The development of nitrifying biofilms and short and long term influences on the nitrification process were studied in a Biofilm-Airlift-Suspension-reactor. The studied changes are (i) startup of nitrification reactor at different dilution rates, (ii) the effect of temperature on N-oxidation capacity, (iii) the short term effect of N-loading rate on conversion to determine the nitrification overcapacity and (iv) long term effect of N-loading rate on conversion to determine the maximum nitrification capacity in this reactor system.
It is shown that the specific nitrification capacity during start-up is constant, 1 g N/(gorg.mat. d), which is high compared to the activated sludge process. The influence of the temperature on the nitrification rate is much less than can be expected from pure culture experiments. On a short term there is only a small nitrification overcapacity in the reactor. The maximum nitrification rate during these experiments was 6 kg N/(m3 d), which is very high compared to the activated sludge process.