Enhancing Biofilm Performance and Ammonia Removal in MBBR Systems Using Nanobubble Aeration: A Pilot-Scale Experimental Study

The recirculating aquaculture system (RAS) provides a sustainable approach to sustaining aquaculture output while reducing environmental pollution and excessive water consumption. Nonetheless, high concentrations of Total Ammonia Nitrogen (TAN) continue to be a significant obstacle in RAS operations. To address this issue, the Moving Bed Biofilm Reactor (MBBR), with bubble aeration, is important for promoting ammonia degradation. Bubble size impacts the effectiveness of bubble aeration, influencing both oxygen transfer and microbial activity. This research involved a 35-day experiment to evaluate the effects of bubble size, produced by nanobubble and coarse bubble aerators, on biofilm development and TAN decrease. The maximum biofilm thickness of 172.88 µm was recorded during nanobubble aeration, which also produced a higher quantity of microbial colonies (293 × 107 CFU) in comparison to coarse bubble aeration (89 × 107 CFU), as validated by Total Plate Count analysis. SEM–EDX imaging additionally demonstrated a more compact and consistent biofilm structure in the presence of nanobubbles. These results align with an increased TAN degradation efficiency, achieving 83.33% with nanobubble aeration, while coarse bubble aeration reached only 50%. The findings indicate that nanobubble aeration enhances biofilm functionality by improving bacterial dispersion and oxygen availability within the biofilm matrix, thereby promoting a more uniform distribution of microorganisms and nutrients. This mechanism represents a promising approach for improving water quality and overall treatment efficiency in recirculating aquaculture systems (RAS).