Mechanistic studies on the effect of easy degradable carbon on pharmaceuticals removal in intermittently fed moving bed biofilm reactors.

This study was conducted to provide for the first time systematic data on how intermittent feeding with carbon (ethanol) affects the kinetics of pharmaceuticals degradation in a moving bed biofilm reactor (MBBR). The relationship between the degradation rate constants (K) of 36 pharmaceuticals and the length of famine was tested with 12 different feast-famine ratios: For 17 pharmaceuticals, intermittent feeding increased K with a factor of 3-17, while for six other pharmaceuticals, it decreased K. Concerning intermittent loading, three dependencies were detected: 1) for some compounds (e.g., valsartan, ibuprofen, iohexol), the K decreased linearly with carbon loading, 2) for three compounds (2 sulfonamides and benzotriazole) K increased linearly with carbon loading 3) for most compounds (e.g., beta blockers, macrocyclic antibiotics, candesartan, citalopram, clindamycin, gabapentin) K had a maximum around 6 d famine (with 2 d feast). Optimizing processes on MBBRs need therefore be conducted based on a prioritization of compounds.