Document Type

Article

Publication Date

2026

DOI

10.1002/wer.70313

Publication Title

Water Environmental Research

Volume

98

Issue

2

Pages

e70313 (1-11)

Abstract

Although hydrothermal liquefaction (HTL) is the leading technology in converting wet biomass into bioenergy, the treatment of its toxic-laden aqueous phase wastewater presents a major challenge on its path toward commercial viability. This study presents the first-ever assessment of sewage sludge-fed HTL wastewater (SS-HTLWW) treatment and toxic compound removal using municipal activated sludge (AS) by optimizing its cultivation condition. It was found that AS with optimized pretreatment can remove up to 91.2% of the soluble chemical oxygen demand (sCOD) in SS-HTLWW, of which up to 82% can be attributed to biological mineralization and adsorption of sCOD by AS. Conventional bioprocess optimization techniques, including overliming, elevated temperatures, and nutrient supplementation, were found to raise the maximum rate of sCOD utilization (Rm) of AS treatment by 44%, 67%, and 45%, respectively. The variation in the maximum degradation potential (Dmax) after 23 days of treatment across all groups was negligible. Adjusting the SS-HTLWW dilution factor from 20× to 10× resulted in no significant difference in Rm or Dmax values due to the counteracting effects of high substrate and inhibitor concentrations. Additionally, AS was able to eliminate almost all N-heterocycles, phenolic compounds, and organic acids found in SS-HTLWW. This suggested that AS can both survive in and mitigate the high level of toxicity associated with SS-HTLWW; however, the high levels of recalcitrant COD after treatment may require further attention before it can be adequately discharged. The insights gained from this study are poised to interest engineers and treatment plant operators in search of efficient strategies for SS-HTLWW management and the broader application of HTL.

Rights

© 2026 The Authors.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Data Availability

Article states: "The data that support the findings of this study are available from the corresponding author upon reasonable request."

ORCID

/0000-0003-3173-6101 (Kumar), 0000-0001-5587-2533 (Umeda)

Original Publication Citation

Li, C., Wang, J., Liu, M., Zheng, Y., Kumar, S., Umeda, I., Mahata, C., Norton, J., & Wang, Z. W. (2026). Harnessing activated sludge for the treatment of hydrothermal liquefaction wastewater: A proof-of-concept study. Water Environmental Research, 98(2), 1-11, Article e70313. https://doi.org/10.1002/wer.70313

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