What is Reverse Osmosis？Ultimate Guide

Reverse osmosis technology has made a significant contribution to the water shortage problem, and its applications can be seen everywhere in our lives. This ultimate guide will thoroughly explain the definition, workings, benefits, applications, and more of reverse osmosis, catering to both beginners and experts alike. Let’s unveil its mysterious veil.

What Is Reverse Osmosis?

Reverse osmosis is an advanced physical membrane filtration technology. It uses a semi-permeable membrane to remove impurities from water to obtain pure water.

Reverse osmosis water treatment technology originated in the 1940s, mainly removing salt from seawater through reverse osmosis to provide crew members with drinkable fresh water. Later, reverse osmosis technology was gradually applied to commercial and industrial fields. With the continuous advancement of technology, the efficiency and performance of reverse osmosis systems have continued to improve, resulting in a gradual reduction in the cost of reverse osmosis technology.

Due to its high desalination rate and tolerance to high TDS (total dissolved solids) concentrations, reverse osmosis technology is widely regarded as a seawater desalination technology. A typical reverse osmosis unit can reduce the TDS concentration of seawater from approximately 35,000 ppm to 1000ppm or less, which is the universal threshold for fresh water.

The application of reverse osmosis in water treatment is almost unlimited, as it can be used as a complementary technology to other water treatment processes to produce high-quality pure water.

How does Reverse Osmosis Work？

Osmosis means that under natural conditions, water molecules with different solute concentrations on both sides of a semipermeable membrane will flow from the side with low solubility to the side with high solubility until the solubility of the solutions on both sides is the same.

Reverse osmosis is the opposite. When pressure is applied to the water inlet side, when the pressure exceeds the osmotic pressure of the solution on that side, the water will flow in the opposite direction of natural osmosis, from the area with higher solute concentration to the area with lower solute concentration.

What is A Reverse Osmosis System and How Does It Work?

Reverse osmosis system refers to pure water equipment using reverse osmosis technology. The system contains high-pressure pumps, reverse osmosis membranes, security filters, and other components.

The raw water is pumped from the raw water tank into the pretreatment system under the action of the high-pressure pump. The pretreatment system typically consists of quartz sand filters, activated carbon filters, and water softeners. This process can filter out colloids, debris, sediments, chlorine, odors, and the majority of larger particles such as mineral ions. Depending on the pH value of the incoming water, chemical agents can also be added to mitigate corrosion and scaling effects on the reverse osmosis equipment.

After pretreatment, the water is forced through a semi-permeable membrane to remove dissolved contaminants. High pressure is applied, mostly reversing the natural osmotic flow. The water after passing through the RO unit is nearly pure water, free of most impurities.

The result is two water streams: one is fresh drinking water (low TDS concentration) and the other is high-concentration wastewater, commonly known as brine. The resulting pure water is stored in a storage tank for user use.

Depending on the customer’s water treatment needs, a post-treatment system can be added after the reverse osmosis process. This stage is mainly an optional step, but is essential due to the need for high-quality fresh water. Its purpose is to further remove trace impurities, odors, and bacteria remaining in the water. The post-filtration system may include activated carbon filters, polishing filter,s and UV sterilization systems.

What Is Reverse Osmosis Water？

Reverse osmosis water is pure water produced after a series of pretreatment and reverse osmosis processes. As an ideal high-quality drinking water and industrial water, it contains almost no dissolved solids, including salts, metal ions, organic compounds, etc.

The pH value of reverse osmosis water is between 6.5-6.8, which is slightly acidic. The average total dissolved solids (TDS) content of reverse osmosis water is 300- 500 ppm, which meets the drinking water guidelines of the World Health Organization. Due to its high purity, reverse osmosis water is widely used in industrial desalination, chemical industry, wastewater treatment, laboratory, food and beverage processing, and other fields.

What Substances Can Reverse Osmosis Remove From Water?

1）Substances that reverse osmosis technology can remove:

The pore size of reverse osmosis membranes ranges from 0.1nm to 0.7nm. Reverse osmosis technology can remove most of the following substances in raw water:

2）Substances that reverse osmosis cannot remove:

Reverse osmosis technology can effectively remove most impurities, but the removal rate is not 100%. Other substances that reverse osmosis technology cannot remove include oxygen, nitrogen, small molecular organic matter, volatile compounds, and toxins and residues produced by microbial metabolism.

Advantages and Limits of Reverse Osmosis

Advantages:

（1）Exceptional salt removal scores.

In addition to significantly reducing the salinity concentration of the feed water, the reverse osmosis system can effectively remove microorganisms, bacteria, viruses, arsenic, chlorides, fluorides, harmful metals and colloids from the raw water.

（2）Inexpensive to maintain.

When high-quality reverse osmosis equipment is used in industrial or commercial projects, its service life is relatively long and does not require frequent maintenance or replacement. In the long run, it can effectively solve water treatment problems while saving customers costs and a lot of repair and replacement parts. Some reverse osmosis equipment manufacturers and suppliers also guarantee the best service for at least 12 months.

（3）Energy recovery and Low energy consumption.

Compared with traditional seawater desalination technologies such as distillation, reverse osmosis membrane technology consumes less energy and has a longer service life. The use of reverse osmosis membrane technology in the industrial field can reduce energy consumption, ensure a long system life and low-cost maintenance.

（4）The quality of the effluent is high and stable

Reverse osmosis technology can remove 99% of pollutants in raw water, turning undrinkable water into drinkable fresh water at any time.

Disadvantages:

In addition to the above advantages, reverse osmosis also has some disadvantages, such as relatively high energy consumption and input costs. In addition, reverse osmosis will produce a large amount of wastewater during operation, which will cause a waste of water resources to a certain extent.

Microfiltration, Nanofiltration, Ultrafiltration, and Reverse Osmosis, Which One is Better?

The difference between microfiltration (MF), nanofiltration (NF), ultrafiltration (UF) and reverse osmosis (RO) mainly lies in the difference in filtration precision.

Microfiltration: Filtering precision ranges from 0.1 to 50 micrometers, effectively removing large particle suspensions, colloids, and bacteria.

Ultrafiltration: Filtering precision ranges from 0.001 to 0.1 micrometers, enabling the removal of substances such as sediment, rust, suspended particles, bacteria, and viruses．

Nanofiltration: The filtration accuracy is 0.001 to 0.01 microns, which can remove substances that can be removed by ultrafiltration, and can also remove some heavy metal ions and certain salt substances in the water, but its desalination rate is relatively low compared with reverse osmosis.

The filtration accuracy of reverse osmosis is about 0.1 nanometers, which only allows water molecules to pass through, and can remove 98% of bacteria, viruses, colloids, rust, suspended particles, sediments and macromolecular organic matter in water.

In short, compared with other membrane filtration technologies, reverse osmosis has higher filtration accuracy and better water quality. However, when choosing a membrane filtration system, its specific water quality requirements must be considered. Reverse osmosis systems are relatively expensive, and if a system with lower filtration accuracy is sufficient, choosing a reverse osmosis system will result in a waste of investment.

Applications Of Reverse Osmosis System

1) Commercial: Some service industries and manufacturing industries require high water quality. For example, hotels, restaurants, resorts, aquariums, food processing plants, stain-free car washes, etc.

2) Industrial: boiler feed water, industrial wastewater, seawater desalination, power plants, refineries, etc.

3) Agricultural irrigation: Rainwater, rivers, and dams have always been the main source of agricultural water, but these raw waters need to be treated before they can be safely used in agriculture. Reverse osmosis is currently the main source of irrigation water in the Middle East and North Africa.

4) Home use: Suitable for villas, off-grid homes or coastal homes. Small solar desalination reverse osmosis units only need to run for a few seconds to produce safe drinking water. In addition, reverse osmosis systems are suitable for installation under sinks.

5) Well water treatment: Well water is usually not suitable for drinking due to high salt, turbidity, color, hardness, odor, and bacteria content. Reverse osmosis can effectively remove salt, rust, and hardness from well water.

Other applications include laboratories, RVs, industrial desalination, electronics manufacturing, the chemical industry, spotless cleaning, biopharmaceuticals, and ultrapure water pretreatment.

How Much Does a Reverse Osmosis System Cost?

Small RO systems are less expensive, typically between $700 and $4,000. Larger RO systems, such as containerized RO plants, can cost between $6,000 and $200,000. Factors that affect the price of the equipment include the technology used, the brand of RO membrane, the capacity, and the brand of the equipment itself.

What Is The Best Reverse Osmosis System？

You can consult professional engineers to obtain expert purchasing advice and customized system solutions. A good reverse osmosis system possesses the following characteristics:

• High filtration accuracy
• High-quality reverse osmosis membrane
• Easy to operate
• Easy to maintain and clean
• Low energy consumption
• High degree of automation
• Stable water output, excellent water quality
• Long equipment life
• Compact design
• High cost performance

How to Choose a Good Reverse Osmosis System？

We have listed 8 points, and you can also determine your own needs and choose the best reverse osmosis system based on the following dimensions:

• Raw water quality: Conduct water quality tests to understand the substances present in the raw water.
• Product water quality requirements: Identify the substances that need to be removed and customize the most appropriate water treatment process.
• Flow rate: Usually measured in LPH (liters per hour), TPD (tons per day), and GPD (gallons per day). You need to confirm the daily water consumption and the number of hours the equipment runs per day.
• Application scenarios: The residential and commercial fields do not require high processing capacity of reverse osmosis equipment. The industrial field requires the use of large reverse osmosis equipment.
• Equipment energy consumption: High system energy consumption will increase operating costs, resulting in differences in the price per ton of water treatment.
• The service life of reverse osmosis membranes and consumables: The higher the quality of the reverse osmosis membrane, the longer the service life. The frequency of replacement of consumables will affect your financial investment.
• Budget: The quality, process, and processing capacity of the product will affect the price. You need to choose the best quality product within your budget.
• Brand and after-sales service: Reliable suppliers and after-sales service can reduce your risk. You can compare some blogs of “Best Reverse Osmosis System Manufacturers” or search for reviews online.

Future Trends in Reverse Osmosis

The emergence of reverse osmosis (RO) technology is a milestone in the field of modern water treatment, bringing hope for solving the problem of water shortage. In the future, RO technology will undoubtedly face the challenges and needs of global freshwater shortage, such as seawater desalination, brackish water desalination, and drinking water treatment.

As mentioned earlier, despite the many advantages of RO, there are still some shortcomings that need to be addressed, including environmental issues and energy efficiency issues. It is crucial to improve the energy efficiency of the system and reduce the emission and consumption of waste and energy. In recent years, the continuous innovation of RO technology has reduced energy consumption from 16 kWh/m³ to about 3 kWh/m³ – 6 kWh/m³.

The development of RO technology also needs to consider clean energy. The use of renewable energy has broadened the application range of RO. In addition, further improving the anti-fouling, high temperature resistance and permeability of RO membranes can reduce the cost of RO systems.

Finally, technological development is rapid and unpredictable. We believe that in the future, RO systems will become more intelligent and automated, further reducing the need for manual monitoring and maintenance.

Summary

NEWater reverse osmosis equipment is available in different capacities and can be customized according to customer requirements to meet a variety of applications for commercial, industrial, and personal use.

Our products include whole-house reverse osmosis systems,  commercial RO systems, seawater desalination RO systems, brackish water RO desalination systems, industrial reverse osmosis systems, containerized/mobile reverse osmosis plants，skid-mounted RO equipment, and portable RO units. Contact us for a free RO system model recommendation！

FAQs:

➤What is RO Membranes？

Reverse osmosis membrane is a nano-scale semi-permeable membrane with high filtration precision, with a filtration precision of 0.0001 micron. According to different materials and structures, the types of reverse osmosis membranes can also be divided into 8 types.

➤Is a Pre-treatment System Required?

When the raw water quality is poor, pretreatment is essential. Some raw water has poor quality and contains a lot of suspended matter and sediment.

If the raw water is not pretreated before entering the reverse osmosis system, the large particles in the water will cause serious damage to the reverse osmosis membrane after entering the reverse osmosis system, affecting the water filtration effect and shortening the service life of the membrane. Cleaning and replacing membrane accessories will also increase water treatment costs.

Here are some processes that are often used in pretreatment systems:

• Quartz sand filter
• Activated carbon filter
• Security filter
• Ion exchange water softener
• Ultrafiltration system
• Microfiltration system
• Antiscalants and antiscalants

➤Can I Drink Reverse Osmosis Water?

Yes, RO water is pure water and does not contain any impurities and contaminants, so it is safe to drink. However, the RO process also removes some trace elements and minerals from the water, making it taste bland, and long-term drinking of RO water may have certain health effects.
However, post-treatment allows you to remineralize the osmotic water. For drinking water recommendations by the WHO recommends adding 30 mg/L of calcium and 10 mg/L of magnesium, respectively.

➤Does Reverse Osmosis Waste Water?

Yes, reverse osmosis systems do waste a certain amount of water. During operation, the reverse osmosis machine produces highly concentrated brine, which is eventually discharged through the wastewater pipe. The ratio of wastewater to treated water is usually about 1:5, or even 1:2.
This means that for every 10 liters of water treated, 2 to 5 liters of wastewater may be produced. However, if designed and managed properly, the amount of wastewater can be controlled. In addition, since these brine has been pre-treated and filtered, the impurity content in the water is not high. The wastewater can be collected and used for flushing toilets and household cleaning.

➤Distilled Water and Reverse Osmosis Water， What is the Difference?

Distilled water: Water is obtained by heating a water source to vaporize it and then condensing to separate the vapor portion. Distilled water contains almost no solutes, but is susceptible to secondary contamination when in contact with storage containers and is not easy to preserve. In addition, the energy consumption in the distillation process is higher than that of reverse osmosis (RO) water, so the purchase cost of distilled water is higher than that of RO water.

RO water: Purified water is obtained by filtering through a reverse osmosis membrane, which removes 98% of impurities in water. However, trace amounts of solutes may still remain in the water. Despite this, RO water has replaced distilled water and is widely used in laboratories due to its cost-effectiveness and efficiency.

Learn More about Distilled VS RO Water

➤Reverse Osmosis System vs.Water Softener, Which is Better?

Reverse Osmosis System: The outstanding advantage of the reverse osmosis system is the high quality of the produced water. The reverse osmosis equipment has a high degree of automation and is easy to operate and maintain. The entire reverse osmosis process does not require acid and alkali regeneration, has no impact on the environment, and the wastewater can be reused.

The limitations of the reverse osmosis system are its high power consumption and high water production cost. In addition, compared with softened water, the water consumption of the reverse osmosis process is relatively high, and the equipment usually occupies a large area.

If you have high requirements for water quality or the content of pollutants in the raw water is high, it is recommended to use a reverse osmosis water purification system.

Water Softener: Use the displacement reaction of ion exchange resin to remove mineral ions from water. Compared with the reverse osmosis system, the water softener is usually smaller in size and has less wastewater discharge.

However, the cost of the reverse osmosis system is usually higher, and the wastewater cannot be recycled like acid and alkaline wastewater. In addition, softened water is only suitable for removing scale in water, and its application range is limited. If you only need to remove calcium and magnesium ions, or the raw water quality is good, you can consider using a softening water device.

➤Bottled Water VS Reverse Osmosis.

The service life of a high-quality reverse osmosis system can reach more than 20 years. Regular maintenance and cleaning are essential during the operation of the equipment. As the core component of the system, the reverse osmosis membrane usually needs to be replaced every 3-5 years to maintain optimal filtration performance and prevent the filtration effect from deteriorating. The service life of the reverse osmosis equipment is affected to a certain extent by the components, materials, and pressure and temperature during operation.

Use a reverse osmosis water purifier to get healthy water quality, and its long-term use cost is much lower than bottled water. You can enjoy pure water at home at any time, save the cost and effort of buying bottled water, and contribute to environmental protection.

➤How Long Does A Reverse Osmosis System Last?

If the original water quality is good and the equipment quality is high, the reverse osmosis system can be used for more than 20 years. Additionally, regular maintenance and cleaning during equipment operation are also key influencing factors.

The reverse osmosis membrane, as the core component of the system, typically needs replacement every 3-5 years to maintain optimal filtration performance and prevent any decline in effectiveness. The lifespan of RO equipment is influenced to a certain extent by the components, materials, as well as the pressure and temperature during operation.