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 filtering technology. It uses the selection of a semipermeable membrane to remove the impurities in water and obtain pure water.

RO water treatment originated in the 1940s. It mainly removes salt from seawater through RO to provide drinkable fresh water for sailors. Later it was gradually used in commercial and industrial fields. With ongoing technological advancements, RO system efficiency and performance continue to improve, leading to a gradual reduction in the cost of RO technology.

It is largely revered as a desalination technology due to its high salt rejection rates and tolerance to high TDS levels. Typical reverse osmosis plants lessen the TDS concentrations of seawater from roughly 35,000ppm to 1000ppm or less, which is the universal threshold for freshwater.

The application of reverse osmosis in water treatment is virtually unlimited given it can be deployed as a complementary technology to other water treatment processes for high-grade purified water.

How does Reverse Osmosis Work?

How does Reverse Osmosis Work?

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

Reverse osmosis, on the other hand, is the opposite process. Pressure is applied to the feed side of the water, and when the pressure exceeds the osmotic pressure of the solution on that side, water flows in the opposite direction of natural osmosis, moving from the region of higher solute concentration to the region of 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.

What is a Reverse Osmosis System and How Does It Work

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 the semi-permeable membranes to eliminate the dissolved pollutants. High pressure is applied to primarily reverse the natural osmotic flow. The water after passing through the RO host is almost pure water without most substances. .

In the end, two streams of water are generated with one being fresh potable water (with a low TDS concentration) while the other stream is highly concentrated wastewater commonly referred to as brine. The pure water produced finally is stored in a storage tank and distributed for use.

Reverse osmosis workflow

Depending on the customer’s water treatment needs, a post-treatment system can be added after the reverse osmosis process. This stage is mainly optional and is necessitated by the need for high-quality freshwater. The purpose is to further remove trace impurities, odors, and bacteria remaining in the water. Post-filtration systems may include carbon filters, polish filters, and UV sterilization systems.

What Is Reverse Osmosis Water?

Reverse osmosis water is pure water produced after a series of pretreatment processes 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, and so on.

The pH of RO water falls within the range of 6.5-6.8, showing weak acidity. The average total dissolved solids (TDS) of reverse osmosis water is 300-500ppm, complying with the drinking water guidelines of the World Health Organization. Reverse osmosis water is widely used in industrial desalination, chemical industry, wastewater treatment, laboratories, food and beverage processing, and other fields due to its high purity.

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:

Substances that RO can remove from 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 organic molecules, volatile compounds, and toxins and residues produced by microbial metabolism.

Advantages and Limits of Reverse Osmosis


(1)Exceptional salt removal scores.

In addition to significantly lowering the salinity concentration of feed water, reverse osmosis systems are exceptional in alienating microorganisms, bacteria, viruses, arsenic, chloride, fluoride, unwanted metals, and colloids from 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. From a long-term perspective, it can efficiently solve water treatment problems and at the same time save customers costs and a large amount of repair and replacement parts costs. Some reverse osmosis equipment manufacturers and suppliers also guarantee optimal 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. When the industrial sector adopts reverse osmosis membrane technology, it can reduce energy consumption and ensure long service life and low-cost maintenance of the system.

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

Reverse osmosis technology can remove 99% of the contaminants in raw water, which allows undrinkable water to be turned into drinkable fresh water at any time.


In addition to the advantages mentioned above, reverse osmosis also has some disadvantages. For example, energy consumption and input costs are relatively high. In addition, reverse osmosis will produce a large amount of wastewater during operation, causing a waste of water resources to a certain extent.

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

The differences among microfiltration (MF), nanofiltration (NF), ultrafiltration (UF), and reverse osmosis (RO) primarily lie in the variance of their filtering 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: Filtering precision ranges from 0.001 to 0.01 micrometers. It can remove substances that ultrafiltration can eliminate and can also remove some heavy metal ions and certain salt substances in water. However, its desalination rate is relatively lower compared to reverse osmosis.

Reverse osmosis has a filtering precision of around 0.1 nanometers, allowing only water molecules to pass through. It can remove 98% of bacteria, viruses, colloids, rust, suspended particles, sediments, and large organic molecules in water.

Microfiltration, Nanofiltration, Ultrafiltration Vs. Reverse Osmosis

In short, reverse osmosis has higher filtration accuracy and better water quality than other membrane filtration technologies. However, when selecting a membrane filtration system, one must consider their specific water quality requirements. Reverse osmosis systems are relatively more expensive, and opting for them when lower filtering precision systems suffice would be wasteful in terms of investment.

Applications Of Reverse Osmosis System

1)Commercial: Some service industries and manufacturing industries that have higher water quality requirements. Such as hotels, restaurants, resorts, aquariums, food processing plants, spot-free car washes, etc.

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

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

4)For your home: Suitable for villas, off-grid, or coastal homes. A small solar desalination reverse osmosis unit operates for just a few seconds to produce water that is safe to drink. In addition, the RO system is suitable for installation under the sink.

5)Well Water Treatment: Well water is often unfit for drinking due to salt, turbidity, color, hardness, odor, and bacteria. Reverse osmosis can effectively remove salt, rust and hardness from well water.

Other applications include laboratory, RV, industrial desalination, electronics manufacturing, chemical industry, spot-free cleaning, biopharmaceuticals, and ultrapure water pretreatment.

Applications Of Reverse Osmosis System

How Much Does a Reverse Osmosis System Cost?

Small-scale reverse osmosis systems have a lower price range, typically between $700 and $4,000. For larger reverse osmosis systems, such as containerized RO plants, prices can range from $6,000 to $200,000. Factors influencing the price of the equipment include the technology involved, the brand of RO membrane, 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 precision
  • High-quality reverse osmosis membrane
  • Easy to operate and run
  • Easy to maintain and clean
  • Low energy consumption
  • High level of automation
  • Stable water output with excellent water quality
  • Long equipment lifespan
  • Compact design
  • High-cost performance

How to Choose a Good Reverse Osmosis System?

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 a water quality test to understand the substances present in your raw water.
  • Product Water Quality Requirements: Clearly define which substances you need to remove and customize the most suitable water treatment process.
  • Flow Rate: Typically measured in LPH (liters per hour), TPD (tons per day), and GPD (gallons per day). You need to confirm the daily water demand and the operating hours of the equipment per day.
  • Application Scenario: The capacity requirements for RO equipment are not very high in residential and commercial sectors. The industrial sector requires the use of large-scale reverse osmosis equipment.
  • Equipment Energy Consumption: High energy consumption of the system will increase operating costs, resulting in differences in the price of processing each ton of water.
  • Lifespan of Reverse Osmosis Membrane and Consumables: Higher quality reverse osmosis membranes have a longer lifespan. The frequency of consumables replacement will affect your financial investment.
  • Budget: The quality, craftsmanship, and capacity of the product will all 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 risks. You can compare some “best reverse osmosis system manufacturers” blogs or search for reviews online.

Future Trends in Reverse Osmosis

The emergence of reverse osmosis (RO) technology has marked a milestone in modern water treatment and brought hope to water scarcity issues. In the future, RO technology will undoubtedly face the challenge and demand of global freshwater scarcity, such as desalination of seawater and brackish water, as well as drinking water treatment.

As mentioned earlier, despite the advantages of RO, there are still some drawbacks that need to be addressed, including environmental concerns and energy efficiency. Improving the energy efficiency of systems and reducing the discharge and consumption of waste and energy are crucial. In recent years, continuous innovation in RO technology has reduced energy consumption from 16 kWh/m3 to approximately 3 kWh/m3 – 6 kWh/m3.

The development of RO technology also needs to consider clean energy. The use of renewable energy sources widens the application of RO. Furthermore, further improvements in the fouling resistance, high-temperature resistance, and permeability of RO membranes can reduce the cost of RO systems.

Future Trends in Reverse Osmosis

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.


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!



➤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?

Pretreatment is indispensable when the raw water quality is poor. Some raw water is of poor quality and contains a large amount of suspended matter and sediment.

No pretreatment measures are taken before raw water enters the RO system, large particles in the water will cause significant damage to the RO membrane after entering the RO system, affecting the water filtration effect and reducing the 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, reverse osmosis water is pure water that does not contain any impurities and contaminants and is therefore safe to drink. However, the reverse osmosis process also removes some trace elements and minerals in the water, making it taste bland, and long-term drinking of RO water may have certain effects on health.

However,post-treatment grants you the opportunity to remineralize your permeate. For drinking water recommendations by the WHO suggest you add 30 mg/L and 10 mg/L of calcium and magnesium respectively.

Substances Can Reverse Osmosis Remove From Water

➤Does Reverse Osmosis Waste Water?

Yes, reverse osmosis systems do waste a certain amount of water. During operation, reverse osmosis machines produce high-concentration brine, which is eventually discharged through wastewater pipes. The ratio of wastewater volume to treated water volume is typically around 1:5 and can even reach 1:2.

This means that for every 10 liters of water treated, there may be 2 to 5 liters of wastewater produced. However, with proper design and management, the volume of wastewater can be controlled. Additionally, since this brine has already undergone pre-treatment filtration, the impurity content in the water is not high. The wastewater can be collected and used for flushing toilets and household cleaning purposes.

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

Distilled Water: Water is obtained by heating a water source to vaporize H2O, and then condensing and separating the vapor portion. Distilled water contains almost no solutes, but it is prone to secondary contamination when in contact with storage containers and is not easy to preserve. Additionally, the energy consumption during the distillation process is higher than that of RO, making the acquisition cost of distilled water higher than RO water.

Reverse Osmosis Water: Pure water is obtained by filtering through a reverse osmosis membrane, removing 98% of impurities in water. However, there may be trace solutes remaining. Nevertheless, due to its cost-effectiveness and efficiency, reverse osmosis water has replaced distilled water and is widely used in laboratories.

Learn More about Distilled VS RO Water

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

Reverse Osmosis System: The outstanding advantage of the RO system is the high quality of RO water. The automation level of reverse osmosis equipment is high, making it easy to operate and maintain. The entire process of reverse osmosis does not require acid-base regeneration, has no environmental impact, and the wastewater can be reused.

The limitations of reverse osmosis systems lie in their high power consumption and high water production costs. Additionally, the process water consumption is relatively higher compared to water softening. Equipment typically occupies a large area.

If you have higher requirements for water quality, or your raw water contains high levels of pollutants, it is recommended to use a reverse osmosis water purification system.

Water Softener: Utilizes the displacement reaction of ion exchange resins to remove mineral ions from water. Water softeners are typically small in size and discharge less wastewater compared to RO systems.

However, the cost is generally higher, and the wastewater cannot be utilized as in the case of acid-base wastewater. Additionally, water softening is only suitable for removing scale from water, with limited application areas. If only the removal of calcium and magnesium ions is needed or if the raw water quality is good, a water-softening device can be considered.

➤Bottled Water VS Reverse Osmosis.

Currently, there are many brands and types of bottled water available on the market, offering convenience and catering to various taste preferences. However, if you opt for a long-term purchase of bottled water, you’ll find it to be a relatively high-cost investment. Moreover, you’ll need to constantly remind yourself to go to the store or supermarket for purchases.

Additionally, bottled water comes in plastic bottles, and there’s no guarantee that they are completely processed and recycled. Plastic waste can cause environmental pollution.

Bottled Water VS Reverse Osmosis

If you use a reverse osmosis water purifier to obtain healthy water its long-term cost of use is lower compared to bottled water. You can access pure water at home anytime, saving the cost and effort of purchasing bottled water and contributing 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.

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