Integration of titrimetric measurement, off-gas analysis and NOx- biosensors to investigate the complexity of denitrification processes

The denitrification process, namely the reduction of nitrate (NO3-) to nitrogen gas (N2), often cannot be simply modelled as a single step process. For a more complete and comprehensive model the intermediates, particularly nitrite (NO2-) and nitrous oxide (N2O), need to be investigated. This paper...

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Bibliographic Details
Published in:Water science and technology 2004-01, Vol.50 (11), p.135-141
Main Authors: McMurray, S H, Meyer, R L, Zeng, R J, Yuan, Z, Keller, J
Format: Article
Language:English
Subjects:
Activated sludge
Bioreactors
Biosensing Techniques - instrumentation
Biosensing Techniques - methods
Biosensors
Complexity
Denitrification
Gas analysis
Integration
Intermediates
Kinetics
Measurement
Models, Chemical
Nitrates
Nitrates - chemistry
Nitrogen - chemistry
Nitrogen compounds
Nitrogen dioxide
Nitrogen oxides
Nitrous oxide
Nitrous Oxide - analysis
Nitrous Oxide - chemistry
Procedures
Reduction
Sensors
Sewage
Sludge
Studies
Time Factors
Waste Disposal, Fluid - methods
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Summary:The denitrification process, namely the reduction of nitrate (NO3-) to nitrogen gas (N2), often cannot be simply modelled as a single step process. For a more complete and comprehensive model the intermediates, particularly nitrite (NO2-) and nitrous oxide (N2O), need to be investigated. This paper demonstrates the integration of titrimetric measurements and off-gas analysis with on-line nitrite plus nitrate (NOx-) biosensors, highlighting the necessity of measuring process intermediates with high time-scale resolution to study and understand the kinetics of denitrification. Investigation of activated sludge from a full-scale treatment plant showed a significant accumulation of NO2-, which appeared to impact on the overall denitrification rate measured as NOx- reduction or N2 production. A different sludge obtained from a lab-scale bioreactor produced N2O instead of N2 as the end product of denitrification. The two examples both illustrate the complexity of denitrification and stress the need for the more versatile and detailed measurement procedures, as presented in this paper.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2004.0681