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Overview of Vacuum Sewer Systems (VSS)

Vacuum sewers are a mechanized system of wastewater transport. Unlike gravity flow, a vacuum sewer system uses the differential air pressure between atmospheric pressure and a partial vacuum maintained in the sewer piping network to permit wastewater transport to a central collection point. Depending on the terrain and local conditions, the differential pressure allows a single central vacuum station to collect wastewater from several thousand individual homes.

Rotary vane vacuum pumps generate an operation pressure typically of -0.5 bar at the vacuum station. Interface valves installed inside the collection chambers work pneumatically. Wastewater flows by means of gravity into each house's collection sump and, once the prescribed fill level inside this sump is reached, the interface valve will open and the resulting differential pressure will transport the wastewater to the vacuum station. Sewers can be laid in flat terrain and up to certain limits may also be counter-sloped. Installation of lines in a saw-tooth profile keeps sewer lines shallow. Once in the vacuum collection tank at the vacuum station, the wastewater is pumped to the discharge point, which could be a gravity-flow sewer, or directly to the wastewater treatment station. Lifting stations are not required.

Vacuum sewers, when properly designed, installed and operational, can present significant cost advantages as well as provide a solution in problematic situations, such as sandy and high ground-water environments.