Regulation 11 - Discharge of sewage
• Subject to the provisions of regulation 3 of this Annex, the discharge of sewage into the sea is prohibited, except when:

.1 the ship is discharging comminuted and disinfected sewage using a system approved by the Administration in accordance with this Annex at a distance of more than 3
nautical miles from the nearest land, sewage which is not comminuted or disinfected at a distance of more than 12 nautical miles from the nearest land, the sewage that has been stored in holding tanks shall not be discharged instantaneously but at a moderate rate when the ship is en route and proceeding at not less than 4 knots;

.2 the ship has in operation an approved sewage treatment plant which has been certified by the Administration to meet the operational requirements referred to in regulation 9.1.1 of this Annex, and
.2.1 the test results of the plant are laid down in the ship's International Sewage Pollution Prevention Certificate; and
.2.2 additionally, the effluent shall not produce visible floating solids nor cause discoloration of the surrounding water.

• When the sewage is mixed with wastes or waste water covered by other Annexes of MARPOL 73/78, the requirements of those Annexes shall be complied with in addition to the requirements of this Annex.