Nitrogen
Removal from Wastewater by Coupling Anammox
and Methane-Dependent Denitrification in a Membrane Biofilm Reactor
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Abstract
This
work demonstrates, for the first time, the feasibility of
nitrogen removal by using the synergy of anammox and denitrifying
anaerobic methane oxidation (DAMO) microorganisms in a membrane biofilm
reactor (MBfR). The reactor was fed with synthetic wastewater containing
nitrate and ammonium. Methane was delivered from the interior of hollow
fibres in the MBfR to the biofilm that grew on the fiber’s
outer wall. After 24 months of operation, the system achieved a nitrate
and an ammonium removal rate of about 190 mgN L<sup>–1</sup> d<sup>–1</sup> (or 86 mgN m<sup>–2</sup> d<sup>–1</sup>, with m<sup>2</sup> referring to biofilm surface area) and 60 mgN
L<sup>–1</sup> d<sup>–1</sup> (27 mgN m<sup>–2</sup> d<sup>–1</sup>), respectively. No nitrite accumulation was
observed. Fluorescence in situ hybridization (FISH) analysis indicated
that DAMO bacteria (20–30%), DAMO archaea (20–30%) and
anammox bacteria (20–30%) jointly dominated the microbial community.
Based on the known metabolism of these microorganisms, mass balance,
and isotope studies, we hypothesize that DAMO archaea converted nitrate,
both externally fed and produced by anammox, to nitrite, with methane
as the electron donor. Anammox and DAMO bacteria jointly removed the
nitrite produced, with ammonium and methane as the electron donor,
respectively. The process could potentially be used for anaerobic
nitrogen removal from wastewater streams containing ammonium and nitrate/nitrite