Cometabolic biotransformation of organic micropollutants under aerobic heterotrophic conditions

The role that heterotrophs present in activated sludge play in the removal of organic micropollutants (OMPs) has not been clearly elucidated despite their increasing relevance in the conception of novel wastewater treatment plant technologies. OMPs are often present in wastewaters at concentrations insufficient to support microbial growth and therefore their biotransformation would occur cometabolically thanks to the action of enzymes involved in the metabolism of primary substrates. Determination of such enzymatic activities could be very useful to better understand the process. In this study, an aerobic heterotrophic reactor spiked with 20 OMPs was set up to assess the role of the heterotrophic population in OMPs biotransformation, to identify the key biotransformation reactions and to decipher the enzymatic activities carrying out such biotransformations. Results have shown that heterotrophs can extensively biotransform the selected OMPs and that the main reactions responsible for OMPs biotransformation were oxidation, hydrolysis and conjugation routes, leading to transformation products potentially formed through oxygenases, dehydrogenases, hydrolases and transferases.