The Impact of Applying an Internal Substrate Selection Strategy to Improve Aerobic Granular Sludge Formation

Municipal wastewater with limited organic substrate concentrations may pose a challenge for the application of aerobic granular sludge technology The objective of this project was to investigate the impact of substrate limitation on granule formation and development. It was hypothesized that an internal selector is necessary to induce sufficient extracellular polymeric substance (EPS) production to form a granular structure. A 70-L aerobic granular reactor (AGR) was constructed at the Lawrence Wastewater Treatment Plant and fed with primary clarifier effluent with variable food to microorganism (F/M) ratios. The findings of this study exhibited that increasing the F/M ratio up to 0.2 g rbCOD/g VSS-d promoted granulation, with up to 60% of the mixed liquor defined as granules. Substrate availability is one of the fundamental mechanisms driving EPS production, and subsequent granulation formation and development.