Dietrich Maier

Removal of Iodinated X-Ray Contrast Media During Drinking Water Treatment

Environmental Context.In recent years, many micro-organic pollutants, e.g. pharmaceuticals and personal care products (PPCP), have been observed to be persisting through wastewater treatment and occurring in the environment. Persistent micropollutants are of particular concern owing to the fact that some of them have been found in drinking water, and iodinated X-ray contrast media (ICM) are one group of such pollutants. Abstract.The present study investigates the removal of five iodinated X-ray contrast media (ICM) during drinking water production from surface water at a full-scale water works, which comprises coagulation/flocculation, intermediate ozonation, in-line filtration and adsorption with activated carbon. The elimination rates over all treatment units for the non-ionic ICM (iomeprol, iopromide, iohexol and iopamidol) were determined to be approximately 70%. In particular, intermediate ozonation can remove 30% on average of the non-ionic ICM, whereas it cannot remove the ionic diatrizoic acid, and the granulated activated carbon filters can achieve a further 50% removal of non-ionic ICM. However, over 100 ng L−1 of ionic diatrizoic acid and 40–100 ng L−1 of non-ionic ICM were found in the produced drinking water.

Factors influencing the mobilisation of polycyclic aromatic hydrocarbons (PAHs) from the coal-tar lining of water mains

Abstract Coal-tar was commonly used as an internal lining for corrosion protection of water pipes from the 19th century. In this project the principal mechanisms leading to the occurrence of Polycyclic Aromatic Hydrocarbons (PAHs) in those water mains were investigated. The results showed that the occurrence of PAHs in a distribution system was linked to the presence of the disinfectants chlorine and chlorine dioxide. In laboratory experiments it was demonstrated that the coal-tar surface represents a substrate for the growth of biofilms which exhibits protective effects. Generally, hostile environmental conditions for microbiological activity of the biofilm such as disinfection, stagnation periods and anaerobic conditions could be identified as important factors which favour the occurrence of PAHs in drinking water. Immediately after stagnation periods an increase of PAH concentrations was observed. Furthermore, it was clearly shown that disturbances in the hydraulic regime such as water hammers, operation of valves and rapid increases in flow velocity can result in enhanced PAH concentrations by the destabilisation of the biofilm matrix or high shear forces affecting the pipe walls resulting in the release of particles highly contaminated with PAHs which may be responsible for the contamination of the drinking water.