The effect of aeration rate on nutrient removal from slaughterhouse wastewater was examined in two 10-L laboratory-scale sequencing batch reactors (SBRs-SBR1 and SBR2) operated at ambient temperature. The contaminants in the slaughterhouse wastewater had average concentrations of 4,000 mg chemical oxygen demand (COD) L-1, 350 mg total nitrogen (TN) L-1 and 26 mg total phosphorus (TP) L-1. The duration of a complete SBR operation cycle was 8 h and comprised four operational phases: fill (7 min), react (393 min), settle (30 min) and draw/idle (50 min). During the react phase, the reactors were intermittently aerated four times at 50-min intervals, 50 min each time. DO, pH and oxidation-reduction potential (ORP) in the reactors were real-time monitored. Four aeration rates-0.2 L air min(-1) in SBR1 for 70 days, 0.4 L air min(-1) in SBR1 for 50 days, 0.8 L air min(-1) in SBR2 for 120 days and 1.2 L air min(-1) in SBR1 for 110 days-were tested. When the aeration rate was 0.2 L air min(-1), the SBR was continuously anaerobic. When the aeration rate was 0.4 L air min(-1), COD and TP removals were 90% but TN removal was only 34%. When the aeration rates were 0.8 and 1.2 L air min(-1), average effluent concentrations were 115 mg COD L-1, 19 mg TN L-1 and 0.7 mg TP L-1, giving COD, TN and TP removals of 97%, 95% and 97%, respectively. It was found that partial nitrification followed by denitrification occurred in the intermittently aerated SBR systems.