Granulation of activated sludge is a novel process for biological treatment of wastewater. These aggregates can be described as a special case of biofilm where microorganisms self-immobilize to form very dense round granules a few mm in diameter. It is regarded as one of the more promising applications mainly due to the excellent separation properties of the granules making the system very compact. High hydraulic loading rates can be applied at the same time as high biomass concentrations can be maintained in the reactor. Wastewater treatment plants that include biological nitrogen removal usually require large reactor volumes. Stricter effluent quality requirements make plant extensions necessary. Due to limited space available more compact process solutions are preferred.
Granules are only formed when the environmental conditions are optimal. This can be achieved in sequencing batch reactors (SBR) where the microorganisms are exposed to large substrate gradients and high turbulence. By shortening the settling time to a few minutes, only microorganisms capable of granule formation can remain in the system. Due to the large granule size, gradients of substrates can be achieved inside them, hence obtaining simultaneous nitrification and denitrification. The aim of this project is to explore the aerobic granular sludge process for treatment of wastewater by studying the microbial community structure and its effect on the biological conversion processes.
The project is carried out at the Division of Water Environment Technology.
Keywords: Nitrogen removal, nutrient removal, granular sludge, sequencing batch reactor, aerobic granules
Malte Hermansson (GU)
Departement of Chemistry and Molecular Biology (University of Gothenburg), Gryaab AB