Summary of commonly used water treatment methods for different water qualities

In the environmental water treatment industry, commonly used water treatment methods generally include:

（1） Sediment filtration method, (II) Water softening method

（3） Activated carbon adsorption method, (IV) deionization method

（5） Reverse osmosis method, (VI) ultrafiltration method

（7） Distillation method, (VIII) UV disinfection method

（9） Biochemical methods, etc.

Now let's introduce the principles and functions of these water treatment methods here, and summarize the commonly used water treatment methods for different water qualities:

1、 Sediment filtration method

The purpose of sediment filtration method is to remove suspended particulate matter or colloidal substances from the water source. If these particulate matter are not removed, it can cause damage to other precision filtration membranes of dialysis water or even block the water path. This is an ancient and relatively simple water purification method, so this step is commonly used in the preliminary treatment of water purification, or if necessary, adding several filters in the pipeline to remove larger impurities.

There are many types of filters used to filter suspended particulate matter, such as mesh filters, sand filters (such as quartz sand), or membrane filters. As long as the particle size is greater than the size of these pores, it will be blocked.

There is another issue worth noting about the sediment filtration method, as particulate matter is constantly blocked and accumulated, and bacteria may breed on these surfaces, releasing toxic substances through the filter, causing a pyrogen reaction. Therefore, it is necessary to replace the filter frequently. In principle, when the pressure difference between the inlet and outlet water increases by five times, the filter needs to be replaced.

2、 Water softening method (water softening equipment)

The softening of hard water requires the use of ion exchange method, which aims to use cation exchange resin to exchange calcium and magnesium ions in hard water with sodium ions, in order to reduce the concentration of calcium and magnesium ions in the water source.

Ca2++2Na EX → Ca-EX2+2Na+1

Mg2++2Na EX → Mg-EX2+2Na+1

The ion exchange resins currently available on the market are spherical synthetic organic polymer electrolytes.

If there is no cation softening in the process of water treatment, not only will calcium and magnesium bodies deposit on the Reverse osmosis membrane, which will reduce the efficiency and even destroy the Reverse osmosis membrane, but also patients are easy to get hard water Syndrome. The Water softening will also cause the problem of bacterial reproduction, so the equipment needs to have a backwash function. After a period of time, it needs to be backwashed once to prevent too many impurities from adsorbing on it.

3、 Activated carbon filter

Activated carbon is made by carbonizing materials such as wood, sawdust, fruit kernels, coconut shells, coal, or petroleum residues at high temperatures. After being made, it needs to be activated with hot air or water vapor. Its main function is to remove chlorine, chloramine, and other soluble organic substances with molecular weights ranging from 60 to 300 Daltons. The surface of activated carbon is granular and the interior is porous. There are many capillaries about 1Onm~lA in the pores, and the internal surface area of 1g of activated carbon is as high as 700-1400m2. These capillaries and particle surfaces are where adsorption occurs.

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4、 Deionization method

The purpose of the deionization method is to remove inorganic ions dissolved in water. Like the Water softening, it also uses the principle of ion exchange resin. Two types of resins are used here - cation exchange resin and anion exchange resin. Cation exchange resin uses hydrogen ions (H+) to exchange cations; The anion exchange resin uses Hydroxide ion ion (OH -) to exchange anions.

After the adsorption capacity of these resins is depleted, they also need to be reduced again, and cation exchange resins require strong acids for reduction; On the contrary, anions require strong bases for reduction. If the anion exchange resin is depleted without reduction, fluoride with weaker adsorption capacity will gradually appear in the water used for dialysis, causing osteomalacia, osteoporosis, and other bone lesions; If the cation exchange resin is depleted, hydrogen ions will also appear in the dialysis water, causing an increase in the acidity of the water. Therefore, the effectiveness of the deionization function needs to be monitored regularly.

Generally, it is determined by the resistance or conductivity of water quality. The ion exchange resin used in the deionization method can also cause the reproduction of bacteria and cause Bloodstream infections, which is worth noting.

5、 Reverse osmosis method

Reverse osmosis can effectively remove inorganic substances, organic substances, bacteria, pyrogens and other particles dissolved in water, which is an important part of dialysis water treatment.

The purification effect of Reverse osmosis can reach the level of ions. The commonly used Semipermeable membrane materials for Reverse osmosis water treatment include fibrous membrane, aromatic polyamides, polyimide or polyfuranes. Its structural shapes include spiral wound, hollow fiber and tubular.

If Reverse osmosis is not pretreated before, it is easy to accumulate dirt on the osmosis membrane, such as calcium, magnesium, iron plasma, which will cause the decline of Reverse osmosis function; Some membranes (such as polyamide) are easy to be damaged by chlorine and chloramine, so pre treatment such as activated carbon and softener is required before Reverse osmosis membrane. So when preparing water for hemodialysis release, this step needs to be prepared.

6、 Ultrafiltration method

Similar to the Reverse osmosis method, the ultrafiltration method also uses a Semipermeable membrane, but it cannot control the removal of ions because the pore size of the membrane is large, about 10-200A. Only bacteria, viruses, pyrogens, and particulate matter can be excluded, while water-soluble ions cannot be filtered.

The ultrafiltration method is mainly used as the pretreatment of Reverse osmosis method to prevent Reverse osmosis membrane from being contaminated by bacteria. It can also be used at the end step of water treatment to prevent upstream water from being contaminated by bacteria in the pipeline. Generally, the difference in inlet and outlet water pressure is used to determine whether the excess filter membrane is effective. Similar to activated carbon, the backwash method is usually used to remove impurities attached to it.

7、 Distillation method

Distillation is an ancient yet effective water treatment method that can remove any non volatile impurities, but cannot eliminate volatile pollutants. It requires a large storage tank for storage, which is an important cause of pollution. Currently, blood dialysis water is not treated in this way.

8、 UV disinfection method

Ultraviolet disinfection is one of the commonly used methods at present. Its sterilization mechanism is to destroy the life Genetic material of bacterial nucleic acid, making it unable to reproduce. The major reaction is that the pyrimidine base in nucleic acid molecules becomes dimer.Generally, the artificial ultraviolet energy of 253.7 nm wavelength of low-pressure mercury discharge lamp (Germicidal lamp) is used.The principle of the ultraviolet Germicidal lamp is the same as that of the fluorescent lamp, except that the interior of the lamp tube is not coated with fluorescent substances, and the material of the lamp tube is quartz glass with high ultraviolet penetration.General ultraviolet devices are classified into irradiation type, immersion type, and flowing type according to their purpose.

9、 Biochemical method

The biochemical water treatment method utilizes various bacteria and microorganisms that exist in nature to decompose and transform organic substances in wastewater into harmless substances, enabling wastewater purification. Biochemical water treatment methods can be divided into Activated sludge, biofilm method, biological oxidation tower, land treatment system and Anaerobic organism water treatment method.

The process of biochemical water treatment method:

Raw water → grid → regulating tank → contact oxidation tank → sedimentation tank → filtration → disinfection → effluent.

The above is a summary of commonly used water treatment methods for different water qualities that Hongjie Water brings to you. We hope it can help you!

Shenzhen Hongjie Water Technology Co., Ltd. is an integrated high-tech enterprise specializing in product development, production, sales, engineering design, installation and commissioning, technical consultation, and sales of supporting materials in the field of industrial water treatment and drinking water treatment. Main products: design, manufacturing, installation, commissioning and maintenance of water treatment equipment such as pure water equipment, Ultrapure water equipment, reverse osmosis equipment, GMP purified water equipment, EDI deionized water equipment, domestic sewage equipment, industrial wastewater equipment, softened water equipment and reclaimed water reuse equipment.