From Big Medical Encyclopedia

BACTERIA BEDS — constructions for sewage treatment by filtering through materials which surface is populated with the microorganisms mineralizing organic matters. First B. f. were constructed in 1893 in England.

B. f. represent the tanks filled with loose filter mediums (crushed stone, gravel, boiler and blast furnace slag, coke, pumice, expanded clay and other similar materials) or blocks from plastic, foamglass. B. f. are subdivided on periodically acting (contact) and continuously acting (drop, or perkolyator). B. f. periodic action are ineffective also in a crust, time are almost not applied. B. f. continuous action on productivity, a design, load of drain waters of 1 m3 of loading material B. f are subdivided on usual, high-loaded and tower, or. big height. Height of a loading layer in usual drop B. f. makes 2, and diameter of fractions of loading material does not exceed 25 — 30 mm.

For the first time the high-loaded B. f. with artificial ventilation were offered in 1929 by N. A. Bazyakina and S. N. Stroganov under the name «aerofilters» and are implemented in Moscow at the Kozhukhovsky station of aeration. In 1936 in the USA began to build the high-loaded B. f. with natural ventilation.

On the high-loaded B. f. by 10 — 12 times loading of waste liquid and twice — height of a layer of loading, and also oversize of grains of a filter medium to 40 — 75 mm is increased by unit of volume that allowed to increase productivity of a construction. Kro me the high-loaded B. f. with natural and artificial air delivery (aerofilters), the high-loaded B. f are applied. with incomplete and full cleaning, with recirculation and without recirculation of drain waters, one-stage and two-level, high and low. B. f. with filter mediums from blocks of plastic or foamglass have the big productivity since the oxidizing power removed from 1 m3 of such filter a day makes 1200 — 1500 of oxygen that in 6 — 7 times more, than with 1 m 3 usual B.'s loadings f.

Tower B. f. are for the first time described in GDR in 1952. They have height to 20 m and small diameter (the relation of diameter to height 1: 6, 1: 8). It allows to divide biological process into phases of cleaning with the specific biocenosis developing at the different levels of the filter. Thanks to it the oxidizing power of tower B. f. reached 3000 g of oxygen on 1 m 3 loadings.

Essence of biological processes on B. f. consists in the following. Through a nek-swarm time after B.'s start-up f. in operation (2 — 3 weeks in warm season) there occurs biological maturing of B. f., expressed that particles of a filter medium or the surface of blocks from plastic, foamglasses become covered by a biological film, biocenosis (see) which it is very various (bacteria, fungi, seaweed, etc.). The microorganisms populating a biofilm oxidize sorbed organic matters, using a part them as plastic material for increase in the biomass, and scoop the energy necessary for the life activity. Products of biochemical oxidation of organic matters are washed away together with the cleared filtrate of drain waters. Oxygen, necessary for biochemical oxidation, comes to thickness of top filling, from sides and from below by natural ventilation, and in some designs of B. f. by artificial blowing off. Viruses, bacteria, eggs of helminths are late a biofilm no more than for 90% and partially perish.

The drain waters which passed through B. f., shall before descent in reservoirs be chlorinated, and the washed-up biofilm to be disinfected on silt platforms, in methane-tanks.

See also Bioscrubbling , Sanitary protection of reservoirs , Drain waters .

Bibliography: Dolivo-Dobrovolsky L. B., Kulsky L. A. both Nakorchevsky V. F. Himiya and water microbiology (bases chemical and bioscrubbling of water), Kiev, 1971; Lapshin M. I. and Stroganov G. N. Himiya and microbiology drinking and drain waters, M., 1938; Stroganov S. N. and K. N Reguluses. Bioscrubbling of drain waters, M. — L., 1934, bibliogr.; Tavartkiladze PI. M. Operation of biofilters with block loading from foamglass in winter conditions, Vodosnabzh. and dignity. tekhn., No. 1, page 11, 1971, bibliogr.; Yakovlev S. V. Artificial biological oxidizers and methods of their calculation, M., 1959; Yakovlev S. V. and Galanin P. I. To calculation of biofilters of high loading, Vodosnabzh. and dignity. tekhn., No. 6, page 4, 1957.

E. I. Goncharuk.