title: Relationship between Organic Carbon and Opportunistic Pathogens in Simulated Glass Water Heaters.
abstract: Controlling organic carbon levels in municipal water has been hypothesized to limit downstream growth of bacteria and opportunistic pathogens in premise plumbing (OPPPs). Here, the relationships between influent organic carbon (0-15,000 µg ozonated fulvic acid /L) and the number of total bacteria [16S rRNA genes and heterotrophic plate counts (HPCs)] and a wide range of OPPPs (gene copy numbers of Acanthamoeba polyphaga, Vermamoeba vermiformis, Legionella pneumophila, and Mycobacterium avium) were examined in the bulk water of 120-mL simulated glass water heaters (SGWHs). The SGWHs were operated at 32-37 °C, which is representative of conditions encountered at the bottom of electric water heaters, with water changes of 80% three times per week to simulate low use. This design presented advantages of controlled and replicated (triplicate) conditions and avoided other potential limitations to OPPP growth in order to isolate the variable of organic carbon. Over seventeen months, strong correlations were observed between total organic carbon (TOC) and both 16S rRNA gene copy numbers and HPC counts (avg. R2 > 0.89). Although M. avium gene copies were occasionally correlated with TOC (avg. R2 = 0.82 to 0.97, for 2 out of 4 time points) and over a limited TOC range (0-1000 µg/L), no other correlations were identified between other OPPPs and added TOC. These results suggest that reducing organic carbon in distributed water is not adequate as a sole strategy for controlling OPPPs, although it may have promise in conjunction with other approaches.
authors.affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. kwilli@vt.edu.
authors.forename: Krista
authors.initials: K
authors.lastname: Williams
authors.affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. apruden@vt.edu.
authors.forename: Amy
authors.initials: A
authors.lastname: Pruden
authors.affiliation: Department of Biological Sciences, Virginia Tech, 5008 Derring Hall, Blacksburg, VA 24060, USA. jofiii@vt.edu.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Falkinham
authors.affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. edwardsm@vt.edu.
authors.forename: Marc
authors.initials: M
authors.lastname: Edwards
authors.affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. kwilli@vt.edu.
authors.forename: Krista
authors.initials: K
authors.lastname: Williams
authors.affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. apruden@vt.edu.
authors.forename: Amy
authors.initials: A
authors.lastname: Pruden
authors.affiliation: Department of Biological Sciences, Virginia Tech, 5008 Derring Hall, Blacksburg, VA 24060, USA. jofiii@vt.edu.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Falkinham
authors.affiliation: Via Department of Civil and Environmental Engineering, Virginia Tech, 401 Durham Hall, Blacksburg, VA 24060, USA. edwardsm@vt.edu.
authors.forename: Marc
authors.initials: M
authors.lastname: Edwards
keywords: Acanthamoeba; Legionella pneumophila; Mycobacterium avium; Pseudomonas aeruginosa; Vermamoeba vermiformis; assimilable organic carbon; biostability; drinking water; opportunistic pathogens; premise plumbing