Modeling
of Simultaneous Anaerobic Methane and Ammonium
Oxidation in a Membrane Biofilm Reactor
- Publication date
- Publisher
Abstract
Nitrogen
removal by using the synergy of denitrifying anaerobic
methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox)
microorganisms in a membrane biofilm reactor (MBfR) has previously
been demonstrated experimentally. In this work, a mathematical model
is developed to describe the simultaneous anaerobic methane and ammonium
oxidation by DAMO and Anammox microorganisms in an MBfR for the first
time. In this model, DAMO archaea convert nitrate, both externally
fed and/or produced by Anammox, to nitrite, with methane as the electron
donor. Anammox and DAMO bacteria jointly remove the nitrite fed/produced,
with ammonium and methane as the electron donor, respectively. The
model is successfully calibrated and validated using the long-term
(over 400 days) dynamic experimental data from the MBfR, as well as
two independent batch tests at different operational stages of the
MBfR. The model satisfactorily describes the methane oxidation and
nitrogen conversion data from the system. Modeling results show the
concentration gradients of methane and nitrogen would cause stratification
of the biofilm, where Anammox bacteria mainly grow in the biofilm
layer close to the bulk liquid and DAMO organisms attach close to
the membrane surface. The low surface methane loadings result in a
low fraction of DAMO microorganisms, but the high surface methane
loadings would lead to overgrowth of DAMO bacteria, which would compete
with Anammox for nitrite and decrease the fraction of Anammox bacteria.
The results suggest an optimal methane supply under the given condition
should be applied not only to benefit the nitrogen removal but also
to avoid potential methane emissions