Mixing effects on decentralized high-solid digester for horticultural waste: Startup, operation and sensitive microorganisms

• Published in: Bioresource technology Vol. 333; p. 125216
• Main Authors: Mao, Liwei, Tsui, To-Hung, Zhang, Jingxin, Dai, Yanjun, Tong, Yen Wah
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-08-2021
• Subjects: High-solid anaerobic digestion; Horticultural waste; Mixing effect; Reactor startup; Sensitive microorganisms; High-solid anaerobic digestion; Horticultural waste; Reactor startup; Mixing effect; Sensitive microorganisms
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2021.125216

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•Horizontal high-solid digester was developed for green park applications.•Mixing effects on the digester’s startup and operation were investigated.•Enhancement of specific methane yield rates was achieved up to 45.5%•Microbial communities under different mixing regimes were studied.
This work studied the use of a horizontal high-solid digester for the decentralized anaerobic treatment of horticultural waste (fallen leaves), where the effect of intermittent mixing by a modified double helical ribbon impeller was investigated. Before experimental verification, the flow pattern and theoretical mixing time were first characterized by CFD simulation. Subsequently, three mixing time intervals (i.e., 3 min/3 hr; 18 min/3 hr; 108 min/3 hr) and one control setup (i.e., without mixing) were compared for their performance during start-up and semi-continuous operation. It was found that minimal mixing was necessary for an efficient digester’s start-up but increased mixing intensity for semi-continuous operation. The results were further interpreted by correlating the digester performance and microbial communities. Those microorganisms sensitive to increased mixing intensity were highlighted and analysed.