Hidrológiai Közlöny 1971 (51. évfolyam)
1. szám - Dr. Öllős Géza: A kutak vízhozamát befolyásoló tényezők
22 Hidrológiai Közlöny 1971. 1. sz. Special Conference Number, Szebellédy, L. This is reflected in the paper by J. Hampl, who gave valuable information concerning experiences gained with NOVODUR-type well filters. 3. Water produetion by bank filtration Another, as regards boundary conditions special case of water produetion with wells is the system of bank filtration. In recent times more and more attention is paid to clear the design, and operational aspects of this type of water produetion. This is understandable, as the water running towards the wells may get polluted most readily in this case, over the infiltration surface. 3.1. Processes at the point of infiltration The pollutants in the raw water entering the bank zone may be as follows: a) Dead matter. Here one should discern inorganic substances (e. g. carbonate precipitates, hydroxide floccules, phosphate, nitráté, micro-pollutants), and organic ones, (e. g. defunct plánt and animal organisms, humus, dissolved organic matter, micro-pollutants). b) Live matter (e. g. algae, bacteria, protozoa, viruses). The elimination of the above pollutants from water, as pointed out by íves, depends first of all on the differences in the size of the soil particles (and the soil pores respectively) and the matter to be filtered. If filtering were a purely mechanical process, the minute particles would, in most cases, not be eliminated. However, the retention of pollutants from water is alsó influenced by the following basic processes (íves) : 1 2 3 5 6 7 8 Inorgonic pollutants Organic pollutants Dissolved oxygen (0 2) Inorgonic debris Algae Organic detritus Filter surface Pre-filter Sediment on filter surface Settling inorgonic substances Settling organic substances Inorgonic dissolved matter Digestible dissolved organic matter Non-digestible dissolved organic matter Organic substances of bacteriai cells Carbon dioxidé (C0 Z) Dissolved oxygen (0 2) Iwl Y777A — diffusion — inertia (in this case less important), — sedimentation-like processes, — hydrodynamic effects, — adhesion, and — biological processes. At the point of infiltration — as filtering is of the slow filtration-type — due to the favourable ambient factors (the simultaneous presence of inorganic, organic matter, as well as dissolved oxygen), the water is biotope, i. e., besides the mechanical processes the chemical ones and — important from our point of view — the biological ones, play the main role in purification technology. Concerning the interpretation of the processes at the point of infiltration, it is expedient to remember the approach of K. Schmidt to slowfilters (Fig. 11). From this flow diagram information is obtained on the pollutants (both organic and inorganic ones) arriving to the infiltration surface, the amount of dissolved oxygen, the completeness of the biological process and, finally, on the water purifying effect of the immediate vicinity of the infiltration point. Inorganic sediments affect infiltration first of all by colmatation, while detritus and algae (in case the light conditions are favourable) play a basic role in the biochemical purification process. Possible differences in the chemical properties of the infiltrating water and that already in the soil, as well as the presence of the different pollutants are usually the conditions for the occurrence of chemical reactions. The rather complex purification process at the point of infiltration may affect basically — the supply conditions, — the choice of bank-zones eligible for water produetion, Bottom © © Br Br Br. Br Br Br \Clumef side © © ~X7 A B^rftJ? W/W A' tt—y—< ~V —\ r y y- -c 'r \ r-> ,—\ Fig. 11. The purification process of slotv filters Fig. 12. Fundamental cases of infiltration
