Membrane Bioreactors (MBR) are becoming increasingly important in the treatment of municipal wastewater. Compared to traditional treatment techniques, MBR's require far smaller surface areas and produce better effluent quality. This publication reports the results and experiences of the first 16 months of operation and the associated research programme of the first full-scale MBR in the Netherlands which entered operation in December 2004. Detailed results of the plants technical performance are presented together with experience of optimising the processes. The design is evaluated and design recommendations are presented. MBR set-up and initialization costs are compared with those of conventional WWTPs. The report confirms the suitability of MBR technology for the treatment of municipal wastewater taking into account the technical performance and cost considerations. This publication will be an invaluable source of reference for all those concerned with the treatment of municipal wastewater.