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September 17, 2003
Earthy-smelling water remains safe to drink
Works and Emergency Services reports that an earthy taste and odour in
Toronto's water supply has become noticeable during the past few days. Taste
and odour 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 odour episodes are caused by the presence of a natural-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 juice.

Two of Toronto's four water filtration plants are permanently retrofitted with
granular activated carbon systems, which run continuously and remove geosmin.
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 odour episode. The carbon systems in
these two plants have been activated and it generally takes some time (from a
few hours to a few days) for the filtered water to reach consumers' taps. The
carbon systems reduce taste and odour but may not eliminate it entirely.

Although it is difficult to predict when conditions will return to normal,
taste and odour episodes will generally dissipate after the lake water
temperature starts to go down (below 15 degrees Celsius).

Additional information about taste and odour episodes is available from the
Ontario Water Works Research Consortium at For information on
Toronto's water and wastewater systems, residents may call Works and Emergency
Services' Waste and Water Education Line at 416-392-4546.

Media contacts:
Patrick Newland, Director, Water Supply Manager, Water Quality, Works and
Emergency Services, 416-392-8220

John Rudnickas, Manager, Water Quality, Works and Emergency Services,



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