Original paper

Zur Nitrifikation in Mosel und Donau

[On Nitrification in the Rivers Moselle and Danube]

Müller, Dieter; Kirchesch, Volker


The effects of nitrification processes on typical reaches of the Moselle and the Danube are compared. The Moselle is a navigable river, regulated by weirs, and polluted with ammonium, whereas the Danube section under consideration is freely flowing and is subjected but to light pollution. In the Moselle the N-BOD is much higher than the C-BOD. In the Danube N-BOD7 represents about 30% of the BOD7. The longitudinal profiles for ammonium and the activity of nitrifying bacteria, characterized by the "Maximum oxygen consumption of nitrifiers under laboratory conditions", show consistently the maximum of nitrifiers downstream of the maximum of the ammonium-content. As a direct measurement of the different processes involved in ammonium metabolism in rivers seems nearly impossible, these processes are quantified with the aid of mathematical simulation techniques. Therefore the mathematical functions which are combined in a waterquality model are used to calculate the rates for NH4-release caused by the degradation of organic substances and by the degradation of algae as well as to determine the increase in NH4 caused by the growth of algae, nitrification by suspended bacteria and nitrification by attached bacteria. The overall effect of nitrification in the Danube is approximately in balance with the ammonium release due to degradation processes, whereas in the Moselle nitrification is of great significance in the reduction of the concentration of ammonium and the decrease in oxygen caused by this process.