Saint Clair Sewer Authority

Wastewater Treatment Plant Major Rehabilitation

Saint Clair, PA

Background: The St. Clair Sewer Authority Wastewater Treatment Plant (WWTP) serves four municipalities and has a design flow of 750,000 gallons per day. The WWTP was originally constructed in 1966 for primary treatment only and upgraded to secondary treatment in 1976. Since 1976, no major improvements had been made. The authority needed to provide a cost effective solution to improve the WWTP in order to meet their permit requirements and keep user rates affordable.

Scope: The project included an Asset Management Plan for evaluating the existing facility, recommending improvements, designing improvements, securing all permits, providing contract and construction administration, and securing funding for the project.

Key project components:

  • Constructed new headworks building including automated bar screen, grit removal system, emergency bypass and better operational controls
  • Converted anaerobic sludge digesters to aerobic sludge digesters
  • Constructed new sludge handling building including installation of sludge rotary press
  • Constructed new ultraviolet light (UV) disinfection system to replace chlorine disinfection system
  • Installation of Stamford baffle system in secondary clarifiers
  • Replacement of existing controls with new SCADA system with remote access



  • All permit limit requirements are being met
  • WWTP can take in increased flows during wet weather events
  • SCADA system has given operators significantly more capabilities to increase WWTP performance
  • Sludge disposal costs were reduced by approximately $50,000/year
  • Maintenance costs have been significantly reduced

Project highlights

  • Needed to meet more stringent permit limits
  • Much of the existing equipment was beyond its useful life
  • Existing technology was outdated
  • Operation and maintenance costs were continually increasing