Effect of nitrite on the N2O and NO production on the nitrification of low-strength ammonium wastewater

Abstract

The effect of nitrite on N2O and NO emission was assessed in a nitrifying lab-scale reactor fed with low strength ammonium wastewater. The effect of nitrite pulse additions (5–50mg NO2−-NL−1) and of step-wisely increasing nitrite concentrations (0–150mg NO2−-NL−1) was studied. For the pulse addition experiments, N2O and NO emissions increased upon pulse addition of nitrite, decreasing to the original concentration once nitrite was consumed. The highest peak emissions were detected at nitrite concentrations of 50mg NO2−-NL−1. For the step-wisely increasing nitrite tests, N2O-N emission per NH4+-N converted increased linearly from 0.16% to 1.5%. NO emissions were substantially affected at nitrite concentrations higher than 50mg NO2−-NL−1, reaching 3.8% NO-N per NH4+-N converted at 150mg NO2−-NL−1. The results provide one of the first evidences of the combined effect of nitrite on N2O and NO emissions, showing a stronger effect on NO emissions at high nitrite concentrations.