Heavy metal wastewater refers to the wastewater containing heavy metals discharged from the industrial processes of mining, metallurgy, machinery manufacturing, chemical industry, electronics, instrumentation and so on. Heavy metal wastewater (such as cadmium, nickel, mercury, zinc, etc.) is one of the industrial wastewater with the most serious environmental pollution and the greatest harm to human beings. Its water quality and quantity are related to the production process. In general, heavy metals in wastewater can not be decomposed and destroyed, but can only transfer their location and physical and chemical forms. The treatment method is to reform the production process first, and use less toxic heavy metals. Chemical precipitation method and ion exchange method are often used to treat the heavy metals in the production site (such as not discharging the production workshop). The treated water can be discharged or reused if the heavy metals are below the discharge standard. Formation of new heavy metal concentrate products for recycling or harmless treatment as far as possible.