Mitigation Of Acid Mine Drainage Research Articles

Recycling Feldspar Mining Waste as Buffering Agent for Acid Mine Drainage Mitigation

Recycling Feldspar Mining Waste as Buffering Agent for Acid Mine Drainage Mitigation

Continuous co-treatment of mine drainage with municipal wastewater

Acid mine drainage (AMD) and municipal wastewater (MWW) are commonly co-occurring waste streams in mining regions. Co-treating AMD at existing wastewater facilities represents an innovative solution for simultaneous AMD reclamation and improved MWW treatment. However, unknowns related to biological processes and continuous treatment performance block full-scale use. The overarching goal of this work was to address questions related to efficacy and performance of continuous processing of AMD in a biological MWW treatment system. Synthetic AMD was co-treated with synthetic MWW in a continuously-operating bench-scale sequencing batch reactor (SBR). SBRs treated MWW with two strengths of AMD (91 and 720 mg/L as CaCO3 Acidity) to capture the variations of coal AMD chemistry and strength observed in the field. Each co-treatment phases lasted 40+ days, during which clarified effluent and settled sludge quality was routinely monitored to determine impacts of co-treatment relative to conventional MWW treatment performance. Co-treatment produced effluent that met key standards for secondary treatment including biochemical oxygen demand (BOD) < 5 mg/L, total suspended solids (TSS) < 20 mg/L, and pH ∼7.0. Addition of AMD also improved treatment performance, increasing Phosphate (PO4) removal by >60% and pathogen removal by an order of magnitude. Furthermore, AMD co-treatment did not exhibit any major impacts on the overall diversity of the wastewater microbial community. Co-treatment sludge had slightly higher settleability and a lower bound water content, but notable changes in sludge morphology was observed. This study demonstrates co-treatment allows for continuous mitigation of AMD without adversely impacting MWW treatment performance in conventional biological MWW processes.

Geochemical and petrological studies of high sulfur coal and overburden from Makum coalfield (Northeast India) towards understanding and mitigation of acid mine drainage

Opencast coal mining produces trash of soil and rock containing various minerals, that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage (AMD) through oxidation pyrite minerals. The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India. In order to have a comprehensive overview of the AMD problem in Makum coalfield, the physico-chemical, geochemical, and petrological characteristics of the coal and overburden (OB) samples collected from the Makum coalfield (Northeast India) were thoroughly investigated. The maceral compositions reveal that coal features all three groups of macerals (liptinite, vitrinite, and inertinite), with a high concentration of liptinite indicating the coal of perhydrous, thereby rendering it more reactive. Pyrite (FeS2) oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and (OB) samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods, and to replicate the actual mine site leaching. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment. The Rare earth element (REE) enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB. These experiments reveal the change in conductivity, acid producing tendency, total dissolved solid(TDS), total Iron(Fe) and dissolved Sulfate(SO42−) ions on progress of the leaching experiments. Moreover, the discharge of FeS2 via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics. A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station. Apart from neutralisation of AMD water, this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water.

Emerging Strategies for Mitigating Acid Mine Drainage Formation and Environmental Impacts: A Comprehensive Review of Recent Advances

Acid mine drainage (AMD) is a significant threat to the environment due to its high acidity and metal ion content. To effectively eliminate pollutants from AMD, various approaches are necessary. This review aims to provide a comprehensive understanding of recent advances in AMD mitigation. While treatment technologies have developed to eliminate AMD, they often produce sludge as a by-product and require expensive maintenance. As a cost-effective alternative, the recovery of AMD resources can reduce toxicity and promote reuse of heavy metals and rare earth elements. This review also analyzes the challenges and prospects of AMD mitigation implementation, including current mitigation conditions and knowledge gaps. Researchers can benefit from this review by gaining insight into research progress in this area, identifying strengths and weaknesses of current AMD mitigation applications, and exploring future research directions.

Genome-guided prediction of acid resistance mechanisms in acidophilic methanotrophs of phylogenetically deep-rooted Verrucomicrobia isolated from geothermal environments.

Verrucomicrobia are a group of microorganisms that have been proposed to be deeply rooted in the Tree of Life. Some are methanotrophs that oxidize the potent greenhouse gas methane and are thus important in decreasing atmospheric concentrations of the gas, potentially ameliorating climate change. They are widespread in various environments including soil and fresh or marine waters. Recently, a clade of extremely acidophilic Verrucomicrobia, flourishing at pH < 3, were described from high-temperature geothermal ecosystems. This novel group could be of interest for studies about the emergence of life on Earth and to astrobiologists as homologs for possible extraterrestrial life. In this paper, we describe predicted mechanisms for survival of this clade at low pH and suggest its possible evolutionary trajectory from an inferred neutrophilic ancestor. Extreme acidophiles are defined as organisms that thrive in extremely low pH environments (≤ pH 3). Many are polyextremophiles facing high temperatures and high salt as well as low pH. They are important to study for both providing fundamental insights into biological mechanisms of survival and evolution in such extreme environments and for understanding their roles in biotechnological applications such as industrial mineral recovery (bioleaching) and mitigation of acid mine drainage. They are also, potentially, a rich source of novel genes and pathways for the genetic engineering of microbial strains. Acidophiles of the Verrucomicrobia phylum are unique as they are the only known aerobic methanotrophs that can grow optimally under acidic (pH 2–3) and moderately thermophilic conditions (50–60°C). Three moderately thermophilic genera, namely Methylacidiphilum, Methylacidimicrobium, and Ca. Methylacidithermus, have been described in geothermal environments. Most of the investigations of these organisms have focused on their methane oxidizing capabilities (methanotrophy) and use of lanthanides as a protein cofactor, with no extensive study that sheds light on the mechanisms that they use to flourish at extremely low pH. In this paper, we extend the phylogenetic description of this group of acidophiles using whole genome information and we identify several mechanisms, potentially involved in acid resistance, including “first line of defense” mechanisms that impede the entry of protons into the cell. These include the presence of membrane-associated hopanoids, multiple copies of the outer membrane protein (Slp), and inner membrane potassium channels (kup, kdp) that generate a reversed membrane potential repelling the intrusion of protons. Acidophilic Verrucomicrobia also display a wide array of proteins potentially involved in the “second line of defense” where protons that evaded the first line of defense and entered the cell are expelled or neutralized, such as the glutamate decarboxylation (gadAB) and phosphate-uptake systems. An exclusive N-type ATPase F0-F1 was identified only in acidophiles of Verrucomicrobia and is predicted to be a specific adaptation in these organisms. Phylogenetic analyses suggest that many predicted mechanisms are evolutionarily conserved and most likely entered the acidophilic lineage of Verrucomicrobia by vertical descent from a common ancestor. However, it is likely that some defense mechanisms such as gadA and kup entered the acidophilic Verrucomicrobia lineage by horizontal gene transfer.

Acid mine drainage mitigation: A review

Acid mine drainage (AMD) or acid rock drainage (ARD) refers to the effluents from coal and metal mines. AMD is a common phenomenon which occurs naturally as a process of rock weathering, but is increased in large scale due to human activities such as construction contracts (transportation corridors, dam build, etc.) and mining operations. This phenomenon denotes the acidic water that is produced during exposure of sulphide minerals (mainly pyrite) to air and water through a natural process, and creates sulphuric acid. AMD is a hazard to animals, aquatic life and human beings as it increases the acidity and dissolves metals. Preventing and treating AMD is an important issue in a mine site not only during operation life but also after the mine is abandoned.

Kinetics of Pyrite Oxidation in Simulated Mine Tailings Pond Conditions

Pyrite oxidation is the predominant source of acid mine drainage (AMD), which is one of the severe environmental impacts of mining. AMD destroys flora and fauna in the nearby ecosystem, and it causes grave health problems to the people. To further the understanding and help in the mitigation of AMD, this electrochemical study investigates the effect of the type and concentration of oxidant, and the presence of impurity (chalcopyrite) to the rate of pyrite oxidation, while simulating the conditions in tailings ponds. Open Cell Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) analysis were done using a three-electrode cell set-up, which is composed of a pyrite rotating disc electrode (RDE), mercury/mercurous sulfate reference electrode in saturated potassium sulfate, and a platinum counter electrode, with a sulfuric acid working electrolyte. Polarization resistance obtained after fitting an electrical circuit to the EIS data was related to the rate of pyrite oxidation, while OCP was used to describe its oxidation mechanism. It was found out that the oxidation of pyrite by ferric ions preferentially occurred rather than by dissolved oxygen. The parameter setting with the lowest relative oxidation rate were: electrolyte with no ferric addition, and with nitrogen purging; and RDE with 10 % chalcopyrite addition. Reaction orders calculated for the effect of ferric ions and dissolved oxygen were equal to 1; but ferric has a higher slope value in the plot. Presence of chalcopyrite in the RDE caused the preferential oxidation of chalcopyrite instead of the pyrite due to their galvanic interaction. To minimize pyrite oxidation, ferric and dissolved oxygen concentration should be minimized, and chalcopyrite impurities should be increased. Keywords: Electrochemical Impedance Spectroscopy, Acid Mine Drainage, Kinetics, Rotating-Disc Electrode, Pyrite

Non-carbonate geochemical options for long-term sustainable acid and metalliferous drainage control at-source

Acid mine drainage (AMD) from mine wastes is a critical environmental issue worldwide. It is caused principally by the oxidation of pyrite (FeS2) through a combination of complex reactions (physical, chemical, and biological), often associated with toxic metals/metalloids with varying toxicity, such as As, Cd, Pb and Zn. This paper is specifically focused on the role of reactive silicate minerals (including aluminosilicates) in contributing to pyrite surface passivation (at-source control for reduced AMD generation) and neutralisation processes for long-term AMD mitigation. The neutralisation potential of (alumino)silicate minerals (those readily accessible on-site) to buffer acid generation at reduced pH levels in the long-term is also discussed in the review. Overall, the review aims to present cost-effective solutions, using readily available (alumino)silicate minerals, to provide long-term neutralisation and precursors required for pyrite surface passivation (source control) for sustainable at-source geochemical AMD control.

Efficient inhibition of heavy metal release from mine tailings against acid rain exposure by triethylenetetramine intercalated montmorillonite (TETA-Mt)

The potential application of triethylenetetramine intercalated montmorillonite (TETA-Mt) in mine tailings treatment and AMD (acid mine drainage) remediation was investigated with batch experiments. The structural and morphological characteristics of TETA-Mt were analyzed with XRD, FTIR, DTG-TG and SEM. The inhibition efficiencies of TETA-Mt against heavy metal release from mine tailings when exposed to acid rain leaching was examined and compared with that of triethylenetetramine (TETA) and Mt. Results showed that the overall inhibition by TETA-Mt surpassed that by TETA or Mt for various heavy metal ions over an acid rain pH range of 3–5.6 and a temperature range of 25–40°C. When mine tailings were exposed to acid rain of pH 4.8 (the average rain pH of the mining site where the mine tailings were from), TETA-Mt achieved an inhibition efficiency of over 90% for Cu2+, Zn2+, Cd2+ and Mn2+ release, and 70% for Pb2+ at 25°C. It was shown that TETA-Mt has a strong buffering capacity. Moreover, TETA-Mt was able to adsorb heavy metal ions and the adsorption process was fast, suggesting that coordination was mainly responsible. These results showed the potential of TETA-Mt in AMD mitigation, especially in acid rain affected mining area.

The use of a passive treatment system for the mitigation of acid mine drainage at the Williams Brothers Mine (California): pilot-scale study

A pilot-scale study was undertaken to assess the feasibility of using a passive treatment system to mitigate the acid mine drainage at the abandoned Williams Brothers Mine site, a remote site located in Sierra National Forest (California). The advantages of implementing passive treatment systems in remote or abandoned mine sites are their low energy and maintenance requirements compared to conventional systems. A pilot-scale system was designed and implemented at the site, which consisted of: (1) an aeration rock channel to facilitate oxidation of ferrous iron to ferric iron; (2) a sedimentation tank to collect iron oxyhydroxide precipitates that could lead to the clogging of the system; (3) a peat biofilter for the removal of dissolved iron and copper; (4) a sulphate-reducing bacteria reactor for the generation of alkalinity and consequent pH increase, and the removal of dissolved nickel, zinc, and residual dissolved iron and copper; and, (5) a re-aeration limestone channel to add alkalinity prior to effluent discharge into the natural receiving environment. The pilot-scale system was monitored over a 17-month period (500 days from July 2007 to November 2008) and performance was determined by monitoring the pH, sulphate and dissolved metal concentrations of the influent acid mine drainage and the effluents from the peat biofilter and sulphate reducing bacteria reactor. A decrease in sulphate concentration was noted in the sulphate reducing bacteria reactor, suggesting sulphate reducing bacteria activity and alkalinity generation. The effluent pH from the system increased from as low as 4.5 to above 6.0, but remained below water quality objectives for the San Joaquin River Basin. Dissolved copper, nickel and zinc removal to below water quality objectives was noted in the peat biofilter to below water quality objectives. Dissolved iron and manganese removal was also observed in the sulphate reducing bacteria reactor. The feasibility of employing this system as a sustainable low cost and low maintenance treatment alternative at the Williams Brothers abandoned mine site to ensure that drainage effluent will meet water quality objectives showed promise. However, long-term monitoring would be required to demonstrate and ensure their long-term effectiveness.

Draft Genome Sequence of a Novel Desulfobacteraceae Member from a Sulfate-Reducing Bioreactor Metagenome.

Sulfate-reducing bacteria are important players in the global sulfur cycle and of considerable commercial interest. The draft genome sequence of a sulfate-reducing bacterium of the family Desulfobacteraceae, assembled from a sulfate-reducing bioreactor metagenome, indicates that heavy-metal– and acid-resistance traits of this organism may be of importance for its application in acid mine drainage mitigation.

Mitigation of Acid Mine Drainage via a Revegetation Programme in a Closed Coal Mine in Southern New Zealand

Acid mine waters (pH 3–5) at the closed Wangaloa coal mine have resulted from surface runoff and groundwater seepage in contact with pyrite-bearing waste rock piles. The low nutrient content, physical factors, and elevated boron levels, all combined with the low pH (down to pH 2) of most waste rocks have limited early planned revegetation and natural plant colonisation. A renewed programme of site rehabilitation, started in 2000, focussed on establishment of near-complete ground cover and functioning ecosystems. Small patches (tens of m2) of low-pH, boron-rich, unvegetated substrates persist after more than 10 years of rehabilitation and introduction of a wide variety of species, but natural colonisation is slowly advancing on these remnants. The rehabilitation has coincided with and contributed to a rise in runoff water pH from ≈4.5 to ≈5.6. This decrease in severity of acid mine drainage (AMD) has apparently become sustainable without further intervention. Near-complete vegetative cover occurred by a combination of a major planting programme and natural colonisation from nearby islands of established native species. Both processes were accompanied by development of functioning ecosystems, and supported by increasing invertebrate diversity and abundance, which are ensuring the persistence of the ameliorative effects on AMD at the site. Vegetation established via natural processes can function ecologically at a higher level than comparable planted vegetation but may not lead to the desired plant cover on some substrates.

Characterization of Geochemical Disposal on Indicate and Mitigation Acid Mine Drainage at Coal Mining South Sumatera Indonesia

Acid mine drainage (AMD) is a term U.S. used to describe command infiltration of acid surface water in the mining areas. The study of process for formation acid mine drainage can't be approached by two methods, the static and kinetic test. In the static test can't determinate acid formation with characterization of rock, can't be approach by Acid base accounting (ABA) method. In the methods of rock is analysis contents of sulfur, pH, Acid Neutralizing capacity and Net Acid Generation (ANG). The Maximum Acid Potential (MPA) can't be approach percent's x 30.6 Kg H2SO4/metric ton. NAPP is difference between the MPA and ANC if NAPP positive the rock is PAF, while negative is NAF. Result of analyzed the Five samples had A,B,C,D and E each have NAPP is 22.48; 84.39; 13:83; 11.33 and -9.22 Kg H2SO4/metric ton. Analyzed samples From A, B, C, and D is category PAF and samples D is UC PAF. The last result property can't be describe command for all samples can't be united states to source of acid mine drainage. And then the future have to methods how to manage the rock for mitigation of acid mine drainage.

The use of passive treatment alternatives for the mitigation of acidic drainage at the Williams Brother mine, California: Bench-scale study

Abstract The aim of the study was to evaluate passive treatment system alternatives to mitigate acid mine drainage (AMD) characterized by low SO 4 2 - and metal concentrations associated with adit drainage at the Williams Brothers Mine located in the Sierra National Forest, California. Surface water from the site drains into the San Joaquin River Basin and a goal of this study was to mitigate AMD to meet water quality objectives for the San Joaquin River Basin. Effluent sampling from the opening of the lowermost adit identified (AMD) characterized by a pH of 3.90, average SO 4 2 - concentration of 101 mg/L and relatively low average metal concentrations of 4.60, 0.074, 0.047 and 0.133 mg/L for Fe, Cu, Ni and Zn, respectively. The bench-scale study involved the testing of three passive treatment systems: (1) a peat biofilter followed by an anoxic limestone drain (ALD); (2) a SO 4 2 - -reducing bacteria (SRB) bioreactor followed by an ALD; and (3) a single SRB bioreactor. Synthetic AMD was produced to represent the AMD characteristics observed at the site. The peat–ALD system efficiently increased the pH of the effluent to an average of 6.95. Metals were reduced to average concentrations of 0.06, 0.008, 0.013 and 0.057 mg/L, respectively, for Fe, Cu, Ni and Zn. The SRB–ALD system increased the effluent pH to an average of 6.47, decreased SO 4 2 - concentrations to an average of 11.6 mg/L and decreased the concentrations of Fe, Cu, Ni and Zn to averages of 1.04, 0.004, 0.016 and 0.025 mg/L, respectively. The SRB system efficiently increased the pH to an average of 6.56 and decreased SO 4 2 - concentrations to an average of 18.8 mg/L. Metal concentrations for Fe, Cu, Ni and Zn were reduced to 0.63, 0.006, 0.010 and 0.027 mg/L, respectively. The peat–ALD and SRB systems were capable of increasing the pH of the AMD to 6.5 to meet water quality objectives. The peat–ALD system was capable of removing Fe and Cu to below water quality objectives, however, removal of other metals was insufficient. The SRB containing systems were incapable of removing Fe to water quality objectives, while sufficient removal of Cu, Ni and Zn was attained. From these results, the most effective treatment system would incorporate a peat biofilter, for Fe and Cu removal and a SRB bioreactor for Cu, Ni and Zn removal. The results of this study demonstrate that passive treatment mitigation of AMD can best be accomplished via the use of a combined treatment system that incorporates a peat biofilter, SRB bioreactor and anoxic limestone drain, thereby accomplishing targeted removal of constituents in individual system components.

Mitigating the generation of acid mine drainage from copper sulfide tailings impoundments in perpetuity: A case study for an integrated management strategy

Acid mine drainage (AMD) is one of the most serious and pervasive challenges facing the minerals industry. Current philosophy in sulfide tailings management takes an end-of-pipe approach which is yet to be shown to be sufficient to prevent post-closure impacts from AMD and guarantee “walk-away” status. An improved, integrated approach to tailings management and AMD mitigation is proposed, whereby conventional tailings are separated with the use of flotation into a largely benign tailings stream and a sulfide-rich product. The key features of this conceptual approach are outlined and partly demonstrated for the case of porphyry-type copper sulfide tailings. The significance of this approach is that it provides a basis for the identification of opportunities for the development of new process designs incorporating waste management systems for mitigating AMD in a manner consistent with the principles of cleaner production and sustainable development.

Developing durable paste backfill from sulphidic tailings

Mitigation of acid mine drainage (AMD) generated from the surface disposal of mine tailings (MT) containing sulphide minerals is one of the major challenges facing the mining industry today. AMD results in acidic effluents containing elevated concentrations of sulphates and metallic and metalloid elements. It can thus cause severe contamination of soils, surface and groundwater, along with devastating environmental damage. Paste backfill is a relatively new technology whereby MT are solidified/stabilised using binders and processed back into the mined space. The cogent reasons supporting this technique include lower operating costs, efficient ground support, reduction in the amount of waste to be disposed of on the surface and significant environmental benefits through better control of pollutants. An additional advantage is that industrial by-products such as cement kiln dust (CKD) and fly ash can be used alone or in combination with Portland cement to enhance the properties of paste backfill and reduce binder cost. The goal of the present research is to examine the strength development of paste backfill prepared using sulphidic MT and industrial by-products (e.g. CKD and fly ash) with or without Portland cement. Furthermore, the pH and sulphate content of paste backfill mixtures was monitored to provide information on both the tailings oxidation process and potential sulphate attack in paste backfill. The findings indicate that utilising industrial by-products in the preparation of paste backfill reduced the availability of calcium aluminate compounds susceptible to sulphate attack associated with cemented paste backfill containing ordinary Portland cement. It is also shown that developing an efficient technique for AMD control through making paste backfill from sulphidic MT can be both feasible and cost-effective.

Mineralogy of the hardpan formation processes in the interface between sulfide-rich sludge and fly ash: Applications for acid mine drainage mitigation

In the present study, experiments in non-saturated leaching columns were conducted to characterize the neoformed phases that precipitate at the interface between two waste residues having different chemical characteristics: an acid mine drainage producer residue (i.e., pyritic sludge) and an acidity neutralizer residue (i.e., coal combustion fly ash). A heating source was placed on top of one of the columns to accelerate oxidation and precipitation of newly formed phases, and thus, to observe longer-scale processes. When both residues are deposited together, the resulting leachates are characterized by alkaline pH, and low sulfate and metal concentrations. Two mechanisms help to improve the quality of the leachates. Over short-time scales, the leaching of pyrite at high pH (as a consequence of fly ash addition) favors the precipitation of ferrihydrite, encapsulating the pyrite grains and attenuating the oxidation process. Over longer time scales, a hardpan is promoted at the interface between both residues due to the precipitation of ferrihydrite, jarosite, and a Ca phase-gypsum or aragonite, depending on carbonate ion activity. Geochemical modeling of leachates using PHREEQC software predicted supersaturation in the observed minerals. The development of a relatively rigid crust at the interface favors the isolation of the mining waste from weathering processes, helped by the cementation of fly ash owing to aragonite precipitation, which ensures total isolation and neutralization of the mine residues.

Chemical characterisation of natural organic substrates for biological mitigation of acid mine drainage

The current approach of the biological treatment of acid mine drainage by means of a passive remediation system involves the choice of an appropriate organic substrate as electron donor for sulphate reducers. Nowadays this selection is one of the critical steps in the performance of such treatment, as this depends to a great extent on the degradability of the organic substrate. Thus, a prior characterisation of the organic substrate predicting its biodegradability would be desirable before embarking on an extensive large-scale application. The aim of this study was to correlate the chemical composition (lignin content) of four different natural organic substrates (compost, sheep and poultry manures, oak leaf) and their capacity to sustain bacterial activity in an attempt to predict biodegradation from chemical characterisation. The results showed that the lower the content of lignin in the organic substrate, the higher its biodegradability and capacity for developing bacterial activity. Of the four organic materials, sheep and poultry manures and oak leaf evolved reducing conditions and sustained active sulphidogenesis, which coupled with the decrease in sulphate concentration indicated bacterial activity. Sheep manure was clearly the most successful organic material as electron donor (sulphate removal >99%), followed by poultry manure and oak leaf (sulphate removal of 80%). Compost appeared to be too poor in carbon to promote sulphate-reducing bacteria activity by itself. Column experiments emphasised the importance of considering the residence time as a key factor in the performance of continuous systems. With a residence time of 0.73 days, sheep manure did not promote sulphidogenesis. However, extending residence time to 2.4 and 9.0 days resulted in an increase in the sulphate removal to 18% and 27%, respectively.

Maryland, the Power Plant Research Program, and the Chesapeake Bay watershed

Chesapeake Bay has long been recognized as a biologically rich ecosystem, one whose wide expanse of shallow estuarine waters is unique in the world. When the biological bounty of the Bay declined dramatically, federal, state, and local governments began restoration efforts on a mammoth scale. While the successes have been many, the lesson of the last few decades has been that this great estuary cannot be restored without addressing the multitude of human activities in the watershed that cumulatively distort its ecological processes and degrade its resources. Today governments, industry, and the public are focusing on three major restoration efforts: reducing nutrient inputs, reducing toxic pollutant loads, and restoring living resources. Recognizing that power generation is an important component of the activities affecting the Bay, the Maryland Department of Natural Resources (DNR) Power Plant Research Program (PPRP) is working in partnership with electric utilities to avoid, minimize, and mitigate adverse impacts on both local and regional scales. Historically, PPRP has participated in cooperative state and industry efforts at Conowingo Dam and other upstream dams on the Susquehanna River (the Bay’s largest freshwater tributary) that have helped quantify impacts to migratory fish, resulting in modifications to dam operations and installation of fish lifts to restore populations of American shad and other anadromous fish. Other restoration projects include mitigation of acid mine drainage in the upper reaches of the watershed, installation of lime dosers in affected streams, investigation of the beneficial uses of coal combustion products for mine reclamation, and operation of a successful hatchery and release program. Currently, PPRP recognizes that its research efforts need to look up the watershed at cumulative effects on a regional scale. Recent research on the regional level undertaken by DNR includes a statewide biological stream survey to provide comprehensive baseline information on the health of freshwater systems in Maryland, and development of reference-based ecological indicators. These indicators are critical for assessing the effects of different degrading activities and measuring progress towards environmental goals. A related cumulative impact model, currently under development, will couple indicators of biological integrity with spatial data on land uses, power-related impacts, and other anthropogenic stressors to evaluate watershed impacts on aquatic systems. As part of model development, the role of vegetated riparian corridors is being evaluated to support watershed-wide initiatives to restore riparian forest buffers on Chesapeake Bay tributaries. These biological survey data and other information are being used to identify biodiversity hotspots in the State and construct maps of ecologically sensitive areas for the evaluation of cumulative effects and targeting of conservation and restoration priorities.

97/03288 Macroscopic to microscopic studies of flue gas desulfurization byproducts for acid mine drainage mitigation

The use of flue gas desulfurization (FGD) systems to reduce SO{sub 2} emissions has resulted in the generation of large quantities of byproducts. These and other byproducts are being stockpiled at the very time that alkaline materials having high neutralization potential are needed to mitigate acid mine drainage (AMD). FGD byproducts are highly alkaline materials composed primarily of unreacted sorbents (lime or limestone and sulfates and sulfites of Ca). The American Coal Ash Association estimated that approximately 20 million tons of FGD material were generated by electric power utilities equipped with wet lime-limestone PGD systems in 1993. Less than 5% of this material has been put to beneficial use for agricultural soil amendments and for the production of wallboard and cement. Four USGS projects are examining FGD byproduct use to address these concerns. These projects involve (1) calculating the volume of flue gas desulfurization (FGD) byproduct generation and their geographic locations in relation to AMD, (2) determining byproduct chemistry and mineralogy, (3) evaluating hydrology and geochemistry of atmospheric fluidized bed combustion byproduct as soil amendment in Ohio, and (4) analyzing microbial degradation of gypsum in anoxic limestone drains in West Virginia.