A great deal of waste water is discharged in the process of mining, but 40% of mine areas in China are seriously short of water, which has restricted the development of mining enterprises' production. Mining area in the northwest is mostly in mountainous areas, and water resources are scarcer. Surface water is mainly intermittent river. The dilution capacity of flow is poor all year round. The wastewater discharged into the river causes pollution. A large amount of mine waste water from mining enterprises is discharged into nearby rivers, which pollutes surface water and groundwater with heavy metals in the waste water. The water quality and the utilization rate both decrease. However, the treatment efficiency of the above waste water is low, and most of it is not utilized, resulting in a large amount of waste water.
Characteristics of mining waste water:
1.It has a high suspended substance content (more sediment) with a mass concentration of 20 ~ 50mg/L.
2.Waste water contains a certain amount of organic matter, mainly contains humic acid, human excreta, blasting residue, etc., and COD is no more than 50mg/L.
3.It has a certain amount of heavy metal.
4.Total dissolved solids (TDS) of mine water are higher, with a mass concentration of 1 ~ 2g/L. 
         With the continuous improvement of global industrial level, metal smelting has brought great changes to people's life. With the development of industry, the problem of waste water pollution is more and more serious. Among them, non-ferrous metal smelting is a typical high pollution process, and the smelting waste water contains a large number of heavy metals. These metals flow into the ecological environment, affecting soil, crops and aquatic organisms. It seriously endangers human life and health too. On the other hand, the waste water will corrode metal, buildings, equipment and so on, which poses a threat to people's production and life. 
Characteristics of metallurgical waste water:
1.It has a lot of waste water.
2.The fluidity of waste water is between the waste gas and solid waste, which is mainly diffused through the surface water flow, resulting in the pollution of soil and water.
3.The composition of waste water is complex, and the concentration of pollutant is high. It is often composed of suspended substance and dissolved substance, with high COD, heavy metal content and greater toxicity. Waste water is acidic and sometimes contains radioactive material. The treatment process is complex and the governance is difficult.
4.It has colors, peculiar smell, which giving people a disgusting appearance.