How to purify sea water


Water is the source of life, and access to clean drinking water is a basic human right that every country and government should guarantee. Currently, there are many ways to obtain water sources in water-scarce areas, including mining groundwater, artificially opening reservoirs and canals, etc. However, in many places on Earth, directly potable water sources are scarce, and groundwater cannot meet the demand. But at the same time, 71% of the surface of the earth is water. The only problem is that most of it is undrinkable because it is sea water with extremely high salt content. There is only a very small amount of fresh water, accounting for about 3%, and 2/3 of it exists in the form of ice in the polar regions of the earth and cannot be used directly.


Therefore, if there is a technology that can purify seawater at a low cost, it will definitely greatly improve the lives of local residents. Fortunately, we now have the corresponding technology, and there is more than one method. Below we’ll look at the process of purifying seawater and the different ways to do it.


Desalination is the process of removing salt and other impurities from seawater. Its purpose is to bring seawater to a level that humans can drink normally. Today, there are many desalination plants around the world, such as Israel, Australia, Saudi Arabia, etc. They use various technologies to purify seawater and ensure it meets drinking water standards.

What are the methods of seawater desalination?

There are two main methods of desalination: distillation and reverse osmosis.

1. Distillation:

Distillation is an ancient but practical method of desalinating seawater. It uses the principle that different substances have different boiling points. We heat seawater to turn it into steam, then produce small water droplets when cooled, and finally collect them. Through this process salt and other impurities are left behind, producing pure water. Although distillation is effective, it is not suitable for large-scale seawater purification. This is because it consumes a lot of energy to produce pure water. Therefore, although early seawater purification plants basically used this method, most of the new seawater purification plants now use reverse osmosis.

2.Reverse osmosis:

Reverse osmosis is the most commonly used method for seawater desalination today. Its principle is to use the extremely small pore size of the reverse osmosis membrane to separate other substances from water. It utilizes high pressure to force seawater through a semi-permeable membrane. The membrane allows water molecules to pass through while blocking salt and other impurities. This process produces safe and potable fresh water. Reverse osmosis is more energy-efficient than distillation, making it a popular choice for seawater desalination plants. However, it should be noted that seawater contains a large amount of salt and many corrosive substances. Therefore, multiple pre-treatments are required before reverse osmosis filtration. The main purpose is to reduce the number of large particles that can clog the reverse osmosis membrane and remove corrosive substances. That is to say, not all reverse osmosis water purification equipment can filter seawater, as the primary design purpose of many water purifiers is for convenient use in homes and vehicles, without considering the need to filter seawater. Therefore, pre-filters are mainly used to filter sediment, absorb discoloration, odor, and residual chlorine. Some particles that are too small for the pre-filter but too large for the RO filter are not removed. If the amount is small, it will not have a significant impact on the RO filter element. However, if the content of such particles in seawater is too high, it can easily cause clogging and damage the filter element.

What are the current challenges facing desalination?

1. Energy consumption: The operation of seawater desalination plants requires a large amount of energy and the operating costs are high.
2. Environmental impact: Salt water or concentrated brine produced by desalination by-products may harm marine life if not treated properly.
3. Cost: Desalinated water is typically more expensive than water from traditional sources, making it harder for low-income communities to obtain it.



Purifying seawater through desalination is a promising solution to the global water crisis. Despite the challenges, we should all believe that as technology advances and investment in R&D increases, desalination will become more efficient and cost-effective. By utilizing distillation or reverse osmosis, we can ensure everyone has access to clean and safe drinking water, no matter where they live.


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