The Department of Environmental Services said the white disks were first spotted on Friday on the beach at Seabrook.
“What we had was a discharge from a wastewater treatment facility along the Merrimack River during one of the heavy rain events we recently had in New Hampshire,” said Jim Martin, spokesman of the New Hampshire DES.
Authorities said the wastewater treatment plant in Hooksett had the discharge problems last Sunday after dealing with excess rain and melting snow.
The discs, about the size of a key with a screen mesh, made their way downstream. In addition to the banks of the Merrimack River and Seabrook, the disks washed up on Plum Island, Salisbury Beach, Mass., and Cashman Park, Newburyport, Mass.
DES said anyone picking up the disks should use plastic gloves because they may harbor bacteria. The disks can be collected into plastic bags and disposed in a landfill.
“(The discs) generally collect bacteria and help to digest the wastewater,” Martin said.
On Sunday, a command center was set up on Plum Island so DES could not only clean up the disks but take water samples to test for bacteria.