Stepwise Precipitation of Heavy Metals from Acid Mine Drainage and Mineral Formation in Sulfate-Reducing Anaerobic Baffled Reactor System
To achieve the fractional precipitation and persistent fixation of multiple heavy metals during the treatment of acid mine drainage(AMD)using sulfate-reducing bacteria(SRB),a five-compartment anaerobic baffled reactor(ABR)was used to treat the simulated AMD.The effects of AMD on system operation efficiency,physical and chemical properties,biological activity and microbial community structure of granular sludge were observed.The characteristics of heavy metal fractional precipitation and precipitated biomore formation in AMD were investigated.The results indicated that the sulfate reduction system of ABR was capable of precipitating cadmium(Cd),zinc(Zn),and iron(Fe)from AMD in a graded manner,with Cd and Zn primarily removed in the first compartment,and Fe predominantly eliminated in the second and third compartments,all with removal rates exceeding 99％.Chemical speciation analysis of granular sludge and SEM observations revealed that the removed heavy metals mainly deposit in sulfide-bound forms in the sludge,subsequently transforming into lattice states and forming irregular particles(0.3～0.7 μm)on the sludge surface.XRD analysis showed that the main phases in the first compartment were sphalerite,wurtzite,and greenockite,while magnetite and pyrite were predominant in compartments two to five.Analysis of microbial community structure demonstrated the crucial roles of Lactobacillus and Desulfovibrio in heavy metal precipitation and mineral formation processes within the reactor.This study provides theoretical basis for the resourceful treatment and mineralization of heavy metals in AMD.
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