title: Modelling simultaneous anaerobic methane and ammonium removal in a granular sludge reactor.
abstract: Anaerobic nitrogen removal technologies offer advantages in terms of energy and cost savings over conventional nitrification-denitrification systems. A mathematical model was constructed to evaluate the influence of process operation on the coexistence of nitrite dependent anaerobic methane oxidizing bacteria (n-damo) and anaerobic ammonium oxidizing bacteria (anammox) in a single granule. The nitrite and methane affinity constants of n-damo bacteria were measured experimentally. The biomass yield of n-damo bacteria was derived from experimental data and a thermodynamic state analysis. Through simulations, it was found that the possible survival of n-damo besides anammox bacteria was sensitive to the nitrite/ammonium influent ratio. If ammonium was supplied in excess, n-damo bacteria were outcompeted. At low biomass concentration, n-damo bacteria lost the competition against anammox bacteria. When the biomass loading closely matched the biomass concentration needed for full nutrient removal, strong substrate competition occurred resulting in oscillating removal rates. The simulation results further reveal that smaller granules enabled higher simultaneous ammonium and methane removal efficiencies. The implementation of simultaneous anaerobic methane and ammonium removal will decrease greenhouse gas emissions, but an economic analysis showed that adding anaerobic methane removal to a partial nitritation/anammox process may increase the aeration costs with over 20%. Finally, some considerations were given regarding the practical implementation of the process.
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium; Department of Civil and Environmental Engineering, University of Washington, Seattle, WA 98195-2700, USA.
authors.forename: M-K H
authors.initials: MK
authors.lastname: Winkler
authors.affiliation: Microbiology, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
authors.forename: K F
authors.initials: KF
authors.lastname: Ettwig
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
authors.forename: T P W
authors.initials: TP
authors.lastname: Vannecke
authors.affiliation: Microbiology, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Stultiens
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Bogdan
authors.affiliation: Microbiology, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Kartal
authors.affiliation: Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium. Electronic address: Eveline.Volcke@UGent.be.
authors.forename: E I P
authors.initials: EI
authors.lastname: Volcke
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D008697:Methane / Q000378:metabolism*; D008962:Models, Theoretical; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid
chemical_list: D064751:Ammonium Compounds; D009573:Nitrites; D012722:Sewage; D008697:Methane
keywords: Anaerobic methane oxidation; Anammox; Granular sludge; Modelling; Simulation