Detailed analysis of various professional terms in pure water treatment
　　
1、 Basic concepts
　　
1. Conductivity: The number of ions that can move between two electrodes with an area of one square centimeter each and a distance of one centimeter apart is called conductivity, measured in μ s/cm.
　　
2. Resistance: reciprocal of conductivity, unit: M Ω/cm.
　　
3. Hardness: refers to the content of calcium and magnesium ions in the water source.
　　
4. pH value: The relative content of acid and alkali in a solution. PH value is a unit of measurement for the negative logarithm (log) of hydrogen ion concentration in water. The pH value is divided into 0-14 levels, and if the pH value is 7.0, the water is neutral; If the pH value is less than 7.0, water is acidic; The pH value is greater than 7.0. Then water is alkaline.
　　
5. Total dissolved solids (TDS): refers to the total solid content dissolved in water, usually referring to mineral content.
　　
6. Alkalinity: Alkalinity refers to the content of substances in water that can accept neutralization reactions between [H+] ions and strong acids. The substances that produce alkalinity in water are mainly the carbonate alkalinity produced by carbonates and the bicarbonate alkalinity produced by bicarbonates, as well as the hydroxide alkalinity produced by the presence of hydroxides.
　　
7. Total Organic Carbon (TOC): Total Organic Carbon (TOC) is a unit of measurement for organic pollution in water, measured in mg/L. TOC is a direct unit of measurement for oxidizable organic compounds.
　　
8. Activated carbon: Granular activated carbon is used to remove odors, odors, chloramines, and some organic compounds from water.
　　
9. NTU: Scattering turbidity is measured by passing a beam of light through the sample water and measuring the turbidity of low turbidity water using a scattering turbidity meter.
　　
10. Permeation: Water flows naturally through a semi permeable membrane from the low concentration solution side to the high concentration solution side until energy reaches equilibrium.
　　
11. SDI: Pollution Index is used to measure the amount of suspended solids in the raw water used in reverse osmosis systems.
　　
12. Resin: Specially manufactured polymer balls used in ion exchange systems to remove dissolved salts from aqueous solutions.
　　
13. LSI: Langelier saturation index is a calculation formula used under specified conditions: temperature, pH value TDS、 Prediction of calcium carbonate precipitation under hardness and alkalinity conditions.
　　
14. Ozone: An unstable and highly active form of oxygen produced by natural lightning or high-voltage charges passing through the air. It is an excellent oxidant and disinfectant.
　　
15. Residual chlorine: The effective chlorine remaining in water after disinfection with chlorine and contact for a certain period of time.
　　
16. Recovery rate: refers to the ratio of the water output of the equipment to the water input, reflecting the size of the equipment's own water consumption.
　　
17. Desalination rate: refers to the ratio of TDS removal from water by reverse osmosis and other methods.
　　
18. Total Escherichia coli: The total Escherichia coli refers to a group of aerobic and facultative anaerobic gram-negative non spore forming bacteria that can ferment lactose at 37 ℃ and produce acid and gas within 24 hours. The total coliforms refer to the number of total coliforms present in each liter of water sample.
　　
19. Total bacterial count: refers to the total bacterial population that grows in 1ml of water (or 1g of sample) after being cultured at 37 ℃ for 24 hours in ordinary agar medium.
　　
20. Pure water, high-purity water: Pure water refers to water purification equipment that removes or reduces salts (mainly strong electrolytes dissolved in water) from water to a certain extent. 1.0-10.0μS/cm， The resistivity (25 ℃) is 0.1-1.0 * 106cm, and the salt content is 1-5mg/L. High purity water refers to water in which almost all conductive media are removed from the water, and colloidal substances, gases, and organic matter that do not dissociate from the water are removed to a very low degree. The salt content of high-purity water is below 0.3mg/L, and the conductivity is less than 0.2 μ s/cm.
　　
2、 Equipment Introduction
　　
1. Precipitation: Precipitation is usually a multi-step process used to reduce turbidity and suspended solids in water. This multi-step process involves adding chemical coagulants or pH regulators to react and generate flocs. The flocs settle in a settling tank due to gravity or are filtered out when water passes through a differential filter. The precipitation process can effectively remove particles larger than 25um.
　　
2. Chemical softening - Lime soda softening: The method of adding lime (CaO) and baking soda (Na2CO3) to water to reduce its calcium and magnesium content is called lime softening method. The goal is to precipitate calcium hydroxide and (hardness) in water. This process has low cost, but the effect is barely satisfactory. The water hardness typically produced is 50-120ppm (3-7gpg). The drawback of this process is that the pH value of the treated water is high, generally ranging from 8.5 to 10.0.
　　
3. Mechanical filter: A mechanical filter is a pressure vessel filled with a specified thickness of filter material. When filled with a single filter material, it is a single-layer mechanical filter. When filled with different types of filter materials, it is a double-layer or multi-media filter.
　　
Function: In the water quality pretreatment system, different particle sizes of quartz sand in the pressure vessel of the multi-media filter are filled according to a certain level. The flocculated raw water passes through the filter layer from top to bottom under a certain pressure, so that suspended solids in the water can be intercepted and removed. The multi-media filter can effectively remove suspended solids, fine particles, total iron and colloids, bacteria, algae and organic matter in the raw water. Its effluent SDI15 (pollution index) is less than or equal to 5, which fully meets the inlet requirements of the reverse osmosis device.
　　
4. Softener: Ion exchange softening device is a commonly used equipment in water treatment process, which is used to remove calcium and magnesium ions that form scale in hard water. In many cases, the use of softened water equipment can remove soluble ions (iron ions). The standard soft water equipment has four main parts: resin column, resin, salt adding device, and valve controller.
　　
The resin column of the soft water equipment contains treated ion exchange resin polystyrene small particles. This type of resin particles initially adsorb sodium ions during the regeneration process, and this resin has a much higher affinity for multivalent ions such as calcium and magnesium ions. Therefore, when hard water flows through the resin, calcium ions and magnesium ions will adsorb onto the resin, while also desorbing ions until equilibrium is reached. At this point, the soft water equipment completes the exchange of sodium ions with calcium and magnesium ions in the water.
　　
During regeneration, NaCl solution is passed through the resin, and hard ions are replaced with sodium ions. The use of high concentration saltwater weakens the affinity between the resin and hard ions. This regeneration process can be repeated infinitely without damaging the resin.
　　
5. Mixed bed: Mixed bed is the abbreviation for mixed ion exchange column, which is a device designed for ion exchange technology. The so-called mixed bed refers to the mixing and filling of a certain proportion of cation and anion exchange resins in the same exchange device to exchange and remove ions from the fluid. Due to the higher specific gravity of the cation resin compared to the anion resin, the anion resin is on top and the cation resin is on the bottom in the mixed bed. The general ratio of resin filling for yang and yin is 1:2, and there are also filling ratios of 1:1.5, which can be selected according to different resins.
　　
6. Reverse osmosis: Reverse osmosis is a widely used membrane separation process that uses pressure to allow water to pass through the membrane, while soluble salts, colloids, organic matter, and microorganisms are trapped on the membrane surface and discharged with concentrated water. It can effectively remove all organic matter and 90% to 99% of ions.
　　
7. Ultrafiltration: Ultrafiltration is between microfiltration and nanofiltration, and there is no clear boundary between the three. Generally speaking, the pore size of ultrafiltration membranes is between 0.05um and 1nm, and the operating pressure is between 0.1-0.5Mpa. Mainly used for intercepting and removing large molecular substances such as suspended solids, colloids, particles, bacteria, and viruses in water.
　　
8. Nanofiltration: Nanofiltration separation, as a new membrane separation technology, has a technical principle similar to mechanical screening. However, the nanofiltration membrane itself is charged. This is an important reason why it still has high desalination performance at very low pressures and can remove inorganic salts even with membranes with molecular weight cut-off of hundreds.
　　
9. Sterilization: Ozone, UV, Chlorine Dioxide
　　
10. Dosing device: flocculant, acid, alkali, bactericide, scale inhibitor
　　
3、 Process Introduction
　　
1. Drinking water treatment
　　
2. Purified water or direct drinking water treatment
　　
3. Boiler water
　　
4. Production process water: food, beverage, chemical industry