Abstract
X-RCM are pharmaceuticals used for displaying soft-tissue or vessels which otherwise would give insufficient contrast in x-ray imaging. Most often they are derivatives of the triiodobenzoic acid and can be classified into ionic compounds with a free acid group and non-ionic compounds where all substituents fo the benzene ring are non-ionisable hydrophilic chains. Since they are applied at high dosages and are renally excreted un-metabolized almost quantitatively within one day the X-RCM are the pharmaceuticals appearing most fre-quently in the aquatic environment. Because of their metabolic stability, high polarity and persistence X-RCM can be found in raw water sources of waterworks. In German rivers X-RCM are detected in concentrations up to several µg/L depending on the waste water fraction. The River Rhine shows almost constantly concen-trations between 20 and 200 ng/L, whereby non-ionic X-RCM are prevalent. Rivers with a high waste water fraction (e.g. Körsch, 70 % waste water), however, contain much higher levels (up to 1,5 µg/L). Municipal sewage plants are not able to eliminate X-RCM sufficiently, neither are they degraded during river bank fil-tration. Furthermore, more advanced technologies such as activated carbon filtration are also insufficient in eliminating X-RCM. X-RCM are not retained during ultrafiltration, only nanofiltration results in a 90 % reduc-tion of concentrations with the side effect of deionizing the water, however. Oxidation technologies such as ozonation as used in waterworks nowadays are not able to totally eliminate X-RCM. Therefore X-RCM are detected in measurable concentrations in drinking water as well. At the TZW further experiments are carried out concerning the oxidation of X-RCM; technologies applied include AOP such as ozone/H2O2, UV-irradiation combined with ozone or H2O2 etc.