DYNAMICS OF N2O PRODUCTION FROM ACTIVATED-SLUDGE

N2O emission from activated sludge basins is the net result of microbi al production and consumption of N2O. In this study semicontinuous and batch laboratory scale experiments were carried out with activated sl udge from a Danish waste water treatment plant in order to elucidate i mportant parameters in N2O production under oxic and anoxic conditions . To distinguish between N2O production from NH4+ and NO2- oxidation u nder oxic conditions, C2H2 and ClO3- were used as selective inhibitors . Our study showed that most of the N2O produced was reduced to N-2 un der anoxic conditions. Shorter N2O residence times in the sludge resul ted in more N2O produced. Most of the N2O emission occurred under oxic conditions, probably because the reduction to N-2 was inhibited by O- 2. We suggest a coupling between NH4+ oxidation and NO2- reduction (ni trifier-denitrification) as responsible for the majority of the N2O pr oduced under oxic conditions, since NH4+ oxidation and high NO2- conce ntrations stimulated N2O production. Increasing temperature, NH4+ and dissolved O-2 concentrations enhanced this effect. (C) 1998 Elsevier S cience Ltd. All rights reserved.