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1. Raw water: Generally refers to natural water sources collected in nature, including groundwater, mountain springs, reservoir water and other natural sources, without any artificial purification treatment. Raw water in the meaning of water treatment includes general municipal tap water, and sometimes refers to untreated industrial wastewater.
Raw water: Generally refers to natural water sources collected in nature, including groundwater, mountain springs, reservoir water and other natural sources, without any artificial purification treatment. Raw water in the meaning of water treatment includes general municipal tap water, and sometimes refers to untreated industrial wastewater.
Municipal tap water: means the water produced after purification and disinfection by tap water treatment plants that meet the corresponding standards for People’s Daily life, production and use.
Surface water refers to the water that exists on the surface of the earth’s crust and is exposed to the atmosphere. It is the general term of four kinds of water bodies, namely rivers, glaciers, lakes and swamps, and is also called “land water”.
Groundwater: water stored in stratigraphic voids, including rock pores, fissures, and karst caverns, below the vadic zone (the geological medium located below the Earth’s surface and above the water surface). Groundwater is found in cracks in the earth’s crust or pores in the soil.
Domestic sewage: mainly refers to the discharge water produced by various kitchen water, washing water and toilet water used in human life, mostly non-toxic inorganic salts. Domestic sewage contains more nitrogen, phosphorus and sulfur, and disease-causing bacteria.
Municipal sewage: General term for sewage discharged into a municipal sewage system. In a combined drainage system, production waste water and trapped rainwater are also included. Municipal sewage mainly includes domestic sewage and industrial sewage, which are collected by urban drainage network and transported to sewage treatment plants for treatment.
Industrial wastewater refers to waste water, sewage and waste liquid generated in the process of industrial production, which contains industrial materials, intermediates and products lost with water and pollutants generated in the process of production.
2. pure water: remove the strong dielectric that is easy to remove in water, and remove the weak electrolytes such as silicic acid and carbon dioxide that are difficult to remove to a certain degree of water. The salt content of pure water is less than 1mg/L, and the conductivity is less than 10μs/cm.
Pure water is divided into: industrial pure water and drinking pure water, industrial pure water quality standards: at 25 degrees Celsius, ordinary pure water: EC=1-10μS/cm; High purity water: EC=0.1-1.0μS/cm; Ultra-pure water: RT=10-18.25MΩ*cm (theoretical extreme value), EC=0.055-0.1μS/cm;
Water quality standard for purified water for pharmaceutical use: conductivity ≤2μS/cm (resistivity ≥ 0.5MΩ *cm), (2010 edition of pharmacopoeia standard)
Pure drinking water quality standard :EC=1-10μS/cm (national standard)
electrical conductivity (EC)* resistivity (RT)=1, the resistivity exceeds 1MΩ*cm, generally expressed by resistivity, vice versa expressed by conductivity.
3. high purity water: remove most of the strong dielectric in the water, and remove the water with trace bacteria, microorganisms, particles and other impurities except the dielectric. The salt content of high purity water is less than 0.3mg/L, and the conductivity is less than 1μs/cm.
4. ultra-pure water: in addition to water molecules, almost all atoms except oxygen and hydrogen are removed from the water. The salt content of ultra-pure water is below 0.1mg/L, the conductivity is less than 0.1μs/cm, and the extreme resistivity can reach 18.25MΩ*cm.
5. softened water: refers to natural water containing a small amount of soluble magnesium salt and calcium salt, it can also be said that the softened treatment of hard water, soft water: 0-60ppm(mg/L). Water treatment generally refers to the water hardness (mainly refers to the water calcium, magnesium ions) to remove or reduce a certain degree of water. In the softening process of water, only the hardness is reduced, and the total salt content is unchanged.
6. demineralized water: refers to the Yang, anion in the water basically removed or reduced to a certain degree of water called demineralized water. The methods of salt removal include distillation, electrodialysis, reverse osmosis, ion exchange and so on. The basic definition is similar to deionized water.
7. deionized water: refers to the pure water after the removal of impurities in the form of ions. International standard: Deionized water completely or incompletely removes ionic substances. Deionization in terms of ionic purity water is broadly equivalent to the interpretation of pure water, and narrowly equivalent to the interpretation of ultra-pure water.
8. distilled water: the raw water is heated and vaporized, and then the water condensed into steam is called distilled water. Generally, the conductivity of distilled water is about 10μs/cm, and the distilled water is distilled again to obtain secondary distilled water, and the distilled water is distilled multiple times, and the conductivity can be reduced to a very low of about 1.0μs/cm.
9. Technical terms in water treatment:
Microfiltration: MF, also known as microporous filtration, belongs to precision filtration. Microfiltration can filter out micro – or nano-scale particles and bacteria in the solution. Microporous filtration is used to separate particles ranging from 0.02 to 10μm, and the pressure required for the process ranges from 0.07 to 0.2MPa.
Ultrafiltration: UF, ultrafiltration is one of the pressure-driven membrane separation technologies. For the purpose of separating large and small molecules, the pore size of the ultrafiltration membrane is between 1-20nm and the operating pressure is 0.1-0.5mpa.
Nanofiltration: NF, nanofiltration is a pressure driven membrane separation process between reverse osmosis and ultrafiltration, nanofiltration membrane pore size range of a few nanometers.
Osmosis is the diffusion of water molecules through a semi-permeable membrane. It seeps from regions of high water molecules (i.e., low-concentration solutions) into regions of low water molecules (i.e., high-concentration solutions).
Osmotic pressure: For a semi-permeable film with different concentrations of aqueous solution on both sides, the extra pressure exerted on one side of the higher concentration to prevent water from permeating from the lower concentration side to the higher concentration side is called osmotic pressure.
Reverse osmosis: RO, reverse osmosis is to artificially pressurize water from a concentrated solution to a low-concentration solution. RO RO reverse osmosis membrane has a small aperture to the nanometer level. At a certain pressure, water molecules can pass through the RO membrane, while inorganic salts, heavy metal ions, organic matter, colloids, bacteria, viruses and other impurities in the source water cannot pass through the RO membrane.
Dialysis, also known as dialysis. A membrane separation operation with concentration difference as the driving force, using the selective permeability of the membrane to the solute to achieve the separation of solute with different properties.
Electrodialysis: ED. When dialysis is performed under the action of an electric field, the migration of charged solute particles (e.g., ions) in a solution through the membrane is called electrodialysis. It is a technique that uses electric fields to separate ions from water. It separates the ions by applying an electric field between the two electrodes to move the charged ions towards the opposite electrode. Seawater desalination, wastewater treatment is more used.
EDI, also known as continuous electric desalting, is a technology that uses an electrochemical reaction to remove ions from water. It produces hydrogen ions and hydroxide ions by electrolysis of water, and then removes the ions from the water by separating the hydrogen ions and hydroxide ions using an ion exchange membrane. Ultrapure water is widely used in preparation.
Water: The part of a solution that passes through a membrane, as concentrated water of a reverse osmosis or nanofiltration system.
Water yield (water flux) : refers to the capacity of the reverse osmosis system, that is, the amount of water passing through the membrane per unit time, usually expressed in tons per hour (t/h) or gallons per day (g/d).
10. Descriptive names about water quality:
Hardness: refers to some metal ions in water that are easy to form precipitates, usually referring to the content of calcium and magnesium ions.
Salt content: The salt content of water, also known as salinity, is the amount of salts contained 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 the amount of various cations and the amount of anions in water.
Desalting rate: the parameter that reflects the performance of the film, usually the desalting rate of the primary RO membrane system is above 97%. It can be simply calculated: (raw water conductivity – electrical conductivity of product water)/ raw water conductivity.
Residual chlorine: the effective chlorine left in water after contact with chlorinated water for a certain period of time.
Ion: an atom loses or gains one or more electrons due to its own or external action so that it reaches a stable structure with the outermost number of electrons of 8 or 2 (helium atoms) or no electrons (four neutrons). This process is called ionization.
Iron, manganese, aluminum: Trace amounts of iron and manganese will cause staining, scaling and taste problems, iron in the reduced state in the form of water-soluble bivalent iron, when in contact with air will gradually oxidize to yellow brown colloidal trivalent iron, and finally precipitate to brown ferric hydroxide. The characteristics of manganese and iron are similar, because the oxides of iron, manganese and aluminum are also one of the reasons for scaling of RO film, it is necessary to analyze its content.
Conductivity: is the conductivity of a solution between two parallel electrodes with a cross-sectional area of 1 cm2 and a distance of 1 cm at a given temperature. It can indirectly indicate the content of dissolved salt in water.
Resistivity: An indicator of the electrical conductivity of water. The higher the resistivity of water, the worse the electrical conductivity of water and the fewer ions it contains. Its common unit is MΩ*CM. It has an reciprocal relationship with the conductivity. For example: the conductivity of water is 0.2μs/cm (microwest per centimeter), then its resistivity is 1/0.2=5(MΩ*CM) (megohm cm).