In Germany, arsenic containing sludges originating from drinking water treatment are mostly disposed of in landfills, though from 2005 this will not be permitted any more due to restrictions of the German landfill directive. Therefore, an appropriate method for the handling of this kind of water works sludge was developed, which is environmentally acceptable, which conforms to the relevant legislation and which additionally saves costs. This method comprises treatment and utilisation of the water works sludge together with sewage sludge at a sewage treatment plant, where the sewage sludge is incinerated and the created ash is used for the filling of mines. The main economic advantage is that no additional investments at the water works, for example for further drying of the sludge, have to be undertaken, because the existing sludge treatment capacities at the waste water treatment plant can be used. Furthermore, there are cost savings because of the short ways between the water works and the waste water treatment plant and no landfill rates have to be paid any more. The ecologic advantage is that the water works sludge is used in mine filling together with the sewage sludge ash. At the same time, the arsenic is safely withdrawn from the biosphere on a long term basis.