Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Abos Bruno: A talajvízdúsítás vízminőségi problémái

Special Conference Number, Szebellédy, L. Hidrológiai Közlöny 1971. 1. sz. 27 directed attractive energy valencies. This hypothesis was accepted in several variations by many experts and the suitable filter effect was explained in this way for a long time. Investigations after World War II indicated the filtering process to be a highly complex one, and to change dynamicallv with the quality of raw water, especially from a biological view. In his book, Bettaque tried to prove the effect of individual factors by a number of experiments. His publications at the same time indicate that there are a great number of factors influencing filtration and successful and suitable filtering depends primarily on the combined effect of these factors. Research work, at present, is continued by the complex approach to examine the optimum effect of individual factors, and the manner in which these factors must be influenced for improved results. Two factors are believed to be pretty well known already which influence the quality of slow filtration. Thus, the efficiency of slow filters filled up with pure sand is improved by colloidal clay of mineral origin. These colloids include alsó alumínium hydroxide, traces of which are usually present in purified water and beneficial to the running in of slow filters. However, during normál operation, colloidal minerals will accelerate clogging of the filter layer. Several researchers succeeded in proving that air (oxygen) introduced under pressure into the sand layer of the slow filter increases the biological filter effect. However, sound technical solutions are as yet unknown to practical use. In groundwater recharging, where the gravel layer between the slow filter and groundwater is not always saturated, the problem is less difficult to solve. The complex mechanism of slow filtration has become one of the main fields of research in water treatment. It is the biological effect of slow filttration, which is alone capable of eliminating even the traces of harmful and disagreable mixed pullutions from water. The limits of this excellent property in the case of different dominant pollutions are as yet unknown and should be studied as soon as possible. In preparing this generál report, the 10 papers submitted to the Conference were studied first: 1. Pusztai, Gy.—Bérezik Á. — Mrs. Vcgh 8., Budapest: Results and problems in research into groundwater recharging at the Municipal Water Works 2. Schiefner K., Budapest: Biological problems in groundwater recharging, on basis of the Borsodszirák experiences 3. Gefjerth K., Preszler I., Budapest: Eutrophication process of groundwater recharging, reflected by changes of somé physical and chemical factors. 4. Widmer, H. P., Basel (Switzerland): Future possibilities for gaining drinking water in Basel 5. Megyessy L., Budapest: Quality aspects of the groundwater recharging operation at Nagybátony 6. Fázold, A., Miskolc: Interpretation of the practical results of groundwater recharging in terms of the theory of slow filtration 7. Fázold, A., Miskolc: Design eriteria for the quality obtained by groundwater recharging 8. Mrs. Dávid, Deli M., Budapest: Laboratory examination of groundwater recharging proeesses 9. Páris, E., Budapest: Improving the quality of water by groundwater recharging 10. Abos, B., Budapest: Pretreatment of raw water before slow filtration. When preparing the present report, the publications in journals and technical books in the last two decades were alsó taken into consideration. In the majority of papers submitted, the proeesses in groundwater recharging, the obtainable water quality and results are considered. Alsó, most papers are devoted to the rapid water purification methods applicable before slow filtration and the quality of water obtained in this way. A special problem is singled out of the complex process of groundwater recharging in one of the papers, which outlines the optimum spacing of wells in groundwater recharging based on studies in a laboratory model, for the case when water production is influenced alsó by bank filtration at varying stages. The papers are representative for part of the main research activities only. Slow filtration proeesses in closed basins are considered by a single author. Slow filters, as the biological filters in the last phase of purification are likely to play a decisive role in future supply projects drawing on surface water. Much greater efforts appear to be warranted in research into this problem. Of the different methods of slow filtration water works favour groundwater recharging in the vicinity of wells already existing, or built with the plants. By this method — especially in peak demand periods — the yield produced from the wells can be increased appreciably. Under suitable hydrogeological conditions, the water reserves stored in the soil can be recharged successfully. This type ofstorage is used at the Nagybátony waterworks. Groundwater recharging projects are very often realized for greatest economic benefits that is to say, the objective is to produce the greatest possible yield, with the least investment. However, this basically correct policy, is often misleading. Without suitable and adequate preliminary studies, which often are rather costly, no groundwater recharging can be expected to operate satisfactory for any extended period. The observation of all complex requirements, the majority of which are already famihar, is essential both in construction and operation, if groundwater recharging is desired to operate profitably for many years. The complex requirements of groundwater recharging are far reaching and demand careful preliminary research in several scientific and technical branches. These preliminary studies are rather often carried out but in part and then not satisfactorily. This concerns first of aü hydrobiological preliminary tests, which are either omitted altogether, or fail to yield the necessary information. Thus, of course, they cannot serve as basic data for design work. The same applies to the suitable and careful choice of prehminary purification of water to be recharged. In generál, prehminary settling of a few days duration is only envisaged, by which rather than improving, the