Response of the performance and succession of denitrification consortium under the variation of nutritional conditions: Mechanisms and characteristics

In the process of wastewater treatment, biomass was typically subjected to variation of nutrient condition. This study investigated the effects of different nutrient condition on denitrification performance and bacterial communities. The results showed that under carbon-to-nitrogen ratio (C/N) was 4, denitrifying sludge (DS) exhibited excellent denitrification performance with influent nitrate (NO₃^--N) concentration in the range of 88.8 ± 9.04–297.5 ± 6.63 mg L⁻¹, maintained total nitrogen removal efficiency (TNRE) of 98.1 ± 1.75 %. While, as influent NO₃^--N concentration reached 408.9 ± 9.56 mg L⁻¹, the denitrification performance was inhibited, and this inhibition was reversible. Under appropriate substrate level (215.0 ± 13.01 mg L⁻¹), the specific denitrification activity (SDA) elevated to 300 % of its original value. Additionally, under starvation stress, although the relative abundance of some starvation-resistant bacteria (such as Actinobacteriota and Lentimicrobium) increased, the TNRE decreased by 7.3 %. During the recovery phase, despite extracellular polymeric substances (EPS) promoted, the TNRE decreased to 78.3 ± 4.7 %. Starvation stress was less favorable to DS for activity recovery than that of feast condition. These findings contribute to elucidating the mechanisms for DS to respond of different nutrient condition.