Unveiling Mechanisms of Nitrous Oxide (N2O) Emissions from Biofilm System
Department of Civil and Environmental Engineering
Wastewater treatment plants can be significant sources of nitrous oxide (N2O), a potent greenhouse gas (GHG) with a global warming potential around 300 times that of carbon dioxide (CO2). The U.S. Environmental Protection Agency estimates that U.S. wastewater treatment plants emit around 5.2 Tg N2O/year as CO2 equivalents, and these amounts are expected to increase in the future.
While our understanding of N2O emissions from suspended-growth processes in wastewater treatment has advanced significantly in recent years, little is known about emissions from biofilm processes. Biofilms are subject to substrate gradients and microbial stratification, leading to distinct behavior.
In this research, mathematical modeling and experimental approaches were used to explore the mechanisms of N2O emissions from nitrifying and denitrifying biofilms. The nitrifying model suggests that N2O emissions can be significantly greater than from suspended-growth systems. The driving factor is the diffusion of hydroxylamine, a nitrification intermediate, from the aerobic to the anoxic regions of the biofilm. Finally, a model was developed to simulate N2O formation and explore the mechanisms of N2O emissions from a biofilm reactor, the denitrifying filter. The findings from this research shed light on mechanisms of N2O emissions from biofilm systems and will help develop strategies to minimize GHG emissions from biofilm systems.
Dr. Sabba is currently a Postdoctoral Fellow in the Department of Civil and Environmental Engineering at Northwestern University. Dr. Sabba obtained a B.S. in Biotechnology for processes and products innovation from University of Bari (Italy), M.S. in Environmental and Industrial Biotechnology from University of Rome “La Sapienza” (Italy), and Ph.D. in Environmental Engineering from University of Notre Dame. His research interests are in biological processes for nutrients removal and resource recovery during water and wastewater treatment, with a special focus on biofilm processes.