Journal
JOURNAL OF ENVIRONMENTAL MANAGEMENT
Volume 281, Issue -, Pages -Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2020.111910
Keywords
Hydrothermal carbonization; Sewage digestate; Sludge dewaterability; Biochemical methane potential; Sludge management
Categories
Funding
- ECOOPERA Coop
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The study found that increasing the hydrothermal carbonization (HTC) treatment time can improve the dewaterability of the treated slurry, but it also results in an increase in ammonium concentration in the HTC liquor (HTCL) and a decrease in methane potential. A treatment time of 1 hour was identified as the optimal trade-off for dewaterability and utilization of HTCL for biogas production.
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 degrees 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 degrees 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.
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