Capability of shallow open-water unit for emerging contaminants attenuation and ecological safety improvement in a treated effluent polishing process. (April 2021) - Wang, Yongkun K.
Graphical abstract: Highlights: Shallow open water unit was operated for quality polishing of treated effluent. Remarkable removal of emerging contaminants (achieved under natural condition. ECs removal was associated with fast re duction of acute toxicity and genotoxicity. Biotoxicity attenuation might be due to chromophoric and aromatic compounds decay. Abstract: Nature-based solutions of polishing treated effluent are drawing increased attention because of their potential to mitigate ecological risks, and the shallow open water unit (SOWU) process is one of the most promising options. In this study, a pilot experiment was conducted to assess the efficiency of SOWU for effluent quality polishing in a municipal wastewater treatment plant targeting 33 residual emerging contaminants (ECs) that were categorized into six groups, namely pharmaceuticals, sunscreens, bactericides, pesticides, flame retardants and phenols. In the 14-day monitoring period, each of the ECs decayed following a first order reaction, and about 61 % total ECs removal was achieved, indicating the remarkable photolysis effect of the SOWU under natural conditions. The significant removal of ECs, especially the very high removals of pharmaceuticals (76 %) and sunscreens (77 %), was associated with the attenuation of both the acute luminescent bacterial toxicity and genotoxicity. From the linear relationship between the acute toxicity and chromophoric dissolved organic matter and that between genotoxicity and UV absorbance at 254 nm, it was likely that the attenuation of biotoxicities resulted from the decay of chromophoric and aromatic compounds. By analyzing several reactive species, the excellent photoreactivity of the SOWU was further identified.