Since the 1950s, seawater desalination technology has become one of the important ways to develop new water sources. Different departments and fields have different requirements for the quality of water used. Let's take a look at the method of seawater desalination treatment technology:
1. The method of sea water desalination treatment technology-distillation method:
A method of heating water to 105°C to evaporate and then condense the steam to obtain distilled water.
Advantages: The equipment is simple in structure, easy to operate, and the fresh water quality is good.
Disadvantages: high energy consumption.
2. The method of sea water desalination treatment technology-electrodialysis:
Using the selective permeability of the anion and cation exchange membrane to the anion and cation in the water, under the action of an external DC electric field, a part of the ions in the water is transferred to another part of the water to achieve the purpose of desalination.
The key technology of this method is the development of a new type of ion exchange membrane. Ion exchange membranes are functional membranes with a thickness of 0.5-1.0mm, which are divided into positive ion exchange membranes (positive membranes) and negative ion exchange membranes (anionic membranes) according to their selective permeability. The electrodialysis method is to alternately arrange positive and negative membranes with selective permeability to form multiple independent compartments. The seawater is desalinated, while the seawater of the adjacent compartments is concentrated, and fresh water and concentrated water are separated. Electrodialysis can not only desalinate seawater, but also can be used as a means of water quality treatment to contribute to the reuse of sewage.
3. The method of sea water desalination treatment technology-ion exchange method:
A method of exchanging the ions on the ion exchange resin with the ions in the water to remove the anions and cations in the water.
4. The method of sea water desalination treatment technology-reverse osmosis membrane method:
The reverse osmosis method is usually also called ultrafiltration method, which is a membrane separation desalination method that was adopted only in 1953. This method uses a semi-permeable membrane that allows only solvents to permeate but not solutes to separate sea water from fresh water. Under normal circumstances, fresh water diffuses to the seawater side through the semi-permeable membrane, so that the liquid level on the seawater side gradually rises until a certain height is reached. This process is permeation.
5. The method of seawater desalination treatment technology-thin film distillation desalination technology:
Thin film distillation is a process in which heated seawater passes through a porous hydrophobic membrane (sometimes called a distillation membrane) to evaporate retrogradely, and the evaporated vapor is condensed on the other side of the membrane.
The hydrophobic membrane functions as the interface between liquid and vapor. This distillation method is different from the conventional distiller, greatly reducing or actually eliminating the vapor space, but the hydrophobic membrane cannot replace the heat exchange surface. In the thin film distillation device, it is necessary to design a heat exchange surface equal to the membrane area. At present, there are three types of thin film distillation devices: air gap type, direct contact type and scavenging pen.
