Functional and structural characterization of polyphosphate-accumulating organisms in aerobic granular biofilms

The "Aerobic Granular Sludge" (AGS) technology for wastewater treatment is basedon dense microbial biofilm in the form of granular aggregates that have an excellentsettling property allowing high biomass concentrations in bioreactors. This promisingbiological treatment of wastewater is a cost-effective and land-saving alternative tothe conventional flocculent activated-sludge technology.A complex microbial community is intertwined in the dense biofilm structure of AGS,and little is known about the roles and the interactions between microorganismswithin this matrix. Moreover, there is a need to understand the fundamental biologicalmechanisms underlying the AGS process to control its stability and performance.In this context, the physiology and the structural organization of the AGS microbialpopulations involved in biological phosphorus removal from the influent are investigated in lab-scale conditions.With the experimental set-up and conditions used, for a microbial community dominated by the genus Ca. Accumulibacter phosphatis, acetate, propionate, and probablysome amino acids (like aspartate or glutamate) could support the biological phosphorus removal from the influent. Glycine was shown to interfere with this metabolismwith an effect proportional to its concentration. Concerning the use of acetate andglucose, microorganisms belonging to Ca. Accumulibacter phosphatis and to an unknown genus of Propionibacteriaceae were likely the primary consumers, respectively.Investigating the organisms involved in the biological phosphorus removal revealedCa. Accumulibacter phosphatis as the primary organism responsible for phosphorustreatment performance. Finally, the spatial organization of the microorganisms inthe AGS showed clusters of microcolonies rather than an organization in layers.