The North River Wastewater Treatment Plant was taken offline Wednesday following a fire in the engine room. Untreated wastewater began flowing into the river beginning at 5:15 p.m. Wednesday.
Mayor Michael Bloomberg said one engine was back in service, and another could return sometime Friday.
Riverbank State Park in Harlem reopened, but two pools there will remain closed until Saturday. The 28-acre recreational complex is on top of the plant.
Pollution advisories were in effect at three beaches on Staten Island and one in Brooklyn. Swimmers and kayakers in New York and New Jersey were urged to stay out of the river.
Scientists from the New Jersey Department of Environmental Protection were closely monitoring the situation with boats. They were conducting scientific modeling of the tides and currents to gauge whether the spill could have an impact on New Jersey.
Their modeling showed that even if repairs were not made until Tuesday, there would not be an impact on Jersey shore points and shellfish beds, according to Larry Ragonese, a state Department of Environmental Protection spokesman.
To the north of the city, the Westchester County Health Department notified its residents to avoid direct contact with the Hudson River through the weekend.
The plant has been in operation since 1976 and treats on average 120 million gallons of wastewater a day.
