Aerobic granular sludge wastewater treatment: From microbial ecology to application


Prof. Christof Holliger, Dr. Julien Maillard, Aline Adler, Arnaud Gelb

Funding agency

Swiss National Science Foundation

Project period

November 2014 – October 2018


Prof. Eberhard Morgenroth & Dr. Nicolas Derlon, ETHZ & Eawag, Switzerland; Dr. Marco Pagni, SIB & Vital-IT, Lausanne, Switzerland.


Aerobic granular sludge (AGS)-based wastewater treatment is a promising alternative to activated sludge systems since AGS-based installations have smaller footprints, higher specific sludge contents resulting in high volumetric loading rates, relatively high solid retention times producing low amounts of waste sludge, and low energy requirements. Extensive research with synthetic wastewater containing mainly VFAs such as acetate and propionate deepened our understanding of AGS systems concerning granule formation, rapid reactor start-up with BNR activated sludge as inoculum, efficient nitrogen removal from COD-limited wastewater, and the main parameters governing the competition between phosphate- and glycogen-accumulating organisms (PAO and GAO, respectively). It provided a basis for developing conceptual and mathematical models that describe interactions in the complex ecosystems that developed even with a simple synthetic wastewater and an optimal bacterial resource management methodology to guarantee stable nutrient removal with high efficiencies. However, preliminary research with real domestic wastewater indicated that the knowledge obtained with synthetic wastewater cannot be directly transferred to wastewater with a complex composition of organic matter containing a multitude of compounds in dissolved or particulate form.
The main objective of this proposal therefore is to understand the influence of the presence of particulate substrates (XS) in the wastewater on the physical, biochemical, and microbial structure of the AGS ecosystem and its functioning. The main hypothesis is that the mechanisms of aerobic granule formation as well as the microbial, physical and biochemical structure and functioning of aerobic granules is governed by the influent composition (e.g., presence/absence of particulate organic matter). Special emphasis will be put on the understanding of the ecosystem functioning since the microbial communities that were present in acetate-propionate cultivated AGS were much more divers then anticipated with populations not known to be able to use volatile fatty acids under anaerobic conditions. They either thrive on carbon and energy sources such as EPS produced by PAO and GAO or they have not yet described metabolic properties. Characterization of PAO and GAO with different up-to-date techniques for single cell investigations is therefore an additional specific objective of this proposal.