Biodegradation of multiple microcystins and cylindrospermopsin in clarifier sludge and a drinking water source: Effects of particulate at- tached bacteria and phycocyanin Ehsan Maghsoudi a,n , Nathalie Fortin b , Charles Greer b , Sung Vo Duy c , Paul Fayad c , Sébastien Sauvé c , Michèle Prévost a , Sarah Dorner a a Polytechnique de Montréal, Civil, Mineral and Mining Engineering Department, P.O. Box 6079, Station Centre- Ville, Montréal, Québec, Canada H3C 3A7 b National Research Council Canada, Energy, Mining and Environment, 6100 Royalmount Ave., Montréal, QC, Canada H4P 2R2 c Department of Chemistry, Université de Montréal, C.P. 6128, Centre-Ville, Montréal, QC, Canada H3C 3J7 article info Article history: Received 3 November 2014 Received in revised form 30 May 2015 Accepted 1 June 2015 Keywords: Biodegradation Microcystin Cylindrospermopsin Clarifier sludge Phycocyanin Sludge management abstract The effects of particulate attached bacteria (PAB) and phycocyanin on the simultaneous biodegradation of a mixture of microcystin-LR, YR, LY, LW, LFand cylindrospermopsin (CYN) was assessed in clarifier sludge of a drinking water treatment plant (DWTP) and in a drinking water source. The biomass from lake water and clarifier sludge was able to degrade all microcystins (MCs) at initial concentrations of 10 mgL 1 with pseudo-first order reaction half-lives ranging from 2.3 to 8.8 days. CYN was degraded only in the sludge with a biodegradation rate of 1.0  10 1 d 1 and a half-life of 6.0 days. This is the first study reporting multiple MCs and CYN biodegradation in the coagulation–flocculation sludge of a DWTP. The removal of PAB from the lake water and the sludge prolonged the lag time substantially, such that no biodegradation of MCLY, LW and LF was observed within 24 days. Biodegradation rates were shown to increase in the presence of C-phycocyanin as a supplementary carbon source for indigenous bacteria, a cyanobacterial product that accompanies cyanotoxins during cyanobacteria blooms. MCs in mixtures degraded more slowly (or not at all) than if they were degraded individually, an important outcome as MCs in the environment are often present in mixtures. The results from this study showed that the majority of the bacterial biomass responsible for the biodegradation of cyanotoxins is associated with particles or bio- logical flocs and there is a potential for extreme accumulation of cyanotoxins within the DWTP during a transient bloom. & 2015 Elsevier Inc. All rights reserved. 1. Introduction Eutrophication of water bodies and subsequent blooms of harmful algae and cyanobacteria are increasingly reported all over the world (Hummert et al., 2001; Kokociński et al., 2009). The ability of cyanobacteria to produce toxins, which can cause severe impacts on human and animal health, has raised concerns among re- searchers and environmental regulators. A bloom of cyanobacteria is commonly composed of different toxin producing species with the potential to produce various cyanotoxins simultaneously; therefore, multiple cyanotoxins have been commonly detected in water bodies during cyanobacterial blooms (Ho et al., 2012c). Al- though toxins commonly occur as mixtures of multiple toxins, until recently, most of the studies on the biodegradation of cyanotoxins have focused on the biodegradation of individual toxins (Ishii et al., 2004; Park et al., 2001). The cyanotoxins that are released into the water during bloom senescence and cell lysis may be biodegraded by bacteria in the water, photo-degraded by sunlight, adsorbed onto suspended particulate matter, or accumulate in aquatic plants or animals (Harada and Tsuji, 1998). Each of these mechanisms contributes to the removal of cyanotoxins in the aquatic phase; however, bio- degradation has been suggested as the dominant elimination pathway (Chen et al., 2008). Particulate matter present in aquatic ecosystems plays an important role in the environmental fate of contaminants by regulating their transport in the dissolved and particulate phases (Håkanson, 2006). During phytoplankton blooms, free individual bacteria colonize and form particle-asso- ciated bacterial (PAB) assemblages (Riemann and Winding, 2001). The PAB communities or flocs are composed of inorganic (e.g., clays and silts) and organic (e.g., detritus and cellular debris) matter (Droppo, 2001; Kirchman, 1993). A considerable portion of microbial activity in water bodies is related to microbial Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety http://dx.doi.org/10.1016/j.ecoenv.2015.06.001 0147-6513/& 2015 Elsevier Inc. All rights reserved. n Corresponding author. Current address: École Polytechnique de Montreal, De- partment of Civil, Geological and Mining Engineering, P.O. Box 6079, Station Cen- tre-Ville, Montreal, Quebec, Canada, H3C 3A7. Fax: þ514 340 5918. E-mail address: ehsan.maghsoudi@polymtl.ca (E. Maghsoudi). Ecotoxicology and Environmental Safety 120 (2015) 409–417