Groundwater in the Great Lakes Basin

Viruses
Viral pathogens continue to be a challenge from a
public health perspective (Rose and Gerba, 1986; Lee,
Levy, Craun, Beach and Calderon, 2002; LeChevallier
et al., 1999; LeChevallier, 1999). There are hundreds of
different viruses which can be excreted in high concentrations
and subsequently detected in sewage (Rose et
al., 2001). They are stable in the environment and are
readily transmitted to groundwater aquifers. Viruses
cause a wide range of clinical symptoms ranging from
acute diarrhea to meningitis to myocarditis (Hass, Rose
and Gerba, 1999). Proposed regulations suggest natural
disinfection as a possible mechanism to treat microbeimpacted
groundwater under favorable conditions.
However, the usefulness of current models employed
to predict viral transport and natural attenuation
rates is limited by the absence of field-scale calibration
data (Yates and Jury, 1995). Recently, viral agents
associated with septic tanks have been implicated in
endemic diarrheal disease in rural areas in Wisconsin,
and children were shown to be at particularly high risk
(Borchardt, Chyou, DeVries and Belongia, 2003). The
coliform indicator bacteria did not prove to be a sufficient
indicator of risk.
All the viruses in Table 2 cause disease in humans.
Enteric viruses (those that replicate in the human GI
tract) come only from human sewage. They can cause
both acute and chronic disease affecting GI tract,
liver, heart and meninges. Adenoviruses, Calciviruses,
Picornaviruses and Rotaviruses cause hundreds of
thousands of cases per year. The exception is Poliovirus,
since the vaccination program has reduced the number
of infections. The enteroviruses include Coxsackie
viruses which are on the CCL. They can cause many
types of disease and often can be detected in sewagecontaminated
water.
Table 2.
Enteric Viruses.
Adapted from American Water Works
Association (AWWA), 1999.
Adenoviruses (Respiratory adenovirus and Enteric
adenovirus)
Coronaviruses (Enteric conronavirus)
Reoviruses (Reovirus and Rotavirus)
Calciviruses (Calcivirus and Noroviruses)
Astroviruses
Parvovirus
Picornavirus (Coxsackie virus A, Coxsackie virus B, ECHO
virus, Hepatitis A virus, Poliovirus)
Viruses are stable and widespread in groundwater due
to several factors: Their survivability is favored by low
temperatures, moisture and absence of ultraviolet light;
their nano-size and negative charge favors transport
though soil; and they have the documented ability to
move as deep as 67 meters and migrate horizontally as
far as 1600 meters. John and Rose (2005) quantitatively
reviewed the survival and inactivation rates of public
health-related microorganisms in groundwater (Table
3). Virus inactivation has been shown to be temperature
dependent with greater inactivation at greater
temperatures; however, this occurs largely at temperatures
greater than 20 o C, whereas most Great Lakes
Basin groundwater is about 10 o C (Table 3). A study by
Yates and Gerba (1985) estimated that virus inactivation
could take as many as 200 to 400 days where
groundwater temperature averages between 8.5 o C and
11 o C (Figure 2).
Using improved molecular techniques (i.e., polymerase
chain reaction), monthly samples from 29 groundwater
sites in the continental United States, the Virgin
Islands and Puerto Rico were analyzed for one year
for enteroviruses, hepatitis A virus, Norwalk virus
and reoviruses (Fout, Martinson, Moyer and Dahling,
2003). Human enteric viruses were detected in 16% of
the groundwater samples analyzed, with reoviruses
being the most frequently detected virus group (Fout
et al., 2003). Other types of groundwater viruses, such
as the adenoviruses, should be monitored since they are
more prevalent in sewage. In another national study
using more precise tests (i.e., using specific primers)
for enteroviruses used in RT-PCR, 40 of 133 samples
(30.1%) tested positive for the presence of enterovirus
RNA (Abbaszadegan, Stewart and LaChevallier, 1999).
Protozoans
The most common protozoans in waterborne outbreaks
are Giardia and Cryptosporidium. Under appropriate
conditions (human GI tract), they can produce infection.
When found in groundwater, these protozoa
signify direct influence of surface water. Their size
(2 - 50 µm) is larger than bacteria and viruses which
normally makes them more susceptible to removal by
filtration. They are more resistant to disinfection than
bacteria or viruses. These two protozoa are usually
found in domestic wastewater (10 2 to 10 5 / litre) (Bitton,
1999). When they are found in groundwater, the well
is probably under the direct influence of surface water
and requires special attention and treatment.
Prions
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Human prion infections including Creutzfeldt-Jakob
Disease (CJD), variant Creutzfeldt-Jakob Disease
(vCJD), Kuru and Fatal Familial Insomnia are relatively