Pumping stations in sewage collection systems are normally designed to handle raw sewage that is fed from underground gravity pipelines.
Pumping stations in sewage collection systems are normally designed to handle raw sewage that is fed from underground gravity pipelines (pipes that are laid at an angle so that a liquid can flow in one direction under gravity). Sewage is fed into and stored in an underground pit, commonly known as a wet well. The well is equipped with electrical instrumentation to detect the level of sewage present. When the sewage level rises to a predetermined point, a pump will be started to lift the sewage upward through a pressurized pipe system from where the sewage is discharged into a gravity manhole. From here the cycle starts over again until the sewage reaches its point of destination – usually a treatment plant.
By this method, pumping stations are used to move waste to a point of higher elevation. In case of high sewage flows into the well (for example during peak flow periods and wet weather) additional pumps will be used. If this is insufficient, or in the case of pumping station failure, a backup in the sewer system can occur, leading to overflow.
Sewage pumping stations are typically designed so that one pump or one set of pumps will handle normal peak flow conditions. Redundancy is built into the system so that in the event that any one pump is out of service, the remaining pump or pumps will handle the designed flow. The storage volume of the wet well between the 'pump on' and 'pump off' settings is designed to minimise pump starts and stops, but is not so long a detention time as to allow the sewage in the wet well to go septic.
Pumping stations can normally be split in pressurised (small size) network (medium size) and main pumping stations (large size pumping stations). For Network and Main pumping stations they can again be split in dry and submerged pump installation.