In accordance with international MARPOL Annex I regulations and federal regulations under 33CFR Subchapter O, for vessels of 400 gross tons and above which are all required to carry an oily-water separator to process bilge slops, what is the design criteria in terms of maximum oil content of the overboard discharge?

Correct Answer: Option B — 15 parts per million

MARPOL Annex I and 33 CFR 151.10 mandate that for vessels 400 gross tons and above, oily-water separators must be designed to ensure that the oil content of the effluent discharged overboard does not exceed 15 parts per million (ppm) under normal operating conditions to protect the marine environment.