The Ootmarsum wastewater treatment plant (WWTP) is owned by the water authority Regge & Dinkel (WRD) and is situated in the municipality of Dinkelland (eastern part of The Netherlands). The WWTP must be modernised, because it discharges the treated wastewater into a water system with considerable ecological vulnerability. In the restructuring plan the urban water chain/cycle was integrated into an ecological water management approach. In cooperation with Grontmij engineering consultants a design study was carried out resulting in the choice for a so-called hybrid system. Such a system combines a conventional system followed by a sand filter with a membrane bioreactor (MBR). With a hybrid MBR, the costs can be reduced relatively to those of a complete MBR plant without making concessions in terms of effluent quality. After an intensive selection procedure NORIT Membrane Technology (NMT) was selected with the novel NORIT AirLift MBR system. The construction work of the 650 m(3)/h plant started in mid-2005 and will be completed by late 2006; start-up of the full scale will be early 2007. As preparation for the full scale plant operation an intensive pilot study is currently being performed in order to develop a start-up protocol, to train operators, to check control philosophies, and to optimise the overall processing.