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You searched for subject:(diffuse layer model). Showing records 1 – 2 of 2 total matches.

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Virginia Tech

1. Davis, Christina Clarkson. Understanding and Predicting Water Quality Impacts on Coagulation.

Degree: PhD, Civil and Environmental Engineering, 2014, Virginia Tech

Effective coagulation is critical to the production of safe, potable drinking water, but variations in the chemical composition of source water can present challenges in achieving targeted contaminant removal and predicting coagulation outcomes. A critical literature review describes factors affecting the hydrolysis reactions of metal salt coagulants and the resulting precipitates. Properties of two key contaminants, turbidity and natural organic matter (NOM), are explored in the context of removal during coagulation, and the influence of co-occurring ions is described. While it is apparent that NOM character determines the minimum achievable organic carbon residual, the effects of water quality—including pH, NOM character and concentration, and concentrations of synergistic and competitive ions—on overall coagulation efficacy and NOM removal may be underestimated. An experimental research plan was devised to investigate the influence of water quality in coagulation and provide data to support the development of a predictive coagulation model. NOM is capable of interfering with ferric iron hydrolysis and influencing the size, morphology, and identity of precipitates. Conversely, calcium is known to increase the size and aggregation of Fe3+ precipitates and increase surface potential, leading to more effective coagulation and widening the pH range of treatment. Experiments and modeling were conducted to investigate the significance of the Fe/NOM ratio and the presence of calcium in coagulation. At the high Fe/NOM ratio, sufficient or excess ferric hydroxide was available for NOM removal, and coagulation proceeded according to expectations based upon the literature. At the low Fe/NOM ratio, however, NOM inhibited Fe3+ hydrolysis, reduced zeta potential, and suppressed the formation of filterable Fe flocs, leading to interference with effective NOM removal. In these dose-limited systems, equilibrating NOM with 1 mM Ca2+ prior to dosing with ferric chloride coagulant increased the extent of Fe3+ hydrolysis, increased zeta potential, decreased the fraction of colloidal Fe, and improved NOM removal. In dose-limited systems without calcium, complexation of Fe species by NOM appears to be the mechanism by which coagulation is disrupted. In systems with calcium, data and modeling indicate that calcium complexation by NOM neutralizes some of the negative organic charge and minimizes Fe complexation, making Fe hydrolysis species available for growth and effective coagulation. Experiments were conducted to investigate the influence of aqueous silica and pH on the removal of natural organic matter (NOM) by coagulation with ferric chloride. Samples with preformed ferric hydroxide were also compared to samples coagulated in situ to assess the role of coprecipitation. The moderate (10 mg/L) and high (50 mg/L) SiO2 concentrations both demonstrated interference with NOM removal at pH 6.5-7.5. In turn, NOM at 2 mg/L as DOC interfered with silica sorption at the moderate silica level and in samples with preformed… Advisors/Committee Members: Edwards, Marc A. (committeechair), Little, John C. (committee member), Eick, Matthew J. (committee member), Knocke, William R. (committee member), Vikesland, Peter J. (committee member).

Subjects/Keywords: coagulation; natural organic matter; ferric chloride; calcium; silica; alkalinity; diffuse layer model

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Davis, C. C. (2014). Understanding and Predicting Water Quality Impacts on Coagulation. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/70883

Chicago Manual of Style (16th Edition):

Davis, Christina Clarkson. “Understanding and Predicting Water Quality Impacts on Coagulation.” 2014. Doctoral Dissertation, Virginia Tech. Accessed November 13, 2019. http://hdl.handle.net/10919/70883.

MLA Handbook (7th Edition):

Davis, Christina Clarkson. “Understanding and Predicting Water Quality Impacts on Coagulation.” 2014. Web. 13 Nov 2019.

Vancouver:

Davis CC. Understanding and Predicting Water Quality Impacts on Coagulation. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2019 Nov 13]. Available from: http://hdl.handle.net/10919/70883.

Council of Science Editors:

Davis CC. Understanding and Predicting Water Quality Impacts on Coagulation. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/70883


Linköping University

2. Alsadi, Zeyneb. Diffuse correlation spectroscopy for estimation of coagulation thickness : a phantom study.

Degree: Biomedical Engineering, 2019, Linköping University

The objective of this preliminary study was to determine the potential of diffuse correlation spectroscopy (DCS) for assessment of coagulation depth. Coagulation of tissue can occur due to a number of different reasons such as thermal or electrical burns or radiofrequency ablation. DCS is a non-invasive optical technique which can be used to determine the optical and dynamic properties of tissue by fitting a theoretical model of photon propagation in multiply scattering tissue to experimental data obtained from measurements. The DCS measurements were performed on two-layered phantom models that represent healthy tissue with high flow properties with a layer of coagulated tissue with low flow properties on top. Three different phantom models were prepared using gelatin-Intralipid gels, PDMS, and nylon as an upper layer, and an Intralipid solution was used for the bottom layer for all three phantoms. DCS measurements were performed on all three phantom models with varying thicknesses of the upper layers, and varying source-detector separations. The acquired data from the DCS measurement were analyzed in MATLAB in order to obtain the electric field temporal autocorrelation function. A theoretical model describing photon propagation in a two-layered medium was fitted to the obtained data in order to extract the desired parameters. The results showed that the thickness of the gelatin-Intralipid gels could be extracted within a 0.5 mm certainty and the thickness of the PDMS phantoms could also be extracted within approximately 0.7 mm. For the nylon phantoms, the results obtained were not good because the fitting was not successful and the thickness was not extracted appropriately. There is potential in DCS for assessment of burn wound depth but further research and development has to be done in the field in order to obtain more accurate and reliable results.

Subjects/Keywords: DCS; Diffuse correlation spectroscopy; Biomedical optics; coagulation; phantom study; coagulation depth; coagulation thickness; diffusion; model; two layer model; Medical Engineering; Medicinteknik

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Alsadi, Z. (2019). Diffuse correlation spectroscopy for estimation of coagulation thickness : a phantom study. (Thesis). Linköping University. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158622

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Alsadi, Zeyneb. “Diffuse correlation spectroscopy for estimation of coagulation thickness : a phantom study.” 2019. Thesis, Linköping University. Accessed November 13, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158622.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Alsadi, Zeyneb. “Diffuse correlation spectroscopy for estimation of coagulation thickness : a phantom study.” 2019. Web. 13 Nov 2019.

Vancouver:

Alsadi Z. Diffuse correlation spectroscopy for estimation of coagulation thickness : a phantom study. [Internet] [Thesis]. Linköping University; 2019. [cited 2019 Nov 13]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158622.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Alsadi Z. Diffuse correlation spectroscopy for estimation of coagulation thickness : a phantom study. [Thesis]. Linköping University; 2019. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-158622

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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