Financing investment needs during the next 20 years for Integrated Water Service facilities which includes aqueducts, sewers, drinking water as well as wastewater treatment plants (WWTPs), is a significant challenge for government institutions all over the world. There is an urgent need for new approaches to help decisions makers in order to evaluate the quality and efficiency of these infrastructures and consequently planning investments in the best possible way. Taking into account only the municipal wastewater sector in Italy, the aim of this study was to develop and apply a planning support tool to numerous WWTPs based on secondary biological processes, able to: (i) assess the plants efficiency identifying also their environmental and technological critical issues; (ii) propose technical solutions through the definition of appropriate Action Plans; (iii) simulate WWTPs improvements quantifying the results of the proposed upgrade and; (iv) extend the results of the WWTPs efficiency evaluation on a regional scale comparing the performance of each District by means of specific indices (technological equipment, legal requirement compliance, treatment capacity). Our main hypothesis was that the evaluation of quality as well as the efficiency of the wastewater treatment facilities is the basis for the estimation of investments. We applied this methodology to large Italian municipal WWTPs with a treatment capacity greater than a 50,000 population equivalent (PE) even though it is possible to consider smaller facilities (excluding small wastewater treatment systems generally with a PE less than 2000 inhabitants). Our results demonstrate that the tool can be implemented using official data such as those provided by the National Institute of Statistics (ISTAT) although some verification is required. Finally, the paper addresses the policy implications due to the methodology application highlighting the importance of having well-defined planning support tools especially for those areas needing further social cohesion policies. The developed case study shows the suitability of our proposal for governmental institutions and water utility companies in Italy, however it could also be extended to other countries. © 2014 Elsevier Ltd.

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