The Multispecies Freshwater Biomonitor (MFB) based on quadropole impedance conversion technique is a “biological early warning system” (BEWS) for online water quality biomonitoring. The aim of this study was to test the MFB with two crustaceans (Gammarus pulex and Daphnia magna) in a drinking water processing plant at the River Rhine: 1) Sensitivity of the test species to short-term acid pulses and alarm-responses in the MFB were studied in the laboratory. 2) Long-term monitoring with Gammarus pulex and Daphnia magna in the MFB was performed in situ. A decrease in pH, especially below pH 6.8, resulted in a significant behavioural response of both species according to the Stepwise Stress Model. After a first escape response of D. magna, both species reacted similarly with decreased activity and G. pulex additionally with increased ventilation. G. pulex survived better than D. magna. The behavioural effects remained in the recovery phase. Long-term monitoring showed stable locomotory behaviour and better survival of G. pulex when compared to D. magna. The MFB can be recommended for drinking water control using G. pulex as test species.

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UV/H 2 O 2 treatment can be part of the process converting surface water to drinking water, but would pose a potential problem when resulting in genotoxicity. This study investigates the genotoxicity of samples collected from the water treatment plant Andijk, applying UV/H 2 O 2 treatment with an electrical energy dose of 0.54 kWh/m 3 and a H 2 O 2 dose of 6 mg/l. Genotoxicity was tested in vitro using the Ames and Comet assay. All samples showed negative results. Samples were also tested in in vivo genotoxicity tests in Eastern mudminnow fish (Umbra pygmaea) by a sister chromatid exchange (SCE) and a Comet assay. No significant increases in SCEs were observed, but gill cells isolated from fish exposed to water obtained immediately after UV/H 2 O 2 treatment and to Lake IJsselmeer water showed significantly increased DNA damage in the Comet assay. All other samples tested negative in this Comet assay. This indicates that DNA damaging compounds may result from the UV/H 2 O 2 treatment, but also that these can be efficiently eliminated upon granular activated carbon (GAC) treatment of the water. It is concluded that when combined with this subsequent GAC treatment, UV/H 2 O 2 treatment for the production of drinking water from surface water is not of concern with respect to genotoxicity.

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