title: The compartment bag test (CBT) for enumerating fecal indicator bacteria: Basis for design and interpretation of results.
abstract: For the past several years, the compartment bag test (CBT) has been employed in water quality monitoring and public health protection around the world. To date, however, the statistical basis for the design and recommended procedures for enumerating fecal indicator bacteria (FIB) concentrations from CBT results have not been formally documented. Here, we provide that documentation following protocols for communicating the evolution of similar water quality testing procedures. We begin with an overview of the statistical theory behind the CBT, followed by a description of how that theory was applied to determine an optimal CBT design. We then provide recommendations for interpreting CBT results, including procedures for estimating quantiles of the FIB concentration probability distribution, and the confidence of compliance with recognized water quality guidelines. We synthesize these values in custom user-oriented 'look-up' tables similar to those developed for other FIB water quality testing methods. Modified versions of our tables are currently distributed commercially as part of the CBT testing kit.
authors.affiliation: NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, USA; Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI, USA. Electronic address: drew.gronewold@noaa.gov.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Gronewold
authors.affiliation: Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Sobsey
authors.affiliation: United States Agency for International Development (USAID), Washington, D.C., USA.
authors.forename: Lanakila
authors.initials: L
authors.lastname: McMahan
mesh_terms: D001419:Bacteria; D004784:Environmental Monitoring / Q000379:methods*; D005243:Feces / Q000382:microbiology; D014871:Water Microbiology; D014876:Water Pollution / Q000032:analysis* / Q000706:statistics & numerical data
keywords: Compartment bag test; Drinking water; Human health; Statistical methods; Water quality