• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 146
  • 111
  • 33
  • 14
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 3
  • 3
  • 3
  • Tagged with
  • 373
  • 94
  • 92
  • 79
  • 56
  • 48
  • 45
  • 35
  • 35
  • 32
  • 29
  • 25
  • 24
  • 24
  • 22
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The influence of soil concentration on flocculation values and the coagulation of sols by gas bubbles

Fisher, Emory Devilla. January 1935 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1935. / Typescript. With this is bound: Chromium hydroxide hydrosols and the Burton-Bishop rule / Emory Fisher and C.H. Sorum. Reprinted from Journal of physical chemistry, vol. XXXIX, no. 1 (Jan. 1935), p. 283-287. Includes bibliographical references.

Mechanisms of filler flocculation with PEO/cofactor dual-component flocculants /

Lu, Chen. Pelton, Robert H. January 2003 (has links)
Thesis (Ph.D.)--McMaster University, 2003. / Advisor: Robert H. Pelton. Includes bibliographical references. Also available via World Wide Web.

Studies of the factors influencing the flocculation and sedimentation of microbial cells in the treatment of kraft mill effluents

Dunlop-Jones, Nicholas January 1982 (has links)
The treatment of paper mill effluents involves a succession of unit processes to remove the impurities that may vary in size by about six orders of magnitude. The process of primary importance in this study was the biological treatment stage, where an understanding of the flocculation and sedimentation of micro-organisms is needed in order to operate it efficiently.

Novel iron precipitates for drinking water treatment

Franklin, Guy Sinclair January 1999 (has links)
No description available.

Rheological and colloidal properties of commercial brewing yeast suspensions

Speers, Robert Alexander January 1991 (has links)
A three part study was carried out to examine rheological, colloidal and floe microstructural aspects of industrial brewing yeast strains. Following a review of the literature, the rheological properties of four yeast strains (two flocculent ale and lager types and their non-flocculent variants) were examined. In related colloidal studies, orthokinetic flocculation rates of these strains as well as their cell surface charge were determined. Floc microstructure was characterized using both light and scanning electron microscopy. In a summary chapter, the cell floc model (a modification of Hunter's elastic floc model) was used to the explain the rheological and colloidal behaviour of brewing yeast suspensions. Flow behaviour studies of the commercial yeast suspensions suspended in a calcium-containing sodium acetate buffer revealed that yeast flocculent characteristics had an important influence on their suspension flow behaviour. As cell concentrations increased, suspension flow properties become increasingly non-Newtonian and could be described by the Casson model at low rates of shear and the Bingham model at shear rates above 100 s⁻¹. The cell floc model was proposed to explain the Bingham flow behaviour of these csuspensions. The Bingham yield stress in these suspensions was believed to be a function of the orthokinetic capture coefficient, cell volume and the energy to break up doublet cells. Increasing temperature tended to lower the Bingham yield stress in lager strains and increase the yield stress in ale strains. A semi-empirical explanation for the viscosity increase of deflocculated cell suspensions and the estimation of pseudo-capture coefficients was presented. Furthermore, studies of the flow behaviour of yeast strains suspended in decarbonated ale and lager beer revealed that: 1) suspensions of flocculent strains show higher yield stress values than their non-flocculent variants, 2) ale strain suspensions tended to have higher yield values than the lager strains and 3) yeast dispersed in beer had higher yield stress values than when suspended in buffered calcium suspensions. This last observation was believed to reflect the influence of ethanol on the cell binding process which has important implications for future measurements of yeast flocculation. Colloidal studies revealed for the first time, that the orthokinetic rate of flocculation of brewing yeast cells could be modelled by a first order equation, as predicted by fundamental colloid theory. While subject to considerable variation, measured rate constants led to the calculation of orthokinetic capture coefficients. Yeast cell zeta potential values generally agreed with literature data but could not be employed in the DLVO model of colloid flocculation to explain measured orthokinetic capture coefficient values. Examination of the cell zeta potential data indicated that the data had non-normal distributions. SEM examination of the four industrial yeast strains suggested that a number of distinct structures mediated cell-to-cell interaction and that intra-strain differences occurred. These findings, along with the observation of non-normal surface charge distributions, indicated that these industrially pure strains had undergone substantial variation. Treatment of the flocculent cells with pronase tended to reduce cell-to-cell contacts. In the summary chapter the cell floe model was employed to describe the rheological behaviour of the yeast suspensions. Estimation of the force needed to separate doublet yeast cells were made using critical shear rate data (i.e., the point at which Bingham flow begins). This estimate was similar to that reported for single antibody bonds and may be due to the presence of lectin-like structures on the yeast cell wall. / Land and Food Systems, Faculty of / Graduate

Starch modification of the flocculation and flotation of apatite

Correa de Araujo, Armando January 1988 (has links)
Although the technical literature contains abundant references on applications of starch in mineral processing, the majority is not concerned with phosphate mineral systems. Nevertheless, the interaction between starch and apatite surfaces is relevant to both selective flocculation and flotation of phosphate ores. The main objective of this thesis is to investigate in detail such interaction in order to provide a more clear understanding on the behaviour of apatite/starch systems. Considerable research effort was dedicated to a thorough characterization of the starch samples used, especially in those aspects most pertinent to the application of starches as flocculants and depressants. Presence of ionic impurities in the starch samples tested was identified by infrared spectroscopy and microelectrophoresis. These impurities (proteins, carboxylic groups and, possibly, phosphate esters)were found to play an important role in the mechanisms governing the interaction of starch macromolecules and mineral surfaces. In a first stage of this research, the interaction between aqueous solutions of starches (and starch fractions - amylose and amylopectin) with calcium ionic species and surfactants (flotation collectors) was investigated. Depression of solution electrical conductivity, experienced in Ca-starch systems, was indicative of chemical reactions taking place (complexation). For surfactants, evidence for their interaction with starch fractions was obtained by UV-Vis. spectroscopy. The spectra of starch/surfactant solutions in the presence of iodine were altered indicating the substitution of iodine species by surfactant molecules at the helical sites of starch macromolecules. The next step involved the study of the adsorption of starch onto both apatite and silica mineral surfaces. Preliminary tests pointed out that a much stronger interaction took place in the case of apatite. Starch adsorption isotherms obtained for fluorapatite and quartz confirmed the preferential adsorption of starch onto the phosphate mineral surface. Both amylose and amylopectin were strongly adsorbed on fluorapatite but the latter polymer displayed the largest extent of interaction on a weight per area basis. The shape of the adsorption isotherms for the two starch fractions on fluorapatite also corroborates the idea of a stronger interaction by amylopectin. In turn, whole starches displayed adsorption isotherms resembling more closely that obtained for amylopectin. Adsorption of starches on fluorapatite was increased considerably in the presence of Ca ionic species. In the absence of externally added Ca ionic species, the amount of Ca released by the mineral surface was dependent upon the amount of starch adsorbed. These two phenomena can be interpreted as indicating the importance of Ca sites and presence of Ca species for the adsorption of starches, hence justifying the preferential adsorption displayed for apatite. Adsorption of starch on quartz surfaces was also enhanced in the presence of Ca ionic species, once more confirming the important role played by calcium on the adsorption of starches. Flocculation studies were also conducted with fluorapatite, kaolinite and quartz suspensions in the presence of different starches. Under the conditions tested, all starches samples failed to promote aggregation of the two non Ca-bearing minerals. In turn, fluorapatite suspensions were flocculated rather strongly by all starches. Maximum flocculation of fluorapatite was achieved at partial polymer coverage conditions. With one exception (amylose), increasing the concentration of the polymers above an optimum level, generated partial re-stabilization of the suspensions, probably via a steric effect. All starches depressed both anionic and cationic flotation of fluorapatite. Amylose was the least effective depressant among all starches, especially for the cationic flotation system. The depressant action was a function of pH and of the relative amounts of polymer and surfactant. Alkaline pH favoured depression, whereas as the collector level was increased, the depressant action was diminished and eventually eliminated. The experimental evidence gathered in the present research supports a chemical mechanism for the interaction between starch and apatite surfaces. Calcium plays a dominant role, and its importance for the adsorption of starches onto mineral surfaces is most probably related to the formation of complexes between starch impurity-related ionic groups and Ca ionic species. Hydrogen bonding and to lesser extent electrostatic forces are also important for the overall interaction between starch and apatite surfaces. The larger extent of interaction for the amylopectin fraction(highest molecular wt.) as compared to that of amylase (lowest molecular wt. fraction) gives support for the accessory role of hydrogen bonding. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Mixing and Energy Relationships in a Flocculation Unit

Wobschall, Colin 10 1900 (has links)
The effects or energy input variation on the mixing obtained in a laboratory flocculation unit were studied. The main parameter was the size and shape or paddles used to induce the mixing. A variation in paddle geometry produced a variation in energy input. The effect of baffles was studied and the effect of flocculator geometry was considered by comparing two different length to width ratios tor a single tank. Theoretical models were used in an attempt to describe a flocculation unit by comparing the experimental tracer output with the predicted theoretical output. Some generally accepted design criteria tor full-scale flocculation units were also compared with experimental results. / Thesis / Master of Engineering (ME)

Field Implementation Of Polyacrylamide For Runoff From Construction Sites

Chowdhury, Rafiqul Islam 01 January 2011 (has links)
Polyacrylamide (PAM) is often used a part of a treatment train for the treatment of stormwater to reduce its turbidity. This study investigated the application of PAM within various treatment systems for a construction site environment. The general concept is to introduce hydraulic principles when placing PAM blocks within an open channel in order to yield high mixing energies leading to high turbidity removal efficiency. The first part of the study observed energy variation using a hydraulic flume for three dissimilar configurations. The flume was ultimately used to determine which configuration would be most beneficial when transposed into field-scale conditions. Three different configurations were tested in the flume, namely, the Jump configuration, Dispersion configuration and the Staggered configuration. The field-scale testing served as both justification of the findings within the controlled hydraulic flume and comprehension of the elements introduced within the field when attempting to reduce the turbidity of stormwater. As a result, the Dispersion configuration proved to be the most effective when removing turbidity and displayed a greater energy used for mixing within the open channel. Consequently, an analysis aid is developed based on calculations from the results of this study to better serve the sediment control industry when implementing PAM blocks within a treatment system. Recommendations are made for modification and future applications of the research conducted. This innovative approach has great potential for expansion and future applications. Continued research on this topic can expand on key elements such as solubility of the PAM, toxicity of the configuration within the field, and additional configurations that may yield more advantageous energy throughout the open channel.

The Effects of TOC on Settling Velocity and Floc Formation Using Alum and Lime as Coagulants

Dunn, Michael T. 01 January 1982 (has links) (PDF)
No description available.

The Kinetics of Particulate Substrate Utilization by Bacterial Films

Boltz, Joshua 20 May 2005 (has links)
There is a need to develop a mathematical expression capable of describing the removal of particulate chemical oxygen demand (PCOD) from wastewaters in biological film systems. In this context, organic particles that are maintained in suspension (i.e., not removed during normal settling) are the focus of experimentation, modeling, and discussion. The goal of this research project is to study the kinetics of PCOD removal from wastewaters by bacterial films, or biofilms. To achieve this objective, a bench-scale rotating disc biofilm reactor (RDBR) was operated using methanol (dissolved substrate), Min-U-Sil 10 (inorganic particulates), and Maizena corn starch (organic particulates) dissolved/suspended in the influent stream. The effect of the ratio of biofilm area to volumetric flow rate passing through the RDBR on the concentration of substrate remaining in the final effluent was determined, and the kinetic relationship was established for both dissolved substrate and particle removal. Exocellular polymeric substances (EPS) were extracted and quantified in order to explain the role of biological flocculation, or bioflocculation, in particulate removal. In the literature, Fick's first law and zero-order kinetics have described the diffusion and biochemical reaction of soluble substrate within the bacterial film matrix (when completely penetrated), respectively. The present study confirms this kinetic behavior for various influent methanol concentrations. On the other hand, the removal of particulates, organic and inorganic, adheres to first-order reaction kinetics. These findings, coupled with the identification of EPS, attribute bioflocculation as the primary removal mechanism of particulates. A mass balance on the biofilm reactor allowed for the development of a comprehensive rate expression for substrate consumption by biofilms when both dissolved and particulate substrates are available. Total chemical oxygen demand (TCOD) is comprised of dissolved chemical oxygen demand (DCOD) and PCOD, each of which can be readily determined through laboratory analysis. An equation was developed that accurately describes the disappearance of TCOD by the bioflocculation of PCOD and consumption of DCOD in the bench scale RDBR.

Page generated in 0.1422 seconds