PCB Technical - PCB board wastewater treatment process principle

In accordance with the designed shunt standard, the wastewater flows into the wastewater storage tanks of each treatment system after being diverted in the production workshop, and then is lifted by the wastewater lifting pumps of each treatment system to enter each treatment process. The processing is performed in the functional pool of each processing system. (PCB circuit board wastewater treatment process principle)

(1) General mixed wastewater W1: This type of wastewater has a large amount of water and a low CODCr concentration. It is mixed with small batches of acid-base wastewater and copper-containing wastewater and then enters the integrated wastewater treatment system (1# system) for treatment. Metal ions and a small amount of organic matter, the treatment process is: flocculation-sedimentation-sand filtration-pH adjustment. The treatment process is as follows: first add ferrous sulfate (for replacement and coagulation), then adjust the pH to about 10, and remove the heavy metal ions (Cu2+) in the wastewater to form hydroxides; then the wastewater enters the flocculation tank to add The flocculant PAM is used for flocculation treatment. After the treatment, the wastewater enters the inclined plate sedimentation tank for sedimentation mud and water separation; the upper clear water overflows into the clear water tank, and then enters the sand filter through the pump for filtration treatment, further reducing the suspended solids content in the effluent. The filtered wastewater enters the final pH adjustment tank and is discharged after the pH is adjusted to 6-9. (Principle of PCB board wastewater treatment process)

(2) High-concentration organic wastewater W2: The CODCr concentration in this wastewater is high. The pretreatment process is: acidification-precipitation. The treatment process is: adding acidulant to adjust the pH to about 5, adding polyferric chloride to condense the oily organic matter in the wastewater into large particles that can be separated from solid and liquid, and then adding an appropriate amount of polymer flocculant PAM. Then the solid-liquid components are separated by pressure filtration, and the pressure filtrate is added to the general organic wastewater pretreatment facility (2# system) in a quantitative and average manner and mixed with general organic wastewater for advanced treatment. (Principle of PCB board wastewater treatment process)

(3) General organic wastewater W3: Mainly comes from the cleaning wastewater of developing and de-filming processes. The concentration of CODCr in the wastewater is relatively high. General organic wastewater is mixed with pretreated high-concentration organic wastewater for advanced treatment. The advanced treatment process: acidification-Fenton oxidation. The oxidation process uses hydrogen peroxide as a high-efficiency oxidant and ferrous sulfate as a catalyst. Under acidic conditions, the divalent iron salt decomposes hydrogen peroxide to generate free hydroxyl radicals. The hydroxyl radicals have extremely strong oxidizing properties, which ultimately remove the organic matter in the wastewater. Oxidized to carbon dioxide and water. After the completion of the reaction, adjust the pH to 10-11, and then add the pump to the 1# system for further processing. (Principle of PCB board wastewater treatment process)

(4) Acid-base wastewater W4: Mainly comes from the acid-base waste water of the production line washing tank, and its main pollution factors are pH, CODCr, etc. After the acid-base wastewater is collected separately, it is added quantitatively and evenly to the 1# system and general mixed wastewater for further treatment.

(5) Copper-containing wastewater W5: Mainly comes from processes such as micro-etching, pickling, browning, pickling, etc. The wastewater contains relatively high copper content, and the main pollution factors are total copper and CODCr. The waste water with high copper content in the micro-etching process is separately treated for copper recovery, and the waste water after copper recovery is quantitatively pumped to the 1# system for further treatment; and the waste water with less copper content in processes such as pickling, browning, and pickling Then directly pump to the 1# system for processing.

(6) Complexing wastewater W6: Mainly comes from the copper precipitation process. This process uses a certain amount of complexed copper. The wastewater contains strong metal ion complexes (such as EDTA). The pollution factor of complexing wastewater is total copper, CODCr, etc., its pretreatment process is: replacement-flocculation-sedimentation-sand filtration. The treatment process is as follows: first adjust the pH to 3 to 4, then add ferrous sulfate, which can effectively replace the metal ions in the form of complexes, and add sodium hydroxide to adjust the pH to about 10, and the soluble The complexed copper is converted into insoluble copper salt, and then the flocculant PAM is added to carry out the flocculation reaction. The polymer flocculant is used to adsorb the copper hydroxide suspended particles in the sewage to form flocs with larger particles that are easy to precipitate; After the sludge settled in the plate sedimentation tank is discharged, the supernatant is filtered by the sand filter and then enters the filtrate collection tank, and then quantitatively enters the pH adjustment tank of the 1# treatment system and is discharged after pH adjustment to 6-9. (Principle of PCB board wastewater treatment process)

(7) Nickel-containing wastewater W7: Nickel-containing wastewater mainly comes from the nickel plating process. The nickel plating waste liquid and the first rinsing water of the nickel plating process are treated as hazardous waste, and the remaining rinsing water enters the pretreatment system for treatment. The treatment process is : Replacement-flocculation-sedimentation-sand filtration. The treatment process is as follows: adjust the pH to 3～4 and then add ferrous sulfate to replace most of the nickel ions in the form of complexes, add alkali to adjust the pH to 10 to form nickel hydroxide precipitation, add the flocculant PAM The flocculation reaction is carried out to make the nickel hydroxide in the wastewater suspend small particles to produce large particles that are easy to settle, and then enter the inclined plate sedimentation tank for sedimentation to separate the mud and water. The flocculation sedimentation process removes most of the nickel ions, and at the same time, the complex in the wastewater is removed. The compound has a certain purification effect, thereby reducing the CODCr in the wastewater. After the settled sludge is discharged, the supernatant is selectively added with a small amount of decomplexing agent according to the nickel content to further destroy the complex and release the complexed nickel ions to facilitate the formation of precipitates. After filtering through a sand filter It enters the filtrate collection tank, and finally enters the pH adjustment tank of the 1# treatment system, and is discharged after the pH is adjusted to 6-9. (Principle of PCB board wastewater treatment process)

(8) Cyanide-containing wastewater W8: mainly comes from the gold plating process. The gold plating solution contains a certain amount of potassium aurous cyanide. The first wash of gold plating is rinsed with non-running water in the tank. When the tank rinse water contains When the gold-cyanide component reaches a certain concentration, it is sent to a qualified unit for disposal with the cyanide-containing electroplating waste liquid (recyclable gold), and the rest of the rinsing wastewater is sent to the pretreatment facility for treatment. The pretreatment process is: pH adjustment - cyanide breaking (oxidation) ). The treatment process is as follows: use sodium hydroxide to adjust the pH to 10, add sodium hypochlorite to generate alkaline chloride, and finally oxidize the cyanide (CN-) to carbon dioxide (CO2) and nitrogen (N2). Then the reacted wastewater is pumped quantitatively and averagely to the complex wastewater storage tank for further advanced treatment to remove metal ions in the wastewater. (PCB design wastewater treatment process principle)