Desalination of water: methods and installation

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2020-04-13 14:00:25

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Scientists believe that humanity has come to a period, when fresh water will spark conflict. To solve this problem in only one way - to find the optimal method of desalination of water.

What is desalination of water

Any liquid in its composition has a certain amount of salts, microorganisms and minerals. Purification of natural water or tap water removes from it harmful substances. But sometimes she has composed a large number of salts that make it unfit for consumption.

The Desalination of water – is to decrease the concentration of dissolved salts. The procedure can carry a total character, when the liquid is deprived of any salt content or partial, when there is a given amount of salt.

Methods

Complete desalination is conducted in the following ways:

  • Distillation, the thermal method.
  • By means of ion exchange.
  • By electrodialysis.
  • Membrane reverse osmosis.

Partial removal of salt is achieved when using these methods:

  • Lime.
  • Barite softening.
  • N-cation exchange.
  • Freezing.

Methods of desalination of water has a cost both financial and energy. The choice of processing method depends on the salt content in the initial liquid, plant performance, cost components of the process (heat, electricity, reagents). Each method has its advantages and disadvantages using technical means.

desalination of water

Partial desalination

Devoid of all impurities water is used in many industrial processes and is necessary for internal use to a very limited number of people. For domestic use requires a water demineralization to a certain extent. Most often occurs softener liquid method of cataniavia.

In the process is to replace the hard salts of the cations of hydrogen, which, in turn, reacts, destroy bicarbonate ions. The products form a compound which is excreted in the form of gas. The degree of purification is measured by the number of the extracted calcium carbonate.

Water Distillation

The Desalination of water using the method of distillation is the oldest and widely used today method. The advantage is its universal accessibility, but the downside – the high cost of the process. For water without additives is used, the distillers. They represent the evaporators are of several types, the difference between which consists in the design, type of energy used. The most common – steam and electric machines, characterized by high cost and large energy consumption.

The Unit is a boiler (or boilers) low pressure, where the liquid turns into steam and separates the concentrate of salts. To get the maximum cleaning in the apparatus the temperature reached a slow boil. In this mode, the heavy impurities do not get into condensing the distillate. One option to reduce cost is to increase the number of stages, but such a setting entails a large initial investment.

The distillation Equipment, in addition to consuming large amounts of energy has an impressive cost of all parts. To ensure a high degree of purity can expensive pipes, valves, heat exchangers, evaporators, made of quartz or platinum. Other materials are unsuitable.

methods of water desalination

Electrochemical method

The Essence of the method is to pass water through the electric field, thus there is transfer of salt ions – the cations are distributed in the direction of the cathode and anions to the anode. The system has three compartments, which are formed by using the cathode and anode diaphragms. In the middle compartment is water prepared for the desalination.

Through the stream flow a constant electric current, which is sort of salts on the cathodic and anodic diaphragm. The method is very expensive equipment costs and costs of electricity, therefore not widely used.

installations for desalting water

Ion exchange

The Most reliable method that achieves water desalination, – ion exchange method. To precipitate impurities in this way allows you to get a more clear fluid for a short period of time, which is important for industrial desalination. Method is the most cost-effective and gives the best cleaning result.

The Method is based on removal of the liquid cations and anions of salts, the cleaning result can achieve different degrees of demineralization,until the complete removal of the salt agents. Desalination of water by ion exchange takes place in the presence of ion exchangers which constitute the water-insoluble polymers containing a movable ion. When conditions prepared by the polymer enters into exchange reaction with ions of salts of the same sign. Placed in the aquatic environment, the resins swell, increasing in size by 1.5-2 times.

With the passage of time the collect ion exchangers dissolved in water salt and compacted. Saturated ion-exchange resins are regenerated, followed by cleaning. The products obtained from saturated ion-exchange resins are referred to as "the eluates", they include solutions of salts and alkalis. Some of them are valuable substances, therefore they are utilized as valuable components.

demineralizata the water

Reverse osmosis

Technological progress and began to be a lack of fresh water give rise to new technologies for desalination and demineralization. A popular way is becoming a method of processing via reverse osmosis, reliability, he ensures the development of membrane technologies. Industrial interest is due to the relatively low energy consumption. Most devices of this principle are used for purification of river water, where their effectiveness is proven many times.

For domestic use installations for water desalination based on reverse osmosis principle, suitable both in terms of energy consumption and the quality of the product. The principle of reverse osmosis is the passage of water under pressure through a membrane that is impermeable to dissolved salts and other impurities. The process of demineralization of water to provide a synthetic semi-permeable membranes, which can't hold some water-dissolved gases (chlorine, carbon dioxide, etc.).

Method of reverse osmosis cleanses water from all impurities, there is a complete demineralization, which is harmful to the human body. In most cases, the average man has to choose between tap water or processed using any filter. The lesser evil is water, devoid of all natural components.

Today, in some countries there are already factories for the production of drinking water, where desalination using reverse osmosis method, and as a complementary tertiary treatment of her withdrawal of dissolved gases. To give her a normal condition, approximate to the natural plants in the purified water add the required salt concentration is verified.

water filtration

Pros and cons of the basic methods

Each of the methods of desalination of water has both positive and negative qualities. Having considered them in detail, you can understand which one to prefer:

  • Ion exchange helps to get the most pure water system is reliable and does not respond to the salinity of the original fluid, requires little equipment costs. The process of demineralization occurs with minimal loss of water flow. The disadvantages of the method is the rapid contamination of the environment with harmful chemicals, high cost of the reagents, the system gets dirty easily and require frequent replacement filters. Recycling of waste and filtering of the parts is fraught with difficulties.
  • Distillation. Installation for the desalination of water, based on the thermal method is used without application of chemical substances, demonstrate good quality of the fluid secreted in the process heat can be used for other purposes. A distinctive feature of this method is the ability to eliminate dissolved gases. The disadvantages of the method are: large power consumption, the need for water, maintenance costs installation (clean all parts), high cost of equipment.
  • Membrane systems are distinguished by simplicity to its original state of water, for the process does not require chemical reagents, easy to maintain. Negative qualities are: preparation of water to process a large volume of water to ensure the operation of the apparatus, large power consumption, which affects the cost of the final product.

Desalination at home

Water Filtration – the most affordable method of purification. For desalting of sea or well fluids at home there are two common methods:

  • Capacity of water to put in the freezer and leave to incomplete freezing. Salt water does not freeze, the ice should melt, and can be used immediately. For extra cleaning should skip melt water through any household filter. The method is called cold distillation.
  • Evaporation. Take two containers of different sizes, the big pour marine/salt water, less is left empty and placed in large dishes. The entire structure can be supplied for heating toplate or leave in the sun, having closed a cover. It is necessary to achieve a slow boil in salted water. Couples deprived of salt will concentrate in empty containers. The evaporation process in the sun will flow much slower. In this method, it is quite a small amount of drinking water.

Desalination, and desalination of water artisanal ways possible, but inefficient. The best option would be the acquisition of household units for cleaning.

the process of desalination of water

Domestic installation

For domestic use most often required system for purification of water. Water filtration can be done in several ways:

  • The Most simple and affordable – a pitcher with replaceable filters.
  • Nozzle filter on the faucet.
  • Table water filters.
  • An Embedded system carrying out the cleaning liquid depending on the placement (only in the kitchen, at the entry point of water supply to the house, multi-stage filters for cleaning water from artesian wells, etc.).

None of the domestic systems cannot completely eliminate salt from the liquid, but to soften the hard water in the state. In this case, you must know what elements it is full, to find a system, cartridges for water filters or reagents. The process of desalination requires overall apparatus, a large area for installation, a large financial investment and the availability of the service system that is inaccessible to a wide range of consumers.

cartridges for water

Domestic cleaning

Today widely following types of water purification:

  • Carbon filtration. The device is a container filled with charcoal, or activated coal. Water passes through the filter, is cleaned from chlorine, oil-containing items, pesticides, microorganisms, bacteria, etc. the Filter is affordable, durable and easy to operate.
  • Fine cleaning. This kind of filters is divided into two types – single-function and multifunction. For any choice of the service required – to constantly change cartridges for water, replace valves, etc.
  • Coarse. Remove large pieces of contamination (sand, rust, sediment, etc.).
  • Deep cleaning. This type of filters are system with reverse osmosis, multi-stage filters, etc.

In most regions of Russia need only additional water treatment as the water resources in the country enough. The only region where there might be a shortage of fresh water – the Crimea, which may need industrial plants for seawater desalination. All devices for carrying out the processes have the patent. Desalination and desalination of water should be made on evidence based methods with mandatory testing results in the laboratory.


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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

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