Diclofenac (DCF) is a common anti-inflammatory pharmaceutical that is often detected in waste wasters, effluents and surface waters. Recently, DCF was included in the watch list of substances in EU that requires its environmental monitoring in the member states. DCF is also known to harmfully affect several environmental species already at concentrations of150 d) favor the DCF elimination due to sludge adaptation. Longer HRTs (>2-3 d) could significantly increase the elimination of DCF during biological wastewater treatment. Bioaugmentation could be used to enhance DCF elimination, however, this requires more research on microbial communities that are able to degrade DCF. Also, further research is needed to gain more information about the deconjugation processes and biotic and abiotic transformation and the nature of transformation products. (C) 2014 Elsevier Ltd. All rights reserved.