Optimized dissolved oxygen and dosing regulation and control method suitable for AO + MBR process

Abstract

The invention relates to the technical field of sewage treatment, and aims to solve the problems that a dissolved oxygen detector is limited in measuring range, an air inlet fan and an air inlet valve in a low-dissolved-oxygen area cannot be guided to act according to dissolved oxygen indexes, an efficient denitrification state cannot be maintained, a dephosphorization agent is added according to effluent total phosphorus, a dephosphorization agent adding point is the tail end of an aerobic II area, the feedback time is long, and the efficiency is high. The invention provides an optimized oxygen dissolving and dosing regulation and control method suitable for an A2O + MBR (Membrane Bioreactor) process, aiming at solving the problems of unstable total phosphorus in effluent caused by low control efficiency in the prior art. The method comprises the steps of data acquisition, medicament adding control and dissolved oxygen control. According to the invention, the opening degree of the fan and the joint action of the valves in the areas to be controlled are controlled through the oxidation-reduction potential, the linkage automatic control of the oxidation-reduction potential of the biochemical pool and the dissolved oxygen in the low dissolved oxygen area and the aerobic area is completed, the actions of the fan and the valves of the aeration system are effectively guided, and the efficient denitrification state can be maintained; the orthophosphate value at the tail end of the aerobic zone is used as the adding basis of the dephosphorization agent, so that the method is more accurate and efficient.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method suitable for 2 Optimizing dissolved oxygen and dosing control methods for O+MBR process. Background Art

[0002] In the traditional municipal sewage treatment plant control mode, in order to ensure that organic matter is fully oxidized and decomposed, and to balance the inhibitory effect of dissolved oxygen in the return sludge on the denitrification reaction, the oxygen content in the aerobic zone of the biochemical pool is usually controlled at 2.0 mg / L or above. With the improvement of the national nitrogen emission standards in the effluent of sewage treatment plants, it is increasingly important to strengthen denitrification in the biochemical reaction process. In order to adapt to the new environmental protection requirements, many sewage treatment plants have carried out upgrading and transformation, and added membrane technology to the original process section. Therefore, the number of municipal sewage treatment plants using MBR technology is increasing.

[0003] like Figure 1 As shown in A 2 In the O+MBR process, sewage sludge is discharged from the membrane area after three-stage return. The first-stage return flows back from the end of the membrane area to the front section of the aerobic zone I to supplement the sludge concentration in the biochemical pool; the second-stage return flows back from the end of the aerobic zone I to the front section of the anoxic zone for denitrification; the third-stage return flows back from the anoxic zone to the anaerobic zone to supplement the sludge concentration in the anaerobic zone and promote the full release of phosphorus by polyphosphate bacteria. The dissolved oxygen control target in the aerobic zone is 2.0 mg / L and above. At the same time, in order to ensure the stable compliance of the total phosphorus in the effluent, auxiliary chemical phosphorus removal is set up.

[0004] Compared with the traditional A 2 O process, A 2 The O+MBR process is connected to a membrane pool at the end of a conventional biochemical pool. The membrane pool maintains a certain amount of aeration, which is equivalent to adding an aeration area at the end of a traditional biochemical pool. The nitrification reaction mainly occurs in the aerobic zone and the membrane pool area.

[0005] Therefore, in A 2 In the O+MBR process, the aerobic zone I can be adjusted to a low dissolved oxygen zone and the dissolved oxygen can be controlled at about 0.5 mg / L. In addition to ensuring the requirements of aerobic reactions, an anaerobic environment can be maintained, which is beneficial to increasing the simultaneous nitrification and denitrification rate, reducing power consumption, reducing the adverse effects of oxygen in the return sludge on the denitrification process, improving the denitrification efficiency, and comprehensively strengthening denitrification.

[0006] Since the lower limit of the dissolved oxygen online detector is 0.5 mg / L, in actual process control, there is often a low dissolved oxygen zone below the lower limit of measurement. At this time, it is impossible to guide the operation of the aerobic zone air intake fan and air intake valve based on the dissolved oxygen index, and the state of efficient denitrification cannot be maintained.

[0007] The main basis for adding traditional chemical phosphorus removal agents is the total phosphorus in the effluent, and the phosphorus removal agent addition point is at the end of the aerobic zone II, which has a long feedback time, low control efficiency, and will cause the total phosphorus in the effluent to be unstable. Summary of the invention

[0008] The present invention aims to provide a 2 The optimized dissolved oxygen and dosing control method of O+MBR process is used to solve the problem of 2 After the aerobic zone I is adjusted to the low dissolved oxygen zone in the O+MBR process, due to the limited range of the dissolved oxygen online detector, the action of the air intake fan and the air intake valve in the low dissolved oxygen zone cannot be guided according to the dissolved oxygen index, and the efficient denitrification state cannot be maintained. The main basis for the addition of phosphorus removal agents is the total phosphorus in the effluent, and the phosphorus removal agent addition point is at the end of the aerobic zone II. The feedback time is long, the control efficiency is low, and it will lead to the problem of unstable total phosphorus in the effluent.

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

[0010] The present invention provides a method suitable for 2 Optimized dissolved oxygen and dosing control method of O+MBR process, among which A 2 The biochemical pool of the O+MBR process includes an anaerobic zone, an anoxic zone, a low dissolved oxygen zone, an aerobic zone and a membrane zone which are connected in sequence. The end of the membrane zone is reversely connected to the front section of the low dissolved oxygen zone, the end of the low dissolved oxygen zone is reversely connected to the front section of the anoxic zone, and the anoxic zone is reversely connected to the anaerobic zone; the end of the aerobic zone is provided with a phosphorus removal agent injection port;

[0011] The method includes data acquisition, reagent dosing control and dissolved oxygen control;

[0012] Data collection includes collecting redox potential data at the end of the anoxic zone, orthophosphate values ​​at the end of the aerobic zone, effluent ammonia nitrogen data, influent flow data, influent water quality data, actual dissolved oxygen values ​​in the low dissolved oxygen zone, and actual dissolved oxygen values ​​in the middle and rear sections of the aerobic zone;

[0013] The control of the agent addition includes: taking the orthophosphate value at the end of the aerobic zone as the basis for adding the phosphorus removal agent, performing PID control calculation through the orthophosphate target value and the actual orthophosphate value at the outlet of the aerobic zone end, and dynamically controlling the addition of the phosphorus removal agent;

[0014] Dissolved oxygen control includes: taking the redox potential at the end of the anoxic zone as the control index, and the effluent ammonia nitrogen data, inlet flow data, inlet water quality data, actual dissolved oxygen value in the low dissolved oxygen zone, and actual dissolved oxygen value in the middle and rear sections of the aerobic zone as auxiliary control parameters to adjust the air volume of the aeration system.

[0015] As the preferred technical solution:

[0016] The control of drug addition specifically includes the following steps:

[0017] S101: setting the orthophosphate target value at the outlet of the aerobic zone end;

[0018] S102: PID control operation is performed according to the orthophosphate target value and the actual orthophosphate value at the end outlet of the aerobic zone obtained by data collection. The PID control operation forms a control deviation according to the orthophosphate target value and the actual orthophosphate value. The proportion, integral and differential of the deviation are linearly combined to form a control amount. The concentration of phosphorus removal agent is obtained according to the control amount.

[0019] S103: Calculating the dosage of the phosphorus removal agent to be added according to the phosphorus removal agent dosage concentration and the actual water output;

[0020] S104: The dosage of the phosphorus removal agent calculated in step S103 is the target dosage of the phosphorus removal agent. PI control operation is performed based on the target dosage of the phosphorus removal agent and the actual dosage of the phosphorus removal agent. The PI control operation constitutes a control deviation based on the target dosage of the phosphorus removal agent and the actual dosage of the phosphorus removal agent. The proportion and integral of the deviation are linearly combined to form a control quantity. The operating frequency of the agent dosing diaphragm pump is controlled based on the control quantity.

[0021] As the preferred technical solution:

[0022] The method further comprises step S105: performing intermittent dosing of the agent dosing diaphragm pump according to the orthophosphate compensation calculation to obtain the dosing amount and dosing time;

[0023] The orthophosphate compensation operation is as follows: when the automatic dosing control system of the dephosphorus removal agent is switched from manual to automatic, stable control is performed, that is, the dosage of the dephosphorus removal agent is gradually adjusted to make it smoothly transition from the dosage in the manual mode to the target dosage in the automatic mode, so that the dephosphorus removal agent dosage control can be switched from manual to automatic with a stable transition.

[0024] As the preferred technical solution:

[0025] The phosphorus removal agent is PAC agent, and the dosage of PAC agent is calculated according to the following formula:

[0026]

[0027] Among them, the liquid volume refers to the actual water output.

[0028] As the preferred technical solution:

[0029] Dissolved oxygen control specifically includes the following steps:

[0030] S201: Setting the target value of redox potential in the anoxic zone;

[0031] S202: Perform peak filtering and arithmetic average filtering on the collected data;

[0032] S203: Perform fuzzy PID control operation according to the redox potential target value and the redox potential actual value to obtain fuzzy control correction values ​​ΔKp, ΔTi, and ΔTd, and obtain Kp(t), Ti(t), and Td(t) values ​​of the fuzzy PID controller according to the initial values ​​of Kp(t-1), Ti(t-1), and Td(t-1) of the fuzzy PID controller and the fuzzy control correction values ​​ΔKp, ΔTi, and ΔTd, respectively;

[0033] S204: PID control operation is performed according to the redox potential target value, the actual redox potential value, and the Kp(t), Ti(t), and Td(t) values. The PID control operation constitutes a control deviation according to the redox potential target value and the actual redox potential value. The deviation e(t) is linearly combined into a control quantity according to the proportion Kp, the integral Ti, and the differential Td to control the fan.

[0034] As the preferred technical solution:

[0035] Step S202 specifically includes:

[0036] The collected real-time operating data such as ORP data at the end of the anoxic zone, effluent ammonia nitrogen data, inlet flow data, inlet water quality data, dissolved oxygen data in the middle and later stages of the low dissolved oxygen zone and aerobic zone are subjected to peak filtering and arithmetic average filtering.

[0037] As the preferred technical solution:

[0038] The method also includes S205: combining actual control needs, according to water inlet flow compensation, ammonia nitrogen excess compensation, start-stop fan air volume connection compensation, pipe pressure excess compensation and fan current compensation, the operation control correction and rectification of the fan and the valve are realized to obtain the air supply volume suitable for the low dissolved oxygen zone and the aerobic zone.

[0039] As the preferred technical solution:

[0040] Step S205 is specifically as follows: combining process experience with the results of fuzzy PID control algorithm calculation to determine a 5-segment control decision tree and compensation control action priority, the priorities from high to low are: fan protection action, fan group start and stop action, ORP, ammonia nitrogen, DO abnormalities, inlet water quality fluctuations, PID control module output, and outputting the final control instruction through the decision tree judgment of the fuzzy PID control result.

[0041] As the preferred technical solution:

[0042] The method further includes S206: each area to be controlled corresponds to a valve for controlling its aeration amount, and the aeration amount of the area to be controlled is determined by the opening size of the valve; each valve controls the air supply provided by the fan to redistribute the air supply provided by the fan according to the different air volume requirements of each area to be controlled, so as to meet the air volume requirements of each area to be controlled;

[0043] S207: performing PID control calculations to solve the required air volume of each area to be controlled according to the target value and actual value of the redox potential in the low dissolved oxygen zone and the target value and actual value of the dissolved oxygen in the aerobic zone;

[0044] S208: Obtain the target air volume required for each area to be controlled, and control the valve opening through PI control operation. The PI control operation forms a control deviation based on the target air volume required and the actual air volume required. The proportion and integral of the deviation are linearly combined to form a control quantity, and the valve is controlled.

[0045] S209: Using the result of the PI control operation as the basis for adjusting the opening of each valve; adjusting the valve opening to match the required air volume of the area to be controlled, thereby achieving linear control of the required air volume of the area to be controlled.

[0046] Among them, the areas to be controlled include low dissolved oxygen areas and aerobic areas.

[0047] As the preferred technical solution:

[0048] Step S203 specifically includes:

[0049] Perform fuzzy processing, define the fuzzy condition set of the fuzzy PID controller input e(t), ec(t) and output ΔKp, ΔTi, ΔTd, and define the fuzzy control rule table of the input e(t), ec(t) and output ΔKp, ΔTi, ΔTd; perform defuzzification processing, obtain the fuzzy control corrections ΔKp, ΔTi, ΔTd according to the fuzzy control rule table during the defuzzification processing, and obtain the Kp(t-1), Ti(t-1), Td(t-1) initial values ​​of the fuzzy PID controller and the fuzzy control corrections ΔKp, ΔTi, ΔTd respectively.

[0050] As the preferred technical solution:

[0051] Step S207 specifically includes: PID control operation forms control deviations according to the target value and actual value of the redox potential in the low dissolved oxygen zone and the target value and actual value of the dissolved oxygen in the aerobic zone, and the deviations are linearly combined to form a control quantity according to the proportion Kp, the integral Ti and the differential Td, and the required air volume of each area to be controlled is solved according to the control quantity.

[0052] As the preferred technical solution:

[0053] In step S102, the PID control algorithm is loaded into the PID controller to perform PID calculation, and the control amount of the added agent is obtained by applying automation technology, and the concentration of the phosphorus removal agent to be added is obtained according to the control amount of the added agent;

[0054] In step S104, the PI control algorithm is loaded into the PI controller to perform PI calculations to obtain a control quantity, and the operating frequency of the drug dosing diaphragm pump is controlled by the PI controller;

[0055] In step S204, the PID control algorithm is loaded into the PID controller, and the operating air volume of the fan is controlled by the PID controller;

[0056] In step S208, the PI control algorithm is loaded into the PI controller, and the opening of the valve is controlled by the PI controller.

[0057] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0058] 1. The present invention adjusts the aerobic zone I from a conventional aerobic zone to a low dissolved oxygen zone, thereby saving electricity costs from the aspect of aeration; a low dissolved oxygen zone is set to create an anaerobic environment, so that nitrifying bacteria and denitrifying bacteria coexist in the same space, and nitrification and denitrification reactions occur simultaneously, thereby strengthening biological denitrification and reducing the addition of denitrification agents; the nitrification liquid returned from the low dissolved oxygen zone to the anoxic zone has a low dissolved oxygen content, which has a small impact on the anoxic environment, thus better maintaining the anoxic environment and enhancing the denitrification efficiency; the addition basis of the chemical phosphorus removal agent is changed from the effluent total phosphorus instrument value to the orthophosphate value at the end of the aerobic zone of the biochemical pool, the original feedback reaction is optimized to a forward feedback reaction, the orthophosphate trend is detected in real time, and the phosphorus removal agent is added timely and accurately according to the orthophosphate value, which is more accurate and efficient, has a short feedback time, and has a high control efficiency, thereby ensuring the stability of the effluent total phosphorus.

[0059] 2. The present invention takes the redox potential at the end of the anoxic zone of the biochemical pool as the control target, and uses the effluent ammonia nitrogen data, inlet flow data, inlet water quality data, dissolved oxygen in the middle and rear sections of the aerobic zone, and dissolved oxygen in the aerobic zone of the membrane pool as auxiliary control parameters to ensure that the effluent meets the discharge standards while strengthening biological denitrification.

[0060] 3. The present invention adopts a control method based on redox potential as a core indicator, so that the dissolved oxygen in the low dissolved oxygen zone is stably controlled within the target value; the redox potential controls the fan opening and the dissolved oxygen control valves in each area to be controlled, and the redox potential of the biochemical pool is automatically controlled with the dissolved oxygen in the low dissolved oxygen zone and the aerobic zone, effectively guiding the action of the fan and valves in the aeration system, solving the difficult problem of low dissolved oxygen control, and controlling the redox potential in the anoxic zone of the biochemical pool at -200 to -80mv, the dissolved oxygen concentration in the low dissolved oxygen zone at 0.1 to 0.5mg / l, and the dissolved oxygen concentration in the aerobic zone at 1 to 2mg / l, thereby stabilizing the low dissolved oxygen denitrification and phosphorus removal effect of the biochemical pool. At the same time, the low dissolved oxygen nitrification liquid flows back to the front anoxic zone, providing more favorable denitrification conditions for its denitrification, which is conducive to maintaining an efficient denitrification state.

[0061] 4. The present invention can be quickly implemented through an automatic control program and integrated with fuzzy PID control to achieve automatic adjustment of PID parameters. It is simple and easy to use and no longer relies on manual adjustment in actual operation, with a high degree of automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 A in the prior art 2 O+MBR process flow chart.

[0063] Figure 2 A improved by the present invention 2 O+MBR process flow chart.

[0064] Figure 3 This is the schematic diagram of the fuzzy PID control algorithm.

[0065] Figure 4 This is the flow chart of water inlet flow compensation.

[0066] Figure 5 This is a flow chart for compensation for excess ammonia nitrogen.

[0067] Figure 6 Flow chart for ORP over-limit compensation.

[0068] Figure 7 Flow chart for compensation of DO exceeding limit in low dissolved oxygen zone.

[0069] Figure 8 This is the flow chart of pipe pressure over-limit compensation.

[0070] Fig. 9 This is the flow chart of wind turbine current compensation.

[0071] Fig.10 This is a flow chart for compensation of air volume connection of start-stop fan.

[0072] Fig.11 Flow chart for compensation of DO exceeding limit in aerobic zone. DETAILED DESCRIPTION

[0073] 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.

[0074] Example 1

[0075] This embodiment proposes a method suitable for A 2 Optimization of dissolved oxygen and dosing control methods for O+MBR process, including Figure 2 As shown, A 2 The biochemical pool of the O+MBR process includes an anaerobic zone, an anoxic zone, a low dissolved oxygen zone, an aerobic zone, and a membrane zone. The anaerobic zone, anoxic zone, a low dissolved oxygen zone, an aerobic zone, and a membrane zone are connected in sequence. The end of the membrane zone is reversely connected to the front section of the low dissolved oxygen zone. The sewage sludge at the end of the membrane zone flows back to the low dissolved oxygen zone. The end of the low dissolved oxygen zone is reversely connected to the front section of the anoxic zone. The sewage sludge at the end of the low dissolved oxygen zone flows back to the anoxic zone. The anoxic zone is reversely connected to the anaerobic zone, and the sewage sludge in the anoxic zone flows back to the anaerobic zone. The dissolved oxygen content in the low dissolved oxygen zone is 0.1-0.5 mg / L. The aerobic zone is aerated normally, and the dissolved oxygen content is about 2.0 mg / L. A reagent addition port is provided at the end of the aerobic zone, and PAC reagent is added from the reagent addition port according to the orthophosphate value at the end of the aerobic zone.

[0076] Compared with the existing A 2 O+MBR process, the present invention adjusts the aerobic zone I from a conventional aerobic zone to a low dissolved oxygen zone, saving electricity costs from the aspect of aeration; a low dissolved oxygen zone is set up to create an anaerobic environment, so that nitrifying bacteria and denitrifying bacteria coexist in the same space, and nitrification and denitrification reactions occur simultaneously, thereby strengthening biological denitrification and reducing the addition of denitrification agents; the nitrification liquid returned from the low dissolved oxygen zone to the anoxic zone has a low dissolved oxygen content, which has a small impact on the anoxic environment, better maintains the anoxic environment, and strengthens the denitrification efficiency; the basis for adding chemical phosphorus removal agents is changed from the effluent total phosphorus instrument value to the orthophosphate value at the end of the aerobic zone of the biochemical pool, optimizing the original feedback reaction to a forward feedback reaction, detecting the orthophosphate trend in real time, and adding the phosphorus removal agent in a timely and accurate manner according to the orthophosphate value, which is more accurate and efficient.

[0077] Since the lower limit of the dissolved oxygen online detector is 0.5 mg / L, in actual process control, it is often below the lower limit. At this time, it is impossible to guide the operation of the air intake fan and the air intake valve in the low dissolved oxygen area based on the dissolved oxygen index, and the state of efficient denitrification cannot be maintained.

[0078] The above applies to A2 Optimization of dissolved oxygen, data collection of dosing control methods, control of chemical addition and dissolved oxygen control in O+MBR process;

[0079] Data collection includes collecting redox potential data at the end of the anoxic zone, orthophosphate values ​​at the end of the aerobic zone, effluent ammonia nitrogen data, influent flow data, influent water quality data, actual dissolved oxygen values ​​in the low dissolved oxygen zone, and actual dissolved oxygen values ​​in the middle and rear sections of the aerobic zone;

[0080] In actual application, an ORP (oxidation-reduction potential) online meter is installed at the end of the anoxic zone, and a DO (dissolved oxygen) online meter is installed in the middle and rear sections of the low dissolved oxygen zone and the aerobic zone. The actual ORP value at the end of the anoxic zone is obtained through the ORP online meter, and the actual dissolved oxygen value in the middle and rear sections of the low dissolved oxygen zone and the aerobic zone is obtained through the DO online meter.

[0081] The agent addition control includes: taking the orthophosphate value at the end of the aerobic zone as the basis for PAC agent addition, performing PID control calculations through the orthophosphate target value and the actual orthophosphate value at the outlet point at the end of the aerobic zone, and dynamically controlling the addition of the phosphorus removal agent; by reasonably controlling the dosage of the PAC agent, the power consumption of the agent addition diaphragm pump and the PAC agent consumption are saved.

[0082] Dissolved oxygen control includes: taking the redox potential at the end of the anoxic zone as the control index, and the effluent ammonia nitrogen data, inlet flow data, inlet water quality data, actual dissolved oxygen value in the low dissolved oxygen zone, and actual dissolved oxygen value in the middle and rear sections of the aerobic zone as auxiliary control parameters to adjust the air volume of the aeration system.

[0083] The control of drug addition specifically includes the following steps:

[0084] S101: Set the orthophosphate target value at the outlet point at the end of the aerobic zone.

[0085] S102: PID control operation is performed according to the orthophosphate target value and the actual orthophosphate value at the end of the aerobic zone outlet obtained by data collection. The PID control operation constitutes a control deviation according to the orthophosphate target value and the actual orthophosphate value. The proportion, integral and differential of the deviation are linearly combined to form a control quantity, and the PAC dosage concentration is obtained according to the control quantity. In actual application, the PID control algorithm is loaded into the PID controller for PID operation to obtain the control quantity, and the PAC agent dosage concentration required to be added is obtained according to the control quantity.

[0086] S103: Calculate the dosage of PAC agent to be added according to the PAC agent concentration and the actual water output. The dosage of PAC agent is calculated according to the following formula:

[0087]

[0088] This formula is the relationship between PAC dosage, PAC dosage concentration, and liquid volume (i.e., actual water output). The required PAC dosage can be calculated through this formula, which solves the PAC dosage control system's dependence on historical data and reduces the complexity of the system.

[0089] S104: Perform PI control operation based on the PAC dosage (i.e., PAC dosage target value) and the PAC dosage actual value calculated in step S103. The PI control operation constitutes a control deviation based on the PAC dosage target value and the PAC dosage actual value. The proportion and integral of the deviation are linearly combined to form a control quantity. The PI control algorithm is loaded into the PI controller to perform PI operation to obtain the control quantity. The operating frequency of the drug dosing diaphragm pump is controlled by the PI controller.

[0090] The operating frequency of the reagent dosing diaphragm pump corresponding to the PAC dosing is controlled according to the PI control operation, so as to dynamically control the reagent dosing diaphragm pump corresponding to the PAC dosing, thereby solving the problem of relying on a fixed frequency for PAC reagent dosing. The reagent dosing can be dynamically controlled by this method.

[0091] S105: intermittent dosing of the agent by the diaphragm pump is performed according to the orthophosphate compensation calculation, and finally the appropriate dosing amount and dosing time are obtained.

[0092] Among them, the orthophosphate compensation operation is: when the PAC automatic dosing control system is switched from manual to automatic dosing, since the actual value of orthophosphate may fluctuate, PAC dosage stability control is required. During the adjustment transition time, the PAC dosage is gradually adjusted to make it smoothly transition from the dosage in manual mode to the target dosage in automatic mode, so that the PAC dosage control can be switched from manual to automatic with a stable transition, and there will be no frequent start-stop and sudden increase in total phosphorus control due to unsatisfactory control.

[0093] In summary, the PAC dosage is determined according to the calculation method of PAC dosage concentration, the dynamic addition of PAC dosage combined with liquid volume is realized, and the automatic control of PAC dosage is completed. In addition, the basis for the addition of chemical phosphorus removal agents is changed from the effluent total phosphorus instrument value to the orthophosphate value at the end of the aerobic zone of the biochemical pool, and the original feedback reaction is optimized to a forward feedback reaction, the orthophosphate trend is detected in real time, and the phosphorus removal agent is added in a timely and accurate manner according to the orthophosphate value, which is more accurate and efficient.

[0094] Dissolved oxygen control specifically includes the following steps:

[0095] S201: Setting the ORP (oxidation-reduction potential) target value of the anoxic zone.

[0096] S202: Peak filtering and arithmetic average filtering are performed on the collected real-time operation data such as the ORP data at the end of the anoxic zone, the effluent ammonia nitrogen data, the inlet flow data, the inlet water quality data, the dissolved oxygen data in the middle and rear sections of the low dissolved oxygen zone and the aerobic zone.

[0097] S203: Perform fuzzy PID control operation according to the ORP target value and the ORP actual value;

[0098] First, fuzzy processing is performed. The input of the fuzzy PID controller is the deviation e(t) and the corresponding deviation change rate ec(t). e(t) is the deviation between the target value and the actual value, e(t) = r(t) - c(t), where ec(t) is the difference between the ORP target value and the ORP actual value, ec(t) is the deviation change rate, ec(t) is the deviation between the current deviation and the previous deviation, ec(t) = e(t) - e(t-1), where ec(t) is the difference between the current ORP difference and the previous ORP difference.

[0099] The fuzzy condition set of input e(t), ec(t) and output ΔKp, ΔTi, ΔTd is defined as a seven-level fuzzy subset {NB, NM, NS, ZO, PS, PM, PB}, where N represents negative, P represents positive, B represents large, M represents medium, S represents small, and ZO represents 0. The membership function of the fuzzy subset is as follows:

[0100]

[0101] The parameter values ​​of a, b, c, d, e, and f are set according to actual operating experience. In this embodiment, the deviation of the initial value X by ±5% is used as the limit value of c and d, the deviation of the initial value X by ±30% is used as the limit value of b and e, and the deviation of the initial value X by ±60% is used as the limit value of a and f.

[0102] Define the fuzzy control rule table of input e(t), ec(t) and output ΔKp, ΔTi, ΔTd. The form of the fuzzy control rule table is IF input THEN output (standard Mamdani form).

[0103] Defuzzification is performed. During the defuzzification, the fuzzy control correction values ​​ΔKp, ΔTi, and ΔTd are obtained according to the fuzzy control rule table. The Kp(t), Ti(t), and Td(t) values ​​of the fuzzy PID controller are obtained by adding the initial values ​​Kp(t-1), Ti(t-1), and Td(t-1) to the fuzzy control correction values ​​ΔKp, ΔTi, and ΔTd. The calculation formula is as follows:

[0104]

[0105] S204: Perform PID control operation according to the ORP target value, the ORP actual value, and the Kp(t), Ti(t), and Td(t) values. The PID control operation forms a control deviation e(t) according to the ORP target value and the ORP actual value. The deviation e(t) is linearly combined into a control quantity u(t) according to the proportion (Kp), the integral (Ti), and the differential (Td). The fan is controlled. The PID control algorithm is loaded into the PID controller, and the operation of the fan is controlled by the PID controller.

[0106] Specifically, the fan guide vane control or fan frequency control is performed through the calculation result of the PID control operation, that is, the PID controller generates a control instruction for the fan guide vane opening or the fan frequency, and the fan guide vane control or fan frequency control is performed by the control instruction.

[0107] S205: In combination with actual control needs, the operation control correction and deviation rectification of the fan and valve are realized according to the water inlet flow compensation, ammonia nitrogen excess compensation, start-stop fan air volume connection compensation, pipe pressure excess compensation and fan current compensation, so as to obtain the air supply volume suitable for the low dissolved oxygen zone and the aerobic zone.

[0108] Specifically: Combine the process experience with the results of the fuzzy PID control algorithm to determine a 5-segment control decision tree and compensation control action priority. The priorities are from high to low: fan protection action, fan unit start and stop action, ORP, ammonia nitrogen, DO abnormalities, inlet water quality fluctuations, PID control module output, and the fuzzy PID control results are output through the decision tree to determine the final control instruction.

[0109] S206: Each area to be controlled (low dissolved oxygen area and aerobic area) has a corresponding valve to control its aeration volume, and the aeration volume of the area to be controlled is determined by the opening size of the valve; each valve controls the air supply provided by the fan to be redistributed according to the different air volume requirements of each area to be controlled to meet the air volume requirements of each area to be controlled.

[0110] S207: PID control operation is performed according to the target value and actual value of the redox potential in the low dissolved oxygen zone and the target value and actual value of the dissolved oxygen in the aerobic zone to obtain the required air volume of each area to be controlled. The PID control operation forms a control deviation according to the target value and actual value of the dissolved oxygen in each area to be controlled, and the deviation is linearly combined according to the proportion (Kp), integral (Ti) and differential (Td) to form a control amount, and the required air volume of each area to be controlled is obtained according to the control amount.

[0111] S208: Obtain the target air volume demand of each area to be controlled respectively, and control the valve opening through PI control operation. The PI control operation constitutes a control deviation based on the target air volume demand and the actual air volume demand. The proportion (Kp) and integral (Ti) of the deviation are linearly combined to form a control quantity to control the valve. The PI control algorithm is loaded into the PI controller, and the valve opening is controlled by the PI controller.

[0112] S209: Using the result of the PI control operation as the basis for adjusting the opening of each valve; adjusting the valve opening to match the required air volume of the area to be controlled, thereby achieving linear control of the required air volume of the area to be controlled.

[0113] The above-mentioned ORP (oxidation-reduction potential) controls the joint action of the fan opening and the DO (dissolved oxygen) control valves in each area to be controlled, completing the linkage automatic control of the ORP of the biochemical pool and the dissolved oxygen in the low dissolved oxygen zone and the aerobic zone, solving the difficult problem of low dissolved oxygen control, and the valve control method is universal, such as butterfly valve, plunger valve, diamond valve, elliptical valve, and ultimately the ORP of the anoxic zone of the biochemical pool is controlled at -200~-80mv, the dissolved oxygen concentration in the low dissolved oxygen zone is controlled between 0.1~0.5mg / l, and the dissolved oxygen concentration in the aerobic zone is controlled between 1~2mg / l, stabilizing the low dissolved oxygen denitrification and phosphorus removal effect of the biochemical pool, and at the same time, the low dissolved oxygen nitrification liquid flows back to the front anoxic zone, providing more favorable denitrification conditions for its denitrification.

[0114] In the above, the water flow compensation, ammonia nitrogen over-limit compensation, ORP over-limit compensation, DO over-limit compensation, start-stop blower air volume connection compensation, membrane system DO over-limit compensation, pipe pressure over-limit protection compensation and blower current protection compensation are described as follows:

[0115] Inlet flow compensation: After the abnormal flow value is processed by the "data processing system", the inlet flow value is dynamically judged. When the inlet flow fluctuation is obviously too large or too small, the guide vane or frequency of the fan is adjusted in advance to compensate for the untimely automatic control of the biochemical pool dissolution caused by the fluctuation of the inlet flow, and reduce the impact of the fluctuation of the inlet flow on the dissolved oxygen control of the biochemical pool, thereby affecting the control effect. The flow chart is as follows Figure 4 shown.

[0116] Ammonia nitrogen over-limit compensation: After the abnormal ammonia nitrogen value is processed by the "data processing system", the ammonia nitrogen in the effluent is judged to be over-limit. When the ammonia nitrogen value in the effluent exceeds the preset value, the air volume needs to be increased, so as to adjust the guide vane or frequency of the fan to supplement the lack of oxygen in the aerobic zone due to the inadequate reaction of ammonia nitrogen, so as to meet the requirements of ammonia nitrogen effluent. The flow chart is as follows: Figure 5 shown.

[0117] ORP over-limit compensation: After the abnormal ORP value is processed by the "data processing system", the ORP of the anoxic zone of the biochemical pool is judged to be over-limit. When the ORP of the anoxic zone of the biochemical pool exceeds the preset value, the air volume needs to be reduced, thereby reducing the guide vanes or frequency of the fan; when the ORP of the anoxic zone of the biochemical pool is lower than the preset value, the air volume needs to be increased, thereby increasing the guide vanes or frequency of the fan. The flow chart is as follows: Figure 6 As shown. ORP exceeding the limit will cause insufficient redox reaction conditions in the biochemical pool. In order to make up for the untimely control and meet the requirements of ORP control, emergency control adjustments are carried out.

[0118] DO over-limit compensation in low dissolved oxygen area: After the abnormal dissolved oxygen value is processed by the "data processing system", the dissolved oxygen in the low dissolved oxygen area is judged to be over-limit. When the dissolved oxygen in the low dissolved oxygen area exceeds the preset value, the air volume needs to be reduced, thereby increasing the guide vanes or frequency of the fan. The flow chart is as follows Figure 7 Exceeding the limit of dissolved oxygen will cause over-aeration or under-aeration. In order to make up for the untimely control and meet the requirements of dissolved oxygen control, emergency control adjustments are made.

[0119] Pipe pressure over-limit compensation: After the abnormal fan supply pipe pressure value is processed by the "data processing system", the fan supply pipe pressure is judged to be over-limit. When the fan supply pipe pressure exceeds the preset value, the air volume needs to be reduced, so as to adjust the fan guide vane or frequency. The flow chart is as follows Figure 8 To ensure the stable operation of the fan, if the duct pressure exceeds the limit, it will not only cause safety hazards, but also cause other fans with low outlet pressure to surge. At this time, reduce the fan guide vane opening or frequency to ensure the safety of the fan duct system.

[0120] Fan current compensation: After the abnormal fan current value is processed by the "data processing system", the fan current over-limit judgment will be carried out. When the fan current value exceeds the preset value, the air volume needs to be reduced, so as to adjust the guide vane or frequency of the fan. The flow chart is as follows Fig. 9 The fan cannot exceed its rated power during stable operation. To protect the normal use of the fan, the fan current should be protected in time when it exceeds the limit.

[0121] Start-stop fan air volume connection compensation: When the fan starts or stops, the air volume will change. This change will cause the dissolved oxygen in the biochemical pool to fluctuate, which is not conducive to the automatic control of dissolved oxygen in the biochemical pool. In order to solve this problem, the start-stop fan air volume connection compensation is formulated to reduce the impact of air volume fluctuations on dissolved oxygen in the biochemical pool when the fan starts and stops, so that the air volume before and after the change of the number of fans can be connected. The flow chart is as follows Fig.10 shown.

[0122] Aerobic zone DO over-limit compensation: After the abnormal dissolved oxygen value is processed by the "data processing system", the dissolved oxygen in the aerobic zone is judged to be over-limit. When the dissolved oxygen in the aerobic zone exceeds the preset value, the air volume needs to be reduced, thereby adjusting the guide vanes or frequency of the fan; when the dissolved oxygen in the aerobic zone is lower than the preset value, the air volume needs to be increased, thereby increasing the guide vanes or frequency of the fan. Excessive dissolved oxygen will cause over-aeration or under-aeration of the membrane system. In order to meet the requirements of dissolved oxygen control in the aerobic zone, the membrane system fan control adjustment and the biochemical pool fan control adjustment are carried out at this time. The flow chart is as follows Fig.11 shown.

[0123] The control algorithm used in this embodiment is:

[0124] Fuzzy PID control algorithm: The fuzzy PID controller used is a two-input and three-output structure. The input of the fuzzy controller is the deviation e(t) and the corresponding deviation change rate ec(t), and the output is the PID controller parameter correction ΔK p , ΔT i , ΔT d When the control system is running, the inputs e(t) and ec(t) are fuzzified, fuzzy inferenced and defuzzified to obtain the correction value ΔK for online correction. p , ΔT i , ΔT d , perform K p , T i , T d Real-time adjustment of the control logic diagram is as follows Figure 3 shown.

[0125] The control deviation is formed according to the given value and the actual output value, and the fuzzy PID control K p , T i , T d The real-time adjusted value is used to linearly combine the deviation in proportion, integration and differentiation to form the control quantity, and the controlled object is controlled. The formula is as follows:

[0126]

[0127] Among them, u(t) is the output signal of the fuzzy PID controller; p is the proportional operator; Kp is the proportional coefficient, Ti is the integral coefficient; Td is the differential coefficient; Kd is the differential gain of the differential coefficient: Kd(t) = Td(t) - Td(t-1); e(t) is the deviation signal of the control system, also called the input signal of the controller, the given target value r(t) and the actual output value c(t) constitute a deviation: e(t) = r(t) - c(t).

[0128] PID control algorithm: The control deviation is formed according to the given value and the actual output value, and the deviation is linearly combined into the control quantity according to the proportion, integration and differentiation to control the controlled object. The formula is as follows:

[0129]

[0130] Among them, u(t) is the output signal of the PID controller; p is the proportional operator; Kp is the proportional coefficient, Ti is the integral coefficient; Td is the differential coefficient; Kd is the differential gain of the differential coefficient: Kd(t) = Td(t) - Td(t-1); e(t) is the deviation signal of the control system, also called the input signal of the controller, the given target value r(t) and the actual output value c(t) constitute a deviation: e(t) = r(t) - c(t).

[0131] PI control algorithm: The control deviation is formed based on the given value and the actual output value. The proportion and integral of the deviation are linearly combined to form the control quantity to control the controlled object. The formula is as follows:

[0132]

[0133] In the above formula, u(t) is the output signal of the PI controller; p is the proportional operator; Kp is the proportional coefficient, which proportionally reflects the deviation signal e(t) of the control system; Ti is the integral coefficient; e(t) is the deviation signal of the control system, also known as the input signal of the controller, and the given target value r(t) and the actual output value c(t) constitute a deviation: e(t)=r(t)-c(t).

[0134] 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 type suitable for A 2 Optimizing dissolved oxygen and dosing control methods for O+MBR process, Features: in, A 2 The biochemical pool of the O+MBR process includes an anaerobic zone, an anoxic zone, a low dissolved oxygen zone, an aerobic zone and a membrane zone which are connected in sequence. The end of the membrane zone is reversely connected to the front section of the low dissolved oxygen zone, the end of the low dissolved oxygen zone is reversely connected to the front section of the anoxic zone, and the anoxic zone is reversely connected to the anaerobic zone; the end of the aerobic zone is provided with a phosphorus removal agent injection port; The method includes data acquisition, reagent dosing control and dissolved oxygen control; Data collection includes collecting redox potential data at the end of the anoxic zone, orthophosphate values ​​at the end of the aerobic zone, effluent ammonia nitrogen data, influent flow data, influent water quality data, actual dissolved oxygen values ​​in the low dissolved oxygen zone, and actual dissolved oxygen values ​​in the middle and rear sections of the aerobic zone; The control of the agent addition includes: taking the orthophosphate value at the end of the aerobic zone as the basis for adding the phosphorus removal agent, performing PID control calculation through the orthophosphate target value and the actual orthophosphate value at the outlet of the aerobic zone end, and dynamically controlling the addition of the phosphorus removal agent; Dissolved oxygen control includes: taking the redox potential at the end of the anoxic zone as the control index, and the effluent ammonia nitrogen data, inlet flow data, inlet water quality data, actual dissolved oxygen value in the low dissolved oxygen zone, and actual dissolved oxygen value in the middle and rear sections of the aerobic zone as auxiliary control parameters to adjust the air volume of the aeration system.

2. The method according to claim 1, which is suitable for A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: The control of drug addition specifically includes the following steps: S101: setting the orthophosphate target value at the outlet of the aerobic zone end; S102: PID control operation is performed according to the orthophosphate target value and the actual orthophosphate value at the end outlet of the aerobic zone obtained by data collection. The PID control operation forms a control deviation according to the orthophosphate target value and the actual orthophosphate value. The proportion, integral and differential of the deviation are linearly combined to form a control amount. The concentration of phosphorus removal agent is obtained according to the control amount. S103: Calculating the dosage of the phosphorus removal agent to be added according to the phosphorus removal agent dosage concentration and the actual water output; S104: The dosage of the phosphorus removal agent calculated in step S103 is the target dosage of the phosphorus removal agent. PI control operation is performed based on the target dosage of the phosphorus removal agent and the actual dosage of the phosphorus removal agent. The PI control operation constitutes a control deviation based on the target dosage of the phosphorus removal agent and the actual dosage of the phosphorus removal agent. The proportion and integral of the deviation are linearly combined to form a control quantity. The operating frequency of the agent dosing diaphragm pump is controlled based on the control quantity.

3. The method according to claim 2, which is suitable for A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: The step S105 is also included: intermittent dosing of the agent by the diaphragm pump according to the orthophosphate compensation calculation to obtain the dosing amount and dosing time; The orthophosphate compensation operation is as follows: when the automatic dosing control system of the dephosphorus removal agent is switched from manual to automatic, stable control is performed, that is, the dosage of the dephosphorus removal agent is gradually adjusted to make it smoothly transition from the dosage in the manual mode to the target dosage in the automatic mode, so that the dephosphorus removal agent dosage control can be switched from manual to automatic with a stable transition.

4. The method according to claim 2, which is suitable for use in A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: The phosphorus removal agent is PAC agent, and the dosage of PAC agent is calculated according to the following formula: Among them, the liquid volume refers to the actual water output.

5. The method according to claim 2, which is suitable for use in A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: Dissolved oxygen control specifically includes the following steps: S201: Setting the target value of redox potential in the anoxic zone; S202: Perform peak filtering and arithmetic average filtering on the collected data; S203: Perform fuzzy PID control operation according to the redox potential target value and the redox potential actual value to obtain fuzzy control correction values ​​ΔKp, ΔTi, and ΔTd, and obtain Kp(t), Ti(t), and Td(t) values ​​of the fuzzy PID controller according to the initial values ​​of Kp(t-1), Ti(t-1), and Td(t-1) of the fuzzy PID controller and the fuzzy control correction values ​​ΔKp, ΔTi, and ΔTd, respectively; S204: PID control operation is performed according to the redox potential target value, the actual redox potential value, and the Kp(t), Ti(t), and Td(t) values. The PID control operation constitutes a control deviation according to the redox potential target value and the actual redox potential value. The deviation e(t) is linearly combined into a control quantity according to the proportion Kp, the integral Ti, and the differential Td to control the fan.

6. The method according to claim 5, which is suitable for A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: It also includes S205: in combination with actual control needs, the operation control correction and deviation rectification of the fan and valve are realized according to water inlet flow compensation, ammonia nitrogen excess compensation, start-stop fan air volume connection compensation, pipe pressure excess compensation and fan current compensation to obtain the air supply volume suitable for the low dissolved oxygen zone and the aerobic zone.

7. The method according to claim 6, which is suitable for use in A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: Step S205 is specifically as follows: combining process experience with the results of fuzzy PID control algorithm calculation to determine a 5-segment control decision tree and compensation control action priority, the priorities from high to low are: fan protection action, fan group start and stop action, ORP, ammonia nitrogen, DO abnormalities, inlet water quality fluctuations, PID control module output, and outputting the final control instruction through the decision tree judgment of the fuzzy PID control result.

8. The method according to claim 6, which is suitable for use in A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: The method further includes S206: each area to be controlled has a valve corresponding to its aeration volume, and the aeration volume of the area to be controlled is determined by the opening of the valve; each valve controls the air supply provided by the fan to be redistributed according to the different air volume requirements of each area to be controlled, so as to meet the air volume requirements of each area to be controlled; S207: performing PID control calculations to solve the required air volume of each area to be controlled according to the target value and actual value of the redox potential in the low dissolved oxygen zone and the target value and actual value of the dissolved oxygen in the aerobic zone; S208: Obtain the target air volume required for each area to be controlled, and control the valve opening through PI control operation. The PI control operation forms a control deviation based on the target air volume required and the actual air volume required. The proportion and integral of the deviation are linearly combined to form a control quantity, and the valve is controlled. S209: Using the result of the PI control operation as the basis for adjusting the opening of each valve; adjusting the valve opening to match the required air volume of the area to be controlled, thereby achieving linear control of the required air volume of the area to be controlled.

9. The method according to claim 7, which is suitable for use in A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: Step S203 specifically includes: Perform fuzzy processing, define the fuzzy condition set of the fuzzy PID controller input e(t), ec(t) and output ΔKp, ΔTi, ΔTd, and define the fuzzy control rule table of the input e(t), ec(t) and output ΔKp, ΔTi, ΔTd; perform defuzzification processing, obtain the fuzzy control corrections ΔKp, ΔTi, ΔTd according to the fuzzy control rule table during the defuzzification processing, and obtain the Kp(t-1), Ti(t-1), Td(t-1) initial values ​​of the fuzzy PID controller and the fuzzy control corrections ΔKp, ΔTi, ΔTd respectively.

10. The method according to claim 8, which is suitable for use in A 2 The method for optimizing dissolved oxygen and dosing control of the O+MBR process is characterized by: Step S207 specifically includes: PID control operation forms a control deviation according to the target value and actual value of dissolved oxygen in each area to be controlled, the deviation is linearly combined into a control quantity according to the proportion Kp, integral Ti and differential Td, and the required air volume of each area to be controlled is solved according to the control quantity.

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