Trace organic contaminants removal from municipal wastewater using the FluHelik reactor: from laboratory-scale to pre-pilot scale

The main goal of this study is to evaluate the feasibility of the innovative FluHelik photoreactor for the removal of antimicrobial drugs at residual concentrations using a photochemical UVC/H2O2 process. Experiment studies were performed using either pure water (PW) or secondary effluent from municipal wastewater treatment plant (EW) fortified with gatifloxacin (GAT) (100 μg L-1) as a model antimicrobial contaminant. Initially, the efficiency of the UVC/H2O2 process towards GAT removal as a function of UVC lamp power (4-11 W), H2O2 dose (25-200 mg L-1), flow rate (20-180 L h-1), flow mode (single vs multiple pass) and matrix (PW or EW) was assessed. Afterwards, the system efficiency was evaluated according to engineering features such as association of reactors in series and scale-up design. The performance of the FluHelik reactor was quantitatively measured through the use of a figure-of-merit, photochemical space-time yield (PSTY), that encompasses the three main contributing factors in UVC/H2O2 systems (i.e. throughput, energy efficiency and photochemical oxidation). In this context, FluHelik scale-up to pre-pilot scale proved to be feasible as similar PSTY values were obtained at both scales for assays performed with EW. In addition, the pre-pilot scale system was able to degrade all pharmaceutical compounds originally detectable in the EW matrix, reducing their concentrations to values below limit of detection. Finally, in order to test whether the treated solution might develop antibiotic resistance when in the environment, antimicrobial activity assays using bacterial cultures of Bacillus subtilis and Escherichia coli were investigated. The antimicrobial activity in the solutions dropped as the reaction time increased.