High-salt wastewater is defined as wastewater with a total salt mass fraction of at least 1% (equivalent to 10,000 mg/L). It mainly comes from chemical plants and oil and gas gathering and processing. This wastewater contains a variety of substances (including salt, oil, organic heavy metals and radioactive substances). Salt-containing wastewater is generated in a wide range of ways, and the volume of water increases every year. Removal of organic pollutants from saline wastewater is critical to the environment.
Treatment using biological methods, high concentrations of saline substances have an inhibitory effect on microorganisms, and treatment using physical and chemical methods is characterized by large investments, high operating costs, and difficulties in achieving the desired purification effect.
The treatment of such wastewater by biological method is still the focus of research at home and abroad. The organic matter of organic wastewater with high salt content varies greatly in terms of the type and chemical properties of the organic matter contained according to the different production processes, but the salts contained are mostly salts such as Cl-, SO42-, Na+, Ca2+, and so on.
Although these ions are essential nutrients for the growth of microorganisms, they play an important role in promoting enzyme reactions, maintaining membrane balance and regulating osmotic pressure in the growth process of microorganisms.
However, if the concentration of these ions is too high, it will inhibit and poison the microorganisms, the main performance: high salt concentration, high osmotic pressure, microbial cell dehydration caused by the separation of cell protoplasm; salt precipitation effect of dehydrogenase activity is reduced; chloride ions are high on the bacteria have a poisonous effect; salt concentration is high, the density of the wastewater increases, the activated sludge is easy to float and lose, which seriously affects the purification effect of the biological treatment system.