Effects of wastewater composition and reactor operating mode on the removal of micropollutants via electrochemical advanced oxidation

When implementing an electrochemical Advanced Oxidation Process (eAOP) for wastewater treatment, the composition of the wastewater to be treated and the selection of the reactor operating mode are key parameters to be considered given their strong influence on the degradation kinetics, energy consumption, operating costs and environmental impacts. To this end, this study investigated the degradation of carbamazepine (CBZ) in different matrices (i.e., pure water vs. synthetic secondary effluent, high vs. low organic/ion content, single vs. multicomponent systems) and under several reactor operating modes (i.e., batch, fed-batch and continuous). The key findings of this research are (i) the self-cleaning capabilities that naturally occurring ionic species in wastewater (i.e., sulfate and nitrate ions) offer even if present at low concentrations and (ii) the significant performance implications resulting from the reactor operation selection. By combining both insights, this study illustrates the opportunities for developing more efficient eAOPs where no additional chemicals are needed, and hence, where secondary waste streams can be mitigated, while energy consumption is minimized and degradation efficiency is enhanced. In particular, treating CBZ-polluted secondary wastewater effluent in fed-batch mode could lead to up to a 2.1-fold increase in degradation and a 60 % reduction in energy with respect to a batch equivalent, despite the hindering effects that competition reactions from other wastewater constituents entailed.