Seawater desalination – benefits and procedures

Drinking water is a valuable asset. Not only in the developing countries is there not enough available to supply the population enough. Even in particularly warm areas, it can be scarce. However, many countries that are located directly by the sea do not have enough water. The reason: seawater is not drinking water, because the contained salt would dry out the body. Animals and plants also do not tolerate salt water. This is where seawater desalination comes into play, with which the salt is filtered out of the seawater to make it into drinking water. How this works is explained below.

Ein Strand an dem man mit Meerwasserentsalzung arbeiten kann.

Seawater desalination for more drinking water

The seawater plays an important role due to the limited availability of drinking water. But to use the water, a desalination of seawater is required. Along the Persian Gulf and the Red Sea, more and more desalination plants are emerging in the Middle East in order to be able to provide enough water for the residents. Around 20 million cubic meters of drinking water are produced each day. In Saudi Arabia, about 70 percent of the water is already produced by this process. The largest desalination plant is currently in Dubai. Two billion liters of seawater are processed every day in the Jabal Ali by seawater desalination to drinking water. Producing drinking water from seawater, which costs as little as possible, could be a very important step for drinking water and nutrition throughout the world.

Dubai, eine Stadt, welche ihr Trinkwasser überwiegend durch Meerwasserentsalzung gewinnt

Different ways of desalination of seawater

Desalting can be done with different processes:

• Seawater desalination by an evaporation technique

A widespread possibility is evaporation technology. Here, the seawater is heated in large facilities. Afterwards, the water rises as steam. It cools down, drips into a pool and thus produces the drinking water, which contains no more salt. The water vapor is collected and cooled, so that it condenses again and the water vapor becomes liquid water without minerals. Minerals are added to the desalinated water afterwards.

• Gas or oil fired desalination plants

The drinking water can also be obtained by gas or oil fired desalination plants. Especially in the oil-rich Gulf states, this method is used.

• Seawater desalination by reverse osmosis

On the offshore island of Heligoland and the Canary Islands, drinking water is extracted through the reverse osmosis process. In this chemical process, the seawater is forced through membranes under very high pressure to reduce the salt content. The plastic membrane lets the water molecules through, but retains the salt components due to the tiny holes in the nanometer range. On the one hand, salt-free water is produced and the brine stays on the other side.

• Freezing process

The freezing process cools the seawater, forming ice crystals. These are free of salts. The problem, however, is that the ice crystals have to be washed, which in turn causes a great need for fresh water.

Seawater desalination is becoming increasingly important

Seawater desalination will be of great importance in the future, because supplying the whole population with clean water is becoming increasingly difficult due to a lack or contamination of existing water. Seawater desalination is already the main source of drinking water in the oil-rich Gulf States. The Arab states have a very high water demand, since only two to three percent of the rain falls on earth here. The groundwater resources are thus very scarce. In addition, it is getting hotter due to climate change. However, desalination requires a lot of energy to operate the plants, which is not readily available in many regions. With reverse osmosis, for example, due to the high pressure per cubic meter of drinking water, an energy input of around 3 kWh must be expected. Thus, the problem of large drinking water shortages will not be so easy to solve in all regions. On the coasts, where there is a lot of wind and in the Middle East, where there is a lot of sun, this energy could be used for seawater desalination. Solar seawater desalination plants desalinate the seawater with the help of solar energy. This is ecologically more sensible than seawater desalination in the Middle East with fossil oil-fired plants. These could all be innovative solutions. But researchers are increasingly working on methods to develop systems that require less energy.

Conclusion

Simply turning the tap to enjoy clean drinking water has long been a given everywhere in the world. If no solutions are found, the vital resource of water could become increasingly scarce. Seawater desalination could be an efficient option. Accordingly, more and more systems are being built that can be used for this purpose. The seawater is thus deprived of salt to increase the drinking water supply of the population. At present, the cost of desalination of seawater is falling thanks to the large, modern and efficient facilities. In part, they only account for one fifth of the costs associated with the traditional production of drinking water. Seawater desalination with low energy expenditure is the goal of the researchers. They want to solve the problem of global water scarcity in the long term.