What is the name of the system that includes all sanitation equipment and fittings designed to receive, treat, vent and discharge sewage?

The appropriate designation for the system encompassing all sanitation equipment and fittings designed for receiving, treating, venting, and discharging sewage is indeed the Treatment System. This term accurately reflects the multifaceted nature of the sanitation processes involved, which include not only the physical collection of sewage but also the subsequent treatment to make it safe for discharge or further handling.

A Treatment System integrates various components such as holding tanks, treatment devices, and associated plumbing that work together to ensure that sewage is adequately processed before being released into the environment or a disposal system. The emphasis on "treatment" highlights the importance of processing sewage to eliminate harmful pathogens and contaminants, thereby safeguarding public health and the environment.

In contrast, other choices refer to more specific aspects of sanitation or waste management. A Retention System typically refers to a method of temporarily holding sewage until it can be treated, without necessarily implying any treatment occurs. A Ventilation System focuses on air circulation within the context of waste systems to prevent odors and maintain air quality but does not encompass the treating or discharging functions. A Disposal System specifically pertains to methods and processes used to get rid of sewage or waste, potentially after treatment, but does not include the entire scope of equipment and processes necessary for effective sewage management.