Which materials may be separated and discharged during 'load on top' procedures?

The correct answer indicates that water and oil mixtures may be separated and discharged during 'load on top' procedures. This process is specifically designed to manage the cargo loading of tankers while ensuring compliance with environmental regulations.

During 'load on top,' a new cargo (often oil) is loaded on top of previously remaining liquids in the tank. This procedure allows for the separation of lighter hydrocarbons from heavier residues, enabling operators to manage the cargo more effectively and minimize waste. The mixture of water and oil typically refers to water that may have mixed with oil or other residues while retaining valuable cargo space and preventing pollution.

Discharging purely oil or just water would not account for the mixture that often occurs in holding tanks, where residues can create challenges during loading and discharging. Heavy metals would not be applicable in this context, as they pertain to different environmental and regulatory concerns not typically addressed during standard loading procedures.

Thus, recognizing that both water and oil mixtures can be handled during these operations is crucial for maintaining efficiency and adhering to environmental standards in maritime operations.