In order to meet the environmental legislative framework in force in Europe and reduce sludge processing and disposal costs, several sludge treatment technologies and management strategies have been proposed in the last two decades. The evaluation of their technical and economic suitability, case by case, may be a challenge, since many aspects are involved, so that a robust decision support system should be used. Within the ROUTES project (founded within the EU Seventh Framework Programme), the authors have developed an assessment procedure which allows rating several technical factors (such as system reliability, complexity, safety aspects, modularity, etc.) and estimating capital and operating costs, in case a plant is being upgraded. The comparison between the original (reference) plant and the modified configuration informs about technical hot spots (which are expressed by a traffic light-type colour code) and cost gaps resulting from the implementation of the new solution.