Precipitation of heavy metals from landfill leachates by microbially-produced sulphide.
Four leachates from two landfills in Sweden were treated for the removal of heavy metals with the aid of sulphate-reducing bacteria (SRB). Both continuous and batch experiments were performed. A packed-bed process was used for sulphide production. The metals studied were As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. The continuous experiments showed that Cd and Cu were most efficiently removed and that Cr was the most difficult to precipitate. In a continuous experiment with one of the leachates, the removal of Cd, Cu and Zn depended upon the retention time in the system. In the batch experiments, precipitation of the metals was a relatively fast process. No significant differences in metal concentrations were found between experiments terminated after a day and those terminated after a week. In a batch experiment involving one of the leachates, the precipitation of Cd and Cu was shown to be dependent upon the metal:sulphide ratio. Removal of the metals increased with an increase in the sulphide:metal ratio up to 45:1. The process with SRB showed an interesting potential for removal of heavy metals from leachates. One of the two leachates for which the highest metal removals were obtained came from a landfill for hazardous waste.
Möller
A
A
Department of Biotechnology, Center for chemistry and chemical engineering P.O. Box 124, SE-22100 Lund, Sweden.
Grahn
A
A
Welander
U
U
D019149:Bioreactors; D011232:Chemical Precipitation; D019216:Metals, Heavy / Q000737:chemistry* / Q000302:isolation & purification*; D012037:Refuse Disposal; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000302:isolation & purification; D016999:Sulfur-Reducing Bacteria / Q000502:physiology*; D014873:Water Pollutants / Q000302:isolation & purification
D019216:Metals, Heavy; D012989:Soil Pollutants; D014873:Water Pollutants