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Methane and nitrous oxide emissions from a fully covered municipal wastewater treatment plant were measured on-line during 16 months. At the plant under study, nitrous oxide contributed three-quarters to the plant's carbon footprint, while the methane emission was slightly larger than the indirect carbon dioxide emission related to the plant's electricity and natural gas consumption. This contrasted with two other wastewater treatment plants, where more than 80% of the carbon footprint came from the indirect carbon dioxide emission. The nitrous oxide emission exhibited a seasonal dynamic, of which the cause remains unclear. Three types of air filter were investigated with regard to their effectiveness to remove methane from the off-gas.

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The SHARON (Single reactor High activity Ammonia Removal Over Nitrite) process is an innovative process that improves the sustainability of wastewater treatment, especially when combined with an Anammox process. It aims at ammonium oxidation to nitrite only, while preventing further nitrate formation. In order to optimize this process by means of modelling and simulation, parameters of the biological processes have to be assessed. Batch tests with SHARON sludge clearly showed that ammonia rather than ammonium is the actual substrate and nitrous acid rather than nitrite is the actual inhibitor of the ammonium oxidation in the SHARON process. From these batch tests the ammonia affinity constant, the nitrous acid inhibition constant and the oxygen affinity constant were determined to be 0.75 mgNH 3 -N L −1 , 2.04 mgHNO 2 -N L −1 and 0.94 mgO 2 L −1 . The influence of pH and temperature on the oxygen uptake rate of SHARON biomass was determined, indicating the existence of a pH interval between 6.5 and 8 and a temperature interval from 35 to 45 • C where the biomass activity is maximal. The kinetic parameters of the SHARON process were determined based on batch experiments. These parameters can now be implemented in a simulation model for further optimization of the SHARON process. LIST OF SYMBOLSb OUR (oxygen uptake rate) temperature dependency parameter c OUR temperature dependency parameter DO dissolved oxygen concentration [mgO 2 L −1 ] K e,NH 4 + acidity constant of the ammonium/ammonia equilibrium K e,HNO 2 acidity constant of the nitrite/nitrous acid equilibrium K NH I,HNO 2 inhibition constant for nitrous acid of ammonium oxidizers [mgHNO 2 -N L −1 ] K NH NH 3 max maximum growth rate of ammonium oxidizers [d −1 ] θ Arrhenius constant

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