Predictive precision aeration method

Abstract

The present invention belongs to the field of sewage treatment and discloses a predictive and precise aeration method, comprising the following steps: Cr , ammonia nitrogen, TN value and designed effluent water quality index value to calculate the theoretical air demand G in real time s ; G s ×K 安 As t 滞 Air supply volume G of the fan unit after time s控 Instruction; the feedback auxiliary control system feeds back the DO value at the end of the aerobic pool in real time, setting the minimum DO value to DO min To prevent anaerobic phosphorus release in the secondary sedimentation tank, if the DO value is greater than DO min , the system does not adjust and continues to run until the new G s控 Adjust after calculation; if the DO value is less than DO min , then the gas supply volume G is increased as needed s增 Increase until the DO concentration in the aerobic pool exceeds DO min The present invention mainly uses feedforward and supplemented by DO feedback, which can ensure the water quality and achieve energy saving and consumption reduction.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a predictive precise aeration method. Background Art

[0002] The activated sludge process is one of the most fundamental and core methods for wastewater treatment, boasting a history spanning over a century and widespread use worldwide. Aeration is typically the most significant energy drain on the activated sludge process (relevant research indicates that it accounts for 50-70% of a wastewater treatment plant's total energy consumption) and is also a major source of indirect carbon emissions. Therefore, aeration has become a key research focus for optimizing wastewater treatment plant operations.

[0003] Oxygen consumption in biological ponds is primarily determined by two factors: the oxygen required for BOD5 removal and the oxygen required for nitrification of NH3-N. Both processes occur in aerobic ponds. Furthermore, theoretically, the denitrification process in anoxic ponds also produces some dissolved oxygen, which reduces the oxygen demand of the aeration system.

[0004] In actual operation, the stable operation of the biological system is usually achieved by controlling the DO concentration at the outlet of the aerobic pool ("feedback type"), as shown in the attached Figure 1 The DO concentration at the aerobic tank outlet is usually controlled at around 2.0 mg / L. When the DO value is less than 1.8 mg / L, the aeration system's air supply is increased by varying the frequency or increasing the number of operating fans, causing the aerobic tank's DO concentration to rise. When the DO value is greater than 2.5 mg / L, the aeration system's air supply is reduced by varying the frequency or reducing the number of operating fans, causing the aerobic tank's DO concentration to fall. This approach achieves a relatively stable DO value in the aerobic tank.

[0005] The basic logic of this method is that, when the influent is normal, as long as the system DO is stable, the entire biological treatment system will be relatively stable, and the effluent quality will be guaranteed. However, actual conditions differ significantly from the designed operating conditions. The actual influent quality often fluctuates and is often far lower than the designed influent quality. This has a variety of impacts, mainly manifested in the following aspects:

[0006] (1) The actual oxygen demand will be significantly lower than the design value.

[0007] Designs are typically based on a 90-95% probability of achieving the desired influent concentration, a relatively conservative fixed value. However, actual values ​​fluctuate and are often below the design value. Furthermore, based on actual national data, due to inefficient sewage collection systems, actual influent BOD5 concentrations are significantly lower than the design value. This means that the actual oxygen demand of the biochemical system will be significantly lower than the design value. Therefore, controlling the DO value at around 2.0 mg / L during operation based on the design value is inherently inefficient, and maintaining a DO concentration around 2.0 mg / L is unnecessary for actual operation.

[0008] (2) The system's buffering capacity for DO is weak, and the DO value is difficult to control.

[0009] Since the actual influent water quality is far lower than the designed influent water quality, the ability of the entire biological system to consume DO will be weaker than the designed value, which also means that the ability to stabilize the DO value is weaker. However, the air supply system has a strong supply capacity, and the situation of "a big horse pulling a small cart" will inevitably occur. Therefore, many sewage treatment plants will experience a situation where the DO value continues to rise and cannot be controlled, resulting in higher system energy consumption.

[0010] (3) The DO values ​​of internal and external reflow are high, which affects the normal operation of the front-end anoxic tank and anaerobic tank.

[0011] Since the system has a weak capacity for DO consumption and a slow consumption rate, both internal and external reflow will carry a higher DO concentration, which will inevitably affect the reaction environment of the front-end anoxic tank and anaerobic tank, thereby affecting the system's denitrification and anaerobic phosphorus release, which is not conducive to the efficient operation of the biological system.

[0012] From the above analysis, we can know that the actual situation is much more complicated than the design conditions, and the traditional "feedback" control method with DO concentration as the control target has certain limitations.

[0013] Many researchers have proposed control methods such as "feedforward + feedback" and "feedforward + model + feedback", but these methods still have the following problems in actual operation:

[0014] (1) The feedback control system maintains a relatively high DO concentration, generally above 1.5 mg / L. Since anaerobic phosphorus release from sludge is likely to occur in the secondary sedimentation tank, the phosphorus removal effect is deteriorated, affecting the effluent P standard. Although a higher DO concentration can prevent anaerobic phosphorus release from the secondary sedimentation tank, it does not save energy.

[0015] (2) In actual operation, the DO concentration in the aerobic pool is difficult to effectively control due to the following reasons:

[0016] ① The influent online monitoring data is not continuous, usually a set of data is generated every 2 hours or so. During this interval, the water quality data will fluctuate to a certain extent (for sewage treatment plants in built-up areas, the influent water quality is relatively stable, and this fluctuation value is generally small);

[0017] ② There are also certain fluctuations in the inlet B / C. The control of aeration air volume is based on theoretical deduction, but often does not take into account a certain margin. When the water quality fluctuates significantly, the calculated theoretical air supply volume may be insufficient, resulting in substandard water outlet indicators.

[0018] (3) Since it takes a certain amount of time for the sewage to travel from the online monitoring point to the aerobic tank, the online monitoring instrument also needs a certain amount of working time from sampling to outputting the results. Usually, the precise aeration control system does not take this time lag into account, which will result in the air supply volume calculated based on the actual water quality data of the inlet water not corresponding to the air supply volume required by the actual water quality at the aeration point of the aerobic tank, thus failing to achieve the effect of precise aeration.

[0019] (4) The existing control method of using activated sludge ASM model technology to simulate the biological reaction process and then control the accurate air distribution of the fan is not yet mature. Since the ASM model mechanism is still under development and there are many model parameters, in addition to the basic data such as design water quantity and water quality, it also includes the reaction kinetics of the biological pool, sedimentation tank and water pump and fan parameters. Its actual requirements are high, the control process is complex, the investment and maintenance of each monitoring instrument are large, and the quality requirements for maintenance personnel are high. Therefore, its actual effect is not ideal, there are certain limitations, and further improvement is needed. Summary of the Invention

[0020] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a "feedforward + feedback assisted" predictive precision aeration method to control the oxygen supply of the biological treatment system, making control easier and operation more energy-efficient.

[0021] In the existing design, the capacity of aerobic and anoxic pools is designed according to the designed inlet and outlet water quality and the most unfavorable temperature (10℃), so the actual outlet water quality should be significantly better than the designed water quality to achieve a new balance.

[0022] The oxygen demand of an aerobic tank is designed based on the design inlet and outlet water quality. The theoretical oxygen demand is calculated, then converted to the standard oxygen demand, and further converted to the standard air supply, which controls fan operation. The higher the DO concentration in the reaction tank, the greater the standard oxygen demand. Furthermore, oxygen transfer efficiency is a factor, which depends on factors such as water depth, aerator efficiency, and DO concentration. Given fixed physical conditions, DO is the only factor that can be adjusted. Therefore, maintaining a low DO level in the reaction tank is a good solution for energy-saving operation.

[0023] Therefore, the present invention provides a control logic for a "feedforward + feedback assisted" predictive precision aeration method to control the oxygen supply of a biological treatment system. The predictive precision aeration method includes the following steps:

[0024] Step 1: Measure the COD of the sewage treatment plant’s influent for several days Cr Statistical analysis is performed on the influent COD using the latest monitoring data. Cr As a benchmark, take the historical COD Cr Historical COD within a certain set ratio range (such as 20%) in the data Cr and the corresponding BOD5 value as a probability distribution data set, calculate the B / C value within a set cumulative probability range (such as 80%) of B / C in the data set and the average value of B / C in the data set, use the average value as the BOD5 conversion coefficient, and calculate the safety factor K of the actual gas supply according to the following formula 安 :

[0025]

[0026] In the formula, B / C is BOD5 / COD Cr The ratio of

[0027] Step 2: Use the sewage treatment plant online monitoring instrument to monitor the sewage treatment plant at intervals of t 工 The measured influent COD Cr , influent ammonia nitrogen, influent TN value, BOD5 conversion coefficient and designed effluent BOD5, total Kjeldahl nitrogen and nitrate nitrogen values ​​to calculate the actual oxygen demand AOR of the aerobic zone; t 工 The working time of the online monitoring instrument from sampling to output of results;

[0028] Step 3: Convert the actual oxygen demand AOR into the oxygen demand SOR under standard conditions (0.1MPa, 20℃) and calculate the standard gas supply G s ;

[0029] Step 4: Actual gas supply volume G s控 Based on theoretical deduction, multiply by a safety factor K greater than 1 安 To calculate, the calculation method is as follows:

[0030] G s控 =G s ×K 安 ;

[0031] Step 5: Control the system at t 滞 Then the gas supply volume G s控 Delivered to the control cabinet of the fan unit, and according to the actual air supply volume G s控 Adjust the fan output volume;

[0032] t 滞 is the time required for sewage to travel from the online monitoring point to the aerobic tank, t 滞 The calculation method is: 滞 =t 停 -t 工 , where t 停 The actual residence time of sewage from the online monitoring point to the aerobic tank;

[0033] Step 6: Feedback auxiliary control system provides real-time feedback of DO value at the end of aerobic pool and sets the minimum DO value. min To prevent anaerobic phosphorus release in the secondary sedimentation tank, if the DO value is greater than DO min , the system will not make any adjustments and will continue to run for a period of time until the new water inlet online monitoring value comes out, and then calculate the new air supply demand and then calculate the G s控 Make adjustments; if the DO value is less than DO min , then according to (DO min - current DO value) multiplied by the volume of the aerobic zone to obtain the oxygen demand AOR of the aerobic zone, and then calculate SOR, G s , K 安 And the air volume G to be increased s增 , with G s增 As the air supply of the fan unit is increased, the air supply is increased until the DO concentration in the aerobic pool exceeds DO min When the aerobic pool reaches a certain proportion (such as 10%), it will stop to ensure the lowest DO content in the effluent of the aerobic pool.

[0034] Preferably, in step 2, the actual oxygen demand AOR in the aerobic zone is calculated as follows:

[0035] AOR=0.001aQ(S o -S e )-cΔX V +b[0.001Q(N k -N ke )-0.12ΔX V ]

[0036] -0.62b[0.001Q(N t -N ke -N oe )-0.12ΔX V ], unit: kgO2 / d;

[0037] Where: S o is the BOD5 concentration of the bioreactor influent (mg / L); S e Design effluent BOD5 concentration for the biological reactor (mg / L); N tis the total nitrogen concentration of the influent measured in the biological reactor (mg / L); N k is the total Kjeldahl nitrogen concentration of the influent measured in the reaction tank (mg / L), and the measured total nitrogen concentration of the influent is used; N ke Design the total Kjeldahl nitrogen concentration of the effluent from the reaction tank (mg / L); N oe = Design the nitrate nitrogen concentration of the effluent from the reaction tank (mg / L); a is the oxygen equivalent of carbon, which is 1.47 when the carbon-containing material is measured as BOD5; b is a constant, the amount of oxygen required to oxidize each kilogram of ammonia nitrogen (kg O2 / kgN), which is 4.57; c is a constant, the oxygen equivalent of bacterial cells, which is 1.42; Q is the influent flow rate of the biological reaction tank (m3 / d); ΔX V is the amount of microorganisms discharged from the bioreactor system (kg / d); 0.12ΔX V It is the nitrogen content in the microorganisms discharged from the biological reactor system (kg / d).

[0038] Preferably, the BOD5 concentration of the bioreactor influent is S o The average value of the influent B / C data set in step 1 is used as the conversion coefficient, and the measured influent COD Cr The value is obtained by multiplying the conversion coefficient.

[0039] Specifically, the BOD5 conversion coefficient in step 2 is the average value of the influent B / C data set in step 1.

[0040] Preferably, in step 3, the actual oxygen demand AOR is converted into the standard oxygen demand SOR according to the following formula:

[0041]

[0042] Where: C S(20) C is the saturation of dissolved oxygen in clean water at 20℃, mg / L; sb(T) is the average dissolved oxygen saturation in the aerobic pool at the design water temperature T℃, mg / L; T is the design water temperature, ℃; C L is the dissolved oxygen concentration in the aerobic tank, mg / L; a is the ratio of the oxygen transfer rate of sewage to the oxygen transfer rate of clean water, which is taken as 0.82; ρ is the pressure correction coefficient, which is taken as 1.0; β is the ratio of the saturated dissolved oxygen in sewage to the saturated dissolved oxygen in clean water, which is taken as 0.95.

[0043] Preferably, the average dissolved oxygen saturation C in the aerobic tank is sb Calculated as follows:

[0044]

[0045] Where: C s is the oxygen saturation under atmospheric pressure, mg / L; p bis the absolute pressure at the outlet of the air diffusion device, Pa; Q t It is the percentage of oxygen when the bubbles leave the water surface of the aerated biological reactor.

[0046] Preferably, the absolute pressure p b Calculate as follows:

[0047] P b =P+9.8×10 3 H

[0048] Where: H is the installation depth of air diffusion, m; P is the atmospheric pressure, which is 1.013×10 5 Pa.

[0049] Preferably, the percentage of oxygen Q t Calculate as follows:

[0050]

[0051] Where: E A is the oxygen transfer efficiency of the air diffusion device, %.

[0052] Preferably, in step 3, the standard gas supply volume G s Calculated as follows:

[0053]

[0054] Where: E A is the oxygen transfer efficiency of the air diffusion device, %.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The aeration control of the present invention is mainly based on feedforward and supplemented by DO feedback, which can not only ensure the water quality but also achieve energy saving and consumption reduction. It is more reasonable in theory and feasible in practice, more energy-saving in operation, and lower carbon emissions of the system.

[0057] 2. The control of air volume is based on theoretical deduction and multiplied by a safety factor K greater than 1. 安 The control system can be adjusted at any time according to the actual operation situation to avoid insufficient air supply due to water quality fluctuations; the value of the safety factor is based on the probability distribution characteristics of the B / C of the sewage treatment plant influent, and the latest monitored influent COD Cr As a benchmark, take the historical COD within a certain set ratio range (such as 20%) above and below it. Cr The corresponding BOD5 value is used as the calculation data set. The B / C value with a cumulative probability of 80% in the data set is initially divided by the average value of the B / C value to obtain the initial value of the safety factor K. The subsequent test data set is further tested to take the latest monitored COD CrCalculate K by taking the B / C value with a cumulative probability of 90% to 70% or above and below 10% to 30%. 安 , determine the appropriate K based on whether the effluent water quality meets the standard 安 , select the best calculation K when the effluent water quality meets the standard 安 Value, get the controlled air volume G s控 ;

[0058] 3. Systematically and scientifically set the lag time t between the supply and demand of DO in the aerobic pool 滞 , according to the “actual residence time” t of sewage from the online monitoring point to the aerobic tank 停 Subtract the working time t of the online monitoring instrument from sampling to output of results 工 Consideration can effectively improve the accuracy of aeration volume prediction;

[0059] Fourth, the DO feedback mechanism at the end of the aerobic tank is retained, and the operating parameters can be adjusted at any time according to the operating conditions in the system, which greatly improves the adaptability of the system. The DO feedback is used to assist in controlling the aeration volume, ensuring the lowest DO content in the effluent of the aerobic tank, reducing energy consumption while preventing anaerobic phosphorus release in the secondary sedimentation tank.

[0060] 5. Conventional online monitoring indicators can be used to control the system without adding any additional monitoring instruments. For renovation projects, only the control program needs to be adjusted, and the system deployment is simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0062] Figure 1 This is a control diagram of the traditional biochemical pond feed-back aeration system;

[0063] Figure 2 This is a schematic diagram of the predictive and precise aeration control of the biochemical pond "feedforward + feedback assistance" provided by the present invention. DETAILED DESCRIPTION

[0064] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0065] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making creative efforts are within the scope of protection of the present invention.

[0066] In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0067] Example 1

[0068] As attached Figure 2 As shown, the oxygen supply control logic of the biological treatment system is changed to the "feedforward + feedback auxiliary" mode, and the real-time changing influent water quality is obtained every 2 hours through the online detection instrument, including influent BOD5, influent ammonia nitrogen, influent TN value, BOD5 conversion coefficient and designed effluent water quality index value (BOD5, total Kjeldahl nitrogen, nitrate nitrogen value), etc., because the influent BOD5 data needs to be measured for more than five days, and the influent COD Cr The data can be measured quickly, so by statistically analyzing the influent BOD5 / COD Cr The average value of the B / C ratio is used as the conversion coefficient, and the influent COD Cr The data is multiplied by the conversion coefficient to obtain the influent BOD5, thereby shortening the monitoring time of the influent BOD5 and making the adjustment of aeration more timely.

[0069] The oxygen demand of the aerobic tank is calculated based on the amount of BOD5 and nitrogen removed. The actual oxygen supply should take into account the influence of factors such as the fluctuation of the influent water volume and water quality and the temperature of the mixed liquid in the reaction tank. According to the "Outdoor Drainage Design Standard" GB50014-2021, the actual oxygen demand AOR of the aerobic zone in the biological reactor can be calculated as follows:

[0070] AOR=0.001aQ(S o -S e )-cΔX V +b[0.001Q(N k -N ke )-0.12ΔX V ]-0.62b[0.001Q(N t -N ke -N oe )-0.12ΔX V ], unit: kgO2 / d;

[0071] Where: S o is the BOD5 concentration of the bioreactor influent (mg / L), is the average value of the influent B / C data set in the statistical step 1 as the conversion coefficient, and is the measured influent COD Cr Value × conversion coefficient to get; S e Design effluent BOD5 concentration for the biological reactor (mg / L); N t is the total nitrogen concentration of the influent measured in the biological reactor (mg / L); N k is the total Kjeldahl nitrogen concentration of the influent measured in the reaction tank (mg / L), and the measured total nitrogen concentration of the influent is used; N ke Design the total Kjeldahl nitrogen concentration of the effluent from the reaction tank (mg / L); N oe = Design the nitrate nitrogen concentration of the effluent from the reaction tank (mg / L); a is the oxygen equivalent of carbon, which is 1.47 when the carbon-containing material is measured as BOD5; b is a constant, the amount of oxygen required to oxidize each kilogram of ammonia nitrogen (kg O2 / kgN), which is 4.57; c is a constant, the oxygen equivalent of bacterial cells, which is 1.42; Q is the influent flow rate of the biological reaction tank (m3 / d); ΔX V is the amount of microorganisms discharged from the bioreactor system (kg / d); 0.12ΔX V It is the nitrogen content in the microorganisms discharged from the biological reactor system (kg / d).

[0072] The actual oxygen demand AOR is converted into the oxygen demand SOR under standard conditions (0.1 MPa, 20°C) by the following formula:

[0073]

[0074] Where: C S(20) C is the saturation of dissolved oxygen in clean water at 20℃, mg / L; sb(T) is the average dissolved oxygen saturation in the aerobic pool at the design water temperature T℃, mg / L; T is the design water temperature, ℃; C L is the dissolved oxygen concentration in the aerobic tank, mg / L; a is the ratio of the oxygen transfer rate of sewage to the oxygen transfer rate of clean water, which is taken as 0.82; ρ is the pressure correction coefficient, which is taken as 1.0; β is the ratio of the saturated dissolved oxygen in sewage to the saturated dissolved oxygen in clean water, which is taken as 0.95.

[0075] Average dissolved oxygen saturation C in aerobic pool sb Calculated as follows:

[0076]

[0077] Where: C s is the oxygen saturation under atmospheric pressure, mg / L; p b is the absolute pressure at the outlet of the air diffusion device, Pa; Q tIt is the percentage of oxygen when the bubbles leave the water surface of the aerated biological reactor.

[0078] Absolute pressure p b Calculate as follows:

[0079] P b =P+9.8×10 3 H

[0080] Where: H is the installation depth of air diffusion, m; P is the atmospheric pressure, which is 1.013×10 5 Pa.

[0081] Oxygen percentage Q t Calculate as follows:

[0082]

[0083] Where: E A is the oxygen transfer efficiency of the air diffusion device, %.

[0084] Gas supply volume G under standard conditions s (m 3 / h) is calculated as follows:

[0085]

[0086] Where: E A is the oxygen transfer efficiency of the air diffusion device, %.

[0087] The control of air volume is based on theoretical deduction and multiplied by a safety factor K greater than 1. 安 , and the control system can be adjusted at any time according to the actual operating conditions to avoid insufficient air supply due to water quality fluctuations. The safety factor K of this embodiment 安 Calculate as follows:

[0088] Measure the influent COD of the sewage treatment plant for several days Cr Statistical analysis is performed on the influent COD using the latest monitoring data. Cr As a benchmark, take the historical COD Cr COD within a certain set ratio range (such as 20%) in the data Cr The corresponding BOD5 value is used as the calculation data set to calculate the B / C value within a set cumulative probability range (such as 80%) of the B / C in the data set and the average value of the B / C in the data set. The average value is used as the conversion coefficient, and the safety factor K of the actual gas supply is calculated according to the following formula: 安 :

[0089]

[0090] In the formula, B / C is BOD5 / COD Cr ratio.

[0091] The safety factor K in this embodiment 安 The value of is based on the probability distribution characteristics of B / C of the sewage treatment plant influent. First, the latest monitored COD Cr As a benchmark, take the historical COD Cr Historical COD of the upper and lower 20% probability distribution in the data Cr The corresponding BOD5 value is used as the probability distribution data set, and the B / C value with a cumulative probability of 80% in the data set (i.e., the cumulative probability of a certain B / C value occurring is 80%) is divided by the average value of the B / C value to obtain the value. Cr =180mg / L, take the COD with a probability distribution of 20% above and below Cr The range is 144~216mg / L, and the corresponding BOD5 value is used as the probability distribution data set. The B / C value with a cumulative probability of 80% in the data set is calculated to be 0.54, and the average value of the B / C value is 0.47. The above conversion coefficient is 0.47, and K 安 =0.54 / 0.47=1.14. The latest monitored COD can be obtained by further testing the data set in turn according to whether the effluent water quality meets the standard. Cr Calculate K by taking the B / C value with a cumulative probability of 90% to 70% or above and below 10% to 30%. 安 .

[0092] Therefore, the best K is selected according to whether the effluent water quality meets the standard. 安 The value is used to obtain the controlled air volume G s控 , actual gas supply volume G s控 Calculate as follows:

[0093] G s控 =G s ×K 安 .

[0094] The system takes into account a time lag. It takes a certain amount of time for the sewage to travel from the online monitoring point to the aerobic pool. This time t 滞 The initial value is based on the “actual residence time” t of the sewage from the online monitoring point to the aerobic tank. 停 Subtract the working time t of the online monitoring instrument from sampling to output of results 工 Consider the following formula:

[0095] t 滞 =t 停 -t 工

[0096] The system should take into account the above parameters t 停 and t工 Adjustable, can be flexibly adjusted according to the actual operating conditions. 2 For example, according to the "Outdoor Drainage Design Standard" GB 50014-2021, the aeration grit chamber residence time is 15 minutes, the anaerobic zone residence time is 1.5 hours, and the anoxic zone residence time is 6 hours. Then tstop = 0.25 + 1.5 + 6 = 7.75 hours. Ignoring the residence time of sewage in the pipeline, the measurement time of influent COD is about 30 minutes (rapid digestion spectrophotometry, rapid digestion method) to 2 hours (dichromate reflux method, spectrophotometry method). The time from sampling to output of the result of the online monitoring instrument, t 工 =3h, then t 滞 =t 停 -t 工 =7.75-3=4.75h.

[0097] Therefore, the control system is 滞 Then the gas supply volume G s控 Delivered to the control cabinet of the fan unit, and according to the actual air supply volume G s控 Adjust the fan output volume.

[0098] The DO meter at the end of the aerobic tank serves as a feedback auxiliary control. Its function is not to monitor whether the DO value is around 2.0 mg / L, but to prevent anaerobic phosphorus release in the secondary sedimentation tank, which would affect the effluent P standard. During the specific design, DO feedback is used to set the initial DO concentration at the end of the aerobic tank to around 0.4-0.5 mg / L as an auxiliary control condition, and the DO value in the system should be adjustable. In actual operation, due to the different conditions of each sewage treatment plant, such as the surface load, diameter-to-depth ratio, and mud hopper size of the secondary sedimentation tank, the DO at the end of the aerobic tank needs to be debugged and monitored to find the appropriate DO concentration to prevent anaerobic phosphorus release in the secondary sedimentation tank.

[0099] The feed-back auxiliary control system provides real-time feedback of the DO value at the end of the aerobic pool and sets the minimum DO value. min To prevent anaerobic phosphorus release in the secondary sedimentation tank, if the DO value is greater than DO min , the system will not make any adjustments and will continue to run for 2 hours until the new water inlet online monitoring value comes out, and then calculate the new air supply demand and then calculate the G s控 Make adjustments; if the DO value is less than DO min , then according to (DO min - current DO value) multiplied by the volume of the aerobic zone to obtain the oxygen demand AOR of the aerobic zone, and then calculate SOR, G s , K 安 And the air volume G to be increased s增 , with G s增 As the air supply of the fan unit is increased, the air supply is increased until the DO concentration in the aerobic pool exceeds DOmin When the aerobic pool reaches a certain proportion (such as 10%), it will stop to ensure the lowest DO content in the effluent of the aerobic pool.

[0100] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A predictive and precise aeration method, characterized by: The following steps are involved: Step 1: Measure the COD of the sewage treatment plant’s influent for several days Cr Statistical analysis is performed on the influent COD using the latest monitoring data. Cr As a benchmark, take the historical COD Cr Historical COD within a certain set ratio range in the data Cr and the corresponding BOD5 value as a probability distribution data set, calculate the B / C value within a set cumulative probability range of B / C in the data set and the average value of B / C in the data set, use the average value as the conversion coefficient, and calculate the safety factor K of the actual gas supply according to the following formula 安 : In the formula, B / C is BOD5 / COD Cr The ratio of Step 2: Use the sewage treatment plant online monitoring instrument to monitor the sewage treatment plant at intervals of t 工 The measured influent COD Cr , calculate the actual oxygen demand AOR of the aerobic zone based on the influent ammonia nitrogen, influent TN value, BOD5 conversion coefficient and designed effluent BOD5, total Kjeldahl nitrogen and nitrate nitrogen values; t 工 The working time of the online monitoring instrument from sampling to output of results; Step 3: Convert the actual oxygen demand AOR into the oxygen demand SOR under standard conditions and calculate the standard gas supply G s ; Step 4: Actual gas supply volume G s控 Based on theoretical deduction, multiply by a safety factor K greater than 1 安 To calculate, the calculation method is as follows: G s控 =G s ×K 安 ; Step 5: Control the system at t 滞 Then the gas supply volume G s控 Delivered to the control cabinet of the fan unit, and according to the actual air supply volume G s控 Adjust the fan output volume; t 滞 is the time required for sewage to travel from the online monitoring point to the aerobic tank, t 滞 The calculation method is: 滞 =t 停 -t 工 , where t 停 The actual residence time of sewage from the online monitoring point to the aerobic tank; Step 6: Feedback auxiliary control system provides real-time feedback of DO value at the end of aerobic pool and sets the minimum DO value. min To prevent anaerobic phosphorus release in the secondary sedimentation tank, if the DO value is greater than DO min , the system will not make any adjustments and will continue to run for a period of time until the new water inlet online monitoring value comes out, and then calculate the new air supply demand and then calculate the G s控 Make adjustments; if the DO value is less than DO min , then according to (DO min - current DO value) multiplied by the volume of the aerobic zone to obtain the oxygen demand AOR of the aerobic zone, and then calculate SOR, G s , K 安 And the air volume G to be increased s增 , with G s增 As the air supply of the fan unit is increased, the air supply is increased until the DO concentration in the aerobic pool exceeds DO min Stop when a certain proportion of 2. The predictive precise aeration method according to claim 1, characterized in that: In the second step, the actual oxygen demand AOR of the aerobic zone is calculated as follows: AOR=0.001aQ(S o -S e )-cΔX V +b[0.001Q(N k -N ke )-0.12ΔX V ] -0.62b[0.001Q(N t -N ke -N oe )-0.12ΔX V ], unit: kgO2 / d; Where: S o is the BOD5 concentration of the bioreactor influent (mg / L); S e Design effluent BOD5 concentration for the biological reactor (mg / L); N t is the total nitrogen concentration of the influent measured in the biological reactor (mg / L); N k is the total Kjeldahl nitrogen concentration of the influent measured in the reaction tank (mg / L), and the measured total nitrogen concentration of the influent is used; N ke Design the total Kjeldahl nitrogen concentration of the effluent from the reaction tank (mg / L); N oe = Design the nitrate nitrogen concentration of the effluent from the reaction tank (mg / L); a is the oxygen equivalent of carbon, which is 1.47 when the carbon-containing material is measured as BOD5; b is a constant, the amount of oxygen required to oxidize each kilogram of ammonia nitrogen (kg O2 / kgN), which is 4.57; c is a constant, the oxygen equivalent of bacterial cells, which is 1.42; Q is the influent flow rate of the biological reaction tank (m3 / d); ΔX V is the amount of microorganisms discharged from the bioreactor system (kg / d); 0.12ΔX V It is the nitrogen content in the microorganisms discharged from the biological reactor system (kg / d).

3. The predictive precise aeration method according to claim 2, characterized in that: Bioreactor influent BOD5 concentration S o The average value of the influent B / C data set in step 1 is used as the conversion coefficient, and the measured influent COD Cr The value is obtained by multiplying the conversion coefficient.

4. The predictive precise aeration method according to claim 1, characterized in that: The BOD5 conversion coefficient in step 2 is the average value of the influent B / C data set in step 1.

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