A control system and method for reducing energy consumption of small-scale domestic sewage treatment

Abstract

The invention discloses a control system and method for reducing energy consumption of small-scale domestic sewage treatment. The system comprises a liquid level measuring device, an air blowing system, a speed regulating device and an energy consumption control device. The overall structure is simple and clear, and the installation is convenient. Universal accessories are used, and the replacement and maintenance are convenient, and the system has strong promotion. The control system is used for the water inlet pool and the aerobic biochemical pool of the small-scale domestic sewage treatment project. The liquid level measuring device can monitor the change of the water level of the water inlet in real time. The water inlet cycle is divided into high load, low load and holiday load metering water inlet cycle according to different water use time, so as to accurately, timely and stably control the oxygen demand of the aeration system. The optimal output power of the air blowing system is adjusted through the precise calculation and coordination of the feedback control module and the feedforward control module, so as to effectively save the energy consumption cost and labor cost of the air blowing system.

Description

Technical Field

[0001] The present invention relates to the technical field of domestic sewage treatment, and in particular to a low-energy consumption treatment system and method for small-scale domestic sewage. Background Art

[0002] At present, small-scale domestic sewage treatment is mainly based on centralized and decentralized biological treatment processes. Its system is mainly composed of screen wells, water inlet tanks or regulating tanks, hydrolysis tanks, aerobic biochemical tanks or MBRs, sedimentation tanks and clear water tanks. The energy consumption in the process of small-scale domestic sewage treatment is large and mainly concentrated on the operating energy consumption of the blower. Due to the unevenness of the flow of small-scale domestic sewage, the blower cannot always be in an effective working state, thereby increasing the operating cost, forcing the operation of the domestic sewage treatment system to become unsustainable, and to a certain extent affecting the sustainable development of the small-scale sewage treatment system. Based on the above reasons, reducing the energy consumption and operating costs of small-scale domestic sewage treatment has become a research hotspot in the sewage treatment process.

[0003] Dissolved oxygen (DO) is an important parameter in the biochemical treatment process of sewage. Its control level and control method greatly affect the sewage treatment efficiency and effluent quality. The blower system that provides dissolved oxygen in the sewage treatment system is the core unit of sewage treatment, and its energy consumption accounts for 50% to 70% of the energy consumption of the sewage treatment system. At present, the blower system in small-scale domestic sewage treatment facilities is usually set to a constant, normally open mode, and does not change in real time according to the changes in the inlet water volume, water quality and other loads of the inlet pool or regulating pool, which often leads to excessive dissolved oxygen, low dissolved oxygen utilization, and energy waste. For small-scale sewage treatment systems with large and regular water volume changes, the blower is generally switched on and off manually to achieve stable effluent and energy saving.

[0004] From the operation of small-scale sewage treatment facilities, the main characteristics of small-scale domestic sewage are that the water volume fluctuations are greater than those of large-scale urban domestic sewage treatment plants, and the dissolved oxygen required by the biochemical treatment unit fluctuates frequently.

[0005] At present, there are three main types of energy-saving control for small-scale domestic sewage treatment blower systems: the operator adjusts the blower windshield and air duct valve in real time. This method requires real-time operation by the operator. Because the water load changes frequently, the above adjustment process has poor real-time control over the dissolved oxygen (DO) in the biochemical system and has no obvious energy-saving effect. For the operation of the sewage blower whose control system has been installed with a frequency converter, when the water load changes regularly, the operator regularly changes the output frequency of the frequency converter to control the working state of the blower and the output of oxygen. This method has a certain energy-saving effect, but requires timely and frequent operation by technicians. For large-scale sewage treatment systems, a dissolved oxygen meter is used to feed back the dissolved oxygen detection signal in the aerobic biochemical pool in real time. After PLC acquisition and strict calculation, a blower operation instruction is obtained. The instruction is fed back to the electric regulating valve of the blower and the outlet pipe to adjust its opening, so as to achieve the blower aeration volume adjustment that matches the organic pollution load with the water load, and achieve the purpose of energy saving. However, for small-scale domestic sewage treatment systems, the above control system is expensive and requires very high technical skills of the operator.

[0006] The air blowing system in domestic sewage treatment facilities is mainly composed of blowers, air supply pipes, various valves and aeration components. It is a process based on the principles of fluid mechanics. The air is sucked in and compressed by the blower and then pushed into the air supply pipe to flow to each aeration component. Finally, the compressed air is diffused into the sewage aerobic treatment system by the aeration component. When the oxygen demand of the sewage aerobic treatment system is constant, the lower the blower input frequency, the lower the energy consumption. Therefore, it is necessary to study the relationship between the blower input frequency and the water volume changes of small-scale domestic sewage at different periods, and optimize the control. Summary of the invention

[0007] The object of the present invention is to provide a control system and method for reducing energy consumption of small-scale domestic sewage treatment, thereby solving the above-mentioned problems existing in the prior art.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A control system for reducing energy consumption of small-scale domestic sewage treatment, comprising a liquid level measuring device, a blast system, a speed regulating device and an energy consumption control device, wherein the liquid level measuring device, the energy consumption control device, the speed regulating device and the blast system are connected in sequence, and the energy consumption control device comprises an energy-saving controller, a feedforward control module, a feedback control module and a frequency judgment module.

[0010] The liquid level measuring device is used to measure the liquid level of a small-scale domestic sewage inlet tank or a regulating tank, and transmit the measurement result to the feedback control module;

[0011] The feedback control module determines the operating frequency required for the air blowing system to be in the optimal operating state under different air volume conditions at different times according to the received measurement results;

[0012] The feedforward control module is used to determine the operating frequency required for the air blowing system to be in the optimal operating state at different stages throughout the year and all weather conditions;

[0013] The frequency determination module is used to compare the frequency output results of the feedforward control module and the feedback control module in real time, and to decide the corresponding operation based on the maximum value of the two, and to determine and record the current optimal input frequency of the air blowing system, so as to manage the overall energy consumption of the air blowing system;

[0014] The speed regulating device obtains the optimal input frequency in the frequency determination module and uses the optimal input frequency to adjust the operating frequency of each blower in the blowing system;

[0015] The energy-saving controller is used to control the blower system to optimally output oxygen supply to the small-scale domestic sewage aerobic biochemical pool according to the real-time liquid level change of the water inlet pool, thereby achieving optimal control of energy consumption.

[0016] Preferably, the liquid level measuring device adopts a liquid level meter that can output analog signals to indicate the liquid level in real time, including one or more ultrasonic liquid level meters or immersion pressure sensors.

[0017] Preferably, the blowing system includes one or more blowers, and the blower is selected from at least one of a centrifugal blower, a Roots blower, a magnetic suspension blower and an air suspension blower.

[0018] A control method for reducing energy consumption of small-scale domestic sewage treatment, using the control system for reducing energy consumption of small-scale domestic sewage treatment, mainly includes the following steps:

[0019] S1, according to the determined special operation law of the small-scale domestic sewage treatment system, the characteristic operation cycles of high load, low load and holiday load are set in the feedforward control module throughout the year;

[0020] S2, assigning values ​​to the operating frequencies of the air blowing system under different load modes according to the characteristics of the operating frequencies of the air blowing system when the water volume in the feedforward control module is in a high load mode, a low load mode, and a holiday load mode;

[0021] S3, according to the water level change rate of the water inlet pool or the regulating pool, determine the oxygen input required in the aerobic biochemical pool, thereby determining the air volume demand, and assigning a value to the operating frequency of the air blowing system after calculation using a feedback control module;

[0022] S4, the frequency determination module receives the output frequency assignment results of the feedforward control module and the feedback control module respectively, takes the maximum value of the two as the final output frequency, and sets the final output frequency as the operating frequency of the blower system.

[0023] Preferably, the feedforward control module in step S2 assigns the operating frequency according to different load modes, mode one is the high load mode, mode two is the low load mode, mode three is the holiday load operating mode, the frequency assignment range is 25 to 50 Hz and can be modified; and the holiday load mode starts to be calculated 1 day in advance of the statutory holidays, and the mode is maintained for 1 to 15 days.

[0024] Preferably, in step S3, the oxygen input required in the aerobic biochemical pool is determined according to the water level change rate of the water inlet pool or the regulating pool, thereby determining the air volume requirement, and the process of setting the output frequency η is specifically as follows:

[0025] When the liquid level difference in the water inlet tank or the regulating tank is calculated to be positive, the output frequency of the feedback control module is set to execute the high-frequency value output mode, and the frequency assignment range is 35 to 50 Hz; when the liquid level difference is calculated to be negative, the output frequency of the feedback control module is set to execute the low-frequency value output mode, and the frequency assignment range is 25 to 40 Hz.

[0026] Preferably, the change in air volume demand is due to oxygen demand, wherein the oxygen demand required for sewage treatment is calculated as follows: O=ka'QLr+b'VN',

[0027] Among them, Q is the flow rate of sewage, Lr is the concentration of organic matter removed by the sewage treatment system, V is the volume of the aerobic biochemical pool of the sewage treatment system, N' is the concentration of volatile suspended matter in the mixed liquor, a' is the oxygen consumption per unit organic matter BOD degradation, ranging from 0.42 to 0.53, b' is the oxygen consumption per unit mixed liquor volatile suspended matter self-oxidation, ranging from 0.11 to 0.188, k is the correction coefficient of oxygen demand for different processes, ranging from 0.2 to 1.0;

[0028] The specific flow calculation process of the blast system is: Q = 0.5KvπD2Lλn

[0029] Where D is the outer diameter of the impeller, L is the length of the impeller, λ is the area utilization coefficient, the value range is 0.521~0.563, n is the selected blower motor impeller speed, Kv is the volumetric efficiency, the value range is 0.7~0.9;

[0030] The calculation formula for the blower motor impeller speed is: n = 60f (1-s) / P

[0031] Among them, F is the power frequency, P is the number of motor pole pairs, and s is the motor slip rate, which ranges from 1.5% to 6%.

[0032] Preferably, in step S5, the frequency determination module receives the output frequency results of the feedforward control module and the feedback control module respectively, takes the maximum value of the two as the final output frequency, and is connected to at least one variable frequency speed regulator.

[0033] The beneficial effects of the present invention are:

[0034] The invention discloses a control system and method for reducing energy consumption of small-scale domestic sewage treatment. The system has a simple and clear overall structure and is easy to install. It uses universal accessories, is easy to replace and maintain, and has strong promotional potential.

[0035] According to different water usage times, the water inlet cycle is divided into high load, low load and holiday load metering. At the same time, the liquid level measuring device can monitor the changes in the inlet water level in real time, so as to accurately, timely and stably control the oxygen demand of the aeration system. Through the precise calculation and coordination of the feedback control module and the feedforward control module, the optimal output power of the blower system is adjusted, effectively saving the energy consumption cost and labor cost of the blower system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of a control system for reducing energy consumption of small-scale domestic sewage treatment provided in Example 1;

[0037] Figure 2 is a flow chart of a control method for reducing energy consumption of small-scale domestic sewage treatment provided in Example 2;

[0038] Among them, 1 is a liquid level meter, 2 is an energy consumption control device, 201 is an energy-saving controller, 202 is a feedforward control module, 203 is a feedback control module, 204 is a frequency judgment module, 3 is a speed regulating device, 4 is a blast system, and 5 is a water inlet pool or a regulating pool. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] Example 1

[0041] This embodiment provides a control system for reducing energy consumption of small-scale domestic sewage treatment, including a liquid level measuring device, a blast system, a speed regulating device and an energy consumption control device. The control system is used in a small-scale domestic sewage treatment project. The small-scale domestic sewage treatment project includes an inlet tank and an aerobic biochemical tank, and some also include a regulating tank and a sedimentation tank. The liquid level measuring device is installed inside the inlet tank and / or the regulating tank. The blast system is used to provide sufficient oxygen to the aerobic biochemical tank, such as Figure 1 As shown, the liquid level measuring device, the energy consumption control device, the speed regulating device and the blast system are connected in sequence. In this embodiment, the energy consumption control device includes an energy-saving controller, a feedforward control module, a feedback control module and a frequency judgment module.

[0042] The liquid level measuring device is used to measure the liquid level of a small-scale domestic sewage inlet tank or a regulating tank, and transmit the measurement result to the feedback control module;

[0043] The feedback control module determines the operating frequency required for the air blowing system to be in the optimal operating state under different air volume conditions at different times according to the received measurement results;

[0044] The feedforward control module is used to determine the operating frequency required for the air blowing system to be in the optimal operating state at different stages throughout the year and all weather conditions;

[0045] The frequency determination module is used to compare the frequency output results of the feedforward control module and the feedback control module in real time, and to decide the corresponding operation based on the maximum value of the two, and to determine and record the current optimal input frequency of the air blowing system, so as to manage the overall energy consumption of the air blowing system;

[0046] The speed regulating device obtains the optimal input frequency in the frequency determination module and uses the optimal input frequency to adjust the operating frequency of each blower in the blowing system;

[0047] The energy-saving controller is used to control the blower system to optimally output oxygen supply to the small-scale domestic sewage aerobic biochemical pool according to the real-time liquid level change of the water inlet pool, thereby achieving optimal control of energy consumption.

[0048] like Figure 1 As shown, the liquid level measuring device in this embodiment adopts a liquid level meter installed in the water inlet tank or the regulating tank, and an ultrasonic liquid level meter or a immersion pressure sensor can be selected. The liquid level meter converts the measured water level value into an electrical signal for real-time transmission; the blowing system in this embodiment also adopts multiple blowers, and the blower can be selected from at least one of a centrifugal blower, a Roots blower, a magnetic levitation blower and an air suspension blower.

[0049] Example 2

[0050] This embodiment provides a control method for reducing the energy consumption of small-scale domestic sewage treatment by using the control system for reducing the energy consumption of small-scale domestic sewage treatment in Embodiment 1, such as Figure 2 As shown, the following steps are included:

[0051] S1. According to the specific operating rules of the determined small-scale domestic sewage treatment system, the characteristic operating cycles of high load, low load and holiday load are set in the feedforward control module throughout the year; among which, for the determined small-scale sewage treatment system, it is mainly based on the amount of domestic sewage treatment to determine the scale of the domestic sewage treatment system, thereby determining the number and specifications of the blowers required.

[0052] S2, assigning values ​​to the blower operating frequencies under different load modes according to the characteristics of the blower operating frequencies when the water volume in the feedforward control module is in a high load mode, a low load mode, and a holiday load mode respectively;

[0053] S3, according to the water level change rate of the water inlet pool or the regulating pool, determine the oxygen input required in the aerobic biochemical pool, thereby determining the air volume demand, and assigning a value to the operating frequency of the air blowing system after calculation using a feedback control module;

[0054] S4, the frequency determination module receives the output frequency assignment results of the feedforward control module and the feedback control module respectively, takes the maximum value of the two as the final output frequency, and sets the final output frequency as the operating frequency of the blower system.

[0055] In this embodiment, the annual water inflow is divided into three modes: high load, low load and holiday load, specifically: Holiday load mode: starts from the day before a statutory holiday of more than three days and lasts for 15 days;

[0056] High load mode: April 1 to October 31, excluding the time in holiday load mode;

[0057] Low load mode: November 1 to March 31, excluding the time in holiday load mode;

[0058] The output frequency assignment of the feedforward control module is set according to each mode. The output frequency assignment range of the high load mode is 35~50HZ by default; the output frequency assignment range of the low load mode is 25~40HZ by default; the output frequency assignment range of the holiday mode is 35~50HZ by default.

[0059] The output frequency assignment process of the feedback control module is as follows: the feedback control module receives the liquid level data difference between the ultrasonic level meter of the water inlet pool or regulating pool at this moment and the previous moment. When the liquid level difference is calculated to be positive, the output frequency of the feedback control module is set to execute the high-frequency value output mode, and the assignment range of this mode is 25-50HZ; when the liquid level difference is calculated to be negative, the output frequency of the feedback control module is set to execute the low-frequency value output mode, and the assignment range of this mode is 25-40HZ. The above assignment ranges can be modified according to actual needs, mainly considering whether to re-assign the modification due to changes in water volume, water quality, and effluent requirements; the total amount of pollutants in this period is calculated according to the change in the water level difference multiplied by the sewage concentration in this period, and then the oxygen requirement is calculated, and the frequency value that should be assigned to the blower is derived from this.

[0060] Specifically, the oxygen consumption required for sewage treatment is calculated as follows: O = ka'QLr + b'VN',

[0061] Among them, Q is the flow rate of sewage, Lr is the concentration of organic matter removed by the sewage treatment system, V is the volume of the biochemical pool of the sewage treatment system, N' is the concentration of volatile suspended matter in the mixed liquor, a' is the oxygen consumption per unit organic matter BOD degradation, ranging from 0.42 to 0.53, b' is the oxygen consumption per unit mixed liquor volatile suspended matter self-oxidation, ranging from 0.11 to 0.188, k is the correction coefficient of oxygen demand for different processes, ranging from 0.2 to 1.0;

[0062] The specific flow calculation process of the blower is: Q = 0.5KvπD2Lλn

[0063] D is the outer diameter of the impeller, L is the length of the impeller, λ is the area utilization coefficient, the value range is 0.521~0.563, n is the impeller speed of the blower motor, Kv is the volumetric efficiency, the value range is 0.7~0.9;

[0064] The calculation formula for the blower motor impeller speed is: n = 60f (1-s) / P

[0065] Among them, F is the power frequency, P is the number of motor pole pairs, and s is the motor slip rate, which ranges from 1.5% to 6%.

[0066] When the energy consumption determination module makes a judgment, the determination time step is a certain duration between 1 and 60 minutes, such as ten minutes, and the output frequency values ​​of the feedforward control module and the feedback control module are continuously determined, and the maximum value of the two is used to determine the variable frequency speed regulator to execute the optimal input frequency of the blower.

[0067] When the energy consumption determination module determines that the output frequency value of the feedforward control module is equal to the output frequency value of the feedback control mode, the decision operation is set to be performed based on the output frequency value of the feedforward control module.

[0068] The frequency determination module stores data at intervals of 1 to 60 minutes, which can be determined according to different scales or needs, so as to perform different data storage and frequency selection. For example, the frequency determination module in this embodiment stores the optimal output frequency, the optimal output air volume of the blower, and the operating power value of the blower every ten minutes to manage the operation status of the blower.

[0069] By adopting the above technical solution disclosed in the present invention, the following beneficial effects are obtained:

[0070] The invention discloses a control system and method for reducing energy consumption of small-scale domestic sewage treatment. The system has a simple and clear overall structure and is easy to install. It uses universal accessories, is easy to replace and maintain, and has strong promotional potential.

[0071] According to different water usage times, the water inlet cycle is divided into high load, low load and holiday load metering. At the same time, the liquid level measuring device can monitor the changes in the inlet water level in real time, so as to accurately, timely and stably control the oxygen demand of the aeration system. Through the precise calculation and coordination of the feedback control module and the feedforward control module, the optimal output power of the blower system is adjusted, effectively saving the energy consumption cost and labor cost of the blower system.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A control system for reducing energy consumption of small-scale domestic sewage treatment, characterized in that: It includes a liquid level measuring device, a blast system, a speed regulating device and an energy consumption control device, wherein the liquid level measuring device, the energy consumption control device, the speed regulating device and the blast system are connected in sequence, and the energy consumption control device includes an energy-saving controller, a feedforward control module, a feedback control module and a frequency determination module; The liquid level measuring device is used to measure the liquid level of a small-scale domestic sewage inlet tank or a regulating tank, and transmit the measurement result to the feedback control module; The feedback control module determines the operating frequency required for the air blowing system to be in the optimal operating state under different air volume conditions at different times according to the received measurement results; The feedforward control module is used to determine the operating frequency required for the air blowing system to be in the optimal operating state at different stages throughout the year and all weather conditions; The frequency determination module is used to compare the frequency output results of the feedforward control module and the feedback control module in real time, and to decide the corresponding operation based on the maximum value of the two, and to determine and record the current optimal input frequency of the air blowing system, so as to manage the overall energy consumption of the air blowing system; The speed regulating device obtains the optimal input frequency in the frequency determination module and uses the optimal input frequency to adjust the operating frequency of each blower in the blowing system; The energy-saving controller is used to control the blower system to optimally output oxygen supply to the small-scale domestic sewage aerobic biochemical pool according to the real-time liquid level changes in the water inlet pool or the regulating pool, thereby achieving optimal control of energy consumption.

2. The control system for reducing energy consumption of small-scale domestic sewage treatment according to claim 1 is characterized in that: The liquid level measuring device adopts a liquid level meter capable of outputting analog signals to indicate the liquid level in real time, including one or more ultrasonic liquid level meters or immersion pressure sensors.

3. The control system for reducing energy consumption of small-scale domestic sewage treatment according to claim 1 is characterized in that: The blowing system includes one or more blowers, and the blower is selected from at least one of a centrifugal blower, a Roots blower, a magnetic suspension blower and an air suspension blower.

4. A control method for reducing energy consumption of small-scale domestic sewage treatment, characterized in that: The control system for reducing energy consumption of small-scale domestic sewage treatment according to any one of claims 1 to 3 mainly comprises the following steps: S1, according to the determined special operation law of the small-scale domestic sewage treatment system, the characteristic operation cycles of high load, low load and holiday load are set in the feedforward control module throughout the year; S2, assigning values ​​to the operating frequencies of the air blowing system under different load modes according to the characteristics of the operating frequencies of the air blowing system when the water volume in the feedforward control module is in a high load mode, a low load mode, and a holiday load mode; S3, according to the water level change rate of the water inlet pool or the regulating pool, determine the oxygen input required in the aerobic biochemical pool, thereby determining the air volume demand, and assigning a value to the operating frequency of the air blowing system after calculation using a feedback control module; S4, the frequency determination module receives the output frequency assignment results of the feedforward control module and the feedback control module respectively, takes the maximum value of the two as the final output frequency, and sets the final output frequency as the operating frequency of the blower system.

5. The control method for reducing energy consumption of small-scale domestic sewage treatment according to claim 4 is characterized in that: In step S2, the feedforward control module assigns the operating frequency according to different load modes, mode 1 is the high load mode, mode 2 is the low load mode, and mode 3 is the holiday load operating mode. The frequency assignment range is 25 to 50 Hz and can be modified; and the holiday load operating mode is calculated one day in advance of the statutory holidays, and the mode is maintained for 1 to 15 days.

6. The control method for reducing energy consumption of small-scale domestic sewage treatment according to claim 4 is characterized in that: In step S3, the oxygen input required in the aerobic biochemical pool is determined according to the water level change rate of the water inlet pool or the regulating pool, thereby determining the air volume requirement and setting the output frequency η. Specifically, the process is as follows: When the liquid level difference in the water inlet tank or the regulating tank is calculated to be positive, the output frequency of the feedback control module is set to execute the high-frequency value output mode, and the frequency assignment range is 35 to 50 Hz; when the liquid level difference is calculated to be negative, the output frequency of the feedback control module is set to execute the low-frequency value output mode, and the frequency assignment range is 25 to 40 Hz.

7. The control method for reducing energy consumption of small-scale domestic sewage treatment according to claim 6 is characterized in that: The change in air volume demand is due to the oxygen demand, where the oxygen demand required for sewage treatment is calculated as: O=ka'QLr+b'VN', Among them, Q is the flow rate of sewage, Lr is the concentration of organic matter removed by the sewage treatment system, V is the volume of the aerobic biochemical pool of the sewage treatment system, N' is the concentration of volatile suspended matter in the mixed liquor, a' is the oxygen consumption per unit organic matter BOD degradation, ranging from 0.42 to 0.53, b' is the oxygen consumption per unit mixed liquor volatile suspended matter self-oxidation, ranging from 0.11 to 0.188, k is the oxygen demand correction coefficient for different processes, ranging from 0.2 to 1.0; The specific flow calculation process of the blast system is: Q=0.5KvπD 2 Lλn; Among them, D is the outer diameter of the impeller, L is the length of the impeller, λ is the area utilization coefficient, the value range is 0.521~0.563, n is the selected blower motor impeller speed, Kv is the volumetric efficiency, the value range is 0.7~0.9; The calculation formula for the blower motor impeller speed is: n=60f(1-s) / P Among them, f is the power supply frequency, P is the number of motor pole pairs, and s is the motor slip rate, which ranges from 1.5% to 6%.

8. The control method for reducing energy consumption of small-scale domestic sewage treatment according to claim 4 is characterized in that: In step S5, the frequency determination module receives the output frequency results of the feedforward control module and the feedback control module respectively, takes the maximum value of the two as the final output frequency, and is connected to at least one variable frequency speed regulator.

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