A PORTABLE VIRUS CONCENTRATOR
FOR USE IN THE FIELD
CRAIG WALLIS and J.L. MELNICK
Department of Virology and Epidemiology,
Bayler College of Medicine, Houston, Texas 77025, U.S.A.
INTRODUCTION
Viruses have been isolated from natural water by bringing small samples back to the
laboratory for concentration and assay. These methods have been reviewed by Berg
(1967) and recently updated by Wallis et al. (1970) and Scarpino (1971). The current
study is concerned with the development of a portable apparatus to efficiently
concentrate viruses from large volumes of water in the field.
MATERIALS AND METHODS
Water and sewage. Houston tap water, dechlorinated by small increments of sodium
thiosulfate, was used. This water is heavily contaminated (dissolved solids, 460 ppm;
solids in suspension, 337 ppm). Two liters of Houston tap water will virtually clog a 90
mm HA Millipore membrane of 0.45 μ average pore diameter (APD). As a model for
viruses potentially present in natural water, polio virus was added to the tap water.
Clarifying filters. Ten-inch "Fulflo" yarn-wound filters made of various textiles and
available at porosities from 100 μ to 1 μ were obtained from the Commercial Filter
Corporation, Lebanon, Indiana. They were housed in see-through cartridge holders rated
at 100 psi in normal temperature ranges, as previously reported (Wallis, Homma and
Melnick, 1972). These filters, which are in the form of tubes, provide depth filtration.
Particles are trapped not only on the surface of the filter but also through the total depth
of the filter elements. The precision winding pattern of the textile covers the entire depth
of the filter tube with hundreds of funnel-shaped tunnels which become gradually finer
from the surface in to the center of the tube and which trap progressively finer particles
as the fluid travels to the center.
a. Removal of particulates. Specially designed polyester or orlon 10 inch filters are
also available from the Commercial Filters Division, in porosities from 100 to 1 μ. They
remove particulate matter from the water without adsorbing complexed salts or viruses.
b. Removal of complexed metals. A specially impregnated ten-inch cotton filter
(Model 39R, Tween-treated) is also available from the same company. These filters
electrostatically remove insoluble metallic salts which interfere with virus adsorption on
the final virus adsorbent. Further, these filters do not remove virus provided that they are
changed as soon as a build-up of "rust" forms; this electrostatic metallic film could bind
viruses (Wallis, 1971).
Virus adsorbent. Viruses are concentrated from large volumes of water on a 10-inch
fibreglass textile depth filter (K-27) or a cellulose acetate filter (W10A-7) and eluted
therefrom. These filters preferentially adsorb viruses when trace amounts of salts are
present, but submicron silts and other submicron solids in tap water pass the filter.
Cellulose membranes rapidly clog under similar conditions.
119
FOR USE IN THE FIELD
CRAIG WALLIS and J.L. MELNICK
Department of Virology and Epidemiology,
Bayler College of Medicine, Houston, Texas 77025, U.S.A.
INTRODUCTION
Viruses have been isolated from natural water by bringing small samples back to the
laboratory for concentration and assay. These methods have been reviewed by Berg
(1967) and recently updated by Wallis et al. (1970) and Scarpino (1971). The current
study is concerned with the development of a portable apparatus to efficiently
concentrate viruses from large volumes of water in the field.
MATERIALS AND METHODS
Water and sewage. Houston tap water, dechlorinated by small increments of sodium
thiosulfate, was used. This water is heavily contaminated (dissolved solids, 460 ppm;
solids in suspension, 337 ppm). Two liters of Houston tap water will virtually clog a 90
mm HA Millipore membrane of 0.45 μ average pore diameter (APD). As a model for
viruses potentially present in natural water, polio virus was added to the tap water.
Clarifying filters. Ten-inch "Fulflo" yarn-wound filters made of various textiles and
available at porosities from 100 μ to 1 μ were obtained from the Commercial Filter
Corporation, Lebanon, Indiana. They were housed in see-through cartridge holders rated
at 100 psi in normal temperature ranges, as previously reported (Wallis, Homma and
Melnick, 1972). These filters, which are in the form of tubes, provide depth filtration.
Particles are trapped not only on the surface of the filter but also through the total depth
of the filter elements. The precision winding pattern of the textile covers the entire depth
of the filter tube with hundreds of funnel-shaped tunnels which become gradually finer
from the surface in to the center of the tube and which trap progressively finer particles
as the fluid travels to the center.
a. Removal of particulates. Specially designed polyester or orlon 10 inch filters are
also available from the Commercial Filters Division, in porosities from 100 to 1 μ. They
remove particulate matter from the water without adsorbing complexed salts or viruses.
b. Removal of complexed metals. A specially impregnated ten-inch cotton filter
(Model 39R, Tween-treated) is also available from the same company. These filters
electrostatically remove insoluble metallic salts which interfere with virus adsorption on
the final virus adsorbent. Further, these filters do not remove virus provided that they are
changed as soon as a build-up of "rust" forms; this electrostatic metallic film could bind
viruses (Wallis, 1971).
Virus adsorbent. Viruses are concentrated from large volumes of water on a 10-inch
fibreglass textile depth filter (K-27) or a cellulose acetate filter (W10A-7) and eluted
therefrom. These filters preferentially adsorb viruses when trace amounts of salts are
present, but submicron silts and other submicron solids in tap water pass the filter.
Cellulose membranes rapidly clog under similar conditions.
119