on the online monitoring data of effluent ammonia nitrogen.

[0069] Based on the water volume and quality of the sewage treatment plant at a certain time, and assuming that the effluent ammonia nitrogen meets the standards, the dissolved oxygen in the aerobic tank is measured and set as the preliminary target value.

[0070] Furthermore, the target value of dissolved oxygen in the aerobic pool is adjusted to avoid excessive set target value of dissolved oxygen in the aerobic pool.

[0071] When setting the target value of dissolved oxygen in the aerobic pool, the ammonia nitrogen may reach the standard when the dissolved oxygen is excessive. In order to achieve the maximum energy saving effect, the target value of dissolved oxygen in the aerobic pool should be adjusted when the ammonia nitrogen in the effluent reaches the standard.

[0072] The adjustment method is:

[0073] Set the second target value of dissolved oxygen, calculate the corresponding fan frequency or valve opening through the PID algorithm, adjust the fan frequency or adjust the valve opening, so that the actual value of dissolved oxygen in the aerobic pool reaches or approaches the second target value of dissolved oxygen, monitor whether the effluent index meets the discharge requirements, if the effluent still meets the standards, continue to set the third target value of dissolved oxygen in sequence, until the final effluent ammonia nitrogen shows a slight upward fluctuation, then the dissolved oxygen target value at this time is determined as the final target value of dissolved oxygen in the aerobic pool. The effluent index here selects the effluent ammonia nitrogen data. When the effluent meets the standards, determine the optimal target value of dissolved oxygen in the aerobic pool.

[0074] S3: Calculate the corresponding fan frequency or valve opening according to the difference between the actual dissolved oxygen value in the aerobic pool and the target dissolved oxygen value in the aerobic pool.

[0075] During the sewage treatment process, the influent water volume and water quality may change. Therefore, the actual value of dissolved oxygen in the aerobic tank is measured by a dissolved oxygen meter, and the actual value of dissolved oxygen in the aerobic tank is fed back to the PLC control cabinet. The PLC control system in the PLC control cabinet calculates the difference between the actual value of dissolved oxygen in the aerobic tank and the target value of dissolved oxygen in the aerobic tank, and calculates the corresponding fan frequency or valve opening according to the difference through the PID algorithm, so as to control the fluctuation of dissolved oxygen in the aerobic tank.

[0076] When the equipment is running, the actual value of dissolved oxygen in the aerobic pool measured by the dissolved oxygen meter is fed back to the PLC control cabinet at regular intervals, and the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool is calculated. The corresponding fan frequency or valve opening is automatically calculated based on the difference through the PID algorithm.

[0077] Using the PID algorithm, a two-dimensional composite function model is established with dissolved oxygen as the first control variable (XDO) and time (t) as the second control parameter. According to the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool, the method for automatically calculating the fan frequency is as follows:

[0078] According to the target dissolved oxygen value of the aerobic pool and the actual dissolved oxygen value of the aerobic pool collected, the dissolved oxygen deviation value is calculated: ΔXDO=XDOm-XDOs, where XDOm is the target dissolved oxygen value of the aerobic pool, XDOs is the actual dissolved oxygen value of the aerobic pool, and ΔXDO is the dissolved oxygen deviation value;

[0079] The frequency to be adjusted ΔF is confirmed by ΔF=d[f(XDOm)-f(XDOs)] / d(Δt), ΔF=minimum adjustment frequency*multiplier, where f is a function of dissolved oxygen and fan frequency, d is a preset fixed factor, which is determined by the operator based on experience; Δt is the set adjustment cycle time;

[0080] The frequency F of the fan is determined by F=F0+ΔF, where F0 is the original frequency of the fan.

[0081] Among them, the setting of Δt (unit: ms) is:

[0082] Δt represents the time period for the control system to read data from the sensor, process data and send instructions. Reasonable setting of pulse time is beneficial to ensure the response speed of the control system, as well as the stability of the system and improve the anti-interference ability.

[0083] If the pulse time is too short, the system will respond too quickly, and the control system will adjust the fan too frequently, which will deteriorate the stability of the system. If the pulse time is set too long, the response speed will be slow, and the interference caused by external conditions (such as inlet water quality, water volume changes, rainstorms, etc.) will not be automatically adjusted, and the anti-interference ability will deteriorate. In practice, due to the influence of factors such as the length of the fan pipeline, the air flow speed in the air intake pipeline, the installation position of the dissolved oxygen meter, and the speed of the water flow, the change in the aeration volume of the fan is reflected in the change of the dissolved oxygen value with a certain time lag, generally several minutes. This should be considered when setting the pulse.

[0084] ΔF setting:

[0085] The minimum adjustment frequency refers to the absolute value of the frequency change of the inverter after each pulse command of the control system is issued. The lower the set value, the smaller the frequency adjustment of the fan and the smoother the operation. The default value is generally the minimum value of 0.01Hz. The multiplier refers to the multiple of the minimum adjustment frequency that the system can calculate based on the actual gap between the actual value and the target value when the actual value of dissolved oxygen is far from the target value of dissolved oxygen, generally without manual intervention.

[0086] The method of automatically calculating the valve opening on the aerobic pool air inlet pipe using the PID algorithm based on the numerical difference between the actual dissolved oxygen value in the aerobic pool and the target dissolved oxygen value in the aerobic pool is:

[0087] According to the target dissolved oxygen value of the aerobic pool and the actual dissolved oxygen value of the aerobic pool collected, the dissolved oxygen deviation value is calculated: ΔXDO=XDOm-XDOs, where XDOm is the target dissolved oxygen value of the aerobic pool, XDOs is the actual dissolved oxygen value of the aerobic pool, and ΔXDO is the dissolved oxygen deviation value;

[0088] The valve opening change value ΔK is determined by ΔK=ΔXDO×C1, where C1 is a preset fixed coefficient factor, and its specific value is determined by the operator based on experience;

[0089] The valve opening K is determined by K=K0+ΔK, where K0 is the original opening of the valve.

[0090] In this embodiment, the valve is an electric valve, that is, an electric regulating valve.

[0091] S4: Automatically adjust the fan frequency or valve opening according to the fan frequency or valve opening determined in step S3.

[0092] According to the fan frequency or valve opening determined in step S3, the direction and speed of the fan frequency converter frequency modulation, the direction and speed of the valve adjustment are judged, and the PLC control system in the PLC control cabinet automatically issues an adjustment instruction to adjust the fan frequency or valve opening. After adjustment, the air flow meter on the aerobic pool intake pipe displays the air volume and feeds back to the PLC control cabinet. In this embodiment, the air flow meter on the aerobic pool intake pipe adopts a vortex flowmeter.

[0093] The specific method of controlling and adjusting the fan frequency or valve opening is:

[0094] When the actual dissolved oxygen value of the aerobic pool measured by the dissolved oxygen meter is less than the target dissolved oxygen value of the aerobic pool, the fan frequency or valve opening is automatically calculated through the PID algorithm according to the difference between the actual dissolved oxygen value of the aerobic pool and the target dissolved oxygen value of the aerobic pool. The PLC control cabinet issues an adjustment instruction accordingly to control the fan inverter to increase the frequency or the electric valve on the aerobic pool air inlet pipe to increase the opening. After the system state stabilizes, the dissolved oxygen meter measures the dissolved oxygen value of the aerobic pool again and feeds it back to the PLC control cabinet; if the target dissolved oxygen value of the aerobic pool is reached, the status quo is maintained, otherwise, further calculation and adjustment are performed.

[0095] When the actual dissolved oxygen value of the aerobic pool measured by the dissolved oxygen meter is greater than the target dissolved oxygen value of the aerobic pool, the fan frequency or valve opening is automatically calculated through the PID algorithm according to the difference between the actual dissolved oxygen value of the aerobic pool and the target dissolved oxygen value of the aerobic pool. The PLC control cabinet issues an adjustment instruction accordingly to control the fan inverter to lower the frequency or the electric valve on the aerobic pool air inlet pipe to reduce the opening degree. After the system state stabilizes, the dissolved oxygen meter measures the dissolved oxygen value of the aerobic pool again and feeds it back to the PLC control cabinet; if the target dissolved oxygen value of the aerobic pool is reached, the status quo is maintained, otherwise, further calculation and adjustment are performed.

[0096] When the deviation between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool is too large, the PLC control system will automatically control to speed up the speed regulation process. When the deviation between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool is small, the PLC control system will automatically control to slow down the speed regulation process to fully ensure the response speed and stability of the system. In the system design, the default is that when the actual value of dissolved oxygen in the aerobic pool is lower than the target value of dissolved oxygen in the aerobic pool, the fan frequency should be increased, that is, the fan speed should be increased; when the actual value of dissolved oxygen in the aerobic pool is higher than the target value of dissolved oxygen in the aerobic pool, the fan frequency should be decreased, that is, the fan speed should be reduced.

[0097] Through the above method, the fan frequency or valve opening is automatically adjusted, and the aeration volume is adjusted so that the actual value of dissolved oxygen in the aerobic tank approaches the target value of dissolved oxygen in the aerobic tank.

[0098] In this embodiment, the fan is a blower.

[0099] The method for determining that the system state is stable includes: when the frequency of the blower inverter and the electric valve on the aerobic pool air inlet pipe are adjusted, it is displayed that the system state is stable.

[0100] S5: Determine whether the adjustment of fan frequency and valve opening meets the standards based on the outlet water ammonia nitrogen data.

[0101] The outlet ammonia nitrogen value is set to NH, and NH is compared with the preset standard value NH0. When NH≤NH0, a standard compliance signal is generated; when NH>NH0, the adjustment process continues. The above methods are used to ensure that the outlet water meets the standard.

[0102] The data collection and calculation methods involved in the present invention are relatively simple and easy to implement; power consumption and medicine (carbon source) costs are the main sources of the direct cost of the entire sewage treatment. Compared with the traditional aeration method, the present invention has the effect of energy saving and consumption reduction under the premise of stable production, and can reduce energy consumption by 10% to 30%; for external interference, it can be adaptively adjusted to a stable operation state in a relatively short time (water quality interference adjustment cycle should be ≤20 minutes, water volume interference adjustment cycle should be ≤15 minutes, temperature and rainfall interference adjustment cycle should be ≤2 minutes, and other interference adjustment cycles such as artificial should be ≤10 minutes); it can realize the demand-based gas supply in the sewage treatment process, reduce the fluctuation range of dissolved oxygen concentration in the biological reaction tank, and the sewage can realize the degradation of organic matter in multiple alternating anoxic and aerobic conditions, and provide good external conditions for the denitrification and phosphorus removal of the treatment system, thereby maximizing the denitrification and phosphorus removal efficiency, and the effluent water quality is more guaranteed to meet the standards.

[0103] For the situation where two groups of AAO processes are operated in parallel, such as a sewage treatment plant using two groups of biochemical pool systems with AAO process, there are originally two fans, one for use and one for backup, both of which are frequency conversion controlled. Electric valves and vortex flowmeters are added to the air inlet pipes of the two aerobic pools, which are used to adjust the air intake volume and meter the air volume of the aerobic pools respectively; online monitoring systems and flowmeters are installed at the front and end of the two groups of processes to measure the inlet and outlet CODcr, inlet and outlet ammonia nitrogen data and inlet and outlet flow rates. Dissolved oxygen meters are installed in the two aerobic pools to measure their dissolved oxygen, and PLC control cabinets are arranged.

[0104] The specific control process is as follows:

[0105] S1: Monitor and collect inlet water data, outlet water data and process instrument data.

[0106] S2: Set the target value of dissolved oxygen in the aerobic pool: Based on the water volume and water quality of the sewage treatment plant at a certain time, the dissolved oxygen in the aerobic pool is measured and set to the initial target value DO = 2.2 mg / L when the effluent ammonia nitrogen meets the standard. When setting the target value of dissolved oxygen in the aerobic pool, the ammonia nitrogen may meet the standard when the dissolved oxygen is excessive. Therefore, the target value of dissolved oxygen in the aerobic pool can be adjusted according to the online monitoring data of effluent ammonia nitrogen to achieve the maximum energy saving effect.

[0107] S3: Since the sewage station uses one fan to supply air to two biochemical systems, the frequency of the fan cannot be adjusted simultaneously for the dissolved oxygen in the two aerobic pools. Therefore, at this time, the actual values ​​of dissolved oxygen in the 1# aerobic pool and the 2# aerobic pool are compared. If the actual value of dissolved oxygen in the 1# aerobic pool DO1 is less than the actual value of dissolved oxygen in the 2# aerobic pool DO2, the fan frequency is calculated to be 35HZ based on the difference between the actual value of dissolved oxygen in the 1# aerobic pool and the target value of dissolved oxygen in the aerobic pool through the PID algorithm. When the valve opening on the air inlet pipe of the 1# aerobic pool is 100%, the actual value of dissolved oxygen in the 1# aerobic pool DO1 reaches or approaches the set target value of dissolved oxygen in the aerobic pool. The valve opening on the air inlet pipe of the 2# aerobic pool is adjusted to 20% to 30%, so that the actual dissolved oxygen value DO2 of the 2# aerobic pool also reaches or approaches the set dissolved oxygen target value of the aerobic pool; if the actual dissolved oxygen value DO1 of the 1# aerobic pool is greater than the actual dissolved oxygen value DO2 of the 2# aerobic pool, the above method is used to first make the actual dissolved oxygen value DO1 of the 2# aerobic pool reach the set dissolved oxygen target value of the aerobic pool, and then make the actual dissolved oxygen value DO1 of the 1# aerobic pool reach the set dissolved oxygen target value of the aerobic pool; at this time, the initial state parameters of the fan, valve and other equipment have been determined;

[0108] When the influent water volume increases or the water quality concentration increases, the dissolved oxygen meter reading will become smaller and deviate from the target value of dissolved oxygen in the aerobic pool. At this time, the PID adjustment cycle of the dissolved oxygen meter is set to Δt = 10S, that is, the value is read once every 10S, the actual value of dissolved oxygen in the aerobic pool is compared with the target value of dissolved oxygen in the aerobic pool, and a basic value is set for the proportion, integral, and differential of the PID adjustment. Through the PID algorithm, the given frequency of the fan is automatically calculated to ensure that the actual value of dissolved oxygen in the 1# aerobic pool reaches the target value of dissolved oxygen in the aerobic pool. Then, the electric valve on the air inlet pipe of the 2# aerobic pool is controlled by the PLC control system, and the opening of the electric valve is adjusted to ensure that the actual value of dissolved oxygen in the 2# aerobic pool also reaches the target value of dissolved oxygen in the aerobic pool.

[0109] S4: Determine whether the adjustment of fan frequency and valve opening meets the standards based on the outlet water ammonia nitrogen data.

[0110] The results obtained from actual use are:

[0111] 1) According to the analysis of the project operation results, the electricity consumption after the transformation was saved by 10% to 30% compared with before the transformation.

[0112] 2) When the inlet ammonia nitrogen content is 15-25 mg / L, the aeration fan frequency is 30 Hz, one electric valve is opened at 100%, and the other electric valve is opened at 20%-30%, the outlet ammonia nitrogen content is always less than 0.5 mg / L.

[0113] Some of the data in the above formulas are dimensionless and numerically calculated. Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0114] Example 2

[0115] like Figure 3 As shown, this embodiment proposes a precise aeration control system based on the AAO process, including a monitoring and acquisition module, a calculation module and a control module; wherein:

[0116] The monitoring and acquisition module is used to monitor and collect inlet and outlet data, outlet data and process instrument data. The inlet and outlet data include inlet and outlet CODcr, inlet and outlet ammonia nitrogen data, inlet and outlet pH values; process instrument data include inlet and outlet flow meter data, aerobic pool dissolved oxygen data, frequency of the fan connected to the aerobic pool, air flow meter data on the aerobic pool inlet pipe and valve opening.

[0117] The calculation module is used to determine the target value of dissolved oxygen in the aerobic pool. When the equipment is running, the actual value of dissolved oxygen in the aerobic pool measured by the dissolved oxygen meter is fed back to the PLC control cabinet at regular intervals. The PID algorithm is used to calculate the corresponding fan frequency or valve opening based on the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool, which is used to control the fluctuation of dissolved oxygen.

[0118] The control module is used to automatically adjust the fan frequency or valve opening according to the determined fan frequency or valve opening. After adjustment, the air flow meter on the air inlet pipe of the aerobic pool displays the air volume and feeds back to the PLC control system. The outlet ammonia nitrogen data is used to determine whether the adjustment of the fan frequency and valve opening meets the standards.

[0119] The system is suitable for most sewage treatment plants, and the investment cost is relatively low; the data collection and calculation methods involved are relatively simple and easy to implement; power consumption and reagent (carbon source) costs are the main sources of direct costs for the entire sewage treatment. Compared with the traditional aeration method, the present invention has the effect of energy saving and consumption reduction under the premise of stable production, and can reduce energy consumption by 10% to 30%; for external interference, it can be adaptively adjusted to a stable operating state in a relatively short time (the water quality interference adjustment cycle should be ≤20min, the water volume interference adjustment cycle should be ≤15min, the temperature and rainfall interference adjustment cycle should be ≤2min, and the artificial and other interference adjustment cycles should be ≤10min); it can realize the demand-based gas supply during the sewage treatment process, reduce the fluctuation range of the dissolved oxygen concentration in the biological reaction tank, and the sewage can realize the degradation of organic matter in multiple alternating anoxic and aerobic conditions, and provide good external conditions for the denitrification and phosphorus removal of the treatment system, thereby maximizing the denitrification and phosphorus removal efficiency, and the effluent water quality is more guaranteed to meet the standards.

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A precise aeration control method based on AAO process, characterized by: The following steps are involved: S1: Monitor and collect inlet data, outlet data and process instrument data; S2: Set the target value of dissolved oxygen in the aerobic pool according to the online monitoring data of effluent ammonia nitrogen; S3: Calculate the corresponding fan frequency or valve opening according to the difference between the actual dissolved oxygen value in the aerobic pool and the target dissolved oxygen value in the aerobic pool; S4: Automatically adjusting the fan frequency or valve opening according to the fan frequency or valve opening determined in step S3; S5: Determine whether the adjustment of fan frequency and valve opening meets the standards based on the outlet water ammonia nitrogen data.

2. The precise aeration control method based on the AAO process according to claim 1, characterized in that: In step S1, the inlet and outlet data include inlet and outlet CODcr, inlet and outlet ammonia nitrogen data, inlet and outlet pH values; the process instrument data include inlet and outlet flow meter data, aerobic pool dissolved oxygen data, the frequency of the fan connected to the aerobic pool, the air flow meter data on the aerobic pool inlet pipe, and the valve opening.

3. The precise aeration control method based on AAO process according to claim 1, characterized in that: Step S2 also includes: adjusting the target value of dissolved oxygen in the aerobic pool, and the adjustment method includes: preliminarily setting the target value of dissolved oxygen, calculating the corresponding fan frequency or valve opening through the PID algorithm, adjusting the fan frequency or adjusting the valve opening to make the actual value of dissolved oxygen in the aerobic pool reach the target value of dissolved oxygen, monitoring whether the effluent index meets the discharge requirements, and if the effluent still meets the standards, continuing to adjust the target value of dissolved oxygen until the effluent index fluctuates, and then determining the target value of dissolved oxygen at this time as the final target value of dissolved oxygen in the aerobic pool.

4. The precise aeration control method based on the AAO process according to claim 1, characterized in that: Step S3 specifically includes: The actual value of dissolved oxygen in the aerobic pool is measured by a dissolved oxygen meter and fed back to the PLC control cabinet. The PLC control system in the PLC control cabinet calculates the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool, and calculates the corresponding fan frequency or valve opening according to the difference through the PID algorithm. When the equipment is running, the actual value of dissolved oxygen in the aerobic pool measured by the dissolved oxygen meter is fed back to the PLC control cabinet at regular intervals.

5. The precise aeration control method based on AAO process according to claim 4 is characterized in that: The fan frequency calculation method includes: According to the target dissolved oxygen value of the aerobic pool and the actual dissolved oxygen value of the aerobic pool collected, the dissolved oxygen deviation value is calculated: ΔXDO=XDOm-XDOs, where XDOm is the target dissolved oxygen value of the aerobic pool, XDOs is the actual dissolved oxygen value of the aerobic pool, and ΔXDO is the dissolved oxygen deviation value; The frequency to be adjusted ΔF is confirmed by using ΔF=d[f(XDOm)-f(XDOs)] / d(Δt), wherein f is a function, d is a preset fixed factor, and Δt is a set adjustment cycle time; The frequency F of the fan is determined by F=F0+ΔF, where F0 is the original frequency of the fan; Valve opening calculation methods include: According to the target dissolved oxygen value of the aerobic pool and the actual dissolved oxygen value of the aerobic pool collected, the dissolved oxygen deviation value is calculated: ΔXDO=XDOm-XDOs, where XDOm is the target dissolved oxygen value of the aerobic pool, XDOs is the actual dissolved oxygen value of the aerobic pool, and ΔXDO is the dissolved oxygen deviation value; The valve opening change value ΔK is determined by ΔK=ΔXDO×C1, where C1 is a preset fixed coefficient factor, and its specific value is determined by the operator based on experience; The valve opening K is determined by K=K0+ΔK, where K0 is the original opening of the valve.

6. The precise aeration control method based on AAO process according to claim 1, characterized in that: Step S4 specifically includes: According to the fan frequency or valve opening determined in step S3, the direction and speed of the frequency modulation of the fan inverter and the direction and speed of the valve adjustment are judged, and an adjustment instruction is automatically issued through the PLC control system in the PLC control cabinet to adjust the fan frequency or valve opening in a related control manner; after the adjustment, the air flow meter on the air inlet pipe of the aerobic pool displays the air volume and feeds back to the PLC control cabinet.

7. The precise aeration control method based on AAO process according to claim 6, characterized in that: When the actual dissolved oxygen value of the aerobic pool measured by the dissolved oxygen meter is less than the target dissolved oxygen value of the aerobic pool, the PLC control cabinet issues an adjustment command to control the fan inverter to increase the frequency or the electric valve on the aerobic pool air inlet pipe to increase the opening degree. After the system state stabilizes, the dissolved oxygen meter measures the dissolved oxygen value of the aerobic pool again and feeds it back to the PLC control cabinet; if the target dissolved oxygen value of the aerobic pool is reached, the status quo is maintained, otherwise, calculation and adjustment are performed again; When the actual dissolved oxygen value of the aerobic pool measured by the dissolved oxygen meter is greater than the target dissolved oxygen value of the aerobic pool, the PLC control cabinet issues an adjustment command to control the fan inverter to lower the frequency or reduce the opening degree of the electric valve on the aerobic pool air inlet pipe. After the system state stabilizes, the dissolved oxygen meter measures the dissolved oxygen value of the aerobic pool again and feeds it back to the PLC control cabinet; if the target dissolved oxygen value of the aerobic pool is reached, the status quo is maintained, otherwise further calculation and adjustment are performed.

8. The precise aeration control method based on AAO process according to claim 1, characterized in that: Step S5 specifically includes: The outlet ammonia nitrogen value is set to NH, and NH is compared with the preset standard value NH0. When NH≤NH0, a compliance signal is generated; when NH>NH0, the adjustment process continues.

9. The precise aeration control method based on AAO process according to claim 1, characterized in that: For the case where two groups of AAO processes are run in parallel, steps S3 and S4 are specifically as follows: The actual dissolved oxygen values ​​of the two aerobic pools are measured by a dissolved oxygen meter, and the actual dissolved oxygen values ​​of the 1# aerobic pool and the 2# aerobic pool are compared. If the actual dissolved oxygen value DO1 of the 1# aerobic pool is less than the actual dissolved oxygen value DO2 of the 2# aerobic pool, the fan frequency is calculated according to the difference between the actual dissolved oxygen value in the 1# aerobic pool and the target dissolved oxygen value of the aerobic pool by the PID algorithm. When the valve opening on the air inlet pipe of the 1# aerobic pool is 100%, the actual dissolved oxygen value DO1 of the 1# aerobic pool reaches the set target dissolved oxygen value of the aerobic pool; 2. #The valve opening on the aerobic pool air inlet pipe is adjusted to 20% to 30%, so that the actual dissolved oxygen value DO2 of the 2# aerobic pool also reaches the set aerobic pool dissolved oxygen target value; if the actual dissolved oxygen value DO1 of the 1# aerobic pool is greater than the actual dissolved oxygen value DO2 of the 2# aerobic pool, then according to the above method, the actual dissolved oxygen value DO1 of the 2# aerobic pool is first made to reach the set aerobic pool dissolved oxygen target value, and then the actual dissolved oxygen value DO1 of the 1# aerobic pool is made to reach the set aerobic pool dissolved oxygen target value; at this time, the initial state parameters of the fan and valve have been determined; When the influent water volume increases or the water quality concentration increases, the dissolved oxygen meter reading becomes smaller and deviates from the target value of dissolved oxygen in the aerobic pool. At this time, the PID adjustment cycle Δt of the dissolved oxygen meter is set, and the actual value of dissolved oxygen in the aerobic pool collected is compared with the target value of dissolved oxygen in the aerobic pool. A basic value is set for the proportion, integral, and differential of the PID adjustment. Through the PID algorithm, the given frequency of the fan is automatically calculated to ensure that the actual value of dissolved oxygen in the 1# aerobic pool reaches the target value of dissolved oxygen in the aerobic pool. Then, the electric valve on the air inlet pipe of the 2# aerobic pool is controlled through the PLC control system. By adjusting the opening of the electric valve, the actual value of dissolved oxygen in the 2# aerobic pool also reaches the target value of dissolved oxygen in the aerobic pool.

10. A precise aeration control system based on AAO process, characterized by: It includes monitoring and acquisition module, calculation module and control module; among which: The monitoring and acquisition module is used to monitor and collect water inlet data, water outlet data and process instrument data; The calculation module is used to determine the target value of dissolved oxygen in the aerobic pool. When the equipment is running, the actual value of dissolved oxygen in the aerobic pool measured by the dissolved oxygen meter is fed back to the PLC control cabinet at regular intervals. The PID algorithm is used to calculate the corresponding fan frequency or valve opening according to the difference between the actual value of dissolved oxygen in the aerobic pool and the target value of dissolved oxygen in the aerobic pool, which is used to control the fluctuation of dissolved oxygen. The control module is used to automatically adjust the fan frequency or valve opening according to the determined fan frequency or valve opening. After adjustment, the air flow meter on the air inlet pipe of the aerobic pool displays the air volume and feeds back to the PLC control system. The outlet ammonia nitrogen data is used to determine whether the adjustment of the fan frequency and valve opening meets the standards.

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