Environmental fate of non-steroidal anti-inflammatory drugs in river water/sediment systems

Laboratory tests were conducted with four non-steroidal anti-inflammatory drugs (naproxen, ibuprofen, diclofenac and ketoprofen) under different redox conditions (aerobic, anoxic, anaerobic and sulfate-reducing conditions) in order to assess abiotic and biotic degradation in a river water/sediment system. The river water was sampled from Sperchios River and the sediment was collected from the banks of a rural stream where the discharge point of a wastewater treatment plant is located. To quantitatively describe degradation kinetics of the selected compounds, pseudo first-order kinetics were adopted. According to the results, it can be stated that the concentration of the substances remained constant or decreased only marginally (p≥0.05) in the sterile experiments and this excludes abiotic processes such as hydrolysis or sorption as major removal mechanisms of the target compounds from the water phase and assign their removal to microbial action. Results showed that the removal rate of the compounds decreases as dissolved oxygen concentration in the river water/sediment system decreases. All compounds were found to be biodegradable under aerobic conditions at dissipation half-lives between 1.6 and 20.1days, while dissipation half-lives for naproxen and ketoprofen increase by a factor of 2 under all tested conditions in the absence of oxygen.