Use of SRB in a Gravel Bed Reactor for Treatment of Acid Mine Drainage Water
John D. Sheppard, Ph.D., McGill University, Quebec, Canada
Darwin Lyew, Ph.D., Biotechnology Research Institute, Montreal, Quebec, Canada

Algal Bioremediation of the Berkeley Pit Lake System-and an In Situ Test Using Limnocorrals
Dr. Grant G. Mitman, Montana Tech of The University of Montana, Butte, MT

The Effect of Drainage Flow and Saturation Conditions on Microbial Pyrite Oxidation in Mine Waste Rock
Joy Jenkins and JoAnn Silverstein, Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, CO  

Bioremediation of Acid Drainage by Means of a Passive Treatment System

Stoyan N. Groudev, Department of Engineering Geoecology, University of Mining and Geology, Studentski grad – Durvenitza, Sofia 1700, Bulgaria, Tel: +359 2 687396, Fax: + 359 2 687396, Email: groudev@mgu.bg
Plamen S. Georgiev, Department of Engineering Geoecology, University of Mining and Geology, Studentski grad – Durvenitza, Sofia 1700, Bulgaria, Tel: +359 2 687396, Fax: + 359 2 687396, Email: ps_georgiev@mgu.bg
Irena I. Spasova, Department of Engineering Geoecology, University of Mining and Geology, Studentski grad – Durvenitza, Sofia 1700, Bulgaria, Tel: +359 2 687396, Fax: + 359 2 687396, Email: spasova@mgu.bg
Marina V. Nicolova, Department of Engineering Geoecology, University of Mining and Geology, Studentski grad – Durvenitza, Sofia 1700, Bulgaria, Tel: +359 2 687396, Fax: + 359 2 687396, Email: mnikolova@mgu.bg
Ludo Diels, VITO, 2400 Mol, Belgium, Hoofd Milieu- en Procestechnologie , Vlaamse instelling voor technologisch onderzoek (Vito), Boeretang 200 , B - 2400 Mol, België, Tel: + 32 (0)14 33 51 00, Fax. + 32 (0)14 58 05 23, Email: ludo.diels@vito.be

Acid drainage waters generated in a uranium deposit were treated by means of a pilot-scale passive system consisting of an alkalizing limestone drain, an anoxic barrier for microbial dissimilatory sulphate reduction and an aerobic rock filter for manganese and organics removal, connected in a series. The waters had a pH in the range of about 2.7 – 3.2 and contained radionuclides (uranium, radium), heavy metals (copper, zinc, cadmium, lead, cobalt, nickel, iron, manganese), arsenic and sulphates in concentrations usually much higher than the relevant permissible levels for waters intended for use in the agriculture and/or industry. The water flow rate through the system varied in the range of about 0.1 – 0.3 l/s. In the alkalizing drain the pH of the waters was increased to values higher than 7 and as a result of this most of the iron was precipitated as hydroxides. A portion of arsenic was also removed mainly by sorption on these hydroxides. The permeable barrier had a volume of 12.5 m³ and was filled by a mixture of solid biodegradable organic substrates (cow manure, plant compost, hydrolysate of rich-in-cellulose wastes from the paper industry, hay). The barrier was inhabited by a microbial community consisting mainly of sulphate-reducing bacteria and other metabolically interdependent microorganisms. In the barrier the non-ferrous metals were precipitated mainly as the relevant insoluble sulphides, and uranium was precipitated mainly as uraninite (UO₂) as a result of the prior reduction of the hexavalent uranium to the tetravalent form. Radium was removed mainly as a result of its sorption by the solid organic matter present in the barrier. Portions of the other metals were also removed in this way. The effluents from the barrier were enriched in dissolved organic compounds and usually still contained manganese in concentrations higher than the relevant permissible level. These effluents were treated in the rock filter where the Mn²⁺ ions were oxidized by different aerobic heterotrophic bacteria to Mn⁴⁺, which were precipitated as MnO₂. The dissolved organic compounds were removed as a result of their oxidation by the heterotrophs inhabiting the filter.

Restoration of Ecosystems and Long-Term Stabilization of Initially Acidic Pit Lakes with a case study at the Gilt Edge Mine Superfund Site, South Dakota

Joseph G. Harrington, ARCADIS, Inc., 630 Plaza Drive, Suite 200, Highlands Ranch CO 80129-2379, Tel: 720 344-3500, Fax: 720-344-3535, Email: jharrington@arcadis-us.com
Kenneth Wangerud, EPA Region VIII Superfund Group, 999 18^th Street, Suite 500, Denver, CO  80202-2466, Email: wangerud.ken@epa.gov
Steven D. Fundingsland, CDM Federal Programs Corp., 1331 17th Street, Suite #1050, Denver, CO 80202, Email: fundingslandsd@cdm.com

EPA NRMRL Mine Waste Technology Program and Region VIII Superfund office have jointly conducted an in-situ remediation and restoration technology demonstration and Treatability Study at the Anchor Hill Pit Lake, Gilt Edge Mine Superfund site.  The treatability study project has been quite successful to date.  The pit lake originally contained 77,000,000 gallons of pH 3 water with elevated heavy metals, sulfate, and nitrate.  The Green World Science® patented process for in situ treatment of metals and other contaminants (exclusively licensed to ARCADIS) was implemented to encapsulate metals; create stable long-term water quality and restore a sustainable ecosystem.  This technology allows for ecosystem restoration in situ and is substantially more cost-effective than treatment through ex situ water treatment facilities.

Concentrations of dissolved COCs have decreased more than 99%, and aquatic standards (cold water biota under chronic exposure) for heavy metals were attained.  Discharge of remediated water from the pit lake to nearby Strawberry Creek began in June, 2004.  Site stakeholders are considering a site-wide water treatment system whereby acidic waters are collected in the pit from across the site (at a rate of up to 150 gpm), treated in the pit lake in a somewhat “batch” mode, and then subsequently discharging these waters to the creek following a pre-filtration step.  This innovative approach, creating a long-term stable ecosystem with low anticipated maintenance requirements for further treatment of acid migration and drainage, has substantial implications on closure strategies for operating and closed pits such as form or may form at mine closures elsewhere throughout the United States.

Results from successful treatment of a uranium mine pit lake in Sweetwater county, WY and a molybdenum mine pit lake in Tonopah, NV will also be presented.

A Geochemical overview of the Berkeley pit-lake, Butte, Montana, USA

C. H. Gammons, Dept. of Geological Engineering, Montana Tech of The University of Montana, Butte, MT 59701, Tel: 406-496-4763, Email: cgammons@mtech.edu
D. A. Pellicori, Montana Tech of the University of Montana, Butte, MT
S. R. Poulson, Dept. of Geological Sciences, University of Nevada-Reno, Reno, NV
J. Madison, and P. Reed, Montana Bureau of Mines and Geology, Butte, MT

The Berkeley pit-lake contains over 100 billion L of highly acidic (pH 2.6), metal-rich water (Fe ~ 1000 mg/L; Zn ~ 600 mg/L; Cu ~ 150 mg/L).  The pit-lake began filling in 1983 when mining of the Butte ore body temporarily ceased, and is still filling at a rate of 7 to10 million L/day.  Most of this influent water is deep groundwater draining ~ 10,000 km of subjacent flooded underground mine workings.  In the past, an additional source of influent water was the Horseshoe Bend spring (HBS), a large, acidic (pH 3.1) seep discharging near the base of a nearby tailings dam.  In 2003, a modern lime treatment facility was built to treat the HBS.  The same facility will eventually treat Berkeley pit-lake water when the lake reaches a critical elevation, some 10+ years from now.      

Two intriguing aspects of the Berkeley pit-lake are that its water quality is much worse than all known influent waters, and that the chemistry of the pit-lake has shown no improvement with time, whereas the water quality of the subjacent flooded mine workings has improved dramatically with time.  In the past 5 years, our research group has combined water quality monitoring, bench-top experiments, and stable isotope investigations to attempt to explain these disparities.  The poor water quality of the pit-lake is attributed to a combination of several factors, including: 1) leaching of metal salts from the pit walls as the lake levels rise; 2) evapo-concentration; and 3) subaqueous oxidation of pyrite by dissolved ferric iron.    A 4^th hypothesis – influx of deep groundwater of poor quality from the direction of the active tailings dam – is also possible, but is difficult to test.

Portions of this study were funded by the U.S. Environmental Protection Agency through its Office of Research and Development under IAG  DW89938870-01-0 through the U.S. Department of Energy (DOE) National Energy Technology Laboratory under Contract DE-AC22-96EW96405.

Treatment of Acid Mine Drainage Wastes in a Membrane Bioreactor

Henry H. Tabak, U.S. EPA, Environmental Research Center, ORD, National Risk Management Research Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45268, Tel: 513-569-7681, Fax: 513-569-7105, Email: tabak.henry@epa.gov
Rakesh Govind, University of Cincinnati, Department of Chemical Engineering, Cincinnati, OH 45221, Tel: 513-556-2666, Fax: 513-556-0217, Email: rgovind@alpha.che.uc.edu

Acid mine drainage (AMD) is a severe pollution problem attributed to past mining activities. AMD is an acidic, metal-bearing wastewater generated by the oxidation of metal sulfides to sulfates by Thiobacillus bacteria in both the active and abandoned mining operations. The wastewaters contain substantial quantities of dissolved solids with the particular pollutants (metal sulfates) dependent upon the mineralization occurring at the mined rock surfaces. The exposure of post-mining residuals to water and air results in a series of chemical and biological oxidation reactions that produce an effluent which is highly acidic and contains high concentrations of various metal sulfates.. The metals (metal sulfates) usually encountered and considered of concern for human risk assessment are: arsenic, cadmium, iron, lead, manganese, zinc and copper. These metals as well as sulfate are considerd serious pollutants of the acid mine drainage. The pollution generated by abandoned mining activities in the area of Butte, Montana has resulted in the designation of the Silver Bow Creek-Butte area known as Berkeley Pit, as the largest superfund (National Protection List) site in U.S.  This paper reports on bench-scale studies conducted to develop a biotreatment method for acid mine water (AMW) using membrane bioreactor systems to maximize the biological sulfate conversion rate and thus enhance the bioremediation of acid mine water from Berkeley Pit as well as other acidic water pit lakes.

Several biotreatment techniques for the treatment of sulfate by sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing AMD. This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of AMW from the Berkeley Pit lake using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase, gas sparged bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane thus preventing mixing with pressurized  hydrogen  gas inside the membrane; no requirement for  gas recycle compressor for hydrogen; membrane surface is suitable for immobilization of active SRB, resulting in formation of biofilms,  thus  preventing washout problems associated with suspended culture reactors; and lower operating costs  in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information will be provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic sludge and sediment source master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been deterrnined using biokinetic models for the master culture and membrane bioreactor systems.  Data will be presented also on the effect of AMW sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40oC), to determine and optimize sulfate conversion for an effective AMD biotreatment.  Pilot-scale studies have generated data on the effect of flow rates of AMW (in MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion rates i. The pilot-scale data indicate that SRB membrane bioreactor systems can be applied toward field-scale biotreatment (sulfate conversiuon) of AMW from Berkeley Pit lake as well as from other acidic water pit lakes and for a  recovery of  high purity metals and a usable water from the AMW wastes.

Use of SRB in a Gravel Bed Reactor for Treatment of Acid Mine Drainage Water

John D. Sheppard, Ph.D., Department of Bioresource Engineering, McGill University, 21,111 Lakeshore Road, Ste-Anne de Bellevue, Quebec, Canada H9X 3V9, Tel: 514-398-7967, Email: john.sheppard@mcgill.ca
Darwin Lyew, Ph.D., Biotechnology Research Institute, NRCC, 6100 Royalmount Ave., Montreal, Quebec, Canada H4P 2R2, Tel: 514-496-2664, Email: darwin.Lyew@nrc.ca

This paper summarizes work that was performed in response to the need by Noranda Technology Inc. to develop alternative technologies for the treatment of acid-mine drainage being produced at various mine sites in Canada. It is based on the use of sulphate-reducing bacteria entrapped in a submerged gravel bed subjected to AMD. The hydrogen sulphide resulting from the reduction of the sulphate in the AMD binds with dissolved metal ions, producing metal sulphide precipitates in the gravel bed, thus becoming essentially immobilized. This work focussed on the relationship between the activity of the SRB and the physical characteristics of the gravel bed such that a rational design procedure could be followed for scale-up from the laboratory to the field. The laboratory experiments were conducted using plexiglas columns containing gravel beds of various characteristics. The reactors had a working volume of 8 L and the AMD was treated by semicontinuous addition. The scale-up criteria was based on the development of two dimensionless numbers, F_SRB and D_SRB, that accounted for the volume of AMD entering the bed (V_c), the total surface area of the gravel in the bed (tSA), the interfacial or superficial surface area between the bed and the AMD (sSA) and the void volume in the bed (V_v). A relationship was shown to exist between the proportion of sulphate removed by the SRB to the product of the ratios of V_c/V_v and sSA/tSA (D_SRB), while the rate of sulphate removal was related to the product of the inverse ratio, V_v/V_c, and sSA/tSA (F_SRB). Based on data from the laboratory-scale gravel bed reactors, the degree of sulphate removal was best with a D_SRB value between 0.0075 and 0.015, while the rate of sulphate removal was inversely proportional to the F_SRB value.

Algal Bioremediation of the Berkeley Pit Lake System-and an In Situ Test Using Limnocorrals

Dr. Grant G. Mitman, Department of Biological Sciences, Montana Tech of The University of Montana, Butte, MT 59701, Tel: 406-490-3177, Email: gmitman@mtech.edu

The Berkeley Pit Lake System is one of the largest contaminated sites in North America and is located near the headwaters of the largest superfund site in the U.S.  It is filling at a rate of about 28.7 million liters per day with metal laden, acidic (pH 2.7) water.  Chlorella ellipsoidea is one of the first autochthonous species of algae from the Berkeley Pit Lake System to be tested for its bioremediative potential.  An experimental matrix was designed for this experiment using a completely randomized design (CRD). The matrix was set up with tissue culture flasks having the following treatments:  Na₂HPO₄ at 0, 25, 50, 75, 100 mg/l, inoculated vs. no- inoculated with algae (187,500 algae/ml final), and filtered (0.2Fm) vs. non filtered pit water as variables,  NaNO₃ amount was fixed at53 mg/ml.  Three replicates were made of each and the experiment lasted 60 days.  The results of this experiment demonstrated significant remediation of most metals.  These results will be presented.  As a result of the success of these experiments, it is hypothesized that these same principles should work (even better) in the Berkeley Pit Lake system if it is nutrified.  In order to more fully test this hypothesis it is important to scale up from imhoff cones to more fully represent the physical and chemical properties of Berkeley Pit Lake System Water for the test.  Therefore, the experiment should occur in the Berkeley Pit.  This will be possible by using Limnocorrals.  These enclosures consist of polyethylene in a cylindrical form (e.g. 1m diameter x 5 m depth) open at the top with camouflaged flotation collars and anchored to the bottom. Limnocorrals have been used for about 40 years for experimental studies in lakes when it is necessary to test biological, physical and chemical properties in situ while varying an aspect of the ecosystem on a small scale to determine the outcome (e.g. nutrients, algae) (Cruikshank 1983). Preliminary results of this experiment will also be presented.

The Effect of Drainage Flow and Saturation Conditions on Microbial Pyrite Oxidation in Mine Waste Rock

Joy Jenkins and JoAnn Silverstein, Dept. Civil, Environmental, and Architectural Engineering , University of Colorado, Boulder, CO

Research on microbial iron and sulfur cycling in the mined rock subsurface has focused on biogeochemical reactions at the water-rock interface. A strategy for remediation of acid mine drainage (AMD) sources is initiation of a shift in microbial populations from dominance of iron oxidizing bacteria to iron and sulfur reducing microorganisms by the addition of biodegradable organic matter.  However, control of AMD formation by organic carbon addition requires an understanding of the role of hydrologic and transport conditions in biogeochemical iron and sulfur transformation. Experiments were conducted using two 37.8-liter (10 gallon) rock microcosm tanks packed with 0.1 – 10-cm rock particles obtained from a mine waste pile near Leadville, CO resulting in 50% porosity.  Filtered deionized water was recirculated through the tanks with a 10-day average hydraulic residence time. One tank was run under saturated conditions and the second was run with trickle flow to achieve 16% saturation. The headspace of both tanks was sparged with air. Production of soluble ferric iron (Fe(III)) and sulfate in the unsaturated tank was significantly higher than in the saturated system, 16 g/L in the unsaturated tank compared with 0.1 g/L in the saturated tank drainage water. Ferrous iron was negligible in the unsaturated tank (< 20 mg/L) whereas it comprised over 75% of the total soluble iron in the saturate tank drainage water, indicating suppression of bacterial iron oxidation. This was consistent with differences in dissolved oxygen, which averaged 4 mg/L in the unsaturated tank compared with 1 mg/L in the saturated tank drainage. The drainage water pH in the unsaturated tank was 1.5, significantly lower than the saturated tank drainage, which had a pH in the range of 2.5 – 3. Results indicate that availability of oxygen is critical to bacterial iron oxidation. Furthermore, significant formation of oxidized iron and sulfate products may occur during periods when drainage flow is minimal.  This indicates that methods to inhibit bacterial pyrite oxidation must be effective during periods of unsaturated flow, perhaps even under snow cover.

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