Effects of Atmospheric Pressure on the Species and Nitrogen Removal Capacity of Heterotrophic Nitrification Bacteria

The inefficiency and high energy consumption of wastewater treatment at high altitudes underscore the need for advanced biotechnological solutions. Heterotrophic nitrification-aerobic denitrification (HNAD) bacteria present promising solutions due to their environmental adaptability and capacity to concurrently remove ammonium (NH4+─N) and nitrate (NO3−─N) under aerobic conditions, thereby significantly enhancing nitrogen removal efficiency. In this study, 12 HNAD strains capable of heterotrophic nitrification were isolated from two wastewater treatment plants (WWTPs) located at different altitudes. These strains demonstrated efficient ammonium removal under the atmospheric pressures corresponding to their respective altitudes. Notably, five strains isolated from the high-altitude WWTP were identified as Pseudomonas spp. and Acinetobacter spp. and selected for further study. These strains exhibited robust NH4+─N removal capabilities under varying atmospheric pressures (70 kPa and 100 kPa), achieving over 94% NH4+─N removal within 72 h. Minimal nitrate was produced (less than 1 mg/L) and no nitrite (NO2−─N) accumulation was observed, confirming their superior nitrogen removal performance. These findings suggest that atmospheric pressure may not significantly influence the performance of heterotrophic nitrification at high altitudes. Overall, the findings challenge the conventional view that atmospheric pressure plays a major role in heterotrophic nitrification in WWTPs at different altitudes and emphasize the potential of HNAD to enhance nitrogen removal efficiency at high altitudes.