Protecting Thermally Hydrolyzed Biosolids from Pathogenic Bacterial Growth by Addition of Compost
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ORIGINAL PAPER
Protecting Thermally Hydrolyzed Biosolids from Pathogenic Bacterial Growth by Addition of Compost Oda K. Svennevik1,2 · Kjell R. Jonassen2,3 · Kine Svensson1 · Live H. Hagen2 · Bjørge Westereng2 · Odd Egil Solheim1 · Pål J. Nilsen1 · Svein J. Horn2 · Lars Bakken2 Received: 3 July 2020 / Accepted: 3 November 2020 © The Author(s) 2020
Abstract Sludge biosolids for agricultural application represent a valuable fertilizer but also a health risk unless pathogens are effectively reduced, and recontamination controlled. The Post Anaerobic Digestion Thermal Hydrolysis Process (Post-AD THP) is gaining interest due to improved dewaterability, reducing the volume and thus transportation costs of biosolids. However, Post-AD THP results in sterile biosolids easily exposed to recontamination by pathogens due to the lack of microbial competitors. In theory, this could be suppressed by establishing a competing community of harmless bacteria. The theory was tested by monitoring the abundance of Escherichia coli (viable counts) and gene abundance (ddPCR) in wastewater recontaminated Post-AD THP biosolids, with and without addition of compost. Respiration, total bacterial population and bacterial diversity (16S rRNA amplicon sequencing) were used to monitor the microbial community. Biosolids from the regulatory approved methods thermophilic AD (TAD) and Pre-AD THP were tested in parallel for comparison. The results demonstrated that regulatory requirements can be reached by storing the TAD and Pre-AD THP biosolids for 3 days after recontamination and the Post-AD THP biosolids for more than 13 days. However, addition of compost suppressed growth of E. coli in Post-AD THP biosolids, reducing the time to comply with regulative requirements. In conclusion, pathogen growth in Post-AD THP biosolids can be controlled by inoculation with compost.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12649-020-01300-1) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article
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Vol.:(0123456789)
Waste and Biomass Valorization
Graphical abstract
Keywords Anaerobic digestion · Biosolids · E. coli · Sanitation · Thermal hydrolysis
Statement of Novelty Safe management and pathogen control of sludge biosolids is essential for its further value as a fertilizer on agricultural land. Indicator bacteria growth after conventional anaerobic digestion (AD) configurations have been thoroughly studied in current literature. However, introduction of new technology such as the post AD thermal hydrolysis process (PostAD THP) challenges the existing body of knowledge and legislations in some countries. Legislations must distinguish between inadequate sanitation in the sludge treatment facility and growth of pathogens due to recontamination during storage and handling. To the best of our knowledge, growth of pathogens due to recontamination in Post-AD THP biosolids has so far not been studied and wil
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