Hidrológiai Közlöny 1969 (49. évfolyam)

1. szám - Dr. Szabó Zoltán: A természetes felszínű vizek és szennyvizek biológiai minősítésének tanulságai

HIDROLÓGIAI KÖZLÖNY 49. ÉVFOLYAM ]. S/ÁM 1—48. oldal Budapest, 1969. január BIOLÓGIA Experiences gained with the biological classification of natural surface waters and wastes* By Dr. phil. SZABÓ ZOI.1ÍN, jun.*« At the Water-Quality Department of t he Research Institute for Water Resources Development several thousand water samples retrieved from different locations have been analvsed since 1954. Classification of these samples has been founded on the one hand on the chemical parameters, and on the other, on the biological analysis of water taken from the surface water [4], [5]. Samples have been retrieved from rivers and lakes (recipients), sewage ponds and effluents from a varicty of structures of artificial sewage and wastes treatment. As far as hydrobiological classification is concerned surface waters are characterized — as is well known — by the society, i. e., biocoenosis developed in them. The degree of pollution, saprobity, of various waters may be determined on the basis of the percentage distribution of bio-indicator organisms present in the biocoenosis. The bio-indicators belong — under conditions prevailing in Hungary —- to one of three main groups. Accordingly polisaprobe (p), alpha-mesosaprobe («) and beta-mesosaprobe (/?) bio-indicators are distinguished [5]. Of course, micro-organisms characteristic for transitory ranges between these main groups alsó exist, which contribute according their character to the determination of the corresponding water classification. The percentage pattern of bio-indicators during the self-purification of natural surface waters is represented in Fig. 1, in terms of water quality. In this diagram the "p" bio-indicators can be represented from the most polluted to the cleanest phase by a curve approaching from 100% to 0% asvmptotically. On the other hand the "{}" bioindicators show an image of the "p" bio-indicator curve, whereas the peak (50%) of the curve illustrating the percentage distribution of the "a" bioindicators occurs at a point where the "p" and "/?" curves have their common point of counterflexure and intersection (at 25%). During the self-purification without external, artificial interference, of stored wastes containing more-or-less readily degraded organic substances (e. g. such originating from sugár refineries, domestic sewage, etc.), the wastes enter the alpha* Paper presented at the 10. Hydrobiological Convention (Tihany, Hungary, October, 1968). ** Research Institute for Water Resources, Budapest. mezosaprobe zone, or the beginning of the zone between the alpha- and beta-mezosaprobe (a/3) zones. The biological changes of water quality in the process of self-purification are shown in terms of the percentage distribution of bio-indicators in Fig. 2. As will be perceived therefrom, the change in the "p" bio-indicators is of the sameorder of magnitude as in the curve shown in Fig. 1, so that this is unchanged. In this case, however, the "a" bio-indicators assume the role of the "(}" bio-indicators and tend from 0% to 100%. The "/?" bio-indicators appear where the curve "p" intersects curve "a" (at about 50%) and show an increasing trend beyond this point. In the biological processes of artificial sewage treatment — on trickling filters, or by the activated sludge method — the raw sewage is changed, in the case of satisfactorv operation, into an effluent of intermediate alpha-mesosaprobe — beta-mesosaprobe (oc/3), or even better, i. e., beta-mesosaprobe (f>) type quality. The changes occurring in the biocoenosis of these artificial biological treatment processes are illustrated in Fig. 3. Curve "p" is seen to be entirelv identical with those shown in Figs. 1 and 2. In these cases the "a" bio-indicators, as shown in Fig. 2, start from 0% and tend towards a peak value which is actually attained where the "p" bio-indicators appear. Beyond this point the percentage value of "a" bio-indicators decreases rapidly, while that of the "/?" bio-indicators shows a rapidly increasing trend. It is interesting to note that the "p" bio-indicators are in full agreement on all three diagrams. This is an indication of the fact that in the decomposition of organic substances entering and accumulating in various waters polisaprobe microorganisms assume with an identical trend the governing role. In other words, the effectiveness of biochemical processes and biological activity occurring iri waters depends on the polisaprobe microorganisms and is controlled by the activity of diverse bacterial species. For the biological evaluation of the degree and effectiveness of artificial sewage treatment a new method has been developed [6], [7], according to which the treatment capacity can be deseribed by a single percentage value Tk,%. This method has been used successfully for determining the degree of self-purification and thus a valuable classifica-