What is Reverse Osmosis?

Today, the growing use of reverse osmosis technology in water treatment has made it a widely sought remedy to address the threat of water scarcity. It can treat seawater, brackish water, groundwater, and wastewater, allowing industries, municipalities, and people in coastal water-scarce areas to efficiently obtain healthy drinking water.
Reverse osmosis equipment can be used in seawater desalination, industrial wastewater treatment and desalination, sewage water reuse, and other fields. So what exactly is reverse osmosis? Why should we use it? Where can reverse osmosis equipment be used? We give you the answer in this article.

1. What is Reverse Osmosis and What Contaminants Does It Remove?

Since its inception as a water treatment solution in 1946, reverse osmosis has revolutionized water treatment. Reverse osmosis is simply a membrane-based filtration process driven by pressure to lessen the magnitude of total dissolved solids in feed water. Additionally, the process eradicates microorganisms, colloids, organic chemicals, metals, bacteria, and viruses found in raw water.

reverse osmosis system

The versatility, resourcefulness, and cost-efficiency of reverse osmosis facilitate its application in both small-scale and large-scale industries. 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. With custom-built machinery, reverse osmosis is deployed in industries, homesteads, commercial entities, and municipalities to generate fresh product water.

Reverse osmosis technology can effectively remove calcium, magnesium, bacteria, viruses, organic matter, inorganic matter, colloidal particles, metal ions, and radioactive substances in water.

2. How Does Reverse Osmosis Work?

Reverse osmosis has for years been at the forefront of the fight against water scarcity. With reverse osmosis, idle natural resources like seawater and groundwater are converted into usable products. The working principle of reverse osmosis is founded on the exertion of foreign pressure to inverse the ordinary osmotic flow. This, in turn, forces the flow of water from highly concentrated streams to lowly concentrated streams.

-Process of reverse osmosis.

The process of reverse osmosis commences once feed water is driven into a pretreatment unit. Here, sediment or carbon filters filter out colloids, debris, microplastics, and typically large contaminants. Depending on the feed water’s pH rating, chemical dosing is also deployed to weaken the corrosive and scaling effects of feed water on the RO equipment.

Figure 1 Reverse osmosis system.

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 reverse osmosis membranes have extremely small-sized perforations (0.0001 microns) which make certain most of the dissolved solids (rejection rate of 95-99.7%) do not pass through the membrane.

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 final stage in a reverse osmosis process involves post-treatment. This stage is mainly optional and is necessitated by the need for high-quality freshwater. Often, the freshwater generated may contain dissolved carbon dioxide since RO membranes are not effective in alienating it from water.

Additionally, 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.

Figure 2 How reverse osmosis works.

-Types of Reverse Osmosis Systems.

Reverse osmosis equipment comes in unique specifications to suit a variety of applications for commercial, industrial and personal use. The following is a list of common reverse osmosis systems:

3. Advantages of Reverse Osmosis.

Improvements in reverse osmosis processes and systems have resulted in an efficient and cost-effective water treatment solution. Modern reverse osmosis systems not only provide high-quality drinking water but also offer efficiency and convenience. They offer impeccable quality, ease of operation, and affordable operating costs. Below, we explain the benefits that reverse osmosis system users are entitled to.

(1)Exceptional salt removal scores.

The reverse osmosis membranes are specifically designed to filter out dissolved salts from feed water. This is greatly enhanced by the use of 0.0001 micron-sized membrane perforations, which eliminate up to 99.7% of dissolved solids. To put this into perspective, desalting seawater with a TDS level of 45,000ppm using reverse osmosis will generate potable water with a TDS level of 1000ppm or lower.

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.

In addition, continued innovation in reverse osmosis technology in recent years has reduced power consumption from 16 kWh/m3 to approximately 3 kWh/m3 – 6 kWh/m3. With the advent of clean energy solar technology for desalination, contemporary reverse osmosis systems are quite affordable and relatively cheap to run.

(4)Customized solutions.

Reverse osmosis equipment can be customized to treat feed water at the flow rate required by the customer. In addition to different capacities and different power options, the equipment can also be customized to fit the customer’s usage scenarios. Compact and modular reverse osmosis systems are easier to install and reduce the use of space resources.

(5)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.

The seawater desalination system can make the water quality of the effluent stable for a long time, and the water quality can meet international drinking water standards.

4. Application Fields of Reverse Osmosis.

The shockwaves of the continually depleting freshwater reservoirs have dealt huge blows to numerous industries across the globe. The ballooning of industrialization has further increased the dependency ratio on existing freshwater sources resulting in over-exploitation. As it stands, the remaining freshwater sources are incapable of adequately meeting the various industrial, commercial, and personal demands for potable water.

Gradual breakthroughs in reverse osmosis technology have provided industries in water-deprived regions with alternative and cost-efficient freshwater sources. Reverse osmosis systems are presently utilized as stand-alone systems or complementary systems for water treatment. Underneath, we explore the diverse sectors making use of reverse osmosis to supplement their freshwater reservoirs.

-Production of fresh drinking water.

The recent development in reverse osmosis technology has prompted a number of municipalities to incorporate RO processes in treating water for residential and commercial facility distribution. Homesteads in arid, semi-arid, and coastal regions also utilize small-sized RO systems to treat saline water.

The impressive impurity rejection rates of reverse osmosis make certain that the potable water generated is free from potentially harmful contaminants. As a matter of fact, over 99.7% of the dissolved solids in raw water are eliminated by RO plants. The water generated by reverse osmosis averages a TDS rating of 300-500ppm, which is in line with the WHO guidelines on drinking water.

Figure 5 Reverse osmosis equipment for households.

-Irrigation.

One of the adverse effects of water scarcity is often food shortage caused by poor crop production in drylands. Rain, river streams, and dams have been the predominant sources of water for agricultural applications but they are prone to depreciation. Reverse osmosis is currently the leading source of irrigation water in the Middle East and Northern Africa.

Additionally, water sourced from wells necessitates treatment to be viable for use in farming. In fact, 70% of the extracted groundwater is utilized in agricultural production thanks to reverse osmosis and other water treatment technologies.

-Laboratory applications.

The primary solvent used in most laboratories is water with applications ranging from basic cleaning of equipment to diluting key solutions for experiments. Reverse osmosis generates varying grades of potable water suitable for distinct laboratory applications.

Certain laboratory applications such as experimentation necessitate highly treated water given the contaminants in raw water could potentially contaminate the solution. Reverse osmosis is often deployed with other water treatment technologies like ultrafiltration and ultraviolet light to generate high-quality purified lab water.

deionized water system for laboratory application

-Industrial applications.

The significant majority of industrial processes are centered on freshwater. This ranges from maintaining hygiene to the production of key products. Raw water is often not suitable for most delicate industrial processes hence most industries utilize reverse osmosis to generate high-grade industrial water.

For instance, the use of raw water with high concentrations of calcium and magnesium could result in fouling of the boiler feed due to scaling. Apart from water softening, reverse osmosis systems are also utilized in industries to treat wastewater before disposal or for reclamation purposes. Industries reliant on reverse osmosis systems include:

●Pharmaceuticals.
●Food and beverages.
●Power generation plants.
●Refineries.

-Commercial applications.

Treated water in commercial entities and activities is an essential commodity serving multiple purposes. Potable water generated by reverse osmosis systems can be sold as bottled water or utilized to deliver services such as car washing. For spotless cars, the water used to carry out the final rinse is treated using reverse osmosis. Underneath are common commercial enterprises exploiting reverse osmosis systems for improved water quality.

  • Business offices/complexes.
  • Carwashes.
  • Hotels and resorts.
  • Water bottling.

5. The Cost of Reverse Osmosis.

In the absence of freshwater sources, water treatment via reverse osmosis is considered a cost-efficient alternative. To utilize reverse osmosis in water treatment, reverse osmosis equipment is needed. Recent breakthroughs in production technologies have lessened the production cost of reverse osmosis equipment.

Additionally, advancements in membrane technologies have fundamentally lowered the operational costs of reverse osmosis systems. For manufacturers like NEWater, this has been translated into affordable prices for local and global customers.

The actual buying price of reverse osmosis systems is provided upon request due to the complexities of different specifications. Different variables that influence the purchasing price of a reverse osmosis unit include the size, specifications such as maximum TDS levels, number of gallons produced in a day (capacity), and the design (skid-mounted, containerized, or bracket type).

Reverse osmosis systems also command various operational costs ranging from installation charges to power consumption. Underneath we break down the various operational charges resulting from the use of RO systems.

Figure 7 Cost Of Reverse Osmosis System.

Power consumption.

Generally, expenditures on power consumption habitually account for over 50% of reverse osmosis systems’ operational costs. However, the innovation and use of highly resourceful energy recovery devices and high-pressure pumps have fundamentally lowered the amount of energy consumed to treat a cubic meter of feed water.

At present, reverse osmosis consumes between 3kwh/m3 to 6kWh/m3 of power, a significant drop from 16kWh/m3 in the 1970s. Factors that influence the power consumption of a reverse osmosis system include the concentration of the feed water and the production capacity. The power consumption cost of a 10,000ton/day seawater RO system is roughly 2.25 yuan per ton of water.

Labor.

The operation of a reverse osmosis system especially at a larger scale necessitates one or several technicians. The wages of these technicians vary depending on the quality and quantity of services provided. Another key determinant of the labor fees is the labor laws and regulations of respective countries. For illustration, the labor charges of seawater RO systems in China are approximately 0.2 yuan/ton of water.

Upkeep and maintenance.

Certain consumables such as chemicals for pretreatment are mandatory in a reverse osmosis system. When broken down, the cost of these consumables is roughly 0.05 yuan per ton of water.

Moreover, there are maintenance costs related to repairs and replacements of filters and membranes. The average replacement cost of RO membranes is estimated to be 0.05 yuan per ton of water as well. The use of high-quality RO membranes by NEWater guarantees at least 3 years of service thereby lowering the operational cost.

Considering all the above-stated expenses, the overall cost of operating a seawater reverse osmosis system (with a daily capacity of 10,000 tons) in China is approximately 4.54 yuan/ton of water.

6. Examples of Reverse Osmosis.

A lot of effort has been put into developing contemporary reverse osmosis technologies and machinery. Compared to earlier reverse osmosis systems, current systems are more efficient, effective, and versatile. Additionally, manufacturers have developed varying types of reverse osmosis systems with exclusive specifications that suit distinct applications.

Figure 7 Commercial Reverse osmosis system.

Nonetheless, all reverse osmosis systems share basic components. Below is a breakdown of the various components that make up a reverse osmosis unit.

  • Pretreatment chamber.
  • Cartridge filters.
  • Semi-permeable membranes.
  • Post-treatment unit.
  • Chemical dosing system.
  • Membrane cleaning system.
  • Stainless steel skid.

NEWater’s reverse osmosis solutions are widely used in varying sectors to treat varying forms of feed water. For the past 20 years, NEWater has supplied thousands of standard and customized reverse osmosis systems to different clients. Underneath, we look at examples of NEWater’s premium reverse osmosis systems.

-Seawater reverse osmosis systems.

There has been an immense upsurge in seawater desalination over the years. This has principally been driven by the infinite availability of seawater and its immunity to climatic change. Reverse osmosis is the primary seawater desalination technology in use with statistics suggesting that there are over 22,000 desalination systems globally.

NEWater offers a wide array of commercial and industrial SWRO plants intelligently designed to desalinate over 99% of dissolved solids present in seawater. Our SWRO systems have extreme TDS tolerance levels (up to 45,000ppm) to facilitate optimum seawater desalination.

-Brackish water reverses osmosis systems.

Brackish water is characterized by its moderate concentration of salts (over 1000 ppm to 12000 ppm). For most applications including human consumption, brackish water is considered unfit thereby prompting treatment. A crucial process in brackish water desalination is reverse osmosis. Reverse osmosis systems are preferred in brackish water treatment because of their high salt rejection rates and efficient power consumption.

Technically, desalinating 1000 gallons of brackish water using a reverse osmosis system will cost less than desalinating the same amount of seawater. NEWater manufactures varying brackish water RO systems for industrial, personal and commercial applications.

Figure 8 Brackish water reverse osmosis system.

-Well water reverse osmosis systems.

To combat water scarcity, over 50% of the global population has turned to well water. Seventy percent of the water generated from private wells is used to bolster the agricultural sector through irrigation. However, raw well water is hardly usable for domestic or irrigation applications prior to treatment.

This is chiefly because of high acidity and the presence of ionic pollutants such as magnesium and calcium. Reverse osmosis has massively aided efforts aimed at improving the quality of groundwater by eradicating water hardness, microorganisms, bacteria, viruses, and organic chemicals found in it.

NEWater has developed distinct well water RO systems specialized to generate high-grade water for households, industries, and businesses. To avert fouling of RO systems in well water treatment, processes like Nanofiltration and ion exchange are deployed as pretreatment.

-Skid-mounted reverse osmosis systems.

Reverse osmosis skids are water treatment systems with components assembled on a metal frame for compatibility. Skid-mounted reverse osmosis systems are excellently designed to facilitate high recoveries and support plug-and-play installation. They have a small footprint and exhibit high impurity rejection rates.

At NEWater, we mount well water systems, seawater desalination equipment, wastewater units, and brackish water desalination equipment on stainless steel skids. This ensures that the system is safe from the tremors caused by the high-pressure pumps and facilitates portability.

Ultrafiltration Skid Features

-Containerized reverse osmosis systems.

A few years back, containerized reverse osmosis systems were touted to be the future of water treatment plants. This is because containerized systems occupy a smaller footprint, enhance mobility, and provide turnkey solutions. Typical containers used to create NEWater’s containerized RO systems are the standard 10ft, 20ft, and 40ft containers.

Common applications of containerized reverse osmosis systems include seawater desalination, brackish water desalination, wastewater treatment, mining, power plants, and construction sites.

 Figure 9 Reverse osmosis skid.

7. Conclusion

NEWater’s mission is to bring new life to water and for the past 2 decades, we have spearheaded the production of comprehensive water treatment systems. Over 20 years, we have manufactured and supplied over 9000 water treatment systems and an extra 2000 customized units. Thanks to our systems, millions of people have unlimited access to high-grade potable water at reasonable rates.

NEWater’s reverse osmosis systems page provides additional information resources on reverse osmosis technologies and systems. If you are interested in any of our systems, you are invited to contact our customer support team or engineers. Contact us now for customized water treatment systems at affordable price points. info@newater.com

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