[Hongjie Water Service] Deep analysis of the advantages and disadvantages of water treatment membrane technology (ultrafiltration, nanofiltration, reverse osmosis)

Nanofiltration membrane: capable of intercepting substances at the nanoscale (0.001 micrometers). The operating range of nanofiltration membranes is between ultrafiltration and reverse osmosis, with a molecular weight of about 200-800 to retain organic matter and a ability to retain dissolved salts ranging from 20% to 98%. The removal rate of soluble monovalent ions is lower than that of high valent ions. Nanofiltration is generally used to remove organic matter and pigments from surface water, hardness and radium from groundwater, and partially remove dissolved salts. It is used for the extraction and concentration of useful substances in food and pharmaceutical production. The operating pressure of nanofiltration membranes is generally 3.5-30 bar.

Reverse osmosis membrane: It is the most refined membrane separation product that can effectively retain all dissolved salts and organic matter with a molecular weight greater than 100, while allowing water molecules to pass through. Reverse osmosis membranes are widely used in processes such as seawater and brackish water desalination, boiler feed water, industrial pure water and electronic grade high-purity water preparation, production of purified drinking water, wastewater treatment, and special separation.

Ultrafiltration membrane: capable of intercepting macromolecules and proteins between 1-20nm. Ultrafiltration membranes allow small molecule substances and soluble solids (inorganic salts) to pass through, while retaining colloids, proteins, microorganisms, and large molecule organic matter. The operating pressure of ultrafiltration membranes is generally 1-5 bar.

The difference between ultrafiltration membranes, nanofiltration, and reverse osmosis

Ultrafiltration membrane: Ultrafiltration membrane is a pressurized membrane separation technology, which allows small molecule solutes and solvents to pass through a specially designed thin film with a certain pore size under certain pressure, while large molecule solutes cannot pass through and remain on one side of the membrane, thereby partially purifying large molecule substances.

Nanofiltration: Nanofiltration, between ultrafiltration and reverse osmosis. Now it is mainly used for water plants or industrial desalination. The desalination rate reaches over 90%. The desalination rate of reverse osmosis can reach over 99%, but if the water quality requirements are not particularly high, using nanofiltration can save a lot of costs.

Reverse osmosis: Reverse osmosis is a membrane separation and filtration technology that uses pressure gauge difference as the driving force. It has been widely used in scientific research, medicine, food, beverage, seawater desalination and other fields. Used for the preparation of space water, purified water, distilled water, etc; Water for alcohol manufacturing and alcohol reduction; Pre preparation of water for industries such as medicine and electronics; Concentration, separation, purification, and water preparation of chemical processes; Boiler feedwater desalination soft water; Desalination of seawater and brackish water; Water and wastewater treatment in industries such as papermaking, electroplating, printing and dyeing.

Comparison of advantages and disadvantages between reverse osmosis membranes and ultrafiltration membranes

The pore size of reverse osmosis membrane is only 1/100 of that of ultrafiltration membrane, so reverse osmosis water treatment equipment can effectively remove chemical pollutants such as heavy metals, pesticides, and trichloromethane from water quality. Ultrafiltration water purifiers are powerless to handle this. The particle pollutants and bacteria that can be removed by ultrafiltration water purifiers can be completely removed by reverse osmosis.

The core components of reverse osmosis and ultrafiltration are both membrane elements, with two main differences:

The reverse osmosis water treatment equipment is 20 pieces per milliliter, with strict requirements. Of course, the effluent quality of the reverse osmosis water treatment equipment is also much better than that of ultrafiltration.

2. The reverse osmosis water treatment equipment provides separate water supply, pure water is used for drinking, and concentrated water is used for washing; Ultrafiltration is generally used as washing water; When the water quality of tap water is relatively high, it can also be used as a drinking water ultra pure water equipment.

The advantages of ultrafiltration: generally no pump, no power consumption, and no electrical safety issues; Few joints, low water pressure, relatively low failure rate and leakage probability; Simple structure and affordable price; Easy to operate, low cost, no need to add any chemical reagents, especially the experimental conditions of ultrafiltration technology are mild, and there is no phase change compared to evaporation and freeze-drying, and it does not cause changes in temperature and pH, thus preventing the denaturation, deactivation, and self dissolution of biological macromolecules. In the preparation technology of biomolecules, ultrafiltration is mainly used for desalination, dehydration, and concentration of biomolecules.

The advantages of reverse osmosis water treatment equipment: water quality is safe and can effectively remove various harmful impurities in water quality; The effect is good for water supply emergencies; The taste of the effluent is good; Can effectively reduce the hardness of water quality, and boiling water containers are not prone to scaling

Application of Different Membranes in Water Treatment

Nanofiltration membrane is an application in the preparation and deep purification of drinking water, as well as in wastewater treatment, including domestic wastewater, textile, printing and dyeing wastewater, tannery wastewater, electroplating wastewater, and papermaking wastewater.

The application of forward osmosis (FO): seawater desalination, industrial wastewater treatment, and landfill leachate treatment

Reverse osmosis membrane: application in conventional water purification, urban sewage treatment, heavy metal wastewater treatment, and oily wastewater treatment.

Working principle and process flow of water treatment membrane technology

Using membrane technology as the core filtration material, supplemented by pretreatment or other equipment, to achieve purification goals.

Raw water → Quartz sand filter → Activated carbon filter → Security filter → Multi stage pump → First stage reverse osmosis membrane (concentrated water recovery) → Multi stage pump → Second stage reverse osmosis membrane (concentrated water recovery) → Pure water

First level reverse osmosis purified water process flow:

Raw water → Quartz sand filter → Activated carbon filter → Security filter → Multi stage pump → First stage reverse osmosis membrane (concentrated water recovery) → Purified water

Mineral water, mountain spring water, and water purification process flow:

Raw water → Quartz sand filter → Activated carbon filter → Security filter → Ultrafiltration membrane → Mineral water, mountain spring water

Process flow of ultrapure water and deionized water:

More information can be found on the official website of Shenzhen Hongjie Water Technology Co., Ltd. www.execro.com. If you need it, you can call the company's hotline for free at 180 3800 0078, and we will be happy to serve you.