60 / 2023-05-31 10:24:08

How processing temperature influence chemical species distribution of trace elements in different sources of anaerobic digestate

Digestate utilization; Metal migration and transformation; Chemical speciation; Temperature effect; Anaerobic digestion; Trace elements bio-availability.

    Temperature treatment is a safety need for post-processing of anaerobic digestate. This will affect the distribution and migration of metal species and thus influence digestate property for re-digestion or returning to field. In this study, three different sources of anaerobic digestate with/without exogenous TEs addition (Fe=10 mg/L，Co=1 mg/L，Ni=1 mg/L) were employed to understand how the different processing temperature (frozen(<-25 ℃), room temperature (~25 ℃), water-bath (~100 ℃), and boiling (~200 ℃) ) influence the chemical species distribution of trace elements (TEs). After step extraction and quantitative analysis by ICP-MS, the results showed that high temperature treatment increased the water-soluble fractions in varying degrees, with maximum increase at 200 ℃, where the water-soluble plus exchangeable fractions of Fe, Co, and Ni reached to 60%, 70%, and 50%, respectively. However, frozen treatment would reduce the exchangeable fractions of TEs  irrespective of digestate source. Therefore, the chemical species distributions of TEs in digestates vary with different processing temperatures, which influences the potential migration ability and bioavailability of TEs.