title: Evaluation of virus reduction efficiency in wastewater treatment unit processes as a credit value in the multiple-barrier system for wastewater reclamation and reuse.
abstract: The virus reduction efficiency of each unit process is commonly determined based on the ratio of virus concentration in influent to that in effluent of a unit, but the virus concentration in wastewater has often fallen below the analytical quantification limit, which does not allow us to calculate the concentration ratio at each sampling event. In this study, left-censored datasets of norovirus (genogroup I and II), and adenovirus were used to calculate the virus reduction efficiency in unit processes of secondary biological treatment and chlorine disinfection. Virus concentration in influent, effluent from the secondary treatment, and chlorine-disinfected effluent of four municipal wastewater treatment plants were analyzed by a quantitative polymerase chain reaction (PCR) approach, and the probabilistic distributions of log reduction (LR) were estimated by a Bayesian estimation algorithm. The mean values of LR in the secondary treatment units ranged from 0.9 and 2.2, whereas those in the free chlorine disinfection units were from -0.1 and 0.5. The LR value in the secondary treatment was virus type and unit process dependent, which raised the importance for accumulating the data of virus LR values applicable to the multiple-barrier system, which is a global concept of microbial risk management in wastewater reclamation and reuse.
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan E-mail: dsano@eng.hokudai.ac.jp.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ito
authors.affiliation: Department of Computer Science, Graduate School of Engineering, Gunma University, Tenjinmachi 1-5-1, Kiryu, Gunma 376-8515, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kato
authors.affiliation: Department of Computer Science, Graduate School of Engineering, Gunma University, Tenjinmachi 1-5-1, Kiryu, Gunma 376-8515, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Department of Urban Engineering, School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 190-8518, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Katayama
authors.affiliation: Department of Soil, Water, and Climate, University of Minnesota, 258 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishii
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan E-mail: dsano@eng.hokudai.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okabe
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan E-mail: dsano@eng.hokudai.ac.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sano
mesh_terms: D000256:Adenoviridae / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D001499:Bayes Theorem; D002713:Chlorine / Q000494:pharmacology; D004202:Disinfectants / Q000494:pharmacology; D004203:Disinfection; D004784:Environmental Monitoring; D008962:Models, Theoretical; D029322:Norovirus / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000821:virology*
chemical_list: D002713:Chlorine; D004202:Disinfectants; D062065:Wastewater