2019, Wünsch, Robin, Plattner, Julia, Cayon, David, Eugster, Fabienne, Gebhardt, Jens, Wülser, Richard, von Gunten, Urs, Wintgens, Thomas

Because organic micropollutants (MP) are frequently detected in river waters that are used as drinking water sources, combining a relatively cost-efficient natural treatment with upstream advanced oxidation processes (AOP) appears promising for their efficient abatement. Such a multi-barrier system can be integrated in drinking water production schemes to minimize risks from potentially hazardous MPs. This study investigates the impact of an UV/H2O2 AOP before soil aquifer treatment (SAT) on the abatement of selected MPs (EDTA, acesulfame, iopamidol, iomeprol, metformin, 1H-benzotriazole, iopromide), dissolved organic matter (DOM) (apparent molecular size distribution, specific UV absorbance at 254 nm – SUVA) and microbial parameters (intact cell count, cell-bound ATP). A pilot plant consisting of an AOP (0.5 m3 h−1, 4 mg L−1 H2O2, 6000 J m−2) and two parallel soil columns (filtration velocity: 1 m d−1, column height: 1 m) was continuously operated over a period of 15 months with Rhine river water pre-treated with rapid sand filtration. The investigations revealed a shift towards longer retention times of the humic substances peak in LC analysis of DOM, lower SUVA and higher biodegradability of DOM after UV/H2O2 treatment. In addition, an overall higher abatement of all investigated MPs by the combined treatment was observed (AOP with subsequent SAT) compared to either process alone. This observation could be explained by an addition of the single treatment effects. The strong primary disinfection effect of the AOP was detectable along the first meter of infiltration, but did not lead to any change in the column performance (i.e., similar abatement of dissolved organic matter).

2018-10, Krahnstöver, Thérèse, Wintgens, Thomas

Wastewater treatment plant effluents often contain anthropogenic micropollutants that can have harmful effects on aquatic ecosystems in the receiving water body. For this reason, more and more plants are being equipped with advanced treatment stages for micropollutant removal, such as ozonation or activated carbon adsorption. If powdered activated carbon (PAC) is used, it is crucial to retain the loaded PAC particles within the system and prevent PAC leakage into the environment. A range of different PAC separation processes is available today, but a systematic method comparison and derivation of practical recommendations is still missing. To fill this gap, we reviewed 27 pilot-, large- and full-scale PAC applications in the field of wastewater treatment with a specific focus on the implemented PAC separation processes. The operating conditions and removal efficiencies of all set-ups were collated and summarized. We also compared analytical methods to determine the residual PAC content in treatment plant effluents with regard to their sensitivity and selectivity. On this basis, recommendations were compiled to efficiently design and operate PAC separation stages and monitor their process quality.