1.Sediment filtration
The purpose of sediment filtration is to remove suspended particulate matter or colloidal matter from raw water. These particulate matter, if not removed, can damage or block other sophisticated filtration membranes. It is commonly used in the preliminary treatment of water purification.
2.Hard water softening method
The softening of hard water needs to use ion exchange method, its purpose is to use cation exchange resin to exchange calcium and magnesium ions in hard water with sodium ions, to reduce the concentration of calcium and magnesium ions in raw water.
3.Activated carbon method
Activated carbon is made of wood, wood scraps, fruit pits, coconut shells, coal or petroleum residue and other substances at high temperature carbonization, made of hot air or water vapor to be activated. Its primary role is to remove chlorine and chloramines and other dissolved organic substances with molecular weights ranging from 60 to 300 Daltons.
4.Deionization
The purpose of deion method is to remove inorganic ions dissolved in water, and hard water softening method, also use the principle of ion exchange resin. These two resins are cation exchange resin and anion exchange resin. Cation exchange resin uses hydrogen ions to exchange cations; Anion exchange resins use hydroxide ions to exchange anions. Hydrogen and hydroxide ions combine to form neutral water.
5.Reverse osmosis
Reverse osmosis can effectively remove dissolved in water inorganic matter, organic matter, bacteria, pyrogen and other particles, is the most important link in water treatment. The so-called "permeation" refers to the separation of two different concentrations of solution by a semi-permeable membrane, so that the lower concentration of water molecules will pass through the semi-permeable membrane to the higher concentration of the other side until the two concentrations are equal. Before equilibrium is reached, if pressure is gradually applied to the higher concentration side, the water molecules will move in the opposite direction, that is, from the higher concentration side to the lower concentration side. This phenomenon is called reverse osmosis.
6.Overfiltration
Ultrafiltration is similar to reverse osmosis in that it also uses a semi-permeable membrane, but it cannot remove ions because of the membrane's larger pore size, about 10 to 200 A. Only bacteria, viruses, pyrogen and particles can be removed, and water-soluble ions cannot be filtered. The main function of ultrafiltration is to act as a pretreatment of reverse osmosis to prevent the reverse osmosis membrane from being contaminated by bacteria. It can also be used in the final steps of water treatment to prevent upstream water from becoming contaminated with bacteria in the pipeline.
7.Distillation process
Distillation is an ancient but effective water treatment method, it can remove any non-volatile impurities, but can not eliminate volatile pollutants, it needs a large tank to store, the tank and the pipeline is an important cause of pollution.
8.Ultraviolet disinfection
Ultraviolet disinfection is one of the commonly used methods. Ultraviolet disinfection does not produce any secondary pollutants, belongs to the latest generation of disinfection technology in the world, it has high efficiency, broad spectrum, low cost, long life, large amount of water, no pollution and other disinfection means incomparable advantages. Its bactericidal mechanism is to destroy the living genetic material of bacterial nucleic acid, making it unable to reproduce. The most important reaction is that the pyrimidine base within the nucleic acid molecule becomes dizygote (dimer). A low pressure mercury discharge lamp (germicidal lamp) is used to produce artificial UV energy of 253.7 nm. The principle of ultraviolet bactericidal lamp is the same as that of fluorescent lamp, only the inside of the tube is not coated with fluorescent material. The material of the tube is quartz glass with high ultraviolet penetration rate. General UV device has irradiation type, soaking type and water type.
9.Biochemical method
Biochemical water treatment method uses a variety of bacteria and microorganisms existing in nature to decompose organic matter in wastewater into harmless substances, so that the wastewater can be purified. Biochemical water treatment methods can be divided into activated sludge method, biofilm method, biological oxidation tower, land treatment system, anaerobic biological water treatment method. Biochemical water treatment process: raw water → grid → regulating tank → contact oxidation tank → precipitate → filtration → disinfection → effluent.
