Heavy metal wastewater uses a large amount of strong acids, strong bases, and heavy metal solutions in the production process, including toxic and harmful chemicals such as cadmium, cyanide, and chromic anhydride. During the process, wastewater, exhaust gas, and waste residue that pollute the environment and harm human health are discharged, making it a heavily polluting industry.

When dealing with heavy metals in wastewater, common methods cannot decompose and destroy them, but can only transfer their existence location and transform their physical and chemical forms. Namely, after chemical reduction and precipitation treatment, heavy metals in wastewater are transformed from dissolved ionic states to insoluble compounds, which precipitate and transfer from water to sludge. After ion exchange treatment, they exist in the regeneration solution. In short, after the treatment of heavy metal wastewater, two products are formed: one is the treated water that has basically removed heavy metals, and the other is the concentrated product of heavy metals - sludge. The treated water with heavy metal concentration lower than the emission standard can be discharged, and it is best to reuse it if it meets the production process water requirements. Most heavy metals in concentrated products have practical value and should be recycled as much as possible. If there is no recycling value, they should be treated harmlessly.