Drinking water biofilm development is affected by the available nutrient levels and the presence of disinfectants. Phosphorus is recognized as another important limiting nutrient besides organic carbon. In this study, drinking water biofilms were developed in annular reactors to examine the effects of phosphorus on the biofilm disinfections with free chlorine and monochloramine. Phosphorus addition was found to increase the biofilm cell number but decrease the exopolysaccharides (EPS) production. The disinfection efficacies of both free chlorine and monochloramine were increased when phosphorus was added into the reactor systems. At the same disinfection dosages, monochloramine showed greater biofilm removal efficiency than free chlorine. Monochloramine could be a better choice than free chlorine in biofilm disinfection when phosphate-based corrosion inhibitors are applied.
Yersinia enterocolitica has been detected in surface water, and drinking untreated water is a risk factor for infection. PCR-based methods have been used to detect Y. enterocolitica in various sample types, but quantitative studies have not been conducted in water. In this study, quantitative PCR (qPCR)-based methods targeting the Yersinia virulence genes ail and yadA were used to survey the Grand River watershed in southern Ontario, Canada. Initial testing of reference strains showed that ail and yadA PCR assays were specific for pathogenic biotypes of Y. enterocolitica; however the genes were also detected in one clinical Yersinia intermedia isolate. A survey of surface water from the Grand River watershed showed that both genes were detected at five sampling locations, with the ail and yadA genes detected in 38 and 21% of samples, respectively. Both genes were detected more frequently at colder water temperatures. A screening of Yersinia strains isolated from the watershed showed that the ail gene was detected in three Y. enterocolitica 1A/O:5 isolates. Results of this study show that Yersinia virulence genes were commonly detected in a watershed used as a source of drinking water, and that the occurrence of these genes was seasonal.
