Zhejiang Huier Coating Environmental Protection Equipment Co., Ltd
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A large amount of wastewater is generated in the coating production line process. The coating wastewater contains lipids, benzene, ethers, alcohols, petroleum, surfactants and other substances that are not easy to degrade. A large amount of wastewater is generated during the pretreatment and painting process. The harmful substances in the wastewater generated in each process stage are also different.
The washing water after degreasing contains a lot of surfactants and emulsified oil. The COD and BOD contents in the water are both greatly exceeded. If this water is not treated and directly discharged into rivers, the organic matter in the wastewater will consume a lot of dissolved oxygen when decomposing in the water, thereby destroying the oxygen balance in the water body and causing the water quality to produce a foul odor.
Traditional pre-treatment uses phosphating coating. The washing water after phosphating contains heavy metals such as nickel ions (Ni+) and zinc ions (Zn2+) that exceed the emission standards. Nickel ions are carcinogens, and nickel metal and nickel alloys are listed in the Class 2B carcinogen list by the World Health Organization's International Agency for Research on Cancer. Excessive zinc has a significant toxic effect on aquatic organisms. Excessive zinc intake can cause poisoning, gastrointestinal symptoms such as vomiting and diarrhea. Chronic zinc poisoning can cause anemia and other symptoms. Animal experiments can cause liver, kidney function and immunity damage. Since phosphating treatment can cause environmental pollution and harm human health, this technology has gradually been replaced by silane technology. No harmful substances such as nickel, zinc, and manganese are produced during the silane treatment process, which is more in line with environmental protection and health requirements.
Paint mist will be generated during the painting process. For normal production, the waste paint mist must be removed from the paint spraying room. A common and effective method is to set a water curtain on the side of the paint spraying line (that is, the entrance of the exhaust duct) to allow the water curtain agent to absorb most of the paint mist. The waste gas not absorbed by the water curtain agent is then treated by the method of treating waste gas. There are many types of paints. Paints and organic solvents in them are toxic, even very toxic. After the water curtain agent absorbs the paint mist, the composition of the water body becomes very complex and very toxic. The organic content is very high. According to analysis, its CODcr is often in the thousands or even tens of thousands of mg/L. The water curtain water can usually be recycled after removing the scum (or sediment), but there are inevitably two situations: one is that part of the water curtain water is discharged as wastewater, and sufficient fresh water and water curtain agent are added; the other is that the water curtain water is completely renewed after a certain period of circulation. If this high-content and highly toxic water curtain water is directly discharged into rivers (lakes) without treatment, the harm it brings to humans is unimaginable, so it must be treated.
