Industrial-Scale Hydrothermal Carbonization of Agro-Industrial Digested Sludge: Filterability Enhancement and Phosphorus Recovery

Michela Lucian, Fabio Merzari, Michele Gubert, Antonio Messineo and Maurizio Volpe
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Michela Lucian: Carborem Srl, Piazza Manifattura 1, 38068 Rovereto, Italy
Fabio Merzari: Carborem Srl, Piazza Manifattura 1, 38068 Rovereto, Italy
Michele Gubert: Carborem Srl, Piazza Manifattura 1, 38068 Rovereto, Italy
Antonio Messineo: Facoltà di Ingegneria e Architettura, Università degli Studi di Enna “Kore”, Cittadella Universitaria, 94100 Enna, Italy
Maurizio Volpe: Carborem Srl, Piazza Manifattura 1, 38068 Rovereto, Italy

Sustainability, 2021, vol. 13, issue 16, 1-15

Abstract: Hydrothermal carbonization (HTC) provides an attractive alternative method for the treatment of high-moisture waste and, in particular, digested sludge. HTC could reduce the costs and environmental risks associated with sludge handling and management. Although it is recognized that the dewaterability of hydrochars produced from digested sludge, even at mild temperatures (180–190 °C), is highly improved with respect to the starting material, the filterability of HTC slurries for the recovery of the solid material (hydrochar) still represents a challenge. This study presents the results of an investigation into the filterability of agro-industrial digested sludge HTC slurries produced by a C-700 Carborem TM HTC industrial-scale plant. The filterability of HTC slurries, produced at 190 °C for 1 h, with the use of acid solutions of hydrochloric acid, sulfuric acid or citric acids, was investigated by using a semi-industrial filter press. The use of sulfuric acid or citric acid solutions, in particular, significantly improved the filterability of HTC slurries, reducing the time of filtration and residual moisture content. The acid treatment also promoted the migration of heavy metals and phosphorus (P) in the HTC filtrate solution. This study demonstrates that P can be recovered via the precipitation of struvite in high yields, recovering up to 85 wt% by mass of its initial P content.

Keywords: hydrothermal carbonization; digested sludge; citric acid; hydrochar filterability; phosphorus recovery; struvite; heavy metals removal; dewaterability (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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