Effects of acidity on bacterial sulfate reduction and metal bioprecipitation in acid rock drainage groundwater using three different carbon sources

Alex Davis

Research output: ThesisMaster's Thesis

125 Downloads (Pure)

Abstract

[Truncated] Large scale column experiments were undertaken to determine the effect of a step decrease in groundwater pH on metal remediation by bioprecipitation using three different carbon sources: (ethanol, molasses and vegetable oil) to promote reducing conditions. Metal contaminated groundwater at pH 5.5 was delivered to four separate soil columns. Three of the columns were amended with one of the carbon sources at a concentration of 1 g/L, while the fourth column was left unamended and used as a control.

Denitrification and copper removal were observed at pH 5.5 in each of the carbon amended columns. Of the three carbon sources, ethanol provided the most effective and reliable carbon source for denitrification and copper removal. Molasses was also suggested to be an effective amendment for the stimulation of denitrification and copper removal. However, due to problems with consistent molasses delivery, fluctuations in the location and extent of denitrification and copper removal were observed. Vegetable oil showed only limited and inconsistent denitrification and copper removal.

Of the three carbon amendments, only ethanol was observed to stimulate sulfate reduction and zinc bioprecipitation at an influent groundwater pH of 5.5. Once steady state sulfate reduction and zinc bioprecipitation had been established in the ethanol amended column, the pH of the influent metal contaminated groundwater was reduced in a single step from 5.5 to 4.25 in the control and ethanol amended columns. The reduction in groundwater pH resulted in a significant increase in groundwater copper concentration in both columns.

Original languageEnglish
QualificationMasters
Publication statusUnpublished - 2005

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