Environmental Engineering and Management Journal November 2012, Vol.11, No. 11, 2073-2076 http://omicron.ch.tuiasi.ro/EEMJ/ “Gheorghe Asachi” Technical University of Iasi, Romania COMPARISON OF CONVENTIONAL AND Vibrio fischeri BIOASSAYS FOR THE ASSESSMENT OF MUNICIPAL WASTEWATER TOXICITY Nora Kováts 1 , Maha Refaey 2 , Bettina Varanka 2 , Károly Reich 2 , Árpád Ferincz 1 , András Ács 1 1 Institute of Environmental Sciences of the University of Pannonia, 10 Egyetem Street, Veszprém, H-8200, Hungary 2 Institute of Environmental Engineering of the University of Pannonia, 10 Egyetem Street, Veszprém, H-8200, Hungary Abstract The bioassay based on the bioluminescence inhibition of Vibrio fischeri has been successfully applied to test municipal wastewater toxicity, in fact, the ISO 11348-3 standard was especially issued to prescribe the application of this test in wastewater toxicity assessment. However, this protocol cannot take into consideration virtual toxicity caused by turbidity or color of the sample tested. On the contrary, the kinetic version of the V. fischeri assay (ISO 21338:2010: Water quality - Kinetic determination of the inhibitory effects of sediment, other solids and colored samples on the light emission of Vibrio fischeri /kinetic luminescent bacteria test/) was developed to mitigate the drawbacks of the original protocol. Municipal wastewaters are often turbid/colored. Two versions of the V. fischeri bioluminescence inhibition assays were applied for municipal wastewater samples, before and after filtering. In most cases, the traditional version of the bioassay detected higher toxicity than the kinetic version, most possibly implying that reduced light emittance caused by solid particles and/or color also contributed to toxicity readings. Key words: Flash, kinetic assay, municipal wastewater, ToxAlert, Vibrio fischeri Received: July 2012, Revised final: October 2012, Accepted: November 2012  Author to whom all correspondence should be addressed: e-mail: kovats@almos.vein.hu; Phone/Fax: +36 88 624442 1. Introduction The bioassay based on the bioluminescence inhibition of Vibrio fischeri is probably the most widely applied bacterial test in wastewater toxicity assessment. Bacterial bioluminescence is attributed to the activation of the enzyme luciferase with luciferin. The attenuation of light emitted by bacteria in presence of a toxicant is related to the inhibition of this reaction. As bioluminescence of V. fischeri is directly linked to respiratory activity, it provides a good indicator of the metabolic status and has been found to be well correlated with in vivo toxicity tests using higher organisms (Kaiser et al., 1994). The earliest commercial application of this biochemical reaction dates back to 1981, when Beckman Instruments introduced its system which is presently marketed under the name ‘Microtox’ (Microbics Corporation, Carlsbad, CA, later on AZUR Environmental) (Bulich and Isenberg, 1981). Other commercial systems exist such as ToxAlert (Merck), LUMIStox (Hach Lange), BioTox (ABOATOX). There are several standardized protocols, proposed first by Bulich (1979) and applied by national (e.g. AFNOR, 1991) or international organizations (ISO, 1998). As V. fischeri is a marine bacterium, the conventional protocol uses aqueous samples (in compliance with ISO 11348-3 (ISO, 2007)). The test has been widely used for assessing municipal wastewater toxicity (Manusadzianas et al., 2003; Wang et al., 2003; Ren, 2004; Ellouze et al., 2009) and is often incorporated in national regulations, e.g. in Hungary the 27/2005 Decree of the Minister for Environmental Affairs and Water Management on the control of discharging used and wastewaters applies.