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The Lorraine mine site in Témiscamingue region (Québec, Canada) was reclaimed with a cover with capillary barrier effects (CCBE) to limit acid mine drainage generation. The main objective of this study is to predict the long-term hydrogeological behaviour of the CCBE at Lorraine site, including the influence of vegetation and climate change (CC). Numerical simulations showed that performance of the CCBE is: (1) not affected by forest vegetation and CC in the saturated zone in the north of the Lorraine site and (2) more sensitive to vegetation in the unsaturated zone in the south where the phreatic level is low. [ABSTRACT FROM AUTHOR]

The growing demand for valuable metals in recent decades has heightened the economic significance of extracting them from dilute solutions. This research carefully assesses the extraction efficiency of the air-assisted solvent extraction (AASX) process for effectively recovering copper from industrial dilute solutions, such as the raffinate of the solvent extraction (SX) plant and heap leach solutions. The results clearly showed that increasing the frother dosage to 50 mg/L improved the Cu extraction from 83.5% to 90.2%, but increasing the frother dosage beyond 50 mg/L did not change this response significantly. Although varying the extractant concentration and silicone oil dosage in the studied range did not affect Cu extraction, it noticeably led to an increase in the barrier metals recovery. Furthermore, a nine-step AASX system was applied to comprehensively evaluate the extraction efficiency of Cu from dilute heap leach solution. Moreover, an impressive 95.1% of Cu recovery (from a solution containing 890 mg/L Cu, 12.32 g/L Fe, 2.64 g/L Zn, and 4.1 g/L Mn) was achieved with selectivity ratios of 149.6, 153.0, and 93.5, for Cu/Fe, Cu/Zn, Cu/Mn, respectively. It could be concluded that the AASX process is an efficient and promising method for extracting Cu from industrial dilute solutions derived from secondary resources, low-grade ores, and acid mine drainages. [ABSTRACT FROM AUTHOR]

The performance of reclamation cover systems could be affected by the colonization of plant roots, which may modify the hydrogeological properties of the construction materials. A four-year field investigation was conducted using six experimental cells with various soil layering designs over AMD-generating tailings reclaimed with an oxygen-barrier cover combined with an elevated water table. Both herbaceous and woody vegetation were installed on top of the cells to compare the influence on the properties of the cover material. Consecutive and undisturbed cores were collected from the cover's functional layer in 2020 and 2021, respectively. Root parameters, such as root length density, and hydrogeological properties were measured on the core samples to assess the possible relationships between the two categories of variables. Root observation trenches were also cut in each cell to better analyze the root density and occurrence profiles. Results showed that, within the four-year monitoring period of the study, both herbaceous and woody vegetation roots mostly colonized the top overburden layer of the cell (>86% visible roots) and barely occupied the functional layer of the reclamation cover (<10% visible roots). The observed maximum desorption rates for the functional layer were lower than the predicted values, which could be a short-term effect of the fine roots. No significant impact of roots on the main hydrogeological variables controlling the oxygen barrier efficiency were noted. At the end of the four-year study period, the hydrogeological behavior of the functional layer in all cells with/without vegetation/additional soil layers was found to be similar. [ABSTRACT FROM AUTHOR]

This document is a list of references cited in a research article on the topic of heavy metal removal from water using biosynthesis of metal-binding natural products. The references include studies on the biosynthesis of metallophores, the adsorption of heavy metals, and the effects of heavy metal pollution on the environment and human health. The research was funded by the Islamic University of Lebanon, Center of Research and Development. [Extracted from the article]

Acid mine drainage (AMD) has caused a great impact on soil, surface water, groundwater, plants or other organisms in the mining environment because of its high acidity, high sulphate content, and contains a variety of heavy metals. AMD treated by carbonate rocks have been regarded as a feasible technology for pollution control and applied widely in mine area. However, to date, the kinetics of the reaction between carbonate rock and AMD have not been investigated, resulting in the lack of systematic theoretical guidance for the implementation of this technology. In this study, effects of carbonate particle sizes and reaction temperature on AMD treatment were investigated. The dissolution efficiency of Ca2+ was used to quantitatively reflect extent of reaction, and the leaching kinetics was analysed based on the shrinking core model. The results showed that carbonate rocks with a particle size of 0.5–1.0 mm had the best pH-enhancing performance for AMD and highest removal efficiency for Fe3+ (>98.00%), while the Mn2+ and SO42− were temperature sensitive. The diffusion of solid product layer was the controlling step of the leaching reaction, and the apparent activation energy of the reaction was 12.63 kJ·mol−1. [ABSTRACT FROM AUTHOR]

The Lousal mine rehabilitation project proactively planned strategic milestones around key local geomorphic landforms and geochemical characteristics. GeoFluv™ method was used to design a rehabilitation topography mimicking natural landforms, on which a built-up soil cover with chemical buffering capabilities and open limestone channels were implemented across the intervention areas. Once these landform restoration works were completed, positive effects are observed in March 2022, with the native vegetation cover (the third main component of the restoration plan) established in most of the recovered area and a visible water quality improvement to the AMD treatment system water. Potentially Toxic Elements (PTEs) concentrations have reduced significantly after the reclamation actions, especially Fe (404 to 34 mg L−1), Zn (65.7 to 15.8 mg L−1) and Cd (122 to 0.8 µg L−1) concentrations. Minor problems detected have been processes of rill erosion associated with the inflow of adjacent watersheds, and the creation of ephemeral reducing conditions resulting from the leaching of the organic amendment of the topsoil. The Lousal mine reclamation project is the first built example in Europe where the concept of geomorphic reclamation has been combined with geochemical remediation in an area with intense acid mine drainage formation. Detailed monitoring of this project's restorative progression throughout 2024 and beyond, should offer learning opportunities and innovations which will benefit future rehabilitation projects, with comparable underlying features. [ABSTRACT FROM AUTHOR]

Acid mine drainage was evaluated using a galvanic (GV) electrochemical system, Al–Cu (anode/cathode), based on a 32 factorial design. The factors analyzed were anodic area/volume ratios (A/V) of 0.037, 0.072, and 0.112 cm2/cm3, and treatment time from 0.25–8 h, and analyses were performed in duplicate with 11 degrees of freedom. The response variables were the total dissolved solids and concentrations of As, Cu, Co, Cr, Pb, Fe, Ni, and S O 4 2 − . The pH, electrical conductivity, and temperature were monitored during the process. Significant differences between treatments were determined by analysis of variance with Tukey's test (p < 0.05) using Statgraphics Centurion XVI.I software. The results showed that a greater electrode surface, A/V ratio, and treatment time improved pollutant removal. The spontaneous reactions generated by the galvanic cell, through the current that flows owing to the potential difference between the Al and Cu electrodes, allows the removal of heavy metals, arsenic, and S O 4 2 − by coagulation and precipitation mechanisms. The removal efficiencies achieved were Cu (99.1%), As (76.6%), Ni (80.2%), Pb (83.6%), Cr (100%), Fe (93.71%), and 92.9% for sulfates. The X-ray diffraction and Raman analyses of the solid fraction indicated that cuprite was formed with a purity of 96%, and the recovery of Cu by the GV system may be a viable option for mining companies. [ABSTRACT FROM AUTHOR]

Acid sludge is an environmental pollutant that is produced daily in large amounts in used engine oil refineries. Recycling this waste is the primary goal of this paper. This study used 'washing with water' and 'neutralization with quicklime' methods to prepare acid sludge for use in bituminous materials as huge potential disposal. The neutralised sludge by the 'washing with water' method was added to bitumen in the wet blending process at 10, 20, and 30 wt%. This product is brittle without proper adhesion and cohesion and cannot meet the standard limits as an acceptable binder. It performs like long-term aged bitumen, reducing penetration and ductility and increasing the aging potential and viscosity. In another method, the neutralised sludge by adding quicklime was added to the asphalt mixture to replace fine aggregates in 50, 75, and 100 wt%. Using this product decreases the aging potential and moisture susceptibility up to 36.4, and increases rutting resistance up to 34.7%, indirect tensile strength up to 17.3%, and resilient modulus up to 17.3%. Despite the presence of large amounts of heavy metals in acid sludge, using this product in asphalt mixtures is an economical and completely hygienic solution for disposing of acid sludge. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) poses a serious challenge to the ecosystem due to its disastrous effect on soil and water resources which contributes to the pollution and reduction of the accessibility of potable water and arable land for agricultural activities. The treatment of contaminated soils using physical, chemical, or thermal methods requires some improvements to meet the required remediation purpose. The purpose of this study is to investigate the application of bioattenuation, wastewater, and air-injection for the remediation of AMD polluted soils. A microcosm comprising 1 kg of polluted soil was amended with varying loadings of domestic and brewery wastewaters for biostimulation treatments, and the bioattenuation received no amendment while the bioventing treatment was supplied with wastewaters and atmospheric air at 3 L/min for 30 mins intervals every 48 h. The investigation conducted under the ambient condition for 28 days recorded average metal removal efficiencies of 12-31% (bioattenuation), 50-66% for all heavy metals (iron, aluminum, copper and zinc) except manganese (28%) (biostimulation) and 56-70% (bioventing) while 32%, 35% and 52% sulfate removal efficiencies were recorded for bioattenuation, bioventing and biostimulation respectively. The study revealed that wastewater and bioventing systems can be efficiently utilized as an eco-friendly approach for the treatment of acid mine contaminated soils and pollution mitigation in the mining environments. In addition, from a comparative point of view, the results of the study further showed that the amendment of wastewater is more effective for sulfate removal while air injection enhanced metal removal from acid mine drainage contaminated soils. The synergetic effects have also been observed; the current study demonstrates that the combined application of biostimulation and bioventing system requires constant monitoring to ensure the provision of appropriate anoxic conditions for biosulfidogenic activity by enhancing sulfate removal while promoting an oxic environment for the oxidation process to facilitate metal removal for the effective treatment of acid mine drainage contaminated soil. [ABSTRACT FROM AUTHOR]

Phytostabilization on sulfidic mine tailings is not yet commonly implemented in the field, making it a crucial area of focus for future reclamation efforts. This greenhouse study aimed to explore cost-effective amendments on metal(loid) immobilisation and identify grass species candidates for phytostabilization. This research found that (1) wheatgrass (Pascopyrum) and ryegrass (Lolium multiflorum) are suitable candidates for phytostabilization, and (2) it is cost-effective to reuse wastes of bauxite residue and compost to promote phytostabilization effectiveness. Compost should be carefully evaluated for phytostabilizing Zn in tailings since the Accumulation Factor and Translocation Factor of all selected species are large than 1. [ABSTRACT FROM AUTHOR]

Overburden is the earth material removed during opencast mining, which is typically not contaminated with toxic materials. After mining operations, overburdens are dumped on exhausted mining sites. However, some opencast mines are not properly backfilled, and this causes harmful environmental effects, such as leaching of acid mine drainage. The flyash produced from thermal power plants is also a major waste that must be disposed of environmentally friendly. This study focuses on filling the voids of an abandoned mine with a mixture of 70% overburden + 30% flyash. A considerable improvement in acid mine drainage characteristics was found after either adding overburden or an overburden and flyash mixture. Sustainable management of coal mines should include the careful restoration of exhausted mines, which can be made possible by repurposing relevant industrial waste. [ABSTRACT FROM AUTHOR]

Coal washing plants produce large amounts of waste, and tailings are generally dumped in piles and impoundments nearby the plants. Sulfide minerals, water infiltration, and oxygen diffusion can result in acid mine drainage (AMD). In this paper, monitoring the AMD generated by a coal washing plant in northeastern Iran was investigated by applying time-lapse 2D and 3D geoelectrical techniques. For this purpose, 2D and 3D geoelectrical surveys with the Dipole-Dipole array were conducted in the area surrounded by an abandoned pile and nearby two impoundments. The surveys were repeated six months after the first measurements to characterize the temporal changes in the medium. 2D geoelectrical time-lapse suggests that the AMD is being generated at the shallower level of the pile. Moreover, the 3D time-lapse and hydrogeochemical analysis indicate that the likely plume is conveyed to the groundwater downstream of the pile. Besides, the results of time-lapse 3D geoelectrical models illustrate that seasonal changes, mainly precipitation, could affect the likely plume and transport it to subsurface layers. [ABSTRACT FROM AUTHOR]

Sulfate-rich effluents have been successfully treated in anaerobic reactors using sulfate-reducing bacteria (SRB). Many authors have demonstrated that these systems require nitrogen and phosphorous supplementation to achieve high sulfate removal rates. However, the resource ratio theory assumes that some species can be dominant according to the nutritional relations used or even without external nutrient supplementation. Thus, this study evaluated the SRB communities in batch reactors without external nitrogen and phosphorus sources based on most probable number (MPN) quantification, denaturing gradient gel electrophoresis (DGGE) analyses and sequencing. The sulfate and chemical oxygen demand (COD) removal and kinetic parameters were also determined. After 100 days of operation, the sulfate and COD removal achieved 71.8 ± 10% and 86.5 ± 10%, respectively. The SRB population increased from 8.106 to 4x1012 MPN 100mL-1, and the richness of SRB bands was much higher at the end of the experiment compared to the inoculum. In addition, the sequenced bands from SRB-DGGE showed similarities to Desulfacinum infernum, Desulfobulbus sp, Syntrophobacter and Desulfomicrobium aestuarii-related sequences. Therefore, biological treatment of acid mine drainage wastewater was effective in the absence of nutrients, lowering costs and providing high sulfate removal efficiency. [ABSTRACT FROM AUTHOR]

This article contributes to the literature on environmental policy controversies. We utilize an Argumentative Discourse Analysis (ADA)-based approachto analyze the struggle for discursive hegemony that took place between competing story-lines in the context of the acid mine drainage (AMD) environmental policy problem, located in the gold mining areas of greater Johannesburg, South Africa. With this article we make a theoretical contribution by presenting and applying an adapted ADA framework strongly focused on the operationalization of key ADA concepts. Our empirical contribution lies in providing a rich and deep analysis of an environmental policy controversy that has not yet been studied from an ADA perspective. In particular, we demonstrate and discuss the complex path to discourse institutionalization followed by the dominant emergent AMD story-line. In conclusion , we recommend steps for updating the ADA approach and developing an accompanying set of guidelines to further enable the operationalization of its concepts. [ABSTRACT FROM AUTHOR]

The Malogne Phosphatic chalk quarry was developed by the rooms and pillars mining method within an area of 67 ha. The site is partially flooded and located in close proximity to important infrastructure as railway, highway, and residential houses. During and after its exploitation several significant ground collapses were registered. The last one, with an area of 1.2 ha and 3 m amplitude occurred in 2015 nearby the railway line. To assess the behavior of the underground openings a combination of in situ structural measurements and laboratory mechanical characterisation in dry and saturated state of the main lithology type in the quarry – white and phosphatic chalk, hard ground and calcarenites, are performed. The UCS of the chalk ranges from 4 to 10 MPa while its tensile strength is between 0.75 and 2.1 MPa. For the hardground, these values are over ten times higher. The results reveal significant influence of the water on the chalk properties by reduction of almost twice its strength. The data obtained was implemented in a conceptual geomechanical model, using the 2D FEM. Numerical results show a failure pattern that was confirmed from the in situ observations. [ABSTRACT FROM AUTHOR]

This paper presents an easy-to-understand and easy-to-use methodology for monitoring the neutralization potential of residues derived from coal preparation. The methodology was developed based on the chemical composition of the waste and the relationship between calcium and sulfur. The effectiveness of this, in the control of residues, is demonstrated through in situ testing in a coal preparation plant in San Juan de Sabinas, Coahuila. The tests were carried out by collecting samples in three waste streams for five days at the plant. The methodology presents a strong linear correlation between the neutralization potential and the Ca/S ratio of 0.91. The estimation of neutralization potential through the Ca/S ratio represents a practical, easy-to-apply methodology that saves time and favors the decision-making required by waste management plans, to avoid the generation of acid drainage in coal waste. [ABSTRACT FROM AUTHOR]

The low pH and high salinity of acid mine drainage (AMD) fundamentally complicates the sorption processes. We explored the selective removal of Cu, Ni and Co ions present in AMD from the excess of ferrous ions of using a chelating resins Lewatit® MonoPlus TP 220 and Lewatit® TP 208. Also, the recovery of metal copper from desorption solution using electrolysis was investigated. The results showed that the most effective sorption of metal ions was achieved with chelating sorbent Lewatit® TP 220. The dynamic capacity of the sorbent under the given conditions (pH= 2.5 ± 0.03, presence of Fe(II/III), Zn(II), Mn(II)) decreased in the following order: Cu(II) (43.3 ± 1.4 g/L) > Ni(II) (22.1 ± 2.1 g/L) > Co(II) (3.6 ± 0.4 g/L). Chelating resin Lewatit® TP 208 under the same conditions showed lower efficiency: Cu(II) (30.6 ± 1.3 g/L) > Ni(II) (9.1 ± 0.17 g/L) > Co(II) (1.3 ± 0.08 g/L). The weak base anion exchanger Purolite® A 832 was successfully used to take up Cu(II) from ammonia solution and easily regenerated with sulfuric acid. The sorption capacity for Cu(II) was calculated to be 19.2 ± 0.5 g/L. Electrolysis experiments were performed with a fluidized bed electrolysis reactor where metallic copper was regenerated from desorption solutions and purified sulfuric acid solutions were obtained. [ABSTRACT FROM AUTHOR]

In order to effectively manage the sludge in the settling ponds, it is necessary to understand the physical properties of the sludge according to the depth in the pond. A new sludge sampling device and method was proposed in this study. Sludge was sampled at three depths in four facilities in South Korea, and the water content, particle size, density, composition, and viscosity of the sediment according to the depth were measured and evaluated. These results can be used to predict the shape of sediment and the lifetime of the settling pond, and to plan and effectively implement sediment removal. [ABSTRACT FROM AUTHOR]

Maximum biosurfactant production was achieved in an optimised process containing pH 8 and 30°C, with waste coconut oil and ammonium sulphate at carbon-to-nitrogen ratio of 1:7. The structural composition of Acinetobacter sp. V2 biosurfactant was polymeric, consisting of a protein complex and a fatty acid. This biosurfactant exhibited stability to different pH and temperature conditions. The emulsifying property was affected by changes in NaCl concentration. The V2 biosurfactant was effective in removing heavy metals present in acid mine drainage effluents and contaminated vegetables. [ABSTRACT FROM AUTHOR]

Improving effective strategies to control acid mine drainage (AMD) in abandoned mine areas is a significant challenge because of water quality issues. AMD is a serious water pollution problem. The water in the area where the mine is located acquires an acidic character, the pH level of the environment decreases, the concentration of heavy metals increases with their dissolution in the acidic environment, and can cause serious environmental pollution by creating a toxic effect for all living things. However, acidic characteristics are not observed in the waters at high pH levels; a basic environment is formed; the heavy metal dissolution slows down; and the precipitation of minerals begins. In such an environment, it is not possible to observe AMD formation and heavy metal pollution. If AMD source is characterized, the most effective strategies can be developed to control the acidic effluents. The main aim of this work was to investigate the potential impact of Ovacik abandoned, coal mine (Cankiri, Turkey) on the water quality in the areas around the mine. Water samples were collected along the open pit area (abandoned), dump sites and coal storage area. Effluent characterizations were investigated for the better evaluation of the water contamination level to develop the successful treatment strategies. In the studies conducted in the same field in 2010–2011, it was determined that the water pH changes between 6.64 and 8.13. Similarly, in this study, the results showed that the pH values of water streams in the abandoned mine were measured between 7.28 and 8.94 with no heavy metal contamination. Although the coal deposit exhibits AMD source minerals, the rock formations which have alkaline content prevented AMD in the considered site. [ABSTRACT FROM AUTHOR]

We investigated the microbial community composition in three different mine tunnels from Hualgayoc (Cajamarca, Peru) and the metabolic activity of acidophilic sulfate-reducing bacteria (aSRB) enriched from acidic sediments of the mining tunnels. Microbial community composition in environmental samples was analyzed by 16S rRNA amplicon sequencing. Metallibacterium and Acidiphilium were found as the most abundant bacteria in PM1 and PM2 sites, respectively, while Cyanobacteria was abundant in PM3 site. Isosphaera and Pseudomonas thrived in the acidic water of PM2 site as well. Sulfate reduction at low pH was then evaluated in microcosm experiments showing activity even at pH 3.4. Hydrogen was the most favorable electron donor in terms of sulfate reducing rates (0.5 mM day−1 at pH 5.1) and sulfide production (4.9 mM at the end of the experiment). Sequences affiliated to Desulfosporosinus and Desulfovibrio were abundant in the hydrogen microcosms (60.3 and 17.8%, respectively). These sequences were not detected in sediments, but their occurrence in the microcosms suggests their low abundance in the studied AMD systems. Our results expand the phyla detected in AMD environments and contribute to the understanding of aSRB for the possibility of applying these microorganisms in bioremediation. [ABSTRACT FROM AUTHOR]

The spontaneous combustion of coal storage piles and gangue piles in coal mines has been resulting in significant resource waste and serious environmental pollution. To solve spontaneous combustion problems, the use of gravity heat pipes to extract internal heat from piles of coal has been proposed. In this paper, a method for selecting the optimum working medium for a heat pipe is presented. In addition, an experimental system was set up to study a gravity heat pipe's heat extraction rate, and a gravity heat pipe heat dissipation experiment was conducted. The experimental results showed that compared with using ethanol or hexane as the working medium, a methanol gravity heat pipe had the highest efficiency and provided the fastest cooling rate. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is the major effluent generated from metal and coal mines, causing serious ecological risks and degradation of aquatic habitats and surrounding soil quality. Biochemical passive reactors (BPRs) are an option for improving AMD affected water. This study investigates the effect of the size and concentration of zerovalent iron nanoparticles (nZVI) on the efficiency of batch BPRs during AMD remediation. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were also used as complementary techniques for the investigation of the changes in microbial cells and nZVI properties after the AMD remediation. The results from the batch experiment showed that the concentration of nZVI increases the pH and decreases ORP during AMD treatment, thus favouring the removal of metals. The results also suggest that metal sulfide precipitation occurred in all the batch with reactive mixture but was greater in reactors amended with nZVI of larger size. This study revealed that the presence of nZVI in the BPR leads to metal removal as well as the inhibition of sulfate-reducing bacteria (SRB) activity. Microscopy study indicated that the addition of nZVI creates a morphological change on certain microorganisms in which the cellular membrane was fully covered with nZVI, inducing cell lysis process. These results show that nZVI is a promising reactive material for the treatment of AMD in BPR systems. [ABSTRACT FROM AUTHOR]

Iron recovered from acid mine drainage (AMD) waters effluent and introduced as an advanced oxidation processes (AOPs) source, namely, Fenton reagent (FR) for municipal wastewater (MWW) treatment. Acid mine drainage-based Fenton reagent's (AMD-FR) experiments were carried out in a lab-scale facility and various operating parameters such as reaction time, solution pH, AMD as the iron source dose and H2O2 concentration were investigated. Box–Behnken design was applied to optimise the multiple variables and a mathematical model was developed with a high correlation coefficient (R2 = 96%). The maximum Chemical Oxygen Demand (COD) removal reached 73% within 30 min of reaction time. Optimum AMD sludge introduced to the system was 41 mg/L and H2O2 of 398 mg/L at the optimum operating pH 2.7. Kinetic study of AMD-FR revealed that COD removal followed the second-order reaction kinetic model. Thermodynamic analysis of the results with positive values of enthalpy (∆H') suggested the endothermic nature of the reaction. Positive Gibbs free energy of activation (∆G') and negative entropy of activation (∆S') values verified the non-spontaneous nature of the oxidation reaction with a low energy of activation barrier (55.59 kJmol−1). [ABSTRACT FROM AUTHOR]

To mitigate the trace elements (TE) dispersion in acid mine drainage (AMD), laboratory experiments were carried out comparing nine agricultural by-products. Five adsorbent materials were selected for adsorption batch experiments. Then, the biosorbents were tested to remove TE from AMD collected from oxidized tailings heaps, using equilibrium experiments. The As adsorption on carbonatite was high (15.4 g kg−1); Cd (4.1 g kg−1) on cow manure; Cu (17.9 g kg−1) on carbonatite; Pb (14.1 g kg−1), and Zn (16.4 g kg−1) on rabbit manure. The Zn adsorption on oat straw and carbonatite was well fit by Freundlich isotherm. The Langmuir equation mimics well Zn and Cd adsorption by peat moss and caw manure; Cu adsorption on peat moss and vermicompost. Except for vermicompost and carbonatite, the adsorption improved as the buffer capacity of the biosorbents increased, following a second-order equation. The FTIR analysis showed that the carboxylic, aromatic, and aliphatic aldehyde groups were involved in TE adsorption. Soluble-As, -Cd, -Cu, and -Zn from AMD were removed (90%) by the addition of 4 and 8% (m/v) of sheep manure, cow manure, rabbit manure, vermicompost, and carbonatite. Lead concentration in AMD was increased due to the addition of the biosorbents. [ABSTRACT FROM AUTHOR]

Novel Diffusive Gradients in Thin Films (DGT) binding agents, Musa cavendishi banana peel (BP) and Moringa Oleifera seeds (MOS) immobilised in agarose gel, have been developed and validated for the determination of Cd, Cu, Pb and Zn in waters. The agarose-BP and agarose-MOS gel disks were characterised by Scanning Electron Microscopy, Energy Dispersive X-ray Spectrometry and Porosimetry by nitrogen adsorption. Elution of analytes from the binding agents was successfully performed with 2 mol L−1 HCl. The accumulation of Cd, Cu, Pb and Zn in DGT devices based on agarose-BP and agarose-MOS (DGT-BP and DGT-MOS) agreed well with the theoretical curves predicted by the DGT equation in synthetic solutions (500 µg L−1 for each analyte). The uptake of DGT-BP and DGT-MOS for Cd, Cu, Pb and Zn was found to be independent of ionic strength of solutions up to 0.005 mol L−1 and for the entire studied pH range (from 3.5 to 8.0). Validation of DGT-BP and DGT-MOS methods was carried out by deploying the devices in spiked river water (the Corumbataí and the Piracicaba river). The recoveries obtained for the natural water matrices ranged between 40% and 150%. DGT-labile concentrations in situ for DGT-BP and DGT-MOS (performed in acid mine drainage) were also consistent with the values measured by conventional DGT-Chelex, albeit DGT-BP had a better binding capacity in acid drainage water. The predictions performed by chemical speciation modelling vMINTEQ were in general agreement for Pb using DGT-MOS (CDGT-MOS/Cdissolved 50% and Pb+2MINTEQ species 41.9%) and for Cu using DGT-BP (CDGT-BP/Cdissolved 55% and Cu+2MINTEQ species 62%). The proposed DGT-BP and DGT-MOS reaffirm the use of residual biomass as binding phase in the DGT technique, featuring low costs in production and 'green' technology approaches. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) causes serious environmental issues once present in the food chain directly affects human health due to its high acidity, the presence of heavy metals and sulphate compounds. For this reason, the constant search for new technologies for the treatment of AMD is becoming increasingly necessary. This review aims to highlight the characteristics and damage caused by AMD and the main treatment approaches. With special emphasis on anaerobic bioreactors containing sulphate-reducing bacteria (SRB) as a sustainable and economical alternative for the treatment of this type of effluent, due to the ability of microorganisms to use toxic metals in their metabolism, besides generating alkalinity in the environment and neutralising acidic compounds. SRB metabolise the electron donor and the sulphate ion, generating hydrogen sulphide and carbonic acid. In this way, future perspectives and major advances involving the treatment of this wastewater through microorganisms were addressed. [ABSTRACT FROM AUTHOR]

Wastes liberation from mining operations has occurred for quite a few centuries, and quarrying has advanced considerably in the twentieth century. Minerals excavating and their further processing generate enormous amounts of waste rocks and tailings, commonly rich in sulfide compounds. Exposure of sulfide-containing minerals to water and air, and actions of indigenous bacterial inhabitants cause the formation and discharge of acid mine drainage (AMD), an acidic flow out comprising of huge amounts of heavy metals and sulfate ions. Sulfur oxidizing bacteria of diverse genera assist in the oxidation of sulfide minerals via different catabolic systems. The huge amount of acidic waste drainage containing soluble metals in the mining associated sites poses a serious environmental hazard. To prevent AMD formation, extensive research studies have been devoted to the mechanisms of oxidation and its prevention. This manuscript reviews the existing state of acid mine drainage and the potential of diverse bacteria associated with sulfur metabolism. Further, this study focuses on the effect of AMD on living organisms and the precise remediation actions which may be relevant to achieve long-term sustainable and cost-effective strategies for the management of mining operations and the associated hazards. [ABSTRACT FROM AUTHOR]

Heavy metal ions are widely recognized for their harmful effects on human health and the environment. Heavy metal ions removal using nanocomposite hydrogel is a promising method for industrial applications and process development owing to their utilization in both kinematic and dynamic adsorption process. There is a need to develop simple, low-cost water purification techniques that use biodegradable bio-based natural polymers like cellulose nanocrystal that have been modified with nanomaterials. These innovative functional cellulose nanocrystals-based nanomaterials have been shown to successfully remove a variety of contaminants from wastewater to acceptable levels. Due to their capacity to hold water in their porous structures, hydrogels are the most commonly used 3D polymer mesh materials for environmental remediation. The application of potential hydrogel for the absorption of Cu2+, Ni2+, Zn2+ and Cd2+ ions from an aqueous solution in a packed bed adsorption column was studied in this work. The adsorbent was studied using FTIR, SEM, XRD and TGA. The influence of breakthrough factors such as bed height (10, 17 and 25 cm) influent concentration (10, 20 and 50 mg/L) and the feed flow rate (10, 20 and 30 mL/min) was assessed. Bed Depth Service Time, Thomas and Yoon–Nelson models were used to fit the experimental data. With an increase in bed height, breakthrough and exhaustion time, the removal efficiency rose to 99.42 ± 0.12 for Cu2+, 99.23 ± 1.16 for Ni2+, 99.36 ± 0.89 for Cd2+ and 98.94 ± 0.48 for Zn2+, but declined with increased flow rate and influent concentration. Better performance was observed at a bed height of 25 cm, an influent metal ion concentration of 10 mg/L and a flow velocity of 10 mL/min. The BDST and Yoon–Nelson models were both successfully used to predict the breakthrough curves of heavy metal ions removal. [ABSTRACT FROM AUTHOR]

The selection process for a technology to treat the mine drainage is influenced by its performance, technical feasibility and cost. For the last decades, the mine industry has been searching for green methods to treat the acid mine drainage (AMD). This study evaluated thermally activated eggshells as a potential alternative for AMD treatment in cold climate. It was found that metal removal efficiency depended on the eggshells' calcination temperature and on the solid: liquid ratio. Eggshells calcined at 900 °C and employed in a solid: liquid ratio of 0.3% increased the pH of a mine effluent from 2.5 to 6.9 at 20 °C and to 9.2 at 4 °C, respectively. Heavy metal concentrations were reduced as follows: As <0.0005 mg/L, Cd 0.00022 and 0.00009 mg/L, Cu 0.0061 and 0.0091 mg/L, Co 0.0338 and 0.0016 mg/L, Cr 0.0015 and 0.0022 mg/L, Fe <0.01 mg/L, Ni 0.0291 and 0.0024 mg/L, Mo <0.0005 mg/L, Se 0.0033 and 0.0044 mg/L, and Zn 0.007 and 0.022 mg/L, at 20 °C and 4 °C, respectively. Consequently, the treated mine effluent satisfied both the Quebec and Canadian regulations. Based on these results, thermally activated eggshells could be efficiently employed for the active and passive treatment of AMD in a cold climate. [ABSTRACT FROM AUTHOR]

The feasibility of using iron extracted from acid mine drainage (AMD) as Fenton's reagent for removal of organics pollutants from polymer and plastics manufacturing effluent was investigated in this study. AMD iron dose, H2O2 concentration and pH were evaluated as the treatment factors for their effects on organics oxidation. Optimum treatment conditions were identified using response surface methodological analysis (RSM), and of the ranges of the treatment factors examined, an optimal treatment combination was found to be AMD iron concentration: 40 mg/L and H2O2: 500 mg/L at pH 2.2, organics removal efficiency as high as 98% for TOC removal was achieved. The removal efficiency increased with temperature up to 40°C and further temperature increases resulted in lower removal efficiencies. The organics oxidation was characterized well by investigating the kinetic order and the process is following the second-order reaction kinetics. The thermodynamic parameters showed that the oxidation reaction was endothermic and non-spontaneous in nature. [ABSTRACT FROM AUTHOR]

This study introduces iron sludge recovered from acid mine drainage (AMD) waste, as advanced oxidation processes, that is, AMD/H2O2 (Fenton's reagent) to treat vehicle-washing wastewater. Vehicle-washing wastewater was collected from car washing facility in West Virginia, USA, and subjected for laboratory-scale batch experiments. Response surface methodological analysis was chosen to optimize the parametric conditions of the Fenton's system. A 15-level of quadratic Box-Behnken design model was applied via response surface methodology to evaluate the effects and interactions of the system variables. The optimized system variables were attained at pH 4.0 using 92 and 354 mg/L of AMD and H2O2 concentrations, respectively, to achieve the maximum predicted organics removals of 91.4%. Analysis of variance, which was applied for statistical data analysis, showed the significant of the quadratic models for treatment. The linear correlation between the total organic carbon (TOC) and chemical oxygen demand (COD), with sufficient accuracy, is providing the possibility of estimating COD from TOC values. Finally, the results showed that the reaction is endothermic, non-spontaneous in nature and follows the second-order reaction kinetics rate. The results of this work signify the importance of using iron from waste effluents for treating wastewater. [ABSTRACT FROM AUTHOR]

According to the characteristics of acid mine drainage (AMD) solution, such as extremely low pH, rich SO4 2−, and Mn2+ pollution ions. In this study, maifanite, bagasse, and sulfate-reducing bacteria (SRB) were used as research objects based on microbial immobilization technology. Response surface methodology was used coupled with the Box–Behnken design. The type, dosage, and particle size of maifanite were used as independent variables. The pH, oxidation-reduction potential, total Fe (TFe) removal efficiency, Mn2+ removal efficiency, SO4 2− removal efficiency, and COD release amount of maifanite-reinforced SRB-immobilized particles were used as response values to optimize the preparation parameters of maifanite-reinforced immobilized particles, and the adsorption characteristics were analyzed. The results showed that the optimal conditions for the preparation of maifanite-reinforced SRB-immobilized particles were as follows: the type, dosage, and particle size of maifanite were Dengfeng maifanite, 0.1 g and 200–300 mesh, respectively. The surface pores of AMD were reduced and FeS, MnS, Fe(OH)3, Mn(OH)2 appeared after treated with maifanite, bagasse, and SRB. The reduction process of SO4 2- by maifanite-enhanced SRB-immobilized particles conformed to the first-order kinetics, and the adsorption process of Mn2+ conformed to the McKay pseudo-second-order kinetic model and the Freundlich isothermal adsorption model. [ABSTRACT FROM AUTHOR]

This study investigated the effect of carbon sources (n = 2) on the performance of a microbial community in an anaerobic moving-bed biofilm reactor (MBBR) treating acid mine drainage (AMD). The 1.5 L anaerobic MBBR was operated across a range of hydraulic retention times – HRT's (3–18 days), using different substrates, i.e. brewing wastewater and lactate as sole carbon sources and electron donors. Maximum sulphate reduction and chemical oxygen demand (COD) consumption rate was 21.94 and 24.28 mg SO 4 2 − L−1 h−1, and 0.473 and 0.697 mg COD L−1 d−1 for brewing wastewater and lactate supplemented bioreactors, respectively, at an HRT of 3 days. The maximum COD/ SO 4 2 − ratio was found to be 2.564 in the bioreactor supplemented with brewing wastewater at an HRT of 15 days. The metal removal above 70% in the system supplemented with brewing wastewater followed the order; Be2+ > Fe2+ > Sr2+ > Pb2+ > Mg2+ > Cu2+ > Zn2+ > Li1+ > Ca2+ in comparison to the system supplemented with lactate, Be2+ > Fe2+ > Sr2+ > Mg2+ > Cu2+ > Li1+ > Zn2+ > Pb2+ after an HRT of 18 days. Complete removal of beryllium (II) was observed irrespective of the carbon source used. The results clearly showed that brewing wastewater can be deployed as a nutritional supplement in environmental remediation of AMD. [ABSTRACT FROM AUTHOR]

Acidophiles play a vital catalytic role in the formation of acid mine drainage (AMD). In this study, acidophilic communities in a stream, two lakes and five ponds in Nanshan Mine, Anhui Province, China were comparatively investigated. Among the three types of AMDs, the stream which originated from a rock wall had the strongest acidity (pH 2.30–2.42), while the ponds (pH 2.35–2.60) formed in mine dump and the two large-scale AMD lakes (pH 2.66–3.05) were less acidic. The chemolithotrophic iron-oxidizer Leptospirillum dominated at the stream starting point with the lowest pH and highest Fe content. However, with streamflow, pH increased and Fe concentration decreased dramatically, and the dominance of Leptospirillum was replaced by the less acid-resistant iron-oxidizer Ferrovum. In contrast to the stream, prokaryotic communities in the ponds were mostly dominated by chemoheterotrophic Acidiphilium because of the abundant organic matter from surrounding mine waste. Both chemolithotrophic Ferrovum and chemoheterotrophic Acidiphilium were abundant in the AMD lakes, which may form a symbiotic relationship around the carbon cycle. Statistical analyses indicated that pH was the predominant environmental factor influencing the prokaryotic communities. As for the eukaryotic communities, the microeukaryotes in the stream were mostly uncultured groups. Both photoautotrophic algae Chrysonebula and chemoheterotrophic fungi were abundant in the ponds, while the two AMD lakes were only dominated by photoautotrophic algae Coccomyxa and Ochromonas. [ABSTRACT FROM AUTHOR]

Sulfate and chemical oxygen demand removal by an anaerobic batch reactor treating of acid mine drainage is modelled. Available models are abundant but excessively complex, with large numbers of free parameters. Here, maximum likelihood and chi-squared hypothesis tests are applied to three simple models, with Malthus-Monod and Fick description, in increasing order of complexity: (i) planktonic single population (of sulfate-reducing bacteria); (ii) planktonic double-competing populations (adding fermentative bacteria); (iii) granule bound double-competing populations. The data set consists of 6 time profiles, sampled from 120 days of operation after stabilization of the reactor in pH 4. Single population is refuted by all profiles, in which the sulfate reduction is 72 % larger than fermentatives. The planktonic double-competing population description is refuted at 119 days, with inner granule diffusion rate as low as 10 % of the previous period. The results showed that, after an operation time, the influence of mass transfer became more evident and the incorporation of Fick's law in the model was fundamental to the description of this trend. All tests and inferences are performed at the 90 % confidence interval due to large systematic uncertainties in the data. [ABSTRACT FROM AUTHOR]

Production of precipitated calcium carbonate (PCC) by indirect carbonation of BOF (Basic Oxygen Furnace) slag usually requires a calcium extraction stage to promote the dissolution of calcium. Previous works have shown that the grinding of BOF slag to smaller particle size accelerates calcium leaching at the expense of a high energy input and further environmental constraints such as dust management. In order to minimize the excessive consumption of energy due to grinding, this study focused on the optimization of calcium extraction from unmilled BOF slag using ammonium chloride (NH4Cl) and ammonium nitrate (NH4NO3). The study was conducted with a solvent-to-slag mass ratio of 10/1, to avoid the dissolution of impurities such as iron, silicon, magnesium and manganese and guarantee minimum equipment costs. The results obtained using umilled BOF slag show that the efficiency of calcium extraction reached ~75% for NH4NO3 and ~69% for NH4Cl in two extraction stages. A calcium carbonate precipitation yields of 80% was reached at 25°C and 6.5bars. Scanning Electron Microscopy (SEM) analysis of the dry PCC obtained showed that it is mostly dependent on the flow rate of CO2 and the carbonation pressure. Finally, the PCC was evaluated for the treatment of acid mine drainage. [ABSTRACT FROM AUTHOR]

The current work addresses the study of the recovery of rare earth elements (REE) from acid mine water by using cationic exchange resin. The acid water was obtained from a closed uranium mine in Brazil. Ion exchange experiments were carried out in batch with three different resins at 25 ± 0.5°C and pH values 1.4, 2.4 and 3.4 (natural). Data were adjusted to the Langmuir equation in order to calculate the maximum loading capacity (qmax) of the resins. The results of qmax for individual REE revealed that the resins present higher loading for La in detriment to the other REE. The Dowex 50WX8 and Lewatit MDS 200 H resins demonstrated favourable sorption profiles to REE, evidenced by values of equilibrium factor (RL) and higher values of the Langmuir constants (b). The separation factors ( α H R E E L R E E ) indicates that resins are more selective for light REE at all pH studied. The selectivity of the resins for the REE can be described as light REE > heavy REE. The pH 1.4 and 3.4 are more favourable for the recovery of REE. [ABSTRACT FROM AUTHOR]

Anglesite: Discovery and Description Beudant ([4], p. 460), in the second edition of his famous I Traité élémentaire de minéralogie i , was the first to use the name anglesite to describe the naturally occurring sulfate of lead from "the mines of Anglesea [ I sic i ]"; however, Beudant did not specifically name Parys Mountain as the source. Nevertheless, as part of a major research project on the history of anglesite from Parys Mountain, Plant, Cot-terell, and Starkey ([11]) successfully located blocks of anglesite-bearing gossan on the southern side of the eastern (Mona) open pit. ANGLESITE, PbSO SB 4 sb , is a simple sulfate of lead, named for the island of Anglesey, in northwest Wales, United Kingdom (fig. 1). [Extracted from the article]

The oxidation of Fe2+ by Acidithiobacillus ferrooxidans (A. ferrooxidans) in acid mine drainage (AMD) is often accompanied by formation of iron hydroxysulfate minerals, such as schwertmannite and jarosite. This study reported that 80 mmol L−1 of Fe2+ could be completely oxidized by A. ferrooxidans LX5 within 48 h, but only 27.7% of the resultant Fe3+ precipitated to form schwertmannite. However, the conversion efficiency to jarosite was much higher (54.5%). The formation of jarosite lasted 120 h, while only 24 h when conversed to schwertmannite. By constructing a cyclic process of 'Cu-reducing coupled with bio-oxidization', the total Fe in AMD could be fully converted into mineral precipitates. The resultant mineral specie could be regulated simply by control the K+ concentration. Thermodynamically, Fe3+ cannot hydrolyze spontaneously to form schwertmannite due to the positive Gibbs free energy ( Δ r G m ∘ = 6.63 kJ mol−1) of the reaction. However, if Fe2+ were biologically oxidized by A. ferrooxidans, the resultant Fe3+ could spontaneously form schwertmannite because the aforementioned coupling reaction has a negative Gibbs free energy ( Δ r G m ∘ = −34.12 kJ mol−1). Even though Fe3+ itself could hydrolyze to form jarosite spontaneously with Δ r G m ∘ = −22.20 kJ mol−1, the coupling reaction of Fe2+ bio-oxidation followed by Fe3+ hydrolysis in the presence of K+ could easily promote the formation of jarosite, which exhibited a great negative Gibbs energy ( Δ r G m ∘ = −67.45 kJ mol−1). [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) has continued to be a major threat leading to the destruction of the ecosystem and contamination of soil and waterbodies. The high sulfate concentration of AMD lowers the soil pH, making the soil more acidic and less productive which contributes to a reduction in the availability of arable land for agricultural purposes. Biological treatment has offered a cost-effective and eco-friendly approach through the introduction of organic substrates, aeration, or genetically modified microorganism to stimulate the contaminated environment and enhance sulfate reduction as opposed to previously used physicochemical methods which were criticized due to their inefficient and non-ecofriendly nature. This study focused on the evaluation of biological treatment through the application of wastewater (biostimulation) and air-injection (bioventing) for sulfate removal from AMD-contaminated soils. AMD-contaminated soil was amended with brewery (BWW) and municipal wastewater (MWW) at varying loading ratios to investigate the possible synergy while atmospheric air was supplied to bioventing treatments only. All treatments were conducted at mesophilic conditions for 28 days. The inability to improve sulfate removal rate through air-injection can be attributed to biosulfidogenesis preference for anoxic as against (high) oxic conditions for optimum performance. The BST and BVT treatment resulted in 34–53% and 27–42% sulfate removal efficiency, respectively. This study showed the efficacy of wastewater biostimulations and bioventing as a promising approach for sulfate and heavy metal removal from AMD-contaminated soils. The techniques have the potentials as vital tools for the mitigation of pollution aftermath in affected communities. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is a wastewater caused by mining activities and sulfide minerals oxidation. It occurs generally as a result of the relation of water, oxygen and microorganisms. In this study, the pH and the temperature of samples were determined around 2 and 20 °C, respectively. The chemical analysis was made by - ICP-MS. Sulfur concentration was found in higher amounts to be 21,892 ppm, 6155 ppm, 7893 ppm, and 31,305 ppm and the amounts of iron were also high with concentrations ranging from 14,318 ppm, 2181 ppm, 2715 ppm, and 13,801 ppm in samples including K2, K3, K4, and K5, respectively. Prokaryotic community fingerprints were obtained by DGGE and 16S rRNA gene clone library. High-throughput sequencing of 16S rRNA gene fragments and qPCR were performed by environmental DNAs. FISH was carried out by interacting probes. The extremely acidic four mine ponds contained high concentrations of sulfate and iron. Archaeal genera Acidiplasma sp. and Ferroplasma sp. with high abundance were determined in sulfate-rich sampling area according to metagenomic approach. Acidithiobacillus, Leptospirillum and Acidiphilium were often found in acid mine ponds. Otherwise, Sulfobacillus sp., Ferrithrix sp., Ferrimicrobium sp., Acidimicrobium sp., and Aciditerrimonas sp. were also obtained at the end of analyses. As a consequence, 16S clone library, metagenomic approach, qPCR and DGGE analysis were combined collaboratively, complementarily and comparatively for acidophilic prokaryotic diversity. [ABSTRACT FROM AUTHOR]

A flight campaign over sites in India using the National Aeronautics and Space Administration (NASA) Airborne Visible Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) was undertaken in 2016. Among the sites overflown were abandoned and active mining sites, Ambaji and Zawar, in northwestern India in the states of Gujarat and Rajasthan. AVIRIS-NG data was examined for signs of acid-generating minerals that could contribute to acid mine drainage and for distinct minerals or changes in spectral absorption features that could be signs of contamination by trace metals released by mining activities. Processing approaches used included an expert system/spectral feature fitting programme, MICA (Material Identification and Classification Algorithm), that matches absorption features in image spectra to those in user-defined library spectra. Also used were low abundance material detection approaches. Over the Ambaji site, the acid-generating mineral jarosite was mapped with the MICA approach and relative abundance was mapped with a low probability detection algorithm. The Zawar mine has a better-defined drainage which was mapped with MICA. A larger number of phyllosilicate minerals were mapped in the Tiri River drainage from the Zawar mine than were observed in similar sized rivers in other Ambaji and Zawar AVIRIS-NG flightlines. The 2.2 μm absorption feature associated with the minerals mapped in these drainages was examined to determine band parameters associated with the absorption. It was determined that minerals mapped, including montmorillonite, muscovite, and illite had a wider scatter in band parameters, principally asymmetry, but to a lesser extent bandwidth, than similar exposures of these mineral classes in the other riverbeds in the AVIRIS-NG scenes. Also mapped in the Tiri River, using a spectral matched filter, were gypsum precipitates. Field samples of this precipitate had high trace metal abundances. The combination of mapping the precipitates, such as gypsum, and an association with distorted absorption features (due to trace metal adsorption) holds the prospect for using imaging spectrometer data to assess the spread of trace metals from mining sites. [ABSTRACT FROM AUTHOR]

The environmental contamination due to mining activities in the Andean region of Bolivia is a serious concern, as it leads to highly acidic (pH 2.4) acid mine drainage (AMD), severely polluted by sulfate (>12,000 mg L−1). Passive bioreactors entailing biological sulfate reduction and removal of metals through sulfide precipitation have been recognized as a promising biotechnology. The reactivity of mixtures containing locally available substrates: sheep manure, compost and straw, was assessed through batch experiments conducted with a synthetic solution simulating the composition of AMD from San José mine (Oruro). The removal of sulfate and metals was successful in all reactors, at the end of the experiment (56 days) sulfate concentrations dropped to 1378–2081 mg L−1, corresponding to a removal efficiency between 84% and 89%, while average removal for Fe, Zn, Pb, and Cd were 99.8%, 98.5%, 94.7%, 98.6%, respectively. The sulfate and metal removal showed three phases. In the first phase, the removal was independent of the organic composition and attributable to pH-controlled mechanisms i.e. adsorption, precipitation of oxy(hydroxides) and co-precipitation. During the second phase, sulfate and metals concentrations remained rather constant; while in the third phase, the removal was affected by the organic matter composition. Sulfate removal rate attained the highest values (227–243 mg L−1 d−1) in the third phase, and it was attributable to biological reduction with not sulfate limitation. The depletion of nutrients rather than the sulfate availability may have limited the sulfate removal at the end of the experiment. [ABSTRACT FROM AUTHOR]

The reactivity of sulphidic cemented paste tailings (CPT) is an indicator which can be used to assess their environmental performance and durability. However, the reactivity is influenced by several factors either alone or in combination with other factors, such as temperature, curing time, and initial sulphate content. In this paper, the combined effect of the initial sulphate content and curing temperature on the reactivity of CPT is experimentally investigated with oxygen consumption (OC) tests. Microstructural analyses of the CPT samples are also performed to understand the impact of the microstructure of the CPTs on their reactivity. The results show that regardless of the binder type, the reactivity of the CPT system is significantly dependent on the curing temperature and initial sulphate content and their interaction. As curing temperature and sulphate concentration increase, the reactivity increases (except for the CPT samples with 5,000 ppm of sulphate). Moreover, the CPT sample with high contents of sulphate (25,000 ppm) and cured at 50°C has the highest reactivity regardless of the type of binder. The addition of mineral admixtures as a partial substitute for Portland cement also has a significant role in reducing the reactivity as compared to samples made only with Portland cement. [ABSTRACT FROM AUTHOR]

The acid mine drainage (AMD) can causes negative impacts to the environment. Physico-chemical methods to treat AMD can have high operational costs. Through passive biological methods, such as anaerobic reactors, sulfate reduction, and recovery of metals are promoted. This study evaluated the performance of a horizontal anaerobic immobilized biomass (HAIB) reactor for the treatment of synthetic AMD using polyurethane foam as support material, and anaerobic sludge as inoculum. Ethanol was used as an electron donor for sulfate reduction, resulting in an influent chemical oxygen demand (COD) in the range of 500–1,500 mg/L and COD/sulfate ratio at 1. A gradual increase of sulfate and COD concentration was applied that resulted in COD removal efficiencies higher than 78%, and sulfate removal efficiencies of 80%. Higher sulfate and COD concentrations associated with higher hydraulic retention times (36 h) proved to be a better strategy for sulfate removal. The HAIB reactor was able to accommodate an increase in the SLR up to 2.25 g SO42−/L d−1 which achieved the greatest performance on the entire process. Moreover, the reactor proved a suitable alternative for reaching high levels of metal removal (86.95 for Zn, 98.79% for Fe, and 99.59% for Cu). [ABSTRACT FROM AUTHOR]

Fly ash and its composites are used as the reactive media of permeable reactive barrier to solve the pollution problem of acid mine drainage. Four simulation models (reaction column) of permeable reactive barrier were established, including Column 1 with fly ash, Column 2 with acid-modified fly ash, Column 3 with a mixture of fly ash, and sulfate-reducing bacteria, and Column 4 with immobilized particles of fly ash combined with sulfate-reducing bacteria. The removal effect of different reactive media in PRB on acid mine drainage was investigated. Results showed that fly ash and its composites could treat acid mine drainage, and the order was: Column 4 > Column 3 > Column 1 > Column 2. The average effluent pH and oxidation-reduction potential values of Column 4 were 7.03 and −236 mV, respectively. The maximum removal percentages of chemical oxygen demand, SO4 2-, Fe2+, and Mn2+ in acid mine drainage by Column 4 were 83%, 85%, 99%, and 84%, respectively. Compared with Column 1 and Column 3, the immobilized particles of fly ash combined with sulfate-reducing bacteria in Column 4 can not only improve the treatment effect of fly ash, but also effectively reduce the influence of external environment on sulfate-reducing bacteria activity, so it is suitable to be used as PRB reactive media to repair acid mine drainage. [ABSTRACT FROM AUTHOR]

The Loskop Dam is the most polluted impoundment in the Olifants River, because it receives pollutants from the entire mine-dominated upper catchment. However, histopathology of fish inhabiting this polluted dam is scantly explored. The current study aimed to investigate the histopathology of the gills and liver of Labeo rosae from Loskop Dam. Alkaline pH was observed throughout the study with most metal concentrations exceeding the water quality guideline for aquatic ecosystems. Regressive changes were the most prominent lesions for both organs with gills showing relatively more pathologies than the liver. Epithelial lifting was 100% prevalent during both seasons in the gills whereas a significant expansion of lipofuscin-laden melanomacrophages (MMCs) showed 100% prevalence in the liver. Gills were significantly different in their prevalence of histopathology between the two seasons, which was not the case for liver. The histopathology recorded in this study shows that the health of L. rosae at Loskop Dam was compromised. Given the exacerbating pollution level in the upper Olifants River, these findings serve as a warning to conservation authorities and emphasise the necessity for regular monitoring of fish health at Loskop Dam to assess pollution levels using fish health as a sensitive indicator to altering pollution levels. [ABSTRACT FROM AUTHOR]

We examined the geochemistry and bacterial and archaeal community structure in the acidic (pH < 2.4) pit lake at Peña de Hierro, near the headwaters of the Río Tinto. The lake has strong vertical gradients in light, O2, pH, conductivity, and dissolved ions. Bacterial and archaeal communities between 0 and 32 m displayed low species richness and evenness. Relatives of iron cycling taxa accounted for 60-90% of the operational taxonomic units (OTUs) throughout the water column. Relatives of heterotrophic, facultative Fe(III)-reducing species made up more than a third of the bacterial and archaeal community in the photic zone. Taxa related to Fe(II) oxidizers Ferrithrix thermotolerans and Acidithix ferrooxidans were also abundant in the photic zone. Below the photic zone, relatives of the lithoautotrophic Fe(II) oxidizers Leptospirillum ferrooxidans and Ferrovum myxofaciens bloomed at different depths within or just below the oxycline. Thermoplasmatales predominated in the deep, microoxic zone of the lake. The microbial population structure of the lake appears to be influenced by the production of oxygen and organic matter by phototrophs in a narrow zone at the lake surface and by strong geochemical gradients present in the water column that create distinct niches for separate Fe(II) oxidizers. [ABSTRACT FROM AUTHOR]

Sulfide-ore copper nickel (SOCN) mining is being considered in water-rich Minnesota. Given pollution resulting from SOCN mining elsewhere, careful scrutiny is necessary examining the risks associated. Health considerations of mining within the Rainy River Watershed, the geographic region at the headwaters of the Boundary Waters Canoe Area Wilderness (BWCAW), Ontario's Quetico Park (Quetico), and Voyageurs National Park (VNP) are examined. This discussion considers toxins released from SOCN mining, examines data regarding degradation of water quality and deleterious environmental impact from SOCN mining elsewhere, considers the most vulnerable populations, and recognizes the broader effects to public health as well as benefits of existing wilderness. Recent federal decisions to reinstate mineral leases and abort the environmental assessment process have placed this unique and irreplaceable region of our country at substantial risk. The overall health and wellness of this region will very likely be negatively affected by SOCN mining, and economic costs will predictably outweigh benefits. In addition, negative impacts on water, fish and wild rice will likely degrade nutritional and tribal resources resulting in violation of usufructuary rights of tribal communities. [ABSTRACT FROM AUTHOR]