61 / 2023-05-31 11:10:24

Study on the dynamic change of alkalinity and microbial community structure along with cobalt speciation distribution in anaerobic digestion system

Trace elements bio-availability; Chemical speciation; Dose-response correlation; Anaerobic digestion; Microbial diversity.

The bioavailability dynamic of trace elements (TEs) in anaerobic digestion (AD) is the key to effectively stimulate the methanogenic activity by TEs. In this study, the relationship between chemical speciation of cobalt (Co) element and AD performance, as well as the corresponding variation of microbial community were studied in different AD systems with different pH values and exogenous addition does of Co. It was found that when pH was initially adjusted to 7.5 and Co dosage of 0.1 mg/kg, cumulative methane production was the highest, reaching 362.6 mL CH₄/g VS. Among the four bioavailable chemical forms, the Co element mainly exists in carbonate state (25%-40%) and organic/sulfide state (30%-47%). The addition of low and medium concentrations of Co elements could not increase the bioavailable cobalt stock. At the initial pH of 8.5, the intermediate alkalinity was positively correlated with the four chemical forms of cobalt with correlation coefficient of 0.4-0.7. In addiction, the water-soluble state showed significant impact on the acidogens and methanogens community. Under the initial pH=8.5 and 6.5, the addition of Co element helped to increase the abundance of acidogens and methanogens, but decreased the their abundance under the initial pH=7.5.