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ACUTE TOXICITY OF HEAVY METALS TO ACETATE-UTILIZING MIXED CULTURES OF SULFATE-REDUCING BACTERIA: EC100 AND EC50
Citation:
Utgikar**, V. P., B. Y. Chen**, N. Chaudhary, H H. Tabak*, J R. Haines*, AND R. Govind. ACUTE TOXICITY OF HEAVY METALS TO ACETATE-UTILIZING MIXED CULTURES OF SULFATE-REDUCING BACTERIA: EC100 AND EC50. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 20(12):2662-2669, (2001).
Description:
Acid mine drainage (AMD) from abandoned mines and acid mine pitlakes is an important environmental contaminant concern and usually contains appreciable concentrations of heavy metals. Since sulfate-reducing bacteria (SRB) are involved in the treatment of AMD, knowledge of acute metal toxicity levels for SRB is essential for proper functioning of the treatment system for AMD. Ultimate toxic concentrations and EC50 for copper and zinc were determined in the present study using non-destructive, rapid physical and ehcmial analytical techniques. The reaction medium used i the experiments was designed specifically (pH and chemical composition) to provide the nutrients necessary for the sulfidogenic activity of the SRB and preclude chemical precipitation of the metal ions under investigation. The toxicity mitigating effects of biosorption of metals ions were also quantified. Anaerobic Hungate tubes were set up (at least in triplicate) and monitored for sulfate reduction activity. The onset of SRB activity was detected by the blackening of the reaction mixture due to formation of insoluble ferrous sulfide. Ultimate toxic concentrations were found to be 12 mg/L for copper and 20 mg/L for zinc. The difference betwen the dissolved metal ion concentraions for non-metal control tubes (tubes not containing copper or zinc) and tubes containing metal ions was used as an indicator of the effect of the metal ion. The 7-day EC50 values were found to be 10.5 mg/L for coper and 16/5 mg/L for zinc. Measurements of the turbidity, pH, bacterial population estimations using most-probable number (MPN) technique and metal recovery in the sulfide precipitate provided supporting supplementary evidence for these values.