How Vacuum Sewerage Systems Work
Vacuum sewerage systems are used for a variety of applications such as emergency and mining camps, green buildings, hospitals, industrial areas and army. The operation principle of these systems is the same in residential areas as in industrial areas, where a vacuum system may replace an old gravity system or septic tank or in a new housing development. It is a sewerage system that uses gravity and differential air pressure to transport sewage rapidly in an intricate network of basically empty pipes from Collection Pits to the main collection tank and then to the point of discharge. Sewage then enters the vacuum system where the atmospheric Flovac Valve is opened into a Collection Pit, and the sewage is forced into the vacuum main. This valve remains open for a short period of time, following which the removal of the sewage from the pit sump allows atmospheric air to enter the suction system and blow the sewage towards the vacuum pump station. Unlike the vacuum sewerage systems before, the transport system in modern vacuum sewerage systems is much faster and does not require a siphon.
A vacuum sewerage collection system should always be treated as a collective system instead of a number of independent components.
The system begins with the design. An engineer surveys the overall catchment area and begins with a master plan. They then decide the number of vacuum pump stations, where the sewage will be delivered, and how each station will service many buildings and houses. Each project is unique in its own way and has its own set of unique challenges, so it is essential to discuss it with the engineers to see if it will be the right solution for that particular project.
The Vacuum Pump Station (VPS) contains a collection tank for the collection of sewage, controls that automate the station, discharge pumps which send the sewage to the treatment plant and vacuum pumps that create a negative pressure in the vacuum mains. Generally, only one VPS is needed in an average-sized catchment. Ideally, a VPS is located in the centre of a catchment area, but it depends on the designer. A backup generator can also be located at the VPS to ensure non stop operation in areas susceptible to hurricanes or cyclones or where power is a problem.
The collection pit contains a 90mm vacuum valve that interfaces the atmosphere coming from the gravity lines with the negative pressure in the vacuum mains which is created by the vacuum pumps at the VPS. It may be located as far as 5 kilometres away from the last collection pit. After 40 litres of sewage enters the pit through the gravity line, air pressure on the controller valve triggers the valve to open, allowing the sewage and then air to enter the vacuum mains at a rate of 4-6 meters per second. The expanding air propels the sewage to the VPS with no requirement of power at the collection pit.