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doi: 10.1007/s10230-010-0111-7pmid: N/A
Mine planning, permitting and operation require reliable water technology in all its aspects: water inflow, water use, water disposal and discharge, and water impact. Mine water evaluations are relied upon by mining companies, mine regulators and the public to determine whether the mine is technically feasible, optimally designed, financially sound, socially acceptable, and environmentally benign. Review of the water management performance of mines world-wide indicates that the results obtained from mine water evaluations are frequently unreliable. The magnitude of error is often significant, and the direction of the error is usually to underestimate mine inflow, water usage, water contamination, water discharge, and/or environmental impacts. Examples of mine water evaluations where the results have proven to be unreliable were used to formulate and illustrate a set of general principles that should be applied to every mine water evaluation to ensure that the results reflect the full range of possible outcomes, with that range centered on the most likely outcome. Mine water evaluations performed using these principles can be demonstrably reliable, credible to all of the mine stakeholders, and improve the profitability, public acceptance, and environmental protection of mining projects.
Barrett, Damian; Moran, Chris; Cote, Claire
doi: 10.1007/s10230-010-0110-8pmid: N/A
In many parts of the world, mine production and expansion are increasingly limited by access to water. One solution is to consider a water market that would allow trading of mine site water (worked water) from wetter mines to drier mines. However, there is currently no policy support for such a market and it is likely that without government support via incentives, mines will continue to favour freshwater use because it is relatively inexpensive. Furthermore, mines have a high capacity to pay for the water they use, and freshwater creates few risks for production. The opportunity provided by water savings within a trading scheme could be viewed as a source of money to provide incentives for the transfer of worked water between mines. In this paper, we present a new method to trade water among mines based on a site water balance assessment utilising historical climate data, and apply this method to a demonstration region containing multiple coal mines. On average, 340 ML could be transferred per year to drier mines but there remains 11,440 ML per year of water demand unable to be met by trading. The direct monetary value of the worked water that could be transferred, derived from additional coal mining, would be significant. Irrigation may be an attractive option if available infrastructure can be used to trade the saved fresh water in existing markets, thereby providing indirect monetary value (i.e. external to coal production). Alternative uses of water savings may have considerable additional non-monetary value that directly affects the mining industry’s social license-to-operate and its security of long term water supply.
Atkinson, L.; Keeping, P.; Wright, J.; Liu, Houmao
doi: 10.1007/s10230-010-0109-1pmid: N/A
The costs and efficiency of dewatering are particularly important at De Beers Canada’s Victor diamond mine in northern Ontario, where the bottom of the water-bearing carbonate country rocks is near the bottom of the planned pit, which limits the available drawdown in the perimeter wells. Most of the inflow to the wells comes from a limited number of discrete zones in the carbonate rocks, resulting in low hydraulic efficiencies. The variable hydrogeologic conditions require efficient pumping over a wide range of yields and lifts, and there are logistical issues associated with the isolated setting and the extreme cold winter temperatures. The hydrogeology of the Victor mine area was characterised over three winter field seasons using packer tests, pumping tests, step-drawdown tests, and downhole logging to define the lateral and vertical variation in the hydraulic conductivity of the carbonate aquifer. Based on these data, wells were designed and submersible pumps with variable frequency drives were installed. Two 3-D numerical groundwater flow models were constructed, one a ‘sub-regional’ model to provide input to the mine feasibility study and permitting process and the other a near-pit ‘window’ model to simulate groundwater conditions in the immediate vicinity of the mine. These models are used in tandem to direct design of the dewatering system, evaluate its effectiveness, and to predict long-term environmental effects.
Douglas, G.; Wendling, L.; Pleysier, R.; Trefry, M.
doi: 10.1007/s10230-010-0106-4pmid: N/A
Process water from the Ranger Uranium Mine requires treatment to meet stringent environmental water quality criteria. The acidic water contains substantial SO4, metals, and U. One novel treatment method under consideration is the use of Na-aluminate to both neutralise the process water and precipitate hydrotalcites. Hydrotalcites are a class of Mg–Al layered double hydroxide minerals with a typical endmember chemical composition: Mg6Al2(A)(OH)16·n(H2O), where A = CO3 2−, SO4 2−, etc. Many acidic wastewaters contain Mg and/or Al in sufficient abundance for hydrotalcite formation upon addition of alkali to achieve solution pH > 5, and Mg and/or Al to attain a Mg:Al ratio of 2 to 3:1. The utility of hydrotalcites lies in their ability to incorporate a range of cationic (Cu2+, UO2 2+), metalloid (AsO4 3−), and (oxy)anionic contaminants (CrO4 2−). The broad spectrum removal of contaminants, including U, also indicates that hydrotalcites and their derivatives could potentially be used as a containment material in nuclear waste repositories. In this study, Ranger process water derived from extraction of U from chloritic schist was treated with Na-aluminate sourced from Bayer process liquor, in combination with NaOH or Ca(OH)2. Hydrotalcites formed as the primary mineral during process water neutralisation with the ability to simultaneously remove a suite of contaminants from solution.
Kihlman, Susanna; Kauppila, Tommi
doi: 10.1007/s10230-009-0096-2pmid: N/A
Two lake sediment cores collected near a closed Cu–Au mine were analyzed for testate amoebas, diatoms, and geochemistry to compare their utility for assessment and monitoring of aquatic impacts of metal mines. Geochemical profiles displayed the mine history as increases in mineral matter-related elements during the mining period, and as post-mining metal peaks. Biotic assemblages co-varied with geochemical shifts, and the most notable ecological changes coincided with the peaks in metal concentrations. Additionally, nutrient enrichment caused a major shift in biotic assemblages. According to the results, the mine affected the lake environment over a relatively large area but the changes were transient. Major ecological effects occurred only after the actual mining period as the tailings weathered, which delayed the metal release. This suggests that mine impacts can be significantly reduced by careful design and after-care of the waste facilities.
Zipper, Carl; Skousen, Jeffrey
doi: 10.1007/s10230-010-0101-9pmid: N/A
Passive treatment of acid mine drainage (AMD) relies on biological, geochemical, and gravitational processes to neutralize acidity. Published design guidelines use sizing ‘rules of thumb’ based on AMD loadings at design flows. Using average performance data for 82 treatment systems, we used regression modeling to investigate the influence of influent net acidity and water loading on alkalinity generation by five treatment system types. Alkalinity generation increases with influent net acidity loading for all system types. Influent net acidity loading can be deconstructed into concentration and water loading components. In bivariate models, water loading was a predictor of alkalinity generation for all five system types but net acidity was significant only for vertical flow systems (VFs). In multivariate models using both components as performance predictors, both influenced alkalinity generation. These relationships were strongest for anaerobic wetlands (AWs), VFs, and open limestone channels; anoxic limestone drains and limestone leach beds demonstrated these influences less consistently. These results reflect the geochemical mechanisms governing the performance of limestone-based passive treatment system: solubility of limestone decreases as dissolved reaction products and pH increase.
Karathanasis, A.; Edwards, J.; Barton, C.
doi: 10.1007/s10230-009-0095-3pmid: N/A
Mine drainage is a significant problem in the Appalachian Plateau due to elevated metal and solute concentrations. Most metals may be removed by oxidation/precipitation or natural buffering, but Mn is more difficult to remove due to its higher solubility. Some mine drainages in southeastern Kentucky have average sulfate and Mn concentrations exceeding 1,300 and 30 mg L−1, respectively. Manganese does not readily form sulfidic minerals, and MnS precipitation following sulfate reduction has not proven to be a promising pathway for permanent Mn immobilization. Our study involved batch experiments with five different organic carbon sources in combination with five inorganic substrates to treat a simulated mine drainage with pH 6.2 and Mn and sulfate concentrations of 90 and 1,500 mg/L, respectively. The Mn removal capacity varied widely between treatment mixtures, from <10 to 100%. Sulfate removal showed a similar divergence, ranging from <10 to >80%. The most effective treatment was provided by the biosolids or wood mulch amendments in combination with the creek sediment. Sulfate reduction levels were not stoichiometrically matched with MnS formation, suggesting that the prevalent Mn removal mechanisms were sorption and precipitation as oxide, oxy-hydroxide and carbonate, rather than Mn-sulfide phases.
Teixeira, Luiz; Santos, Juliana; Costa, Victor; Yokoyama, Lidia; Sarmiento, Cristian
doi: 10.1007/s10230-010-0100-xpmid: N/A
We report preliminary studies on the precipitation of manganese compounds by oxidation with Caro’s Acid (peroxomonosulphuric acid, H2SO5) or hydrogen peroxide (H2O2), from solutions with [Mn] = 1.2 g/L to achieve residual [Mn] <1 mg/L at a pH range of 5–9. It was found that with the addition of sodium carbonate and either Caro’s acid or hydrogen peroxide, it was possible to reduce manganese from 1.2 g/L to less than 1 mg/L in 60 min (batch reaction) at 25°C (at pH ≥ 5 using H2SO5, and pH = 9 using H2O2). By comparison, simple hydroxide precipitation under the same conditions at pH = 9 would only lower [Mn] to 165 mg/L.
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