Global ETD Search

1	Colloid Formation for the Removal of Natural Organic Matter during Iron Sulfate Coagulation Masters, Erika N. 31 July 2003 (has links) Removal of organic matter is increasingly important to drinking water utilities and consumers. Organic matter is a significant precursor in the formation of disinfection by-products (DBPs). The maximum contaminant levels for (DBPs) are decreasing and more DBPs are believed carcinogenic. Traditional coagulation focuses on the removal of particulate matter and in the last decade soluble species have also been targeted with high coagulant doses. However, colloidal matter is smaller than particulate matter and therefore not easily removed by conventional drinking water treatment. This research focused on the conversion of soluble organic matter to colloids using relatively low doses of ferric sulfate coagulant and the subsequent removal of the colloids by filtration during drinking water treatment. The goal is to achieve enhanced removal of soluble organic matter with minimal chemical costs and residual formation. This study investigated the effects of pH, iron coagulant dose, turbidity, organic matter concentration, and temperature on colloid formation. Characterization of the colloidal organic matter was attempted using zeta potential and sizing analyses. Cationic low molecular weight, nonionic high molecular weight, and cationic medium molecular weight polymers were evaluated on their removal of colloidal organic matter. Colloidal organic matter formation was affected by changes in coagulation pH, coagulant dose, and organic matter concentration, whereas turbidity and temperature did not significantly impact colloid formation. Decreased coagulation pH caused increased organic carbon removal. As coagulant dose was increased, colloid formation initially increased to maximum and subsequently rapidly decreased. Colloid formation was increased as the organic matter concentration increased. Due to low sample signal, the colloids could not be characterized using zeta potential and sizing analyses. In addition, polymers were ineffective for aggregating colloidal organic matter when used as flocculant aids. / Master of Science organic matter colloid ferric iron sulfate coagulation
2	Investigations of the Physical and Analytical Chemistry of Iron in Aqueous Solutions Patten, James 12 November 2014 (has links) Although iron occurs at extremely low concentrations in the world’s oceans, it is essential for all living organisms. It is the limiting nutrient in High Nutrient Low Chlorophyll (HNLC) areas of the ocean, and exerts critically important influences on levels of atmospheric CO2 and the global carbon cycle. Understanding the chemical processes that govern the fluxes and biogeochemistry of oceanic iron requires thorough assessment of the aqueous physical chemistry of iron and analytical techniques capable of measuring iron at sub-nanomolar concentration measurements. This dissertation extends prior work on the physical and analytical chemistry of iron through (a) investigation of the complexation of iron by silicate in aqueous solutions, (b) investigation the solubility of ferric hydroxide using spectrophotometric procedures over a wide range of pH (c) utilization of novel in-situ instrumentation for iron measurements in seawater. Previous investigations of ferric iron complexation by silicate ions (SiO(OH)-3) included no measurements at ionic strengths greater than 0.15 molal and produced formation constant estimates at zero ionic strength that differed by more than a factor of two. In this work ferric silicate formation constants were measured at ionic strengths of 0.1, 0.3 and 0.7 molal by ultraviolet absorbance spectroscopy. The dependence of the ferric silicate formation constant on ionic strength at 25° C, summarized using the Bronsted-Guggenheim-Scatchard specific ion interaction (SIT) model, indicated that the ionic strength dependence of the ferric silicate formation constant, (written as Si ∗β1 = [FeSiO(OH)23+][H+][Fe3+]-1[Si(OH)04]-1) can be expressed as: log Si *β1 = (-0.125 ± 0.042) - (2.036 I0.5)/(1+ 1.5I0.5) + (0.588 ± 0.094) I. The result obtained at zero ionic strength is in good agreement with the average result obtained in four previous studies, but with a substantially reduced level of uncertainty. The solubility of ferric iron in aqueous sodium perchlorate solutions at the ionic strength of seawater was determined by use of novel automated spectrophotometric procedures. Two colorimetric measurement chemistries were utilized to measure dissolved ferric iron concentrations in equilibrium with precipitated amorphous ferric hydroxide over a range of pH between 4.0 and 12.0. Soluble iron concentrations decreased from approximately 3.2 micromolar at pH 4.0 to subnanomolar levels between pH 7.5 and 9.5, and rose to approximately 0.1 micromolar at pH 12. The results of this investigation were in good agreement with solubility results obtained in previous investigations of iron solubility in seawater at circumneutral pH, and previous results obtained in sodium chloride at high pH, but differed from previous results obtained in sodium chloride between pH 7 and pH 9. In view of the agreement between solubility results obtained in seawater and sodium perchlorate (this work) and, in contrast, results in sodium chloride that were more than an order of magnitude lower than were obtained in seawater and sodium perchlorate, it is advisable that further solubility investigations are performed in sodium chloride solutions. The iron measurement procedures developed for the investigation of ferric iron solubility were incorporated in an in situ spectrophotometric instrument. The Spectrophometric Elemental Analysis System (SEAS) utilizes long pathlength absorbance spectrometry (LPAS) combined with colorimetric protocols to achieve the sensitivity required to measure analytes at nanomolar concentration levels. The M-SEAS was initially tested on cruises in the Eastern Gulf of Mexico in June 2013 and November 2013. Due to limited opportunity for deployments of M-SEAS during these cruises, iron concentration data was obtained from only three casts. During these casts the heater pressure vessel flooded due to a compromised seal, causing the temperature of both channels to be strongly affected by ambient seawater. Further measurements of iron with the M-SEAS instrument in profiling mode will require an engineering analysis and redesign of the faulty seal. The international GEOTRACES program has stated that an improved understanding of the biogeochemical cycles and largescale distributions of trace-elements and isotopes will inform many areas of environmental research, from climate science to planning for future global change. As the only instrument currently capable of continuous in situ measurements of iron, the M-SEAS instrument should greatly enhance capabilities for investigation of iron biogeochemistry. Ferric Iron Silicate Solubility M-SEAS Complexation Marine Biology
3	Hydrologic investigation of coal mine spoil near Howard Williams Lake, Perry County, Ohio Turney, Douglas C. January 1996 (has links) No description available. Engineering, Civil Hydrologic Investigation Coal Mining Ferric Iron
4	Uptake, Absorption, and Adsorption Kinetics of Ferrous and Ferric Iron in Iron-replete and Iron-deficient Rats Ummadi, Madhavi 01 May 1994 (has links) Various concentrations of ferrous and ferric iron solutions were held at room temperature for 60 min before they were assayed for ferrous iron, which may be unstable due to oxidation. The ferrous and ferric solutions (in pH 2 HCl) were maintained as such for 60 min without the use of chelators. There was no significant oxidation of ferrous iron. Also, four different levels of each ferrous and ferric iron were injected into proximal duodenal loops of rat intestine and uptake was determined at four different time intervals. Two iron-replete rats were assigned to each of the treatments. The in situ experiments showed that iron was taken up rapidly from pH 2.0 solutions of ferrous and ferric iron. Maximum amount of iron was taken up in the first 10 min. Uptake of ferrous iron was significantly greater (p < 0.05) than uptake of ferric iron, and there were significant differences in total uptake among the four iron levels used. Uptake, absorption, and adsorption kinetics of both ferrous and ferric iron were determined in situ for both iron-replete and iron-deficient rats. Deficiency caused greater uptake and absorption, confirming a biological adaptation of these processes. Both uptake and absorption were greater for ferrous than for ferric iron and were possibly taken up by different pathways or by a ferrous-ferric pathway with preference for ferrous. Uptake and absorption kinetics were biphasic for both ferrous and ferric iron. The first phase demonstrated saturation kinetics and was followed by a nonsaturable phase at higher concentrations of luminal iron. Iron deficiency altered the uptake and absorption kinetics of ferrous and ferric iron, but not always in a similar manner, suggesting that ferrous and ferric iron were each taken up by a separate pathway. Indications were that enhanced absorption during deficiency was largely due to adaptation of ferric uptake. Iron adsorption was directly proportional to luminal iron concentration, but it was greater for ferric than for ferrous, possibly due to charge interactions. Iron deficiency caused increased adsorption of both ferrous and ferric iron, supporting the notion that adsorption acts to maintain iron in a form available for uptake. Uptake Absorption Adsorption Kinetics Ferrous Iron Ferric Iron Iron-replete Iron-deficient Rats Nutrition
5	Numerical simulation of anaerobic reductive dechlorination of CAHs in continuous flow systems Mustafa, Nizar Ahmad 14 December 2011 (has links) Halogenated organic compounds have had widespread and massive applications in industry, agriculture, and private households, for example, as degreasing solvents, flame retardants and in polymer production. They are released to the environment through both anthropogenic and natural sources. The most common chlorinated solvents present as contaminants include tetrachloroethene (PCE, perchloroethene) and trichloroethene (TCE). These chlorinated solvents are problematic because of their health hazards and persistence in the environment, threatening human and environmental health. Microbial reductive dechlorination is emerging as a promising approach for the remediation of chlorinated solvents in aquifers. In microbial reductive dechlorination, specialized bacteria obtain energy for growth from metabolic dechlorination reactions that convert PCE to TCE, cis-1,2-dichloroethene (cDCE), vinyl chloride (VC), and finally to benign ethene. Field studies show incomplete dechlorination of PCE to ethene due to lack of electron donors or other populations competing for the electron donor. Mathematical models are good tools to integrate the processes affecting the fate and transport of chlorinated solvents in the subsurface. This thesis explores the use of modeling to provide a better understanding of the reductive dehalogenation process of chlorinated solvents and their competition with other microorganisms for available electron donors in continuous flow systems such as a continuous stirred tank reactor (CSTR) and a continuous flow column. The model is a coupled thermodynamic and kinetic model that includes inhibition kinetics for the dechlorination reactions, thermodynamic constraints on organic acids fermentation and has incorporated hydrogen competition among microorganisms such as homoacetogenesis, sulfate reducers and ferric iron reducers. The set of equations are coupled to those required for modeling a CSTR. The system of model equations was solved numerically using COMSOL 3.5 a, which employs finite-element methods. The kinetic model was verified by simulation results compared to previously published models and by electron balances. The simulation process progressed by simulating the anaerobic reductive dechlorination, coupled with thermodynamic limitation of electron donor fermentation in batch systems to the modeling of CSTR, and finally to simulate anaerobic reductive dechlorination in continuous flow column, aquifer column including the processes of advection, dispersion and sorption along with the microbial processes of dehalogenation, fermentation, iron and sulfate reduction. The simulations using the developed model captured the general trends of the chemical species, and a good job predicting the dynamics of microbial population responses either the CSTRs or continuous flow column. Although, the kinetic of anaerobic dechlorination processes of chlorinated solvents in those systems have been researched in the past, little progress has been made towards understanding the combined effects of the dechlorination and thermodynamic constraints in continuous flow systems. This work provides a rigorous mathematical model for describing the coupled effects of these processes. / Graduation date: 2012 CSTR continuous-flow column dehalogenation ferric iron sulfate electron donor thermodynamic fermentation Bioremediation -- Mathematical models
6	NMR als Mittel zur Beobachtung der gelösten Eisen-Konzentration im Porenraum von Sedimenten / Using Magnetic Resonance Measurements to observe the dissolved iron concentration in the pore space of sediments Mitreiter, Ivonne 29 April 2011 (has links) (PDF) In der vorliegenden Arbeit wurde die Methode der magnetischen Kernspinresonanz (NMR) eingesetzt, um beim Schadstoffabbau stattfindende Prozesse und geochemische Reaktionen zerstörungs- und beprobungsfrei zu untersuchen. Dies ist möglich, da die gelösten Elektronenakzeptoren Sauerstoff und Eisen paramagnetisch sind und somit einen Ein uss auf die NMRRelaxationszeiten ausüben. Der lineare Zusammenhang zwischen der gelösten Sauerstoff- beziehungsweise Eisen-Konzentration und den NMR-Relaxationsraten 1/T1 und 1/T2 wurde quantifiziert. Weiterhin wurde der bereits bekannte Einfluss der Matrixoberflächen von porösen Medien auf die Relaxation von Wasser nachgewiesen. Die paramagnetischen Zentren auf Sandoberflächen führen ebenfalls zu einer Verkürzung der Relaxationszeiten. Es wurde gezeigt, dass die kleinsten Korngrößen der verwendeten Sande den größten Einfluss auf die Oberflächenrelaxation haben. Wird die Oberflächenrelaxation berücksichtigt, ist auch in porösen Medien die ermittelte lineare Abhängigkeit der Relaxationszeiten von der Ionenkonzentration anwendbar, um den Gehalt an gelösten paramagnetischen Ionen aus Relaxationsmessungen zu ermitteln. Beispielhaft wurde der Anstieg der Eisen(III)-Konzentration in der Porenlösung von natürlichen Sanden infolge der Auflösung eisenhaltiger Mineralien von den Oberflächen zeitlich und räumlich detailliert betrachtet. Eine durchgeführte Modellierung zeigte, dass das Reaktionssystem zu Beginn der Reaktion von der Diffusion dominiert wird, am Ende dann die Reaktionsgeschwindigkeit der bestimmende Parameter ist. Die beim biologischen Schadstoffabbau auftretenden Redoxprozesse des Eisens wurden durch rein chemische Reaktionen unter Verwendung von Oxidations- und Reduktionsmitteln simuliert. Die zeitlich und räumlich detaillierte Beobachtung des Anstiegs beziehungsweise des Abfalls der gelösten Eisen(III)-Konzentration in der (Poren-)Lösung war mit NMR-Relaxometrie trotz der Schnelligkeit der Reaktionen möglich. Mit Hilfe der anschliessenden Modellierung wurde der wichtige Einfluss des pH-Wertes auf den genauen Ablauf der Reaktionen deutlich gemacht. Nur in sehr sauren pH-Bereichen (pH < 3) liegen die Eisen(III)-Ionen in Lösung vor. Weiterhin wurde der Einfluss der Mikroorganismen selbst auf die NMR-Relaxations- und Diffusionsmessungen untersucht. Im Rahmen dieser Arbeit wurde an Medien mit Lactobacillus und Penicillium eine Verschiebungen in den Relaxationszeitverteilungen hin zu kleineren Relaxationszeiten gemessen. Dies basiert auf der bereits bekannten Verringerung der Mobilität der Spins innerhalb der Biomasse. Für Bakterien von Geobacter metallireducens konnte erstmals der Verbrauch von Eisen(III)-Ionen durch Reduktion während des Wachstum anhand der ansteigenden T2-Relaxationszeit gezeigt werden. Nuklear Magnetische Resonanz Eisen(II)-Ionen Eisen(III)-Ionen Versauerung Redoxreaktion reaktive Transportmodellierung nuclear magnetic resonance ferric iron ferrous iron acidification redox reaction reactive transport modelling ddc:530
7	NMR als Mittel zur Beobachtung der gelösten Eisen-Konzentration im Porenraum von Sedimenten Mitreiter, Ivonne 07 April 2011 (has links) In der vorliegenden Arbeit wurde die Methode der magnetischen Kernspinresonanz (NMR) eingesetzt, um beim Schadstoffabbau stattfindende Prozesse und geochemische Reaktionen zerstörungs- und beprobungsfrei zu untersuchen. Dies ist möglich, da die gelösten Elektronenakzeptoren Sauerstoff und Eisen paramagnetisch sind und somit einen Ein uss auf die NMRRelaxationszeiten ausüben. Der lineare Zusammenhang zwischen der gelösten Sauerstoff- beziehungsweise Eisen-Konzentration und den NMR-Relaxationsraten 1/T1 und 1/T2 wurde quantifiziert. Weiterhin wurde der bereits bekannte Einfluss der Matrixoberflächen von porösen Medien auf die Relaxation von Wasser nachgewiesen. Die paramagnetischen Zentren auf Sandoberflächen führen ebenfalls zu einer Verkürzung der Relaxationszeiten. Es wurde gezeigt, dass die kleinsten Korngrößen der verwendeten Sande den größten Einfluss auf die Oberflächenrelaxation haben. Wird die Oberflächenrelaxation berücksichtigt, ist auch in porösen Medien die ermittelte lineare Abhängigkeit der Relaxationszeiten von der Ionenkonzentration anwendbar, um den Gehalt an gelösten paramagnetischen Ionen aus Relaxationsmessungen zu ermitteln. Beispielhaft wurde der Anstieg der Eisen(III)-Konzentration in der Porenlösung von natürlichen Sanden infolge der Auflösung eisenhaltiger Mineralien von den Oberflächen zeitlich und räumlich detailliert betrachtet. Eine durchgeführte Modellierung zeigte, dass das Reaktionssystem zu Beginn der Reaktion von der Diffusion dominiert wird, am Ende dann die Reaktionsgeschwindigkeit der bestimmende Parameter ist. Die beim biologischen Schadstoffabbau auftretenden Redoxprozesse des Eisens wurden durch rein chemische Reaktionen unter Verwendung von Oxidations- und Reduktionsmitteln simuliert. Die zeitlich und räumlich detaillierte Beobachtung des Anstiegs beziehungsweise des Abfalls der gelösten Eisen(III)-Konzentration in der (Poren-)Lösung war mit NMR-Relaxometrie trotz der Schnelligkeit der Reaktionen möglich. Mit Hilfe der anschliessenden Modellierung wurde der wichtige Einfluss des pH-Wertes auf den genauen Ablauf der Reaktionen deutlich gemacht. Nur in sehr sauren pH-Bereichen (pH < 3) liegen die Eisen(III)-Ionen in Lösung vor. Weiterhin wurde der Einfluss der Mikroorganismen selbst auf die NMR-Relaxations- und Diffusionsmessungen untersucht. Im Rahmen dieser Arbeit wurde an Medien mit Lactobacillus und Penicillium eine Verschiebungen in den Relaxationszeitverteilungen hin zu kleineren Relaxationszeiten gemessen. Dies basiert auf der bereits bekannten Verringerung der Mobilität der Spins innerhalb der Biomasse. Für Bakterien von Geobacter metallireducens konnte erstmals der Verbrauch von Eisen(III)-Ionen durch Reduktion während des Wachstum anhand der ansteigenden T2-Relaxationszeit gezeigt werden. info:eu-repo/classification/ddc/530 ddc:530
8	Identifikation von Genen und Mikroorganismen, die an der dissimilatorischen Fe(III)-Reduktion beteiligt sind / Isolation of Genes and Microorganisms Involved in Dissimilatory Fe(III)-Reduction Özyurt, Baris 21 January 2009 (has links) No description available. 500 Naturwissenschaften allgemein Mathematics and Computer Science Metagenomik dissimilatorische Fe(III)-Reduktion Dissimilatory iron reduction DIR dissimilatory oxido-reduction of iron dissimilatory iron(III) reduction metal reduction ferricironreduction microbial iron respiration bacterial respiration microorganisms for energy production dissimilatory iron reducing bacteria dissimilatory metal reducing bacteria DMRB energy production electricity energy transduction microbial electricity electron donor electron acceptor electron transfer carbon source carbohydrate mannit mannitol biofilm mineral mineral formation microbial degradation ribosomal proteins cytochromes hypothetical proteins enzymes oxidation reduction ferric iron iron oxide Fe(II) Fe(III) soluble iron insoluble iron ferric reductase activity iron mineral formation mineralisation <i>E. coli</i> Escherichia coli environmental microorganisms life in extreme environments uncultivable bacteria soil microbial ecology anaerobic growth anaerobic incubation environmental sequences environmental DNA DNA extraction functional screening metagenomic metagenome meta-genome microbial ecology environmental genomics soil metagenome BACs sequencing bioinformatics microbial communities 16S rRNA phylogenetics 30 42.30 42.30 58.30 42.49 58.30 42.13 RA W

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