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Schlagwörter:
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Zusammenfassung:
The reject water of anaerobic digestors still contains high levels of
methane and ammonium that need to be treated before these effluents can
be discharged to surface waters. Simultaneous anaerobic methane and
ammonium oxidation performed by nitrate/nitrite-dependent anaerobic
methane-oxidizing(N-damo) microorganisms and anaerobic
ammonium-oxidizing(anammox) bacteria is considered a potential solution
to this challenge. Here, a stable coculture of N-damo archaea, N-damo
bacteria, and anammox bacteria was obtained in a sequencing batch
reactor fed with methane, ammonium, and nitrite. Nitrite and ammonium
removal rates of up to 455mg N-NO(2)(-)L(-1)day(-1) and 228mg N-NH4+L-1
were reached. All nitrate produced by anammox bacteria (57mg
N-NO(3)(-)L(-1)day(-1)) was consumed, leading to a nitrogen removal
efficiency of 97.5%. In the nitrite and ammonium limited state, N-damo
and anammox bacteria each constituted about 30-40% of the culture and
were separated as granules and flocs in later stages of the reactor
operation. The N-damo archaea increased up to 20% and mainly resided in
the granular biomass with their N-damo bacterial counterparts. About 70%
of the nitrite in the reactor was removed via the anammox process, and
batch assays confirmed that anammox activity in the reactor was close to
its maximal potential activity. In contrast, activity of N-damo bacteria
was much higher in batch, indicating that these bacteria were performing
suboptimally in the sequencing batch reactor, and would probably be
outcompeted by anammox bacteria if ammonium was supplied in excess.
Together these results indicate that the combination of N-damo and
anammox can be implemented for the removal of methane at the expense of
nitrite and nitrate in future wastewater treatment systems.
