Water purification industry information

Commonly used water treatment methods

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Update time : 2021-09-16 11:33:28
Commonly used water treatment methods are: (1) sediment filtration method, (2) hard water softening method, (3) activated carbon adsorption method, (4) deionization method, (5) reverse osmosis method, (6) ultrafiltration method, (7) Distillation method, (8) Ultraviolet disinfection method, etc.
1. Sediment filtration method

The purpose of the sediment filtration method is to remove the suspended particulate matter or colloidal matter in the water source. If these particulate matter is not removed, it will damage the other delicate filter membranes of the dialysis water or even block the waterway. This is the oldest and simplest water purification method, so this step is often used in the preliminary treatment of water purification, or if necessary, several more filters are added to the pipeline to remove larger impurities. There are many types of filters used to filter suspended particulate matter, such as mesh filters, sand filters (such as quartz sand, etc.) or membrane filters. As long as the particle size is larger than the size of these holes, it will be blocked. The ions dissolved in the water cannot be blocked.

2. Hard water softening method

The softening of hard water requires the 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 the water source.

Three, activated carbon

Activated carbon is carbonized by dry distillation of wood, wood chips, fruit cores, coconut shells, coal or petroleum bottom residue at high temperature, and it needs to be activated with hot air or water vapor after it is made. Its main function is to remove chlorine and chloramines and other soluble organic substances with a molecular weight of 60 to 300 Daltons. The surface of the activated carbon is granular and the inside is porous. There are many capillaries with a size of about 10nm~lA in the pores. The internal surface area of ​​1g of activated carbon is as high as 700-1400m2, and the inner surface of these capillaries and the surface of the particles are where the adsorption is.

Four, deionization method

The purpose of the deionization method is to remove the inorganic ions dissolved in water. Like the hard water softener, it also uses the principle of ion exchange resin. Two resins are used here-cation exchange resin and anion exchange resin. Cation exchange resins use hydrogen ions (H+) to exchange cations; and anion exchange resins use hydroxide ions (OH-) to exchange anions. Hydrogen ions and hydroxide ions combine to form neutral water.

Five, reverse osmosis method

The reverse osmosis method can effectively remove inorganic substances, organic substances, bacteria, pyrogens and other particles dissolved in water, and is the most important part of the treatment of dialysis water. The so-called "osmosis" refers to the separation of two solutions of different concentrations by a semi-permeable membrane, where the solute cannot penetrate the semi-permeable membrane, and the water molecules of the lower concentration will pass through the semi-permeable membrane to the other with higher concentration. Until the concentrations on both sides are equal. Before reaching equilibrium, you can gradually apply pressure on the higher concentration side, and the aforementioned water molecule movement state will temporarily stop. At this time, the required pressure is called "osmotic pressure" (osmotic pressure). pressure)", if the applied force is greater than the osmotic pressure, the water will move in the opposite direction, that is, from the high concentration to the low concentration. This phenomenon is called "reverse osmosis".

Sixth, ultrafiltration method

The ultrafiltration method is similar to the reverse osmosis method in that it also uses a semi-permeable membrane, but it cannot control the removal of ions because the membrane has a large pore size, about 10-200A. It can only exclude bacteria, viruses, pyrogens and particulate matter, but cannot filter water-soluble ions. The main function of the ultrafiltration method is to act as a pretreatment of the reverse osmosis method to prevent the reverse osmosis membrane from being contaminated by bacteria. It can also be used in the final step of water treatment to prevent upstream water from being contaminated by bacteria in the pipeline. Generally, the difference between the inlet water pressure and the outlet water pressure is used to judge whether the ultrafiltration membrane is effective. Similar to activated carbon, the reverse flushing method is usually used to remove impurities attached to it.

Seven, distillation

Distillation is an ancient but also effective water treatment method. It can remove any non-volatile impurities, but cannot eliminate volatile pollutants. It requires a large water storage tank for storage. This water storage tank and delivery pipe are An important cause of pollution, hemodialysis water does not need to be treated in this way.

8. Ultraviolet disinfection method

UV disinfection is one of the commonly used methods. Ultraviolet disinfection does not produce any secondary pollutants. It belongs to the latest generation of disinfection technology in the world. It has the advantages of high efficiency, broad spectrum, low cost, long life, large water volume, no pollution and other disinfection methods. It has gradually become a mainstream disinfection method in western developed countries. Its bactericidal mechanism is to destroy the life genetic material of bacterial nucleic acid, making it impossible to reproduce. The most important reaction is that the pyrimidine base in the nucleic acid molecule becomes a dimer. Generally, the artificial 253.7nm wavelength ultraviolet energy of low-pressure mercury discharge lamp (germicidal lamp) is used. The principle of the ultraviolet germicidal lamp is the same as that of the fluorescent lamp, except that the inside of the lamp tube is not coated with fluorescent material, and the material of the lamp tube is quartz glass with high ultraviolet transmittance. Generally, UV devices are classified into irradiation type, immersion type and flowing water type according to their use.

9. Biochemical Law

The biochemical water treatment method uses various bacteria and microorganisms that exist in nature to decompose the organic matter in the 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, and anaerobic biological water treatment method. The process of the biochemical water treatment method: raw water→grid→conditioning tank→contact oxidation tank→sedimentation site→filtration→disinfection→effluent.
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