It is necessary to mark that in most cases water prefiltration by a filter comes true by a not one method, but their combination. Just the same complex approach gives the best results.
The simplest method of water treatment. Mechanical water treatment is provided by catching particles of nonsolutes due to the difference of sizes of particles and channels of filter, the cleared water flows on that. Simpler speaking, water passes through an original "sieve".
Particles, detained by a filter, size is determined by the diameter of channels in water filter's material, water (id est by the sizes of opening in a "sieve") flows on that.
For example, the columns, filled by a granular absorbent carbon with the diameter of granules of a 0,1 - 1 mm (100 - 1000 microns), are able to detain effectively particles approximately the same size. Greater part of uncut-in in water particles has much less - 0,1-20 microns. Indeed, microorganismsare not denied during mechanical filtration, because their size is 0,4 - 3 microns.
Mechanical filtration is widely used on the municipal stations of waste water treatment. This type of cleaning is especially actual when water is taken from open sources: the rivers, lakes, storage pools.
In municipal apartments mechanical filtration is presented by the use of pre-filters (pre-cleaning filters).
The ionic exchange is a specific case of persorption of the charged particles (ions), when absorption of one ion is accompanied by an exit in solution of other ion entering in the complement of sorbent. Thus an ion being of that in water undesirable is fixed on a sorbent. Thus, there is "substituting" for one ions (we will name them "harmful") on other (we will name them "harmless").
Sorbents working on such mechanism, are named ion exchange materials or ion-exchangers. Ion-exchangers are able to extract one cut-in salts from water, substituting for them other salts (for example, salts of calcium and magnesium can be replaced on natrium salt).
Mostly in the process of waste water treatment an ionic exchange is used for moving away from water cations of heavy metals (for example, lead), presenting a hazard for a man health , and also for releasing from nitrates.
Another application of ion-exchangers is hard-water softening, id est moving away from water surplus maintenance of calcium and magnesium ions.
Substantial description of ion exchange resins is their exchange capacity, id est ability to "substitute" for the certain amount of "harmful" ions. One of the main properties of ion exchange resins is their capacity for a regeneration after resource exhausting.
The reverse osmose is water treatment through a reverse osmose membrane. Water at such method of cleaning is skipped through a membrane (original "sieve"), the pores of that skip water, but does not skip cut-in in it admixtures (indeed, setting skips no admixtures - neither harmful nor useful).
System of reverse osmose allows to get water of very high degree of cleaning (near to distilled). The reverse osmose is able to delete from water even univalent ions, for example, ions of natrium and chlorine.
Reverse osmose setting necessarily must contain an absorbent carbon, because a membrane does not detain low-molecular high-volatile organic (type of chloroform) and bacteria.
The quality of water, filtered by such setting is stabil.
Based on difficult redoxreactions that take place in water at affecting it's strong electric current and result in formation of the so-called "live" and "dead" water.
This method is economical, because allows to attain a high yield at small expenses.
The electrocleaning is widespread in Russia, but is not used in the way of life in the west (used only for the industrial cleaning, but not for drinkable water treatment).
The electrocleaning really allows to clean water from all microorganisms. But part of organic substances collapses also. In addition, as exact composition of initial water is unknown, nobody knows how the strong electric current affects substances contained in water, an how will this substances react inter se . As a result of these reactions quite "uneatable" compounds can turn out.
Less widespread type of water treatment. In the distillation systems water evaporates at first, and then condenses.
Id est, distillation is a process of cleaning of liquids, consisting in evaporation of liquid with subsequent devaporation. Thus there is dividing of liquid multicomponent mixtures into different on composition factions by partial evaporation of mixture and condensation of appearing steams.
It is possible to dissociate liquid from hard permeates in it or liquids with the strongly different temperatures of boiling.Distilled water is relatively clean, but process of distillation is expensive.
Distillation systems also must necessarily contain absorbent carbon, because there is no another way to clean low-molecular high-volatile organic (type of chloroform).
Persorption. Sorbents. Sorbing filters
Persorption is absorption of admixtures from gas or liquid by solids, witch are called sorbents.
Process of the sorbing cleaning consists of key-in of gas or liquid through the vessel filled by a sorbent - sorbing filter. If the mode of filtration and sorbent are chosen correctly, then the desired result is arrived - it is moving away harmful admixtures from gas or liquid. Just like this gas-masks and filters work for water.
It will not be a strong overstatement to say that sorbing filters - it coal filters first of all. An absorbent carbon is the most widely used sorbents producible millions of t/ies. It is the universal sorbent applied for moving away admixtures of the most different chemical nature.
Activating allows to get a sorbent with the area of pores about 1000-1500 square meters on a 1 gramme of coal. These extraordinarily high sizes explains extraordinarily high efficiency of activated coal.