Efficacy of activated carbon filtration and ozonation to remove persistent and mobile substances-A case study in two wastewater treatment plants

Persistent and mobile (PM) substances are able to spread quickly in the water cycle and were thus identified as poten-tially problematic for the environment and water quality. If also toxic (PMT) or very persistent and very mobile (vPvM) their regulation under REACH as substances of very high concern is foreseen. Yet, knowledge on the effectiveness of advanced wastewater treatment in removing PM-substances from WWTP effluents is limited to few rather well-known chemicals. The occurrence and behavior of 111 suspected and known PM-substances was investigated in two wastewater treatment plants employing either powdered activated carbon (PAC, full-scale) or ozonation with sub-sequent sand/anthracite filtration (pilot-scale) and an additional granular activated carbon (GAC) filtration was inves-tigated. 72 of the 111 PM-substances analyzed were detected at least once in the secondary effluent of either wastewater treatment plant, resulting in total concentrations of 104 mu g/L and 40 mu g/L, respectively. While PAC re-moved 32 % of PM-substances well, the total PM burden in the effluent was only reduced from 103 mu g/L to 87 mu g/L. Ozonation and the subsequent sand/anthracite filtration was able to reduce the PM burden in wastewater from 40 mu g/L to 19 mu g/L, showing a higher removal efficacy than PAC in this study. The additional GAC filtration fur-ther reduced the total PM-concentration to 13 mu g/L. Among the investigated PM-chemicals detected were constituents of ionic liquids: The anion hexafluorophosphate was one of few chemicals that was detected in effluent concentrations >1 mu g/L and could not be removed by the processes studied, showing that for some chemicals preventive actions may be required.