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首页> 外文学位 >Biodegradation and bioremediation of hexachlorocyclohexane isomers, chlorinated ethenes, chlorinated benzenes and benzene.
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Biodegradation and bioremediation of hexachlorocyclohexane isomers, chlorinated ethenes, chlorinated benzenes and benzene.

机译：六氯环己烷异构体，氯化乙烯，氯化苯和苯的生物降解和生物修复。

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摘要

Groundwater at an industrial site is contaminated with alpha- hexachlorocyclohexane (HCH) and gamma-HCH (i.e., lindane) (0.3-0.5 ppm). Other contaminants in the 1-15 ppm range include 1,2,4-trichlorobenezene (TCB), 1,2-dichlorobenzene (DCB), 1,3-DCB, 1,4-DCB, chlorobenzene (CB), benzene, trichloroethene (TCE) and cis-1,2-dichloroethene (cDCE). The aquifer consists of a shallow layer of soil over fractured dolomite, where most of the contaminant mass resides. The objective of this study was to compare (1) anaerobic reductive dechlorination of the polychlorinated contaminants, followed by aerobic biodegradation of the daughter products (mainly DCBs, CB, and benzene); and (2) aerobic biodegradation of alpha- and gamma-HCH, TCB, DCBs, CB and benzene, followed by anaerobic reduction of TCE and cDCE to ethene. Conventional wisdom suggests that sequential anaerobic and aerobic conditions are desirable for bioremediating sites contaminated by mixtures of polychlorinated organics. The results of this microcosm study suggest that a sequential aerobic and anaerobic approach may be more successful, although implementing this in the field presents some major challenges.;In the microcosm study for an industrial site contaminated with HCH isomers (predominantly gamma-HCH), we observed rapid anaerobic biodegradation of gamma-HCH to benzene and chlorobenzene. The pattern and rate of activity suggested that gamma-HCH may be used as a terminal electron acceptor. Using inoculum from microcosms that exhibited high rates of gamma-HCH reduction, enrichment cultures were developed in groundwater from the industrial site and subsequently transferred to an anaerobic mineral medium without loss of gamma-HCH dechlorination. The culture was further enriched in a sulfate free media with two different types of buffers (bicarbonate and HEPES) and gamma-HCH as the only terminal electron acceptor and hydrogen as electron donor. Electron balance calculations in the bicarbonate buffered enrichment cultures revealed that only a small fraction of the hydrogen was involved in gamma-HCH dechlorination; most was consumed for acetogenesis. Based on the fraction of electron equivalents used for gamma-HCH dechlorination in HEPES-buffered enrichment culture and the ability to transfer this culture with gamma-HCH as the sole terminal electron acceptor, this study is the first to demonstrate chlororespiration of gamma-HCH. Molecular analysis of enrichment cultures (in bicarbonate and HEPES buffered medium) in this study did not provide sufficient information to associate a specific microbe with chlororespiration of gamma-HCH. The development of gamma-HCH dechlorinating culture in this study will improve our understanding of remediation of gamma-HCH by natural attenuation and engineered approaches.;Using inoculum from a microcosm that exhibited aerobic transformation of cis-dichloroethene (cDCE) and trichloroethene (TCE) commensurate with biodegradation of the monoaromatic compounds, enrichment cultures were developed in groundwater by providing benzene, chlorobenzene, dichlorobenzene isomers and 1,2,4-trichlorobenzene as carbon and energy sources. These enrichments were subsequently transferred to a mineral salt medium and were grown on each of the monoaromatic compounds separately and were successfully maintained through several transfers. Isolates growing on benzene, chlorobenzene, 1,2-dichlorobenzene and 1,3-dichlorobenzene were identified as Rhodococcus, Ralstonia, Variovorax and Ralstonia, respectively, by their 16S rRNA gene sequences. The yield measured on the isolates growing on corresponding substrates ranged from 0.36-0.45 mg biomass/mg substrate, with highest yield on benzene and lowest yield on 1,3-dichlorobenzene. Cometabolic transformation of cDCE and TCE evaluated based on pseudo-first order cometabolic degradation rate constant, transformation capacity and transformation yield for resting cells were observed to be on the low end of the reported values on phenol or toluene grown isolates. Cometabolic transformation of cDCE and TCE was also evaluated with growing cells of each isolate and were observed to be on low end of reported values for TCE and this is the first study to report for cDCE. In general, the cometabolic transformation parameters observed for cDCE were greater than TCE. The results of this study confirm the potential for cometabolism of cDCE and TCE during aerobic growth on benzene, CB, 1,2-DCB and 1,3-DCB. This is especially relevant for natural attenuation scenarios when these compounds occur as co-contaminants and may be transported from an anaerobic to an aerobic environment.;The major findings from this dissertation are; (i) aerobic/anaerobic treatment should be considered as an alternative to anaerobic/aerobic treatment for bioremediation of complex mixtures of chlorinated contaminants, (ii) chlororespiration of gamma-HCH was demonstrated for the first time and this improves the opportunities for in situ bioremediation, and (iii) aerobic cometabolism of cDCE and TCE with aromatic contaminants helps to explain the potential pathways for natural attenuation of complex mixtures. (Abstract shortened by UMI.)
机译：工业现场的地下水被α-六氯环己烷（HCH）和γ-HCH（即林丹）（0.3-0.5 ppm）污染。 1-15 ppm范围内的其他污染物包括1,2,4-三氯苯（TCB），1,2-二氯苯（DCB），1,3-DCB，1,4-DCB，氯苯（CB），苯，三氯乙烯（TCE）和顺式1，2-二氯乙烯（cDCE）。含水层由破裂的白云石上的浅层土壤组成，大部分污染物都存在于此。这项研究的目的是比较（1）多氯污染物的厌氧还原脱氯，然后子产物（主要是DCB，CB和苯）的好氧生物降解； （2）将甲型六氯环己烷和丙型六氯环己烷，三氯甲烷，二氯苯，六氯苯和苯进行好氧生物降解，然后将三氯乙烯和三氯乙烷厌氧还原为乙烯。传统观点认为，连续的厌氧和好氧条件对于由多氯有机物混合物污染的生物修复部位是理想的。该微观研究的结果表明，尽管在野外实施有氧和厌氧的顺序方法可能会更成功，但在实地实施该方法带来了一些重大挑战。我们观察到γ-六氯环己烷快速厌氧生物降解为苯和氯苯。活性的模式和速率表明，γ-六氯环己烷可用作终端电子受体。使用来自具有高γ-六氯环己烷减少率的微观世界的接种物，在工业现场的地下水中开发了富集培养物，随后将其转移到厌氧矿物培养基中，而不会损失γ-六氯环己烷的脱氯作用。该培养物进一步富含无硫酸盐的培养基，其中含有两种不同类型的缓冲液（碳酸氢盐和HEPES），且γ-六氯环己烷是唯一的末端电子受体，氢是电子供体。在碳酸氢盐缓冲的富集培养物中的电子平衡计算表明，只有小部分的氢参与了γ-六氯环己烷的脱氯反应。大部分用于产乙酸。根据HEPES缓冲的浓缩培养物中用于γ-六氯环己烷脱氯的电子当量分数以及以γ-六氯环己烷作为唯一末端电子受体转移这种培养物的能力，本研究首次证明了γ-六氯环己烷的氯呼吸作用。在这项研究中，对富集培养物（在碳酸氢盐和HEPES缓冲液中）的分子分析没有提供足够的信息，无法将特定的微生物与丙型六氯环己烷的氯呼吸作用相关联。这项研究中γ-六氯环己烷脱氯培养物的发展将增进我们对通过自然衰减和工程方法修复γ-六氯环己烷的了解。与单芳族化合物的生物降解相适应，通过提供苯，氯苯，二氯苯异构体和1,2,4-三氯苯作为碳和能源，在地下水中开发了富集培养物。随后将这些富集物转移至无机盐培养基中，并分别在每种单芳族化合物上生长，并通过几次转移成功维持。生长在苯，氯苯，1，2-二氯苯和1，3-二氯苯上的分离株通过其16S rRNA基因序列分别被鉴定为红球菌，Ralstonia，Variovorax和Ralstonia。在相应底物上生长的分离物测得的产量为0.36-0.45 mg生物量/ mg底物，苯的最高产量，而1,3-二氯苯的最低产量。根据拟一级代谢速率降解速率常数，静息细胞的转化能力和转化产量评估的cDCE和TCE的代谢转化率在报告的苯酚或甲苯分离株数值的低端。还用每种分离株的生长细胞评估了cDCE和TCE的新陈代谢转化，观察到其在TCE报道值的低端，这是首次报道cDCE的研究。通常，对cDCE观察到的代谢转化参数大于TCE。这项研究的结果证实了好氧生长在苯，CB，1,2-DCB和1,3-DCB上cDCE和TCE发生新陈代谢的潜力。当这些化合物作为共污染物存在并且可能从厌氧环境转移到有氧环境时，这对于自然衰减场景尤为重要。 （i）对于含氯污染物的复杂混合物的生物修复，应考虑使用有氧/厌氧处理代替厌氧/有氧处理，（ii）首次证明了丙型六氯环己烷的氯呼吸作用，这增加了原位生物修复的机会，并且（iii）cDCE和TCE与芳香族污染物的有氧代谢代谢有助于解释复杂混合物自然衰减的潜在途径。 （摘要由UMI缩短。）

著录项

  • 作者

    Elango, Vijaikrishnah.;

  • 作者单位

    Clemson University.;

  • 授予单位 Clemson University.;
  • 学科 Biology Microbiology.;Environmental Sciences.;Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 266 p.
  • 总页数 266
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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