UV Disinfection in a Shoebox: City of Pacifica Reuse Disinfection Improvements

Presentation Description: The City of Pacifica, a small seaside community south of San Francisco, first deployed ultraviolet (UV) disinfection for wastewater treatment in 1996 at their Calera Creek Water Recycling Plant (WRP) to establish vital wetlands at the newly constructed plant. Early adoption of UV allowed environmental reuse enhancements and later Title 22 reuse. This single-channel UV system was installed in a below grade gallery (“the shoebox”) and has reached the end of its useful life. It must be replaced. Enter the Shoebox!

Part 1: A Brief History
An overview of the Calera Creek WRP to get the audience familiarized with the location and the critical community resources, the Calera Creek Wetlands and the Pacific Ocean, to which the Plant discharges. This section also includes a brief introduction to Title 22 and the City's reuse applications.

Part 2: The UV Replacement Project – the Challenges
The challenges of this project bring to light the innovative solutions deployed to make this project feasible. The following subsections highlight each challenge and the solutions applied.

Access: Opening the Shoebox - covers the limited entry options for both demolition and installation. The project team used 3D scanning and modeling to establish access and spatial analysis for equipment and complex electrical and communication systems. (Fly-through Demo)

Constructability: Deploy the Shoehorn - shows the disruptive demolition requirements for the existing system and highlights the opportunities for improvements due to the reconfiguring from a single channel to dual channels. Not to mention doing all of this while bypass pumping from the shoebox.

Continuous Treatment: Keeping the Lights On – discusses the unique requirement for UV disinfection during construction and the creative solution used to reach 12 MGD of temporary UV treatment.

Part 3: UV Selection
A brief overview of UV disinfection and the advancement of UV technology for wastewater disinfection. This leads into the huge benefit of the newer lamp and operational technology. The City will realize significant energy consumption savings during Title 22 production and low flow disinfection. We cover the comparative cost and payback between technologies and close with the Project’s next steps into construction in 2024-2025.