Quantitative microbial risk assessments for drinking water facilities: evaluation of a range of treatment strategies

Abstract

Quantitative microbial risk assessments (QMRA) was conducted for 10 drinking water facilities located in Canada. Monthly risk estimates were based upon a suite of reference pathogens for the raw water, as well as detailed process assessments that considered the variability treatment at individual treatment facilities. The majority of the facilities (9 out of 10) maintained risk levels significantly below the World Health Organization's target of 10⁻⁶ DALY per person per year. Cryptosporidium was shown to be the most significant contributor for microbial risk at all locations. Potential treatment specific failure scenarios were evaluated; most treatment facilities were capable of withstanding partial filtration and disinfection failures as a result of the multi-barriers employed.