Among natural resources water takes the special place: first life on the Earth appeared in water medium, water is in the structure of all living organisms and is the resource an economic activity is impossible without; oceans and seas occupy 70.8% (510,000,000 km2), of total Earth surface. Water reserves on the Earth are large - l,400,000,000 km3, but about 96 % of this volume belongs to salt water of the great oceans. Fresh water reserves are slight - about 35,000,000 km3, incidentally, 70 % of it is concentrated in ice, almost 30 % of world reserves are underground waters and only some part of it is accessible, a part of water is in a ground, atmosphere, living organisms. The waters of rivers, lakes, bogs make a minor part hydrosphere less than 200,000 km3 (or less than 0,02 %).
Water consumption is constantly growing. Under condition of increasing volume of water-supply and ejection sewage into reservoirs the main danger consists in deterioration of water quality. Annually more than 450 km3 of waste water is ejected into rivers and other water reservoirs, and about half of them without previous purification.
The main reservoirs polluters are insufficiently purified industrial and public utilities, and also cattle-breeding complexes sewage; rain and melted snow waters washing off polluters from the city territories and fields, polluting from atmosphere which are caused by-precipitation.
The industry uses over 20 % of water reserves. The greater amount of it is used for cooling electric power station and other technologies. During the last ten years' need for water in industry grew owing to applying modern water-retaining technologies. The most water-retaining technologies are chemical, pulp and paper, and metallurgical industry. For example, 1 ton of ready made synthesized fiber takes 2,500 5,000 m3 of water; plastic 500 1000 m3; papers from 400 up to 800 m3; pig-iron -160 200 m3.
In public utilities water is used for sufficing of household needs, working of consumer service establishments, which approximately make 15 % from industrial water consumption. The resident of large a city, for example, Moscow, Kiev, daily uses about 300 400 liters of water. At the same time the residents of such cities as London, Paris daily use about 160liters of water. As we see, wasting of water in our country is considerably larger, than in other countries.
Industrial water wasting is rather slight; it is mainly reasoned by processes of evaporation, which are the most intensive in thermal and atomic power stations, and also at the ferrous metallurgy.
Industrial sewage contains various harmful substances. Sewage of instrument-making and machine-building plants contains saline of various metals (copper, nickel, chromium, cadmium), and waste water of galvanic workshops - cyanide. Sewage of chemical industry is most dangerous because it contains complicated organic substances. Sewage of cities is polluted by people wastes: washing-up liquids, dyes and also industrial wastes.
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Recently synthetic surface-active substances soap, washing-up liquids, emulsifiers which are widely used in household activities and technological processes became extended polluters. The special group of polluters is formed by pesticides due to washing them off and falling from the air while plane spraying. These substances are fatal to all living organisms in water reservoirs.
According to phase-dispersion state in water all polluters are divided into soluble, colloidal and insoluble substances, and by an origin - into mineral, organic and bacterial ones. Mineral polluter includes solid suspension (sand, clay, slags) and solutions of acids, alkalis, salines. Organic polluters have in their structure nitrogen, phosphorus, carbon, potassium and other substances. They are formed in reservoirs as result of biological processes of living things and also get with rain waters which wash off fertilizers from fields. A widespread organic polluter is petroleum and its products. Organic polluters create appropriate medium for development of bacteria, viruses, fungus and other microorganisms very dangerous for people. The special kind of contamination is thermal source of which are power stations emissions of thermal waters. Particularly dangerous are radioactive substances getting into reservoirs with precipitation.
Naturally water self-refinement is large enough, but not unlimited. When reservoirs polluting reaches a critical level, the water's not only losing its biological properties, but even getting unacceptable for household or even industrial needs. Polluting of water kills flora and fauna of reservoirs.
Now increasing quantity of polluters doesn't attract public concern so much as the properties of polluters (insoluble, sparingly soluble, toxic). Among such polluters petroleum and radioactive waste are necessary to emphasize. About 10,000,000 tons of petroleum gets into oceans from various sources of planet annually. The petroleum film, isolates water from an atmospheric air, reduces intensity of water evaporation and breaks ecological balance in hydrogen medium.
The consequences of local polluting of ocean waters in some cases are hard to foresee. In Japan unknown before mass diseases are detected; the cause is found in taking with food fish poisoned with mercury ingredients of sewage accumulated in Minamata bay. The Minamata disease, as it's appeared, is transmitted from generation to generation.
There is a complex of measures reducing biosphere waters contamination:
1 Working out technologies containing little water or wasteless with the closed return cycles for intermediate purification or cooling water and waste utilization;
2 Improvement of technologies for reducing of sewage volume by burial of polluters concentrated solutions in terrestrial bowels;
3 Applying of various methods for purifying water polluted by industrial and household waste;
4 Reduction of farming industry chemicalixation due to efficiency of biological and other agrotechnical measures to provide protection from plants infection and pests;
5 Improvement of tankers constructions of inland water transport and navy, technology for marine petroleum production for decreasing petroleum quantity which gets into the ocean; realization of measures on purification of surface of water areas of see and river ports from petroleum polluters.
The purification of sewage is destruction or extraction of some substances, and decontamination is extraction of morbific microorganisms out of waste water. For purification of waste water purifying structures are used. For purification of city and industrial sewage mechanical, biological and physical-chemical methods for refinement are used. The universal method for extraction of organic substances is the biological method.
