Structural Health Monitoring of Biofilms for Sustainable Reactive Nitrogen Management

Biofilms - microbial communities attached to surfaces - play critical roles in both engineered bioreactors and natural environments. Despite the importance of biofilm structure as an essential mediator of biofilm growth and activity, little is known about the relationship between biofilm structure and mechanical properties that control retention of biomass in biofilms, nor how these properties are modulated by commonly used engineering controls in biofilm reactors. To address this knowledge gap, the PIs propose to employ a novel methodology, termed Optical Coherence Elastography (OCE), to probe the relationship between mesoscale biofilm viscoelastic mechanical properties, structure, and bulk nitrogen (N) transformation rates. The project team will employ OCE to develop fundamental understanding of biofilm properties in partial nitritation and combined nitritation-anammox biofilm reactors: two promising technologies for energy-efficient wastewater treatment that depend directly on retention and activity of key N-cycling microbial populations in biofilms. Efforts will be organized around two specific objectives: Objective 1: Investigate how commonly used engineering controls of hydrodynamic regime, surface loading rate, and feeding strategy influence coupling between mesoscale mechanical properties, mesoscale physical structure, and microscale composition in partial nitritation biofilms. Objective 2: Determine how mesoscale biofilm properties control key functional outcomes (bulk N transformation and biomass detachment rates) in partial nitritation and combined nitritation-anammox biofilms. To integrate fundamental scientific advances with engineering applications, the project team will link microscale-mesoscale-macroscale biofilm phenomena observed in laboratory bioreactors to predictive model development and to performance of full-scale biofilm-based wastewater treatment systems.