Water safe to drink despite odd taste,
Published August 31, 2004
TORONTO -- The city's tap water is still safe to drink
despite a noticeable change in taste and odour in recent
In a news release, Toronto Works and Emergency Services
said that taste and odour changes are caused by seasonal
biological changes in Lake Ontario, typically in the late
summer or early fall.
The changes are caused by the presence of a naturally
occurring compound called geosmin at extremely low levels
-- measured in parts per trillion -- in Lake Ontario.
Geosmin is not harmful to public health and the city's
water quality is not otherwise affected.
Simple home remedies may be used to reduce taste and
odour in drinking water, such as keeping a jug of water
in the fridge and adding ice cubes or a few drops of lemon
Two of Toronto's four water filtration plants are permanently
retrofitted with interim granular-activated carbon systems,
which reduce geosmin, but do not eliminate it entirely.
The other two water filtration plants -- R. L. Clark
in the west end and F. J. Horgan in the east end -- have
powdered-activated carbon systems, which must be activated
when a change in taste and odour occurs. Once activated,
the carbon systems in these two plants take up to a few
days for the filtered water to reach consumers' taps.
Although it is difficult to predict when conditions will
return to normal, taste and odour episodes generally dissipate
when lake water temperature starts dips below 15 degrees
Additional information about taste and odour episodes
is available from the Ontario Water Works Research Consortium
at www.owwrc.com. For information on Toronto's water and
wastewater systems, residents may call Works and Emergency
Services' Water Education Line at 416-392-4546.