Publication Details

AFRICAN RESEARCH NEXUS

SHINING A SPOTLIGHT ON AFRICAN RESEARCH

Aqueous Phase from Hydrothermal Liquefaction: Composition and Toxicity Assessment

Water (Switzerland), Volume 15, No. 9, Article 1681, Year 2023

The main obstacle to the widespread use of hydrothermal liquefaction (HTL) for waste and wet biomass recycling is the formation of a significant amount of highly polluted wastewaters. This paper presents an analysis of the chemical composition and toxicity of aqueous phase from the HTL (HTL-AP) of primary and secondary sludge. It was shown that HTL-AP has a high level of organic pollution (total organic carbon (TOC) = 4.2–9.6 g/dm3, chemical oxygen demand (COD) = 7.9–14.0 g/dm3, BOD5 = 6.0–8.1 g/dm3) and high biological toxicity for traditional test organisms (so that dilution ratio, ensuring the death of no more than 50% of organisms (DR50), varied within 64.7–142.2 and 44.9–81.7 for Artemia salina and Paramecium caudatum, respectively). An analysis of HTL-AP composition with NMR-spectroscopy method allowed us to establish that the share of carbon in aliphatic chains was 34.05–41.82% and the content of carbon in carboxyl groups and aromatic rings was 26.42–34.44%. As a result, we can conclude that the main HTL-AP components are fatty carboxylic acids and their derivatives, aromatic carboxylic acids. The content of aldehydes, ketones, and lignin is less than 8%. Biological treatment of HTL-AP in a lab-scale aerobic reactor turned out to be successful, so average COD reduction was 67–95%. Sludge from an industrial waste water treatment plant (petrochemical sector) with a microorganism concentration of 2.7 g/dm3 was used as inoculum. HTP-AP was diluted 1:10 with tap water. The duration of the process was 18 h.
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Citations: 8
Authors: 8
Affiliations: 6
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Environmental