Working Principle of a Wastewater or Sewage Lift Station

Wastewater / Sewage Lift Stations or Pump Stations are used for pumping Wastewater or Sewage from Lower Elevation to Higher Elevation. Lift Stations are set up for Places where the elevation of the source is not sufficient for gravity flow and/or when the use of gravity conveyance will result in excessive excavation and higher construction costs.

Lift Stations in sewage collection systems are normally designed to handle raw sewage that is fed from underground gravity pipelines (pipes that are sloped 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 called a sewer force main if the sewage is transported some significant distance. The pumping station may be called a lift station if the pump merely discharges into a nearby gravity manhole. From here the cycle starts all 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 higher elevations. In the 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 failure of the pumping station, a backup in the sewer system can occur, leading to a sanitary sewer overflow of the discharge of raw sewage into the environment.

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Sewage Lift 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 minimize pump starts and stops, but is not so long a retention time as to allow the sewage in the wet well go to the STP.

The interior of a sewage pump station is a very dangerous place. Poisonous gases, such as methane and hydrogen sulphide, can accumulate in the wet well; an ill-equipped person entering the well would be overcome by fumes very quickly. Any entry into the wet well requires the correct confined space entry method for a hazardous environment. To minimize the need for entry, the facility is normally designed to allow pumps and other equipment to be removed from outside the wet well. There must be provision of 2 or More Manholes into the Station for Proper ventilation for the person working inside, A Manhole is dedicated for Entrance and the other will be for extra ventilation.

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THE LIFESPAN OF A LIFT STATION

For the most part, a customer can anticipate a life expectancy of 15 – 20 years or more from steel lift stations. This is more than adequate in most cases, since the anticipated flow rates are usually designed for only ten years of expansion. Steel lift stations are coated with a high solids epoxy paint system and further protected by anodes to deter cathodic action.

When a concrete structure (not provided by PCS) is desired, PCS can provide the equipment package to be installed in the concrete structure in the field by the installing contractor.

 

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