Abstract
Iodinated contrast media (ICM), which are used for radiological visualization of human tissue and cardiovascular system, are poorly biodegradable; hence, new methods of their removal are sought. In this study, the effectiveness of selected X-ray ICM removal by means of UV and UV/TiO2 pretreatment processes from synthetic hospital wastewater was demonstrated. The following compounds were investigated: iodipamide, iohexol, and diatrizoate. The experiments were as follows: (i) estimated susceptibility of the ICM to decay by UV radiation in different aquatic matrices, (ii) determined an optimal retention time of hospital wastewater in the UV reactor, (iii) determined optimum TiO2 concentration to improve the effectiveness of the UV pretreatment, and (iv) investigated removal of ICM by combination of the photochemical and biological treatment methods. The quantum yields of selected ICM decay in deionized water (pH = 7.0) were established as 0.006, 0.004, and 0.029 for iohexol, diatrizoate, and iodipamide, respectively. Furthermore, the experiments revealed that diatrizoate and iohexol removal in the UV/TiO2 process is more efficient than in UV process alone. For diatrizoate, the removal efficiency equaled to 40 and 30 %, respectively, and for iohexol, the efficiency was 38 and 27 %, respectively. No significant increase in iodipamide removal in UV and UV/TiO2 processes was observed (29 and 28 %, respectively). However, highest removal efficiency was demonstrated in synthetic hospital wastewater with the combined photochemical and biological treatment method. The removal of diatrizoate and iohexol increased to at least 90 %, and for iodipamide, to at least 50 %.
Highlights
The occurrence and ecotoxicological effects of the pharmaceuticals in the aquatic environment have been defined as one of the most emerging problems in the environmental chemistry (Daughton and Ternes 1999; Halling-Sorensen et al 1998; Heberer 2002; Kummerer 151 Page 2 of 122001, 2009)
The selected Iodinated contrast media (ICM) represent to groups: iodipamide and diatrizoate are considered as ionic contrast media, while iohexol is considered as a nonionic contrast medium
3.1 Photolysis of Selected ICM in Aquatic Solution with Quantum Yield Determination. This part of the study determined the susceptibility of selected ICM to degradation by the polychromatic UV radiation, emitted by the medium-pressure Hg lamp
Summary
The occurrence and ecotoxicological effects of the pharmaceuticals in the aquatic environment have been defined as one of the most emerging problems in the environmental chemistry (Daughton and Ternes 1999; Halling-Sorensen et al 1998; Heberer 2002; Kummerer 151 Page 2 of 122001, 2009). More than 80 pharmaceutically active compounds, including iodinated X-ray contrast media, have been detected up to the microgram per liter levels in sewage, surface, and ground waters (Heberer 2002; Mompelat et al 2009). Iodinated X-ray contrast media (ICM) are frequently applied in clinical diagnosis for imaging soft tissues such as blood vessels and organs (Christiansen 2005). The structure of ICM is based on a benzene ring containing three iodine substituents which increase X-ray absorption and thereby allow for visualization of the organ or tissue. These polar atoms ensure high water solubility. In Germany alone, approximately 500 t annum−1 of ICM are applied (Schulz et al 2008), with hospital wastewater as the main source of ICM (Knodel et al 2011)
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