Premium
Application of Quantitative Microbial Risk Assessment at 17 Canadian Water Treatment Facilities
Author(s) -
Tfaily Randa,
Papineau Isabelle,
Andrews Robert C.,
Barbeau Benoit
Publication year - 2015
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.5942/jawwa.2015.107.0141
Subject(s) - disinfectant , continuous stirred tank reactor , risk assessment , environmental science , water treatment , filtration (mathematics) , environmental engineering , mathematics , medicine , chemistry , statistics , computer science , computer security , pathology
A quantitative microbial risk assessment model developed by Health Canada was applied at 17 water treatment plants (WTPs) located throughout Ontario and Quebec, Canada. Four source water characterization methods were compared that considered Escherichia coli , Giardia , and Cryptosporidium . In addition, three strategies to evaluate chemical disinfection performances were compared (median disinfectant exposure [CT 50 ], regulatory disinfectant exposure [CT 10 ], and continuous‐stirred tank reactors in‐series [N‐CSTR, where N is the number of CSTRs in the series]). The N‐CSTR approach provides more reliable risk estimates because it is less sensitive to high inactivation conditions (when compared with use of CT 10 or CT 50 ). Predicted risk estimates for the 17 WTPs revealed that only two did not comply with the 10 –6 disability‐adjusted life years (World Health Organization) and 10 –4 risk of infection (US Environmental Protection Agency) reference levels because of the poor performance of direct filtration without coagulation. This publically available quantitative microbial risk assessment model could help WTP managers assess overall treatment performance via a systematic evaluation process.