Personal hygiene products, drugs, pesticides, leftover paint: many things we use every day leave traces in the water if they enter the body of water as human waste, industrial sewage, percolation from agricultural surfaces, or from other sources. With modern methods of analysis, these so-called micro-pollutants can be traced down to the range of a few nanograms (parts in a billion) per litre of water.
The IWW Water Centre1 in Mülheim and the Institute for Environmental Engineering at Aachen University2 recently carried out a major study on these tiny particles. They investigated the concentration in which the effective agents of some commonly used drugs, X-ray contrast mediums, and flame retardants can be identified in the River Ruhr.
They found that the concentration of these particles in the Ruhr was far below the value defined by the German Drinking Water Commission ("Deutsche Trinkwasser-kommission") as being safe for a life-long use as drinking water. Nonetheless, the Ruhrverband with support from the North Rhine-Westphalian Ministry of the Environment is currently testing more processes for removing micro-pollutants from waste water. In a pilot experiment at the Schwerte sewage treatment plant, oxidation and adsorption processes will soon be tested under service conditions; the results will be compared to the ones achieved by conventional sewage treatment. Not only the methods of analysis, but also the processes for removing trace residue are thus constantly under review. At the same time, it seems rather unlikely that micro-pollutants can ever be completely removed from the water. The concentrations in which the currently known compounds are present in the Ruhr, however, are harmless for both human beings and the environment.
1 Rheinisch-Westfälisches Institut für Wasser - IWW Zentrum Wasser
2 Institut für Siedlungswasserwirtschaft der RWTH Aachen