Microbial Quality and Risk Assessment of Alternative Sources of Drinking Water Impacted by Waste Water: An Analysis of NC Type 2 Reclaimed Water for Potable Reuse Public Deposited

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  • March 20, 2019
  • Bailey, Emily
    • Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
  • Recent North Carolina reclaimed water legislation has proposed a new potable reuse scheme that involves the use of the combination of tertiary treated, dual disinfected reclaimed water with currently used drinking water sources of surface water in a ratio of at least 80% surface water and up to 20% reclaimed, followed by storage for a minimum of 5 days and treatment by conventional drinking water treatment processes. However, the tertiary treated, dual disinfected reclaimed water proposed by NC, for potable reuse and designated as type 2 has not been evaluated for microbial quality or examined in full-scale production scenarios. The goal of this research was to collect real world data on type 2 reclaimed water by conducting field studies on the performance of NCT2 like reclaimed water producing treatment facilities, as well as to evaluate the risk of exposure to this water in potable reuse scenarios by conducting microbiological water quality analyses and then quantitative microbial risk assessments (QMRAs). Field samples of wastewater and water were collected over a one-year period from 4 NCT2RW producing facilities, along with sewage impacted surface waters considered candidates for the 80/20 combination as sources for drinking water production. Water samples were examined for the microbial indicators specified in the NC legislation and for representative pathogens of public health interest. Based on microbial water quality analyses and QMRA analysis, there is evidence that the risks associated with either consumption associated with potable reuse or agricultural risks associated with exposure to raw fruits and vegetables, are not reduced below the annual risk level of 1 x 10-4 set by US EPA for drinking water. Relatively high concentrations of human enteric viruses, especially culturable enteric adenoviruses as well as microscopically detectable protozoan parasites were detectable in samples of NCT2RW that met the water quality requirements for the regulated fecal indicator microorganisms. These results have implications for the practical use of this type of reclaimed water as a source of drinking water and produce irrigation in the future, compared to its current use only for landscape irrigation.
Date of publication
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Rights statement
  • In Copyright
  • Simmons, Otto, III
  • Sobsey, Mark
  • MacDonald Gibson, Jacqueline
  • Knappe, Detlef
  • Stewart, Jill
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017

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