Design and preparation of advanced oxidation processes (AOPS) pilot scale trials for removal of pharmaceuticals from wastewater treatment effluent

Abstract

Pharmaceutical residues in treated wastewater are a concern because normal treatment processes are not designed for their removal. They can harm aquatic life and lead to antibiotic resistance. Regulatory measures now focus on advanced treatment techniques to eliminate these pollutants. Advanced oxidation processes (AOPs) show great potential for pharmaceutical removal. However, many AOP studies only focus on synthetic wastewater in lab scale which does not reflect the realistic condition. Therefore, studies using real wastewater effluent and pilot-scale processes are necessary. This thesis focused on preliminary testing of pilot-scale AOP trials for pharmaceutical removal from Mikkeli wastewater treatment plant (WWTP) effluent. The photocatalytic pilot unit was first tested with Rhodamine B (RhB). Dark adsorption (0.5 g/L TiO2), photolysis, and UV/TiO2 photocatalysis at low, medium and high UVA light intensity conditions of around 65, 210 and 350 mW/cm² were tested. Complete RhB removal was achieved at 210 and 350 mW/cm² light intensities during photocatalysis. Then, WWTP effluent was treated under the same experimental conditions. Target pharmaceutical analysis was not performed in this thesis. Instead, dissolved organic carbon (DOC), UV₂₅₄ absorbance, and fluorescence excitation-emission matrix (EEM) spectroscopy were used as surrogate parameters. These parameters did not directly measure pharmaceutical removal. They were used to compare treatments, narrow down the operating range, and choose the best preliminary settings before conducting expensive and time-consuming pharmaceutical analysis. The strongest changes were observed during UV/TiO2 photocatalysis, especially at 210 and 350 mW/cm² light intensities. At the end of photocatalytic treatment, UV₂₅₄ decreased more than DOC, with reductions of 83% and 81% compared with 43% and 37% at 210 and 350 mW/cm² light intensities, respectively. EEM results also showed 95-97% fluorescence intensity reduction after 180 min under higher light intensities (210 and 350 mW/cm²). Since medium light intensity (210 mW/cm²) performed similarly to high light intensity (350 mW/cm²) using 0.5 g/L TiO2, it was selected for future tests and target pharmaceutical sampling.