The hazards of painting wastewater
A large amount of wastewater will be generated in the coating production line process. The coating wastewater contains lipids, benzene, ethers, alcohols, petroleum, and surfactants, which are not easily degradable. A large amount of wastewater is generated in the process of pretreatment and painting .The composition of harmful substances in the wastewater produced during each process stage is also different.
Washing water after degreasing
The washing water after degreasing contains a lot of surfactants and emulsified oil, and the COD and BOD contents in the water exceed the standard by a large amount. If this water is not treated, it will be directly discharged into rivers. It will consume a large amount of dissolved oxygen, thereby destroying the balance of oxygen in the water body and causing the water quality to produce foul smell.
Washing water after phosphating
Traditional pre-treatment uses phosphating coating, and the washing water after phosphating contains nickel ions (Ni+), zinc ions (Zn2+) and other heavy metals that exceed the discharge standard.Nickel ions are carcinogens, and nickel metal and nickel alloys are included in the list of 2B carcinogens by the International Agency for Research on Cancer of the World Health Organization.Excess zinc has obvious toxic effects on aquatic organisms. Excessive zinc intake can cause poisoning, gastrointestinal symptoms such as vomiting and diarrhea, chronic zinc poisoning can cause symptoms such as anemia, and animal experiments can cause liver and kidney dysfunction. Immunity is compromised.
Since phosphating treatment will cause environmental pollution and endanger human health, this technology has been gradually replaced by silane technology. No harmful substances such as nickel, zinc, and manganese will be produced during silane treatment, which is more in line with environmental protection and health requirements.
Waste water from painting process
Paint mist will be generated during the painting process, and the discarded paint mist must be removed from the spray booth for normal production. A common and effective method is to set a water curtain on the side of the painting line (that is, the entrance of the air duct) so that the water curtain The water curtain agent absorbs most of the paint mist, and the exhaust gas not absorbed by the water curtain agent is treated by the method of treating exhaust gas.There are many kinds of lacquers, and the lacquers and the 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 complicated, the toxicity is also very high, and the content of organic matter is very high. According to the analysis, its CODcr is often several thousand or even tens of thousands of mg/liter.
Water curtain water can be recycled after removing scum (or sediment) usually, but there must be two situations: one is that the part of water curtain water is discharged as waste water, and enough fresh water and water curtain agent are replenished; The second is that the water curtain water is completely renewed after being recycled for a certain period of time.If the water curtain water with high content and high toxicity is directly discharged into rivers (lakes) without treatment, the harm to human beings is unimaginable, so it must be processed.
