Modern technologiesTechnologies

Converting salt water into drinking water

Processing salt water into drinking water – water desalination systems
Innovative water desalination methods
What is vacuum distillation?
Nanofiltration and reverse osmosis
Processing salt water into drinking water – a few words about reverse osmosis

Processing salt water into drinking water - water desalination systems

Converting salt water into drinking water is an extremely important process, considering that 97% of the water in the world is salt (sea) water. As we know, sea water contains a high concentration of sodium, magnesium, calcium and potassium ions. Interestingly, it is also rich in chlorides, unlike fresh water, which is dominated by carbonates. It is worth knowing that among salty water reservoirs there are more or less saline reservoirs. The Red Sea is the saltiest, with about 40 grams of salt per liter of water. By comparison, the Baltic Sea contains only about 5 grams. With the increase in the world’s population, the desalination process has become one of the most important, given the fact that there are regions where it is not easy to get safe drinking water.

The water desalination system has been known for years and means the reduction of salt and all other minerals from sea water. There are many ways to desalinate water: from the most primitive to the more advanced. We are all familiar with the phenomenon of evaporation or freezing of water. They allow us to obtain a product in the form of sweet drops of water. The most popular plants where we desalinate water are located in Jebel Ali in the USA and in the United Arab Emirates. During the year, employees of these factories are able to produce as much as 300 million cubic meters of fit water!

Innovative water desalination methods

So how to effectively desalinate water and which of the available methods can be the most effective? Today, the most popular treatment for water desalination is distillation. Here we have in mind in particular vacuum distillation. Researchers have also developed a solar distillation process. It’s all about solar panels. This method is not so popular yet, but so far it seems to be the most promising in terms of costs. The neutral impact of this process on the environment is also a big advantage. Known water desalination treatments are also: reverse osmosis process, nanofiltration and freezing.

What is vacuum distillation?

We have known and used vacuum distillation for years. This is one of the overarching ways that allows us to obtain fresh water from the sea. So what is the vacuum distillation process? Simply put, this treatment consists in separating volatile compounds from a liquid that is a mixture. Here we exploit the tendency of such compounds to evaporate from the mixture at low atmospheric pressure, without the need to increase the temperature. Under such conditions, these compounds reach a higher speed. If we enclose this mixture in the so-called distillation tank and lower the pressure, then the volatile compounds will aspirate to evaporate. These compounds are then captured and under the influence of the condensation process they return to their original state of aggregation – liquid.

This procedure can be performed on a small and industrial scale. A vacuum distillation device does not have to be as complicated as those in specialized oil refineries. Equipment in refineries is designed to separate up to tens of different hydrocarbon compounds. Another thing about water desalination. Things are easier here. The vacuum distiller is therefore an effective water desalination device.

Nanofiltration and reverse osmosis

The processes that we will discuss in this paragraph are somewhat identical, considering that they belong to pressure membrane processes. What does this mean in practice? In both methods, let’s use the phenomenon of diffusion, as well as the force effect. Membranes work based on this effect. It is taken from ultrafiltration. In the nanofiltration process, we use a semi-permeable membrane. It has large pores, so we have greater water permeability compared to reverse osmosis, in which these pores are negligible. The membrane performs the function of separating monovalent and polyvalent ions, the latter of which are destroyed. The advantage of nanofiltration is that it needs low pressure to work properly, which saves energy.

This process also allows us to retain approximately 50% more fresh water compared to the reverse osmosis treatment. On the other hand, the residues of some elements in the water, through which we obtain hard water, can be regarded as a defect. Here we have in mind calcium and magnesium, the presence of which in water manifests itself, for example, in the sediment in the kettle. Sounds familiar, right? The advantage of this process is the fact that harmful pesticides, nitrates, heavy metals, viruses, bacteria and calcium carbonate are removed from the water.

Processing salt water into drinking water - a few words about reverse osmosis

Reverse osmosis, compared to nanofiltration, is a desalination system in which we use the phenomenon of solvent diffusion through a semi-permeable membrane. This membrane separates solutions, provided that we are dealing with solutions of different concentrations. Where does this nomenclature come from? Compared to spontaneous osmosis, reverse osmosis can go from a solution with a higher concentration to a solution with a lower concentration. In this way, we obtain a significant difference in the concentrations of both solutions, but for the process to proceed properly, we must engage a pressure membrane with a higher value and direct it in the opposite direction than the osmotic pressure that occurs naturally.

As you can see, scientists have developed a lot of ways to obtain drinking water from the sea. The question is whether the current most popular methods will be superseded in the future and will they solve the current global problems of drinking water shortages in selected regions once and for all?

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