AC25 A Flexible Future - How Split Flow BNR Opens Doors to Future Possibilities

CWEA Members: $35.00
Non-Members $45.00

San Francisco Bay Area wastewater utilities are facing nutrient discharge regulations that impact near-term and long-term decision making. The City of Sunnyvale Water Pollution Control Plant (WPCP) balanced aging infrastructure needs with future nutrient to develop a phased approach for upgrading their treatment plant to remove nutrients.

The existing treatment facilities at the WPCP are aging assets and cannot meet anticipated future discharge regulations for nitrogen. The City decided to be an early adopter in nutrient reduction and to implement a two-phased secondary treatment upgrade to transition to a conventional activated sludge (CAS) BNR process. Carollo/Jacobs recently completed the design for the $300M Secondary Treatment and Dewatering Project. The construction of the Phase 1 secondary treatment facility and Demon deammonification sidestream treatment facility is in progress. The CAS facilities will operate in parallel with the existing oxidation pond treatment train and the Demon sidestream facility will treat return stream from a new dewatering process.

Dealing with aging infrastructure and a tight site, this phased approach allows the City lots of flexibility. Delaying the second phase of the project allows the City to:
• Defer costs and maintain financial flexibility
• Allow process intensification technology to mature
• Maximize site space and right size phase 2

This presentation will provide an overview of the project and review key factors that influenced the decision to implement split flow and sidestream treatment, and explore elements of the design that were implemented to successfully manage the split flow operation and flexibility for future expansion.

This presentation may be of interest to design engineers, decision makers, planners, or others charged with navigating future regulations and developing strategies to optimize performance and nutrient load management. The City of Sunnyvale is on their way towards implementing their Program that began in 2016. Key decisions on implementing split flow and optimizing the Phase 1 Secondary Treatment and Dewatering Project design have maintained flexibility for the City for what comes next.

Learning Objectives:
Understand how a phased approach to a process upgrade can delay capital investment and increase future flexibility.
Identify creative solutions that address multiple drivers such as aging infrastructure and new regulations.
Describe the benefits of planning ahead.