Section 312 of the US federal Clean Water Act regulates sewage discharges from vessels, and is implemented jointly by the US Environmental Protection Agency (USEPA) and the US Coast Guard.
“Sewage” is defined under the Clean Water Act as “human body wastes and the waste from toilets and other receptacles intended to receive or retain body wastes”, and includes grey water discharges from commercial vessels (as defined at 33 U.S.C. 1322(a)(10)) operating on the Great Lakes. Under section 312 of the Clean Water Act, vessel sewage is controlled by regulating the equipment that treats or holds the sewage (marine sanitation devices), and through the establishment of areas in which the discharge of sewage from vessels is not allowed (no discharge zones).
Here is the USEPA information on No Discharge Zones (NDZ).
Here is the USEPA information on Marine Sanitation Devices (MSDs).
Here are the NDZ in USEPA Region 2.
Here is the (USEPA Region 2) second opportunity for public comment on an NDZ for Lake Erie.