PROMOTING LOW-PH BIOLOGICAL IRON(II) OXIDATION OF ACID MINE DRAINAGE AT HUGHES BOREHOLE: FIELD AND LABORATORY EXPERIMENTS
Open Access
- Author:
- DeSa, Trinh Cong
- Graduate Program:
- Environmental Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 23, 2009
- Committee Members:
- William D Burgos, Thesis Advisor/Co-Advisor
William D Burgos, Thesis Advisor/Co-Advisor - Keywords:
- biological
acid mine drainage
Fe(II) oxidation
low-pH - Abstract:
- Fe(II) oxidation at a low-pH acid mine drainage (AMD) site in Pennsylvania was enhanced by physical modifications to the existing iron mound. Hughes Borehole discharges approximately 1000 gallons per minute of pH 4 AMD that contains high concentrations of Fe (100 mg/L) and numerous trace metals. Long-term monitoring of the site showed that biological Fe(II) oxidation occurred across the mound without human intervention, but during the majority of the year very little Fe(II) was removed before the AMD reached the effluent end of the mound. Maximizing the removal of Fe and other metals on the preexisting iron mound could substantially increase the efficiency of conventional passive treatment systems such as limestone drains or wetlands. On-mound channel reactors along with laboratory-scale “gutter” reactors were constructed to determine optimal conditions for passive biological Fe(II) oxidation. Fe(II) was much more efficiently removed from gutter reactors that contained iron mound sediment than ones without any sediment. Residence times of 5-10 hours were shown to remove close to 100% of dissolved influent Fe(II) and 75% of dissolved total Fe. Additionally the reactors performed better as the age of the sediments increased and consequently shorter residence times of 1-2 hours were also capable of removing substantial amounts of the influent Fe(II). The addition of surface area to the on-mound reactors improved Fe(II) oxidation at residence times of 30 minutes or less. The results of this study can be used to help design and implement large-scale treatment systems for low-pH AMD discharges.