The main sources of zinc in electroplating and metalworking wastewater are electroplating or pickling tow liquids. Contaminants are transferred to rinse water after the metal rinsing process. The pickling process involves immersing the metal (zinc or copper) in a strong acid to remove oxides on the surface, followed by immersing in brighteners containing strong chromic acid to enhance the light. The waste water contains a large amount of hydrochloric acid, heavy metal ions such as zinc and copper, and organic brighteners, etc. The toxicity is high, and some of them contain carcinogenic, teratogenic, and mutagenic highly toxic substances, which are extremely harmful to humans. Therefore, the electroplating wastewater must be carefully recycled to eliminate or reduce its environmental pollution. Electroplating wastewater treatment equipment consists of conditioning tanks, chemical tanks, reduction tanks, neutralization reaction tanks, pH adjustment tanks, flocculation tanks, inclined tube sedimentation tanks, van filter presses, clear water tanks, air flotation reactions, activated carbon filters, etc. . Typical Electroplating Wastewater Treatment Process Diagram Electroplating Wastewater Treatment Process Description: The passivation concentrate is pumped into the reducing tank with a lift pump, and the sulfuric acid is added to the reducing tank through a metering pump so that the pH of the reducing tank reaches 2-3. The reducing agent sulfite is added to the reducing tank through a metering pump to reduce the hexavalent chromium to trivalent chromium. After the reduction treatment passivation solution and pretreatment, galvanized and nickel-plated water wash water enters the large adjustment tank, and various waste waters are fully homogenized in the adjustment tank and then lifted by the lift pump to the reaction tank 1 through the metering pump. Into CaCl2 to destroy the Zn2+ complex, in the reaction tank 2 through the metering pump into NaOH, adjust the pH value in the 9-11 range, then the wastewater flows into the reaction tank 3, through the metering pump into the coagulant PAM into In the inclined plate sedimentation tank, sludge formed by the formation of metal hydroxides sinks into the sludge hopper, and the supernatant is allowed to flow into the neutralization tank for acid-base adjustment, and the pH is adjusted to be in the range of 6 to 9 before discharge. Sludge in the inclined plate sedimentation tank is regularly discharged to the sludge tank, processed into a mud cake by a chamber type filter press and transported deep into the ground, and the sludge water is returned to the conditioning tank.
