title: Assessing Methanobrevibacter smithii and Clostridium difficile as not conventional faecal indicators in effluents of a wastewater treatment plant integrated with sludge anaerobic digestion.
abstract: Wastewater treatment plants (WWTP) are an important source of surface water contamination by enteric pathogens, affecting the role of environmental water as a microbial reservoir. We describe the release to the environment of certain anaerobes of human and environmental concern. The work was focused on emerging microbial targets. They are tracing, by RT-qPCR, on WWTP effluents, both liquid and solid, when an anaerobic digestion step is included. The focus is placed on Clostridium spp. with the specific quantification of Clostridium perfringens, as typical bioindicator, and Clostridium difficile, as emerging pathogen not only confined into nosocomial infection. Moreover methanogens were quantified for their involvement in the anaerobic digestion, and in particular on Methanobrevibacter smithii as major methanogenic component of the human gut microbiome and as not conventional faecal indicator. In the water samples, a reduction, statistically significant, in all microbial targets was observed (p < 0.01), 2 log for the total bacteria, 1.4 log for the Clostridium spp. and M. smithii, 1 log for total methanogens, C. perfringens and C. difficile. The AD process contribute to a significant change in microbial levels into the sludge for total bacteria and total methanogens (p < 0.01), both when the input sludge are primary and secondary, while for the presence of Clostridium spp. and C. difficile there was not a significant change. The produced data are innovative showing which is the diffusion of such anaerobic microorganisms throughout the WWTP and opening a discussion on the implementation of possible techniques for a more efficient microbial removal from effluents, particularly bio-solids, to reduce the potential release of pathogens into the environment.
authors.affiliation: Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126 Torino, Italy. Electronic address: valeria.romanazzi@gmail.com.
authors.forename: Valeria
authors.initials: V
authors.lastname: Romanazzi
authors.affiliation: Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126 Torino, Italy. Electronic address: silvia.bonetta@unito.it.
authors.forename: Silvia
authors.initials: S
authors.lastname: Bonetta
authors.affiliation: Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126 Torino, Italy. Electronic address: stefania.fornasero@unito.it.
authors.forename: Stefania
authors.initials: S
authors.lastname: Fornasero
authors.affiliation: SMAT - Depuratore di Castiglione Torinese, Società Metropolitana Acque Torino S.p.A., Corso XI Febbraio 14, 10152 Torino, Italy. Electronic address: margherita.deceglia@smatorino.it.
authors.forename: Margherita
authors.initials: M
authors.lastname: De Ceglia
authors.affiliation: Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126 Torino, Italy. Electronic address: giorgio.gilli@unito.it.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Gilli
authors.affiliation: Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126 Torino, Italy. Electronic address: deborah.traversi@unito.it.
authors.forename: Deborah
authors.initials: D
authors.lastname: Traversi
mesh_terms: D001421:Bacteria, Anaerobic / Q000502:physiology; D019149:Bioreactors; D016360:Clostridioides difficile / Q000502:physiology*; D005160:Facility Design and Construction; D005243:Feces / Q000382:microbiology; D006801:Humans; D007558:Italy; D041581:Methanobrevibacter / Q000502:physiology*; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology
chemical_list: D012722:Sewage
keywords: Anaerobe; Anaerobic digestion; Clostridium; Methanogens; Wastewater treatment plant; qRT-PCR