『Abstract
Denitrification processes have been studied for many decades
in both the laboratory and the field, and current work investigates
heterotrophic and autotrophic denitrification reactions. Physical,
chemical and microbiological parameters have been shown to control
these degradation processes and the fate of nitrogen. In this
paper, we describe results and modelling of denitrification reactions
in batch and flow-through column experiments. The processes controlling
the fate of nitrate and, more specifically, its reduction mediated
by micro-organisms are explained in detail by a multi-step process.
Modelling involves a rate law describing microbial respiration.
Batch experiment data and the results of thermo-kinetic modelling
of biogeochemical processes are in relatively good agreement,
indicating that the coupled numerical approach is suitable for
simulating each individual mechanism involved in denitrification
phenomena. The calculated mass-balance indicates that about 40%
of the carbon from acetate is used for anabolism and 60% for catabolism.
The kinetic parameters estimated from the batch experiments are
also suitable for reactive transport modelling of laboratory flow-through
column experiments. In these experiments performed on pyrite-bearing
schist, 60% of the nitrate reduction is attributed to heterotrophic
micro-organisms and 20% to autotrophic bacteria. These results
also indicate that for denitrification in the presence of acetate,
the thermodynamic factor in the coupled thermodynamic.kinetic
law can be disregarded and denitrification kinetics will be governed,
for the most part, by electron donor/acceptor concentrations.
This consistency between the results of closed and open systems
is a prerequisite for the field-scale use of this type of numerical
approach and the efficient and safe management of nitrogen sources.
Breaking down the process into several steps makes it possible
to focus on the main parameters that enhance the denitrification
rate.
Keywords: Denitrification; Thermodynamic driving force; Kinetics;
Micro-organisms』
1. Introduction
2. Experiments and modelling
2.1. Experimental approach
2.1.1. Choice of experimental conditions
2.1.2. Batch experiments
2.1.3. Flow-through column experiment
2.1.4. Analytical procedure
2.2. Numerical modelling approach
2.2.1. Thermodynamic and biological coupling
2.2.2. Numerical modelling approach
2.2.3. Thermo-kinetic simulation of denitrification processes
3. Results and discussion
3.1. Batch experiments
3.1.1. N-species
3.1.2. pH pattern
3.1.3. Acetate as the electron donor
3.1.4. Biomass growth
3.1.5. Remarks on the thermodynamic potential factor
3.2. Flow-through column experiment
4. Conclusions
Acknowledgement
References