Treatment of water by oxidation processes – Testing schemes for assessment of toxicity
A number of technical and natural processes leads to the transformation of chemicals in the aquatic environment. These processes include ozonation and ultraviolet radiation. Even otherwise stable chemicals can be eliminated in this, for example from drinking and waste water. Is, however, the transformation of the chemicals identical to a reduced environmental risk? Based on a tight link between understanding chemical transformation processes, chemical analytics and biological assays, we develop strategies that allow to address this question. The so-called effect-driven assessment is at the heart of this procedure.
The effect-driven assessment approach is based on the toxic potential of the parent compound and of the mixtures arising from transformation processes, as determined by biological testing. If, during transformation, the toxic potential of a mixture decreases in proportion to the disappearance of the parent compound, it can be assumed that toxicity is dominated by the parent compound, and the transformation products are not relevant for the environmental risk assessment. Only if the toxicity of the mixture is greater than would be expected for the parent compound are further steps required to identify the toxicologically active substance(s) (Figure 1). This would include, for example, a combination of fractionation and biological and chemical analysis. We have so far explored this strategy for a number of different chemical classes and biological effects in defined water samples as well as complex matrices.