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Wastewater
Treatment Articles Index
How Sewage Pump Stations Operate
Most sewage pump stations operate on a float-type system. As the wastewater flows into the wet well by gravity, the water level in the wet well rises until the maximum operating level is reached. At the high level, a float switch is actuated to turn on a pump. With the pump running, the water level falls. The pump keeps running until the water level reaches the low level. At the low level, another float switch is actuated to turn off the pump. The cycle is repeated several times during the day. The station can include a high water alarm that alerts you when the pump has failed or isn't pumping out fast enough to keep up with the flow.
Types of Sewage Pump Stations
Five types of commonly used sewage pump stations include:
1. Submersible Non-Clog
1a. Submersible Grinder
2. Wet-well Mounted (Vacuum or Self-primed)
3. Factory-built Dry Pit station with separate wet well
4. Built-in-Place Station with separate wet well
Each type is described in detail below.
1. Submersible Non-Clog (See Submersible Non-Clog drawing)
A submersible non-clog pump operates underwater. The motor is sealed water-tight and designed to operate while being submerged in the wastewater. A non-clog pump can handle solids as large as a tennis ball without clogging. The pumps are removable for maintenance without a person entering the wet well. A pump can be easily hoisted out on guide rails by a person standing on the ground surface. The electrical control panel is mounted on posts above ground. This type of station normally includes a separate valve chamber. It is considered the lowest cost sewage pump station for many applications.
1a. Submersible Grinder
A submersible grinder pump is similar to a non-clog pump except that it grinds up the solid matter in sewage rather than pumping it. A grinder pump can have smaller discharge piping than a non-clog pump.
2. Wet-Well Mounted (See Wet-Well Mounted drawing)
In a wet-well mounted pump station, the pumps are located at ground level above the wet well. The water rises up from the wet well to the pump through a vertical suction pipe. The pumps can be self-priming or primed with a small vacuum pump. The pumps, valves, and control panel are located above grade. The equipment is usually housed in a removable, insulated, and heated fiberglass enclosure. This is a relatively economical installation.
3. Factory-Built Dry Pit (See Factory-Built Dry Pit
drawing)
In a factory-built dry pit station, the pumps, valves, piping, and controls are factory installed inside a cylindrical steel chamber. The pumps are usually of the non-clog type. The motor is mounted on top of the pump. The pump chamber is delivered to the site as a prefabricated package and installed underground next to a separate wet well. A cylindrical tube is needed to provide access to the pump station from the ground surface. The access tube is connected to the pump chamber in the field. A portable engine-driven pump can be used as standby in case of a power failure.
4. Built-in-Place (See Built-in-Place drawing)
In this type of station, both the wet well and dry well are constructed of reinforced concrete on-site. The aboveground structure is often brick and block. The pumps, piping, valves, and control panel are field installed. This type of station is more appropriate for the larger capacity installations. An engine-driven generator can be installed for use in case of a power failure.
Wastewater Treatment Articles Index
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