If a reverse-osmosis freshwater generating unit has a high salinity alarm associated with the freshwater outlet, what should be done?

Correct Answer: Option D — The membrane modules should be flushed and cleaned.

High salinity in the freshwater output indicates that the semi-permeable membranes are either fouled, scaled, or damaged, allowing salts to pass through. Flushing and cleaning the membrane modules is the standard corrective action to restore membrane performance and ensure the distillate meets purity standards for shipboard use.