From Big Medical Encyclopedia

FILTERS — the devices intended for department of impurity or division of mixes of the substances which are in various aggregate states having a different degree of dispersion and an electrodawn-zhennosti. Filters call also devices, the detaining sound or electromagnetic waves of different frequencies and energy. According to it distinguish F. liquid, gas, molecular (see Molecular sieves), ionic, sound, light — light filters (see Photometry), x-ray (see. X-ray apparatus), etc.

Basic element of any F. the filter medium is, in quality to-rogo use metal gauzes, fabrics, sand, an anthracitic crumb, expanded clay, crushed slags, active coal, silica gel, granulated natroncalc, aluminosilicates, ion-exchange resins and other polymers, water, solutions of acids, alkalis, kompleksoobrazovatel (for a delay of gaseous and vaporous substances).

Depending on a type of a filter medium, aggregate state and properties of components of the filtered mix division on filters is carried out at the expense of a mechanical delay, processes of sorption (see Absorption, Adsorption, Sorption), owing to distinction of speeds of passing of different molecules through the filtering environment, ion exchange or due to power loss of the corresponding waves. Passing of the filtered mix through the filtering environment is provided usually with distinction of the baric or osmotic pressure, potential difference or wave energy.

Apply to purification of air and other gases fabric, paper, oil, coal, limy, gravel, water (water veils) F., and also T. from artificial polymeric materials, napr, Petryanov's tissue (see Respirators, Sanitary protection of free air).

For purification of milk and other liquid foodstuff use lamellar, disk, sheet, cartridge, tape, fabric (filters of Nutcha) and others F.

Water treatment (see) in utility water supply it is most often made by means of sandy F.

On filtration rate of water distinguish slow and ambulances F. Slow filters represent big concrete or brick tanks, at the bottom to-rykh there is a drainage system, and over it — a layer from the gravel supporting a filter-bed of sand from 0,9 to 1,5 m thick with a particle size of 0,1 — 0,35 mm. Water through slow F. filters by gravity with a speed of 0,1 — 0,3 m/hour, being exempted from suspended particles and microorganisms (to 99%) what promotes biol to. the film, edges is formed on the surface of sand in several days of work of such F. Medlennye F. are easy-to-work, but in connection with small productivity can be used only in small settlements. Ambulances F. eyeliners for rinsing water and trenches for its collecting and assignment consist of the same elements, as slow, and also. Filtration rate in them to 7 — 8 m! hour. Increase in productivity is reached use of coarse-grained sand with a particle size up to 1,2 mm. Reliability of clarification of water is provided with its preliminary coagulating. At the same time on the surface of sand the filtering film consisting of the flakes of a coagulant and colloid suspensions which were in water is formed. At a thickening of a film and increase in resistance of filtering over admissible size all mass of sand is washed out by a reversed current of the water pumped from below up through an admission of rinsing water. Rinsing water with the filtered particles of dirt and flakes of a coagulant is taken away through trenches in the sewerage.

In the two-line filter AMS (Academy of Municipal Services) the drainage system is located in the thickness of sand at a depth about 0,5 m from a surface. The ground mass of the filtered water moves from below up. Smaller part for prevention of carrying out of sandy loading moves on a surface, i.e. is filtered in the regular way. It allows to increase filtration rate to 12 — 15 m/hour.

For water treatment also contact clarifier is used. At this method of cleaning all water is pumped from below up, gathers for the surfaces of sand and is taken on trenches to distribution channel, and from there in a pure tank.

Field filters represent the technical devices mounted on vehicles of a special purpose or figurative. They are intended for water treatment or air in field conditions from natural pollution, and also for their disinfecting and neutralization at pollution owing to use of weapons of mass defeat. As filter mediums sand, an anthracitic crumb, sulfonated coal, karbofer-rogel, cotton and other porous materials are used.

For water treatment in field conditions use the avtofiltro-valny station MAFS-3, to-ruyu mount on the car. It consists of the filter filled with a crumb from anthracite, two dekhlorator purifying water of excess amount of the chlorine added to it and also from nek-ry harmful substances, and communications for water delivery. In the trailer transport motor-pumps, rubber tanks, rubber hoses, a reserve of reagents, filter mediums, the tool and spare parts. For quality control of water at the station there are laboratory sets. Productivity of the station 7,5 m* / hour, a running time (filter run) — to the 20th hour. Time of expansion — i1/2 of hour, coagulation —

1 hour.

As other means of water treatment in field conditions serves the army filtration plant VFS-2,5 different from MAFS-3 technology of processing of water and smaller productivity. In it process of coagulation and chlorination is combined with filtering of water through the weighed layer of a coagulant; besides, water is irradiated with UV rays for what there is a block of bactericidal UF-lamps (see. Bactericidal lamps).

On company, battalion and other field points of water supply use fabric-coal filters, e.g. TUF-200, to-rogo is included in the package actually the filter, the manual pump, tanks for water, tarpaulin buckets, filter mediums, reagents. The weight of all set — 80 kg. The filter represents the metal cylinder with a bottom and the screwed cover, entrance and output unions. A filter medium are a fabric bag from moleskinovy serge and active coal.

In the absence of F. industrial production water can be purified by F., made of make-shifts. For this purpose use wooden and iron barrels, metal tanks or strong wooden boxes. Stack a drainage layer from brushwood on a bottom of capacity, small pebble or small crushed stone, over it load the washed wood charcoal in a fabric bag, is even higher — the bank sand or a fabric bag from coarse calico or a moleskin processed by reagents. Water is filtered by drift.

Purification of air in field conditions in cabins and manned departments of special cars is most often carried out by method of separation and filtering. The separator forcing air through F., separates coarse particles of dust, actually F. purifies air of fine particles of dust, including of harmful impurity. Therefore furnace charge of field air filters essentially does not differ from furnace charge of filters for collective means of protection (see).

Apply the respirators (see) various design

having an appearance of a mask to protection of a respiratory organs of people against dust. As

a filter medium for respirators use cotton wool, felt, paper, Petryanov's tissue.

Bibliography: Zhukov A. I., M about N -

gayt And. JI. and P about d z and l of l of e r I. D. Methods of purification of production sewage, M., 1977; At r and M. G.

Filters with floating loading for a mudflow-hozvodosnabzheniya, M., 1978, bibliogr.;

it, Water treatment on granular filters, Lviv, 1980, bibliogr.;

Knop V. and Tesye V. Tekhnika of ensuring purity of air, the lane with it., M., 1970; To about and N about in V. F. Cleaning of a drinking and service water, M., 1971; P and r at m about in A. I. Dedusting of air, M., 1981; The Guide to hygiene of water supply, under the editorship of S. N. Cherkin-sky, M., 1975; Encyclopaedic dictionary of military medicine, t. 5, Art. 757, M., 1948. N. F. Koshelev, V. I. Barabanov;

P. N. Kurpita (field filters).