MSN 1807 sets out the "moderate rate of flow" requirement for discharging sewage from a ship while underway under MARPOL Annex IV. Which of the following best describes what this requirement is intended to achieve, and how is the rate generally assessed?

A. It requires sewage to be discharged in a single rapid burst to minimise the time the discharge valve is open

B. It requires that sewage (treated or comminuted/disinfected) is discharged at a moderate rate while the ship is en route and proceeding at not less than 4 knots, so the effluent disperses rather than forming a visible slick or concentrated discharge near the ship

C. It only applies to passenger ships of 200GT and above and has no relevance to cargo ships

D. It requires the discharge rate to be reduced to zero whenever the ship is within 12nm of land, regardless of treatment

A. All plastics must be retained on board for discharge to a port reception facility — discharge of plastics into the sea is prohibited under all circumstances

B. Plastics may be burned in the incinerator and the ash discharged overboard

C. Plastics can be discharged if ground down to less than 25mm

D. They may be discharged overboard once the vessel is more than 12nm from the nearest land

A. Only the engineer needs to be present; deck crew are not involved

B. SOPEP equipment only needs to be available if bunkering more than 50% of capacity

C. Nothing specific — bunkering is routine and does not need pre-checks

D. A pre-bunkering checklist completed (hose connections, drip trays, communication with the barge/terminal, spill response equipment ready and accessible), a dedicated watch maintained throughout, and SOPEP equipment immediately available