An anaerobic membrane reactor (AnMBR) treating municipal wastewater was evaluated. The experiments were performed using a pilot-scale up-flow anaerobic sludge blanket reactor with a submerged tubular ultrafiltration membrane at a hydraulic retention time of 8 hours. The system worked at an intermittent filtration mode (4 min on/1 min off) with and without nitrogen gas bubbling during the relaxation time (IF4NP and IF4P, respectively). The chemical oxygen demand (COD) removal achieved by the AnMBR was 68.6% and 87.9% for IF4P and IF4NP. Nitrogen bubbling also improved the filtration performance, as the elapsed time to reach 40 kPa for IF4NP and IF4P were 443 and 108 hours, respectively. Results show that intermittent filtration combined with nitrogen bubbling during the period of relaxation was an effective operation strategy in order to minimize membrane fouling and to increase COD removal.