Inducing Aerobic Granulation in Continuous-Flow Reactors using Shear Variability

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CBET-1336544Francis de los Reyes and Joel DucosteNorth Carolina State UniversityAerobic granulation is perhaps one of the most exciting developments in aerobic wastewater treatment, promising the ability to treat higher flows of higher strength wastewater in smaller reactors, with fewer problems with settling and separation of biomass, and with the ability to treat a variety of organic substrates, as well as simultaneously removal of nitrogen and phosphorus. If aerobic granular sludge can be developed in existing wastewater treatment facilities, the impacts would be widespread. Yet despite the promise, full-scale implementation of continuous flow aerobic granular sludge reactors has not happened. Continuous flow reactors theoretically provide more stable environments, need less automation, and can be designed by engineers using smaller test systems. However, the formation of aerobic granules from non-granular biosolids in continuous flow reactors is not understood. Based on prior research, it is hypothesized that the key to inducing aerobic granulation is not the sequencing batch mode, but the ability of a bioreactor to provide variable shear. This research will test this hypothesis and investigate the mechanistic links between reactor hydrodynamics, microbial responses, and ultimately granulation under aerobic conditions. A combination of approaches, including analysis of microbial morphological changes in a micro-reactor, molecular microbial analysis of populations and genes in lab-scale reactors, and use of computational fluid dynamics and Lagrangian sensors, will be used to show how shear variability is a necessary condition for aerobic granulation. Finally, this research will demonstrate scale up by constructing and operating a continuous-flow pilot-scale reactor to induce aerobic granulation. This combined approach will show how aerobic granular sludge technology can be used to retrofit existing activated sludge plants, potentially providing a significant leap in aerobic treatment technology, and impacting thousands of wastewater treatment plants around the world.The development of aerobic granular biomass reactors has excited the wastewater treatment industry, as it represents an innovative, efficient, compact, and potentially more sustainable method for treating wastewater. Aerobic granular biomass reactors can treat high strength wastewaters containing organics. This project will potentially benefit municipal and industrial wastewater treatment plants including those that perform nutrient removal. Developing aerobic granules in existing wastewater treatment plants represents a leap in technology with economic and efficiency benefits for the nation's wastewater infrastructure. The results from this innovative research will also generate information that can be used in the classroom and foster learning through excitement of discovery.