Separating powdered activated carbon (PAC) from wastewater - Technical process options and assessment of removal efficiency

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.