A novel control method for nitritation: The domination of ammonia-oxidizing bacteria by high concentrations of inorganic carbon in an airlift-fluidized bed reactor

Abstract

A novel nitritation method based on the addition of inorganic carbon (IC) was verified using an airlift-fluidized bed reactor packed with sponge cubes. A continuous-treatment experiment demonstrated that the type of nitrification—nitrite or nitrate accumulation—could be controlled by the addition of different alkalinity sources (NaHCO 3 or NaOH, respectively). The maximum rate of ammonia oxidation at 30 °C was 2.47 kg-N/(m 3 d), with nitrate formation of less than 0.5% of the converted ammonia. Nitrite accumulation of over 90% was maintained stably over 250 days at 30 °C and was achieved even at 19 °C. Qualitative and quantitative shifts of nitrifying bacteria in the biofilm were monitored by real-time PCR and T-RFLP analysis. Ammonia-oxidizing bacteria (AOB) were dominant but nitrite-oxidizing bacteria (NOB) were eliminated in the reactor when NaHCO 3 was used as the alkalinity source. From the kinetic data, we inferred that high IC concentrations drive stable nitritation by promoting a higher growth rate for AOB than for NOB.