Inhibition of acid mine drainage and immobilization of heavy metals from copper flotation tailings using a marble cutting waste

Acid mine drainage （AMD） with high concentrations of sulfates and metals is generated by the oxidation of sulfide beating wastes. CaCO3-rich marble cutting waste is a residual material produced by the cutting and polishing of marble stone. In this study, the feasibility of using the marble cutting waste as an acid-neutralizing agent to inhibit AMD and immobilize heavy metals from copper flotation tailings （sul- fide-beating wastes） was investigated. Continuous-stirring shake-flask tests were conducted for 40 d, and the pH value, sulfate content, and dissolved metal content of the leachate were analyzed every 10 d to determine the effectiveness of the marble cutting waste as an acid neu- tralizer. For comparison, CaCO3 was also used as a neutralizing agent. The average pH value of the leachate was 2.1 at the beginning of the experiment （t = 0）. In the experiment employing the marble cutting waste, the pH value of the leachate changed from 6.5 to 7.8, and the sul- fate and iron concentrations decreased from 4558 to 838 mg/L and from 536 to 0.01 mg/L, respectively, after 40 d. The marble cutting waste also removed more than 80wt% of heavy metals （Cd, Cr, Cu, Ni, Pb, and Zn） from AMD generated by copper flotation tailings.

Acid Mine Drainage and Heavy Metal Pollution from Solid Waste in the Tongling Mines, China

Based on investigation of the characteristics of solid waste of two different mines, the Fenghuangshan copper mine and the Xinqiao pyrite mine in Tongling, Anhui province in central-east China, the possibility and the differences of acid mine drainage （AMD） of the railings and the waste rocks are discussed, and the modes of occurrence of heavy metal elements in the mine solid waste are also studied. The Fenghuangshan copper mine hardly produces AMD, whereas the Xinqiao pyrite mine does and there are also differences in the modes of occurrence of heavy metal elements in the railings. For the former, toxic heavy metals such as Cu, Pb, Zn, Cd, As and Hg exist mostly in the slag mode, as compared to the latter, where the deoxidization mode has a much higher content, indicating that large amounts minerals in the waste rocks have begun to oxidize at the earth surface. AMD is proved to promote the migration and spread of the heavy metals in mining waste rocks and lead to environmental pollution of the surroundings of the mine area.

Operational state monitoring and fuzzy fault diagnostic system of mine drainage

A system to monitor the operational state of a coal mine drainage system is presented, fault problems are diagnosed and solved. The system includes a Single Chip Microprocessor (SCM) Atmega169 and an industrial PC used as a master-slave structure. Characteristic parameters of the drainage system were extracted and analysed. As well, a research project on the fault diagnosis of centrifugal water pump based on a fuzzy synthetic evaluation method is initiated. The proposed monitoring and fault diagnostic system can improve the automation, safety, reliability, economy and efficiency of mine drainage systems considerably, decrease blindness and shorten the time required for water pump maintenance.

Inhibition of hematite on acid mine drainage caused by chalcopyrite biodissolution

Even though biodissolution of chalcopyrite is considered to be one of the key contributors in the formation of acid mine drainage(AMD),there are few studies to control AMD by inhibiting chalcopyrite biodissolution.Therefore,a novel method of using hematite to inhibit chalcopyrite biodissolution was proposed and verified.The results indicated that chalcopyrite biodissolution could be significantly inhibited by hematite,which consequently decreased the formation of AMD.In the presence of hematite,the final biodissolution rate of chalcopyrite decreased from 57.9%to 44.4%at 20 day.This in turn suggested that the formation of AMD was effectively suppressed under such condition.According to the biodissolution results,mineral composition and morphology analyses,and electrochemical analysis,it was shown that hematite promoted the formation and accumulation of passivation substances(jarosite and Cu2-xS)on chalcopyrite surface,thus inhibiting the biodissolution of chalcopyrite and limiting the formation of AMD.

An effective way to treat the iron-rich acid mine drainage from coal mining in Guizhou’s mountainous areas

Acid Mine Drainage(AMD)from coal mining is a serious environmental issue which affects water quality,ecology,and the overall landscape of the basin.A large number of coal mine tailings in the mountainous regions of Guizhou Province,China were unattended and iron-rich AMD was directly discharged to the rivers.This discharge leaves the river―yellow‖and heavily polluted.This study tries to find an efficient and economical method for treating iron-rich AMD.We sampled AMD water in two sites:Yangliujie town of Duyun city(hereafter,called Yangliujie),and Xinglong Coal Mine,Duliu town of Guiding county(hereafter,called Xinglong).We performed iron removal laboratory experiment with Cement-Bentonite Agent(CBA,80%cement and 20%bentonite)in 500 mL AMD water from Yangliujie,scale-up experiment in 15 L AMD water from both Yangliujie and Xinglong,and engineering application in Xinglong respectively.Laboratory experiment results showed the iron removal rate can reach 99.8%and the removal rate depends on the CBA dosage and the treatment time.In the scale-up experiment,we found that Fe concentration could be reduced from 587.0 to 0.2 mg/L when adding 20 g/L CBA to the AMD water and aerating for 3 hours.As sampled water in Xinglong has a very high Fe concentration(Fe 1019.8 mg/L)and the concentration varies with seasons,it is not economical to add the CBA directly to the AMD water.Considering the abundant and cheap limestone resources in Guizhou,we used a twostep treatment method,first we added CaCO3 to raise the pH,and then we took the supernatant liquor and added CBA to the liquor.It was shown that 15 g/L of CBA was a good dosage for iron removal with Fe concentration being reduced from 1019.8 to 0.3 mg/L when CaCO3 was used to raise the pH.The best treatment realized over 99.9%iron removal,99.2%NH3-N removal,98.9%CODMn removal,and heavy metals in the treated water were reduced to under the limit stipulated in the―Environmental Quality Standards of Surface Water in China‖.Thus in the engineering application,we used this two-step treatment method.After the treatment,the pH of the iron-rich AMD(pH 2.86,Fe 2624.6 mg/L)increased to 8.53,the concentration of Fe was reduced to 59.5 mg/L,NH3-N decreased from 16.15 to less than 0.05 mg/L,CODMn decreased from 323.33 to 24.57 mg/L,heavy metals except Fe and Mn were reduced to under the limit of surface water.In conclusion,the use of CBA can effectively remove Fe and other heavy metals from the iron-rich AMD and adjust the pH value to the range of a natural water body.

Study on the Treatment of Acid Mine Drainage Containing Fe^(2+) and Mn^(2+) Using Modified Spontaneous Combustion Gangue

The high concentrations of Fe^(2+) and Mn^(2+) in acid mine drainage make it difficult and expensive to treat.It is urgent that we find a cheap and efficient adsorption material to treat Fe^(2+) and Mn^(2+).As a solid waste in mining areas,coal gangue occupies a large area and pollutes the surrounding environment during the stacking process.Developing a method of resource utilization is thus a research hotspot.In this study,we modified spontaneous combustion gangue using NaOH,NaCl,and HCl by chemically modifying the minerals.We determined the optimal conditions for treating Fe^(2+) and Mn^(2+) in acid mine drainage with spontaneous combustion gangue and modified coal gangue using the single factor test method.Based on results of the static test,two dynamic test columns,column No.1(spontaneous combustion gangue)and column No.2(NaOH modified spontaneous combustion gangue),were constructed,and the repair effects of acid mine drainage were compared and analyzed using dynamic experiments.The results show that overall,NaOH modified spontaneous combustion gangue is the most efficient at removing the Fe^(2+) and Mn^(2+) in acid mine drainage.The optimal conditions for NaOH modification are an NaOH concentration of 3 mol/L,a liquid to solid ratio of 2 L/kg,and a modification time of 8 h.The overall efficiency of column No.2 at removing Fe^(2+) and Mn^(2+) from acid mine drainage is better than that of column No.1.Among them,the average removal efficiency of Fe^(2+)and Mn^(2+) from acid mine drainage in column No.2 were 97.73%and 44.82%,respectively.The above results show that NaOH modified spontaneous combustion gangue is a good adsorbent,which has application potential in wastewater remediation,as it can achieve the purpose of“treating dust with waste”.

The Dynamic Experiment on Treating Acid Mine Drainage with Iron Scrap and Sulfate Reducing Bacteria Using Biomass Materials as Carbon Source

The study is aimed at the problem of high content of Cr^(6+),Cr^(3+)and SO_(4)^(2-)is high and low pH value in acid mine drainage(AMD).Moreover,treatment of AMD by sulfate reducing bacteria(SRB)requires the addition of carbon source,while the treating effectiveness is not good enough on its own.The sugarcane slag,the corn cob and the sunflower straw were selected as the SRB carbon source cooperating with iron scrap to construct the dynamic columns 1,2 and 3.The mechanism of removing Cr^(6+),Cr^(3+),SO_(4)^(2-)and H+and the regularity of sustained release of carbon source and TFe release was studied in AMD.The removal efficiency of heavy metal ions,the ability of sustained release of carbon source,and the ability of adjusting acid by the three dynamic columns were compared.The result shows that the average removal rates of Cr^(6+),Cr^(3+)and SO_(4)^(2-)in effluent of dynamic column 1,filled by sugarcane slag,iron scrap and SRB,were 96.9%,67.1%and 54.3%.The average release of TFe and chemical oxygen demand(COD)were 4.4 and 287.3 mg/L.Its average pH was 6.98.Compared with the performance of dynamic columns 1,2 and 3,dynamic column 1 performed best in removing Cr^(6+),Cr^(3+)and SO_(4)^(2-)from AMD and controlling the release of COD and TFe,adjusting the pH of the solution.The study is of significance in treatment of AMD by taking for biomass materials as SRB carbon source in cooperation with iron scrap.

A novel acidophile community populating waste ore deposits at an acid mine drainage site

Waste ore samples （pH 3.0） were collected at an acid mine drainage （AMD） site in Anhui, China. The present acidophillc microbial community in the waste ore was studied with 16S rRNA gene clone library and denaturing gradient gel electrophoresis （DGGE）. Eighteen different clones were identified and affiliated withActinobacteria, low G ＋ C Gram-positives, Thermomicrobia, Acidobacteria, Proteobacteria, candidate division TM7, and Planctomycetes. Phylogenetic analysis of 16S rRNA gene sequences revealed a diversity of acidophiles in the samples that were mostly novel. It is unexpected that the moderately thermophilic acidophiles were abundant in the acidic ecosystem and may play a great role in the generation of AMD. The result of DGGE was consistent with that of clone library analysis. These findings help in the better understanding of the generation mechanism of AMD and in developing a more efficient method to control AMD.

Removal of Copper from Acid Mine Drainage (AMD) or Acid Rock Drainage (ARD)

Acid mine drainage is wastewater from a mine having a low pH and an elevated level of dissolved heavy metals. These metals are harmful to aquatic, animal and human life. This paper looks at the removal of copper from acid mine drainage using ion exchange to less than 1 mg/l. A weak acidic cation resin was used. Spectrophotometric determination of copper with sodium diethyldithiocarbamate was used to determine the copper concentrations in the treated water. Using regression analysis, the experimental results gave a correlation coefficient of 0.977 and a coefficient of determination of 99.5%. Results indicated that the higher the flows rate the shorter the period after which the copper concentration in the treated water reaches 1 mg/l. At pH 3.85 and 5.09, the resin performed better and at pH above 6.62 and between pH 3.0 and below the resin’s does not perform well. The higher the resin height the greater is the resin exchange capacity and the longer it takes for the copper concentration to reach 1 mg/l in the treated water. The higher the wastewater copper concentration the shorter the time it takes the resin to reach 1 mg/l. The results for this experiment indicated that acid mine drainage can be treated well by ion exchange resins, but it is also very important to establish suitable operating conditions.

The Key Factor of Acid Mine Drainage (AMD) in the History of the Contribution of Mining Industry to the Prosperity of the United States and South Africa: A Review

Mining industry has significantly contributed to the prosperity of the nation with economic growth, whereas mining operation has caused Acid Mine Drainage (AMD) with the abandonment of mines. As some researchers suggest, the history of AMD is, generally, affected by the change in not only mining industry but also in social and economic conditions. Thus, historical analysis is an effective way to find the key factors of AMD. In this study, in order to find the key factors of AMD, we examine the history of the United States (U.S.) and South Africa, where their economy had been developed owing to the large-scale mining, based on the findings in the previous studies. The results indicated that the abandoned mines due to the economic depression triggered AMD in the U.S. and South Africa. While the U.S. had progressively adopted anti-AMD methods in terms of prevention, prediction, and remediation (PPR) as a comprehensive approach, especially since the 1970s onwards because of the rise of environmental consciousness as well as strict regulations, South Africa is at the early stage of implementing the regulations following PPR. The public attention should be directed to environmental conservation in addition to the implementation of the regulations in South Africa. The improvement in socio-economic conditions is, additionally, necessary for the rise of environmental consciousness in South Africa in the light of the three pillars of sustainable development: social, economic, and environmental elements.

Nanomineralogy of evaporative precipitation of efflorescent compounds from coal mine drainage

Efflorescent nanophases(NPs) are found as a transitory accumulation of potentially hazardous elements(PHEs),particularly in tropical climates. The central objective of this study was to investigate the distribution of PHEs with NPs through the evaporative formation structures(EFS) of enormously PHEs-rich coal-mine drainages(CMD). The EFS were studied in natural coal mine drainage for five months in order to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in nature. The largest coal-fired power plant in South America, located in south Brazil, is used as an example of such a problem. In this work, a novel methodology for the analysis of PHEs in CMD precipitates is proposed for this affected coal area.The analytical method, combining X-Ray Diffraction(XRD) and advanced electron microscopies, shows the importance of nanomineralogy in understanding different circumstances of coal contamination. Several ultrafinenanoparticles(UNPs) were identified in the sampled soils and river sediments together with the PHEs. A decrease in PHEs was identified in association with UNPs. However, further investigations are required with regard to the mobility of PHEs in water, atmosphere, soils, and sediments. The EPS was thoroughly studied, acquiring suitable understanding with investigational facts for Ca and Fe-sulphates, pickeringite, and several amorphous phases.

Prediction of mine drainage generation potential and the prevention method of the groundwater pollution in the Gümüskoy(Kütahya)mineralization area,NW Turkey

One of the leading factors of seepage contamination is mine drainage,which creates serious ecological risks on the environment both during operation and post-mining times.In this study,experimental processes have been carried out to determine the occurrence of mine drainage in the Gümüskoy(Kütahya)mineralization area(Northwest Turkey).The prevention method for potential mine drainage occurrence has been also discussed.High enrichment was observed which are directly related to mineralization in trace element concentrations,especially in potentially toxic metals such as Ag,Cd,Mo,Ba,Bi,and Zn.Based on short-term tests,mine drainage formation has not been expected according to the p H(7.36-9.38),contact leaching,and acid-base accounting studies.However,in the long-term,acid generation potential has been expected because of weathering and oxidation in terms of rock type and mineralization in the area.Therefore,in order to prevent groundwater contamination in the event of a possible formation of mine drainage,the hydraulic conductivity of the stock area bedrock was evaluated by the in situ tests performed in the field and it was found to be moderately permeable(K=1.9×10^-6 m/s).In order to make the stock area bedrock impermeable,natural clay will be laid and compressed at the base of the stock area.When the finite elements were modeled by seepage analysis,the seepage discharge to be formed on the base rock at a depth of 5 m was determined as 3.17×10^-19 m^3/s.Since the discharge value determined in the seepage analysis after modeling is very close to zero,contamination of possible ground and surface water will be prevented.

Construction of Dry Cover System for Prevention of Acid Mine Drainage at Mine Waste Dump in Open Cast Coal Mines, Indonesia

Acid Mine Drainage (AMD) which occurs when sulfide minerals are exposed to water and oxygen with an excavation is one of the serious environmental problems in the world. A dry cover system is generally constructed in waste dump for the prevention of AMD in Indonesia by virtue of low cost and availability of waste rocks for a cover layer. However, the failure of the system caused by the lack of information related to the construction of cover system in mines, which leads to AMD, has been reported recently in Indonesia. In this study, the field investigation was conducted in pit and waste dump in open cast coal mine in Indonesia with the aim of obtaining the information on the construction of a cover layer and backfilling conditions of waste rocks in the waste dump. The rock samples taken in two areas of the mine were analyzed by geochemical analysis and sequential extraction with acids. The results indicated that Net Acid Producing Potential (NAPP) of the rocks in the waste dump down to 100 cm depth in both areas was from 10 to 30 kg H2SO4/ton, suggesting that Potentially Acid Forming (PAF) was backfilled in a cover layer. The backfill of PAF was contrary to the concept of cover system, which caused the failure of constructing a cover layer. The cause of the failure was likely attributed to the shortage of cover rocks which are classified as Non Acid Forming (NAF) or the failure of proper placement of them by an operational problem in the areas. Moreover, the results of the extraction with acids suggested that the form of iron and sulfur has to be taken into account to discuss the occurrence of AMD.

Ladle Slag of Electric Steelmaking as Alkaline Agent on Controlling of Acid Mine Drainage Generation

Commercial coal production in the southern region of Brazil (comprising the Paraná, Santa Catarina, and Rio Grande do Sul states) has been occurring since the beginning of the twentieth century. Regarding the Santa Catarina coalfields, about 60% - 65% of the ROM coal is discharged at dump deposits as waste. These wastes can lead to the formation of acid mine drainage (AMD), a source of ground and surface water pollution. One of the technologies used for preventing AMD consists of the alkaline additive method. Thus, the aim of this work was to study, at laboratory scale, the DAM control by blending coal waste with a metallurgical slag. A coal-tailing sample was collected from a coal mine, and the slag was obtained from a semi-integrated steel plant. Static tests were carried out by the acid-base account method to determine the balance between the acid-producing and acid-consuming (neutralizing) mineral components of the samples. Kinetic tests were conducted in humidity cells, following the ASTM D 5744-96 method, for a period of 80 weeks. The results showed that the coal tailing generates AMD. However, environmental problems can be minimized by mixing the coal waste with the metallurgical slag in 1:1 or 1:1.5 proportions. The kinetic experiments proved that, in this condition, the lixiviation presents a higher pH and a lower concentration of acidity, metals, and sulfate. Finally, it is possible to conclude that the blending slag in coal tailing deposits can be a viable alternative for DAM control in coal mining.

Effects of acid mine drainage on photochemical and biological degradation of dissolved organic matter in karst river water

Dissolved organic matter(DOM)can be removed or transformed by photochemical and biological processes,producing the negative effect of transforming organic carbon into inorganic carbon,which plays a vital role in the karst carbon cycle.However,acid mine drainage(AMD)will affect this process,so the degradation of DOM in karst river water(KRW)needs to be studied in this context.In this study,to reveal the evolution processes of DOM under photochemical and biological conditions in AMD-impacted KRW,AMD and KRW were mixed in different ratios under conditions of visible light irradiation(VL),biodegradation(BD),ultraviolet irradiation(UV)and ultraviolet irradiation+biodegradation(UV+BD).The average DOC concentrations in samples after mixing AMD and KRW in different proportions decreased significantly(by 23%)in UV+BD,which was 1.2–1.4 times higher than under the other conditions and would lead to a significant release of inorganic carbon.Further analysis of the fluorescence parameters via parallel factor analysis(PARAFAC)revealed that the DOM fluorescence components in AMD comprised mainly protein-like substances derived from autochthonous components,while the DOM fluorescence components in KRW were mainly humic-like substances with both autochthonous and allochthonous sources.Therefore,AMD could promote both the photochemical and biological degradation of DOM in karst receiving streams,resulting in the conversion of DOC to inorganic carbon.The results showed that the synergistic effects of UV+BD and AMD accelerated the degradation of DOM and the release of inorganic carbon in KRW,thus affecting the stability of the karst carbon cycle.

Fe(Ⅱ)-mediated transformation of schwertmannite associated with calcium from acid mine drainage treatment

Schwertmannite is an important Fe(Ⅲ)-oxyhydroxysulfate in acid mine drainage (AMD) polluted areas and its stability depends on surrounding environmental factors and previously bound elements.The treatment and neutralization of AMD normally involve the use of lime,which leads to the discharge of abundant Ca in the mining area.Such an environmental disturbance brings up an important and less considered problem of how the reductive transformation of schwertmannite associated with coexisting Ca occurred.Here,the Fe(Ⅱ)-mediated transformation of Ca-adsorbed schwertmannite and subsequent Ca repartitioning behaviors were investigated.Results showed that adsorbed Ca had a weak inhibitory effect on Fe(Ⅱ)-mediated schwertmannite transformation.Release of SO_(4)2-and SEM images both indicated that transformation rates of schwertmannite decreased under the influence of adsorbed Ca.XRD patterns indicated that adsorbed Ca altered schwertmannite transformation pathways and product compositions upon treatment with 0.4 mmol/L Fe(Ⅱ).The end products of Sch notably contained both goethite and lepidocrocite;however,transformation products of SchCa only contained goethite all along.Approximately 33.5%of the surface adsorbed-Ca was released into solution within 6 hr after Fe(Ⅱ) injection.Aqueous Ca behaved in a“first release and then im-mobilization”manner,which indicated dissolution and secondary mineralization drove Ca migration during the Fe(Ⅱ)-mediated transformation of SchCa.Adsorbed Ca blocked the surface sites for subsequent Fe(Ⅱ) adsorption,limited the Fe(Ⅱ)-Fe(Ⅲ) ETAE,and decreased the transformation rates.This work sheds light on the complex geochemical behavior of schwertmannite under the influences of environmental perturbations in AMD environments.

Hydrogeochemical and mineralogical characteristics related to heavy metal attenuation in a stream polluted by acid mine drainage:A case study in Dabaoshan Mine,China

Dabaoshan Mine,the largest mine in south China,has been developed since the 1970s.Acid mine drainage （AMD） discharged from the mine has caused severe environmental pollution and human health problems.In this article,chemical characteristics,mineralogy of ocher precipitations and heavy metal attenuation in the AMD are discussed based on physicochemical analysis,mineral analysis,sequential extraction experiments and hydrogeochemistry.The AMD chemical characteristics were determined from the initial water composition,water-rock interactions and dissolved sulfide minerals in the mine tailings.The waters,affected and unaffected by AMD,were Ca-SO4 and Ca-HCO3 types,respectively.The affected water had a low pH,high SO42 and high heavy metal content and oxidation as determined by the Fe^2＋ /Fe^3＋ couple.Heavy metal and SO4^2- contents of Hengshi River water decreased,while pH increased,downstream.Schwertmannite was the major mineral at the waste dump,while goethite and quartz were dominant at the tailings dam and streambed.Schwertmannite was transformed into goethite at the tailings dam and streambed.The sulfate ions of the secondary minerals changed from bidentate-to monodentate-complexes downstream.Fe-Mn oxide phases of Zn,Cd and Pb in sediments increased downstream.However,organic matter complexes of Cu in sediments increased further away from the tailings.Fe^3＋ mineral precipitates and transformations controlled the AMD water chemistry.

Using fluorescence-based microplate assay to assess DOM-metal binding in reactive materials for treatment of acid mine drainage

One potential drawback of compost-based passive bioreactors,which is a promising biotechnology for acid mine drainage（AMD） treatment,is the transport of dissolved organic matter（DOM）-metal complexes in surface waters.To address this problem,the objective of this study was to assess the maximum capacity of organic substrates to release soluble DOM-metal complexes in treated water. The reactivities of DOM in maple wood chips and sawdust,composted poultry manure,and leaf compost were quantified toward Cd2＋,Ni2＋,Fe2＋,and Cu2＋ using fluorescence quenching.The DOM showed the highest reactivity toward Fe,but a limited number of available sites for sorption,whereas DOM-Cd complexes exhibited the lowest fluorescence quenching.Overall,the DOM from a mixture of wastes formed higher concentrations of DOM-metal complexes relative to sole substrates.Among DOM-metal complexes, the concentrations of DOM-Ni complexes were the highest.After reaching steady-state,low concentrations of DOM-metal complexes were released in treated water,which is in agreement with theoretical predictions based on geochemical modeling.Therefore,in addition to physicochemical characterization,fluorescence quenching technique is recommended for the substrate selection of bioreactors.

Effects of acid drainage from abandoned coal mines on the microbial community of Shandi River sediment,Shanxi Province

The discharge of acid mine drainage from abandoned high sulfur(S)coal mines has caused serious pollution in the Shandi River,Yangquan,Shanxi Province.To determine the impact of long-term acid mine drainage on the microorganisms in the river,we collected river sediments from a polluted tributary(Group P)and the mainstream of Shandi River(Group R)to study the bacterial diversity and community composition.The results showed that the tributary was seriously polluted by acid drainage from abandoned coal mines,with the pH value of the sediment being<2.5,resulting in the low bacterial richness and diversity of the tributary samples.Acidophillic Fe-and S-metabolizing bacteria,such as Metallibacterium,Acidiphilium,and Acidithiobacillus,were the dominant genera in Group P samples,while the Group R was dominated by the neutral anaerobic iron-reducing bacteria Geothrix and Geobacter.Results of principal co-ordinates analysis(PCoA)revealed that the bacterial communities are significantly different between groups P and R,and the significant different species were mainly attributed to phylum Proteobacteria,Actinobacteria,and Acidobacteria.The distribution of the microbial community is mainly influenced by pH,and the Fe and Cd concentrations.Metallicactrium,the dominant genus,is negatively correlated with pH(R^(2)=-0.95)and positively correlated with Fe(R^(2)=0.99),while Geothrix and Geobacter,are mainly affected by the heavy metals.This study determined the impact of river pollution caused by abandoned coal mine drainage,especially on the microbial diversity and community composition within the river sediment.

Bioremediation Process and Bioremoval Mechanism of Heavy Metal Ions in Acidic Mine Drainage

Acidic mine drainage（AMD） containing acidity and a broad range of heavy metal ions is classified as hazardous, and must be properly treated. The removal mechanism of heavy metal ions in acidic mine drainage containing Cu^2＋, Fe^2＋, and Zn^2＋ with biological method was studied here. Using 20 mmol/L ethanol as carbon source, Desulfovibrio marrakechensis, one of sulfate reducing bacteria（SRB） species, grew best at 35℃ and pH=6.72 with concentrations of 10, 55 and 32 mg/L for Cu^2＋, Fe^2＋ and Zn^2＋, respectively. The removal efficiency for each ion mentioned above was 99.99%, 87.64% and 99.88%, respectively. The mineralogy and surface chemistry of precipitates were studied by means of energy dispersive spectrometer（EDS）, X-ray photoelectron spectroscopy（XPS）, X-ray diffraction（XRD） combined with control tests. The experimental results demonstrate that the removal mechanism of heavy metal ions by Desulfovibrio marrakechensis is comprehensive function of chemical precipitation, adsorption and bioprecipitation. The biogenic iron sulfide solid was characterized as greigite（Fe3S4）, while the zinc sulfide solid was characterized as sphalerite（ZnS）.