Simulated Acid Mine Drainage Research Articles

Growth of three bacteria in arsenic solution and their application for arsenic removal from wastewater

The present paper compares the arsenic removal capacities of three bacterial strains namely, Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 form wastewater (simulated acid mine drainage) containing arsenic (As(III):As(V)::1:1), Fe, Mn, Cu and Zn in the concentration of 15 mg/l, 10 mg/l, 2 mg/l, 5 mg/l and 10 mg/l respectively, in bulk liquid phase. Growth patterns of these bacteria in presence of arsenic in solution as well as under starvation have also been investigated as the acid mine drainage normally does not contain organic carbon and also contains high arsenic. At the nutrient broth concentration of 1.25 g/l and in presence of 15 mg/l arsenic sufficient growth of these strains have been observed. However, growth of Ralstonia eutropha MTCC 2487 has been found slightly more than Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374. Arsenic removal capacities of Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 from simulated acid mine drainage are approximately 67%, 60% and 61% respectively. It has also been observed that arsenic concentration of 15 mg/l prolongs the stationary phase of these strains. pH and temperature for the above studies have been maintained at 7.1 +/- 0.1 and 29 +/- 1 degrees C, respectively.

Molecular microbial ecology of lignocellulose mobilisation as a carbon source in mine drainage wastewater treatment

The community structure of complex microbial consortia which develop in lignocellulose packed passive treatment systems for acid mine drainage remediation were investigated. An understanding of interactions between these populations is important in determining mechanisms by which such systems operate. A degrading packed bed reactor was packed with lignocellulositic material as a sole carbon source and fed continuously with simulated acid mine drainage. Samples were collected every two months at different depths of the reactor to isolate the total genomic DNA and PCR amplify section of 16S rDNA gene. PCR primers, GM5F and 907R incorporating GC clamp were used to amplify 586-bp region of 16S rDNA gene. Denaturing gradient gel electrophoresis (DGGE) indicated clearly a highly differentiated pattern of r-DNA – derived amplificates between different depths of the bioreactor. Predominant DGGE bands were further excised, reamplified, cloned and sequenced. Sequencing analysis revealed phylogenetic affiliation of specific bacterial populations in different depths of the bioreactor. Water SA Vol. 30 (5) 2005: pp.658-661

Assessment of changes in the microbial community of constructed wetland mesocosms in response to acid mine drainage exposure

Changes in the bacterial community in the interstitial water of 5 different constructed wetland mesocosms were studied over a 22-day period following exposure to simulated acid mine drainage (AMD). The community-level physiological profile (CLPP) of each mesocosm was assessed using substrate utilization patterns gathered via BIOLOG™ ECO plates. Principal component analysis (PCA) of the BIOLOG™ ECO plate data proved feasible and useful in characterizing the interstitial bacterial community in the constructed wetland mesocosms based on mesocosm characteristics such as fixed biological regime development and plant presence, and was also used to successfully track changes in the interstitial bacterial community in response to AMD exposure. Clustering analysis of the BIOLOG™ ECO plate data was used to characterize the interstitial bacterial community and to validate the mesocosm groupings observed through PCA ordination. The calculation of substrate-based diversity indices from the BIOLOG™ ECO plate data was used to assess the robustness and the degree of change shown by the metabolic fingerprint of the interstitial bacterial community within the mesocosms. The interstitial bacterial community in the constructed mesocosms was shown to be significantly affected after exposure to AMD. Exposure to AMD caused similar bacterial species to detach from the fixed biotic regime of the mesocosms. It was also shown that mesocosms planted with Phragmites australis did not experience as great an ecological shift in the microbial ecology of the interstitial water after exposure to AMD as did the unplanted mesocosms. The substrate-based diversity indices for the planted mesocosms were also found to be more stable, after exposure to AMD, than those for the unplanted mesocosms. It is possible that the interaction between the plant root system and the substrate biological regime, collectively called the rhizosphere, may create a more ecologically robust and stable treatment system.

含鉄酸性坑廃水における常温下でのフェライト生成に対する共存イオンの影響―含鉄坑廃水処理における常温フェライト法の適用（第２報）―

The feasibility of making ferrite at ambient temperature from aqueous solutions of simulated acid mine drainage was investigated following our previous report. In this paper, qualitative and quantitative effects of coexisting ions such as Mn(II), Zn(II), Al(III) and Si(IV), on ferrite formation were investigated.As the first step, influences of several coexisting ions on the settling volume of the precipitates were investigated. In the case of Mn(II) or Zn(II) coexisting system, which are well known to have the capacity to substitute to the part of the lattice of ferrite, the settling volume increased a little, but in the case of Al(III) or Si(IV) coexisting system, which are known to impede ferrite formation, the settling volume considerably increased. However, the interference of Al(III) or Si(IV) to ferrite formation was weakened in the sludge recycling system.Secondly, their influences on the yield of magnetite or ferrite, which are calculated by the total oxygen consumption in the aerial oxidation reaction test, were investigated. The yield of magnetite decreases with an increase of Al(III) or Si(IV), but their interferences on ferrite formation were weakened in the presence of restored magnetite seed.Thirdly, their influences on the reaction rate in the aging process were also examined by solid-solid reaction test in which Fe(OH)2, FeOOH and coexisting ions reacted directly in reduction atmosphere and at a fixed pH. The reaction coefficient considerably decreased not only by Al(III) or Si(IV), but also by Mn(II) or Zn(II), which are estimated not to impede ferrite formation.

Advances in Seeded Ambient Temperature Ferrite Formation for Treatment of Acid Mine Drainage

Advances in the seeded ambient temperature ferrite process for treatment of acid mine drainage (AMD) are described. Magnetite formation requires that the oxidation rate of ferrous to ferric does not exceed the rate at which ferrous iron is incorporated into the crystal structure (dehydroxylation-crystallization). If the oxidation rate is too high, then ferric-only oxides form, an effect exacerbated by the presence of calcium. NaOH was used to raise the pH of simulated AMD, which also contained calcium so as to simulate the use of lime (i.e., the dissolved Ca/ Fe2+ concentration was maintained at 1:1 bythe coaddition of CaCl2 because this is the Ca/Fe ratio that occurs when pH is elevated by the dissolution of lime). Raising the pH to 10.5 causes Fe2+ to precipitate as "ferrous intermediate" (FI), which is then partially oxidized to magnetite (Fe2+Fe3+2O4). The inhibitory effect of calcium is overcome by a combination of magnetite seed particles, high FI concentrations, and aging. High FI concentrations are easily obtained, even from AMD low in Fe2+, by a contact stabilization reactor-settler sequence. Results for simultaneous removal of cobalt, a metal found in significant concentrations in South African AMD, are also presented.

English

Recent laboratory and field studies have shown that injection of Edible Oil Substrate (EOS ® ) into the subsurface can provide an effective, low-cost alternative for the enhanced anaerobic bioremediation of a variety of pollutants including acid mine drainage (AMD). EOS ® is prepared from a mixture of slowly biodegradable emulsified oil (e.g. soybean oil) and easily biodegradable substrates. As AMD impacted water flows thought the treated zone, EOS ® stimulates growth of iron and sulfate reducing bacteria, increasing the pH, reducing sulfate, and immobilizing iron, copper, nickel, zinc and related toxic metals. All materials used in the process are Generally Recognized As Safe (GRAS), food-grade materials (21 CFR 184.1400) for in situ application. The impact of EOS ® treatment on AMD was evaluated in both batch and flow-through column experiments. Batch microcosms were constructed with AMD generating spoils from a former coal mine in Sequatchie Valley, TN, simulated acid mine drainage, and a small liquid inoculum from an anaerobic treatment wetland. Sulfate declined from 1,800 mg/L to 10 mg/L, pH increased from 2.6 to 6.4 and iron was precipitated in a 2:1 molar ratio with sulfate removal. These results demonstrate that EOS ® addition can be very effective in treating AMD and the initial pH does not significantly inhibit microbial growth. Laboratory columns were also packed with mine spoils and received a one time treatment of EOS ® with a microbial inoculum. Simulated AMD was then pumped through the columns with a four-day hydraulic retention time. During passage through the EOS ® treated columns, pH increased from less than 3 to near 6, SO4 was reduced by 75%, and aluminum, copper and zinc were reduced to below the analytical detection limit. In this system, effluent dissolved iron concentrations appear to be controlled by the amount of dissolved sulfide available for precipitation.

Magnetic Seed in Ambient Temperature Ferrite Process Applied to Acid Mine Drainage Treatment

Due to its environmental consequences, acid mine drainage (AMD) has been recognized as a major challenge to the global mining industry. Through the innovative use of magnetic seeds, a versatile ambient temperature ferrite (ATF) process has been developed to treat AMDs containing such nonferrous heavy metal ions as Cu2+, Zn2+, Ni2+, Mn2+, and Al3+. These metal ions proved detrimental to ferrite formation using the existing ATF process, particulary when lime was used as neutralizer. The use of magnetic seeds in the ATF process minimized the interference. The role of the chemical environment in ferrite formation from an AMD with the addition of magnetic seeds was investigated. Compared with the conventional seed processes, controlling the solution chemistry resulted in a reduced amount of seed needed to recover an equal amount of crystalline magnetic precipitates. With a relatively short processing period (less than 2.5 h), up to 100% of the precipitates were magnetically recovered from a simulated AMD. The ...

Advances in the Ambient Temperature Ferrite Process Applied to Acid Mine Drainage Treatment

Treating acid mine drainage (AMD) using ambient temperature ferrite (ATF) process is attractive but challenging due to the complex nature of AMD solution chemistry. Calcium, associated with sulfate and ferric oxy-hydroxides, has been shown to interfere with ferrite formation. A novel process has been developed based on the use of carbonates to scavenge the soluble calcium followed by neutralization with carefully controlled solution chemistry. With this process, magnetic precipitates of spinel structure are formed from a simulated AMD within a practically feasible reaction period, while producing an environmentally safe effluent.

Modeling Biooxidation of Iron in Packed-Bed Reactor

Acid mine drainage (AMD) from active and abandoned mines continues to be an important source of water pollution in the US and around the world. AMD typically has high levels of acidity, sulfate, and metals. A model based on Monod kinetics and originally developed for use with rotating biological contactors was modified for use with a packed-bed column reactor. The reactor was filled with expanded polystyrene beads to immobilize chemolithotrophic bacteria and fed up to 570 mg L{sup {minus}1} ferrous iron [Fe(II)] in simulated acid mine drainage. A tracer study indicated changing behavior as a function of hydraulic residence time (HRT), with a transition from complete mix flow behavior to plug flow behavior as HRT decreased. The Fe(II) oxidation efficiency exceeded 95% until the HRT was reduced below 0.5 h. The reactor performance could be predicted with the model using estimates from the literature for {cflx u} and Y. The experimentally determined half-saturation constant K{sub s} was found to range from 5 to 12 mg L{sup {minus}1}. The maximum volumetric capacity constant R{sub max} was estimated to be {approximately}360 mg Fe(II)h{sup {minus}1} L{sup {minus}1} beads under complete mix flow conditions but appeared to be as high as 724 mg Fe(II)h{supmore » {minus}1} L{sup {minus}1} beads as conditions approached plug flow at short HRTs.« less

An adsorption process for metal recovery from acid mine waste: The Berkeley Pit problem

AbstractAn adsorption process comprised of inorganic chemically active adsorbents (ICAAs) has been developed for recovery of Fe(III), Cu(II), Zn(II), Cd(II) and Pb(II) from acid mine drainage solutions similar to the Berkeley Pit near Butte, Montana. ICAAs are prepared by immobilization of chelating agents on the ceramic supports. The detailed laboratoryscale studies are executed to determine selectivity and operating conditions of each ICAA for individual metal ions. This paper presents results of separation studies using several ICAAs materials with simulated acid mine drainage solutions similar to the Berkeley Pit. Three most suitable ICAA materials have the potential to remove and recover desired metal ions from acidic streams without neutralization. Accordingly, an integrated adsorption process with three independently operating stages can be devised. Three fixed‐bed adsorbers, comprised of ICAA(A), ICAA(C), and ICAA(D), selectively removed Fe(III), Cu(II), and Zn(II) Cd(II) and Pb(II) respectively, from the acidic stream. In addition, the last bed, comprised of ICAA(D), acts as an acid scavenger and increases the pH of the effluent to greater than 7, which can then be discharged in an environmentally safe manner. The adsorbed metal ions can be recovered as pure metal salts by stripping with sulfuric acid, and the regenerated bed can then be used for future cycles.

Fundamental Study of an Ambient Temperature Ferrite Process in the Treatment of Acid Mine Drainage

The feasibility of making ferrite at ambient temperature from solutions of simulated acid mine drainage is explored. The X-ray diffraction and saturation magnetization of the precipitates obtained clearly show that the spinel ferrite can be made at ambient conditions and pH 9−11. The optimum molar ratio of Fe3+ to Fe2+, a critical parameter for ferrite formation, is found to be 1.75. The effect of [Zn2+] and [Ca2+] in solution on ferrite formation was investigated. The former has no effect on the magnetic properties of ferrite, but the saturation magnetization of the ferrite decreases with an increase of [Ca2+]. The results suggest that an ambient temperature ferrite process for acid mine drainage is worthy of further investigation.

Comparison of two methods for predicting trace elements from fly ash on acid mine spoils

Abstract Laboratory leaching experiments were conducted to simulate fly ash weathering in acidic environments and to determine the metal and metalloid release characteristics of several fly ash materials. Fly ash was placed in small cylinders and continuously leached with 0.1N sulfuric acid (H2SO4) or simulated acid mine drainage (AMD). Leachates were monitored for metals and metalloids. When a fly ash was leached with H2SO4 up to its neutralizing capacity only 10 to 30% of the total metals or metalloids were released. At equal levels of total acidity, more metals were released by H2SO4 than by AMD probably due to the creation of new oxides or hydroxides of iron (Fe) providing sites for adsorption of metals or metalloids.

Use of Cellulosic Substrates for the Microbial Treatment of Acid Mine Drainage

AbstractA mixed aerobic‐anaerobic microbial treatment process was developed previously for acid mine drainage (AMD) using straw as a substrate. The process was effective only if AMD was supplemented with sucrose. The present study was conducted to determine which, if any, of three cellulosic materials could sustain the microbial treatment of AMD without the addition of a sucrose amendment and to determine the effect of the retention time on the performance of the reactors. The performance of small reactors that treated simulated AMD in the continuous mode was evaluated using alfalfa (Medicago sativa L.) hay, timothy (Phleum pratense L.) hay, and straw with a 5‐d retention time. Parameters measured were pH, Fe, Al, sulfate, and ammonium. Timothy hay and straw sustained AMD mitigation for 3 wk, and thereafter all activity ceased. After the reactors ceased treating AMD, the mitigative activities were reinitiated by the addition of sucrose, but not by urea. Alfalfa sustained AMD mitigation for a longer time period than either straw or timothy. The effect of three retention times, 3.5, 7, and 35 d, was then investigated for reactors containing fresh alfalfa. Increasing the retention time resulted in better metal removal and a greater pH increase. With a 7‐d retention time, 75 L of simulated AMD were neutralized from a pH of 3.5 to a pH value greater than 6.5. Reactors operating with a 3.5‐d retention time treated only 58.3 L of simulated AMD before failing. Ammonium was detected in effluents of active reactors. The results of this study indicate that a low maintenance microbial treatment system can be developed with alfalfa as a substrate without the addition of a sucrose amendment.

Factors controlling the removal of sulfate and acidity from the waters of an acidified lake

Although Lake Anna, an impoundment in Central Virginia, receives acid mine drainage (AMD) from Contrary Creek, the effects of the AMD pollution on the lake are less severe than expected. Previous work at Lake Anna has shown that bacterial sulfate reduction in the lake sediments plays an important role in the recovery of the lake from the AMD inputs. Sulfate removal rates were measured in sediment microcosms under a variety of experimental conditions to determine the factors controlling the rate of sulfate and acidity removal from the lake water. Sulfate removal rates were not significantly different over the short term (3 weeks) in summer sediment microcosms incubated at 6 vs 26 °C. Winter sediment microcosms showed no significant sulfate removal during the 18 day experiment when incubated at either 6 or 28 °C. Thus there is a strong seasonal temperature effect in Lake Anna sediments but no significant short term effect. Simulated AMD, with and without Fe, was added to sediment microcosms collected from an unpolluted part of the lake. The microcosms with Fe had significantly higher rates of sulfate removal indicating that Fe plays an important role in transporting sulfate to the sediment and/or in preventing oxidation of the reduced sulfide. After 27 days, from 54 to 96% of the added sulfate in the simulated AMD was recovered as FeS or S0 in the top 4 cm of sediment. In a separate experiment, 35S-SOinf4sup2−was found to attach to precipitating Fe oxyhydroxides (1.5 to 4.7 mol SOinf4sup2−mol−1 Fe precipitate) upon mixing Contrary Creek (AMD) and Lake Anna waters. Results of this study suggest that sulfate removal may be more rapid in metal rich AMD systems thans in metal poor systems characteristic of those which receive acidic deposition.

Occurrence and Prediction of Acid Drainages

During some land excavations, sulfide minerals are exposed to the atmosphere, and they oxidize and subsequently produce acid drainages. A method to monitor rock characteristics and to identify potentially acid-producing strata has been developed. Samples of dark shales were exposed to simulated weathering tests and periodically leached with deionized water, simulated acid rain and acid mine drainage. The leachate quality was monitored and related to the whole rock analysis. Samples with low concentrations of calcareous material and low total sulfur contents produced mildly acidic leachates when leached with water and acid rain. Samples with high concentrations of calcareous material and high sulfur contents were found initially to neutralize the simulated acid drainage and generate acidity. A strong relationship was found to exist between the effluent quality and the carbonate-sulfur ratio.