STARK WATER TREATMENT: Pure water treatment process and treatment principle
What is pure water treatment?
Pure water means that pure water generally uses urban tap water as the water source. Through multi-layer filtration, harmful substances such as microorganisms can be removed, but at the same time, minerals required by the human body such as fluorine, potassium, calcium, and magnesium are removed.
Due to the uncontrolled discharge of industrial wastewater, domestic wastewater and agricultural pollution, the current surface water not only contains mud, sand, animal and plant decay. There are also a large number of substances such as bleach, pesticides, heavy metals, lime, iron and other substances that endanger human health. The long-term accumulation of these pollutants in the human body is extremely harmful to human health, and can cause cancer, mutagenesis, and distortion. True killer. However, the traditional tap water production process not only cannot remove the organic compounds in it, but if chlorine is added in tap water production, it will generate new and stronger organic pollution such as chloroform, which makes tap water more mutagenic than natural water. Moreover, after the tap water leaves the factory, it needs to go through a long water delivery pipeline system, especially the water tank on the roof of high-rise residential buildings, there is a relatively serious "secondary pollution". This type of water, of course, cannot be drunk raw. Even if it is boiled, it can only sterilize but not remove harmful chemicals. Furthermore, drinking pure water can not only eliminate harm to health, but also benefit health and longevity. Because the purer the water, the better the function of the carrier, the stronger the ability to dissolve various metabolites in the body, the easier it is to be absorbed by the human body, which is beneficial to the production of body fluid to quench thirst and relieve fatigue. Therefore, in order to maintain health, improve people's health, develop pure water business, and produce high-quality drinking water, pure water treatment is to purify tap water twice, and further filter harmful substances such as chlorides and bacteria in tap water to achieve elimination. bacteria and disinfection effect.
The method of pure water treatment
1. Membrane microfiltration (MF) pure water treatment
Membrane microporous filtration methods include three forms: depth filtration, screen filtration, and surface filtration. Depth filtration is a matrix made of woven fibers or compressed materials, and uses inert adsorption or capture to retain particles, such as commonly used multi-media filtration or sand filtration; depth filtration is a relatively economical way to remove 98 % or more of suspended solids, while protecting the downstream purification unit from being blocked, so it is usually used as a pretreatment.
Surface filtration is a multi-layer structure. When the solution passes through the filter membrane, particles larger than the pores inside the filter membrane will be left behind and mainly accumulate on the surface of the filter membrane, such as the commonly used PP fiber filtration. Surface filtration can remove more than 99.9% of suspended solids, so it can also be used as pretreatment or clarification.
The sieve filter membrane basically has a consistent structure, just like a sieve, leaving particles larger than the pore size on the surface (the pore measurement of this filter membrane is very accurate), such as the terminal used in ultrapure water machines Use point security filters; mesh filtration Microfiltration is generally placed at the end-use point in the purification system to remove the last remaining traces of resin flakes, carbon chips, colloids and microorganisms.
2. Activated carbon adsorption pure water treatment
Activated carbon adsorption is a method in which one or more harmful substances in water are adsorbed on the solid surface and removed by utilizing the porous nature of activated carbon. Activated carbon adsorption has a good effect on removing organic matter, colloids, microorganisms, residual chlorine, odor, etc. in water. At the same time, because activated carbon has a certain reducing effect, it also has a good removal effect on oxidants in water.
Since the adsorption function of activated carbon has a saturation value, when the saturated adsorption capacity is reached, the adsorption function of the activated carbon filter will be greatly reduced. Therefore, it is necessary to pay attention to analyze the adsorption capacity of activated carbon, and replace the activated carbon in time or carry out disinfection and recovery by high-pressure steam. However, at the same time, the organic matter adsorbed on the surface of activated carbon may become a nutrient source or breeding ground for bacterial reproduction, so the problem of microbial reproduction in the activated carbon filter is also worthy of attention. Regular disinfection is necessary to control bacterial growth. It is worth noting that in the initial stage of using activated carbon (or the initial stage of operation of newly replaced activated carbon), a small amount of very fine powdered activated carbon may enter the reverse osmosis system with the water flow, resulting in fouling of the reverse osmosis membrane flow channel and causing operation. Pressure rises, permeate production drops, and pressure drop across the system rises, and this damage is difficult to recover with conventional cleaning methods. Therefore, the activated carbon must be rinsed and the fine powder removed before the filtered water can be sent to the subsequent RO system. Activated carbon has a great effect, but attention should be paid to disinfection and new activated carbon must be rinsed clean during use.
3. Reverse osmosis (RO) pure water treatment
Reverse osmosis means that when a pressure greater than the osmotic pressure is applied on the side of the concentrated solution, the solvent in the concentrated solution will flow to the dilute solution, and the flow direction of this solvent is opposite to the direction of the original osmosis. This process is called reverse osmosis. This principle is used in the field of liquid separation for purification, impurity removal, and treatment of liquid substances.
The working principle of reverse osmosis membrane: a membrane that is selective for permeable substances is called a semi-permeable membrane, and a membrane that can only permeate a solvent but cannot permeate a solute is generally called an ideal semi-permeable membrane. When the same volume of dilute solution (such as fresh water) and concentrated solution (such as salt water) are placed on both sides of the semipermeable membrane, the solvent in the dilute solution will naturally pass through the semipermeable membrane and flow to the concentrated solution side spontaneously, This phenomenon is called penetration. When the osmosis reaches equilibrium, the liquid level on the side of the concentrated solution will be higher than the liquid level of the dilute solution by a certain height, that is, a pressure difference is formed, and this pressure difference is the osmotic pressure. Reverse osmosis is a reverse migration movement of osmosis. It is a separation method that separates the solute and solvent in the solvent by means of the selective interception of the semipermeable membrane under the pressure drive. It has been widely used in the purification of various solutions. The most common application example is in the water treatment process, using reverse osmosis technology to remove impurities such as inorganic ions, bacteria, viruses, organic matter and colloids in raw water to obtain high-quality pure water.
4. Ion exchange (IX) pure water treatment
Ion exchange pure water equipment is a traditional water treatment process that replaces various anions and cations in water through anion and cation exchange resins. The anion and cation exchange resins are matched in different proportions to form an ion exchange cation bed system. Anion bed system and ion exchange mixed bed (compound bed) system, and the mixed bed (compound bed) system is usually used in the terminal process of producing ultrapure water and high purity water after reverse osmosis seepage and other water treatment processes. It is one of the irreplaceable means for preparing ultrapure water and high purity water. The effluent conductivity can be lower than 1uS/cm, and the effluent resistivity can reach more than 1MΩ.cm. According to different water quality and usage requirements, the effluent resistivity can be controlled between 1~18MΩ.cm. It is widely used in the preparation of ultra-pure water and high-purity water in industries such as electronics, electric power ultra-pure water, chemical industry, electroplating ultra-pure water, boiler feed water and medical ultra-pure water.
The salts contained in the raw water such as Ca(HCO3)2, MgSO4 and other calcium and magnesium sodium salts, when flowing through the exchange resin layer, the cations Ca2+, Mg2+, etc. are replaced by the active groups of the cation resin, and the anions HCO3-, SO42-, etc. Replaced by the active groups of the anion resin, the water is thus ultra-purified. If the bicarbonate content in the raw water is high, a degassing tower should be set up between the anion and cation exchange columns to remove CO2 gas and reduce the load of the anion bed.
5. Ultraviolet (UV) ultrapure water treatment
The main process of cell reproduction is: the long chain of DNA is opened. After opening, the adenine units of each long chain look for thymine units to join, and each long chain can copy the same chain as the other long chain that has just been separated. , restore the complete DNA before the original division, and become a new cell basis. Ultraviolet rays with a wavelength of 240-280nm can break the ability of DNA to produce proteins and replicate. Among them, ultraviolet rays with a wavelength of 265nm have the strongest killing ability to bacteria and viruses. After the DNA and RNA of bacteria and viruses are damaged, their ability to produce proteins and reproductive capacity have been lost. Because bacteria and viruses generally have a very short life cycle, bacteria and viruses that cannot reproduce will die quickly. Ultraviolet rays are used to prevent the survival of microorganisms in tap water so as to achieve the effect of sterilization and disinfection.
Only artificial mercury (alloy) light sources can output sufficient ultraviolet intensity (UVC) intensity for engineering disinfection. The ultraviolet germicidal lamp tube is made of quartz glass. The mercury lamp is divided into three types according to the difference of mercury vapor pressure in the lamp after lighting and the difference of ultraviolet output intensity: low-pressure low-intensity mercury lamp, medium-pressure high-intensity mercury lamp lamps and low pressure high intensity mercury lamps.
The bactericidal effect is determined by the irradiation dose received by the microorganisms, and at the same time, it is also affected by the output energy of ultraviolet rays, which is related to the type of lamp, light intensity and use time. As the lamp ages, it will lose 30%-50% of its intensity. .
The ultraviolet irradiation dose refers to the amount of ultraviolet rays of a specific wavelength required to achieve a certain bacterial inactivation rate: irradiation dose (J/m2) = irradiation time (s) × UVC intensity (W/m2) The greater the irradiation dose, the higher the disinfection efficiency. Due to the size requirements of the equipment, the general irradiation time is only a few seconds. Therefore, the UVC output intensity of the lamp has become the most important parameter to measure the performance of the ultraviolet light disinfection equipment.
6. Ultrafiltration (UF) pure water treatment
Ultrafiltration technology is a high-tech widely used in water purification, solution separation, concentration, extraction of useful substances from wastewater, and wastewater purification and reuse. It is characterized by simple use process, no heating, energy saving, low-pressure operation, and small footprint of the device.
Ultrafiltration (UF) pure water treatment principle: Ultrafiltration is a membrane separation process based on the separation principle of sieving and pressure as the driving force. , bacterial cushion and macromolecular organic matter. It can be widely used in the separation, concentration and purification of substances. The ultrafiltration process has no phase inversion and operates at room temperature. It is especially suitable for the separation of heat-sensitive substances. It has good temperature resistance, acid and alkali resistance and oxidation resistance. It can be used continuously for a long time under the conditions of below 60℃ and pH of 2-11. .
Hollow fiber ultrafiltration membrane is the most mature and advanced form of ultrafiltration technology. The outer diameter of the hollow fiber is 0.5-2.0mm, and the inner diameter is 0.3-1.4mm. The wall of the hollow fiber is covered with micropores. The raw water flows under pressure on the outside or the inner cavity of the hollow fiber, forming an external pressure type and an internal pressure type respectively. Ultrafiltration is a dynamic filtration process, and the trapped substances can be removed with the concentration, without blocking the surface of the membrane, and it can run continuously for a long time.
7. EDI pure water treatment
The working principle of EDI ultrapure water treatment equipment: Electrodeionization (EDI) system is mainly under the action of DC electric field, the directional movement of dielectric ions in the water through the separator, and the selective permeation of ions by the exchange membrane to improve water quality. A scientific water treatment technology for purification. Between a pair of electrodes of the electrodialyser, usually anion membrane, cation membrane and separators (A, B) are alternately arranged in groups to form a concentration chamber and a thin chamber (that is, cations can pass through the cationic membrane, and anions can pass through the cathode. membrane). The cations in the fresh water migrate to the negative electrode through the cationic membrane and are intercepted by the negative membrane in the concentration chamber; the anions in the water migrate to the positive electrode towards the negative membrane and are intercepted by the cationic membrane in the concentration chamber, so that the number of ions in the water passing through the fresh chamber gradually decreases, It becomes fresh water, and the water in the concentration chamber, due to the continuous influx of anions and cations in the concentration chamber, the dielectric ion concentration continues to rise, and becomes concentrated water, so as to achieve the purpose of desalination, purification, concentration or refining.
Advantages of EDI ultrapure water treatment equipment:
(1) No need for acid-base regeneration: In the mixed bed, the resin needs to be regenerated with chemicals and acid-base, while EDI eliminates the handling and heavy work of these harmful substances. protect the environment.
(2) Continuous and simple operation: in the mixed bed, the operation process becomes complicated due to the change of each regeneration and water quality, while the water production process of EDI is stable and continuous, and the water quality of the produced water is constant. Complicated operating procedures, the operation is greatly simplified.
(3) Reduced installation requirements: EDI system has a smaller volume than a mixed bed with a similar water treatment capacity. It adopts a building block structure and can be flexibly constructed according to the height and scent of the site. Modular design makes EDI easy to maintain during production work
8. Ozone sterilization ultra pure water treatment
The disinfection principle of ozone (O3) is: the molecular structure of ozone is unstable at normal temperature and pressure, and it quickly decomposes into oxygen (O2) and a single oxygen atom (O); the latter has strong activity and is extremely harmful to bacteria. Strong oxidation will kill it, and the excess oxygen atoms will recombine into ordinary oxygen atoms (O2) by themselves, and there is no toxic residue, so it is called a non-polluting disinfectant. Viruses, Escherichia coli, Pseudomonas aeruginosa and miscellaneous bacteria, etc.) have extremely strong killing ability, and are also very effective for killing mycin.
(1) The sterilization mechanism and process of ozone belong to the biochemical process, which oxidizes and decomposes the glucose oxidase necessary for the oxidation of glucose inside the bacteria.
(2) It directly interacts with bacteria and viruses, destroys their organelles and ribonucleic acid, decomposes macromolecular polymers such as DNA, RNA, proteins, lipids and polysaccharides, and destroys the metabolic production and reproduction process of bacteria.
(3) Penetrates the cell membrane tissue, invades the cell membrane and acts on the outer membrane lipoprotein and the internal lipopolysaccharide, causing the cells to permeate and distort, resulting in cell lysis and death. And the genetic genes, parasitic strains, parasitic virus particles, bacteriophages, mycoplasmas and pyrogens (bacterial and viral metabolites, endotoxins) in the dead bacteria are dissolved and denatured to die.