N2O production in a single stage nitritation/anammox MBBR process

12
10
4.5
3.75
N₂O (µmol/l)
8
6
4
2
3
2.25
1.5
0.75
DO (mg/l)
N₂O
(µmol/l)
DO
(mg/l)
0
0
0 50 100 150 200
Time (min)
Figure 3. Concentration profiles of N 2O and O 2 during prolonged unaerated period.
At first the N2O accumulation is rather linear, when DO decreases under 1 mg/l the
accumulation rate of N2O is reduced until a maximum concentration is reached at DO
concentrations close to 0 mg/l. The N2O concentration is constant under a period of 20-
50 minutes and then slowly starts to decrease as seen in Figure 3.
Continuous aeration
Measurements with continuous aeration were performed at DO concentrations of ~1.5
mg/l and ~1 mg/l. To be able to determine the production of N2O gas during these
operation conditions the aeration was turned off. The unaerated period was chosen to
20 minutes to be comparable with the measurements done during intermittent aeration.
Measurement proceeded 20 minutes after the aeration was switched on again. Two
measurements were performed at a constant aeration with a DO concentration of ~1.5
mg/l and ~1 mg/l respectively a typical profile of O2 and N2O concentrations are shown
in Figure 4.
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