The Hagerstown waste-water treatment center has stopped functioning, sending as much as 5.7 million gallons of raw sewage into the Potomac River every day, a state environmental official said yesterday.
Richard J. McIntire, spokesman for the Maryland Department of the Environment, said the plant was disabled Friday afternoon by a chemical from a nearby truck company.
The chemical killed the microbes that clean the water at the plant.
"The waste water can't be treated because the microbes are dead. Those bugs eat the waste-water material and clean it up," McIntyre said.
He said that the plant cannot be shut down because the whole system could back up.
So officials are warning counties along the Potomac River, including Washington and Frederick counties, whose residents use the water for drinking or for recreation.
The counties can draw drinking water from other areas, he said.
"This is a public health threat," McIntyre said.
He said plant officials are waiting for the chemical to be washed out of the system before reintroducing another set of microbes.
How the chemical got into the system is under investigation.
The truck company from where officials believe the chemical originated has a pretreatment plant that cleans water before it sends it to the public system.
McIntyre said officials are examining whether that system malfunctioned.
Residents might notice changes in the river because of the sewage, he said.
"You might see some foaming. You are probably going to see some discoloration."