Protocol for the measurement of nitrous oxide fluxes from biological wastewater treatment plants.

The overarching goal herein was to develop a protocol that could be used to generate consistent information on the generation and emission of nitrous oxide (N(2)O) from open-surface wastewater treatment bioreactors. The developed protocol was reviewed and endorsed by the United States Environmental Protection Agency (USEPA), whereupon it was used to determine N(2)O emissions from a wide array of wastewater treatment processes across the United States. Scaled-down variants of the protocol have also since been adopted for lab-scale measurements. The protocol consists of a combination of elements that entail real-time online measurement of headspace N(2)O concentrations, supplemented by discrete measurements of liquid-phase N(2)O and other routinely monitored wastewater and process parameters. Notably, the advective flow rate of headspace gas is also directly measured.