Scope and aim


Granular sludge offers ways to retain biomass, intensify wastewater treatment processes, and recover used water resources. Continuous research and development since late sixties resulted in breakthrough innovations. Granular sludge science and engineering moved from anaerobic conversions to aerobic-anaerobic ammonium oxidation and full biological nutrient removal. Granulation has first been observed in anaerobic upflow filters and clarigesters. Formation and application of methanogenic granular consortia has intrigued scientists and engineers for decades. Partial nitritation/anammox and "aerobic" granular sludges opened up a new field of ecological engineering to steer new-generation processes.

Functionalities have been pursued across redox conditions. Anaerobic, fermentative, heterotrophic and autotrophic, nitrifying and denitrifying, and even phototrophic conversions have been studied. Reactions combination and populations interactions under diffusional resistances revealed the complexity of these tiny biofilm ecosystems. Original reactor designs vary from slender continuously operated reactors with  3-phase separation to wide sequencing batch reactors. Managing microbial and hydraulic selection pressures for granule formation and retention is crucial. All systems aim at high rates and compactness.

Bio-analytical breakthroughs fostered microbial ecology, ecophysiology, and systems microbiology integration to characterize selection mechanisms  and distributed metabolisms. This provides a framework for a better understanding of microbial drivers of granular sludge formation and stability as basis for improved and innovative designs. Granular biofilms consist of microorganisms and extracellular polymeric substances (EPS) that provide cohesive, hydrophobic, and gelling properties. Granular sludge EPS extracts display different rheological features than flocs. Avanced physical-chemical and molecular research will unravel relations between EPS characteristics and microbiome features.

Resources factories are driven by granular sludge on top of high standards for environmental protection. Besides biogas production, innovative anaerobic systems propel the carboxylate platform. Lipid-rich algal granules steer biofuel production. High-value exopolymers can be recovered from waste granular sludge biosolids, and find application in the industry.

A community of engineers and scientists developed around granular sludge. We aim to bridge pioneers, international leaders, and new-generation experts across disciplines to critically discuss the state-of-the-art and anticipate the future of granular sludge. We convey colleagues from all continents to join us in Delft, for enthusiastic debates and networking.


David Weissbrodt and Merle de Kreuk (Conference Chairs)

Delft, January 15, 2017