Improving Plant Performance | Wastewater Engineering

DAN CONNOLLY, PE | Manager, Water and Wastewater Engineering and Design

City of Bethlehem | Fine Bar Screen and Detritor Upgrades

The City of Bethlehem selected SSM to provide engineering services to improve the preliminary treatment processes at the City’s wastewater treatment plant (WWTP). The WWTP, permitted for 20 MGD, receives flow from the City’s combined sewer collection system and can experience storm flows as high as 50 MGD. Existing preliminary treatment equipment included four traveling rake screens with 5/8” vertical bar spacing, and four detritors. The primary goal of the project was to replace the existing screens with four new flexible rake screens having 1/4” vertical bar spacing. As a result, debris collected from each pair of screens is processed by a new washer/compactor reducing organics and the volume of the material to be disposed. In addition to addressing future changes to the detritor system, engineering services included preparation of PADEP WQM Part II Permit, preparation of contract documents, bid phase management and construction inspection.

Additional project work included installation of new slide gates to isolate the screens; replacement of the existing floor grating; replacement of severely corroded doors; repair of the concrete channels; and application of a new protective coating. The new screens improve the overall performance of the WWTP by reducing the amount of rags and plastics collecting in downstream tanks and eliminate problems caused by blinding of the screens during wet weather events.