Wastewater toxicity screening of non-ionic surfactants by Toxalert (R) andMicrotox (R) bioluminescence inhibition assays

The toxic response of commonly used non-ionic surfactants with different bi oluminescence inhibition assays (ToxAlert(R) 100 and Microtox(R) were estab lished. The 50% effective concentration (EC50) values were determined for e very standard substance using each assay, together with toxicity units (TU) . A sigmoidal curve was fitted and the (EC50) was calculated. Chemical analysis and bioassays were used in conjunction to provide a deter mination of aquatic toxicity in wastewaters. This methodology was applied t o real samples of influent and effluent wastewater treatment works in Spain and Portugal and also for untreated textile wastewater effluents. The protocol used in this paper involved different steps. First, the aquati c toxicity evaluation for every effluent was carried out using ToxAlert(R)1 00. For every one, a sigmoidal curve was fitted, the (EC50) and the toxicit y impact index (TII50) were calculated. Second, the identification and quan tification of polar organic cytotoxic substances and their contribution to the total toxicity was obtained, using sequential solid-phase extraction (S SPE) followed by liquid chromatography-mass spectrometry (LC-MS). The use of toxicity results tin terms of bioluminescence inhibition) like a screening parameter, is proposed. This procedure excludes the chromatograp hic analysis if the sample has less than the 20% inhibition. Overall, this procedure presented here helps to reduce the large number of samples and su b-samples that need to be processed in wastewater monitoring. (C) 2001 Else vier Science B.V. All rights reserved.