Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Kolin László: A vízminőség szerepe és változásai tározókban

Hidrológiai Közlöny 1971. 1. sz. 55 The role of, and changes in, the quality of water in reservoirs K O 1II, LÁSZLÓ Civ. Engr., (Consulting Enterprise for Civil Engineering, Budapest) 1. The importance of the quality of water, stored for supply The two main problems faced when desiring to supply water of the required quantity and quahty, are the meeting of rapidly growing demands, and the produetion by complex and expensive procedures good quality drinking water from supplies which are becoming increasingly polluted. In order to even out the differences between the uniform rate of produetion and variable consumption, which may even show outstanding peaks, storage hasins of possibly large capacity are inevitable. Owing to the various technological difficulties and considerable operating expenses involved in the produetion of good quality drinking water, special importance should be devoted to the requirement, that the once perfect quality of drinking water should not deteriorate during storage. This applies equally to the taste, odour and optical appearence of water, but especially to its bacterial quahty. Although the above requirement should be fairly obvious, and in spite of the fact that the problem has received considerable attention during the past decades, we are still not in the position to state that this problem has been attributed the significance it actuallv deserves in the design and construction of storage basins. In fact, storage basins are the last unit in the treatment-svstem or converselv, they are the unit nearest to the consumer, and thus they should be regarded as an organic part of the supply-system. Unfortunately, storage basins are still designed without consulting a water-treatment expert and this may have serious consequences during operation. The importance of conserving the quahty of water during storage is increasingly appreciated by engineers dealing with similar problems. The question is receiving growing attention all over the world, as reflected alsó by the papers submitted on the subject to the 2nd CONFERENCE ON WATER QUALITY AND WATER TECHNOLOGY. 2. Papers submitted to the second conference on water quality and technology Up to the deadline the following papers have been received: Dr. Hanlcó, Z.— Dr. Szabó, Z. — Akantisz, Zs. : Model tests 011 the Pécs — Üszög storage-basin and the determination of micro-sediments on the site. Dr. Hankó, Z,. : Hydraulic model studies on a 10.000 cu. m capacity storage basin. Dl. Langer, W. : Hydraulic aspects in t he design of storage basins — design eriteria (in Germán) Lohr, A. : Contemporary trends in the design and operation of drinking-water reservoirs. (in Germán) Schmidt, J. : Storage reservoirs with spiral-bafHes. (in Germán) The present generál report, has been compiled by relying mainly on the above papers. The paper Dr. Öllős, G. : Hydraulic considerations governing the design of basins for the storage of drinking water was alsó available, whieh is scheduled for publishing in 1970. in the Hidrologiai Tájékoztató. Although the problems relating to the hvdraulics, water quality, model—testing, and structural design of storage basins are dealt with in detail and thoroughly in the papers submitted, the rather small number of the papers is an indication of the novelty of these questions and alsó of the fact, that relatively few experts are considering these important and highly complex problems. 3. Research into the design of storage basins, and into the changes of water quality in them. The present situation and trends of development The fundamental prerequisite for maintaining the quality of water in storage basins, is that the flow pattern in the basin should be uniform, that is, that each water particle should remain for the same length of time in the basin. This can be realized by providing operation in accordance with the "Piston-Principle" within the basin, where the entire volume contained moves at a uniform velocity, preventing the development of stagnation areas. This is impossible to achieve, unless the geometry of the basin, the inlet- and outiét points and the location and arrangement of internál baffles are studied in detail, consequentlv the conservation of water quahty depends on the careful consideration of flow conditions The technological functions and hydraulic conditions in the basin, are thus closelv interrelated. In principle it is recognised— both at home and abroad—that no major storage basin project must be realized, unless it is preceded by hydraulic model tests. Of the papers submitted, the problems of hydraulic model testing are analysed in considerable detail in the papers by A. Lohr andZ. Hankó. Lohr has performed model tests before constructing a storage basin in Munich, while the tests by Hankó preceded the construction of the basins at Pécs—Üszög, in order to ensure perfect flow-conditions in them. In should be noted further, that from 1963 to 1966 extensive experiments were performed in Hungary at the BUILDING RESEARCH INSTITUTE to obtain better information on the flow conditions in basins. According to Lohr, research is centered around the following fundamental problems: — determination of the similaritv law most truly representing geometrical and hydraulic conditions, — the correct choice of the material for the model test (water, air), - ensuring the identity of boundary conditions. 'The new method of testing introduced by Z. Hankó led to the conclusion that the invariance of the Froude number alone is insufficient for ensuring the similaritv of flow patterns in the model and