Application of
Standards for
Bacteriological Quality of Public Drinking Water Supplies
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If the required continuous
disinfection is not being provided, an immediate boil water advisory is
recommended.
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Bacteriological samples
shall be taken at representative locations in the distribution system
and must include the beginning and the end of the system, in accordance
with the recommended number of samples. Disinfection residuals must be
checked and recorded for each sampling point. For potable water dispensing units (PWDUs), disinfection residuals need not be checked.
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If no disinfectant residual
is detected at the sampling location, the operator of the system shall
be advised of the fact that no residual is detected, and in consultation
with the appropriate authorities and in accordance with existing
guidelines, remedial action shall be initiated. This may include the
issuing of a boil water advisory for the area affected by the lack of
disinfectant residual.
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If the bacteriological test
reveals the presence of E.coli, re-sampling of the site, as well
as up and downstream locations, should be carried out within 24 hours.
However, a boil water advisory may be recommended before the re-sampling
results are known depending upon the extent of E.coli
contamination in the initial testing, combined with knowledge of other
problems pertaining to the water system. Regardless, if the repeat test
reveals the presence of E.coli, a boil water advisory is
recommended.
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If the bacteriological test
reveals the presence of total coliforms, but no E.coli,
re-sampling of the site, as well as up and downstream locations, should
be carried out as soon as is practically possible. If the consecutive
test confirms the presence of total coliforms, but no E.coli, a
boil water advisory is recommended for water systems that have only
disinfection but no additional water treatment (such as coagulation,
sedimentation, filtration or equivalent technologies) or have no
significant operational procedures and controls over the water system.
Regardless, remedial action shall commence in consultation with the
water system operator.
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If repeat samples cannot be
taken as per paragraphs 4 and 5, a boil advisory is recommended.
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Reporting of results
pertaining to these standards shall be done in accordance with the
provincial "Guidelines for the Issuance of Boil Water
Advisories".
Rescinding of Boil Water Advisories:
Boil advisories may be
rescinded upon correction of the condition(s) which led to the boil
advisory. At least two consecutive samples must meet the bacteriological
and disinfection standards. All officials must be advised.
Rev: July 2, 2008
Application of
Standards for Bacteriological Quality of Private Wells
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Drinking water samples from
private wells submitted to the Public Health Laboratory or Government
Service Centres for bacteriological analysis will be tested for the
presence of both total coliform bacteria and the fecal indicator
Escherichia coli (E.coli). If neither are detected the sample fully
meets the standard.
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If the bacteriological test
reveals the presence of 1 to 10 total coliforms, but no E.coli,
in a 100 mL sample, the drinking water is considered satisfactory and is
adequate for private consumption. No further action is necessary
except further routine testing.
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If the bacteriological test
reveals the presence of more than 10 total coliforms, but no E.coli,
in a 100 mL sample, the drinking water is considered substandard
but not to pose an immediate health risk. Disinfection of the water
source should be recommended to the owner. Retesting should be carried
out following disinfection of the water source. Until disinfection is
carried out and retest results are known, the water may be boiled before
being consumed or an alternative safe source of drinking water may be
used.
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If the bacteriological test
reveals the presence of E.coli, the drinking water is considered unsatisfactory
and unsafe for drinking. It is recommended that the drinking water be
boiled and that corrective action be taken to deal with fecal
contamination entering the well. Retesting should be carried out
following appropriate corrective action.
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Reporting of the results
will be carried out in accordance with the provincial document "Reporting
of Bacteriological Results from Private Water Supplies".
Rev: April 9, 2002
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