title: Biofilm stratification during simultaneous nitrification and denitrification (SND) at a biocathode.
abstract: The aeration of the cathode compartment of bioelectrochemical systems (BESs) was recently shown to promote simultaneous nitrification and denitrification (SND). This study investigates the cathodic metabolism under different operating conditions as well as the structural organization of the cathodic biofilm during SND. Results show that a maximal nitrogen removal efficiency of 86.9 ± 0.5%, and a removal rate of 3.39 ± 0.08 mg NL(-1)h(-1) could be achieved at a dissolved oxygen (DO) level of 5.73 ± 0.03 mg L(-1) in the catholyte. The DO levels used in this study are higher than the thresholds previously reported as detrimental for denitrification. Analysis of the cathodic half-cell potential during batch tests suggested the existence of an oxygen gradient within the biofilm while performing SND. FISH analysis corroborated this finding revealing that the structure of the biofilm included an outer layer occupied by putative nitrifying organisms, and an inner layer where putative denitrifying organisms were most dominant. To our best knowledge this is the first time that nitrifying and denitrifying microorganisms are simultaneously observed in a cathodic biofilm.
authors.affiliation: The University of Queensland, Advanced Water Management Centre, St Lucia, QLD 4072, Australia.
authors.forename: Bernardino
authors.initials: B
authors.lastname: Virdis
authors.forename: Suzanne T
authors.initials: ST
authors.lastname: Read
authors.forename: Korneel
authors.initials: K
authors.lastname: Rabaey
authors.forename: René A
authors.initials: RA
authors.lastname: Rozendal
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Yuan
authors.forename: Jürg
authors.initials: J
authors.lastname: Keller
mesh_terms: D018441:Biofilms; D058440:Denitrification; D004563:Electrochemistry; D004566:Electrodes; D017404:In Situ Hybridization, Fluorescence; D058465:Nitrification; D009584:Nitrogen / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism
chemical_list: D009584:Nitrogen; D010100:Oxygen