In what year did the CNO mandate the use of CHT systems on ships?

The correct answer is 1972, as this year marks the point when the Chief of Naval Operations (CNO) established the requirement for ships to implement Collection, Holding, and Transfer (CHT) systems. This mandate was part of a broader initiative to enhance environmental protection and manage wastewater disposal effectively from naval vessels. Implementing CHT systems allowed ships to store sewage safely and discharge it in compliance with environmental regulations while at sea, thereby minimizing pollution and protecting marine ecosystems.

Understanding this historical context is crucial as it underscores the importance of such systems in promoting sanitation and environmental standards within naval operations.