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

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 startup 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.

Automated summary

The study investigated the use of a horizontal high-solid digester for decentralized anaerobic treatment of horticultural waste, focusing on the effect of intermittent mixing by a modified double helical ribbon impeller. CFD simulation was used to characterize the flow pattern and theoretical mixing time before experimental verification. Results showed that minimal mixing was necessary for efficient digester startup, while increased mixing intensity was needed for semi-continuous operation. The study also correlated digester performance with microbial communities, highlighting and analyzing microorganisms sensitive to increased mixing intensity.