A new development for the treatment of domestic wastewater is a technology based on aerobic granular sludge. Granular sludge can be developed under specific process conditions. Because of the unique properties of this granular sludge, high volumetric loading rates of aeration tanks can be applied. Thanks to excellent settling properties, the separation of treated wastewater and granular sludge can take place at high hydraulic loading rates. Depending on the chosen process configuration good effluent quality can be obtained, complying with the stringent effluent requirements regarding nitrogen and phosphorus, which can be expected in the future. In this way aerobic granular sludge has the potential to contribute significantly to wastewater treatment management. This report describes the results of research carried out at the Technical University of Delft.