Back River Wastewater Treatment Plant Activated Sludge Plant #4

This $300 million project for a new Activated Sludge Plant was part of a comprehensive Enhanced Nutrient Removal upgrade to modernize the Back River Wastewater Treatment Plant to meet higher environmental standards. The renovation included improvements to reduce the excess nutrients, such as phosphorous and nitrogen, that discharge into the Back River and the Chesapeake Bay. The new Activated Sludge Plant includes six large concrete reactors, an underground pipe gallery to convey sewage into the reactor, a flow distribution structure, a large concrete transfer pad, twelve 120-foot diameter secondary clarifiers, three new sludge pumping stations, a blower building, and a chemical storage building. CEI provided full structural designs for this expansive construction project.


  • Structural designs included a graduated air piping system, 70 feet in diameter at its widest point, to introduce air into the reactor from the base of the tank.
  • CEI provided designs for six large concrete reactors, each 120 feet wide by 500 feet long.
  • Due to the weight and size of the reactors, each is supported by auger cast-pile foundations.


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  • Architect:
    KCI Technologies
  • Owner:
    Baltimore City Department of Public Works