CN107235600B

CN107235600B - Electroplating wastewater treatment method, treatment system and application

Info

Publication number: CN107235600B
Application number: CN201710446892.1A
Authority: CN
Inventors: 韩全; 张恒
Original assignee: Guangdong Yeanovo Environmental Protection Co ltd
Current assignee: Guangdong Shangchen Environmental Technology Co ltd
Priority date: 2017-06-14
Filing date: 2017-06-14
Publication date: 2021-05-18
Anticipated expiration: 2037-06-14
Also published as: CN107235600A

Abstract

The invention provides an electroplating wastewater treatment method, which is characterized by sequentially comprising the following steps: (1) respectively pretreating metal wastewater, organic wastewater, complexing wastewater, cyanide-containing wastewater, nickel-containing wastewater, zinc-containing wastewater and chromium-containing wastewater to obtain pretreated water; (2) mixing the pre-treated water obtained in the step (1) and concentrating to obtain high-salt concentrated water and reuse water; (3) mixing the high-salinity concentrated water obtained in the step (2) with the pre-treated water obtained in the step (1) for biochemical treatment; (4) carrying out hyperconcentration treatment on the biochemical treatment water obtained in the step (3) to obtain ultrahigh salt concentrated water; (5) evaporating and crystallizing the ultrahigh-salt concentrated water obtained in the step (4) to obtain recycled water and crystals; the method is simple to operate and stable to operate, so that zero discharge or low discharge of comprehensive electroplating wastewater in electroplating production is achieved, and high-purity recovery of metal ions in the wastewater is realized.

Description

Electroplating wastewater treatment method, treatment system and application

Technical Field

The invention relates to a wastewater treatment method and a wastewater treatment system, in particular to a treatment method and a treatment system for zero discharge of electroplating wastewater.

Background

In the treatment of electroplating wastewater, chemical precipitation, electrolysis, general ion exchange and other treatment methods are commonly used in the treatment process. However, the above treatment methods have certain limitations and cannot achieve zero emission.

The chemical precipitation method is a method frequently used for treating electroplating wastewater at present, and the method needs to add a large amount of acid and alkali, and simultaneously needs to add ferrous sulfate and polyaluminium chloride, so that the salt content of water discharge is increased, and the discharge of residual metal ions in the water still cannot reach the standard. Therefore, because the content of the controlled substances specified by the wastewater discharge standard is extremely low, excessive chemicals are required to be added to reach the discharge standard, the cost is high, and the wastewater cannot be recycled as process water. In addition, the chemical sedimentation method cannot directly recover metal ions in the wastewater, and simultaneously generates a large amount of sludge, the sludge contains a large amount of metal ions, and the sludge needs to be treated again, so that secondary pollution is caused.

The treatment process of the electrolytic method is mature and stable in operation, but because the content of controlled substances specified by the discharge standard is extremely low, the treatment method has the disadvantages of high power consumption and high treatment cost during the electrolysis of wastewater, is easy to generate toxic gas, and is difficult to treat until the wastewater reaches the standard and is discharged.

The common ion exchange method adopts organic framework ion exchange resin, can effectively remove various harmful ions in the wastewater, and can recycle water, but the treatment method needs large resin dosage, is difficult to treat regenerated liquid, consumes a large amount of acid and alkali, and has high treatment cost; in addition, during the regeneration of the resin, the resin is largely broken due to the regeneration, shrinkage and expansion of the resin, and the economic efficiency is not high. If the reverse osmosis membrane is used for concentrating and treating electroplating wastewater and simultaneously pure water is recycled, the process is only applied to the wastewater system treatment of single high-valence ions, so the use has limitation.

It can be seen that various treatment methods for electroplating wastewater have many problems, most or all of the wastewater cannot be recycled even the existing equipment of each electroplating plant is fully utilized, and valuable metals in the wastewater cannot be effectively separated and recovered.

Disclosure of Invention

The invention aims to overcome the problems and defects in the prior art and provide a treatment method and a corresponding treatment system for zero discharge of electroplating wastewater, which are simple to operate, stable to operate, low in cost and high in treatment efficiency, so that the zero discharge or low discharge of the electroplating wastewater in electroplating production is realized, high-purity recovery of metal ions in the wastewater is realized, the production water consumption of the electroplating industry is saved, the pollution of the electroplating industry to the environment is remarkably reduced, the use amount of acid and alkali is reduced, resources can be effectively saved, the production cost is reduced, the recovery of equipment investment is realized, and the clean production and sustainable development of the electroplating industry are promoted and promoted.

The purpose of the invention is realized by the following technical scheme:

the invention provides an electroplating wastewater treatment method, which is characterized by sequentially comprising the following steps:

(1) respectively pretreating metal wastewater, organic wastewater, complexing wastewater, cyanide-containing wastewater, nickel-containing wastewater, zinc-containing wastewater and chromium-containing wastewater to obtain pretreated water;

(2) mixing the metal wastewater pretreatment water, the organic wastewater pretreatment water, the complexing wastewater pretreatment water, the cyanide-containing wastewater pretreatment water, the nickel-containing wastewater pretreatment water, the zinc-containing wastewater pretreatment water and the chromium-containing wastewater pretreatment water obtained in the step (1) and performing biochemical treatment to obtain biochemical treatment water;

(3) concentrating the biochemical treatment water obtained in the step (2) to obtain concentrated high-salinity concentrated water and reuse water;

(4) carrying out evaporation crystallization treatment on the concentrated high-salinity concentrated water obtained in the step (3) to obtain recycled water and crystals;

wherein the standard of the recycled water is as follows: pH 6-8, conductivity less than or equal to 50, COD less than or equal to 30 and turbidity less than or equal to 1.

Preferably, in the step (1),

the pH value of the metal wastewater is 3-6;

preferably, the pH of the organic wastewater is 2-11;

preferably, the pH value of the complex electroplating wastewater is 2-6, and the complex electroplating wastewater contains copper, nickel, SS and COD;

preferably, the chromium-containing wastewater has a pH of 2-4 and contains pollutants such as hexavalent chromium, trivalent chromium, sulfuric acid, nitric acid, oxides, COD and the like;

preferably, the nickel-containing wastewater has pH4-6 and contains pollutants such as nickel, SS, COD and the like;

preferably, the cyanide-containing wastewater has pH of 8-11 and contains contaminants such as copper ions, zinc, SS and COD;

preferably, the zinc-containing wastewater has pH 6-8 and contains pollutants such as zinc ions, SS, COD and the like; wherein Zn in the zinc-containing wastewater²⁺Is 30-50 mg/L.

Preferably, in the step (1), the step of pretreating the metal wastewater comprises:

(a-1) introducing the metal wastewater into a complex breaking pool, and adding sulfuric acid into the complex breaking pool until the pH value is 2-3;

(a-2) introducing the wastewater treated in the step (a-1) into a pH adjusting tank, and adding sodium hydroxide until the pH is 9-10;

(a-3) introducing the wastewater treated in the step (a-2) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(a-4) introducing the wastewater treated in the step (a-3) into a precise control efficient precipitation system;

preferably, in the step (a-1), a 10% sulfuric acid solution is added to adjust the pH;

preferably, in the step (a-2), a 10% sodium hydroxide solution is added to adjust the pH;

preferably, in the step (a-3), the coagulant is an inorganic coagulant, more preferably FeCl₃(ii) a Preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the time interval between the addition of the coagulant and the flocculant is 20-40 min;

preferably, the pH of the wastewater treated by the step (a-3) is 8-9;

preferably, in the step (a-4), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; preferably, the wastewater treated in the step (a-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; preferably, the pressure of the sedimentation treatment tank is 2-3 Mpa;

preferably, after the metal wastewater is pretreated, the COD of the metal wastewater is less than or equal to 100mg/L, and the SS of the metal wastewater is less than or equal to 100 mg/L.

Preferably, in the step (1), the organic wastewater is pretreated by:

(b-1) introducing the metal wastewater into a complex breaking pool, and adding sulfuric acid into the complex breaking pool until the pH value is 2-3;

(b-2) introducing the wastewater treated in the step (b-1) into a pH adjusting tank, and adding sodium hydroxide until the pH is 9-10;

(b-3) introducing the wastewater treated in the step (b-2) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(b-4) introducing the wastewater treated in the step (b-3) into a precise control efficient precipitation system;

preferably, in the step (b-1), a 10% sulfuric acid solution is added to adjust the pH;

preferably, in the step (b-2), a 10% sodium hydroxide solution is added to adjust the pH;

preferably, in the step (b-3), the coagulant is an inorganic coagulant, more preferably FeCl₃(ii) a Preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the time interval between the addition of the coagulant and the flocculant is 20-40 min;

preferably, the pH of the wastewater treated in the step (b-3) is 8-9;

preferably, in the step (b-4), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, an effluent weir and a sludge hopper; preferably, the wastewater treated in the step (b-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; preferably, the pressure of the sedimentation treatment tank is 2-3 Mpa;

Preferably, in the step (1), the step of pretreating the complexing wastewater is as follows:

(c-1) introducing the complex electroplating wastewater into a complex breaking tank, adding sulfuric acid into a zinc breaking tank until the pH value is 2-3, and then adding sodium hypochlorite until the ORP value is 300-400 mv;

(c-2) introducing the wastewater treated in the step (c-1) into a pH adjusting tank, and adding sodium hydroxide until the pH is 10-11;

(c-3) introducing the wastewater treated in the step (c-2) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(c-4) introducing the wastewater treated in the step (c-3) into a precise control efficient precipitation system;

preferably, in the step (c-1), a 10% sulfuric acid solution is added to adjust the pH; preferably, sodium hypochlorite solution with the concentration of 10 percent is added to adjust the ORP value;

preferably, in the step (c-2), a 10% sodium hydroxide solution is added to adjust the pH;

preferably, in the step (c-3), the coagulant is an inorganic coagulant, more preferably FeCl₃(ii) a Preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the time interval between the addition of the coagulant and the flocculant is 20-40 min;

preferably, the pH of the wastewater treated in the step (c-3) is 8 to 9;

preferably, in the step (c-4), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; preferably, the wastewater treated in the step (c-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; preferably, the pressure of the sedimentation treatment tank is 2-3 Mpa;

preferably, after the complexing wastewater is pretreated, the COD of the complexing wastewater is less than or equal to 100mg/L, and the SS of the complexing wastewater is less than or equal to 100 mg/L.

Preferably, in the step (1), the step of pretreating the cyanide-containing wastewater is as follows:

(d-1) introducing the cyanide-containing wastewater into a cyanide breaking pool, and adding sodium hydroxide into the cyanide breaking pool until the pH value is 10-11;

(d-2) adding an oxidant into the wastewater treated in the step (d-1), and stirring until the ORP value is 300-400 mv;

(d-3) adding sulfuric acid into the wastewater treated in the step (d-2) until the pH value is 6.5-7; adding oxidant, and maintaining for 15-30min until CO is generated₂And N₂；

(d-4) introducing the wastewater treated in the step (d-3) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(d-5) introducing the wastewater treated in the step (d-4) into a precise control efficient precipitation system;

preferably, in the step (d-1), sodium hydroxide with the concentration of 8-15% is added to adjust the pH;

preferably, in the step (d-2), the oxidant is sodium hypochlorite solution; preferably, the concentration of the sodium hypochlorite solution is 8-15%; preferably, the stirring time is 15-30 min; preferably, the stirring temperature is 15-35 ℃;

preferably, in the step (d-3), the pH is adjusted by adding sulfuric acid with the concentration of 8-15%; preferably, the oxidant is a sodium hypochlorite solution; preferably, the concentration of the sodium hypochlorite solution is 8-15%;

preferably, in the step (d-4), the coagulant is an inorganic coagulant, more preferably FeCl₃(ii) a Preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the time interval between the addition of the coagulant and the flocculant is 25-35 min;

preferably, in the step (d-5), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, an effluent weir and a sludge hopper; preferably, the wastewater treated in the step (d-4) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and sludge is deposited in a sludge hopper; preferably, the pressure of the sedimentation treatment tank is 2-3 Mpa;

preferably, after the cyanide-containing wastewater is pretreated, the COD of the cyanide-containing wastewater is less than or equal to 100mg/L, and the SS of the cyanide-containing wastewater is less than or equal to 100 mg/L.

Preferably, in the step (1), the nickel-containing wastewater is pretreated by:

(e-1) introducing the nickel-containing wastewater into a pH adjusting tank, and adding sodium hydroxide to adjust the pH to 10-11;

(e-2) introducing the wastewater treated in the step (e-1) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(e-3) introducing the wastewater treated in the step (e-2) into a precise control efficient precipitation system;

preferably, in the step (e-1), a 10% sodium hydroxide solution is added to adjust the pH;

preferably, in the step (e-2), the coagulant is an inorganic coagulant, more preferably FeCl₃(ii) a Preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the coagulant and flocculant are addedThe time interval is 20-40 min; preferably, the pH of the wastewater treated in the step (e-2) is 10-11;

preferably, in the step (e-3), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; preferably, the wastewater treated in the step (e-2) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and sludge is deposited in a sludge hopper;

preferably, after the nickel-containing wastewater is pretreated, the COD is less than or equal to 100mg/L, and the SS is less than or equal to 100 mg/L.

Preferably, in the step (1), (1-1) the zinc-containing wastewater is introduced into a zinc breaking tank, sulfuric acid is added into the zinc breaking tank until the pH value is 2-3, and then sodium hypochlorite is added until the ORP value is 300-400mv, so as to carry out zinc breaking reaction;

(f-2) introducing the wastewater treated in the step (f-1) into a pH adjusting tank, and adding sodium hydroxide until the pH is 8.5-9.5;

(f-3) introducing the wastewater treated in the step (f-2) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(f-4) introducing the wastewater treated in the step (f-3) into a precise control efficient precipitation system;

preferably, in the step (f-1), a 10% sulfuric acid solution is added to adjust the pH; preferably, sodium hypochlorite solution with the concentration of 10 percent is added to adjust the ORP value;

preferably, the zinc breaking reaction time of the step (f-1) is 20-30 min;

preferably, in the step (f-2), a 10% sodium hydroxide solution is added to adjust the pH;

preferably, in the step (f-3), the coagulant is an inorganic coagulant, more preferably PAC; preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the time interval between the addition of the coagulant and the flocculant is 20-40 min;

preferably, the pH of the wastewater treated in the step (f-3) is 8 to 9;

preferably, in the step (f-4), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; preferably, the wastewater treated in the step (f-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; preferably, the pressure of the sedimentation treatment tank is 2-3 Mpa;

preferably, after the zinc-containing wastewater is pretreated, the COD is less than or equal to 100mg/L, and the SS is less than or equal to 100 mg/L.

Preferably, in the step (1), the step of pretreating the chromium-containing wastewater comprises the following steps:

(g-1) introducing the chromium-containing wastewater into a chromium breaking tank, adding sulfuric acid into the chromium breaking tank until the pH value is 2-3, and then adding sodium sulfite into the chromium breaking tank until the ORP value is 230-270mv to carry out chromium breaking reaction;

(g-2) introducing the wastewater treated in the step (g-1) into a pH adjusting tank, and adding sodium hydroxide until the pH is 8-9;

(g-3) introducing the wastewater treated in the step (g-2) into a chemical reaction tank, adding a coagulant, then adding a flocculant, and stirring for 20-30 min;

(g-4) introducing the wastewater treated in the step (g-3) into a precise control efficient precipitation system;

preferably, in the step (g-1), a 10% sulfuric acid solution is added to adjust the pH; preferably, sodium sulfite solution with the concentration of 10 percent is added to adjust the ORP value;

preferably, the chromium breaking reaction time of the step (g-1) is 20-30 min;

preferably, in the step (g-2), a 10% sodium hydroxide solution is added to adjust the pH;

preferably, in the step (g-3), the coagulant is an inorganic coagulant, more preferably PAC; preferably, the flocculant is an organic flocculant, more preferably PAM; preferably, the time interval between the addition of the coagulant and the flocculant is 20-40 min;

preferably, the pH of the wastewater treated in the step (g-3) is 8 to 9;

preferably, the ORP value of the wastewater treated by the step (g-3) is 230-270 mv;

preferably, in the step (g-4), the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; preferably, the wastewater treated in the step (1-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; preferably, the pressure of the sedimentation treatment tank is 2-3 Mpa;

preferably, after the chromium-containing wastewater is pretreated, the COD is less than or equal to 100mg/L, and the SS is less than or equal to 100 mg/L.

Preferably, in the step (2), the biochemical treatment step is: mixing the metal wastewater pretreatment water, the organic wastewater pretreatment water, the complexing wastewater pretreatment water, the chromium-containing wastewater pretreatment water, the cyanide-containing wastewater pretreatment water, the nickel-containing wastewater pretreatment water and the zinc-containing wastewater pretreatment water obtained in the step (1), and sequentially feeding the mixed water into an anaerobic tank, an aerobic tank and a membrane bioreactor;

preferably, the anaerobic pool comprises anaerobic bacteria; preferably, the anaerobic bacteria are selected from one or more of yeast, nitrate bacteria, clostridium or bacteroides;

preferably, the yeast, nitrate, clostridia or bacteroides are acclimatized to be salt-tolerant;

preferably, the aerobic tank contains aerobic microorganisms;

preferably, the aerobic microorganism is selected from one or more of bacillus, rhizobium, nitrobacteria or mould;

preferably, the bacillus, rhizobium, nitrifier or mould is acclimated to be salt tolerant;

preferably, the membrane bioreactor consists of a hollow fiber membrane component and a membrane pool; preferably, the hollow fiber membrane module is located in the membrane tank;

preferably, the pore diameter of the hollow fiber membrane is 0.01-0.1 μm;

preferably, the pH after the biochemical treatment is 6 to 8.

Preferably, in the step (3), the concentration treatment step is: sequentially passing the biochemical treatment water obtained in the step (2) through a primary nanofiltration system, a primary reverse osmosis system and a secondary reverse osmosis system;

preferably, the primary nanofiltration system is formed by sequentially connecting a precision filter and a primary nanofiltration membrane;

preferably, the filter element of the precision filter is melt-blown PP cotton;

preferably, the filter element pore size of the precise microporous filter is 5 μm;

preferably, the primary nanofiltration membrane is an industrial grade high-desalination-rate nanofiltration membrane;

preferably, the aperture of the primary nanofiltration membrane is 1-2 nm;

preferably, the rejection rate of the primary nanofiltration membrane to sodium ions is 50-70%; preferably, the rejection rate of the primary nanofiltration membrane on heavy metal ions and salts is more than 97%;

preferably, the membrane feeding pressure of the primary nanofiltration system is 1.0-1.5 Mpa;

preferably, the relative molecular mass cut-off range of the primary nanofiltration system is 150-300 daltons;

preferably, the pH of the water entering the primary nanofiltration system is 6-8;

preferably, the permeate of the primary nanofiltration system can be used as reuse water;

preferably, the concentrated solution of the primary nanofiltration system enters a primary reverse osmosis system.

Preferably, in the step (3), the first-stage reverse osmosis system is formed by sequentially connecting a precision filter and a first-stage reverse osmosis membrane;

preferably, the filter element of the precision filter is melt-blown PP cotton;

preferably, the first-stage reverse osmosis membrane is a brackish water reverse osmosis membrane;

preferably, the rejection rate of the first-stage reverse osmosis membrane on heavy metal ions and salts is more than 98 percent;

preferably, the aperture of the primary reverse osmosis membrane is 0.1-1 nm;

preferably, the membrane inlet pressure of the primary reverse osmosis system is 1.8 Mpa;

preferably, the pH of the water entering the primary reverse osmosis system is 5-6;

preferably, the primary reverse osmosis system is adjusted in pH by adding hydrochloric acid;

preferably, hydrochloric acid with the concentration of 0.2-0.5% is added to adjust the pH;

preferably, the permeate of the primary reverse osmosis system returns to the primary nanofiltration system;

preferably, the concentrate of the primary reverse osmosis system enters a secondary reverse osmosis system.

Preferably, in the step (3), the secondary reverse osmosis system is formed by sequentially connecting a precision filter and a secondary reverse osmosis membrane;

preferably, the filter element of the precision filter is melt-blown PP cotton;

preferably, the secondary reverse osmosis membrane is a seawater reverse osmosis membrane;

preferably, the rejection rate of the secondary reverse osmosis membrane on heavy metal ions and salts is more than 99.5%;

preferably, the aperture of the secondary reverse osmosis membrane is 0.1-1 nm;

preferably, the membrane inlet pressure of the secondary reverse osmosis system is 4-5 Mpa;

preferably, the pH of the water entering the secondary reverse osmosis system is 6 to 8;

preferably, the secondary reverse osmosis system is adjusted in pH by adding hydrochloric acid;

preferably, the concentration of the hydrochloric acid is 0.2-0.5%;

preferably, the permeate of the secondary reverse osmosis system returns to the primary nanofiltration system;

preferably, the concentrate of the secondary reverse osmosis system is the high salinity concentrate.

Preferably, in the step (4), the evaporative crystallization treatment step is: sequentially passing the high-salinity concentrated water obtained in the step (3) through a heat exchanger, a concentration evaporator and an evaporation crystallizer;

preferably, the operating temperature of the heat exchanger is 80-100 ℃;

preferably, the operating pressure of the heat exchanger is 0.05-0.1 MPa;

preferably, the concentration evaporator is formed by sequentially connecting a heating chamber, a separation chamber, a circulating chamber, a liquid distributor and a demister;

preferably, the evaporative crystallizer is formed by sequentially connecting a separation chamber, a salt leg, a thickener and a crystallization kettle;

preferably, the condensed water of the high-salinity concentrated water after passing through the concentration evaporator returns to the secondary reverse osmosis system;

preferably, the concentrated high-salt water passes through a concentration evaporator to obtain concentrated high-salt water;

preferably, the concentrated high-salinity concentrated water has the salinity of 30-35%;

preferably, the concentrated high-salinity concentrated water passes through an evaporative crystallizer to obtain a crystal substance and condensed water; preferably, the crystal is sodium sulfate and/or sodium chloride; preferably, the condensed water is used as reuse water.

The invention also provides a treatment system of the electroplating wastewater treatment method, which comprises a metal wastewater pretreatment unit, an organic wastewater pretreatment unit, a complexing wastewater pretreatment unit, a cyanide-containing wastewater pretreatment unit, a nickel-containing wastewater pretreatment unit, a zinc-containing wastewater pretreatment unit and a chromium-containing wastewater pretreatment unit, wherein the pretreatment units are respectively and sequentially communicated with a biochemical treatment unit, a concentration treatment unit and an evaporative crystallization treatment unit.

Preferably, the metal wastewater pretreatment unit comprises a complex breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the organic wastewater pretreatment unit comprises a complex breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the complexing wastewater pretreatment unit comprises a complexing breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the cyanide-containing wastewater pretreatment unit comprises a cyanide breaking tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the nickel-containing wastewater pretreatment unit comprises a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the zinc-containing wastewater pretreatment unit comprises a zinc breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the chromium-containing wastewater pretreatment unit comprises a chromium breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated; preferably, the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper.

Preferably, the biochemical treatment unit comprises an anaerobic tank, an aerobic tank and a membrane bioreactor which are communicated in sequence;

preferably, the membrane bioreactor consists of a hollow fiber membrane component and a membrane pool;

preferably, the hollow fiber membrane module is located in the membrane tank;

preferably, the pore diameter of the hollow fiber membrane is 0.01 to 0.1 μm;

preferably, the pH after the biochemical treatment is 6 to 8.

Preferably, the concentration treatment unit comprises a first-stage nanofiltration system, a first-stage reverse osmosis system and a second-stage reverse osmosis system which are sequentially communicated.

preferably, the filter element of the precision filter is melt-blown PP cotton;

preferably, the aperture of the primary nanofiltration membrane is 1-2 nm;

Preferably, the first-stage reverse osmosis system is formed by sequentially connecting a precision filter and a first-stage reverse osmosis membrane;

preferably, the filter element of the precision filter is melt-blown PP cotton;

preferably, the aperture of the primary reverse osmosis membrane is 0.1-1 nm;

preferably, the membrane inlet pressure of the primary reverse osmosis system is 1.6-2.0 Mpa;

preferably, hydrochloric acid is added at a concentration of 0.2-0.5% to adjust the pH.

Preferably, the secondary reverse osmosis system is formed by sequentially connecting a precision filter and a secondary reverse osmosis membrane;

preferably, the filter element of the precision filter is melt-blown PP cotton;

preferably, the aperture of the secondary reverse osmosis membrane is 0.1-1 nm;

Preferably, the evaporative crystallization unit comprises a heat exchanger, a concentration evaporator and an evaporative crystallizer which are communicated in sequence;

preferably, the evaporative crystallizer consists of a separation chamber, a salt leg, a thickener and a crystallization kettle which are connected in sequence.

The electroplating wastewater treatment method or the treatment system of the electroplating wastewater treatment method is applied to treatment of electroplating wastewater.

The treatment method or the treatment system provided by the invention is applied to treatment of electroplating wastewater.

In order to overcome the defects in the electroplating wastewater treatment in the prior art, the invention provides a method for treating electroplating wastewater

The metal wastewater pollutants are mainly various bath solutions and drainage of 'running, overflowing, dripping and leaking' caused by leakage of a plating bath and poor operation or management; besides, the floor of the workshop is washed and the polar plate is brushed by water, etc. The pollutants are mainly heavy metals such as chromium, nickel, zinc, copper and the like.

The organic waste water pollutant is mainly cleaning waste water produced in the procedures of oil removal, degreasing, rust removal, activation and the like in the preparation process before plating, and the main pollutants are organic matters, suspended matters, petroleum, phosphate, trace metal ions, antirust oil, a release agent, polishing wax, metal oxides and other impurities.

The chromium-containing wastewater is mainly wastewater generated in the working procedures of cleaning a plated part, cleaning a polar plate, passivating zinc and other plated parts, electrolytic polishing of stainless steel, anodizing of aluminum, treating the plated part and the like after a chromium plating process, has a pH of 2-4, and mainly contains pollutants such as hexavalent chromium, trivalent chromium, sulfuric acid, nitric acid, oxides, COD and the like;

the invention discloses a method for analyzing the source of nickel-containing wastewater pollutants, which comprises the following steps: the nickel-containing wastewater is mainly wastewater generated in working procedures of cleaning a plated part, cleaning a polar plate and the like after a nickel plating process, and the pH value of the nickel-containing wastewater is 4-6, and the nickel-containing wastewater mainly contains pollutants such as nickel, SS, COD and the like;

the invention discloses a method for analyzing the source of cyanide-containing wastewater pollutants, which comprises the following steps: the cyanide-containing wastewater is mainly wastewater generated in the working procedures of cleaning a plated part, cleaning a polar plate, passivating zinc and other plated parts, electrolytic polishing of stainless steel, anodizing aluminum, treating the plated part and the like after an electroplating process, has the pH of 8-11, and contains pollutants such as copper ions, zinc, SS, COD and the like;

the invention discloses a method for analyzing the pollutant source of zinc-containing wastewater, which comprises the following steps: the zinc-containing wastewater is mainly wastewater generated in the working procedures of cleaning a plated part, cleaning a polar plate, passivating the plated part such as zinc and the like, electrolytic polishing of stainless steel, anodic oxidation of aluminum, treatment of the plated part and the like after an electroplating process, and has the pH of 6-8 and contains pollutants such as zinc, SS, COD and the like;

the source analysis of the complex electroplating wastewater pollutants comprises the following steps: the complex waste water is mainly a working section of adopting complex metal to carry out electroplating in the electroplating process, mainly comprises copper salt and phosphate to form a plating solution, nickel sulfate, nickel acetate and the like are taken as main salts, hypophosphite, sodium borohydride, borane, hydrazine and the like are taken as reducing agents, and various auxiliary agents, reducing agents, potassium pyrophosphate, potassium citrate, nitrilotriacetic acid, additives and the like are added; the wastewater mainly comprises copper, nickel, SS, COD and other substances.

The invention relates to a pretreatment process of metal electroplating wastewater, which comprises the following steps: introducing the metal wastewater into a complex breaking tank, and adding sulfuric acid with the concentration of 10% into the complex breaking tank until the pH value is 2-3; then introducing the wastewater into a pH adjusting tank, and adding 10% sodium hydroxide to adjust the pH to 9-10; introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. In advection typeOr the sedimentation area of the vertical sedimentation tank is divided into a series of shallow sedimentation layers by utilizing the inclined parallel pipes, and the treated and settled sludge moves and is separated in each sedimentation shallow layer, so that sludge-water separation is realized. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The invention discloses an organic electroplating wastewater pretreatment process which comprises the following steps: introducing the metal wastewater into a complex breaking tank, and adding sulfuric acid with the concentration of 10% into the complex breaking tank until the pH value is 2-3; then introducing the wastewater into a pH adjusting tank, and adding 10% sodium hydroxide to adjust the pH to 9-10; introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. Wastewater enters the bottom of the sedimentation treatment tank through a water distribution system and flows downwardsAnd the sludge enters the inclined pipe from the top, the sludge is separated from the water in the inclined pipe, the sludge sinks into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into a sludge treatment system, and the wastewater after the sludge-water separation flows upwards to enter an effluent weir at the top of the tank and then enters a next treatment system.

The invention discloses a pretreatment process of complexing electroplating wastewater, which comprises the following steps: introducing the metal wastewater into a complex breaking tank, and adding sulfuric acid with the concentration of 10% into the complex breaking tank until the pH value is 2-3; adding sodium hypochlorite with the concentration of 10% to the ORP value of 300-400mv, introducing the wastewater into a pH adjusting tank, and adding sodium hydroxide with the concentration of 10% to adjust the pH to 10-11; introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The invention discloses a cyanide-containing wastewater pretreatment process which comprises the following steps: introducing the cyanide-containing wastewater into a cyanide breaking tank, and adding a sodium hydroxide solution with the concentration of 8-15% into the cyanide breaking tank until the pH value is 10-11; then adding sodium hypochlorite with the concentration of 8-15% to the ORP value of 300-400mv, and then adding the waste waterAdding 8-15% sulfuric acid to regulate pH to 6.5-7; adding sodium hypochlorite with concentration of 8-15%, and maintaining for 15-30min until CO is generated₂And N₂(ii) a Introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The nickel-containing wastewater pretreatment process comprises the following steps: the invention discloses a pretreatment process of complexing electroplating wastewater, which comprises the following steps: introducing the metal wastewater into a chromium breaking pool, and adding sulfuric acid with the concentration of 10% into the chromium breaking pool until the pH value is 2-3; adding sodium hypochlorite with the concentration of 10% to the ORP value of 300-400mv, introducing the wastewater into a pH adjusting tank, and adding sodium hydroxide with the concentration of 10% to adjust the pH to 10-11; introducing the treated wastewater into a chemical reaction tank, adding PAC, adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The zinc-containing wastewater pretreatment process comprises the following steps: introducing the zinc-containing wastewater into a zinc breaking tank, and adding sulfuric acid with the concentration of 10% into the zinc breaking tank until the pH value is 2-3; adding sodium hypochlorite with the concentration of 10 percent until the ORP value is 300-400mv, introducing the wastewater into a pH adjusting tank, and adding sodium hydroxide with the concentration of 10 percent to adjust the pH to 8.5-9.5; introducing the treated wastewater into a chemical reaction tank, adding PAC, adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The invention discloses a pretreatment process of chromium-containing wastewater, which comprises the following steps: introducing the chromium-containing wastewater into a chromium breaking tank, and adding sulfuric acid with the concentration of 10% into a zinc breaking tank until the pH value is 2-3; adding sodium hypochlorite with the concentration of 10% to the ORP value of 230-270mv for chromium breaking reaction, introducing the wastewater into a pH regulating tank, and adding sodium hydroxide with the concentration of 10% to regulate the pH to 8-9; introducing the treated wastewater into a chemical reaction tank, adding PAC, adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The biochemical treatment process of the electroplating wastewater comprises the following steps: mixing the obtained pretreatment water, and sequentially feeding the mixed pretreatment water into an anaerobic tank, an aerobic tank and a membrane bioreactor; removing most of COD, ammonia nitrogen, SS and other substances in the wastewater through biodegradation of the A/O/MBR; the anaerobic process of the invention utilizes the function of anaerobic bacteria under the condition of no dissolved oxygen or under the condition of oxygen deficiency to hydrolyze and acidify organic matters, remove the organic matters in the wastewater, improve the biodegradability of the sewage and be beneficial to the subsequent aerobic treatment process; the aerobic process is that under aerobic condition, organic matter is oxidized and decomposed under the action of aerobic microbe, the concentration of organic matter is reduced, the amount of microbe is increased, the organic matter in sewage is adsorbed on the surface of active sludge and biomembrane and contacts with the surface of microbe cell, small molecular organic matter can enter microbe body through cell wall directly, and large molecular organic matter must be hydrolyzed into small molecular under the action of extracellular enzyme-hydrolase and then taken into cell body by microbe. The organic matter is finally decomposed into CO₂And H₂O; the membrane bioreactor comprises a hollow fiber membrane component and a membrane pool, wherein the hollow fiber membrane component is positioned in the membrane pool, and because the hollow fiber membrane has a pore diameter of 0.01-0.1 mu m, zoogloea and free bacteria can be completely retained in the membrane pool, so that mud-water separation is achieved, various suspended particles, bacteria, algae, turbidity and organic matters are effectively removed, and excellent effluent quality with the effluent suspended matters close to zero is ensured. The efficient interception function of the membrane bioreactor can effectively intercept nitrifying bacteria, so that the nitrification reaction is smoothly carried out, and ammonia nitrogen is effectively removed; meanwhile, macromolecular organic matters which are difficult to degrade can be intercepted, and the retention time of the macromolecular organic matters in the biochemical reaction tank is prolonged, so that the macromolecular organic matters are decomposed to the maximum extent.

The concentration treatment process of the electroplating wastewater comprises the following steps: the biochemical treatment water sequentially passes through a primary nanofiltration system, a primary reverse osmosis system and a secondary reverse osmosis system; in order to realize zero discharge of electroplating wastewater, the rear end of the biochemical treatment system is provided with a concentration treatment system for treating strong brine generated by the biochemical treatment system; the concentration treatment system is a process combining multi-stage concentration and nanofiltration/reverse osmosis concentration, and gradually reduces the water amount of the high-salt-content wastewater (the salt content of the obtained high-salt concentrated water is 40-60g/L) through the step-by-step concentration of the membrane, so that the investment and the operating cost of a subsequent evaporative crystallization system are reduced; the concentration treatment process reduces the concentrated brine to be treated in a subsequent evaporation crystallization system by 80 percent compared with a conventional concentration treatment system, reduces the investment cost of the whole wastewater treatment system by 20 to 30 percent, reduces the running cost of wastewater treatment by 30 to 40 percent, and improves the automation degree of the system.

The electroplating wastewater evaporation crystallization treatment process comprises the following steps: the high-salinity concentrated water obtained by concentration treatment sequentially passes through a heat exchanger, a concentration evaporator and an evaporation crystallizer; the wastewater is treated to the evaporation crystallization stage and then is completely recycled, so that the zero discharge of the electroplating wastewater is realized; the waste water firstly enters a heat exchanger in the evaporative crystallization system, and the O in the waste water is removed through heat exchange₂And CO₂And (3) gas and waste water after heat exchange enter a concentration evaporator for evaporation concentration, when the salt concentration of the waste water is 30-35%, namely before sodium sulfate and sodium chloride are crystallized, the waste water is sent to an evaporation crystallizer to obtain crystals and condensed water, and the condensed water is used as reuse water. The evaporative crystallization system utilizes mechanical temperature increasing equipment to cause negative pressure of the waste water evaporation part, so that energy can be saved, compressed waste water steam is heated and pressurized to enter the outside of a concentration evaporator, latent heat is transferred to a pipe, the pipe is condensed into condensed water, and meanwhile, salt-containing waste water in the pipe is evaporated. The evaporative crystallization system has the characteristics of small volume, small occupied area, low energy consumption and high thermal efficiency, the power consumption of one ton of waste water is 16-20kwh, the thermal efficiency is 27 times that of a single-effect flash evaporation system and 7 times that of a four-effect flash evaporation system, the evaporative crystallization system is the most advanced evaporative concentration system at present, the generated crystals can be treated or sent to related departments for purification and utilization, and the main components of the evaporative crystallization system are sodium sulfate and sodium chloride.

The advantages of the evaporative crystallization system are as follows: (1) the system adopts mixed process water supply, so that the ton water power consumption of the same water making tonnage device is reduced by 40-50% compared with the foreign technology; (2) because the mixed process of the system supplies water, the high-salinity concentrated water passing through the concentration treatment system sequentially enters the low-temperature effect from the high-temperature effect of the evaporative crystallization system, the concentration is gradually increased, and the temperature is gradually reduced. The increase of the concentration of the high-temperature effect feed water caused by circulating feed water from low-temperature effect to high-temperature effect in foreign technologies is avoided, and the scaling and corrosion conditions of high-temperature effect are effectively reduced; (3) the high-salinity concentrated water passing through the concentration treatment system is uniformly distributed on the concentration evaporator, so that the defect that the spray head type water supply in the existing evaporative crystallization system is not uniform and is easy to block is avoided; (4) the vacuum system adopts a differential pressure air extractor, and the designed differential pressure is accurately formed among the effects, so that the system is stable and reliable in operation.

The treatment system of the electroplating wastewater treatment method adopts a Programmable Logic Controller (PLC), simultaneously realizes the automatic control and monitoring of electric appliances and instruments, and adopts an industrial personal computer to monitor the operation process state and the operation parameters of the system. In addition, the system is periodically flushed by a permeate liquid to flush pollutants on the membrane surface and protect the membrane; and an on-line chemical cleaning system is established, so that long-term, stable and efficient operation of the system can be ensured.

Compared with the prior art, the electroplating wastewater treatment method provided by the invention not only improves the wastewater reuse rate to 99.67%, but also can greatly reduce the treatment cost, reduce the solid waste production and the metal ion resource in the wastewater, and thoroughly realize zero discharge of the wastewater.

The electroplating wastewater treatment method and the treatment system have the beneficial effects that:

(1) according to different reaction conditions of various heavy metal ions, the pretreatment process of the electroplating wastewater adopts online monitoring instruments such as pH, ORP and the like, automatically controls a metering pump to quantitatively feed chemicals, adds the chemicals to fully react with the wastewater, and carries out solid-liquid separation treatment through a precisely controlled high-efficiency precipitation system, so that the removal rate of the heavy metal ions can reach 99.99%.

(2) The biochemical process of the electroplating wastewater adopts an A/O/MBR process, the system consists of a biochemical tank, a membrane component and a membrane tank, and the activated sludge can be completely retained in the membrane tank, so that various pollutants such as various suspended particles, bacteria, organic matters and the like can be retained for a long time, and can be fully removed, the quality of effluent is ensured to be excellent, and SS is almost zero. The process has high volume load and strong adaptability to water quality and water quantity, and adopts the domesticated special microorganism with salt tolerance to remove the wastewater with high salt content and hard-to-degrade COD with high efficiency and good denitrification effect.

(3) The electroplating wastewater concentration process adopts a special membrane concentration technology to concentrate the salt in the wastewater by more than 30 times according to the technology of combining desalination concentration and fine desalination concentration, and the produced water of an advanced treatment system can be directly reused for production. The special membrane concentration technology has the characteristics of high efficiency desalination rate under high flow rate, higher mechanical strength, longer service life, capability of playing a function under lower operation pressure, good chemical stability and high cost performance.

(4) The electroplating wastewater evaporative crystallization adopts a German special vapor compression technology, and comprises a distilled water heat exchanger, a concentration evaporator, a crystallizer, a centrifuge and the like, when the evaporator is used for treating wastewater, the heat energy required by the wastewater evaporation is provided by the heat energy released during the condensation of vapor and the cooling of condensed water, and no latent heat is lost during the operation process, so that the wastewater is evaporated at low temperature and negative pressure. When the compressor compresses, the pressure and the temperature are increased, and the high enthalpy steam is used as a heat source again to fully recover the heat of the distilled water and the concentrated solution, thereby saving the energy consumption. During evaporation, the evaporation outside the pipe is adopted, so that the efficiency is high and the scale in the pipe is never accumulated.

The electroplating wastewater treatment method and the treatment system provided by the invention have the advantages that through the technical route of wastewater diversion, classification treatment, wastewater recycling and resource recovery, the electroplating wastewater is completely recycled for production after being treated by adopting a heavy metal high-precision removal technology, a high-salinity wastewater biochemical technology, a special membrane concentration technology and a mechanical negative pressure evaporation crystallization technology, the zero discharge of the wastewater is realized, the wastewater recycling rate is improved to 99.67%, the cyclic utilization of water resources is realized to the maximum extent, pollutants in the wastewater are converted into solids for recycling, and the zero discharge of the wastewater is completely realized.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic view of an integrated electroplating wastewater treatment system according to the present invention.

Detailed Description

The invention is illustrated below with reference to specific examples. It will be understood by those skilled in the art that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention in any way.

The experimental procedures in the following examples are conventional unless otherwise specified. The raw materials and reagent materials used in the following examples are all commercially available products unless otherwise specified.

Example 1

(1) Pretreating the electroplating wastewater to obtain pretreated water

The invention relates to a pretreatment process of metal electroplating wastewater, which comprises the following steps: introducing the metal wastewater into a complex breaking tank, and adding sulfuric acid with the concentration of 10% into the complex breaking tank until the pH value is 2-3; then introducing the wastewater into a pH adjusting tank, and adding 10% sodium hydroxide to adjust the pH to 9-10; introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. Wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, and sludge is sunk into the tank under the action of gravityThe sludge bucket at the bottom is discharged into a sludge treatment system, and the wastewater after mud-water separation flows upwards into a water outlet weir at the top of the tank and then enters the next treatment system.

The invention discloses an organic electroplating wastewater pretreatment process which comprises the following steps: introducing the metal wastewater into a complex breaking tank, and adding sulfuric acid with the concentration of 10% into the complex breaking tank until the pH value is 2-3; then introducing the wastewater into a pH adjusting tank, and adding 10% sodium hydroxide to adjust the pH to 9-10; introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The invention discloses a pretreatment process of complexing electroplating wastewater, which comprises the following steps: introducing the metal wastewater into a complex breaking tank, and adding sulfuric acid with the concentration of 10% into the complex breaking tank until the pH value is 2-3; adding sodium hypochlorite with the concentration of 10% to the ORP value of 300-400mv, introducing the wastewater into a pH adjusting tank, and adding sodium hydroxide with the concentration of 10% to adjust the pH to 10-11; introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirringStirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The invention discloses a cyanide-containing wastewater pretreatment process which comprises the following steps: introducing the cyanide-containing wastewater into a cyanide breaking tank, and adding a sodium hydroxide solution with the concentration of 8-15% into the cyanide breaking tank until the pH value is 10-11; then adding sodium hypochlorite with the concentration of 8-15% to the ORP value of 300-400mv, and then adding sulfuric acid with the concentration of 8-15% into the wastewater to adjust the pH value to 6.5-7; adding sodium hypochlorite with concentration of 8-15%, and maintaining for 15-30min until CO is generated₂And N₂(ii) a Introducing the treated wastewater into a chemical reaction tank, adding FeCl₃Adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation system with an inclined pipe arranged in a sedimentation zoneAnd (4) a sedimentation tank. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The nickel-containing wastewater pretreatment process comprises the following steps: introducing the nickel-containing wastewater into a pH adjusting tank, and adding 10% sodium hydroxide to adjust the pH to 10-11; introducing the treated wastewater into a chemical reaction tank, adding PAC, adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

The invention discloses a pretreatment process of chromium-containing wastewater, which comprises the following steps: introducing the chromium-containing wastewater into a chromium breaking tank, and adding sulfuric acid with the concentration of 10% into the chromium breaking tank until the pH value is 2-3; adding sodium sulfite with the concentration of 10 percent to the ORP value of 230-270mv for chromium breaking reaction, introducing the wastewater into a pH regulating tank, and adding sodium hydroxide with the concentration of 10 percent to regulate the pH to 8-9; introducing the treated wastewater into a chemical reaction tank, adding PAC, adding PAM, and stirring for 20-30 min; finally, introducing the treated wastewater into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; can effectively remove the floc sediment formed by the metallic nickel. The precise control efficient sedimentation system is a controllable precise efficient sedimentation tank with an inclined pipe arranged in a sedimentation zone. The settling area of the horizontal or vertical settling pond is divided into a series of shallow settling layers by inclined parallel pipes, and the treated and settled sludge moves and is separated in each settling shallow layer to realize sludge-water separation. The separation method is divided into three different separation modes of reverse (different) flow, cocurrent flow and direction-finding flow according to the mutual movement direction of the two. Every two parallel pipes are equivalent to a shallow sedimentation tank, so that the sedimentation distance of particles is shortened, the effective sedimentation area of the sedimentation tank is increased, and the treatment efficiency of the sedimentation tank is greatly improved. The wastewater enters the bottom of the sedimentation treatment tank through the water distribution system, the wastewater enters the inclined pipe from bottom to top, mud and water are separated in the inclined pipe, the sludge is deposited into a sludge hopper at the bottom of the tank under the action of gravity and is discharged into the sludge treatment system, and the wastewater after mud and water separation flows upwards to enter an effluent weir at the top of the tank and then enters the next treatment system.

(2) Performing biochemical treatment on the pretreated water to obtain biochemical treated water

Mixing the pretreatment water obtained in the step (1), and sequentially feeding the mixed pretreatment water into an anaerobic tank, an aerobic tank and a membrane bioreactor; the anaerobic pool comprises anaerobic bacteria, wherein the anaerobic bacteria are one or more of saccharomycetes, nitrate bacteria, clostridium or bacteroides, and the aerobic pool comprises aerobic microorganisms, and the aerobic microorganisms are one or more of bacillus, rhizobia, nitrobacteria or mould; then enters a membrane bioreactor, the membrane bioreactor consists of a hollow fiber membrane component and a membrane pool, the hollow fiber membrane component is positioned in the membrane pool, the aperture of the hollow fiber membrane is 0.01-0.1 mu m, the pH value after biochemical treatment is 6-8, and most of COD, ammonia nitrogen, SS and the like in the wastewater can be removedA substance; the anaerobic process of the invention utilizes the function of anaerobic bacteria under the condition of no dissolved oxygen or under the condition of oxygen deficiency to hydrolyze and acidify organic matters, remove the organic matters in the wastewater, improve the biodegradability of the sewage and be beneficial to the subsequent aerobic treatment process; the aerobic process is that under aerobic condition, organic matter is oxidized and decomposed under the action of aerobic microbe, the concentration of organic matter is reduced, the amount of microbe is increased, the organic matter in sewage is adsorbed on the surface of active sludge and biomembrane and contacts with the surface of microbe cell, small molecular organic matter can enter microbe body through cell wall directly, and large molecular organic matter must be hydrolyzed into small molecular under the action of extracellular enzyme-hydrolase and then taken into cell body by microbe. The organic matter is finally decomposed into CO₂And H₂O; the membrane bioreactor can retain all the zoogloea and free bacteria in the membrane pool, thereby achieving mud-water separation, effectively removing various suspended particles, bacteria, algae, turbidity and organic matters, and ensuring the excellent effluent quality with the effluent suspended solids close to zero. The efficient interception function of the membrane bioreactor can effectively intercept nitrifying bacteria, so that the nitrification reaction is smoothly carried out, and ammonia nitrogen is effectively removed; meanwhile, macromolecular organic matters which are difficult to degrade can be intercepted, and the retention time of the macromolecular organic matters in the biochemical reaction tank is prolonged, so that the macromolecular organic matters are decomposed to the maximum extent.

(3) Concentrating the biochemical treatment water to obtain high-salinity concentrated water and reuse water

The biochemical treatment water sequentially passes through a primary nanofiltration system, a primary reverse osmosis system and a secondary reverse osmosis system; the primary nanofiltration system is formed by sequentially connecting a precision filter and a primary nanofiltration membrane industrial grade high-desalination rate nanofiltration membrane, wherein a filter element of the precision filter is melt-blown PP cotton, and the aperture of the precision microporous filter is 5 mu m; the aperture of the primary nanofiltration membrane is 1-2nm, when water to be treated passes through the primary nanofiltration membrane, the rejection rate of sodium ions is 50%, and the rejection rate of heavy metal ions and salt is 98%; the membrane inlet pressure of the primary nanofiltration system is 1.0-1.5 Mpa; the relative molecular mass interception range of the primary nanofiltration system is 300 daltons; the permeate of the primary nanofiltration system can be used as reuse water.

The concentrated solution of the treated water passing through the primary nanofiltration system enters a primary reverse osmosis system, the primary reverse osmosis system is formed by sequentially connecting a precision filter and a primary reverse osmosis membrane brackish water reverse osmosis membrane, the aperture of the primary reverse osmosis membrane is 0.1-1nm, the membrane inlet pressure of the primary reverse osmosis system is 1.6-2.0Mpa, the pH is adjusted to be 5-6 by 0.2% hydrochloric acid, and the rejection rate of heavy metal ions and salt is 99% by the primary reverse osmosis membrane; the permeate of the treated water passing through the primary reverse osmosis system returns to the primary nanofiltration system, and the concentrated solution enters the secondary reverse osmosis system. The secondary reverse osmosis system is formed by sequentially connecting a precision filter and a secondary reverse osmosis membrane seawater reverse osmosis membrane; the membrane inlet pressure of the secondary reverse osmosis system is 4-5 Mpa; the rejection rate of heavy metal ions and salt is 99.9% through the secondary reverse osmosis membrane by adjusting the hydrochloric acid content to 6-8% by 0.2%; the permeate of the treated water passing through the secondary reverse osmosis system returns to the primary nanofiltration system, the concentrated solution is high-salt concentrated water, the salt content of the high-salt concentrated water is 40g/L, in addition, the secondary reverse osmosis system also comprises a security filter, the aperture is 5 mu m, and a filter element is melt-blown PP cotton.

In order to realize zero discharge of electroplating wastewater, the rear end of the biochemical treatment system is provided with a concentration treatment system for treating strong brine generated by the biochemical treatment system; the concentration treatment system is a process combining multi-stage concentration and nanofiltration/reverse osmosis concentration, and gradually reduces the water amount of the high-salt-content wastewater (the salt content of the obtained high-salt concentrated water is 40g/L) through the step-by-step concentration of the membrane, so that the investment and the operating cost of a subsequent evaporative crystallization system are reduced; the concentration treatment process reduces the concentrated brine to be treated in a subsequent evaporation crystallization system by 80 percent compared with a conventional concentration treatment system, reduces the investment cost of the whole wastewater treatment system by 30 percent, reduces the running cost of wastewater treatment by 40 percent, and improves the automation degree of the system. The concentration treatment process of the nickel-containing wastewater carries out preconcentration through a precision filter and a primary nanofiltration system, permeate liquid passing through the primary nanofiltration system can be used as reuse water after ion exchange, and concentrated liquid of the primary nanofiltration system enters a primary reverse osmosis system; the permeate of the primary reverse osmosis system returns to the primary nanofiltration system, and the concentrated solution of the primary reverse osmosis system enters the secondary reverse osmosis system; and the permeate of the secondary reverse osmosis system returns to the primary nanofiltration system, and the concentrated solution of the secondary reverse osmosis system is the high-salinity concentrated water.

(4) Carrying out evaporation crystallization treatment on the high-salinity concentrated water to obtain recycled water and crystals

Sequentially passing the high-salinity concentrated water through a heat exchanger, a concentration evaporator and an evaporation crystallizer; the operation temperature of the heat exchanger is 80-100 ℃, the operation pressure of the heat exchanger is 0.05-0.1MPa, and the concentration evaporator is formed by sequentially connecting a heating chamber, a separation chamber, a circulating chamber, a liquid distributor and a demister; the evaporative crystallizer is formed by sequentially connecting a separation chamber, salt legs, a thickener and a crystallization kettle; the condensed water of the high-salinity concentrated water after passing through the concentration evaporator returns to the secondary reverse osmosis system; the concentrated solution obtained after the high-salinity concentrated water passes through the concentration evaporator is concentrated high-salinity concentrated water, and the salt content is g/L; the concentrated high-salinity concentrated water passes through an evaporative crystallizer to obtain a crystal and condensed water; the obtained crystal is sodium sulfate and/or sodium chloride; and the condensed water is returned to the workshop as reuse water for continuous use.

Wherein, the concentration evaporator is composed of a plurality of evaporators connected in series, low-temperature (about 90 ℃) heating steam is introduced into the first effect to heat feed liquid therein, so that the feed liquid generates almost equivalent evaporation with the temperature lower than that of the steam. The steam produced is introduced into the second effect as heating steam, causing the feed liquid of the second effect to evaporate at a lower temperature than the first effect. This process is repeated until the final effect. The first effect condensate water returns to the heat source, other effect condensate water is collected and then output as desalted water, and one part of steam is input and can evaporate multiple times of water to be output. Meanwhile, the feed liquid is sequentially concentrated from the first effect to the last effect, and the feed liquid is supersaturated at the last effect and crystallized and separated out. Thereby realizing the solid-liquid separation of the feed liquid.

The technical parameters of the evaporative crystallization system for treating concentrated water are as follows:

(1) the desalted water has a salt content (TDS) of less than 10ppm

(2) Consumption of steam for desalting per ton is (1/effect number)/90% t/t

(3) The electric power consumption of the desalinated water is 2-4 kwh/t

Comparative example 1

(1) Firstly, taking electroplating wastewater, introducing the electroplating wastewater into a pH adjusting tank, adding sodium hydroxide to adjust the pH, and reacting for 20-25 min; and introducing the wastewater into a chemical reaction tank, adding a coagulant PAC and a flocculant PAM, and stirring for 25 min. And introducing the wastewater into a precipitation system for mud-water separation, introducing the sludge into a sludge treatment system, and introducing the supernatant into a biochemical system.

(2) The pretreated water sequentially enters an anaerobic tank, an aerobic tank and a biochemical sedimentation tank; wherein, the anaerobic pool contains anaerobic bacteria, and the aerobic pool contains aerobic microorganisms; then enters a biochemical sedimentation tank, and the biochemical sedimentation tank consists of a water distribution area, a sludge area, a separation area and a water outlet weir; the SS of the effluent of the biochemical sedimentation tank is 30mg/L, the COD is 50mg/L, 40 percent of the effluent of the biochemical sedimentation tank reaches the standard and is discharged, and 60 percent of the effluent enters a membrane concentration system.

(3) The effluent after biochemical treatment sequentially passes through a precision filter and a reverse osmosis membrane device; wherein the filter element of the precise filter is PP cotton, and the aperture of the precise microporous filter is 5 mu m; the membrane inlet pressure of the reverse osmosis system is 1.2-1.6Mpa, the pH value is adjusted to 5-6 by hydrochloric acid, and the rejection rate of heavy metal ions and salt is 99% by the reverse osmosis membrane; the concentrated solution of the reverse osmosis membrane returns to the pretreatment system for treatment, the conductivity of the permeate of the reverse osmosis membrane is 200 and 300 mu S/cm, which accounts for about 60 percent of the total wastewater, and the permeate is recycled to the production line as reuse water.

In conclusion, the above description of the embodiments of the present invention is not intended to limit the present invention, and those skilled in the art can make various changes or modifications according to the present invention without departing from the spirit of the present invention, which falls within the scope of the appended claims.

Claims

1. The electroplating wastewater treatment method is characterized by comprising the following steps in sequence:

wherein, in the step (1), the step of pretreating the metal wastewater comprises the following steps:

(a-1) introducing the metal wastewater into a complex breaking pool, and adding sulfuric acid with the concentration of 10% into the complex breaking pool until the pH value is 2-3;

(a-2) introducing the wastewater treated in the step (a-1) into a pH adjusting tank, and adding 10% sodium hydroxide until the pH is 9-10;

(a-3) introducing the wastewater treated in the step (a-2) into a chemical reaction tank, and adding a coagulant FeCl₃Then adding flocculant PAM, and stirring for 20-30 min;

(a-4) introducing the wastewater treated in the step (a-3) into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper, and the wastewater treated in the step (a-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; wherein the pressure of the sedimentation treatment tank is 2-3 Mpa;

the organic wastewater pretreatment comprises the following steps:

(b-1) introducing the metal wastewater into a complex breaking pool, and adding sulfuric acid with the concentration of 10% into the complex breaking pool until the pH value is 2-3;

(b-2) introducing the wastewater treated in the step (b-1) into a pH adjusting tank, and adding 10% sodium hydroxide until the pH is 9-10;

(b-3) introducing the wastewater treated in the step (b-2) into a chemical reaction tank, and adding a coagulant FeCl₃Then adding flocculant PAM, and stirring for 20-30 min;

(b-4) introducing the wastewater treated in the step (b-3) into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; introducing the wastewater treated in the step (b-3) into the water distribution system, the sedimentation treatment tank and the inclined pipe in sequence; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; wherein the pressure of the sedimentation treatment tank is 2-3 Mpa;

the steps of the complex wastewater pretreatment are as follows:

(c-1) introducing the complex electroplating wastewater into a complex breaking pool, adding 10% sulfuric acid into the complex breaking pool until the pH value is 2-3, and then adding 10% sodium hypochlorite until the ORP value is 300-400 mv;

(c-2) introducing the wastewater treated in the step (c-1) into a pH adjusting tank, and adding 10% sodium hydroxide until the pH is 10-11;

(c-3) introducing the wastewater treated in the step (c-2) into a chemical reaction tank, and adding a coagulant FeCl₃Then adding flocculant PAM, and stirring for 20-30 min;

(c-4) introducing the wastewater treated in the step (c-3) into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; introducing the wastewater treated in the step (c-3) into the water distribution system, the sedimentation treatment tank and the inclined pipe in sequence; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; wherein the pressure of the sedimentation treatment tank is 2-3 Mpa;

the cyanogen-containing wastewater pretreatment comprises the following steps:

(d-1) introducing the cyanide-containing wastewater into a cyanide breaking pool, and adding 8-15% sodium hydroxide into the cyanide breaking pool until the pH value is 10-11;

(d-2) adding an oxidant into the wastewater treated in the step (d-1), and stirring until the wastewater is OThe RP value is 300-400 mv; wherein the oxidant is sodium hypochlorite solution with the concentration of 8-15%; (d-3) adding sulfuric acid with the concentration of 8-15% into the wastewater treated in the step (d-2) until the pH value is 6.5-7; adding sodium hypochlorite solution with concentration of 8-15%, and maintaining for 15-30min until CO is generated₂And N₂；

(d-4) introducing the wastewater treated in the step (d-3) into a chemical reaction tank, and adding a coagulant FeCl₃Then adding flocculant PAM, and stirring for 20-30 min;

(d-5) introducing the wastewater treated in the step (d-4) into a precise control efficient precipitation system, wherein the precise control efficient precipitation system is formed by sequentially connecting a water distribution system, a precipitation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper, and the wastewater treated in the step (d-4) is sequentially introduced into the water distribution system, the precipitation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and sludge is deposited in a sludge hopper; wherein the pressure of the sedimentation treatment tank is 2-3 Mpa;

the nickel-containing wastewater pretreatment comprises the following steps:

(e-1) introducing the nickel-containing wastewater into a pH adjusting tank, and adding 10% sodium hydroxide to adjust the pH to 10-11;

(e-2) introducing the wastewater treated in the step (e-1) into a chemical reaction tank, and adding a coagulant FeCl₃Then adding flocculant PAM, and stirring for 20-30 min;

(e-3) introducing the wastewater treated in the step (e-2) into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper; introducing the wastewater treated in the step (e-2) into the water distribution system, the sedimentation treatment tank and the inclined pipe in sequence; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and sludge is deposited in a sludge hopper;

the zinc-containing wastewater pretreatment comprises the following steps:

(f-1) introducing the zinc-containing wastewater into a zinc breaking tank, adding 10% sulfuric acid into the zinc breaking tank until the pH value is 2-3, and then adding 10% sodium hypochlorite until the ORP value is 300-400mv to carry out zinc breaking reaction;

(f-2) introducing the wastewater treated in the step (f-1) into a pH adjusting tank, and adding 10% sodium hydroxide until the pH is 8.5-9.5;

(f-3) introducing the wastewater treated in the step (f-2) into a chemical reaction tank, adding a coagulant PAC, then adding a flocculant PAM, and stirring for 20-30 min;

(f-4) introducing the wastewater treated in the step (f-3) into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper, and the wastewater treated in the step (f-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; wherein the pressure of the sedimentation treatment tank is 2-3 Mpa;

the method for pretreating the chromium-containing wastewater comprises the following steps:

(g-1) introducing the chromium-containing wastewater into a chromium breaking tank, adding 10% sulfuric acid into the chromium breaking tank until the pH value is 2-3, and then adding 10% sodium sulfite into the chromium breaking tank until the ORP value is 230-270mv to carry out chromium breaking reaction;

(g-2) introducing the wastewater treated in the step (g-1) into a pH adjusting tank, and adding 10% sodium hydroxide until the pH is 8-9;

(g-3) introducing the wastewater treated in the step (g-2) into a chemical reaction tank, adding a coagulant PAC, then adding a flocculant PAM, and stirring for 20-30 min;

(g-4) introducing the wastewater treated in the step (g-3) into a precise control efficient precipitation system; the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper, and the wastewater treated in the step (1-3) is sequentially introduced into the water distribution system, the sedimentation treatment tank and the inclined pipe; the supernatant after the treatment enters an effluent weir to obtain pretreated water, and the obtained sludge is deposited in a sludge hopper; wherein the pressure of the sedimentation treatment tank is 2-3 Mpa;

in the step (2), the biochemical treatment step is as follows: mixing the metal wastewater pretreatment water, the organic wastewater pretreatment water, the complexing wastewater pretreatment water, the chromium-containing wastewater pretreatment water, the cyanide-containing wastewater pretreatment water, the nickel-containing wastewater pretreatment water and the zinc-containing wastewater pretreatment water obtained in the step (1), and sequentially feeding the mixed water into an anaerobic tank, an aerobic tank and a membrane bioreactor; the membrane bioreactor consists of a hollow fiber membrane component and a membrane pool; wherein the hollow fiber membrane module is positioned in the membrane pool, and the aperture of the hollow fiber membrane is 0.01-0.1 μm;

in the step (3), the concentration treatment step is: sequentially passing the biochemical treatment water obtained in the step (2) through a primary nanofiltration system, a primary reverse osmosis system and a secondary reverse osmosis system;

the primary nanofiltration system is formed by sequentially connecting a precision filter and a primary nanofiltration membrane, wherein a filter element of the precision filter is melt-blown PP cotton, and the aperture of the filter element is 5 mu m; the primary nanofiltration membrane is an industrial grade high-desalination-rate nanofiltration membrane, and the aperture of the primary nanofiltration membrane is 1-2 nm; wherein the membrane inlet pressure of the primary nanofiltration system is 1.0-1.5 Mpa; the concentrated solution of the primary nanofiltration system enters a primary reverse osmosis system;

the first-stage reverse osmosis system is formed by sequentially connecting a precision filter and a first-stage reverse osmosis membrane; the filter element of the precision filter is melt-blown PP cotton, and the aperture of the filter element is 5 mu m; the first-stage reverse osmosis membrane is a brackish water reverse osmosis membrane, and the aperture of the first-stage reverse osmosis membrane is 0.1-1 nm; the membrane inlet pressure of the primary reverse osmosis system is 1.8Mpa, the permeate of the primary reverse osmosis system returns to the primary nanofiltration system, and the concentrated solution of the primary reverse osmosis system enters the secondary reverse osmosis system;

the secondary reverse osmosis system is formed by sequentially connecting a precision filter and a secondary reverse osmosis membrane, wherein a filter element of the precision filter is melt-blown PP cotton, and the aperture of the filter element is 5 mu m; the secondary reverse osmosis membrane is a seawater reverse osmosis membrane, and the aperture of the secondary reverse osmosis membrane is 0.1-1 nm; the membrane inlet pressure of the secondary reverse osmosis system is 4-5Mpa, the permeate of the secondary reverse osmosis system returns to the primary nanofiltration system, and the concentrated solution of the secondary reverse osmosis system is the high-salinity concentrated water;

in the step (4), the evaporation crystallization treatment step is as follows: sequentially passing the high-salinity concentrated water obtained in the step (3) through a heat exchanger, a concentration evaporator and an evaporation crystallizer, wherein the operating temperature of the heat exchanger is 80-100 ℃, and the operating pressure is 0.05-0.1 MPa; the concentration evaporator is formed by sequentially connecting a heating chamber, a separation chamber, a circulating chamber, a liquid distributor and a demister; the evaporative crystallizer is formed by sequentially connecting a separation chamber, salt legs, a thickener and a crystallization kettle; the condensed water of the high-salinity concentrated water after passing through the concentration evaporator returns to the secondary reverse osmosis system; the high-salinity concentrated water passes through a concentration evaporator to obtain concentrated high-salinity concentrated water, and the concentrated high-salinity concentrated water passes through an evaporation crystallizer to obtain a crystal and condensed water; the crystal is sodium sulfate and/or sodium chloride; the condensed water is used as reuse water;

wherein the standard of the recycled water is as follows: pH is 6-8, conductivity is less than or equal to 50 mu S/cm, COD is less than or equal to 30mg/L, and turbidity is less than or equal to 1 NTU.

2. The process of claim 1, wherein in step (1),

the pH value of the metal wastewater is 3-6;

the pH value of the organic wastewater is 2-11;

the pH value of the complex electroplating wastewater is 2-6, and the complex electroplating wastewater contains copper, nickel, SS and COD;

the pH value of the chromium-containing wastewater is 2-4, and the chromium-containing wastewater contains hexavalent chromium, trivalent chromium, sulfuric acid, nitric acid, oxides and COD pollutants;

the nickel-containing wastewater has pH of 4-6 and contains nickel, SS and COD pollutants;

the cyanide-containing wastewater has pH of 8-11 and contains copper ions, zinc, SS and COD pollutants;

the zinc-containing wastewater has pH 6-8 and contains zinc ions, SS and COD pollutants; wherein Zn in the zinc-containing wastewater²⁺Is 30-50 mg/L.

3. The process according to claim 1, wherein in step (a-3), the time interval between the addition of the coagulant and the flocculant is 20-40 min.

4. The process according to claim 1, wherein the pH of the wastewater treated in the step (a-3) is 8 to 9.

5. The treatment method according to claim 1, wherein the metal wastewater is pretreated to have COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

6. The process according to claim 1, wherein in step (b-3), the time interval between the addition of the coagulant and the flocculant is 20-40 min.

7. The treatment method according to claim 1, wherein the pH of the wastewater treated in the step (b-3) is 8 to 9.

8. The treatment method according to claim 1, wherein the metal wastewater is pretreated to have COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

9. The process according to claim 1, wherein in step (c-3), the time interval between the addition of the coagulant and the flocculant is 20-40 min.

10. The process according to claim 1, wherein the pH of the wastewater treated in the step (c-3) is 8 to 9.

11. The treatment method according to claim 1, wherein the complex wastewater after pretreatment has COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

12. The process according to claim 1, wherein in the step (d-2), the stirring time is 15 to 30 min; the stirring temperature is 15-35 ℃.

13. The process according to claim 1, wherein in step (d-4), the time interval between the addition of the coagulant and the flocculant is 25 to 35 min.

14. The method according to claim 1, wherein the cyanogen-containing wastewater is pretreated to have COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

15. The process according to claim 1, wherein in step (e-2), the time interval between the addition of the coagulant and the flocculant is 20 to 40 min; the pH of the wastewater treated in the step (e-2) is 10 to 11.

16. The treatment method according to claim 1, wherein the nickel-containing wastewater is pretreated to have COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

17. The process according to claim 1, wherein the zinc breaking reaction time of step (f-1) is 20 to 30 min.

18. The process according to claim 1, wherein in step (f-3), the time interval between the addition of the coagulant and the flocculant is 20 to 40 min.

19. The process according to claim 1, wherein the pH of the wastewater treated in the step (f-3) is 8 to 9.

20. The treatment method of claim 1, wherein the zinc-containing wastewater is pretreated to have COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

21. The process according to claim 1, wherein the reaction time for breaking chromium in step (g-1) is 20 to 30 min.

22. The process according to claim 1, wherein in step (g-3), the time interval between the addition of the coagulant and the flocculant is 20 to 40 min.

23. The treatment method according to claim 1, wherein the pH of the wastewater treated in the step (g-3) is 8 to 9.

24. The treatment process as claimed in claim 1, wherein the ORP value of the wastewater treated in step (g-3) is 230-270 mv.

25. The method according to claim 1, wherein the chromium-containing wastewater is pretreated to have COD less than or equal to 100mg/L and SS less than or equal to 100 mg/L.

26. The process of claim 1, wherein in step (2), the anaerobic pond contains anaerobic bacteria; the anaerobic bacteria are selected from one or more of yeast, clostridium and bacteroides; the yeast, the clostridium or the bacteroides is domesticated to have salt tolerance.

27. The treatment method according to claim 1, wherein in the step (2), the aerobic tank contains aerobic microorganisms;

the oxygen microorganism is selected from one or more of bacillus, rhizobium, nitrobacteria and mould;

the bacillus, the rhizobium, the nitrifying bacteria or the mould are domesticated to have salt tolerance.

28. The process according to claim 1, wherein in the step (2), the post-biochemical treatment has a pH of 6 to 8.

29. The treatment method as claimed in claim 1, wherein the rejection rate of the primary nanofiltration membrane on sodium ions is 50-70%; the rejection rate of the first-stage nanofiltration membrane on heavy metal ions and salts is more than 97%.

30. The treatment method as claimed in claim 1, wherein the relative molecular mass cut-off range of the primary nanofiltration system is 150-300 daltons;

the pH value of the water entering the primary nanofiltration system is 6-8;

and the permeate of the primary nanofiltration system is used as reuse water.

31. The process of claim 1, wherein in step (3),

the rejection rate of the first-stage reverse osmosis membrane to heavy metal ions and salts is more than 98%.

32. The process of claim 1, wherein;

the pH value of the water entering the first-stage reverse osmosis system is 5-6;

the pH of the first-stage reverse osmosis system is adjusted by adding hydrochloric acid with the concentration of 0.2-0.5%.

33. The process of claim 1, wherein in step (3),

the rejection rate of the secondary reverse osmosis membrane to heavy metal ions and salts is more than 99.5%.

34. The process of claim 1 wherein the pH of the water entering the secondary reverse osmosis system is from 6 to 8;

the pH value of the secondary reverse osmosis system is adjusted by adding hydrochloric acid;

the concentration of the hydrochloric acid is 0.2-0.5%.

35. The process of claim 1, wherein in step (4), the concentrated high salinity concentrated water has a salinity of 30-35%.

36. A treatment system for carrying out the method of treating electroplating wastewater according to any one of claims 1 to 35, wherein the system comprises a metallic wastewater pretreatment unit, an organic wastewater pretreatment unit, a complexing wastewater pretreatment unit, a cyanide-containing wastewater pretreatment unit, a nickel-containing wastewater pretreatment unit, a zinc-containing wastewater pretreatment unit, a chromium-containing wastewater pretreatment unit, and the pretreatment units are respectively connected to a biochemical treatment unit, a concentration treatment unit, and an evaporative crystallization treatment unit in this order;

the metal wastewater pretreatment unit comprises a complex breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the organic wastewater pretreatment unit comprises a decomplexing tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the complexing wastewater pretreatment unit comprises a complexing breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the cyanide-containing wastewater pretreatment unit comprises a cyanide breaking tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the nickel-containing wastewater pretreatment unit comprises a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the zinc-containing wastewater pretreatment unit comprises a zinc breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the chromium-containing wastewater pretreatment unit comprises a chromium breaking tank, a pH adjusting tank, a chemical reaction tank and a precise control efficient precipitation system which are sequentially communicated;

the precise control efficient sedimentation system is formed by sequentially connecting a water distribution system, a sedimentation treatment tank, an inclined pipe, a water outlet weir and a sludge hopper;

the biochemical treatment unit comprises an anaerobic tank, an aerobic tank and a membrane bioreactor which are communicated in sequence; the membrane bioreactor consists of a hollow fiber membrane component and a membrane pool, wherein the hollow fiber membrane component is positioned in the membrane pool, and the aperture of the hollow fiber membrane is 0.01-0.1 mu m;

the concentration treatment unit comprises a primary nanofiltration system, a primary reverse osmosis system and a secondary reverse osmosis system which are sequentially communicated;

the primary nanofiltration system is formed by sequentially connecting a precision filter and a primary nanofiltration membrane; the filter element of the precision filter is melt-blown PP cotton; the aperture of the filter element of the precision filter is 5 mu m; the primary nanofiltration membrane is an industrial grade high-desalination-rate nanofiltration membrane; the aperture of the primary nanofiltration membrane is 1-2 nm;

the first-stage reverse osmosis system is formed by sequentially connecting a precision filter and a first-stage reverse osmosis membrane; the filter element of the precision filter is melt-blown PP cotton; the aperture of the filter element of the precision filter is 5 mu m; the first-stage reverse osmosis membrane is a brackish water reverse osmosis membrane; the aperture of the first-stage reverse osmosis membrane is 0.1-1 nm;

the secondary reverse osmosis system is formed by sequentially connecting a precision filter and a secondary reverse osmosis membrane; the filter element of the precision filter is melt-blown PP cotton; the aperture of the filter element of the precision filter is 5 mu m; the secondary reverse osmosis membrane is a seawater reverse osmosis membrane, and the aperture of the secondary reverse osmosis membrane is 0.1-1 nm;

the evaporative crystallization unit comprises a heat exchanger, a concentration evaporator and an evaporative crystallizer which are sequentially communicated;

wherein the concentration evaporator is formed by connecting a heating chamber, a separation chamber, a circulating chamber, a liquid distributor and a demister in sequence; the evaporative crystallizer is formed by sequentially connecting a separation chamber, a salt leg, a thickener and a crystallization kettle.

37. The treatment system of claim 36, wherein the post-biochemical treatment pH is 6-8.

38. The treatment system of claim 36, wherein the rejection rate of the primary nanofiltration membrane for sodium ions is 50-70%; the rejection rate of the first-stage nanofiltration membrane on heavy metal ions and salts is more than 97%.

39. The treatment system of claim 36, wherein the primary nanofiltration system has a membrane inlet pressure of 1.0 to 1.5 Mpa.

40. The treatment system as claimed in claim 36, wherein the relative molecular mass cut-off range of the primary nanofiltration system is 150-300 dalton;

the pH value of the water entering the primary nanofiltration system is 6-8;

the permeate of the primary nanofiltration system is used as reuse water;

and the concentrated solution of the primary nanofiltration system enters a primary reverse osmosis system.

41. The processing system of claim 36,

42. The treatment system of claim 36, wherein the primary reverse osmosis system has a membrane inlet pressure of 1.6 to 2.0 Mpa;

the pH value of the first-stage reverse osmosis system is adjusted by adding hydrochloric acid with the concentration of 0.2-0.5%;

the permeate of the first-stage reverse osmosis system returns to the first-stage nanofiltration system;

and the concentrated solution of the first-stage reverse osmosis system enters a second-stage reverse osmosis system.

43. The processing system of claim 36,

44. The treatment system of claim 36, wherein the secondary reverse osmosis system has a membrane inlet pressure of 4 to 5 Mpa;

the pH value of the water entering the secondary reverse osmosis system is 6-8;

adding 0.2-0.5% hydrochloric acid to adjust pH;

the permeate of the secondary reverse osmosis system returns to the primary nanofiltration system;

and the concentrated solution of the secondary reverse osmosis system is the high-salinity concentrated water.

45. Use of the treatment method of any one of claims 1 to 35 or the treatment system of any one of claims 36 to 44 in the treatment of electroplating wastewater.