A flat type membrane bioreactor (MBR) with a pore size of 0.038 mu m and having a total surface area of 540 m(2) was operated intermittently for over a year in METU campus at Ankara to treat domestic effluents from dormitories and academic village. At the first stage the MBR plant was operated continuously for 140 days with hydraulic retention times ranging between 18 and 22 h. During this period, sludge concentration increased from an initial 2.4 g/L to 21 g/L. The plant consistently produced fully nitrified effluents when DO was kept over 2.0 mg/L. Over 99.99% BOD5 removal and 95% COD removals were achieved in the system. When DO concentration was 2 mg/L and mixed liquor suspended solids, MLSS, concentration was 16 g/L, simultaneous nitrification and denitrification was observed in the system. The effluent turbidity, was always below 1 NTU, equal to or below that of tap water, and around 6-7 log coliform removals with close to zero/100 mL effluent counts were achieved.