Impact of multi-ionic stress on sulfur-based autotrophic denitrification process

Nitrite accumulation poses a significant challenge in treating highly saline nitrogenous wastewater biologically, and the nitrite-based sulfide autotrophic denitrification (NiSAD) process has shown outstanding effectiveness in nitrite removal. Nevertheless, its capacity to withstand salinity in the presence of diverse salt ions remains uncertain. Therefore, this study investigated the individual and combined stresses of NaCl, KCl and MgCl2 on NiSAD process. Denitrification performance was found susceptible to high salinity, and its inhibition was significantly correlated with the type of ions exposed, while IC50 of specific denitrification activity were 5.14 % (NaCl), 6.48 % (KCl) and 2.03 % (MgCl2), respectively. Dual and triple stresses exposure indicate that combined influence of NaCl, KCl and MgCl2 on denitrification performance was characterized by antagonism. Specifically, the order of inhibition intensity was Mg2+>K+>Na+, highlighting the more pronounced impact of ion strength on denitrification inhibition. Metagenomic analysis suggests that the system contains multiple genes associated with osmotic adaptation, indicating its potential for salt tolerance. It would enhance the understanding of the NiSAD process's response to multi-ionic stresses, thereby expanding its potential applications to a wider range of complex salt-containing wastewaters.