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Characterization, Cleanup, and Revitalization of Mining Sites

Cleanup Technologies

A range of traditional and innovative technologies may be appropriate for remediation at current and former mining sites. EPA's Office of Research and Development's Engineering Technical Support Center (ETSC) provides assistance to EPA regional offices, states, and communities on the design, function, and application of these technologies. ETSC scientists and engineers work closely with the Superfund program and other EPA programs that address remediation of mining sites, and also collaborate with state governments, universities, and private entities to develop new approaches and remediation technologies for mining wastes.

A resource, Review of Peer Reviewed Documents on Treatment Technologies Used at Mining Waste SitesAdobe PDF Logo, by EPA's Office of Superfund Remediation and Technology Innovation, provides a comprehensive evaluation of mine treatment technologies used to remediate waste rock, tailings, pit lakes, water from adits, underground workings, leachate, groundwater and surface water. The guide includes a description of each technology, detailed case study evaluation(s), costs, limitations, lessons learned, and provides references to find additional information on a given technology. Pre-and post-treatment data collected from peer-reviewed case studies for several treatment technologies is provided in the Appendices of the guide to allow users to further assess the effectiveness of various treatment technologies.

EPA's Office of Superfund Remediation and Technology Innovation's 2014 report, Reference Guide to Treatment Technologies for Mining-Influenced WaterAdobe PDF Logo, highlights select mining-influenced water (MIW) treatment technologies used or piloted as part of remediation efforts at mine sites. The report includes short descriptions of treatment technologies and information on the contaminants treated, pre-treatment requirements, long-term maintenance needs, performance, and costs. Sample sites illustrate considerations associated with selecting a technology. Website links and sources for more information on each topic are also included. Appendix A of the guide summarizes the technologies discussed in the body of the report, as well as additional technologies or products designed as passive or low-cost treatment options.

The Interstate Technology and Regulatory Council's (ITRC) web-based technical and regulatory guidance site, Mining Waste Treatment Technology Selection, is a tool for selecting an applicable technology or suite of technologies for remediation of mining sites. The guidance uses a series of questions to point users to a set of treatment technologies that may be applicable to a particular site. The website provides an overview of each technology with information about its applicability, advantages, limitations, performance, stakeholder and regulatory considerations, and lessons learned, as well as links to applicable case studies.

The EPA Abandoned Mine Site Characterization and Cleanup Handbook (2000)Adobe PDF Logo provides a compendium of information gained during many years of experience on mine site cleanup projects. Chapter 10 summarizes several conventional and innovative (as of 2000) treatment technologies; collection, diversion, and containment technologies; reuse, recycle, and reclamation; and institutional controls.

The technology information below is adapted from the technology overviews on ITRC's Mining Waste Technology Selection site, with a link to the entry for each technology.

Mining Solid Waste

Capping, Covers, and Grading — Capping, or covering of solid mining waste, is an effective treatment technology that can be used as a short-term, interim measure or as a long-term or final action. Installation of a cap or cover on solid mining waste can reduce or eliminate erosion, fugitive dust emissions, and infiltration of water to prevent the migration of contaminants. A variety of materials is available and the technology can be modified to adapt to site-specific conditions. Caps and covers can be used alone or with other treatment technologies. The cap or cover must be maintained to ensure its effectiveness. Institutional controls also may be required.

  • First Five-Year Review Report Holden Mine Site Okangan-Wenatchee National Forest Chelan County, WashingtonAdobe PDF Logo
    USDA, Forest Service, Pacific Northwest Region, 74 pp, 2018
    The Holden Mine produced about 200 million lbs of Cu, 40 million lbs of Zn, two million ounces of Ag, and 600,000 ounces of Au from ~10 million tons of ore. Excavation of 60 miles of underground tunnels produced 8.5 million tons of mill tailings placed on 90 acres of U.S. National Forest lands as well as 300,000 yd3 of waste rock piles. Direct release of hazardous materials from the mine, including acid mine drainage, heavy metals (Al, Cd, Cu, Fe, Pb, and Zn), and iron sulfide, affected about 125 acres of land. The remedy is being conducted in two phases. Phase 1, which began in 2013 with completion expected in 2018, includes regrading and capping the tailings and main waste rock piles, constructing a groundwater barrier wall and groundwater collection system around Tailings Pile 1 and the Lower West Area, constructing a new groundwater treatment facility, beginning in situ soil treatment (e.g., application of agricultural lime) in areas of interest, implementing institutional controls, and initiating performance verification monitoring. Phase 2 is expected to begin in 2023. In situ treatment is still under technical review and consideration for implementation due to environmental constraints, potential destruction of established forests and habitats, rough topography, and practicability of the remedy.

  • Laboratory and Field-Based Assessment of the Effects of Sediment Capping Materials on Zinc Flux, Bioabailability, and ToxicityAdobe PDF Logo
    Cervi, E.C., K. Thiamkeelakul, M. Hudson, A. Rentschler, S. Nedrich, S.S. Brown, et al.
    Environmental Toxicology and Chemistry 39(1)240-249(2020)
    A former mining site was remediated and restored with a focus on disconnecting mine spoils from groundwater and managing the quantity and quality of runoff. However, a remaining task is to ensure that concentrations of Zn in the stream outflow of a pit lake are reduced below water quality standards. The efficacy of AquaBlok™, limestone, and limestone-bone char capping materials for decreasing Zn dissolution from sediments under natural and reasonable worst-case conditions (pH = 5.5) was evaluated. Field exposures were conducted in situ in limnocorrals and ex situ in core tube mesocosms. Simultaneous in situ and ex situ toxicity tests were conducted using Daphnia magna, Hyalella azteca, and Chironomus dilutus exposed to surficial sediments, caps, and hypolimnetic overlying waters for 4 d. No differences in responses between treatments involving sediment capping materials in both in situ and ex situ tests were observed, likely due to dissolved Zn in surface water being below the hardness-adjusted threshold effects levels (164 µg/L). Both studies provided site-specific data to select an effective remedy with reduced uncertainty compared to laboratory and chemistry-only approaches.

  • Evapotranspiration Covers at Uranium Mill Sites
    Caldwell, T.G., S. Tabatabai, J.M. Huntington, G.E. Davies, and M. Fuhrmann.
    Vadose Zone Journal 21(5):e20222(2022)
    This update reviews the current state of the science regarding evapotranspiration (ET) covers and considerations for long-term applications. Waste isolation is a key strategy to mitigate risk from municipal solid waste (MSW) and hazardous waste streams. Conventional covers at MSW facilities are designed for a 30-yr post-closure period where compacted soils and geosynthetics are used to minimize percolation into buried waste. ET covers have shown beneficial use for MSW management by encouraging infiltration, storage, and precipitation transpiration to minimize percolation. Uranium Mill Tailings Radiation Control Act sites were covered by a clay radon barrier, creating tortuous flow paths that allow radioactive decay and attenuation of short-lived, 222Rn gas. An ET-radon cover may provide greater resilience for long-term waste isolation by exploiting natural processes instead of resisting them.
  • Global Cover System Design: Technical Guidance DocumentAdobe PDF Logo
    International Network for Acid Prevention (INAP), 216 pp, 2017
    Designed primarily for those investigating the use of cover systems on mine sites, this document offers a "best practice" summary to assist mine operators, designers, and regulators to address the role cover systems play over the life of the mine, from early conceptualization to long-term performance monitoring. A conceptual model illuminates how cover system designs might affect contaminant and acidity loading. The model attempts to determine when the varying roles of cover system design (e.g., control of net percolation or oxygen ingress) might influence loadings. Acknowledgment of these unique relationships provides an opportunity to optimize cost-effective management of metal loading and acid rock drainage. The cover system design tool walks users through relevant climatic factors to optimize cover system design alternatives and meet desired performance design criteria.

Chemical Stabilization Using Phosphate and Biosolids Treatment — This technology addresses soil, sediment, or mine tailings at remote, rural, and urban locations and can be used for small and large volumes of wastes. Phosphate treatment can be used by itself or with other technologies as an interim or final remedy. Ex situ treatment is more widely used than in situ and frequently is applied in conjunction with off-site disposal. In situ treatment has proven effective at reducing the bioavailability of lead and other heavy metals and providing a relatively nontoxic growth medium for previously barren mine/mill waste. In situ treatment has been used in mines as a coating on exposed ore surfaces but the technology has not been widely used to stabilize lead-contaminated soil in residential settings. Chemical phosphate treatments use a variety of phosphate species, but phosphoric acid has been demonstrated to be the most effective. Organic sources of phosphate such as biosolids or composted animal wastes also are used to stabilize, reclaim, and revegetate barren mine and mill wastes.

  • Restoration and Risk Reduction of Lead Mining Waste by Phosphate-Enriched Biosolid AmendmentsAdobe PDF Logo
    Li, N., X. Tang, J. Yang, and Z. Sun. | Scientific Reports 11:8965(2021)
    A field study was conducted to stabilize Pb using six phosphate (P)-enriched biosolid amendments in contaminated mining wastes (average of 1004 mg Pb/kg) at the Jasper County Superfund site in Missouri. The six amendments were Mizzou doo compost (MD), spent mushroom compost (SMC), turkey litter compost (TLC), composted chicken litter (CCL), composted sewage sludge (CSS), and triple superphosphate (TSP). Kentucky tall fescue seeds were planted following the treatments, and soil and plant samples were collected and analyzed 8-10 years post-treatment. In all cases, the biosolid treatments resulted in significant reductions in bioaccessible Pb (96.5-97.5%), leachable Pb (95.0-97.1%), and plant tissue Pb (45.5-90.1%) in the treated wastes, as compared with the control. Treatments had no significantly toxicological effect on soil microbial community. Analysis of the Pb fractionation revealed that Pb risk reduction was accomplished by transforming labile Pb fractions to relatively stable species through the chemical stabilization reactions induced by the treatments. The solid-phase microprobe analysis confirmed the formation of pyromorphite or pyromorphite-like minerals after treatment. Among the six biosolid amendments examined, SMC and MD treatments were most effective in stabilizing and reducing Pb risk.
  • Bonita Peak Mining District Biocement-A Pilot StudyAdobe PDF Logo
    EPA Region 8, 2 pp, 2019
    Environmental Toxicology and Chemistry 39(1)240-249(2020)
    One of the leading sources of metals loading to nearby waterways originates from the runoff of contaminated soils from mine tailings in the Bonita Peak Mining District. To stabilize the solid media in source areas, EPA is implementing a BioCement pilot study on the north side of the former Kittimac Mill. BioCement technology provides an innovative erosion control strategy that uses "microbial induced calcite precipitation." to solidify loose soils into rock. Four 5' x 15' areas of the Kittimac site will be treated with BioCement over two months. If successful, this technology will be used to stabilize additional tailings and soil.

Electrokinetics — The electrokinetic remediation (ER) process is an in situ soil processing technology that separates and removes metals and organic contaminants from low-permeability soil, mud, sludge, and marine dredging. ER uses electrochemical and electrokinetic processes to desorb, and then remove, metals and polar organics. Targeted contaminants for electrokinetics are heavy metals, anions, and polar organics. Contaminant concentrations that can be treated range from a few parts per million (ppm) to tens of thousands ppm. There have been few commercial applications of electrokinetic remediation in the United States.

  • In Situ Electrokinetic (EK) Remediation of the Total and Plant Available Cadmium (CD) in Paddy Agricultural Soil Using Low Voltage Gradients at Pilot and Full Scales
    Cao, Z., Y. Sun, Y. Deng, X. Zheng, S. Sun, M. Romantschuk, and A. Sinkkonen.
    Science of The Total Environment 785:147277(2021)
    A 14-day electrokinetic (EK) remediation was carried out in a field pilot (4 m2) test and a full-scale (200 m2) application at a Cd-contaminated paddy agricultural field near a mining area. A low voltage of 20 V was applied at both scales; the voltage gradients were 20 V/m (pilot) and 4 V/m (full scale). Samples were taken from near the anode and cathode, and in the middle of the electric field, in 0-10 cm, 10-20 cm, and 40-50 cm soil layers. After EK remediation, a significant portion of the total Cd was removed in all the layers at the pilot-scale, by 87%, 72%, and 54% from the top down; 74% was removed in the 0-10 cm layer at full scale. Significant removal (64%) of plant-available Cd was observed in the 0-10 cm layer at the pilot scale. The percentage reduction of the electrical conductivity and removal efficiency of the total Cd was higher near the anode than the cathode. The soil pH was elevated near the cathode but stayed below pH 6 due to the sufficient supply of lactic acid. After remediation, the concentration of the total Cd dropped below the 0.4 mg/kg dry wt soil hazard threshold for agricultural paddy fields in China. A total energy of 2 kW·h and 0.6 kW·h was consumed at the pilot and full scales, respectively.

  • Electrokinetic Remediation of Manganese and Zinc in Copper Mine Tailings
    Ortiz-Soto, R., D. Leal, C. Gutierrez, A. Aracena, A. Rojo, and H.K. Hansen.
    Journal of Hazardous Materials 365:905-911(2019)
    In an evaluation of the effect of initial acidity and electric field intensity on the electrokinetic remediation of Mn and Zn from mine tailings at a Chilean copper mine, experiments focused on the effect of the applied electric field (1 and 2 V/cm), the H2SO4 concentration during pretreatment (1 and 2 mol/L) and the interaction between these factors in Mn and Zn concentration. From the obtained results, Mn and Zn can be removed from the analyzed tailings, with maximum net removal of 31.88% and 17.95%, respectively. Electromigration enhancement was confirmed by an analysis of variance with a significance level of 10% for the soluble and total metal concentration in the cathodic zone, where total concentration was increased to 24% and 11% for Zn and Mn, respectively.
  • Acid Pond Sediment and Mine Tailings Contaminated with Metals: Physicochemical Characterization and Electrokinetic Remediation
    Karaca, O., C. Cameselle, and K.R. Reddy.
    Environmental Earth Sciences 76(12):[408](2017)
    Mine tailings and acid pond sediment from a former mining area in Canakkale (Turkey) were analyzed for physical (e.g., moisture content, particle size, specific gravity, and hydraulic conductivity) and chemical parameters (e.g., organic content, pH, ORP, and EC) as well as metal content and sequential extraction analysis in an attempt to evaluate their risk as a source of contaminants. Column tests demonstrated that Fe and Pb can be released to waterbodies in contact with the solid materials. Pb was released more easily than Fe due to its content in the more labile fractions in the sequential extraction analysis. When electrokinetic remediation was tested for metals removal from mine tailings and sediment, the technique removed 20% of Pb and Fe in 9 days of treatment at 1 VDC/cm. Metals removal efficiency was strongly affected by metal speciation. Electrokinetics removed metal fractions I-IV, especially in the closest section to the anode of the solid matrix, and the metals accumulated in the following sections. Results suggested that Fe and Pb could be removed from the mine tailings and sediment effectively if the advance of the acid front was favored and the treatment time increased, but considering the physicochemical characterization and electrokinetic treatment results, other green and more sustainable remedial strategies must be proposed for mitigation of environmental risks of former mining areas, such as metals immobilization and stabilization via phytocapping.

Excavation and Disposal — Excavation and disposal of contaminated soil, sediment, or tailings is an effective and proven technology that usually involves the removal of contaminated material with heavy equipment. This technology can be modified to adapt to site-specific conditions. Soil, sediment, or tailings can be removed so that the remaining contaminant concentrations meet cleanup goals. Excavated soil, sediment, or tailings can be disposed of either on-site (in an approved repository constructed for this purpose or another location where the exposure pathways allow the material to be beneficially reused) or off-site in a permitted disposal facility. Excavation and disposal can be used by itself as an interim or final remedy or with other technologies.

Soil Amendments — Cleanup treatments at mining sites may involve the addition of amendments to the contaminated soil. Soil amendments are materials added to soils to revitalize and make them suitable for sustaining plant life or development. Mining sites with contaminated or disturbed soils exhibit a variety of problems that often can be addressed effectively and directly through the use of soil amendments. Project managers could evaluate their effects in the subsurface, their potential for eventual transport to surface waters, and their possible subsequent adverse effects on plant and animal communities.

  • Can a Blend of Amendments Be An Important Component of a Rehabilitation Strategy for Surface Coal Mined Soils?
    Abraha, A.B., E.H. Tesfamariam, and W.F. Truter.
    Sustainability 11: 4297(2019)
    The role of different amendments to alleviate compaction problems in rehabilitated mine soils were quantified in this study using 5 single amendments and 3 different blends of amendments mixed thoroughly with degraded mine soil in a 1:3 (amendment:soil) ratio. Two additional unamended soils with different bulk densities (BD) were included as benchmarks. Amendment applications reduced BD by 4-20%, enhanced infiltration rate by 15-70%, increased porosity by 5-35% and increased plant available water (PAW) by 9-33% compared with the unamended soils. Between amendments, the blends of amendments reduced BD by 9-16%, enhanced infiltration rate by 17-59%, increased porosity by 6-32%, and PAW by 4-28% compared with single amendments. A blend of amendments had better soil restoration capacity through improving porosity, infiltration rate, and plant-available water. This article is Open Access at https://www.mdpi.com/2071-1050/11/16/4297.
  • Phytostabilization of ZN and CD in Mine Soil Using Corn in Combination with Biochars and Manure-Based Compost
    Sigua, G.C., J.M. Novak, D.W. Watts, J.A. Ippolito, T.F. Ducey, M.G. Johnson, et al.
    Environments 6(6):69(2019)
    The effect of biochar additions (BA) with or without manure-based compost (MBC) was evaluated on shoots biomass, roots biomass, uptake, and the bioconcentration factor (BCF) of Zn and Cd in corn (Zea mays L.) grown in mine soil. Biochar additions of beef cattle manure (BCM), poultry litter (PL), and lodgepole pine were applied at 0, 2.5, and 5.0% (w/w) in combination with different rates (0, 2.5, and 5.0%, w/w) of MBC, respectively. Shoots and roots uptake of Cd and Zn were significantly affected by BA, MBC, and the interaction of BA and MBC. Corn plants that received 2.5% PL and 2.5% BCM had the greatest Cd and Zn shoot uptake, respectively. Corn plants with 5% BCM had the greatest Cd and Zn root uptake. When averaged across BAs, the greatest BCF for Cd in the shoot (92.3) was from application of BCM and the least BCF was from application of PL (72.8). The incorporation of biochar enhanced phytostabilization of Cd and Zn. Concentrations of water-soluble Cd and Zn were lowest in soils amended with manure-based biochars, which improved the biomass productivity of corn. This article is Open Access at https://www.mdpi.com/2076-3298/6/6/69.
  • Effects of Composted Biosolids and Manuer Applications for Prairie and Wetland Restoration on Remediated Mine Lands: Oronogo-Duenweg Mining Belt Site, Webb City, MO Adobe PDF Logo
    Nichols, J., S. Hamilton, D.E. Mosby, and E. Gramlich.
    Missouri Dept. of Natural Resources/U.S. Fish and Wildlife Service, 136 pp, 2017
    In a 2-year pilot study conducted to evaluate the potential environmental benefits and impacts of using composted manure products as a soil amendment on lead and zinc mine lands, different compost mixtures composed of cattle manure, poultry litter, municipal biosolids, wood chips, and conventional fertilizers were tested in both upland and wetland soils. Test plots established using the different compost mixtures were sampled to evaluate potential contaminants in stormwater runoff, changes in bioavailability and plant uptake of soil metals, and plant growth and diversity. Overall results of this study indicate that cattle manure-based composted soil amendments tended to perform better than the other amendments in terms of providing the best growth medium for the seeded native vegetation and producing relatively low levels of excess nutrients and metals in surface runoff. Few differences were observed in effects between the high (80 tons/acre) and low (40 tons/acre) application rates. The researchers concluded that application rates, within the range tested, could be scaled according to site-specific soil conditions without a significant increase in potential negative environmental impacts.
  • Using Organic Amendments to Restore Soil Physical and Chemical Properties of a Mine Site in Northeastern Oregon, USA Adobe PDF Logo
    Page-Dumroese, D.S., M.R. Ott, D.G. Strawn, and J.M. Tirocke.
    Applied Engineering in Agriculture 34(1):43-55(2018)
    The U.S. Department of Agriculture, Forest Service, in cooperation with the City of Bend, Oregon, initiated a mine tailing reclamation project in the Umatilla National Forest in northeastern Oregon to determine the benefits of surface-applied organic amendments. Researchers established a field study using organic amendments applied to gold dredgings capped with 10 cm of loam and showing little evidence of regeneration. Study plot applications consisted of biochar, biosolids, or wood chips singly or in combination. Each plot was divided in half, and one half was seeded with native grasses and forbs, and the other was planted with a combination of California brome and Jepson's blue wild rye. After two growing seasons, no significant differences were observed in plant cover between the planted or seeded plots, but soil properties were significantly altered by individual treatments. Combination treatments improved nutrient availability and soil moisture and grew up to twice as much plant cover as the control plots.
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Mining-Influenced Water (MIW)

Aeration Treatment Systems — Aeration is a relatively simple and effective treatment process in which mechanical introduction of oxygen is used to enhance the oxidation and decrease the solubility of metals in MIW. Aeration can be used with other treatment technologies and often is applied together with acid-neutralizing agents, chemical oxidants, flocculants, and settling basins. The array of aeration technologies can be used at a broad range of sites that vary in site and flow conditions.

Anoxic Limestone Drains (ALD) — ALDs are low-cost, passive treatment systems that can be used to treat the acidity of MIW under specific geochemical conditions. ALDs are easy to construct and maintain, and consist of a buried bed of limestone engineered to intercept anoxic, acidic MIW and add alkalinity through dissolution of the limestone. ALDs can be used alone, but are more commonly used together with other treatment technologies such as constructed wetlands. They can be installed in remote locations and utilities are not required for implementation. The effectiveness of most ALD systems declines over time and they eventually require maintenance or replacement.

  • Review of Passive Systems for Acid Mine Drainage Treatment Adobe PDF Logo
    Skousen, J., C.E. Zipper, A. Rose, P.F. Ziemkiewicz, R. Nairn, L.M. McDonald, and R.L. Kleinmann.
    Mine Water Environment 36(1):133-153(2017)
    This paper reviews the current state of passive system technology development for the treatment of acid mine drainage, provides results for various system types, and offers guidance for system sizing and effective operation.
  • Passive Biological Treatment of Mine Water to Reduce Conductivity: Potential Designs, Challenges, and Research Needs Adobe PDF Logo
    Smyntek, P.M., R.C. Wagner, L.-A. Krometis, S.C. Sanchez, T. Wynn-Thompson, and W.H.J. Strosnider.
    Journal of Environmental Quality 46:1-9(2017)
    Passive biological treatment systems can be effective in removing acidity and metals from mine water, but review of current literature suggests that their ability to reduce conductivity appears somewhat limited. Some systems, particularly those that do not incorporate limestone into their construction materials, have been observed to reduce conductivity by 30-40%, which might prove useful as a pretreatment or finishing component of a larger treatment system, or in the treatment of legacy discharges. Design optimization will require identification of the ionic constituents responsible for primary conductivity constituents in various regions, long-term monitoring data of current systems that might not have been designed primarily to treat conductivity, and evaluation of the environmental factors governing underlying biogeochemical processes responsible for specific ion removals. Ideally, field-scale monitoring efforts will concurrently evaluate downstream impacts on aquatic ecology.

Biochemical Reactors — Passive treatment refers to processes that do not require frequent human intervention, operation, or maintenance, and typically employ natural construction materials, natural treatment media, and promote growth of natural vegetation. Biochemical reactors (BCRs) are an engineered passive treatment system that use microorganisms to remove contaminants from MIW. An organic substrate is typically used to promote microbial and chemical reactions that reduce concentrations of metals, acidity and sulfate. BCRs can be lower-maintenance treatment options for mining site cleanups and offer significant opportunities to reduce the environmental footprint associated with treatment of MIW.

Community Guide

  • Bioremediation for Acid Mine Drainage and Heavy Metals Contamination
    Uy, B. and L. Fairchok. Geo Engineer, April 21, 2021
    One method of remediating acid mine drainage includes the usage of bioreactors powered by sulfate-reducing bacteria (SRB). Sulfate-reducing bacteria are grown with some organic material, like cow manure or peat. These bacteria, in anaerobic conditions, use the organic carbon (CH2O) from these environments to reduce sulfate (SO42-) to sulfide (H2S), which reacts with the dissolved metal ions created by the reactions with pyrite and water to precipitate them. This decreases available concentrations of sulfate and dissolved metal ions from the original acid mine effluent, neutralizes pH from reduction of sulfate and removal of free hydronium (H3O+) ions, and additionally produces the pH buffer bicarbonate (HCO3-), which increases the pH of the acid mine effluent (produces alkalinity). By exposing this effluent to these bacteria, cleaner water can be discharged from mines. Case studies of Lilly and Orphan Boy Mine and Sure Thing Mine are presented and compared to understand the efficiencies of bioreactors with sulfate-reducing bacteria and the evolution in their designs. The mines are both located within similar regions in mountainous Montana, with similar climate, geology, and contaminants, but have very different methods of using sulfate-reducing bacteria in bioreactors. Because the remediation of Lilly and Orphan Boy Mine occurred before Sure Thing, the design ideology and lessons learned can be compared from one mine to the other. https://www.geoengineer.org/education/web-class-projects/ce-176-environmental-geotechnics/assignments/bioremediation-for-acid-mine-drainage-heavy-metals-contamination#sure-thing-mine
  • Assessment of Bed Hydraulics and Metal Loadings in a Passive Vertical Flow Bioreactor in Commerce, Oklahoma
    Cremeans, M.M., J.F. Devlin, T.C. Osorno, and R.W. Nairn.
    Groundwater Monitoring & Remediation 39(3):40-47(2019)
    A passive vertical flow bioreactor (VFBR) engineered treatment pond was used to remediate groundwater contaminated from improperly abandoned, over-drilled, and cased legacy boreholes at the Mayer Ranch in Commerce, Oklahoma. The VFBR promoted metal sorption and precipitation as sulfides by established reducing conditions in the groundwater. To verify that operations were unhindered by nonuniform flow in the VFBR, a flow uniformity assessment was done using a streambed point velocity probe (SBPVP), which was independently validated with a water balance. The outflow calculated from the SBPVP data came within 30% of the value suggested by measured inflow rates to the pond, supporting the conclusion that flow through was occurring with a satisfactory level of uniformity. Water flow rates through the reactive bed were up to an order of magnitude greater than those employed in prior column testing, contributing to metal loading rates estimated to be 2 orders of magnitude greater than those tested in the columns. Rapid chemical reactions that likely occurred close to the pond water-sediment interface contributed to the treatment system achieving its design objectives. More information https://projects.itrcweb.org/miningwaste-guidance/cs14_commerce.htm
  • Voluntary Reclamation and Remediation of the Former Garfield Vanadium Mine Site, Rifle, Colorado Part I: Remedial Investigation, Remedy Selection, and Reclamation
    Nielsen, B., C. Beul, J. Rusch, and L. Santisteban. | Technical Sessions: Smart Mining: Resources for a Connected World, 24-27 Feb 2019, Denver, Colorado. p 106 [plus Part II, p 107], 2019
    The Garfield Mine is a legacy vanadium mine in western Colorado. The site's multiple mine openings, waste rock piles, and adit seepages were voluntarily remediated through the Colorado Voluntary Cleanup Program (VCUP). The remediation process involved performing the site investigation under the supervision of a licensed radioactive materials handler while working with VCUP and the state's Radiation Management Unit. The remedial action objectives (RAOs) under VCUP included preventing direct human or biotic exposure to the waste rock and radiation emitting from the waste rock and maintaining the existing undeveloped character of the surrounding landscape. The site-wide design involved regrading, installation of an infiltration barrier and rock cover, a diversion channel, and a biologically based passive remediation water treatment system. The full-scale biologically based system, operational since 2017, was chosen to reduce metal concentrations and radionuclides in adit seepage (sulfate, Se, Zn, U, Ra, and gross alpha and beta particles) and prevent discharge from the site. The system consists of a sulfate-reducing biochemical reactor and post-treatment aerobic polishing cells that provide year-round operation and zero discharge of effluent. After 12 years of site investigations, the remedial action was completed in 2016 and 2017 with all RAOs met and a no-further-action determination granted in 2018.

  • Passive Multi-Unit Field-Pilot for Acid Mine Drainage Remediation: Performance and Environmental Assessment of Post-Treatment Solid Waste
    Vasquez, Y., C.M. Neculita, G. Caicedo, J. Cubillos, J. Franco, M. Vasquez, A. Hernandez, and F. Roldan. | Chemosphere [Published online 23 November 2021 prior to print]
    The performance of a passive multi-unit field pilot to treat AMD from a coal mine in Colombia Andean Paramo was assessed. The multi-unit field-pilot combined a pre-treatment unit (550 L) filled with dispersed alkaline substrate and six passive biochemical reactors (PBRs; 220 L) under open (PBRs-A) and closed (PBRs-B) configurations to the atmosphere. The AMD quality was 1200 ± 91 mg/L Fe, 38.0 ± 1.3 mg/L Mn, 8.5 ± 1.6 mg/L Zn, and 3200 ± 183.8 mg/L SO42-, at pH 2.8. The input and output effluents were monitored to establish AMD remediation. Physicochemical stability of the post-treatment solids, including metals (Fe2+, Zn2+, and Mn2+) and sulfates for environmental contamination from reactive mixture post-treatment, was also assessed. A total removal of 74% SO42-, 63% Fe2+, and 48% Mn2+ in the PBRs-A, and 91% SO42, 80% Fe2+, and 66% Mn2+ removal was achieved in the PBRs-B. A 99% removal for Zn2+ was achieved in both without significant differences (p < 0.05). A study of the physicochemical stability of the post-treatment solids showed the PBRs could produce acidic leachates capable of releasing large quantities of Fe and Mn if they are disposed of under oxidizing conditions; contact with water or any other leaching solutions must be avoided. The different PBR configurations induced changes in the performance of the passive multi-unit field pilot during AMD remediation.
  • Successful Passive Treatment of Sulfate Rich Water Adobe PDF Logo
    Robinson, J., J. Dodd, I. Andrews, J. Gusek, L. Josslyn, and E. Clarke.
    Proceedings of the 14th IMWA Congress, Mine Water Management for Future Generations, 12-15 July, virtual, 8pp, 2021
    A passive sulfate reduction system with iron scrubbers was identified as the most viable option to treat elevated sulfate in landfill leachate. Bench-scale trials were conducted using a biochemical reactor with different proportions of wood chips, straw, manure, limestone, and biochar to culture sulfate-reducing bacteria. The concept of 'bugs on booze' was also trialed using a fixed bed anaerobic bioreactor, where alcohol was added to enhance the sulfate reducer activity. The resulting treated leachate was then passed through haematite, magnetite, and iron filings to remove sulfide generated by the bacteria, with an aerobic wetland used to polish the effluent. The success of the bench-scale project led to a pilot-scale system being constructed and monitored in Spring 2020. Results confirmed the success of the bench-scale testing and provided useful insights to manage the system, particularly in winter months.
  • Land Application Disposal System Design for Biochemical Reactor Treated Effluent
    Anton, N.R., D.T. Shanight, C.S. Storrar, M.J. Fischer, E.M. Janoviak, and B. Lala
    36th Annual Meeting of the American Society of Mining & Reclamation, 3-7 June, Big Sky, MT, 26 slides, 2019
    At the mine waste repository for the Upper Tenmile Creek Mining Area Superfund site, Montana, collected leachate water has been managed in an active water treatment plant and pilot biochemical reactor system, with disposal to a land application disposal (LAD) system since 2003. In 2018, the design was completed for a full-scale leachate passive treatment system utilizing parallel BCR cells, post-treatment settling, aeration, limestone channels, and a gravity-operated LAD system. The new system construction will begin in 2019, and the existing water treatment infrastructure will be decommissioned after the new system is operational and functional. The presentation includes the critical passive treatment design components and provides details of the pre-design investigation and design approach for the LAD system, including field siting for the LAD, test pits, soil lithology logging, permeability testing, soil metal sorption studies, metal sorption capacity and water balance calculations, and hydraulic design of the LAD.
    More information: https://projects.itrcweb.org/bcr-1/Content/Appendix%20B%20Case%20Studies/B15%20Luttrell%20Case%20Study.htm
  • 2014 Treatability Study Date Evaluation: Barker-Hughesville Mining District Superfund Site Adobe PDF Logo
    U.S. EPA Region 8, 1050 pp, 2017
    In 2014, two treatability studies were conducted for the Barker-Hughesville Mining District Superfund Site as part of the remedial investigation/feasibility study process. Year 2 of the Danny T Adit study continued the 2013 year 1 field pilot study to evaluate various passive and semi-passive methods for treatment of the Danny T Mine adit water. The bench-scale study for the Tiger Mine was focused on potential in situ-based treatments that could be deployed inside the underground mine workings area. A representative mine discharge water (Tiger mine adit TI-AD004, the "Firehose" adit) was collected in bulk and analyzed at the treatability laboratory in batch container tests with various reagents. The report summarizes each of these studies, including their objectives, experimental and sampling procedures, results, conclusions, and recommendations.
  • Selenium, Uranium, and Nitrate: Treatment of Troublesome Contaminants in Mining Wastewaters - EBR Case Studies
    Opara, A., J. Adams, J. Fudyma, and J. Bowden.
    Journal of American Society of Mining and Reclamation 7(2):19-34(2018)
    This paper discusses an application of the electro-biochemical reactor (EBR) technology for Se, U, and NO3 bio-reduction and removal from mining wastewaters. Three case studies are presented, based on laboratory bench- and onsite pilot-scale trials with significantly different mining waters, each contaminated with varying concentrations of Se, U, and NO3. The EBR was demonstrated on all three sites to treat the waters to <0.5-3.2 µg/L Se, <0.1-0.8 µg/L U, and <0.02-<2 mg/L NO3-N.
  • Operation and Maintenance of Passive Treatment Systems
    Hedin, R.
    The 23rd British Columbia MEND Metal Leaching/Acid Rock Drainage Workshop, Vancouver. 32 slides, 2016
    Passive treatment of contaminated mine drainage is less costly than active treatment, but its reliability is sometimes questioned. A simple approach is presented that has been used to design effective passive treatment systems in Pennsylvania. Three systems that demonstrate commonly utilized passive technologies are described along with long-term monitoring data: (1) the Marchand system of oxidation/settling ponds and a constructed aerobic wetland; (2) the Anna S system of vertical flow ponds and aerobic wetlands; and (3) the Scootac system of a drainable limestone bed and settling pond. The systems have provided highly reliable and effective treatment for 3 to 18 years. The data demonstrate that properly designed, constructed, and maintained passive treatment systems are a highly cost-effective solution for contaminated mine discharges.
    Slides: http://bc-mlard.ca/files/presentations/2016-22-HEDIN-operation-maintenance-passive-treatment-systems.pdf
    Paper: http://www.hedinenv.com/pdf/NAMLP_Effective_Passive_Treatment_Paper.pdf
  • Year-Round Performance of a Passive Sulfate-Reducing Bioreactor that Usess Rice Bran as an Organic Carbon Source to Treat Acid Mine Drainage
    Sato, Y., T. Hamai, T. Hori, H. Habe, M. Kobayashi, and T. Sakata.
    Mine Water and the Environment [Publication online 2 Sep 2017 prior to print]
    The project objective was to demonstrate the stable operation of a sulfate-reducing bioreactor for at least a year in terms of continuous acid mine drainage (AMD) sulfate reduction and metal removal. The 35-L bioreactor contains sulfate-reducing bacteria (SRB) and a packed inoculum layer of a mixture of rice husks, limestone, and field soil covered with rice bran. During operation, the AMD input flow rate was adjusted to 11.7 mL/min (hydraulic retention time 50 h). Throughout the year, physicochemical analyses of system input and output AMD samples revealed that both pH and oxidation-reduction potential values remained consistent with the process of sulfate reduction by SRB, although this reduction was stronger in summer than in winter. Metal concentrations at the outlet port of <0.33 mg/L Zn, <0.08 mg/L Cu, and <0.005 mg/L Cd more than met Japan's national effluent standards. Illumina sequencing of 16S rRNA genes revealed the dominance of Desulfatirhabdium butyrativorans-related species within the bioreactor.
  • Closed Loop for AMD Treatment Waste Adobe PDF Logo
    Zamzow, K. and G. Miller. IMWA 2017: Mine Water & Circular Economy (Wolkersdorfer, C. et al., eds.). IMWA, Vol II:1103-1110(2017)
    The Leviathan is an abandoned former copper and sulfur mine located in the Sierra Nevada of the Western United States. Acid mine water at the site is addressed in four compost-free, open-pond, alcohol-based bioreactors that have operated since 2003, treating 11.4 to 15.1 million liters of drainage annually. To take advantage of a local opportunity, a manufacturing waste product rich in alcohols from biodiesel (BD) production at a nearby agricultural farm was used in a 55-day pilot study as a replacement for the ethanol usually used in the bioreactor system. Final results showed that although sulfate reduction was not as high as previous years, most metals were removed below effluent discharge requirements, particularly when appropriate hydraulic residence time was achieved. The investigators observed that cold climates may challenge consistent delivery of BD waste from storage tank to bioreactor.
  • Passive Treatment of Highly Contaminated Iron-Rich Acid Mine Drainage Adobe PDF Logo
    Neculita, C.M., T.V. Rakotonimaro, B. Bussiere, T. Genty, and G.J. Zagury.
    2017 National Meeting of the American Society of Mining and Reclamation, Morgantown, WV, 9-13 April. ASMR, Champaign, IL. 43 slides, 2017
    An investigation of the effectiveness of acid mine drainage treatment systems—DAS (dispersed alkalinity substrate) units, consisting of coarse organic matrix (wood chips) and neutralizing materials (calcite, magnesia), and a mixed treatment system comprising passive biochemical reactors (PBRs: wood waste-based and constructed wetlands)—compared the performance of a 2-yr lab study and two field treatment installations. In the lab, DAS-calcite, DAS-dolomite, or DAS-wood ash for iron pretreatment, prior to sulfate removal by PBR, was followed by a final polishing unit. In the field, a pilot tri-unit (two passive biochemical reactors separated by a wood-ash unit) system was installed on the Lorraine rehabilitated mine site and monitored over a 5-yr period. Up to 99% Fe removal occurred during lab testing (using two DAS-wood ash pretreatment units) relative to the field pilot (76% Fe removal). On East-Sullivan, a second rehabilitated mine site, a 14-yr monitoring dataset for a mixed treatment system showed the progressive improvement of water quality over time. Iron concentration declined 98%, and regulation requirements (Fe < 3 mg/L) were obtained in most of the discharge locations.

  • Performance of a Sulfidogenic Bioreactor Inoculated with Indigenous Acidic Communities for reating an Extremely Acidic Mine Water
    Gonzales, D., Y. Liu, D.V. Gomez, G. Southam, S. Hedrich, P. Galleguillos, C. Colipai, et al.
    Minerals Engineering 131:370:375(2019)
    This study tested the performance of a low pH sulfidogenic bioreactor inoculated with an indigenous microbial community to treat mine-impacted water. The inoculum was obtained from anaerobic sediments collected from an acidic river located in northern Chile. The sulfidogenic bioreactor system (2.3 L) was operated as a continuous flow mode unit for 99 days at 30°C and fed with synthetic water based on the chemical composition of the acidic river. The bioreactor pH was set to 4.5 initially and was increased in stages to pH 6.0 during the experiment. Results show that zinc concentrations in liquors draining the bioreactor were below the detection level in most of the samples analyzed. Increasing the glycerol concentration increased the removal of iron (70%), but generated acetic acid (from 1 to 5 mM). Microbial populations changed with varying operation parameters, and a known acetogenic sulfidogen (Desulfoporosinus acididurans) became more dominant over time.
  • Low-Cost Biological Treatment of Metal- and Sulphate-Contaminated Mine Water Adobe PDF Logo
    Neale, J.W., H.H. Muller, M. Gericke, and R. Meuhlbauer.
    Mine Water & Circular Economy (Wolkersdorfer, C. et al., eds.). IMWA, Vol I:453-461(2017)
    A passive biological sulfate reduction process was developed using a substrate mix comprising wood chips, wood shavings, hay, lucerne, and cow manure to address mine-affected water from a South African coal mine. The process achieved over 90% sulfate removal, raised the pH level above 7, and precipitated the metals. Operating parameters were optimized to increase process kinetics, and the results were used to design a pilot plant that will be operated at the mine to treat several hundred liters of water per day.
  • Passive Biological Treatment of Mine Water to Reduce Conductivity: Potential Designs, Challenges, and Research Needs Adobe PDF Logo
    Smyntek, P.M., R.C. Wagner, L.-A. Krometis, S.C. Sanchez, T. Wynn-Thompson, and W.H.J. Strosnider.
    Journal of Environmental Quality 46:1-9(2017)
    Passive biological treatment systems can be effective in removing acidity and metals from mine water, but review of current literature suggests that their ability to reduce conductivity appears somewhat limited. Some systems, particularly those that do not incorporate limestone into their construction materials, have been observed to reduce conductivity by 30-40%, which might prove useful as a pretreatment or finishing component of a larger treatment system, or in the treatment of legacy discharges. Design optimization will require identification of the ionic constituents responsible for primary conductivity constituents in various regions, long-term monitoring data of current systems that might not have been designed primarily to treat conductivity, and evaluation of the environmental factors governing underlying biogeochemical processes responsible for specific ion removals. Ideally, field-scale monitoring efforts will concurrently evaluate downstream impacts on aquatic ecology.

Chemical Precipitation — Chemical precipitation is a flexible, permanent technology used to treat MIW, including acid mine drainage, neutral drainage, and pit lake water. Chemical precipitation processes involve adding chemical reagents and then separating the precipitated solids from the cleaned water. Typically, the separation occurs in a clarifier, although separation by filtration or with ceramic or other membranes also is possible. When chemical precipitation is used in pit lakes or other water bodies, the precipitated solids can remain in the bottom of the pool. This technology can be used by itself or in conjunction with other treatments.

  • Treatment of Mine Drainage with Significant Topographical Constraints: Case Study of the Bodennec Site (France)
    Jacob, J.C., M. Save, and Y. Menard. Mine Water and the Environment [Publication online 3 Mar 2018 prior to print]
    The Bodennec lead and zinc mine site produces circumneutral mine drainage that contains 8 mg/L of dissolved iron, whereas the Fe water quality objective is 3 mg/L at the outlet. The water treatment installation in use, based on three settling ponds, could not reach this objective, and the site lacked sufficient surface area to build additional ponds or a passive treatment plant. A pilot-scale NaOH system comprising a pump controlled by a flow meter was built on site to assess the feasibility of a low-maintenance system to effect treatment via injection of a small volume of concentrated NaOH solution into the water. A solar panel connected to a battery supplied the system with electricity. Given the stability of the pH in the drainage no pH probe was needed. A final water treatment plant based on this pilot was built in 2017.
  • Copper Mine Tailings Valorization Using Microbial Induced Calcium Carbonate Precipitation
    de Oliveira, D., E.J. Horn, and D.G. Randall.
    Journal of Environmental Management 298:113440(2021)
    The solidification of copper mine tailings was studied using microbial-induced calcium carbonate precipitation (MICP) to valorize the waste stream. The toxicity of copper on Sporosarcina pasteurii, the ureolytic bacteria which drives the MICP process, was investigated using bio-columns. The bio-columns produced from copper mine tailings had a compressive strength of 0.54 MPa, lower than bio-columns produced from beach sand (1.85 MPa). The low porosity of the copper mine tailings limited the depth to which the MICP reaction could successfully occur, resulting in the formation of a 1.8 mm ± 0.4 mm crust around the outer extremities of the bio-columns. Particle size was a key deciding factor, and, as a result, MICP is not suitable to produce 'thick' bio-cemented materials from small particles (<100 µm), such as mine tailings. However, the method could produce thinner materials such as bio titles or could potentially be used to cement together toxic dust particles that typically form on mine tailing heaps.

Constructed Treatment Wetlands — Constructed treatment wetlands are man-made biologically active systems such as bogs, swamps, or marshes with saturated soils and at least periodic surface or near-surface water designed specifically to treat contaminants in surface water, groundwater, or waste streams. This technology is a valid treatment option for a variety of waste streams, including MIW, remedial wastewaters, agriculture waste streams, and industrial waste streams. Constructed treatment wetlands have also been used for "wet capping" of solid wastes and are often called "capped mine wastes in a wetlands setting." Constructed treatment wetlands can be used with other technologies to extend the operational lifespan of the systems or enhance the removal performance of specific constituents of concern.

  • Passive Treatment of Circumneutral Mine Drainage from the St. Louis Mine Tunnel, Rico CO: Part 3-Horizontal Wetlands Treatment Train Pilot StudyAdobe PDF Logo
    Sobolewski, A.B., A.C. Riese, T.J. Moore, and A.R. Brown.
    Mine Water and the Environment (2022)
    A study tested the performance of a demonstration-scale horizontal wetlands passive treatment train comprised of a settling basin, surface flow wetland, horizontal-flow anerobic wetland, aeration channel, and rock drain at the Rico-Argentine site. Mine drainage from the St Louis Tunnel is circumneutral most of the year, with spring freshets increasing flow, decreasing pH, and increasing metal concentrations. Total Zn, Cd, and Mn effluent concentrations met project treatment goals (PTGs) 75, 96.9, and 100% of the time, respectively, and 93.9, 100, and 100% of the time for the dissolved metals. Most PTG exceedances occurred during the freshet events. Most Zn and Cd attenuation was attributed to sulfide precipitation in the anaerobic cell and capture/filtration of suspended ZnS particles in the anaerobic wetland and rock drain. Manganese was attenuated in the aerobic portion of the anaerobic cell as Mn oxides and carbonates. Oxidation of Mn occurred in the rock drain as biogenically formed Mn oxides adhered to the rock matrix. Carryover of dissolved sulfides from the anaerobic cell limited the rock drain's Mn removal efficiency. Low temperatures did not significantly affect biological activity within the system; the effects of seasonal water quality were more important.
  • Effects of Cattails and Hydraulic Loading on Heavy Metal Removal from Closed Mine Drainage by Pilot Scale Constructed Wetlands
    T.T. Nguyen, S. Soda, A. Kanayama, and T. Hamai
    Water 13(14):1937(2021)
    Removal of heavy metals from neutral mine drainage of a closed mine in the Kyoto prefecture was demonstrated using pilot-scale constructed wetlands (CWs). The CWs were filled with loamy soil and limestone and were planted with or without cattails. The hydraulic retention time (HRT) in the CWs was shortened gradually from 3.8 to 1.2 days during 3.5-months of operation. A short HRT of 1.2 days in the CWs was sufficient to achieve the effluent standard for Cd (0.03 mg/L). The CWs planted with or without cattails reduced the average Cd concentrations from 0.031 to 0.01 and 0.005 mg/L, Zn from 0.52 to 0.14 and 0.08 mg/L, Cu from 0.07 to 0.04 and 0.03 mg/L, and As from 0.011 to 0.006 and 0.006 mg/L. Heavy metals were removed mainly by adsorption to the soil in both CWs. The biological concentration factors in cattails were >2 for Cd, Zn, and Cu. The translocation factors of cattails for all metals ranged from 0.5 to 0.81. Sulfate-reducing bacteria (SRB) were detected only from soil in the planted CW. Although cattails were a minor sink, the plants contributed to metal removal by rhizofiltration and incubation of SRB and may have produced sulfide precipitates in the rhizosphere.
  • The Treatment of Acid Mine Drainage Using Vertically Flowing Wetland: Insights into the Fate of Chemical Species
    Nguegang, B., V. Masindi, T.A.M. Msagati, and M. Tekere.
    Minerals 11:477(2021)
    Acid mine drainage (AMD) was treated in a vertically flowing wetland enriched with Vetiveria zizanioides as a decontaminating media and soil as the substrate. Water percolated through the substrate was collected and characterized every five days for 30 days. Results revealed a tolerant index of 1.03 for Vetiveria zizanioides and a net reduction of metals and sulfate. The removal efficacy of chemical species was observed to obey the following order: Fe (71.25%) > Zn (70.40%) > Mn (62%) > Al (56.68%) > SO4 2− (55.18%) > Ni (35%) > Cu (18.83%). The removal of chemical species was further aided by the used substrate, which could be attributed to the accumulation of chemical species on the soil through precipitation, adsorption, and phytoretention. Substrate plays a significant role in removing metals, while the grass and external factors accounted for the remaining chemical species attenuation. The distribution of chemical species was predominantly in the roots, except manganese, which was transferred in the shoot (67%). AMD chemical species present in the substrate and the grass components confirmed that the plants played a huge role in removing contaminants. The PH REdox EQuilibrium geochemical model confirmed that metals existed as di-and-trivalent complexes in AMD. Available metals were precipitated as metals hydroxides and oxy-hydrosulfates by the substrate. Results indicate that vertically flowing wetland can be used for passive treatment of AMD, particularly at active and abandoned mines.
    This article is Open Access at https://www.mdpi.com/2075-163X/11/5/477/htm
  • Case Study: Performance of the Operating Demonstration-Scale Constructed Wetland Treatment System at Minto Mine
    Bouchard, E., C. Prentice, R. Herbert, R. Martz, B. Eisner, V. Friesen, and M. Simair.
    41st British Columbia Mine Reclamation Symposium, 17-20 September, Williams Lake, BC, 2018
    The Minto Mine is following a phased approach for the design and implementation of a Constructed Wetland Treatment System (CWTS) for water treatment at closure. The CWTS is currently in the demonstration-scale and optimization stage preceding full-scale implementation. The CWTS has successfully treated constituents of potential concern in the mine site's sub-arctic continental climate. Carex aquatilis (aquatic sedge) and aquatic mosses (bryophytes) from natural wetlands onsite were used for planting, while water mine-impacted seepage water was used as feed water. The CWTS was designed to target specific physicochemical parameters for treatment (confirmed and refined through off-site pilot-scale testing), which enable denitrifying selenium- and sulfate-reducing bacteria to treat nutrients, metals, and metalloids in the water. The CWTS treated targeted constituents of potential concern in the following extents and percentages: cadmium 80% (from 0.0261 µg/L to 0.0092 µg/L), copper 65% (from 49.1 µg/L to 17.3 µg/L), molybdenum 58% (from 6.3 µg/L to 2.7 µg/L), selenium 89% (from 4.0 µg/L to 0.5 µg/L), zinc 98% (from 49.2 µg/L to 1.9 µg/L), and nitrate as N 97% (from 6.5 mg/L to 0.19 mg/L). Continued trials were underway in 2018 to investigate treatment under a wider range of operational conditions.
  • Operation and Maintenance of Passive Treatment Systems
    Hedin, R.
    The 23rd British Columbia MEND Metal Leaching/Acid Rock Drainage Workshop, Vancouver. 32 slides, 2016
    Passive treatment of contaminated mine drainage is less costly than active treatment, but its reliability is sometimes questioned. A simple approach is presented that has been used to design effective passive treatment systems in Pennsylvania. Three systems that demonstrate commonly utilized passive technologies are described along with long-term monitoring data: (1) the Marchand system of oxidation/settling ponds and a constructed aerobic wetland; (2) the Anna S system of vertical flow ponds and aerobic wetlands; and (3) the Scootac system of a drainable limestone bed and settling pond. The systems have provided highly reliable and effective treatment for 3 to 18 years. The data demonstrate that properly designed, constructed, and maintained passive treatment systems are a highly cost-effective solution for contaminated mine discharges.
    Slides: http://bc-mlard.ca/files/presentations/2016-22-HEDIN-operation-maintenance-passive-treatment-systems.pdf Adobe PDF Logo
    Paper: http://www.hedinenv.com/pdf/NAMLP_Effective_Passive_Treatment_Paper.pdf Adobe PDF Logo
  • Constructed Wetland Design and Optimization for Metal and Metalloid Treatment at the Minto Mine in the Yukon, Canada
    Haakensen, M., V. Friesen, and R. Herbert.
    Technical Program: The 12th International Symposium on Mining with Backfill, 19-22 February 2018, Denver, CO.
    A 2-year site-specific demonstration of a constructed wetland treatment system was conducted for Capstone Mining Corporation's Minto Mine (Yukon). Biogeochemical technologies such as microbial community profiling were used to guide system design in a site-specific context. Pilot-scale tests enabled selection of the optimal full-scale demonstration design from several options and tested different predicted closure water chemistries. The selected design treats the water for Cd, Cu, and Se, with polishing achieved for several additional metals. Removal rate coefficients were developed for modeling and sizing of full-scale systems. The Government of Yukon recognized the project with the 2017 Robert E. Leckie Award for responsible and innovative exploration and mining practices to Capstone subsidiary Minto Explorations Ltd. See the details of this demonstration project in the report, Minto Mine Constructed Wetland Treatment Research Program: Demonstration-Scale 2017, at https://emrlibrary.gov.yk.ca/minerals/MajorMines/minto/reclamation-and-closure-plan-2016-01/appendices/appendix-a3-wetland-treatment-research-program-demostration-cwts.pdf.

  • Effective Treatment of Acid Mine Drainage Using a Combination of MGO-Nanoparticles and a Series of Constructed Wetlands Planted with Vetiveria Zizanioides: A Hybrid and Stepwise Approach
    Nguegang, B., V. Masindi, T.A.M. Makudali, and M. Tekere.
    Journal of Environmental Management 310:114751(2022)
    Acid mine drainage (AMD) was treated in a study using a hybrid approach that combined a nano-and-biotic system synergistically integrated in a stepwise and modular fashion. The treatment chains were composed of different stages, including neutralization using activated magnesite or MgO-nanoparticles (NPs) (Stage 1) and polishing using a series of wetlands (Stage 2) in a stepwise connection. In Stage 1, actual AMD was treated with MgO-NPs at a ratio of 1:100 (1 g/100 mL – w/v ratio), 500 rpm of mixing speed, and 1 hour of hydraulic retention time (HRT). In Stage 2, the final water was fed into three interconnected constructed wetlands with different flow modalities [(subsurface vertical flow (SSVF-CW), free water surface flow (FWS-CW), and subsurface horizontal flow (SSHF-CW)], for further purification and polishing. The product water and substrate were collected daily at the outlet and bottom of each wetland. After treatment, the pH of the product water increased from 2.6 to 10.4. Significant removal of inorganic contaminants was observed in the following removal sequence: Fe (99.8%) ≥ Al (99.5%) ≥ Mn (99.24%) ≥ Zn (98.36%) ≥ Cu (97.38%) ≥ Ni (97.7%) ≥ SO42- (80.59%). Reduced electrical conductivity was also observed (86%). Step 1 partially removed the metals and sulfate while Step 2 effectively removed SO42- and EC levels, thus denoting stellar combination and complementary performance for the hybrid system in an integrated fashion. Analytical instruments underpin and succinct the fate of chemical species in raw and product MgO-NPs, substrates, and the grass. The product water conformed to the prescribed standards for effluent discharge, proving that the synergy of neutralization and bioremediation could yield the desired results in mine water management.
  • Remediation of Acid Mine Drainage-Impacted Wter by Vetiver Grass (Chrysopogon Zizanioides): A Multiscale Long-Term Study
    Kiiskila, J.D., D. Sarkar, S. Panja, S.V. Sahi, and R. Datta.
    Ecological Engineering 129:97-108(2019)
    The study developed a cost-efficient and sustainable floating treatment wetland system using vetiver grass (Chrysopogon zizanioides). Year-long large- and small-scale hydroponic experiments were used to determine the effectiveness of vetiver for treating acid mine drainage-impacted waters from the Tab-Simco mine site in southern Illinois. For the large-scale mesocosm study, vetiver rafts were suspended in 100-gal containers. Water quality was monitored every 28 days and at the end of the experiment (364 days); plant health was monitored by measuring changes in biomass and recording visual changes in root and shoot coloration and morphology. There was higher net removal of Fe (81%) and Pb (81%) with lower removal of Ni (38%), Zn (35%), SO42- (28%), Mn (27%), Cr (21%), Al (11%) and Cu (8.0%). Toxicity characteristic leaching procedure showed that vetiver biomass was not hazardous waste as a result of metal accumulation. From the small-scale experiment, there was near complete removal of SO42- (91%) and metals (90-100%) with the exception of Pb (15%) and Cu (0.0%).
  • A Preliminary Study to Design a Floating Treatment Wetland for Remediating Acid Mine Drainage-Impacted Water Using Vetiver Grass (Chrysopogon Zizanioides)
    Kiiskila, J.D., D. Sarkar, K.A. Feuerstein, and R. Datta.
    Environmental Science and Pollution Research 24(36):27985-27993(2017)
    A study is underway to develop a low-cost and sustainable floating wetland treatment (FWT) system for acid mine drainage (AMD) at the abandoned Tab-Simco coal mining site in Illinois using vetiver grass. Tab-Simco AMD is highly acidic (mean pH 2.64) and contains high levels of sulfate and metals. A 30-d greenhouse study conducted to screen and optimize the necessary parameters to design a FWT system showed significant sulfate removal, resulting in increased pH, particularly at higher planting densities. Vetiver also helped in metal removal: high amounts of Fe, Zn, and Cu were removed, with relatively lower amounts of Pb, Al, and Ni. Iron plaque formation on the root was observed, which increased metal stabilization in roots and lowered root-to-shoot metal translocation. Vetiver was tolerant of AMD, showing minimal change in biomass and plant growth. A large-scale mesocosm study is now in progress as the next step to develop a vetiver-based FTW system for AMD treatment.
  • Review of Passive Systems for Acid Mine Drainage Treatment Adobe PDF Logo
    Skousen, J., C.E. Zipper, A. Rose, P.F. Ziemkiewicz, R. Nairn, L.M. McDonald, and R.L. Kleinmann.
    Mine Water Environment 36(1):133-153(2017)
    This paper reviews the current state of passive system technology development for the treatment of acid mine drainage, provides results for various system types, and offers guidance for system sizing and effective operation.

Diversionary Structures — Diversionary structures are designed to prevent clean water from coming into contact with mining solid waste (net acid-producing materials) and to divert MIW to treatment or collection systems and away from sensitive environments. These include engineered channels, tunnels, pipelines, or other structures to divert surface water run-on or MIW runoff; engineered slurry walls, sheet pile walls, grouting, or other subsurface structures to divert or contain groundwater; and bulkheads and plugs in mine workings to control influx or discharge of MIW. Diversionary structures can be used to reduce the volume of, or exposure to, MIW. They also can be used to prevent erosion of mining waste and transport of soluble metals into surface water.

Electrocoagulation — Electrocoagulation refers to a group of technologies that use an electrical current that coagulates organic constituents and suspended solids in water. The coagulated organics have the ability to adsorb certain ionic constituents, making it possible to separate a flocculent with most of the suspended organics and some of the ionic constituents removed. Another variant of this system oxidizes an iron or aluminum anode to form an iron or aluminum hydroxide flocculent that can co-adsorb/co-precipitate some ions. The electrocoagulation process is complex and site- and contaminant-specific. These systems may be effective in certain niche applications. Detailed bench and pilot studies are required before implementing the technique.

In Situ Treatment of Mine Pools and Pit Lakes — This emerging technology for treating MIW involves injecting or placing substances (including carbon sources such as molasses or alcohol with nutrients) or alkaline materials such as lime directly into the mine pool or pit lake to neutralize the MIW and produce anaerobic conditions to precipitate metals in place. The addition of a carbon source leads to the formation of a sulfate-reducing bioreactor. Some metals are less soluble in their reduced form, including selenium, chromium and uranium. These oxidized metals can be removed from the water as solids. In situ treatment of solid mining waste in the form of residual minerals in mine walls, tailings, or waste rock involves the application of amendments such as potassium permanganate, phosphate or biosolids, and carbon substrate to stabilize the metals in place and reduce the formation of leachate or inhibit the migration of metals.

  • Pit Lake Treatment at the Reclaimed Former Farley Mine
    Bonner, D., J. Forbort, J. Vogan, C. Leask, W. Nixdorf, O. Beruar, and R. Frost
    2020 Mine Design, Operation & Closure Conference, 18-20 August, virtual, 26 minutes, 2020
    The presentation details the reclamation, acid rock drainage management, and pit lake treatment approaches at a former mine in Manitoba. Reclamation involved consolidating sulfide mineral-bearing tailings and installing cover systems over the tailings, stormwater diversion systems, and an impermeable cover system over a waste rock stockpile. During reclamation activities, approximately 900 million gallons of ARD were treated using an interim ARD treatment system to create a freeboard for future ARD management and in situ treatment of ARD within the pit lake. The freeboard from this water treatment yielded storage for four years. A recent pit lake water treatment campaign was completed to create a freeboard, using an innovative approach to facilitate effective treatment by offloading quicklime directly from the bulk delivery trucks without the need for a slaker.
    See times 1:25-1:51: https://www.youtube.com/watch?v=k3XVMlRL0gQ&list=UU1haRH1iNK0LYbYrtuTFROg&index=5

  • In-Pit Batch Treatment of Arsenic: Laboratory Studies and Field TrialAdobe PDF Logo
    Mine Environment Neutral Drainage Program, 71 pp, 2019
    Lab and field studies were conducted to demonstrate in-pit batch treatment of arsenic-contaminated water in mine pits using ferric sulfate. The overall objective of the investigation was to demonstrate that in-pit batch treatment of arsenic represents a viable and economical alternative to traditional water treatment applications. Phase 1 was a bench-scale study to define the design criteria, including the attainable treatment efficiencies, the required reagent dosages, and the sludge production rates. Phase 2 was a field-scale treatment trial that evaluated the practicality and efficacy of in-pit batch treatment of arsenic within the Night Hawk Lake Mine open pit, as informed by the results in Phase 1. Total and dissolved arsenic concentrations at 3 depths were compared pre- and post-treatment in 3 sampling events at two stations (NHP 1 and NHP2). Immediately post-treatment, total arsenic concentration at the surface at NHP1 decreased from 0.6 mg/L to 0.01 mg/L total arsenic with a dissolved concentration <0.002 mg/L for a treatment efficiency of ~98 within the surface depths. The mid-depth samples for the same sampling event were ~0.03 and 0.01 mg/L for the total and dissolved arsenic concentrations, respectively. The arsenic concentrations at depth remained close to the initial concentrations before treatment.

  • Realizing Beneficial End Uses from Abandoned Pit LakesAdobe PDF Logo
    McCullough, C.D., M. Schultze, and J. Vandenberg.
    Minerals 10:133(2020)
    This publication reviews published case studies of abandoned mine pit lakes, including common attributes and reasons that led to successful repurposing as beneficial end uses. Recommendations are given for all stages of mine closure planning to prevent pit lake abandonment and to achieve successful closure with beneficial end uses.

Ion Exchange — Ion exchange is well-established treatment technology that involves the interchange (or exchange) of ions between a solid medium and MIW. The solid medium can be commercially produced or made from naturally occurring substances (e.g., peat or zeolites). Synthetic organic resins are used predominantly because their characteristics can be tailored to specific applications. Ion exchange can be applied to dissolved constituents, cations or anions to treat mine discharges with various flow rates and can be used as a stand-alone technology or with other treatment technologies. The ability to regenerate resin and recover metals provides a potential additional benefit of this approach.

Ion Flotation — Ion flotation is a common separation technology that concentrates metal ions from solution so they can be collected and disposed of or recycled. A surfactant with an opposite charge of the target ions is used to attract metal ions, and air bubbles carry the material to the surface of the solution. Ion flotation can be used to remove heavy metal ions from wastewater, but the process also is being studied to remove uranium from mine water by adding biological or synthetic rhannolipids, a type of biosurfactant. Biological or synthetic rhamnolipids can be made using sustainable production methods, and are biodegradable, recyclable and have low toxicity. As a separation process, ion flotation has low energy requirements, small space requirements, relatively low costs, and occurs quickly. The process is most effective when site-specific conditions, such as water chemistry, are considered.

  • New Technique Yields Promising Results for Uranium Removal in the Field Adobe PDF Logo
    National Institute of Environmental Health Sciences, Research Brief 326, 2 pp, 2022
    This Research Brief presents a new study using an ion flotation process to remove uranium from groundwater near abandoned mines. The performance of biologically derived and synthetic rhamnolipids was evaluated. Both forms of rhamnolipids were found to remove uranium via ion flotation for acidic solutions and will be most effective when site-specific conditions are considered.

Microbial Mats — A constructed microbial mat is an aquatic bioremediation system that uses naturally occurring, living organisms (primarily cyanobacteria) to rapidly remove metals from MIW. Cyanobacteria are photosynthetic and can be grown like plants, harvested, and dried until needed. Microbial mats grow rapidly, can survive harsh environmental conditions, and can tolerate high concentrations of compounds that are toxic to plants or algae. They are called "constructed" mats because they are grown using a standard technique that is inexpensive and requires minimal training. Microbial mats can be used as a stand-alone technology or with other technologies to treat dissolved organic and inorganic constituents, including a variety of metals, metalloids, radionuclides, and oxyanions, and can treat mine discharges collected in ponds and slow-flowing leachate. Sunlight intensity is an important requirement, and, like all biological systems, system performance decreases during winter seasons.

Passive Technologies — Passive treatment (passivation) of acid-generating material involves oxidizing or protecting the sulfide surface from water and oxygen. Techniques for reducing metal sulfide oxidation involve removing oxygen, water, bacteria, or the sulfide minerals, all of which contribute to the generation of acid mine drainage. All passivation technologies use a spray-on application, either as a solution (phosphate) or as a slurry (silica). It is one of the few treatment methods that can be used to treat exposed pit walls. Although laboratory and small-scale pilot data are available, this new technology has not been applied on a large scale and there are very limited data on long-term performance. In addition, several studies have indicated that there is an initial release of other constituents into the environment when passivation is applied. Techniques to control and possibly treat this release may be needed and regulatory approval obtained before releasing these constituents. This technology may be used alone or with other technologies.

  • Innovative Strategies for the Management of Metal Impacted Waters
    Mancini, S. | REMTECH 2021: The Remediation Technologies Symposium, Banff, AB, Canada, 13-15 October, 18 slides, 2021
    This presentation provides an overview of the development, design, and implementation of passive treatment technologies. Case studies on applying technologies, including in situ and ex situ treatment reactors such as Gravel Bed Reactors™ and bioreactors, phytotechnologies, constructed and engineered wetlands, pit lake in-pit treatment, and permeable reactive barriers are included. Deploying mobile treatment systems to mine sites, such as containerized columns and "wetlands on wheels," is also discussed as an important stage to facilitate treatability studies, regulatory approval, and advancement of technology application to full-scale. Each technology is discussed as a function of its implementability from a perspective of site-specific conditions, effectiveness, and expected impact on the local environment. Further, treatment system configurations, treatment mechanisms, and seasonality are explored to highlight the flexibility of their application in the context of various industry treatment needs.
  • Effect of an Extreme Flood Event on Solute Transport and Resilience of a Mine Water Treatment System in a Mineralised Catchment
    Mayes, W.M., M.T. Perks, A.R.G. Large, J.E. Davis, C.J. Gandy, P.A.H. Orme, and A.P. Jarvis.
    Science of The Total Environment 750:141693(2021)
    The Coledale Beck catchment contains the UK's first passive metal mine water treatment system. The catchment experienced an extreme rainfall event in December 2015 that equated to a 1 in 200-year event. The solute dynamics monitoring record for the site provided an opportunity to assess the effects of a major storm event on (1) catchment-scale solute transport and (2) the resilience of the new and novel passive treatment system to extreme events. Changes in system hydraulic efficiency explained a modest decline in treatment efficiency over time. There was no apparent flushing of the mine system during the storm event that could have compromised treatment system performance. Analysis of metal transport in the catchment downstream of the mine show the resilience of passive mine water treatment systems to extreme events and the importance of catchment-scale monitoring to ensure the continued effectiveness of treatment initiatives after major perturbation.
  • Passive Treatment of Acid-Mine Drainage
    Zipper, C., J. Skousen, and C. Jage.
    Virginia Cooperative Extension, Publication 460-133, 14 pp, 2018
    This publication presents guidance to design passive treatment systems for acid mine drainage. The mechanisms governing these systems' treatment effectiveness and performance are clearly described.
  • Performance of Passive Systems for Mine Drainage Treatment at Low Temperature and High Salinity: A Review
    Ali, H.E.B., C.M. Neculita, J.W. Molson, A. Maqsoud, G.J. Zagury.
    Minerals Engineering 134:325-344(2019)
    This paper reviews the principal parameters and processes that influence the quality of mine drainage (MD) and the performance of passive treatment of MD in cold climates. Major factors that affect treatment performance of passive systems are highlighted, such as low temperature, contamination level, and salinity. This review also discusses the effect of MD contamination level on passive biochemical reactor (PBR) efficiency. The effect of high salinity is discussed, with its potential to increase or decrease metal and sulfate removal depending on the major ions present. Reactive transport models used to predict long-term MD treatment efficiency are also considered. Further studies are needed to evaluate the simultaneous combined effect of these parameters on the performance of PBRs.
    For more information: https://www.imwa.info/docs/imwa_2018/IMWA2018_BenAli_245.pdf Adobe PDF Logo
  • Performance Review of a Passive Treatment System for FE, AS, MN at the Empire Mine State Historic Park
    Schipper, R., N. Gallagher, T. Rutkowski, S. Lofholm, and G. Leach. | Technical Sessions: Smart Mining: Resources for a Connected World, 24-27 Feb 2019, Denver, Colorado. p 76, 2019
    The Empire Mine State Historic Park contains 367 miles of now-flooded underground workings. Following closure, discharged mining-influenced water (MIW) contained arsenic, iron, and manganese in excess of federal and state standards. A full-scale passive treatment system (PTS), in operation since November 2011, was designed and constructed to treat the MIW and meet the permit limits. The PTS flowrate varies seasonally and has averaged 160 gpm with a peak near 1000 gpm. Metal removal results for the system have improved over time, corresponding with maturation of the PTS. Since February 2013, the PTS has provided effective removal of permitted metals to trace levels. In addition to metals removal, the PTS has also increased pH, increased dissolved oxygen, and reduced turbidity.
  • Toward Sustainability of Passive Treatment in Legacy Mining Watersheds: Operational Performance and System Maintenance
    Nairn, R.W., J.A. LaBar, L.R. Oxenford, N.L. Shepherd, B.K. Holzbauer-Schweitzer, J.G. Arango, Z. Tang, D.M. Dorman, C.A. Folz, J.I. McCann, J.D. Ingendorf, H.T. Stanfield, and R. C. Knox. | Proceedings from the postponed 14th IMWA Congress, "Mine Water Solutions," 2020
    A 12-year regular performance evaluation was conducted for a large, multi-process unit passive treatment system (PTS) at the Tar Creek Superfund site, which receives ≈1000 m3/day artesian-flow lead-zinc mine water. Since 2008, the PTS has consistently retained >95% of targeted metal mass. Regular, periodic, and rehabilitative maintenance commitments were also documented.
    See pages 123-128: https://www.imwa.info/docs/imwa_2020/IMWA_2020_proceedings.pdfAdobe PDF Logo
  • Twomile Run AMD Restoration Swamp Area Passive Treatment System Virtual Tour
    Wolfe, N. | 2021 PA Abandoned Mine Reclamation Conference, 27-28 October, Virtual, 37 minutes, 2021
    Restoration efforts of the Twomile Run watershed in western Clinton County, once impaired by abandoned coal mines, resulted in the recovery and reconnection of 6 miles of native brook trout stream. The largest and most significant of the nine treatment systems constructed is the Swamp passive treatment system due to its severe water quality and upstream position in the watershed. Design of the collection system was complicated by the presence of gas pipelines. Constructed in 2012, the treatment system includes settling ponds, vertical flow ponds in parallel with limestone and compost, and wetlands. Raw water entering the system averages 92 gal/min with pH 2.99, acidity 437 mg/L, Fe 54 mg/L, and Al 22 mg/L. The average effluent pH is 7.6 with 169 mg/L alkalinity, and both Fe and Al concentrations are < 1 mg/L. Though the water quality is considered high-risk, the system has performed reliably with minimal maintenance. https://www.youtube.com/watch?v=M07iQhKI7-U&feature=youtu.be

  • Passive Treatment of AMD Using a Full-Scale Up-Flow Mussel Shell Reactor, Bellvue Coal Mine, New ZealandAdobe PDF Logo
    Trumm, D., J. Pope, and H. Christenson.
    Proceedings of the 14th IMWA Congress, Mine Water Management for Future Generations, 12-15 July, virtual, 7 pp, 2021
    Results of the first full-scale up-flow mussel shell reactor to treat acid mine drainage (AMD) at the abandoned underground Bellvue Coal Mine are presented. The system consists of five 30,000-L plastic water tanks with associated alkathene piping and plastic valves to convey AMD from the adit and equally distribute it to the base of each tank. The water flows upwards through treatment media and is discharged into Cannel Creek. Each tank is filled with ~24 m3 of fresh mussel shells, broken into pieces ~5 cm long. The discharge piping is ~22 cm above the top of the shells to maintain a free water surface above the shells and ensure the reactor remains under reducing conditions. The tanks were filled with AMD and left static for 10 weeks before operation to allow reducing conditions to establish and iron-reducing and sulfate-reducing bacteria to populate the tanks. During site visits, field parameters were measured, and water samples were collected from the inlet and the system's outlet and Cannel Creek upstream and downstream of the confluence with the treated AMD. The system increased the pH from a median of 2.74 to a median of 6.94 and lowered metal concentrations by 97.2% (Fe), 99.8% (Al), 98.2% (Zn), and 97.0% (Ni).
  • Full-Scale Reducing and Alkalinity Producing System (RAPS) for the Passive Remediation of Polluted Mine Water from a Flooded Abandoned Underground Coal Mine, Carolina, South AfricaAdobe PDF Logo
    Dube, G.M., T. Mello, V. Vadapalli, H. Coetzee1, K. Tegegn, R. Lusunzi, S. Moja1, M. Malatji, M.E. Sinthumule, and R. Ramatsekisa.
    Proceedings of the 14th IMWA Congress, Mine Water Management for Future Generations, 12-15 July, virtual, 7 pp, 2021
    A reducing and alkalinity producing system (RAPS) named CaroRap was implemented to remediate coal mine water in South Africa. RAPS combines the mechanisms of anaerobic treatment wetlands and anoxic limestone drains to improve water quality by processes including calcite dissolution and sulfate reduction through sulfate-reducing bacteria (SRB). After four weeks of operation, the system, which included RAPS 1 and an oxidation pond, increased the pH to an average of 5.6 (from an average of 2.9) and increased alkalinity to ~35.8 mg/L. The increases were attributed to bicarbonate ions released from the dissolution of limestone. The system reduced total iron (Fe) by 92% and Al by 58.8%. There are limitations regarding adequate removal of Mn and SO4, and optimization measures will be explored further.
  • Full-Scale Demonstration Tests of Passive Treatment System by Jogmec in JapanAdobe PDF Logo
    Hayashi, K., T. Washio, Y. Masaki, T. Hamai, T. Sakata, M. Sakoda, M. Kobayashi, N. Masuda, and N. Sato.
    Proceedings from the postponed 14th IMWA Congress - "Mine Water Solutions," 2020
    Full-scale demonstration tests (flow rate 100 L/min) of a biological passive treatment system were conducted at an abandoned mine site in Japan to treat acid mine drainage (AMD) containing iron and zinc. Aerobic and anaerobic vertical-flow bioreactors utilized iron-oxidizing and sulfate-reducing bacteria (SRB). In the aerobic reactor, AMD containing 35 mg/L of Fe was treated to below the wastewater standards by using a water transfer method, such as a cascade. In the anaerobic process, the applicability of a process using ethanol or rice bran as organic resources of SRB was studied. See pages 106-109.
  • Neutralization and Uptake of Pollutant Cations from Acid Mine Drainage (AMD) Using Limestones and Zeolites in a Pilot-Scale Passive Treatment System
    Silva, D., C. Weber, and C. Oliveira. ǀ Minerals Engineering 170:107000(2021)
    A passive pilot-scale acid mine drainage treatment system was developed using open channels of calcitic (CL-I and CL-II) and dolomitic (DL-I and DL-II) limestone beds and mixtures with natural zeolites (NZ) and functionalized zeolites (FZ). Several parameters were examined, including pH, electrical conductivity, total acidity, total alkalinity, and concentrations of aluminum, iron, and manganese ions. DL-I, CL-II, and mixtures of CL-II/NZ and CL-II/FZ increased pH levels from 3.3 to 7.9, 8.2, 7.9, and 7.6, respectively; increased total alkalinity levels from 0 mg CaCO3/L to 20, 107, 42 and 34 mg CaCO3/L, respectively; and reduced total acidity levels by 95, 91, 90 and 90%, respectively. All beds promoted aluminum, iron, and manganese ion removal, but the CL-II/FZ mixture was the most efficient due to neutralization and a higher uptake of manganese ions (~99%). Results reveal ways to transform passive treatment systems using limestone beds and unconventional materials such as zeolites, combine neutralization and adsorption mechanisms in the same operation, ensure a simple maintenance and operational system and improve the economic and environmental sustainability of related processes.
  • 2014 Treatability Study Date Evaluation: Barker-Hughesville Mining District Superfund Site Adobe PDF Logo
    U.S. EPA Region 8, 1050 pp, 2017
    In 2014, two treatability studies were conducted for the Barker-Hughesville Mining District Superfund Site as part of the remedial investigation/feasibility study process. Year 2 of the Danny T Adit study continued the 2013 year 1 field pilot study to evaluate various passive and semi-passive methods for treatment of the Danny T Mine adit water. The bench-scale study for the Tiger Mine was focused on potential in situ-based treatments that could be deployed inside the underground mine workings area. A representative mine discharge water (Tiger mine adit TI-AD004, the "Firehose" adit) was collected in bulk and analyzed at the treatability laboratory in batch container tests with various reagents. The report summarizes each of these studies, including their objectives, experimental and sampling procedures, results, conclusions, and recommendations.

Permeable Reactive Barrier Systems — A permeable reactive barrier (PRB) is a continuous, in situ permeable treatment zone designed to intercept and remediate a contaminant plume. The treatment zone may be created directly using reactive materials such as iron or indirectly using materials designed to stimulate secondary processes, such as by adding carbon substrate and nutrients to enhance microbial activity. With most PRBs, the reactive material is in direct contact with the surrounding aquifer material. PRBs are designed to be more permeable than the surrounding aquifer materials, enabling contaminants to be treated while groundwater readily flows through. (ITRC 2005).

ITRC. 2005. Permeable Reactive Barriers: Lessons Learned/New Directions. PRB-4. Washington, D.C.: Interstate Technology — Regulatory Council, Permeable Reactive Barriers Team. www.itrcweb.org

  • Pilot Test of the Permeable Reactive Barrier for Removing Uranium from the Flooded Gunnar Pit Adobe PDF Logo
    Kong, D., L. McGilp, A. Klyashtorin1, I. Wilson, and L.D. Wilson.
    Journal of Geoscience and Environment Protection 8:155-176(2020)
    Iron oxide coated sand (IOCS) media was applied in an experimental permeable reactive barrier to remove U contaminated floodwater from a mine pit. The mine pit contains ˜3.2 million m3 of water contaminated by dissolved U (1.2 mg/L), Ra-226 (0.4 Bq/L), and minor concentrations of other contaminants that is seeping over the pit rim into Lake Athabasca. Hydrous ferric oxide sorbents and their supported forms onto silica sands were prepared, characterized, and tested in bench-scale adsorption kinetic experiments in a field trial. A pilot permeable reactive barrier was fabricated and field-tested to provide technical data to design a full-scale permeable barrier employing the IOCS media.

  • A Permeable Reactive Barrier (PRB) for the Removal and Immobilization of Selenium in Seep Water and Shallow Groundwtater at a Phosphate Mine in Southern Idaho: Results of Bench Scale Testing
    Walker, W.J., D. Tooke, M. Wright, J. Hamilton, C. Schreier, and J. Peterson.
    Journal American Society of Mining and Reclamation 7(3):20-44(2018)
    A bench study was designed to determine the efficacy of a permeable reactive barrier (PRB) for removing elevated Se in groundwater and seep water at the toe of an overburden storage area at a phosphate mine in Idaho. The study consisted of three main parts: (1) characterization work designed to determine the basic chemistry of the site-water under consideration for treatment and the components of the proposed PRB, (2) batch leaching studies designed to assess the chemistry changes that each media component is expected to contribute to the overall water chemistry of the seep or groundwater in contact with the media, and (3) column studies consisting of vertical, 2-inch columns filled with the PRB media. Results indicated that the media proposed as components of the PRB posed no chemical changes of concern and resulted in rapid development of reducing conditions sufficient for Se reduction and immobilization. The groundwater Se, initially about 1 mg/L, was reduced to < 0.02 mg/L in the first 3 hours of column contact time, well below the 0.05 mg/L water quality goal.
  • Prospect for Treating Antimony-Laden Mine Wastewater Using Local Materials
    Ji, X., S. Liu, H. Juan, J. Jiang, A. He, E. Bocharnikova, and V. Matichenkov.
    Mine Water and the Environment 36(3):379-385(2017)
    Wastewater from the world's largest antimony mine (in Hunan, China) contains high levels of metal and metalloid contaminants (As, Cd, Hg, Pb, Se, and Sb). A study of the effectiveness of low-cost local industrial by-products [coal fly ash (CFA) and Ca-Si slag from the metals industry] and traditional agents [limestone, diatomaceous earth (DE), and zeolite] to treat the wastewater led to the ranking of their relative effectiveness: CFA > Ca-Si slag > DE > limestone > zeolite. CFA and Ca-Si slag removed 9.9 to 85.5% of As, Cd, Hg, Pb, Se, and Sb from wastewater. The CFA and Ca-Si slag could be employed as commercial filters or biogeochemical barriers to protect surface water and groundwater, and a similar approach might be used at other mines.

Pressure-Driven Membrane Separation Technologies — Pressure-driven membrane separation (PDMS) processes are tools used to separate media. Commonly used processes for treatment of MIW include reverse osmosis, nanofiltration, ultrafiltration, and microfiltration. Any of these technologies can be used for surface and groundwater influenced by mining waste, but the particular tool used depends on the cleanup goal for the site. PDMS processes use semi-permeable membranes to reduce the concentration of the selected solutes in a feed solution. They produce a permeate stream containing materials that pass through the membrane, and a concentrate or waste stream that contains the materials filtered out of the feed solution. Passage through the membrane matrix is controlled by the application of a "driving force," which includes mechanical pressure, concentration or chemical potential, and temperature or electrical potential (Mortazavi 2008).

  • Mine-Affected Water Minimization Technology - 3 Years of Development Adobe PDF Logo
    Drak, A.
    Water in Mining Conference, 9-10 April, Toronto, ON, 34 slides, 2019
    The MaxH2O Desalter technology was pilot-tested to measure its effectiveness of treating acid mine drainage. The system removes sulfate ions by crystallization of calcium sulfate in the Crystalactor® while concentrating the wastewater in a reverse osmosis (RO) system. During the pilot, continuous crystallization of the calcium sulfate in the integrated salt precipitation unit maintained the saturation index in the range of 800%-1,200% during operation. The system operated without the addition of chemicals other than antiscalant and produced pellets of more than 90% dry solids content that do not require further sludge dewatering treatment. Depending on the effluent requirements, the obtained RO brine stream can be partially or completely blended with the RO product, further increasing the total recovery of the system.
  • Land Application Disposal System Design for Biochemical Reactor Treated EffluentAdobe PDF Logo
    Anton, N.R., D.T. Shanight, C.S. Storrar, M.J. Fischer, E.M. Janoviak, and B. Lala
    36th Annual Meeting of the American Society of Mining & Reclamation, 3-7 June, Big Sky, MT, 26 slides, 2019
    At the mine waste repository for the Upper Tenmile Creek Mining Area Superfund site, Montana, collected leachate water has been managed in an active water treatment plant and pilot biochemical reactor system, with disposal to a land application disposal (LAD) system since 2003. In 2018, the design was completed for a full-scale leachate passive treatment system utilizing parallel BCR cells, post-treatment settling, aeration, limestone channels, and a gravity-operated LAD system. The new system construction will begin in 2019, and the existing water treatment infrastructure will be decommissioned after the new system is operational and functional. The presentation includes the critical passive treatment design components and provides details of the pre-design investigation and design approach for the LAD system, including field siting for the LAD, test pits, soil lithology logging, permeability testing, soil metal sorption studies, metal sorption capacity and water balance calculations, and hydraulic design of the LAD.
    More information: https://projects.itrcweb.org/bcr-1/Content/Appendix%20B%20Case%20Studies/B15%20Luttrell%20Case%20Study.htm

  • Membrane Technology Applied to Acid Mine Drainage From Copper Mining
    Ambiado, K., C. Bustos, A. Schwarz, and R. Borquez.
    Water Science and Technology 75(3):705-715(2017)
    The performance of two commercial spiral-wound membranes—NF99 and RO98pHt (Alfa Laval)—was compared in an evaluation of pilot-scale treatment by nanofiltration (NF) and reverse osmosis (RO) of high-strength acid mine drainage (AMD) from copper mining. Results showed high ion removal under optimum pressure conditions, which reached 92% for the NF99 membrane and 98% for the RO98pHt membrane. Sulfate removal reached 97% and 99% for NF99 and RO98pHt, respectively. Removal percentage for Cu, Al, Fe, and Mn surpassed 95% in both membranes. Although concentration polarization limited NF performance at higher pressures, permeate fluxes observed in NF were five times greater than those obtained by RO, with only slightly lower divalent ion rejection rates.
  • The Effect of Electro-Activation and Eggshell Powder on the Neutralization of Acid Mine Drainage
    Kastyuchik, A., A. Karam, and M. Aider.
    Journal of Sustainable Mining 16(3):73-82(2017)
    Acid neutralization and the precipitation of metals present in acid mine drainage (AMD) were carried out by electro-activation with ion-exchange membranes, which is based on the self-generation of necessary conditions for acid neutralization and metal precipitation. The treatment of sulfide mine tailings (SMT) was carried out using an electro-activation cell-generated alkaline solution in the cathode compartment. After 60 min of electro-activation, a pHcatholyte of 7.9-9.6 (depending on the experimental conditions) was obtained. The absence of Fe and other trace metal ions in the catholyte provide evidence that SMT electro-activation promotes the precipitation of insoluble trace metals in the cathode compartment. This approach can be applied to real conditions in combination with a pretreatment of SMT neutralization using biological calcareous amendments, such as eggshell powder. This paper is Open Access at https://www.sciencedirect.com/science/article/pii/S2300396017300617.
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Mining-Influenced Water and Solid Waste

Backfilling and Subaqueous Disposal — Backfilling and subaqueous disposal technologies can be effective treatment alternatives for remediation of solid mining wastes and MIW. Subaqueous disposal involves removing surface material and placing it underground and underwater, thus eliminating direct contact exposures. Typically, subaqueous disposal is applied to sulfide-containing solid mining wastes to reduce oxidation, which limits acid generation and release of metals. Subaqueous disposal also is used to dispose of non-acid-generating solid mining wastes through backfilling. Solid mining wastes are disposed of into deep submarine environments, natural lakes, pit lakes, subsidence features, underground mines, and surface mines. Subaqueous disposal also includes injection of MIW and process waters into geologic formations below the depth of fresh groundwater, but this has not been widely practiced.

  • How to Assess Potential Biological Effects of Subaqueous Disposal of Mine Tailings: Literature Review and Recommended Tools and Methodologies
    Campbell, P.G.C. and W.A. Price.
    Mine Environment Neutral Drainage Program, MEND Report 2.19.1, 158 pp, 2018
    Subaqueous disposal (SAD) or flooding of sulfide-rich tailings in constructed facilities is a method used at some mine sites to mitigate the formation of acid mine drainage. The primary SAD mitigation mechanism is limitation of oxygen ingress into water-filled pores, which greatly reduces sulfide oxidation, minimizes metal leaching, and prevents acidic drainage development. The overall biological performance of such facilities is not well understood. In particular, a major gap in understanding relates to the biological colonization of such facilities, the health of biological communities that are established, and the influence of those communities on water and sediment geochemistry. This report contains an introduction, an extensive literature review (Sections 2-7), and a set of recommendations on tools and methodologies that might be used to assess the biological effects of submerged tailings.

In Situ Biological Treatment — In situ biological source treatment consists of isolating the source of MIW by establishing an in situ biological layer on exposed metal sulfide surfaces (Jin et al. 2008b). This is typically accomplished by injecting inoculum (e.g., wastewater effluent) and substrate into the subsurface material. The in situ biological source treatment can achieve satisfactory results without the cost of excavation and material handling. The process typically has two components: (a) developing an anaerobic environment through the injection and distribution of inoculums and substrates; and (b) forming and maintaining a biological film that impedes the release of products of iron reduction. A complete analysis of the MIW and the treatment material, including seasonal and formulation variations, must be completed before selecting an in situ biological source treatment system. Bench-scale tests exploring variations in the treatment material and the material to be treated are invaluable when determining whether an in situ biological source treatment system is applicable and the type of treatment material that is suitable for the site.

Jin, S., P. H. Fahlgren, J. M. Morris, and R. B. Gossard. 2008b. "Biological Source Treatment of Acid Mine Drainage Using Microbial and Substrate Amendments: Microcosm Studies," Mine Water and the Environment 27(1): 20-30.

  • Pilot Study of In Situ Biological Treatment at the Silver King Mine, Keno Hill, Yukon Adobe PDF Logo
    Gault, A.G., J.M. Harrington, C. Robertson, M.C. Simair, and V.P.M. Friesen.
    11th ICARD IMWA 2018 Annual Conference, September 10-14, Pretoria, South Africa. IMWA Proceedings (Volume I), 2018
    Part of closure planning for the United Keno Hill Mines site in central Yukon, Canada included evaluating options for long-term treatment of several flowing adits in which Cd and Zn are the principal contaminants of concern. A 3.5-year in situ pilot test conducted at the Silver King Mine was initiated to evaluate the potential closure strategy to treat Cd and Zn using in situ biological treatment. Pumped mine water was mixed with methanol or molasses as a carbon source and reinjected to create an environment ideal for sulfate-reducing bacteria to grow, precipitating Zn and Cd in the process. Four molasses injections were performed in 2015, each lasting between 24 and 42 days, and 2 additional injections of methanol followed in 2016, totaling 105 days. Genomic analysis confirmed the presence of sulfate-reducing bacteria dominated by members of the Desulfosporosinus genus. Following carbon injection, Zn and Cd concentrations declined by more than 90%. Despite rising slowly over time, Zn and Cd concentrations remained below both their pre-treatment concentrations and the effluent quality standards such that carbon injections on an annual basis may maintain low metal concentrations.

  • The MnDRIVE Transdisciplinary Project Implementation of Smart Bioremediation Technology to Reduce Sulfate Concentrations in NE Minnesota Watersheds
    Hudak, G., L. Estepp, and P. Schoff.
    University of Minnesota Duluth, Natural Resources Research Institute. NRRI/TR-2017/17, 155 pp, 2017
    This MnDRIVE-supported project continues a long-running set of experiments to address issues associated with mining-impacted waters. Results to date show both promise and challenges for floating sulfate-reducing bacterial bioreactors as currently configured. Functional tests show that the bioremediation process can decrease aqueous sulfate concentrations in water substantially. The potential advantages of this bioremediation system include low power demand that can be satisfied by on-site solar photovoltaic panels, year-round operation with minimal need for human intervention, reasonable capital costs, low operating costs, and minimal waste production. In addition, the bioreactors used in this study are extremely flexible and adaptable; they have been designed as interchangeable modules that can operate in series or in parallel and will accommodate changes in flow rate. The bioreactor platform might be most useful as a preliminary stage to reduce sulfate concentrations in water prior to treatment by conventional energy- and material-intensive methods, such as reverse osmosis or ion exchange, both of which have limited efficiency in high-sulfate environments. The bacterially mediated reduction in sulfate could substantially decrease the burden on those more expensive systems and thus increase the cost-effectiveness of the remediation system as a whole. http://conservancy.umn.edu/handle/11299/190404 See more information on the problem of mining-related sulfate generation in Minnesota in a series of reports at https://www.dnr.state.mn.us/lands_minerals/dnr_so4_research.html.
  • Attenuation of Acid Rock Drainage with a Sequential Injection of Compounds to Reverse Biologically Mediated Pyrite Oxidation in the Chattanooga Shale in Tennessee
    Byl, T.D., R. Oniszczak, D. Fall, P.K. Byl, D.E. Young, and M.W. Bradley.
    U.S. Geological Survey Karst Interest Group Proceedings, San Antonio, Texas, May 16-18, 2017: U.S. Geological Survey Scientific Investigations Report 2017-5023:37(2017)
    A study was conducted to disrupt chemolithotrophic bacteria responsible for acid rock drainage (ARD) associated with the Chattanooga Shale in Tennessee's karstic central basin. Researchers used chemical treatments to foster an environment favorable for competing microorganisms to attenuate the biologically induced ARD. Chemical treatments were injected into flow-through microcosms consisting of 501 grams of pyrite-rich shale pieces inoculated with ARD bacteria. Treatments included a sodium hydroxide-bleach mix, a sodium lactate solution, a sodium lactate-soy infant formula mix—each treatment with or without phosphate buffer, or injected sequentially with sodium hydroxide. The optimal treatment was a sequential injection of 1.5 g sodium hydroxide, followed by 0.75 g lactate and 1.5 g soy formula dissolved in 20 mL water. The pH of the discharge water rose to 6.0 within 10 days, dissolved-iron concentrations dropped <1 mg/L, the median alkalinity increased to 98 mg/L as CaCO3, and the stimulated sulfur-reducing and slime-producing bacteria populations exhibited an increase in estimated population counts. The ARD-attenuating benefits of the optimal treatment remained evident after 33 weeks. The other treatments provided ARD-attenuating effects but were tempered by problems such as high phosphate concentrations, short longevity, or other shortcomings.

Phytotechnologies — Phytotechnologies use plants to remediate various media impacted with different types of contaminants. There are six basic phytoremediation mechanisms that can be used to clean up mining-contaminated sites: phytoextraction, phytodegradation, phytovolatilization, rhizodegradation, phytosequestration, and phytohydraulics. These technologies can be applied to address certain issues associated with mining solid wastes and MIW, and also can stabilize tailings and act as a hydraulic control for drainage. Phytotechnologies are a common component of mining reclamation and restoration projects that establish a plant cover as a final remedy. Establishing phytotechnologies requires careful selection of plant species and soil amendments. Most phytotechnologies can be applied to both organic and inorganic contaminants and to soil/sediment, surface water, and groundwater. Phytotechnologies also can be applied simultaneously to various combinations of contaminant types and impacted media. Establishment of vegetation can be enhanced by using native soil or other amendments to offset the often poor growing conditions offered by the tailings material.

  • In Situ Restoration of Soil Ecological Function in a Coal Gangue Reclamation Area After 10 Years of Elm/Popular Phytoremediation
    Bai, D.-S., X. Yang, J.-L. Lai, Y.-W. Wang, Y. Zhang, and X.-G. Luo.
    Journal of Environmental Management 305:114400(2022)
    Soil ecological health risks and toxic effects of coal gangue accumulation were examined after 10 years of elm/poplar phytoremediation. Soil enzyme activities, ionome metabolism, and microbial community structure changes were analyzed at shallow (5-15 cm), intermediate (25-35 cm), and deep (45-55 cm) soil depths. Soil acid phosphatase activity in the restoration area increased by 4.36-7.18 fold. Soil concentrations of Cu, Pb, Ni, Co, Bi, U, Th, and the non-metallic element S were reduced. The repair effect was shallow > middle > deep. Redundancy analysis showed that S and Na are important driving forces for the microbial community distributions at shallow soil depths. The Kyoto Encyclopedia of Genes and Genomes (KEGG) function prediction indicated enhancement of the microbial function of the middle-depth soil layers in the restoration area. Phytoremediation enhanced the biotransformation of soil phosphorus in the coal gangue restoration area, reduced the soil content of metals, significantly changed the structure and function of the microbial community, and improved the overall soil ecological environment.

  • Arsenic Uptake by Pteris Vittata in a Subarctic Arsenic-Contaminated Agricultural Field in Japan: An 8-Year Study
    Kohda, Y. H.-T., G. Endo, N. Kitajima, K. Sugawara, M.-F. Chien, C. Inoue, and K. Miyauchi.
    Science of The Total Environment 831:154830(2022)
    The phytoremediation potential of tropical and subtropical As-hyperaccumulating fern Pteris vittata was investigated in an As-contaminated field near an abandoned goldmine in a subarctic area of northeast Japan. This study aimed to decrease the risk of water-soluble As in soil while nurturing the soil and respecting the plant life cycle for sustainable phytoremediation over eight years. The field was tilled and planted with new fern seedlings every spring, and grown ferns were harvested every autumn. Fronds, rhizomes, and roots of the fern were analyzed separately for biomass and As after harvesting each year. Frond biomass was significantly affected by the yearly change in weather conditions. As concentration in fronds was maintained at a 100-150 mg/kg dry weight. The accumulated As in P. vittata was higher than that of As-hyperaccumulator fern Pteris cretica, the native fern in the field trial area. Harvested biomass of P. vittata per plant was also higher than that of P. cretica. More than 43.5 g As/154 m2 (2.82 kg of As per hectare) was removed via phytoremediation during the experiment. Because of the short-term plant growth period and soil tilling process, total As in soil did not show significant depletion. However, the water-soluble As in the surface and deeper soil decreased to 10 µg/L (Japan Environmental Quality Standard for water-soluble As in soil).
  • Phytostabilization of Acidic Mine Tailings with Biochar, Biosolids, Lime, and Locally-Sourced Microbial Inoculum: Do Amendment Mixtures Influence Plant Growth, Tailing Chemistry, and Microbial Composition?
    Trippe, K.M., V.A. Manning, C.L.Reardon, A.M. Klein, C. Weidman, T.F. Ducey, J.M. Novak, D.W. Watts, H. Rushmiller, K.A. Spokas, J.A. Ippolito, and M.G. Johnsong.
    Applied Soil Ecology 165:103962(2021)
    Amendment mixtures composed of lime, biochar, biosolids (LBB), and locally sourced microbial inoculum (LSM) were evaluated to alleviate the constraints that hinder phytostabilization success in acid mine tailings. A greenhouse study that simulated in situ conditions to measure the influence of LBB-LSM amendment blends on plant growth, plant nutrients, metal concentrations, microbial function, and microbial community structure was conducted. Blue wildrye was grown in tailings collected from the Formosa mine site amended with various combinations of LBB-LSM. The above and belowground biomass of plants grown in mine tailings amended with LBB was 3-4 times larger than the biomass of plants grown in tailings amended with lime. Although the LSM addition did not influence immediate plant growth, it did affect nutrient content and altered the rhizosphere community composition.
  • Optimization of Combined Phytoremediation for Heavy Metal Contaminated Mine Tailings by a Field-Scale Orthogonal Experiment
    Li, X., X. Wang, Y. Chen, X. Yang, and Z. Cui.
    Ecotoxicology and Environmental Safety 168: 1-8(2019)
    The combined application of plant, microorganism, and amendment on the phytoremediation of heavy metals was optimized as a remediation technique for mine tailings by a field-scale orthogonal experiment aimed to achieve the maximum phytoremediation effect. Soybean, Mucor circinelloides, and A3 amendment were used as the plant, microorganism, and amendment materials. With the application, effective fractions of copper, zinc, lead, cadmium, and manganese were immobilized for decreased bioavailability, indicating the phytostabilization served as a major repair pathway. Plant length and biomass in the treatments were significantly higher than that in the control, indicating their phytoremediation potentials were enhanced. The final contents of heavy metals in soil were decreased, and the removal rates of soil heavy metals were in the order of Pb > Cd > Cu > Zn > Mn. Temporal variations of soil microorganism populations indicated that the abundance of soil microorganism in the treatments was significantly higher than that in the control, and bacteria became the dominant microbial species.
  • Dynamics of Bacterial Communities Mediating the Treatment of an As-rich Acid Mine Drainage in a Field Pilot
    Laroche, E., C. Casiot, L. Fernandez-Rojo, A. Desoeuvre, V. Tardy, O. Bruneel, et al.
    Frontiers in Microbiology 9:3169(2018)
    Bacterial diversity was characterized in a field-pilot bioreactor treating extremely arsenic (As)-rich acid mine drainage (AMD) in situ over a 6-month monitoring period. Over the monitoring period, iron (Fe)-oxidizing bacteria dominated the biogenic precipitate. Parameters that exerted a control on the bacterial communities potentially involved in the water treatment process included dissolved oxygen, temperature, pH, dissolved sulfates, arsenic and Fe(II) concentrations and redox potential. The ubiquity and the physiological diversity of the bacteria identified, as well as the presence of bacteria of biotechnological relevance, suggested that this treatment system could be applied to the treatment of other AMD. This article is Open Access at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6309452/.
  • Aided Phytostabilisation Reduces Metal Toxicity, Improves Soil Fertility and Enhances Microbial Activity in Cu-Rich Mine Tailings
    Touceda-Gonzalez, M., V. Alvarez-Lopez, A. Prieto-Fernandez, B. Rodriguez-Garrido, et al.
    Journal of Environmental Management 186(2):301-313(2017)
    A phytostabilization field trial was implemented in spring 2011 in Cu-rich mine tailings in NW Spain. The tailings were amended with composted municipal solids and planted with a grass (Agrostis capillaris) and with willow (Salix spp.) and poplar (Populus nigra L.) trees. Compost amendment improved soil properties, such as pH and fertility, and decreased soil Cu availability, leading to the establishment of a healthy vegetation cover. Both compost amendment and plant root activity stimulated soil enzyme activities and induced important shifts in the bacterial community structure over time. The beneficial effects of the phytostabilization process were maintained at least three years after treatment.

  • Distinguishing Reclamation, Revegetation and Phytoremediation, and the Importance of Geochemical Processes in the Reclamation of Sulfidic Mine Tailings: A Review
    Xie, L. and D. van Zyl.
    Chemosphere 252:126446(2020)
    Reclamation, revegetation, and phytoremediation concepts and relationships are clarified in this article to aid in the design of an appropriate reclamation plan during mine closure stage. Amended phytostabilization is the most promising technique to reduce metal (loid)s mobility in sulfidic tailings. The review stresses the importance of inorganic geochemical processes in the direct revegetation on sulfidic mine tailings and emphasizes their potential as an anticipated research direction in the near future.
  • Innovative and Sustainable Approach for Phytoremediation of Mine Tailings: A ReviewAdobe PDF Logo
    Punia, A.
    Waste Disposal & Sustainable Energy 1:169-176(2019)
    This review looks at innovating a sustainable solution to stabilize mine tailings using bioremediation and phytoremediation.

  • Metal Lability and Mass Transfer Response to Direct-Planting Phytostabilization of Pyritic Mine Tailings
    Hammond, C.M., R.A. Root, R.M. Maier, and J. Chorover.
    Minerals 12(6):757(2022)
    Metal lability trends were investigated following a direct-planting phytostabilization trial at a Superfund mine tailings site in semi-arid central Arizona. Unamended tailings were characterized by high concentrations (mmol/kg) of Fe (2,100), S (3,100), As (41), Zn (39), and Pb (11), where As and Pb exceeded Arizona non-residential soil remediation levels. Phytostabilization treatments included a no-compost control, 100 g/kg compost with seed, and 200 g/kg compost with and without seed to the top 20 cm of the tailings profile. All plots received supplemental irrigation to double the mean annual precipitation. Tailings cores up to 90 cm were collected at planting and every summer for three years. The cores were sub-sectioned at 20 cm increments, then analyzed via total digestion and an operationally-defined sequential extraction for elemental analysis. Calculations of a mass transfer coefficient were normalized to Ti as an assigned immobile element. Pb was recalcitrant and relatively immobile in the tailings environment for the uncomposted control and composted treatments, with a maximum variation in the total concentration of 9-14 mmol/kg among all samples. Metal lability and translocation above the redox boundary (ca. 30 cm depth) were governed by acid generation, where surficial pH was measured as low as 2.7 ± 0.1 in and strongly correlated with the increased lability of Mn, Co, Ni, Cu, and Zn. There was no significant pH effect on V, Cr, or Pb availability. Translocation to depths was highest for Mn and Co though Zn, Ni, Cr, and Cu were also mobilized. Adding organic matter enhanced Cr mobilization from the near-surface to 40-60 cm depth (pH > 6) during the phytostabilization study compared to the control. Increased enrichment of some metals at 60-90 cm indicates that the long-term monitoring of elemental translocation is necessary to assess the efficacy of phytostabilization to contain subsurface metal contaminants and thereby protect the surrounding community from exposure. This article is Open Access at https://www.mdpi.com/2075-163X/12/6/757.
  • Electrokinetic-Enhanced Phytoremediation of Uranium-Contaminated Soil Using Sunflower and Indian Mustard
    Larson, S.L., J.H. Ballard, J. Li, K. Guo, Z. Arslan, J.R. White, F.X. Han, J. Zhang, Y. Ma, and C.A. Waggoner, Army Corps of Engineers Document No. ERDC/EL MP-20-4, 14 pp, 2020
    Research examined the effects of electrokinetic treatments on plant uptake and bioaccumulation of uranium in soil from various sources, including mine tailings and ore wastes around abandoned mines and U redistribution in soils affected by planting and electrokinetic treatments. Soil was spiked with 100mg/kg UO2, UO3, and UO2(NO3)2. After sunflower and Indian mustard grew for 60 days, 1 voltage of direct current was applied across the soils for 9 days. U uptake in both plants was enhanced by electrokinetic treatments from soil spiked with UO3 or UO2(NO3)2. U accumulated more in roots than in shoots. Electrokinetic treatments were effective in lowering soil pH near the anode region. Overall, U removal efficiency reached 3.4-4.3% from soils with UO3 and uranyl with both plants, while efficiency in soil with UO2 was 0.7-0.8%. Electrokinetic remediation treatment enhanced U removal efficiency (5-6%) from soils with UO3 and uranyl but was 0.8-1.3% from soil spiked with UO2, indicating significant effects of U species and electrokinetic enhancement on U bioaccumulation.
  • Copper Phytoextraction and Phytostabilization Potential of Wild Plant Species Growing in the Mine Polluted Areas of Armenia
    Ghazaryan, K.A., H.S. Movsesyan, H.E. Khachatryan, N.P. Ghazaryan, T.M. Minkina, et al.
    Geochemistry: Exploration, Environment, Analysis 19(2):155-163(2018)
    The phytoremediation potential of 16 native wild plant species growing in Cu-contaminated soils of a mining region in Armenia was evaluated in this study. In roots of dominant plant species, Cu concentrations varied between 55 mg/kg (Hypericum perforatum) and 775 mg/kg (Thymus kotschyanus), and in shoots of plants in the range from 33 mg/kg (Teucrium orientale) and 243 mg/kg (Phleum pratense). The high contents of soil organic matter and clay in the soil facilitated the decrease of the ratio Cubioavailable/Cutotal and, as a result, the decrease of Cu accumulation capability of plants. Thymus kotschyanus, Phleum pratense and Achillea millefolium had the highest phytostabilization potential of all the studied species due to high bioconcentration factors of their roots and low translocation factors registered in these plants.
  • Effects of Vegetation Pattern and Spontaneous Succession on Remediation of Potential Toxic Metal-Polluted Soil in Mine Dumps
    Chen, F., Y. Yang, J. Mi, R. Liu, H. Hou and S. Zhang.
    Sustainability 11(2):397(2019)
    Plant growth, soil fertility, and the capacity of potential toxic metals (PTMs) using different vegetation patterns were investigated over 10 and 17 years to understand the role of vegetation pattern and spontaneous succession in the early phase of mine restoration projects. To do this, field and lab experiments on different vegetative patterns were conducted using combinations of rehabilitative plants (RP) and local plants (LP) at a metal mining dump in Sichuan, China. Phytoremediation using a simple vegetation pattern of RPs Agave sisalana and Neyraudia reynaudiana achieved a PTM pollution index of 9.28% lower, a soil fertility index of 21.86% lower, and biodiversity index of 73.69% lower than a complex vegetative pattern using RPs and LPs. Phytoremediation with a 10-year RP and LP pattern had a PTM pollution index 4.04% higher, a soil fertility index 4.48% lower, and a biodiversity index 12.49% lower than the 17-year RP and LP pattern. Results indicate the importance of choosing a suitable vegetation pattern to prevent spontaneous vegetation succession and ensure phytoremediation. This article is Open Access at https://www.mdpi.com/2071-1050/11/2/397/htm.
  • Phytostabilization of ZN and CD in Mine Soil Using Corn in Combination with Biochars and Manure-Based Compost
    Sigua, G.C., J.M. Novak, D.W. Watts, J.A. Ippolito, T.F. Ducey, M.G. Johnson, et al.
    Environments 6(6):69(2019)
    The effect of biochar additions (BA) with or without manure-based compost (MBC) was evaluated on shoots biomass, roots biomass, uptake, and the bioconcentration factor (BCF) of Zn and Cd in corn (Zea mays L.) grown in mine soil. Biochar additions of beef cattle manure (BCM), poultry litter (PL), and lodgepole pine were applied at 0, 2.5, and 5.0% (w/w) in combination with different rates (0, 2.5, and 5.0%, w/w) of MBC, respectively. Shoots and roots uptake of Cd and Zn were significantly affected by BA, MBC, and the interaction of BA and MBC. Corn plants that received 2.5% PL and 2.5% BCM had the greatest Cd and Zn shoot uptake, respectively. Corn plants with 5% BCM had the greatest Cd and Zn root uptake. When averaged across BAs, the greatest BCF for Cd in the shoot (92.3) was from application of BCM and the least BCF was from application of PL (72.8). The incorporation of biochar enhanced phytostabilization of Cd and Zn. Concentrations of water-soluble Cd and Zn were lowest in soils amended with manure-based biochars, which improved the biomass productivity of corn. This article is Open Access at https://www.mdpi.com/2076-3298/6/6/69.
  • Remediation of Acid Mine Drainage-Impacted Wter by Vetiver Grass (Chrysopogon Zizanioides): A Multiscale Long-Term Study
    Kiiskila, J.D., D. Sarkar, S. Panja, S.V. Sahi, and R. Datta.
    Ecological Engineering 129:97-108(2019)
    The study developed a cost-efficient and sustainable floating treatment wetland system using vetiver grass (Chrysopogon zizanioides). Year-long large- and small-scale hydroponic experiments were used to determine the effectiveness of vetiver for treating acid mine drainage-impacted waters from the Tab-Simco mine site in southern Illinois. For the large-scale mesocosm study, vetiver rafts were suspended in 100-gal containers. Water quality was monitored every 28 days and at the end of the experiment (364 days); plant health was monitored by measuring changes in biomass and recording visual changes in root and shoot coloration and morphology. There was higher net removal of Fe (81%) and Pb (81%) with lower removal of Ni (38%), Zn (35%), SO42- (28%), Mn (27%), Cr (21%), Al (11%) and Cu (8.0%). Toxicity characteristic leaching procedure showed that vetiver biomass was not hazardous waste as a result of metal accumulation. From the small-scale experiment, there was near complete removal of SO42- (91%) and metals (90-100%) with the exception of Pb (15%) and Cu (0.0%).
  • A Combined Chemical and Phytoremediation Method for Reclamation of Acid Mine Drainage-Impacted Soils
    RoyChowdhury, A., D. Sarkar, and R. Datta.
    Environmental Science and Pollution Research [Publication online 13 March 2019 prior to print]
    This study utilized the metal-binding and acid-neutralizing capacity of an industrial by-product, drinking water treatment residuals (WTRs), and the extensive root system of a metal hyper-accumulating, fast-growing, non-invasive, high-biomass perennial grass, vetiver (Chrysopogon zizanioides L.) to prevent soil erosion. Aluminum-based and calcium-based WTRs were used to treat acid mine drainage (AMD)-impacted soil collected from the Tab-Simco coal mine in Carbondale, IL. A 4-month greenhouse column study performed using 5% and 10% w/w WTR application rates showed that soil erosion decreased in the soil-WTR-vetiver treatments. A scaled-up simulated field study was performed using 5% WTR application rate and vetiver. Soil pH increased from 2.69 to 7.2, and soil erosion indicators such as turbidity (99%) and total suspended solids (95%) in leachates were significantly reduced. See more on this study in A. RoyChowdhury's dissertation at https://digitalcommons.montclair.edu/etd/86/.
  • Phytoremediation of Selenium-Impacted Water by Aquatic Macrophytes
    Nattrass M., N.R. McGrew, J.I. Morrison, and B.S. Baldwin.
    Journal American Society of Mining and Reclamation 8(1):69-79(2019)
    The bioavailability of selenium (Se) chemical form and concentration on plant uptake were evaluated to determine the potential of aquatic macrophytes to improve water quality in a constructed wetland. The experiment was arranged as a 2x2 factorial nested within a split-split plot design replicated three times. Selenium treatments were applied to cattail (CT), duckweed (DWD), fanwort (CAB), soft rush (SR), muskgrass (MG), and unplanted controls (UNP) as a 4-L solution of either sodium selenite or sodium selenate to a total volume of 30 L at 0, 500, or 1000 µg/L Se. After six days, CT and MG-planted microcosms significantly decreased aqueous Se by 75 and 74%, respectively, compared to 61% for UNP. The aqueous fraction of microcosms planted to CAB, DWD, and SR were similar to UNP controls. Plant tissue Se content in CT was significantly less than CAB, DWD, or MG, suggesting CT has the potential to volatilize Se. Given its abundance and efficacy, CT is likely a suitable species for Se removal in constructed wetlands supplied with either selenite or selenate-impacted waters.
  • Mine Tailing Disposal Sites: Contamination Problems, Remedial Options and Phytocaps for Sustainable Remediation
    Karaca, O., C. Cameselle, and K.R. Reddy.
    Reviews in Environmental Science and Bio/Technology 17(1):205-228(2018)
    This review examines the use of phytocapping for the remediation of mine tailing deposits and abandoned mine areas. Phytocapping is a cost-effective technique that provides erosion control, landscape rehabilitation, improvement of soil properties for further colonization by more demanding vegetal species, reduction of metals leachability toward groundwater, and metals stabilization or immobilization. The most critical step in phytocapping is development of the initial vegetative cover because of the biotoxicity of the mine soil and mine tailings. Several amendment materials can be used to ameliorate soil conditions, serve as a source of nutrients, and create a favorable environment for plants to take root. Local fast-growing plant species are preferred because their adaptation to the soil and climate conditions favors their self-propagation. Available to view at https://www.researchgate.net/publication/321149964_Mine_tailing_disposal_sites_
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  • Floating Wetland Treatment of Acid Mine Drainage Using Eichhorina Crassipes (Water Hyacinth)
    Palihakkara, C.R., S. Dassanayake, C. Jayawardena, and I.P. Senanayake.
    Journal of Health and Pollution 8(17):14-19(2018)
    The applicability of water hyacinth (Eichhornia crassipes), a tropical aquatic plant with reported heavy metal hyperaccumulation, was investigated in microcosm floating wetland treatment systems designed to remediate acid mine drainage with Cu and Cd concentrations exceeding threshold limits. Water hyacinth demonstrated the capability to reduce both Cu and Cd concentrations, except at an initial concentration of 4 mg/L of Cu, which was toxic to the plants; at 4 mg/L the plants had low metals accumulations and rapid dying was evident. This paper is Open Access at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6221439/.
  • Phytoremediation of Industrial Mines Wastewater Using Water Hyacinth
    Saha, P., O. Shinde, and S. Sarkar.
    International Journal of Phytoremediation 19(1):87-96(2017)
    For the Sukinda chromite mines area of Orissa, India, research is underway to develop a suitable phytoremediation technology for effective removal of Cr(VI) from mine wastewater using a water hyacinth species (Eichhornia crassipes). This plant was observed to remove 99.5% Cr(VI) of the processed water in 15 days, not only removing Cr(VI) but also reducing total dissolved solids, biological oxygen demand, chemical oxygen demand, and other elements of water. After an initial 5-L study, the same removal efficiency was achieved in a larger experiment performed using 100 L of mine wastewater. This paper is Open Access at https://www.tandfonline.com/doi/full/10.1080/15226514.2016.1216078?cookieSet=1. Although water hyacinth is a problematic invasive species in the United States and other countries, researchers nonetheless are studying the potential for using its fast-growing, metal hyperaccumulating properties for water remediation under controlled conditions. See more at https://theconversation.com/invasive-tropical-plant-removed-metal-pollutants-from-british-river-new-study-100403.
  • Uranium Mine Waste Phytostabilization With Native Plants: A Case Study from Brazil
    Alves, L.J., F.C. Nunes, M.N.V. Prasad, P.A.O. Mangabeira, E. Gross, D.M. Loureiro, H.H.S. Medrado, and P.S.F. Bomfim.
    Bio-Geotechnologies for Mine Site Rehabilitation, Elsevier Inc. ISBN: 978-0-12-812986-9, Chapter 17:299-322(2018)
    This chapter presents the different techniques applied over the course of 14 years to the rehabilitation of a uranium mine in a semiarid climate with semiarid thorny scrub vegetation (Caatinga biome) in Brazil. The main rehabilitation strategies employed were the use of engineered blankets composed of plant fibers, the prospection of native grass species adapted to long periods of drought, and the use of legume species.
  • Phytoextration of Potentially Toxic Elements by Six Tree Species Growing on Hazardous Mining Sludge
    Mleczek, M., P. Golinski, M. Krzeslowska, M. Gasecka, Z. Magdziak, P. Rutkowski, S. Budzynska, B. Waliszewska, T. Kozubik, Z. Karolewski, and P. Niedzielski.
    Environmental Science and Pollution Research 24(28):22183-22195(2017)
    The phytoextraction abilities of six tree species—Acer platanoides L., Acer pseudoplatanus L., Betula pendula Roth, Quercus robur L., Tilia cordata Miller, Ulmus laevis Pall.— were compared following cultivation on mining sludge contaminated with As, Cd, Cu, Pb, Tl, and Zn. All six tree species survived on the unpromising substrate. With the exception of A. pseudoplatanus, the analyzed tree species showed a bioconcentration factor (BCF) > 1 for Tl, with the highest value for A. platanoides (1.41), although the translocation factor (TF) for this metal was < 1 in all the analyzed tree species. A. platanoides showed the highest BCF and a low TF and thus could be a promising species for Tl phytostabilization. This paper is Open Access at https://link.springer.com/article/10.1007/s11356-017-9842-3.
  • Potential of Eucalyptus Camaldulensis for Phytostabilization and Biomonitoring of Trace-Element Contaminated Soils
    Madejon, P., T. Maranon, C.M. Navarro-Fernandez, M.T. Dominguez, J.M. Alegre, B. Robinson, and J.M. Murillo. PLoS ONE 12(6):e0180240(2017)
    In a study of the use of trees to immobilize trace metals (phytostabilization), researchers investigated the chemical composition of leaves and flower buds of Eucalyptus camaldulensis in seven sites along the Guadiamar River valley (SW Spain), an area contaminated by a mine spill in 1998. E. camaldulensis trees in the spill-affected area and adjacent non affected areas were growing on a variety of soils with pH from 5.6 to 8.1 at low concentration of plant nutrients. The spill-affected soils contained up to 1069 mg/kg As and 4086 mg/kg Pb. E. camaldulensis tolerated elevated trace metal concentrations in soil and had low trace metal concentrations in the aerial portions compared to other species growing in the same environment. Despite the relatively low concentration of trace metals in leaves, they were significantly correlated with the soil-extractable Cd, Mn, and Zn, but not Cu and Pb. This tree species generally is tolerant of impoverished and contaminated soils, grows fast, has a deep root system, and is suitable for phytostabilization of soils contaminated by trace metals owing to the low transfer of metals from soil to aboveground organs. Eucalyptus leaves also could be used for biomonitoring the soil extractability of Cd, Mn, and Zn (but not Cu or Pb). This paper is Open Access at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180240.

Reuse and Reprocess Technologies — Reuse and Reprocessing (R2) technologies are applicable where mining wastes can be put to cost-effective, beneficial use directly or following reprocessing or treatment, or where reprocessing of the waste will render it safe for permanent disposal at the mine site. R2 technologies can be used for remediation of many types of mine waste. Examples include direct use of chat-pile material as an asphalt component, reuse of contaminated soil as cover material for site remediation, or use of waste rock and leach-pad material as construction material, either directly or following treatment or reprocessing. R2 technologies can be employed almost anywhere and in any climate as long as a market exists for the beneficial product. The technologies usually are used with mine waste contaminated with metals, but waste containing other contaminants, such as radionuclides, cyanide, and certain organic chemicals, also may be suitable. R2 technologies can be applied alone, but often are applied with treatment technologies that address the contaminants in the material, making it safe for reuse or conversion into a usable form.

  • Mine Water Use, Treatment, and Reuse in the United States: A Look at Current Industry Practices and Select Case Studies
    Miller, K.D., M.J. Bentley, J.N. Ryan, K.G. Linden, C. Larison, B.A. Kienzle, L.E. Katz, A.M. Wilson, J.T. Cox, P. Kurup, K.M. Van Allsburg, J. McCall, J.E. Macknick, M.S. Talmadge, A. Miara, K.A. Sitterley, A. Evans, K. Thirumaran, M. Malhotra, S.G. Gonzalez, J.R. Stokes-Draut, and S. Chellam. ǀ ACS ES&T Engineering [Published online 20 October 2021 before print]
    Current practices in mine water are identified, including how water is used in mining, influent, and effluent water quality, treatment technologies, and end uses to inform future research on implementable, reliable, and cost-effective advanced water treatment in the mining sector. Available literature was reviewed to evaluate mining in the U.S., and a techno-economic assessment on water use and disposal for three detailed case studies applicable to lithium, uranium, and copper mines was performed. Case studies highlight specific industry examples of distinct extraction methods, geographical regions, and mined commodities. Hypothetical scenarios based on case study baselines revealed potential impacts to mine water available for beneficial reuse using novel water treatment technologies and alternate water management strategies. The paper concludes by assessing national-level impacts resulting from the reuse of treated mine source water.
  • Efficient Methodologies in the Treatment of Acid Water from Mines with Recovery of Byproducts Adobe PDF Logo
    Aduvire1, O., M. Montesinos, and N. Loza.
    Proceedings of the 14th IMWA Congress, Mine Water Management for Future Generations, 12-15 July, virtual, 7 pp, 2021
    A staged acid-water treatment methodology is presented to make byproduct recovery economical and reduce contamination by diminishing the amount of non-usable slurry. Direct and staged treatment results are compared, including which byproducts were collected at different pH levels during staged treatment. Experimental neutralization and precipitation tests were conducted using various reagents and pH values to obtain the dosing of reagents and the treatment sequence. Based on the results of the tests and the hydrogeochemical characterization of the effluents, the processes and stages to consider are chosen in the design of the processing facility. These methodologies may reduce the costs of treating mine water, extend the life of waste deposits, reduce the discharge of solid and liquid waste into the environment, and allow the recovery and collection of by-products with potential economic use.
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