Simultaneous Nitrogen and Benzoic Acid Removal of Pseudomonas sp. A2 and Its Potential Application in Wastewater...

Inorganic nitrogen and organic pollutants are commonly coexisted in various wastewaters. Bacteria capable of removing multiple pollutants simultaneously possess unique advantages in wastewater treatment. In this study, the heterotrophic nitrification-aerobic denitrification (HNAD) bacterium Pseudomonas sp. A2 simultaneously possessed the ability to degrade benzoic acid. Experimental data demonstrated that strain A2 exhibits outstanding nitrogen removal performance, with the maximum removal rates of 13.87 and 12.69 mg/L/h for ammonium and nitrate, respectively. Approximately 99.42% of ammonium and 100% of nitrate were efficiently removed under optimal conditions: sodium succinate as carbon source, C/N ratio 14, 30°C, pH 7.0, and shaking speed of 160 rpm. Batching test and genome analysis suggested that A2 achieved heterotrophic nitrification with hydroxylamine as an intermediate and reduced nitrate to N₂ under aerobic condition. Additionally, strain A2 could utilize benzoic acid as an electron donor for nitrogen removal, though the nitrogen removal efficiency decreased significantly. Genomic analysis indicated that strain A2 may degrade benzoic acid via both the ortho pathway and the protocatechuate pathway. Bioaugmentation with strain A2 improved both nitrogen removal performance and stability of sequencing batch reactor (SBR), suggesting its potential in application. The discovery of strain A2 enriches the understanding of the nitrogen removal mechanism of HNAD bacteria and provides novel insights into the simultaneous removal of nitrogen and benzoic acid from wastewater.