The fate of heavy metals in the Ruhr system and their influence on drinking water quality

The fate of heavy metals in the Ruhr basin is described from factory to drinking water. Due to elimination and retention processes the total nickel load, for example, is diminished from 500 tons per year in crude wastewater to only 20 t/a in river water close to the mouth. Heavy metal retention rates in subsoil are determined using boron as tracer element. In the sediments of river impoundments heavy metals are retained by 20%. In order to reduce remobilization processes it is suggested to restrict the application of organic complex-forming substances. Moreover, operation of existing industrial pretreatment plants has to be improved.