1, Sand filtration: sand filtration is the simplest and most economical way of treatment.
The working principle is that the water flow through the sand layer is dispersed and flows through different gaps. The smaller the sand particles, the smaller the gap between the sand particles, and the gap between the sand particles is irregular, so that the gap is small enough to hang some of the impurities in the water. The thicker the sand layer, the better the filtration effect. The advantage is economic, the disadvantage is that the filtration precision is not high, the water in the bacteria, viruses, colloids and dissolved substances almost no effect. Especially for tap water, a relatively high-quality water source when there is not much coarse impurities, its filtration effect is even less obvious. In addition to the need for regular flushing impurities, otherwise it is easy to produce secondary pollution.
2, pottery grain, Maifan stone, quartz sand, etc.:
The principle of filtration of such materials and sand filtration is generally similar. Only a small number of micropores exist on the surface of such materials. These microporous water in some of the tiny impurities have a certain retention effect. But its effect is very small, in addition, this kind of material in the water soak time is long enough, the water body has a certain mineralization effect.
3, PP cotton filter:
PP cotton filter core is made of multiple layers of plant fibers superimposed on each other, the body of water through multiple layers of fibers with a certain density, most of the visible particles, some of the color can be retained and adsorbed by the PP cotton layer. In the traditional filtration materials, PP cotton layer is a better filter material, high-quality PP cotton filter cartridges and its filtration accuracy of up to 0.45µ or so, most of the visible matter can be retained in the body of water has a retention effect. Filter material cost is low, the economy is better. Its main disadvantage is: although the precision is higher than sand filtration. But still can not play a role in the water body bacteria, viruses, colloids, dissolved impurities. Usually 4-6 months need to be replaced once, can not be reused.
4, Activated carbon filtration:
Activated carbon is a relatively good water treatment materials, in the common household water treatment equipment, there are particles and block two kinds of activated carbon components. Activated carbon material for water treatment, first in the activated carbon particles layer has the same filtration principle as sand filtration. But activated carbon water treatment is more reflected in its adsorption function. Activated carbon in the firing process in the surface layer to form a lot of microporous. Water through these microporous through the activated carbon particles. Most of the impurities in the water through the process will be retained by the micropores inside the activated carbon particles. Activated carbon filtration in addition to the same effect of sand filtration, more importantly, it can have a better adsorption effect on the color of the water, odor, part of the organic matter. Activated carbon surface and internal microporous the more, the better the adsorption effect. Economy is moderate. Because activated carbon has adsorption effect on organic matter, but also can intercept part of the bacteria, so the activated carbon body is easy to become a breeding ground for bacteria and other microorganisms (bacteria in the temperature of 30 ℃ - 40 ℃, and the full presence of organic matter under the conditions of fission in about 20 minutes), so the activated carbon is very easy to become a source of bacteria and other microorganisms of the water body of the secondary pollution. Activated carbon cartridges need to be replaced regularly under domestic conditions.
5, Ceramic filter:
Ceramic filter is the use of ceramic in the firing process of the formation of microporous band of water filtration to the United Kingdom "Dalton" as a representative of the ceramic filter gallbladder, filtration precision of about up to 0.1µ or so, can be more than the bacterial impurities in the tap water for effective retention (because of the smallest bacterial length of the unit is about 0.2µ). After the ceramic filter tap water should be able to reach the standard of drinking water (if the "boiled water" can reach the standard of drinking water as a reference, the boiled water is only in the boiling process to kill the bacteria in the tap water, other impurities are not removed). But the ceramic filter on the tap water in the colloid and dissolved substances almost no retention effect. From ensuring drinking water health requirements are still quite a distance. In addition, ceramic filter price is relatively high, ceramic microporous easy to block, short filtration life (about 2 tons of water). Trouble to use (household filter 1 ton of tap water must be frequently scrubbed or scrape the ceramic wall with a razor blade to normal use).
6, Molecular sieve filter:
Molecular sieve filter represented by the U.S. Siegel, its appearance as a textile with a cotton cylinder, its filtration and adsorption principle is similar to the PP cotton cartridge, except that its accuracy is slightly higher than the PP cotton, its material on the color and odor adsorption performance is better. The filtration precision is about 0.1µ, the color and odor adsorption ability is slightly stronger than activated carbon. Through its filtered tap water can basically reach the standard of drinking water. But its shortcomings are: ① high cost; ② short life of the cartridge (about 1000 liters of water).
7, KDF Filter:
Is a copper-zinc alloy material, its working principle is to remove chlorine, heavy metals in water through redox reaction. Chlorine, heavy metals alone from the point of view, its effect is slightly better than activated carbon, but its requirements of the working conditions is that the KDF layer is high enough, and the water flow rate is slow (to ensure that enough reaction time). Otherwise the effect is not obvious. Secondly, the water will carry a kind of iron odor after passing through the KDF layer. Short service life? The removal of impurities other than ions is not ideal, and the cost is high.
8, electric field (the main technology used in water ionizer) and range:
Its working principle is to establish an electric field in the water flow channel, in the process of water flow through. Positively charged metal ions in the water body is easy to move down to the position close to the negative electrode of the electric field. And the water body with negatively charged ligand ions are easy to move to the positive direction. The water flow exits at two outlets near the positive and negative flow respectively. In this way, in the outlet near the negative pole of the electric field, the metal ions are on the high side, and it is easy to form alkali by combining with hydroxide ions in the water. Near the positive pole near the exit of the ligand ions bias more with the water hydrogen ions combine easily to form acids. Because of the human food in the weak acidic food mostly, so most people most of the time the body is in a weak acidic state, so if the timely supplementation of acidic and alkaline water can neutralize the body's weak acidic state. Make the human body in a neutral state (not easy to get sick). Weakly acidic water is also used for sterilization and other purposes. The shortcomings of this technology are: ① electric field can only play a role in the body of water ionic substances, bacteria and viruses that are not charged with any effect, that is to say, it can not remove the harmful substances in the body of water. ② weakly acidic and weakly alkaline is only a relative concept, it is difficult to make the different human body's different degree of weak acidity and the degree of weak alkalinity of the water body to match. (iii) Weakly alkaline ionized water is a kind of medical auxiliary water, and people generally cannot identify whether their bodies are weakly acidic or not. If the body happens to be in a weakly alkaline state, drinking alkaline water will accelerate the disease, so the use of electric field principle of water ionizer can only be used under the guidance of a doctor.
Ion exchange resin is widely used in water treatment. Ion exchange resin can be divided into anion resin and cation resin, according to the function can be divided into water softening resin, the production of pure water mixed bed resin, resin used to remove heavy metals and remove fluorine, iron, organic matter, arsenic and other elements of the resin.
10, Membrane Filteration technology:
Membrane separation technology is a new technology developed in the middle of the 20th century. By the Western scientific and technological community as: one of the three high-tech in the 21st century, the most development potential. U.S. official documents say: "18th century electrical appliances changed the entire industrial process, and the 20th century membrane separation technology will change the entire industrial landscape. Japan is the membrane separation technology called "21st century base plate technology". "The membrane industry plays a strategic role in most industries in the 21st century". China's Minister of Chemical Industry said: "Whoever masters membrane technology will master the future of the chemical industry". Membrane separation technology is the mother technology of nanotechnology, and the purification of any nanomaterials must be realized through membrane separation technology.
Membrane separation technology is characterized by two main features: first, very high separation precision; second, selective permeability (affinity performance).
Classification and characteristics of membrane separation technology:
a. Reverse osmosis membrane (referred to as RO membrane):
Reverse osmosis membrane belongs to the non-porous membrane, the fluid can only through the affinity performance and permeation through the membrane layer. Such as reverse osmosis membrane for water treatment, it can remove almost all impurities in the water body (dissolved in the water of monovalent ions retention rate of up to 99.5% or more). At present all the world's astronauts living cycle water is filtered with reverse osmosis membrane. 88% of the world's desalination projects are treated with reverse osmosis membrane. The United States, Britain, China and most other countries in the reverse osmosis membrane technology after the maturity of the Pharmacopoeia have been adjusted accordingly, the production of water for intravenous injections in the medical requirements for: "reverse osmosis or tertiary distillation of water can be used for intravenous injection of water".
The disadvantages of using reverse osmosis membrane manufacturing household drinking water are:
① high cost (membrane materials and the use of relatively high costs)
② need to pre-treatment process to improve the quality of incoming water
③ Concentrated water emissions, pure water and concentrated water ratio is generally 15:85, a waste of water resources.
b. Nanofiltration membrane (referred to as NF membrane):
The molecular weight cut-off is between 200-6000 equivalents, and its membrane pore is about 0.0001µ to 0.001µ (nanometer scale). Using NF membrane to treat tap water, the retention rate of dissolved monovalent ions in the water body is about 50%, and the retention rate of dissolved divalent ions is more than 90%. Basically, it can remove the harmful substances in the water body, and at the same time play a dual function of water purification and water softening. At present, the world's application of the typical project is the United States 21st century water plant (diversion of half of the tap water by nanofiltration membrane deep processing and the other half of the tap water combined for domestic drinking).
c. Ultra-filtration membrane (UF membrane):
The molecular weight of retention is between 6000-100,000, and the membrane pore is between 0.01µ-0.001µ. Using ultrafiltration membrane to filter tap water can effectively remove bacteria, microorganisms, colloids, rust, sludge and other harmful impurities in the water body. Since the colloid content in tap water is large, the ultrafiltration membrane takes away some of the dissolved ions (about 20%) in the process of retaining the colloids. At the same time, it can effectively retain minerals and trace elements in tap water. It is a good material for deep processing of tap water. Now the material used for hemodialysis virus filtration in various medical places is ultrafiltration membrane.
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