Low-voltage stimulated denitrification performance of high-salinity wastewater using halotolerant microorganisms

Nitrate is a common contaminant in high-salinity wastewater, which has adverse effects on both the environment and human health. However, conventional biological treatment exhibits poor denitrification performance due to the high-salinity shock. In this study, an innovative approach using an electrostimulating microbial reactor (EMR) was explored to address this challenge. With a low-voltage input of 1.2V, the EMR reached nitrate removal kinetic parameter (kNO3-N) of 0.0166-0.0808 h-1 under high-salinities (1.5%-6.5%), which was higher than that of the microbial reactor (MR) (0.0125-0.0478 h-1). The mechanisms analysis revealed that low-voltage significantly enhanced microbial salt-in strategy and promoted the secretion of extracellular polymeric substances (EPS). Halotolerant denitrification microorganisms (Pseudomonas and Nitratireductor) were also enriched in EMR. Moreover, the EMR achieved a NO3-N removal efficiency of 73.64% in treating high-salinity wastewater (salinity 4.69%) over 18-cycles, whereas the MR only reached 54.67%. In summary, this study offers an innovative solution for denitrification of high-salinity wastewater.