Aerobic Granular Sludge

This chapter introduces the characteristics, formation mechanisms, start-up methods, microbiological features, storage methods, pollutant removal efficiency, application in wastewater treatment, and combination with other technologies of aerobic granular sludge. Aerobic granular sludge exhibits diverse physical and chemical properties such as settleability, specific gravity and moisture content, mechanical strength, shape and size, porosity, cell surface hydrophobicity, and extracellular polymeric substance (EPS). Its formation is influenced by various factors including substrate, dissolved oxygen, EPS, metal ions, surface charges, hydraulic selection pressure, settling time, temperature, seed sludge, and pH. Formation mechanisms involve several theories like self-condensation hypothesis, selective pressure-driven hypothesis, EPS hypothesis, and others. Start-up methods include shortening settling time, increasing organic load, ion addition, different seed sludge, carrier addition, and inoculation with special strains. Microbiology encompasses EPS-producing bacteria, denitrifying bacteria, phosphorus-removing bacteria, and refractory organic matter removing bacteria. Aerobic granular sludge finds applications in various wastewater treatment sectors such as printing and dyeing wastewater, aquaculture wastewater, chemical wastewater, pharmaceutical wastewater, domestic sewage, and pulp and paper wastewater. Additionally, combining it with technologies like membrane bioreactors, microbial fuel cells, microalgae systems, and continuous-flow reactors enhances treatment efficiency. The chapter also provides prospects for the future development of aerobic granular sludge in wastewater treatment.