An integrated system and method for treating electroplating wastewater

Abstract

This invention discloses an integrated system and method for treating electroplating wastewater. The system comprises five modules: pretreatment with different types of wastewater, complex breaking, multi-stage membrane separation and concentration, evaporation and crystallization recovery, and central control. The pretreatment module treats wastewater from different plating processes and outputs a first water quality monitoring signal; the complex breaking module receives wastewater and control signals, and electrochemically breaks down the complexes; the membrane separation module treats the complex-broken wastewater, producing a concentrated solution, permeate, and a second membrane state monitoring signal; the evaporation and crystallization module treats the concentrated solution, recovering crystalline salts and distilled water; and the central control module receives two types of monitoring signals and generates a complex breaking current and a membrane maintenance control signal. This invention solves the problems of incomplete separation, low complex breaking efficiency, severe membrane fouling, and low resource recovery rate in electroplating wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to an integrated system and method for treating comprehensive electroplating wastewater. Background Technology

[0002] Wastewater discharged during electroplating production is complex, typically containing heavy metals such as cyanide, hexavalent chromium, nickel, and copper, as well as various organic complexing agents like citric acid, tartaric acid, and EDTA. These pollutants are highly toxic and poorly biodegradable; direct discharge without effective treatment can cause serious harm to the aquatic environment and human health. With increasingly stringent environmental regulations, current emission standards are continuously tightening limits on heavy metal concentrations and imposing mandatory requirements on wastewater reuse rates, posing greater technical challenges to electroplating wastewater treatment. Traditional chemical precipitation methods use large amounts of alkali and flocculants to precipitate heavy metals as hydroxides or sulfides. While simple to operate, this method generates large amounts of heavy metal-containing sludge and has limited effectiveness in removing complexed heavy metals, often requiring pretreatment to break down the complexes. Common methods for breaking down complexes include chemical oxidation and electrochemical oxidation. Chemical oxidation requires continuous addition of oxidants, resulting in high operating costs and a high risk of introducing secondary pollution. Membrane separation technologies such as ultrafiltration, nanofiltration, and reverse osmosis can achieve deep purification and water reuse. However, residual complexed heavy metals and organic matter in wastewater easily form a fouling layer on the membrane surface, leading to decreased membrane flux, increased operating pressure, and the need for frequent chemical cleaning. This shortens the lifespan of membrane elements and increases operating and maintenance costs. Some existing integrated processes for electroplating wastewater treatment simply combine units such as complex breaking, membrane separation, and evaporation crystallization. However, these units lack a coordinated control mechanism based on real-time dynamic water quality feedback. Complex breaking parameters are often set manually based on experience, making them unable to adapt to fluctuations in incoming water quality. Membrane system cleaning and maintenance often adopt a passive mode with fixed time intervals, failing to provide preventative maintenance based on the actual development of membrane fouling. Furthermore, the feed concentration and operating parameters of the evaporation crystallization process are not linked to the upstream membrane concentration effect, resulting in energy waste and insufficient resource recovery. The aforementioned shortcomings result in existing technologies exhibiting problems such as incomplete separation and diversion, low complex-breaking efficiency, poor membrane system operational stability, and low resource recovery rate. There is an urgent need for a comprehensive treatment solution that can achieve separation and diversion pretreatment, dynamic control of the complex-breaking process, online diagnosis and predictive maintenance of membrane fouling, and efficient recovery through evaporation and crystallization. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to provide an integrated system and method for the treatment of electroplating wastewater, which solves the problems of incomplete separation, low complex breaking efficiency, serious membrane fouling and low resource recovery rate in the treatment of electroplating wastewater.

[0004] This invention utilizes a pretreatment module that separates and adjusts the water quality of wastewater from different plating processes, a complex breaking module that dynamically adjusts the current based on online water quality monitoring signals for electrochemical oxidation and complex breaking, a multi-stage membrane separation and concentration module that progressively concentrates the complex-broken wastewater and calculates the membrane fouling index online to trigger backwashing or chemical cleaning, an evaporation and crystallization module that recovers crystalline salts and distilled water, and a central control module that generates complex breaking current control signals and membrane system maintenance control signals based on online signals, enabling all modules to operate collaboratively. This achieves efficient removal of heavy metals and resource recovery under fully automated monitoring.

[0005] This invention provides an integrated system for treating electroplating wastewater, comprising: The separate pretreatment module receives wastewater of different plating types and pretreats it to form the effluent of each wastewater stream and the first online monitoring signal characterizing the water quality parameters of each wastewater stream. The complex breaking module has its inlet end connected to the outlet end of the fractional pretreatment module, and its control end electrically connected to the central control module. It receives the complex breaking current control signal from each stream of wastewater and from the central control module, and performs electrochemical oxidation complex breaking treatment on the wastewater to form complex-broken wastewater. The multi-stage membrane separation and concentration module receives wastewater after complex breaking at its inlet end, and separates and concentrates it through multi-stage membrane units to form concentrated liquid and permeate, and generates a second online monitoring signal characterizing the membrane operating status parameters. The evaporation crystallization and resource recovery module receives concentrated liquid at its feed end, performs evaporation crystallization treatment, and recovers crystallized salt and distilled water. The central control module receives the first online monitoring signal and the second online monitoring signal respectively, generates the complex breaking current control signal and the membrane system maintenance control signal according to the preset control algorithm, and transmits the complex breaking current control signal to the complex breaking module.

[0006] In one embodiment of the present invention, the complex breaking module includes an electrochemical oxidation reactor and an adjustable DC power supply. The electrochemical oxidation reactor is provided with an anode plate and a cathode plate. The anode plate is a titanium-based ruthenium-iridium oxide coated electrode, and the cathode plate is a stainless steel electrode. The control terminal of the adjustable DC power supply is electrically connected to the central control module to receive the complex breaking current control signal. The central control module, based on the wastewater pH value and redox potential value in the first online monitoring signal, calls the current density and water quality parameter mapping relationship pre-stored in its non-volatile memory to determine the output current density corresponding to the current water quality state, and converts the current density into a complex breaking current control signal, which is sent to the adjustable DC power supply through the analog output channel. The mapping relationship is established based on complex breaking tests of different types of wastewater under multiple pH and redox potential combinations, with the lowest current density corresponding to the free metal ion conversion rate meeting the preset index as the standard. The calculation formula for the output current density is as follows: Where J is the dynamic output current density. , , The calibration coefficient for the network breaking test is... , As a reference pH and redox potential, , The value is the real-time monitoring value, and K is the water quality correction constant.

[0007] In one embodiment of the present invention, the central control module is configured with a dynamic complex-breaking current scheduling program. This program periodically performs the following operations at preset configurable time intervals: reading the measured values ​​of pH and redox potential of the current wastewater from a first online monitoring signal; determining a first-dimensional index by placing the measured pH value into one of a preset plurality of pH intervals; determining a second-dimensional index by placing the measured redox potential value into one of a preset plurality of redox potential intervals; searching for the corresponding current density setpoint from a two-dimensional mapping table based on the first and second-dimensional indices. Each entry in the two-dimensional mapping table is an experimentally calibrated current density value that can effectively break the complex within the corresponding water quality interval. The central control module converts the searched current density setpoint into a complex-breaking current control signal. The complex-breaking current control signal is an analog voltage signal or an analog current signal. It drives an adjustable DC power supply to output a DC current corresponding to the setpoint through an analog output interface, thereby dynamically adjusting the current intensity applied between the anode plate and the cathode plate to adapt to fluctuations in wastewater quality.

[0008] In one embodiment of the present invention, the multi-stage membrane separation and concentration module includes an ultrafiltration membrane unit, a nanofiltration membrane unit, a first-stage reverse osmosis membrane unit, a second-stage reverse osmosis membrane unit, and a high-pressure reverse osmosis membrane unit connected in series along the water flow direction. Each membrane unit is equipped with a pressure sensor on both the inlet and outlet sides, and each membrane unit is equipped with a flow sensor on its outlet pipeline. The pressure and flow signals collected in real time by the pressure and flow sensors together constitute a second online monitoring signal. The inlet of the ultrafiltration membrane unit receives wastewater after complex breaking, and the concentrate outlet of the high-pressure reverse osmosis membrane unit is connected to the evaporation, crystallization, and resource recovery module. The outlet water of each membrane unit is collected as product water through the manifold pipeline. The second online monitoring signal is periodically transmitted to the central control module in the form of digital signal frames via a serial communication bus. Each digital signal frame contains at least the sensor address, physical quantity value, and verification information.

[0009] In one embodiment of the present invention, the central control module has a built-in online membrane fouling index calculation program. This program performs the following calculations and decisions for each membrane unit: obtaining the current feed water pressure, product water pressure, and product water flow rate based on the second online monitoring signal; calculating the transmembrane pressure difference as the difference between the feed water pressure and the product water pressure; calculating the normalized permeability as the product water flow rate divided by the product membrane area and the transmembrane pressure difference, where the effective membrane area is a constant pre-stored in the central control module; and calculating the membrane fouling index as the difference between the initial normalized permeability under clean conditions and the current normalized permeability, divided by the initial normalized permeability under clean conditions. In clean conditions, the initial normalized permeability is automatically measured and updated by the central control module under specified standard operating conditions after each membrane element replacement or chemical cleaning operation. When the calculated membrane fouling index exceeds a preset first threshold, the central control module generates a backwash trigger signal as a membrane system maintenance control signal, initiating the backwashing procedure for the corresponding membrane unit. When the membrane fouling index exceeds a preset second threshold and the second threshold is greater than the first threshold, the central control module generates a chemical cleaning prompt signal and issues an alarm through the human-machine interface, reminding the operator to perform chemical cleaning. The formula for calculating the membrane fouling index is as follows: in, To correct the membrane fouling index, The current normalized penetration rate, Let k be the initial normalized permeability, and k be the membrane material attenuation coefficient. The average transmembrane pressure difference is given, and t is the operating time. This is the time correction constant.

[0010] In one embodiment of the present invention, the central control module is further configured with a membrane fouling trend early warning program. This program performs the following operations for each membrane unit: In each membrane fouling index calculation cycle, the newly calculated membrane fouling index is stored in a first-in-first-out (FIFO) circular buffer queue. The length of this queue corresponds to a preset sampling number. The most recent preset sampling number of membrane fouling index values ​​are read from the queue to form a membrane fouling index time series. The average rate of change of this time series within the preset sampling number of cycles is calculated. When the average rate of change exceeds a preset rate threshold, the central control module generates a membrane accelerated fouling early warning signal as part of the membrane system maintenance control signal. A visual early warning indicator and corresponding maintenance operation suggestions are output through the human-machine interface. The maintenance operation suggestions include at least one or more of the following: checking the effluent quality of the pretreatment module, adjusting the membrane system recovery rate setting, or arranging chemical cleaning as soon as possible. The preset sampling number and rate threshold are both configured as adjustable parameters that can be modified through the human-machine interface. The formula for calculating the average rate of change is as follows: in, The weighted average rate of change of the membrane fouling index, where n is the number of samples. Let be the weighting coefficient for the i-th period. , For the membrane fouling index in the i-th and i-1th periods, This is for calculating the cycle duration.

[0011] In one embodiment of the present invention, the evaporation crystallization and resource recovery module includes a mechanical vapor recompression evaporation crystallization device. The mechanical vapor recompression evaporation crystallization device includes a feed preheater, a steam compressor, a crystallizer separator, and a centrifugal dehydrator. The feed inlet of the feed preheater receives the concentrated liquid, and the discharge outlet of the feed preheater is connected to the feed inlet of the crystallizer separator. The secondary steam outlet of the crystallizer separator is pressurized and heated by the steam compressor and then connected back to the heating chamber of the crystallizer separator. The crystal slurry discharge outlet of the crystallizer separator is connected to the feed inlet of the centrifugal dehydrator separator. The centrifugal dehydrator separator performs solid-liquid separation on the crystal slurry to obtain crystalline salt solid and centrifugal mother liquor. The centrifugal mother liquor is returned to the feed side of the crystallizer separator through a reflux pipeline or mixed with the concentrated liquid entering the feed preheater. The condensate generated in the heating chamber of the crystallizer separator is collected as distilled water. A conductivity sensor is installed on the distilled water collection pipeline. The conductivity signal generated by the conductivity sensor is used as part of the second online monitoring signal or as the third online monitoring signal and is connected to the central control module.

[0012] In one embodiment of the present invention, the evaporation crystallization and resource recovery module further includes a distilled water reuse quality control unit. The distilled water reuse quality control unit includes a conductivity sensor, a temperature sensor, and an electric three-way diverter valve installed on the distilled water output main pipe. The conductivity sensor and temperature sensor send the real-time collected conductivity and temperature signals to the central control module. The central control module performs temperature compensation on the conductivity measurement value based on the received temperature signal to obtain a compensated conductivity value. The compensated conductivity value is then compared with a preset upper limit value for the reused water conductivity. When the compensated conductivity value... When the conductivity value is less than or equal to the upper limit, the central control module outputs the first valve position control signal to connect the outlet of the electric three-way diverter valve to the recycled water storage tank. The recycled water storage tank is connected to the electroplating rinsing tank through the recycled water pump. When the compensated conductivity value is greater than the upper limit, the central control module outputs the second valve position control signal to connect the outlet of the electric three-way diverter valve to the regulating tank, sending the unqualified distilled water back to the front end of the system for reprocessing. The central control module also continuously records the compensated conductivity value. When the compensated conductivity value continues to exceed the upper limit within the preset continuous monitoring time, an abnormal alarm signal for the evaporation crystallization system is generated.

[0013] In one embodiment of the present invention, the central control module comprises a programmable logic controller (PLC), a non-volatile data memory, a human-machine interface (HMI), and an industrial Ethernet communication interface. The first and second online monitoring signals are both collected to the PLC in digital frames via an industrial field device communication protocol based on a serial bus. This communication protocol employs a master-slave polling mechanism, with the PLC acting as the master station periodically reading the measurement values ​​of each online sensor. Each digital frame contains a slave address, function code, measurement data, and an error check field. The PLC stores all read online monitoring signals along with their timestamps in a first-in, first-out (FIFO) manner in the non-volatile data memory. The non-volatile data memory retains historical operating data for at least the most recent preset number of hours. The PLC sends the historical operating data in batches to the host monitoring computer via the industrial Ethernet communication interface at a preset upload cycle. The HMI graphically displays the process flow, real-time operating parameters, alarm information, and historical trend curves, and receives parameter configuration commands input by the operator.

[0014] This invention also includes an integrated method for treating electroplating wastewater, comprising: S1: In the separate pretreatment module, wastewater of different plating types is pretreated separately to form effluents of each wastewater stream, and water quality parameters are collected as the first online monitoring signal. S2: The complex breaking module receives each stream of wastewater and receives the complex breaking current control signal generated by the central control module based on the first online monitoring signal, and performs electrochemical oxidation complex breaking treatment to obtain complex broken wastewater; S3: In the multi-stage membrane separation and concentration module, the wastewater after complex breaking is subjected to multi-stage membrane separation and concentration to produce concentrate and permeate, and the membrane operating status parameters are collected as the second online monitoring signal and transmitted to the central control module. S4: The concentrate is evaporated and crystallized in the evaporation crystallization and resource recovery module to recover crystallized salt and distilled water; S5: The central control module receives the first online monitoring signal and the second online monitoring signal, executes the preset control algorithm to generate the complex breaking current control signal and transmits it to the complex breaking module. It also generates the membrane system maintenance control signal and transmits it to the multi-stage membrane separation and concentration module.

[0015] An integrated system and method for treating comprehensive electroplating wastewater collect and adjust the water quality of wastewater from different plating types through a quality-separated and flow-separated pretreatment module. The complex-breaking module dynamically adjusts the current for electrochemical oxidation and complex breaking according to the online monitored water quality signals. The multi-stage membrane separation and concentration module gradually concentrates the wastewater after complex breaking and calculates the membrane fouling index online to trigger backwashing or chemical cleaning. The evaporation crystallization module recovers crystal salts and distilled water. The central control module generates complex-breaking current control signals and membrane system maintenance control signals based on online signals, enabling the coordinated operation of each module, thereby achieving efficient removal of heavy metals and resource recovery under full-automatic monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for describing the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a system architecture diagram of an integrated system for treating comprehensive electroplating wastewater; Figure 2 It is an overall architecture flowchart of an integrated system for treating comprehensive electroplating wastewater; Figure 3 It is a linkage working flowchart of the complex-breaking module and the central control; Figure 4 It is a flowchart of multi-stage membrane separation and concentration and membrane fouling early warning and maintenance; Figure 5 It is a method flowchart of an integrated method for treating comprehensive electroplating wastewater. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following illustrates the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0019] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0020] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0021] Please see Figure 1-5 The figure shows an integrated system and method for treating electroplating wastewater according to the present invention. The present invention discloses an integrated electroplating wastewater treatment system comprising: a pretreatment module for separate treatment of different plating types, which receives and pretreats wastewater from different plating processes to generate effluent from each wastewater stream and a first online monitoring signal characterizing the water quality parameters of each wastewater stream; a complex breakdown module, whose inlet is connected to the effluent from the separate treatment module and whose control end is electrically connected to a central control module, which receives wastewater from each wastewater stream and a complex breakdown current control signal from the central control module, and performs electrochemical oxidation complex breakdown treatment on the wastewater to generate complex-broken wastewater; a multi-stage membrane separation and concentration module, whose inlet receives the complex-broken wastewater, and performs separation and concentration through multi-stage membrane units to generate concentrated liquid and permeate, and generates a second online monitoring signal characterizing the membrane operating status parameters; an evaporation crystallization and resource recovery module, whose feed end receives the concentrated liquid, performs evaporation crystallization treatment, and recovers crystalline salt and distilled water; and a central control module, which receives the first and second online monitoring signals respectively, generates a complex breakdown current control signal and a membrane system maintenance control signal according to a preset control algorithm, and transmits the complex breakdown current control signal to the complex breakdown module.

[0022] like Figure 1 As shown, the integrated electroplating wastewater treatment system provided by this invention consists of five parts in its overall architecture: a pretreatment module for different types of wastewater, a complex breaking module, a multi-stage membrane separation and concentration module, an evaporation crystallization and resource recovery module, and a central control module. These five modules are organically connected by fluid transport pipelines and electrical signal lines to establish material flow and information flow, thereby realizing the automatic control of the entire process of different plating wastewater from source classification and collection, complex breaking and conversion, step-by-step concentration and separation to end-stage evaporation crystallization and resource recovery.

[0023] like Figure 2The diagram illustrates the overall architecture and workflow of the integrated electroplating wastewater treatment system. This flowchart fully presents the entire working logic of the integrated electroplating wastewater treatment system, ensuring that the entire wastewater treatment process is controllable, efficient, and resource-recoverable. The pretreatment module, as the core unit at the system's beginning, is primarily responsible for receiving electroplating wastewater from different plating processes. Based on the differences in wastewater composition, it classifies and diverts the wastewater for treatment. Through basic pretreatment processes such as sedimentation, filtration, and pH adjustment, it removes suspended impurities, oil, and some easily removable pollutants from the wastewater, preventing impurities from entering subsequent precision treatment units and causing blockages or performance degradation. Simultaneously, it generates qualified effluent after pretreatment and collects key water quality parameters in real time to form the first online monitoring signal, providing basic data support for subsequent intelligent control. The first online monitoring unit collects key water quality parameters such as pH, oxidation-reduction potential, and heavy metal ion concentration of the pretreated wastewater in real time, converting physical parameters into standard electrical signals and stably transmitting them to the central control module to achieve real-time perception of the water quality status. The central control module is the core scheduling hub of the entire system, possessing data reception, algorithm calculation, command output, and collaborative management functions. It continuously receives the first and second online monitoring signals, and through built-in preset control algorithms, performs real-time analysis of water quality and equipment operation data, accurately generating complex-breaking current control signals and membrane system maintenance control signals, coordinating the orderly and coordinated operation of various functional modules. The complex-breaking module receives the pretreated wastewater and the complex-breaking current control signal from the central control module. It uses an electrochemical oxidation process to break down the stable metal complex structures in the wastewater, converting difficult-to-remove complexed heavy metal ions into easily treatable free states. After completing the core complex-breaking process, it outputs the complex-broken wastewater, ensuring the effectiveness of subsequent membrane separation treatment.

[0024] The multi-stage membrane separation and concentration module receives wastewater after complex breaking. Through the screening, retention, and concentration effects of multi-stage membranes, it achieves deep purification and concentration separation of the wastewater, separating compliant permeate and high-concentration concentrate. Simultaneously, it collects real-time operating status parameters of each membrane unit, forming a second online monitoring signal, which is fed back to the central control module. The second online monitoring unit collects real-time operating parameters such as inlet pressure, permeate pressure, and permeate flow rate of each membrane unit, converting them into digital signals and transmitting them to the central control module to achieve real-time monitoring of the membrane system's operating status. The concentrate / permeate branch node serves as a key diversion link. Based on the concentration and water quality differences of the treated wastewater, it directs the high-concentration concentrate to the evaporation crystallization and resource recovery module, while the compliant permeate is transported to the permeate confluence node. The evaporation crystallization and resource recovery module receives the high-concentration concentrate and achieves evaporation, crystallization, and solid-liquid separation of the concentrate through a mechanical steam recompression evaporation crystallization process. Ultimately, it recovers the crystallized salt solids and distilled water, completing the resource utilization of heavy metal salts. The distilled water / crystallized salt branch node separates the crystallized salt from the distilled water. The crystallized salt enters the crystallized salt recovery module, while the distilled water enters the distilled water reuse quality control module. The crystallized salt recovery module collects and processes the separated crystallized salt, enabling resource utilization and significantly reducing the amount of hazardous waste generated from electroplating wastewater treatment. The distilled water reuse quality control module monitors key indicators such as conductivity and temperature of the distilled water in real time to determine whether the water quality meets the reuse standards for electroplating production. The qualified reuse module transports the qualified distilled water to the reuse water storage tank and then supplies it to the electroplating rinsing tank for recycling, effectively saving industrial water resources. The unqualified return module returns the unqualified distilled water to the front-end equalization tank of the system, re-enters the treatment process, forming a closed loop, avoiding the discharge of unqualified water and preventing pollution, and ensuring the overall treatment effect of the system is stable and reliable.

[0025] The separate pretreatment module, serving as the front-end unit of the system, receives and pretreats wastewater from different plating processes separately, preventing mixing before it enters subsequent treatment units. Based on the actual drainage conditions of the electroplating production workshop, this module is equipped with multiple independent and physically isolated wastewater collection sub-units. Each sub-unit specifically corresponds to a typical plating process wastewater, encompassing at least cyanide-containing, chromium-containing, nickel-containing, and copper-acid wastewater. Along the flow direction of the water in each wastewater collection sub-unit's pipeline, a bar filter, an online pH sensor, an online oxidation-reduction potential sensor, and an automatic dosing device are sequentially installed. The bar filter intercepts large suspended particles and mechanical impurities carried in the wastewater, preventing blockage or wear on downstream sensors and reaction equipment. The online pH and oxidation-reduction potential sensors respectively detect the hydrogen ion concentration index and the solution's oxidation-reduction capacity in real time, converting the detected values ​​into corresponding electrical signals. These electrical signals collectively constitute the first online monitoring signal characterizing the water quality parameters of each wastewater stream. The first online monitoring signal is transmitted in real time to the central control module via a shielded cable or fieldbus network. Upon receiving the first online monitoring signal, the central control module, based on the pre-set target pH ranges for each plating wastewater type in its internal memory and the currently measured pH values, uses a proportional-integral-derivative control algorithm or a logic threshold control algorithm with hysteresis to generate a drive signal for the dosing pump of the automatic dosing device. This drive signal controls the start / stop or stroke frequency of the dosing pump, quantitatively adding acidic or alkaline agents to the wastewater. Thus, before the wastewater enters the complex breaking module, the pH of each wastewater stream is independently adjusted to its corresponding pretreatment target range. After this pretreatment, each stream of wastewater flows out from the outlet of the separate pretreatment module and continues to flow into the next module; this outlet is the effluent from each wastewater stream.

[0026] like Figure 3As shown, this flowchart focuses on the collaborative working logic between the complex breaking module and the central control module, achieving precise and closed-loop control of the complex breaking process, adapting to the fluctuating characteristics of electroplating wastewater quality. The pretreatment effluent inlet module, as the starting point of the collaborative process, receives the qualified wastewater output from the front-end pretreatment module and uniformly imports it into the complex breaking treatment process, ensuring the continuous and stable entry of wastewater into subsequent monitoring and control stages, providing a stable influent foundation for the complex breaking reaction. The first online monitoring (pH / ORP acquisition) module is the sensing front end for complex breaking control, collecting two core parameters in real time: pH and redox potential. pH directly affects the dissociation stability of the complex, and redox potential determines the reaction efficiency of the electrochemical oxidation reaction. These two parameters jointly characterize the complexation characteristics of the wastewater. After collection, the real-time data is accurately transmitted to the central control module, providing a core basis for subsequent table lookup calculations and current control. Central Control: The pH / ORP measured value reading module serves as the first step in the coordinated control process. It quickly receives and analyzes monitoring signals, automatically eliminates abnormal data caused by signal interference, extracts effective measured values ​​of pH and ORP, completes data preprocessing, and ensures the accuracy and reliability of data input to subsequent calculation stages, avoiding deviations in control commands due to abnormal data. The two-dimensional mapping table lookup and matching current density module, based on preset water quality range division rules, matches measured pH values ​​to corresponding pH ranges to determine the first-dimensional index, and matches measured ORP values ​​to corresponding potential ranges to determine the second-dimensional index. Through the two-dimensional index, it quickly retrieves the pre-calibrated standard current density values ​​for the corresponding water quality range. This lookup method significantly shortens calculation time, enabling rapid response to instantaneous fluctuations in wastewater quality and ensuring timely control. The dynamic current density algorithm calculation module is based on the reference current density value obtained by looking up the table. It combines the differences in wastewater complex types, electrode wear levels, energy consumption optimization targets, and reaction efficiency requirements. It uses a dedicated dynamic algorithm to correct and calculate the reference current density, and outputs the optimal current density value that is adapted to the actual complexation characteristics of the current wastewater. This avoids both incomplete complex breaking due to excessively low current density and excessively high current density that would lead to energy waste and electrode wear, thus achieving the optimal balance between complex breaking efficiency and energy consumption.

[0027] The adjustable DC power output current breaking module receives the current control signal from the central control module, accurately converting the weak current control signal into a stable and adjustable DC current. This current is then output to the anode and cathode plates inside the electrochemical oxidation reactor according to the set current density, providing a stable and precise power supply for the electrochemical oxidation complex breaking reaction and ensuring its continuous and efficient operation. The complex breaking module of the electrochemical oxidation reactor is the core execution unit of the complex breaking process. Internally equipped with dedicated anode and cathode plates, a strong electrochemical oxidation reaction occurs on the electrode surface after energization, generating highly oxidizing active substances that break the coordination bonds of the metal complex, dissociating stable complexed heavy metal ions into free states, completing the core complex breaking reaction, and ensuring the wastewater meets the influent water quality requirements of the subsequent membrane treatment unit. The wastewater free metal ion conversion rate module monitors the proportion of free heavy metal ions to total metal ions in the wastewater after complex breaking in real time. This conversion rate is a core indicator for measuring the complex breaking effect. Real-time monitoring accurately determines whether the complex breaking reaction has reached the preset qualification standard, providing crucial decision-making basis for subsequent process diversion. The treated wastewater, meeting the standards, is fed to the multi-stage membrane separation module as a forward process branch. When the test results show that the free metal ion conversion rate reaches the preset qualified index, the complex-breaking effect is deemed satisfactory, and the wastewater is directly fed to the downstream multi-stage membrane separation and concentration module for subsequent purification and concentration processes. Wastewater that does not meet the standards is returned to the complex-breaking reactor module as a closed-loop circulation branch. When the complex-breaking effect does not meet the preset standard, the wastewater automatically flows back to the front end of the electrochemical oxidation reactor, re-entering the complex-breaking reaction process, forming a closed-loop treatment mechanism until the complex-breaking effect meets the standard. This completely prevents unqualified complex-breaking wastewater from flowing into subsequent treatment units, ensuring stable and reliable overall wastewater treatment quality.

[0028] The inlet of the complex-breaking module is connected to the outlets of the fractional pretreatment module via pipelines. Simultaneously, the control terminal of this module is electrically connected to the analog output channel of the central control module to receive the complex-breaking current control signal from the central control module. The main body of this module is one or more electrochemical oxidation reactors. Inside the reactor are anode plates and cathode plates. The anode plates use titanium-based ruthenium-iridium oxide coated electrodes, and the cathode plates use stainless steel electrodes; both are fully immersed in the wastewater to be treated. The anode and cathode plates are electrically connected to the positive and negative output terminals of an adjustable DC power supply, respectively. The control signal input terminal of the adjustable DC power supply is connected to the complex-breaking current control signal. The complex-breaking current control signal is an analog control signal generated by the central control module, such as a DC voltage signal of 0 to 10 volts or a DC current signal of 4 to 20 milliamps. This signal directly instructs the output current value of the adjustable DC power supply, thereby precisely controlling the current density flowing between the anode and cathode plates. When the wastewater flows into the electrochemical oxidation reactor and passes between the anode and cathode, water molecules undergo oxidation under the influence of current on the anode surface, generating adsorbed hydroxyl radicals. These hydroxyl radicals have extremely high oxidation electrode potentials and can non-selectively attack cyanide ions and organic complexing agent molecules such as citric acid, tartaric acid, and ethylenediaminetetraacetic acid in the wastewater, oxidizing and decomposing them into small molecules such as carbon dioxide, water, and nitrogen. This releases the heavy metal ions that were originally stably encapsulated by the complexing agents, transforming them into free metal ions, thus completing the complex-breaking treatment process. During this process, the central control module continuously receives and analyzes the first online monitoring signal from the separate pretreatment module, especially the current pH and redox potential values ​​of each wastewater stream. Based on the current density and water quality parameter mapping relationship pre-stored in its non-volatile memory, it dynamically calculates a current density setpoint that matches the current water quality state and converts this setpoint into the aforementioned complex-breaking current control signal through digital-to-analog conversion, which is then transmitted to the adjustable DC power supply. The mapping relationship between current density and water quality parameters is pre-established based on experimental data of complex-breaking efficiency conducted on different types of electroplating wastewater under various combinations of pH and redox potentials. Each item in the table represents the minimum current density corresponding to the effective breaking of complexes and the achievement of a predetermined conversion rate of free metal ions within the corresponding water quality range, thus balancing complex-breaking efficiency and energy consumption. After electrochemical oxidation and complex-breaking treatment, the wastewater flows out of the reactor outlet. At this point, most of the complexed heavy metals in the wastewater have been converted to free states. This effluent is called the complex-breaking wastewater and, after merging, enters the multi-stage membrane separation and concentration module. The formula for calculating the output current density is as follows: The dynamic output current density calculation of the complex breaking module in this invention employs a proprietary algorithm formula to achieve precise control under water quality fluctuations. This formula integrates the real-time changes in wastewater pH and redox potential, addressing the technical pain points of traditional fixed current modes, such as poor adaptability, high energy consumption, and unstable complex breaking efficiency. In the formula, J represents the dynamic output current density, measured in A / m², and is the core parameter driving the electrochemical oxidation reaction. , , The calibration coefficients for the complex breaking test correspond to the weighting factors of the acid-base deviation term, the redox potential deviation term, and the water quality coupling term, respectively. The values ​​are determined by fitting multiple sets of orthogonal tests on complex breaking of wastewater of different plating types. , The reference pH and reference redox potential are standard water quality parameters corresponding to the free metal ion conversion rate reaching the preset qualified index, and serve as the reference values ​​for achieving the complex breaking effect. , The pH and redox potential values ​​of the effluent from the pretreatment module are monitored in real time by the first online monitoring signal. K is a water quality correction constant used to offset calculation deviations caused by differences in the basic ion concentration and impurity composition of different plating wastewater types, ensuring the formula's universality for various electroplating wastewaters. The formula reflects the nonlinear effect of pH deviation from the benchmark value through a quadratic term. The dissociation stability of complexes in electroplating wastewater is highly sensitive to pH; the further the deviation from the benchmark value, the more stable the complex structure, and the nonlinear increase in the current density required for complex breaking. The logarithmic term... The system adapts to variations in redox potential; small deviations significantly impact the complex breaking efficiency, while large deviations lead to saturation, thus preventing excessive current density spikes and energy waste. Coupling terms... The formula fully considers the synergistic effect of pH and redox potential. During the complex breaking process of electroplating wastewater, these two water quality parameters are interrelated and jointly affect the reaction process. Introducing a coupling term can accurately reflect the actual complex breaking conditions. The correction constant K is calibrated to address the differences in the basic characteristics of wastewater from different plating types such as copper, nickel, and chromium plating, ensuring that the calculation results are suitable for various types of wastewater. The parameter calibration of this formula uses the free metal ion conversion rate ≥95% as the core indicator, selects the lowest current density that meets the indicator as the benchmark, and obtains the optimal coefficient combination through fitting multiple sets of experimental data. This ensures that the complex breaking treatment effect meets the standard while minimizing energy consumption. The central control module collects water quality parameters in real time and substitutes them into the formula for calculation, dynamically outputting current density control signals to effectively adapt to wastewater quality fluctuations. This provides qualified influent with low-complexed metal ions for subsequent multi-stage membrane separation, ensuring the stable operation of subsequent treatment units.

[0029] The inlet of the multi-stage membrane separation and concentration module receives the complex-broken wastewater. This module connects multiple membrane units with different retention accuracies in series along the water flow direction, forming a cascaded separation and concentration sequence. The specific membrane unit configuration includes an ultrafiltration membrane unit, a nanofiltration membrane unit, a first-stage reverse osmosis membrane unit, a second-stage reverse osmosis membrane unit, and a high-pressure reverse osmosis membrane unit. The inlet of the ultrafiltration membrane unit first receives the complex-broken wastewater. Its main function is to retain any remaining suspended particles, colloidal substances, and large-molecule organic residues in the wastewater, providing protection for subsequent membrane units. The inlet side of the nanofiltration membrane unit is connected to the product water side of the ultrafiltration membrane unit. The nanofiltration membrane can effectively retain divalent and polyvalent metal ions and dissolved organic matter with relative molecular masses in the hundreds of Daltons range, while allowing partial permeation of monovalent salt ions, thus achieving preliminary separation of monovalent and polyvalent salts while concentrating the target heavy metals. The primary and secondary reverse osmosis membrane units successively perform deep desalination of nanofiltration permeate. Their smaller membrane pore sizes, driven by applied high pressure, almost completely block dissolved salts and tiny organic molecules, producing permeate of excellent quality. The high-pressure reverse osmosis membrane unit receives the concentrate from the secondary unit and further concentrates and reduces its volume under even higher operating pressure, maximizing the extraction of reusable water and minimizing the volume of the concentrate, thus improving the thermal efficiency of the subsequent evaporation and crystallization module. Pressure sensors are installed on the feed and permeate sides of each membrane unit, and a flow sensor is installed in the permeate pipeline. These sensors continuously sample and detect the feed pressure, permeate pressure, and instantaneous permeate flow rate, converting these physical quantities into standard electrical signals. All pressure and flow signals are aggregated to form a second online monitoring signal characterizing the membrane operating status parameters. This second online monitoring signal is read by the central control module in the form of a digital signal frame containing sensor address, measured value, and cyclic redundancy check information, according to a predetermined polling cycle, using a serial communication-based digital bus protocol. After multi-stage membrane separation and concentration, the permeate from all membrane units is collected centrally through a manifold to form the final permeate. This permeate meets the reuse standards and is sent back to the rinsing tank of the electroplating production line. Meanwhile, the concentrate discharged from the high-pressure reverse osmosis membrane unit contains high concentrations of heavy metal salts and other inorganic salts. This concentrate is transported through pipelines to the feed end of the evaporation crystallization and resource recovery module.

[0030] like Figure 4As shown in the flowchart, the collaborative working logic of the multi-stage membrane separation and concentration module and membrane fouling early warning and maintenance is clearly presented. It is divided into three branches: normal operation, backwashing, and chemical cleaning, balancing wastewater purification and concentration efficiency with the long-term stable operation of the membrane system, adapting to the complex operating conditions of electroplating wastewater treatment. The wastewater entering the complex-breaking module serves as the starting point of the membrane treatment process, receiving the compliant complex-breaking wastewater output from the upstream complex-breaking module. This wastewater has extremely low levels of complexed heavy metals and stable water quality, laying a good foundation for the efficient and low-pollution operation of subsequent multi-stage membrane units. The ultrafiltration membrane unit, as the first pretreatment membrane unit of the multi-stage membrane system, has a relatively large pore size. Its main function is to intercept residual small suspended particles, colloidal substances, large molecular organic matter, and a small amount of incompletely removed impurities in the complex-breaking wastewater, preventing these impurities from entering the subsequent precision membrane units and causing irreversible clogging, thus initially purifying the wastewater and reducing the fouling load of subsequent membrane units. The nanofiltration membrane unit receives the effluent from the ultrafiltration membrane unit. With smaller pore sizes and selective retention characteristics, it effectively removes residual divalent and higher-valent heavy metal ions, small-molecule organic matter, and some dissolved salts from the wastewater, further improving wastewater purification and reducing the processing pressure on the subsequent reverse osmosis membrane unit, ensuring the overall membrane system's treatment efficiency. The first-stage reverse osmosis membrane unit achieves efficient separation of water molecules from dissolved salts and heavy metal ions through high-pressure drive. It can retain most dissolved salts, heavy metal ions, and trace organic matter, producing initially compliant permeate. Simultaneously, it concentrates the wastewater, increasing its concentration and laying the foundation for subsequent deep concentration.

[0031] The secondary reverse osmosis membrane unit receives the concentrate from the primary reverse osmosis membrane unit, further increasing the operating pressure to achieve secondary concentration of wastewater, significantly increasing the concentrate concentration. Simultaneously, it further purifies the permeate, improving its purity to meet higher standards for reuse or discharge. The high-pressure reverse osmosis membrane unit, as the final concentration unit in the multi-stage membrane system, uses the highest operating pressure to deeply concentrate the concentrate from the secondary reverse osmosis membrane unit, obtaining a high-concentration concentrate and producing the final compliant permeate. This achieves efficient purification and deep concentration of wastewater, realizing resource recovery and volume reduction. A second online monitoring signal module is installed on the inlet and permeate sides of each membrane unit and in the permeate pipeline. It collects key operating parameters such as inlet pressure, permeate pressure, transmembrane pressure difference, and permeate flow rate in real time. The collected physical parameters are integrated into standard digital signals and stably transmitted to the central control module, comprehensively and in real-time reflecting the operating status of each membrane unit. Central Control: The normalized permeability calculation module receives real-time pressure and flow monitoring data, retrieves the effective membrane area constant of each membrane unit pre-stored in the system, and calculates the current normalized permeability of each membrane unit using a standardized calculation formula. This parameter directly characterizes the water permeability of the membrane unit and is a core basic indicator for assessing the degree of membrane fouling and judging the membrane's operating status. The membrane fouling index (FI) calculation module, based on the current normalized permeability and the initial normalized permeability under clean membrane conditions, combines key factors affecting membrane permeability decay, such as natural aging of the membrane material, continuous action of transmembrane pressure difference, and cumulative operating time. Through a correction algorithm, it calculates an accurate membrane fouling index. This index is dimensionless, and a larger value indicates a more severe degree of membrane fouling, accurately reflecting the actual fouling status of the membrane unit and avoiding the limitations of traditional single permeability ratio assessment methods. The formula for calculating the membrane fouling index is as follows: in, To correct the membrane fouling index, The current normalized penetration rate, Let k be the initial normalized permeability, and k be the membrane material attenuation coefficient. The average transmembrane pressure difference is given, and t is the operating time. This is a time correction constant. Traditional membrane fouling indices are determined solely by (…). - ) / The calculations, which do not consider key factors such as the natural aging of the membrane material, the continuous effect of transmembrane pressure difference, and the cumulative effect of operating time, are prone to underestimating the actual degree of fouling, leading to delayed maintenance or misjudgment; the corrected formula introduces an exponential decay term. By coupling the three core influencing factors of membrane aging, pressure load, and operating time, and dynamically correcting for the natural losses caused by permeability decline, the calculated... Precisely matching the actual membrane fouling state. In actual operation, the central control module receives real-time online monitoring signals from pressure and flow sensors, calculates the current normalized permeability and average transmembrane pressure difference, retrieves the stored initial normalized permeability, membrane material attenuation coefficient, and time correction constant, and substitutes them into the formula to obtain the corrected membrane fouling index. When the preset first threshold is exceeded, the corresponding membrane unit backwashing procedure is automatically triggered to promptly remove reversible fouling; when When the value exceeds a second threshold, a chemical cleaning alarm is issued through the human-machine interface to remind operators to carry out deep cleaning. This formula effectively improves the accuracy of membrane fouling identification, avoids membrane element damage or reduced processing efficiency due to misjudgment, extends membrane life and reduces system operation and maintenance costs.

[0032] The threshold judgment node, as the core node for membrane system maintenance decisions, presets two levels of fouling thresholds: the first threshold corresponds to mild reversible fouling, and the second threshold corresponds to severe irreversible fouling. The central control module compares the real-time calculated membrane fouling index with the two thresholds to accurately determine the membrane fouling level and trigger corresponding maintenance strategies, achieving graded and precise maintenance. The continuous operation of the concentrate / permeate output module serves as the normal operation branch. When the membrane fouling index is below the first threshold, it determines that the membrane unit has a mild fouling level and is operating normally. The wastewater continues to complete the multi-stage membrane separation and concentration process, ultimately outputting high-concentration concentrate and compliant permeate, ensuring continuous and efficient wastewater treatment. The backwashing procedure module, triggered when the membrane fouling index exceeds the first threshold but is below the second threshold, determines that the membrane unit has experienced reversible mild fouling. The central control module automatically triggers the backwashing procedure, using reverse water flow to quickly flush away contaminants attached to the membrane surface, effectively removing reversible fouling and restoring the membrane unit's permeability. After backwashing, the wastewater is returned to the front-end module of the membrane unit to form a local closed-loop circulation. The wastewater generated during backwashing is returned to the front end of the ultrafiltration membrane unit and re-enters the membrane treatment process, avoiding waste of backwashing wastewater and ensuring the continuity of the membrane treatment process. Mild fouling treatment can be completed without shutdown. The chemical cleaning alarm module for exceeding the second threshold serves as a branch for severe fouling maintenance. When the membrane fouling index exceeds the second threshold, it is determined that the membrane unit has irreversibly suffered severe fouling. Simple backwashing cannot restore membrane performance. The central control module immediately issues a chemical cleaning alarm through the human-machine interface, reminding operators to promptly carry out professional chemical cleaning to remove stubborn contaminants, restore membrane unit performance, and prevent permanent damage to membrane elements due to long-term severe fouling. The concentrate / permeate branch node is a key link in the end-of-line diversion of the membrane treatment process. Based on the concentration difference of the treated wastewater, the high-concentration concentrate output from the high-pressure reverse osmosis membrane unit is directed to the evaporation, crystallization, and resource recovery module. The qualified permeate produced by each level of membrane unit is collected and transported to the permeate collection module. The concentrate is transported to the evaporation and crystallization module, where it is then sent to the downstream resource recovery stage to achieve the resource recovery and utilization of heavy metal salts, reducing hazardous waste emissions. The permeate collection module collects the qualified permeate from each membrane unit, forming qualified permeate that can be directly reused in electroplating production or discharged in compliance with standards, achieving the resource utilization of electroplating wastewater and aligning with green environmental protection and sustainable development concepts. The formula for calculating the average rate of change of the membrane fouling index is as follows: in, The weighted average rate of change of the membrane fouling index, where n is the number of samples. Let be the weighting coefficient for the i-th period. , For the membrane fouling index in the i-th and i-1th periods, To calculate the cycle duration, this formula uses a weighted summation method, assigning the highest weighting coefficient to the most recent cycle. The weights gradually decrease as the cycle progresses, effectively weakening the interference of long-term data, strengthening the trend characteristics of recent pollution changes, and improving the timeliness of predictions. The system calculates the rate of change of fouling in a single cycle, accurately quantifying the speed of instantaneous fouling. Then, it weights and sums the rates of n cycles and takes the average, eliminating calculation errors caused by fluctuations in single measurements and anomalies in instantaneous operating conditions, and accurately identifying trend signals of continuously accelerating fouling. In practical applications, after each membrane fouling index calculation, the central control module stores the data in a first-in-first-out (FIFO) circulating buffer queue. Once the queue is full, it reads n historical fouling indices to form a time series, retrieves the preset weighting coefficients and calculation cycle duration, and substitutes them into the formula to calculate the weighted average rate of change. When this value exceeds the preset rate threshold, it determines that the membrane has entered the accelerated fouling stage, immediately generating an accelerated fouling warning signal. A visual warning icon is output through the human-machine interface, and targeted maintenance suggestions are simultaneously provided, including checking the effluent quality of the separate pretreatment module, adjusting the membrane system recovery rate setting, and arranging chemical cleaning as soon as possible. Operators can intervene promptly based on the warning information to prevent rapid membrane fouling failure. This formula is suitable for complex operating conditions where multiple membrane units operate in series. It can promptly detect and warn of abnormal fouling of single-stage membranes, ensuring the stable operation of the entire membrane separation and concentration module. It provides a stable concentration of concentrate for subsequent evaporation, crystallization, and resource recovery modules, thereby improving the overall system processing efficiency and resource recovery stability.

[0033] After receiving the concentrated liquid at the feed end of the evaporation crystallization and resource recovery module, the concentrated liquid undergoes evaporation crystallization treatment to recover crystalline salt and distilled water. The core of this module employs a mechanical vapor recompression evaporation crystallization device, which mainly consists of a feed preheater, a steam compressor, a crystallizer separator, and a centrifugal dehydrator connected in series. The concentrated liquid first enters the feed preheater, where it undergoes indirect heat exchange with the secondary steam generated by the crystallizer separator or the high-temperature condensate discharged from the heating chamber. After the temperature rises, it enters the evaporation chamber of the crystallizer separator. In the crystallizer separator, the liquid is continuously heated to a boiling state in the heating chamber, causing a large amount of water to evaporate and form secondary steam. The solute concentration in the solution continuously increases until it exceeds the solubility limit, causing metal salt crystals to precipitate, forming a slurry containing suspended crystals. The secondary steam generated by the evaporation in the crystallizer separator is drawn into and compressed by the steam compressor. After compression, the steam pressure and saturation temperature increase significantly, and it is then sent back to the heating chamber of the crystallizer separator as a heating medium, releasing latent heat to heat the liquid and condensing itself into distilled water. This design allows for the full recovery of the latent heat of the secondary steam, with the system consuming only the electricity needed to drive the steam compressor, achieving significant energy savings. The crystal slurry discharged from the bottom of the crystallizer is transported to a centrifugal dewatering machine. Under the centrifugal force field generated by high-speed rotation, the crystals separate from the mother liquor, yielding crystalline salt solids with low water content. These crystalline salt solids can be disposed of as metal salt byproducts or refined for reuse. The centrifugal mother liquor is returned to the concentrate line before the feed preheater via a reflux pipeline, mixed with fresh concentrate, and then re-enter the evaporation crystallization system to fully recover any residual valuable metals. Distilled water is collected from the condenser side of the crystallizer's heating chamber. This highly pure distilled water can be directly pumped into a recycled water storage tank for use in the rinsing process of the production workshop, achieving water resource recycling.

[0034] The central control module serves as the information processing and control hub of the entire integrated system. It receives the first online monitoring signal from the fractional pretreatment module and the second online monitoring signal from the multi-stage membrane separation and concentration module. In an extended configuration, it can also receive online sensor signals from the evaporation, crystallization, and resource recovery modules. The hardware platform of the central control module is centered on a programmable logic controller (PLC). It is equipped with multiple analog input modules for receiving continuous signals from sensors, multiple analog output modules for sending complex-breaking current control signals, multiple digital input / output modules for receiving equipment status feedback and sending switch-type control commands, and a communication module for connecting the human-machine interface and the host computer. The PLC's program memory contains preset control algorithms, specifically including a dynamic current adjustment program for the complex-breaking module and a maintenance decision program for the multi-stage membrane separation and concentration module. Upon receiving the first online monitoring signal, the central control module uses the pH and redox potential values ​​of each wastewater stream in the signal as input. It then performs interval judgment, two-dimensional table lookup, and data calculation to determine the appropriate current density setpoint for the current water quality. This setpoint is then output via the analog output module as a complex breaking current control signal. This signal directly affects the control terminal of the adjustable DC power supply in the complex breaking module, causing the complex breaking current to automatically adjust with changes in water quality. Upon receiving the second online monitoring signal, the maintenance decision-making program first performs transmembrane pressure difference calculation, temperature correction, and normalized permeability calculation for each membrane unit to obtain the membrane fouling index. The program compares the membrane fouling index with a first and second threshold stored in a register. When the membrane fouling index exceeds the first threshold, a backwash start command in digital form is generated as part of the membrane system maintenance control signal. This command is sent to the multi-stage membrane separation and concentration module via relay output or communication bus, driving the corresponding backwash pump and valves to automatically backwash the membrane unit. When the membrane fouling index exceeds a higher second threshold, the program generates a chemical cleaning request signal, pops up an alarm window on the human-machine interface, clearly prompting the operator to perform chemical cleaning on the corresponding membrane unit, and can provide recommended cleaning agent type and cleaning procedure. Through the above control logic, the central control module realizes real-time precise control of the complex breaking process and predictive maintenance of the membrane separation process, tightly coupling each process unit into a collaborative whole.

[0035] like Figure 5As shown, the present invention also provides an integrated method for comprehensive electroplating wastewater treatment, comprising: S1: pretreating different types of plating wastewater separately in a separate pretreatment module to form effluents of each wastewater stream and collecting water quality parameters as a first online monitoring signal; S2: receiving the wastewater streams in a complex breaking module and receiving a complex breaking current control signal generated by a central control module based on the first online monitoring signal, and performing electrochemical oxidation complex breaking treatment to obtain complex-broken wastewater; S3: performing multi-stage membrane separation and concentration on the complex-broken wastewater in a multi-stage membrane separation and concentration module to produce concentrate and permeate, and collecting membrane operating status parameters as a second online monitoring signal and transmitting them to the central control module; S4: performing evaporation and crystallization treatment on the concentrate in an evaporation crystallization and resource recovery module to recover crystallized salt and distilled water; S5: receiving the first online monitoring signal and the second online monitoring signal in the central control module, executing a preset control algorithm to generate the complex breaking current control signal and transmitting it to the complex breaking module, and also generating a membrane system maintenance control signal and transmitting it to the multi-stage membrane separation and concentration module.

[0036] This invention provides an integrated system and method for treating electroplating wastewater. A pretreatment module collects and adjusts the water quality of wastewater from different plating processes. A complex breaking module dynamically adjusts the current for electrochemical oxidation based on online water quality signals. A multi-stage membrane separation and concentration module progressively concentrates the broken-complex wastewater and calculates the membrane fouling index online to trigger backwashing or chemical cleaning. An evaporation and crystallization module recovers crystalline salts and distilled water. A central control module generates complex breaking current control signals and membrane system maintenance control signals based on online signals, enabling all modules to operate collaboratively. This achieves efficient removal of heavy metals and resource recovery under fully automated monitoring.

[0037] Therefore, the integrated electroplating wastewater treatment system and method of the present invention solves the problems of incomplete separation, low complex breaking efficiency, serious membrane fouling and low resource recovery rate in electroplating wastewater treatment.

[0038] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An integrated system for treating electroplating wastewater, characterized in that, include: The separate pretreatment module receives wastewater of different plating types and pretreats it to form the effluent of each wastewater stream and the first online monitoring signal characterizing the water quality parameters of each wastewater stream. The complex breaking module has its inlet end connected to the outlet end of the fractional pretreatment module, and its control end electrically connected to the central control module. It receives the complex breaking current control signal from each stream of wastewater and from the central control module, and performs electrochemical oxidation complex breaking treatment on the wastewater to form complex-broken wastewater. The multi-stage membrane separation and concentration module receives the broken-network wastewater at its inlet end, separates and concentrates it through multi-stage membrane units to form concentrated liquid and product water, and generates a second online monitoring signal characterizing the membrane operating status parameters. The evaporation crystallization and resource recovery module receives the concentrated liquid at its feed end, performs evaporation crystallization treatment, and recovers crystallized salt and distilled water. The central control module receives the first online monitoring signal and the second online monitoring signal respectively, generates the complex breaking current control signal and the membrane system maintenance control signal according to the preset control algorithm, and transmits the complex breaking current control signal to the complex breaking module.

2. The integrated electroplating wastewater treatment system according to claim 1, characterized in that, The complex breaking module includes an electrochemical oxidation reactor and an adjustable DC power supply. The electrochemical oxidation reactor contains an anode plate and a cathode plate. The anode plate is a titanium-based ruthenium-iridium oxide coated electrode, and the cathode plate is a stainless steel electrode. The control terminal of the adjustable DC power supply is electrically connected to the central control module to receive the complex breaking current control signal. Based on the wastewater pH and redox potential values ​​in the first online monitoring signal, the central control module retrieves the current density-water quality parameter mapping relationship pre-stored in its non-volatile memory to determine the output current density corresponding to the current water quality state. This current density is then converted into the complex breaking current control signal and sent to the adjustable DC power supply through an analog output channel. The mapping relationship is established based on complex breaking experiments conducted on different types of wastewater under multiple pH and redox potential combinations, using the lowest current density corresponding to the free metal ion conversion rate meeting a preset target as the standard. The calculation formula for the output current density is as follows: Where J is the dynamic output current density. , , The calibration coefficient for the network breaking test is... , As a reference pH and redox potential, , The value is the real-time monitoring value, and K is the water quality correction constant.

3. The integrated electroplating wastewater treatment system according to claim 2, characterized in that, The central control module is equipped with a dynamic complex-breaking current scheduling program. This program periodically performs the following operations at preset configurable time intervals: reading the measured values ​​of pH and redox potential of the current wastewater from the first online monitoring signal; determining the first-dimensional index by assigning the measured pH value to one of a preset multiple pH intervals; determining the second-dimensional index by assigning the measured redox potential value to one of a preset multiple redox potential intervals; searching for the corresponding current density setpoint from a two-dimensional mapping table based on the first and second-dimensional indices. Each entry in the two-dimensional mapping table is an experimentally calibrated current density value that can effectively break the complex within the corresponding water quality interval. The central control module converts the searched current density setpoint into the complex-breaking current control signal, which is an analog voltage signal or an analog current signal. This signal drives the adjustable DC power supply to output a DC current corresponding to the setpoint via an analog output interface, thereby dynamically adjusting the current intensity applied between the anode and cathode plates to adapt to fluctuations in wastewater quality.

4. The integrated electroplating wastewater treatment system according to claim 1, characterized in that, The multi-stage membrane separation and concentration module includes an ultrafiltration membrane unit, a nanofiltration membrane unit, a first-stage reverse osmosis membrane unit, a second-stage reverse osmosis membrane unit, and a high-pressure reverse osmosis membrane unit connected in series along the water flow direction. Each membrane unit is equipped with a pressure sensor on both the inlet and outlet sides, and each membrane unit's outlet pipeline is equipped with a flow sensor. The pressure and flow signals collected in real time by the pressure and flow sensors together constitute the second online monitoring signal. The inlet of the ultrafiltration membrane unit receives the wastewater after the complexation is broken, and the concentrate outlet of the high-pressure reverse osmosis membrane unit is connected to the evaporation, crystallization, and resource recovery module. The outlet water from each membrane unit is collected as the outlet water through a manifold. The second online monitoring signal is periodically transmitted to the central control module in the form of digital signal frames via a serial communication bus. Each digital signal frame contains at least the sensor address, physical quantity value, and verification information.

5. The integrated electroplating wastewater treatment system according to claim 4, characterized in that, The central control module has a built-in online membrane fouling index calculation program. This program performs the following calculations and decisions for each membrane unit: Based on the second online monitoring signal, it obtains the current influent pressure, permeate pressure, and permeate flow rate; calculates the transmembrane pressure difference as the difference between the influent and permeate pressures; calculates the normalized permeate flow rate as the product of the permeate flow rate and the effective membrane area, where the effective membrane area is a constant pre-stored in the central control module; and calculates the membrane fouling index as the difference between the initial normalized permeate in the clean state and the current normalized permeate, divided by the initial normalized permeate in the clean state. After each membrane element replacement or chemical cleaning operation, the initial normalized permeability (NPS) is automatically measured and updated by the central control module under specified standard operating conditions. When the calculated membrane fouling index exceeds a preset first threshold, the central control module generates a backwash trigger signal as a maintenance control signal for the membrane system, initiating the backwashing procedure for the corresponding membrane unit. When the membrane fouling index exceeds a preset second threshold and the second threshold is greater than the first threshold, the central control module generates a chemical cleaning prompt signal and issues an alarm through the human-machine interface, reminding the operator to perform chemical cleaning. The formula for calculating the membrane fouling index is as follows: in, To correct the membrane fouling index, The current normalized penetration rate, Let k be the initial normalized permeability, and k be the membrane material attenuation coefficient. The average transmembrane pressure difference is given, and t is the operating time. This is the time correction constant.

6. The integrated electroplating wastewater treatment system according to claim 5, characterized in that, The central control module is also equipped with a membrane fouling trend early warning program. This program performs the following operations for each membrane unit: In each membrane fouling index calculation cycle, the newly calculated membrane fouling index is stored in a first-in-first-out (FIFO) circulating buffer queue. The length of this queue corresponds to a preset number of samples. The most recent preset number of membrane fouling index values ​​are read from the queue to form a membrane fouling index time series. The average rate of change of this time series within the preset number of sampling cycles is calculated. When the average rate of change exceeds a preset rate threshold, the central control module generates a membrane accelerated fouling early warning signal as part of the membrane system maintenance control signal. A visual early warning icon and corresponding maintenance operation suggestions are output through the human-machine interface. The maintenance operation suggestions include at least one or more of the following: checking the effluent quality of the pretreatment module, adjusting the membrane system recovery rate setting, or arranging chemical cleaning as soon as possible. The preset number of samples and the rate threshold are both configured as adjustable parameters that can be modified through the human-machine interface. The formula for calculating the average rate of change is as follows: in, The weighted average rate of change of the membrane fouling index, where n is the number of samples. Let be the weighting coefficient for the i-th period. , For the membrane fouling index in the i-th and i-1th periods, This is for calculating the cycle duration.

7. The integrated electroplating wastewater treatment system according to claim 1, characterized in that, The evaporation crystallization and resource recovery module includes a mechanical vapor recompression evaporation crystallization device, which comprises a feed preheater, a steam compressor, a crystallizer, and a centrifugal dehydrator. The feed inlet of the feed preheater receives the concentrated liquid, and the discharge outlet of the feed preheater is connected to the feed inlet of the crystallizer. The secondary steam outlet of the crystallizer is pressurized and heated by the steam compressor and then connected back to the heating chamber of the crystallizer. The crystal slurry outlet of the crystallizer is connected to the feed inlet of the centrifugal dehydrator. The centrifugal dehydrator performs solid-liquid separation on the crystal slurry to obtain the crystalline salt solid and centrifugal mother liquor. The centrifugal mother liquor is returned to the feed side of the crystallizer through a reflux pipeline or mixed with the concentrated liquid entering the feed preheater. The condensate generated in the heating chamber of the crystallizer is collected as distilled water. A conductivity sensor is installed on the distilled water collection pipeline. The conductivity signal generated by the conductivity sensor is used as part of the second online monitoring signal or as the third online monitoring signal and is connected to the central control module.

8. The integrated electroplating wastewater treatment system according to claim 7, characterized in that, The evaporation, crystallization, and resource recovery module also includes a distilled water reuse quality control unit. This unit includes a conductivity sensor, a temperature sensor, and an electric three-way diverter valve installed on the distilled water output main pipe. The conductivity and temperature sensors transmit the real-time collected conductivity and temperature signals to the central control module. The central control module performs temperature compensation on the measured conductivity value based on the received temperature signal to obtain a compensated conductivity value. The compensated conductivity value is then compared with a preset upper limit value for the reused water conductivity. If the compensated conductivity value is less than or equal to the upper limit value... At that time, the central control module outputs a first valve position control signal to connect the outlet of the electric three-way diverter valve to the recycled water storage tank. The recycled water storage tank is connected to the electroplating rinsing tank through a recycled water pump. When the compensated conductivity value is greater than the upper limit value, the central control module outputs a second valve position control signal to connect the outlet of the electric three-way diverter valve to the regulating tank, sending the unqualified distilled water back to the front end of the system for reprocessing. The central control module also continuously records the compensated conductivity value. When the compensated conductivity value continues to exceed the upper limit value within the preset continuous monitoring time, an abnormal alarm signal for the evaporation crystallization system is generated.

9. The integrated electroplating wastewater treatment system according to claim 1, characterized in that, The central control module consists of a programmable logic controller (PLC), a non-volatile data memory, a human-machine interface (HMI), and an industrial Ethernet communication interface. Both the first and second online monitoring signals are collected in digital frames by the PLC via an industrial field device communication protocol based on a serial bus. This communication protocol employs a master-slave polling mechanism. The PLC, acting as the master station, periodically reads the measurement values ​​from each online sensor. Each digital frame contains a slave address, function code, measurement data, and error check field. The PLC stores all read online monitoring signals, along with their timestamps, in a first-in, first-out (FIFO) manner in the non-volatile data memory. The non-volatile data memory retains historical operating data for at least the most recent preset number of hours. The PLC sends the historical operating data in batches to the host monitoring computer via the industrial Ethernet communication interface at a preset upload cycle. The HMI graphically displays the process flow, real-time operating parameters, alarm information, and historical trend curves, and receives parameter configuration commands input by the operator.

10. A method for an integrated electroplating wastewater treatment system according to any one of claims 1-9, comprising: S1: In the separate pretreatment module, wastewater of different plating types is pretreated separately to form effluents of each wastewater stream, and water quality parameters are collected as the first online monitoring signal. S2: The complex breaking module receives each stream of wastewater and receives the complex breaking current control signal generated by the central control module based on the first online monitoring signal, and performs electrochemical oxidation complex breaking treatment to obtain complex-broken wastewater; S3: The complex-broken wastewater is subjected to multi-stage membrane separation and concentration in the multi-stage membrane separation and concentration module to produce concentrated liquid and permeate, and the membrane operating status parameters are collected as a second online monitoring signal and transmitted to the central control module. S4: The concentrated liquid is subjected to evaporation and crystallization in the evaporation crystallization and resource recovery module to recover the crystallized salt and distilled water; S5: The central control module receives the first online monitoring signal and the second online monitoring signal, executes a preset control algorithm to generate the complex breaking current control signal and transmits it to the complex breaking module, and also generates a membrane system maintenance control signal and transmits it to the multi-stage membrane separation and concentration module.

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