[Implement of completely autotrophic nitrogen removal in EGSB reactor and its operation optimization].

An expanded granular sludge bed (EGSB) reactor inoculated simultaneously with aerobic ammonium oxidation sludge and anaerobic ammonium oxidation sludge were start-up to enrich completely autotrophic nitrogen removal granular sludge. Total nitrogen (TN) removal rate reached 0.101 kg x (m3 x d)(-1). Based on hypothesis of boundary layer, the transfer process between granular sludge and bulk liquid was modified, which was coupled with substance transfer process in granular sludge and aerobic ammonium oxidation, anaerobic ammonium oxidation, nitrite oxidation process, and completely autotrophic nitrogen removal model was found. The model was validated with the experimental results. According to simulation results, the operation of the reactor was optimized, TN removal efficiency and TN removal rate were increased from 52% to 61% and 0.103 kg x (m3 x d)(-1) to 0.114 kg x (m3 x d)(-1) respectively.

[Ammonia oxidation kinetics of ammonia oxidizer mixed culture under the conditions of O2 and trace NO2 mixed gasses].

The kinetics of the NO2-dependent ammonia oxidation was developed for ammonia oxidizer mixed culture when there was no molecular oxygen in the batch tests. The kinetics parameters were determined, where the half saturate coefficient of NO2 was 0.821 micromol x L(-1), inhibition coefficient of NO2 concentration was 1.721 micromol x L(-1), and the maximum ammonia oxidation rate were 0.144 mg x (mg x h)(-1). After adding the volume fraction of O2 was 2% to trace NO2, the ammonia oxidation rates increased obviously. The maximum ammonia oxidation rate, 0.198 mg x (mg x h)(-1) occurred under the condition of the mixed gasses containing the volume fraction of O2 was 2% and 50 x 10(-6) NO2. Under the condition of mixed gasses containing the volume fraction of O2 was 21% to trace NO2, the ammonia oxidation rates further increased greatly. The maximum ammonia oxidation rate, 0.477 mg x (mg x h)(-1) occurred when the volume fraction of O2 was 21% and 100 x 10(-6) NO2 in the mixed gas, which is 3 times higher than the general aerobic ammonia oxidation rate. The function for NO2 apparently to enhance ammonia oxidation was suggested. The kinetics model of ammonia oxidation under the conditions of O2 and trace NO2 mixed gasses was developed. The model was validated by the results of ammonia oxidation experiments under the conditions of the mixed gasses containing 2% O2 and trace NO2. The mechanism for NO2 to enhance ammonia oxidation under the conditions of O2 and trace NO2 mixed gasses was discussed.