Integrated self-cleaning sewage purification treatment device

Abstract

The application discloses an integrated self-cleaning sewage purification treatment device and belongs to the technical field of sewage treatment, solves the problem that micro-bubble interference causes PLC misjudgment of membrane performance attenuation and excessive cleaning, membrane assembly accumulatively bears 40% more than design chemical corrosion, causes PVDF membrane chain breakage, hydrophilic group loss and performance drop, damaged membrane surface hydrophobic adsorption superposition instrument interference, forms a self-accelerating destructive closed loop problem of perception, control and execution layer, and the application uses water production tank liquid level back calculation of real water production as reliable flow reference not affected by micro-bubble interference, continuously compares with electromagnetic flowmeter reading, when deviation occurs, automatically switches liquid level back calculation flow to control suction pump, avoids bubble misdirection blind speed-up, only when membrane water passing capacity really decreases and bubble interference is slight, drug cleaning is allowed, otherwise, only aeration scrubbing and clean water back flushing are allowed, when cumulative sodium hypochlorite contact amount exceeds the safe upper limit, forced pump stop alarm is given, and clean membrane is prevented from being damaged by miswashing caused by bubble deviation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to an integrated self-cleaning wastewater purification and treatment device. Background Technology

[0002] The self-cleaning wastewater purification system integrates multi-stage wastewater purification processes with automated cleaning mechanisms. Wastewater sequentially passes through a screen, grit chamber, coagulation, biochemical filtration, and disinfection system to remove pollutants. Each easily clogged component is equipped with a corresponding cleaning structure to maintain flow efficiency. The system relies on differential pressure, flow rate, and level sensors to transmit operational data. An automatic control device initiates the cleaning process periodically or on demand. The filter uses reverse water flow or rotary suction to remove accumulated impurities. The membrane module combines water and air flushing with chemical soaking to remove surface contaminants. The aeration components reduce pore clogging through pulsed air flushing. The entire cleaning process can be carried out simultaneously with the water treatment process, significantly reducing downtime for cleaning, slowing down filter media and membrane element wear, reducing manual maintenance costs, and enabling the equipment to maintain a stable water flow rate over a long period. It is suitable for continuous wastewater discharge scenarios, and the treated water meets relevant standards for discharge or recycling.

[0003] When the system operates automatically in constant flux mode during the summer and relies on continuous air scrubbing, timed backwashing, and PLC-automatically determined enhanced chemical backwashing and in-situ cleaning to maintain membrane performance, the microbubbles generated by the vacuum suction of the self-cleaning permeate cause extremely low amplitude signal deviations in the electromagnetic flowmeter and online turbidity meter in the permeate main pipe. These deviations are masked by the seasonal feed water load, leading the PLC to simultaneously misjudge accelerated membrane permeability decline and membrane interface disturbances. Consequently, the PLC automatically increases the suction pump speed, shortens the chemical cleaning cycle, and prematurely triggers in-situ chemical cleaning. This results in the membrane module being subjected to nearly 40% more sodium hypochlorite and a proportionally increased citric acid erosion over approximately ninety days. This caused the PVDF membrane fibers to break down and lose hydrophilic groups, resulting in a sharp drop in elongation at break from 120% to less than 40%, a decrease in logarithmic removal rate from 6.0 to 5.2, an increase in surface contact angle of about 15 degrees, and a nearly three-fold increase in membrane pore dispersion coefficient. The enhanced adsorption of dissolved microbial products and organic colloids by the hydrophobic sites on the damaged membrane surface, in turn, superimposed on the instrument signals that were already interfered with by bubbles. Ultimately, under the combined effect of microbubble interference in the sensing layer, logical misjudgment in the control layer, and physical damage and biochemical backlash in the execution layer, a destructive closed loop that accelerated itself and did not trigger any hardware fault alarms was formed. It was not discovered until the total number of bacteria in the produced water exceeded the standard for three consecutive weeks.

[0004] Therefore, an integrated self-cleaning wastewater purification and treatment device is proposed to solve or alleviate the above problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing an integrated self-cleaning wastewater purification and treatment device.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An integrated self-cleaning wastewater purification and treatment device includes a membrane tank, which includes a tank body, a membrane module submerged and installed in the tank body, an aeration pipe located directly below the membrane module and connected to a blower via an air supply pipe, a water production system connected to the water production port of the membrane module, a backwash pump connected to the water production tank, a dosing metering pump connected to the water production system, online instruments, and a programmable logic controller. The water production system includes a water production manifold, a water production vacuum suction pipeline, a suction pump, and a water production valve connected in sequence. The water production vacuum suction pipeline has an electromagnetic flow meter and an online turbidity meter connected in series on the suction pump's suction side, and a pressure transmitter installed on the suction pump's outlet side. The outlet of the water production valve is connected to the inlet of the water production tank. The inlet of the backwash pump is connected to the water production tank, and its outlet is connected to the water production vacuum suction pipeline via the backwash valve. The dosing metering pump is connected to the water production system via a dosing pipeline, and its circuit is equipped with an online residual chlorine detector. The speed signals of each online instrument and the suction pump are connected to the analog input module of the programmable logic controller (PLC). The analog output module of the PLC is connected to the frequency converter of the suction pump, and the digital output module is connected to the start / stop control terminals of each pump and valve. The programmable logic controller synchronously collects and filters signals from various channels, and calculates the actual permeate flow rate, which is not affected by air bubbles in the pipeline, based on the change in the permeate tank water level. It then identifies and corrects the deviation caused by air bubbles in the permeate flow rate and turbidity reading. The corrected flow rate is used to estimate the membrane's actual water flow capacity. Chemical cleaning is only allowed when the water flow capacity has indeed decreased and the air bubble interference is not severe. At the same time, the speed range of the suction pump is limited, and chemical cleaning is forcibly stopped when the cumulative chemical dosage reaches the safety limit. During periods without air bubbles, the threshold for identifying air bubbles and the turbidity benchmark are automatically calibrated.

[0007] Preferably, after synchronously acquiring and filtering signals from various channels, the programmable logic controller (PLC) calculates the actual permeate flow rate, unaffected by air bubbles in the pipeline, based on the change in the permeate tank water level. This serves as a reference for identifying and correcting deviations in the permeate flow rate and turbidity readings caused by air bubbles. The corrected flow rate is then used to estimate the membrane's actual flow capacity. Chemical cleaning is only permitted when the flow capacity has indeed decreased and air bubble interference is not severe. Simultaneously, the speed adjustment range of the suction pump is limited, and chemical dosing is forcibly stopped when the cumulative chemical dosage reaches the safety limit. Furthermore, the threshold for identifying air bubbles and the turbidity benchmark are automatically calibrated during periods without air bubbles. Specifically, the following steps are included: S1 synchronously collects the product water tank level, the original reading of the electromagnetic flowmeter, the original reading of the online turbidity meter, the suction pump speed, and the transmembrane pressure difference, and performs filtering and preprocessing on each signal. S2 calculates the liquid level reference flow rate, which is not affected by air bubbles in the product water pipeline, by determining the slope of the liquid level change based on the liquid level and combining it with the horizontal cross-sectional area of ​​the product water tank. S3 uses the high-frequency fluctuation of the electromagnetic flowmeter's original reading and the steady-state bias between the electromagnetic flowmeter's original reading and the liquid level reference flow rate as two dimensions to detect bubble interference and comprehensively determine the bubble interference indicator. Based on the bubble interference indicator, S4 dynamically and confidently weights and fuses the original reading of the electromagnetic flowmeter with the liquid level reference flow to obtain the fused flow rate, and uses the fused flow rate as the feedback input for the adjustment of the suction pump speed in constant flux control. S5 performs bubble scattering compensation on the original reading of the online turbidity meter based on the relative deviation between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, and obtains the compensated turbidity for auxiliary diagnosis. S6 converts the fused flow rate into instantaneous membrane flux, then combines it with the transmembrane pressure difference to calculate instantaneous permeability, and finally obtains filtered permeability reflecting the membrane fouling trend through low-pass filtering; S7 triggers enhanced chemical backwashing or in-situ chemical cleaning when the filter penetration meets the true attenuation condition and the proportion of time with the bubble interference flag being true within the same evaluation period is lower than the preset proportion limit; otherwise, only physical backwashing and air wiping are maintained. S8 applies step size and cumulative change limits to the adjustment of the suction pump speed and monitors the cumulative chlorine exposure. When the increase in chlorine exposure exceeds the preset safety threshold within a preset time period, chemical cleaning is forcibly prohibited and an alarm is triggered. When the bubble interference flag remains false for a period of time up to the preset calibration window duration, the S9 uses the signal within that window to perform online adaptive updates to the turbidity compensation baseline and the bubble interference detection threshold.

[0008] Preferably, step S1 synchronously acquires the product water tank level, the original reading of the electromagnetic flowmeter, the original reading of the online turbidity meter, the suction pump speed, and the transmembrane pressure difference, and performs filtering preprocessing on each signal, specifically including the following steps: S1.1: At a sampling frequency of not less than 1 Hz, synchronously collect the liquid level of the product water tank, the original reading of the electromagnetic flow meter, the original reading of the online turbidity meter, the speed of the suction pump and the transmembrane pressure difference, and assign a unified timestamp to each signal; S1.2: Perform median filtering on each signal in real time to remove isolated spike-type outliers; S1.3: Store the filtered signals into a circular buffer of a preset length for use in subsequent sliding window calculations in steps S2 to S9.

[0009] Preferably, step S2 calculates the liquid level change slope based on the liquid level and combines it with the horizontal cross-sectional area of ​​the product water tank to obtain the liquid level reference flow rate unaffected by air bubbles in the product water pipeline, specifically including the following steps: S2.1: Within the preset first sliding window, perform linear fitting on the liquid level data sequence of the product water tank, and obtain the slope of the liquid level change over time as the liquid level change slope. S2.2: Multiply the slope of the liquid level change by the horizontal cross-sectional area of ​​the product water tank to obtain the instantaneous true product water flow rate; S2.3: Perform a first-order low-pass filter on the instantaneous actual product water flow rate to obtain a liquid level reference flow rate that is not affected by air bubbles in the product water pipeline, and use it as a common reference for steady-state bias detection in step S3, flow fusion in step S4, and turbidity compensation in step S5.

[0010] Preferably, step S3 uses two dimensions—the high-frequency fluctuation of the electromagnetic flowmeter's original reading and the steady-state offset between the electromagnetic flowmeter's original reading and the liquid level reference flow rate—to detect bubble interference and comprehensively determine the bubble interference indicator. Specifically, this includes the following steps: S3.1: Within the preset second sliding window, calculate the coefficient of variation of the original reading of the electromagnetic flowmeter as an indication of the high-frequency fluctuation dimension; S3.2: Within the preset third sliding window, calculate the average value of the difference between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, and use it as an indication of the steady-state bias dimension. The duration of the third sliding window is longer than that of the second sliding window. S3.3: When the coefficient of variation is greater than the preset fluctuation threshold, or the absolute value of the steady-state bias is greater than the preset bias threshold, the bubble interference flag is set to true; otherwise, it is set to false. S3.4: Output the bubble interference flag to steps S4, S5, S7 and S9 as a common state criterion for each step.

[0011] Preferably, step S4 involves dynamically weighting and fusing the original reading of the electromagnetic flowmeter with the liquid level reference flow rate based on the bubble interference indicator to obtain the fused flow rate. This fused flow rate is then used as the feedback input for adjusting the speed of the suction pump in constant flux control. Specifically, this includes the following steps: S4.1: Within the preset fourth sliding window, the proportion of sampling points with the bubble interference flag set to true is counted out of the total number of sampling points in that window, and this proportion is used as the bubble time percentage. S4.2: Calculate the dynamic confidence weight of the original reading of the electromagnetic flowmeter based on the proportion of bubble time. The dynamic confidence weight decreases as the proportion of bubble time increases and is limited to not being lower than the preset minimum weight. S4.3: The original reading of the electromagnetic flowmeter and the liquid level reference flow rate are weighted and summed using dynamic confidence weights and their complements to obtain the fused flow rate; S4.4: The fused flow rate is sent to the constant flux controller as feedback for the adjustment of the suction pump speed, replacing the original reading of the electromagnetic flow meter.

[0012] Preferably, step S5 involves performing bubble scattering compensation on the original reading of the online turbidity meter based on the relative deviation between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, to obtain the compensated turbidity for auxiliary diagnosis. Specifically, this includes the following steps: S5.1: Divide the difference between the liquid level reference flow rate and the original reading of the electromagnetic flow meter by the liquid level reference flow rate, and take the larger of the difference and zero to construct the bubble density index; S5.2: Subtract the product of the compensation coefficient and the bubble density index from the original reading of the online turbidity meter, and then subtract the turbidity compensation baseline to obtain the compensated turbidity; S5.3: The compensated turbidity is used for auxiliary diagnosis and trend recording of membrane fouling, and is not used as a criterion for triggering chemical cleaning.

[0013] Preferably, step S6 converts the fused flow rate into instantaneous membrane flux, then calculates the instantaneous permeability by combining it with the transmembrane pressure difference, and obtains the filtered permeability reflecting the membrane fouling trend through low-pass filtering. Specifically, this includes the following steps: S6.1: Divide the fused flow rate by the total membrane area to obtain the instantaneous membrane flux; S6.2: Divide the instantaneous membrane flux by the absolute value of the transmembrane pressure difference to obtain the instantaneous permeability; S6.3: Perform a first-order low-pass filter on the instantaneous permeability to obtain the filtered permeability that reflects the long-term trend of membrane fouling, and output it to step S7 as the basis for attenuation judgment.

[0014] Preferably, in step S7, when the filter penetration meets the true attenuation condition and the proportion of time during which the bubble interference flag is true is lower than the preset upper limit, chemical enhanced backwashing or in-situ chemical cleaning is triggered; otherwise, only physical backwashing and air wiping are maintained. Specifically, this includes the following steps: S7.1: Determine whether the filter penetration is continuously lower than the preset penetration lower limit within the most recent consecutive preset number of sampling periods, and whether the absolute value of its decreasing slope is greater than the preset slope threshold. If both conditions are met, the true penetration attenuation condition is deemed to be met. S7.2: Determine whether the percentage of time during which the bubble interference flag is true within the same evaluation period is lower than the preset percentage upper limit. If so, the bubble interference exclusion condition is met. S7.3: Chemical backwashing or in-situ chemical cleaning is triggered only when the actual permeability decay condition and the bubble interference elimination condition are met simultaneously. S7.4: When the actual permeability decay condition is met but the bubble interference elimination condition is not met, chemical cleaning is temporarily suspended, and only physical backwashing and air wiping are maintained, and a bubble interference warning is issued.

[0015] Preferably, step size and cumulative change limits are applied to the adjustment of the suction pump speed in step S8, and the cumulative chlorine exposure is monitored. When the increase exceeds a preset safety threshold within a preset time period, chemical cleaning is forcibly prohibited and an alarm is triggered. Specifically, the steps include the following: S8.1: Limit the absolute value of the difference between the target speed of the suction pump calculated by the constant flux controller and the current actual speed to within the preset maximum step size; S8.2: Accumulate the absolute value of each speed adjustment change within a preset rolling time. When the accumulated value reaches the preset upper limit, the speed will no longer be increased. S8.3: Integrate the effective chlorine concentration on the membrane surface over time to obtain the cumulative chlorine exposure; S8.4: Before each chemical cleaning is started, calculate the increase in cumulative chlorine exposure over a preset time period from the current time. If the increase exceeds the preset safety threshold, forcibly prohibit the current and subsequent chemical cleaning and output a cumulative chlorine exposure exceeding the limit alarm until manually unlocked.

[0016] The present invention has the following beneficial effects: This invention uses the rise and fall of the product water tank level within a unit of time to calculate the actual product water volume, thus obtaining a reliable flow rate reference unaffected by microbubbles in the pipeline. The reading of the electromagnetic flowmeter on the product water pipe is continuously compared with this reference. If the flowmeter reading is found to be consistently low or fluctuating due to bubbles, the system automatically switches to using the flow rate calculated from the liquid level to control the suction pump, preventing the pump from blindly increasing its speed due to being misled by bubbles. At the same time, chemical cleaning of the membrane is only allowed when both conditions are met: the membrane's water flow capacity is indeed steadily decreasing and the bubble interference is not severe. Otherwise, only aeration scrubbing and clean water backwashing are performed. The system continuously accumulates the total amount of sodium hypochlorite recently contacted by the membrane. Once the amount exceeds the safety limit given by the membrane manufacturer, chemical cleaning is forcibly stopped and an alarm is triggered. This prevents clean membranes from being mistakenly treated as dirty membranes and repeatedly cleaned with chemicals when reading deviations are caused by bubbles. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a structural block diagram of the present invention; Figure 2 This is a cumulative dosage curve for various embodiments of the present invention; Figure 3A bar chart showing the comparison of membrane performance in various embodiments of the present invention; Figure 4 This is a bar graph showing the time required for water production to meet standards in various embodiments of the present invention.

[0019] In the diagram: 1. Equalization tank; 2. Anaerobic tank; 3. Anoxic tank; 4. Aerobic tank; 5. Membrane tank; 6. Product water tank. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0025] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] An integrated self-cleaning wastewater purification and treatment device, such as Figure 1 As shown, the system includes an equalization tank 1, an anaerobic tank 2, an anoxic tank 3, an aerobic tank 4, a membrane tank 5, and a product water tank 6 connected sequentially along the water flow direction. The outlet of the equalization tank 1 is connected to the anaerobic tank 2 via a lift pump. The outlet of the anaerobic tank 2 is connected to the anoxic tank 3 via an overflow. The outlet of the anoxic tank 3 is connected to the aerobic tank 4 via an overflow. The outlet of the aerobic tank 4 is connected to the membrane tank 5 via an overflow. The product water outlet of the membrane tank 5 is connected to the product water tank 6 via a product water vacuum suction pipeline. The product water tank 6 is disinfected and then discharged or reused. The bottom of the membrane tank 5 is connected to the front end of the anoxic tank 3 and the front end of the anaerobic tank 2 via a sludge return pump, and is connected to the sludge storage tank via a sludge discharge pipe.

[0027] Membrane tank 5 includes a tank body, membrane modules submerged and installed within the tank body, an aeration pipe located directly below the membrane modules and connected to a blower via an air supply pipe, a permeate system connected to the permeate inlet of the membrane modules, a backwash pump connected to permeate tank 6, a dosing and metering pump connected to the permeate system, online instruments, and a programmable logic controller. The membrane modules are composed of multiple bundles of polyvinylidene fluoride hollow fiber membrane filaments encapsulated in a collection tray. Multiple membrane modules are installed in parallel on the same membrane frame and converged to the permeate manifold via branch pipes. The permeate system includes a permeate manifold, a permeate vacuum suction pipeline, a suction pump, and a permeate valve connected in sequence. The permeate vacuum suction pipeline has an electromagnetic flow meter and an online turbidity meter connected in series on the suction side of the suction pump, and a pressure transmitter is installed on the outlet side of the suction pump. The outlet of the water valve is connected to the inlet of the product water tank 6; the inlet of the backwash pump is connected to the product water tank 6, and the outlet is connected to the product water vacuum suction pipeline via the backwash valve; the dosing metering pump is connected to the product water system via the dosing pipeline, and an online residual chlorine detector is installed on its circuit. The online instruments include the membrane tank 5 level gauge installed in the tank body, the product water tank 6 level gauge installed in the product water tank 6, the electromagnetic flow meter, the online turbidity meter, the pressure transmitter, the online residual chlorine detector, and the gas flow meter installed in the gas supply pipeline. The speed signals of each online instrument and the suction pump are connected to the analog input module of the programmable logic controller. The analog output module of the programmable logic controller is connected to the frequency converter of the suction pump, and the digital output module is connected to the start and stop control terminals of each pump and each valve. After synchronously acquiring and filtering signals from various channels, the programmable logic controller calculates the actual permeate flow rate, which is unaffected by air bubbles in the pipeline, based on the water level change in the permeate tank 6. This serves as a reference for identifying and correcting the deviation caused by air bubbles in the permeate flow rate and turbidity readings. The corrected flow rate is then used to estimate the membrane's actual water flow capacity. Chemical cleaning is only allowed when the water flow capacity has indeed decreased and the air bubble interference is not severe. At the same time, the speed range of the suction pump is limited, and chemical dosing is forcibly stopped when the cumulative chemical dosage reaches the safety limit. During periods without air bubbles, the threshold for identifying air bubbles and the turbidity benchmark are automatically calibrated.

[0028] The programmable logic controller (PLC) performs the following methods during operation, including the following steps: S1.1: At a sampling frequency of not less than 1 Hz, synchronously collect the liquid level of product water tank 6, the original reading of electromagnetic flowmeter, the original reading of online turbidity meter, the speed of suction pump and transmembrane pressure difference, and assign a unified timestamp to each signal; S1.2: Perform median filtering on each signal in real time to remove isolated spike-type outliers; S1.2.1: The window length for median filtering is three, meaning the current sample value is replaced by the median of three adjacent sample values; S1.3: Store the filtered signals into a circular buffer of a preset length for use in the sliding window calculations of subsequent steps S2 to S9; S1.3.1: The length of the circular buffer is not less than the number of sampling points required by the longest sliding window in steps S2 to S9; S1.3.2: Acquisition, timestamp assignment, filtering, and buffering are performed in parallel for all signals to ensure that all signals are aligned on the same time base; S2.1: Within the preset first sliding window, perform linear fitting on the liquid level data sequence of the production water tank 6, and obtain the slope of the liquid level change over time as the liquid level change slope. S2.1.1: The least squares method is used for linear fitting, and the slope of the fitted line is used as the slope of the liquid level change. S2.2: Multiply the slope of the liquid level change by the horizontal cross-sectional area of ​​the water production tank 6 to obtain the instantaneous actual water production flow rate; S2.2.1: The water production tank 6 is a regular column, and its horizontal cross-sectional area is taken as a constant; S2.3: Perform a first-order low-pass filter on the instantaneous actual production water flow rate to obtain a liquid level reference flow rate that is not affected by air bubbles in the production water pipeline, and use it as a common reference for steady-state bias detection in step S3, flow fusion in step S4, and turbidity compensation in step S5. S2.3.1: The first-order low-pass filter is: the current liquid level reference flow rate is equal to the filter coefficient multiplied by the current instantaneous actual water production flow rate, plus one minus the filter coefficient multiplied by the liquid level reference flow rate at the previous moment, and the filter coefficient takes a value between zero and one. S2.3.2: The periodic reverse water intake in the permeate pipeline due to timed permeate backwashing is gated and excluded. During this period, the liquid level reference flow rate is not updated, so that the liquid level reference flow rate only reflects the liquid level change caused by membrane permeate. S3.1: Within the preset second sliding window, calculate the coefficient of variation of the original reading of the electromagnetic flowmeter as an indication of the high-frequency fluctuation dimension; S3.1.1: The coefficient of variation is the ratio of the standard deviation of the original readings of the electromagnetic flowmeter within the second sliding window to its mean. When the mean is zero, the coefficient of variation is set to zero. S3.2: Within the preset third sliding window, calculate the average value of the difference between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, and use it as an indication of the steady-state bias dimension. The duration of the third sliding window is longer than that of the second sliding window. S3.2.1: The steady-state bias is used to characterize the persistent system offset of the original reading relative to the level reference in order to capture low-amplitude but constant-direction bubble low-reading interference. S3.3: When the coefficient of variation is greater than the preset fluctuation threshold, or the absolute value of the steady-state bias is greater than the preset bias threshold, the bubble interference flag is set to true; otherwise, it is set to false. S3.3.1: The initial values ​​of the preset fluctuation threshold and the preset bias threshold are determined by the mean of the corresponding indicators during the bubble-free stable operation period plus three times the standard deviation; S3.4: Output the bubble interference flag to steps S4, S5, S7 and S9 as a common state criterion for each step; S3.4.1: The bubble interference indicator is derived by combining the logical OR operation of the high-frequency fluctuation dimension and the steady-state bias dimension, so that both intermittent bubbles and continuous bias bubbles can be detected. S4.1: Within the preset fourth sliding window, the proportion of sampling points with the bubble interference flag set to true is counted out of the total number of sampling points in that window, and this proportion is used as the bubble time percentage. S4.2: Calculate the dynamic confidence weight of the original reading of the electromagnetic flowmeter based on the proportion of bubble time. The dynamic confidence weight decreases as the proportion of bubble time increases and is limited to not being lower than the preset minimum weight. S4.2.1: The dynamic confidence weight is the larger of the preset minimum weight and one minus the decay coefficient multiplied by the bubble time ratio, and the decay coefficient is not less than one; S4.2.2: The minimum weight is preset to be greater than zero so that some of the original readings are retained for monitoring even when bubbles persist; S4.3: The original reading of the electromagnetic flowmeter and the liquid level reference flow rate are weighted and summed using dynamic confidence weights and their complements to obtain the fused flow rate; S4.3.1: In the weighted summation, the weight of the liquid level reference flow rate is one minus the dynamic confidence weight; S4.4: The fused flow rate is sent to the constant flux controller as feedback for the adjustment of the suction pump speed, replacing the original reading of the electromagnetic flow meter; S4.4.1: The higher the bubble time ratio, the more the fused flow rate is biased towards the liquid level reference flow rate, thereby cutting off the path of excessive suction pump speed caused by low bubble read feedback; S5.1: Divide the difference between the liquid level reference flow rate and the original reading of the electromagnetic flow meter by the liquid level reference flow rate, and take the larger of the difference and zero to construct the bubble density index; S5.2: Subtract the product of the compensation coefficient and the bubble density index from the original reading of the online turbidity meter, and then subtract the turbidity compensation baseline to obtain the compensated turbidity; S5.2.1: The compensation coefficient is a positive value, determined by offline calibration or initial bubble injection test; S5.2.2: Turbidity compensation baseline characterizes the turbidity baseline shift when there are no bubbles, and is periodically updated by step S9; S5.3: The compensated turbidity is used for auxiliary diagnosis and trend recording of membrane fouling, and is not used as a criterion for triggering chemical cleaning alone; S5.3.1: When the bubble density index is approximately zero, the compensated turbidity retains only the baseline offset correction; S6.1: Divide the fused flow rate by the total membrane area to obtain the instantaneous membrane flux; S6.1.1: The total membrane area is the sum of the effective filtration areas of the membrane modules, and is taken as a constant; S6.2: Divide the instantaneous membrane flux by the absolute value of the transmembrane pressure difference to obtain the instantaneous permeability; S6.2.1: When calculating instantaneous permeability, the absolute value of the transmembrane pressure difference should be used in the calculation; S6.3: Perform a first-order low-pass filter on the instantaneous permeability to obtain the filtered permeability that reflects the long-term trend of membrane fouling, and output it to step S7 as the basis for attenuation judgment. S6.3.1: The first-order low-pass filter is formed by multiplying the current filter penetration by the current instantaneous penetration, adding one and subtracting the filter coefficient multiplied by the previous moment's filter penetration. The filter coefficient takes a value between zero and one, and is used to filter out measurement noise and retain the long-term attenuation trend. S7.1: Determine whether the filter penetration is continuously lower than the preset penetration lower limit within the most recent consecutive preset number of sampling periods, and whether the absolute value of its decreasing slope is greater than the preset slope threshold. If both conditions are met, the true penetration attenuation condition is deemed to be met. S7.1.1: The descent slope is obtained by performing least-squares linear fitting on the most recent preset number of consecutive filtered penetration values ​​in chronological order. A significant descent is determined when the slope is negative and the absolute value is greater than the preset slope threshold. S7.2: Determine whether the percentage of time during which the bubble interference flag is true within the same evaluation period is lower than the preset percentage upper limit. If so, the bubble interference exclusion condition is met. S7.2.1: The time percentage in the bubble interference exclusion condition is the ratio of the number of sampling points with the bubble interference flag being true to the total number of sampling points during the evaluation period; S7.3: Chemical backwashing or in-situ chemical cleaning is triggered only when the actual permeability decay condition and the bubble interference elimination condition are met simultaneously. S7.3.1: When starting chemical enhanced backwashing or in-situ chemical cleaning, use the preset standard reagent concentration and contact time; S7.4: When the actual permeability decay condition is met but the bubble interference elimination condition is not met, chemical cleaning is temporarily suspended, and only physical backwashing and air wiping are maintained, and a bubble interference warning is issued. S7.4.1: When chemical cleaning is temporarily suspended, record the suspension event and the corresponding percentage of bubble interference for operation and maintenance analysis; S8.1: Limit the absolute value of the difference between the target speed of the suction pump calculated by the constant flux controller and the current actual speed to within the preset maximum step size; S8.1.1: When the difference between the target speed of the suction pump and the current actual speed exceeds the preset maximum step size, the pump will gradually approach the target speed by the maximum step size. S8.2: Accumulate the absolute value of each speed adjustment change within a preset rolling time. When the accumulated value reaches the preset upper limit, the speed will no longer be increased. S8.3: Integrate the effective chlorine concentration on the membrane surface over time to obtain the cumulative chlorine exposure; S8.3.1: The effective chlorine concentration on the membrane surface is approximated by the online residual chlorine detection value in the chemical cleaning circuit; S8.4: Before each chemical cleaning is started, calculate the increase in cumulative chlorine exposure over a preset time period from the current time. If the increase is greater than the preset safety threshold, forcibly prohibit the current and subsequent chemical cleaning and output a cumulative chlorine exposure exceeding the limit alarm until manually unlocked. S8.4.1: The preset safety threshold is the upper limit of cumulative chlorine exposure recommended by the membrane manufacturer for the corresponding preset time period; S8.4.2: After chemical cleaning is forcibly prohibited, only continuous air wiping and timed physical backwashing are retained until the membrane condition is assessed on-site by authorized personnel and the lock is manually released. S9.1: Monitor the bubble interference indicator. When the duration of its continuous false value reaches the preset calibration window duration, trigger a parameter self-calibration. S9.2: Update the turbidity compensation baseline within the calibration window; S9.2.1: When there is an offline laboratory turbidity value in the calibration window, the updated turbidity compensation baseline is obtained by adding the learning rate to the current turbidity compensation baseline and multiplying it by the difference between the offline laboratory turbidity value and the average original reading of the online turbidity meter in the window. S9.2.2: When there is no laboratory offline turbidity value in the calibration window, the current turbidity compensation baseline is exponentially smoothed with the mean of the original online turbidity meter readings in the window to obtain the updated turbidity compensation baseline; S9.3: Update the preset fluctuation threshold and preset bias threshold within the calibration window; S9.3.1: The preset fluctuation threshold is updated exponentially by adding three times the standard deviation to the mean of the coefficient of variation within the calibration window; S9.3.2: The preset bias threshold is updated exponentially by adding three times the standard deviation to the mean of the absolute values ​​of the steady-state bias within the calibration window; S9.4: Return the updated turbidity compensation baseline to step S5, and return the updated fluctuation threshold and bias threshold to step S3 to form an adaptive closed loop for the parameters. S9.4.1: The learning rate in all the above updates is between zero and one to ensure that the parameters drift smoothly as the pipeline characteristics and water quality change slowly.

[0029] In summary, S2 uses the water level in product water tank 6 to calculate the flow rate. This step introduces two new problems. First, the water level changes very little per unit time, and differentiating the water level to calculate the rate of change amplifies the measurement noise of the water level gauge, causing fluctuations in the calculated reference flow rate. Second, periodic backwashing draws water from product water tank 6 periodically, so the water level change no longer only reflects the membrane permeate flow rate. If these two problems are ignored, the reference flow rate given by S2 is not clean, and all subsequent comparisons and fusions based on it will be incorrect. The solution is to use S2's internal low-pass filtering and backwashing period gating to remove errors. S3 uses the average deviation over a period of time rather than the instantaneous value, and S4 only increases the use of the reference flow rate when the proportion of bubbles is high. This method of taking the average and weighting by proportion reduces the impact of residual fluctuations in the reference flow rate, which means that S3 and S4 jointly absorb the noise introduced by S2.

[0030] S3 adds a steady-state bias dimension, which might mistake a slow decrease in permeate flow caused by actual membrane aging as a steady-state low caused by air bubbles. Because when a membrane naturally fouls and ages, the actual permeate flow will gradually decrease at the same pump speed, and a continuous deviation will appear between the flow meter reading and the reference flow rate. S3 alone cannot distinguish between air bubbles and actual membrane aging. If only S3 is used, it might be mistakenly interpreted as air bubble interference when the membrane actually needs cleaning, thus delaying cleaning and neglecting to clean the membrane that should be cleaned. S6 calculates permeability, i.e., the ratio of permeate capacity to pressure difference. Actual membrane aging will cause a real decrease in permeability, while false air bubble deviations will not change the actual permeability. S7 further requires both a real decrease in permeability and the absence of dominant air bubbles to be met before taking action. Therefore, S3 is responsible for marking deviations, S6 for judging whether the deviation is due to actual fouling, and S7 for the final decision. These three steps combined can distinguish between false air bubble signals and actual membrane aging, avoiding the possibility of neglecting cleaning when S3 exists alone.

[0031] In addition, S4 changes the pump feedback from the flow meter reading to the fused flow rate. This incorporates the water level back-calculation reference from S2 into the fused flow rate. However, water level back-calculation naturally has a lag. When the proportion of air bubbles is high and the weight is heavily biased towards the reference flow rate, the feedback sent to the constant flow pump will be slower. The pump's response may be delayed or even fluctuate slightly. If only S4 is used, the pump may become unstable due to the feedback lag. Therefore, S8 sets upper limits on the magnitude of each pump speed adjustment and the cumulative adjustment over a period of time. Even if the feedback from S4 is delayed or fluctuates temporarily, the pump can only adjust slowly in small steps and will not oscillate violently. This keeps the pump instability caused by the feedback lag introduced by S4 within a safe range.

[0032] To verify the protective effect of this device on the membrane module, six parallel membrane tanks 5 with identical water quality and quantity, influent load, membrane brand and batch, and aeration, scrubbing and timed backwashing conditions were selected from this wastewater treatment device. Six control methods were applied to each tank as a comparative example, and the tanks were continuously operated for about 90 days, with a focus on the peak influent period in summer.

[0033] Example 1 is the original control group, which is operated only according to traditional constant flux control and routine chemical cleaning automatic judgment, without any bubble treatment; Example 2 only adds the back-calculated flow rate from the liquid level of the product water tank 6 as a reference, but does not participate in the control; only the deviation is recorded. Example 3 uses flow fusion to correct the suction pump speed regulation based on Example 2, but chemical cleaning is still triggered according to the original criteria; Example 4 only uses a two-condition release for chemical cleaning, that is, chemical addition is only allowed when the water flow capacity is actually reduced and the bubble interference is not serious, but the pump speed is not adjusted. Example 5 only activates the cumulative chlorine exposure limit mandatory discontinuation as a line of defense; the rest remain the same. Example 6 is the complete set of this method, that is, the flow fusion, dual-condition release, chlorine exposure limit and bubble-free period self-calibration are all enabled.

[0034] Six groups of equipment were used to record daily and synchronously the deviation of the flow meter on the product water side from the actual product water volume, the average daily speed of the suction pump, the daily and cumulative dosage of sodium hypochlorite, and to measure the membrane fiber breakage elongation, the logarithmic removal rate of indicator bacteria, the membrane contact angle and the membrane pore dispersion at the beginning and end of the process. At the same time, the total number of bacteria in the product water was monitored throughout the process to see if it exceeded the standard.

[0035] The monitoring results are as follows: like Figure 2 As shown in the figure, the horizontal axis represents the number of operating days, and the vertical axis represents the cumulative sodium hypochlorite dosage. The six curves are distinguished by their line type and endpoint markings: Example 1 is the thickest solid line with the steepest slope and a continuous upward curve, indicating that it was misled by the false bubble signal and the dosage was continuously increased, resulting in a steady increase in the cumulative dosage; Example 3 is a dotted line, indicating that the frequency of dosing was slightly reduced due to the correction of pump speed and the mitigation of the false decrease in water flow capacity, with a moderate slope; Example 4 is a short dashed line, indicating that the curve slowed down significantly in the middle and later stages due to the double-condition interception of dosing; Example 5 is a long dashed line, which was close to the control in the early stage but was forcibly cut off after reaching the upper limit of chlorine exposure, resulting in a horizontal step; Example 2 is a thin solid line with hollow circle markings, indicating that it was only recorded and not intervened, and its curve almost overlapped with the control; Example 6 is a medium-thick solid line with solid square markings, indicating that it had the smallest and most stable slope and was close to the bottom throughout. As shown in the figure, all treatment groups involved in the control were able to reduce the cumulative dosage, with the complete group showing the slowest growth, indicating that the device reduces unnecessary dosage through multiple stages.

[0036] like Figure 3 As shown, in Example 1, both columns were the shortest, reflecting that the membrane had been washed with excessive reagent to the point of significant embrittlement and a marked decrease in retention capacity. Example 2 was similar, indicating that simply observing the membrane without intervention was ineffective. The column heights in Examples 3 and 4 were moderately high, indicating that adjusting the pump speed or intercepting the dosing alone could mitigate the damage, but not completely. In Example 5, the column height significantly increased due to the forced capping of the total chlorine content, showing that this protective barrier directly safeguarded the membrane material. In Example 6, both columns were the tallest and closest to the factory standard, indicating that the membrane's mechanical strength and filtration accuracy were best preserved through the combined effect of multiple processes. Therefore, the degree of membrane performance retention corresponds consistently to the degree of inhibition of dosing in each group, with the complete group providing the most comprehensive protection.

[0037] like Figure 4As shown, the strip in Example 1 is the shortest, exceeding the standard in the early middle section, reflecting the decrease in filtration accuracy and the earliest microbial penetration after the membrane was washed and damaged. Example 2 follows closely behind, also exceeding the standard relatively early. The strips in Examples 3 and 4 are significantly longer, with the exceeding of the standard delayed to the later stages. The strip in Example 5 is even longer, with only a slight exceeding of the standard near the end. The strip in Example 6 runs through the entire length and ends with a hollow square, indicating that the produced water remained qualified and did not exceed the standard throughout the entire observation period. It can be clearly seen that the more completely this device is used, the longer the qualified state of the produced water is maintained, indicating that this device protects the membrane from accidental washing damage and ultimately safeguards the microbial safety of the effluent.

[0038] The working principle is as follows: When the device is running, the mud-water mixture in aerobic tank 4 flows into membrane tank 5. The suction pump draws out clean water by creating a vacuum inside the membrane fibers. The clean water then enters the product water tank 6 after passing through the electromagnetic flow meter and online turbidity meter on the product water pipe. The problem lies in this vacuum suction section. Because the water releases the dissolved air under negative pressure, it forms many tiny bubbles that mix with the clean water and flow through these two instruments. This causes the flow meter reading to be consistently lower by about 2% and the turbidity reading to be consistently higher by a few tenths of a degree. This deviation is very small and coincides with the increase in influent volume in summer. The increased chemical consumption is mistaken for a normal phenomenon of increased water volume, so no one noticed it for a long time. The original controller mistakenly thought that the membrane was getting dirtier and increased the suction pump while frequently adding chemicals for cleaning. In 90 days, the membrane was damaged.

[0039] To prevent this misjudgment at its source, this device first synchronously retrieves signals such as liquid level, flow rate, turbidity, pump speed, and transmembrane pressure difference at a fixed frequency during the data acquisition phase and performs a deburring process to ensure that the data used later is clean and accurate. Then, instead of simply relying on the flow meter, it monitors the water level in the product water tank 6 and calculates the actual amount of clean water entering the tank during that period by multiplying the height of the water level rise over a certain period by the cross-sectional area of ​​the tank. Since water level changes only relate to the actual product water volume, the presence or absence of air bubbles in the pipeline does not affect the amount of water stored in the tank. This provides a reliable flow rate reference that is not misled by air bubbles. The device then processes the flow... The flow meter reading is compared with this reference in two ways. First, we check whether the flow meter reading fluctuates abnormally. Second, and more importantly, we check whether it is consistently lower than the reference value over a long period of time. It is this latter, consistently lower value that can best detect the tiny false signals that were originally hidden within the normal range. Once air bubble interference is detected, the device automatically adjusts the trust ratio of the two flow rates according to the severity of the interference. The more air bubbles there are, the more the flow rate calculated from the water level is used to direct the suction pump. In this way, the pump will not be fooled by the air bubbles into thinking the reading is too low and will speed up excessively. This avoids the situation where the pump speed is too high and the filter cake layer on the membrane surface is compressed more and more, which will actually accelerate the clogging.

[0040] At the same time, the turbidity reading is adjusted to remove the artificially high value caused by bubble scattering. However, this compensated turbidity is only used to assist in the judgment and not to determine whether to add chemicals. Next, the device uses a reliable flow rate to calculate the actual water flow capacity of the membrane and performs a smoothing process to see the long-term trend. Only when the water flow capacity is indeed continuously decreasing and decreasing significantly, and the bubble interference is not serious during this period, is chemical cleaning allowed to be started. Otherwise, only aeration scrubbing and clean water backwashing are performed, thus avoiding the use of false bubble signals to trigger chemical cleaning. Further down the line, a hard defense is set up. On the one hand, the device limits the speed adjustment range of the suction pump each time and the cumulative adjustment amount within one hour to prevent excessive speed increase. On the other hand, it continuously accumulates the total amount of sodium hypochlorite that the membrane has recently come into contact with, including the effective chlorine added during enhanced backwashing and in-situ cleaning. Once this cumulative amount exceeds the safety limit given by the membrane manufacturer, chemical dosing is forcibly stopped and an alarm is triggered. It can only be unlocked after manual confirmation. This ensures that even if all the previous judgments fail, the membrane will not be repeatedly eroded by excessive chemicals to the point of breakage.

[0041] Finally, the device will automatically calibrate the turbidity benchmark and the threshold value for detecting bubbles during clean periods when there are no bubbles. This ensures that it can keep up with pump wear and slow changes in water quality and remain sensitive. Through this step-by-step process, the slight deviation caused by bubbles is identified and corrected before entering the control judgment. The two actions that could damage the membrane, namely pump speed and chemical dosing, are both constrained within a safe range. The process of damaging the membrane, which would have continued to grow stronger without reporting any hardware failure, is cut off at the root.

[0042] Furthermore, conventional wastewater treatment plants often suffer from a lack of calibration for online flow meters, leading to undetected reading drift. Conventional MBRs typically only have one permeate flow meter, relying solely on its reading. However, if the probe becomes scaled, aged, contains entrained gas, or the pipe section is not fully filled, the flow meter will slowly drift. Without any independent reference point, the drift can remain dormant for a long time. In contrast, this device uses the 6 water levels in the permeate tank to calculate an independent, real flow rate as a reference, effectively providing the flow meter with a permanent online calibration benchmark. Any reading drift from any source will be detected as long as the flow meter and this reference do not align consistently. This solves the problem of a single sensor being unable to verify its accuracy and drift going undetected; air bubbles are merely one contributing factor to the drift.

[0043] Furthermore, conventional wastewater treatment and purification devices rely entirely on automatic determination of a single pollution indicator for chemical cleaning, which can easily lead to over-cleaning. The conventional practice often involves automatic chemical dosing as soon as permeability falls below a threshold or differential pressure reaches a certain point. If that indicator itself is distorted by any disturbance, the device will add chemicals, resulting in excessively frequent chemical cleaning and unnecessary depletion of membrane lifespan in the long run. This device adds a release condition to chemical cleaning: confirmation that the pollution is genuine and the current judgment is reliable. This changes the dosing process from washing based on a single indicator reaching a certain point to washing only after reliable confirmation, thus avoiding the inherent tendency for over-cleaning.

[0044] Meanwhile, conventional wastewater treatment and purification devices lack strict constraints on the total amount of chemicals and suffer from cumulative chemical damage to the membrane. Conventional wastewater treatment and purification devices generally only care about the concentration and duration of a single cleaning, without monitoring how much chlorine the membrane has been exposed to recently. Therefore, even if each cleaning is compliant, the long-term accumulation may quietly exceed the membrane material's tolerance without anyone triggering an alarm. However, this device continuously accumulates the total amount of available chlorine and sets a safety upper limit, with mandatory shutdown if the limit is exceeded. This is equivalent to putting a master switch on the membrane's chemical resistance lifespan. This solves the problem of chronic membrane damage caused by only looking at single cleanings and not cumulative effects. Whether the over-limit is caused by misjudgment or habitual over-frequent maintenance, it can be contained.

[0045] Furthermore, conventional constant-flux wastewater treatment and purification devices suffer from the problem of the suction pump blindly increasing its speed and accelerating membrane fouling when the flow feedback is disturbed. Conventional constant-flux control only recognizes the flow meter feedback. Once the feedback is too low, the pump speeds up to compensate, which compresses the filter cake on the membrane surface and causes actual fouling to occur even faster. This is a weakness of constant-flux control itself. This device changes the pump feedback to a fused flow rate that is not affected by pipeline disturbances and limits the pump speed adjustment range, so that the pump will not over-excite itself due to any feedback distortion.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An integrated self-cleaning wastewater purification and treatment device, characterized in that, The membrane tank (5) includes a tank body, a membrane module submerged and installed in the tank body, an aeration pipe located directly below the membrane module and connected to a blower via an air supply pipe, a water production system connected to the water production port of the membrane module, a backwash pump connected to the water production tank (6), a dosing metering pump connected to the water production system, online instruments, and a programmable logic controller. The water production system includes a water production manifold, a water production vacuum suction pipeline, a suction pump, and a water production valve connected in sequence. The water production vacuum suction pipeline has an electromagnetic flow meter and an online turbidity meter connected in series on the suction side of the suction pump, and a pressure transmitter is provided on the outlet side of the suction pump. The outlet of the water production valve is connected to the inlet of the water production tank (6). The inlet of the backwash pump is connected to the water production tank (6), and the outlet is connected to the water production vacuum suction pipeline via the backwash valve. The dosing metering pump is connected to the water production system via the dosing pipeline, and an online residual chlorine detector is provided on its circuit. The speed signals of each online instrument and the suction pump are connected to the analog input module of the programmable logic controller. The analog output module of the programmable logic controller is connected to the frequency converter of the suction pump, and the digital output module is connected to the start and stop control terminals of each pump and each valve. After synchronously collecting and filtering the signals from each channel, the programmable logic controller calculates the actual production water flow rate, which is not affected by air bubbles in the pipeline, based on the water level change in the production water tank (6). It then identifies and corrects the deviation caused by air bubbles in the production water flow rate and turbidity reading. The actual water flow capacity of the membrane is then calculated based on the corrected flow rate. The cleaning is only allowed when the water flow capacity has indeed decreased and the air bubble interference is not severe. At the same time, the speed adjustment range of the suction pump is limited, and the dosing is forcibly stopped when the cumulative dosing reaches the safety limit. The threshold for identifying air bubbles and the turbidity benchmark are automatically calibrated during the air bubble period.

2. The integrated self-cleaning wastewater purification and treatment device according to claim 1, characterized in that, After synchronously collecting and filtering the signals from each channel, the programmable logic controller calculates the actual permeate flow rate, which is not affected by air bubbles in the pipeline, based on the water level change in the permeate tank (6). It then identifies and corrects the deviation caused by air bubbles in the permeate flow rate and turbidity reading. The actual water flow capacity of the membrane is then calculated based on the corrected flow rate. Chemical cleaning is only allowed when the water flow capacity has indeed decreased and the air bubble interference is not severe. At the same time, the speed range of the suction pump is limited, and chemical cleaning is forcibly stopped when the cumulative chemical dosage reaches the safety limit. The threshold for identifying air bubbles and the turbidity benchmark are automatically calibrated during the air bubble-free period. The specific steps include the following: S1 synchronously collects the liquid level of the product water tank (6), the original reading of the electromagnetic flow meter, the original reading of the online turbidity meter, the speed of the suction pump and the transmembrane pressure difference, and performs filtering and preprocessing on each signal; S2 calculates the liquid level change slope based on the liquid level and combines it with the horizontal cross-sectional area of ​​the product water tank (6) to obtain the liquid level reference flow rate that is not affected by air bubbles in the product water pipeline. S3 uses the high-frequency fluctuation of the electromagnetic flowmeter's original reading and the steady-state bias between the electromagnetic flowmeter's original reading and the liquid level reference flow rate as two dimensions to detect bubble interference and comprehensively determine the bubble interference indicator. Based on the bubble interference indicator, S4 dynamically and confidently weights and fuses the original reading of the electromagnetic flowmeter with the liquid level reference flow to obtain the fused flow rate, and uses the fused flow rate as the feedback input for the adjustment of the suction pump speed in constant flux control. S5 performs bubble scattering compensation on the original reading of the online turbidity meter based on the relative deviation between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, and obtains the compensated turbidity for auxiliary diagnosis. S6 converts the fused flow rate into instantaneous membrane flux, then combines it with the transmembrane pressure difference to calculate instantaneous permeability, and finally obtains filtered permeability reflecting the membrane fouling trend through low-pass filtering; S7 triggers enhanced chemical backwashing or in-situ chemical cleaning when the filter penetration meets the true attenuation condition and the proportion of time with the bubble interference flag being true within the same evaluation period is lower than the preset proportion limit; otherwise, only physical backwashing and air wiping are maintained. S8 applies step size and cumulative change limits to the adjustment of the suction pump speed and monitors the cumulative chlorine exposure. When the increase in chlorine exposure exceeds the preset safety threshold within a preset time period, chemical cleaning is forcibly prohibited and an alarm is triggered. When the bubble interference flag remains false for a period of time up to the preset calibration window duration, the S9 uses the signal within that window to perform online adaptive updates to the turbidity compensation baseline and the bubble interference detection threshold.

3. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, The S1 synchronously collects the liquid level of the product water tank (6), the original reading of the electromagnetic flowmeter, the original reading of the online turbidity meter, the speed of the suction pump, and the transmembrane pressure difference, and performs filtering and preprocessing on each signal, specifically including the following steps: S1.1: At a sampling frequency of not less than 1 Hz, synchronously collect the liquid level of the product water tank (6), the original reading of the electromagnetic flowmeter, the original reading of the online turbidity meter, the speed of the suction pump and the transmembrane pressure difference, and assign a unified timestamp to each signal; S1.2: Perform median filtering on each signal in real time to remove isolated spike-type outliers; S1.3: Store the filtered signals into a circular buffer of a preset length for use in subsequent sliding window calculations in steps S2 to S9.

4. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, The S2 method calculates the liquid level change slope based on the liquid level and combines it with the horizontal cross-sectional area of ​​the product water tank (6) to obtain the liquid level reference flow rate that is not affected by air bubbles in the product water pipeline. The specific steps include the following: S2.1: Within the preset first sliding window, perform linear fitting on the liquid level data sequence of the water production tank (6) and obtain the slope of the liquid level change over time as the liquid level change slope; S2.2: Multiply the slope of the liquid level change by the horizontal cross-sectional area of ​​the water production tank (6) to obtain the instantaneous actual water production flow rate; S2.3: Perform a first-order low-pass filter on the instantaneous actual product water flow rate to obtain a liquid level reference flow rate that is not affected by air bubbles in the product water pipeline, and use it as a common reference for steady-state bias detection in step S3, flow fusion in step S4, and turbidity compensation in step S5.

5. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, S3 uses two dimensions—the high-frequency fluctuation of the electromagnetic flowmeter's original reading and the steady-state offset between the electromagnetic flowmeter's original reading and the liquid level reference flow rate—to detect bubble interference and comprehensively determine the bubble interference indicator. Specifically, it includes the following steps: S3.1: Within the preset second sliding window, calculate the coefficient of variation of the original reading of the electromagnetic flowmeter as an indication of the high-frequency fluctuation dimension; S3.2: Within the preset third sliding window, calculate the average value of the difference between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, and use it as an indication of the steady-state bias dimension. The duration of the third sliding window is longer than that of the second sliding window. S3.3: When the coefficient of variation is greater than the preset fluctuation threshold, or the absolute value of the steady-state bias is greater than the preset bias threshold, the bubble interference flag is set to true; otherwise, it is set to false. S3.4: Output the bubble interference flag to steps S4, S5, S7 and S9 as a common state criterion for each step.

6. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, S4, based on the bubble interference indicator, dynamically and confidently weights and fuses the original reading of the electromagnetic flowmeter with the liquid level reference flow rate to obtain the fused flow rate. This fused flow rate is then used as the feedback input for adjusting the suction pump speed in constant flux control. Specifically, the steps include: S4.1: Within the preset fourth sliding window, the proportion of sampling points with the bubble interference flag set to true is counted out of the total number of sampling points in that window, and this proportion is used as the bubble time percentage. S4.2: Calculate the dynamic confidence weight of the original reading of the electromagnetic flowmeter based on the proportion of bubble time. The dynamic confidence weight decreases as the proportion of bubble time increases and is limited to not being lower than the preset minimum weight. S4.3: The original reading of the electromagnetic flowmeter and the liquid level reference flow rate are weighted and summed using dynamic confidence weights and their complements to obtain the fused flow rate; S4.4: The fused flow rate is sent to the constant flux controller as feedback for the adjustment of the suction pump speed, replacing the original reading of the electromagnetic flow meter.

7. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, Step S5, based on the relative deviation between the original reading of the electromagnetic flowmeter and the liquid level reference flow rate, performs bubble scattering compensation on the original reading of the online turbidity meter to obtain the compensated turbidity for auxiliary diagnosis. Specifically, this includes the following steps: S5.1: Divide the difference between the liquid level reference flow rate and the original reading of the electromagnetic flow meter by the liquid level reference flow rate, and take the larger of the difference and zero to construct the bubble density index; S5.2: Subtract the product of the compensation coefficient and the bubble density index from the original reading of the online turbidity meter, and then subtract the turbidity compensation baseline to obtain the compensated turbidity; S5.3: The compensated turbidity is used for auxiliary diagnosis and trend recording of membrane fouling, and is not used as a criterion for triggering chemical cleaning.

8. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, S6 converts the fused flow rate into instantaneous membrane flux, then calculates the instantaneous permeability by combining it with the transmembrane pressure difference, and obtains the filtered permeability reflecting the membrane fouling trend through low-pass filtering. Specifically, it includes the following steps: S6.1: Divide the fused flow rate by the total membrane area to obtain the instantaneous membrane flux; S6.2: Divide the instantaneous membrane flux by the absolute value of the transmembrane pressure difference to obtain the instantaneous permeability; S6.3: Perform a first-order low-pass filter on the instantaneous permeability to obtain the filtered permeability that reflects the long-term trend of membrane fouling, and output it to step S7 as the basis for attenuation judgment.

9. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, When the filter penetration meets the true attenuation condition and the proportion of time during which the bubble interference flag is true is lower than the preset upper limit, step S7 triggers enhanced chemical backwashing or in-situ chemical cleaning; otherwise, only physical backwashing and air wiping are maintained. Specifically, the steps include the following: S7.1: Determine whether the filter penetration is continuously lower than the preset penetration lower limit within the most recent consecutive preset number of sampling periods, and whether the absolute value of its decreasing slope is greater than the preset slope threshold. If both conditions are met, the true penetration attenuation condition is deemed to be met. S7.2: Determine whether the percentage of time during which the bubble interference flag is true within the same evaluation period is lower than the preset percentage upper limit. If so, the bubble interference exclusion condition is met. S7.3: Chemical backwashing or in-situ chemical cleaning is triggered only when the actual permeability decay condition and the bubble interference elimination condition are met simultaneously. S7.4: When the actual permeability decay condition is met but the bubble interference elimination condition is not met, chemical cleaning is temporarily suspended, and only physical backwashing and air wiping are maintained, and a bubble interference warning is issued.

10. The integrated self-cleaning wastewater purification and treatment device according to claim 2, characterized in that, The S8 applies step size and cumulative change limits to the adjustment of the suction pump speed and monitors the cumulative chlorine exposure. When the increase exceeds a preset safety threshold within a preset time period, chemical cleaning is forcibly prohibited and an alarm is triggered. Specifically, the steps include the following: S8.1: Limit the absolute value of the difference between the target speed of the suction pump calculated by the constant flux controller and the current actual speed to within the preset maximum step size; S8.2: Accumulate the absolute value of each speed adjustment change within a preset rolling time. When the accumulated value reaches the preset upper limit, the speed will no longer be increased. S8.3: Integrate the effective chlorine concentration on the membrane surface over time to obtain the cumulative chlorine exposure; S8.4: Before each chemical cleaning is started, calculate the increase in cumulative chlorine exposure over a preset time period from the current time. If the increase exceeds the preset safety threshold, forcibly prohibit the current and subsequent chemical cleaning and output a cumulative chlorine exposure exceeding the limit alarm until manually unlocked.

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