N2O production in a single stage nitritation/anammox MBBR process

Appendix B
Calculations of N2O emissions
The purpose is to calculate the produced amount of nitrous oxide as percentage of
removed inorganic nitrogen.
It is assumed that the MBBR is behaving like an ideal completely stirred tank reactor,
(CSTR), and that the general mass balance equation for a given component can be
implied:
eq.(3.1)
The in and output terms are molar fluxes over the reactor boundary, acquired as the
product of the volumetric flow rates, Q (m/s) and the concentrations, c (mole/l).
Production within the system is described by the kinetic rate equation, r (mole/m 3 s)
times the reactor volume, V (m 3 ), (negative sign indicating consumption instead of
production). Accumulation is quantified by the molar change of a substance per unit
time, described by a time dependent differential including the concentration, c (mol/l)
and the reactor volume, V (m 3 ). The mass balance equation for a component j can be
rewritten as:
( )
mol/s
eq.(3.2)
For a reacting system like the MBBR where some substances are consumed and others
are produced various kinds of substances will be passing the system borders in the
influent, effluent and through the gas phase, see Figure B1.
Figure B1. Mass transfer over the MBBR system boundaries.
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