Exam Question

(a) Description of a Vacuum Sewage System
A vacuum sewage system is an innovative method for transporting sewage that does not rely on gravity. Instead of using large volumes of water and the natural downward flow of gravity, it uses a pressure differential (vacuum) to pull sewage through the pipes. Water is only used for rinsing the toilet bowl, not for moving the waste itself. This allows for both limited vertical lifts and long horizontal transportation of sewage.
The system works by using a vacuum created by an eductor, which pulls the sewage into a sewage tank. A pressure switch controls the system by automatically starting and stopping a centrifugal pump to maintain the vacuum in the lines. The water in the sewage tank acts as the driving force for the eductor.
(b) Analysis of the System