The efficacy of tangential flow hollow fiber Ultrafiltration (TFHFU) as a means of concentrating poliovirus 2 (Sabin) from large volumes of tap water was studied. Initially, hydrodynamic studies using 50-1 tap water feed solutions were conducted to evaluate transmembrane flux as a function of axial flow rates (or Reynold's numbers, Re). With increasing Reynold's number, flux-decline rates were reduced. As a result, experimental duration was shortened from 110 min at Re=300 to 30 min at Re=1728. In all cases, radial flow was assisted by a vacuum force applied to the outside of the hollow fibers. Virus recovery capability was evaluated using 20-, 50-, and 100-1 feed samples seeded with poliovirus 2 from 604 to 0.5 pfu/ml.
All virus experiments were conducted at Re=1728 and a vacuum force of 3.27 × 104 Pa. The mean duration of the 20-, 50-, and 100-1 experiments was 13, 42, and 79 minutes, respectively. The overall average virus recovery from all experiments was 69.1 ± 24.6%.
In operating the tangential-flow hollow fiber ultrafiltration module in its normal recycle-mode with low turbidity waters (<10 NTU), the expected steady flux-decline resulting from membrane fouling was not observed. Instead, the transmembrane permeation flux was maintained at a relatively constant value especially near the end of the experiments when the solute concentration in the feed increased the fastest. Increased feed water temperature resulting from the addition of pumping energy during recycle is responsible for this unexpected advantage. Final temperatures never exceeded a point at which virus inactivation would occur. For high turbidity feed waters (75 to 85 NTU), obtained by the addition of kaolin clay, virus recoveries varied from 30 to 49%, Final turbidities at the termination of a 50-1 run were from 950 to >1000 NTU. In spite of the high turbidity, the mean experiment duration for dehydrating 50 liters of turbid feed water was 39 minutes; approximately the same as for the low-turbidity tap water runs.
A Modified EPA Method 1623 that Uses Tangential Flow Hollow-fiber Ultrafiltration and Heat Dissociation Steps to Detect Waterborne Cryptosporidium and Giardia spp.
