Great Lakes Article:

Water safe to drink despite odd taste, odour
National Post
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 days.

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 juice.

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 Celsius.

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.