For ships less than 400 gross tons, what are the discharging options under Annex I?

• A. Oil and oily mixtures must be retained for discharge ashore or discharged through 15 ppm oil separating equipment.
• B. Oil must be discharged directly into sea without treatment.
• C. Oil must be stored and never discharged.
• D. Oil must be burned in boiler.

Answer: (A)

The main idea here is how MARPOL Annex I allows small ships to manage oily waste without releasing pollution directly into the sea. For ships under 400 gross tons, the rules give two compliant paths: either keep the oil on board and discharge it ashore at an approved reception facility, or discharge the oily wastewater through an approved oil–water separator so the effluent contains no more than 15 parts per million of oil.

This is the best choice because it matches the allowable options that minimize environmental impact: treatment to a very low oil content or retention for port disposal. It reflects that direct discharge into the sea is not permitted, and that simply storing oil “forever” isn’t the practical, permitted approach—retention is allowed specifically for discharge ashore, not an indefinite no-discharge rule. The option about burning oil in a boiler isn’t a standard compliant method for disposing of oily mixtures under Annex I, and discharging untreated oil directly into the sea is prohibited.