The Difference between 1 Stage And 2 Stage RO Water Treatment

As an efficient and environmentally friendly water treatment method, reverse osmosis technology is widely used in various fields. Both the 1 stage reverse osmosis system and the 2 stage reverse osmosis water treatment system play an important role in meeting different water quality requirements. Understanding the difference between them will help you choose the most suitable industrial reverse osmosis water treatment solution according to actual needs.

1. Differences in process flow

(I) 1 stage reverse osmosis water treatment

1. Raw water pretreatment: This is the first step of the entire reverse osmosis water treatment. The main purpose is to remove large particle impurities, suspended matter, some colloids and microorganisms in the raw water. Usually, mechanical filtration, activated carbon adsorption, softening treatment and other methods are used to ensure that the water entering the reverse osmosis membrane is relatively pure, reduce pollution and blockage of the membrane, and extend the service life of the membrane.

2. 1 stage reverse osmosis membrane filtration: The pretreated water enters the 1 stage reverse osmosis device, and the high pressure pump provides sufficient pressure to enable water molecules to overcome the osmotic pressure on the surface of the reverse osmosis membrane and selectively permeate from the high pressure side to the low pressure side, thereby achieving efficient interception of impurities such as dissolved salts and organic matter in the water. This process is the core link of the entire reverse osmosis water filtration system, which can effectively reduce the conductivity of water and improve the purity of water quality.

3. Simple subsequent treatment: After the 1 stage reverse osmosis water is discharged, in order to meet specific usage requirements, some simple subsequent treatments will be carried out, such as ultraviolet disinfection, ozone disinfection, etc., to further kill the microorganisms that may remain in the water and ensure the biological safety of the discharged water.

(II) 2 stage reverse osmosis water treatment

1. Raw water pretreatment: The pretreatment steps are basically the same as those of the 1 stage reverse osmosis water treatment, both of which are for the preliminary purification of raw water to create good conditions for the subsequent reverse osmosis process.

2. 1 stage reverse osmosis membrane filtration: Also using high pressure pumps and reverse osmosis membranes, the pretreated raw water is subjected to the first deep desalination and impurity removal, reducing the dissolved solids content in the water and improving the water quality.

3. Temporary storage of 1 stage pure water tank: For the 2 stage reverse osmosis water treatment machine with larger capacity, the water treated by the 1 stage reverse osmosis first enters the 1 stage pure water tank for temporary storage, which can balance the water production of the 1 stage reverse osmosis and the water inlet demand of the 2 stage reverse osmosis, play a role of buffering and regulation, and ensure the stable operation of the system. At the same time, this process also helps to monitor and control the water quality of the 1 stage reverse osmosis outlet to ensure that the water quality meets the standard.

In addition, the 1 stage pure water tank can also directly provide you with 1 stage reverse osmosis pure water to meet your diverse water needs. In some application scenarios, you can flexibly choose to use 1 stage pure water or continue 2 stage reverse osmosis treatment according to actual needs to achieve higher flexibility and economy.

4. 2 stage reverse osmosis membrane filtration: The pure water taken out of the 1 stage pure water tank is further deeply treated by the 2 stage reverse osmosis membrane. Since the 1 stage reverse osmosis has removed most of the impurities, the 2 stage reverse osmosis membrane can more effectively intercept the trace dissolved salts and organic matter remaining in the water, further reduce the conductivity of the water, and make the outlet water quality reach a higher purity standard.

5. Subsequent deep treatment: After the 2 stage reverse osmosis effluent, deep treatment is often carried out to meet the high water quality requirements. Among them, EDI is a key component. It uses ion exchange resin and electric field to further remove ions in the water and improve the chemical purity of the water quality; at the same time, ultraviolet sterilization uses the strong oxidizing property of ultraviolet rays to efficiently kill residual microorganisms in the water to ensure the biological safety of the effluent. This series of deep treatment measures ensures that the effluent water quality is stable at an extremely high level and meets the strict requirements of various high-tech industries.

2. Difference in effluent water quality

(I) 1 stage reverse osmosis water treatment

1. Conductivity: The effluent of 1 stage reverse osmosis water treatment usually has a conductivity between 3-10μs/cm. Under ideal conditions of stable operation, the conductivity can generally be controlled at ≤10μs/cm, which means that the residual ion content in the water is relatively low, the water quality is relatively pure, and it can meet the water needs of most general industrial, commercial and some civil fields.

2. Desalination rate: The desalination rate is generally between 98% and 99%. In other words, it can effectively remove most of the dissolved salts in the water, such as sodium ions, calcium ions, magnesium ions and other common salt components, thereby reducing the hardness of the water, improving the taste and chemical properties of the water, and providing a relatively high-quality water source for subsequent use.

(II) 2 stage reverse osmosis water treatment

1. Conductivity: The conductivity of the effluent from the 2 stage reverse osmosis water treatment is usually between 1-5μs/cm, and the conductivity is generally ≤5μs/cm during stable operation. Such a low conductivity indicates that the ion content in the water is extremely low and the water quality is extremely pure, which can meet the demand for ultrapure water in high-tech industries such as electronics and pharmaceuticals, and provide a stable high quality water source for the production process of these industries.

2. Desalination rate: The desalination rate can reach more than 99.5%, which can almost remove all dissolved salts in the water. For some special process waters with extremely high requirements for water purity, such as semiconductor chip manufacturing, high-precision instrument cleaning, etc., this high desalination rate 2 stage reverse osmosis water treatment is essential, which can ensure that the quality and performance of the product are not affected by water quality.

3. Differences in application fields

(I) 1 stage reverse osmosis water treatment

1. Food industry: In the process of food processing, water treated with 1 stage reverse osmosis water can be used as formula water for preparing various beverages, food raw materials, etc. to ensure the taste and quality of the product; it can also be used as production water for cleaning equipment, fruits and vegetables, etc. to avoid impurities from contaminating food and meet food hygiene and safety standards.

2. Beverage industry: For beverage production, water treated with 1 stage reverse osmosis water can not only be used as formula water to prepare beverages that meet taste requirements, but also be used for washing water in the production process to ensure the cleanliness of packaging materials such as beverage bottles and cans, prevent the growth of microorganisms and the mixing of impurities, and ensure the quality and safety of beverages.

3. Breeding and planting industry: In the breeding industry, water treated with 1 stage reverse osmosis can remove harmful substances and pathogens in the water, provide animals with clean and healthy drinking water, promote animal growth, and improve breeding efficiency; in the planting industry, it can be used to irrigate greenhouse crops, flowers, etc., to avoid soil salinization, provide plants with a suitable growth environment, and improve crop yield and quality.

(II) 2 stage reverse osmosis water treatment

1. Cosmetics industry: In the production of cosmetics, high-purity water from 2 stage reverse osmosis water treatment is one of the basic raw materials, which can ensure the quality and use effect of the product and avoid adverse reactions such as skin irritation caused by water quality problems. It is used in the preparation of various cosmetics such as lotions, creams, and essences to ensure that the products do not contain impurities, making the cosmetics more delicate and stable, and improving the use experience.

2. Power industry: In thermal power plants, boiler feed water requires extremely high purity to prevent scaling and corrosion inside the boiler. 2 stage reverse osmosis water treatment can provide high-purity water that meets the requirements to ensure the safe and efficient operation of the boiler; at the same time, in the cooling water system, the use of 2 stage reverse osmosis treated water can also reduce the scaling and corrosion of cooling water on equipment, extend the service life of equipment, and improve power generation efficiency.

3. Electronics industry: In the process of semiconductor chip manufacturing, the demand for ultrapure water is extremely demanding, and 2 stage reverse osmosis water treatment is one of the key steps to obtain ultrapure water. Ultrapure water is used in chip cleaning, photolithography and other process links, which can prevent impurities from contaminating the chip surface and affecting the chip performance and yield; in terms of integrated circuit cleaning, high purity 2 stage reverse osmosis water can completely remove tiny particles and ions on the circuit board, ensuring the reliability and stability of the circuit, and is an important link in the quality assurance of electronic products.

4. Pharmaceutical industry: In the pharmaceutical production process, water treated by 2 stage reverse osmosis water is used as process water for drug synthesis, extraction and other processes to ensure the purity and quality of drugs; in terms of preparation water, high-purity water is the basis for the preparation of various dosage forms of drugs, such as tablets, injections, etc., to ensure the safety and effectiveness of drugs; in terms of washing water, it is used to clean drug packaging materials, production equipment, etc., to prevent impurities from mixing into drugs, and meet the GMP (Good Manufacturing Practice) requirements for drug production; in the preparation of injection water and sterile water, 2 stage reverse osmosis water treatment is an important link in the early pretreatment, and then after distillation and other processes, injection water and sterile water that meet the pharmacopoeia standards are prepared for the production of injections, infusions and other products.

5. Chemical industry: In the process of chemical synthesis, high-purity water treated by 2 stage reverse osmosis water can be used as a reaction medium to avoid the influence of impurities on chemical reactions, ensure the accuracy of reactions and the purity of products; in the production of cosmetics and skin care products, high-purity water is one of the basic raw materials, which can ensure the quality and use effect of products and avoid adverse reactions such as skin irritation caused by water quality problems.

6. Drinking water project: In some places with high requirements for drinking water quality, such as high-end residential areas, schools, hospitals, etc., the use of 2 stage reverse osmosis water treatment technology can deeply purify tap water and prepare drinking water close to ultrapure water, providing people with healthy and safe direct drinking water and improving the quality of life.

4. Differences in equipment composition

(I) 1 stage reverse osmosis water treatment

1. Raw water pretreatment equipment: including quartz sand filter, activated carbon filter, water softener, etc. The quartz sand filter is used to remove large particle impurities such as suspended matter and silt in the raw water; the activated carbon filter adsorbs organic matter, odor, residual chlorine, etc. in the water; the water softener removes hardness ions such as calcium and magnesium in the water through ion exchange resin to prevent the reverse osmosis membrane from scaling.

2. 1 stage reverse osmosis membrane assembly: This is the core part of the entire equipment, consisting of reverse osmosis membrane, membrane shell, high pressure pump, etc. The reverse osmosis membrane has selective permeability and can intercept dissolved salts and impurities in the water; the membrane shell is used to protect and fix the reverse osmosis membrane; the high-pressure pump provides sufficient pressure for the raw water to overcome the osmotic pressure and pass through the reverse osmosis membrane.

3. Booster pump: In some cases, the raw water pressure is not enough to meet the working requirements of the reverse osmosis membrane. The role of the booster pump is to increase the raw water pressure to a suitable range to ensure that the reverse osmosis membrane can operate normally and improve water treatment efficiency.

4. Monitoring equipment such as flow meters and pressure gauges: used to monitor the flow rate, pressure and other parameters in the water treatment process in real time, so that operators can understand the equipment operation status in time, adjust the operation parameters, and ensure the stable and reliable water treatment effect.

5. Disinfection equipment: such as ultraviolet disinfection equipment, ozone generator, etc., used to disinfect the reverse osmosis effluent, kill bacteria, viruses and other microorganisms remaining in the water, and ensure the biological safety of the effluent.

(II) 2 stage reverse osmosis water treatment

1. Raw water pretreatment equipment: The composition is the same as the pretreatment equipment of the 1 stage reverse osmosis water treatment, and it also plays the role of preliminary purification of raw water, laying the foundation for the subsequent reverse osmosis process.

2. 1 stage reverse osmosis membrane assembly: Its structure and function are consistent with the 1 stage reverse osmosis membrane assembly in the 1 stage reverse osmosis water treatment. It is responsible for the first deep desalination and impurity removal of the pretreated raw water, reducing the dissolved solids content in the water, and providing better water quality for the 2 stage reverse osmosis treatment.

3. 1 stage pure water tank: For the 2 stage reverse osmosis water purification equipment with larger capacity, the 1 stage pure water tank is used to temporarily store the water treated by the 1 stage reverse osmosis, which plays a role of buffering and regulation. At the same time, the 1 stage pure water tank can also directly provide pure water of the 1 stage reverse osmosis to meet your diverse water needs. The material of the pure water tank is usually stainless steel or food-grade plastic, which has good corrosion resistance and sealing, and can ensure that the water quality is not polluted during the temporary storage process.

4. 2 stage reverse osmosis membrane assembly: The 2 stage reverse osmosis membrane assembly is a key part of the 2 stage reverse osmosis water treatment. It has the same material and basic principle as the 1 stage reverse osmosis membrane, and usually uses high-efficiency reverse osmosis membranes such as polyamide composite membranes. The purpose of the 2 stage reverse osmosis is to purify the water in the 1 stage pure water tank at a deeper level, further remove the residual trace dissolved salts and organic matter, and make the effluent water quality reach a higher purity standard.

5. 2 stage booster pump: Provide sufficient water inlet pressure for the 2 stage reverse osmosis membrane to ensure the smooth progress of the 2 stage reverse osmosis process. Since the pressure of the first-stage reverse osmosis water may be low, the second-stage booster pump can increase the water pressure to the working pressure range required by the second-stage reverse osmosis membrane, thereby improving the efficiency and effect of water treatment.

6. Monitoring equipment such as flow meters and pressure gauges: They are also used to monitor the flow rate, pressure and other parameters during the second-stage reverse osmosis water treatment process, so that operators can grasp the operation of the equipment in real time, find and deal with abnormal problems in time, and ensure the stable operation of the entire water treatment system.

7. Disinfection equipment: After the second-stage reverse osmosis water is discharged, disinfection treatment is also required to ensure the biological safety of the final water. The type and use of disinfection equipment are similar to those of disinfection equipment in the first-stage reverse osmosis water treatment. They are selected and configured according to your specific needs and application scenarios.

8. EDI ion exchange deep treatment equipment: EDI (electrodeionization) ion exchange technology is usually used to continuously remove ions from water through the action of an electric field, while avoiding the problems of traditional activated carbon adsorption and periodic regeneration of ion exchange resins. EDI can not only effectively remove residual anions and cations in the water, but also further reduce the conductivity, so that the water quality reaches the level of ultrapure water, meeting the needs of special application scenarios with extremely high water quality requirements.

5. Difference in operating costs

(I) 1 stage reverse osmosis water treatment

1. Membrane replacement cost: Since there is only one set of reverse osmosis membrane components in 1 stage reverse osmosis water treatment, and the water quality requirements for treatment are relatively lower than those of 2 stage reverse osmosis, the membrane replacement cycle is relatively long and the replacement cost is relatively low. In general, the service life of the reverse osmosis membrane is about 1-5 years, and the specific replacement time depends on factors such as raw water quality, operating conditions, and maintenance.

2. Power consumption: The power consumption of 1 stage reverse osmosis water treatment mainly includes the power consumption of high-pressure pumps, booster pumps, and disinfection equipment. Since the treatment process is relatively simple and the equipment operating power is relatively low, the power consumption is relatively small. The specific power consumption varies according to factors such as equipment scale, water treatment volume, and equipment efficiency.

(II) 2 stage RO water treatment

1. Membrane replacement cost: 2 stage RO water treatment includes 2 sets of RO membrane components, one for the 1 stage and the other for the 2 stage. The replacement cost of the membrane is relatively high. The replacement cycle of the 1 stage RO membrane is similar to that of the 1 stage RO water treatment. Since the 2 stage RO membrane treats high purity water after the 1 stage RO water treatment, its replacement cycle is longer than that of the 1 stage RO membrane. But in general, the replacement cost of the 2 sets of membrane components is higher than that of the 1 stage RO water treatment.

2. Power consumption: The power consumption of the 2 stage RO water treatment includes the power consumption of the high pressure pump, booster pump and subsequent deep treatment equipment (such as EDI ion exchange, etc.) of the 1 stage and 2 stage RO water purification systems. Since the treatment process is longer and the equipment has a higher operating power, the power consumption is relatively high.

6. Differences in maintenance requirements

(I) 1 stage RO water treatment

1. Regularly replace the pretreatment filter element: The pretreatment filter element is a key component to ensure the normal operation of the reverse osmosis membrane and needs to be replaced regularly. Under normal circumstances, the service life of quartz sand is relatively long, generally about 2-3 years. If the inlet water quality is poor and contains a large amount of suspended matter or impurities, backwashing needs to be performed more frequently and the replacement cycle needs to be shortened. The activated carbon in the activated carbon filter is generally replaced every 6-12 months, and the ion exchange resin in the water softener is generally replaced every 1-2 years. The replacement cycle will be adjusted according to the raw water quality and actual usage to ensure that the pretreatment effect is stable and reliable.

2. Regularly check and maintain equipment such as booster pumps: The booster pump is a key equipment for providing pressure for raw water, and its operating status needs to be checked regularly, including motor current, voltage, bearing temperature, sealing condition, etc. At the same time, check the inlet and outlet valves, pipe connections, etc. of the pump to ensure that there is no leakage or blockage. Other equipment such as flow meters, pressure gauges and other monitoring equipment also need to be calibrated and maintained regularly to ensure their measurement accuracy and reliability.

(II) 2 stage reverse osmosis water treatment

1. Regularly replace the pretreatment filter element: The replacement cycle and requirements of the pretreatment filter element are similar to those of the 1 stage reverse osmosis water treatment. It needs to be replaced regularly according to the raw water quality and usage to ensure the pretreatment effect and provide good influent water quality for the subsequent reverse osmosis process.

2. Regularly check and maintain the 1 stage and 2 stage booster pumps and other equipment: The 1 stage and 2 stage booster pumps are used to provide sufficient influent water pressure for the 1 stage and 2 stage reverse osmosis membranes respectively. Their operating status needs to be checked regularly, including motor current, voltage, bearing temperature, sealing condition, etc. At the same time, check the pump's inlet and outlet valves, pipe connections, etc. to ensure that there is no leakage or blockage. Other equipment such as flow meters, pressure gauges and other monitoring equipment also need to be calibrated and maintained regularly to ensure their measurement accuracy and reliability.

7. Conclusion

There are significant differences between the 1 stage reverse osmosis water purification system and the 2 stage reverse osmosis water purification system in terms of process flow, effluent water quality, application areas, equipment composition, operating costs and maintenance requirements. 1 stage reverse osmosis water treatment machines are suitable for general industrial and commercial fields with relatively low water quality requirements. They have the advantages of simple equipment, low operating costs, and easy maintenance. 2 stage reverse osmosis water treatment machines are suitable for various high-tech industries with extremely high water quality requirements, such as electronics, pharmaceuticals, and electricity. They can provide high purity ultrapure water, but the equipment is complex, the operating cost is high, and the maintenance requirements are strict. In practical applications, the appropriate reverse osmosis water treatment method should be selected based on specific water quality requirements, budgets, operating costs, and other factors. With the continuous advancement of science and technology and the increasing tension of water resources, reverse osmosis water treatment technology will be more widely used and continuously developed in the future, providing more reliable water treatment solutions for the sustainable development of various industries.

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