Seawater desalination has become an increasingly important technology to address water scarcity, especially in regions with limited freshwater resources. Reverse osmosis (RO) desalination is one of the most widely used and efficient methods for removing salt and other impurities from seawater, making it suitable for drinking, irrigation, and other uses.
The process works by applying pressure to force water through a semipermeable membrane, separating salt and other impurities from the water molecules. This blog will provide an in-depth look at the reverse osmosis desalination process, its benefits, and its limitations.
The physical phenomenon known as osmosis occurs when two liquids with different concentrations that are separated by a semi-permeable membrane come into contact and naturally try to balance each other out. Lower-concentration liquid passes through the membrane in the direction of the higher-concentration liquid.
In reverse osmosis, water tends to flow from a higher concentration liquid to a lower concentration liquid through the RO membrane, and then produce usable water. The permeate is the freshwater that produces water, and the remaining concentrate is brine.
Reverse osmosis is a type of filtration, which mainly uses semi-permeable membranes to block larger molecules, salt, and other pollutants in seawater through its small enough gaps, allowing only pure water to pass through, thereby achieving the purpose of seawater desalination.
Reverse osmosis is the process of forcing seawater through a semipermeable membrane that lets water molecules pass through but keeps out all other contaminants, including salt. Below is a step-by-step breakdown of the reverse osmosis desalination procedure:
Step 1: First set up the reverse osmosis seawater desalination system, and install a water inlet pump at the source of seawater.
Step 2: Preliminary treatment of the introduced seawater to remove impurities such as seaweed and other organic matter.
Step 3: Pressurize the treated seawater to pass through the half-membrane, where only water molecules can pass through the half-membrane, and salt and other impurities will be blocked.
Step4: Pump the produced fresh water into closed containers for storage, undergo secondary treatment (such as remineralization and chlorination processes), and then transport and use
Step 5: The remaining influent water and salt solution are diluted and discharged back to the ocean.
Most of the arid and severely water-scarce regions (such as the Middle East, the southern United States, Australia, etc.) have widely used seawater treatment systems to better meet the water needs of local people’s life and production. The seawater desalination process can effectively remove about 3% of the salt in seawater. Seawater desalination has the following advantages:
Seawater treatment is mostly a modular system, the compact design of the system can save economic costs, and it is easy to install and move. Ideal for municipal or commercial potable water applications, providing large volumes of usable water while saving space.
The current water source situation is very worthy of attention, not only to protect water use but more importantly, to increase available water resources. With more than 95% of all water on Earth, the ocean happens to be a very good choice as an available resource for drinking water.
There is another way of desalination treatment is a thermal variant. Its working principle is similar to the water circulation system, which evaporates water and then condenses it to produce clean water. This method can effectively remove unwanted particulate matter, but the work efficiency is low, and the amount of pure water produced is not as much as the RO system.
The water after reverse osmosis treatment is very pure. And we also need to put the minerals in the water that people need back into the water, which involves the process of remineralization, which can also be used to adjust the pH of the water.
The advantages of the seawater treatment system are so obvious that clean and safe water can be obtained very well, so why do some places still not use the system? Precisely because of some limitations of its system:
The reverse osmosis membrane is relatively fragile, and it is easy to cause membrane fouling, which affects the use effect and shortens the life span. It is very necessary to pretreat seawater, which can filter out some larger pollutants and impurities and reduce the loss of membranes.
The reverse osmosis system will continuously pump seawater, pressurize and force seawater into the membrane container, which is a constant flow process. In some systems, the necessary pressure can even be as high as 1000 psi (69 bar). In reality, it is possible to retrieve the osmotic pressure energy that has been stored in the concentrate, which lowers the overall cost of energy.
Many developing countries do not have the ability, resource construction, and operating costs to carry out seawater desalination system projects. Moreover, the seawater desalination process also needs to consume a lot of economic costs to operate. Compared with the treatment costs of groundwater and other surface water sources, marine treatment systems are obviously more expensive.
Although desalination systems are becoming commonplace in the market, certain regions require higher concentrations due to greater water demand. According to incomplete statistics, nearly 20,000 seawater desalination plants have used these systems. Among them, the Middle East and North Africa account for a large part, and seawater desalination machines are mostly used in these regions.
Although the use of seawater desalination systems in the Middle East and other regions continues to expand, it is expected that the use of Asia, South America, and other regions will gradually increase in the future. The technical upgrade of the system is directly related to the output of pure water, and the system upgrade will also reduce the energy consumption required for water production, so the seawater desalination system will become more popular.
Seawater desalination mainly uses reverse osmosis technology to separate water molecules from seawater to obtain pure water. The advantages of desalination are significant and many industrial and commercial production activities benefit from it, such as power plants, oil fields, and other industrial uses.
Brother Filtration offers a variety of filtration solutions and has more than 15 years of experience in the water treatment industry. You can trust us at any time and get in touch with us right away because we offer professional technical guidance and high-quality service.