|HAMPTON ROADS SANITATION DISTRICT VIRGINIA INITIATIVE PLANT|
RAW WASTEWATER INFLUENT PUMP STATION
CLIENT: Hampton Roads Sanitation District
Northwest Hydraulic Consultants was retained by HDR Engineering Inc. to provide a conceptual design review of the Preliminary Treatment Facility Raw Wastewater Influent Pump Station for the Hampton Roads Sanitation District Virginia Initiative Plant, and then construct and test a physical hydraulic model of the preferred initial design. The overall objective of the model study was to optimize the hydraulic design of the screen channels and wet well to provide uniform flow to the pumps.
The 1:6 scale model study determined that the initial design was subject to unacceptable sub‑surface vortices entering all pumps. In addition, the velocity fluctuations measured at the pump impeller location were outside the specified criterion.
Modifications to the initial design were developed to produce more uniform flow in the screen channels and wet well, and reduce solids deposition in the screen channels. With these modifications installed, the surface and sub‑surface vortices, flow pre-swirl, and the velocity distribution and velocity fluctuations were all within acceptable limits.