The strong greenhouse gas nitrous oxide (N2O) can be emitted from wastewater treatment systems as a byproduct of ammonium oxidation and as the last intermediate in the stepwise reduction of nitrate to N2 by denitrifying organisms. A potential strategy to reduce N2O emissions would be to enhance the activity of N2O reductase (NOS) in the denitrifying microbial community. A survey of existing literature on denitrification in wastewater treatment systems showed that the N2O reducing capacity (VmaxN2O/N2) exceeded the capacity to produce N2O (VmaxNO3/N2O) by a factor of 2e10. This suggests that denitrification can be an effective sink for N2O, potentially scavenging a fraction of the N2O produced by ammonium oxidation or abiotic reactions.