CONCENTRATION OF VIRUSES
FROM SEAWATER
T.G. METCALF, C. WALLIS and J.L. MELNICK
Department of Virology and Epidemiology,
Bayler College of Medicine, Houston, Texas 77025, U.S.A.
INTRODUCTION
Detection of viruses in seawater usually is possible only after sampling large volumes of
water. Concentration of viruses has been necessary before their presence can be
demonstrated. Concentration is influenced by the salt content, suspended sediments and
membrane-coating components of seawater. These factors have placed restraints on the
volume of water sampled and degree of success achieved with existing methods for
recovery of virus from marine waters.
Development of equipment capable of processing essentially clean water at a rate of
300 gallons per hour with concentration of viruses on cellulose membranes has been
reported (Wallis, Homma and Melnick, 1972 a). Use of textile 10-inch depth filters with a
surface area of 3.5 square feet have been used to concentrate viruses (Wallis, Homma, and
Melnick, 1972b). The filters permitted rapid flow rates and did not clog in the presence
of silts. Since seawater contains adequate salts to enhance virus adsorption, clarification
procedures to remove suspended sediments could lead to simultaneous removal of virus.
Failure to remove sediments could cause clogging of virus adsorbing filters and prevent
sampling of large volumes of water. Examination of large volumes of seawater, then, calls
for clarifying filters capable of removing suspended sediments but not virus, and permit
high flow rates with passage of virus to virus adsorbing filters. Filters selected for
collection of virus also must be shown to be free from any virus penetration effect caused
by membrane-coating components (MCC), those nutrients or organic substances in water
which compete with virus for reactive sites on virus adsorbents (Wallis and Melnick, 1967).
The study was conducted to determine methods for clarification of large volumes of
seawater without virus removal. Special attention was directed to the ability of textile
filters to collect virus from seawater without interference from MCC-induced effects.
MATERIALS AND METHODS
Seawater. Artificial seawater of the following composition was used in the laboratory:
3.35% NaCl, 0.15% CaCl 2 , 0.4% MgCl 2 , and 0.1% KC1, giving an equivalent of 40,000
ppm salts. Field studies were conducted in the Houston ship channel and estuary waters
of the Texas coast at Galveston.
Filters. Ten-inch "Fulflo" yarn-wound filters of cotton, orlon, polypropylene,
polyester, cellulose acetate, viscose, fiberglass, and dynel composition were studied for
their virus retention capacity. Filters were available at porosities ranging from 100 μ to 1
μ. The filters were housed in clear plastic holders capable of withstanding 100 psi. These
filters are tubular in form and provide depth filtration which traps particles not only on
the surface but also throughout the total depth of the filter elements. This gives a much
greater solids retention capacity than is found with surface filter media of the same
dimensions. Approximately 1/2 to 1 lb. of solids will be retained before replacement is
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FROM SEAWATER
T.G. METCALF, C. WALLIS and J.L. MELNICK
Department of Virology and Epidemiology,
Bayler College of Medicine, Houston, Texas 77025, U.S.A.
INTRODUCTION
Detection of viruses in seawater usually is possible only after sampling large volumes of
water. Concentration of viruses has been necessary before their presence can be
demonstrated. Concentration is influenced by the salt content, suspended sediments and
membrane-coating components of seawater. These factors have placed restraints on the
volume of water sampled and degree of success achieved with existing methods for
recovery of virus from marine waters.
Development of equipment capable of processing essentially clean water at a rate of
300 gallons per hour with concentration of viruses on cellulose membranes has been
reported (Wallis, Homma and Melnick, 1972 a). Use of textile 10-inch depth filters with a
surface area of 3.5 square feet have been used to concentrate viruses (Wallis, Homma, and
Melnick, 1972b). The filters permitted rapid flow rates and did not clog in the presence
of silts. Since seawater contains adequate salts to enhance virus adsorption, clarification
procedures to remove suspended sediments could lead to simultaneous removal of virus.
Failure to remove sediments could cause clogging of virus adsorbing filters and prevent
sampling of large volumes of water. Examination of large volumes of seawater, then, calls
for clarifying filters capable of removing suspended sediments but not virus, and permit
high flow rates with passage of virus to virus adsorbing filters. Filters selected for
collection of virus also must be shown to be free from any virus penetration effect caused
by membrane-coating components (MCC), those nutrients or organic substances in water
which compete with virus for reactive sites on virus adsorbents (Wallis and Melnick, 1967).
The study was conducted to determine methods for clarification of large volumes of
seawater without virus removal. Special attention was directed to the ability of textile
filters to collect virus from seawater without interference from MCC-induced effects.
MATERIALS AND METHODS
Seawater. Artificial seawater of the following composition was used in the laboratory:
3.35% NaCl, 0.15% CaCl 2 , 0.4% MgCl 2 , and 0.1% KC1, giving an equivalent of 40,000
ppm salts. Field studies were conducted in the Houston ship channel and estuary waters
of the Texas coast at Galveston.
Filters. Ten-inch "Fulflo" yarn-wound filters of cotton, orlon, polypropylene,
polyester, cellulose acetate, viscose, fiberglass, and dynel composition were studied for
their virus retention capacity. Filters were available at porosities ranging from 100 μ to 1
μ. The filters were housed in clear plastic holders capable of withstanding 100 psi. These
filters are tubular in form and provide depth filtration which traps particles not only on
the surface but also throughout the total depth of the filter elements. This gives a much
greater solids retention capacity than is found with surface filter media of the same
dimensions. Approximately 1/2 to 1 lb. of solids will be retained before replacement is
109