Pros and cons of seawater desalination using RO

Seawater desalination using  RO technology is undoubtedly the future of drinking water production for coastal communities and island nations in current times of water scarcity. It is already heavily used in a few countries. Saudi Arabia, the United Arab Emirates, and the United States are the three largest producers of drinking water desalination by capacity in the world, followed by Australia, China, and Kuwait.

These seawater desalination systems are typically used by coastal communities, providing a practically unlimited supply of feedwater. After knowing some details about the applications of seawater desalination technology.

Some basics of seawater desalination using RO

The ultimate goal of the desalination process is to remove salts present in seawater, which are concentrated at a rate ranging between 3-3.5%. There are also other components in seawater that need to be dealt with as well, such as color, silica, and microorganisms. To do this, the process begins by drawing ocean water through a suction pump from a beach well or from a suction pipe buried in the seafloor. This water enters the equalization tank or basin.

Through this process, the water undergoes pre-treatment. Pretreatment typically consists of one or more filtration units that remove particles larger than 1 nanometer. This pretreatment process is very important to reduce the risk of RO membrane contamination.

In the RO process, pressure is applied to overcome the osmotic pressure. Therefore, water flows across the membrane into an area of lower salt concentration, letting the salts flow through it into a concentrated solution (brine). The resulting clean water is put through a post-treatment process which includes remineralization and residual disinfection. Finally, the resulting brine concentrate is carefully discharged back into the ocean in a dispersed manner. This offloading process is designed and designed to significantly reduce any negative impact on the local marine ecosystem.

By using reverse osmosis seawater treatment systems, coastal communities and island nations can have access to clean, safe water.

Advantages of seawater desalination using reverse osmosis technology

Standard systems

Modular systems are designed to be compact, and easy to transport and install in order to reduce capital costs. They are great for municipal or commercial drinking water applications (e.g. hotels) where space may be limited but need to supply a large number of people.

Expansion of drinking water sources

The driving force behind desalination. It is important to be more sustainable about the state of our current water sources, but alternatives are also necessary when they are available. The ocean happens to be a pretty big alternative. With the world’s oceans being a viable source of drinking water, this would increase humanity’s most valuable resource by a huge margin. Keep in mind that the oceans account for about 95+% of all the water on Earth.

High yield

The only other desalination treatment currently in use is of the thermal type. It works in the same way as the water cycle, where water evaporates into steam, and when it condenses it provides clean water. This method is very effective in removing unwanted particles, but collecting and condensing the steam is inefficient and produces much lower amounts of pure water than reverse osmosis. For the same volume of water production, thermal processes require approximately three times the amount of seawater.

Very pure water

After reverse osmosis, the water becomes so pure that we have to restore minerals to it. The process removes water minerals that humans need as well as the tastes we know. Therefore, the post-remineralization process takes care of this and regulates the pH.

Disadvantages of desalinating seawater using reverse osmosis technology

Pretreatment required

Reverse osmosis membranes are very sensitive. Therefore, unless some more resistant membrane materials are developed, pretreatment is an important requirement. Without it, the membrane can become practically useless, reducing yield or producing impure water. Improperly treated seawater can deposit particles on the membrane. These contaminants affect proper membrane flow and pressure which increases operating costs.

Higher energy use

Reverse osmosis systems are continuous flow processes in which fluids are constantly pumped and pressure is constantly applied to cylindrical membrane vessels. The required pressure can be up to 1000 psi (69 bar) in some systems. However, the osmotic pressure energy stored in the concentrated solution can actually be recovered to reduce overall energy costs. A commonly used technology is the rotary pressure exchanger. The flowing seawater is pressurized by pistons within channels inside the exchanger which are pressurized by the high-pressure reject stream from the reverse osmosis unit. Reusing kinetic energy from salt water can efficiently reduce energy costs.

These negatives can be reduced if you turn to institutions with long experience in this field. The availability of regular maintenance service and trained technical experts is one of the most important elements. That must be available in the institution that you will deal with. Do you want to learn more about the pros and cons of desalinating seawater via reverse osmosis, and how it can be a useful source of drinking water? Contact the water treatment experts at Carewater Solutions.