Production and decomposition of nitrous oxide during biological denitrification

Nitrate (NO3) was reduced with methanol (MeOH) over denitrification-filter sludge in a closed reactor. The initial reaction product was nitrous oxide (N2O). It accumulated to a maximum (N2Omax) and was then rapidly reduced to nitrogen (N-2) At the time of maximum accumulation (t(max)), 50 to 80% of the nitrate-nitrogen reduced was in the form of N2O. These results led to a higher estimate of N2O emission from biological denitrification than previously considered. The results also suggest the concept of a multistage anoxic reactor in which nitrate can be reduced to N-2 with minimal emission of N2O. The design would provide for retention of N2O in the upstream stages and reduction of N2O downstream.