Common water treatment methods include: (I) sediment filtration method, (II) hard water softening method, (III) activated carbon adsorption method, (IV) deionization method, (V) reverse osmosis method, (VI) excess filtration method, (VII) distillation method, (VIII) ultraviolet disinfection method, etc.

1、 Sediment filtration

The purpose of sediment filtration method is to remove suspended particulate matter or colloidal matter from the water source. If these particles are not removed, they will damage other precision filtration membranes of 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 filters will be added to the pipeline to remove large impurities. There are many types of filters used to filter suspended particulate matter, such as mesh filter, sand filter (such as quartz sand) or membrane filter. As long as the particle size is larger than the size of these holes, it will be blocked. For ions dissolved in water, they can't be stopped.

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 water source.

3、 Activated carbon

Activated carbon is made of wood, sawdust, fruit core, coconut shell, coal or oil residue by carbonization at high temperature. After being made, it needs to be activated by hot air or steam. Its main function is to remove chlorine, ammonia chloride and other dissolved organic substances with molecular weight of 60 to 300 daltons. The surface of activated carbon is granular and the interior is porous. There are many capillaries about 1onm ~ La in the pores. The internal surface area of 1G activated carbon is as high as 700-1400m2, and the inner surface and particle surface of these capillaries are the place of adsorption.

4、 Deionization method

The purpose of deionization method is to remove inorganic ions dissolved in water. Like hard water softener, it also uses the principle of ion exchange resin. In this, two resins are used - cation exchange resin and anion exchange resin. Cation exchange resin uses hydrogen ion (H +) to exchange cations; The anion exchange resin uses hydroxyl ions (OH -) to exchange anions, and hydrogen ions and hydroxyl ions combine with each other to form neutral water.

5、 Reverse osmosis

Reverse osmosis can effectively remove inorganic matter, organic matter, bacteria, pyrogen and other particles dissolved in water. It is the most important link in the treatment of dialysis water. The so-called "osmosis" It refers to the separation of two solutions with different concentrations by a semi permeable membrane. If the solute cannot pass through the semi permeable membrane, the water molecules with 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, the pressure can be gradually applied on the party with higher concentration, and the movement state of the above water molecules will stop temporarily. At this time The required pressure is called "osmotic pressure". If the applied force is greater than the osmotic pressure, the movement of water will go in the opposite direction, that is, from the high concentration to the low concentration. This phenomenon is called "reverse osmosis".

6、 Excess filtration

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

7、 Distillation

Distillation is an ancient but effective water treatment method. It can remove any nonvolatile impurities, but it can not eliminate volatile pollutants. It needs a large water storage tank for storage. This water storage tank and delivery pipe are an important cause of pollution. The water for blood dialysis is not treated in this way.

8、 Ultraviolet disinfection

Ultraviolet 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 gradually become a mainstream disinfection method in western developed countries because of its incomparable advantages such as high efficiency, broad spectrum, low cost, long life, large water volume and no pollution. Its sterilization mechanism is The most important reaction is that the pyrimidine base in the nucleic acid molecule becomes a dimer. Generally, a low-pressure mercury discharge lamp (sterilization lamp) is used The principle of ultraviolet sterilization lamp is the same as that of fluorescent lamp, except that the interior of the lamp tube is not coated with fluorescent substances, and the material of the lamp tube is quartz glass with high ultraviolet penetration rate. General ultraviolet devices are divided into irradiation type, immersion type and flow type according to their uses.

9、 Biochemical method

Biochemical water treatment method uses various bacteria and microorganisms existing in nature to decompose and convert organic matter in wastewater into harmless substances to purify wastewater. 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 biochemical water treatment method is: raw water → grid → regulation Tank → contact oxidation tank → sedimentation area → filtration → disinfection → effluent.