Evaluation of an Ultrafiltration-Based Procedure for Simultaneous Recovery of Diverse Microbes in Source Waters

Abstract

In this study, hollow-fiber ultrafiltration (UF) was assessed for recovery of Escherichia coli, Clostridium perfringens spores, Cryptosporidium parvum oocysts, echovirus 1, and bacteriophages MS2 and ΦX174 from ground and surface waters. Microbes were seeded into twenty-two 50-L water samples that were collected from the Southeastern United States and concentrated to ∼500 mL by UF. Secondary concentration was performed for C. parvum by centrifugation followed by immunomagnetic separation. Secondary concentration for viruses was performed using centrifugal ultrafilters or polyethylene glycol precipitation. Nine water quality parameters were measured in each water sample to determine whether water quality data correlated with UF and secondary concentration recovery efficiencies. Average UF recovery efficiencies were 66%-95% for the six enteric microbes. Average recovery efficiencies for the secondary concentration methods were 35%-95% for C. parvum and the viruses. Overall, measured water quality parameters were not significantly associated with UF recovery efficiencies. However, recovery of ΦX174 was negatively correlated with turbidity. The recovery data demonstrate that UF can be an effective method for concentrating diverse microbes from ground and surface waters. This study highlights the utility of tangential-flow hollow fiber ultrafiltration for recovery of bacteria, viruses, and parasites from large volume environmental water samples.

Keywords: Centricon Plus-70; groundwater; immunomagnetic separation (IMS); pathogen detection; polyethylene glycol; surface water; ultrafiltration.

Figure 1

One-way ANOVA for UF percent recovery. Diamonds represent means (line near the center of each diamond), with 95% confidence intervals for each mean (the vertical span), based on the pooled estimate of the standard error. Comparison circles summarize the results of the multiple comparison procedure. The selected mean has bold, red circle and variable label (in this Figure, E. coli). Means that are not significantly different from the selected mean have unbolded, red circles and variable labels. Means that are significantly different from the selected mean have gray circles and gray italicized variable labels. In this example, the mean for E. coli is significantly different from the mean for echovirus 1, but is not significantly different from the mean for other microbes.

Figure 2

UF recovery efficiency by turbidity, for ΦX174, with spline (a); and linear regression line overlaid (b).