Bioleaching of heavy metals from contaminated alkaline sediment by auto- and heterotrophic bacteria in stirred tank reactor

Bioleaching Xiangjiang River alkaline sediment contaminated by multiple heavy metals was investigated. Multiple metals in alkaline sediment possess significant toxicity to aquatic organisms or humans and will greatly inhibit bioleaching. The bioleaching method using autotrophic bacteria mixed with heterotrophic bacteria can solve this problem successfully. The experiment results showed that bioleaching efficiencies of Zn, Mn, Cu, and Cd were 95.2 %, 94.2 %, 90.1 %, and 84.4 %, respectively. Moreover, the changes of heavy metal concentrations in different fractions in contaminated sediment before and after bioleaching were analyzed by selective sequential extraction, and it was discovered that the main fractions of Zn, Mn, Cu and Cd after bioleaching are Fe-Mn oxide, organic associated form and a residual form. Its biotoxicity decreased greatly. The bioleaching heavy metals from sediment using autotrophic bacteria combined with heterotrophic bacteria can effectively improve the bioleaching efficiency and reduce toxicity.

Microbial diversity of soil bacteria in agricultural field contaminated with heavy metals

In this study we evaluated the bacterial diversity in a soil sample from a site next to a chemical industrial factory previously contaminated with heavy metals. Analysis of 16S rDNA sequences amplified from DNA directly extracted from the soil revealed 17 different bacterial types （genera and/or species）. They included Polyangium spp., Sphingomonas spp., Variovorax spp., Hafina spp., Clostridia, Acidobacteria, the enterics and some uncultured strains. Microbes able to tolerate high concentrations of cadmium （500μmol/L and above） were also isolated from the soil. These isolates included strains of Acinetobacter （strain CD06）, Enterobacter sp. （strains CD01, CD03, CD04 and CD08） （similar strains also identified in culture-independent approach） and a strain of Stenotrophomonas sp. The results indicated that the species identified from direct analysis of 16S rDNA of the soil can be quite different from those strains obtained from enrichment cultures and the microbial activities for heavy metal resistance might be more appropriately addressed by the actual isolates.

Removal of Heavy Metals from Aqueous Solutions Using Bacteria

The accumulation of heavy metals by microbial biomass with high surface area to volume ratio holds great potential for heavy metal removal in both soluble and paritcular forms, especially when the heavy metal concentrations are low (<50 mg/L). E. coli and B. subtilis are effective agents for metal removal. We further investigated the effect of pH, temperature, equilibration time, and pre treatment reagents on the removal of Pb(Ⅱ), Cd(Ⅱ) and Cr(Ⅵ) from aqueous solutions by E. coli and B. subtilis. E. coli and B. subtilis were cultivated for 60 hours, the experimentally determined optimal cultivation time before they were used in metal removal experiments. Under the optimal conditions of pH 6.0, equilibration temperature 30 °C and equilibration time 1 hour, 63.39% and 69.90% Cd(Ⅱ) can be removed by E. coli and B. subtilis. Under the optimal conditions of pH 5.5, equilibration temperature 30 °C and equilibration time 1 hour, 68.51% and 67.36% Pb(Ⅱ) can be removed by E. coli and B. subtilis. And under the optimal conditions of pH 5.5, equilibration temperature 30 °C, and equilibration time 1 hour, 60.26% and 54.56% Cr(Ⅵ) can be removed by E. coli and B. subtilis. Chemical treatment of cultivated bacteria (0.1 mol/L NaOH, 0.1 mol/L HCl, 30% ethanol, and distilled water) affects the efficiency of metal removal by E. coli and B. subtilis. Pretreatment of biomass by NaOH enhanced Cd(Ⅱ), Pb(Ⅱ) and Cr(Ⅵ) removal, while pretreatment by HCl, ethanol and distilled water reduced Cd(Ⅱ), Pb(Ⅱ) and Cr(Ⅵ) removal. For metal removal from industrial waste discharges, pretreated biomass of E. coli can remove 68.5% of Cd and 58.1% of Cr from solutions, while pretreated biomass of B. subtilis can remove 62.6% of Cd and 57% of Cr from solutions.

Heavy-Metal Tolerance and Antibiotic Susceptibility of Red Pigmented Bacteria Isolated from Marine Environment

This study was undertaken to determine heavy metal resistance and antibiotic susceptibility of three non-pathogenic red pigmented bacteria namely WPRA3, SM11-3j and SC-G18, isolated from marine environments of Malaysia. The bacteria isolates were identified by 16S rRNA sequencing and by biochemical and morphological tests. The 16S rRNA gene sequences of all isolates showed ≥96% similarity to Serratia spp. Antibiotic susceptibility test of isolates was assayed according to the Kirby-Bauer disc diffusion method. All isolates were highly resistant to beta-lactam antibiotics, but were susceptible to quinolone antibiotics. Minimum inhibitory concentration (MIC) of nine heavy metals (Ni2+, Co2+, Cr3+, Zn2+, Mn2+, Pb2+, Hg2+, Cd2+ and Cu2+) against the bacteria isolates were determined via the plate-dilution method. The isolates exhibited resistance to Ni2+, Co2+, Cr3+ and Zn2+. Isolates WPRA3 and SM11-3j showed higher multiple tolerances to heavy metals. The results obtained indicate that bacteria from marine environments of Malaysia present interesting metabolic activities, which should be studied and explored for potential biotechnological applications.

Heavy Metal Accumulation in Plants on Mn Mine Tailings

The Xiangtan Manganese (Mn) Mine in the middle of Hunan Province, China, has been mined since 1913 with mine tailings including excavated wastes, wastewater, and smelting wastes. A survey was conducted on the Mn mine tailing soils and eight plants on the Mn mine tailings. The concentrations of soil Mn, Pb, and Cd and the metal-enrichment traits of these eight plants were analyzed simultaneously. Exceptionally high concentrations of these three metals were found in the soils, especially on the tailing dam. Each plant investigated in this study accumulated the three heavy metals, but no hyperaccumulator of these metals was found. However, analysis indicated that Poa pratensis Linn., Gnaphalium affine D. Don, Pteris vittata L., Conyza canadensis (L.) Cronq., and Phytolacca acinosa Roxb. possessed specially good metal-enrichment and metal-tolerant traits. P. pratensis, G. affine, and P. vittata were Pb-tolerant plants; and C. canadensis, P. pratensis, and G. affine were Cd-tolerant plants. P. acinosa had a great tolerance to Mn. and it was a valuable plant for on-site phytoremediation. Phragmites communis Trin. was found to have high metal tolerance and economic benefit as a raw material for paper and should be considered for soil remediation. G. affine and C. canadensis had excessive accumulation of Mn and could be useful in phytoremediation. However, although P. pratensis was a good accumulator, it was not a suitable plant for soil remediation because its biomass was too little.

Hydrocarbon-Degrading Bacteria and Paraffin from Polluted Seashores 9 Years after the Nakhodka Oil Spill in the Sea of Japan

Pollution of petroleum hydrocarbons, in particular oil spills, has attracted much attention in the past and recent decades. Oil spills influence natural microbial community, and physical and chemical properties of the affected sites. The biodegradation of hydrocarbons by microorganisms is one of the primary ways by which oil spill is eliminated from contaminated sites. One such spill was that of the Russian tanker the Nakhodka that spilled heavy oil into the Sea of Japan on January 2, 1997. The impact of the Nakhodka oil spill resulted in a viscous sticky fluid fouling the shores and affected natural ecosystems. This paper describes the weathering of hydrocarbon-degrading bacteria （genus Pseudomonas） and crystallized organic compounds from the Nakhodka oil spill-polluted seashores after nine years. The Nakhodka oil has hardened and formed crust of crystalline paraffin wax as shown by XRD analysis （0.422, 0.377, and 0.250 nm d-spacing） in association with graphite and calcite after 9 years of bioremediation. Anaerobic reverse side of the oil crust contained numerous coccus typed bacteria associated with halite. The finding of hydrocarbon-degrading bacteria and paraffin wax in the oil crust may have a significant effect on the weathering processes of the Nakhodka oil spill during the 9- year bioremediation.

Fungal Leaching of Heavy Metals from Sediments Dredged from the Deûle Canal, France

Filamentous fungi were used to leach heavy metals from dredged sediments in semi-pilot scale air-lift bioreactors. Prior to the bioleaching experiments, a physico-chemical characterization of the sediments comprising a sequential extraction study was conducted. The sediments turned out to highly contaminated with heavy metals. Most of the studied metals were found to be strongly linked to the matrix because of their association with the sulphides and with the organic matter. The conditions that favored the solubilization of heavy metals by the filamentous fungi turned out to be favorable for the activity of the sediments organotrophic bacterial microflora as well. The latter played a key role in the biosolubilization process by producing organic acids under temporary anoxic conditions. Better solubilization results (Mn: 77%, Zn: 44%, Cu: 12%, Cd and Pb: <2%) were thus obtained in the uninoculated sugar treatment in comparison to the fungal treatment. In general, organotrophic leaching was found to be limited by the poor nature of the organic acids and by their microbial consumption under sugar limited conditions. It was therefore restrained to the relatively mobile metals, namely those linked to the acid-soluble and reducible fractions of the sediments.

Occurrence and Evaluation of Chromium Reducing Bacteria in Seepage Water from Chromite Mine Quarries of Orissa, India

Chromium pollution due to leaching and weathering of chromite mine overburden in mine seepage water is a serious environmental problem. In an attempt to explore the indigenous chromate resistant and reducing bacteria from chromite mine quarry seepage, 145 aerobic, heterotrophic bacteria were isolated from 14 mine seepage samples derived from chromite mines of Sukinda valley and Baula-Nuasahi belt in Orissa, India. A total of 109 isolates which were tolerant to 2 mM Cr(VI) showed different degrees of Cr(VI) reducing activ-ity in complex KSC medium and synthetic Vogel Bonner (VB) broth. Ten isolates belonging to genera like Pseudomonas, Acinetobacter, Alcaligenes, Cupriavidus and Corynebacterium were selected on the basis of their chromate reducing efficiency and it was found that they could reduce more than 50 and 75% of Cr(VI) in VB broth and KSC medium respectively. The sole Gram-positive isolate, Corynebacterium paurometabo-lum SKPD 1204 (MTCC 8730) showed maximum chromate reducing capacity in both VB broth (63.7%) and KSC medium (92%) and was capable of reducing nearly 95% of the total Cr(VI) in the mine seepage when it was grown in the mine seepage supplemented with 2% VB concentrate.

Removal of Radioactivity from Sediment Mud and Soil and Use for Cultivation of Safe Vegetables in Fukushima, and Removal of Toxic Metals Using Photosynthetic Bacteria

The immobilized photosynthetic bacterium, Rhodobacter shpaeroides SSI (SSI), cultured on porous 2 cm ceramic beads, effectively removed and recovered 20 mg/L of non-radioactive Cs (almost 100%) and Sr (≌50%), after 3 - 5 days of aerobic treatment. Toxic and heavy metals such as Hg, Cr, Pb and As were also removed, almost 100%, after 6days of aerobic treatment. A practical method of removal of radioactivity of 10 - 30 μSv/h, caused mainly by radioactive Cs released from the accident at the Daiichi Nuclear Power Plant on 11th March 2011, from sediment mud and soil in Fukushima, Japan, was also carried out. Using immobilized SSI beads, more than 90% and 42% - 73% of radioactive Cs was removed and recovered from sediment mud and soil, respectively, after 3 - 14 days of aerobic treatment in an outdoor 60 L vessel. The weight and mass of the harvested beads could be reduced by more than 97% after desiccation. This technology of removal and recovery had therefore, considerable advantages over other technologies that demanded very large storage facilities in Fukushima. After removal of radioactivity from polluted soil, vegetables like Komatsuna (Turrip leaves) and Chingensai (Green pakchoi) were cultivated on remediated soil. Safe vegetables grown on these treated soils showed a radioactivity content lower than the recommended limit for edible foods in Japan, i.e. less than <100 Bq/kg. Treatment by SSI beads, therefore, appeared to be a compact and suitable technology that could make significant contributions towards agricultural recovery in radioactively polluted areas of Fukushima.

Effect of Distance of Sanitary Pits on the Microbial and Heavy Metal Levels in Hand Dug Well Water Samples Consumed by People Living in Akwuke, Enugu South Local Government Area of Enugu State

Studies were carried out to assess the effect of distance of sanitary pits on the microbial and heavy metal levels in hand dug well water samples consumed by people living in Akwuke, Enugu South Local government area of Enugu State, using standard biochemical and spectrophotometric analysis. The well water samples were digested with aqua-regia and four heavy metals (Pb, Cd, Cu and Zn) were assayed in the well water samples at sampling distances of 3, 6 and 10 m respectively from the sanitary pits. The range of mean bacterial counts (cfu/g) for the four detected pathogenic bacteria; S. aureus, Klebsiella pnemeoniae, Echerichia coli and Salmonella enteritidis were 83 - 3730, 510 - 870, 50 - 2535 and 240 - 3420 Cfu/g at sampling distances of 3, 6 and 10 m respectively from the sanitary pits. The mean bacteria counts of the four detected pathogenic organisms in the well water sample at sampling distances of 3 and 6 m respectively from the sanitary pits were above the WHO recommended threshold limits for a safe drinking water. The mean bacterial counts of Salmonella enteritidis in the well water samples of sampling distance of 10 m from the sanitary pits was above the WHO recommended permissible limits. At sampling distances of 3, 6 and 10 m from the sanitary pits, the mean range of Pb, Cd, Cu and Zn in the well water samples were, 0.03 - 0.3, 0.02 - 0.05, 0.46 - 1.71 and 1.63 - 7.03 μg/g respectively. The mean levels of Pb and Cd in the well water samples at sampling distances of 3 and 6 m respectively from the sanitary pits were above their respective WHO recommended threshold limits. The mean heavy metals (Cd, Pb, Cu and Zn) in the well water samples at sampling distances of 3, 6, and 10 m respectively from the sanitary pits were statistically significant at p < 0.05.

微生物菌剂与植物协同修复铅污染土壤

为了有效修复和美化污染的土壤环境,降低重金属的污染,将培养生物菌剂与2种富集植物联合修复铅(Pb)污染的土壤,通过微生物培养、高效液相色谱、微生物群落多样性分析等方法,研究土壤中重金属残留、酶活性、叶绿素含量、重金属抗性菌、微生物数量和群落多样性。结果表明:Pb污染浓度为400 mg/kg,分别经过联合修复30 d和60 d,土壤中重金属浓度分别下降了19.61%、19.48%,60 d比30 d吸附率分别提高了16.82%、17.83%。过氧化氢酶由对照组的5.6 mg/kg增加到11.4、15.9 mg/kg;碱性磷酸酶的活性由45.6 mg/kg增加到88.4、93.4 mg/kg;蔗糖酶的活性由4.2 mg/kg增加到9.6、9.9 mg/kg;脲酶的活性由32.6 mg/kg增加到66.3、71.2 mg/kg。叶绿素的含量分别增加9.16%、9.18%。重金属抗性菌检出量分别减少21.31%和20.27%。细菌、真菌和放线菌的数量最高增加了97.68%、67.63%、210.09%。微生物群落多样性和丰度也相应增加2.7%、2.9%。可见污染土壤经过微生物菌剂与植物联系修复后,植物的光合作用增强,加快重金属的吸附和转运,提高酶活性,提升植物对重金属的耐受性,重金属抗性菌数量显著降低,微生物群落多样性增加;阐明微生物菌剂和植物协同作用下对重金属污染土壤的强化修复机制,为高效治理土壤污染提供科学依据。

SRB的分离鉴定及其对酸性矿山废水的处理

针对酸性矿山废水高浓度硫酸盐和金属离子以及低pH的污染情况,从矿区煤矸石堆的底泥和浸出液中筛选鉴定出一株硫酸盐还原菌,根据其形态特征以及16SrRNA基因序列进行鉴定,研究碳源、温度、pH、初始硫酸盐浓度对该菌株生长和还原硫酸盐的影响,并利用该菌株处理酸性矿山废水。菌株经过16SrRNA基因测序后,鉴定为Citrobacter freundii,命名为S1(NCBI登录号:PP273014)。菌株S1在35℃、pH为7.0、SO_(4)^(2-)浓度2000 mg/L的条件下生长最旺盛。菌株S1对酸性矿山废水中TFe、Mn^(2+)、Zn^(2+)和SO_(4)^(2-)均有一定的处理效果,接种7 d后去除率分别为81.96%、35.08%、52.92%和63.24%,废水pH从4.38提高到了6.6左右。

不同外源Cd(Ⅱ)对Pseudomonas aeruginosa EPS的胁迫效应--产量、组分、吸附特性变化及其机制

以CdCl_(2)、CdSO_(4)和Cd(NO_(3))_(2)为胁迫因子,比较了不同阴离子在胁迫/诱导过程中对Pseudomonas aeruginosa(P.aeruginosa)胞外聚合物(EPS)的产量和特性的影响以及对Cd(II)吸附性能的变化.研究发现,当Cd(NO_(3))_(2)胁迫/诱导浓度为50mg/L时,EPS产量达到214.91mg/g VSS,其中蛋白质含量达到136.75mg/g VSS,较胁迫/诱导前增加了409.31%.此时EPS的吸附性能最好,对Cd(II)的平衡吸附量最大,较胁迫/诱导前增加了近一半.HPLC分析表明,EPS蛋白质中氨基酸的变化与EPS的吸附特性密切相关.3D-EEM、XPS和FTIR结果表明,EPS中C=O、C-N和N-H含量增加,有利于重金属的结合.竞争吸附实验发现,EPS对Cd(II)的亲和力高于Zn(II).

细菌介导重金属转化过程及金属组学研究方法

重金属污染依然是我国严重的环境问题之一。在重金属胁迫下,微生物可通过复杂的过程,对重金属进行转化,降低重金属的毒性,其中转化涉及的分子机制广受关注。目前,在上述机制相关研究中,对转化过程中重金属的衡量多局限于总量的测定,而对其赋存形态的研究不足,导致难以取得有效进展。对细菌介导重金属的转化过程及金属在其中的赋存形态进行综述,探讨了金属组学研究方法在其中的应用,重点针对重金属的颗粒态与蛋白质结合态进行分析、表征和鉴定,为微生物介导重金属的转化研究提供新视角。

生物吸附剂在含重金属离子废水处理中的研究进展

高效、节能、环保的含重金属离子废水处理技术是如今的研究重点之一,生物吸附法因其对环境友好的特性以及优秀的吸附性能,在含重金属离子废水处理的领域内有着较大的潜力。近些年来,国内外研究者从酵母、生物质、细菌、藻类等方面对生物吸附剂进行探索研究,以期让其更好的应用于实际。主要是从生物吸附剂材料分类和生物吸附机理两方面,对目前的生物吸附剂研究进展进行总结和归纳,并对其未来的发展做出相应展望。

硫酸盐还原菌修复四川某典型铜矿选冶渣复合重金属污染研究

为实现铜矿选冶渣复合重金属污染的修复治理,以四川某铜矿选冶渣为研究对象,采用硫酸盐还原菌为固化/稳定化微生物,探讨了其生长特性、溶液中重金属离子变化规律及修复效果。结果表明,硫酸盐还原菌在修复铜矿选冶渣时生长迅速,适合作为修复复合重金属污染的微生物;由于铁、锌、铜、铅等重金属活性差异较大,因此其固化效果亦有显著差异;修复30 d时,重金属Cu、Pb、Zn、Fe的最佳接种量分别为5%、10%、15%和15%,生物有效性降低率分别为72.36%、98.37%、43.01%和79.31%;随着固化时间的增加,溶液中重金属离子的浓度先增后减,但并不影响其修复效果。因此,硫酸盐还原菌可同时修复多种重金属离子,有效解决某铜矿选冶渣中铁锌铜铅的复合重金属污染。

无机氮和重金属对渤海不同区域沉积物中厌氧氨氧化菌的影响差异

厌氧氨氧化菌(anaerobic ammonium oxidation,Anammox)是驱动厌氧氨氧化过程、去除海洋沉积物中氮元素的重要引擎。为分析无机氮和重金属对厌氧氨氧化菌的影响,以渤海沉积物中厌氧氨氧化菌为研究对象,采用Illumina高通量测序技术和实时荧光定量PCR技术对渤海13个站位表层沉积物中AMX16S rDNA基因进行检测,分析其群落结构以及重金属含量对群落结构和多样性的影响。结果表明,渤海沉积物中厌氧氨氧化菌类群可归为14门、8纲、9目、5科、8属、26种,其中浮霉菌门(Planctomycetota)在渤海沉积物中占主导地位,且在中部区域丰度最高;相对丰度最高的属为Candidatus Scalindua。沉积物中重金属Hg在南部区域浓度最高。随机森林分析结果显示,南部区域厌氧氨氧化菌群落结构变化可能与沉积物中的NH4+、Hg和Cr含量密切关联,在北部区域可能与Pb含量密切相关,而在中部区域可能与NO2-含量密切相关。AMX16S rDNA丰度与重金属Cr和Cu、总氮以及沉积物粒度显著正相关(P<0.05)。研究表明,渤海具有丰富的微生物资源和厌氧氨氧化菌,具有代谢多种污染物的潜力。研究结果为认识近海污染对微生物的地理分布格局、群落生态位分化提供了依据。

SRB对AMD湿地处理系统沉积物中重金属的钝化作用研究

湿地沉积物既是重金属污染的汇,也是重金属污染的源,沉积物修复技术中的微生物钝化技术是实现重金属原位修复的一种重要手段。以酸性矿山废水(Acid Mine Drainage,AMD)湿地沉积物为对象,研究了硫酸盐还原菌(Sulphate Reducing Bacteria,SRB)对湿地沉积物中铁(Fe)、锰(Mn)、铜(Cu)和锌(Zn)释放及形态的影响,探究了SRB对沉积物中重金属的钝化效果。结果表明:在沉积物中接种SRB可不同程度地提高浸出液p H、电导率(EC)值,降低氧化还原电位(Eh)和硫酸盐(SO_(4)^(2-))浓度,当SRB的接种体积大于100 mL时,浸出液中Fe、Mn、Cu的浓度显著降低,当接种体积为200 mL时,浸出液Zn的浓度显著降低;接种SRB可使沉积物中Fe由弱酸提取态和可还原态转为可氧化态,使可还原态Mn向弱酸提取态及可氧化态转化,而沉积物中Cu、Zn则由弱酸提取态向可氧化态转化;接种14 d后,SRB接种体积为200 mL的处理组中沉积物中Fe、Mn的钝化效率最高,接种体积为100 mL的处理组中SRB对Cu和Zn的钝化效果最为明显。