Photocatalytic Treatment of Pharmaceuticals in Real Hospital Wastewaters for Effluent Quality Amelioration

Konstas Konstas,Albanis Albanis,Konstantinou Konstantinou,Kosma Kosma

doi:10.3390/w11102165

Abstract

The presence of pharmaceutically active compounds (PhACs) in the wastewater effluents has confirmed that conventional wastewater treatment technologies are not sufficiently effective in the pharmaceuticals’ removal. The objective of the present study was to evaluate and compare the photocatalytic degradation of PhACs using TiO2-P25, graphitic carbon nitride (g-C3N4, CN) and a heterojunction of perovskite strodium titanate and graphitic carbon nitride SrTiO3/g-C3N4 (20% g-C3N4, 20CNSTO) photocatalytic materials, in hospital wastewater effluents, by simulated solar irradiation. The experiments were performed by using real wastewater samples collected from the university hospital wastewater treatment plant (WWTP) effluent of Ioannina city (Northwestern Greece) and inherent pharmaceutical concentration levels. The analysis of the samples was accomplished by solid phase extraction followed by liquid chromatography-Orbitrap high-resolution mass spectrometry. In the cases of TiO2 and CN, more than 70% of the initial concentration (e.g., venlafaxine) was degraded after 90 min, while 20CNSTO presented lower photocatalytic performance. Furthermore, some compounds were sporadically detected (e.g., fluoxetine) or their concentrations remained stable during the photocatalytic treatment time period (e.g., trimethoprim). In total 11 transformation products (TPs) were formed along the degradation processes and were identified by using liquid chromatography high resolution mass spectrometry.

Highlights

Hospital wastewaters (HWW) are known as one of the main sources of pharmaceutical active compounds (PhACs) in the environment [1,2]
In view of the above, this study focuses on the application of photocatalysis for pharmaceutically active compounds (PhACs) removal in real unspiked HWW effluents by combining simulated solar light and different photocatalytic semiconductors
The aims of the present work are: (i) To identify the PhACs present in real HWW effluents by solid phase extraction tandem liquid chromatography coupled to high-resolution mass spectrometry (SPE/LC-HRMS) analytical methodology; (ii) to evaluate and compare the photocatalytic degradation of PhACs under different semiconductors; TiO2 -P25, graphitic carbon nitride (g-C3 N4, CN) and a heterojunction of perovskite and graphitic carbon nitride, SrTiO3 /g-C3 N4 (20% g-C3 N4, 20CNSTO) in HWW effluents using simulated solar irradiation; (iii) to identify the transformation products (TPs) formed in the different photocatalytic processes by means of LC-HRMS

Summary

Introduction

Hospital wastewaters (HWW) are known as one of the main sources of pharmaceutical active compounds (PhACs) in the environment [1,2]. HWW is a complex water matrix, burdened with high concentrations of pharmaceuticals and metabolites, disinfectants, heavy metals, reagents, microorganisms, etc. Conventional wastewater treatment plants (WWTPs) are not manufactured to treat water containing pharmaceuticals at trace levels and the applied treatments have been found to be ineffective to remove them [1,5]. Pharmaceuticals in hospital effluents exist in low concentrations (may vary from ng L−1 to mg L−1 ), they might pose a potential threat to the ecology of the receiving environment, such as feminization of organisms, microbiological resistance or the accumulation of these compounds in. The presence of pharmaceuticals in the environment does not need to be persistent in order to cause negative effects, since the high degree of transformation or removal that they are able to incur can be overlapped by their continuous release into the environment [4]

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Conclusion