Denitrification kinetics indicates nitrous oxide uptake is unaffected by electron competition in Accumulibacter

• No N 2 O accumulation was observed for Accumulibacter in the presence of multiple electron acceptors. Electron competition did not limit reduction nitrite or by Accumulibacter. Competibacter has truncated denitrification pathway. Denitrifying phosphorus removal is a cost and energy efficient treatment technology that relies on polyphosphate accumulating organisms (DPAOs) utilizing nitrate as terminal acceptor. Denitrification multistep process, but many do possess complete pathway, leading to intermediates such nitrous oxide (N O), potent greenhouse gas ozone depleting substance. Candidatus are prevalent denitrifying processes and, according genomic analyses, appear vary their abilities based lineage. kinetics absence inhibition from free acid strong indicator capabilities exposed long-term Thus, we investigated preferential use nitrogen oxides involved two enrichments competitor – glycogen organism Competibacter. We modified metabolic model predict rates when nitrate, were added acceptors different combinations. Unlike previous studies, no lead Despite sufficient internal storage polymers (polyhydroxyalkanoates, PHA) source each step, extent dependent dominant enrichment. showed denitrification, whereas limited nitrite. These findings indicate DPAOs can contribute lowering emissions under partial nitritation conditions.