Brackish water is the water that the alkalinity is greater than hardness, and contains a large amount of neutral salt, pH value is greater than 7, mostly distributed in coastal areas. Brackish water is not suitable for drinking because of its high hardness and salt content. It needs to be treated with the corresponding technology before it can be drunk.

Dilution method

Distillation

Distillation is the process of heating brackish or sea water to boil and evaporate, and then condensing the steam into fresh water. Distillation is the earliest desalination method of brackish water. Its main advantages are simple structure, easy operation and good fresh water quality. There are many kinds of distillation, such as multi - effect evaporation, multi - stage flash distillation, compressed steam distillation, membrane distillation, and etc..

Electrodialysis method

Electrodialysis method is a membrane separation technique that separate the anions and cations in salt water by utilizing the anion exchange membrane under the action of electric field to reduce the salt concentration in the fresh water chamber and obtain fresh water. The electrodialysis device uses the ions to migrate in a directional way under the action of electric field, and achieves the purpose of desalting by selecting permeable ion exchange membrane. Electrodialysis (Electrodialysis) desalination technology of brackish water has been quite mature. It has many advantages, such as simple process, high desalination rate, low cost of water production, convenient operation and no environmental pollution, but it has some disadvantages, such as strict requirements on water quality and pretreatment of raw water.

Reverse osmosis

Reverse osmosis means that adds a higher pressure on the side of concentrated solution than natural osmosis ,reverses the natural osmosis direction, and pushes the ions in the solution to the other side of the semi-permeable membrane, which is contrary to the normal osmosis process in nature, so it is called "reverse osmosis". This device is called reverse osmosis device.

The method of desalinating brackish water by reverse osmosis can remove more than 90 % of dissolved salts and more than 99 % of colloidal microorganism and organic matter from the water. Compared with other water treatment methods, it has the advantages of no phase change, normal temperature operation, simple equipment, high efficiency, less floor space, convenient operation, less energy consumption, wide range of adaptability, high degree of automation and good water quality.