Nanobubble Pretreatment as a Biocatalytic Process Intensification Strategy: Stabilizing BNR at Yucaipa Valley Water District

Presentation Description: The Henry N. Wochholz Regional Water Recycling Facility (WRWRF) in Yucaipa, California, experienced reoccurring seasonal process upsets that disrupted BNR, compromised effluent quality, and triggered operational challenges such as biomass die-off, loss of nitrification, poor settleability, high turbidity, and MF system fouling. These upsets, suspected to be linked to inhibitory slug loads, historically occurred at least twice annually and required intensive operator intervention.

To address these challenges, nanobubble (NB) pretreatment was implemented upstream of primary treatment. NBs are ultra-fine gas bubbles ( < 200 nm) that remain suspended in liquid and exhibit unique properties that make them highly effective in enhancing wastewater treatment performance. Their electrochemical surface activity attracts and destabilizes hydrophobic compounds, disrupting emulsions and surfactant accumulation. Their high interfacial area, stability, and Brownian motion improve interactions between microbial communities and substrates. Most notably, NBs catalytically enhance enzymatic reactions, accelerating the hydrolysis of slowly biodegradable COD into readily biodegradable COD—improving substrate availability and utilization. These biocatalytic effects represent a novel advancement in process intensification for the wastewater sector.

Over a seven-month demonstration period (November 2024 – May 2025), the facility reported no seasonal upsets for the first time in years.

In primary treatment, the facility observed a 16% increase in TSS removal and a 3% increase in primary sludge VS content. Primary effluent COD and ammonia were reduced by 16% and 13%, respectively, despite a 7% increase in influent ammonia. COD removal improved by 11%.

In secondary treatment, average SVI improved by 20%, RAS TSS increased by 14%, and MLSS increased by 29%. Secondary effluent ammonia and nitrate decreased by 67% and 6%, while COD dropped by 25%.

At the plant level, net ammonia removal increased by 19%, and blower energy per pound of ammonia removed dropped by 24%, indicating a 20% gain in BNR capacity.

This presentation will provide an overview of the NB pretreatment system and performance outcomes. It will also explore how NB technology supports Title 22 reuse compliance and enhances operational ease by reducing labor, chemical use, energy demand, and downtime associated with process upsets and biological inhibition—ultimately lowering O&M costs and improving system reliability.