What Limits the Productivity of Acid Mine Drainage Treatment Ponds?

Abstract.  Acid mine drainage (AMD) treatment ponds are very common in the U.S. Appalachian coal region and are the main source of many headwater streams. Though the water that discharges from these ponds generally meets state and federal water quality standards, there is a distinct lack of productivity in most of these ponds. Our first objective was to compare the productivity of chemically-treated, biologically-treated, and untreated AMD ponds with uncontaminated (reference) ponds. Next, we used principal component analysis and multiple regression of 20 physicochemical characteristics of these ponds to resolve which factor(s) were responsible for inhibiting productivity. We discovered that chemically-treated AMD ponds and untreated AMD ponds exhibited significantly less gross primary productivity (GPP) than reference ponds; biologically-treated ponds (containing AMD that has passed through a wetland) did not vary significantly from reference ponds. Chemically-treated ponds also had significantly less net primary productivity (NPP) than reference ponds. Community respiration did not vary among the pond types. Our test results indicated that soluble reactive phosphate concentration explained most of the variance in both GPP and NPP. Apparently, phosphate availability, not metal toxicity, regulated phytoplankton productivity in these ponds.     

Passive Treatment of Circumneutral Mine Drainage from the St. Louis Mine Tunnel,Rico CO: Part 2—Vertical Biotreatment Train Pilot Study

This is the second of three papers dealing with metal-bearing circumneutral mine drainage from the inactive Rico-Argentine mine site located at an elevation of ≈ 2740 m (9000 feet) in the San Juan mountain range in southwestern Colorado. This paper evaluates two years of mine drainage treatment using a passive system that included a vertical-flow engineered biotreatment cell. The collapsed St. Louis Tunnel (SLT) discharges circumneutral mine water from several sources that contains elevated concentrations of Cd, Cu, Fe, Mn, Zn. A demonstration-scale 114 L/min (30 gpm) gravity-flow passive treatment system was installed, consisting of a settling basin (utilizing coagulant addition to improve suspended solids settling efficiency), an anaerobic sulfate-reducing bioreactor, and an aeration cascade for effluent polishing. The treatment system generally met target treatment goals for Cd, Cu, Fe, and Pb. Nanophase ZnS in system effluent decreased the frequency of meeting total Zn project treatment goals. Unexpectedly high levels of Mn removal were observed in both the anaerobic bioreactor and the aeration cascade. Large seasonal variations in influent metals concentrations and pH present the greatest challenge in managing system performance.

     

Passive Treatment of Circumneutral Mine Drainage from the St. Louis Mine Tunnel,Rico CO: Part 3—Horizontal Wetlands Treatment Train Pilot Study

Mine drainage from the St Louis Tunnel (located at the Rico-Argentine Site) is circumneutral most of the year, with spring freshets increasing flow, decreasing pH and increasing metals concentrations. This study was designed to test the performance of a demonstration-scale horizontal wetlands passive treatment train, comprised of a settling basin, surface flow wetland, horizontal-flow anaerobic wetland, aeration channel, and rock drain, during two years of influent water chemistry at a constant 113 L/min (30 gpm) flow rate. 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 (influent transition zone) 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.

     

Hydrogeochemistry of the Getchell Underground Mine––Part 1: Mine Water Chemistry

The Getchell underground operations in Northern Nevada intersect groundwater associated with marble and hornfel lithologies and a sulfide bearing ore hosted within a 30-km long shear zone system. The deposit is classified as Carlin-type gold mineralization. A distinct feature of the mineralization is the high proportion of arsenic sulfides present in the ore and associated altered wallrock. This results in an intense arsenic enrichment, with some zones containing as much as 30% arsenic, and 0.5–2% arsenic throughout the mineralized envelope. Most of the groundwater in the area is well buffered by the calcareous host rocks and show a macrochemistry of Ca-Na-HCO₃. Along the shear zone and in zones within the hornfel host rock, the waters are less alkaline and more saline, and have a chemistry of Na-Mg-Ca-SO₄-HCO₃. This latter water type occurs in sulfide-bearing zones. Arsenic speciation analysis and theoretical predictions demonstrate that higher arsenic concentrations are associated with reducing conditions, with higher Na/Ca ratios, and with low concentrations of Fe. In these waters, As occurs as arsenite, along with trace concentrations of mono-methyl arsonic acid and di-methyl arsinic acid. Natural attenuation of As appears to occur along groundwater flow paths due to co-precipitation and adsorption onto hydrous ferric oxide particles. However, elevated As is still a notable feature of groundwater quality throughout the Kelly Creek basin. This elevated As occurs in bedrock groundwater during underground mine development, rather than in near-surface alluvium groundwater. Due to this and the protracted history of mining, it is not possible to define a true background value for water quality in the area other than acknowledging that bedrock groundwater is mineralized and has little association with seasonal recharge and water quality in the alluvium cover.     

The Distribution of Antimony and Arsenic in Waters of the Dúbrava Abandoned Mine Site, Slovak Republic

The abandoned Dúbrava Mine, situated in the northern part of the Nízke Tatry Mts in the middle of Slovakia, was the most significant producer of antimony (Sb) in the former Czechoslovakia. Mine drainage from adits (containing up to 9,300 μg/L of Sb), mine waste dumps, and the leachate from mine tailings contribute Sb and arsenic (As) into nearby Palud?anka Creek and groundwater. Some drinking water resources have been closed due to excessive Sb concentrations; the concentration of Sb in one household well (126 μg/L) far exceeds the Sb drinking water limit of 5 μg/L. Although Sb is attenuated by dilution and adsorption on ferric iron in stream sediment in the Palud?anka Creek, Sb concentrations increase downstream of the mine tailings and then remain almost constant, leading to concentrations of 128 μg/L at the northern boundary of the study area. The dissolved As concentrations in the mine drainage are much lower than Sb, ranging from 4 to 62 μg/L. Flow and transport modeling confirmed the observed contamination pattern and the major role of the mine adits. Results of this study indicate serious Sb contamination, which could be mitigated by treatment of the adit discharges.     

Geochemical Behavior of Mine Tailings and Waste Rock at the Abandoned Cu–Mo–W Azegour Mine (Occidental High Atlas, Morocco)

The abandoned Azegour mine is located in the High Atlas Mountains of Marrakesh (Morocco), and was mined for Cu, Mo, and W. About 850,000 t of waste rocks and tailings were deposited on the surface and have been exposed to weathering for 40 years. The remaining acid-producing potential (AP), acid-neutralizing potential, and geochemical behavior of the Azegour Cu-and Mo-rich tailings were investigated. The tailings were found to contain 9.6–19 wt% sulfur, mostly as sulfate (gypsum, anhydrite, and jarosite) while the waste rocks contain less (1.25–6.58 wt%) sulfur. The waste rocks and tailings contain 0.21–9.24 wt% Mo and 0.003–2.78 wt% Cu. The gangue is mostly composed of quartz, talc, chlorite, pyrophyllite, actonolite, clinoptilolite, and alusite. Lead, zinc, cobalt, arsenic, titanium, and nickel are also present. The calcium, which is mainly expressed as calcite, gypsum, scheelite, and powellite, is present at higher concentrations in the waste rocks (18–22 wt% Ca) than in the tailings (4.7–8.6 wt% Ca). Static ABA determinations showed that the Azegour mine wastes still have high AP, 38–205 kg CaCO₃/t in the waste rocks and 46–387.7 kg CaCO₃/t in the tailings. This was confirmed in weathering cell tests, where the Azegour tailings leachate had a pH range of 1.98–3.19 and high concentrations of SO₄ (468–45,400 mg/L), Ca (230–675 mg/L), Fe (3–55,900 mg/L), Mn (0.1–1,430 mg/L), and Cu (2.3–9,000 mg/L). The Mo concentrations were high (35 mg/L) during the two first weeks of kinetics tests; W concentrations were below the 0.005 mg/L detection limit.     

In Situ Mine Water Treatment: Field Experiment at the Flooded Königstein Uranium Mine (Germany)

Within the WISMUT environmental remediation programme, the rehabilitation of the former uranium mine at Königstein is a very special case due to its use of underground leaching and its location near the Elbe River. The mine water is acidic, oxidizing, and polluted with uranium and other contaminants, and must be pumped to the surface and treated. In-situ water treatment approaches have been investigated to optimise further flooding and shorten the period of conventional water treatment. In 2010/2011, a field-scale experiment was carried out: about 120 t of alkalinity were successfully injected into the partially flooded mine. Tracer signals and geochemical reactions achieved general expectations. Based on the results, a site-specific technology concept was developed to flood the mine to its natural decant level.     

A Bauxsol™-based Permeable Reactive Barrier for the Treatment of Acid Rock Drainage

Abstract.   Permeable reactive barriers (PRBs) have generally been used to treat low flow and/or low contaminant loads of acid rock drainage (ARD). Bauxsol, a product made from seawater-neutralized red mud (a by-product of alumina refining) buffers pH at 8.8 and has been shown to remove >99% of heavy metals loadings at >1000 meq/kg, which would make it an ideal medium for PRBs. Unfortunately, Bauxsol is very fine-grained (>90% of the material <10 µm) and therefore, possesses a very low hydraulic conductivity. Consequently, sand/Bauxsol mixtures were trialed to determine hydraulic conductivity and ARD treatment capacities. Column tests indicated that the sand/Bauxsol mixtures maintain a higher hydraulic conductivity when used to treat ARD than when used with tap water. A 75:25 sand: Bauxsol filter with a 130 mm thick layer of reactive media had a hydraulic conductivity of 3.06 x 10^-5 m/s and except for Al, treated a highly contaminated ARD to ANZECC (2000) drinking water guidelines. A field trial of a 1 m³ PRB (70:30 sand:Bauxsol mixture) with a hydraulic conductivity of 9.8 x 10^-5 m/s treated about 45,000 L of highly contaminated ARD to the ANZECC (2000) drinking water standards, and about 27,000 L of this water had heavy metal loadings reduced to the ANZECC (2000) Protection of Aquatic Ecosystem guideline of >90% species protection.The metal binding preference of Cu>Pb>Zn>Mn displayed by the PRB is consistent with the pKa of hydration values and it appears that MOH⁺ formation dominates the removal of these metals. However, other removal processes appear to apply for Fe, Al, and Cd. Overall metal removal efficiencies ranged from 91.22% for Mn to >99.99% for Cu. Analysis of dried spent Bauxsol indicates that bound metals are not readily leachable, allowing the spent media to be disposed safely in a landfill.     

A study of law of coal-and-gas outburst ＆ its controlling factors in Kailuan Mine Area, China

On basis of an analysis of the geological condition, law of gas outburst and materials about coal-and-gas outburst, this paper summarized the characteristics associated with coal-and-gas outburst of Zhaogezhuang Mine and studied the factors controlling coal-and-gas outburst such as stress, coal structure and gas pressure, content of gas. Then, based on a comparison of effects of in-situ stresses, coal structure and gas on coal-and-gas outburst of Zhaogezhuang Mine, the paper concludes that the major geological factors that control coal-and-gas outburst of Zhaogezhuang Mine are in-situ stresses and coal structure.     

Tailings Mineralogy and Geochemistry at the Abandoned Haveri Au–Cu Mine,SW Finland

Fourteen samples from the Haveri Au–Cu mine tailings were studied by reflected-light microcopy, scanning electron microscopy, X-ray powder-diffraction, and sequential extraction methods, and 12 water samples were analyzed for total and dissolved elements to delineate the extent of sulfide oxidation and its impact on nearby surface waters. Water-soluble, adsorbed-exchangeable-carbonate (AEC), Fe (oxy)hydroxides, Fe oxide, and Fe sulfide fractions were extracted sequentially. The oxidation layer was found to vary from 50 to 140 cm: the upper part was nearly depleted in primary sulfides, especially pyrrhotite [Fe_(1?x)S] and pyrite (FeS₂); in the lower part, discontinuous cemented layers were detected. Secondary Fe (oxy)hydroxides and Fe oxyhydroxysulfates were abundant in the oxidation layer and were slightly enriched in trace elements, including As (up to 80 mg/kg), Cu (300 mg/kg), and Zn (150 mg/kg). Almost half of the As (average 25 mg/kg) were present as secondary minerals susceptible to redissolution. The pH of the vadose tailings varied from 2.46 to neutral, and the total sulfur content varied from 1 to 6.5% (average 2.9%). Aqua regia extraction showed that the Haveri tailings are characterized by low concentrations of the elements Cd, Cr, Pd, and slightly elevated concentrations of As, which are present at very low concentrations in the surface water (<6 μg/L). However, runoff that flows on top of the tailings and discharges into the nearby lake carries Co, Cu, Ni, and Zn (concentrations of each range from 500 to 1,800 μg/L). Additionally, dissolution of sulfides and Fe precipitates may mobilize trace metals in the ground water. Thus, overall, there is a small continuous release of AMD into Lake Kirkkojärvi, but the environmental impacts to the lake are presently small.     

Numerical scheme for elastoplastic parameter identification and finite element analysis of wall-slope of the Fushun West Open Pit Mine

The elasto brittle plastic finite element analysis has been taken on the prediction for the deformation of the northwall of an open pit of Fushun, China. Numerical simulation has been made on the reinforcement measures of the slope structure. Using parameter identification techniques and connecting with elasto bdttle plastic finite element program, the displacement back analysis has been made on the matedal parameters of the rockslope. The equivalent parameter values of the real slope structure have been obtained. The process of the rapid increment of the slope‘s deformation caused by open mining dudng 1987 ~ 1990 has been reappeared through the numerical simulation.     

Detection of Abandoned Coal Mine Goaf in China’s Ordos Basin Using the Transient Electromagnetic Method

Mine Water and the Environment - Early coal mining and management methods left a large number of unknown goafs in China’s important Ordos Basin, which has restricted the safe production in...     

Analysis of soft rock roadway deformation mechanism in Zhangshuanglou Mine

On basis of ground stress surveying and analysis of physical nature and mechanics character of rock, the deformation mechanism of west main roadway in Zhangshuanglou Mine is studied. It is put forward that engineering mechanics nature, infiltration of water and con-centrated stress on pillar are the main factors to affect stability of the west main roadway. The overall thinking used to restore the roadway is raised.     

Influence Analysis of Mining’s Effect on Failure Characteristics of a Coal Seam Floor with Faults: A Numerical Simulation Case Study in the Zhaolou Coal Mine

A fluid–solid coupled numerical simulation was carried out for the Zhaolou coal mine using Flac3D software. The results showed that: (1) when the failure depth of the floor exceeded the extension depth of the floor rock mass and the hydrostatic seepage pressure of the fractured structure surface exceeded the stress state of the fractured element, floor water inrush will occur. (2) With other factors being equal, if the footwall is mined first, the pore pressure concentration near the fault is more obvious, and the floor-confined water is lifted 10–25 m higher than when the hanging-wall is mined first. Mining the floor adversely affects its plastic zone, and the failure depth is ≈?10 m greater than when the hanging wall is mined first. (3) When advancing against the fault dip, the pore pressure concentration near the fault is more obvious, and the floor confined water is lifted 5–20 m higher than when the mine advances along the fault dip. Again, mining the floor first disrupts the floor plastic zone, and the failure depth is approximately 5 m greater than when the mine is advanced along the fault dip. (4) The risk of floor-water inrush is minimized when the hanging-wall is mined first and the mine advances along the fault dip; the risk is greatest when the footwall is mined first and is advanced against the fault dip. These results provide a theoretical basis for preventing mine water inrush.     

Geochemistry of Mine Tailings from Processing of Siderite–Cu Ores and Mobility of Selected Metals and Metalloids Evaluated by a Pot Leaching Experiment at the Slovinky Impoundment,Eastern Slovakia

This work describes the geochemistry, mineralogy, and mobility of selected metals (Cu, Pb, Zn) and metalloids (As, Sb) in a tailings impoundment in the village of Slovinky (eastern Slovakia). The tailings were covered unevenly by slag from processing of Cu wastes. The tailings and slag both have negligible potential for acid mine drainage formation, thus neutral to alkaline conditions predominate, as shown by high paste pH values of the tailings (7.66–8.83) and neutral drainage, with pH values above 7.50. Weathering of the most abundant primary sulfides (chalcopyrite, pyrite, and arsenopyrite) releases low concentrations of As, Cu, Pb, Sb, and Zn from the tailings impoundment and in leachates from a 150 days pot leaching experiment. This is explained mostly by formation of secondary ferric oxyhydroxides (as weathering rims on the surfaces of primary sulfides or individual grains),which incorporate 4.09 wt% of As, 17.2 wt% of Cu, 1.20 wt% of Pb, 15.0 wt% of Sb, and 1.59 wt% of Zn. Elevated contents of metals and metalloids in weathering rims formed on slag components like glasses, metallic grains, and residues of blast-furnace lining indicate that secondary solid phases are controlling the mobility of the potentially toxic elements. Generally, with the exception of Cu, no separate secondary compounds of the metals or metalloids were found. The potentially toxic elements are mainly immobilized by ferric oxyhydroxides and other iron mineral phases in the tailings impoundment.     

Practical Application of Mechanical Rack Track Locomotive in Shigejie Coal Mine

Inthepastdecade,tentypesofracktracklocomotivesdrivenbyenvironmentfriendlyflameproofdieselengineandequippedwithpolyurethanewrappeddrivingwheel(hereinaftercalled'dieselengineracktracklocomotive')havebeendevelopedand40setsofthesetransportsystemshavebeenmanufactUredfordomesticcoalminestoimprovethepoorworkingconditionsofundergroundauxiliaryiT3nsportation.NowChinahasbecomeoneofafewcountriesintheworldthatappliesthistechnologytotheadvanceddieselenginerackrailtransportsystemincoalmines.Generally,thedo…     

Best regards to the fellow of West-china in the field of rock-soil,drilling

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Mine Closure of Pit Lakes as Terminal Sinks: Best Available Practice When Options are Limited?

In an arid climate, pit lake evaporation rates can exceed influx rates, causing the lake to function as a hydraulic terminal sink, with water levels in the pit remaining below surrounding groundwater levels. We present case studies from Western Australia for two mines nearing closure. At the first site, modelling indicates that waste dump covers for the potentially acid forming (PAF) material would not be successful over the long term (1,000 years or more). The second site is a case study where PAF management is limited by the current waste rock dump location and suitable cover materials. Pit lake water balance modelling using Goldsim software indicated that both pit lakes would function as hydraulic terminal sinks if not backfilled above long-term equilibrium water levels. Poor water quality will likely develop as evapoconcentration increases contaminant concentrations, providing a potential threat to local wildlife. Even so, the best current opportunity to limit the risk of contaminant migration and protect regional groundwater environments may be to limit backfill and intentionally produce a terminal sink pit lake.