• Mueller, Jochen
• Macova, Miroslava
• Toze, Simon
• Hodgers, Leonie
• Bartkow, Michael
• Escher, Beate

Abstract

A bioanalytical test battery was used for monitoring organic micropollutants across an indirect potable reuse scheme testing sites across the complete water cycle from sewage to drinking water to assess the efficacy of different treatment barriers. The indirect potable reuse scheme consists of seven treatment barriers: (1) source control, (2) wastewater treatment plant, (3) microfiltration, (4) reverse osmosis, (5) advance oxidation, (6) natural environment in a reservoir and (7) drinking water treatment plant. Bioanalytical results provide complementary information to chemical analysis on the sum of micropollutants acting together in mixtures. Six endpoints targeting the groups of chemicals with modes of toxic action of particular relevance for human and environmental health were included in the evaluation: genotoxicity, estrogenicity (endocrine disruption), neurotoxicity, phytotoxicity, dioxin-like activity and non-specific cell toxicity. The toxicity of water samples was expressed as toxic equivalent concentrations (TEQ), a measure that translates the effect of the mixtures of unknown and potentially unidentified chemicals in a water sample to the effect, which a known reference compound would cause. For each bioassay a different representative reference compound was selected. The TEQ were observed to decrease across the seven treatment barriers in all six selected bioassays. Each bioassay showed a differentiated picture representative for a different group of chemicals and their mixture effect. The TEQ of the samples across the seven barriers were in the same order of magnitude as seen during previous studies in wastewater and advanced water treatment plants and reservoirs. Treatment in Barrier 2 (wastewater treatment plant) resulted in water that exhibited a much lower response in all selected bioassays.A further decrease in biological effects in the water was observed after microfiltration (Barrier 3) and reverse osmosis treatment (Barrier 4), as well in water sampled from an alternative advanced water treatment process that is comprised of ozonation followed by biologically activated carbon filtration. Detection limits of the bioassays, comparable to or lower than the quantification limits of the routine chemical analysis, allowed monitoring of the presence and removal of micropollutants post Barrier 2 and in drinking water. The results obtained by bioanalytical tools were reproducible, robust and consistent with previous studies assessing the effectiveness of the wastewater and advanced water treatment plants. The results of this study indicate that bioanalytical results expressed as TEQ are useful to assess removal efficiency of micropollutants throughout all treatment steps of water recycling.

Topics

• impedance spectroscopy
• compound
• Carbon
• toxicity