Modeling Kinetics and Inhibition of Chloroethene Reductive Dechlorination in Mixed Culture PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Modeling Kinetics and Inhibition of Chloroethene Reductive Dechlorination in Mixed Culture PDF full book. Access full book title Modeling Kinetics and Inhibition of Chloroethene Reductive Dechlorination in Mixed Culture by Qi Meng. Download full books in PDF and EPUB format.
Author: Qi Meng
Publisher:
ISBN:
Category :
Languages : en
Pages : 161
Get Book Here
Book Description
Chlorinated ethenes such as tetrachloroethene (PCE) and trichloloethene (TCE) are among the most prevalent contaminants in soil, sediments and groundwaters. Currently, Insitu bioremediation via anaerobic reductive dechlorination has become a widely used technology for groundwater contaminated with chlorinated ethenes. To better understand the reductive dechlorination remediation process and the inter-relationships among the complex microbial communities that comprise it, a comprehensive biokinetic model was recently developed at Cornell University by Gretchen Heavner, a modification of an earlier Cornell model developed by Donna Fennell. The Heavner model uses specific biomasses based on quantitative PCR-based population data, and under some conditions can accurately predict kinetics of dechlorination, fermentation of electron donors, and competition for electron donors between dechlorinators and methanogens, and generation of methane. However, the platform used to run the model - STELLA® (High Performance Systems) - is cumbersome for simulation of long time-spans, limiting the model's utility. Furthermore, the model uses an empirical, "mRNA-tuning" technique to improve data fits at high PCE-loadings, which makes the model descriptive, rather than predictive, in such cases. Additionally, electron donor fermentation is not predicted well at high electron-donor feeding rates. The overall purpose of this thesis research was to address some of the limitations of the Heavner model. The STELLA® model was successfully converted to run in MATLAB® using Runge-Kutta 4th-order integration. The model fits at high-PCE and high electron-donor loadings were improved by utilizing the inhibitory effects of high PCE on dechlorination and methanogenesis, and by postulating additional pathways of butyrate's fermentation and acetate's hydrogenation to storage products. Model simulations indicate that by adding 2nd-order Haldane inhibition instead of mRNA tuning, the model revised in this thesis research predicts the dechlorination, methanogenesis and donor fermentation well over a broad range of PCE feeding rates. Moreover, when simulating donor fermentation at high-PCE-loadings, butyrate's fermentations and acetate's hydrogenation to storage products must be considered to obtain a mass balance between butyrate consumption and product formation.
Author: Qi Meng
Publisher:
ISBN:
Category :
Languages : en
Pages : 161
Get Book Here
Book Description
Chlorinated ethenes such as tetrachloroethene (PCE) and trichloloethene (TCE) are among the most prevalent contaminants in soil, sediments and groundwaters. Currently, Insitu bioremediation via anaerobic reductive dechlorination has become a widely used technology for groundwater contaminated with chlorinated ethenes. To better understand the reductive dechlorination remediation process and the inter-relationships among the complex microbial communities that comprise it, a comprehensive biokinetic model was recently developed at Cornell University by Gretchen Heavner, a modification of an earlier Cornell model developed by Donna Fennell. The Heavner model uses specific biomasses based on quantitative PCR-based population data, and under some conditions can accurately predict kinetics of dechlorination, fermentation of electron donors, and competition for electron donors between dechlorinators and methanogens, and generation of methane. However, the platform used to run the model - STELLA® (High Performance Systems) - is cumbersome for simulation of long time-spans, limiting the model's utility. Furthermore, the model uses an empirical, "mRNA-tuning" technique to improve data fits at high PCE-loadings, which makes the model descriptive, rather than predictive, in such cases. Additionally, electron donor fermentation is not predicted well at high electron-donor feeding rates. The overall purpose of this thesis research was to address some of the limitations of the Heavner model. The STELLA® model was successfully converted to run in MATLAB® using Runge-Kutta 4th-order integration. The model fits at high-PCE and high electron-donor loadings were improved by utilizing the inhibitory effects of high PCE on dechlorination and methanogenesis, and by postulating additional pathways of butyrate's fermentation and acetate's hydrogenation to storage products. Model simulations indicate that by adding 2nd-order Haldane inhibition instead of mRNA tuning, the model revised in this thesis research predicts the dechlorination, methanogenesis and donor fermentation well over a broad range of PCE feeding rates. Moreover, when simulating donor fermentation at high-PCE-loadings, butyrate's fermentations and acetate's hydrogenation to storage products must be considered to obtain a mass balance between butyrate consumption and product formation.
Author: Seungho Yu
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 394
Get Book Here
Book Description
Author: Joseph Bryce Lotrario
Publisher:
ISBN:
Category : Bioremediation
Languages : en
Pages : 346
Get Book Here
Book Description
The addition of exogenously supplied hydrogen stimulates PCP reductive dechlorination and increases bacterial growth. While research focuses mainly on pure cultures, few exist capable of aryl reductive dechlorination, and few markers exist to identify reductively dechlorinating bacteria within mixed cultures. Furthermore, most active bioremediation projects stimulate mixed cultures of native biota. This work describes a method to estimate reductively dechlorinating bacterial growth within a mixed soil culture under controlled environmental conditions. The experiments discussed in this paper were performed in a fed-batch reactor. The reactor was operated in a way to maintain environmental conditions such as pH, E[subscript H], headspace concentration, and temperature constant while substrate is allowed to degrade without the corruption of additional changes. Substrate utilization and cell growth were examined under an array of environmental conditions. This dissertation examined the correlation between hydrogen concentration and the growth rate of reductively dechlorinating bacteria. Under low hydrogen partial pressures, between 9.4 x 10−5 and 2.9 x 10−4 atm, the growth rate of reductively dechlorinating bacteria increased as predicted by dual Monod kinetics with respect to hydrogen and chlorophenol concentration; however, studies showed that the relationship was more complex. At higher concentrations of hydrogen, the observed growth rate of reductively dechlorinating bacteria declined. A dual Monod kinetics model with hydrogen substrate inhibition approximates experimental data. Reductive dechlorination of 2,3,4,5-tetrachlorophenol and 3,4,5-trichlorophenol were also studied. Pentachlorophenol reductive dechlorination primarily produces 3,4,5-trichlorophenol via 2,3,4,5-tetrachlorophenol. The reductive dechlorination of 2,3,4,5-tetrachlorophenol parallels that of pentachlorophenol, and the estimated growth rates based on pentachlorophenol and 2,3,4,5-tetrachlorophenol are very similar. Reductive dechlorination of 3,4,5-trichlorophenol was catalyzed by the PCP reductively dechlorinating bacterial culture after a lag period. 3,4,5-Trichlorophenol was not maintained for extended periods, and multiple additions of 3,4,5-trichlorophenol did not result in measurable growth.
Author: Dusty Rose V. Berggren
Publisher:
ISBN:
Category : Bioremediation
Languages : en
Pages : 145
Get Book Here
Book Description
Chlorinated ethenes are common groundwater contaminants that may be treated through in-situ bioremediation. Relationships between the reducing environment, available electron donors and acceptors, reaction kinetics, and microbial community composition must be further understood to successfully engineer remediation schemes in the complex subsurface environment. This thesis work investigated the effect of sulfate reduction on a dehalogenating culture grown under very controlled conditions. Two chemostats containing the Point Mugu (PM) culture were maintained using an influent containing tetrachloroethene (PCE) as an electron acceptor and lactate as a fermenting electron donor. One of these chemostats, PM-5L, was used as a control, while the influent to the PM-2L chemostat was amended with sulfate on an equal electron-equivalent basis to PCE. The effluent composition of these two chemostats was monitored over time, and periodic batch rate tests and molecular analyses were performed with cells harvested from the chemostat to elucidate the changes in performance and microbial composition within the chemostat culture. A numerical model based on Monod kinetics with competitive inhibition was developed to fit data from batch PCE-to-ethene rate tests by simultaneously solving for the k[subscript m]X parameters of each CAH dechlorination step given a standard set of Ks values. Non-linear regression of multi-equilibrium VC Monod test data provided the Monod parameters (k[subscript m]X and K[subscript s]) for VC dechlorination. These parameters were used to quantify changes in dechlorinating performance of each chemostat over time and compare the performance of the two chemostats. The effluent chemical composition of the PM-5L chemostat appeared to be steady after approximately six residence times, with 1120 uM PCE being transformed to 98% ethene and 2% VC, H2 tensions remaining between 2-3 nM, acetate around 4.3 mM, and biomass around 23 mg protein/L. Batch rate tests during this time showed rapid rates of transformation for all CAHs, agreeing well with chemostat performance. The k[subscript m]X parameters derived from the PCE-to-ethene data and the pseudo-mixed order rate coefficient of VC dechlorination determined through multi-equilibrium VC Monod tests also remained essentially constant over the one-year period of study. Changes in the PM-2L chemostat performance following the initiation of sulfate reduction were observed. Sulfate reduction began almost immediately after its addition to the chemostat, and total sulfide concentrations rose to 100-300 uM. Chemostat performance with respect to CAH and H2 concentrations was roughly steady over approximately 250 days, with PCE being dechlorinated to 9 uM cis-DCE, 230 uM VC, and 860 uM ethene under H2 tensions around 4 nM. Total protein levels nearly doubled during this period, increasing from 25 to 47 mg protein/L. Sulfate reduction then rapidly increased to completion, resulting in 620-720 uM dissolved sulfide and a decrease in the H2 concentration to 2 nM. At this time, the extent of PCE dechlorination also decreased to 280, 760, and 80 uM cis-DCE, VC, and ethene, respectively. Batch rate tests showed a decrease in all chlorinated ethene reduction rates; however, VC dechlorination was the most effected by sulfate reduction, showing a 97% reduction in rate following sulfate addition. Multi-equilibrium VC rate tests were impossible to conduct following the sharp increase in sulfate reduction in the chemostat due to lack of measurable dechlorination over a days' time. A simple chemostat model employed Monod kinetics for the series of CAH reactions to determine the steady-state extent of dechlorination in the chemostat predicted by the best-fit kinetic parameters of each PCE-to-ethene rate test. The extent of dechlorination was well-modeled for the PM-5L chemostat when a H2 limitation factor of 0.3 was applied to the rate of each CAH. Using a dual Monod kinetic model with H2 as the electron donor, the limitation factor corresponded with a half-velocity coefficient (K[subscript H]) of 4.6 nM. When this same K[subscript H] was used to model the PM-2L chemostat, a greater extent of dechlorination was predicted than what was observed in the chemostat, possibly suggesting other inhibitory factors of dechlorination were present in the PM-2L chemostat. DNA and RNA analyses of cells periodically harvested from the chemostat were performed by Ian P.G. Marshall at Stanford University. His work revealed shifts in the chemostats' Dehalococcoides population over time. Analysis of the PM-5L culture using the H2ase chip he developed and a clone library of hupL genes showed that the Dehalococcoides population was predominately related to strains BAV-1 or CBDB1/GT and did not undergo a significant shift over time. Clone libraries constructed for cells harvested from the PM-2L chemostat revealed two shifts in the chemostat Dehalococcoides population. A genetically homogenous strain relative of BAV-1 was eliminated following a decline in chemostat H2 tensions from around 27 nM to 2 nM and a corresponding increase in dehalogenation efficiency. In a second shift, a strain 195 relative outcompeted the CBDB1/GT relatives following enhanced sulfate reduction. A general decrease in the Dehalococcoides concentration within the chemostat culture was also suggested by qPCR analysis of Dehalococcoides 16S genes. These molecular results correlated well with the decline in VC reduction rates reported in batch kinetic tests given the characteristic co-metabolic VC reduction of the dominant strain 195 relative and overall lower concentrations of Dehalococcoides. Our work suggests that sulfate reduction in the anaerobic chemostat environment caused a shift in the dechlorinating microbial population to a strain with less efficient VC reduction. This shift was also accompanied by a decline in Dehalococcoides concentration within the culture. Both of these factors contributed to the decline in chlorinated ethene transformation rates observed through batch rate tests. Competition for H2 was not expected to be the primary cause for the changes observed in the PM-2L chemostat. Long-term batch tests involving the control culture are proposed to elucidate whether sulfide or other factors of sulfate reduction are responsible for this shift, and to confirm the suspected role of H2 competition between dechlorination and sulfate reduction in the chemostat-grown PM culture.
Author: Brian L. Murphy
Publisher: Academic Press
ISBN: 0124047076
Category : Science
Languages : en
Pages : 747
Get Book Here
Book Description
The third edition of Introduction to Environmental Forensics is a state-of-the-art reference for the practicing environmental forensics consultant, regulator, student, academic, and scientist, with topics including compound-specific isotope analysis (CSIA), advanced multivariate statistical techniques, surrogate approaches for contaminant source identification and age dating, dendroecology, hydrofracking, releases from underground storage tanks and piping, and contaminant-transport modeling for forensic applications. Recognized international forensic scientists were selected to author chapters in their specific areas of expertise and case studies are included to illustrate the application of these methods in actual environmental forensic investigations. This edition provides updates on advances in various techniques and introduces several new topics. Provides a comprehensive review of all aspects of environmental forensics Coverage ranges from emerging statistical methods to state-of-the-art analytical techniques, such as gas chromatography-combustion-isotope ratio mass spectrometry and polytopic vector analysis Numerous examples and case studies are provided to illustrate the application of these forensic techniques in environmental investigations
Author: Lorenz Adrian
Publisher: Springer
ISBN: 3662498758
Category : Science
Languages : en
Pages : 620
Get Book Here
Book Description
This book summarizes the current state of knowledge concerning bacteria that use halogenated organic compounds as respiratory electron acceptors. The discovery of organohalide-respiring bacteria has expanded the range of electron acceptors used for energy conservation, and serves as a prime example of how scientific discoveries are enabling innovative engineering solutions that have transformed remediation practice. Individual chapters provide in-depth background information on the discovery, isolation, phylogeny, biochemistry, genomic features, and ecology of individual organohalide-respiring genera, including Dehalococcoides, Dehalogenimonas, Dehalobacter, Desulfitobacterium and Sulfurospirillum, as well as organohalide-respiring members of the Deltaproteobacteria. The book introduces readers to the fascinating biology of organohalide-respiring bacteria, offering a valuable resource for students, engineers and practitioners alike.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 868
Get Book Here
Book Description
Author: Hans F. Stroo
Publisher: Springer Science & Business Media
ISBN: 1461441153
Category : Technology & Engineering
Languages : en
Pages : 421
Get Book Here
Book Description
This volume provides a review of the past 10 to 15 years of intensive research, development and demonstrations that have been on the forefront of developing bioaugmentation into a viable remedial technology. This volume provides both a primer on the basic microbial processes involved in bioaugmentation, as well as a thorough summary of the methodology for implementing the technology. This reference volume will serve as a valuable resource for environmental remediation professionals who seek to understand, evaluate, and implement bioaugmentation.
Author: Renshou Fu
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 346
Get Book Here
Book Description
Author: Michael D. Annable
Publisher: Springer Science & Business Media
ISBN: 1402068751
Category : Technology & Engineering
Languages : en
Pages : 196
Get Book Here
Book Description
This publication comprises the presentations made at the NATO Advanced Research Workshop held in Sinaia, Romania 9 – 11 October, 2006. The contributions represent a unique cross section of issues and challenges related to contaminated site management. These range from low cost solutions to petroleum contaminated sites to advances in biological treatment methods. The publication is meant to foster links between groups facing challenges cleaning up contaminated sites.
