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Turbidity and Health Risk
South
East Kelowna Irrigation District
Turbidity is a water
quality term that refers to fine suspended particles of clay, silt, organic and
inorganic matter, plankton, and other microscopic organisms that are picked up
by water as it passes through a watershed.
Which water sources
are most affected by turbidity?
Turbidity levels are
much higher in water from surface water sources (e.g. streams, rivers, and
lakes) than from groundwater sources.
Some surface water
sources exhibit high turbidity levels during periods of high precipitation or
snow melt (e.g. spring runoff).
How is turbidity
measured and reported?
Turbidity, which is
measured and reported in nephelometric turbidity units (NTU), is an optical
measurement of water’s ability to scatter and absorb light rather than transmit
it in straight lines.
Turbidity levels can
range from less than 1 NTU to more than 1,000 NTU. At 5 NTU water is visibly
cloudy; at 25 NTU it is murky.
How often is my water
tested, and for what?
Water intended for
drinking is measured against physical, chemical, radiological, and
microbiological standards outlined in the federal Guidelines for Canadian
Drinking Water Quality.
To that end, your
water is tested regularly for viruses, bacteria (e.g. E-coli), parasites (e.g.
Giardia and Cryptosporidium), and turbidity.
The guidelines
recommend that water intended for drinking have a turbidity level < I NTU.
How will elevated
levels of turbidity be reported?
In keeping with the
Guidelines for Canadian Drinking Water Quality and B.C.’s Drinking Water
Protection Act, water suppliers will notify customers of turbidity levels that
exceed 1 NTU. A Turbidity Index on the supplier’s website will indicate if the
water is ‘Good’ (< 1 NTU), ‘Fair’ (1-5 NTU), or ‘Poor’ (>5 NTU), and
provide recommendations for each.
‘Fair’ and ‘Poor’
ratings will also be publicized through the media. To subscribe to an automatic
email notification service, please contact your water utility.
Is turbidity a health
concern?
Turbidity is not so
much a health concern as an indicator of health risk.
Science has proven
that as turbidity increases, the risk to human health also increases — particularly
for at-risk populations such as newborns, the elderly, and people with
compromised immune systems (e.g. those with HIV/Aids, undergoing chemotherapy,
or taking anti-rejection drugs.)
Why is turbidity an
important water quality indicator?
Bacteria, viruses,
and parasites such as Giardia and Cryptosporidium can attach themselves to the
suspended particles in turbid water.
These particles then
interfere with disinfection by shielding contaminants from the disinfectant
(e.g. chlorine). Nor is chlorine effective in deactivating Cryptosporidium.
What are accepted
water-industry standards for turbidity, and who sets them?
Health Canada’s
Guidelines for Canadian Drinking Water Quality recommend that surface water
suppliers aim for turbidity levels <1 NTU at the point of disinfection.
The guidelines state
that a water supplier with turbidity levels > 1 NTU should notify the public
of the increased health risk, and that a turbidity level > 5 NTU should
trigger a Boil Water Notice.
The guidelines also
recommend filtration for water from all surface water sources, and specific
water quality parameters for each type of filtration used.
These standards are
reflected in B.C.’s Drinking Water Protection Act, and advocated by IH in its
4-3-2-1-0 treatment objectives.
What are Interior
Health’s 4-3-2-1-0 treatment objectives?
In 2004 — after
carefully examining B.C.’s Drinking Water Protection Act, the Guidelines for
Canadian Drinking Water Quality, and standards set by the U.S. Environmental
Protection Agency — IH defined new water treatment goals for water suppliers
within its region.
The 4-3-2-1-0
treatment objectives recommended 4-log (99.99 percent) inactivation and/or
removal of viruses, 3-log (99.9 percent) inactivation and/or removal of Giardia
and Cryptosporidia, dual treatment (e.g. filtration and disinfection), <1
NTU turbidity, and 0 total or fecal coliforms.
Who is responsible
for ensuring my drinking water is safe?
In keeping with
B.C.’s Drinking Water Protection Act, Interior Health is responsible for
overseeing source-to-tap assessments of all drinking water systems, and
monitoring operational standards, including turbidity testing, monitoring,
reporting, and public notification.
IH’s Drinking Water
Team (in its Health Protection Division) works closely with the region’s 1,300
water suppliers to ensure compliance with the act and corresponding
regulations.
As outlined in the
act, IH requires each water system serving more than 300 connections to:
- employ certified operators;
- undertake a drinking water sampling program;
- conduct continuous on-line turbidity sampling
and recording of raw water for each surface source;
- conduct continuous online monitoring of the
disinfection process;
- perform
Giardia performance monitoring as prescribed by the public health engineer;
- implement a cross-connection control program;
- develop well protection plans for each well
source;
- review and update emergency response plan
annually;
- provide long-term plans for source, treatment,
and distribution system improvements; and
- report prescribed monitoring results to the
public health engineer monthly.
And, as also required
by the act, IH staff are working with water suppliers via the Turbidity
Education and Notification Campaign to ensure customers are aware of potential
health risks posed by increased turbidity, and are informed of turbidity spikes
that may compromise their health.
How do Interior
Health and my water supplier respond to elevated turbidity levels?
Surface water
suppliers serving more than 300 connections are required by IH to monitor and
report turbidity levels on an ongoing basis.
If turbidity levels
rise above the federally recommended level of 1 NTU, a water supplier must
notify IH, monitor bacteriological levels and chlorine residuals within the
distribution system, and notify customers of increased health risks using the
Turbidity Index.
If turbidity levels
exceed 5 NTU, and if IH deems it necessary, the water supplier will initiate an
Emergency Response Plan.
The public will be
notified of the resulting Boil Water Notice via the water supplier’s website
and through the media.
What precautions
should I take if the water is turbid?
The Province of B.C.
recommends that newborns and people with compromised immune systems drink
boiled water or safe alternative at all times if they’re served by an
unfiltered surface water source.
When turbidity levels
range from 1-5 NTU, IH and water suppliers recommend that children, the
elderly, people with compromised immune systems, and anyone seeking additional
protection drink boiled water or a safe alternative.
When turbidity levels
exceed 5 NTU, IH and water suppliers recommend that all users drink boiled
water or a safe alternative.
How can I protect my
children?
IH and water
suppliers recommend that newborns (up to six months) drink boiled water or a
safe alternative at all times.
They also suggest
that children drink boiled water or a safe alternative if turbidity levels
exceed 1 NTU.
You can provide them
with water that has been boiled (at a rolling boil) for at least one minute,
bottled or distilled water, or water that has been filtered through a
well-maintained treatment device.
You might also want
to inform that there is a far greater risk of gastrointestinal illness from
poor hygiene (e.g. not washing their hands well and often).
How do I boil my tap
water to make it safe for drinking?
Water must be boiled
(at a rolling boil) for at least one minute and then stored in a clean, covered
container in the fridge.
What are safe
alternatives to tap water?
Safe alternatives to
tap water include bottled or distilled water, or water filtered through a
well-maintained in-home treatment device.
Point-of-entry
systems treat all water entering your home. They effectively remove colour,
sediment, and minerals.
Activated-carbon
backwashing filters work well, as do reverse osmosis and filtration systems,
which also remove or inactivate parasites such as Giardia and Cryptosporidium.
Point-of-use systems
treat water intended for drinking or cooking.
Usually hooked into
the kitchen faucet or installed below the sink, they treat water using reverse
osmosis, carbon filtration, or distillation.
Point-of-use systems
that remove particles one micron or less in diameter are effective against
parasites.
Filters in this
category include those using reverse osmosis, those labeled as ‘absolute’
one-micron filters, and those certified by NSF International under NSF Standard
#53 for cyst removal.
Whatever system you
choose, follow installation and maintenance directions carefully.
Poorly-maintained
units can actually pose serious health risks. IH can provide you with
information about bottled water and other alternatives.
Can I get my
point-of-use water treatment device tested?
Yes. Testing is
available at private analytical laboratories. Bacteriological testing is about
$40; chemical testing is about $300.
Is bottled water
safe?
In Canada, bottled
water products are considered food items and, as such, are monitored by the
Canadian Food Inspection Agency.
Members of the
Canadian Bottled Water Association are also subject to the standards of the
association. Bottled water plants in B.C.’s interior are inspected by IH public
health staff.
Are grocery store
water systems tested?
Yes. IH conducts
bacteriological testing on grocery store water systems at least twice a year.
How long can I keep
bottled water?
Water can support
microbial growth, and like any other product has a shelf life.
Shelf life depends on
the type of water bottled and the treatment methods used.
You can consult with
bottled water companies about the shelf lives of their products.
Should bottled water
be refrigerated?
As water can support
microbial growth, bottled water should be refrigerated once it’s opened.
Will my coffee maker
purify the water?
No. The coffee filter
may remove some turbidity and the heat may kill some bacterial, but neither
Giardia nor Cryptosporidium will be removed or inactivated.
Is it safe to brush
my teeth with turbid water?
Yes, unless a Boil
Water Notice is in effect.
Is it safe to wash my
vegetables in turbid water?
Yes, unless a Boil
Water Notice is in effect.
Is it safe to bathe
or shower with turbid water?
Yes, but children
should be discouraged from drinking bath water or chewing facecloths.
South
East Kelowna Irrigation District
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