Congratulations to Christian Köhler for its PhD defense!

In October, Christian Köhler from the LIST defended his PhD thesis at the University of Luxembourg. The thesis, entitled "The Influence of Macro-substrates and Conditioning on Pharmaceutical Removal Rates by Moving Bed Biofilm Reactors", was supervised by Prof. Dr Joachim Hansen, professor in engineering science and hydraulic engineering. Apart from the LIST co-supervision by Dr Paul Schosseler and Tom Gallé, the multi-scale approach in Christian Köhler's PhD project involved some collaboration and co-supervision of Prof. Paul Wilmes from the Luxembourg Centre for System Biology (LCSB) and Prof. Peter Vanrolleghem, from the Canada research chair on water quality modelling at the Laval University in Quebec City, Canada.

The study focused on the fate of pharmaceuticals during biological wastewater treatment. In particular, metabolic strategies of bacteria degrading pharmaceuticals were investigated within moving bed biofilm reactor (MBBR) processes. Two main objectives were tracked. On the one hand, it was to unfold the impact of macro-substrates in terms of type and molecular complexity on the activity of microorganisms and consequently pharmaceutical degradation performance. On the other hand, the study was set out to explore the adaptation of metabolic means regarding exoenzymes and consortia structure during continuous (long-term) exposure to pharmaceuticals. Accordingly, the ability to increase microbial competences during pharmaceutical short-term pulses was the general target of investigation. Both conditions continuous substance flow and short-term peak loads of pharmaceuticals are believed to occur in urban WWTPs.

The outstanding comprehensive character of the study which encompassed sophisticated experimental design and powerful analytical tools from different scientific domains uncovered some interesting insights in pharmaceutical degradation processes. The results finally show how biomass is reacting towards the presence of primary carbon sources and organic micro-pollutants. The outcomes highlight the importance of WWTP influent characterization being indicative for metabolic activity and therefore degradation capacity of pharmaceuticals. The study further suggests that pharmaceutical metabolism and cometabolism co-exist during biological treatment processes. Co-metabolism is the decisive actor when adaption time is relatively short. Further, the study indicates some potential of process enhancement of WWTPs ranging from straightforward implementations such as external carbon sources to more elaborated processes of bioaugmentation.