Evaluation of a Filtration/Dispersion Method for Enumeration of Particle‐associated Escherichia coli

Abstract

The transport processes of microorganisms in storm‐generated flows have not been clearly elucidated, limiting the ability of computational models to effectively design and evaluate watershed remediation plans. Although several studies have identified association with particulates as a critical factor in predicting microbial transport and fate, no generally accepted method exists for the identification of the planktonic and particle‐associated fractions of microorganisms in water samples. In this study, a filtration/dispersion method proposed for quantification of these fractions was verified using laboratory‐composed samples of bovine Escherichia coli and sterile topsoil. A statistical experimental design allowed quantification of potential sources of experimental error (e.g., filter retention, die‐off), although no significant sources of methodological error were identified. On average, 78% of E. coli cells were particle associated after 1 h of contact time. Further application of the method was illustrated by an isotherm experiment examining the association of a bovine strain of E. coli with sterile topsoil. Further examination of this method in laboratory or field‐based studies of microbial partitioning between the planktonic and particulate phases in surface runoff appears justified.