What type of certified MSD is solely used for the storage of sewage and flush water at ambient air pressure and temperature?

The correct answer is Type III Marine Sanitation Device (MSD). Type III MSDs are specifically designed for the storage of sewage and flush water without treatment, maintaining them at ambient air pressure and temperature. This type of device ensures that waste is properly contained and can be discharged only at approved locations, such as a shoreside pump-out facility. As such, Type III devices play an essential role in protecting the marine environment by preventing improper discharge of untreated waste.

The other types of MSDs have different functions: Type I and Type II MSDs are designed for the treatment of sewage, allowing for the discharge of treated waste into the water, while Type IV MSDs can include variations that may use additional features such as holding tanks or other systems designed for different conditions. The distinction of Type III as solely for storage highlights its critical environmental safeguard function, ensuring that sewage is not released into marine waters without treatment, thus contributing to the overall regulatory compliance and environmental protection efforts.