Anaerobic co-digestion of food waste, bio-flocculated sewage sludge, and cow dung in CSTR using E(C2)Tx synthetic consortia
Hemant Thakur, Rashmi Ira, N. K. Verma, Vikas Sharma, Shrawan Kumar, Atul Dhar, Tulika Prakash, Satvasheel Powar
Abstract
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 visualise the mixing and temperature distribution within the digesters, and the velocity and temperature profiles were obtained using Ansys Fluent.