How to make water fresh. Desalination of sea water: technologies of the modern world Do they make drinking water from sea water
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Over 97.5% of the water on Earth contains salt, and desalination is the process of removing salt from water. More than 60 billion liters of desalinated water are produced daily, with much of it entering the Gulf countries as drinking water. It is a challenge for engineers around the world to find a desalination method that is cheap enough to bring desalinated water to poor and remote areas of the Earth. Currently, there are several methods used to desalinate water in large quantities, including direct osmosis, carbon nanotubes, and biomimetics. However, evaporation is still the most common way to obtain desalinated water. All desalination methods produce hazardous by-products such as concentrated brine, which pose an environmental hazard to fresh water and animals. Perhaps you want to know how water is desalinated on a small scale for a variety of reasons, such as the desire to teach students if you are a teacher, or to quench your thirst if you suddenly get lost at sea. One method of desalination (using the Sun) is evaporation. The method is quite simple and can be performed in various ways, which are discussed below.
One of the most important problems modern world is the shortage of drinking water. The issue of its shortage is relevant for almost all countries and continents. The essence of the task is not the extraction or delivery of fresh water, but its production from salt water (https://reactor.space/government/desalination/) .
Relevance of the problem
If the water contains up to one gram of salt per liter, it is already suitable for consumption in limited quantities. However, if this indicator approaches the ratio of ten grams per liter, such a liquid can no longer be drunk. There are also a number of restrictions for drinking water regarding the content of microorganisms and organic components in it. Thus, obtaining a pure liquid is a rather complex multilevel process.
The most popular way to obtain drinking water is desalination. Moreover, this method is relevant not only for regions with an arid climate, but also for Europe and America. Making fresh water from salt water is The best way problem solving.
A variety of fluid deposits with a high salt content can be found in almost any region of the planet. There are no conditions for the reproduction of microorganisms. The brines lie at a relatively large depth, which excludes the occurrence of external pollution by hazardous chemical elements. You can also get fresh water from sea water. In this article, we will look at the most popular ways to solve this problem.
Distillation of water by boiling
This technique has been used since ancient times. There are several types of distillation in use today. The bottom line is to bring the liquid to a boil, and condense the vapor. The result is desalinated water.
Two popular technologies are used to produce a liquid in a significant volume. One of them is called multi-column distillation. The essence of the technology is to bring the liquid to a state of boiling in the first column. The resulting steam is used to transfer heat to the rest of the columns. This technique is effective. With its help, you can get fresh water on an industrial scale. However, this technology is very energy intensive. Therefore, in our time it is used quite rarely.
Flash distillation has been found to be more efficient. The essence of the technology is the evaporation of salty liquid in special chambers. In them, the pressure indicator is gradually reduced. Accordingly, to obtain water vapor, a lower temperature indicator is needed. That is why this technology is more efficient.
There are two more methods of distillation: membrane and compression. They arose as a result of the modernization of the first two technologies. Membrane distillation is based on the use of a hydrophobic type membrane that acts as a cooling coil. It retains water while letting steam through. Compressive distillation is based on the use of compressed (superheated) steam in the first column.
All of these technologies have the same drawback. They are too energy intensive. It takes four hundred and twenty kilojoules to heat a liquid from zero to one hundred degrees. And to change the state of water from liquid to gaseous, it will already take two thousand two hundred and sixty kilojoules. Equipment operating on the principle of the considered technologies consumes three and a half or more kilowatts per hour per cubic meter the resulting desalinated liquid.
Distillation by the sun
In southern countries, solar energy is used to carry out the distillation process. This allows you to significantly reduce the cost of desalination of salt water. To perform the distillation process, you can use solar panels or directly thermal energy Sun. The simplest in technical terms is the technology based on evaporators. The latter are special prisms made of glass or plastic into which salty liquid is poured.
As a result, solar energy raises the temperature of the water. The liquid begins to evaporate and precipitates in the form of condensate on the walls. The drops emerging from the steam flow into special receivers. As you can see, the technology is very simple. Of its minuses, it is worth highlighting the low rate of efficiency. It does not exceed fifty percent. Therefore, this technology is used only in poor regions. With its help, it is possible to provide fresh water at best to a small village.
Many engineers continue to work on modernizing the considered technology. Their main goal is to increase the output of such systems. For example, the use of capillary films can significantly improve the performance of solar distillers.
It should be noted that systems powered by alternative energy sources are not the main tool in obtaining fresh water. Although, their use does not require significant costs for the distillation process.
Other methods can be used to remove salt from a liquid. technical solutions. A fairly popular method of water purification is electrodialysis. To implement the method, a pair of membranes is used. One of them is necessary for the passage of cations, and the second is used exclusively for anions. Particles are distributed over membranes under the influence of direct current. Such a solution is often implemented in conjunction with solar and wind generators.
Reverse osmosis
Water desalination technologies are constantly improving. Reverse osmosis is becoming more and more popular these days. The bottom line is the use of a semi-permeable membrane. A saline liquid passes through it. As a result, particles of salt impurities remain on the side where the pressure indicator is excessive.
The reverse osmosis method is the most economical. Especially if it is used for desalination of water with non-critical salt content. In this case, one kilowatt-hour of energy can be enough to produce one cubic meter of water. Therefore, reverse osmosis technology is considered the most promising.
Results
Each water desalination method has its own characteristics. To produce fresh water on an industrial scale, it is necessary to select the most economical and efficient option. The reverse osmosis method is by far the most effective.
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We live in a unique place - the Earth, which, although it has a lot of land, is still mostly covered with water. We swim in it, we navigate it, and most importantly, we drink it. Unlike many animals, we are unable to get enough fluid just from fruits and vegetables – we need to drink regularly to stay hydrated. But only the body of water has another unique property - it is almost all salty. The percentage of fresh water is surprisingly small. Yes, we are used to it, because such water enters our homes and is sold in stores. But what if we suddenly did not have access to fresh water, if we only have sea water? Then it needs to be refreshed. Let's see how this can be achieved.
You will need:
This method is also called sublimation. It is easily implemented even in living conditions, although it will not provide a large amount of liquid.
Take an ordinary saucepan, into which salt water is poured. Next, you need to cover this pan with a lid and put on fire. Gradually, condensation will accumulate on its cover.
However, even when the cover is removed most of fresh drops will flow back into the pan, therefore it is necessary to slightly improve this impromptu device.
- A hole is drilled in the lid of the pot.
- A flexible tube is inserted into it, for example, a coil from a moonshine still.
- Its other end is lowered into an empty vessel.
- Next, you need to cover the tube with a damp cloth so that the steam in it cools.
- It will condense and fall into an empty vessel.
As a result, only salt will end up in the heated pan, and only distilled water will remain in the second vessel.
Please note, however, that there will be no salt in such a liquid at all, and therefore thirst will be quenched poorly.
It is better to pour a small amount of salt water into it.
With this method, special precipitating reagents are used. They interact with the salts found in sea water and form compounds that are insoluble. Therefore, they settle and they can be filtered out without any problems.
This approach has its disadvantages, in particular, the high cost of reagents, the slowness of the reaction, a large number of necessary reagents.
Therefore, this method is used very rarely, but in everyday life it is not used and almost never at all.
This method is predominantly industrial and has been used for a long time. It is based on the use of two semi-permeable membranes made of cellulose acetate or polyamide. Small water molecules can pass through them without any restrictions, while larger salt ions, as well as other impurities, are trapped and prevented further.
It is difficult to achieve desalination of a large amount of liquid in this way, and in everyday life such a method is difficult to implement - it is suitable for industrial enterprises.
This desalination method seems to be very simple in its idea, but in its implementation it is quite labor- and resource-intensive. The idea is based on the fact that salt does not get into the ice when frozen, because the formation of ice occurs only from water molecules.
The largest amount of fresh water in nature is found in all kinds of glaciers.
Usually the Eskimos resort to this method. They expose a container of salt water to frost, and then wait until ice crystals form there. This ice is collected and melted - and the water is drinkable.
Once again to the issue of obtaining suitable drinking water in extreme conditions.
What to do on a hike when drinking water is not provided on the way? For example, there will be swamps, lakes, rivers, estuaries, seas. But there will be no clean and fresh water.
Usually, they take special water-disinfecting tablets with them on a hike, remember grandmother's recipes for disinfecting water with herbs, disinfecting water with peroxide or potassium permanganate.
This is all well suited for fresh and relatively clear water. This, in principle, you can simply boil for about twenty minutes and calmly cook on it.
But what to do if the hike provides for a meeting only with salt water? For example, the southern coast of Crimea and the Kerch Peninsula, where there is something to see, have very few sources of fresh water.
You can, of course, buy fresh water. But in such places it is quite expensive. And if the day is arranged far from civilization?
It turns out that there is only one way out - to carry water with you. And this is somewhat inconvenient, to add a five-liter eggplant with water to a 15 kg backpack.
In order to avoid such inconveniences, an experiment was carried out to desalinate sea water using a distillation process.
What is distillation
Distillation- this is when the water boils, the steam above it collects, cools, turns back into water in the receiver tank.
Why does distillation purify water from salts? Because salts boil at more high temperature than water. Therefore, water evaporates first. Without salts. What to do with sea water.
What happens if the water that is being distilled contains substances that boil at a lower temperature? For example, volatile organic substances? They will evaporate first. Therefore, one of the principles of distillation is not to direct the vapor collector directly into the receiving device, but to let the water boil seriously.
Also an important principle of distillation is good vapor cooling. The performance of the device directly depends on the cooling efficiency. If part of the steam is not cooled, but evaporates, then, accordingly, less pure water will be obtained.
So, how did we carry out the distillation of sea water in practice.
Seawater distillation in practice
Location : beach north of the village of Podmayachnoe near the city of Kerch. To the nearest store with water, stomp for at least half an hour in the heat. There, of course, it is beautiful - cliffs, layers of fossils, etc. But it's hot.
Water source: Sea of Azov. Not very salty sea, salinity is about 10 grams per liter. Compared to it, the salinity of the Black Sea is 16-20 grams per liter.
Materials and equipment :
* two bricks;
* bonfire;
* tourist kettle;
* curved aluminum tube;
* Glass bottle;
* a hole in the sand;
* mug for sea water;
* a lot of firewood and a lot of patience
The distillation procedure is very simple. Sea water - in a kettle, a kettle - on fire. Hole in the ground. A glass bottle was buried in it at an angle. Only the neck protruded from the sand, into which the steam-transmitting tube was inserted.
Everything - the water boiled, passed through the tube into the bottle, where it cooled. For better cooling the bottle was poured with cold (relatively, of course) sea water. Salt water was added to the kettle as it evaporated.
Now know-how technology:
I. The first thing that was adjusted was the level of sea water in the kettle. Sea water should occupy less than half of the volume, preferably one third. This is necessary to increase the intensity of vaporization. It is not known why the pair in this case is formed more, but it turned out that this is so.
II. Further, the transmission tube must not be watered to cool the steam. The cooling water turned out to be insidious, and flowed down a tube (by the way, about 80 cm long) from below into a bottle of clean water. Accordingly, the taste of purified water was not very good.
III. Then, plastic bottle for the receiving device is better not to take. Because it is twisted by steam. Although, if there is no glass at hand, plastic will do. In the place where the camp was located, both plastic and glass bottles were present in abundance.
results: for 30-40 minutes of distillation in the described way, about 350 milliliters of water are purified.
conclusions
The tried and tested distiller perfectly purifies sea water. Salts in the resulting water are not tasted. Apparently, they are simply not there :) The cleaning process requires a fairly large amount of fuel. Thorough cooling of the receiving tank almost doubles the distiller's performance. A tested distiller, taking into account all sorts of corrections and problems, can provide 2-3 people with clean water for 2-3 days per day. In order to supply more people with clean water for a longer time, either a more advanced distiller is needed (which will make its design heavier and difficult to transport), or make a tried distiller personal equipment (each participant purifies the right amount of water for a day).
Thus, the studies carried out have shown excellent results of sea water purification by the marching method. Most importantly, the weight of the kettle and the steam tube did not exceed 500 grams.
Today in the world, the problem of drinking water- it is quite small. Africa, for example, is provided with this resource by only 30 percent of the required amount.
Other countries to this mainland carried out
drinking water deliverypossible, but this is still not enough. It was this situation that prompted scientists to think about whether it is possible to make drinking water out of sea water? In fact, perhaps even at home, although this is a long process. This will require a distillation cube or a moonshine still. In this case, the law of physics is used, according to which salts cannot completely dissolve in water. That is, after evaporation, the minerals remain at the bottom.sea water sweep
Having driven sea water through the moonshine still, after boiling it, you will get ready-to-drink drinking water with a minimum amount of impurities. In its composition, it is more like distilled water, which does not conduct electricity. Therefore, it is quite difficult to get drunk on it. But pharmacies sell the so-called "enrichers", adding just a few drops of them, you can get the water that the human body needs. So, in total, the production of drinking water from sea water costs a little more than the production of mineral water.
How to make drinking water from sea water in natural conditions?
It is not difficult to turn sea water into drinking water if you create a kind of moonshine from improvised means. This will require a hole, which is wrapped inside with a film, several large stones and hay. Water poured into the hole is covered with hay. Stones are placed on top, which are also covered with a film. After the water heats up, it will begin to evaporate, and when it becomes cool, it will condense on the stones. Of course, there will be very little water, but enough to at least quench your thirst.