Scientific and Technical Report No. 26The Use of Water Quality and Process Models for Minimizing Wastewater Utility Greenhouse Gas Footprints provides an understanding of the processes that are responsible for the major contributions to GHG emissions from WWTP and sewer systems (e.g. heterotrophic denitrification, autotrophic nitrification, autotrophic denitrification, methanogenesis). This knowledge is translated into mathematical models that can be embedded in system/plant-wide models allowing multi-criteria optimisation.