Aerobic Granular Sludge
The activated sludge (AS) system has played a vital role in treating domestic and industrial wastewaters for over a century. However, with its high capital and operational costs and large land area requirements, it is becoming increasingly clear that the AS system cannot meet the demands of a growing population. The aerobic granular sludge (AGS) system offers a promising alternative, with a potential 75% reduction in footprint and up to 60% cost savings compared to AS, while providing comparable or better effluent quality. With more than 100 full-scale AGS plants already in operation or under construction worldwide, the AGS system has the potential to become the standard for biological wastewater treatment. However, despite its significant advantages, there is a lack of research on the underlying mechanisms of community assembly of microbial aggregates in AGS systems. The AGS system provides a unique microbial ecosystem where different-sized microbial aggregates coexist, with granules representing the majority and distributed over the height of the reactor, with large granules more often present at the bottom and flocs at the top during the non-aeration phase. This spatial segregation can result in different biological niches because of differences in substrate availability at specific depths, unlike the conventional activated sludge system where biomass is homogeneously distributed.
The proposed study aims to differentiate between growing and nongrowing important microbial communities belonging to functional groups responsible for nitrogen and phosphorus removal using a genome-resolved metatranscriptomics approach. This will be achieved by identifying active and non-active populations across a series of microbial size aggregates present in the AGS system. Furthermore, the study will measure the rates of specific PAO activity in batch incubation experiments across a series of microbial size aggregates and compare them with the genome-resolved metatranscriptomics results. This will provide a better understanding of the life cycle of the spherical granular biofilm of the AGS system and enhance the stability and function of the AGS system.