Basic knowledge of water

  1. The salt content of water: also the degree of mineralization, which indicates the amount of salts in the water, and can also be expressed as the sum of various anions and cations in the water.
  2. Hardness: the total concentration of metal ions in water after cations and anions combine to form scale.
  3. Softened water: refers to the water that removes or reduces the hardness of water (mainly calcium and magnesium ions in water) to a certain extent. During the softening process of water, only the hardness decreases, while the total salt content remains unchanged.
  4. Conductivity and resistance: The purer the water, the lower the salt content, the higher the resistivity and the lower the conductivity. Ultrapure water hardly conducts electricity. Conductance is equal to the reciprocal of resistance.
  5. PH value and pH value: The PH value of water is the negative logarithm of the concentration of hydrogen ions in water, also known as the hydrogen ion index. It can be known that the aqueous solution is alkaline, neutral and acidic.
  6. The molecular formula of water is H2O, and the relative molecular weight is 18.015. In water molecules, hydrogen accounts for 11.9% and oxygen accounts for 88.81%.
  7. High-quality water: rough filtration, fine filtration, ultrafiltration, sterilization and other processes are used on the basis of municipal water supply (or water that meets the standard). High-quality drinking water obtained by deep processing.
  8. Groundwater: It is the water formed by the infiltration and flow of rainwater through the soil and strata. In its long process and extensive contact, more salts are dissolved, and the hardness is extremely high, but at the same time, the groundwater is filtered layer by layer and suspended. There are few substances, the water is clear, and the turbidity is low. 8. Pure water: clean water with almost no impurities obtained by using water treatment equipment with high desalination rate, the conductivity is generally 1.0~0.1μS/cm,
  9. Mineralized water: The pure mineralized water containing trace elements is obtained by using a special process in relatively pure raw water and adding ore rocks.
  10. Mineral water: precious water resources in nature, after simple treatment by sterilization and filtration, are supplied to consumers as commercial drinking water.
  11. Desalted water: refers to the water in which salts (mainly strong electrolytes soluble in water) are removed or reduced to a certain extent. 1.0-10.0μS/cm, resistivity (25℃) 0.1-1.0*106cm, the salt content is 1-5mg/L.
  12. Pure water: refers to the removal or reduction of strong electrolytes and weak electrolytes (such as SiO2, CO2, etc.) in water to a certain extent. Its conductivity is generally: 1.0-0.1μS/cm, resistivity 1.0-10.0*106Ω·cm. Salt content <1mg/L.
  13. Ultrapure water: It refers to the water in which the dielectric in the water is almost completely removed, and the non-decomposable gases, colloids and organic substances (including bacteria, etc.) are also removed to a very low level. Its conductivity is generally 0.1-0.55µS/cm, and its resistivity (25℃) is 10.0*106Ω·cm. Salt content <0.1mg/L. Ideal pure water (theoretically) has a conductivity of 0.05µS/cm and a resistivity (25℃) of 18.3*106Ω•cm.
  14. Surface water: refers to the water of rain and snow, rivers, lakes and oceans. In addition to the extremely high salt content of the ocean, the important characteristics of other surface waters are low salt content and low hardness, but high pollution impurities. Municipal water supply (tap water) mainly refers to municipal water supply that has been treated by a waterworks. This is the most common way to drink water. Due to the huge differences in source water in different regions, the national standards are also relatively loose. After precipitation, filtration, and chlorination disinfection in the water plant. delivered to thousands of households. In this way, the water quality is relatively stable, and generally there will not be too many fluctuations, but the water can be described as rough processing and has a wide range of uses. Moreover, the secondary pollution caused by the long transportation or storage process is also very serious. People have to boil it before using it. In addition to sterilizing, boiling can not remove other dirt, and some substances even become thicker and more harmful to the human body.
  15. Magnetization: The treatment of water by the magnetic field effect is called the magnetization of water.
  16. Mineralization: refers to adding beneficial minerals to clean water. It should be pointed out that: First, this water must be clean water after strict treatment. Because the impurities in the water sometimes react with the ore to produce other substances; second, the ore must be strictly screened, and can be used after decarbonization and turbidity through special processes such as high-temperature distillation.
  17. Adsorption water purification technology
    It mainly refers to the adsorption technology of substances with adsorption capacity such as activated carbon. Here is a brief introduction to some of the characteristics of activated carbon: Activated carbon is widely used in the purification, dehydrogenation, degreasing and deodorization of drinking water and industrial water such as food industry, chemical industry, and electric power. Typically, it can remove 63%-86% of colloidal substances; around 50% of iron; and 47%-60% of organic substances.
  18. Precision filtration technology
    The microporous filter element and filter membrane made of special materials use their uniform pore size to retain particles, bacteria, etc. in the water, so that they cannot be removed and retained through the filter element and filter membrane. Precision filtration can filter micron (µm) or nanometer (nm) particles and bacteria. It is also widely used in the advanced treatment of water.
  19. Ultrafiltration technology
    Ultrafiltration is a membrane separation technology. That is, under a certain pressure (the pressure is 0.07-0.7Mpa, the highest is not more than 1.05Mpa), water flows on the membrane surface, water and dissolved salts and other electrolytes are tiny particles that can penetrate the ultrafiltration membrane, while the molecular weight is large. Particles and colloidal substances are blocked by the ultrafiltration membrane, so that part of the particles in the water can be separated. The pore size of the ultrafiltration membrane is determined by the retention test of substances with a certain molecular weight, and is expressed in terms of molecular weight.
  20. Nanofiltration and reverse osmosis technology
    Nanofiltration: also known as loose reverse osmosis, its basic principle is the same as reverse osmosis, but the salt rejection rate is slightly lower than reverse osmosis. “Infiltration” is a physical phenomenon. When two kinds of water with different concentrations of salts are separated by a semi-permeable membrane, it will be found that the water on the side with less salt content will infiltrate the membrane to the salt content. On the high water side, try adding a pressure, and the result can also stop the above infiltration. The pressure at this time is called the osmotic pressure. If the pressure is increased further, the water can permeate in the opposite direction, leaving the salt behind. Therefore, the principle of membrane osmotic desalination is to apply a pressure greater than the natural osmotic pressure in salty water (such as raw water), so that the permeation proceeds in the opposite direction, and the water molecules in the raw water are pressed to the other side of the membrane to become This is the principle of nanofiltration and reverse osmosis desalination.
  21. Ion exchange
    The so-called ion exchange is the equal charge reaction between the ions in the water and the ions on the ion exchange resin. The reaction process of ion exchange can be taken as an example of the exchange reaction process of H+ cation exchange resin HR and Na+ in water: HR+Na+=Na++H+ It can be seen from the above formula: in the ion exchange reaction, cations (such as Na) in water are transferred to the resin, and an exchangeable H on the ion exchange resin is transferred to the water. The transfer of Na from water to the resin is an ion replacement process. The process of exchanging H on the resin into water is called the free process. Therefore, as a result of the free and replacement process, Na and H exchange positions, this change is called ion exchange.
  22. Sterilization and disinfection
    Water disinfection methods can be divided into two types: chemical and physical. Physical disinfection methods include heating method, ultraviolet method, ultrasonic wave and other methods; chemical methods include chlorination method, ozone method, heavy metal ion method and other oxidant methods. Here is only a brief introduction to the ultraviolet (uv) method in the physical disinfection method and the ozone (O3) method in the chemical disinfection method:
  23. Ultraviolet rays: When the mercury lamp is ignited, it can emit ultraviolet rays with a wavelength of 1400Å-4900Å (1Å=10-10m). This light can penetrate the cell wall of bacteria, kill microorganisms, and achieve the purpose of disinfection and sterilization. UV wavelengths work best around 2600Å. Ultraviolet disinfection is mainly used in drinking water with a small treatment volume. Its characteristics are: strong killing ability, short contact time; simple equipment, convenient operation and management, the treated water is colorless, odorless, and free of poisoning hazards; it will not increase the chlorine ions that appear temporarily like oxygen kills. However, ultraviolet rays do not have the continuous killing effect of residual chlorine, and the mercury lamp has a short service life, is expensive, and treats a small amount of water.
  24. Ozone: Ozone is a blue gas with a special fishy smell at room temperature, and its molecular formula is O3. Ozone is an allotrope of oxygen, which can be decomposed into a single oxygen atom by itself at room temperature, and a single oxygen atom has a strong oxidizing property. Ozone can oxidize and denature the proteins of bacteria, fungi and other bacteria, making electrolytes ineffective, killing bacterial propagules and spores, viruses, fungi, etc., and destroying botulinum toxin, and can remove and kill air, Toxic substances and bacteria in water and food can remove odor and are widely used in disinfection and sterilization of food production. In the process of disinfection and sterilization, ozone only produces non-toxic oxides, and the excess ozone is finally reduced to oxygen, and there is no residue on the sterilized items, which can be directly used for the disinfection and sterilization of food.

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