Optimization of the treatment and disposal of sewage sludge in the ATO of Como: options and scenarios assessment.

9 Abstract Sludge produced by municipal wastewater treatment plants (WWTPs) amounts to only a few percent by volume of the processed wastewater, but its management accounts for up to 50% of total operating costs. Innovative solutions are being studied in order to minimize its production and to find new dis- posal ways which are more cost-effective and less impacting on the environment. In the Province of Como, sludge management is one of the main issues. In this work, the situation is described, mainly referring to the biggest plants, both in quantitative and qualitative terms. Then actu- al disposal routes are analyzed, which mainly concern agricultural reuse. New treatment and disposal solutions are assessed, mainly concentrating on thermal conversion processes: incineration and pyrol- ysis/gasification. Sludge management scenarios are simulated, taking into account chains of technolo- gies and analyzing the final economic and environmental results. Furthermore, varying some simula- tion parameters, a sensitivity analysis is provided. Thermal conversion processes and electrodewatering seem to be cost-effective technologies which can be further investigated for a comprehensive project of diversification of sludge disposal routes in the ATO of Como. Finally, the problem of transparent and clear data gathering is mentioned, with the aim of developing a new WWTPs database, called SYST&MS. Keywords: sludge – disposal – incineration – pyrolysis – electrodewatering – database