Assessment of storm water ecotoxicity using a battery of biotests

As part of the European Union 5th Framework Programme (EU FP5) sustainable storm water management project DayWater, an international monitoring programme was established to investigate the ecotoxicity of highway and urban runoff samples. This involved the collection of samples from a total of 35 storm events from sites in Sweden (Luleå and Stockholm), Germany (Wuppertal), and France (Nantes). To enable both chronic and acute end points to be addressed, the ecotoxicity tests were performed using rotifers (Brachionus calyciflorus), bacteria (Vibrio ficherii), and algae (Pseudokirchneriella subcapitata). Samples collected at the Stockholm site were additionally analysed for a range of water quality parameters enabling this site to be considered from a combined physico-chemical and ecotoxicological perspective. This paper provides an overview of the results of the whole monitoring programme and demonstrates that storm water frequently exerts a toxic effect. Although the levels of ecotoxicity detected were found to vary greatly in relation to sites, storm events and test organisms, further analysis demonstrated a moderately strong correlation between the responses of algae and rotifer tests. Microtox was generally found to be the most responsive test in terms of both frequency of detection of toxicity and level at which a toxic impact could be detected.