Evaluation of deammonification process performance at different aeration strategies.

In a deammonification process applied in the moving bed biofilm reactor (MBBR) oxygen is a crucial parameter for the process performance and efficiency. The objective of this study was to investigate different aeration strategies, characterised by the ratio between non-aerated and aerated phase times (R) and dissolved oxygen concentrations (DO). The series of batch tests were conducted with variable DO concentrations (2, 3, 4 mg L(-1)) and R values (0-continuous aeration; 1/3, 1, 3-intermittent aeration) but with the same initial ammonium concentration, volume of the moving bed and temperature. It was found that the impact of DO on deammonification was dependent on the R value. At R=0 and R=1/3, an increase of DO caused a significant increase in nitrogen removal rate, whereas for R=1 and R=3 similar rates of the process were observed irrespectively of the DO. The highest nitrogen removal rate of 3.33 g N m(-2) d(-1) (efficiency equal to 69.5%) was obtained at R=1/3 and DO=4 mg L(-1). Significantly lower nitrogen removal rates (1.17-1.58 g N m(-2) d(-1)) were observed at R=1 and R=3 for each examined DO. It was a consequence reduced aerated phase duration times and lesser amounts of residual nitrite in non-aerated phases as compared to R=1/3.