Coupling hydrothermal carbonization and anaerobic digestion for sewage digestate management: Influence of hydrothermal treatment time on dewaterability and bio-methane production

Mostafa Ahmed; Gianni Andreottola; Sherien Elagroudy; Mohamed Shaaban Negm; Luca Fiori

doi:10.1016/j.jenvman.2020.111910

Coupling hydrothermal carbonization and anaerobic digestion for sewage digestate management: Influence of hydrothermal treatment time on dewaterability and bio-methane production

J Environ Manage. 2021 Mar 1:281:111910. doi: 10.1016/j.jenvman.2020.111910. Epub 2021 Jan 2.

Authors

Mostafa Ahmed¹, Gianni Andreottola², Sherien Elagroudy³, Mohamed Shaaban Negm⁴, Luca Fiori⁵

Affiliations

¹ Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123, Trento, Italy; Public Works Department, Faculty of Engineering, Ain Shams University, 1 ElSarayat St., Abassia, Cairo, Egypt.
² Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123, Trento, Italy.
³ Public Works Department, Faculty of Engineering, Ain Shams University, 1 ElSarayat St., Abassia, Cairo, Egypt; Egypt Solid Waste Management Center of Excellence, Ain Shams University, 1 ElSarayat St., Abassia, Cairo, Egypt.
⁴ Public Works Department, Faculty of Engineering, Ain Shams University, 1 ElSarayat St., Abassia, Cairo, Egypt.
⁵ Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123, Trento, Italy. Electronic address: luca.fiori@unitn.it.

PMID: 33401118
DOI: 10.1016/j.jenvman.2020.111910

Abstract

Hydrothermal carbonization (HTC) technology is addressed in the framework of sewage digestate management. HTC converts digestate into a stabilized and sterilized solid (the hydrochar) and a liquor (HTCL) rich in organic carbon. This study aims to optimize the HTC operating parameters, namely the treatment time, in terms of hydrochar production, HTC slurry dewaterability, HTCL bio-methane yields in anaerobic digestion (AD), and process energy consumption. Digestate slurry was processed through HTC at different treatment times (0.5, 1, 2 and 3 h) at 190 °C, and the dewaterability of the treated slurries was addressed through capillary suction time and centrifuge lab-testing. In addition, biochemical methane potential (BMP) tests were conducted for HTCL under mesophilic conditions. Results show that by increasing the HTC treatment time the dewaterability was further improved, ammonium concentration in HTCL increased, and methane potential of HTCL decreased. 0.5 h HTCL had the highest bio-methane potential of 142 ± 3 mL CH₄/g COD yet the treatment time was not sufficient for improving the slurry's dewaterability. HTC treatment time of 1 h at 190 °C was identified as the optimum trade-off for improved dewaterability and utilisation of HTCL for biogas production. 1 h HTCL bio-methane potential can cover around 25% of the HTC and AD thermal and electrical energy needs without considering the eventual use of the hydrochar as a biofuel.

Keywords: Biochemical methane potential; Hydrothermal carbonization; Sewage digestate; Sludge dewaterability; Sludge management.

MeSH terms

Anaerobiosis
Biofuels
Carbon
Methane*
Sewage*

Substances

Biofuels
Sewage
Carbon
Methane