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

Abstract

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 upgrade 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 profitability (incremental return on investment > 15.1%) can be obtained when the market disposal cost is above 30.5-39.6 € per wet tonne of sludge. Based on our recent market survey, the sludge disposal price is well above the break-even values.

Biosolids: What are the different types of reuse?

“…Therefore, in last few years, BS reuse in agriculture has declined or even stopped in some European countries such as Finland, Slovenia, Sweden, the Netherlands, Greece and Belgium and stricter regulations have been introduced (Praspaliauskas and Pedi sius, 2017; Tyagi and Lo, 2011). This aspect is due to consumer's demand on food safety and quality (Zhang et al, 2019). Moreover, the potential presence of organic and inorganic micropollutants caused a strong opposition from the farmers and food industries, fearing that the soil would be contaminated and not utilizable for food production (Aemig et al, 2019).…”

What Advanced Treatments Can Be Used to Minimize the Production of Sewage Sludge in WWTPs?

“…For minimizing the production of SS, electrochemical treatments are generally coupled with the use of pressure. Among the pressurized electro-dewatering treatments, electro-osmosis is arousing a growing interest [120][121][122].…”

Life cycle assessment applied to waste management in Italy: A mini-review of characteristics and methodological perspectives for local assessment

“…The return of wastewater to the environment after treatment through irrigation (Moretti et al, 2019), by digestate (Monlau et al, 2015) or other products (Valentino et al, 2017) is also investigated. Footprints (Caivano et al, 2017; Caniani et al, 2019), economic (Zhang et al, 2019) and social (Di Maria and Sisani, 2019) aspects are also analysed.…”