Type III marine sanitation devices offer the least environmental impact of all marine sanitation devices. Types I and II also reduce the environmental impact of sewage by treating the waste before it is discharged.
The Type III marine sanitation device is a holding tank for sewage that can be emptied onshore at appropriate facilities. This type of marine sanitation device provides the least environmental impact, because the waste is not discharged into the open water. Types I and II marine sanitation devices reduce environmental impact by treating sewage before it is discharged into the open water. Sewage is soaked in chemicals that reduce the bacterial count and reduce solid waste to a liquid form without visible particles.