FIELDS OF IRRIGATION — the land plots prepared for natural bioscrubbling of drain waters.
Principle of a soil method of cleaning drain waters (see) it is based on natural ability of soils to biochemical, to oxidation of the organic matters coming to it before the simple connections acquired by plants. Process proceeds in aerobic conditions and is carried out as a result of life activity of soil microorganisms (see. Soil ).
The first P. of the lake in Russia were constructed in 1887 in Odessa, in 1895 in Kiev and in 1898 in Moscow.
However with growth of the cities, development of the industry, sharp increase in amount of sewage P. of the lake were overloaded and ceased to answer the main appointment — cleaning and neutralization of waters. On P. lakes began to carry out only filtering of drain waters without their use for cultivation of page - x. cultures. Such sites received the name of fields of filtering. The device of fields - filterings is limited and it is reasonable only as a temporary measure, napr, at new construction of settlements, cities, the industrial enterprises. Broad application of P. of the lake was found in connection with melioration of page - x. lands (so-called agricultural fields of irrigation).
Modern P. lakes represent system of engineering constructions, on to-rykh cleaning or after-treatment of household, trade and livestock drain waters is made. The item of the lake can be divided into the following groups: utility fields of irrigation, on to-rykh a dignity. - tekhn. tasks are combined with cultivation of page - x. plants; fields of filtering where it is carried out bioscrubbling (see) the clarified drain waters by filtering through the soil horizons without their use in the agricultural purposes; the agricultural fields of irrigation representing the specialized hydromeliorative systems which are under construction on lands of collective farms and state farms, soil after-treatment on such fields it is combined with use of the purified drain waters for irrigation and fertilizer of page - x. grounds.
The best by efficiency of use for P. lakes are easy sandy and sandy soils. The surface of the field is broken into sites (cards) from 0,5 to 16 hectares and protected with an earth shaft 0,8 — 1 m high. The surface of cards leave equal or cut furrows. The irrigating network consists of pipelines, settlers, the pump station, the regulating tanks, channels and the parting irrigation network. Water delivery on fields happens by gravity through open channels. On fields of filtering mechanically purified drain waters move in the card the continuous gulf in the summer a layer of 20 — 30 cm, in the winter — to 75 cm, after filtering of waste liquid plow up the surface of the card and again fill with water. On utility P. of the lake drain waters arrive on strips and furrows that it is more preferable about a gigabyte. points of view. Agricultural fields of irrigation (seasonal and year-round) differ in the device, equipment and the equipment, agrotechnical and operational receptions. Drain waters on such fields come on gravity or pressure piping to constant irrigating network. On pipelines or by means of the water-sprinkler they move in the map of the field corresponding to the plan of watering. Irrigation is carried out by the disinfected drain waters with use existing in the irrigated agriculture of ways of watering: on furrows, strips, flooding, subterranean irrigation, overhead irrigation. The last is allowed only on the sites located not closer than 1000 m from settlements and 100 m from the main roads. The best in a dignity. the relation the subterranean irrigation which is completely excluding contact of plants with a drain water is.
The size of loading is defined in each case depending on P.'s type of the lake, soil, climatic, hydrological conditions and the need of plants for moisture and nutrients. Standard daily rates of loading fluctuate from 40 to 125 m3/hour for fields of filtering, from 15 to 50 m3/hectare for utility fields of irrigation and from 5 to 20 m3/hectare for agricultural fields of irrigation.
Efficiency of neutralization on the islands who are correctly exploited by P. is higher, than on other constructions biol, sewage treatments, and reaches on ammonia 98%, on bacteria of 99,9%, oxidability of drains decreases in tens, and biochemical oxygen requirement (military industrial complex) in hundreds of times. From all ways of soil cleaning and after-treatment of drain waters preference shall be given to agricultural P. by the lake where the problem of effective after-treatment of drain waters is at the same time solved, sanitary protection of reservoirs (see) and increases in fertility of lands due to utilization of the elements which are in drains, such as potassium, phosphorus, nitrogen, calcium, etc. These constructions are most economic, and the small loadings causing smaller pollution of the soil and the best conditions of a mineralization of organic matters allow to be afraid to a lesser extent of deterioration in results of cleaning in the course of long operation.
Dignity. requirements to P. of the lake are directed to the prevention of emergence and spread of bacterial and viral intestinal infections and helminthoses among the lakes working at P. and the surrounding population; on prevention of pollution of surface and subsoil waters and providing a high level of cleaning of drains on these constructions.
Islands draw the conclusion about a possibility of the device P. bodies a dignity. services on the basis of satisfactory results of analyses of incidence of intestinal infections and helminthoses around P.'s construction by the lake for the last 3 — 5 years and on condition of providing a zone of a gap between P. the lake and the settlement (250 — 300 m from agricultural fields of irrigation and 500 — 1000 m from fields of filtering). The device P. of the lake in the territory with a bias more than 0,03 °, with an egress of carstified and jointed breeds, with a depth of subsoil waters less than 1,25 m from the Earth's surface, and also in a zone 1-g about and the 2nd belt a dignity is not allowed. protection of sources of water supply, mineral waters and resorts.
On P. cultivation of such pages is authorized to the lake - x. plants, as commercial, grain crops, fodder herbs, wood and shrubby plantings. Cultivation of vegetables (including potatoes), berries, fruit and melon cultures is forbidden.
For assessment of overall performance of P. the island is carried out sanitary and bacteriological, sanitary and virologic, sanitary and helmintologic and a dignity. - the chemical analysis of drain waters before and after treatment facilities, and also P.'s soil of the lake in the terms provided by the project or local a dignity. bodies; drainage and subsoil waters in a zone of influence of P. of the lake at least once a quarter, the soil from depth from 3 to 25 cm two times a year, page - x. cultures after watering and before harvesting. In the village - x. products define the specific ingredients which are available in irrigation water. At contents in a drain water more than 100 mg/l of nitrogen carry out control of the content of nitrates in the grown-up pages - x. plants.
Bibliography: Hygiene of agricultural fields of irrigation, under the editorship of H. N. Litvinova, etc., M., 1962, bibliogr.; To Goncharuka. I. Constructions of underground filtering of household drain waters, Kiev, 1967, bibliogr.; Lvovich A. I. Practice of design of agricultural fields of irrigation, M., 1968, bibliogr.; To and N and r d about in I. P. Use of drain waters on ZPO, M., 1977; Matveev P. N. Hygienic bases of development of agricultural fields of irrigation, M., 1976, bibliogr.; M and sh at-stin E. N, Pertsovskaya M. I. and Gorbov V. A. Sanitary microbiology of the soil, M., 1979, bibliogr.; P about-manenko N. A. and Hizhnyak N. I. Hygienic assessment of agricultural fields of irrigation, Kiev, 1975, bibliogr.
V. A. Gorbov, N. I. Tonkopy.