N2O production in a single stage nitritation/anammox MBBR process

Chapter 4
4. Results
4.1 Process performance
Variations in nitrogen concentration of the influent medium, flow rate, temperature and
pH are shown in Table 7 and Figure 13. Variations in nitrogen concentration shown in
Figure 13 are the sum of influent nitrogen compounds accounted for in Table 7. The
figure also shows variations in oxygen concentrations during aeration.
Table 7. Characteristics of influent feed, flow rates, temperature and pH during the operation
period 09/07/09-15/12/09.
Nitrogen mg/l
NH 4-N NO 2-N NO 3-N Q l/h T °C pH
264.5 ± 24.5 19.7 ±12.4 3.6 ±2.1 0.48 ±0.06 30.0 ±0.8 7.3-7.8
Changes of nitrogen concentrations in the effluent water are shown together with %
nitrogen reduction and the total nitrogen removal in Table 8 and Figure 13. The Effluent
nitrogen illustrated in Figure 13 is the sum of effluent nitrogen compounds seen in Table
8.
Table 8. Average concentrations of inorganic nitrogen in effluent water, reduction rates and
removal rates during the operation period 09/07/09-15/12/09.
Nitrogen mg/l
NH 4-N NO 2-N NO 3-N
Reduction % Removal gN/m 2 d
82.4 ±44.0 6.3 ±1.7 32.3 ±9.5 58 ±13 1.1 ±0.2
On the 28 th of September the operation mode was changed to continuous aeration,
aiming at a DO level of ~1.5 mg/l. It took around one week to get a stable performance
at the desired oxygen level. For measurements at even lower oxygenation the oxygen
concentration was further decreased to ~1.0 mg/l.
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