title: Nitrite reduction and methanogenesis in a single-stage UASB reactor.
abstract: In this study, nitrite reduction and methanogenesis in a single-stage upflow anaerobic sludge blanket (UASB) reactor was investigated, using high-strength synthetic domestic wastewater as substrate. To assess long-term effects and evaluate the mechanisms that allow successful nitrite reduction and methanogenesis in a single-stage UASB, sludge was exposed to relatively high nitrite loading rates (315 ± 13 mgNO(2)(-)-N/(l.d)), using a chemical oxygen demand (COD) to nitrogen ratio of 18 gCOD/gNO(2)(-)-N, and an organic loading rate of 5.4 ± 0.2 gCOD/(l.d). In parallel, the effects of sludge morphology on methanogenesis inhibition were studied by performing short-term batch activity tests at different COD/NO(2)(-)-N ratios with anaerobic sludge samples. In long-term tests, denitrification was practically complete and COD removal efficiency did not change significantly after nitrite addition. Furthermore, methane production only decreased by 13%, agreeing with the reducing equivalents requirement for complete NO(2)(-) reduction to N₂. Apparently, the spatial separation of denitrification and methanogenesis zones inside the UASB reactor allowed nitrite reduction and methanogenesis to occur at the same moment. Batch tests showed that granules seem to protect methanogens from nitrite inhibition, probably due to transport limitations. Combined COD and N removal via nitrite in a single-stage UASB reactor could be a feasible technology to treat high-strength domestic wastewater.
authors.affiliation: Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands; Grupo Biotecnología de Procesos para el Ambiente (BioProA), Instituto de Ingeniería Química, Facultad de Ingeniería, Universidad de la Republica, Herrera y Reissig 565, CP.11300, Montevideo, Uruguay E-mail: lborges@fing.edu.uy.
authors.forename: L I
authors.initials: LI
authors.lastname: Borges
authors.affiliation: Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands.
authors.forename: C M
authors.initials: CM
authors.lastname: López-Vazquez
authors.affiliation: Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: García
authors.affiliation: Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands; Department of Water Management, Section Sanitary Engineering, Delft University of Technology, P. O. Box 5048, Delft 2600, GA, The Netherlands.
authors.forename: J B
authors.initials: JB
authors.lastname: van Lier
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism*; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors / Q000145:classification; D058440:Denitrification; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D009584:Nitrogen; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology
chemical_list: D008697:Methane; D009573:Nitrites; D009584:Nitrogen; D012722:Sewage; D062065:Wastewater