N2O production in a single stage nitritation/anammox MBBR process

Chapter 3
3. Material and Methods
3.1 Partial nitritation/anammox laboratory MBBR .
A 7.5 litre laboratory MBBR fed with a synthetic medium was used to estimate the N2O
emissions from a single stage nitritation/anammox system. The reactor was initially
started in October 2008 with a carrier material with already established biofilm derived
from Himmerfjärdsverkets full scale DeAmmon ® reactor which is a single stage reactor
for ammonium reduction to dinitrogen gas. The used carrier was AnoxKaldnes K1
biocarrier with a protected surface area of 500 m 2 /m 3 . The total volume of carriers in
the reactor was 3.5 litres which corresponds to about 3400 carriers, a total protected
area of 1.7 m 2 and a filling degree of 46.7%. Figure 10 shows the laboratory set up of the
MBBR system.
Figure 10. The left part of the figure shows a photograph of the MBBR system, the schematic
drawing to the right shows the main features of the MBBR system.
The temperature of the MBBR was kept at around 30 °C. A thermostat bath recirculating
warm water through the jacketed double walls of the reactor was used to maintain the
temperature. pH of the reactor was controlled with a pH electrode connected to a
regulator unit. The regulator controlled a peristaltic pump supplying the reactor with
2M H2SO4 when needed. The synthetic medium was fed to the reactor with a Watson
Marlow peristaltic pump. Aeration and mixing of the system was obtained with two
aquarium pumps that supplied the reactor with air through a punched bottom plate, (2
mm Ø). A top mounted stirrer was used to keep the system mixed during anoxic periods,
see Figure 10 for system description. A timer was used to control the duration of aerated
and mechanical mixed periods.
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