Here's a list of U.S. locations where you must padlock your overboard discharge valve and must not discharge even treated waste.
Device that performs environmentally friendly treatment of waste so it can be legally discharged overboard. Can be used with manual or electric toilets. The LectraSan is for use in salt water; the Puresan in fresh water.
Rectangular polyethylene tanks in many sizes, with top-mount hose fittings to reduce odor, and vacuum relief valves to prevent damage from high-vacuum dockside pumps,
This might help you meet the MSD regulations with a tankless toilet. Five-gallon tank designed to fit around the base of Raritan and other manufacturers' compact models. Portable or permanent mounting.
Seamless polyethylene tanks and fittings made to fit the space on your boat. 200+ rectangular and 100 non-rectangular shapes available.