Effects of oxygen concentration and moisture content of refuse on nitrification, denitrification and nitrous oxide production

The purposes of this study were to evaluate the potential production of nitrous oxide (N2O), which is known as a greenhouse gas, to identify the reaction responsible for it and to examine the effects of oxygen and moisture content on nitrification, denitrification and N2O production. Applying a tracer method using a 15N-isotope into an oxygen controllable reactor with artificial refuse proved that biological denitrification was a main source of released N2O even when the oxygen of the bulk atmosphere was as high as 15%. Calculating the mass balance for nitrogenous compounds showed that only denitrification occurred as the sole microbial process when the bulk oxygen was 0–5%. With increasing oxygen above 5% nitrification also began to occur simultaneously with denitrification. As the bulk space of the refuse became aerobic, the total amount of N2 produced from denitrification decreased but the proportion of N2O in the (N2 + N2O) increased. Denitrification was the main source of released N2O when the moisture content was between 40–60% and oxygen 10%. The amounts of nitrification, denitrification and N2 production increased as the moisture content increased.