An innovative microbial electrochemical ultraviolet photolysis cell (MEUC) for efficient degradation of carbamazepine

Abstract

Discharge of recalcitrant pharmaceuticals into aquatic environments can lead to serious negative environmental effects. While traditional wastewater treatment plants (WWTPs) are efficient for a wide range of non-toxic pollutants (i.e. ammonia), some wastewater streams contain recalcitrant toxic trace micropollutants such as pharmaceuticals that cannot be removed by the treatment processes that are typically employed in common WWTPs. Herein, an innovative 20 L microbial electrochemical ultraviolet photolysis cell (MEUC) was developed for the first time by the integration of a UV irradiation and a bioelectrochemical system, which exhibited efficient treatment of carbamazepine-a model pharmaceutical compound. Notably, neither the UV irradiation nor the bioelectrochemical system alone could effectively eliminate carbamazepine. The effect of operational parameters including applied voltage, cathodic aeration rate, UV intensity, and hydraulic retention time were evaluated. The obtained results elucidated that the degradation of carbamazepine was consistent with pseudo-first-order reaction kinetics, and required a lower energy input than traditional advanced oxidation processes. Five main transformation products were identified, and probable transformation pathways were established. Furthermore, the eco-toxicity as tested by Vibrio fischeri showed no significant bioluminescence inhibition by the treated carbamazepine effluent. Finally, the MEUC system was further tested with a real wastewater matrix, which again exhibited effective removal of carbamazepine. This paper provides a proof-of-concept verification of the novel MEUC system, which contributes insight for the subsequent vigorous development of the application of such efficient and cost-effective technologies for the treatment of trace pharmaceuticals wastewater.