Population dynamic of microbial consortia in a granular activated carbon-assisted biofilm reactor: Lessons from modelling

Abstract

In this work, experimental and long-term mathematical modelling approaches were combined to investigate mechanisms and drivers influencing on microbial consortia dynamics in an anaerobic granular biofilm reactor whereby dominantly anaerobic ammonium oxidation (anammox) and heterotrophic denitrifying bacteria can attach and grow on granular activated carbon (GAC). For this mean, a novel biofilm model including soluble microbial products (SMP) and extracellular polymeric substance (EPS) was developed to explain kinetics and abundance of independent microbial groups in terms of relative biovolume fraction and the spatial localization of bacteria in biofilm layers. The model was calibrated, validated and the model accuracy was checked using measured total nitrogen concentration and microbial biovolume fractions. For estimation of biovolume fraction an innovative enhanced protocol for quantitative fluorescence in-situ hybridization (qFISH), in-situ microscopy and digital image analysis for the cultivation-independent microorganisms was established. The model with EPS kinetics fits better for the bacteria groups of anammox bacteria, AOB and NOB compared to the model without EPS. Real-time producing BAP and UAP is simulated and it was presumed that he growth and existence of heterotrophs in anammox biofilm systems increase due to considering the autotrophic production of SMP.