Electroplating wastewater treatment system and treatment process

Abstract

The invention provides an electroplating wastewater treatment system and process, the treatment system comprises a chromium-containing wastewater treatment unit, a cyanide-containing wastewater treatment unit and a comprehensive wastewater treatment unit, and the treatment process comprises cyanide-containing wastewater treatment, chromium-containing wastewater treatment and comprehensive wastewater treatment. The method comprises the following steps: respectively treating chromium-containing wastewater and cyanide-containing wastewater to reduce the content of chromium and cyanide in the wastewater, mixing the treated wastewater, settling, and finally discharging after reaching the standard, arranging a comprehensive wastewater adjusting tank, a reflux pipeline, a backwashing pipe and the like to introduce liquid in a middle water tank, a filter tank and a filter press as cleaning water into the comprehensive wastewater adjusting tank, and recycling the cleaning water. And the effects of water quality homogenization and water quantity buffering are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to an electroplating wastewater treatment system and a treatment process. Background Art

[0002] Electroplating wastewater is the wastewater containing various pollutants such as metal ions, acids, alkalis and organic matters generated during the electroplating production process. Electroplating wastewater contains a variety of heavy metal ions, such as chromium, nickel, copper, zinc, cadmium, etc., and may also contain cyanides, fluorides, acids, alkalis and various organic additives, with complex and diverse compositions. Among them, heavy metal ions and cyanides are highly toxic and can cause serious harm to the environment and human health. For example, hexavalent chromium is a strong carcinogen. After cyanide enters the human body, it will inhibit the activity of cell respiration enzymes, leading to tissue hypoxia and asphyxiation death. If electroplating wastewater is directly discharged without effective treatment, it will cause serious pollution to the environment such as water bodies and soil. Heavy metal ions will accumulate in water bodies and soil, affecting the survival of aquatic organisms and the ecological balance, and may also be transmitted through the food chain, causing harm to organisms at higher trophic levels. At the same time, acidic or alkaline wastewater will change the pH value of water bodies and soil, destroying the acid-base balance of the ecological environment. The water quality and quantity of wastewater generated by different electroplating processes and production scales vary greatly, and during the production process, the generation quantity and pollutant concentration of wastewater will also fluctuate with time, bringing certain difficulties to wastewater treatment. Summary of the Invention

[0003] Object of the Invention: In order to overcome the above deficiencies, the present invention provides an electroplating wastewater treatment system and a treatment process, aiming to solve the above technical problems.

[0004] Technical Solution: In order to achieve the above object, the present invention provides an electroplating wastewater treatment system, including a chromium-containing wastewater treatment unit, a cyanide-containing wastewater treatment unit and a comprehensive wastewater treatment unit; The chromium-containing wastewater treatment unit includes a chromium-containing wastewater regulating tank and a reduction tank, and the chromium-containing wastewater regulating tank is connected to the reduction tank; The cyanide-containing wastewater treatment unit includes a cyanide-containing wastewater regulating tank, a primary cyanide-breaking tank and a secondary cyanide-breaking tank. The cyanide-containing wastewater regulating tank is communicated with the primary cyanide-breaking tank, and the primary cyanide-breaking tank is communicated with the secondary cyanide-breaking tank; The comprehensive wastewater treatment unit includes a liquid treatment module and a sludge treatment module. The liquid treatment module includes a comprehensive wastewater regulating tank, a reaction tank, a flocculation tank, a sedimentation tank, an intermediate water tank and a filtration tank connected in sequence. The outlet of the filtration tank is connected to the discharge port; Both the chromium-containing wastewater treatment unit and the cyanide-containing wastewater treatment unit are communicated with the comprehensive wastewater regulating tank, and the sedimentation tank is connected to the sludge treatment module.

[0005] Further, the sludge treatment module includes a sludge thickening tank and a filter press. One end of the sludge thickening tank is connected to the sedimentation tank, and the other end is connected to the filter press. Both the sludge thickening tank and the filter press are connected to the comprehensive wastewater regulation tank through a reflux pipeline.

[0006] Further, the intermediate water tank and the filtration tank are also connected through an anti - flushing pipeline. An anti - flushing pump is provided on the anti - flushing pipeline. The filtration tank is connected to the comprehensive wastewater regulation tank through the anti - flushing pipeline.

[0007] Further, pH meters and ORP meters are provided in the reduction tank, the first - stage cyanide - breaking tank, and the second - stage cyanide - breaking tank.

[0008] Further, a pH meter is provided in the reaction tank, a pH adjustment tank is provided in the intermediate water tank, and a pH meter is provided in the pH adjustment tank.

[0009] An electroplating wastewater treatment process includes the following steps: S1. The chromium - containing wastewater is introduced into the chromium - containing wastewater regulation tank and sulfuric acid is added to adjust the pH value to 2 - 3. Then it is introduced into the reduction tank to reduce hexavalent chromium to trivalent chromium, and then introduced into the comprehensive wastewater regulation tank. The cyanide - containing wastewater is introduced into the cyanide - containing wastewater regulation tank to adjust the pH value to 10.5 - 11, and then successively introduced into the first - stage cyanide - breaking tank and the second - stage cyanide - breaking tank for cyanide - breaking reaction, and then introduced into the comprehensive wastewater regulation tank. The wastewater containing other heavy metals is introduced into the comprehensive wastewater regulation tank together. S2. Cleaning water is introduced into the comprehensive wastewater regulation tank to stabilize the pollutant concentration in the comprehensive wastewater and preliminarily adjust the pH value. During this process, compressed air is introduced at the bottom of the comprehensive wastewater regulation tank. S3. The comprehensive wastewater in the comprehensive wastewater regulation tank is introduced into the reaction tank. NaOH and polyaluminum chloride are added to the reaction tank. NaOH adjusts the pH value to 10 - 11, and polyaluminum chloride undergoes a preliminary flocculation reaction in the comprehensive wastewater. Compressed air is introduced at the bottom of the reaction tank. S4. The comprehensive wastewater enters the flocculation tank. Polyacrylamide with a concentration of 1 - 3 mg / L is added to the flocculation tank. Compressed air is introduced at a high speed at the bottom of the flocculation tank for 1 - 3 min, and then slowly introduced for 10 - 30 min. S5. After passing through the flocculation tank, it is introduced into the sedimentation tank. The sedimentation time is 30 - 60 min. Among them, the solid waste is transferred to the sludge treatment module for treatment, and the wastewater is introduced into the intermediate water tank. The wastewater first passes through the pH adjustment tank, sulfuric acid is added to the pH adjustment tank to adjust the pH value, and then it passes through the intermediate water tank and enters the filtration tank for filtration and then is discharged. Compressed air is introduced at the bottom of both the pH adjustment tank and the filtration tank.

[0010] Preferably, in S1, sodium sulfite is added to the reduction pool as a reducing agent to reduce hexavalent chromium to trivalent chromium. The ORP meter in the reduction pool monitors the oxidation-reduction potential of the wastewater to ensure that hexavalent chromium is completely reduced. First, sodium hypochlorite is added to the first-stage cyanide-breaking pool as an oxidant to oxidize cyanide to cyanate. After being introduced into the second-stage cyanide-breaking pool, sulfuric acid is first added to the second-stage cyanide-breaking pool to adjust the pH value to 8-9, and then sodium hypochlorite is continuously added to decompose cyanate into carbon dioxide and nitrogen.

[0011] Preferably, the treatment steps of the sludge treatment module in S5 are as follows: solid waste enters the sludge thickening pool in the sludge pool for sedimentation and thickening. The supernatant in the sludge thickening pool is introduced into the comprehensive wastewater adjustment pool, and the sediment at the lower layer is transported to a filter press. The filtrate generated by the filter press is introduced into the comprehensive wastewater adjustment pool, and the filter residue is transported out.

[0012] Preferably, a part of the liquid in the intermediate pool enters the filter pool from the bottom through the backwash pipeline, a part of the upper-layer liquid in the filter pool is introduced into the comprehensive wastewater adjustment pool through the backwash pipeline, and the supernatant in the sludge thickening pool and the filtrate generated by the filter press are introduced into the comprehensive wastewater adjustment pool through the reflux pipeline.

[0013] From the above technical solutions, it can be seen that the present invention has the following beneficial effects: 1) The present invention provides an electroplating wastewater treatment system and treatment process. First, the chromium-containing and cyanide-containing wastewater are treated separately to reduce the chromium and cyanide content in the wastewater, and then the treated wastewater is mixed for sedimentation treatment, and finally discharged up to standard. 2) In the electroplating wastewater treatment system provided by the present invention, cleaning water is introduced into the comprehensive wastewater adjustment pool, and the source of the cleaning water is the upper-layer liquid in the intermediate pool, the filter pool and the filtrate generated by the filter press. Compressed air is introduced into the comprehensive wastewater adjustment pool to stir the pool to fully mix the wastewater, balance indicators such as pH, heavy metal concentration, and temperature, make the pollutant concentration of the influent of the subsequent treatment unit stable, facilitate the control of treatment process parameters, ensure the stability of the treatment effect, and at the same time, the acidic and alkaline substances in the wastewater can be preliminarily neutralized therein; electroplating production is usually intermittent, the discharge of cleaning wastewater is discontinuous, and the flow fluctuates greatly. Cleaning water is introduced into it to equalize the water volume. 3) The present invention uses a backwash pump to pump the liquid in the intermediate pool into the bottom of the filter pool in the reverse direction to wash the filter media in the filter pool, strip the adsorbed pollutants and discharge them with the wash water, and restore the permeability and adsorption capacity of the filter material. Brief Description of the Drawings

[0014] Figure 1 It is a schematic structural diagram of a chemical tail gas purification tower described in the present invention Figure 2 It is a schematic structural diagram of the anti-backflush device described in the present invention.

[0015] In the figure: 101 - chromium-containing wastewater regulation tank, 102 - reduction tank, 201 - cyanide-containing wastewater regulation tank, 202 - primary cyanide-breaking tank, 203 - secondary cyanide-breaking tank, 301 - comprehensive wastewater regulation tank, 302 - reaction tank, 303 - flocculation tank, 304 - sedimentation tank, 305 - intermediate water tank, 306 - filtration tank, 307 - pH adjustment tank, 308 - backwash pump, 401 - sludge thickening tank, 402 - filter press. Detailed implementation manners

[0016] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] As Figure 1 shown, a electroplating wastewater treatment system includes a chromium-containing wastewater treatment unit, a cyanide-containing wastewater treatment unit and a comprehensive wastewater treatment unit; The chromium-containing wastewater treatment unit includes a chromium-containing wastewater regulation tank 101 and a reduction tank 102. The chromium-containing wastewater regulation tank 101 is connected to the reduction tank 102 through a pipeline, and a lift pump is provided on the pipeline. The cyanide-containing wastewater treatment unit includes a cyanide-containing wastewater regulation tank 201, a primary cyanide-breaking tank 202 and a secondary cyanide-breaking tank 203. The cyanide-containing wastewater regulation tank 201 is communicated with the primary cyanide-breaking tank 202 through a pipeline, and a lift pump is provided on the pipeline. The primary cyanide-breaking tank 202 is communicated with the secondary cyanide-breaking tank 203. The comprehensive wastewater treatment unit includes a liquid treatment module and a sludge treatment module. The liquid treatment module includes a comprehensive wastewater regulation tank 301, a reaction tank 302, a flocculation tank 303, a sedimentation tank 304, an intermediate water tank 305 and a filtration tank 306 which are connected in sequence. The outlet of the filtration tank 306 is connected to a discharge port; a lift pump is provided between the comprehensive wastewater regulation tank 301 and the reaction tank 302, and the sedimentation tank 304 adopts an inclined tube sedimentation tank. Both the chromium-containing wastewater treatment unit and the cyanide-containing wastewater treatment unit are communicated with the comprehensive wastewater regulation tank 301, and the sedimentation tank 304 is connected to the sludge treatment module.

[0018] Among them, the sludge treatment module includes a sludge thickening tank 401 and a filter press 402. One end of the sludge thickening tank 401 is connected to the sedimentation tank 304, and the other end is connected to the filter press 402. Both the sludge thickening tank 401 and the filter press 402 are connected to the comprehensive wastewater regulation tank 301 through a reflux pipeline. The sediment sludge in the inclined tube sedimentation tank 304 is sent to the sludge thickening tank 401 for concentration through a sludge pump and then sent to the filter press 402 through a pneumatic diaphragm pump. The filter press 402 adopts a box-type filter press.

[0019] Specifically, the intermediate water tank 305 and the filtration tank 306 are also connected by a backwashing pipeline, and a backwashing pump 308 is provided on the backwashing pipeline. The filtration tank 306 is connected to the comprehensive wastewater regulation tank 301 through the backwashing pipeline. The backwashing pump 308 pumps the liquid in the intermediate water tank 305 into the filtration tank 306 from the bottom. Among them, the filtration tank 306 is a sand filtration tank.

[0020] In a preferred solution, pH meters and ORP meters are provided in the reduction tank 102, the first-stage cyanide-breaking tank 202, and the second-stage cyanide-breaking tank 203.

[0021] Among them, a pH meter is provided in the reaction tank 302, a pH callback tank 307 is provided in the intermediate water tank 305, and a pH meter is provided in the pH callback tank 307. Acidic or alkaline substances are added to the pH callback tank 307 to accurately adjust the pH value of the wastewater to an appropriate range. At the same time, the pH callback tank 307 can serve as a buffer area to allow the wastewater to be fully mixed in the tank, making the water quality more stable and uniform, which helps the subsequent treatment units to operate under relatively stable conditions, improving the stability and reliability of the treatment effect, and reducing the impact on the treatment equipment and process due to water quality fluctuations.

[0022] As Figure 2 shown, an electroplating wastewater treatment process includes the following steps: S1. The chromium-containing wastewater is introduced into the chromium-containing wastewater regulation tank 101 and sulfuric acid is added to adjust the pH value to 2-3. Then it is introduced into the reduction tank 102 to reduce hexavalent chromium to trivalent chromium, and then introduced into the comprehensive wastewater regulation tank 301; the cyanide-containing wastewater is introduced into the cyanide-containing wastewater regulation tank 201 to adjust the pH value to 10.5-11, and then sequentially introduced into the first-stage cyanide-breaking tank 202 and the second-stage cyanide-breaking tank 203 for cyanide-breaking reaction, and then introduced into the comprehensive wastewater regulation tank 301; the wastewater containing other heavy metals is introduced into the comprehensive wastewater regulation tank 301 together; S2. Cleaning water is introduced into the comprehensive wastewater regulation tank 301 to stabilize the pollutant concentration in the comprehensive wastewater and initially adjust the pH value. During this process, compressed air is introduced at the bottom of the comprehensive wastewater regulation tank 301; since the pollutant concentration in the electroplating cleaning wastewater fluctuates greatly, and the concentrations of heavy metal ions, acid-base substances, and surfactants in the wastewater discharged from different electroplating processes and different production periods vary significantly. The comprehensive wastewater regulation tank 301 can mix the wastewater with different concentrations evenly, making the pollutant concentration in the influent of the subsequent treatment units stable, facilitating the control of treatment process parameters, ensuring the stability of the treatment effect, and at the same time, the acid-base substances in the wastewater can be initially neutralized in it; electroplating production is usually intermittent, the discharge of cleaning wastewater is discontinuous, and the flow rate fluctuates greatly. Cleaning water is introduced into it to equalize the water volume; S3. Feed the comprehensive wastewater in the comprehensive wastewater regulation tank 301 into the reaction tank 302, add NaOH and polyaluminum chloride to the reaction tank. The NaOH adjusts the pH value to 10 - 11, and the polyaluminum chloride undergoes a preliminary flocculation reaction in the comprehensive wastewater. Compressed air is introduced into the bottom of the reaction tank 302. The pH value in the reaction tank is adjusted according to the heavy metal elements in the wastewater. For example, for wastewater containing copper, zinc, and nickel, the pH is 8.5 - 9.5; for wastewater containing lead and cadmium, the pH is 10 - 11. S4. The comprehensive wastewater enters the flocculation tank 303, and polyacrylamide with a concentration of 1 - 3 mg / L is added to the flocculation tank 303. Compressed air is introduced at a high speed into the bottom of the flocculation tank 303 for 1 - 3 minutes, and then slowly introduced for 10 - 30 minutes. S5. After passing through the flocculation tank 303, it is fed into the sedimentation tank 304. The sedimentation time is 30 - 60 minutes. Among them, the solid waste is transferred to the sludge treatment module for treatment, and the wastewater is fed into the intermediate water tank 305. The wastewater first passes through the pH adjustment tank 307, and sulfuric acid is added to the pH adjustment tank 307 to adjust the pH value. Subsequently, it enters the filter tank 306 through the intermediate water tank 305 for filtration and then is discharged. Compressed air is introduced into the bottoms of both the pH adjustment tank 307 and the filter tank 306.

[0023] Specifically, in step S1, sodium sulfite is added to the reduction tank 102 as a reducing agent to reduce hexavalent chromium to trivalent chromium. The ORP meter in the reduction tank 102 monitors the oxidation-reduction potential of the wastewater to ensure that hexavalent chromium is completely reduced. The ORP meter monitors that the oxidation-reduction potential ≤ 250 mV, and the reaction time is at least 20 minutes. First, sodium hypochlorite is added to the first-stage cyanide-breaking tank 202 as an oxidizing agent to oxidize cyanide to cyanate. After it is fed into the second-stage cyanide-breaking tank 203, sulfuric acid is first added to the second-stage cyanide-breaking tank 203 to adjust the pH value to 8 - 9, and then sodium hypochlorite is continuously added to decompose cyanate into carbon dioxide and nitrogen. Similarly, when the first-stage cyanide-breaking tank reacts, the ORP meter monitors that the oxidation-reduction potential ≥ 300 mV, and when the second-stage cyanide-breaking tank reacts, the ORP meter monitors that the oxidation-reduction potential ≥ 600 mV.

[0024] Specifically, the treatment steps of the sludge treatment module in step S5 are as follows: The solid waste enters the sludge thickening tank 401 of the sludge pond for sedimentation and thickening. The supernatant in the sludge thickening tank 401 is fed into the comprehensive wastewater regulation tank 301, and the sediment at the lower layer is transported to the filter press 402. The filtrate generated by the filter press 402 is fed into the comprehensive wastewater regulation tank 301, and the filter residue is transported out.

[0025] Specifically, a part of the liquid in the intermediate water tank 305 enters the filtration tank 306 from the bottom through the backwashing pipeline. A part of the upper layer liquid in the filtration tank 306 is introduced into the comprehensive wastewater regulation tank 301 through the backwashing pipeline. The supernatant liquid on the upper layer of the sludge thickening tank 401 and the filtrate generated by the filter press 402 are introduced into the comprehensive wastewater regulation tank 301 through the reflux pipeline. The liquid in the intermediate water tank 305 performs backwashing on the filtration tank 306 through the backwashing pump 308. The backwashing intensity is 12 - 15 L / (m²·s). By scouring the filter media with a reverse high-speed water flow, the adsorbed pollutants are stripped and discharged with the washing water, restoring the permeability and adsorption capacity of the filter media. The supernatant liquid on the upper layer of the filtration tank 306, the sludge thickening tank 401, and the filtrate generated by the filter press 402 are introduced into the comprehensive wastewater regulation tank 301 as washing water.

[0026] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements can still be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. An electroplating wastewater treatment system, characterized in that, It includes a chromium-containing wastewater treatment unit, a cyanide-containing wastewater treatment unit, and a comprehensive wastewater treatment unit; The chromium-containing wastewater treatment unit includes a chromium-containing wastewater regulating tank (101) and a reduction tank (102), and the chromium-containing wastewater regulating tank (101) is connected to the reduction tank (102); The cyanide-containing wastewater treatment unit includes a cyanide-containing wastewater regulating tank (201), a primary cyanide-breaking tank (202), and a secondary cyanide-breaking tank (203). The cyanide-containing wastewater regulating tank (201) is communicated with the primary cyanide-breaking tank (202), and the primary cyanide-breaking tank (202) is communicated with the secondary cyanide-breaking tank (203); The comprehensive wastewater treatment unit includes a liquid treatment module and a sludge treatment module. The liquid treatment module includes a comprehensive wastewater regulating tank (301), a reaction tank (302), a flocculation tank (303), a sedimentation tank (304), an intermediate water tank (305), and a filtration tank (306) connected in sequence. The outlet of the filtration tank (306) is connected to the discharge port; Both the chromium-containing wastewater treatment unit and the cyanide-containing wastewater treatment unit are communicated with the comprehensive wastewater regulating tank (301), and the sedimentation tank (304) is connected to the sludge treatment module.

2. The electroplating wastewater treatment system according to claim 1, characterized in that, The sludge treatment module includes a sludge thickening tank (401) and a filter press (402). One end of the sludge thickening tank (401) is connected to the sedimentation tank (304), and the other end is connected to the filter press (402). Both the sludge thickening tank (401) and the filter press (402) are connected to the comprehensive wastewater regulating tank (301) through a reflux pipeline.

3. The electroplating wastewater treatment system according to claim 1, wherein, There is also a backwashing pipeline connecting the intermediate water tank (305) and the filtration tank (306). An anti-backwashing pump (308) is provided on the backwashing pipeline, and the filtration tank (306) is connected to the comprehensive wastewater regulating tank (301) through the backwashing pipeline.

4. A electroplating wastewater treatment system according to claim 1, wherein, pH meters and ORP meters are provided in the reduction tank (102), the primary cyanide-breaking tank (202), and the secondary cyanide-breaking tank (203).

5. A electroplating wastewater treatment system according to claim 1, characterized in that, A pH meter is provided in the reaction tank (302), a pH adjustment tank (307) is provided in the intermediate water tank (305), and a pH meter is provided in the pH adjustment tank (307).

6. A plating wastewater treatment process, implemented based on the plating wastewater treatment system described in any one of claims 1-5, characterized in that, It includes the following steps: S1. The chromium-containing wastewater is introduced into the chromium-containing wastewater regulating tank (101), sulfuric acid is added to adjust the pH value to 2-3, then it is introduced into the reduction tank (102) to reduce hexavalent chromium to trivalent chromium, and then it is introduced into the comprehensive wastewater regulating tank (301); The cyanide-containing wastewater is introduced into the cyanide-containing wastewater regulating tank (201) to adjust the pH value to 10.5-11, and then it is successively introduced into the primary cyanide-breaking tank (202) and the secondary cyanide-breaking tank (203) for cyanide-breaking reaction, and then it is introduced into the comprehensive wastewater regulating tank (301); The wastewater containing other heavy metals is introduced into the comprehensive wastewater regulating tank (301) together; S2. Cleaning water is introduced into the comprehensive wastewater regulating tank (301) to stabilize the pollutant concentration in the comprehensive wastewater and preliminarily adjust the pH value. During this process, compressed air is introduced at the bottom of the comprehensive wastewater regulating tank (301); S3. Introduce the comprehensive wastewater in the comprehensive wastewater regulation tank (301) into the reaction tank (302), add NaOH and polyaluminum chloride to the reaction tank. The NaOH adjusts the pH value to 10 - 11, and the polyaluminum chloride undergoes a preliminary flocculation reaction in the comprehensive wastewater. Compressed air is introduced into the bottom of the reaction tank (302). S4. The comprehensive wastewater enters the flocculation tank (303), and polyacrylamide with a concentration of 1 - 3 mg / L is added to the flocculation tank (303). Compressed air is introduced into the bottom of the flocculation tank (303) at a high speed for 1 - 3 minutes, and then slowly introduced for 10 - 30 minutes. S5. After passing through the flocculation tank (303), it is introduced into the sedimentation tank (304). The sedimentation time is 30 - 60 minutes. Among them, the solid waste is transferred to the sludge treatment module for treatment, and the wastewater is introduced into the intermediate water tank (305). The wastewater first passes through the pH adjustment tank (307), and sulfuric acid is added to the pH adjustment tank (307) to adjust the pH value. Subsequently, it enters the filtration tank (306) through the intermediate water tank (305) for filtration and then is discharged. Compressed air is introduced into the bottoms of both the pH adjustment tank (307) and the filtration tank (306).

7. A plating wastewater treatment process according to claim 6, characterized in that, In step S1, sodium sulfite is added to the reduction tank (102) as a reducing agent to reduce hexavalent chromium to trivalent chromium. The ORP meter in the reduction tank (102) monitors the oxidation-reduction potential of the wastewater to ensure that hexavalent chromium is completely reduced. First, sodium hypochlorite is added to the first-stage cyanide-breaking tank (202) as an oxidant to oxidize cyanide to cyanate. After being introduced into the second-stage cyanide-breaking tank (203), sulfuric acid is first added to the second-stage cyanide-breaking tank (203) to adjust the pH value to 8 - 9, and then sodium hypochlorite is continuously added to decompose cyanate into carbon dioxide and nitrogen.

8. A process for treating electroplating wastewater according to claim 6, characterized in that, In step S5, the treatment steps of the sludge treatment module are as follows: The solid waste enters the sludge thickening tank (401) for sedimentation and thickening. The supernatant in the sludge thickening tank (401) is introduced into the comprehensive wastewater regulation tank (301), and the sediment at the lower layer is transported to the filter press (402). The filtrate generated by the filter press (402) is introduced into the comprehensive wastewater regulation tank (301), and the filter residue is transported out of the factory.

9. A plating wastewater treatment process according to claim 6, wherein, Part of the liquid in the intermediate water tank (305) enters the filtration tank (306) from the bottom through the backwashing pipeline. Part of the upper layer liquid in the filtration tank (306) is introduced into the comprehensive wastewater regulation tank (301) through the backwashing pipeline. The supernatant in the sludge thickening tank (401) and the filtrate generated by the filter press (402) are introduced into the comprehensive wastewater regulation tank (301) through the reflux pipeline.

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