Viruses pathogenic to humans have been found in wells and drinking water due to the improper placement of wastewater disposal operations (e.g., septic tanks, wastewater infiltration basins) and inadequate removal of the organisms as the wastewater percolated through the soil. In order to develop well head protection criteria that are protective of public health, it is necessary to understand the mechanisms that control virus retention and removal in porous media. In this study, we report the results of a series of experiments on virus transport through sand columns (9.2 cm in diameter and 10.5 or 20 cm long) under saturatedflow conditions. Two bacteriophages, MS-2 and φX-174, were used in the experiments. Virus solution was applied to the lower end of the column as a constant input, and samples were collected at the effluent end. A virus transport and fate model, partially calibrated with the transport parameters obtained from Brtracer experiments, was used to evaluate the retention and inactivation characteristics of the viruses. We found that, while MS-2 was not sorbed by the Ottawa sand, a significant amount of the applied φX-174 was retained but not inactivated in the columns. This was probably due to the difference in their isoelectric points. Retention of φX-174 exhibited trends consistent with first-order attenuation that increased with residence time; however, the sand was found to have a finite sorption capacity for φX-174. This study also demonstrates that virus sorption can be evaluated more effectively with a wellcontrolled column flow system than by the commonly used batch equilibration method.

A pilot-scale study investigating the use of low-pressure, high-intensity UV radiation for disinfection of urban wastewater was conducted. The inactivation of coliform bacteria, wastewater-indigenous enteric viruses, seeded poliovirus, and seeded F-specific coliphage was studied. During the course of the pilot study, infectious human adenoviruses were isolated from 15 of 16 large-volume samples of UVdisinfected secondary-and tertiary-treated wastewater. Half of the tertiarytreated, UV-disinfected effluent samples from which the adenoviruses were isolated had total coliform concentrations that complied with California's Water Recycling Criteria. To determine the relative UV resistance of the adenovirus isolates, purified viruses were seeded into tertiary-treated wastewater and exposed to low-pressure, high-intensity, collimated UV radiation. A dose of approximately 170 mW-s/cm 2 was required to achieve 99.99% inactivation. These findings suggest that UV doses effective at meeting certain wastewater regulations for total coliform bacteria may not provide suitable inactivation of the UV-resistant human adenoviruses. Water Environ. Res., 75, 163 (2003).

Batch sorption experiments were carried out with the bacteriophages MS2 and φX174. Two types of reactor vessels, polypropylene and glass, were used. Consistently lower concentrations of MS2 were found in the liquid phase in the absence of soil (control blanks) than in the presence of soil after mixing. High levels of MS2 inactivation (∼99.9%) were observed in control tubes made of polypropylene (PP), with comparatively little loss of virus seen in PP tubes when soil was present. Minimal inactivation of MS2 was observed when the air-water interface was completely eliminated from PP control blanks during mixing. All batch experiments performed with reactor tubes made of glass demonstrated no substantial inactivation of MS2. In similar experiments, bacteriophage φX174 did not undergo inactivation in either PP or glass control blanks, implying that this virus is not affected by the same factors which led to inactivation of MS2 in the PP control tubes. When possible, phage adsorption to soil was calculated by the Freundlich isotherm. Our data suggest that forces associated with the air-water-solid interface (where the solid is a hydrophobic surface) are responsible for inactivation of MS2 in the PP control tubes. The influence of air-water interfacial forces should be carefully considered when batch sorption experiments are conducted with certain viruses.

Bacteriophages have been widely used as surrogates for human enteric viruses in many studies on virus transport and fate. In this investigation, the fates of three bacteriophages, MS2, R17, and φX174, were studied in a series of dynamic batch experiments. Both MS2 and R17 readily underwent inactivation in batch experiments where solutions of each phage were percolated through tubes packed with varying ratios of glass and Teflon beads. MS2 and R17 inactivation was the result of exposure to destructive forces at the dynamic air-water-solid interface. φX174, however, did not undergo inactivation in similar studies, suggesting that this phage does not accumulate at air-water interfaces or is not affected by interfacial forces in the same manner. Other batch experiments showed that MS2 and R17 were increasingly inactivated during mixing in polypropylene tubes as the ionic strength of the solution was raised (φX174 was not affected). By the addition of Tween 80 to suspensions of MS2 and R17, phage inactivation was prevented. Our data suggest that viral inactivation in simple dynamic batch experiments is dependent upon (i) the presence of a dynamic air-water-solid interface (where the solid is a hydrophobic surface), (ii) the ionic strength of the solution, (iii) the concentration of surface active compounds in the solution, and (iv) the type of virus used.

A pilot study investigating the efficacy of low pressure, high intensity ultraviolet (UV) radiation for disinfection of urban wastewater was conducted. The pilot study utilized a small-scale version of the Ultra Guard UV treatment system provided by UV Systems Technology, Inc. (Burnaby, Canada). The primary objective was to determine whether low pressure, high intensity UV irradiation could potentially be used to meet the California Water Reclamation Criteria (CWRC) for total coliform bacteria in reclaimed water and to determine its potential for a 99.99% reduction of two model enteric viruses (MS2 coliphage and poliovirus). UV pilot unit inactivation of the total and fecal coliform bacteria, sewage indigenous F-specific coliphage, seeded F-specific coliphage (MS2), sewage indigenous enteric viruses, and seeded poliovirus type I in tertiary treated wastewater was investigated. During the course of the pilot study, an infectious adenovirus was isolated from UV disinfected tertiary and secondary treated wastewater. The virus was detected in 15 of 16 experiments involving large volume (352-697 L) sampling and analysis for indigenous enteric viruses and seeded poliovirus. The adenovirus was identified via electron microscopy and enzyme immunoassay after WEFTEC 2000 isolation using traditional cell culture based methods. Tertiary treated samples in which the adenovirus was detected received calculated UV doses in the range of 34-71 mWsec/cm 2 . Turbidity and total coliform bacteria levels in these samples were within the CWRC standards of <2 NTU and no greater than 23 MPN/100 mL for a single sample (30 d sampling period), respectively. Overall, total coliform bacteria were effectively removed from UV disinfected tertiary effluent indicating that low pressure, high intensity UV irradiation could potentially be used to meet the stringent CWRC. Seven-day total coliform median values were not determined from the pilot unit data, however, a conservative estimate suggests that a dose of approximately 60 mW-sec/cm 2 would be sufficient to meet the 7-d median concentration of no more than 2.2 MPN/100 mL for the last 7 samples taken. A 4-log 10 removal of seeded MS2 and indigenous F-specific coliphage in the pilot unit experiments (tertiary effluent) was achieved at doses of 70 and 50 mW-sec/cm 2 , respectively. The seeded poliovirus was not detected in UV treated secondary or tertiary effluents, however, problems with the concentration protocol prevented documentation of a specific 4-log 10 removal of the virus. Comparative collimated UV irradiation studies indicated that the isolated adenovirus was more UV resistant than MS2 coliphage and poliovirus type I. Doses of approximately 33, 112, and 183 mW-sec/cm 2 were required to achieve a 4-log 10 removal of poliovirus, MS2, and the isolated adenovirus, respectively. These findings indicate that UV doses found to be effective at meeting the stringent CWRC total coliform standards may not provide suitable reduction of some naturally occurring pathogenic viruses such as adenovirus...