The studies were carried out with simulated domestic wastewater (300 +/- 10 and 500 mg COD/L) and real domestic wastewater (290 10 mg COD/L). During these studies different organic loading rates (0.29, 0.82 and 1.1 kg COD/m(3)d for Set land Set II, and 0.29 and 0.62 kg COD/m(3)d for Set III), hydraulic retention times (11, 15, 25 h), temperatures (10, 15, 25 degrees C) and at different anaerobic sludge concentrations (about 5, 10 g VSS/L) in the reactor were applied and the performance of the reactor was tested. It was observed that treatment of low strength wastewaters under low temperature was possible. Even at the lowest temperature applied and lowest sludge amount the total organic matter (COD) removal was 65.2%. However, the COD removal and methane production decreased with decreasing temperature and HRT. The COD removal efficiencies decreased when the system was fed with settled real domestic wastewater probably due to more complex structure of the domestic wastewater and the presence of suspended solids even in small concentrations. These results showed that the ASBR process can be used for treatment of low strength wastewaters at low temperatures. (C) 2011 Elsevier B.V. All rights reserved.