The performance of a 10 L sequencing batch reactor (SBR) treating slaughterhouse wastewater was examined at ambient temperature. The influent wastewater comprised 4672 +/- 952 mg chemical oxygen demand (COD)/L, 356 +/- 46 mg total nitrogen (TN)/L and 29 10 mg total phosphorus (TP)/L.. The duration of a complete cycle was 8 h and comprised four phases: fill (7 min), react (393 min), settle (30 min) and draw/idle (50 min). During the react phase, the reactor was intermittently aerated with an air supply of 0.8 L/min four times at 50-min intervals, 50 min each time. At an influent organic loading rate of 1.2 g COD/(L d), average effluent concentrations of COD, TN and TP were 150 mg/L, 15 mg/L and 0.8 mg/L, respectively. This represented COD, TN and TP removals of 96%, 96% and 99%, respectively. Phase studies show that biological phosphorus uptake occurred in the first aeration period and nitrogen removal took place in the following reaction time by means of partial nitrification and denitrification. The nitrogen balance analysis indicates that denitrification and biomass synthesis contributed to 661X, and 34% of TN removed, respectively. (C) 2008 Elsevier Ltd. All rights reserved.