Environmental and economic assessment of electro-dewatering application to sewage sludge: A case study of an Italian wastewater treatment plant

The objective of this study is to evaluate the feasibility of implementing electro-dewatering (EDW) as an add-on unit to the existing conventional dewatering units with the aim of increasing the final dry solids content and reducing the subsequent handling and energy costs of sewage sludge management. The assessment was carried out by focusing on a case study, a small wastewater treatment plant (WWTP) in the Milan metropolitan area. Various indicators were used to evaluate the environmental impact and economic performance. Primary data, such as operating data from the case study WWTP and economic data from an EDW equipment manufacturer, were extracted and used in the modelling. Four scenarios were set up and compared, which address the current and future sludge management schemes in Italy. The results suggest that it is environmentally and economically feasible to implement the EDW up-grade if the sludge disposal follows the incineration route. More specifically, when small WWTPs deliver their EDW-dewatered sludge to a centralised incineration facility, this will enable to reduce the global warming impact of the system up to 135 kg CO2-eq. per dry tonne of sludge. In addition, good profit-ability (incremental return on investment > 15.1%) can be obtained when the market disposal cost is above 30.5-39.6 (sic) per wet tonne of sludge. Based on our recent market survey, the sludge disposal price is well above the break-even values. (C) 2018 Elsevier Ltd. All rights reserved.