Biodegradation of ibuprofen, diclofenac and carbamazepine in nitrifying activated sludge under 12 °C temperature conditions

Pharmaceuticals constitute a well-known group of emerging contaminants with an increasing significance in water pollution. This study focuses on three pharmaceuticals extensively used in Finland and which can be found in environmental waters: ibuprofen, diclofenac and carbamazepine. Biodegradation experiments were conducted in a full-scale Wastewater Treatment Plant (WWTP) and in laboratory-scale Sequencing Batch Reactors (SBRs). The SBRs were operated at 12 °C, with a sludge retention time (SRT) 10-12 d and organic loading rates (OLRs) of 0.17, 0.27 and 0.33 kg BOD7 m- 3d- 1. Ibuprofen was found to biodegrade up to 99%. The biodegradation rate constants (kbiol) for ibuprofen were calculated for full-scale and laboratory processes as well as under different laboratory conditions and found to differ from 0.9 up to 5.0 l gSS− 1 d− 1. Diclofenac demonstrated an unexpected immediate drop of concentration in three SBRs and partial recovery of the initial concentration in one of the reactors. High fluctuating in diclofenac concentration was presumably caused by removal of this compound under different concentrations of nitrites during development of nitrifying activated sludge. Carbamazepine showed no biodegradation in all the experiments.