Interlaboratory study of the bioluminescence inhibition tests for rapid wastewater toxicity assessment

Several toxicity procedures are currently being used for the wastewater toxicity assessment. We have undertaken an interlaboratory comparison of the use of different bioluminescence inhibition toxicity tests based on Vibrio fischeri, in order to evaluate their reproducibility for the rapid wastewater toxicity assessment. Twenty-two laboratories took part in this study organized by the Institut Català de Tecnologia (ICT) and the Consejo Superior de Investigaciones Cientificas (CSIC). During the exercise, six series of six samples were analyzed along 5 months. Every batch of samples was composed by three real samples and three standard solutions. The real samples were: an untreated effluent of a paper industry, a sample from a first settlement of a wastewater treatment plant (WWTP) and the final effluent of the WWTP. The goals of the interlaboratory study were to evaluate the repeatability (r) and reproducibility (R) when different laboratories conduct the test, the influence of different matrix samples, the variability between different tests based on the same principle: the bioluminescence inhibition of V. fischeri, but involving different commercial devices and to determine the rate at which participating laboratories successfully completed tests initiated. The maximum number of outlier values was corresponding to a non-treated effluent from a paper industry. This also was the most complex and toxic sample analyzed. An increase on the non-convergent values obtained for the participants was observed at higher matrix complexity and at lower toxicity level. In comparison with other editions of this interlaboratory study the matrixes of real samples analyzed were more complex, nevertheless the final variability coefficient for the exercise was nearby to the average value for the past editions. Due to the high complexity of some samples involved in this intercalibration the stability of real samples were also followed during the test. On the other hand, no relation was found between final results and the different devices, as show the cluster analysis.