SBR to MBR Raceway Conversion: Advancing Mountain House's Water Recycling and Resiliency

Presentation Description: Mountain House Community Service District (MHCSD), a rapidly growing community situated near Tracy, CA (On the westernmost boundary of San Joaquin County), commenced construction in 2001 and initially built a 1 MGD wastewater treatment plant (WWTP). In 2005, MHCSD expanded the WWTP to 3 MGD, which employed sequencing batch reactors (SBRs) and trickling filters. As the population increased from 5,000 to 15,000 individuals (with 50,000 planned population), the facility needed an additional expansion to 5.4 MGD. MHCSD seized the opportunity to replace and upgrade the SBRs and trickling filters with Membrane Bioreactors (MBRs). Not only does this address MHCSD’s growing population, but it also upgrades the WWTP to a water recycling facility (WRF) and provides flexibility for increased capacity as needed.
The shift to MBR technology offers several advantages over SBRs, including superior effluent quality through membrane-based solid-liquid separation, automated operation reducing labor requirements, and improved stability due to efficient sludge particle retention. This upgrade promises enhanced efficiency and overall performance for the upgraded WRF, providing better wastewater treatment outcomes for the community it serves. The disinfected MBR effluent will be able to meet unrestricted Title 22 reuse and thus reduce water supply demand and enhance water supply resiliency.

Implementing this $50M, multi-year plant upgrade includes the significant challenge of reliably meeting discharge NPDES compliance while converting the underground SBR basins to continuous flow aeration basins, akin to changing the engine while the car is still running. The entire team (owner, operator, contractor, engineer, and construction manager) collaborated closely on how to seamlessly convert and integrate the old SBR basins into the new MBR treatment train. This process requires a 30-day shutdown followed by startup and seeding of the MBR system.

MHCSD’s forward-thinking approach to replace SBRs with MBRs addresses environmental concerns, enhances public health, and optimizes resource management and resiliency. With the facility now entering the final construction and start-up phases to efficiently treat wastewater for the thriving community, this presentation will include lessons learned during both the planning and implementation stages and will help owners and their teams recognize a path forward to success.