Rough filtration: refers to mechanical filtration to remove suspended matter, colloid, turbidity, color, odor, etc. in water. The main filtering methods are clarification tank, quick filter tank, sand filter tank, sand filter, multi-media filter, activated carbon filter, disc filter, high-efficiency fiber filter, etc.
Fine filtration: The filtration membrane made of special material has higher filtration accuracy. Common are microfiltration membranes and filter elements.
Ultrafiltration: It is a membrane filtration to remove macromolecules, colloids and bacteria. High filtration accuracy, common is ultrafiltration membrane. The ultrafiltration membrane cannot remove ions in water, that is, it has no salt removal function. It can be used for reverse osmosis pretreatment or fine treatment after reverse osmosis. It can also be used alone. Ultrafiltration is a tangential flow and pressure-driven filtration process of fluids and separates particles according to their molecular weight. The pore size of the ultrafiltration membrane is in the range of about 0.002-0.1 microns. Dissolved substances and substances smaller than the pore size of the membrane can be used as the permeate filter membrane, and the substances that cannot pass the filter membrane are concentrated in the discharge liquid. Therefore, the produced water contains water, dissolved solids and small molecular weight substances, while colloids, suspended particles, high molecular weight organics, bacteria, viruses and protozoa will be removed by filtration.
Reverse osmosis: Reverse osmosis, referred to as RO, is a membrane separation technology developed in the 1960s. Its principle is that raw water passes through a reverse osmosis membrane under the action of high pressure, and the solvent in the water diffuses from high concentration to low concentration to achieve separation, The purpose of purification and concentration is called reverse osmosis because it is opposite to the direction of penetration in nature. Reverse osmosis can remove bacteria, viruses, colloids, organic matter and more than 98% of soluble salts in water. The method has the characteristics of low running cost, simple operation, high degree of automation , and stable effluent water quality. Compared with other traditional water treatment methods, it has obvious advantages and is widely used in various industries related to water treatment.
Various inorganic salts in water ionize to form cations and anions. When passing through a hydrogen-type ion exchanger layer, cations in water are replaced by hydrogen ions, which is the principle of salt removal in cation beds .
Various inorganic salts in water are ionized to form cations and anions. When passing through the OH-type ion exchanger layer, the anions in water are replaced by OH- ions, which is the principle of salt removal in anion beds.
A mixed bed is an ion exchange device in which cation and anion exchange resins are mixed and packed in the same exchange column according to a certain ratio. The uniformly mixed resin layer, cation resin and anion resin are closely staggered. Each pair of cation resin and anion resin particles is similar to a set of multiple beds, so the mixed bed can be regarded as a non-array multiple bed running in series. Since the hydrogen ions and hydroxide ions that enter the water after mixed ion exchange immediately generate water molecules with a low ionization degree, it is unlikely to form counter ions during cation or anion exchange, which can make the exchange reaction proceed very thoroughly, so the mixed bed The quality of the effluent water is better than that of a double bed composed of cation and anion exchange series, and it can produce finished water with a relatively high purity.
EDI: EDI technology is a new salt removal process that combines electrodialysis and ion exchange. This equipment takes the advantages of both electrodialysis and mixed-bed ion exchange to make up for each other's shortcomings. The medicine is regenerated, and H + and OH- generated by ionization are used to achieve the purpose of regenerating the resin. EDI has high requirements for the influent water. It must be reverse osmosis water or water quality equivalent to reverse osmosis water.