Overcoming Real-World Challenges in MABR: Modeling, Microbial Insights, and Pilot Testing for Intensification

Presentation Description: Intensification is a common alternative for water resource recovery facilities seeking to expand capacity or meet more stringent effluent limits on a constrained site. The membrane aerated biofilm reactor (MABR) is an intensification technology that combines biofilm and activated sludge treatment by delivering oxygen through gas-permeable membranes to a nitrifying biofilm.
As part of an alternatives analysis for a facility in Southern Oregon, MABR was evaluated alongside other alternatives. The main drivers were stringent nutrient limits, limited capacity, and space constraints. Given the limited full-scale operating experience for MABRs, evaluation relied on process modeling and pilot testing. Steady-state and dynamic modeling estimated nitrifying biomass in the biofilm and mixed liquor, assessed variability, and identified potential upset risks. Modeling was tailored to local climate and loading conditions to evaluate MABR performance across seasonal variability and quantify benefits over conventional processes. These results indicated that MABR could help meet nutrient targets within site constraints.
A pilot with three Veolia ZeeLung cassettes in an upflow, flow-through tank configuration was then utilized to characterize nitrification performance under representative variability and flow conditions. An early operational challenge was debris in the pilot influent that risked clogging the membranes. Because it was present in both influent and return activated sludge, effective protection required screening the mixed liquor. After several iterations, the team developed a reliable approach, offering guidance for future MABR pilots and other applications where mixed liquor screening is critical, such as MBR startups.
Continuous monitoring used YSI probes for ammonia (NH₃) and combined nitrite + nitrate (NOx), supplemented with laboratory analyses. Testing included a steady-state phase to measure nitrification rate (NR), oxygen transfer rate (OTR), and oxygen transfer efficiency (OTE), and a challenge phase simulating wet-weather flows to evaluate biofilm stability under hydraulic scour. Biofilm thickness was assessed visually and via laboratory methods. Microbial analysis by digital PCR quantified ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and comammox to evaluate abundance and activity. Combined with measured performance and operational lessons learned, these results were incorporated into the facility’s process model to improve predictive accuracy and support an informed, decision on process intensification.