Comparison of benthic macroinvertebrate indices for the assessment of the impact of acid mine drainage on an Irish river below an abandoned Cu-S mine

A range of macroinvertebrate indices were compared to assess the most appropriate metric for the assessment of acid mine drainage (AMD) in a low alkalinity, highly erosional river in south-east Ireland. Differences were found in the ability of indices to discriminate AMD impact with the Brillouin, BMWP score, Margalef and Shannon Indices the most precise. Taxon richness was also strongly correlated with AMD indicator parameters (e.g. pH alkalinity, sulphate, Zn and Fe) at impacted sites being an equally reliable metric. The response of the community structure to AMD in this river does not fulfil the optimum criteria for either diversity or biological indices, which may explain the variation in the success of different indices seen in this and other studies. The development of indices that model the expected community response to AMD more accurately or are based on the response of indicator species to AMD pollutants are required.     

Co-treatment of acid mine drainage with municipal wastewater: performance evaluation

Co-treatment of acid mine drainage (AMD) with municipal wastewater (MWW) using the activated sludge process is a novel treatment technology offering potential savings over alternative systems in materials, proprietary chemicals and energy inputs. The impacts of AMD on laboratory-scale activated sludge units (plug-flow and sequencing batch reactors) treating synthetic MWW were investigated. Synthetic AMD containing Al, Cu, Fe, Mn, Pb, Zn and SO₄ at a range of concentrations and pH values was formulated to simulate three possible co-treatment processes, i.e., (1) adding raw AMD to the activated sludge aeration tank, (2) pre-treating AMD prior to adding to the aeration tank by mixing with digested sludge and (3) pre-treating AMD by mixing with screened MWW. Continuous AMD loading to the activated sludge reactors during co-treatment did not cause a significant decrease in chemical oxygen demand (COD), 5-day biochemical oxygen demand, or total organic carbon removal; average COD removal rates ranged from 87–93 %. Enhanced phosphate removal was observed in reactors loaded with Fe- and Al-rich AMD, with final effluent TP concentrations <2 mg/L. Removal rates for dissolved Al, Cu, Fe and Pb were 52–84 %, 47–61 %, 74–86 % and 100 %, respectively, in both systems. Manganese and Zn removal were strongly linked to acidity; removal from net-acidic AMD was <10 % for both metals, whereas removal from circum-neutral AMD averaged 93–95 % for Mn and 58–90 % for Zn. Pre-mixing with screened MWW was the best process option in terms of AMD neutralization and metal removal. However, significant MWW alkalinity was consumed, suggesting an alkali supplement may be necessary.     

Impact of acid mine drainage on benthic communities in streams: the relative roles of substratum vs. aqueous effects

Restoration of streams impacted by acid mine drainage (AMD) focuses on improving water quality, however precipitates of metals on the substrata can remain and adversely affect the benthos. To examine the effects of AMD precipitates independently of aqueous effects, four substrata treatments, clean sandstone, clean limestone, AMD precipitate-coated sandstone and coated limestone, were placed in a circumneutral stream of high water quality for 4 weeks. Iron and Al were the most abundant metals on rocks with AMD precipitate. and significantly decreased after the exposure. Precipitate on the substrata did not significantly affect macroinvertebrate or periphyton density and species composition. In an additional experiment, percent survival of caged live caddisflies was significantly lower when exposed in situ for 5 days in an AMD affected stream than in a reference stream. Caddisfly whole-body concentrations of all combined metals and Fe alone were significantly higher in the AMD stream. Whole-body metal concentrations were higher in killed caddisflies than in live, indicating the importance of passive uptake. The results suggest the aqueous chemical environment of AMD had a greater affect on organisms than a coating of recent AMD precipitate on the substrata (ca. 0.5 mm thick), and treatment that improves water quality in AMD impacted streams has the potential to aid in recovery of the abiotic and biotic benthic environment.     

Synthesising acid mine drainage to maintain and exploit indigenous mining micro-algae and microbial assemblies for biotreatment investigations

The stringent regulations for discharging acid mine drainage (AMD) has led to increased attention on traditional or emerging treatment technologies to establish efficient and sustainable management for mine effluents. To assess new technologies, laboratory investigations on AMD treatment are necessary requiring a consistent supply of AMD with a stable composition, thus limiting environmental variability and uncertainty during controlled experiments. Additionally, biotreatment systems using live cells, particularly micro-algae, require appropriate nutrient availability. Synthetic AMD (Syn-AMD) meets these requirements. However, to date, most of the reported Syn-AMDs are composed of only a few selected heavy metals without considering the complexity of actual AMD. In this study, AMD was synthesised based on the typical AMD characteristics from a copper mine where biotreatment is being considered using indigenous AMD algal-microbes. Major cations (Ca, Na, Cu, Zn, Mg, Mn and Ni), trace metals (Al, Fe, Ag, Na, Co, Mo, Pb and Cr), essential nutrients (N, P and C) and high SO₄ were incorporated into the Syn-AMD. This paper presents the preparation of chemically complex Syn-AMD and the challenges associated with combining metal salts of varying solubility that is not restricted to one particular mine site. The general approach reported and the particular reagents used can produce alternative Syn-AMD with varying compositions. The successful growth of indigenous AMD algal-microbes in the Syn-AMD demonstrated its applicability as appropriate generic media for cultivation and maintenance of mining microorganisms for future biotreatment studies.     

Behavioural and feeding responses of Echinogammarus meridionalis (Crustacea, Amphipoda) to acid mine drainage

As a result of mining activities the exposure of metal sulphides to oxidation takes place with consequent release of acid mine drainage (AMD). Biomonitoring instruments have been proven to have the best deterrent effect upon polluters. A new approach in online biomonitoring, with the Multispecies Freshwater Biomonitortrade mark (MFB), was developed combining behavioural and feeding responses of the Portuguese indigenous benthic shredder, Echinogammarus meridionalis (Pinkster, 1973) (Crustacea, Amphipoda). These endpoints, along with mortality, were measured and analyzed for a gradient of sublethal doses of AMD. Original river water was used as the control and three doses of treatments were attained by adding increasing volumes of AMD to the control. The increase in AMD concentration and concomitant decrease in pH and increase in the concentration of most metals was followed by an overall increase of the mortality, decrease of locomotion/feeding activity and inhibition of the feeding rate. Mortality was observed in the two highest concentrations of AMD. Significant decrease in average locomotion/feeding activity took place in the second treatment. Although an inhibition of feeding was observed along the gradient of AMD concentration only in the highest concentration the feeding rate was significantly reduced.     

Mechanisms of phosphorus removal by cement-bound ochre pellets

Hydrous ferric oxide (here termed ‘ochre’) sludge, an abundant waste product produced from the treatment of acid mine drainage (AMD), was used in this study for the removal of phosphorus (in the form of phosphate ions) from contaminated waters. The phosphorus uptake capacities of both raw and pelletized AMD solids were compared using batch and column tests. Addition of a cement binder to the AMD solids during pellet production led to significantly increased P-loading of the resultant solids compared to the raw sludge. Additionally, the pellets were found to continue to remove P in tests up to 7 d in duration whereas the unbound AMD sludge appeared to approach equilibrium with phosphate solution after approximately 60 min of contact time. In line with previous studies P uptake by the AMD solids was found to be primarily via adsorption. By contrast calcium phosphate precipitation was found to be the dominant removal mechanism for the cement-bound ochre pellets with a relatively small proportion of removal attributable to the AMD solids. SEM–EDX analysis of the surface of used pellets showed a Ca:P molar ratio close to that of hydroxyapatite (HAP). Continuous column tests on these pellets showed a rapid decrease in P removal capacity by the pellets over time, attributable to the formation of a passivating HAP surface layer.     

Geochemical characteristics of dissolved rare earth elements in acid mine drainage from abandoned high-As coal mining area,southwestern China

Acid mine drainage (AMD) represents a major source of water pollution in the small watershed of Xingren coalfield in southwestern Guizhou Province. A detailed geochemical study was performed to investigate the origin, distribution, and migration of REEs by determining the concentrations of REEs and major solutes in AMD samples, concentrations of REEs in coal, bedrocks, and sediment samples, and modeling REEs aqueous species. The results highlighted that all water samples collected in the mining area are identified as low pH, high concentrations of Fe, Al, SO₄ ^2? and distinctive As and REEs. The spatial distributions of REEs showed a peak in where it is nearby the location of discharging of AMD, and then decrease significantly with distance away from the mining areas. Lots of labile REEs have an origin of coal and bedrocks, whereas the acid produced by the oxidation of pyrite is a prerequisite to cause the dissolution of coal and bedrocks, and then promoting REEs release in AMD. The North American Shale Composite (NASC)-normalized REE patterns of coal and bedrocks are enriched in light REEs (LREEs) and middle REEs (MREEs) relative to heavy REEs (HREEs). Contrary to these solid samples, AMD samples showed slightly enrichment of MREEs compared with LREEs and HREEs. This behavior implied that REEs probably fractionate during acid leaching, dissolution of bedrocks, and subsequent transport, so that the MREEs is primarily enriched in AMD samples. Calculation of REEs inorganic species for AMD demonstrated that sulfate complexes (Ln(SO₄)⁺and Ln(SO₄)₂ ^?) predominate in these species, accounting for most of proportions for the total REEs species. The high concentrations of dissolved SO₄ ^2? and low pH play a decisive role in controlling the presence of REEs in AMD, as these conditions are necessary for formation of stable REEs-sulfate complexes in current study. The migration and transportation of REEs in AMD are more likely constrained by adsorption and co-precipitation of Fe-Al hydroxides/hydroxysulfate. In addition, the MREEs is preferentially captured by poorly crystalline Fe-Al hydroxides/hydroxysulfate, which favors that sediments also preserve NASC-normalized patterns with MREEs enrichment in the stream.

     

Numerical simulations of pyrite oxidation and acid mine drainage in unsaturated waste rock piles

Numerical simulations of layered, sulphide-bearing unsaturated waste rock piles are presented to illustrate the effect of coupled processes on the generation of acid mine drainage (AMD). The conceptual 2D systems were simulated using the HYDRUS model for flow and the POLYMIN model for reactive transport. The simulations generated low-pH AMD which was buffered by sequential mineral dissolution and precipitation. Sulphide oxidation rates throughout the pile varied by about two orders of magnitude (0.004-0.4 kg m-3 year-1) due to small changes in moisture content and grain size. In the fine-grained layers, the high reactive surface area induced high oxidation rates, even though capillary forces kept the local moisture content relatively high. In waste rock piles with horizontal layers, most of the acidity discharged through vertical preferential flow channels while with inclined fine grained layers, capillary diversion channeled the AMD to the outer slope boundary, keeping the pile interior relatively dry. The simulation approach will be useful for helping evaluate design strategies for controlling AMD from waste rock.     

Acid neutralization within limestone sand reactors receiving coal mine drainage

Pulsed bed treatment of acid mine drainage (AMD) uses CO2 to accelerate limestone dissolution and intermittent fluidization to abrade and carry away metal hydrolysis products. Tests conducted with a prototype of 60 L/min capacity showed effective removal of H+ acidity over the range 196-584 mg/L (CaCO3) while concurrently generating surplus acid neutralization capacity. Effluent alkalinity (mg/L CaCO3) rose with increases in CO2 (DC, mg/L) according to the model Alkalinity=31.22+2.97(DC)0.5, where DC was varied from 11-726 mg/L. Altering fluidization and contraction periods from 30s/30s to 10s/50s did not influence alkalinity but did increase energy dissipation and bed expansion ratios. Field trials with three AMD sources demonstrated the process is capable of raising AMD pH above that required for hydrolysis and precipitation of Fe3+ and Al3+ but not Fe2+ and Mn2+. Numerical modeling showed CO2 requirements are reduced as AMD acidity increases and when DC is recycled from system effluent.     

Mining, the environment and the treatment of mine effluents

The environmental impact of mining on the ecosystem, including land, water and air, has become an unavoidable reality. Guidelines and regulations have been promulgated to protect the environment throughout mining activities from start-up to site decommissioning, in particular, the occurrence of acid mine drainage (AMD), due to oxidation of sulfide mineral wastes, has become the major area of concern to many mining industries during operations and after site decommissioning. AMD is characterised by high acidity and a high concentration of sulfates and dissolved metals. If it cannot be prevented or controlled, it must be treated to eliminate acidity, and reduce heavy metals and suspended solids before release to the environment. This paper discusses conventional and new methods used for the treatment of mine effluents, in particular the treatment of AMD.     

Haneş and Valea Vinului (Romania) closed mines Acid Mine Drainages (AMDs) – Actual condition and passive treatment remediation proposal

Acid Mine Drainages (AMDs) from Hane? and Valea Vinului (Romania) closed mines were considered for characterization and treatment using a local zeolitic volcanic tuff, ZVT, (M?cica?, Cluj County, Romania). Water samples were collected from two locations, before and after discharging point in case of Hane? mine, and on three horizons in case of Valea Vinului mine. Physico-chemical (pH, total solid, heavy metal ions concentration) analyses showed that the environment is strongly affected by these AMD discharges even if the mines were closed years ago. Iron, manganese and zinc were the main pollutants identified in Hane? mine AMD, while zinc is the one mainly present in case of Valea Vinului AMD. A batch technique (no stirring) in which the ZVT was put in contact with the AMD sample was proposed as a passive remediation technique. ZVT successfully remove heavy metal ion from AMD. According to heavy metal ion concentrations, removal efficiencies are reaching 100%, varying as follows, Fe²⁺ > Zn²⁺ > Mn²⁺. When the ZVT was compared with two cationic resins (strong, SAR and weak acid, WAR) the following series was depicted, SAR > ZVT > WAR.     

磁黄铁矿氧化机理及酸性矿山废水防治的研究进展

磁黄铁矿是矿山尾矿堆中最为常见且分布很广的一种硫化铁矿物.由于硫化物矿物氧化后不仅产生酸性废水,还会释放出大量可溶的、生物可利用形态的微量金属,并且酸性环境会进一步增强这些有毒金属的移动性,因此是造成矿山周围水体环境污染的罪魁祸首.为了阻止或降低磁黄铁矿的自然风化反应速度从而达到源头治理酸性矿山废水的目的,首先必须研究它在各种条件下的氧化机理、氧化产物和氧化速度.对近年来国外在磁黄铁矿晶体结构、反应活性以及酸性矿山废水的产生与防治等方面的研究进行了综述.     

Corrosion control when using passively treated abandoned mine drainage as alternative makeup water for cooling systems

Passively treated abandoned mine drainage (AMD) is a promising alternative to fresh water as power plant cooling water system makeup water in mining regions where such water is abundant. Passive treatment and reuse of AMD can avoid the contamination of surface water caused by discharge of abandoned mine water, which typically is acidic and contains high concentrations of metals, especially iron. The purpose of this study was to evaluate the feasibility of reusing passively treated AMD in cooling systems with respect to corrosion control through laboratory experiments and pilot-scale field testing. The results showed that, with the addition of the inhibitor mixture orthophosphate and tolyltriazole, mild steel and copper corrosion rates were reduced to acceptable levels (< 0.127 mm/y and < 0.0076 mm/y, respectively). Aluminum had pitting corrosion problems in every condition tested, while cupronickel showed that, even in the absence of any inhibitor and in the presence of the biocide monochloramine, its corrosion rate was still very low (0.018 mm/y).     

An integrative assessment of a watershed impacted by abandoned mined land discharges

The Ely Creek watershed in Lee County, VA, USA, contains an abundance of abandoned mined land areas with acid mine drainage (AMD) that contaminate the majority of the creek and its confluence into Stone Creek. Acidic pH measurements ranged from 2.73 to 5.2 at several stations throughout the watershed. Sediments had high concentrations of iron (approximately 10,000 mg kg-1), aluminum (approximately 1,500 mg kg-1), magnesium (approximately 400 mg kg-1) and manganese (approximately 150 mg kg-1), and habitat was partially to non-supporting at half of the stations due to sedimentation. Benthic macroinvertebrate surveys at six of 20 stations sampled in the watershed yielded no macroinvertebrates, while eight others had total abundances of only one to nine organisms. Four reference stations contained > or = 100 organisms and at least 13 different taxa. Asian clam in situ toxicity testing supported field survey results. Laboratory, 10-day survival/impairment sediments tests with Daphnia magna and Chironomus tentans and 48-h water column bioassays with Ceriodaphnia dubia indicated environmental stress to a lesser degree. Ten parameters that were directly influenced by AMD through physical, chemical, ecological and toxicological endpoints were assimilated into an ecotoxicological rating (ETR) to form a score of 0-100 points for the 20 sampling stations, and the lower the score the greater the AMD stress. Twelve of the 15 sampling stations influenced by AMD received an ETR score of 13.75-57.5, which were categorized as severely stressed (i.e. comprised the < 60 percentile category) and worthy of the highest priority for future ecological restoration activities in the watershed.     

Behavioural responses of indigenous benthic invertebrates (Echinogammarus meridionalis, Hydropsyche pellucidula and Choroterpes picteti) to a pulse of Acid Mine Drainage: a laboratorial study

The drainage of abandoned mines leads to several ecological problems, particularly the acidification of surface freshwater systems and heavy metal contamination. In order to study the possibility of using the behavioural early warning responses of Portuguese indigenous benthic invertebrates to detect an acute short-term pulse of Acid Mine Drainage (AMD), experiments with the Multispecies Freshwater Biomonitor MFB™ were performed and locomotion and ventilation were measured as endpoints. AMD was collected from the “São Domingos” mine (Southeast Portugal) and the following species were selected: Echinogammarus meridionalis (Pinkster, 1973), Hydropsyche pellucidula (Curtis, 1834) and Choroterpes picteti (Eaton, 1870). For simulating the pulsed exposure, AMD was added to river water where invertebrates were collected and pH was lowered until reaching 3.5. The effects of H⁺ and heavy metals were discriminated using HCl positive controls. In addition to behaviour, mortality was registered. E. meridionalis was the most sensitive species in terms of mortality and behavioural endpoints, followed by C. picteti and H. pellucidula. E. meridionalis early warning responses consisted of increased locomotion with subsequent increase in ventilation, whereas for C. picteti only an increase in locomotion was observed. H. pellucidula showed no early warning responses. This work demonstrates the suitableness of using benthic invertebrates' behavioural early warning responses for detecting spikes of pollutants like AMD.     

Characterization of iron-metabolizing communities in soils contaminated by acid mine drainage from an abandoned coal mine in Southwest China

Environmental Science and Pollution Research - Acid mine discharge (AMD) has been demonstrated to have significant impacts on microbial community composition in the surrounding soil environment....     

Sulfate-reducing bacterial community shifts in response to acid mine drainage in the sediment of the Hengshi watershed,South China

Environmental Science and Pollution Research - Sulfate-reducing bacteria (SRB) are an attractive option for treating acid mine drainage (AMD) and are considered to be of great significance in the...     

Multiphase transfer processes in waste rock piles producing acid mine drainage: 2. Applications of numerical simulation

Acid mine drainage (AMD) results from the oxidation of sulfides, mainly pyrite, present in mine wastes, either mill tailings or waste rock. This is the second of two papers describing the coupled physical processes taking place in waste rock piles undergoing AMD production. Since the oxidation of pyrite involves the consumption of oxygen and the production of heat, the oxidation process initiates coupled processes of gas transfer by diffusion and convection as well as heat transfer. These processes influence the supply of oxygen that is required to sustain the oxidation process. This second paper describes a numerical simulator used to represent the interaction of these coupled transfer processes. Numerical simulations are applied to two large sites with extensive characterization programs and widely different properties and behavior that were described in the first paper. The South Dump of the Doyon mine in Canada is permeable and has a high pyrite oxidation rate, thus making temperature-driven air convection the main oxygen supply mechanism. The Nordhalde of the Ronnenberg mining district in Germany contains lower permeability material which is less reactive, thus leading to a more balanced contribution of gaseous diffusion and convection as oxygen supply mechanisms. Overall, simulations allow a coherent representation of the conditions monitored within the waste rock piles and the confirmation of their physical properties. Conceptual simulations are also carried out to illustrate the potential effect of border membranes and layered co-mingling as mitigation methods used to control AMD production in either active or future waste rock piles.     

Diel cycles of arsenic speciation due to photooxidation in acid mine drainage from the Iberian Pyrite Belt (Sw Spain)

Twenty four hours diel cycles of arsenic speciation in Acid Mine Drainage (AMD) due to photooxidation have been reported for the first time. AMD samples were taken during 48 h (31st March and 1st April, 2005) at 6 h intervals from the effluent of a massive abandoned polymetallic sulphide mine of the Iberian Pyrite Belt (Sw Spain). Samples were preserved in situ using cationic exchange prior to analysis by coupled high performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation. The results indicated the presence of inorganic arsenic species with daily means of 262mugl(-1) for As(V) and 107 microg l(-1) for As(III). No marked diel trend was observed for As(V). However, a marked diel trend was observed for As(III) in the two studied days, with maximum concentrations during nighttime (141-143 microg l(-1)) and minimum concentrations at daytime (72-77 microg l(-1)). This difference in concentration during daytime and nighttime is ca. 100%. A similar diel cycle was observed for iron. An explanation for the arsenic diel cycles observed is the light induced photooxidation of As(III) and the elimination of As(V) due to its adsorption onto Fe precipitates during the daytime. Furthermore, the diel changes in arsenic speciation emphasize the importance of designing suitable sampling strategies in AMD systems.     

Macroinvertebrate community response to acid mine drainage in rivers of the High Andes (Bolivia)

Several High Andes Rivers are characterized by inorganic water pollution known as acid mine drainage (AMD). The aim of this study was to assess the relationship between metal concentrations in the sediments and the macroinvertebrate communities in two river basins affected by AMD. In general, the taxon diversity of the macroinvertebrate community at the family level was low. The concentrations of Cd, Cu, Zn, Pb and Ni at mining sites were higher than at unpolluted sites. The pH of the water was alkaline (7.0-8.5) in unpolluted sites, whereas it dropped to very low values (<3) at mining sites. Redundancy Analysis (RDA) showed that pH was the best predictor of macroinvertebrate community richness. The number of macroinvertebrate families decreased gradually with increasing acidity, both in pools and riffles, though it is suggested that riffle communities were more affected because they are in closer contact with the acid water.