System and method for treating printed circuit board (PCB) wastewater

A method for treating printed circuit board (PCB) wastewater, comprising:

• (S1) collecting production wastewater from a production system;
• and collecting domestic wastewater from a living system;
• (S2) pretreating the production wastewater and the domestic wastewater separately to obtain primary treated wastewater;
• and allowing the primary treated wastewater to enter a biochemical system or a recovery system;
• (S3) treating the primary treated wastewater by the biochemical system to obtain secondary treated wastewater, and collecting the secondary treated wastewater to the recovery system;
• (S4) treating the secondary treated wastewater by the recovery system to obtain process water and domestic water, and generating concentrated water at the same time;
• wherein the process water enters the production system for use;
• and the domestic water enters the living system for use;
• and
• (S5) allowing the concentrated water to enter a concentrated water treatment system for treatment to meet a discharge standard;
• wherein in step (S2), the pretreating comprises a first pretreatment and a second pretreatment;
• the first pretreatment comprises:
• (S211) treating high-concentration organic wastewater, low-concentration organic wastewater, ink wastewater, complex copper wastewater, copper-ammonia wastewater, and domestic wastewater, respectively;
• and
• combining treated high-concentration organic wastewater with the low-concentration organic wastewater;
• (S212) mixing treated organic wastewater, treated ink wastewater, treated complex copper wastewater, treated copper-ammonia wastewater, and treated domestic wastewater to obtain first mixed wastewater, and treating the first mixed wastewater followed by feeding to the biochemical system;
• the second pretreatment comprises:
• (S221) treating copper-containing wastewater, nickel-containing wastewater, cyanide-containing wastewater, and silver-containing wastewater, respectively;
• and
• combining treated cyanide-containing wastewater with the nickel-containing wastewater;
• and
• (S222) mixing treated cyanide-containing wastewater, treated copper-containing wastewater, treated nickel-containing wastewater, and treated silver-containing wastewater to obtain second mixed wastewater, and treating the second mixed wastewater followed by feeding to the recovery system;
• in step (S211), the high-concentration organic wastewater is treated through steps of:
• collecting the high-concentration organic wastewater followed by feeding to an acidification tank;
• adjusting the high-concentration organic wastewater to pH 2˜4 with an acid followed by stirring and feeding to a first coagulation tank;
• adding an alkali to adjust pH;
• and adding a first coagulant, and after undergoing sedimentation in a first sedimentation tank, allowing a supernatant to enter a low-concentration organic wastewater treatment unit;
• the low-concentration organic wastewater is treated through steps of:
• collecting the low-concentration organic wastewater and the supernatant followed by mixing to obtain mixed organic wastewater;
• subjecting the mixed organic wastewater to Fenton oxidation in a first reaction tank for 1˜2 h to remove organic matters, with pH controlled to 2˜4;
• adding a reducing agent followed by feeding to enter a first reactor;
• and adding a second coagulant in the first reactor followed by sedimentation to collect an effluent to a mixed wastewater treatment unit;
• the ink wastewater is treated through steps of:
• collecting the ink wastewater, and treating the ink wastewater in a deinking tank;
• and adding an amphoteric coagulant, followed by feeding to a second sedimentation tank for precipitation;
• the complex copper wastewater is treated through steps of:
• collecting the complex copper wastewater;
• adding a sulfide as a breaking agent in a decomplexation tank;
• adding an alkali liquor in a pH adjustment tank to adjust pH to 8˜9;
• adding a third coagulant to a second reactor for precipitation;
• and collecting an effluent to the mixed wastewater treatment unit;
• the copper-ammonia wastewater is treated through steps of:
• collecting the copper-ammonia wastewater;
• adding an acid to a second pH adjustment tank to adjust pH to 4˜7 followed by stirring and feeding to a second reaction tank;
• mixing the copper-ammonia wastewater with NaClO followed by reaction for 30˜60 min;
• adjusting pH to 8˜9, and adding a fourth coagulant to a third reactor for coagulation and precipitation;
• and collecting an effluent to the mixed wastewater treatment unit;
• and
• the domestic wastewater is treated through steps of:
• filtering the domestic wastewater through a coarse screen and a fine screen followed by oil removal in an oil-separation tank and sedimentation in a third sedimentation tank;
• and collecting an effluent to the mixed wastewater treatment unit;
• in step (S212), the treatment of the first mixed wastewater comprises:
• collecting the treated organic wastewater, the treated ink wastewater, the treated complex copper wastewater, the treated copper-ammonia wastewater, and the treated domestic wastewater followed by mixing to obtain the first mixed wastewater in a collection tank;
• adjusting pH to 7˜9 in a third pH adjustment tank followed by feeding to a second coagulation tank;
• and adding ferrous ions and poly aluminum chloride (PAC) for coagulation followed by precipitation in a fourth sedimentation tank;
• and
• collecting an effluent to the biochemical system;
• in step (S221), the cyanide-containing wastewater is treated through steps of:
• collecting the cyanide-containing wastewater;
• adding an alkali to a fourth pH adjustment tank to adjust pH to 9˜11;
• adding hydrogen peroxide to a fourth reaction tank followed by reaction for 20˜40 min;
• and collecting an effluent to a collection tank;
• the nickel-containing wastewater is treated through steps of:
• collecting the nickel-containing wastewater in the collection tank;
• adding an acid to a fifth pH adjustment tank to adjust pH to 2˜3;
• adding Fenton reagent or NaClO to a second decomplexation tank followed by reaction for 50˜70 min, stirring and feeding to a fourth reactor;
• adjusting pH to 10˜11, and adding a fifth coagulant to the fourth reactor followed by precipitation for 10˜30 min;
• and collecting a supernatant to a second mixed wastewater treatment unit;
• the copper-containing wastewater is treated through steps of:
• collecting the copper-containing wastewater followed by feeding to a fifth reactor;
• adjusting pH to 8˜9;
• adding a sixth coagulant followed by precipitation for 10˜15 min;
• and collecting a supernatant to the second mixed wastewater treatment unit;
• and
• the silver-containing wastewater is treated through steps of:
• collecting the silver-containing wastewater;
• adding NaOH at a front end of a sixth reactor followed by mixing by a pipeline mixer, adding a seventh coagulant for precipitation;
• and collecting a supernatant to the second mixed wastewater treatment system;
• and
• step (S222) comprises:
• collecting the treated cyanide-containing wastewater, nickel-containing wastewater, copper-containing wastewater and silver-containing wastewater in the second mixed wastewater treatment unit to produce the second mixed wastewater;
• allowing the second mixed wastewater to flow into a fifth reaction tank, and adding ferrous sulfate under acidic conditions for reaction;
• adjusting pH to 8˜10 in a sixth pH adjustment tank;
• adding sodium sulfide to a third coagulation tank for reaction;
• adding an eighth coagulant followed by reaction for 10˜15 min and feeding to a fifth sedimentation tank for precipitation;
• and collecting a supernatant to the recovery system.