Nitrification kinetics, N2O emission, and energy use in intermittently aerated hybrid reactor under different organic loading rates

Abstract

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 N2O 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 N2O emission was recorded when the reactor operated with a longer duration of aerated sub-phases.

Changes in Nitrification Kinetics and Diversity of Canonical Nitrifiers and Comammox Bacteria in a Moving Bed Sequencing Batch Biofilm Reactor—A Long-Term Study

“…S.II.1.). This aligns with the observations made for the biofilm from hybrid systems [17,18]. Data presented in Figure 5 also suggest that irrespective of the research stage, nitriteoxidizing bacteria showed greater activity, which is consistent with qPCR results, where NOB were the predominant bacterial group in all samples.…”

“…The analysis of the data collected from batch tests shows that changes introduced in MBSBBR operation parameters had a greater effect on the activity of ammonia-oxidizing bacteria. Previous studies also reported that the activity of ammonia oxidizers was more susceptible to changes in system operation than those capable of oxidizing nitrite [17,18]. It is worth emphasizing that in that case, the biofilm came from a hybrid reactor, where, next to this form of biomass, also activated sludge developed.…”

“…observed decline in NitOR value can be primarily attributed to a decrease in the activity of NOB due to no significant change in their number (less than 8%). After the change in the OLR and NLR, in the case of the biofilm from the hybrid system, a decrease in the rate of nitrite nitrogen oxidation was also observed [18]. In contrast, Yang and Yang (2011), conducting research in a moving bed membrane bioreactor with SND, observed a decrease in the nitrite oxidation rate after increasing the R value [39].…”

“…In our previous studies, we explored the presence of Comammox bacteria and canonical nitrifiers. However, these studies were conducted in a moving bed sequencing batch biofilm reactor operating as a hybrid technology with biomass in the form of activated sludge and biofilm [17,18]. The focus was on analyzing how changes in aeration strategy and DO concentration affected the size of their populations and activities.…”