Dead-end hollow-fiber ultrafiltration for recovery of diverse microbes from water

Abstract

Dead-end ultrafiltration (DEUF) is an alternative approach to tangential-flow hollow-fiber ultrafiltration that can be readily employed under field conditions to recover microbes from water. The hydraulics of DEUF and microbe recovery for a new DEUF method were investigated using 100-liter tap water samples. Pressure, flow rate, and temperature were investigated using four hollow-fiber ultrafilter types. Based on hydraulic performance, the Asahi Kasei REXEED 25S ultrafilter was selected for microbe recovery experiments. Microbe recovery experiments were performed using MS2 bacteriophage, Enterococcus faecalis, Clostridium perfringens spores, and Cryptosporidium parvum oocysts. Microbes were recovered from ultrafilters by backflushing using a surfactant solution. Average flow rates were 2.1 liters/min for 100-liter water samples having turbidities of 0.28 to 4.3 nephelometric turbidity units (NTU), and no evidence of appreciable filter clogging was observed. The DEUF average recovery efficiencies for each study analyte in tap water were as follows: for E. faecalis, 93% +/- 16%; for MS2, 57% +/- 7.7%; for C. perfringens spores, 94% +/- 22%; and for C. parvum, 87% +/- 18%. Average microbe recoveries for tap water amended with surface water (average turbidity = 4.3 NTU) were as follows: for E. faecalis, 78% +/- 12%; for MS2, 73% +/- 13%; for C. perfringens, 57% +/- 21%; and for C. parvum, 83% +/- 21%. These data demonstrate that DEUF is an effective method for recovering diverse microbes from water and should be a useful tool for field-based environmental investigations.

FIG. 1.

Schematic of the dead-end UF setup for filtering water samples.

FIG. 2.

Schematic of the setup for backflushing hollow-fiber ultrafilters.

FIG. 3.

Pressure and flow rates for the following ultrafilters when filtering tap water at 18°C (open symbols) or 4.8°C (shaded symbols): Exeltra Plus 210 (A and B) (○ and •, respectively), F200NR (C) (⋄), REXEED 21S (D and E) (▵ and ▴, respectively), and REXEED 25S (F and G) (□ and ▪, respectively).