Performance of Aerobic Granular Sludge Bioreactor Seeded with Flocculated Activated Sludge From an Iraqi Municipal Wastewatere Treatment Plant


Aerobic granular activated sludge is an attractive and promising process for intensive and high-rate biological nutrient removal (BNR) and secondary clarification in a single reactor.This work reportsthe performance of aerobic granular sludge sequential batch reactor (SBR) seeded with flocculated activated sludge collected from an Iraqi municipal wastewater treatment plant, using synthetic wastewater. The conditions under which the successful cultivation of aerobic granular sludge was done are as follows: influent chemical oxygen demand (COD) was 1100 mg/l, volumetric exchange rate was 50%, aeration time was 10 hr, anoxic time was 2 hr aerationand sludge settling time was about 0.5 min. After 90 days, the dominant granules size was 1.5-3.5 mm. The granules became regular in shape with smooth surface, sharp boundaries and compact in structure. The biomass concentration in the reactor in terms of MLSS was 4100 mg/l. Sludge volume index (SVI) was 60 ml/g. High syntheticCOD removal and simultaneous nitrification and denitrification during aerobic phase was observed. Subjection of themature granules to a low COD municipal wastewater the activity of the granules was significantly reduced.