Effects of substrate loading on co-metabolic transformation pathways and removal rates of pharmaceuticals in biofilm reactors br

This study focused on the effects of substrate (raw wastewater) on the biological removal of 20 pharmaceuticals in movingbed biofilm reactors. This is thefirst study discriminating experimentally between effects of adaptation (45 d) andstimulation (100h) on the removal of micropollutants. The results presented in this paper show: i) Tramadol andvenlafaxine are subject to microbialN-oxidation (besides the known demethylation). ii) Changes in substrate loading,changed the preferential degradation pathways, e.g., fromN-oxidation (under starvation) toN-demethylation of bothmodel compounds: tramadol and venlafaxine, during adaptation and stimulation to high substrate supply. iii) In starvingbiofilms, the effects of stimulation on removal rates are minor (-100 to +150 %) in comparison to those caused by adaptation (-100 to +700 %). iv) Adaptation to high loadings resulted in increased removal rates (up to 700 % inselected cases) v) Adaptation to high loadings followed by high loading of stimulation, resulted in the highest increase of removal rates (+49 % to +1800 %) for hard-to-degrade compounds (e.g., diclofenac). All in all, this study shows that the efficiency of biofilm reactors is heavily dependent on their adaptation to substrate

Automated summary

This study investigates the effects of substrate on the biological removal of pharmaceuticals in moving bed biofilm reactors. The study finds that adaptation and stimulation have different effects on the removal rates, with adaptation leading to significant increases and stimulation having minor effects. Changes in substrate loading also influence the preferential degradation pathways.