Anaerobic co-digestion of food waste, bio-flocculated sewage sludge, and cow dung in CSTR using E(C2)Tx synthetic consortia

In the current study, a E(C2)Tx synthetic consortia was tested for anaerobic co-digestion of food waste (FW), bio-flocculated sewage sludge (BFS)/ raw wastewater (RW) and cow dung (CD) at varying proportions in 0.25 L and 6.5 L mesophilic continuously stirred tank reactors. Anaerobic co-digestion of FW with CD and RW at the ratio of 1:1:8 in 0.25 L batch-reactor with E(C2)Tx inoculum resulted in the highest H2 production with least CO2 release. The microbial dynamics of FW:CD:RW samples were studied using 16S metagenomic sequencing which indicated a predominance of hydrolysing microbes at the end point of the digestion cycle. Subsequently, the experiments were scaled up in two continuous digesters, namely, R1 (fed with 50% FW and 50% BFS) and R2 (fed with 2% FW and 98% BFS) with 6.5 L working volume at 2.5 g VS L-1D-1 organic loading rate (OLR) for 120 days. The highest VFA production of 19,183 mg L-1 and 3,265 mg L-1 with maximum bio-methane yield of 142.21-and 225.03-mL CH4g-1 VSadded were recorded in reactors R1 and R2, respectively. In addition, a numerical analysis was conducted to visualize the mixing and temperature distribution within the digesters, and the velocity and temperature profiles were obtained using Ansys Fluent. & COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

In this study, anaerobic co-digestion of food waste, bio-flocculated sewage sludge, and cow dung was tested using a synthetic consortia called E(C2)Tx. The co-digestion resulted in the highest hydrogen production and least carbon dioxide release. Metagenomic sequencing showed the dominance of hydrolysing microbes during the digestion process. The experiments were scaled up in two continuous digesters, and the highest VFA production and bio-methane yield were recorded.