Structural Health Monitoring of Biofilms for Sustainable Reactive Nitrogen Management

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Nitrogen pollution in water causes numerous environmental and public health problems. Among the most pressing include the contamination of drinking water sources with nitrates and stimulation of harmful algal blooms. Although we have known about the importance of controlling nitrogen nutrient release for decades, new and more efficient technologies are needed to prevent nitrogen pollution. A promising technology to remove nitrogen pollution from wastewater is the use of membrane bioreactors. Membrane bioreactors use biofilms (naturally occurring microbial communities attached to surfaces) to create the appropriate conditions for efficient nitrogen removal. This project will develop new state-of-the-science tools and advanced modeling approaches to address gaps in our understanding of the mechanical and structural properties of biofilms. Doing so will help improve the performance of bioreactors to efficiently clean water and prevent nitrogen pollution. Biofilms are very common in nature, so results of this research will benefit many other scientific areas, including the removal of other pollutants from water and preventing the growth of harmful biofilms. Additional benefits of this project include the training of underrepresented students, thus increasing the diversity of the Nation’s STEM workforce. Educational outreach to grade-school students and community groups will increase understanding of the importance of controlling nitrogen pollution and increase the scientific literacy of the Nation. 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, relatively little is known about the relationship between biofilm structure and mechanical properties that control retention of biomass in the biofilm. This knowledge gap must be addressed if we are to understand how these properties can be modulated to increase efficiency 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. These two promising technologies for energy-efficient wastewater treatment depend directly on precise control of the retention and activity of key N-cycling microbial populations in biofilms. Efforts will be organized around two specific objectives. Objective will be to investigate how commonly used engineering controls (hydrodynamic regime, surface loading rate, and feeding strategy) influence coupling between mesoscale mechanical properties, mesoscale physical structure, and microscale composition in partial nitritation biofilms. The second objective is to 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 for full-scale biofilm-based wastewater treatment systems. Improved understanding of mesoscale biofilm structure, biomechanics, and emergent system function will provide a basis for effective monitoring, modeling, and control of biofilm properties in engineered bioreactors, analogous to structural health monitoring for civil infrastructure and mechanical devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.