Phototransformation of selected pharmaceuticals during UV treatment of drinking water.
The kinetics of Ultraviolet C (UV-C)-induced direct phototransformation of four representative pharmaceuticals, i.e., 17alpha-ethinylestradiol (EE2), diclofenac, sulfamethoxazole, and iopromide, was investigated in dilute solutions of pure water buffered at various pH values using a low-pressure and a medium-pressure mercury arc lamp. Except for iopromide, pH-dependent rate constants were observed, which could be related to acid-base equilibria. Quantum yields for direct phototransformation were found to be largely wavelength-independent, except for EE2. This compound, which also had a rather inefficient direct phototransformation, mainly underwent indirect phototransformation in natural water samples, while the UV-induced depletion of the other pharmaceuticals appeared to be unaffected by the presence of natural water components. At the UV-C (254 nm) drinking-water disinfection fluence (dose) of 400 Jm(-2), the degree of depletion of the select pharmaceuticals at pH=7.0 in pure water was 0.4% for EE2, 27% for diclofenac, 15% for sulfamethoxazole, and 15% for iopromide, indicating that phototransformation should be seriously taken into account when evaluating the possibility of formation of UV transformation products from pharmaceuticals present as micropollutants.
Canonica
Silvio
S
Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland. canonica@eawag.ch
Meunier
Laurence
L
von Gunten
Urs
U
D004008:Diclofenac / Q000528:radiation effects*; D004997:Ethinyl Estradiol / Q000528:radiation effects*; D007472:Iohexol / Q000031:analogs & derivatives* / Q000528:radiation effects; D013420:Sulfamethoxazole / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000528:radiation effects*; D018508:Water Purification / Q000379:methods
D014874:Water Pollutants, Chemical; D004008:Diclofenac; D004997:Ethinyl Estradiol; D007472:Iohexol; C038192:iopromide; D013420:Sulfamethoxazole