Production and Destination of Sewage Sludge in the Piemonte Region (Italy): The Results of a Survey for a Future Sustainable Management

Abstract

The management of sewage sludge originated from municipal wastewater treatment plants (WWTPs) is an urgent issue. In 2019, the local authority of the Piemonte region started a survey with the aim of collecting recent data concerning wastewater and sludge management in the WWTPs located in its own territory. The survey’s results revealed that 60% of the sludge (51,000 t, as dry substance, d.s.) produced by the local WWTPs was recovered or disposed of outside of the region, and a similar amount of sludge was recovered in agriculture directly or after composting. The increase in the costs to accommodate sewage sludge in recovery or disposal plants, followed to a recent Italian Sentence (27958/2017), and the more and more stringent requirements fixed by lots of European countries for the application of sludge in agriculture, are pushing the Piemonte region authority to re-organize its own network for sludge management, with solutions based onto proximity and diversification. Whether the provisions of the current German legislation are applied in the future also in Italy, approx. 90% of sewage sludge produced into the Piemonte region should be incinerated, with a subsequent step of phosphorous recovery. The new regional plan, according to the Regional Address Deed, should consider a diversification of sludge treatment and recovery practices. On this basis, a need for new plants for around 40,000 t d.s./y could be planned.

Sewage Sludge Management at District Level: Reduction and Nutrients Recovery via Hydrothermal Carbonization

“…Among all possible strategies, hydrothermal carbonization (HTC) of municipal sewage sludge has been recently recognized as a promising technology for efficient waste volume reduction and recovery of bioenergy and nutrients [ 6 , 7 ], such as phosphorus and nitrogen. HTC is a thermochemical process in which moist biomass is carbonized at a temperature between 180 and 250 °C and a reaction time of 0.5–8 h at saturated vapor pressure, leaving the water in the liquid phase.…”

“…In this context, the increasing management costs and environmental problems make urgent the application of innovative solutions for the development of technologies for the valorization, reduction and safe disposal of sewage sludge. Among all possible strategies, hydrothermal carbonization (HTC) of municipal sewage sludge has been recently recognized as a promising technology for efficient waste volume reduction and recovery of bioenergy and nutrients [6,7], such as phosphorus and nitrogen. HTC is a thermochemical process in which moist biomass is carbonized at a temperature between 180 and 250 °C and a reaction time of 0.5-8 h at saturated vapor pressure, leaving the water in the liquid phase.…”

Analysis of the variation of costs for sewage sludge transport, recovery and disposal in Northern Italy: a recent survey (2015–2021)

“…Once treated, sludge is managed mainly by recovery and reuse in agriculture or for energy production by means of incineration, or disposed of by landfilling (Ciesĺik et al 2015;Shaddel et al 2019). The most practiced route for sludge management in Europe is the reuse on land (Eurostat 2021), regulated by the Sewage Sludge Directive 86/278/EEC (Bianchini et al 2016;Collivignarelli et al 2020;Campo et al 2021). The flexibility in national implementation provided by the Directive resulted in a variety of approaches and limit values adopted by each member State (Hudcová et al 2019;Gianico et al 2021).…”

“…In Italy, over time, regulations posed more restrictive limits for the reuse of sludge in agriculturesuch as the recent Law 109/2018 (Italian Parliament 2018) that introduced new limits for hydrocarbons, some organic micropollutants and restricted limit values for some heavy metals. However, improved technologies related to digestion, dewatering and thickening in the sludge line of WWTPs enhanced the potential of its recovery such as for energy production, together with higher competition and increased demand which affected the cost of sludge management (Campo et al 2021).…”

Sewage Sludge as N-Fertilizers for Crop Production Enabling the Circular Bioeconomy in Agriculture: A Challenge for the New EU Regulation 1009/2019

“…Nevertheless, not all sewage sludge is produced by the biological treatment of municipal wastewaters: it can also be produced by manufacturing activities (e.g., food, pharmaceutical, chemical and textile industries). For example, about 10 million tonnes (dry matter) of municipal sewage sludge are produced annually in Europe (EU-28) [17], whereas the food industries in Europe generate about 20 million (dry matter) tonnes of sewage sludge [18]. Industrial wastewaters usually result from standardized production processes, and their quality, as well as the quality of the resulting sewage sludge is often higher than that of municipal wastewaters and municipal sewage sludge.…”