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Summary of basic knowledge of water treatment
Author:Dongda Environment Time:2020-12-23 Clicks:181
      1. Turbidity:
      Refers to the degree of turbidity of water, which is an optical effect caused by a certain amount of suspended matter (including colloidal substances) in the water. The unit is expressed in NTU. Turbidity is one of the main characteristics that determine whether water is polluted in appearance. The standard unit of turbidity is defined as the turbidity constituted by 1mgSi02 as 1 degree.
      2. Flocculant:
      Agents that can cause colloidal particles to coagulate and bridge to cause flocculation.
      3. Total alkalinity:
      It refers to the total amount of substances in the water that can neutralize strong acids.
      4. Acidity:
      It refers to the total amount of substances in the water that can neutralize with strong alkalis.
      5. Hardness:
      Refers to some metal ions that are easy to form precipitates in water, usually referring to the content of calcium and magnesium ions.
      6. Conductivity:
      It is the conductance of the solution between two parallel electrodes with a cross-sectional area of ​​1 cm 2 and a distance of 1 cm at a certain temperature. Can indirectly indicate the content of dissolved salt in the water.
      7. Resistivity:
      It is an indicator that reflects the conductivity of water. The greater the resistivity of water, the worse the conductivity of water, and the fewer ions contained in the water. Its common unit is MΩ.CM. It has a reciprocal relationship with conductivity. For example, if the conductivity of water is 0.2μs/cm, its resistivity is 1/0.2=5 (MΩ.CM).
      8. TDS (total dissolved solids):
      It is the remaining inorganic matter after filtering out suspended solids (SS) and colloids and evaporating all the water. The unit is ppm or mg/l, which can be measured with a TDS instrument. It also reflects the ion content in the water. There is a rough correspondence between it and conductivity: For the sodium chloride reference solution, a TDS value of 1 ppm corresponds to a conductivity of 2 μs/cm.
      9. PH value:
      The relative content of acid and base in the solution. The pH value is a unit of measurement for the negative logarithm (log) of the hydrogen ion concentration in water. The pH value is divided into 0~14 levels, the pH value is 7.0, the water is neutral; the pH value is less than 7.0, the water is acidic; the pH value is greater than 7.0. Then the water is alkaline.
      10. Alkalinity:
      Alkalinity refers to the content of substances in the water that can accept the neutralization reaction of [H+] ions with strong acids. The substances that produce alkalinity in water are mainly carbonate alkalinity produced by carbonate and bicarbonate alkalinity produced by bicarbonate, and hydroxide alkalinity produced by the presence of hydroxide.
      11. SDI:
      Pollution Index-used to measure the amount of suspended solids in the raw water used by the reverse osmosis system.
      12. Recovery rate:
      Refers to the ratio of the flow of product water produced by the system to the flow of influent water.
      13. Desalination rate:
      The parameter reflecting the performance of the membrane, usually the salt rejection rate of the first-stage RO membrane system is above 97%. It can be simply calculated: (Raw water conductivity-product water conductivity)/Raw water conductivity.
      14. Salt content:
      The salt content of water is also called salinity, which means the amount of salt in the water. Since various salts in water generally exist in the form of ions, the salt content can also be expressed as the sum of various cations and anions in the water.
      15. Pure water:
      Pure water refers to water that not only removes the strong dielectric that is easily removed from water, but also removes weak electrolytes such as silicic acid and carbon dioxide that are difficult to remove from water to a certain extent. The salt content of pure water is below 1.0mg/L, and the conductivity is less than 3μs/cm.
      16. Suspended solids (SS):
      Refers to the solid matter suspended in water, including inorganic matter, organic matter, silt, clay, and microorganisms that are insoluble in water. The content of suspended solids in water is one of the indicators to measure the degree of water pollution. It is the solid amount obtained by drying the retentate on the filter paper at a temperature of 103-105 degrees after the water sample is filtered. Unit mg/l.
      17. Ultra-pure water:
      Ultra-pure water, also known as high-purity water, refers to the water that removes almost all the conductive media in the water, and removes the indissociable colloidal substances, gases and organic matter in the water to a very low level. The salt content of ultrapure water is below 0.1 mg/L, and the conductivity is less than 0.1 μs/cm.
      In addition to strict requirements on salt content or conductivity, pure water and ultrapure water also have strict index limits on the content of various metal ions in the water, the content of organic matter, the particle size and number of particles, and the number of microorganisms.
      18. Distilled water:
      Distilled water is the water that the raw water is heated to vaporize, and then the steam is condensed into distilled water. Generally, the conductivity of distilled water is about 10μs/cm. Once distilled water is distilled again to obtain twice distilled water, and multiple distillations to obtain multiple distilled water, the conductivity can be reduced to a very low level of about 1.0μs/cm.
      19. Antiscalant:
      Scale inhibitors are a class of agents that can disperse insoluble inorganic salts in water, prevent or interfere with the precipitation and scaling of insoluble inorganic salts on metal surfaces, and maintain good heat transfer effects in metal equipment.
      20. EDI:
      EDI (Electrodeionization) is abbreviated as continuous electric desalination, which is a new type of ultrapure water preparation technology gradually developed in the 1990s. It cleverly integrates electrodialysis technology and ion exchange technology, through the selective permeation of anion and cation by the anion and cation exchange membrane and the exchange of ions by the ion exchange resin, the directional migration of ions to concentrated water is realized under the action of a direct current electric field. In order to complete the deep desalination of water to obtain ultrapure water, the water molecules are electrolyzed into hydrogen ions and hydroxide ions to regenerate the resin, eliminating the traditional acid-base chemical regeneration.
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