A rigorous laboratory and field study to measure and compare low sulfide waste rock and drainage characteristics at various scales has been designed and implemented. The field study was constructed at the Diavik diamond mine in the Northwest Territories, Canada. Three well-instrumented, 15 m high test piles and three sets of 2 m scale experiments were constructed from run of mine waste rock. Diavik waste rock is comprised of granite and metasedimentary biotite schist country rock. The biotite schist contains the sulfide minerals, principally pyrrhotite. Diavik segregates waste rock based on sulfur content. One test pile contains waste rock with 0.035 wt. % S, within the operational sulfur target of < 0.04 wt. % S for lower sulfur waste rock designation. The second pile contains waste rock with 0.053 wt. % S, lower than the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock designation. The third pile contains a core of 0.082 wt. % S waste rock which is within the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock. The third pile has been re-contoured and capped by a 1.5 m of till and 3 m of lower sulfide waste rock as per the current reclamation plan for the higher sulfide waste rock pile. The test piles were built using standard end-dumping and push-dumping methods. Instrumentation was installed at the base of each pile and on four angle of repose tip faces, as well as in the covers of the third pile. Instrumentation was selected to measure matrix flow, pore water and bulk pile geochemistry, gas-phase oxygen and carbon dioxide concentrations, temperature evolution, microbiological populations, permeability to air, and thermal conductivity, and to resolve mass and flow balances. Instruments were designed to permit measurements at multiple scales. During pile construction samples of the < 50 mm fraction of waste rock were collected. The samples were analysed for sulfur content and particle size distribution. Particle size distributions for the lower and higher sulfur waste rock are similar but the higher sulfur waste rock has a higher proportion of fines. Particle size distributions for both waste rock types suggest the piles have rock-like characteristics rather than soil-like characteristics. Sulfur concentrations vary with the scale of measurement: concentrations of smaller size fractions are higher than larger size fractions. Acid-base accounting using standard methods and site-specific mineralogical information suggest that the waste rock is acid generating. However, when acid-base accounting is compared to effluent pH and alkalinity, the data suggest these calculations may be conservative. Drainage effluent from the higher sulfide test pile was measured for field parameters (pH, Eh, alkalinity) and dissolved cations, anions and nutrients. The geochemical equilibration model MINTEQA2 was used to interpret potential geochemical controls on solution chemistry. The pH decreases to < 5, concomitant with the minimum alkalinity of < 1 mg L-1 (as total CaCO3), suggesting all available alkalinity is consumed by acid-neutralizing reactions. Sulfate concentrations reach 1995 mg L-1. Calculated saturation indices of Al (oxy)hydroxides and Al hydroxysulfate species, and pH suggest Al oxyhydroxide dissolution is buffering pH at times. Concentrations of Fe (< 0.37 mg L-1), Fe (II) and calculated saturation indices of Fe(III) (oxy)hydroxide species suggests that Fe is predominantly Fe(III) and Fe is being controlled by secondary mineral precipitation. The dissolved trace metals Mn (<19.2 mg L-1), Ni (<10.4 mg L-1), Co (<1.8 mg L-1), Zn (<0.9 mg L-1), Cd (<0.015 mg L-1) and Cu (<0.05 mg L-1) show increasing trends in the effluent water. No dissolved trace metals appear to have secondary mineral controls. Elevated SO4, Al, Fe dissolved metals Ni, Co, Zn, Cd and Cu, and depressed pH values suggest sulfide mineral oxidation is occurring in the test pile containing 0.053 wt. % S.

The aim of the study was to map the extent of Fe, Cu, Pb, As, Zn and S contamination in the area surrounding the Nasa silver mine. The mine operated between 1635 and 1810 with some prospecting performed in 1889, and has become infamous for the gruesome ways that the indigenous people were treated during the early years of operation. This study tested three hypotheses through a geochemical survey: 1) sulfide oxidation is still active in the abandoned mine, 2) the soil downslope of the mine is contaminated by mine drainage, and 3) the stream downslope of the mine is affected in the same way. All three hypotheses were valid, as the results showed that still, &gt;200 years after mining operations ceased, signs of the historical mining are clearly visible in the surrounding environment. Acidic conditions were discovered in surface waters close to the waste rock piles, which indicates active sulfide oxidation. In addition, elevated levels of Fe, Cu, Pb, As, Zn and S were found in both soil and stream sediment downslope of the mines, as compared to reference localities upstream the mine (p &lt;0.05). These results suggest that previous assessments of the mine being no threat to the environment may not be entirely correct. This study illustrates how mining waste can continue to affect the local, sub-arctic environment long after mining operations have ceased.

A rigorous laboratory and field study to measure and compare low sulfide waste rock and drainage characteristics at various scales has been designed and implemented. The field study was constructed at the Diavik diamond mine in the Northwest Territories, Canada. Three well-instrumented, 15 m high test piles and three sets of 2 m scale experiments were constructed from run of mine waste rock. Diavik waste rock is comprised of granite and metasedimentary biotite schist country rock. The biotite schist contains the sulfide minerals, principally pyrrhotite. Diavik segregates waste rock based on sulfur content. One test pile contains waste rock with 0.035 wt. % S, within the operational sulfur target of < 0.04 wt. % S for lower sulfur waste rock designation. The second pile contains waste rock with 0.053 wt. % S, lower than the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock designation. The third pile contains a core of 0.082 wt. % S waste rock which is within the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock. The third pile has been re-contoured and capped by a 1.5 m of till and 3 m of lower sulfide waste rock as per the current reclamation plan for the higher sulfide waste rock pile. The test piles were built using standard end-dumping and push-dumping methods. Instrumentation was installed at the base of each pile and on four angle of repose tip faces, as well as in the covers of the third pile. Instrumentation was selected to measure matrix flow, pore water and bulk pile geochemistry, gas-phase oxygen and carbon dioxide concentrations, temperature evolution, microbiological populations, permeability to air, and thermal conductivity, and to resolve mass and flow balances. Instruments were designed to permit measurements at multiple scales. During pile construction samples of the < 50 mm fraction of waste rock were collected. The samples were analysed for sulfur content and particle size distribution. Particle size distributions for the lower and higher sulfur waste rock are similar but the higher sulfur waste rock has a higher proportion of fines. Particle size distributions for both waste rock types suggest the piles have rock-like characteristics rather than soil-like characteristics. Sulfur concentrations vary with the scale of measurement: concentrations of smaller size fractions are higher than larger size fractions. Acid-base accounting using standard methods and site-specific mineralogical information suggest that the waste rock is acid generating. However, when acid-base accounting is compared to effluent pH and alkalinity, the data suggest these calculations may be conservative. Drainage effluent from the higher sulfide test pile was measured for field parameters (pH, Eh, alkalinity) and dissolved cations, anions and nutrients. The geochemical equilibration model MINTEQA2 was used to interpret potential geochemical controls on solution chemistry. The pH decreases to < 5, concomitant with the minimum alkalinity of < 1 mg L-1 (as total CaCO3), suggesting all available alkalinity is consumed by acid-neutralizing reactions. Sulfate concentrations reach 1995 mg L-1. Calculated saturation indices of Al (oxy)hydroxides and Al hydroxysulfate species, and pH suggest Al oxyhydroxide dissolution is buffering pH at times. Concentrations of Fe (< 0.37 mg L-1), Fe (II) and calculated saturation indices of Fe(III) (oxy)hydroxide species suggests that Fe is predominantly Fe(III) and Fe is being controlled by secondary mineral precipitation. The dissolved trace metals Mn (<19.2 mg L-1), Ni (<10.4 mg L-1), Co (<1.8 mg L-1), Zn (<0.9 mg L-1), Cd (<0.015 mg L-1) and Cu (<0.05 mg L-1) show increasing trends in the effluent water. No dissolved trace metals appear to have secondary mineral controls. Elevated SO4, Al, Fe dissolved metals Ni, Co, Zn, Cd and Cu, and depressed pH values suggest sulfide mineral oxidation is occurring in the test pile containing 0.053 wt. % S.

<p>Natural and constructed clay liners are routinely used to contain waste and wastewater. The impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at pH > 1.0. The impact of sulfuric acid leachate characterized by pH < 1.0, including potentially negative pH values on the geochemistry and mineralogy of clays is, however, not clear.</p> <p>To address this deficiency a series of batch and diffusion cell studies, investigating the geochemical and mineralogical impacts of H₂SO₄ solutions (pH 5.0 to -3.0), were conducted on three mineralogically distinct clays (Kc, Km, and BK). Batch testing was conducted at seven pH treatments (5.0, 3.0, 1.0, 0.0, -1.0, -2.0 and -3.0) using standardized sulfuric acid solutions for four exposure periods (14, 90, 180, and 365 d). Aqueous geochemical, XRD, and Si and Al XANES analyses showed: increased dissolution of aluminosilicates with decreasing pH and increasing exposure period; preferential dissolution of aluminosilicate Al-octahedral layers relative to Si-tetrahedral layers; formation of an amorphous silica-like phase that was confined to the surface layer of the altered clay samples at pH ⤠0.0 and t ⥠90 d; and precipitation of anhydrite and a Al-SO₄-rich phase (pH ⤠-1.0, t ⥠90 d).</p> <p>The diffusive transport of H₂SO₄ (pH =1.0, -1.0, and -3.0) through the Kc and Km clays for 216 d was examined using single reservoir, constant concentration, diffusion cells. The diffusive transport of H⁺ within the cells was modeled using 1-D transport models that assumed no absorption, linear absorption, and non-linear absorption of H⁺. The absorption isotherms were calculated from the pH 5.0, 3.0, and 1.0 batch experiment results, which were assumed representative of H⁺ absorption at pH < 1.0. However, model results indicated that the batch test results can not account for the observed H⁺ consumption in all cells and greatly underestimate the amount of H⁺ consumption in the pH -1.0 and -3.0. In the Kc and Km diffusion cells, above-background Ca, Al, Fe, and Si aqueous concentrations were associated with depth intervals characterized by decreased pH values. Respective peak concentrations of 325, 403, 176, 11.7, and 1.38 x 10³ μmol g^-1 (Kc) and 32.4, 426, 199, 7.2, and 1.22 x 10³ μmol g^-1 (Km) were measured in the pH -3.0 cells. XRD results showed that the elevated concentrations corresponded to the loss of carbonates and montmorillonite peaks and decreased peak intensities for illite and kaolinite in depth intervals with pH ⤠1.0, in the Kc and Km pH -1.0 and -3.0 cells.</p> <p>The combined results of these studies indicated that the long-term diffusion of H₂SO₄ through clays at pH < 1.0 will result in a large amount of primary phase dissolution; however, this will be accompanied by precipitation of soluble Ca and Al sulfate salts and amorphous silica, especially at pH ⤠0.0. Additionally, the presence of even a small amount of carbonate will serve to greatly buffer the diffusive transport of H₂SO₄ through clays, even at a source pH of -3.0.</p>

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xiii, 379 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.

Bellvue Mine is an abandoned coal mine on the West Coast of the South Island which discharges severe acid mine drainage (AMD) into the nearby Cannel Creek. This site is unique in that iron is in a ferrous or reduced form at the mouth of the mine, but due to the slope of the site, the AMD becomes aerated and subsequently the iron oxidises into ferric form as it moves downstream. Research was conducted to examine the geochemistry of the AMD at the site and investigate the performance of selected passive treatment systems at this site, with a view to informing decisions for passive treatment at other comparable mines on the West Coast. A range of small-scale trial passive remediation systems were installed, including an anoxic limestone drain (ALD), a bioreactor, and two mussel shell reactors. Results from the trials showed that the mussel shell reactor treating oxidised water was the most effective at reducing the concentration of dissolved metals in the AMD. A range of factors including hydraulic residence time, geochemistry of the Bellvue Mine discharge, and unexpected equipment issues all contributed to the results of the trials, and are important factors that need to be taken into consideration when designing a full-scale system for this site and others.

Mining-Influenced Water (MIW) poses major environmental issues in New Zealand and worldwide due to a legacy of unmitigated mining activities. As conventional MIW treatment technologies can be very costly in terms of chemical and energy inputs, cheaper and environmentally-friendly alternative remediation strategies have been developed. These so-called passive treatment technologies include a range of engineered systems relying on biogeochemical processes able to mitigate the acidity and to immobilize the metals in MIW. The present research, built on previous work conducted at the University of Canterbury, investigated the use of waste materials in mesocosm lab-scale sulfate-reducing bioreactors (SRBR) to treat actual mining-influenced water (MIW) sourced at an active coal mine in New Zealand. Specifically, this study investigated using waste mussel shells as an alkaline amendment (instead of the more conventional material limestone), with organic waste materials such as wood byproducts and compost in complex substrate mixtures in upward-flow SRBR. The influence of hydraulic retention times of approximately 3 and 10 days (HRT; i.e. the contact time between the MIW and the substrate mixtures in the SRBR) on the treatment performances was also evaluated. Overall, each system successfully treated the MIW (e.g. increased the pH > 6 and removed >78 % of the metals, except Mn) during the first 5-month treatment period, while during the second 5-month period, the treatment systems containing limestone and/or operating at a short HRT started to show signs of decreased efficiency. Generally, the system containing mussel shell and operating at a long HRT was constantly the most efficient system. Over the whole 41-week period of treatment, key metal removal efficiencies ranged between 97.6 and 99.7 % (Al), 83.9 and 95.2 % (Fe), and 9.2 and 38.8 % (Mn). Sulfate removal, in terms of moles of sulfate removed per cubic meter of substrate per day, was on average below the design values of 0.3 mol/m3/d, and ranged between 0.03 and 0.55 mol/m3/d (median values were 0.26 to 0.3 mol/m3/d during the first 5-month period but dropped to 0.094 to 0.1 mol/m3/d during the second 5-month treatment period). The SRBR containing mussel shell instead of limestone resulted in significantly higher alkalinity generation (between 32 to 85 % higher) and higher metal removals (between 0.6 % higher for Al and 14 % higher for Ni). These results were mainly attributed to the unique mineralogy of the mussel shell which comprises of aragonite with traces of calcite, while limestone comprises of pure calcite with traces of quartz. The statistical analyses showed that the sulfate reduction was not significantly affected by the alkalinity source. Similarly, systems operating at a longer HRT (10 days instead of 3 days) showed better treatment performances than systems operating at a short HRT in terms of alkalinity generation (44 to 62% higher), metal removal (between 0.5 % higher for Al to 15 % higher for Ni, and between 17 to 23 % higher for Mn), and sulfate reduction (50 to 77 % higher). Overall, the systems operation on a longer HRT were dominated by a more reduced environment facilitating the precipitation of metal sulfides, while the reactors running on a shorter HRT were constantly maintained out of equilibrium by the continuous addition of fresh MIW. Chemical and mineralogical analyses performed on the spent substrates suggested that the metals were removed through precipitation as, and adsorption onto, metal sulfides (Fe, Zn, Ni, Cu), (oxy)hydroxides (Al, Fe, Zn), and carbonates (Mn, Zn). Mn, a metal known to be harder to remove from solution was likely removed through the precipitation of rhodochrosite (MnCO3) and via adsorption onto the organic matter. These results generally corroborated the results obtained using the geochemical modeling PHREEQC. Overall, this study showed that mussel shells are not only a sustainable and effective alternative to mined limestone, but their use in SRBR would also result in a better treatment of MIW. Additionally, even though an increase in HRT resulted in a better contaminant removal, a HRT of approximately 3 days was sufficient to remove about 80% of all metals (except Mn). Therefore, the difficult choice of an optimal HRT must balance the need to meet a specific effluent quality while keeping the treatment time reasonably short, and an intermediate retention time of approximately 6 days could be optimal.

This research was completed to assess passive treatment methods for mitigation of acid mine drainage (AMD) at a former mine site in British Columbia. The objectives were to determine if suitable passive treatment methods were available, and if concentrations of Cd, Zn, and other key contaminants in groundwater could be reduced to below regulatory standards during bench-scale testing. Biological treatment with sulphate reducing bacteria (SRB) was selected, and bench-scale treatment testing was conducted using columns amended with low cost organic sources. Removal of more than 99% Cd, 93% Co, 96 % Cu, 86% Ni and 98% Zn was observed, resulting in metals concentrations in treated effluent consistently lower than applicable groundwater standards. Sustainability attributes of treatment with SRB and the potential to recover valuable metals are discussed, and recommendations for further testing and implementation are provided.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains x, 86, [22] p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 58-63).

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 170 p. : ill. (some col.), maps. Vita. Includes abstract. Includes bibliographical references.