Evaluation of Bioassays and Wastewater Quality ... - Oekotoxzentrum

5.1. Risk quotients of three relevant micropollutants during wastewater
treatment
Figure 7 shows results of the pilot study at the WWTP Vidy Lausanne for the three priority
substances. The change of the risk quotients and quality classes during wastewater treatment for
the 3 rd MC is shown. The respective quality criterion (AA-EQS) for the pain killer diclofenac is
50 ng/L, for the anticonvulsant carbamazepin 500 ng/L and for the antibiotic clarithromycin
60 ng/L (Götz et al., 2010).
Figure 7: Evolution of risk quotients during wastewater treatment: measured environmental
concentrations (MECs) from the screening of 120 substances at the Eawag and risk quotients (RQs) of
three selected micropollutants during wastewater treatment in the 3 rd measurement campaign (MC).
During wastewater treatment, the water quality regarding the three substances increased
significantly, from poor water quality up to good quality for diclofenac; from good to very good
water quality for carbamazepin; and from insufficient to good water quality for clarithromycin in
undiluted wastewater. During biological treatment the respective substance concentrations
decreased between 0.9 and 1.2 fold compared to the influent, and during PAC-UF or ozonation-
SF treatment the concentrations decreased additionally 7 to 46 fold compared to the biological
treatment. At the Regensdorf pilot study a similar improvement of water quality was observed.
In the adjacent watercourses, those values will be even lower due to the additional dilution. For
rivers usually a dilution factor of 10 is assumed, and for lake Geneva an estimated 50 fold
dilution showed the best correlation with the actually measured concentrations (Morasch et al.,
2010).
Swiss Centre for Applied Ecotoxicology, Eawag/EPFL · Überlandstrasse 133 · CH-8600 Dübendorf
www.oekotoxzentrum.ch
31