(cest2017_00931) Evaluation of nitrous oxide gaseous emissions from a partial nitritation reactor operating under different conditions

摘要

In this study, continuous measurements ofnitrous oxide gaseous emissions from a lab-scale partialnitritation (PN) chemostat treating ammonium-rich (1500mgN/L) synthetic wastewater were performed, in order toachieve a deeper knowledge about its potentialenvironmental impact. The reactor was operated atconstant hydraulic retention time (HRT, 1 d) and nitrogenloading rate (NLR, 1500 mgN/L·d), with different influentalkalinity/nitrogen molar ratios (alk/N, 1 and 1.3) anddissolved oxygen concentrations (DO, 5.0, 3.0, 2.0, 1.5 and1.0 mgO2/L). As DO ranged between 5.0 and 1.5 mgO2/L,the partial conversion of ammonium to nitrite wassuccessfully achieved, with a negligible production ofnitrate and nitrous oxide. When alk/N was increased from1 to 1.3 (DO was not limiting, i.e. 2 mgO2/L), the increasein ammonium-nitrogen removal rate (ANRR, from 717±17to 945±21 mgNH4-N/L·d) and the simultaneous decreasein specific N2O-N production (from 0.33±0.01 to0.23±0.01% of ANRR) were observed. When DO was setto 1.0 mgO2/L, partial nitritation was irreversiblycompromised, and a corresponding increase in specificN2O-N production was observed (from 0.22±0.01 to0.61±0.03% of ANRR). The results indicate a clearcorrelation between N2O production and autotrophicammonium to nitrite oxidation rate.