Improved nitrogen removal performance by enhanced denitratation/anammox as decreasing temperature for municipal wastewater treatment.

• Improved NRE from 72.2% to 77.2% was firstly achieved as temperature decreases. • More tolerance of PD at low temperature increased nitrite substrates for anammox. • Ca. Brocadia increased by 167% and focused on biofilm (0.27%) at low temperature. • Anammox contribution improved from 41.8% to 60.2% and responsible for better NRE. Low temperature is one of the obstacles in mainstream anammox. This study aimed to evaluate the stability of a step-feed bioreactor dominated by denitratation/anammox (PD/A) for treating municipal wastewater with decrease in temperature (21.5 °C→12.6 °C). During long-term operation, nitrogen removal efficiency (NRE) was improved from 72.2% (21.5 °C→14.9 °C) to 77.2% (stable at 13.9 °C) with influent and effluent total inorganic nitrogen of 44.6 and 10.1 mg N/L. Better low temperature tolerance of nitrate reduction than nitrite reduction enhanced denitratation and increased nitrite substrates for anammox. Microbial structure analysis revealed that Ca. Brocadia increased by 167% and reached 0.27% on biofilm at low temperature. Finally, anammox contribution improved from 41.8% to 60.2%, saving organic carbon for denitrification, which was responsible for better NRE. Moreover, Ferribacterium, Dechloromonas , and Thauera were the major denitrifiers distributed in suspended sludge. Overall, this study provides an optimistic prospect for promoting anammox in mainstream applications at low temperature. [Display omitted] [ABSTRACT FROM AUTHOR]