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Aerobic granulation of activated sludge was achieved in a pilot-scale sequencing batch reactor (SBR) for the treatment of low-strength municipal wastewater (<200mgL⁻¹ of COD, chemical oxygen demand). The volume exchange ratio and settling time of an SBR were found to be two key factors in the granulation of activated sludge grown on the low-strength municipal wastewater. After operation of 300 days, the mixed liquor suspended solids (MLSS) concentration in the SBR reached 9.5gL⁻¹ and consisted of approximate 85% granular sludge. The average total COD removal efficiency kept at 90% and NH₄⁺-N was almost completely depleted (∼95%) after the formation of aerobic granules. The granules (with a diameter over 0.212mm) had a diameter ranging from 0.2 to 0.8mm and had good settling ability with a settling velocity of 18–40mh⁻¹. Three bacterial morphologies of rod, coccus and filament coexisted …