High salt refers to highly saline wastewater

High-salt wastewater refers to the waste water with total dissolved solids greater than 3.5%, and at least a mass fraction of more than 1% measured in sodium chloride, containing chloride ions, sodium ions and sulfate ions and other components. A large amount of high-salt wastewater will be produced in the production process of a variety of industries, such as materials, metallurgy, chemical industry, paper making and so on.

Generally, the composition is complex and the content of pollutants is high. It contains high inorganic ions such as Cl-, SO42-, Na+ and Ca2+, as well as organic matter with medium and low carbon chains such as glycerol. It has adverse effects on water body and surrounding soil environment.

The amount of high-salt wastewater produced reaches 5% in the total wastewater, which still increases at a rate of 2% every year. In recent years, the amount of waste salt produced in our country is increasing. It is estimated that the annual production amount is more than 30 million tons.

The safe, economical and effective disposal of industrial waste salt and high-concentration saline wastewater has become a bottleneck problem restricting the development of related industries producing industrial waste salt and high-concentration saline wastewater. In 2021, the National Hazardous Waste List officially included distillation and reaction residues in a variety of production processes, waste mother liquor and waste cleaning liquid of reaction tanks and containers in the hazardous waste list. If the waste salt is not properly treated, it will directly lead to the pollution of surface water, groundwater and soil.

At present, the waste salt is generally treated by centralized storage, which is faced with high storage and management costs and difficult for enterprises to afford. It has become a "bottleneck" problem that restricts the development of enterprises. At the same time, industrial waste salt is also an important chemical raw materials. If waste salt of chemical by-production can be recovered and used as salt for industrial raw materials, it can not only eliminate its pollution to the environment, but also make full use of salt resources to realize the resource utilization and recycling of by-production salt.