Nitrification kinetics, N(2)O emission, and energy use in intermittently aerated hybrid reactor under different organic loading rates

This study investigated the impact of intermittent aeration strategies and reduction in the reactor’s organic and nitrogen loading rates on the course of particular stages of the nitrification process, as well as energy consumption and N(2)O emissions in a hybrid reactor with nitrification/denitrification. Each of the analysed series revealed the greatest ammonia oxidation activity in activated sludge flocs. The highest activity of nitrite nitrogen oxidation was demonstrated in the case of biofilm. A reduction in the reactor’s organic and nitrogen loading rate value had a greater effect on changes in the activity of ammonia-oxidizing bacteria than nitrite-oxidizing bacteria. In a system where the operation of air pumps was controlled through switching them and off according to the adopted ratio between non-aerated and aerated sub-phase times and the assumed oxygen concentration, a reduction in the duration of aerated sub-phases caused no decrease in energy use for aeration. Lower N(2)O emission was recorded when the reactor operated with a longer duration of aerated sub-phases. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13762-022-04715-6.