Inactivation of enteric indicator bacteria and system stability during dry co-digestion of food waste and pig manure

Jiang, Yan and Dennehy, Conor and Lawlor, Peadar G. and Hu, Zhenhu and Zhan, Xinmin and Gardiner, Gillian E. (2018) Inactivation of enteric indicator bacteria and system stability during dry co-digestion of food waste and pig manure. Science of the Total Environment, 612. pp. 293-302. ISSN 0048-9697

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Provision of digestate with satisfactory biosafety is critical to land application of digestate and to the anaerobic digestion approach to treating manure and food waste (FW). No studies have been conducted on digestate biosafety in dry co-digestion systems. The aim of this study was to assess the inactivation efficiency and possible inactivation mechanism for three enteric indicator bacteria and the system stability during dry mesophilic anaerobic co-digestion of FW and pig manure (PM). The effects of two different inocula were examined at a rate of 50% based on volatile solids (VS): digestate taken from existing dry co-digestion digesters and dewatered anaerobic sludge from a local wastewater treatment plant. The FW/PM ratios of 50:50 and 75:25 on a VS basis were also assessed. The results showed that using digestate as the inoculum and a FW/PM ratio of 50:50 led to stable dry co-digestion, with the specific methane yield (SMY) of 252 mL/gVSadded. Total volatile fatty acid (VFA) concentration was a significant inhibition factor for methane production during dry co-digestion (P < 0.001). The data also showed that dry co-digestion of FW and PM effectively inactivated enteric indicator bacteria. E. coli and total coliforms counts decreased below the limit of detection (LOD, 102 CFU/g) within 4–7 days, with free VFA identified as a significant inactivation factor. Enterococci were more resistant but nonetheless the counts decreased below the LOD within 12 days in the digestate inoculum systems and 26–31 days in the sludge inoculum systems. The residence time was the most significant inactivation factor for enterococci, with the free VFA concentration playing a secondary role at high FW/PM ratio in the sludge inoculum system. In conclusion, digestate as inoculum and the FW/PM ratio of 50:50 were preferable operation conditions to realize system stability, methane production and enteric indicator bacteria inactivation.

Item Type: Article
Additional Information: Funding Information: Funding for this study was provided by the Green Farm project supported by a Science Foundation Ireland Investigator Project Award (Ref: 12/IP/1519 ). Publisher Copyright: © 2017 Elsevier B.V.
Uncontrolled Keywords: /dk/atira/pure/subjectarea/asjc/2300/2305
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Depositing User: Admin SSL
Date Deposited: 19 Oct 2022 23:07
Last Modified: 04 Aug 2023 01:40

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