May 1, 1984 - diameter filter holder (Millipore Corp., Bedford, Mass.) (Fig. 1). ... C A 3-p.m-pore-size prefilter was placed on top of a 30S Zeta-plus filter.
APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Aug. 1984, p. 431-432
Vol. 48, No. 2
0099-2240/84/080431-02$02.00/0 Copyright © 1984, American Society for Microbiology
NOTES
Simple Field Method for Concentration of Viruses from Large Volumes of Water GARY A. TORANZOS,1* CHARLES P. GERBA,1 AND HENRY HANSSEN2
Departments of Microbiology and Immunology and Nutrition and Food Science, University of Arizona, Tucson, Arizona 85721,1 and Department of Microbiology and Parasitology, School of Medicine, University of Antioquia, Medellin, Colombia2
Received 6 February 1984/Accepted
1
May 1984
A pressure spray tank was adapted to supply positive pressure for processing water samples for concentrating viruses with microporous filters under field conditions. This low-cost system allows water to be processed in locations where electric current is not readily available or where light-weight portable equipment is
required.
Until a decade ago, examination of waters for viral pollution was rarely attempted because of inadequate methodology (3, 5). Since the development of methods for detecting enteric viruses in large volumes of water and concentrating them, a lot of effort has been put into simplifying the methodology. Wallis et al. (9) reported the development of a portable virus concentrator which could be used to process water in the field by adsorbing the viruses to microporous filters. The main disadvantages of this method were that the equipment was bulky and expensive and that the sampling sites had to be accessible to vehicles, tanks of pressurized nitrogen, and a current generator. Current methods involving the use of microporous filters require positive pressure to process the water as well as to elute the virus once it has been adsorbed to the filters (2). The positive pressure needed to process the water can be provided by an electric pump or by using nitrogen gas (1). The application of these methods under field conditions is therefore limited by the availability of these materials. In our experience this probleni becomes acute in primitive areas and developing nations, where these materials are not readily available or where transport is difficult. To overcome these handicaps, we have recently adapted a lightweight, low-cost, plastic spray tank for use in concentrating viruses from water with microporous filters. A spray can, capable of containing approximately 11 liters (Universal-Gerwin Division, Inc., Saranac, Mich.), was equipped with quick disconnects (Snap Tite, Inc., Union City, Pa.) and connected to either a 47-mm- or 142-mmdiameter filter holder (Millipore Corp., Bedford, Mass.) (Fig. 1). Water to be processed was fed directly into the pressure tank, and pressure was applied manually. When chlorinated water was processed, sodium thiosulfate could be added directly to the pressure tank to deactivate the chloride. We have successfully used this system in recent field studies to concentrate viruses onto positively charged 30S Zeta-plus and 1-MDS Virozorb filters (AMF, CUNO Division, Meriden, Conn.). These filters have the advantage over negatively charged filters in that pH adjustment or addition of cation salts is not required before processing the water (6, 7). In recent extensive field use of this system, more than 100 *
samples of tap water, sewage, and surface water were processed for virus. The effect of turbidity on the volumes which could be processed with the described system is shown in Table 1. This system appears to be capable of processing from 10 to >22 liters of finished tap water (turbidity < 1.0 nephelometric turbidity unit) with the 47-mm-diameter filters and from 22 to >154 liters with the 142-mm-diameter filters. This system is therefore capable of processing water volumes well within the range required for current virus enumeration standards set by many governments (8). It is also useful for applying positive pressure when eluting the viruses adsorbed to the filters with common eluents such as beef extract (4). The pressure tank can also be used when eluting viruses from the larger pleated filter cartridges (1). This system is very useful for field studies in localities with no facilities for nitrogen cylinders or electric power for pumps. It is also lightweight and can easily be transported with a shoulder strap. The spray can used ih this study could
A B
.C D
FIG. 1. Apparatus for concentrating viruses from water. A, Manual pump; B, pressure relief valve; C, quick disconnect (male);
D, quick disconnect (female); E, filter assembly unit.
Corresponding author. 431
432
APPL. ENVIRON. MICROBIOL.
NOTES TABLE 1. Volumes of water passed through filters
Type of water
Tap water
Raw sewage Seawater
Turbidity range (NTU)a
0.4-1.5 1.6-3.0 3.1-4.0 >4.0
10-15.0
Vol processed (liters) with indicated filter 142-mm diam' 47-mm diamb
11->22 3.5-9 NDd 1.5 0.10 ND
22->154 22-77 33-44 20-44 2.7-10.5 44-55
a NTU, Nephelometric turbidity units. b Two Virozorb 1-MDS filters were used in series. C A 3-p.m-pore-size prefilter was placed on top of a 30S Zeta-plus filter. d ND, Not done.
possibly be replaced by any available brand. The system costs less than $30.00 and replaces a system (i.e., stainless steel pressure vessel, gas regulator, and gas cylinder) costing $400 to $600. This project was supported in part by a grant from the Tinker Foundation through the University of Arizona Latin American Area Center. LITERATURE CITED 1. Gerba, C. P., S. R. Farrah, S. M. Goyal, C. Wallis, and J. L. Melnick. 1978. Concentration of enteroviruses from large vol-
2.
3. 4.
5.
6.
7. 8. 9.
umes of tap water, treated sewage, and seawater. Appl. Environ. Microbiol. 35:540-548. Goyal, S. M., and C. P. Gerba. 1982. Concentration of viruses from water by membrane filters, p. 59-116. In C. P. Gerba and S. M. Goyal (ed.), Methods in environmental virology. Marcel Dekker, Inc., New York. Hill, W. F., Jr., E. W. Akin, and W. H. Benton. 1971. Detection of viruses in water: a review of methods and application. Water Res. 5:967-995. Katzenelson, E., B. Fattal, and T. Hostovesky. 1976. Organic flocculation: an efficient second-step concentration method for the detection of viruses in tap water. Appl. Environ. Microbiol. 32:638-639. Liu, 0. C., D. A. Brasher, H. R. Seraichekas, J. A. Barnick, and T. G. Metcalf. 1971. Virus in water. I. A preliminary study on a flow-through gauze sampler for recovering virus from waters. Appl. Microbiol. 21:405-410. Sobsey, M. D., and J. S. Glass. 1980. Poliovirus concentration from tap water with electropositive adsorbent filters. AppI. Eriviron. Microbiol. 40:201-210. Sobsey, M. D., and B. L. Jones. 1979. Concentration of poliovirus from tap water using positively charged microporous filters. Appl. Environ. Microbiol. 37:588-595. Sproul, 0. J. 1983. Public health, financial and practical considerations of virological monitoring and quality limits. Water Sci. Technol. 15:33-41. Wallis, C., A. Homma, and J. L. Melnick. 1972. A portable virus concentrator for testing water in the field. Water Res. 6:1249-1256.
