Influence of aeration conditions on nitrogen removal rate in one stage partial nitritation/anammox process

In a partial nitrification/anammox process applied in the moving bed biofilm reactor (MBBR), oxygen is an important parameter for the process performance and efficiency. The objective of this study was to investigate different aeration strategies, characterized by the ratio between non - aerated and aerated phase duration (R) and dissolved oxygen concentration (DO). Experiments were carried out in a MBBR of 200 L filled with 40% of AnoxKaldnes biocarriers. Moreover activities of different groups of bacteria under each investigated aeration strategies were studied by SAA (Specific Anammox Activity), OUR (Oxygen Uptake Rate) and NUR (Nitrate Utilization Rate) tests. Four different aeration strategies were introduced in the system with DO 3 mg/l and R=0, DO 3.5 mg/l and R = 1/3, DO 3 mg/l and R = 1/3, and DO 3.5 mg/l and R = 1; air supply was decreased gradually. The obtained results showed that with the same level of DO concentration (3 mg/l) but different R (0, 1/3), nitrogen removal efficiencies were similar, which meant that with R = 1/3, energy could be saved without any loss of the process efficiency. The highest nitrogen removal efficiency of 88 % and nitrogen removal rate of 3.11 g N /m2·d were obtained at R = 1/3 and DO = 3.5 mg/l. A proper duration of non-aerated phase could improve anaerobic conditions in the biofilm and decrease possible inhibition effects of oxygen on anammox bacteria.
QC 20120214