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 mgNO2−-N/(l.d)), using a chemical oxygen demand (COD) to nitrogen ratio of 18 gCOD/gNO2−-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/NO2−-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 NO2− 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.
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Research Article|
August 24 2015
Nitrite reduction and methanogenesis in a single-stage UASB reactor
L. I. Borges;
1Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands
2Grupo 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
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C. M. López-Vazquez;
C. M. López-Vazquez
1Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands
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H. García;
H. García
1Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands
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J. B. van Lier
J. B. van Lier
1Sanitary Engineering Chair Group, Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands
3Department of Water Management, Section Sanitary Engineering, Delft University of Technology, P. O. Box 5048, Delft 2600, GA, The Netherlands
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Water Sci Technol (2015) 72 (12): 2236–2242.
Article history
Received:
January 06 2015
Accepted:
August 17 2015
Citation
L. I. Borges, C. M. López-Vazquez, H. García, J. B. van Lier; Nitrite reduction and methanogenesis in a single-stage UASB reactor. Water Sci Technol 16 December 2015; 72 (12): 2236–2242. doi: https://doi.org/10.2166/wst.2015.446
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