Alkalinity generation in a vertical anoxic limestone drain (VALD) at an abandoned coal mine discharge near Hartshorne, Oklahoma was evaluated. The VALD consists of a 9-m 2 abandoned vertical air shaft filled with approximately 22 m of >90% CaCO 3 limestone overlying approximately 34 m of dolomitic stone. The VALD and a downstream passive treatment system were designed to treat a net-acidic discharge (~40 L/min) characterized by elevated concentrations of metals (Fe 765 mg/L; Mn 18 mg/L; Na 1900 mg/L), anions (Cl-225 mg/L; SO 4 2-7800 mg/L), with pH 5.4 and net-acidity 1400 mg/L. System construction was completed in late 2005, but discharge from the VALD did not occur until January 2007 due to a prolonged regional drought. Upon initial discharge, alkalinity concentrations from the VALD outflow were 550±14 mg/L. During the first year of operation, alkalinity concentrations consistently remained >400 mg/L. The effects of elevated pCO 2 , mine water ionic strength, detention time, and other factors impacting alkalinity concentrations exiting the VALD were assessed. It appears that multiple factors, especially the brackish nature of these particular mine waters, influence treatment effectiveness. In addition, the down-gradient 12-cell passive treatment system is effectively removing metals and discharging net alkaline waters to the receiving stream.
Artesian discharges of net alkaline, ferruginous waters from abandoned underground lead-zinc mines cause considerable surface water degradation at the Tar Creek Superfund Site, part of the historic Tri-State Mining District of Oklahoma, Kansas and Missouri. Two perennial borehole discharges, identified as the lowest elevation mine water discharge points in the district, have flowed unabated for almost 30 years and considerably degraded the physical, chemical and biological integrity of a first-order tributary to Tar Creek. Based on a comprehensive water quality and quantity characterization study, a large multi-cell passive treatment system was designed to receive approximately 1000 L/minute of mine water flowing from these abandoned boreholes (pH 5.95±0.06, total alkalinity 393±18 mg/L CaCO 3 , total acidity 364±19 mg/L CaCO 3 , Fe 192±10 mg/L, Zn 11±0.7 mg/L, Cd 17±4 ug/L, Pb 60±13 ug/L and As 64±6 ug/L). The objectives of this project include: i) remediation of polluted mine waters to acceptable quality for maintenance of the receiving water body aquatic community, ii) demonstration of the first mine water treatment facility of any kind in the Tri-State Mining District, and iii) technology transfer to speed application of this technology to other locations. The passive treatment system includes an initial oxidation pond followed by parallel treatment trains (to facilitate research and experimentation) consisting of aerobic wetlands, vertical-flow bioreactors, re-aeration ponds (with active aeration via wind and solar power) and horizontal-flow limestone beds. Waters from the parallel trains are recombined in a polishing wetland prior to final discharge. Total design surface water elevation change in the entire system is approximately 1.8 m. Prior to system implementation, the abandoned boreholes required rotosonic over-drilling to establish hydraulic control. In addition, diversion of storm water flows from an approximately 470-ha upgradient watershed was necessary. During construction, a third mine water discharge was discovered and incorporated into the design. This system represents a state of the art ecological engineering research site for passive treatment of mine waters.
The viability of removing less commonly addressed metals (e.g., Cd, Cu, Ni, and Pb) in a passive cotreatment concept was tested using a microcosm-scale, three-stage batch reactor system in which acid mine drainage from an abandoned adit on Cerro Rico de Potosí and raw municipal wastewater from Potosí, Bolivia, were introduced at a 5:1 ratio. The acid mine drainage had pH 3.58, acidity 1080 mg L as CaCO equivalent, and elevated concentrations of dissolved Al, Fe, Mn, Zn, Cd, Cu, Ni, and Pb, among other metals/metalloids. The municipal wastewater had pH 9.05 and alkalinity 418 mg L as CaCO equivalent, with 5.6 and 38 mg L of nitrate and phosphate, respectively. Previous analyses noted substantial pH increase, phosphate removal, denitrification, and removal of Al, Fe, Mn, and Zn. Prompted by these results, subsequent analyses were conducted for the current study, which noted that dissolved concentrations of Cd, Cu, Ni, and Pb decreased by 78.5, 18.3, 25.5, and 45.9%, respectively. Additionally, concentrations of Ce, Cr, Gd, and La decreased throughout the system. The study revealed the broader applicability of passive cotreatment of acid mine drainage and municipal wastewater, specifically for removing metals that are often difficult to address with conventional passive treatment approaches, such as Cd, Cu, Ni, and Pb. Results could be applicable for treatment alternatives in developing and developed countries where these waste streams occur in close proximity.
We report a preliminary assessment of ferrate [Fe(VI)] for the treatment of acid mine drainage (AMD), focused on precipitation of metals (i.e., iron [Fe] and manganese [Mn]) and subsequent removal. Two dosing approaches were studied to simulate the two commercially viable forms of Fe(VI) production: Fe(VI) only, and Fe(VI) with sodium hydroxide (NaOH). Subsequent metal speciation was assessed via filter fractionation. When only Fe(VI) was added, the pH remained <3.6, and the precipitation of Mn and Fe was <30 and <70%, respectively, at the highest, stoichiometrically excessive Fe(VI) dose. When NaOH and Fe(VI) were added simultaneously, precipitation of Mn was much more complete, at doses near the predicted oxidation stoichiometric requirement. The optimal dosage of Fe(VI) for Mn treatment was 25 μM. The formation of Mn(VII) was noted at Fe(VI) dosages above the stoichiometric requirement, which would be problematic in full‐scale AMD treatment systems. Precipitation of Fe was >99% when only NaOH was added, indicating that oxidation by Fe(VI) did not play a significant role when added. The Fe(III) and Al(III) particles were relatively large, suggesting probable success in subsequent removal through sedimentation. Resultant Mn‐oxide particles were relatively small, indicating that additional particle destabilization may be required to meet Mn effluent goals. Ferrate seems viable for the treatment of AMD, especially when sourced through onsite generation due to the coexistence of NaOH in the product stream. More research on the use of Fe(VI) for AMD treatment is required to answer extant questions. Core Ideas Ferrate is likely a viable option for acid mine drainage treatment. Oxidation of manganese with ferrate and NaOH approached stoichiometric prediction. Resultant particles may challenge downstream clarification.
Like many large abandoned mining areas, the Tri-State Mining District of the central US is plagued by numerous environmental problems, including contaminated soils, tailings, waste rock, and water, with subsequent detrimental impacts to human and ecological health. In one of the major basins of the district, the Tar Creek watershed, impacts to surface waters were once deemed to be due to "irreversible man-made damages", resulting in minimal effort to address environmental risk from these legacy mine waters over the past 30 years. However, recent watershed-scale environmental monitoring studies, along with completion and evaluation of a full-scale passive treatment demonstration project, indicate that this may no longer be the case. Evaluation of artesian discharges indicates significant evolution of mine pool water quality (e.g., decreased metal concentrations, increased pH and alkalinity) since first flush. In-stream water quality, although still not meeting designated beneficial uses, has also changed. Substantial surface water degradation due to waste rock and tailings runoff and leachate is still problematic, but large-scale land reclamation (including wholesale removal and underground injection) is ongoing. Conceptual designs for watershed-scale passive treatment implementation have been developed and indicate that both artesian mine discharges and remaining runoff/leachate waters may be treatable in a cost-effective and sustainable manner. Recent voluntary relocation efforts, resulting in the dissolution of historic mining communities, provide opportunities for watershed-scale remediation and restoration. However, long-term operation and maintenance obligations for the proposed passive systems, incorporating the cultural and social needs of Native American tribes, requires sustained commitment of technical and financial resources. Promising initial results, coupled with results from other ongoing remediation efforts, warrant further exploration and reevaluation of previous administrative decisions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
334 Leonard St
Brooklyn, NY 11211
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.