AcknowledgementsThis research was supported by the Shenzhen government

The PCR amplifications were extracted from 2% agarose gels and purified using the Agencourt® AMPure XP Beads (A63881, Beckman, USA). Then, the quality of gene library was detected using Qubit® 2.0 Fluorometer (Q32866, Invitrogen, USA) and Agilent 2100 Bioanalyzer (G2939AA, Agilent, USA). After that, the qualified amplifications were paired-end sequenced (2 × 250/300 nt multiplex) on an Illumina MiSeq platform at Zhejiang Institute of Microbiology (Hangzhou, Zhejiang, China) according to the standard protocols and software (Data collection software, Illumina).
3. Results and discussion
3.1. Long-term denitrification performance of the two reactors
The nitrate removal efficiency and volumetric removal rate of the two reactors during the whole experimental BMS-707035 are shown in Fig. 2. Both Reactor I and Reactor II achieved appreciable nitrate removal efficiency with an exception of stage I during which synthetic RAS wastewater was used (Fig. 2A and B). In stage I, the average denitrification rates of both reactors were approximate 0.02 kg NO3−-N m−3 d−1 (Fig. 2C and D). This result was relative lower when compared with other report that achieved approximate 0.3 kg NO3−-N m−3 d−1 denitrification rate after 70 days experiment at 25 °C (Wu et al., 2013). In this study, low temperature (19 ± 1 °C) during the start-up period might be the main reason, since it strongly affected the hydrolysis efficiency of carbon source and the activity of the denitrifying bacteria (Chu and Wang, 2013).