Electroplating wastewater concentration and filtration system and method based on two-stage RO (Reverse Osmosis)

Abstract

The invention discloses an electroplating wastewater concentration and filtration system and method based on secondary RO, and relates to the field of electroplating wastewater concentration and filtration, and the system comprises a pretreatment unit, a primary RO unit, a secondary RO unit, a concentration treatment unit and a control unit. According to the electroplating wastewater concentration and filtration system and method based on the secondary RO, secondary RO treatment can further improve water quality on the basis of primary RO, molecular pollutants and salt of different sizes can be gradually removed by accurately designing performance parameters and an arrangement mode of two stages of RO membrane assemblies, and compared with traditional primary RO treatment, the system and the method have the advantages that the water quality is improved, and the cost is reduced. According to the system, the recycling rate of the electroplating wastewater can be increased to 90% or above from 60%-70%, the taking amount of fresh water is greatly reduced, meanwhile, the water quality of secondary RO fresh water can meet the high requirement for rinsing water in the electroplating process, the product quality can be effectively guaranteed, the defective rate caused by the water quality problem is reduced, and the production benefit is improved.

Description

Technical Field

[0001] The present invention relates to the field of concentration and filtration of electroplating wastewater, and in particular to a system and method for concentration and filtration of electroplating wastewater based on secondary RO. Background Art

[0002] Electroplating wastewater refers to various wastewaters generated during the electroplating production process. Its sources include plated parts cleaning wastewater, discarded and updated electroplating solution, plating tank leakage and flushing wastewater.

[0003] The wastewater reuse rate of traditional primary RO treatment is low, requiring more fresh water, which will have a certain impact on the overall process water quality.

[0004] Therefore, it is necessary to propose a secondary RO-based electroplating wastewater concentration and filtration system and method to solve the above problems. Summary of the Invention

[0005] The main purpose of the present invention is to provide a system and method for concentrating and filtering electroplating wastewater based on secondary RO, which can effectively solve the problems in the background technology.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A secondary RO-based electroplating wastewater concentration and filtration system includes a pretreatment unit, a primary RO unit, a secondary RO unit, a concentration treatment unit, and a control unit. The pretreatment unit includes a grid and a regulating tank, a chemical precipitation tank, a sand filter, and an activated carbon adsorption device.

[0008] The first-stage RO unit includes a high-pressure pump and a first-stage RO membrane assembly;

[0009] The secondary RO unit includes a secondary high-pressure pump and a secondary RO membrane assembly;

[0010] The concentration processing unit includes a nanofiltration membrane device and an evaporation crystallization device;

[0011] The control unit includes a data acquisition and processing module, an automatic control module, a fault alarm and diagnosis module, and a remote monitoring module.

[0012] Preferably, the screen adopts a combination of coarse and fine screens. The gap between the coarse screen bars is 10-20mm, which is used to intercept larger lumps and floating objects in the wastewater. The gap between the fine screen bars is 3-5mm, which is used to further remove smaller suspended matter and prevent it from entering subsequent pipes and equipment. The regulating tank uses a stirring device to fully mix the electroplating wastewater, and the liquid level sensor and the flow controller are linked to ensure that the wastewater flow fluctuation entering the subsequent treatment unit is controlled within ±10%.

[0013] Preferably, the chemical precipitation tank adopts an inclined plate precipitation structure with an inclined plate inclination angle of 60°, which is used to improve precipitation efficiency and shorten precipitation time.

[0014] Preferably, the sand filtration and activated carbon adsorption device includes a sand filtration device and an activated carbon adsorption device. The sand filtration device adopts a multi-layer filter material structure, which is, from bottom to top, a gravel layer with a particle size of 5-10mm and a thickness of 100-150mm, a coarse sand layer with a particle size of 1-2mm and a thickness of 200-300mm, and a fine sand layer with a particle size of 0.5-1mm and a thickness of 300-400mm. The activated carbon adsorption device is filled with columnar activated carbon, the iodine value of which is not less than 900mg / g and the specific surface area is greater than 1000m 2 / g.

[0015] Preferably, the high-pressure pump and the secondary high-pressure pump are both stainless steel centrifugal pumps, the high-pressure pump head is 1.5-2.5 MPa, and the secondary high-pressure pump head is 2.0-3.0 MPa.

[0016] Preferably, the first-stage RO membrane assembly adopts a polyamide composite membrane, the membrane element is a spiral wound structure, and the arrangement of the membrane assembly adopts a one-stage two-stage type. The first-stage membrane element is used for preliminary concentration of wastewater, and the second-stage membrane element is used for further concentration of the first-stage concentrated water. The first-stage membrane flux is 15-20L / (m 2 ·h), the second section membrane flux is 10-15L / (m 2 ·h); The secondary RO membrane assembly uses a finer polyamide composite membrane than the primary RO membrane. The membrane element adopts a disc-tube structure and the membrane flux is 8-12L / (m 2 ·h).

[0017] Preferably, the nanofiltration membrane in the nanofiltration membrane device is made of aromatic polyamide, the operating pressure is 1.0-1.5MPa, and a cross-flow filtration method is adopted. The membrane surface flow rate is controlled at 0.3-0.5m / s. The nanofiltration membrane device is chemically cleaned after 7-15 days of use, and the cleaning agents are citric acid and sodium hydroxide; the evaporation crystallization device adopts mechanical vapor recompression evaporation technology, and the MVR evaporator consists of an evaporator body, a compressor, and a heat exchanger. The evaporator body adopts a falling film evaporator, and the heat exchange tube is made of titanium alloy. The compressor compresses the secondary steam generated by evaporation and heats it up and returns it to the evaporator as a heat source to improve energy utilization. Its compression ratio is 1.2-1.5.

[0018] Preferably, the data acquisition and processing module is used to collect the signals of each sensor in real time, filter and convert them to obtain accurate operating parameter values, and store them in the data register of the PLC. Historical data can be queried at any time, and the data storage time is not less than 1 year;

[0019] The automatic control module automatically controls the speed of the high-pressure pump, the opening of the valve, and the dosage of the reagent based on the preset process parameters;

[0020] The fault alarm and diagnosis module is used to monitor the fault signals of the equipment in the system in real time, including but not limited to pump overload, motor failure, and sensor failure;

[0021] The remote monitoring module connects the PLC to the remote monitoring center based on industrial Ethernet to realize remote monitoring function.

[0022] A method for concentrating and filtering electroplating wastewater based on secondary RO includes the following steps:

[0023] S1: Remove bulk, floating and suspended solids from electroplating wastewater through two coarse and fine screens;

[0024] S2: Sodium hydroxide is added to the electroplating wastewater to adjust the pH value to 8-9, so that the chromium ions form chromium hydroxide precipitation. For nickel ions and copper ions, lime milk is continued to be added to increase the pH value to 10-11, generating nickel hydroxide and copper hydroxide precipitation. At the same time, polyacrylamide flocculant is added at a dosage of 2-5 mg / L. Based on the flocculation effect, the precipitation particles are aggregated and grown, and the sedimentation is accelerated. The supernatant after precipitation enters the sand filter and activated carbon adsorption device through overflow, and the sediment is transported to the sludge treatment system by the sludge pump for dehydration;

[0025] S3: The electroplating wastewater that has passed through the chemical precipitation tank enters the sand filtration and activated carbon adsorption device to remove residual fine suspended matter, organic matter, and residual chlorine. The sand filtration device removes residual fine suspended matter in the wastewater, reducing the suspended matter content in the effluent to less than 5 mg / L. It is used to adsorb organic matter and residual chlorine in the electroplating wastewater, reducing the risk of contamination to the RO membrane. The activated carbon adsorption device adopts a countercurrent regeneration method and is regularly regenerated with steam and sodium hydroxide solution. The regeneration cycle is 15-30 days.

[0026] S4: The electroplating wastewater is input into the primary RO unit through a high-pressure pump. After being treated in the primary RO unit, the electroplating wastewater is input into the secondary RO unit through a secondary high-pressure pump. The primary RO fresh water enters the secondary RO unit for further treatment, and the primary RO concentrated water enters the concentration treatment unit. The secondary RO concentrated water is returned to the primary RO water inlet for circulation treatment;

[0027] S5: Electroplating wastewater enters the nanofiltration membrane device, through which the heavy metal ions in the primary RO concentrated water are further concentrated. The nanofiltration fresh water can be returned to the primary RO inlet and the regulating tank for further treatment, and the nanofiltration concentrated water enters the evaporation crystallization device;

[0028] S6: After being treated by the nanofiltration membrane device, the electroplating wastewater is input into the evaporation crystallization device. During the evaporation process, the liquid level and temperature parameters in the evaporator are monitored in real time by liquid level sensors and temperature sensors, and the steam flow and feed flow are automatically adjusted to ensure the stability of the evaporation process. The salt and heavy metal salts in the electroplating wastewater gradually crystallize and precipitate during the evaporation process. The crystallized salt is separated and collected by centrifugation and filtration, and can be recycled and properly treated as hazardous waste. The condensed water produced by evaporation is reused in the system and discharged.

[0029] Compared with the prior art, the present invention provides a system and method for concentrating and filtering electroplating wastewater based on a secondary RO system, which has the following beneficial effects:

[0030] 1. This electroplating wastewater concentration and filtration system and method based on secondary RO can further improve water quality on the basis of primary RO. By precisely designing the performance parameters and arrangement of the two-stage RO membrane components, it can achieve the gradual removal of pollutants and salts of different molecular sizes. Compared with traditional primary RO treatment, this system can increase the reuse rate of electroplating wastewater from 60%-70% to more than 90%, greatly reducing the amount of fresh water used. At the same time, the water quality of secondary RO fresh water can meet the high requirements for rinsing water in the electroplating process. For example, in the production of some high-precision electroplated parts, the impurity content in the water is extremely strict. The secondary RO fresh water of this system can effectively ensure product quality, reduce the defective rate caused by water quality problems, and improve production efficiency.

[0031] 2. The electroplating wastewater concentration and filtration system and method based on secondary RO, the nanofiltration membrane can effectively separate heavy metal ions from monovalent ions and small molecular organic matter at relatively low pressure, reducing the difficulty and energy consumption of subsequent evaporation and crystallization. Taking an enterprise that treats 100 tons of electroplating wastewater per day as an example, after using nanofiltration membrane pretreatment, the scale of the evaporation and crystallization equipment can be reduced by 30%-40%, and the energy consumption can be reduced by 20%-30%, greatly reducing the treatment cost. At the same time, the selective separation characteristics of the nanofiltration membrane help to recover valuable metal ions in the wastewater, such as nickel and chromium, thereby improving the efficiency and purity of resource recovery, and having significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a system block diagram of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0034] Example 1:

[0035] like Figure 1As shown, a plating wastewater concentration and filtration system based on secondary RO includes a pretreatment unit, a primary RO unit, a secondary RO unit, a concentration treatment unit, and a control unit. The pretreatment unit includes a grid and a regulating tank, a chemical precipitation tank, a sand filter, and an activated carbon adsorption device.

[0036] The first-stage RO unit includes a high-pressure pump and a first-stage RO membrane assembly;

[0037] The secondary RO unit includes a secondary high-pressure pump and a secondary RO membrane assembly;

[0038] The concentration processing unit includes a nanofiltration membrane device and an evaporation crystallization device;

[0039] The control unit includes a data acquisition and processing module, an automatic control module, a fault alarm and diagnosis module, and a remote monitoring module.

[0040] The screen is a combination of coarse and fine screens. The gap between the coarse screen bars is 10-20mm, which is used to intercept larger lumps and floating objects in the wastewater. The gap between the fine screen bars is 3-5mm, which is used to further remove smaller suspended matter and prevent it from entering subsequent pipes and equipment. The regulating tank uses a stirring device to fully mix the electroplating wastewater. Based on the linkage between the liquid level sensor and the flow controller, the wastewater flow fluctuation entering the subsequent treatment unit is ensured to be controlled within ±10%.

[0041] The chemical precipitation tank adopts an inclined plate precipitation structure with an inclination angle of 60° to improve precipitation efficiency and shorten precipitation time.

[0042] The sand filtration and activated carbon adsorption device includes a sand filtration device and an activated carbon adsorption device. The sand filtration device adopts a multi-layer filter material structure, which is composed of a gravel layer with a particle size of 5-10mm and a thickness of 100-150mm, a coarse sand layer with a particle size of 1-2mm and a thickness of 200-300mm, and a fine sand layer with a particle size of 0.5-1mm and a thickness of 300-400mm. The activated carbon adsorption device is filled with columnar activated carbon, whose iodine value is not less than 900mg / g and the specific surface area is greater than 1000m 2 / g.

[0043] The high-pressure pump and the secondary high-pressure pump are both stainless steel centrifugal pumps. The high-pressure pump head is 1.5-2.5MPa, and the secondary high-pressure pump head is 2.0-3.0MPa.

[0044] The first-stage RO membrane assembly adopts polyamide composite membrane, the membrane element is spiral wound structure, the arrangement of the membrane assembly adopts a one-stage two-stage type, the first-stage membrane element is used for preliminary concentration of wastewater, and the second-stage membrane element is used for further concentration of the first-stage concentrated water. The first-stage membrane flux is 15-20L / (m 2 ·h), the second section membrane flux is 10-15L / (m 2·h); The secondary RO membrane assembly uses a finer polyamide composite membrane than the primary RO membrane. The membrane element adopts a disc-tube structure and the membrane flux is 8-12L / (m 2 h),

[0045] The nanofiltration membrane in the nanofiltration membrane device is made of aromatic polyamide, with an operating pressure of 1.0-1.5MPa and a cross-flow filtration method. The membrane surface flow rate is controlled at 0.3-0.5m / s. The nanofiltration membrane device is chemically cleaned after 7-15 days of use, and the cleaning agents are citric acid and sodium hydroxide. The evaporation crystallization device adopts mechanical vapor recompression evaporation technology. The MVR evaporator consists of an evaporator body, a compressor, and a heat exchanger. The evaporator body adopts a falling film evaporator, and the heat exchange tube is made of titanium alloy. The compressor compresses and heats the secondary steam generated by evaporation and returns it to the evaporator as a heat source to improve energy utilization. Its compression ratio is 1.2-1.5.

[0046] The data acquisition and processing module is used to collect the signals of each sensor in real time, filter and convert them to obtain accurate operating parameter values, and store them in the data register of the PLC. Historical data can be queried at any time, and the data storage time is not less than 1 year;

[0047] The automatic control module automatically controls the speed of the high-pressure pump, the opening of the valve, and the dosage of the reagent based on the preset process parameters;

[0048] The fault alarm and diagnosis module is used to monitor the fault signals of the equipment in the system in real time, including but not limited to pump overload, motor failure, and sensor failure;

[0049] The remote monitoring module connects the PLC to the remote monitoring center based on industrial Ethernet to realize remote monitoring function.

[0050] Example 2:

[0051] A method for concentrating and filtering electroplating wastewater based on secondary RO includes the following steps:

[0052] S1: Remove bulk, floating and suspended solids from electroplating wastewater through two coarse and fine screens;

[0053] S2: Sodium hydroxide is added to the electroplating wastewater to adjust the pH value to 8-9, so that the chromium ions form chromium hydroxide precipitation. For nickel ions and copper ions, lime milk is continued to be added to increase the pH value to 10-11, generating nickel hydroxide and copper hydroxide precipitation. At the same time, polyacrylamide flocculant is added at a dosage of 2-5 mg / L. Based on the flocculation effect, the precipitation particles are aggregated and grown, and the sedimentation is accelerated. The supernatant after precipitation enters the sand filter and activated carbon adsorption device through overflow, and the sediment is transported to the sludge treatment system by the sludge pump for dehydration;

[0054] S3: The electroplating wastewater that has passed through the chemical precipitation tank enters the sand filtration and activated carbon adsorption device to remove residual fine suspended matter, organic matter, and residual chlorine. The sand filtration device removes residual fine suspended matter in the wastewater, reducing the suspended matter content in the effluent to less than 5 mg / L. It is used to adsorb organic matter and residual chlorine in the electroplating wastewater, reducing the risk of contamination to the RO membrane. The activated carbon adsorption device adopts a countercurrent regeneration method and is regularly regenerated with steam and sodium hydroxide solution. The regeneration cycle is 15-30 days.

[0055] S4: The electroplating wastewater is input into the primary RO unit through a high-pressure pump. After being treated in the primary RO unit, the electroplating wastewater is input into the secondary RO unit through a secondary high-pressure pump. The primary RO fresh water enters the secondary RO unit for further treatment, and the primary RO concentrated water enters the concentration treatment unit. The secondary RO concentrated water is returned to the primary RO water inlet for circulation treatment;

[0056] S5: Electroplating wastewater enters the nanofiltration membrane device, through which the heavy metal ions in the primary RO concentrated water are further concentrated. The nanofiltration fresh water can be returned to the primary RO inlet and the regulating tank for further treatment, and the nanofiltration concentrated water enters the evaporation crystallization device;

[0057] S6: After being treated by the nanofiltration membrane device, the electroplating wastewater is input into the evaporation crystallization device. During the evaporation process, the liquid level and temperature parameters in the evaporator are monitored in real time by liquid level sensors and temperature sensors, and the steam flow and feed flow are automatically adjusted to ensure the stability of the evaporation process. The salt and heavy metal salts in the electroplating wastewater gradually crystallize and precipitate during the evaporation process. The crystallized salt is separated and collected by centrifugation and filtration, and can be recycled and properly treated as hazardous waste. The condensed water produced by evaporation is reused in the system and discharged.

[0058] The performance of the method of the present invention is compared with that of the prior art method, wherein the present invention is recorded as an embodiment and the prior art is recorded as comparative examples 1 and 2. The following is a comparison table:

[0059] Recycling rate (%) Heavy metal removal rate Operating energy consumption Concentration multiple Example 90 99 Reduce by 30%-40% 20-30 times Comparative Example 1 60 80 Higher 5-10 times Comparative Example 2 70 90 Higher 5-10 times

[0060] It can be seen that the process of the present invention has obvious advantages.

[0061] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A secondary RO-based electroplating wastewater concentration and filtration system, comprising a pretreatment unit, a primary RO unit, a secondary RO unit, a concentration treatment unit, and a control unit, characterized in that: The pretreatment unit includes a grid and a regulating tank, a chemical precipitation tank, a sand filter and an activated carbon adsorption device; The first-stage RO unit includes a high-pressure pump and a first-stage RO membrane assembly; The secondary RO unit includes a secondary high-pressure pump and a secondary RO membrane assembly; The concentration processing unit includes a nanofiltration membrane device and an evaporation crystallization device; The control unit includes a data acquisition and processing module, an automatic control module, a fault alarm and diagnosis module, and a remote monitoring module.

2. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 1 is characterized in that: The screen adopts a combination of coarse and fine screens. The gap between the coarse screen bars is 10-20mm, which is used to intercept larger lumps and floating objects in the wastewater. The gap between the fine screen bars is 3-5mm, which is used to further remove smaller suspended matter and prevent it from entering subsequent pipes and equipment. The regulating tank uses a stirring device to fully mix the electroplating wastewater. Based on the linkage between the liquid level sensor and the flow controller, it is ensured that the wastewater flow fluctuation entering the subsequent treatment unit is controlled within ±10%.

3. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 2, characterized in that: The chemical precipitation tank adopts an inclined plate precipitation structure with an inclined plate angle of 60°, which is used to improve precipitation efficiency and shorten precipitation time.

4. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 1, characterized in that: The sand filtration and activated carbon adsorption device comprises a sand filtration device and an activated carbon adsorption device. The sand filtration device adopts a multi-layer filter material structure, which comprises, from bottom to top, a gravel layer with a particle size of 5-10 mm and a thickness of 100-150 mm, a coarse sand layer with a particle size of 1-2 mm and a thickness of 200-300 mm, and a fine sand layer with a particle size of 0.5-1 mm and a thickness of 300-400 mm. The activated carbon adsorption device is filled with columnar activated carbon, the iodine value of which is not less than 900 mg / g and the specific surface area is greater than 1000 m 2 / g.

5. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 1 is characterized in that: The high-pressure pump and the secondary high-pressure pump are both stainless steel centrifugal pumps, the high-pressure pump head is 1.5-2.5 MPa, and the secondary high-pressure pump head is 2.0-3.0 MPa.

6. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 1, characterized in that: The first-stage RO membrane assembly adopts a polyamide composite membrane, and the membrane element is a spiral wound structure. The arrangement of the membrane assembly adopts a one-stage two-stage type. The first-stage membrane element is used for preliminary concentration of wastewater, and the second-stage membrane element is used for further concentration of the first-stage concentrated water. The first-stage membrane flux is 15-20L / (m 2 ·h), the second section membrane flux is 10-15L / (m 2 ·h); The secondary RO membrane assembly uses a finer polyamide composite membrane than the primary RO membrane. The membrane element adopts a disc-tube structure and the membrane flux is 8-12L / (m 2 ·h).

7. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 1, characterized in that: The nanofiltration membrane in the nanofiltration membrane device is made of aromatic polyamide, the operating pressure is 1.0-1.5MPa, and a cross-flow filtration method is adopted. The membrane surface flow rate is controlled at 0.3-0.5m / s. The nanofiltration membrane device is chemically cleaned after 7-15 days of use, and the cleaning agents are citric acid and sodium hydroxide. The evaporation crystallization device adopts mechanical vapor recompression evaporation technology. The MVR evaporator consists of an evaporator body, a compressor, and a heat exchanger. The evaporator body adopts a falling film evaporator, and the heat exchange tube is made of titanium alloy. The compressor compresses and heats the secondary steam generated by evaporation and returns it to the evaporator as a heat source to improve energy utilization. Its compression ratio is 1.2-1.

5.

8. The electroplating wastewater concentration and filtration system based on secondary RO according to claim 1 is characterized in that: The data acquisition and processing module is used to collect the signals of each sensor in real time, filter and convert them to obtain accurate operating parameter values, and store them in the data register of the PLC. Historical data can be queried at any time, and the data storage time is not less than 1 year; The automatic control module automatically controls the speed of the high-pressure pump, the opening of the valve, and the dosage of the reagent based on the preset process parameters; The fault alarm and diagnosis module is used to monitor the fault signals of the equipment in the system in real time, including but not limited to pump overload, motor failure, and sensor failure; The remote monitoring module connects the PLC to the remote monitoring center based on industrial Ethernet to realize remote monitoring function.

9. A method for concentrating and filtering electroplating wastewater based on a secondary RO system, comprising: The following steps are included: S1: Remove bulk, floating and suspended solids from electroplating wastewater through two coarse and fine screens; S2: Sodium hydroxide is added to the electroplating wastewater to adjust the pH value to 8-9, so that the chromium ions form chromium hydroxide precipitation. For nickel ions and copper ions, lime milk is continued to be added to increase the pH value to 10-11, generating nickel hydroxide and copper hydroxide precipitation. At the same time, polyacrylamide flocculant is added at a dosage of 2-5 mg / L. Based on the flocculation effect, the precipitation particles are aggregated and grown, and the sedimentation is accelerated. The supernatant after precipitation enters the sand filter and activated carbon adsorption device through overflow, and the sediment is transported to the sludge treatment system by the sludge pump for dehydration; S3: The electroplating wastewater that has passed through the chemical precipitation tank enters the sand filtration and activated carbon adsorption device to remove residual fine suspended matter, organic matter, and residual chlorine. The sand filtration device removes residual fine suspended matter in the wastewater, reducing the suspended matter content in the effluent to less than 5 mg / L. It is used to adsorb organic matter and residual chlorine in the electroplating wastewater, reducing the risk of contamination to the RO membrane. The activated carbon adsorption device adopts a countercurrent regeneration method and is regularly regenerated with steam and sodium hydroxide solution. The regeneration cycle is 15-30 days. S4: The electroplating wastewater is input into the primary RO unit through a high-pressure pump. After being treated in the primary RO unit, the electroplating wastewater is input into the secondary RO unit through a secondary high-pressure pump. The primary RO fresh water enters the secondary RO unit for further treatment, and the primary RO concentrated water enters the concentration treatment unit. The secondary RO concentrated water is returned to the primary RO water inlet for circulation treatment; S5: Electroplating wastewater enters the nanofiltration membrane device, through which the heavy metal ions in the primary RO concentrated water are further concentrated. The nanofiltration fresh water can be returned to the primary RO inlet and the regulating tank for further treatment, and the nanofiltration concentrated water enters the evaporation crystallization device; S6: After being treated by the nanofiltration membrane device, the electroplating wastewater is input into the evaporation crystallization device. During the evaporation process, the liquid level and temperature parameters in the evaporator are monitored in real time by liquid level sensors and temperature sensors, and the steam flow and feed flow are automatically adjusted to ensure the stability of the evaporation process. The salt and heavy metal salts in the electroplating wastewater gradually crystallize and precipitate during the evaporation process. The crystallized salt is separated and collected by centrifugation and filtration, and can be recycled and properly treated as hazardous waste. The condensed water produced by evaporation is reused in the system and discharged.

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