There are many brands in the water purification industry, and the water treatment methods are complex. Some rely on a single treatment method, while others rely on a variety of filter membranes and filter media. But from a technical point of view, all changes are inseparable from its origin. Today, Xiaobian will take you to understand what this "origin" is about, so that you can have a clear understanding of various water purification technologies, configurations, advantages and disadvantages.

1. Principle of domestic and commercial water purifiers

    According to the accuracy of filtration pore size and the removal ability of dissolved ions, water purification membranes include microfiltration, ultrafiltration, nanofiltration and reverse osmosis. The main filtration methods of drinking water are ultrafiltration, nanofiltration and reverse osmosis. The details are as follows:

one point one   Ultrafiltration membrane (UF)

Hollow fiber ultrafiltration membrane wire: 0.5-2.0 mm, inner diameter: 0.3-1.4 mm, hollow fiber tube wall is full of micropores, the filtration precision is 0.5-0.01 μ m, the pore size can intercept the molecular weight of substances up to thousands to hundreds of thousands. The raw water flows under pressure outside the membrane or in the inner cavity to form external pressure type and internal pressure type respectively. Ultrafiltration is a dynamic filtration process, the intercepted substances can be eliminated with the concentration reduction, without blocking the membrane surface, and can be operated continuously for a long time. Ultrafiltration membrane is one of the earliest developed polymer separation membranes, which can remove bacteria, colloids, organic matter and other impurities larger than 0.01 micron.

one point one one   Internal pressure ultrafiltration membrane and its principle

one point one two   External pressure ultrafiltration membrane and its principle

one point two   Nanofiltration membrane (NF)

Nanofiltration is a kind of membrane separation technology between ultrafiltration and reverse osmosis. Its molecular weight is in the range of 80-1000 and pore size is 1 nm, so it is called nanofiltration. Nanofiltration technology is a kind of membrane separation technology separated from RO Technology, which is the continuation and development branch of ultra-low pressure RO Technology. For a long time in the past, nanofiltration membrane was known as low pressure reverse osmosis membrane (LPRO). Now, nanofiltration technology has been separated from reverse osmosis technology and become an independent separation technology between ultrafiltration and reverse osmosis technology. It has been widely used in drinking water preparation, pharmaceutical water preparation, food industry, environmental protection and many other fields, It has become an important branch of membrane separation technology.

Principle: nanofiltration membrane, like ultrafiltration and reverse osmosis membrane separation process, is also a membrane separation process driven by pressure difference, which is an irreversible process. The separation mechanism can be described by charge model (space charge model and fixed charge model), pore model and electrostatic repulsion and steric hindrance model.

Advantages: compared with other membrane separation processes, one of the advantages of nanofiltration is that it can intercept small molecular weight organics and high valence ions passing through ultrafiltration membrane, and dialysis part of inorganic salts and minerals intercepted by reverse osmosis membrane, that is, it can make "concentration" and desalination proceed simultaneously. Can maximize the removal of all pollutants in the water, and can retain the body's mineral needs.

one point three   Reverse osmosis membrane (RO)

Ro is the abbreviation of reverse osmosis membrane, which means: reverse osmosis / reverse osmosis. Generally, the flow mode of water is from low concentration to high concentration. Once the water is pressurized, it will flow from high concentration to low concentration, which is the so-called reverse osmosis principle. Because the pore size of RO membrane is 5 parts per million of hair（   zero point zero zero zero one   (micron)  ,  Generally, bacteria and viruses are 5000 times more than the naked eye. Therefore, only water molecules can pass through. Any other impurities, ions and heavy metals are discharged from the waste water pipe, and the produced water is pure water. This method is used in all processes of seawater desalination and the recovery and treatment of spaceman wastewater. Therefore, RO membrane is also known as high-tech "artificial kidney" in vitro. At present, the top RO membrane is used for polymer filtration in medical, military and civil fields at home and abroad. In 2013, the year-on-year growth rate of reverse osmosis water purification equipment was as high as 77.6%. In the future, reverse osmosis membrane treatment technology will become the most mainstream product technology.

two   Auxiliary filter material of water purifier

The main purification method of water treatment is membrane filtration technology, but the auxiliary filter material is also very critical. Its function is to remove some impurities in water at low cost and protect the main high-precision filter membrane.

Auxiliary filter materials include but are not limited to: activated carbon, KDF, resin, PP cotton, metal filter, quartz sand, etc. as auxiliary water purification means to achieve the purpose of comprehensive treatment.

2.1 PPC

PP cotton filter core is made of polypropylene (PP) by hot melting, and its precision is from 1 um to 1 um   5um。 It is a kind of filter element with high efficiency, low pressure difference, long service life and wide applicability.

Main functions: remove the physical pollutants larger than the diameter of the filter hole, remove the granular impurities larger than 5 microns in the water through the logistics interception screen,   Such as: suspended solids, sediment, red insects, rust, colloid and other large volume substances, reduce the turbidity of water.

Scope of application: widely use of pure water, food and drinking water pre filtration treatment; With RO reverse osmosis membrane, nanofiltration membrane, ultrafiltration membrane as pre-treatment.

Replacement cycle: the water treatment capacity is generally 5 tons, and the replacement cycle is 3-6 months, which depends on the quality of source water and water consumption.

two point two   Activated carbon

Manufacturing process: water treatment activated carbon is generally made of high-quality coconut shell and refined by series production process, with black appearance. The advantages are well-developed pore structure, large specific surface area and strong adsorption performance. The filtration pore expansion area of 1G coconut shell activated carbon is about 2000 square meters. The reservoir has low resistance, stable chemical properties and easy regeneration. According to the need, it can be made into powder, particle, sintered rod or fiber. Different water treatment plants are suitable for different activated carbon properties

Main functions: remove residual chlorine, color, odor, heavy metals and other toxic and harmful substances through super adsorption capacity, and improve the taste of water.

Scope of application: widely used in pure water, food and drinking water treatment process; Combined with nanofiltration membrane, RO reverse osmosis membrane, ultrafiltration membrane as pre filtration pretreatment.

two point three   Copper zinc alloy (KDF)

KDF is a kind of high purity copper zinc alloy, which has long service life and can be recycled. The principle of water treatment by KDF is to use redox reaction, KDF can exchange electrons with oxidizing harmful substances in water, and turn many harmful substances into harmless substances. In order to remove heavy metal ions, heavy metal ions are replaced with zinc ions.

two point four   Softening resin

Introduction: softening, that is, reducing the hardness of water. The softened water system consists of three parts: ion exchange part, salt regeneration part and control part. Ion exchange technology is the working principle of softening system, and its main body is ion exchange resin. Because the hardness of water is mainly formed and expressed by calcium and magnesium, cation exchange resin is generally used to replace Ca2 + and Mg2 + (the main component of scale formation) in water. With the increase of Ca2 + and Mg2 + in resin, the efficiency of resin to remove Ca2 + and Mg2 + gradually decreases. Therefore, when the softened water equipment is used for a period of time, 25% NaCl regeneration part is needed to regenerate the resin to restore the efficiency of the resin and improve the service life of the resin. The control part can realize the automatic operation of the whole system, and automatically regenerate the salt according to the operation time of the system or the amount of water.

two point five   Silicon phosphorus crystal

Silicophosphate crystal is a kind of glassy ball made of soda, phosphoric acid, calcium carbonate and other active ingredients at 1200-1700 ℃. It plays a positive role in water system anti-corrosion, scale inhibition and prolonging the service life of equipment.

two point six   Water softener (high purity sodium chloride)

Soft water salt, also known as ion exchange resin regeneration agent. Its main chemical composition is sodium chloride (NaCl), the content is more than 99.5%, the general shape is ball agent.

When more and more impurities are adsorbed by resin of soft water equipment, its adsorption capacity will gradually decrease. In order to remove the impurities adsorbed by resin (mainly calcium, calcium, magnesium and magnesium ions), sodium ion (NA) needs to be used to replace the impurity ions adsorbed by resin (mainly calcium, calcium, magnesium and magnesium ions) through ion exchange by backwashing, This process is also called regeneration of ion exchange resin.

two point seven   Other auxiliary filter materials

Including metal screen, quartz sand, mineralized ball, Maifan stone, etc