Seawater desalination

Seawater desalter

1. What is a seawater desalination unit? Scope of application.

2. Seawater desalination by reverse osmosis method

2.1 Description of the principle of operation.

2.2 Scope of application.

3 Comparison of Wagner seawater desalination units with other manufacturers.

1. What is a water desalination unit? Scope of application.

With the growth of the population of the Earth more and more often and more acutely arises the question of availability of the main resources necessary for human life. First of all, we are talking about water, as the quality of vital activity of the organism directly depends on the fulfillment of the daily need for drinking water.

Lack of fresh water available from the internal water resources of the earth can be compensated by using sea water, but due to its unsuitability for consumption the question arises "how to turn dead water into living water?".

The answer to this question is the creation of a desalination system, the main function of which is to process seawater to remove salty particles. This is a labor-intensive industrial process, which, however, does not indicate that salt-free water is potable. Since there are other trace elements present in ocean water besides salt, the degree to which they are present in the final product dictates its applications.

Fig. 1 - Installation diagram

For example, on seagoing ships, where it is less profitable to carry a supply of potable water loaded from land than to produce it on site, there are several types of desalination units. Some produce water for the needs of the human body, others supply distilled water for the operation of machinery, and still others recycle water suitable for washing the deck, for example.

In addition to individual examples of shipbuilding with relatively small water requirements, there are other examples of desalination systems. These are zones with desert and arid climate, as well as island type of settlement. The lack of local water bodies is compensated for by the presence of the sea around, and in this case the scale of processing means serving national and state needs. Residential areas, industrial clusters, and business infrastructure are all powered by water that has undergone desalination.

Given the enormous production capacity, the question of profitability, productivity, and availability of production is an issue. When working with one of the main natural resources, mankind has to take into account the fact that desalination must not harm the environment through the emission of waste products, and must also have proven safety for humans. Therefore, it is the ratio between the quality and the cost of the produced water that formed the basis for the development of modern desalination systems.

Because of its high toxicity, the chemical method of desalination is less and less common: this method uses a chemical compound based on barium and silver, which acts on the salt particles, transforming it into a solid state. The heavy sludge was easily removed from the water, but removing the chemicals themselves proved to be a much more difficult and expensive process.

With the wave of popularization of "green", i.e. environmental science, there is more and more talk about natural ways of extracting drinking water through vaporization. This method is environmentally friendly and extremely simple to use: sea water is added to a special structure and heated. As a result, fresh steam is produced and decanted into a separate tank. This method of desalination is called distillation. But it is extremely difficult to build a huge distillation plant capable of supplying water to a city.

2. Seawater desalination by reverse osmosis.

There is another available method, which by its qualitative characteristics of safety and simplicity surpasses even vaporization. Its essence is as follows: salt water is passed through special semipermeable membranes under high pressure, resulting in a clean, devoid of any impurities, drinking water. This type of desalination is called reverse osmosis.

2.1 Principle of operation

Reverse osmosis is a physical process in which a more concentrated liquid is transformed into a less concentrated one. In this case, the unit of concentration is sea salt.

The density of the membranes is so high that only H2O molecules can pass through it, which under normal conditions would not be sufficient, so the intense pressure is the lever that triggers the purification process.

2.2 Field of application

The production of reverse osmosis plants is so affordable that it is believed - one dollar invested will yield 16 tons of fresh water. However, this was not always the case: at the dawn of the introduction of this system, it was expensive and used only for military purposes, on submarines. Today, the prospectivity and cheapness of production make it possible to introduce reverse osmosis technology everywhere - from the largest stations to kitchen taps. At the same time, this type of desalination has its own complexities and nuances that must be taken into account.

Semi-permeable membranes retain almost all elements contained in water, but allow gases to pass through: oxygen, chlorine, carbon dioxide. As a result, the resulting water may have a specific flavor. In addition, free of impurities, water is deprived of those that are necessary for the human body, so additional mineralization and enrichment of such water is another step in obtaining quality drinking water, complicating the process.

At the same time, in the case of serving medical needs, water obtained through reverse osmosis technology is considered conditionally sterile and is widely used in medical institutions.

Also do not forget that water, which does not contain salts and other technological impurities, is widely used in industry for maintenance of various mechanized installations that need cooling with "empty" water.

The reverse osmosis semi-permeable membrane provides water with a level of purity that is still being debated, even though this method was introduced into widespread use back in the 1960s. The whole point is that some researchers consider this type of completely de-mineralized water to be nothing more than a solvent that does not replenish the necessary amount of nutrients.

Another point of view of experts, on the contrary, indicates that so budget and widespread method of obtaining clean drinking water is the only correct way to develop desalination systems. Their arguments incline to the fact that it is now, in the age of high growth of industrial and urban development potential, that water should be, first of all, free from nitrates and other pathogenic factors that can have a negative impact on the human body and cause various diseases.

3. Comparison of Wagner seawater desalination units with other manufacturers

High demand gives birth to supply, and high competition leads to the fact that in the market of modern desalination systems, working on the method of reverse osmosis, can lead only those samples that are able to offer more performance and durability for less money.

Industrial reverse osmosis systems "Wagner" allow supplying drinking water to all key positions of human activity: cooking, drinking, use in hygiene and sanitary procedures - both for personal purposes and for places of mass gathering, including children.

The Wagner system ensures product quality that meets all SanPin standards for drinking water.

In addition, the Wagner system demonstrates excellent affordability, not only in terms of pricing, but also in terms of application. The compact size and high-tech control methods allow the Wagner system to work in small spaces, even in private homes.

The simplicity of operation compensates for the possible difficulties that are usually associated with the use of additional water treatment systems: in the case of Wagner, there are no operational problems to be solved, as the system can be customized to meet the individual requirements of the application.

In the case of other reverse osmosis systems, standard type membranes are used, whereas the "Wagner" system implies quite wide possibilities of correlation of the result: the efficiency of purification from impurities can be from 85% to 98% depending on what tasks are intended to solve the use of this water.

The problem of additional mineralization, which will saturate drinking water with natural elements, is also solved: if necessary, water is enriched with all the necessary elements of the Mendeleev table.

Don't know what type of equipment you need? Wagner system specialists will help you to choose the right model, as well as arrange for regular chemical maintenance of membranes, which will keep the system working at the proper level for a longer period of time.

Not sure how to operate this machine? "Wagner" is equipped with the ability to set automatic operation, so you will not need to intervene in the operation of the system.

The domestic production of "Wagner" allows you to guarantee full service in the shortest possible time, with the support of a technician and dispatcher. In addition, the Russian origin of "Wagner" makes its price lower than foreign counterparts.

What useful things you will learn from the content of this article:

1. What seawater desalination is used for

2. the field of application of seawater desalination

3. methods of seawater desalination

4. Comparison of seawater desalination methods

5. Conclusions and recommendations

Desalinated seawater has been used for various needs for a long time. But before it can be consumed, it must be purified from sea salt and other impurities contained in seawater. Everyone knows that sea water is salty. And using it for any purpose without pre-treatment is not recommended. There are various methods of desalination of such water. And for each specific case a different technology and equipment is selected. In the modern world, it is an alternative to fresh water sources. Which are not only disappearing, but many change the composition of water. Especially desalinization is relevant for objects located near the source of salt water. In this way it is possible to save significantly on pipelines and electricity. Most often, seawater is used in various spheres of industry and agriculture. Shipping and oil rigs cannot do without desalinization. And in the household segment it is sea water that is sometimes purified. It concerns settlements remote from big cities, hotels and sanatoriums located near water.

Mankind has been familiar with desalinization for a long time. And every year the technology, as well as equipment, is modernized. Costs of resource consumption are decreasing and productivity is increasing. But you can not just take and put any filtration system. Given the distinctive features of sea and fresh water. Due to its higher salinity, sea water is more aggressive, although it contains a lower concentration of other harmful substances. The deterioration of the ecological situation also negatively affects its quality. And if desalination used to be enough, nowadays more thorough treatment is required. When selecting technology and equipment should be as careful as possible to pay attention to the nuances of both the technology itself and the necessary requirements. There are several methods of desalination and each has its own advantages and disadvantages. That is why it is so important to work out all the subtleties.

1. Why seawater is desalinated

Water is a vital element of all spheres. This applies to both domestic. As well as industrial use. Of course, fresh water bodies or other sources are a priority. But due to the deteriorating environmental situation. such sources are becoming fewer and fewer. And their water quality is deteriorating. So new sources of water are becoming necessary. Seawater is one of them. But. As stated earlier, it is not used without treatment, i.e. desalinization. In addition to a large concentration of salts, sea water, like any other water, contains harmful impurities. They can be in different amounts, depending on many factors.

Most often, seawater is used on ships or industries located near the seas. For ships, special autonomous devices have been developed, which can safely and quickly treat a large volume. In addition, the safety and environmental friendliness of the technology is very important.

Different applications require their own degree of contaminant treatment. For example, for drinking water treatment, strict regulations apply. For technical water, the regulations are less stringent. If we consider ship desalination, in this sphere water is also used for steam generators and accumulator batteries. And this is also a different degree of filtration.

Technologies developed for desalination are constantly being improved. This does not mean that the existing methods are not relevant. They are simply modernized for new conditions, energy consumption is reduced, productivity and service life are increased. In other words, all costs are minimized and output is increased. But it is pointless to just take any desalting equipment. Each method is oriented to certain working conditions.

The methods can also be combined to adjust the degree of purification or for the best results under specific conditions.

Fig.1 Seawater desalination on ships

It is worth realizing that process water can be purified less completely than drinking water. Chemical substances are used to accelerate the reaction. But this method of treatment is not recommended for desalinization of drinking water. Reagents can remain in the water and adversely affect human health. And the installation of additional filtration elements is a new cost, increasing the size of installations.

Besides, all chemical agents require timely resupply, which is not very convenient for long-distance ships. That is why it is so important to choose the right desalting method and equipment. Take into account all subtleties and specifics of treatment.

2. Scope of application of seawater desalinizers

Desalination is required where fresh water is not available. Or its transportation to the destination is too complicated. For example, when a reservoir or well is several thousand kilometers away. You will have to lay pipes and ensure uninterrupted supply. This is too troublesome and not profitable. Especially if there is another source of water nearby. Ships, industrial enterprises, agricultural farms and even household consumption fall into these categories.

Shipping. In this area, seawater is the only reliable and constantly available source of fresh water. Some ships call at ports to replenish fresh water supplies as in the old days. But it is not always convenient and sometimes it is not possible. If they are long-distance ships or submarines, they cannot be resupplied for a long time and need desalination systems. In addition to drinking water, technical, process, feed and other water is needed.

Oil rig. Another application where water desalination is required. Such rigs are located in the seas and oceans. They are reached more often by air transportation. And, of course, it is inconvenient to constantly supply fresh water in this way. Therefore, the towers are equipped with an autonomous desalinization system.

Agriculture. This sphere uses water for irrigation, drinking. And requires the consumption of a fairly large volume daily. Desalinizers are necessary in those places of agriculture, where for climatic or other reasons there is no access to fresh water, such as deserts and steppes.

Domestic use. At the moment, this is the category with the least seawater consumption. Most often these are sanatoriums, hotels and other resort facilities with salt water wells. Cafes and restaurants can also be added here.

Summarizing the spheres of application, we can say that all objects that are near the sea consume sea water. It is less energy intensive and thus costs can be reduced.

The equipment is selected based on the method of filtration and the specifics of production. The main factors are the capacity, method, operating costs and the cost of the equipment itself. Almost any system can be modernized.

3. Seawater desalination methods

There are several desalination methods that are effective and used in various applications. They can be used to filter not only sea water. But also any salt water. Any method presented has proven to be an effective desalination method. It is important to remember that different areas require different filtration methods. It is possible to combine an already established treatment scheme with desalination by adding new filtration elements.

Fig. 2 Wagner desalination plants

Seawater can have different salinity levels, depending on the region and the environmental situation. This should also be taken into account when choosing a technology. Some methods are able to eliminate salts only in small concentrations, while others are focused on the maximum. And now let's analyze the main methods that are used in desalinization:

With the help of chemical means. As is already clear from the name, the main cleaning element is reagents. Most often barium or silver salts are used. When chemicals are added, a reaction starts and a precipitate is formed. This method is suitable only for purification of technical water. Yes, the chemical reaction is fast and it is possible to ensure the removal of salts in a large amount of water at one time. But it will require a significant volume of reagents. It will also require a doser. It is he who will control the supply of chemicals in the water. If the added substances will be a lot, they will remain unused and will only worsen the composition of the water. If not enough is added, the method will simply not be effective. Therefore, before adding reagents it is worth calculating their amount, depending on the concentration of salts and other impurities. It is possible to combine methods to achieve the most positive effect.

The advantages of the method are in the speed of reaction and high productivity. Of the disadvantages can be distinguished narrow focus, only for technical water. Aggressiveness of substances and their consumption. Therefore, this method is not used very often. Or only for a certain type of water. To correct the composition will require the installation of additional purification modules.

Evaporation. Another well-known method of desalinization, which was widely used in shipbuilding. The essence is the conversion of water into vapor with the help of special equipment called a distiller. It can be both household and industrial. It is possible to process a large volume of water, but energy consumption increases significantly.

Of the advantages of the method can be highlighted environmental friendliness, the possibility of desalinization of large quantities of water. From the disadvantage - a large consumption of electricity. Also with constant use, the tenons are formed on the scale, which is quite difficult to remove.

Since heating is a very high consumption of resources, distillation is not the most common method of desalination. Modern plants are, of course, already more modernized, but it still loses out compared to other methods.

It is very common to find this method in camping equipment. To desalinate water in extreme conditions, you need to heat it. But such devices allow you to desalinate a very small volume of water. And it is more likely to be suitable for very urgent situations. But just in case, the equipment can be useful. Recently, during construction and repair of marine vessels, yachts, boats, the method of evaporation is replaced by desalination by reverse osmosis, because such units have greater productivity, compactness, minimal power consumption.

Ion substitution. This method is based on the use of ionic resin. It consists of granules that attract contaminants, giving up sodium molecules. The filtration time depends on the initial water parameters. Such as temperature and percentage of contamination. In addition, the ionic resin itself comes with different characteristics and granule diameter. The method is more commonly used in heavy metallurgy.

The advantages of the method are, again, environmental friendliness and low resource consumption. But it is obligatory to replenish the feed material. And this is a cost of operation. Alternatively, the resin can be washed or regenerated. To do this, it is enough to wash with a strong salt solution. But then this concentrate must be utilized.

Reverse osmosis technology. One of the most modern, economical, and therefore popular methods of desalination of seawater, not only for desalination, but also for the removal of other substances. The filter is a special membrane. Its surface is porous. And the smaller the pore diameter, the finer the purification will be. But at the same time, the performance is reduced. The principle of action in the passage of water flow through the membrane. Thus, all impurities remain in the concentrate. And the clean water stream goes to the consumer. This is one of the first methods of seawater purification, which is still relevant today.

When using this technology, it is obligatory to control the pressure. When it rises, the filter element deforms. And the membrane ceases to fulfill its functions. Because simply it begins to pass all contaminants, including salts. With reduced pressure, the cleaning process itself will become quite long.

Of the advantages can be emphasized compactness of the equipment and low power consumption. Also the system can be modernized. For example, by installing a special controller, which will make the process automatic. Cleaning of the membrane is carried out by washing with ordinary water. If there are any deposits on it, due to the aggressive effects of harmful substances, it is soaked in a special solution. Among the disadvantages of the method are a large volume of water or concentrate, which goes for disposal. It is in it that all contaminants remain. If the water has a high concentration of salts, then the membrane will need to be changed more often. Well, and the last nuance is the cost of the equipment itself. Due to the high pressure required for desalination of water by reverse osmosis method it is necessary to install special corrosion-resistant marine pumps with high pressure. These pumps are characterized by high cost.

Despite the existing disadvantages, this method of purification is used almost everywhere. The point is not only in environmental friendliness, but also in versatility. Due to the fact that no chemicals are used, desalinated water can be used for drinking. To increase the service life of membrane elements it is necessary to pre-clean them from mechanical and organic impurities. All water, including sea water, contains large mechanical impurities. These can cause damage. You should not forget about timely flushing. After all, if the cells fill up, then the quality of water will significantly decrease. If you observe all the operating conditions, then the membrane will serve for quite a long time. Moreover, this method does not require any special conditions.

Electrodialysis. This technology is similar to membrane purification. But the water flow is not under pressure, but with the help of an electric field. Cations and anionites move oppositely, separated by a membrane. Such elements are more robust than in the reverse osmosis method. And can withstand higher loads. The advantages of the method are its economy and low operating costs. Also the main advantage is the ability to remove a certain type of salt. The membranes used are unpretentious to the original characteristics of water and can desalinate hot water.

Crystallization. This method is based on freezing. Fresh water at sub-zero temperatures turns to ice, and all the impurities in it take much longer to freeze. Therefore, a certain volume of water is exposed to cold. The resulting ice, having melted, can even be drunk. It will already be fresh water. Freezing occurs in several ways: natural or artificial. Of course, natural crystallization is a long process and is not possible everywhere. Therefore, artificial freezing is used more often. For this purpose, liquid butane is added to the water. The advantages of this method are not so many. It is a low consumption of resources. At the same time, the method is not environmentally friendly, since reagents are used. And it will not be possible to desalinate a large amount of water at once.

4. Comparison of seawater desalination methods

There is no universal method, which is suitable for any production and for any water characteristics. That is, for each sphere, even for each enterprise a different desalination system is selected. In addition, any method has its own requirements, as well as the equipment. There are more modern and not quite relevant methods. What is suitable for domestic use may not be acceptable for industries or ships. If it is necessary to desalinate a large volume of water every day, the chemical method or the installation of a distiller is quite sufficient. However, it is undesirable to use such water for drinking. For filtration from salts, electrodialysis or reverse osmosis is more suitable. They use only a membrane for desalination and do not involve any chemicals.

The main criterion is the conditions under which desalination can best take place. Desalination units can be installed either separately or in an existing treatment scheme. Reconstruction of an existing system is carried out if it is necessary to increase the capacity or replace the equipment. Also almost any equipment is subject to automation. If you buy a ready-made installation, controllers are most often included.

Do not forget about the maintenance of systems. The equipment necessarily needs to be checked. This checks not only the operability, but also any deformations, the need for cleaning or filter replacement.

Every year, the equipment is modernized. Why do this? To reduce resource consumption and increase productivity. These are the main criteria for modernization. Ideally, when desalination is handled by a single method without installing additional filtration elements. In addition, seawater contains not only salts but also other impurities. Therefore, the most universal technology is reverse osmosis. It allows not only to make water fresh, but also completely remove all contaminants. At the same time, such water can be used for domestic purposes. Because no chemicals are used in the purification process.

Fig. 3 Operating principle of the desalination unit

Before selecting a treatment technology, the water should be analyzed. To determine what impurities are present in it. Reverse osmosis technology and ionic resin are the best to cope with additional contaminants. But it will require pre-cleaning for the membrane method and salt solution for regeneration, for ionic resin.

Automation of the system is mandatory. After all, if the filter is clogged, it will not be able to perform its functions. And if you do not monitor it at all, then there will be deformation, in the case of membranes. And then restore the whole desalination scheme is possible only by replacing the filter elements. But, as a rule, the controller is already included in the complete set of ready-made systems. It allows not only to remind about the necessity of washing, but also to activate it independently. More advanced settings depend on the controller model.

5. Conclusions and recommendations

Desalination plants play an important role in every field of production. Naturally, such plants are only relevant when desalinating seawater. Thanks to a variety of methods and equipment, it is possible to select the most optimal scheme.

Much depends on the initial characteristics of the water. If there are too many salts, you can use reagents, in the case of technical water. Or install additional filtration elements. Such equipment is indispensable on ships. Where high water consumption is required.

The materials from which the equipment is made must be of high quality. Because salt water is quite aggressive environment.

For each specific case is selected a different method of purification. It depends on the concentration of salt in the water and the presence of other impurities. All equipment that is used in desalinization should be made of quality materials.

Today, a large number of different models are available on the market. They differ in size, performance, degree of filtration and technology. If you choose the optimal modification, you can significantly reduce costs and increase productivity.

Do not forget that each equipment has its own requirements for the original source. For example, the salt content. Or, in the case of reverse osmosis, pressure, water temperature. Exceeding the required parameters will lead to poor-quality or incomplete desalination, which negates the entire filtration technology. In addition, desalination of water must comply with all regulations. This is necessary for different degrees of purification. If you take batteries, for example. Which are used in the shipping industry. In this case, only completely empty, distilled water is suitable. If we consider technical, then in the possible relaxation, since it does not require such a thorough purification.

When choosing equipment, be sure to take into account all the subtleties, so that later you do not have to supplement the system. First, the water is analyzed, the level of salinity and the presence of other impurities. After that, it is calculated exactly the capacity that is needed. Calculations are made for the operation of the system. If you do not comply with all the requirements, the system will simply fail. This can be affected by infrequent washing of filters at high loading, low or high pressure, unacceptable water temperature.

One of the main factors is service. This applies not only to the filter elements themselves, but also to the components. If there are any changes, it is mandatory to adjust the system. This can be done by adding additional filter elements or pumping stations. This necessity is due to the reduction of the load on the equipment.

Also when choosing a desalinizer it is worth paying attention to the manufacturer. Price-quality ratio. Provided warranty and equipment of the device.