Current water quality monitoring practices mainly rely on targeted chemical analysis of a selected set of compounds (e.g. priority compounds). This compound-oriented approach, however, does not cover the entire load of pollution and may overlook the presence of the vast majority of biologically active chemicals. Effect-oriented testing approaches can overcome this limitation by measuring the effect of the total mixture of compounds that are present in a sample. The CALUX® assay panel is particularly suitable for this purpose since it detects several key adverse effects in relation to water quality. Specific trigger values have been defined allowing routine monitoring of water quality and water processing steps.