Works and Emergency Services reports that an earthy odor in
Toronto's water supply has become noticeable during the past few days. Taste
and odor episodes are caused by seasonal biological changes in Lake Ontario and
typically occur in the late summer or early fall. Toronto's tap water continues
to be safe to drink during these episodes.
Taste and odor episodes 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 odor in drinking water, such as keeping a jug
of water in the fridge and adding ice cubes or a few drops of lemon juice.
Two of Toronto's four water filtration plants (Island and
R.C. Harris) 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 at
the time of a taste and odor episode. Once activated, the carbon systems in
these two plants take some time (from a few hours 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 odor episodes will generally dissipate after the
lake water temperature starts to go down (below 15 degrees Celsius).
Additional
information about taste and odor episodes is available from the Ontario Water
Works Research Consortium at www.owwrc.com.
Source: City of Toronto
