Annex IVapplies to discharges of sewage into the sea. Annex IV applies to all ships over 400 gross tons engaged in international voyages or to ships less than 400 gross tons certified to carry more than 15 persons. The Annex requires the installation of holding tanks or approved sewage treatment devices. 

Section 312 of FWPCA, as amended, requires the installation of a Marine Sanitation Device (MSD), a sewage treatment devices to prevent the discharge of untreated or inadequately treated sewage into U.S. waters. The Act requires every vessel that operates in U.S. waters and equipped with an installed toilet to have a certified and operable MSD. A vessel with no installed toilet is not subject to the provisions of section 312. Installed toilets that are not equipped with a certified MSD, and that discharge raw sewage directly over the side are illegal. Section 312(g)(2) of the FWPCA directs the Coast Guard to certify MSDs and 33 CFR 159 sets out equipment construction and operation requirements. 

 For more information on Annex IV and vessel compliance, see the Annex IV page at  http://www.uscg.mil/hq/cg5/cg5213/msd.asp.