Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Dr. Bolberitz Károly: Természetes vizekben előforduló mikroszennyező anyagok fajtái és hatásai

Special Conference Number, Szebellédy, L. Hidrológiai Közlöny 1971. 1. sz. 35 fied form, in the layers at greater depth, i.e., below 1 m, oil adhereing to suspended particles becomes the predominant form. Thin-layer chromatography in the study of phenole derivatives yielded more detailed data on the occurrence of these unwanted pollutants in Danube water. The fact that the totál quantity of phenole derivatives determined with the help of chromatography is higher than the figures obtained by the colorimetric method should be little surprising, since the known colour reactions with individual phenole derivatives yield very different colour intensities, which are, however, as a rule lower than that of phenole. The objective of the studies conducted by Mrs. Six was to determine the extent of pollution caused by the industry in the two towns situated along the Moson-Danube, namely Mosonmagyaróvár and Győr. Over the round 70 km long reach 13 sampling points have been selected and samples have been retrieved for five years with a frequency ranging from 9 to 19 per year. Besides the usual components, the samples were analysed alsó for phenole and anion-active detergents, and the results of these latter analyses have been processed. The results grouped and averaged for individual sampling points and years give clear indications of the increase of pollution caused by discharging domestic, yet primarily industrial wastes. The highest value of detergent-pollution remained invariably below the limit considered allowable and showed, on the contrary, even a definite improving trend, when annual averages were compared. This was attributed, logically, to the spreading use of soft detergents. On the other hand, the data on phenolic pollution, especially downstream of the discharging points at Győr, show an alarming increase. These concentrations are hundred- and even thousand times as high as the allowable values. Although these extrernely high pollution figures are obviously due to the circumstance that the samples have been taken from the banks, in sections where no proper mixing occurred, so that they are hardly representative for the pollution in the entire Danube branch at the particular section, the extent and increase of pollution is sufficiently high to call for effective countermeasures in order to control them. In the paper by Popovska, reporting on the investigations performed on the Lansky reservoir mentioned before, only the conclusions concerning the origin of odour in water are described, although the other results were alsó of considerable interest. However, these have already been published in a paper by the Czechoslovakian Academy of Sciences. The last group of questions associated with the problem of micro-pollution, is concerned with the procedures by which these pollutants can be minimized, or even eliminated completely during the treatment technology. These questions are of paramount importance, since for the time being there appears to be no hope for preventing their entrance into water and their number is even expected to grow in the future. Consequently the efforts aiming at the reduction of the quantities discharged must be flanked by such aiming at the development of methods by which these can be reduced below the allowable limit in the course of treat ment. Obviously, the cancerogeneous substances are of greatest interest in this respect. As demonstrated by the extensive studies by Professor Borneff, their presence is so widespread, that aromatic-polycyclic substances could even be used as indicators for the extent of pollution in water. Since the method developed for demonstrating the presence of these substances is an extrernely sensitive one, the pollution of water is indicated many times more reliably and sensitively than by the coli-count, or by the value of oxygen consumption. The allowable limit values suggested by Borneff are: for groundwater 50 jug/cu.m, for water after treatment 100 /ig/cu.m. A concentration of 200 jug/cu.m is regarded as always objectionable. In view of the fact that in the waters of Hungary polycyclic compounds are frequcntly above this limit, special significance should be attributed to the experiments performed largely by Borneff for determining the extent by which these concentrations are reduced in different methods of treatment. As already known from the works of other authors, the rate at which the polycyclic substances are decomposed during disinfection with chlorine gas is a very slow one, with a half-life of 2 to 3 hours. This method of treatment is therefore unsatisfactory. Treatment with chlorine dioxidé was found to be substantially superior, the half-life being no more than 15 to 30 minutes and under exposure of 2 to 3 houi's more than 90% of the benziprene present was decomposed. Using ozone, 99% of the benziprene can be removed. Adsorption by activated carbon was found effective at concentrations higher than allowable only. The experiments by Borneff have demonstrated further three-fourths of the polycyclic compunds present in water to be associated with materials suspended in water, consequently these can be removed together with the latter. Experiments conducted with different river waters yielded evidence for the fact that filtration through the soil itself, and even simple settling for a few hours will reduce appreciably these pollutants in surface waters. According to experiments under way at four major treatment plants, careful and efficient filtration is capable of reducing the quantity of cancerogeneous compounds to 20 to 50% of the originál concentration, while a removal of 90% is alsó possible on a secondary filter. Clarifying with the addition of alumínium sulphate, or ferri-chloride will further improve this efficiency to 98.5%, The removal of dangerous radioactive substances is of an importance comparable to that of the cancerogeneous compounds. This problem is relegated for the time being to the sphere of wastes treatment, by which its significance is by no means reduced. Indeed, everyone is well aware of the fact that given sufficient time, all wastes find access to surface water of which an increasing proportion is used as drinking water. The objective of the detailed investigations by