Sulfide-based autotrophic denitrification process with efficient nitrogen removal under high salinity stress: Threshold behaviors and recovery enhanced via glutamate supplementation.

The sulfide-based autotrophic denitrification (SAD) has become one of the hotspots in the wastewater treatment due to the urgent requirement for carbon emission reduction. However, it faces a great challenge from the high salinity of nitrogenous wastewaters. In this study, a SAD system was investigated to treat the nitrogenous wastewater under high salinity stress, achieving 99.82 % nitrogen removal at 2.57 % salinity. With the further salinity elevation, the SAD system suffered collapse at the salinity of 5.14 %wt, while it was partially reversed by 1 mmol/L glutamate dosing. The good adaptation of SAD system to the high salinity stress was ascribed to the enrichment of salinity-tolerant microbial populations, as well as limited Na accumulation and the antioxidant metabolic compensation. Proteobacteria and Campilobacterota were identified as the dominant phyla, and the relative abundance of Proteobacteria were observed to increase with the whole salinity elevation. The high salinity stress on SAD system was ascribed to the combined effect of osmotic stress and ionic toxicity, and the ionic toxicity was inferred as the primary contributor to the performance collapse by inducing the sharp increase of intracellular reactive oxygen species and cellular rupture. Glutamate supplementation mitigated reactive oxygen species -induced oxidative stress and DNA damage, resulting in partial recovery of denitrification performance (60.56 ± 2.64 %). The microbial network analysis and community assembly supported above conclusions. The information of this study is helpful for the innovation and application of SAD processes, even other bioprocesses under the high salinity stress.