Comparative analysis of high salt wastewater treatment technology

1、 Source and composition of high salt wastewater:

High salt wastewater refers to wastewater containing organic matter and at least 3.5% total dissolved solids (TDS) by mass concentration. This type of wastewater has a wide range of sources. Firstly, in various industrial production processes such as chemical, pharmaceutical, petroleum, papermaking, dairy processing, and food canning, a large amount of wastewater is discharged. The water not only contains high concentrations of organic pollutants, but also a large amount of calcium and sodium ions; Secondly, in order to fully utilize water resources, many coastal cities directly use seawater as industrial production water or cooling water. Some places use seawater for firefighting, flushing toilets and roads. Although this part of sewage does not contain a large amount of toxic substances, it is large in volume, high in salt content, and difficult to treat.

2、 Characteristics of high salt wastewater:

The types and chemical properties of organic compounds in high salt organic wastewater vary greatly depending on the production process, but the salt substances contained are mostly Cl -, SO42-, Na+, Ca2+and other salt substances. Although these ions are essential nutrients for microbial growth, playing an important role in promoting enzyme reactions, maintaining membrane balance, and regulating osmotic pressure during microbial growth, if the concentration of these ions is too high, they can have inhibitory and toxic effects on microorganisms. High salt concentration, high osmotic pressure, and dehydration of microbial cells in high salt wastewater cause cell protoplast separation; Salt precipitation reduces dehydrogenase activity; High chloride ions have toxic effects on bacteria; High salt concentration increases the density of wastewater, and activated sludge is prone to floating and loss, which seriously affects the purification effect of biological treatment systems. Excessive inorganic salts can cause the gradual death of microorganisms in the activated sludge system, reduce the amount of sludge, increase suspended solids in the effluent, and excessively high inorganic salt concentration can lower COD removal efficiency. Therefore, this type of concentrated salt wastewater needs to be treated separately.