Investigating the role of adsorption and biodegradation in the removal of organic micropollutants during biological activated carbon filtration of treated wastewater

Municipal water recycling may expose humans and the environment to trace organic contaminants. We assessed biological activated carbon (BAC) filtration for removal of organic micropollutants (MPs). Adsorption experiments were carried out in batch reactors containing secondary effluent and new granular activated carbon (GAC) and preloaded BAC media. Results show that BAC has good potential for removal of dissolved organic carbon (40%) and MPs (60-95%). The primary objective was to better understand removal mechanisms of representative MPs at environmentally relevant concentrations. Adsorption and biodegradation of 20 compounds of varying physico-chemical properties were investigated by inhibiting the biomass with azide. Average removal of compounds by adsorption on GAC was 88 +/- 5% with no influence of azide. Average BAC removal was 72 +/- 15%, reduced to 59 +/- 20% after azide addition, showing that biological activity is important for MP removal. Comparison of MP removal by BAC and BAC + azide showed a more important impact of the inhibition on the removal of negatively charged compounds. Sustained removal of recalcitrant compounds showed that BAC maintained sorption capacity. These results highlight the advantage of a combination of adsorption and biodegradation as compared to other biofiltration techniques for the long-term attenuation of MPs.