United States
Environmental Protection
Agency
Municipal Environmental Research ^
Laboratory 't
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-024 August 1982
Project Summary
Removal of Virus from
Public Water Supplies
J, T. O'Connor, L. Hemphill, and C. D. Reach, Jr.
Assays of concentrated raw Mis-
souri River water for the presence of
naturally occurring human enterovir-
uses resulted in the recovery of polio-
viruses, Coxsackie viruses, and ECHO
viruses. Virus concentrations were
found to be highest in the winter and
spring, when river flows (and there-
fore the effects of dilution) were low-
est. Statistically significant inverse
correlations were found between
virus recoveries and conventional
microbiological indicators of water
contamination (total coliform. fecal
coliform, and standard plate counts).
An evaluation of the effectiveness
of water treatment at a plant in Lex-
ington, Missouri, indicated that pre-
sedimentation plus the addition, of
lime resulted in the reduction of virus
levels. Concentrates derived from
1.9-m3 (500-gal) samples of treated
drinking water were assayed. No iso-
lates were obtained from the 65 sam-
ples analyzed.
Batch disinfection studies were
conducted using raw Missouri River
water treated with chlorine, chloram-
ine, chlorine dioxide, or ozone.
Though virus levels were very low and
data were limited, ozone and chlorine
dioxide appeared to be most capable
of inactivating viruses under the con-
ditions employed.
Studies of the effectiveness of
physical removal processes were con-
ducted using water treatment pilot
plants constructed of stainless steel
and housed in a 12.2-m (40-ft)
tractor-trailer. Because raw water vir-
uses were present in insufficient
numbers, bacteriophage-seeded stu-
dies were conducted. Results indi-
cated that a virus reduction of one or
two orders of magnitude was
obtained by physical removal pro-
cesses alone. A comparison of con-
ventional treatment versus direct
filtration indicated that comparable
removal could be obtained by both
processes, although conventional
treatment was somewhat more con-
sistent in performance. Reductions in
•other microbial indicators paralleled
virus removals, indicating the effec-
tiveness of the indicators as monitors
of virus removals.
The final portion of the study was
conducted by the Capital City Water
Treatment Plant in Jefferson City,
Missouri. Chlorine and chloramine
were applied in parallel pilot-plant
units for the disinfection of Missouri
River water. Both disinfectants were
capable of producing a finished water
that met bacteriological standards.
Chloramine, however, proved to be
more stable than chlorine.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory,
Cincinnati. OH. to announce key find-
ings of the research project that is
fully documented in a separate report
of the same title (see. Project Report
order information at back).
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Introduction
The efficiency of drinking water treat-
ment processes for the removal and
inactivation of viruses has been studied
extensively. Because of the lack of
methods for detection and enumeration
of naturally occurring viruses at the lev-
els at which they are present in most
operating treatment plants, virus levels
are usually increased by adding
laboratory-propagated viruses. The
adequacy of such studies for modellfng
or simulating actual water treatment
conditions has frequently been questi-
oned. In an attempt to conduct treat-
ment efficiency studies using only
naturally occurring viruses, an operat-
ing water treatment plant using poor
quality source water was identified and
used as the study site.
Preliminary studies indicated that the
source water contained sufficient natu-
rally occurring viruses to make the
study feasible. Although virus levels
were not consistently high throughout
the course of the 3-year study, substan-
tial information on the effects of water
treatment unit processes on naturally
occurring viruses and microbial indica-
tor organisms was obtained.
Results
Longitudinal Studies of
Virus in Missouri River
Source Water
Throughout the study, naturally
occurring human enteroviruses were
found in Missouri River water at the
Lexington, Missouri, water treatment
plant intake. An average of 2.5 viruses
were recovered in 216 samples of
approximately 0.38 m3 (100 gal) each.
Polioviruses were most. abundant
(69%), followed by Coxsackie (11%) and
ECHO viruses (5%). Of the total, only
10% of the virus particles were reco-
vered on the 3- to 5-fjm pore size prefil-
ters, indicating that most of the
recovered virus particles were notasso-
ciated with the suspended sediment in
Missouri River water.
Virus concentrations were found to
average 10 plaque-forming units
(pfu)/0.38 m3 (100 gal) in the winter
and spring of 1977, 1.5 pfu/0.38 m3
(100 gal) in the summer and fall, and 5
pfu/0.38 m3( 100 gal) in the winter artd
spring of 1978 (Figure 1). If the virus
concentrations are normalized with
respect to river flow, the virus flow in
the Missouri River at Lexington appears
to be more nearly constant throughout
the year. But seasonal winter and
spring virus flow peaks appear to
persist.
Statistically significant inverse corre-
lations were obtained between concen-
trations of virus and microbiological
indicators (fecal coliform, total coliform,
and standard plate counts). These
results, coupled with winter and spring
virus flow peaks, indicate that conven-
tional microbial parameters may not
always prove useful as quantitative
indicators of virus contamination.
Field-Scale Studies of Virus
Removal by Treatment
Processes
Samples were taken of the presettled,
lime-treated, and finished water at the
Lexington, Missouri, water treatment
plant over the period of December 2,
1976, to March 22,1978. In 21 samples
taken of presented water, a total of 39
viruses were recovered. Seven viruses
were recovered from 14 samples taken
after adding lime to the raw water.
Finally, no viruses were recovered from
the 71 finished water samples (1.9 m3
(500 gal)) collected.
The results from the survey of plant
performance indicate that the overall
water treatment process at Lexington,
Missouri, is consistently effective in
reducing viruses to below detectable
limits. Moreover, preliminary treatment
of raw Missouri River water with lime
appeared to result in a measurable
inactivation of the viruses present.
Chemical Disinfection for
Virus Inactivation
Ozone and chlorine dioxide both
showed potential for inactivating the
human enteroviruses present in raw
Missouri River water when sufficient
dosage and time were provided. Chlo-
rine and chloramine, however,
appeared to be only marginally effective
against viruses when applied to raw
water. In general, the reduction of vir-
uses to below detectable limits was
accompanied by near-total destruction
of fecal and total coliforms and by
reductions in standard plate counts of
two to three orders of magnitude. The
comparatively low numbers of acid-fast
bacteria and yeast found in raw Mis-
souri River water appear to limit their
use as indicator organisms.
Physical Removal of Virus
Particles
As part of the study of the physics
removal of virus-sized particles fron
Missouri River water, a mobile wate
treatment research facility was con
structed. Twin water treatment pilo
plants were built and mounted in i
tractor-trailer. A separate, limited
edition internal report entitled Con
struct/on Plans and Operations Manua
for USEPA Mobile Water Treatment
Facility was prepared to provide subse
quent operators of the pilot plant facility
with design calculations, shop draw-
ings, fabrication notes, and instructions
for operation, maintenance, and safety.
For the physical removal studies, bac-
teriophage MS2 was seeded into raw
Missouri River water as a surrogate for
human enteroviruses to increase the
number of virus particles present, to
shorten the time between sampling and
obtaining the experimental results, and
to reduce costs.
Coagulation with aluminum sulfate
followed by sedimentation and dual-
media filtration resulted in an overall
removal of 93% of seeded bacterio-
phage. Comparable removals were
obtained with respect to fecal and total
coliforms, fecal streptococci, and stand-
ard plate count organisms.
In other studies on removal of natu-
rally occurring MS2 bacteriophages,
coagulation with a cationic polyelectro-
lyte followed by direct filtration resulted
in an 87% removal of seeded MS2
bacteriophage.
With direct filtration, results were
more erratic than those obtained with
conventional treatment. Again, the
removal of other indicator organisms
paralleled the removal of MS2
bacteriophage.
Turbidity reductions reflected orga-
nism removals. Influent turbidities
ranged from 19 to 180 NTU. Effluent
turbidities ranged from 1 to 7 NTU for
conventional treatment. Direct filtration
produced turbidities in the range of 0.4
to 8.5 NTU, except for a single high
value of 77 NTU. This turbidity break-
through occurred during a period of
high influent turbidity.
Overall, one- to two- order-of-
magnitude removal of seeded virus and
other microbial indicators of pollution
was obtainable by both conventional
water treatment and direct filtration
under proper operating conditions.
Direct filtration, however, was more
subject to upset during periods of high
influent turbidities.
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Figure 1. Virus in raw Missouri River water, December 1976 through December 1978..
3
1978
iu.oovDM«MrnwnNaomce: MB -559-017/0792
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Chlorine Versus Chloramine
for Water Disinfection
Studies of organism removal and dis-
infection by chlorine and chloramine at
Jefferson City, Missouri, began with a
comparison of organism reductions
with and without the addition of
chlorine.
Aluminum sulfate coagulation and
sedimentation removed 80% to 85% of
the standard plate count organisms.
With filtration, organism removal
increased to 90%. Adding chlorine
increased organism reductions to
99.9% or more.
The subsequent comparison of chlo-
rine versus chloramine (each added
before the rapid mix tank) indicated that
both disinfectants were effective in
attaining bacteriological drinking water
standards. Moreover, chloramine pro-
duced an order of magnitude fewer
trihalomethanes.
With the inclusion of GAC post-
adsorbers in the pilot-plant operation at
Jefferson City, Missouri, it was possible
to observe the removal of trihalome-
thanes as well as the reduction in total
organic carbon and substances that
have trihalomethane-forming potential.
Comparable disinfection could be
achieved with chlorine and chloramine,
but effluent trihalomethanes were
lower with chloramine than with the
use of both chlorine and GAC.
Summary and Conclusions
The results of the virus removal stu-
dies indicate that both sedimentation
processes using coagulants and various
types of filtration processes usually
remove more than 90% of the viruses
present in the water. Results of the
pilot- and field-scale studies tended to
be similar to those of the laboratory-
scale studies. Process control is the
primary factor determining the effi-
ciency of removal processes. The varia-
bility in removal efficiencies of the
coagulation-flocculation and filtration
processes points up the need for main-
taining adequate disinfection in addi-
tion to the removal processes. The
efficiency with which turbidity is
removed by sedimentation and filtration
generally indicates the efficiency of
virus removal.
Other Reports Based on This
Research
The following publications are based
on research conducted under this grant
and have been published or are in
preparation.
Reach, Jr., C. D., Hemphill, L, Akin,
E., and O'Connor, J. T. "Naturally-
Occurring Human Enteroviruses in
Missouri River Water." (In prepara-
tion; to be submitted to Water
Research.)
Reach, Jr., C. D., Hoff, J. C., Logsdon,
G., and O'Connor, J. T. "Chemical
Inactivation and Physical Removal ol
Naturally-Occurring Human Entero-
virus in Missouri River Water." (In
preparation; to be submitted to Jour-
nal American Water Works Assoc.)
Reach, Jr., C. D., Hoff, J. C., Logsdon,
G., and O'Connor, J. T. "Chlorine ver-
sus Chloramine for the Disinfection
of Missouri River Water." (In prepara-
tion; to be submitted to Journal
American Water Works Assoc.)
Reach, C. D., O'Connor, J. T., and
Hamphill, L. 'Virus and Bacterial
Quality of Missouri River." Proc.
Annual Meeting of American Water
Works Association. Part I. pp. 519-
529. 1979.
Reed, G. D., Reach, Jr., C. D., and
O'Connor, J.T. "Trihalomethane
Precursor Removal under Two Modes
of Disinfection." Journal American
Water Works Association (accepted
for publication).
The full report was submitted in ful-
fillment of Grant No. R-804903-02 by
the University of Missouri-Columbia
under the sponsorship of the U.S. Envir-
onmental Protection Agency.
J. T. O'Connor. L. Hemphill. and C. D. Reach, Jr. are with the University of
Missouri. Columbia, MO 65211.
John C. Hoff is the EPA Project Officer (see below).
The complete report, entitled "Removal of Virus from Public Water Supplies,"
(Order No. PB 82-230 327; Cost: $15.00, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
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