A, sediment filtration method

The purpose of sediment filtration method is to remove suspended particles or colloidal substances from water sources. If these particles are not removed, it will damage other precision filtration membranes of dialysis water and even block the waterway. This is the oldest and simplest water purification method, so this step is often used in the pre-treatment of water purification, or if necessary, more filters will be added to the pipeline to remove large impurities. There are many kinds of filters used to filter suspended particles, such as screen filter, sand filter (such as quartz sand) or membrane filter. As long as the particle size is larger than that of these holes, it will be blocked. It is impossible to stop water-soluble ions.

Second, the hard water softening method

The softening of hard water requires ion exchange method, which aims to exchange calcium and magnesium ions with sodium ions in hard water by cation exchange resin to reduce the concentration of calcium and magnesium ions in water source.

Three. activated carbon

Activated carbon is made of wood, sawdust, stone, coconut shell, coal or petroleum residue by high temperature carbonization, and it needs to be activated by hot air or steam after being made. Its main function is to remove chlorine, chloramines and other soluble organic substances with molecular weight of 60 to 300 daltons. The surface of activated carbon is granular and the inside is porous. There are many capillaries with the size of 10n m ~ lA in the pores. The inner surface area of 1g activated carbon is as high as 700- 1400m2, and the inner surface of these capillaries and the surface of particles are adsorption.

Four. Deionization method

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

Verb (abbreviation of verb) reverse osmosis method

Reverse osmosis can effectively remove dissolved inorganic, organic, bacterial, pyrogen and other particles in water, which is the most important part of dialysis water treatment. Permeation refers to the separation of two solutions with different concentrations by a semipermeable membrane, in which solutes cannot penetrate the semipermeable membrane, so water molecules with lower concentration will penetrate the semipermeable membrane to reach the other side with higher concentration until the concentrations on both sides are equal. Before reaching equilibrium, pressure can be gradually applied on the side with higher concentration to temporarily stop the movement of the water molecules. The pressure required at this time is called "osmotic pressure". If the applied force is greater than the osmotic pressure, water will move in the opposite direction, that is, from the example with high concentration to the side with low concentration. This phenomenon is called "reverse osmosis".

Six, ultrafiltration method

Ultrafiltration is similar to reverse osmosis, but it also uses semi-permeable membrane. However, due to the large pore size of the membrane, about 10-200 A, it is impossible to control the removal of ions, only bacteria, viruses, pyrogens and particles can be excluded, and water-soluble ions cannot be filtered. The main function of ultrafiltration is as pretreatment of reverse osmosis to prevent reverse osmosis membrane from being contaminated by bacteria. It can also be used in the last step of water treatment to prevent upstream water from being polluted by bacteria in the pipeline. Generally, the difference between inlet pressure and outlet pressure is used to judge whether the filtration membrane is effective or not. Similar to activated carbon, backwashing is usually used to remove impurities attached to it.

Seven, distillation method

Distillation is an ancient and effective water treatment method. It can remove any non-volatile impurities, but it cannot eliminate volatile pollutants. It needs a large storage tank for storage, but this storage tank and pipeline are the important causes of pollution. Hemodialysis water is not treated like this.

Eight, ultraviolet disinfection method

Ultraviolet disinfection is one of the common methods. Ultraviolet disinfection does not produce any secondary pollutants and belongs to the latest generation of disinfection technology in the world. Because of its incomparable advantages such as high efficiency, broad spectrum, low cost, long life, large amount of water and no pollution, it has gradually become the mainstream disinfection method in western developed countries. Its sterilization mechanism is to destroy the life genetic material of bacterial nucleic acid, making it unable to reproduce. The most important reaction is that pyrimidine bases in nucleic acid molecules become dimers. Low-pressure mercury discharge lamp (germicidal lamp) is generally used for artificial ultraviolet energy, and the wavelength is 253.7nm. The principle of ultraviolet germicidal lamp is the same as that of fluorescent lamp, except that fluorescent substances are not coated inside the lamp tube, and the material of the lamp tube is timely glass with high ultraviolet transmittance. General ultraviolet devices are divided into irradiation type, immersion type and running water type according to their uses.

Nine, biochemical method

Biochemical water treatment method is to use all kinds of bacteria and microorganisms existing in nature to decompose the organic matter in wastewater into harmless substances and purify the 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. Process flow of biochemical water treatment method: the raw water grid adjustment tank contacts with the oxidation tank to filter and disinfect the effluent.