How to Retrofit to MBR and Keep the Water Flowing: The Story of Riverside, California

The City of Riverside will convert its Plant 1 at the Regional Water Quality Control Plant to a membrane bioreactor (MBR) and increase capacity from 20 mgd to 32 mgd in two phases (Phase I —26 mgd and Phase II — 32 mgd). Existing rectangular final clarifiers will be modified for additional biological treatment zones and provide a location for the membranes. It will be necessary to keep the existing facility in operation during construction of the improvements. Maintaining operation during construction, addition of biological treatment volume and hydraulic improvements to support MBR recycle flows present significant constructability challenges requiring careful consideration. This paper focuses on the innovative process design and approach to the existing facility retrofit required for this large MBR project.