Hydrothermal carbonization (HTC) technology can convert various types of waste biomass into a carbon-rich product referred to as hydrochar. In order to verify the potential of hydrochar produced from stabilized sewage sludge to be an adsorbent for bacterial pathogen removal in water treatment, the Escherichia coli's removal efficiency was determined by using 10 cm sand columns loaded with 1.5% (w/w) hydrochar. Furthermore, the removal of E. coli based on intermittent operation in larger columns of 50 cm was measured for 30 days. Since the removal of E. coli was not sufficient when the sand columns were supplemented with raw hydrochar, an additional cold-alkali activation of the hydrochar using potassium hydroxide was applied. This enabled more than 90% of E. coli removal in both the 10 cm and 50 cm column experiments. The enhancement of the E. coli removal efficiency could be attributed to the more hydrophobic surface of the KOH pre-treated hydrochar. The idle time during the intermittent flushing experiments in the sand-only columns without the hydrochar supplement had a significant effect on the E. coli removal (p < 0.05), resulting in a removal efficiency of 55.2%. This research suggested the possible utilization of hydrochar produced from sewage sludge as an adsorbent in water treatment for the removal of bacterial contaminants.@en

Aims: To determine the pathogenic virus removal performance of an adsorbent produced from hydrothermal carbonization of sewage sludge. Methods and Results: The removal of human pathogenic rotavirus and adenovirus was investigated with columns of 10 cm saturated sand with and without amendments of 1·5% (w/w) hydrochar. Virus concentrations were determined with reverse transcription (RT) quantitative polymerase chain reaction (qPCR). The experiments with sand showed 1 log removal, while the columns with 1·5% (w/w) hydrochar amendment showed 2 to >3 log removal for both viruses. Deionized (DI) water flushing into the virus-retaining columns revealed that the secondary energy minimum played a larger role in the attachment of rotavirus onto hydrochar surfaces than adenovirus. Improved virus removal may be attributed to the introduction of hydrophobic and/or meso-macro surface structures of the hydrochar providing favourable attachment sites for viruses. Conclusions: Hydrochar amended sand beds showed improved virus removal efficiencies exceeding 99·6% corresponding to 2·4 log removal. The addition of humic acid in the influent did not hinder the adsorptive removal of viruses. Significance and Impact of the Study: This study suggests that hydrochar derived from sewage sludge can be used as an adsorbent for virus removal in water treatment.

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