Papers by Keyword: Acid Mine Drainage (AMD)

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Authors: Ling Tan, Hui Yun, Xia Yi Xu, Jia He, Hai Yan Wu, Guan Zhou Qiu, Xin Xing Liu, Jian Ping Xie
Abstract: The diversity of microbial community is well studied in past decades, however, the functional gene diversity in AMD and sediment are still unclear. In this study, four samples, which included two mine drainages and two sediments were taken from two typical copper mines in the southeast of China. Community DNA from the AMD and corresponding sediments were were extracted, purified, amplified, labeled and hybridized with GeoChip 2.0. The results showed that total 28, 126, 1131, 1875 functional genes were detected in DX_110, YP_NK, DX_110N, YP_NKN, respectively, which including carbon and nitrogen fixation, carbon degradation, methane metabolism, ammonification, nitrification, denitrification, nitrogen reduction, sulfur reduction and metal resistance genes. Sediment nearby the mine drainage may play an important role in microbial geochemical processes, since more functional genes and higher diversity were detected in sediment than in AMD.
Authors: Davor Cotoras, Cristian Hurtado, Pabla Viedma
Abstract: Sulfate is a pollutant present in the mining waste water and acid mine drainage. High levels of sulfate can generate important environmental problems. One of the alternatives proposed for the treatment of water with high levels of sulfate is the use of sulfate-reducing microorganisms. This work describes the synergistic combination of a treatment system for the removal of metals by biosorption with the strain Bacillus sp. NRRL-B-30881 to reduce the inhibiting concentration of metals in waters, followed by a new process of sulfate removal that uses a halotolerant sulfate-reducing microbial consortium. The results show that the sulfate reducing consortium can be cultured and is able to reduce the sulfate concentration using cheaper complex organic substrates like spirulina, cellulose and industrial starch. The sulfate reducing consortium was cultured on a bioreactor with Celite R-635, as support material. Using this bioreactor it was possible to reduce the sulfate concentration in the culture medium in batch or semi-continuous operation. An acid mine drainage was pretreated by lime and treated by biosortion in order to increase the pH and reduce the heavy metals concentration. Subsequently the remaining sulfate was removed by the developed process. This integrated biological process represents a more economical alternative for the removal of metal by biosortion and the removal of sulfate using a sulfate reducing consortium.
Authors: Yuta Era, Tsuyoshi Hirajima, Keiko Sasaki, Naoko Okibe
Abstract: The potential utility of mesophilic/moderately thermophilic acidophiles was investigated for immobilization of arsenic (As) as scorodite (FeAsO4·2H2O) at moderate temperatures (35–45 °C). Here, the acid-tolerant mesophile Thiomonas cuprina Hö5 and acidophilic moderately thermophile Acidimicrobium ferrooxidans ICP were selected as As (III)- and Fe (II)- oxidizers, respectively. Due to a difference in their optimal growth pHs, a 2-step reaction consisting of the 1st As (III) oxidation step followed by the Fe (II) oxidation + precipitation step was studied. In our previous study, the optimal [Fe (II)]ini/[As (III)]ini molar ratio for bioscorodite formation at 70 °C was shown to be around 1.4. However, setting the same molar ratio at moderate temperatures (35-45 °C) resulted in formation of unstable amorphous ferric arsenate. Lowering the ratio to ≤ 1.0 led to precipitation of crystalline bioscorodite with > 90% As (III) removal at 45 °C.
Authors: Lorena Escudero, Jonathan Bijman, Guajardo M. Mariela, Juan José Pueyo Mur, Guillermo Chong, Cecilia Demergasso
Abstract: To understand the microbial community inhabiting in an acidic salt flat the phylogenetic diversity and the geochemistry of this system was compared to acid mine drainage (AMD) systems. The microbial community structure was assessed by DNA extraction/PCR/DGGE and secuencing for the 16S rRNA gene and the geochemistry was analyzed using several approaches. Prediction of metagenome functional content was performed from the 16S rRNA gene survey using the bioinformatics software package Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). The geochemical results revealed a much lower iron concentration in the salt flat than in AMD systems (39 and 21804 mg L-1, respectively) and a significant difference in chloride levels. Sequences inferred to be from potential sulfur metabolizing organisms constituted up to 70% of the microbial community in the acidic salt flat meanwhile predominat iron-metabolizing acidophile populations were reported in AMD systems. Interestingly, the microbial assemblage in the acidic salt flat was dominated by mixotrophic and organotrophic sulfur oxidizers as well as by photoautotrophic acidophiles. Our results suggests that the salt concentration in Salar de Gorbea (average Cl-= 40 gL-1) is in the limit for the occurrence of chemolithotrophic oxidation of sulfur compounds. In addition, the investigation allows concluding that salinity rather than extremes of pH is the major environmental determinant of microbial community composition.
Authors: Si Min Liu, Yu Long Liu, Jia Yu Song, Hao Deng
Abstract: The aim of the study is to investigate removal of Cu, Ni, Zn, Cd and Pb in acid mine drainage (AMD) using modified oxygen releasing compounds (MORCs) of which CaO2 is the main ingredient. When the MORCs are placed into AMDs, OH- will be released gently and continuously which can neutralize H+ and precipitate heavy metal ions as hydroxide/carbonates. Four types of artificial AMDs contained Cu, Ni, Zn, Cd and Pb ions with/without sulfate were prepared in the laboratory. The removal rates of the heavy metals were measured after adding MORCs to the artificial AMDs. The results showed that the removal rates of Cu, Ni, Zn, Cd and Pb in all 4 artificial AMDs, after 72 hours, are more than 97%, even to 100%. However, after 96 hours, Cu, Ni, Zn, Cd and Pb deposits can be re-dissolved by 16.4%, 11.2%, 7.0%, 5.0% and 4.8%, respectively, in the single-metal artificial AMDs; Pb and Cd deposits are more stable. Sulfate in the multi-metal artificial AMD hardly has effects on re-dissolution of the heavy metal deposits; and only Ni deposits in the single-metal AMD with sulfate and Cu deposits in the single-metal AMD without sulfate are re-dissolved significantly. It suggested that the MORCs should be an efficient material to remove Cu, Ni, Zn, Cd and Pb from AMDs after 72 hours than lime or limestone.
Authors: Li Wei Chen, Xiao Chun Xu, Qiao Qin Xie, Jie Ying Huang
Abstract: Based on the investigation of the characteristics of the waste rocks of Xinqiao pyrite mine in Tongling, the possibility of AMD was discussed, and the speciation of Pb in the waste rocks was studied by the improved five steps sequential extraction method. The results reveal that the NP is less than the AP, the waste rocks have a high acid potential and produce AMD. The speciation of Pb in the waste rocks exist mainly in the silicate, secondly in deoxidize and oxidizable mode. But the Pb contents in the deoxidize mode are correlative to the total contents in waste rocks, if the waste rocks react with the AMD, the Pb in the deoxidize and oxidizable modes may easily release from the waste rocks. So the Pb has high environmental risk.
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