Environmental Biotechnology in Water and Wastewater Treatment

Environmental biotechnology “manages microbial communities to provide services to society.” The key services today include detoxifying contaminated water and soil to reclaim lost resources and converting diffuse energy in biomass to forms easily used by society. Two timely examples are the reduction of oxidized water contaminants (e.g., nitrate, perchlorate, selenate, and chlorinated solvents) and the production of methane, hydrogen, and electricity. The key science underlying environmental biotechnology is microbial ecology, which has advanced rapidly in the past 20 or so years through the proliferation of new genomics-based techniques to characterize the communities’ structure and function. The genomic methods provide detailed information that helps us understand what aspects of the microbial community need to be managed to ensure that it provides the desired service. Often, we achieve the management goals through partnering the microorganisms with modern materials and physical/chemical processes. The membrane biofilm reactor and microbial fuel cells offer excellent examples of exciting new technologies that come directly from this kind of partnering.     

Importance of the iron cycle in biohydrometallurgy

After the discovery in the 1940s that acid mine drainage was mainly a consequence of the metabolism of chemolithoautotrophic microorganisms able to oxidize metal sulfides, mostly pyrite, much research has been performed to understand the ecology and the physiology of the microorganisms involved. At first, to prevent this environmental problem, and later to improve the efficiency of biohydrometallurgical processes. Until recently, bioenergetic considerations focused most of the attention on the sulfur oxidizing microorganisms. The demonstration that ferric iron was mainly responsible for the oxidation of pyrite has had profound implications not only on the comprehension of the phenomena but also on the microbial ecology of the correspondent systems. The Tinto River (Southwestern Spain) is an acidic environment with a high concentration of ferric iron generated by the metabolic activity of chemolithotrophic microorganisms growing in the rich complex sulfides of the Iberian Pyritic Belt (IPB). The use of conventional as well as molecular ecology tools identified the most representative members of the chemolithotrophic community of the Tinto Basin as prominent members of the iron cycle, highlighting the importance of this element in the oxidation of sulfides. Contrary to what was expected, the sulfur cycle seems to operate with rather low efficiency in the Tinto ecosystem. Interestingly enough, anaerobic geomicrobiology seems to play an important role in the system. All these observations strongly suggest that the iron cycle is extremely important for biohydrometallurgical processes in which sulfidic minerals are involved. An understanding of the properties of these versatile microorganisms and their ecology is essential to guarantee efficient and reliable biohydrometallurgical operations.     

Microbes Assisted Mineral Flotation a Future Prospective for Mineral Processing Industries: A Review

The latest advancements in mineral biotechnology developed environmental benign microbial flotation processes for mineral beneficiation. Several studies were conducted to evaluate the microbes and microbial metabolites as flotation reagents for separation of gangue materials from valuable minerals. The available scientific literatures on microbial flotation process suggest that, interactions of minerals with cells of certain bacteria and microbial metabolites have a significant effect on their surface properties. As a consequence, bacterial cells belong to genera Acidithiobacillus, Leptospirillum, Mycobacterium, Staphylococcus, and Bacillus, etc., and microbial metabolites such as bio-surfactants, extracellular polymeric substances (EPS) and nucleic acid have been used as collectors and surface modifiers in the mineral flotation process. The characteristic properties of the microbial surfactants such as their abilities to lower surface tensions and foaming capacity prompted their application as frother in mineral flotation process. To date, microbial flotations have primarily studied in laboratory scale; however, there is ample scope to expand this eco-friendly process for mineral processing industries. The current review addresses the recent developments and applications of microorganisms and bio-molecules in mineral flotation processes.     

Biodiversity at the molecular level: the domains, kingdoms and phyla of life

The results of comparative sequence analysis, mainly of small subunit (SSU) ribosomal (r)RNA sequences, have suggested that all of cellular life can be placed in one of three domains: the Archaea, Bacteria or Eucarya. There is some evidence that the Archaea may not be a monophyletic assemblage, but as yet this issue has not been resolved. Most of the lineages, and all of the deepest ones, in the tree based upon SSU rRNA sequences, are microbial. Traditional ideas of classification such as Whittaker's five kingdom scheme do not adequately describe life's diversity as revealed by sequence comparisons. There are many microbial groups that demonstrate much greater amounts of SSU rRNA sequence divergence than do members of the classical kingdoms, Animalia, Plantae and Fungi. The old microbial kingdoms Monera and Protista are clearly paraphyletic but as yet there is no consensus as to how they should be reorganized in taxonomic terms. New data from environmental analysis suggests that much of the microbial world is unknown. Every environment which has been analysed by molecular methods has revealed many previously unrecorded lineages. Some of these show great divergence from the sequences of cultured microorganisms suggesting that fundamentally new microbial groups remain to be isolated. The relationships of some of these new lineages may be expected to affect how the tree of life is organized into higher taxa, and to also influence which features will be recognized as synapomorphies. There is currently no objective measure whereby microbial diversity can be quantified and compared to the figures which are widely quoted for arthropods and other Metazoa.     

Recent Developments in the Bioprocessing of Minerals

Microorganisms are finding increasing use in minerals engineering. Goals include both enhancement of mineral engineering operations and remediation of mineral industry wastes. Some of the applications, such as biologically assisted leaching of sulfide ores and biooxidation of refractory sulfide gold ores. are established commercial processes. Others, such as the use of organisms for the removal of heavy metal ions from dilute aqueous streams, are nearing commercial application. Other uses of microorganisms are potentially possible. These include use of microorganisms in leaching non-sulfide ores, the flocculation or flotation of minerals and remediation of toxic chemicals discharged from mineral engineering operations. Genetic engineering of microorganisms and adaptation of existing strains are important potential tools in many of these applications, as is also the identification of new, novel and useful organisms.     

基于Lotka-Volterra的生物浸铀微生物生长动力学模型研究

前人研究表明,生物浸铀过程中浸矿和辅助浸矿微生物两者间存在协同作用,两者相互促进提高生物浸铀效率。浸矿和辅助浸矿微生物是如何相互促进,使彼此更好地得到生长,两者相互促进生长动力学模型是什么?Lotka-Volterra模型被广泛应用在两种间相互作用下生物数量增长模型研究中,对于生物浸铀中浸矿和辅助浸矿微生物生长动力学模型研究具有借鉴意义。由Lotka-Volterra模型得出了浸矿和辅助浸矿微生物独立共生和竞争共生方程,根据浸矿和辅助浸矿微生物协同特性建立了其生长动力学模型,由模型再推导出浸矿和辅助浸矿微生物协同作用稳定态点,该稳定态点与试验结果相差较小,说明生物浸铀浸矿和辅助浸矿微生物生长动力学模型拟合效果较好。将Lotka-Volterra模型应用到生物浸铀中,具有新颖性,提供了新的研究视角,对完善生物浸铀中微生物协同问题、提高生物浸铀效率具有重要的理论与实际意义。     

植物-微生物联合修复重金属的研究进展

重金属污染严重威胁到农作物安全和人体健康。植物修复重金属污染方面已有大量研究,其中植物-微生物联合修复被认为是改善重金属含量的一种有效方法。就近年来植物-微生物联合修复重金属的机理进行了评述,总结了近5年植物-微生物联合修复应用于重金属污染的研究。植物与微生物的协同作用,微生物与植物间形成联合体可以在很大程度上减轻环境对植物的影响。此外,微生物通过提高植物的抗性、降低重金属毒性、促进植物生长等方式增强植物修复重金属的能力。由于污染环境的复合性和复杂性,未来植物-微生物-金属相互作用的分子机制研究和开发植物-微生物联合修复的新技术开发将会成为重点。     

Microbial degradation of xenobiotics in the environment

Biodegradation of naturally occurring organic compounds follows their synthesis. In contrast, man-made compounds, also known as xenobiotics, are often refractory to degradation. The main reason is that they cannot be recognized by naturally present organisms and therefore do not enter common metabolic pathways. The physical and chemical characteristics of the compounds, as well as environmental factors, may influence their biodegradability. Some compounds may be transformed only in the presence of another compound which appears as a carbon and energy source. Very often compounds are degraded sequentially through the activity of a series of different organisms. The main degraders in nature are microorganisms, mostly bacteria and some fungi. These organisms, due to their rapid rates of multiplication and great metabolic potential, are able to adapt to new substrates. Selection of degradative potent microorganisms and their successive adaptation to a naturally persistent compound might be a powerful means for environmental detoxification. Although numerous laboratory experiments have given positive results, very few are applicable on a large scale. It is necessary to select microorganisms or microbial communities capable of controlled degradation of persistent organic chemicals without their transformation to other, more hazardous compounds. Better understanding of metabolic pathways for the biodegradation of specific organic compounds as well as more thorough knowledge of degrading microorganisms will make purposeful application of biodegradation possible.     

Bacterial succession in bioheap leaching

Bioheap leaching of secondary copper ores is applied commercially at operations in Chile, Australia, and Myanmar. Bioheap leaching of sulfidic refractory gold ores has been demonstrated at large scale. There is limited comprehension of what actually occurs microbiologically in full-scale bioheap operations, despite the commercial achievement of copper ore bioheap leaching and the anticipated technical and commercial success of gold ore bioheap leaching. Copper bioheaps are typically inoculated with the bacteria contained in the raffinate or intermediate leach solution, whereas, sulfidic refractory gold ore bioheaps can be inoculated with bacteria developed in a separate reactor. Chemical and physical conditions within bioheaps change radically from the time the bioheap is stacked and inoculated until bioleaching is completed. Redox, acidity, temperature, oxygen and solution chemistry conditions vary widely during the oxidation period. Such conditions likely select for microorganisms or may, in fact, effect a succession of organisms in portions of the bioheap. Bioheap solutions are recycled and constituent build-up over time also affects the microbiology. Organic entrapment in the raffinate from the solvent extraction circuit may influence microbial activity. Heterotrophic microorganisms may also play some role in bioheap leaching. Understanding the microbiology of bioheaps is key to advancing commercial bioheap applications. Such knowledge will increase the ore types as well as the diversity of mineral deposits that can be processed by bioheap technology. It will also enable better control of conditions to improve leach rates, metal recoveries and costs. This paper briefly explains commercial practices, describes chemical, physical and microbiological monitoring of bioheaps, considers conditions that control microbial populations in bioheaps, and examines the types of ore deposits that could be bioleached, if the microbiology was elucidated.     

Psychological environments: Expanding the scope of human ecology.

Distinguishes between ecology, human ecology, and social ecology. Studies of 8 specific environments and of scales for measuring each one have resulted in the concept of 3 broad categories or dimensions: relationship dimensions, personal development or goal orientation dimensions, and systems maintenance and change dimensions. These dimensional categories, and their application to studies of the 8 environments, are described and discussed. The scales developed by other investigators for measuring environments are analyzed in terms of these categories and appear to be basically consistent with them. The importance of the study and assessment of environments lies in their effect on the functioning of the individual. Although it is difficult, if not impossible, to formulate criteria for the ideal environment which would satisfy everyone's requirements, suggestions are made regarding the optimum methods of making environmental changes. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

微生物法修复铀污染环境研究进展

随着我国核工业的快速发展,铀资源的开采量不断增加,由此带来铀尾矿的大量堆积,导致铀及其化合物在周围生态环境中的含量迅速增加,对环境造成污染。因此,如何安全、高效治理铀污染环境,已成为亟需解决的环境科学与工程问题。传统针对铀污染环境的修复技术多采用物理、化学等方法,但这些修复技术具有成本高、易造成环境二次污染的局限性,而微生物修复技术的出现,可为铀污染环境的修复提供一种绿色、经济、稳定及可持续的修复方法。首先介绍了铀在环境中的危害,详细阐述了铀污染环境微生物修复技术的机制,并分析了其修复铀污染环境的影响因素,最后指出了铀污染环境微生物修复技术目前存在的问题,并对其进行了展望。     

微生物燃料电池碳基阳极材料的研究进展

微生物燃料电池（Microbial fuel cells, MFCs）是一种绿色能源技术,通过微生物的催化氧化代谢污水中的有机物同时产生电能,具有清洁环境和产电的双重优势,为可生物降解及可循环利用的废弃物转变成清洁能源提供了潜在的机会,在环境治理和能源利用方面表现出较好的应用前景。然而,目前相对较低的产电效率限制了MFCs的实际应用,其中阳极电极是产电微生物富集和传递电子的重要场所,与电池极化、电子导电性、生物相容性密切相关,是影响电池性能和运行成本的关键因素。碳纳米材料具有导电性好、比表面积大、孔隙率高、成本低等特点,被认为是微生物燃料电池重要的阳极材料,得到了广泛的研究和关注。本文主要从阳极电极种类、电极结构设计和电极材料改性等方面总结改善电极生物相容性、增加产电微生物附着量、提高反应活性位点的方法,并对提高产电性能的机理进行论述。最后对碳基电极材料进行展望,以期为制备高电化学活性的阳极材料提供理论指导。      

Sensing and Field Data Capture for Construction and Facility Operations

Collection of accurate, complete, and reliable field data is not only essential for active management of construction projects involving various tasks, such as material tracking, progress monitoring, and quality assurance, but also for facility and infrastructure management during the service lives of facilities and infrastructure systems. Limitations of current manual data collection approaches in terms of speed, completeness, and accuracy render these approaches ineffective for decision support in highly dynamic environments, such as construction and facility operations. Hence, a need exists to leverage the advancements in automated field data capture technologies to support decisions during construction and facility operations. These technologies can be used not only for acquiring data about the various operations being carried out at construction and facility sites but also for gathering information about the context surrounding these operations and monitoring the workflow of activities during these operations. With this, it is possible for project and facility managers to better understand the effect of environmental conditions on construction and facility operations and also to identify inefficient processes in these operations. This paper presents an overview of the various applications of automated field data capture technologies in construction and facility fieldwork. These technologies include image capture technologies, such as laser scanners and video cameras; automated identification technologies, such as barcodes and Radio Frequency Identification (RFID) tags; tracking technologies, such as Global Positioning System (GPS) and wireless local area network (LAN); and process monitoring technologies, such as on-board instruments (OBI). The authors observe that although applications exist for capturing construction and facility fieldwork data, these technologies have been underutilized for capturing the context at the fieldwork sites as well as for monitoring the workflow of construction and facility operations.     

铬污染的微生物吸附技术研究进展

近年来,铬在工业生产中得到了广泛的应用,随之而来的含铬污染物对周围环境造成严重的污染和破坏,铬污染的修复已成为亟待解决的环境问题.微生物在铬污染的生物修复中发挥着重要的作用.它因铬污染修复过程中环保有效,安全可靠且无二次污染等优点,引起了相关学者们的广泛关注.首先简述了铬污染危害及传统处理技术,重点综述了微生物作为生物...     

Chemical and electrochemical basis of bioleaching processes

The bioleaching of sulfide minerals involves electrochemical and chemical reactions of the mineral with the leach liquor and the extra-cellular polysaccharide layers on the microorganisms. The microorganisms derive energy by oxidising the sulfur moiety and ferrous iron, which can be interpreted using electrochemistry and chemiosmotic theory. Recently, significant advances have been made in understanding the mechanism by which the bioleaching of sulfide minerals occurs. Kinetic models based on the proposed mechanism are being used successfully to predict the performance of continuous bioleach reactors. The measurement of oxygen and carbon dioxide consumption rates together with the measurement of redox potentials has led to this further elucidation of the mechanism of bioleaching of sulfide minerals and enabled the kinetics of the sub-processes involved to be determined separately. It has been shown that bioleaching involves at least three important sub-processes, viz., attack of the sulfide mineral, microbial oxidation of ferrous iron and some sulfur moiety. The overall process occurs via one of two pathways depending on the nature of the sulfide mineral, a pathway via thiosulfate resulting in sulfate being formed or a polythionate pathway resulting in the formation of elemental sulfur. For the case of pyrite, the primary attack of the sulfide mineral is a chemical ferric leach producing ferrous iron. The role of the bacteria is to re-oxidise the ferrous iron back to the ferric form and maintain a high redox potential as well as oxidising the elemental sulfur that is formed in some cases. The first two sub-processes of chemical ferric reaction with the mineral and bacterial oxidation of the ferrous iron are linked by the redox potential. The sub-processes are in equilibrium when the rate of iron turnover between the mineral and the bacteria is balanced. Rate equations based on redox potential or ferric/ferrous-iron ratio have been used to describe the kinetics of these sub-processes. The kinetics have been described as a function of the ferric/ferrous-iron ratio or redox potential which enables the interactions of the two sub-processes to be linked at a particular redox potential through the rate of ferrous iron turn-over. The use of these models in predicting bioleach behaviour for pyrite is presented and discussed. The model is able to predict which bacterial species will predominate at a particular redox potential in the presence of a particular mineral, and which mineral will be preferentially leached. The leach rate and steady state redox potential can be predicted from the bacterial to mineral ratio. The implications of this model on bioleach reactor design and operation are discussed. Research on the chemistry and electrochemistry of the ferric leaching of sulfide minerals and an electrochemical mechanism for ferrous iron oxidation based on chemiosmotic theory will be presented and reviewed.     

锌的生物浸出技术现状及研究进展

锌是现代工业所必需的有色金属,属于很重要的战略资源,其在世界所有金属产量中排名第四,仅次于铁、铝和铜。随着低品位难处理锌资源的种类和产量的不断增加,以及湿法冶金技术的不断发展,锌的生物浸出技术得到了研究人员的广泛关注,并展示出了良好的潜在应用前景。本文首先较为详细的介绍了含锌资源的矿物特征,并对其生物可浸性进行了分析。其次,对目前锌的生物浸出体系,所用浸矿菌种,浸出过程所涉及的电化学、热力学、动力学以及浸出机理进行了归纳总结;接着,对锌的生物浸出技术现状和工艺新进展进行了阐述。最后,展望了锌的生物浸出工艺的发展趋势及后续的研究热点。研究表明高效浸锌菌种的选育驯化、与之相匹配的工艺及装备研发,是锌的生物浸出当今研究热点及未来发展方向。      

Scientific and Technological Challenges in Mineral Processing

Due to increasingly complex mineralogy, steadily decreasing ore grades and ever increasing economic and environmental pressures, the mineral processing industry over the past decade had to evolve appropriate means to treat these difficult-to-process ore deposits. Some of the important emerging trends and the evolutionary changes which have occurred in mineral processing technology; are reviewed. This includes the areas of quantifying mineral liberation, in the design of new size reduction devices like high pressure rolls mills, advances in gravity separation and magnetic separation, development of new flotation machines like column flotation and flash flotation, design and testing of new flotation reagents and the new technologies based on a combination of physical and chemical separation methods are reviewed. The challenging areas of current research efforts have been highlighted.     

浸矿微生物与矿物相互作用的研究方法与技术

深入研究和理解浸矿微生物与矿物之间的相互作用机制对于提高金属浸出效率及控制酸性矿坑水的形成是必须的.研究浸矿微生物与矿物之间的相互作用过程中,各种理论方法和检测探测技术起到了决定性的作用.为了使各种方法技术更加深入地应用于研究中,文中概述了研究浸矿微生物-矿物相互作用的物理化学方法,表面成分检测方法以及微观形貌探测技术,并指出各种研究方法技术的结合是更好地探测浸矿微生物-矿物相互作用的发展方向.