Contribution of treated wastewater to the microbiological quality of Seine River in Paris Laurent Moulin a, *, Fanny Richard a , Sabrina Stefania a , Marion Goulet a , Sylvie Gosselin a , Alexandre Gonc¸alves b , Vincent Rocher b , Catherine Paffoni b , Aure´lien Dume`tre c a EAU DE PARIS, 144 Avenue Paul Vaillant-Couturier, 75014 Paris, France b SIAAP, Direction du De´veloppement et de la Prospective, 82 Avenue Kle´ber, 92700 Colombes, France c UMR MD3 Relations Hoˆte-Parasites, Pharmacologie et The´rapeutique, Faculte´ de Pharmacie, 27 Boulevard Jean Moulin, 13385 Marseille cedex 05, France article info Article history: Received 3 February 2010 Received in revised form 26 May 2010 Accepted 15 June 2010 Available online 22 June 2010 Keywords: Cryptosporidium Giardia Enterovirus Bacterial indicators wastewater Drinking water abstract Urban part of Seine River serving as drinking water supply in Paris can be heavily contaminated by Cryptosporidium spp. and Giardia duodenalis. In the absence of agricultural practice in this highly urbanized area, we investigated herein the contribution of treated wastewater to the microbiological quality of this river focusing on these two parasites. Other microorganisms such as faecal bacterial indicators, enteroviruses and oocysts of Toxoplasma gondii were assessed concurrently. Raw wastewaters were heavily contaminated by Cryptosporidium and Giardia (oo)cysts, whereas concentrations of both protozoa in treated wastewater were lower. Treated wastewater, flowed into Seine River, had a parasite concentration closed to the one found along the river, in particular at the entry of a drinking water plant (DWP). Even if faecal bacteria were reliable indicators of a reduction in parasite concentrations during the waste- water treatment, they were not correlated to protozoal contamination of wastewater and river water. Oocysts of T. gondii were not found in both raw and treated wastewater, or in Seine River. Parasitic contamination was shown to be constant in the Seine River up to 40 km upstream Paris. Altogether, these results strongly suggest that treated wastewater does not contribute to the main parasitic contamination of the Seine River usually observed in this urbanized area. ª 2010 Elsevier Ltd. All rights reserved. 1. Introduction Cryptosporidium spp. and Giardia duodenalis are anthropozoonotic protozoa causing mild to severe worldwide diarrhoeal diseases in humans. They are transmitted via the fecaleoral route, by food or water contaminated by Cryptosporidium oocysts and Giardia cysts. These transmission stages are shed in large quantities (10 8 e10 9 ) with the faeces of infected hosts (Fayer, 2004; Thompson, 2004). They remain infective for months in water and are highly resistant to harsh conditions including chemical disinfection (Betancourt and Rose, 2004). Surface waters such as rivers, natural and artificial lakes serve as drinking water supplies in areas where underground resources are scarce or cannot be used appropriately for drinking water production. However, surface waters can be significantly contaminated by Cryptosporidium oocysts and Giardia cysts that are transported from soil to water by agri- cultural or urban runoffs (Xiao and Fayer, 2008). Additionally, parasites from final effluents of wastewater treatment plants (WWTPs) can also enter surface waters in appreciable amount as reported in several European countries (Caccio` et al., 2003; Karanis et al., 2006; Roberston et al., 2006; Castro-Hermida * Corresponding author. Tel.: þ33 140847707; fax: þ33 140847709. E-mail address: laurent.moulin@eaudeparis.fr (L. Moulin). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 44 (2010) 5222 e5231 0043-1354/$ e see front matter ª 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2010.06.037