Charakterisierung des chemischen Zustandes der Limmat zwischen Zürichsee und Wettingen (1974–1978)

In connection with the enlargement and updating of the Werdhölzli sewage treatment plant, research was undertaken on the chemistry of that part of the River Limmat lying between Lake Zürich and Wettingen from 1974 to 1978. The extensive amount of data involved was subjected to statistical analysis and the results are being interpreted. In general, the chemical condition of the water of the Limmat river upstream from the Werdhölzli sewage plant can be described as good. In order to attain the desired water quality criteria downstream of the waste-water outfall of the plant, pollution in therms of ammonium nitrogen and organic substances must be reduced. The performing of a chemical pre-precipitation process has brought about a sizable reduction in the phosphorus concentration of the Limmat river downstream of the plant; the values are now below the required water quality limits.