Solid-phase denitrification systems using biodegradable polymers are promising for wastewater treatment; however, little is known about the relationship between microbial communities and effluent quality in these systems. In this study, we evaluated the performance of a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-supported denitrification system in the treatment of wastewater with high nitrate concentrations with respect to the microbial community structure and dominant bacteria. An

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... age denitrification rate of 1.11 g/(L d) could be achieved at an influent NO 3 --N concentration of 80 mg/L and hydraulic retention time (HRT) of 1.5 h. Compared to the HRT, the influent NO 3 --N concentration had a greater effect on the denitrification efficiency at the same NO 3 --N loading rate (NLR). Microbial community analysis using Miseq Illumina sequencing showed that the genera Diaphorobacter and Dechloromonas were predominant. The nitrate removal efficiency was positively correlated with the Dechloromonas abundance, and the NLR was negatively correlated with Diaphorobacter. Heatmap analysis showed that the denitrification function dominated over all stages, which may explain the good performance of the PHBV-supported denitrification system. These findings clarify the effect of the influent nitrate load on microbial functional abundance and community structure as well as the molecular determinants of solid-phase denitrification efficiency.