In a series of p H 7 continuous-flow column experiments, removal of the bacteriophage MS-2 by attachment to silica beads had a strong, systematic dependence on the amount of hydrophobic surface present on the beads. With no hydrophobic surface, removal of phage at p H 5 was much greater than at pH 7. Release of attached phage at both pH values did occur, but was slow; breakthrough curves exhibited tailing. Poliovirus attached to silica beads at pH 5.5 much more than at pH 7.0, and attachment was also slowly reversible. Time scales for phage and poliovirus attachment were of the order of hours. The sticking efficiency factor (a), reflecting microscale physicochemical influences on virus attachment, was in the range of 0.0007-0.02. Phage release was small but measurable under steady state conditions. Release was enhanced by lowering ionic strength and by introducing beef extract, a high-ionic-strength protein solution. Results show that viruses experience reversible attachment/detachment (sometimes termed sorption), that large chemical perturbations are needed to induce rapid virus detachment, and that viruses should be quite mobile in sandy porous media. Even small amounts of hydrophobic organic material in the porous media (>0.001%) can retard virus transport.

Transport of the bacteriophage PRD‐1, bacteria, and latex microspheres was studied in a sandy aquifer under natural‐gradient conditions. The field injection was carried out at the U.S. Geological Survey's Toxic Substances Hydrology research site on Cape Cod. The three colloids and a salt tracer (Br−) moved along the same path. There was significant attenuation of the phage, with PRD‐1 peak concentrations less than 0.001 percent of Br− peaks 6 m from the source; but the low detection limit (one per ml) enabled tracking movement of the PRD‐1 plume for 12 m downgradient over the 25‐day experiment. Attenuation of phage was apparently due to retention on soil particles (adsorption). Attenuation of bacteria and microspheres was less, with peak concentrations 6 m from the source on the order of 10 and 0.4 percent of Br−, respectively. Injection of a high‐pH pulse of water 20 days into the experiment resulted in significant remobilization of retained phage, demonstrating that attached phage remained viable, and that PRD‐1 attachment to and detachment from the sandy soil particles was highly pH dependent. Phage behavior in this experiment, i.e. attenuation at pH 5.7 and rapid resuspension at pH 6–8, was consistent with that observed previously in laboratory column studies. Results illustrate that biocolloids travel in a fairly narrow plume in sandy (relatively homogeneous) media, with virus concentrations dropping below detection limit several meters away from the source; bacteria concentrations above detection limits can persist over longer distances.

No abstract

Water disinfection systems utilizing electrolytically generated copper and silver ions (200 and 20, 400 and 40, or 800 and 80 ,ug/liter) and low levels of free chlorine (0.1 to 0.4 mg/liter) were evaluated at room (21 to 23°C) and elevated (39 to 40°C) temperatures in filtered well water (pH 7.3) for their efficacy in inactivating Legionella pneumophila (ATCC 33155). At room temperature, a contact time of at least 24 h was necessary for copper and silver (400 and 40 ,ug/liter) to achieve a 3-log1o reduction in bacterial numbers. As the copper and silver concentration increased to 800 and 80 pg/liter, the inactivation rate significantly (P s 0.05) increased from K = 2.87 x 10-3 to K = 7.50 x 10-3 (loglo reduction per minute). In water systems with and without copper and silver (400 and 40 ,g/liter), the inactivation rates significantly increased as the free chlorine concentration increased from 0.1 mg/liter (K = 0.397 log1o reduction per min) to 0.4 mg/liter (K = 1.047 log1o reduction per min). Compared to room temperature, no signfficant differences were observed when 0.2 mg of free chlorine per liter with and without 400 and 40 ,ug of copper and silver per liter was tested at 39 to 40°C. All disinfection systems, regardless of temperature or free chlorine concentration, showed increase inactivation rates when 400 and 40 ,ug of copper and silver per liter was added; however, this trend was significant only at 0.4 mg of free chlorine per liter.

No abstract