Aerobic granular sludge—a case report

Aerobic granular sludge was observed in a Sequencing Batch Reactor (SBR) in which a synthetic urban wastewater containing sodium acetate as an organic substrate was fed, and dissolved oxygen (DO) was controlled at low concentration (0.7–1.0 mg/l) Microscope examination showed that the morphology of the granules was nearly spherical (0.3–0.5 mm in diameter) with a very clear outline. The granular sludge had a good settleability (Sludge Volume Index (SVI) between 80–100 ml/g) and high COD removal and nitrification activities (2.16 g(TOC)/g(SS) • d and 0.24 g(NH3-N)/g(SS) • d). With granular sludge, high quality effluent was obtained for treatment of synthetic wastewater under low DO.