Abstract Acid Mine Drainage Research Articles

The Combined Application of Surface Floating Wetlands and Bottom Anaerobic to Remediate AMD-Contaminated Lakes

Acid mine drainage (AMD) causes environmental pollution that affects many countries with historic or current mining industries. The eco-remediation system (RW) which combined surface floating wetlands and bottom anaerobic sediments (SFW-BAS) was selected for AMD-contaminated lakes (AMDW). Meanwhile, AMDW and nature aquatic ecosystems (NW) were set as the control groups, respectively. The parameters, including pH, Eh, Fe, Mn, SO42−, and the degradation rate of the native dominant plant litter were investigated to assess the effects of remediation. The results showed that the average of pH, Eh, and EC, was 2.73, 484.08 mv, and 2395.33 μs·cm−1, respectively. The average content of SO42−, Fe, Mn, Cu, Zn, and Pb was 2190 mg·L−1, 40.2 mg·L−1, 4.6 mg·L−1, 249.2 μg·L−1, 1563 μg·L−1, and 112.9 μg·L−1, respectively. The degradation rate of plant litters in AMDW ranged from 14.5% to 22.6%. However, RW ultimately improved the water quality and the degradation of litters. RW has a good effect on buffering the acidity, ranging from 3.96 to 7.41. The pH of RW (6.14) is close to that of NW (7.41). The average content of SO42−, Fe, Mn, Cu, Zn, and Pb was 2071 mg·L−1, 3.4 mg·L−1, 2.4 mg·L−1, 85.3 μg·L−1, 607.4 μg·L−1, and 47.8 μg·L−1, respectively, which showed good pollutant removal performance. The degradation rate of plant litters in RW ranged from 27.8% to 32.6%. Therefore, RW can be used to remediate AMDW.

Utilization Of Fly Ash In Heavy Metal Removal From Acid Mine Drainage

Acid mine drainage (AMD) contains very toxic heavy metal with strong acidity. The high concentration of heavy metals in AMD have the potential as a major contamination sources that affect human life, aquatic and other natural resources. In this study, the removal of heavy metals was carried out by using low-cost industrial waste material which is fly ash. The adsorption capacity of fly ash was determined by two methods which are batch adsorption and tank remediation test. The effects of quantity of dosage, pH and heavy metal concentration were investigated. Fly ash consist of carbonate minerals (>50%) with high potential as adsorbent material to treat acid mine. The maximum adsorption rate for fly ash occurred at pH 5 for Pb, pH 7 for Zn and pH 3 for Cu. Adsorption capacity also increased with increasing dose. Fly ash as high alkaline material remediated and neutralized AMD solution from acidic phase (pH 2.11) to neutral phase (pH 7.09). Increasing pH value during treatment process will increase the capacity of the removal of heavy metals.

Efficiency of a flocculent consisting of bentonite clay and fly ash for the removal of pollutants in AMD

Abstract Acid mine drainage was collected from the western decant in Krugersdorp, South Africa, to conduct a series of laboratory tests using 200 mL of AMD in five beakers dosed with increasing bentonite clay and decreasing pulverised fly ash respectively (flocculent-A) to establish accurate FA:BC dosing ratio. Two similar sets of experiments were conducted using a combination of bentonite clay and fly ash demineralized with distilled water (flocculent-B) and the other samples with tap water (flocculent-C). The pH, electrical conductivity (EC), turbidity and toxic metals were analyzed before and after experiments, i.e. As, Co, Zn and Pb, and treated in a jar test at 250 rpm for 2 min and reduced to 100 rpm for 10 min, allowed to settle for 1 hour after which the measurements were conducted. Turbidity removal of the samples of flocculent-A was slightly lower (72.5–75.1%) compared to that of flocculent-B and C (95.3–97.3%). On the other hand, FA:BC of 3:1 showed the highest turbidity removal. Toxic metals removal (85.9–94.8%) in the samples with flocculent-B and C is also higher compared to that of flocculent A. The SEM micrographs of the samples with flocculent-B and C showed large flocs indicating optimal sorption.

A Critical Review of Acid Mine Drainage Treatment

Acid mine drainage has been reported to cause various environmental and human health problems. Acid mine drainage is formed due to the oxidation of sulfide minerals to water and air. This paper reports the efforts that have been made in the management and treatment of acid mine drainage. Thirty papers from reputable publishers are used as references. Efforts to prevent the formation of acid mine drainage can be made by making proper drainage and dewatering systems, making non-acid formations for rocks that have the potential to be oxidized. Active and passive treatment methods can be used to treat acid mine drainage. The active treatment method uses materials and chemicals to reduce pollutant parameters, while the passive method utilizes natural processes to reduce pollutant parameters in acid mine drainage. The combination of active and passive methods using novel materials that have been researched is recommended to produce the best system that can thoroughly remove pollutants in acid mine drainage.

Steel slag as a potential adsorbent for efficient removal of Fe(II) from simulated acid mine drainage: adsorption performance and mechanism.

Acid mine drainage is an extraordinarily acidic and highly heavy metal ion-contaminated leachate, seriously threatening the environment. In this work, an industrial solid waste of steel slag is the adsorbent to remediate the simulated acid mine drainage containing a large amount of Fe(II) ions. Due to the excellent physicochemical properties and structures, steel slag exhibited remarkable Fe(II) removal performance. Its maximum removal efficiency was up to 100%. The initial pH, the dosage and particle size of steel slag, and initial concentration of heavy metal ions on Fe(II) removal efficiency were determined. The pseudo-second-order model and Freundlich isotherm model well described the adsorption behavior of steel slag, implying that the adsorption of Fe(II) by steel slag was mainly multilayer chemisorption. The thermodynamic study demonstrated that the adsorption process was endothermic and spontaneous; the enthalpy change was calculated to equal 91.21kJ/mol. Mechanism study showed that the entire removal process of Fe(II) by steel slag was completed by electrostatic adsorption, chemical precipitation, and surface complexation in cooperation, and the chemical precipitation was the dominant mechanism. Meaningfully, this study provides a valuable strategy and path for engineering applications of AMD remediation by steel slag, which is prospective as an ideal candidate for Fe(II) ions elimination, inspiring the future development of "Treating the wastes with wastes."

Experimental Study on Biological Treatment of Copper in Acid Mine Drainage after Iron Removal

Acid mine drainage is characterized by low pH value, many types of heavy metals, high concentration of heavy metals and great environmental damage. Copper precipitation by sulfate reducing bacteria is a common method. In this experiment, the AMD after iron removal was treated by an upflow anaerobic bioreactor. The effects of HRT, carbon source type, carbon source dosage and reactor temperature on the operation of the reactor were studied. The optimum process parameters were determined: HRT was 12h, formic acid was used as carbon source and the dosage was 0.5g/L, and the temperature was 30 °C. Under the process conditions, the Cu concentration in the reactor effluent decreased to 0.043mg/L, and the recovery rate of Cu metal was 99.9%. The mechanism of copper deposition in the reactor was studied by characterization of the structure and morphology of the precipitated product and the analysis of the microbial community structure in the effluent of the reactor.

Application of neural network techniques to predict the heavy metals in acid mine drainage from South African mines.

Acid Mine Drainage (AMD) is the formation and movement of highly acid water rich in heavy metals. Prediction of heavy metals in the AMD is important in developing any appropriate remediation strategy. This paper attempts to predict heavy metals in the AMD (Zn, Fe, Mn, Si and Ni) from South African mines using Neural Network (NN) techniques. The Backpropagation (BP) neural network model has three layers with the input layer (pH, SO42- and total dissolved solids (TDS)) and output layer (Cu, Fe, Mn and Zn). After BP training, the NN techniques were able to predict heavy metals in AMD with a tangent sigmoid transfer function (tansig) at hidden layer with five neurons and linear transfer function (purelin) at output layer. The Levenberg-Marquardt back-propagation (trainlm) algorithm was found as the best of 10 BP algorithms with mean-squared error (MSE) value of 0.00041 and coefficient of determination (R) for all (training, validation and test) value of 0.99984. The results indicate that NN can be considered as an easy and cost-effective technique to predict heavy metals in the AMD.

Removal of iron and sulphate during acid mine drainage treatment using laboratory successive alkalinity producing system and its behavioural relationship

Abstract Acid Mine Drainage (AMD) is one of the persistent water pollution problems in many coal mines of U.S.A. and Canada. Only few mines in India face this problem. The treatment of acid mine water has become a statutory requirement in almost all mines of the world. Metal removal and alkalinity generation is essential feature of any AMD treatment system but sulphate removal from acid mine drainage is still given the secondary importance. In the present study, four AMDs were treated in laboratory Successive Alkalinity Producing System (SAPS) for five different hydraulic retention times (HRT). The total iron removal and corresponding sulphate removal along with net alkalinity generation were studied during AMD treatment process by SAPS. A complete removal of total iron and sulphate removal of over 59% have been achieved. The study revealed that the total iron removal and sulphate removal increases with increase in HRT and its removal exhibited linear relationship. A substantial increase in alkalinity was also found after SAPS treatment. The findings of the study can be utilized in design of SAPS for removal of iron and sulphate during treatment of AMD in mining areas.

16S rRNA Gene-Based Profiling of the Microbial Community in an Acid Mine Drainage Fe Precipitate at Libiola Mine (Liguria, Italy)

Acid mine drainage (AMD) is a common environmental problem in many sulphide mines worldwide, and it is widely accepted that the microbial community plays a major role in keeping the process of acid generation active. The aim of this work is to describe, for the first time, the microbial community thriving in goethite and jarosite Fe precipitates from the AMD of the Libiola mine. The observed association is dominated by Proteobacteria (>50%), followed by Bacteroidetes (22.75%), Actinobacteria (7.13%), Acidobacteria (5.79%), Firmicutes (2.56%), and Nitrospirae (1.88%). Primary producers seem to be limited to macroalgae, with chemiolithotrophic strains being almost absent. A phylogenetic analysis of bacterial sequences highlighted the presence of heterotrophic bacteria, including genera actively involved in the AMD Fe cycle and genera (such as Cytophaga and Flavobacterium) that are able to reduce cellulose. The Fe precipitates constitute a microaerobic and complex environment in which many ecological niches are present, as proved by the wide range of bacterial species observed. This study is the first attempt to quantitatively characterize the microbial community of the studied area and constitutes a starting point to learn more about the microorganisms thriving in the AMD of the Libiola mine, as well as their potential applications.

Prokaryotic Community Determination of Metal-Rich Acidic Environment by Comparative Methods

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.

Treatment of AMD using a combination of saw dust, bentonite clay and phosphate in the removal of turbid materials and toxic metals

Abstract Acid mine drainage collected from the western decant in South Africa was treated in a series of small-scale laboratory experiments. 200 mL of the sample was poured into five 500 mL glass beakers using flocculants formed by mixing size-optimized 1.5 g of bentonite clay with 3.5 g saw dust and 1.0 g of Na3PO4 in triplicates (experiment A). Four similar sets of control experiments were conducted using the same amount of bentonite clay and saw dust with varying Na3PO4, contents in AMD treatment; the rationale being to determine the efficiency of Na3PO4 (experiments B, C and D). The results show that conductivity has an influence in the removal of the turbid materials. The removal efficiency of toxic metals using a flocculant containing 220 μm bentonite clay particle size and 0.012 or 0.25 M of Na3PO4 is higher than 96% when compared to that of the samples dosed with a flocculant containing 0.05 M Na3PO4, which is less than 91%. The flocculant also showed optimal removal efficiency of both turbid materials and toxic metals, i.e. removal efficiency within a range 96.5–99.3%. The flocculants containing 0.025 M Na3PO4 showed optimal removal efficiency of turbidity, colour, toxic metals and natural organic compounds.

A Review of Technologies Used in Handling The Acid Mine Drainage Challenge: Perspectives on Using Green Liquor Dregs As a Sustainable Option For Treatment of Acid Mine Drainage

Acid mine drainage (AMD) is one of the repercussions that result from earth-moving activities around the sulfide-bearing mineral hosts. The detrimental effects associated with this AMD are driven by its characteristics, which include low pH and high concentrations of sulfate and toxic dissolved metals. Traditionally, the prevention and treatment of AMD are achieved by using technologies that use, amongst other, naturally occurring soils and carbonates. However, the continual use of these materials may eventually lead to their depletion. On the other hand, industrial by-products have been proven to occupying land that could have otherwise been used for profitable businesses. Additionally, the handling and maintenance of landfills are costly. In this current trend of a circular economy that is driven by industrial symbiosis, scientists are concerned with valorizing industrial by-products. One such by-product is the green liquor dregs (GLD) from Kraft mills. The neutralizing and geotechnical properties of these wastes have prompted the research pioneers to seek their potential use in handling the challenges associated with AMD. In this review, the formation AMD, trends in technologies for treatment and prevention of AMD are critically analyzed. This includes the feasibility of using GLD as an alternative, promising sustainable material.

Acid mine drainage treatment using zero-valent iron nanoparticles in biochemical passive reactors

ABSTRACT 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.

The removal of Mg2+ and Ca2+ and turbidity from aqueous solution employing copolymerization of ethyl acrylate onto guar gum

Abstract Acid mine drainage collected from decant in Krugersdorp, South Africa, was treated in a series of laboratory experiments using synthesized copolymer of guar gum-g-polymer (GG) for the removal of calcium and magnesium and turbidity. 250 mL of sample and 25 mL distilled water were added into 16 Erlenmeyer flasks. The samples were irradiated in a micro-oven at 900 W for 3 min and the mixtures were placed in a soxhlet extractor for homopolymerization, after which they were dried and crushed. The results showed an exponential increasing adsorption efficiency of calcium removal with increasing pH range 2–4, and a slight increase between the pH range 4–8. On the other hand, the results showed a continuous increasing adsorption removal efficiency of magnesium with increasing pH in a range 2–8. The results showed a slight increasing adsorption efficiency of calcium removal with increasing dosage between 15 and 25 mg/L of GG, an exponential increase between 15 and 35 mg/L and resuming a slight increase between 45 and 55 mg/L dosage. On the other hand, the results showed an exponential increasing adsorption efficiency of magnesium removal between 15 and 54 mg/L dosage and slight increasing trend between 45 and 55 mg/L dosage.

Clean Technology for the Treatment and Modelling of Acid Mine Drainage Effluent

Acid Mine Drainage (AMD) exists as a phenomenon that involves the release of acidic water and metal conjugates, in and around mines, degrading the surrounding water environment. A real-time mining effluent is treated using low-cost adsorption technology using Combined Vegetable Waste Carbon (CVWC) as sorbent. Batch sorption was reviewed to know the effect of process factors on the removal of Cadmium (Cd), Zinc (Zn), and Iron (Fe). A two-level CCD (Central Composite Design) with three factors was adopted in the optimization of process factors. Also, the same factors were considered to review the ANNs (Artificial Neural Networks), model. A comparative statistical analysis was performed for the experimental data based on RMSE and R2 values in both RSM (Response Surface Methodology) and ANNs models. This study revealed that the ANNs model was well fit compared to RSM and this would probably reduce the experimental trials thereby reducing cumbersome calculations.

Acid neutralizing capacity minerals in Barani Pit PT Agincourt Resources Martabe, North Sumatera: alternative agent on neutralizing acid mine drainage

Acid Mine Drainage (AMD) is produced when sulfide-bearing material is exposed to oxygen and water. The mine may accelerate this natural reaction due to the wide and rapid exposure of sulfide minerals. Although economical ores are considered environmental pollutants, there are several elements that act as acid neutralizing capacity (ANC) mineral are associated with the ore, especially silicate minerals. Currently, PT Agincourt Resources Martabe has only relying on the use of carbonates mineral groups to handle the AMD issue. In fact, the geological condition in this area is formed of typically alumina-rich and alkaline minerals which are capable to neutralize the AMD as well. The aim of this study is to determine ANC minerals from the rock formations that has impact to neutralize the AMD in Barani Pit. The methods are geological field observation, mineral determination using spectral analysis, and assay analysis that provides data to sort the recommended ANC minerals. The ANC minerals from the rock formations and wastes within Barani Pit, other than calcite, are muscovite, illite, smectite, kaolinite, dickite and gypsum. The knowledge about these alternative ANC minerals might give contribution to reduce and solve the risk of acid mine drainage polluting the environment.

The effect of uranium, radium and thorium speciation on the removal of radioactivity from acid mine drainage using ion exchange

Acid mine drainage samples were collected from the central basin of the Witwatersrand basin in South Africa to study the removal of radioactivity. The samples were analyzed for gross alpha/beta activity, specific radionuclides, metals and anions concentration. The pH of the acid mine drainage samples was then varied and ion-exchange column experiments were carried out to remove radioactivity from acid mine drainage. The gross alpha activity ranged between 60 and 75 Bq/L and gross beta activity ranged from 56 to 70 Bq/L. The speciation of uranium, thorium and radium was modelled using Joint Expert Speciation System. The speciation had a big influence on the removal of radioactivity from acid mine drainage using ion exchange resin. The optimum pH was determined to be 8. Acid mine drainage samples treated at this pH showed gross alpha activity below the detection limit of 0.03 Bq/L for all samples and gross beta activities below 5 Bq/L for 9 of the 10 treated samples

Grass cellulose as cost-effective energy source for biological sulphate removal

Acid mine drainage (AMD) needs to be treated before it is discharged to water courses. The biological sulphate removal technology can be applied for the removal of salinity (sulphate), acidity and metals, the main pollutants in AMD. The aim of this study was to demonstrate that sulphate removal can be achieved using the fermentation products of grass-cellulose as cost-effective carbon and energy sources. Two studies were conducted. In the first study (an experimental period of 32 d) two stirred anaerobic batch reactors with a volume of 2.5 l each were operated at 37 to 39 °C and at a pH of 6.7 to 6.9. Both reactors contained grass cuttings, sulphate-reducing bacteria and rumen fluid. The test reactor contained sulphate-rich water and the control reactor tap water. The results from this study indicated that grass cellulose could serve as an energy source for biological sulphate removal. In the second experiment a 20 l continuously fed one-stage reactor containing grass cuttings, rumen fluid and immobilised sulphate-reducing bacteria, was fed synthetic sulphate-rich feed water. The results showed that sustained sulphate removal could be achieved when operating this reactor. The butyric and propionic acids formed were mainly utilised as the electron donors for the sulphate reduction, which resulted in increased levels of acetic acid. A clear relationship existed between the rate of sulphate reduction and the COD/VFA concentration in the reactors. It was concluded that sustained sulphate removal was achieved operating the continuously fed reactor using grass-cellulose as the carbon and energy sources.

Prediction and Remediation of Water Quality in Monitoring Potential of Acid Mine Drainage

Acid Mine Drainage (AMD) associated with both active and abandoned mining operations related to sulfide minerals, oxidation of pyrite affording an acidic solution that contains toxic metal ions. Result shows that pH value of water in Kg. Aur, Chini and Sg. Lembing are acidic with value of 2.81, 4.16 and 3.60 respectively. Maximum concentrations of heavy metals in the study area are: Pb (0.2 mg/L), Cd (0.05 mg/L), Zn (5.1 mg/L), Cu (5.2 mg/L), Mn (10.9 mg/L), Cr (0.2 mg/L), Ni (0.2 mg/L), As (0.005 mg/L) and Fe (202.69 mg/L). Prediction of acid formation using acid-base calculations from all samples shows high potential acid production between 22.84-2500.16 kg CaCO3/tonne. The ratio of Neutralization (NP) with Acid Potential (APP) shows a very low value (ratio<1) Sg. Lembing (0.02), Chini (0.08), Selinsing (0.31) and Kg. Aur (0.81). Analysis from the tank experiment after 30 days shows pH of LFS, bentonite, activated carbon and zeolite change to 6.11, 3.91, 2.98 and 2.71 respectively. Three mine sites experiencing AMD are Kg. Aur, Chini and Sg. Lembing. Active neutralization treatment successfully shows LFS has great potential to control AMD based on their ability to neutralize the pH and remove heavy metals in the mine water. Meanwhile, the second adsorbent material is bentonite followed by activated carbon and zeolite.

Biogeochemical Characterization of Metal Behavior from Novel Mussel Shell Bioreactor Sludge Residues

Acid mine drainage (AMD) remediation commonly produces byproducts which must be stored or utilized to reduce the risk of further contamination. A mussel shell bioreactor has been implemented at a coal mine in New Zealand, which is an effective remediation option, although an accumulated sludge layer decreased efficiency which was then removed and requires storage. To understand associated risks related to storage or use of the AMD sludge material, a laboratory mesocosm study investigated the physio-chemical and biological influence in two conditions: anoxic storage (burial deep within a waste rock dump) or exposure to oxic environments (use of sludge on the surface of the mine). Solid phase characterization by Scanning Electron Microscopy (SEM) and selective extraction was completed to compare two environmental conditions (oxic and anoxic) under biologically active and abiotic systems (achieved by gamma irradiation). Changes in microbial community structure were monitored using 16s rDNA amplification and next-generation sequencing. The results indicate that microbes in an oxic environment increase the formation of oxyhydroxides and acidic conditions increase metal mobility. In an oxic and circumneutral environment, the AMD sludge may be repurposed to act as an oxygen barrier for mine tailings or soil amendment. Anoxic conditions would likely promote the biomineralization of sulfide minerals in the AMD sludge by sulfate reducing bacteria (SRB), which were abundant in the system. The anoxic conditions reduced the risk of trace metals (Zn) associated with oxides, but increased Fe associated with organic material. In summary, fewer risks are associated with anoxic burial but repurposing in an oxic condition may be appropriate under favorable conditions.