Vízügyi Közlemények, 1935 (17. évfolyam)

Kivonatok, mellékletek - Kivonat a 2. számhoz

23 Fine, non-settling, or colloidal particles and dissolved organic matter are removed by using chemicals called coagulants. Aluminium sulphate is generally employed as a coagulant. Its effects are : 1. It forms a flocky precipitate with the basic constituents of the water, and the flocks mechanically take with the suspended impurities of the water. 2. The flocks having an immense aggregate surface are able to adsorb a large amount of dissolved and colloidal matter. 3. By hydrolisation of the aluminium sulphate, positive aluminium ions of three valence are produced, which form precipitate with the negative colloids. 4. At the same time sulphate ions of negative charge are also formed, which have a precipitating effect on the positive colloids. In many recent instances, ferrosulphate has been used instead of aluminium sulphate. Water is softened by adding lime to it, dosed in the coagulation or the sedimentation basin. In order to secure an equilibrium of the lime and the carbonic acid, recarbonisation of the water may be necessary. The carbonic acid is dosed in the sedimentation basin. Then the filtration of the water follows. Recently the use of active carbon has been widely adopted for the purpose of improving the taste and odour of water. The bactériologie purification of water is effected by employing chemicals, usually chlorine ; copper compounds are added to prevent the growth of algae. The purification of surface waters is not a simple problem, and the different solutions are seldom cheap, but in supplying drinking water, financial sacrifices, even heavy ones, must if necessary be made in order to meet hygienic requirements. The question, whether a water supply should be served with surface or ground-water, depends on the quality and quantity of the water available, the purpose of the consumption, and the costs of production. European cities generally attempt to supply groundwater which, as a rule, is of good quality. The use of surface water is advisable only if it is not possible to obtain ground-water in the required quality and quantity. XI. IRRIGATIONS IN TURKESTAN. By ARTHUR POWELL DAVIS. Translated by K. GUBÄNYI. (Pages 313—320.) In 1911 Mr. Davis, an engineer, proposed to the Tsar's government the irrigation of the Golodnaja Steppe. According to Mr. Davis's statement, there are at present 442,000 hectares under irrigation in the valley of the Amu-Darja river, and 3,138,000 hectares in all can be irrigated. On the upper reach of the river, in the Vais valley, 40,000 hectares are irrigated, which area will in a short time be doubled. To-day the Amu-Darja river discharges its water into the Aral Sea, but originally it opened into the Caspian. When the river is used for irrigation, the water level of the Aral Sea will be considerably lowered, and a large part of the sea bottom can be cultivated, but the table of the ground water is so high that these areas will be available for agricultural purposes only after laying out a careful drainage system.