Marshall Municipal Utilities

Raw Sewage Pump Building

Raw Sewage Pump Building

The raw sewage pump building area, located at the south end of the plant, is where the first portion of the plant preliminary treatment occurs. We have one Vulcan automatic coarse bar screen at the raw sewage building that removes objects 3/4 inch or larger from the waste stream. We also have one manually cleaned coarse bar screen that is used when the Vulcan unit is undergoing maintenance.

The raw sewage building has three Fairbanks Morse 12-inch centrifugal pumps that are capable of moving a designed 11.3 million gallons per day (MGD) peak flow into the treatment process. These pumps are operated with variable frequency drive (VFDs). The VFDs drive the pumps at different operating speeds depending on the flow. From here, the flow is pumped to the grit removal and preaeration building.

Flow Equalization Basin

Next to the raw sewage building is the flow equalization (FEQ) building. This structure is mostly underground. There are three Fairbanks Morse submersible pumps in this structure that move any flows, up to 5.3 MGD, in excess of what the raw sewage pumps can handle to the FEQ basin.

The FEQ basin was designed to store any flow that the treatment plant cannot handle due to high flows during rain events. The basin will hold 9.6 million gallons of wastewater and has a concrete bottom. About two-thirds of the height of the basin sides are concrete-lined. The top third of the basin walls is soil with crown vetch vegetation. We can use the FEQ basin as a catch basin also if we need to work on equipment that requires us to shut the plant process pumps down for a short time. Wastewater pumped to the FEQ basin is gravity fed back into the treatment process at the grit removal and preaeration building. This occurs after the plant flow drops back to normal or we have completed necessary maintenance.