Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Dr. Öllős Géza: A 2. Vízminőségi és Víztechnológiai Kongresszus összefoglalása

60 Hidrológiai Közlöny 1971. 1. sz. Special Conference Number, Szebellédy, L. 3. The approach concerning treatment processes and technology must be made more inclusive. This is illustrated by the following two examples. a) Any movement of water through porous média, such as — filtration (e.g. rapid filtration), and — the seepage of subsurface waters should be considered as processes in treatment technology, regardless whether of natural, or artificial origin. This wider interpretation should then offer a realistic theoretical foundation to the solution of any problem associated with water supply. b) In view of the increasing role of régiónál water supply systems, more attention must be devoted to the influence of convyance and distribution systems, further reservoirs on water quality, especially if different waters are mixed, where nutrients remain in the water in a quantity higher than the not readily determined threshold value (e.g. industrial pipelines), where such substances may accumulate, or where the quality of water is affected appreciablv by the products of microorganisms, or chemical reactions. It thus follows that beyond the purely hydraulic dimensioning of treatment structures, the conveying and storage facilities must alsó be designed and operated on the basis of the generál approach to treatment technology. 4. The importance of making greater allowance for material properties must be emphasised. This is strikingly illustrated by the practical application of the results of theoretical colloid chemistry to treatment processes. Thus for instance the close cooperation of experts from many fields, patient, thorough and excellently instrumented research work is required for obtaining a better understanding on a variety of factors, such as the role and order of magnitude of surface forces, which plav a dominant part in various filtration processes, and on the potential control of these forces in the technology of treatment. As a further example, mention may be made of the distribution of a variety of materials along the path of seepage, the variations in the distribution thereof, as these may influence the variations and explain the occasional deterioration of water quality. The relevant material properties may be — the granulometry of the originál filter material, — the distribution of dissolved oxygen, — the distribution of nutrients, — the distribution of micro-organisms, — the distribution of the end products of biochemical reactions, and — the distribution of substances produced by chemical reactions. All these distributions may materially influence the quality and quantity of water regarded as purified. In systems resulting in biological treatment the distribution of ambient factors may vary as a complex function of similar distributions. This latter problem may be significant when assessing the operation of activated carbon filters. 5. Careful consideration appears to be the only method for determining the time of residence of raw water in the individual stages of the treatment system. The time of residence may affect the quality of water either positively, or negatively. The generál trend appears to consist in extending the time of residence and in making greater use of the positive effects resulting therefrom. Of course, this is in response to changed conditions. Reference is made in this connection to the surface storage of more highly polluted river waters before admittance to the conventional structures of treatment, or to the spreading use of slow filtration. This is the price paid for the exploitation of the beneficial effects of primarily biological processes. In such instances the time of residence assumes paramount significance. (It should be remembered here that owing to the presence of phytoplancton organisms, etc., negative effects may alsó occur.) In other cases, e.g. in conveying and storage facilities, extended times of residence due to stagnation should be avoided. Unfortunately, the design criteria necessary for eliminating similar deterioration of quality are not fully understood yet. 6. Many positive conclusions have been derived alsó from studies related to micro-pollutants. In generál, there is a certain—and not unfounded— concern observable because of their presence. This is understandable, when considering their manyfold types, the difficulties of their determination and the problems encountered when attempting to demonstrate their sanitary effect. As a consequence, they cause growing concern to .water supply experts. The present efforts at the solution of these problems seem to be directed at the reasonable combination of disinfection methods, at the inclusion of biological treatment processes and at the extension of the time of residence of water in the treatment system. Since these solutions appear to be far from perfect, understandable efforts are made, as evidenced repeatedly by the Conference proceedings, at preventing these micropollutants from finding access to waters. Concerning the micro-pollutants it would be indeed reassuring, if — the truly harmful and liarmless substances could be separated in a reliable manner, — analytical techniques could be improved to make the quantitative determination of micropollutants more accurate, and — the mg/lit coneentration philosophy of frequently adverse consequences could be discarded. In this context close cooperation with sanitary experts must be realized in the future. These relationships will be evidently reinforced by life itself, since it will be eventually the response of biological organisms consuming the water supplied, i.e., the degree of toxicity of this product, which will furnish the criteria for assessing the activity related to water supply. The remarks and comments of experts engaged in public health are