This project involved designing modifications and other improvements to the Theresa Street Wastewater Treatment Plant (WWTP). In October 2012, improvements included a pumping station with mechanically cleaned screens, a combination pre-aeration and grit removal unit, an additional primary sedimentation basin, and a new sludge digester. An existing digester was re-piped, and the team added a heat exchanger and sludge recirculation facilities.
Additional improvements were made to the plant’s two influent pumping stations in October 2013. The north influent pump station, Building A-3, was originally built in 1973 and included raw sewage pumps number 5 (RSP-5) and number 6 (RSP-6). Raw sewage pump number 7 (RSP-7) was added in 1987 when the pump station was upgraded. The last improvement occurred in 1998 where raw sewage pump number 8 (RSP-8) was installed.
All the pumps are extended, vertical-shaft, dry-pit pumps where the volutes are at the lower level and the motors are located above on the main operating level. The city had been experiencing maintenance issues with RSP-7, which has reached the end of its useful life.
Olsson was retained to evaluate removing and designing a replacement for RSP-7 with a 15 million of gallons per day (MGD), 215 horsepower, dry-pit submersible pump. The design included structurally modifying the raw wastewater pumping building, upgrading the electrical grid, and installing a new variable frequency drive (VFD). Other improvements included modifying the pump and motor, installing new 24- and 30-inch piping and valve configurations, and replacing the existing welded-steel flanged pipe and fittings with ductile-iron flanged pipe and fittings. The Nebraska Department of Environmental Quality provided the necessary review and construction permit, as required. This project is currently being prepared for bidding and construction.
In addition, the University of Nebraska-Lincoln’s Nebraska Innovation Campus (NIC) is located next to the Theresa Street WWTP. With 1.8 million square feet of building space to heat and cool, Olsson designed a Centralized Renewable Energy System (CRES) that used the plant’s treated wastewater to heat and cool the buildings. Read more about the CRES here.
The system began operating August 2014, and, at full expansion, will pump an estimated 28 million gallons of water per day to heat and cool NIC buildings.