Biogeochemical transformation of mercury driven by microbes involved in anaerobic digestion of municipal wastewater

Anaerobic digestion (AD) with municipal wastewater contained heavy metal mercury (Hg) highly affects the utilization of activated sludge, and poses severe threat to the health of human beings. However, the biogeo-chemical transformation of Hg during AD remains unclear. Here, we investigated the biogeochemical trans -formation and environmental characteristics of Hg and the variations of dominant microbes during AD. The results showed that Hg(II) methylation is dominant in the early stage of AD, while methylmercury (MeHg) demethylation dominates in the later stage. Dissolved total Hg (DTHg) in the effluent sludge decreased with time, while THg levels enhanced to varying degrees at the final stage. Sulfate significant inhibits MeHg formation, reduces bioavailability of Hg(II) by microbes and thus inhibits Hg(II) methylation. Microbial community analysis reveals that strains in Methanosarcina and Aminobacterium from the class of Methanomicrobia, rather than Del-taproteobacteria, may be directly related to Hg(II) methylation and MeHg demethylation. Overall, this research provide insights into the biogeochemical transformation of Hg in the anaerobic digestion of municipal waste-water treatment. This work is beneficial for scientific treatment of municipal wastewater and effluent sludge, thus reducing the risk of MeHg to human beings.

Automated summary

This study investigated the biogeochemical transformation and environmental characteristics of mercury (Hg) in anaerobic digestion (AD) of municipal wastewater, as well as the variations of dominant microbes. The results showed that Hg(II) methylation is dominant in the early stage of AD, while methylmercury (MeHg) demethylation dominates in the later stage. Sulfate significantly inhibits MeHg formation and Hg(II) methylation by microbes. Microbial community analysis revealed that certain strains may be directly related to Hg(II) methylation and MeHg demethylation. Overall, this research provides insights into the biogeochemical transformation of Hg in AD, contributing to the scientific treatment of municipal wastewater and reducing the risk of MeHg to human beings.