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Bradbury, K. R.; Borchardt, Mark A.; Gotkowitz, Madeline B.; Hunt, R. J. / Assessment of virus presence and potential virus pathways in deep municipal wells
[DNR-197] (2008)

Abstract,   pp. 2-3 PDF (761.9 KB)

Page 2

  Assessment of Virus Presence and Potential Virus Pathways in Deep
                                Municipal Wells
Among the many waterbome pathogens of humans, enteric viruses have the greatest
potential to move deeply through the subsurface environment, penetrate aquitards, and
reach confined aquifers. Previous research revealed the presence of viruses in water from
two of three deep bedrock wells sampled in Madison, WI. Virus presence in these wells
was particularly surprising because the wells were cased through a regional aquitard
thought to provide protection for the wells. This present study is a follow-up to the
previous work and is intended to (1) obtain a time series of virus, isotopic, and
geochemical data from several municipal wells completed in a deep bedrock aquifer, (2)
use these data sets to evaluate virus presence and, if present, the potential sources of the
viruses and pathways to the wells, and (3) evaluate the possibility that virus transport
occurs through the well casing, grout or annular space.
During 2007 and 2008 we sampled six deep municipal wells for viruses on an
approximately monthly basis. Three of these wells had shallow casings, and three were
cased through a regional aquitard. We also collected virus samples from local lakes and
from untreated sewage and sampled groundwater and lake water for major inorganic ions
and isotopes of hydrogen and oxygen.
Viruses were detected at least twice in every one of the six wells, but no well was virus-
positive in every sampling round. Overall, 43 percent of the samples were virus-positive,
and virus concentrations ranged from 0.00 to 6.15 genomic copies per liter (gc/1), with a
mean of 0.47 gc/l. Samples from three wells were positive for virus infectivity. Lake
samples were positive 78 percent of the time, and ranged from 0.00 to 27.6 gc/l, with a
mean of 5.8 gc/l. Not surprisingly, Madison sewage was extremely high in viruses, with
all samples positive, and concentrations ranging from about 50,000 to over two million
gc/l, with a mean of 581,000 gc/l. Virus results varied significantly with time, and there
is apparent correlation between virus levels in sewage, lakes, and groundwater.
Several different species (serotypes) of viruses were identified in wells, sewage, and lake
water during this study, and in many cases wells and sewage contained identical virus
serotypes. Detected viruses include Enteroviruses echovirus 3, echovirus 6, echovirus
11, Coxsackie A16 and B4, Adenoviruses 2, 6, 7, 41, as well as Gl norovirus and
Rotovirus. The apparent correlation between viral serotypes found in sewage, lakes, and
groundwater suggests very rapid transport from the sources to wells. Viral serotypes vary
seasonally and annually, and so correlation between surface and subsurface serotypes
would be unexpected if transport times from the surface to groundwater exceed many
months. The Madison Lakes are probably not the main source of the viruses found in the
wells as lake water contained some but not all of the serotypes found in the wells, and
wells without lake-derived water had viruses present. Furthermore, the 180/2H signature
of water produced by these wells is not consistent with a significant lake water

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