Abstract

This report presents the results of a repeated evaluation of the organic toxicity contained in water of the rivers Rhine and Meuse, the lakes "Ketelmeer" and "Wolderwijd", and the canal "Noordzeekanaal" in 1993. The toxicity of untreated water samples as well as selectively concentrated organic constituents was measured with the luminescent bacteria test, Microtox. The toxicity is expressed as the so-called pT-value (10log (EC20, t=.../100)), relating toxicity to environmental acceptability criteria. According to preformulated acceptability criteria, hardly any of the observed pT-values reflects favourable conditions.