We have evaluated nitrogen removal at three treatment plants (mannersdorf, Germerswang, See) in order to determine the relationship between effluent temperature, evapotranspiration, substratum, loading rates and the different types of nitrogen.

The results showed a very high and almost complete denitrification. In most of the plants nitrification was the limiting factor. Evapotranspiration was found to be one of the strongest factors supporting nitrification. Influence of the effluent temperature was significantly lower. Investigations on influence of the substratum showed better results for nitrification and denitrification on fine material containing clay. Conclusions for research and plant design are given.