Source and composition of high salt industrial wastewater

High salt industrial wastewater comes from many industrial processes, which produce wastewater containing high concentration of salt. The salt in these wastewater is mainly derived from the dissolution of raw materials, production processes or byproducts, salts generated by chemical reactions, and salt additives that may be used to regulate process conditions. Specifically, the sources of high-salt industrial wastewater include but are not limited to the following:

Many raw materials and products in the industrial production process are salts or can be converted into salts, in addition, some chemical processes need to add a large number of salts to adjust the reaction conditions, such as pH, ionic strength, etc., these salts will also enter the wastewater after the reaction. Secondly, it is the concentrated brine produced in the process of seawater desalination and seawater utilization. In the process of seawater desalination and direct utilization, a large amount of concentrated salt water will be produced. In addition, there are some specific industries such as pharmaceutical, printing and dyeing, electroplating, etc., will also produce high-salt wastewater. In the pharmaceutical process, some raw materials and products are salts or can be converted to salts, and salts may also be added to the production process as reactants or regulators. The printing and dyeing and electroplating industries may produce wastewater containing high concentration of salt due to cleaning equipment, products and other processes.

The total salt content of industrial calcium salt wastewater can reach 1%-3.5%, the main components include sodium chloride (NaCl), sodium sulfate (Na2SO4), potassium chloride (KCl), calcium chloride (CaCl) and other inorganic salts, of which Na+, Cl-, SO42- ions account for more than 90% of the total inorganic salt ions. At the same time, there are glycerin, low carbon chain compounds and other organic compounds. In addition, the wastewater may also contain heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), as well as oil, suspended substances and other harmful substances such as radioactive substances, which have potential harm to the environment and ecosystem. At the same time, the composition of industrial high-salt wastewater is complex, and the composition concentration of wastewater from different sources is quite different, which brings certain difficulty to treatment. In addition, high-salt wastewater is usually highly corrosive and heavily polluting, and has high requirements for treatment equipment and materials.