Effect of low-frequency ultrasound pre-treatment to inoculum on performance of microbial fuel cell (MFC) was evaluated. Mixed anaerobic sludge was pre-treated with ultrasonication duration of 2.5, 5, 7.5, and 15 min, and the performance of MFC using this inoculum was compared with the MFC inoculated without any pre-treatment to the sludge. The effect of combined pre-treatment, using ultrasonication and heating of the inoculum, on performance of the MFC was also evaluated. Maximum power density during polarization in a MFC inoculated with ultrasonication pre-treatment to the sludge for 5 min (40 kHz, 120 W) was 2.5 times higher than that obtained without any pre-treatment to the inoculum sludge. Substrate removal was higher in the MFC with ultrasonicated inoculum, than inoculum without any pretreatment and combined pre-treated with ultrasonication and heating. These results evidently demonstrated the advantages of ultrasonication pre-treatment to the inoculum for enhancing power and organic matter removal of the MFC. (c) 2009 Elsevier Ltd. All rights reserved