Conference on Environmental Science and Technology

The study compared the impact of different aeration strategies on nitrification kinetics and population size of canonical nitrifiers (AOB, NOB) and Comammox bacteria in two variants of sequencing batch reactors using moving bed technology: pure (MBSBBR) and hybrid (IFAS-MBSBBR). The results showed that in both reactor types highly efficient, stable nitrification process was achieved, regardless of aeration started modifications. In both reactors, increasing the ratio between nonaerated and aerated subphases time (R) led to a decrease in the ammonia oxidation rate (AOR), while lowering the dissolved oxygen concentration (DO) promoted the activity of ammonia oxidizing bacteria. Additionally, in both reactors, the biofilm served as an environment where NOB bacteria were more active. In MBSBBR, NOB were the most numerous group of nitrifiers. Despite similarities, several differences were observed between the analysed technologies. In MBSBBR, NOB were the dominant nitrifiers in all samples, whereas in the biofilm of IFAS-MBSBBR, AOB and Comammox bacteria were more prevalent. Another significant difference is how the change in aeration strategy from continuous to intermittent affected the abundance of Comammox bacteria. In MBSBBR, an increase in the Comammox bacteria population was observed, whereas, in the biofilm from IFAS-MBSBBR, this change led to a sharp decrease in their number. Interestingly, a parallel increase in Comammox bacteria was observed in the activated sludge form of IFAS-MBSBBR. Furthermore, the response of Comammox bacteria to changes in DO levels varied. In MBSBBR, their frequency increased, while in the biofilm from IFAS-MBSBBR, no significant effect was noted. However, a decrease in the Comammox population was observed in the activated sludge of IFAS-MBSBBR. These findings highlight both commonalities and significant differences between the two technologies. However, it is important to note that the reactors were not operated under identical conditions, which likely influenced the observed differences.