Concerns about musty-smelling water led Lake Oswego's treatment plant operators to start treating drinking water for taste and odor problems last week.
The city has recently received quite a few questions from water customers about the 'swampy' smell and taste of liquid pouring from their taps, although the problem typically arises annually, according to the city.
Officials said drinking the water does not pose a risk to anyone's health.
'We want customers to know the earthy-smelling water is not a health issue,' said Kari Duncan, the city's water treatment manager, in a public statement. 'It just makes water less pleasant to drink.'
The smell comes from algae in the Clackamas River that tends to develop at the end of each summer, when water temperatures are relatively warm and the days are sunny. This year may have seen the problem worsen because the river water was a few degrees warmer than usual, officials said. It would likely go away naturally as water temperatures drop and rain brings new water into the river.
But to ensure everyone's water tastes OK, starting Sept. 30, Lake Oswego treatment plant operators began using powdered activated carbon to remove the offensive smell and taste.
'We don't start this action until after we have received taste and odor complaints, because there are no instruments to detect the odor at the low levels that the human nose can detect it,' Duncan said.
In addition, the city's operation division dispatched crews to flush water lines. It typically takes about a week to clear the system of the 'objectionable' water, according to city staff.
'Flushing the lines will help draw down reservoirs that don't turn over as quickly in the fall as they do in the hot summer months,' explained Lake Oswego Public Works Director Guy Graham.
Water plant upgrades now in the planning process will allow operators to be proactive rather than reactive in dealing with these sorts of issues.
Lake Oswego is moving to a new ozone treatment system, which removes taste- and odor-producing compounds from the water before it reaches customers' faucets.
The treatment method is also considered effective for removing contaminants such as pharmaceuticals and personal hygiene products.