Process water properties from hydrothermal carbonization of chemical sludge from a pulp and board mill

Mikko Mäkelä*, Julia Forsberg, Christer Söderberg, Sylvia H. Larsson, Olli Dahl

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

17 Citations (Scopus)
177 Downloads (Pure)


Hydrothermal carbonization (HTC) can be used to break down sludge structure and generate carbonaceous hydrochar suitable for solid fuel or value-added material applications. The separation of char and the reaction medium however generates a filtrate, which needs to treated before potential discharge. Thus, this work determined filtrate properties based on HTC temperature and sludge moisture content and estimated the discharge emissions and the potential increase in analyte loads to an industrial wastewater treatment plant based on derived regression models. Direct discharge of HTC filtrate would significantly increase effluent emissions at the mill, indicating the filtrate treatment is crucial for the future implementation of HTC at pulp and paper mills. Recycling the HTC filtrate to the wastewater plant would lead to only a nominal increase in effluent flow, but would increase the suspended solids, BOD, COD and total nitrogen loads by 0.1–0.8%, 3.8–5.3%, 2.7–3.1% and 42–67%, respectively, depending on HTC temperature.

Original languageEnglish
Pages (from-to)654-659
JournalBioresource Technology
Publication statusPublished - Sept 2018
MoE publication typeA1 Journal article-refereed


  • Biosolids
  • Experimental design
  • Hydrothermal treatment
  • Multiple linear regression
  • Principal component analysis
  • Wastewater treatment


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