How to Treat High Salinity Organic Wastewater?

The organic matter of high salinity organic wastewater varies greatly depending on the production process, and the types and chemical properties of the organic matter contained are quite different, but they all contain a large amount of inorganic salts, which inhibit the growth of microorganisms, thereby increasing the difficulty of biological treatment. In addition, the discharge of these inorganic salts will have irreversible effects on soil and water bodies.

High salinity wastewater is one of the historical technical problems in wastewater treatment. Conventional physical, chemical, physicochemical and biochemical technologies have limited ability to treat salt-containing wastewater, and the desalination effect is not ideal. According to research reports at home and abroad, the main technologies for treating high salinity wastewater are biological method, membrane method, evaporation method, and ion exchange method.

1. Biological Treatment Method

Biological treatment technology is suitable for treating salty wastewater with a salt content of less than 1%. High concentration of inorganic salt and changes in salinity have an inhibitory effect on microorganisms. The main manifestations are: high salt concentration, high osmotic pressure, and dehydration of microbial cells cause cell protoplasm separation; high salt concentration makes activated sludge easy to float and lose, which seriously affects the biological treatment system purification effect; salting-out effect reduces dehydrogenase activity; high chloride ion is toxic to bacteria.

2. Evaporation Treatment Method

Evaporation refers to the process of removing the solvent from the solute by heating the solvent in the solution. Currently, the most widely used heating and evaporation technologies include multi-stage flash evaporation technology, low-temperature multi-effect distillation technology, and mechanical vapor recompression technology. Among them, multi-effect distillation technology and MVR technology are often used to treat high salinity wastewater, and MVR technology is the most energy-saving and cost-saving.     

3. Membrane Treatment Method

Compared with traditional water treatment methods, membrane technology has the advantages of good treatment effect, recycling of wastewater and recovery of useful components, etc. It is an effective technology for wastewater recycling. Various membrane separation technologies such as microfiltration, ultrafiltration, reverse osmosis and electrodeionization are combined in industrial water treatment to achieve the purpose of removing pollutants and desalination.

Hongtek provides a series of microfiltration products, such as Melt Blown Cartridges, string wound cartridges and Pleated Filter Cartridges, that are suitable for pre-filtration of high salinity organic wastewater with high removal efficiency and simple operation.

4. Electrical Treatment Method

The electrochemical method is suitable for the treatment of low-content organic wastewater with COD of 0.01~1g/L. Although it is beneficial to reduce energy consumption under high salt conditions, the metal plates are easy to wear and replace frequently. The electrolysis of wastewater containing sodium chloride, whether it is the ion-exchange membrane method or the diaphragm method, cannot meet the electrolysis requirements due to the problem of organic matter, and there are problems in the selection of grades, safety, and subsequent treatment.

In actual engineering applications, due to the complex water quality and large fluctuations, the stable operation of the membrane separation combined integrated process is facing huge challenges. Based on the current engineering application, the selection of the zero-discharge process of high salinity wastewater resources must start from water quality characteristics of the wastewater, and optimize the operation mode of pretreatment process and the concentration process of high saline water in the latter section through the combination of membrane separation and membrane concentration integrated process technology.