Comparison of nitrification performance in SBR and SBBR with response to NaCl salinity shock: Microbial structure and functional genes.

Ammonia removal by nitrifiers at the extremely high salinity poses a great challenge for saline wastewater treatment. Sequencing batch reactor (SBR) was conducted with a stepwise increase of salinity from 10 to 40 g-NaCl·L−1, while sequencing batch biofilm reactor (SBBR) with one-step salinity enhancement, their nitrification performance, microbial structure and interaction were evaluated. Both SBR and SBBR can achieve high-efficiency nitrification (98% ammonia removal) at 40 g-NaCl·L−1. However, SBBR showed more stable nitrification performance than SBR at 40 g-NaCl·L−1 after a shorter adaptation period of 4–15 d compared to previous studies. High-throughput sequencing and metagenomic analysis demonstrated that the abundance and capability of conventional ammonia-oxidizing bacteria (Nitrosomonas) were suppressed in SBBR relative to SBR. Gelidibacter , Anaerolineales were the predominant genus in SBBR, which were not found in SBR. NorB and nosZ responsible for reducing NO to N 2 O and reducing N 2 O to N 2 respectively had s strong synergistic effect in SBBR. This study will provide a valuable reference for the startup of nitrification process within a short period of time under the extremely high NaCl salinity. [Display omitted] • High efficiency nitrification was achieved in SBR and SBBR at the salinity of 40 g-NaCl L−1. • SBBR showed more stable nitrification performance than SBR after adapting to 4% NaCl salinity within 20 days. • No nitrite accumulation was found at the stable nitrification period under varying salinity. • More abundant microbial diversity prevailed in SBBR, especially anaerobic bacteria replacing nitrifiers as the dominant genus. • Synergistic interactions between norB and nosZ were induced by microaerobic zones in SBBR. [ABSTRACT FROM AUTHOR]