Evaluation of Bioassays and Wastewater Quality ... - Oekotoxzentrum

Biological wastewater treatment presented decreased effects as indicated by most in vitro
bioassays measuring effects on specific cellular mechanisms. Exceptions were progesterone-like
activity, which increased. An explanation might be that this substance class was insufficiently
removed during biological treatment, or that breakdown products contributed to this effect. In
general, the measured concentrations of progesterone-like acting substances (e.g. progesterone,
a steroid hormone involved in the menstruation cycle, pregnancy and embryogenesis of humans
and other species, and medroxyprogesterone or levonorgestrel, synthetic progestogens similar
to progesterone) were low and ranged from 0.11 ng/L (EN, 2 nd MC) to 2.6 ng/L (SB, 1 st MC) (see
Table 13, Appendix). Those concentrations were in the same range as data from earlier studies
on effluent samples and surface waters (Kolodziej and Sedlak, 2007; Van der Linden et al.,
2008). Known effect concentration data of these substances for aquatic organisms are rare, and
ranged from 156 ng/L for the western clawed frog (Xenopus tropicalis) (Kvarnryd et al., 2011) up
to 5000 μg/L for adult rainbow trout (Billard et al., 1981). Therefore, these data are difficult to
interpret, and further investigation is needed before the environmental relevance of this finding
can be established. The influent samples were cytotoxic to cell cultures used in the H295R
steroidogenesis assay .
Glucocorticoid like acting substances (i.e. steroid hormones affecting the metabolism of glucose
and reducing immune activity, e.g. cortisol, corticosterone) were unaffected by biological
treatment. Concentrations of those substances (expressed as dexmethasone equivalent
concentrations) ranged from < 4 ng/L (PAC-UF, 2 nd -4 th MC) to 140 ng/L (LF, 2 nd MC) (see Table
12, Appendix). The lowest effect concentration for aquatic organisms found in the literature was
3.46 µg/L for the African clawed frog (Xenopus laevis) exposed to corticosterone (Lorenz et al.,
2009), which is 24 times higher than the highest measured value in the pilot study. However as
toxicity data regarding this substance class are still rare no final conclusion on the environmental
relevance of the measured concentrations can be drawn.
The effect of biological treatment on photosystem II inhibiting herbicides showed variable results.
Ozonation and PAC-UF decreased effects as indicated by all in vitro bioassays used, with one
exception. In the H295R steroidogenesis assay, the advanced treatment processes were not
able to reduce the slight inhibition of testosterone production, which was present in biologically
treated wastewater.
Sand filtration by itself showed variable results. These results are discussed in more detail in
chapter 4.3.4.
The net effect of ozonation plus sand filtration was a decrease in toxicity for most in vitro
bioassays.
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