Alkaline Injection of Concentrated Sodium Hydroxide Solution into an Acidic Surface Mine Spoil Aquifer

A series of NaOH solution injection experiments were performed as trials for in situ remediation of an acid-producing surface-mine spoil. Both 20 and 50% (w/w) concentrated NaOH solutions were employed. While the spoil immediately down-gradient of the injection wells was neutralized, only about 23% of the introduced Na was recovered at the spring discharge in 3 years of post-injection monitoring. This rate of transport was far slower than the estimated advection rates in the aquifer, indicating that substantial retardation of both Na and the associated alkalinity occurred. This retardation is ascribed to: precipitation of alkaline-earth carbonate hydroxide minerals, as well as metal hydroxide precipitates, consuming injected alkalinity; and reduction of hydraulic conductivity in the peralkaline (pH > 13) “plume” region due to plugging by reaction products. It is likely that Na and alkalinity will continue to leak from this plume region for many years, but at too slow a rate to neutralize AMD at current concentrations. Future injection efforts of this type may be feasible but should use lower concentrations and should be focused further down-gradient, in closer proximity to the springs, where ground water velocities are higher.     

Tracking the prokaryotic diversity in acid mine drainage-contaminated environments: A review of molecular methods

The negative impact of acid mine drainage (AMD) on public and environmental health by degrading the aquatic and terrestrial ecosystem with a drastic decrease in pH and elevated levels of toxic heavy metals, metalloids and radionuclides necessitate the development of environmentally sustainable technologies to remediate AMD. The development of appropriate strategies for controlling and/or abating the detrimental effects of AMD in natural and mining environments primarily depends on the diversity and compositions of the local acidophilic microbial communities (those which can grow at pH ? 3) which catalyze the reactions of AMD by production of sulfuric acid and ferric iron. Robust method(s) to track the AMD-promoting microbial communities will not only provide information about their ecophysiological role in extreme environments but also help sustain the reliability of remediation technologies. This paper provides an overview on the phylogenetic diversity of prokaryotes present in AMD-impacted environments, and different molecular methods that have been used to track the diversity of these acidophiles. Additionally, the high-throughput methods (metagenomics, metaproteomics and microarrays) that link prokaryotic phylogeny to their function in AMD systems are also discussed.     

Physico-chemical gradients and meromictic stratification in Cueva de la Mora and other acidic pit lakes of the Iberian Pyrite Belt

A marked vertical trend of increasing temperature and dissolved metal concentrations is observed in the monimolimnia of some meromictic pit lakes of the Iberian Pyrite Belt (IPB) in SW Spain. Temperature differences between the chemocline and the pit lake bottom can be as high as 15°C (e.g. Herrerías), and the respective concentration of some metals (e.g. Fe) and metalloids (e.g. As) can increase by several orders of magnitude (e.g. Cueva de la Mora). The redox conditions also change drastically from the upper and oxygenated mixolimnion (strongly oxidizing) to the lower and anoxic monimolimnion (moderately reducing). Processes such as the inflow of metal–sulphate laden ground water from flooded shafts and galleries, and other factors such as the pit geometry or the relative depth of the lakes, must be considered to account for the observed stratification pattern. The vertical profiles of physico-chemical parameters and water chemistry obtained in Cueva de la Mora and other meromictic pit lakes of the IPB are also compatible with a reactive bottom in which several geochemical and microbial reactions (including reductive dissolution of Fe³⁺ minerals, bacterial reduction of Fe³⁺ and SO₄ ²⁻ in pore waters within the sediments, and decomposition of organic matter) could be taking place.     

Preparation of immobilized sulfate reducing bacteria (SRB) granules for effective bioremediation of acid mine drainage and bacterial community analysis

Heavy metal-resistant immobilized sulfate-reducing bacteria (SRB) granules were prepared to treat acid mine drainage (AMD) containing high concentrations of multiple heavy metal ions using an up-flow anaerobic packed-bed bioreactor. The bioreactor demonstrated satisfactory performance at influent pH 2.8 and high concentrations of metals (Fe 463 mg/L, Mn 79 mg/L, Cu 76 mg/L, Cd 58 mg/L and Zn 118 mg/L). The effluent pH ranged from 7.8 to 8.3 and the removal efficiencies of Fe, Cu, Zn and Cd were over 99.9% except for Mn (42.1–99.3%). The bacterial community in the bioreactor was diverse and included fermentative bacteria and SRB (Desulfovibrio desulfiricans) involved in sulfate reduction. The co-existing anaerobic fermentative bacteria (Clostridia bacterium, etc.) with the ability to use lactate as electron donor could explain the differences between actual lactate consumption and what would be expected based solely on sulfate reduction.     

Sequential precipitation of Cu and Fe using a three-stage sulfidogenic fluidized-bed reactor system

The exposure of sulfides, such as pyrite (FeS₂) to water and air leads to the formation of acidic metal and sulfate containing waters, generally referred to as acid mine drainage (AMD). Under anaerobic conditions and in the presence of a suitable electron and carbon source, sulfate-reducing bacteria (SRB) can reduce sulfate to hydrogen sulfide which can precipitate metals as low-solubility sulfides. In the present study, a three-stage fluidized-bed reactor (FBR) system was operated at 35 °C with ethanol as an electron and carbon source for SRB to sequentially precipitate Cu and Fe from synthetic AMD. The system consisted of two pre-settling tanks before a sulfidogenic FBR for the sequential precipitation of Cu and Fe with biogenic H₂S gas and HS⁻ containing effluent, respectively. Cu and Fe precipitation efficiencies were over 99% and sulfate and COD removals 60-90%. Biologically produced alkalinity increased the initial pH of the AMD from 3.0 to neutral values.     

Alkalinity generation and metals retention in a successive alkalinity producing system

Alkalinity generation and metals retention were evaluated during the initial year of operation of a treatment wetland, consisting of four 185 m² inseries cells comprised of alternating vertical-flow anaerobic substrate wetlands (VFs) and surface-flow aerobic settling ponds (SFs). The substrate in the VFs consists of spent mushroom substrate (SMS) and limestone gravel, supplemented with hydrated fly ash in a 20∶10∶1 ratio by volume. Approximately 15±4 L/min of acid mine drainage (AMD) from an abandoned underground coal mine in southeastern Oklahoma, USA, was directed to the system in October 1998 (mean influent water quality: 660 mg L⁻¹ net acidity as CaCO₃ eq., pH 3.4, 215 mg L⁻¹ total Fe, 36 mg L⁻¹ Al, 14 mg L⁻¹ Mn, and 1000 mg L⁻¹ SO₄ ⁻²). Flow through the first VF resulted in substantial increases in alkalinity, decreased metal concentrations and circumneutral pH. 258±84 mg L⁻¹ of alkalinity was produced in the first VF by a combination of processes. Final discharge waters were net alkaline on all sampling dates (mean net alkalinity=136 mg L⁻¹). Total Fe and Al concentrations decreased significantly from 216±45 to 44±28 mg L⁻¹ and 36±6.9 to 1.29±4.4 mg L⁻¹, respectively. Manganese concentrations did not change significantly in the first two cells, but decreased significantly in the second two cells. Mean acidity removal rates in the first VF (51 g m⁻² day⁻¹) were similar to those previously reported.     

The Passive Prevention of ARD in Underground Mines by Displacement of Air with a Reducing Gas Mixture: GaRDS

There are few effective remedial strategies capable of reducing or preventing pollutant loads from underground mines. The Gas Redox and Displacement System (GaRDS) is a new approach devised for stabilising sulphide minerals by manipulating the atmosphere in mining voids. This prevention technique offers the potential for passive, low cost, and effective control of acid drainage from underground mines at sites where flooding is not feasible. GaRDS utilises reducing gas mixtures generated by anaerobic bacterial activity to displace oxygen without impeding drainage from the workings. These gas mixtures halt sulphide oxidation and acid generation, and can precipitate secondary sulphides from the accumulated drainage water. The GaRDS technique has significant advantages for mine operators who wish to temporarily close a mine, implement a low-cost, passive acid drainage prevention strategy, and retain the option of reopening the mine if metal prices increase. It is fully compatible with conventional ARD closure strategies for underground mines, and is expected to rapidly improve drainage water quality emerging from enclosures and prevent further sulphide oxidation. A field demonstration of the GaRDS technique has commenced at an adit in an historical mining district in Australia (Zeehan Mineral Field in Tasmania). The aim is to develop a generic technology that will find widespread application to both existing and historical acid drainage problems and prevent future problems arising at mine closure.     

Start-up,adjustment and long-term performance of a two-stage bioremediation process,treating real acid mine drainage,coupled with biosynthesis of ZnS nanoparticles and ZnS/TiO2 nanocomposites

Acid mine drainage (AMD) generation is a widespread environmental problem in Europe, including Portugal. Previous experience has shown that a combined process consisting of an anaerobic sulphate-reducing bioreactor, following neutralization with calcite tailing, produces water complying with legal irrigation requirements from synthetic AMD. Aiming the treatment of real AMD a new bioreactor was inoculated with a SRB enrichment obtained from sludge from a local WWTP anaerobic lagoon. In the initial batch phase, sulphate supplementation was needed to achieve high sulphate-reducing bacteria counts before continuous feeding of AMD was started. The system quickly achieved good performance, proving it is easy to start-up. However, this time the neutralization step failed to keep bioreactor affluent pH higher than 5 for longer than three weeks. This was due to armouring of calcite by precipitates of various metals present in AMD. A new configuration, replacing a packed-bed column by a shallow contact basin, proved to be more robust, avoiding clogging, short-circuiting and providing long-term neutralization. The treated effluent, with excess of biologically generated sulphide, was successfully used to synthesize zinc sulphide nanoparticles, both in pure form and as a ZnS/TiO₂ nanocomposite, thus proving the feasibility of coupling an AMD bioremediation system with the synthesis of metal sulphide nanoparticles and nanocomposites.     

PLC在矿井排水系统中的应用

随着科学技术的高速发展,工业上的自动化检测技术也由传统的继电器控制模式向新型的全自动控制技术演变。PLC自动控制检测系统在矿井排水系统中运用较为广泛,利用其自动检测机制和重要参数控制技术,根据水仓水位的高低以及系统的用电机制进行峰值的测量,成功地控制水泵的运行,达到矿井自动合理排水的效果。根据作者多年的工作经验,详细地阐述了PLC在矿井排水系统中的应用功能,并对PLC系统的设计提出了方案。     

Assessment of Metal Attenuation in a Natural Wetland System Impacted by Alkaline Mine Tailings,Cobalt, Ontario,Canada

A natural wetland in the Farr Creek drainage basin near Cobalt, Ontario was studied because its floor is covered with alkaline mine tailings that contain elevated levels of metals, including As, Co, Cu, and Zn, due to mining that occurred intermittently from 1904 to the 1980s. Our objectives were to characterize the biogeochemical interactions occurring throughout the wetland and to assess its ability to effectively attenuate the metal contamination. We were not able to conclusively determine if this wetland is a net source or net sink for As, Co, Cu, and Zn; it is not clear whether this wetland has reached its capacity for attenuating these trace elements. Both oxidizing and reducing bacteria were quantified and found to be prevalent throughout the wetland, with similar population densities. It is likely that the presence of localized oxic zones in the root zones of Typha latifolia supported the oxidizing bacteria populations observed. The results indicate the importance of understanding the conditions in systems being used to treat mine drainage, as well as the importance of having a detailed understanding of the metals of concern in the mine waste.     

智能控制技术在棉花坑矿井排水系统中的应用

通过对棉花坑矿井排水系统现状的调查分析,提出了基于人工智能控制的排水系统软件及结构设计。该系统通过检测水仓水位和用电高峰、平段、低谷期等相关参数,实现矿井排水系统智能化控制;可自动合理调度水泵运行,具有故障预警、报警功能,节约了人工和能耗成本,经济效益明显。     

测定瓦斯抽放管路流量的涡街气体流量计设计

通过与煤矿管道瓦斯抽放中采用的孔板流量计相比较,涡街流量计是煤矿瓦斯抽放管道流量测量的理想仪表。为了解决在小流量测量和管道周围存在周期振动的场合下涡街流量计显示出的不足,提出了一种新的信号处理法。通过大量试验证明,设计出了适合在煤矿瓦斯抽放管路中使用的新型涡街流量计。     

煤矿矿井水泵房排水系统设计

煤矿矿井水泵的控制是关系到煤矿井下安全生产的重要措施。文章探讨了煤矿矿井水泵房自动排水系统的基本构成以及系统的工作原理,并且对系统在实际运行中的关键技术以及系统的功能特性进行了研究。     

Implications of Predicted Hydrologic Changes on Lake Senftenberg as Calculated Using Water and Reactive Mass Budgets

Lake Senftenberg, Germany, is a post-mining lake that was flooded 30 years ago. It is anticipated that the levels of the surrounding post-mining lakes will rise, and that this will lead to a reversal of groundwater flow and consequently to an increase of acidifying groundwater flux into the lake. A tool to predict the future water quality of Lake Senftenberg has been developed. Present and future groundwater fluxes were calculated using a 3D hydraulic model of the surrounding aquifers. Oscillating hydraulic fluxes within the saturated and the unsaturated zones of the island within the lake, caused by continuous lake level changes, were calculated using a 2D sub-model. Mass fluxes into the lake from the aquifers, from the island, and from the River Schwarze Elster were determined by sampling or by laboratory experiments and were coupled with the hydraulic fluxes. The fluxes of acidifying components from the island sediments and sulfide oxidation products from drained zones were determined in laboratory experiments. Sediment erosion due to rill and gully formation after significant lake level change were calculated. The amount of acidifying compounds released from the eroded sediments was determined by laboratory experiments. The input of alkalinity due to the sedimentation of biomass was estimated. Gaseous partial pressures and mineral phases were used to describe the geochemical boundary conditions of the resulting lake water.     

Treatment of Mine Water by a Microbial Mat: Bench-scale Experiments

Abstract.   We investigated the treatment of acid mine drainage (AMD) by a blue-green algae-microbial consortium and substrate (containing powdered goat manure, wood chips, and soil) in 1 m³ bench scale biological treatment test cells. The microbial mat resulted from the interaction of bacteria and filamentous blue-green algae (predominantly Oscillatoria spp). The experiments were carried out for different water column heights, and were evaluated for 24, 48, 72, 96, and 168 hours of retention. Within 24 hours of retention, the pH increased from 2.93 to 6.78 as net alkalinity went from -125 mg/L to 197 mg/L as CaCO₃. Turbidity decreased by 33–54%, sulphate decreased by 23–29%, and hardness decreased by 19 to 26%. We also observed that: 95% of the Fe, 79–97% of the Cu, 84–86% of the Zn, 88% of the Pb, 59–83% of the Co, 22–62% of the Ni, and 28–45% of the Mn were removed. A blue-green algae/microbial mat consortium may be a cost–effective treatment technique for removing metals from AMD.     

智能控制卧潜排水系统在下组煤开采中的应用研究

通过对潜水电泵结构研究与优化,使其能满足卧式安装的要求,形成一套完整的智能控制卧潜排水系统应用技术。卧潜排水系统具有不怕水淹、安装硐室尺寸小,便于安装、检修等优点;智能控制系统实现了对矿井潜水泵站运行过程自动优化控制、安全保护和信息管理。该技术适用于水文地质条件复杂、有突水威胁的矿井排水系统。     

PLC在煤矿主排水泵自动控制系统中的应用研究

介绍了一套煤矿主排水泵自动控制系统的设计方案及PLC在煤矿主排水控制系统中的应用,并分析其功能设计、层次结构以及应用研究。PLC通过监控水位变化等因素,实现了水泵的开启和停止的自动化以及故障诊断的自动化等。     

Development of a new covering strategy in Indonesian coal mines to control acid mine drainage generation: a laboratory-scale result

The waste dump of sulphide-containing rocks is one of the potential acid mine drainage sources, since it contains a huge amount of readily oxidised sulphide mineral, due to its exposure to air and water. The application of the dry cover system is regarded as one of the best practices since it prevents acid mine drainage of the waste rock dump at the surface coal mine. However, the implementation of the dry cover system in field practice has faced several obstacles due to the limited number of cover materials. The nature of geological condition is considered to be a controlled issue, whilst the problem is the mining method and equipment size. This article describes the acid generation mechanism and its control, application of cover system and the problems that are faced in Indonesian coal mines, whilst discussing the preliminary laboratory results of multi-layer cover systems. It finally proposes a new covering strategy in an attempt to overcome the problem.     

Labview技术在煤矿井下排水监控系统中的应用

本次设计的系统采用的是数据采集卡以及虚拟仪器技术Labview,从而实现了数据的实时采集以及排水系统的实时监控,并且能够实现对煤矿井下的液位、水压等关键数据进行记录、显示以及历史查询。希望本研究能够有效地提升煤矿井下的排水系统工作效率,确保系统的稳定性,保障煤矿的安全生产。     

Impact of Temperature and Loading on the Mitigation of AMD in Peat Biofilter Columns

The mitigation of AMD at Canadian mine sites using passive treatment technologies requires a combined strategy that minimizes the effect of climatic variability on the treatment performance of the system. A vertical-flow combined passive treatment system was developed consisting of an oxidation/precipitation basin for excess iron removal; an unsaturated flow peat biofilter for heavy metal sorption and the reduction of oxygen concentrations; a sulfate reducing bacteria bioreactor for alkalinity generation and sulfate reduction; and, an anoxic limestone drain for alkalinity addition. Laboratory investigations were undertaken to characterize AMD mitigation through the peat biofilter under unsaturated flow conditions and to assess its performance in the combined passive system. Peat column sorption studies were conducted at 20 and 0°C to assess the effect of temperature on metal retention. At 0°C, a metal removal efficiency of Cd < Mn < Zn < Al < Ni < Cu < Fe was noted. At 20°C, however, sulfate-reducing conditions developed in the column as a result of the flow regime, which facilitated the establishment of anaerobic zones within the peat column, leading to a significant increase in effluent pH and metal removal. Sequential extraction indicated that Fe, Cu, and Al were typically bound to the organic matter fraction, while Mn, Zn, Ni, and Cd were primarily associated with the exchangeable fraction.