130
Discussion
MALINA, J.F., J.L. MARSHALL, and B.D. MOORE (1972) Poliovirus Removal by Diatomaceous
Earth Filtration, Technical Report to Johns-Manville Products Corporation, Manville, New Jersey.
SCHAUB, S.A. (1972) "Adsorption, Infectivity and Subsequent Elution of A Mammalian Picornavirus
from Suspended Solid Material in Water," Unpublished Ph. D. Dissertation, The University of
Texas at Austin. 155 pp.
SCHAUB, S.A. and B.P. SAGIK (1972) "Adsorption and Infectivity of Viruses on Sediment in Natural
Waters," Applied Microbiology (in press).
SORBER, CA., J.F. MALINA, Jr., and B.P. SAGIK (1971) Virus Rejection by the Reverse OsmosisUltra filtration Processes. Technical Report EHE 71-9, CRWR-82, Environmental Health
Engineering Research Laboratories, Center for Research in Water Resources, The University of
Texas at Austin. 86 pp.
SORBER, CA., B.P. SAGIK, and J.F. MALINA, Jr. (1971) "Monitoring of Low-Level Virus in
Natural Waters," Applied Microbiology 22, pp. 334-338.
SORBER, CA., J.F. MALINA, Jr., and B.P. SAGIK (1972) "Quantitative Procedure for Evaluating
the Performance of Water and Wastewater Treatment Processes at Naturally Occurring Virus
Levels," Environmental Science & Technology 6, pp. 438-441.
WALLIS, C , S. GRINSTEIN, J.L. MELNICK, and J.E. FIELDS (1969) "Concentration of Viruses
from Sewage and Exreta on Insoluble Polyelectrolytes,'M/?p//e WALLIS, C , A. HOMMA, and J.L. MELNICK (1972) "Apparatus for Concentrating Viruses from
Large Volumes," Journal American Water Works Association 64, pp. 186-196.
Dr. Melnick's reply to Dr. Malina
In reply to Dr. Malina our portable apparatus is not limited to testing clean water. We have used it
for testing sewage and Dr. Metcalf has indicated its usefulness in testing estuary and sea water. We have
shown its application in the field with naturally occurring human viruses. Clogging of the initial filters
is avoided by changing the filter during the run.
Our paper was concerned with monitoring human viruses that occur in sewage and other waters
(and not with laboratory strains of a rat virus and a bacterial virus used by Malina). We found that the
portable virus concentrator allows us to detect such natural viruses even when they are present in such
low concentration that they could not be detected by any other available method. Thus, we know our
apparatus works effectively day-in and day-out in being able to detect human viruses in sewage, in
streams, and in estuaries. Our apparatus can detect viruses present in fresh water or in seat water.
Malina has mainly described his specialized laboratory studies with two viruses that are not found
in sewage. One is EMC, a virus of rats, and the second is T2, a virus of certain bacteria. With these
viruses, he has run into problems using his methods (not our methods). I would suggest that he turn
his efforts toward examining waste and other waters for viruses that are regularly found there and that
he would find life easier if he used our virus concentrator. Even if a fraction of the virus may be
adsorbed to some of the solids lost on clarifying filters, it is simple to run the apparatus for another
hour and process an additional 400 gallons of sample. In our studies we have found that no more than
10% of the virus may be detected on the solids trapped by the clarifying filters.
Dr. Coin, France
Dr. Coin drew attention in 1969 to the difference in recovery of virus according to whether one
used high concentrations or those existing under natural conditions. He agreed it was necessary to
work with large volumes of water and that this posed the problem of recovering viruses removed by
membrane minimum value.
Reply
Methods have been worked out that satisfactorily recover viruses from cellulose membranes. One
method that assures virtually 100% virus recovery utilizes an eluent of 0.05 M glycine buffer at pH
11.5. See Wallis, Henderson, and Melnick: Applied Microbiology 23, 476-480, 1972.
E.M. Nupen, South Africa
What is the author's view of Berg's statement that no virus should be detectable in 100 gals? Why
choose 100 gals and why not 1,000 gals?
Reply
The volume selected for testing must comply with methods that are available. As illustrated in our
paper, methods are available for carrying out virus concentration procedures in the field, so that 100
to 400 gallons can be sampled in a practical manner. Failure to detect virus in such volumes monitored
at regular intervals would seem to assure safety.
Discussion
MALINA, J.F., J.L. MARSHALL, and B.D. MOORE (1972) Poliovirus Removal by Diatomaceous
Earth Filtration, Technical Report to Johns-Manville Products Corporation, Manville, New Jersey.
SCHAUB, S.A. (1972) "Adsorption, Infectivity and Subsequent Elution of A Mammalian Picornavirus
from Suspended Solid Material in Water," Unpublished Ph. D. Dissertation, The University of
Texas at Austin. 155 pp.
SCHAUB, S.A. and B.P. SAGIK (1972) "Adsorption and Infectivity of Viruses on Sediment in Natural
Waters," Applied Microbiology (in press).
SORBER, CA., J.F. MALINA, Jr., and B.P. SAGIK (1971) Virus Rejection by the Reverse OsmosisUltra filtration Processes. Technical Report EHE 71-9, CRWR-82, Environmental Health
Engineering Research Laboratories, Center for Research in Water Resources, The University of
Texas at Austin. 86 pp.
SORBER, CA., B.P. SAGIK, and J.F. MALINA, Jr. (1971) "Monitoring of Low-Level Virus in
Natural Waters," Applied Microbiology 22, pp. 334-338.
SORBER, CA., J.F. MALINA, Jr., and B.P. SAGIK (1972) "Quantitative Procedure for Evaluating
the Performance of Water and Wastewater Treatment Processes at Naturally Occurring Virus
Levels," Environmental Science & Technology 6, pp. 438-441.
WALLIS, C , S. GRINSTEIN, J.L. MELNICK, and J.E. FIELDS (1969) "Concentration of Viruses
from Sewage and Exreta on Insoluble Polyelectrolytes,'M/?p//e WALLIS, C , A. HOMMA, and J.L. MELNICK (1972) "Apparatus for Concentrating Viruses from
Large Volumes," Journal American Water Works Association 64, pp. 186-196.
Dr. Melnick's reply to Dr. Malina
In reply to Dr. Malina our portable apparatus is not limited to testing clean water. We have used it
for testing sewage and Dr. Metcalf has indicated its usefulness in testing estuary and sea water. We have
shown its application in the field with naturally occurring human viruses. Clogging of the initial filters
is avoided by changing the filter during the run.
Our paper was concerned with monitoring human viruses that occur in sewage and other waters
(and not with laboratory strains of a rat virus and a bacterial virus used by Malina). We found that the
portable virus concentrator allows us to detect such natural viruses even when they are present in such
low concentration that they could not be detected by any other available method. Thus, we know our
apparatus works effectively day-in and day-out in being able to detect human viruses in sewage, in
streams, and in estuaries. Our apparatus can detect viruses present in fresh water or in seat water.
Malina has mainly described his specialized laboratory studies with two viruses that are not found
in sewage. One is EMC, a virus of rats, and the second is T2, a virus of certain bacteria. With these
viruses, he has run into problems using his methods (not our methods). I would suggest that he turn
his efforts toward examining waste and other waters for viruses that are regularly found there and that
he would find life easier if he used our virus concentrator. Even if a fraction of the virus may be
adsorbed to some of the solids lost on clarifying filters, it is simple to run the apparatus for another
hour and process an additional 400 gallons of sample. In our studies we have found that no more than
10% of the virus may be detected on the solids trapped by the clarifying filters.
Dr. Coin, France
Dr. Coin drew attention in 1969 to the difference in recovery of virus according to whether one
used high concentrations or those existing under natural conditions. He agreed it was necessary to
work with large volumes of water and that this posed the problem of recovering viruses removed by
membrane minimum value.
Reply
Methods have been worked out that satisfactorily recover viruses from cellulose membranes. One
method that assures virtually 100% virus recovery utilizes an eluent of 0.05 M glycine buffer at pH
11.5. See Wallis, Henderson, and Melnick: Applied Microbiology 23, 476-480, 1972.
E.M. Nupen, South Africa
What is the author's view of Berg's statement that no virus should be detectable in 100 gals? Why
choose 100 gals and why not 1,000 gals?
Reply
The volume selected for testing must comply with methods that are available. As illustrated in our
paper, methods are available for carrying out virus concentration procedures in the field, so that 100
to 400 gallons can be sampled in a practical manner. Failure to detect virus in such volumes monitored
at regular intervals would seem to assure safety.