Performance and microbial structure of partial denitrification in response to salt stress: achieving stable nitrite accumulation with municipal wastewater

Abstract The effects of inorganic salts on partial denitrification (PD) was investigated in a sequencing batch reactor for simultaneously treating saline nitrate sewage and municipal wastewater. After 230-day operation, a high nitrate-to-nitrite transformation ratio (NTR) of ∼80% was achieved with the salinity of 1.25 wt% and the initial chemical oxygen demand to nitrate ratio of 3.7. Microbial community analysis revealed that, Thauera was remained predominant in PD system but with a relative abundance decreasing from 53.02% (0.0 wt%) to 42.36% (1.25 wt%). Moreover, as a suitable ratio of nitrite to ammonia (∼1.6) in effluent was obtained, it would be a promising method to treat saline nitrate sewage by combing PD with anammox.