The feasibility of thermophilic (55 degrees C) anaerobic treatment of an alcohol distillery wastewater (cane molasses vinasse) was studied using a 140 l upflow anaerobic sludge blanket (UASB) reactor for a period of 430 days. Organic loading rates were applied up to 28 kg chemical oxygen demand (GOD) m(-3) d(-1) by reducing hydraulic retention time (HRT) at a fixed influent concentration of 10 g COD l(-1). Chemical oxygen demand removals during the entire experimental period were relatively low (39-67%), while biochemical oxygen demand (BOD) removals were more satisfactory (more than 80%). The biodegradability of the vinasse used in this study was assessed by a serum vial test. The test revealed that methane production rates from the vinasse were only 1/36, 1/32, 1/25 and 1/23 as great as those from H-2/CO2, acetate, glucose and another type of vinasse (malt), respectively. The poor performance of the reactor for COD elimination can probably be attributed to the low degradability of the waste itself. Methanogenic activity of the retained sludge increased 24 times, for acetate, and 13 times, for H-2/CO2, as much as that of the inoculum sludge. The optimum temperature of methanogenic activity of the sludge depended on the substrate used; i.e. 60 degrees C for acetate, 60-65 degrees C for H-2/CO2, and around 55 degrees C for the waste. (C) 1996 Elsevier Science Ltd.