Highly effective removal of nitrate from saline wastewater by glucose-enhanced sulfur autotrophic system

Abstract

The denitrification performance of the elemental sulfur autotrophic denitrification (S0AD) system requires improvements to broaden its applicability for treating nitrate (NO3−-N) wastewater contaminated with high salinity. Therefore, this work investigated the denitrification performance and mechanism of the glucose-enhanced (C:N ratio = 1) S0AD system with saline wastewater (0–15 g/L). The results showed that by adding glucose, our research successfully constructed the elemental sulfur autotrophic/heterotrophic denitrification (HS0AD) system, which showed a stable NO3−-N removal efficiency above 95 % and lower effluent sulfate generation. The NO3−-N removal efficiency of the HS0AD system was over 95.62 % with wastewater containing different salinity levels. With increasing salinity, the glucose utilization efficiency increased from 65.23 % to 74.35 %. Microbial community analysis showed that adding glucose promoted the growth of the Proteobacteria phylum and stimulated its activity under salt stress. High salinity (≥10 g/L) reduced the microbial diversity at the genus level. However, the growth of salt-tolerant denitrifying bacteria (Thiobacillus and Vitellibacter) still enabled efficient denitrification performance with the system. These microorganisms can resist high salinity stresses by releasing proteins. All results indicated that the glucose-enhanced system shows great nitrate removal potential, even under salt stress. These conclusions provide a theoretical basis for applying a synergistic system to treat saline wastewater contaminated with NO3−-N.