Mechanisms of nitrous oxide (N2O) formation and reduction in denitrifying biofilms. Issue 12 (29th August 2017)

• Record Type: Journal Article
• Authors: Sabba, Fabrizio; Picioreanu, Cristian; Nerenberg, Robert
• Is Part Of: Biotechnology and bioengineering. Volume 114:Issue 12(2017)
• Page Start: 2753
• Page End: 2761
• Publication Date: 2017-08-29
• Subjects: biofilms -- denitrification -- greenhouse gases -- modeling -- nitrous oxide; Biotechnology -- Periodicals; Bioengineering -- Periodicals; 660.6
• DOI: 10.1002/bit.26399
• Languages: English
• ISSNs: 0006-3592

Abstract

Abstract: Nitrous oxide (N2 O) is a potent greenhouse gas that can be formed in wastewater treatment processes by ammonium oxidizing and denitrifying microorganisms. While N2 O emissions from suspended growth systems have been extensively studied, and some recent studies have addressed emissions from nitrifying biofilms, much less is known about N2 O emissions from denitrifying biofilm processes. This research used modeling to evaluate the mechanisms of N2 O formation and reduction in denitrifying biofilms. The kinetic model included formation and consumption of key denitrification species, including nitrate ( N O 3 − ), nitrite ( N O 2 − ), nitric oxide (NO), and N2 O. The model showed that, in presence of excess of electron donor, denitrifying biofilms have two distinct layers of activity: an outer layer where there is net production of N2 O and an inner layer where there is net consumption. The presence of oxygen (O2 ) had an important effect on N2 O emission from suspended growth systems, but a smaller effect on biofilm systems. The effects of N O 3 − and O2 differed significantly based on the biofilm thickness. Overall, the effects of biofilm thickness and bulk substrate concentrations on N2 O emissions are complex and not always intuitive. A key mechanism for denitrifying biofilms is the diffusion of N2 O and other intermediates from one zone of the biofilm to another. This leads to zones of N2 O formation or consumption transformations that would not exist in suspended growth systems. Abstract : In presence of excess of electron donor, denitrifying biofilms have two distinct layers of activity: an outer layer with net N2 O production, and an inner layer with net consumption. Oxygen has smaller effect on biofilms than on suspended growth systems, and the effects differ significantly with biofilm thickness. A key mechanism for N2 O emissions in denitrifying biofilms, not present in suspended growth systems, is the diffusion of N2 O and other intermediates from one zone of the biofilm to another.