Can anaerobic intermediate stages affect the biotransformation and sorption of pharmaceutical compounds?

Batch experiment was conducted to investigate if anaerobic intermediate stages can affect bio-transformation and sorption performance of selected pharmaceutical compounds (stimulant caffeine (CAF), anti-diabetic drug gliclazide (GCZ) and anti-hypertensive drug prazosin (PRZ)). The outcome revealed that CAF was removed solely via biotransformation and followed the methanogenic pathway. Sorption was significant during the fermentation stage for hydrophobic GCZ and PRZ although both compounds continued to biotransform in the later stage of incubation. While more than 95% removal of all compounds was achieved after 30 d of incubation under anaerobic mesophilic condition, further incubation to Day 90 resulted in re-occurrences of GCZ and PRZ in the aqueous and solid phase. Biotransformation of hydrophilic and hydrophobic compounds could not be represented in the same kinetic model considering sorption and retransformation displayed significant effect to the model. This study also reported the first removal of GCZ and PRZ under anaerobic condition.