Efficient removal of nitrate and ammonium by strain Pseudomonas poae EH-E3 under acidic pH and low-temperature conditions

The combined effect of low temperature and an acidic environment may restrict the growth and metabolic activity of microorganisms involved in nitrogen removal. To overcome poor biological nitrogen removal efficiency during low-temperature treatment of acidic wastewater, a novel pure strain of Pseudomonas poae EH-E3 was successfully isolated and screened based on its strong heterotrophic nitrification and aerobic denitrification capacity. Strain EH-E3 could completely eliminate inorganic nitrogen sources of nitrate within 30 h and ammonium within 20 h at 15 °C and pH 5.0, with corresponding removal efficiencies for total nitrogen of 95.13% and 91.35%, respectively. Nitrogen balance testing indicated that strain EH-E3 removed 43.25% of ammonium, 45.72% of nitrate, and 51.20% of nitrite in the form of gaseous products. Enzyme activity assays revealed that the specific activities of ammonia monooxygenase, nitrate reductase, and nitrite reductase were 0.533, 0.956, and 0.011 U/mg proteins, respectively. These findings suggest that strain EH-E3 has strong potential for use in low-temperature treatment of acidic wastewater. • Cold-tolerant denitrification shows adaptability to a wide pH range (4.5-9.0). • pH 5.0 facilitated denitrification of strain EH-E3 at 15 °C. • 50 mg/L NO 3 - -N and NH 4 + -N can be completely eliminated at 15 °C under pH 5.0. • AMO, NR and NiR were detected as 0.533, 0.956 and 0.011 U/mg proteins.