Authorities in Washington and Arlington, Virginia, advised all 920,000 residents Wednesday to boil their drinking water after discovering that algae blooms in the Potomac River had raised pollution levels in a reservoir.
The boil water advisory, which applies to the Pentagon, Arlington National Cemetery and Reagan National Airport, will remain in effect until authorities confirm it is safe to drink, the District of Columbia Water and Sewer Authority said in a statement.
John Lisle, a spokesman for the Washington water company, said it was unusual for a citywide boil-water advisory to be in effect, adding that in his 11 years working there, he had never seen such a comprehensive warning.
Cloudy or hazy water can be a sign of poor water quality, Arlington County said in a statement. The water can contain bacteria, viruses and parasites that can cause nausea, cramps, diarrhea and headaches, authorities said. Babies, children, the elderly and people with weakened immune systems may be more vulnerable, authorities said.
Customers should throw away any drinks or ice made after 9 p.m. Wednesday, authorities said. They should also boil water for at least a minute and let it cool before using it to drink, brush teeth, wash food, prepare baby food, make ice or feed pets, they said.
After noticing the increase in algae and cloudiness, the United States Army Corps of Engineers, which manages the Washington Aqueduct, said Wednesday it had increased its filter capacity by washing existing filters and purchasing additional filters.
The Washington Water Authority said the turbidity was found at the Dalecarlia Water Treatment Plant. The Washington Aqueduct reduced the amount of water it received there, initially moving all water treatment to the area’s other facility, the McMillan plant.
But amid concerns about water shortages, particularly in light of potential fires, aqueduct operators decided to resume pumping from the Dalecarlia facility, the water company said.
Mr. Lisle added that the decision to use the Dalecarlia plant’s water was also made in part because the Fourth of July holiday typically brings an increase in water use. It was unclear when the advisory would be lifted, he said.
Fairfax Water, a water utility that serves another Northern Virginia suburb, said no boil water warnings had been issued because the utility had already stopped receiving water from the Washington Aqueduct earlier Wednesday.