SITUATION:

The 45 MGD Cherry Creek Lift Station is one of several sites that pump wastewater to the Southside Wastewater Treatment Plant in southwest Tulsa, Oklahoma. Maintenance had become a serious issue: the single rake bar screens (Figure 1) used at the facility were allowing debris and rags to get through, impacting the operation of the pumps and other downstream processes. The result was that the lift pumps had to be de-ragged on a monthly basis, which was very labor-intensive. Operators had to enter the bottom of the channel to remove debris and to reach routine maintenance areas, as well as deal with other screen access restrictions for maintenance above the channel.

SOLUTION:
In 2013, the City of Tulsa decided to replace the single rake bar screens with a Hydro-Dyne solution consisting of two Hydro-Dyne Bull Shark Heavy Duty Through Flow Screens with 6mm lace link “slotted” grids (Figure 2). These screens provide significantly lower screen height above the operating deck, stainless steel links that can handle large impact loads, higher capture of solids, and can more effectively handle storm flow first flush. In addition, the Hydro-Dyne solution required:

• A Sluice and Whitetip Washing Compactor to transport, dewater and compact solids removed from the system (Figure 3)
• A parabolic weir downstream of the screens to maintain optimum downstream level and minimize grit settling (Figure 4)
• Structural components and drive designed to withstand and operate under 33ft head differential
• A modular frame designed to install with overhead limitations