Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Dr. Öllős Géza: A kutak vízhozamát befolyásoló tényezők

Special Conference Number, Szebellédy, L. Hidrológiai Közlöny 1971. 1. sz. 21 are in a praetically fixed position. Their velocity of movement may be regarded as zero. From the point of nutrient utilization it is the difference between the velocities of the bacteria and the nutrient which is significant. The higher the relatíve velocity, the higher the rate of supply on the contact surfaces and the nutrient-uptake opportunitv of the bacteria (and thus alsó the reaction rate) increases. This may be offered as an explanation for the fact that as the seepage velocity — and together with it the Re-number — increases (the motion mav even become turbulent), the conditions for the rapid profilication of bacteria become more favourable. Research work on this problem deserves priority. 'In somé instances — as indicated in the paper of W. Mevius — the possibility of calcium and magnesium carbonate deposition must alsó be allowed for within the gravel pack and the orifices of the filter pipe. This may oceur, for instance when waters of different quality from different aquifers mingle — a fact to be considered in the future — and alsó as a result of pollution of subsurface waters from the surface. The clogging processes in the immediate vicinity of the well — especially the biological phenomena — may be influenced considerably by the boundary conditions in the upper part of the seepage system. These factors are discussed in the paper of Kulhavy: The capillary fringe above the groundwater contains usually dissolved oxygen in favourable quantities, offering advantageous ambient circumstances for the micro-organism. - Precipitation seeping in through the surface may carry components to the water flowing towards the well, by which the chloride (Fig. 8.) or nitráté content (Fig. 9.) of the water may change considerably. —• The amount of oxygen dissolved in the seeping water, the oxydation processes, nitrification, the possible denitrification, are im portant ambient factors from the point of micro-organisms in the water. This is indicated by Kulliavy, who maintains that the number of micro-organisms in the water of wells, can be related to the mean value of dissolved oxygen (Fig. 10.) — It is alsó pointed out that external factors mav cause the greatest changes in the components of groundwater quality in periods of groundwater level variation. An important role is attributed by W. Mevius alsó the "breathing of wells". Accordingly, the ambient factors controlling biological clogging, are highly important in the life of a well. Biological " clogging may occur if (according to Hasselbarth and Lüdemann) iron- and manganese bacteria are present in the water, - the amount of bivalent iron exceeds 0,2—0,5 mg/l, — the redoxpotential of water, related to the regular hydrogen electrode exceeds the value of - 10 mV± =0 mV and the rH = E

H

2o/0,0992 + + 2pH value exceeds 14,5±1, respectivelv, i L . WB 1962-1963 aW2 1962-1963 Cl 'p.p. m Fig. 8. Variation in chloride ions due to injiltrating precipitation Precipitation in mm Fig. í). Variation in nitráté concentration due to infiltrating precipitation Water nnimals in lm

3 of water Fig. 10. Relation between the number oj animál microorgcinisms and dissolved oxygen — the seepage velocity of water exceeds the natural value. Though part of the processes described above appear alsó independently from the material of the well, the ehoice of material is still decisive.