Segui questo link per vedere altri tipi di pubblicazioni sul tema: Flocculation.
Tesi sul tema "Flocculation"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Flocculation".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Cousland, Bryan. "Flocculation and flocculating mutants of Pseudomonas putida." Thesis, University of Strathclyde, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291993.
Testo completo
2
Domingo, Jody L. (Jody Lawren). "Stationary phase-specific expression of dominant flocculation genes for controlled flocculation of yeast." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/49788.
Testo completoAbstract (sommario):
Thesis (MSc)--University of Stellenbosch, 2003.<br>ENGLISH ABSTRACT: Flocculation can be defined as the asexual aggregation of yeast cells in a liquid
environment. This aggregation of cells, also referred to as "floc formation", will in most
cases lead to rapid settling or sedimentation. However, in so-called top-fermenting yeast
strains, the floes can move to the surface of the liquid growth substrate to form a thin layer,
called a "velum", that has been compared to other microbial biofilms.
The factors that trigger flocculation can be divided into two groups, physical/chemical
(e.g. sugar content, the presence of inorganic salts, organic solvents, ethanol
concentration, pH, agitation etc.) and genetic factors (genes that encode for proteins that
are either directly or indirectly involved in flocculation). In top-fermenting yeast strains,
several physical and chemical factors that trigger the process have been described,
including ethanol concentration, the presence of organic solvents, the absence of
molecular oxygen and the presence of inorganic salts (Ca2+ and Mg2+). These factors
appear to affect the cell hydrophobicity and the cell surface charge. As for genetic factors,
no specific genes have thus far been associated with flocculation in top fermenting yeast
strains.
In bottom-fermenting yeast strains, the physical and chemical factors that affect the
process are similar to the ones described for top-fermenting yeast strains, but include,
more specifically, the concentration of hexoses in the media (mannose or glucose), which
may inhibit the process. Indeed, flocculation in bottom-fermenting yeast strains has been
divided into the NewFlo type (inhibited by both mannose and glucose) and the Fl01 type
(inhibited by mannose) on the basis of the inhibitory effect of specific sugars. Various
genes have been associated with the flocculation of bottom-fermenting yeast strains.
Through genetic analysis, the genes have been categorised into dominant genes, semidominant
genes and recessive genes.
In order to better understand the role of some of the proteins responsible for
flocculation in S. cerevisiae, and to create strains whose flocculation properties would
correspond to those wanted in the wine and beer industries, three of the dominant
flocculation genes, FL01, FL05 and FL011, were placed under the control of the
promoters of the stationary phase-induced genes, ADH2 and HSP30. This was achieved
by replacing the native promoters of the flocculation genes with the heterologous
promoters through homologous recombination. The laboratory strain FY23, which is nonflocculent
due to the absence of the transcription factor that is required for flocculation,
F108p,was used as a model system.
Some of the transformed strains showed high flocculation, especially when the genes
were placed under control of the ADH2 promoter. In addition to this, the strains carrying a
modified FL011 gene showed increased adhesion to solid agar media and were able to
invade the growth substrate. These strains also showed an increased velum-forming ability
when grown in media containing only non-fermentable carbon sources.<br>AFRIKAANSE OPSOMMING: Flokkulasie kan gedefinieër word as die ongeslagtelike aggregasie van gisselle in 'n
vloeibare medium. Hierdie aggregasie van selle, kan ook na verwys word as flok formasie,
en in meeste gevalle lei dit tot In vinnige sedimentering. In oppervlak-fermenterende giste,
beweeg die flokke na die oppervlakte van die vloeibare medium om sodoende 'n flor -lagie
te vorm. Hierdie verskynsel was ook al gevind in ander organismes.
Verskeie faktore is verantwoordelik vir die effektiwiteit van flokkuklasie. Hierdie faktore
kan in twee groepe verdeel word, nl. fisiese en chemiese faktore (byv. suikerkonsentrasie,
die teenwoordigheid van anorganiese soute, organiese oplossings, etanol konsentrasie,
pH, ens.) en genetiese faktore (gene wat kodeer vir die proteïene wat of direk of indirek
betrokke is by flokkulasie). In oppervlak-fermenterende giste is daar al heelwat informasie
beskikbaar omtrent fisies en chemiese faktore se effekte op flokkulasie. Van die faktore
waarvan heelwat informasie beskikbaar is sluit in, etanol konsentrasie, die
teenwoordigheid van organiese oplossings, die afwesigheid van molekulêre suurstof en
die teenwoordigheid van anorganiese soute (Ca2+ en Mg2+). Hierdie faktore toon 'n effek of
hidrofobisiteit en elektriese lading op die seloppervlakte. Geen genetiese faktore kon tot
dusver gekoppel word aan flokkulasie in oppervlak-fermenterende giste nie.
Benede-oppervlak fermenterende giste se fisies en chemiese faktore wat effektiwiteit
van flokkulasie beïnvloed is dieselfde as die van oppervlak-fermenterende giste, maar sluit
in meer spesifiek, die konsentrasie van heksoses in die media (nl. mannose en glukose),
wat 'n inhiberende effek het op flokkulasie. Die benede-oppervlak fermenterende giste se
flokkulasie kan in twee segmente verdeel word nl. die NewFlo tipe (word geïnhibeer deur
die teenwoordigheid van mannose en glukose) en die Flo1-tipe (word geïnhibeer deur
slegs die teenwoordigheid van mannose). Verskeie gene was ook al geidentifiseer wat die
effektiwiteit van flokkulasie beïnvloed in benede-oppervlak fermenterende giste. Hierdie
gene kan in drie kategorieë opverdeel word, nl dominante-, semi-dominante- en
ressessiewe flokkulerende gene.
Ten orde 'n beter begrip te kry rondom die proteïene verantwoordelik vir die meeste
effektiwiteit ten opsigte van flokkulasie in S. cerevisiae, asook om giste te manipuleer om
spesifieke flokkulasie eienskappe te toon volgens die belange van die wyn en bierindustrieë,
was drie dominante flokkulerende gene, nl. FL01, FL05, en FL011, onder
regulering van stationêre fase-geïnduseerde promotors, PADH2 en PHSP30, geplaas. Dit was
verkry deur die vervanging van die wilde tipe promotors van die drie gene met die
stationêre fase-geïnduseerde promotors deur middel van homoloë rekombinasie. Die
laboratorium gisras, FY23, wat 'n nie-flokkulerende gisras is vanweë die afwesigheid van
'n transkripsionele faktor, Flo8p, wat verantwoordelik is vir die aktivering van belangrike
gene in flokkulasie, was gebruik as 'n wilde tipe ras.
Sommige van die transformante het In hoë mate van flokkulasie getoon, veral wanneer
onder die regulering van die PADH2. Tesame met laasgenoemde verskynsel, was daar gevind dat FL011-transformante 'n verhoging in hul vermoeë het om te bind aan die agar
en ook om die agar te penetreer. Laasgenoemde gisrasse het ook die vermoë getoon om
'n flor-lagie te vorm bo-op die oppervlakte van die medium, maar slegs wanneer dit in niefermenteerbare
koolstofbronbevattende media opgegroei word.
3
Chin, Ching-Ju. "Particle flocculation in stirred tanks." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/21253.
Testo completo
4
Kazi, Noor Mohammed. "Pneumatic flocculation in water treatment." Thesis, Nottingham Trent University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283273.
Testo completo
5
Bilgen, Sedat. "Shear flocculation of fine cassiterite." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304300.
Testo completo
6
Thomas, David N. "Flocculation modelling in wastewater treatment." Thesis, Cranfield University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323835.
Testo completo
7
Khan, M. M. "Selective flocculation of lead-zinc concentrate." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355440.
Testo completo
8
Waterson, Joanne. "Selective flocculation by small particle adsorption." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279824.
Testo completo
9
Jones, David Andrew Ross. "Depletion flocculation of sterically-stabilized particles." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364692.
Testo completo
10
Ramirez, Mendoza Rafael. "Flocculation controls in a hypertidal estuary." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2010209/.
Testo completoAbstract (sommario):
Estuaries are ephemeral geological formations in constant change, which is being accelerated by human intervention. Fine sediments are an important characteristic of estuarine systems upon which anthropogenic and natural activities depend. An important feature of fine sediments is their cohesiveness, following which individual particles aggregate into the so-called flocs or break-up due to turbulent motions. Throughout the flocculation process (aggregation and break-up), flocs change their properties of size, density and settling velocity with consequences on suspended sediment transport, primary productivity and contamination. The prediction of possible changes in flocculation represents an important tool to help in decision making. Although some knowledge has been gained from laboratory and field investigations, the behaviour of the flocs in real conditions is still not well understood. Even though formulations to describe changes in floc dynamics have been proposed, there is a wide disparity between studies. The aim of this research is to contribute to the knowledge of the flocculation process and propose novel methods for the implementation in numerical models, via a case study in the Dee Estuary. The Dee is a hypertidal Estuary located in Liverpool Bay, with surface tidal currents over 1 m/s. The effects of turbulence generated by the strong tidal currents and waves on floc properties are of particular interest. The possibility of a simple formulation for the flocculation process is also investigated in order to be implemented in a state of the art coupling of hydrodynamic (POLCOMS), turbulence (GOTM) and waves (WAM) numerical models. To achieve these objectives, hourly data of grain size, volume concentration and current velocity from a mooring deployed in the Welsh Channel and water samples from a research vessel taken from 12 February to 9 March on 2008 have been used. The high sampling rate for the currentv elocities enables the calculation of turbulent stress, turbulent kinetic energy, shear rate, Kolmogorov microscale and dissipation. Mass concentrations were obtained froma series of water samples collected from a research vessel during the 12-14th February 2008, which were used to convert volume concentration into mass concentration. Three hydrodynamic regimes have been distinguished from the observations: “current only” (negligible effect of waves), “combined currents-waves” (important effects from both forcings) and “wave dominant”. Quarter-diurnal variability of floc size was present during the first two regimes. Observations showed aggregation of flocs during periods of low turbulence with higher magnitude during low water slack than during high water slack. Break-up occurred concurrently with high turbulence periods during flood and ebb phases with higher magnitudes after ebb. Differences are likely due to turbulent stress asymmetries related with mixing and periodic stratification even though freshwater input was low. The “current only” regime was used to investigate the changes in floc settling velocities in relation with turbulent stress. A simple semi-empirical formulation was proposed and implemented in the numerical models. This expression depends on a single variable, which can be obtained from the turbulence model, and is both physically and mathematically correct. Model results qualitatively reproduced the neap-spring variability and the quarter-diurnal variability of floc settling velocities and suspended sediment concentration. During the “combined currents-waves” regime, waves were tidally modulated and led to enhanced aggregation and break-up, with higher floc size range than during the “current only” regime. Wave tidal modulation and quarter-diurnal variability of floc size were lost when waves were dominant. Flocs sizes exhibited a low range related to wave height. Inverse relationships between turbulent properties and median grain size were found for the three regimes, with higher scatter of data for the Kolmogorov microscale and shear rate due to different floc behaviour during flood and ebb phases. Turbulent kinetic energy showed a better relationship with floc size, which suggests its use as a floc size predictor instead of turbulent stresses.
11
Son, Minwoo. "Flocculation and transport of cohesive sediment." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041095.
Testo completo
12
Jones, Franca. "The mechanism of Bayer residue flocculation." Thesis, Curtin University, 1998. http://hdl.handle.net/20.500.11937/844.
Testo completoAbstract (sommario):
The aim of this study was to determine the mechanism of Bayer residue flocculation. Hematite was chosen as the test substrate as it is a common Bayer residue mineral. Batch settling tests were used to gain an understanding of the aggregation mechanism and to compare the effect of different parameters on flocculation performance. Flocculant adsorption isotherm measurements were related to changes in flocculation performance. Infrared spectroscopy was used to ascertain the configuration of adsorbed flocculant on the hematite surface.Batch settling tests showed that under strong caustic conditions hematite is naturally coagulated and that flocculation occurs via a bridging mechanism. This was confirmed by results which showed that factors which affect the bridging efficiency of the flocculant had an impact on aggregation. In particular, temperature and caustic concentration were found to greatly influence flocculation performance. This is due mainly to changes in the viscosity of the liquor, but may also be linked to the kinetics of particle-particle and particle-flocculant collisions resulting in a less efficient aggregation process. Ionic strength did not impact on performance as the flocculant was at a limiting size for synthetic liquors containing TC >/= 50 and TA >/= 10.Increasing ionic strength did not increase the adsorption density of the flocculant on hematite nor did altering the salt cation species from Na(subscript)2+ to Ca(subscript)2+. It can be concluded, therefore, that the flocculant is chemisorbed through surface complexation, since if it were electrostatically bound an increase in flocculant adsorption should have been observed with increasing ionic strength or cation charge. The surface complexation mechanism was supported by infrared results which showed that the flocculant vibrational bands were shifted on adsorption. The magnitude and direction of the shift suggests a bridging bidentate structure at pHs >/+ 11, while a monodentate structure exists at pH 7. In the presence of calcium there is also some electrostatically adsorbed flocculant at pH 7, with the calcium being in a bidentate chelating structure, but this is not observed at much higher pHs.The flocculant had an adsorption isotherm best described by a Langmuir-Freundlich expression with a monolayer coverage of ~ 164 mu g m(subscript)-2 of hematite. The adsorption density was lowered by the presence of carbonate and silicate and the action of both is thought to be due to their adsorption on active sites blocking polymer adsorption. Carbonate has an impact on flocculant adsorption at concentrations > 10 mg g(subscript)-1 while in the case of silicate ~0.2 mg g(subscript)-1 is required for the adsorption density of the flocculant to be affected. While it has been confirmed that silicate does adsorb on hematite, it was not possible to determine whether this was adsorption of a silicate species or an aluminosilicate species.X-ray photoelectron spectroscopy (XPS) showed conclusively that sodium is not involved in the adsorption of the carboxylate to the hematite surface. The lower peak shift between the backbone carbon and the carboxylate carbon suggests that the carboxylate is bonded directly to iron which has a low effective charge.Flocculant adsorption was atomistically modelled using decanoate and decandioate molecules. Modelling supported the results from XPS and infrared analysis and showed the carboxylate oxygen atoms in both organic molecules bonded directly to the surface iron atoms. Adsorption was preferred on near unhydrated surfaces with the most stable adsorption configuration being a non-symmetrical bridging bidentate structure as inferred from the infrared results.
13
Jones, Franca. "The mechanism of Bayer residue flocculation." Curtin University of Technology, School of Applied Chemistry, 1998. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10520.
Testo completoAbstract (sommario):
The aim of this study was to determine the mechanism of Bayer residue flocculation. Hematite was chosen as the test substrate as it is a common Bayer residue mineral. Batch settling tests were used to gain an understanding of the aggregation mechanism and to compare the effect of different parameters on flocculation performance. Flocculant adsorption isotherm measurements were related to changes in flocculation performance. Infrared spectroscopy was used to ascertain the configuration of adsorbed flocculant on the hematite surface.Batch settling tests showed that under strong caustic conditions hematite is naturally coagulated and that flocculation occurs via a bridging mechanism. This was confirmed by results which showed that factors which affect the bridging efficiency of the flocculant had an impact on aggregation. In particular, temperature and caustic concentration were found to greatly influence flocculation performance. This is due mainly to changes in the viscosity of the liquor, but may also be linked to the kinetics of particle-particle and particle-flocculant collisions resulting in a less efficient aggregation process. Ionic strength did not impact on performance as the flocculant was at a limiting size for synthetic liquors containing TC >/= 50 and TA >/= 10.Increasing ionic strength did not increase the adsorption density of the flocculant on hematite nor did altering the salt cation species from Na(subscript)2+ to Ca(subscript)2+. It can be concluded, therefore, that the flocculant is chemisorbed through surface complexation, since if it were electrostatically bound an increase in flocculant adsorption should have been observed with increasing ionic strength or cation charge. The surface complexation mechanism was supported by infrared results which showed that the flocculant vibrational bands were shifted on adsorption. The magnitude and direction of ++<br>the shift suggests a bridging bidentate structure at pHs >/+ 11, while a monodentate structure exists at pH 7. In the presence of calcium there is also some electrostatically adsorbed flocculant at pH 7, with the calcium being in a bidentate chelating structure, but this is not observed at much higher pHs.The flocculant had an adsorption isotherm best described by a Langmuir-Freundlich expression with a monolayer coverage of ~ 164 mu g m(subscript)-2 of hematite. The adsorption density was lowered by the presence of carbonate and silicate and the action of both is thought to be due to their adsorption on active sites blocking polymer adsorption. Carbonate has an impact on flocculant adsorption at concentrations > 10 mg g(subscript)-1 while in the case of silicate ~0.2 mg g(subscript)-1 is required for the adsorption density of the flocculant to be affected. While it has been confirmed that silicate does adsorb on hematite, it was not possible to determine whether this was adsorption of a silicate species or an aluminosilicate species.X-ray photoelectron spectroscopy (XPS) showed conclusively that sodium is not involved in the adsorption of the carboxylate to the hematite surface. The lower peak shift between the backbone carbon and the carboxylate carbon suggests that the carboxylate is bonded directly to iron which has a low effective charge.Flocculant adsorption was atomistically modelled using decanoate and decandioate molecules. Modelling supported the results from XPS and infrared analysis and showed the carboxylate oxygen atoms in both organic molecules bonded directly to the surface iron atoms. Adsorption was preferred on near unhydrated surfaces with the most stable adsorption configuration being a non-symmetrical bridging bidentate structure as inferred from the infrared results.
14
Bergström, Roger. "Fibre flocculation during twin-wire roll forming." Licentiate thesis, KTH, Fibre and Polymer Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1606.
Testo completoAbstract (sommario):
<p>At the division of Paper Technology a forming unitconsisting of headbox, forming roll unit and reservoir systemfor suspension recirculation has been constructed, with themain purpose to experimentally study the paper forming event byvisually following the fibre flow phenomena in the formingzone.</p><p>The effect of various running parameters upon the pressuredistribution, which is in correlation to the flow phenomenaoccuring during forming, has been studied with a flush mountedpressure sensor. Some combinations of running parametersresulted in highly oscillating pressure pulses, which wereevaluated by their wavelength.</p><p>The visualisation was made with a high-speed video cameraand a pulsed laser light source. The forming zone was observedvia a mirror mounted on the forming roll, thus following aspecific small area of the forming zone. This made it possibleto follow floc motions relative to the forming roll/wire. Theflocs were found to move towards the wire due to the dewateringflow wereupon the bottom part of the floc was pinned to thewire. If the suspensionspeed is different from the wire speedthe floc will be stretched out, because the upper part of thefloc has a slightly different speed in comparison to the bottompart. If this speed difference is high enough, the flocs maysplit and thus contribute to fragmentation.</p><p>The floc-floc interaction has been studied in a Couetteapparatus. It has been observed that voids in the suspensionplay a central role for the floc break-up process. The reasonis belived to be that voids induce movement inside thesuspension, which is a prerequisite for floc break-up. Thefloc-floc relative movements have been found to obey simplelaws of rack-and-pinion principles.</p>
15
Yan, Huawei. "Fibre suspension flocculation under simulated forming conditions." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3794.
Testo completoAbstract (sommario):
<p>A flow loop system for study of fibre flocculation insuspensions has been developed. The system is designed tosimulate the flow conditions in a paper machine headbox. It isequipped with a radial distributor feeding a step diffuser pipepackage, after which the flow is contracted in a 2-D nozzle.The flow system is also equipped with a secondary flowcontraction with an area reduction ratio of 2:1 after theheadbox nozzle, mimicking accelerations that may take placeduring forming. The flow system is equipped with heating andcooling devices for the study of temperature effects on fibresuspension flocculation. An online dosage device for the studyof chemical effects on fibre suspension flocculation is alsoincluded. The maximum flow velocity in the system is 16m/s.</p><p>Flowing fibre suspensions were studied using a high speedCCD video camera and transmitted infra-red laser light pulseillumination. Images were taken either separately before andafter or along the secondary contraction. Images of fibreflocculation were evaluated by power spectrum analysis, and themean floc size and the flocculation index were calculated. Aconcept of mean floc area reduction, based on power spectrum,has been introduced to characterise the fibre network insuspensions. By comparingthe fibre flocculation before andafter the secondary contraction, or by following the fibreflocs along the secondary contraction, floc rheologyinformation can be obtained. The effects of chemical additivesand fibre surface modification can also be studied by comparingthe corresponding fibre flocculation.</p><p>For a bleached softwood kraft pulp suspension at a fibreconcentration of 5 g/l, the fibre flocs along the secondarycontraction have been manually evaluated, and the resultsconfirm that the power spectrum analysis is applicable. Ca 1/5of the flocs were broken into two by the contraction. The meanfloc size increases in MD while in CD it decreases during theflow contraction. Both the floc aspect ratio and the flocorientation in MD increase during the flow contraction. The netfibre floc area is decreased and the fibre flocs areconcentrated by the flow contraction, which is confirmed by anincrease of gray value of the flocs in the light transmissionimages. The dewatering of fibre flocs may thus have alreadybeen started in the suspension before reaching the wires in theforming zone.</p><p>Some physical influences on fibre suspension flocculationhave been investigated. The results confirm that fibreconcentration and fibre length are the dominating factorsaffecting fibre suspension flocculation. Increasing absoluteflow velocity has an insignificant effect on fibre flocs in theflow contraction. Suppressing turbulence, by increasingsuspension viscosity via a decrease of medium temperature,shows a clear effect on reducing fibre suspensionflocculation.</p><p>Some chemical influences on fibre suspension flocculationhave also been investigated. A retention aid, flocculant,cationic polyacrylamide, C-PAM, increases fibre suspensionflocculation by a bridging mechanism, and a formation aid,class II, anionic polyacrylamide, A-PAM, decreases fibresuspension flocculation by suppressing turbulence. Fibresuspension flocculation can also be reduced by surfacemodification with carboxymethyl cellulose, due to a reductionof the friction between fibres. The amount of fibre dispersiondepends on the ionic form of the grafted CMC, due to theelectrostatic repulsion between negatively charged groups onthe grafted CMC moieties. Xyloglucan, a non-ionic polymer,which is strongly adsorbed on cellulosic fibre surfaces, showsa similar influence on reduction of fibre suspensionflocculation by decreasing the friction between fibres.</p><p>The fibre flocculation data in the flow loop system werealso compared with the corresponding paper formation data inthe sheets produced on a pilot paper machine, both with andwithout chemical additives. The results show that the fibresuspension flocculation is well correlated with the paper sheetformation: when the fibre suspension flocculation is increased,the corresponding paper sheet formation deteriorates,especially in the large scale range.</p>
16
Ritcey, Lisa Louella. "Cell wall properties affecting brewing yeast flocculation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0028/MQ31635.pdf.
Testo completo
17
Anderson, Sandie Lanclyn. "Flocculation of clay suspensions using synthetic polymers." Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183126556.
Testo completo
18
Ashmore, Matthew Howard. "Flocculation studies on model colloids using chitosan." Thesis, Nottingham Trent University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324728.
Testo completo
19
Sidhu, Balwinder Kaur. "Flocculation characterization of metered dose inhaler suspensions." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335852.
Testo completo
20
Govender, Patrick. "Industrial yeast strains engineered for controlled flocculation." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1450.
Testo completoAbstract (sommario):
Thesis (PhD (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2009.<br>In many industrial fermentation processes, Saccharomyces cerevisiae yeast should ideally meet two partially conflicting demands. During fermentation a high suspended yeast count is of paramount importance to maintain a rapid fermentation rate, whilst efficient flocculation should ideally be initiated only on completion of the primary alcoholic fermentation, so as to enhance product clarification and recovery. Most commercial wine yeast strains are non-flocculent, probably because this trait was counter-selected to avoid fermentation problems. In this study, we assessed molecular strategies to optimise the flocculation behaviour of non-flocculent laboratory and wine yeast strains. For this purpose, the chromosomal copies of three dominant flocculation genes, FLO1, FLO5 and FLO11, of a non-flocculent S. cerevisiae laboratory strain (FY23) and two commercial wine yeast strains (BM45 and VIN13) were placed under the transcriptional control of the stationary phase-inducible promoters of the S. cerevisiae ADH2 or HSP30 genes.
Under standard laboratory media and culture conditions, all six promoter-gene combinations resulted in specific flocculation behaviours in terms of timing and intensity. The data show that the strategy resulted in the expected and stable expression patterns of these genes in both laboratory and industrial wine yeast strains. Most importantly, the data confirm that inducible expression of the native FLO1 and FLO5 open reading frames, albeit to varying degrees, are responsible for a quantifiable cell-cell adhesion phenotype that can be characterized as a Flo1 flocculation phenotype. On the other hand, we found that inducible expression of the native FLO11 ORF under these conditions resulted in flor/biofilm formation and invasive growth phenotypes. However, the specific impact of the expression of individual dominant FLO genes with regard to characteristics such as flocculation efficiency, cell wall hydrophobicity, biofilm formation and substrate adhesion properties showed significant differences between the commercial strains as well as between commercial and laboratory strains. These adhesion phenotype differences may at least in part be attributed to wine yeast FLO gene open reading frames containing significantly smaller intragenic repeat regions than laboratory strains.
The data show that the ADH2 regulatory sequences employed in this study were unsuitable for the purpose of driving FLO gene expression under wine-making conditions. However, HSP30p-based FLO1 and FLO5 wine yeast transformants displayed similar flocculent phenotypes under both synthetic and authentic red wine-making conditions, and the intensities of these phenotypes were closely aligned to those observed under nutrient-rich YEPD conditions. The fermentation activities of
HSP30p-based transgenic yeast strains were indistinguishable from that of their parental host wine yeast strains. The chemical composition of wines obtained using transgenic yeast strains were similar to those produced by parental strains. The BM45-derived HSP30p-FLO5 transformant in particular was capable of generating compacted or ‘caked’ lees fractions, thereby providing a distinct separation of the fermented wine product and lees fractions. Furthermore, in this study we report a novel FLO11 induced flocculation phenotype that seems to exclusively develop under authentic red wine-making conditions. This strong FLO11 flocculation phenotype was not wine yeast strain dependant, possessed both Ca2+-dependant and Ca2+-independent flocculation characteristics and was insensitive to inhibition by both glucose and mannose. A distinct advantage of this unique FLO11 phenotype was highlighted in its ability to dramatically promote faster lees settling rates. Moreover, wines produced by HSP30p-FLO11 wine yeast transformants were significantly less turbid than those produced by their wild type parental strains. The benefit of this attractive property is it facilitates simpler and faster recovery of wines and also promotes greater volume recovery of the wine product.
21
Hietala, N. (Noora). "Removal of perfluorinated compounds by coagulation-flocculation." Bachelor's thesis, University of Oulu, 2016. http://urn.fi/URN:NBN:fi:oulu-201607262611.
Testo completoAbstract (sommario):
Perfluorinated compounds are chemical compounds with carbon-fluorine bond, they are used in commercial products. The goal of this thesis was to find out how coagulation-flocculation method remove perfluorinated compounds from water. Occurrence of perfluorinated compounds in waters and soil were researched and methods of observing these concentrations in the nature. Different concentrations on different points of waste water treatment plants and drinking water treatment plants were also researched. Main focus was to study different coagulation methods. Research methods used in this thesis included research of previous studies, focusing on most recent studies. Findings were that perfluorinated compounds can be found worldwide, both soil and water. Perfluorinated compounds can be removed from water by coagulation-flocculation process. It was also found that the removal efficiency by using different coagulant methods varied. Using conventional coagulants did not reach as good removal efficiency as when enhanced coagulation was being used. The best removal rate was achieved when natural M.oleifera or CBHyC was used as a coagulant<br>Perfluoratut yhdisteet ovat kemiallisia yhdisteitä, joissa on hiili-fluorisidos. Perfluorattuja yhdisteitä käytetään useissa kuluttujatuotteissa. Työn tavoitteena oli selvittää kirjallisuuden pohjalta kuinka hyvin koagulaatio-flokkulaatiomenetelmä poistaa perfluorattuja yhdisteitä vedestä. Haluttiin myös selvittää kirjallisuuden avulla perfluorattujen yhdisteiden esiintymistä luonnossa. Työssä pyrittiin selvittämään yhdisteiden pitoisuusmääriä maaperässä, luonnonvesissä, jäteveden puhdistuslaitoksissa ja juomaveden puhdistuslaitoksissa. Työn tutkimusmenetelmänä käytettiin kirjallisuustutkimusta, keskittyen alan uusimpiin mahdollisiin julkaisuihin. Perfluorattuja yhdisteitä esiintyy maailmanlaajuisesti maaperässä, luonnonvesissä, sekä jäteveden puhdistuslaitoksissa että juomaveden puhdistuslaitoksissa. Koagulaatio-flokkulaatiomenetelmällä pystytään poistamaan perfluorattuja yhdisteitä vedestä, Poistumistehon hyötysuhde tavallisella koagulanteilla ei ole yhtä tehokas kuin uusilla koagulanteilla, kuten esimerkiksi luonnonmukaisilla koagulanteilla
22
Gärde, Jenny. "TREATMENT OF WASTE WATER FROM A FISH CONSERVATION INDUSTRY : Flocculation Experiment and Analysis." Thesis, Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-17183.
Testo completoAbstract (sommario):
Tjörn is a cluster of islands, located in Västra Götaland’s county, on the west coast of Sweden. A fishing industry called Kädesholmen Seafood AB is located at Kädesholmen, one of the larger islands of Tjörn. The industry produces different types of fish preserves. The resulting waste water is polluted with mostly nutrients and organic matter in high concentrations. In lack of other treatment alternatives, the waste water is collected and transported to Trollhättan for biological degradation. Sweco, a consulting company, has been working together with Klädesholmen Seafood AB to establish a local treatment alternative for the fishing industry’s waste water. The ambition is to find a pretreatment option that enables treatment of the waste water in the municipal waste water treatment plant at Tjörn. Currently a pretreatment system consisting of a flocculation step followed by a flotation step is investigated as a possibility. The system would reduce especially organic matter and nutrient content of the waste water, but also other contaminations to some extent. The subject of my master’s thesis was to perform a small scale investigation of the pretreatment alternative mentioned above. Waste water effluent collected from the industry was tested in combinations with three different flocculation chemicals; ferric chloride, Ekoflock 71 and Ekoflock 90, at different dosages and pH- levels. The aim was to obtain as high separation of contaminations from the water as possible. The flocculation results of each series were evaluated visually, according to a five grade scale. The test series with the most successful separation of sludge- and clear water phase were sampled for analysis. A limited physical and chemical characterization was performed at Halmstad University. The parameters analyzed were pH, conductivity and nutrients. The results were used for determining the success of the flocculation experiment. The flocculation experiment resulted in a discovery of a successful span for flocculation to occur, regarding both chemical dosage and pH- level. Ferric chloride proved to be more successful in separating the two phases (water- and sludge phase) from each other than the other two flocculation chemicals. The addition of chemicals caused a decrease in pH and therefore the addition of NaOH was needed to increase pH to a level beneficial for the reaction to occur. The analysis showed a decline of nutrients in the water, but not as much as anticipated. Little or no difference of conductivity was obtained and pH was low after flocculation, even with addition pH elevating substances during the flocculation. The conclusion; flocculation is a possible treatment option for the waste water. However, large amounts of flocculation chemicals are required and the reduction of pollutants is poor. A modification of the flocculation process or another form of treatment alternative is preferable.
23
Niu, Haibo. "Flocculation and settling properties of discharged drilling waste /." Internet access available to MUN users only, 2003. http://collections.mun.ca/u?/theses,159920.
Testo completo
24
Strand, Sabina P. "Interactions between Chitosans and Bacteria : Flocculation and Adhesion." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-108.
Testo completo
25
Hartley, William H. "High-Speed Imaging of Polymer Induced Fiber Flocculation." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14627.
Testo completoAbstract (sommario):
This study presents quantitative results on the effect on individual fiber length during fiber flocculation. Flocculation was induced by a cationic polyacrylamide (cPAM). A high speed camera recorded 25 second video clips. The videos were image-analyzed and the fiber length and the amount of fiber in each sample were measured. Prior to the flocculation process, fibers were fractionated into short and long fibers. Trials were conducted using the unfractionated fiber, short fiber, and long fiber. The short and long fibers were mixed in several trials to study the effect of fiber length. The concentration of cPAM was varied as well as the motor speed of the impeller (RPM). It was found that the average fiber length decreased more rapidly with increasing motor speed. Increasing the concentration of cPAM also led to a greater decrease in average fiber length. A key finding was that a plateau was reached where further increasing the amount of cPAM had no effect. Hence, fibers below a critical length resisted flocculation even if the chemical dose or shear was increased. This critical length was related to the initial length of the fiber.
26
Klemedsson, Shicarra. "Flocculation of natural organic matter in Swedish lakes." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85118.
Testo completoAbstract (sommario):
Flocculation is an important part of the carbon cycle. It is therefore crucial to understand how flocculation is regulated and how different environmental factors impact. A dilemma is that it has been found difficult to measure flocculation experimentally. In this thesis, flocculation of dissolved organic carbon in a Swedish lake was measured in a series of laboratory experiments. The method used was Dynamic Light Scattering (DLS). DLS is used to determine the size distribution profile of, for instance, small particles in suspension. DLS measures Brownian motion and relates it to the particle size by measuring the fluctuation in scattering intensity. It is not very effective to measure the frequency spectrum contained in the intensity fluctuations directly, so instead, a digital auto correlator is used. Since factors such as pH, salinity and calcium chloride content varies in lakes and is thought to have an impact on flocculation, this was investigated as well. As pH was changed in a range of 3 to 9, small changes in size distribution could be detected. Salinity and calcium chloride content have quite an impact on flocculation. Time also has a great impact, samples that were set to rest for a week showed a significant increase in particle size. For DLS to work, the samples need to be filtered of centrifuged to get rid of large particles. Different types of filters were tested to see which filter material was the best to use. When filtering the water we only want to filter out the large particles. Natural organic matter has a hydrophobic component which adsorbs to some filter types but not to others. It is crucial to know which filters this hydrophobic component adsorbs to, so that the loss of dissolved organic carbon during filtration can be minimalized.
27
Kuczynski, Leszek W. "Evaluation of the flocculation process in granular media." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4801.
Testo completo
28
Liem, L. E. "Flocculation mixing by means of vertically oscillating grids." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/NQ34802.pdf.
Testo completo
29
Yu, Zhimin. "Flocculation, hydrophobic agglomeration and filtration of ultrafine coal." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/NQ39010.pdf.
Testo completo
30
Hibberd, David. "Use of ultrasound to characterise polymer induced flocculation." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267709.
Testo completo
31
Hughes, Jonathan. "The flocculation of Zymomonas mobilis for ethanol production." Thesis, University of Huddersfield, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290989.
Testo completo
32
Moran, Paul James. "The flocculation and downstream processing of microbial suspensions." Thesis, University of Huddersfield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390633.
Testo completo
33
Radford, Stewart John. "Depletion flocculation and rheology of sodium caseinate emulsions." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396924.
Testo completo
34
Gill, R. I. S. "The flocculation of kaolinite suspensions using cationic polyacrylamide." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353463.
Testo completo
35
Aunins, John Grant. "Induced flocculation of animal cells in suspension culture." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14330.
Testo completo
36
Bavarian, Farshad. "Coal cleaning by microbial desulfurization and selective flocculation /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487683756127698.
Testo completo
37
Kajornatiyudh, Sittiporn. "Bacterial extracellular polymers and flocculation of activated sludges." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/52313.
Testo completoAbstract (sommario):
The extracellular polymers produced by bacteria play an important role in bacterial aggregation or bacterial flocculation in secondary waste treatment. The mechanisms responsible for this floc formation are thought to be polymer induced adsorption and interparticle bridging among bacterial cells or between bacterial cells and inorganic colloids. The efficiency of the processes following flocculation in the treatment line such as sedimentation, sludge thickening, and sludge dewatering depends on the extent of this bacterial flocculation.
In this research, sludge samples from under various substrate conditions were examined for type, molecular weight, physical characteristics„ and quantity of extracellular polymers so that the general characteristics of the various polymers could be established. An attempt was made to determine if a relationship exists between the state of bacterial aggregation and the polymer characteristics. This research also investigated the sludge physical properties. The effect of various parameters such as pH, divalent cation (mixture and concentration), and mixing (period and intensity) on dewatering properties were studied.
A major goal of this study was to develop a flocculation model for activated sludge. This model could be used to determine if plants can increase the efficiency of waste treatment and sludge thickening and sludge dewatering processes.<br>Ph. D.
38
Nguyen, Thu Ha. "Flocculation dynamics of cell-associated suspended particulate matter." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23148.
Testo completoAbstract (sommario):
Transport of suspended particulate matter (SPM) plays a vital role in controlling large-scale processes related to geophysical flows such as dispersal and sinking of organic matter and contaminants to offshore and deep waters, nutrient cycles, food web stability, morphodynamics and sedimentation in both limnetic and pelagic ecosystems. Although it has been recognized that small-scale microbial processes can introduce substantial differences to the way in which SPM moves in natural waters, the extent to which the attached biological matter affects SPM dynamics is still not well characterized. This thesis focuses on quantifying the attached biomass fraction on SPM aggregates and investigating its contribution to SPM flocculation dynamics, which consequently control SPM aggregate geometrical properties and transport. A novel laboratory-based Optical Measurement of Cell Colonization (OMCEC) system and a microbiological-physical model (BFLOC2) are the main achievements of this thesis that allow the analyses of the correlations between environmental conditions, aggregate-attached biomass fraction, cell colonization patterns, aggregate size, fractal dimension and settling velocity. OMCEC is an experimental system that can simultaneously measure the material composition, geometric properties, and motion of individual suspended aggregates in a non-invasive and non-destructive way. OMCEC consists of a full-color high-resolution optical system and real-time algorithms for (i) material segmentation based on light spectra emission analysis, (ii) quantification of various geometrical properties, and (iii) motion detection with micro particle tracking velocimetry (μPTV). OMCEC was applied herein on three types of aggregates: cell-associated minerals, cell-associated microplastics, and three-phase aggregates made of minerals, microplastics, and biological matter. OMCEC application on Saccharomyces cerevisiae-colonized minerals at four sucrose concentrations showed the likelihood of cell colonization to increase with increasing nutrient concentration. The attached biomass fraction was found to increase nonlinearly regarding an increase of aggregate size but almost constant with fractal dimension variation. Cell distribution on mineral surfaces was then analyzed and classified into three colonization patterns: (i) scattered, (ii) well-touched, and (iii) poorly-touched, with the second being predominant. Cell clusters in the well-touched pattern were found to have lower fractal dimension than those in the other patterns. A strong correlation of colonization patterns with aggregate biomass fraction and properties suggests dynamic colonization mechanisms from cell attachment to minerals, to joining of isolated cell clusters, and finally cell growth over the entire aggregate. OMCEC application on microplastics (MPs) being colonized by natural biological matter from Hawkesbury River, NSW, Australia demonstrated that the biomass fraction of MP aggregates has substantial control over their size, shape and, most importantly, their settling velocity. Polyurethane MP aggregates made of 80% biological matter had an average size almost double that of MP aggregates containing 5% biological matter and sank two times slower. Based on our experimental data, we introduce a settling velocity equation that accounts for the shape irregularity and fractal structure of MP aggregates. This equation can capture the settling velocity of both virgin MPs and cell-associated MP aggregates with 7% error and can be applied widely to predict the settling flux of MP aggregates made of different polymers and various types of biological matter. To consider the complex genesis of cell-associated mineral aggregates, the BFLOC2 model was introduced to predict aggregate geometry and settling velocity under simultaneous effects of hydrodynamic and biological processes. While minerals can contribute to aggregate dynamics through collision, aggregation, and breakup, living microorganisms can colonize and establish food web interactions that involve growth and grazing, and modify the aggregate structure. Modeling of cell-associated mineral aggregate dynamics over a wide range of environmental conditions showed that maximum aggregate size, biomass fraction, and settling velocity could occur at different optimal environmental conditions. Unlike mineral aggregates, which have maximum size when shear rates tend to zero, a relative maximum size of cell-associated mineral aggregates can be reached at intermediate shear rates as a result of microbiological processes. The settling velocity was ultimately controlled by aggregate size, fractal dimension, and biomass fraction. The innovative aspect of this thesis is the simultaneous quantification of composition, architecture, and settling velocity of individual aggregates. Therefore, it puts forth the analysis and prediction of cell colonization impacts on dynamics and transport of suspended particulate matter in natural waters. The output of this thesis can be used in natural water monitoring programs to estimate the biological content based on SPM size, capacity dimension, and settling velocity, which can be measured using in-situ methods. Furthermore, the evidence and tools to quantify the sinking and floating of microplastic subjected to bio-fouling can be implemented in microplastics transport models to enable the three-dimension modeling of both low- and high-density microplastics. The BFLOC2 model can be coupled to traditional sediment transport models to better describe the sediment formation dynamics, thus giving a more precise prediction of sedimentation and carbon flux to deep waters and offshore.
39
Shen, Xiaoteng. "Modeling flocculation and deflocculation processes of cohesive sediments." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1539616853.
Testo completoAbstract (sommario):
The transport and fate of cohesive sediments are responsible for many engineering, environmental, economic and policy issues that relate to, for example, siltation and dredging in navigation channels, water quality, water turbidity, pollutant transports, and biological ecosystem responses. Our current understanding, however, is insufficient to conduct accurate quantitative predictions of these processes. This is because the cohesive particles in natural waters will flocculate, which determines the settling, and thus the deposition behaviors. The simulation of flocculation processes is a primary challenge since the time variation of Floc Size Distribution (FSD) is controlled by a partial differential equation that also contains the integration of FSD itself. Previous models either address less characteristic sizes, which produce biased FSDs, or are incapable of modeling a relative large study domain in order to better express the FSDs with more size groups. In this study, a cohesive sediment flocculation model developed based on the framework of Population Balance Model (PBM) is solved by the Quadrature Method of Moments (QMOM). This PBM�QMOM flocculation model has reasonably compromised by both the model robustness and model efficiency. The former lies in the capability of describing the time evolution of the FSDs with a maximum of eight size classes, and the latter is reflected in its efficiency to solve PBM with transport terms and the potential to be coupled in a flow-mud estuary model. The model predictions are compared to both the analytical (or trusted class method) results for general PBMs (i.e., beyond the scope of specific research field), and the published experimental results of kaolinite suspension and colloidal montmorillonite. After that, an experimental activity has been carried out to develop a Sony NEX-5R camera system (with extension tubes and close-up) to automatically acquire floc images under various controlled environments, and to use MATLAB software to process the FSDs. This process is validated by the results of two set of sample particles. The validated camera system is first applied in a five liter mixing chamber to investigate the effects of salinity and selected organic matters on kaolinite flocculation. Then, the camera system is improved and assembled in a waterproof house for underwater use to provide data for a conceptual one-dimensional application in a relatively large turbulence tank. The flow field of the tank is measured by an acoustic Doppler velocimetry. The flocculation processes in the mixing chamber or cylindrical tank are modeled by PBM�QMOM and validated by camera statistical FSDs. While chemical and biological effects are not explicitly included in PBM�QMOM (implicitly included in fitting parameters) at this time to address the basic mechanisms of flocculation, these effects can be further extended when the process itself is better understood through other laboratory experiments or field measurements.
40
Okaiyeto, Kunle. "Evaluation of flocculating potentials and charecterization of bioflocculants produced by three bacterial isolates from Algoa Bay, South Africa." Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/2633.
Testo completoAbstract (sommario):
Flocculation has been widely adopted as one of the most effective methods to remove colloidal particles in water or wastewater treatment. Synthetic flocculants are conventionally used because of their high flocculating efficiency and cost-effectiveness. However, they have been reported to have hazardous properties and implicated in some serious health problems including senile dementia and neuro-toxicity, as well as being recalcitrant in the environment. Consequently, efforts are being geared away from the use of synthetic flocculants in water and wastewater treatment. Hence, the need for safe and eco-friendly flocculants has become imperative. Compared with synthetic flocculants, bioflocculants have special advantages such as safety, biodegradability and harmlessness to the environment and humans; attributes which make them potential alternatives in water treatment, downstream as well as fermentation processes. In the current study, the potentials of bacterial isolates recovered from Algoa Bay in the Eastern Cape Province of South Africa for bioflocculant production were investigated. The bacterial isolates were identified by polymerase chain reaction (PCR) as belonging to the Bacillus genus. The analysis of 16S ribosomal deoxyribonucleic acid (rDNA) nucleotide sequence of isolate M72 showed 99 percent similarity to Bacillus toyonensis strain BCT-7112 and was deposited in the GenBank as Bacillus toyonensis strain AEMREG6 with accession number KP406731. Likewise, the 16S rDNA nucleotide sequences of isolates M69 and M67 showed 98 percent sequence similarity to Bacillus licheniformis strain W7 and Bacillus algicola strain QD43 respectively; and M67 isolate was subsequently deposited in the GenBank as Bacillus sp. AEMREG7 with accession number KF933697.1. The results of the nutritional requirements and fermentation conditions revealed that optimum inoculum size for REG-6 production was 4 percent (v/v), while 5 percent (v/v) and 3 percent (v/v) were most favourable for MBF-W7 and MBF-UFH production respectively. Glucose was the best carbon source for the production of bioflocculants (REG-6 and MBF-UFH) by Bacillus toyonensis AEMREG6 and Bacillus sp. AEMREG7 respectively, while maltose supported optimum bioflocculant (MBF-W7) production by Bacillus specie. Inorganic nitrogen (NH4NO3) was the favoured nitrogen source for both REG-6 and MBF-W7 production, while mixed nitrogen sources [yeast extract + urea + (NH4)2SO4] supported the maximum production of MBF-UFH. The initial medium pH for REG-6 was 5, while MBF-W7 and MBF-UFH were both maximally produced at the initial pH of 6. After a 96 h cultivation period under optimal culture conditions, 3.2 g of purified REG-6 with a maximum flocculating activity of 77 percent was recovered from 1 L fermented broth of Bacillus toyonensis AEMREG6. Yields of 3.8 g and 1.6 g pure bioflocculants with the respective highest flocculating activities of 94.9 percent and 83.2 percent were also obtained from 1 L, 72 h-fermented broths of Bacillus licheniformis and Bacillus sp. AEMREG7 respectively. Furthermore, all the three bioflocculants (REG-6, MBF-W7 and MBF-UFH), displayed thermal stability within the temperature range of 50 to 100 oC, with strong flocculating activities of over 80 percent against kaolin suspension over a wide range of pH range (3–11) and relatively low dosage requirements of 0.1-03 mg/ml in the presence of divalent cations in the treatment of kaolin clay suspension and Thyme River waters. Chemical composition analyses of the bioflocculants showed them to be glycoproteins with a predominantly polysaccharide backbones as shown by the following carbohydrate/protein (w/w) ratios: 77.8 percent:11.5 percent (REG-6); 73.7 percent:6.2 percent (MBF-W7) and 76 percent:14 percent (MBF-UFH).
41
Hecker, Richard. "The characterisation of polyacrylamide flocculants." Thesis, Curtin University, 1998. http://hdl.handle.net/20.500.11937/2010.
Testo completoAbstract (sommario):
Polyacrylamide is widely used as a flocculant but the influence of the molecular mass distribution upon flocculant activity is poorly understood. This thesis outlines the successful characterisation of ultrahigh molecular mass polyacrylamide solutions in terms of discrete solvated polymer coils and coil agglomerates. These features were correlated with the observed flocculation, demonstrating a number of solution state features required to improve flocculation activity.Aqueous solutions of polyacrylamide exhibit time-dependant behaviour affecting viscosity and polymer agglomeration. Improving the solvation of the polymer suppressed the agglomerates, as did manipulation of hydrogen bonding through the presence of salts. Limiting agglomeration through improved solvation apparently lowers a barrier to polymer interaction, such that the coils disperse but become more susceptible to reagglomeration under mild shear. These solvent modifications did not fully suppress the agglomerates.To fractionate polyacrylamide into a molecular mass distribution, flow field-flow fractionation (flow FFF) was chosen, coupled to a multi-angle laser light scattering (MALLS) photometer and a differential refractometer for molecular mass and concentration sensitive detection, respectively. For the first time, the analysis of high molecular mass polyacrylamides in water using the flow FFF-MALLS technique has been reported. However, a number of difficulties needed to be overcome, including shear artefacts, sample agglomeration and polymer-membrane interactions.Both polyacrylamide standards and commercial flocculants were amenable to the technique. Commercial flocculants were found to vary not only with regard to viscosity and mean molecular mass, but also with sub- and supramicron size agglomerates. The flow FFF technique is size-sensitive, which for some low molecular mass samples displayed an unusually wide elution profile, in apparent conflict with the molecular mass sensitive MALLS detector. It was concluded that polyacrylamide in solution exists simultaneously in three states: discrete polymer coils, entanglements of a several coils, and agglomerates with supramicron diameters.This thesis concluded with a comparison between the characterised polyacrylamides and observed flocculation activity on a standard kaolin substrate. Results show polymer with supramicron agglomerates produce the largest and most shear-resistant kaolin aggregates with a definite optimum agitation intensity. Higher molecular mass flocculants with less agglomeration bind fine particles under more gentle conditions but are deficient under increasing stress. Flocculants exhibiting coil entanglements showed poor activity and formed only small aggregates. A modified flocculation mechanism was proposed, in which supramicron polymer agglomerates play a critical role.
42
Bragg, Amanda Leann. "Phosphorus reduction in dairy effluent through flocculation and precipitation." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1646.
Testo completoAbstract (sommario):
Phosphorus (P) is a pollutant in freshwater systems because it promotes eutrophication. The dairies in the North Bosque and its water body segments import more P than they export. Dairies accumulate P-rich effluent in lagoons and use the wastewater for irrigation. As more P is applied as irrigation than is removed by crops, P accumulates in the soil. During intense rainfall events, P enters the river with stormwater runoff and can become bio-available. Reducing the P applied to the land would limit P build up in the soil and reduce the potential for P pollution. Since wastewater P is associated with suspended solids (SS), the flocculants, poly-DADMAC and PAM, were used to reduce SS. To precipitate soluble P from the effluent, NH4OH was added to raise the pH. Raw effluent was collected from a dairy in Comanche County, TX, and stored in 190-L barrels in a laboratory at Texas A&M University. Flocculant additions reduced effluent P content by as much as 66%. Addition of NH4OH to the flocculated effluent raised the pH from near 8 to near 9, inducing P precipitation, further reducing the P content. The total P reduction for the best combination of treatments was 97%, a decrease from 76 to 2 mg L-1. If this level of reduction were achieved in dairy operations, P pollution from effluent application would gradually disappear.
43
Landazuri, Natalia. "Effects of flocculation on retrovirus processing, delivery and transduction." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6884.
Testo completoAbstract (sommario):
The efficiency of retrovirus-mediated gene transfer can be dramatically enhanced by inducing flocculation of viruses. Addition of oppositely charged polymers to virus stocks resulted in the formation of virus-polymer complexes. The complexes specifically incorporated virus particles and only few other proteins, were not cytotoxic, did not reduce the stability of the viruses, and were large enough to sediment, delivering the viruses to the cells more rapidly than by simple diffusion. Increases in the rate of transport of viruses correlated with increases in the rate of transduction, as the polymers did not affect the efficiency of post-binding steps of transduction. The formation of virus-polymer complexes also permitted concentrating viruses and purifying the stocks from inhibitors of transduction. Pelleting of the complexes followed by resuspension of the pellet in a reduced volume of fresh cell culture medium resulted in substantial enhancement of transduction. Purified virus stocks could be used in smaller quantities than unprocessed stocks to achieve a given level of gene transfer and reduced uncertainties about the relationship between the amount of virus used and the number of genes transferred. When using high concentrations of purified viruses, the efficiency of gene transfer was dependent on the number of envelope proteins displayed on the surface of each virus particle. Viruses with a low number of envelope proteins transduced cells more efficiently than did viruses with a high number of envelope proteins, and allowed more integrations of the transgene per target cell. In contrast, when the number of envelope proteins per virus particle was high, transduction appeared to be limited by a reduction in availability of functional receptors for viruses pseudotyped with the same envelope. Taken together, this novel method for processing retrovirus stocks and a better understanding of major limitations of transduction should simplify efforts to predict the outcome of retrovirus transduction protocols and should help to increase the likelihood that human gene therapy protocols will succeed.
44
Correa, de Araujo Armando. "Starch modification of the flocculation and flotation of apatite." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28657.
Testo completoAbstract (sommario):
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.<br>Applied Science, Faculty of<br>Mining Engineering, Keevil Institute of<br>Graduate
45
Al-Khalili, Reya Sadik. "Contact flocculation filtration using natural coagulants for developing countries." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/30172.
Testo completoAbstract (sommario):
Contact flocculation filtration using natural cationic polyelectrolytes extracted from seeds of the tree M.oleifera were found to be effective in the treatment of low turbidity waters. The coagulant was dosed immediately prior to the filter inlet, with subsequent flocculation and deposition occurring in the filter bed. This single stage treatment option was considered appropriate for developing countries, due to observed treatment performance, robustness of operation and reduced treatment costs. This work extends and complements previously successful studies on the treatment of medium to high turbidity raw waters using M.oleifera seed. Laboratory studies using twin 100 mm diameter filter columns, were undertaken with the following variables: turbidities of 5-75 NTU; filtration rates of 5-20 m/h; filter depths of 70 and 120 cm; dual and single media beds, and media sizes of 0.50-1.00 mm and 0.85-1.70 mm. Deeper beds and smaller media were found to considerably reduce filtrate turbidity when using M.oleifera seed. The consequent headloss increase was only significant with the higher turbidity waters; dual media beds were most effective on such waters. Turbidity removal was reduced at higher filtration rates (10m/h), due to lower retention times in the bed, and increased detachment of retained particles causing early turbidity breakthrough. Higher filtration rates with another natural coagulant, chitosan, increased turbidity removal and prolonged the time to breakthrough, due to the reduction in surface removal in the filter. At lower loading rates (5 NTU at 5 m/h), removal with M.oleifera seed was comparable with chitosan and aluminium sulphate, with the additional advantage of a lower headloss. Optimisation of the hydraulic variables for a specific coagulant was considered necessary to ensure maximum output and filtrate quality. Field trials on a low turbidity natural raw water indicated that M.oleifera reduced the turbidity by >95% and bacterial numbers by 100% at the optimum dose. Despite the rise in organic matter in the final water, trihalomethane levels were not excessive.
46
Zhan, Yihong. "Latices as flocculants in selective flocculation of mineral suspensions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/NQ46455.pdf.
Testo completo
47
Davy, Steven Colin. "On the mechanism of flocculation in NewFlo Saccharomyces species." Thesis, Oxford Brookes University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432711.
Testo completo
48
Cornelissen, Alex. "The chemistry and technology of water cleaning by flocculation." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387927.
Testo completo
49
Pallipurath, Radhakrishnan A. N. "Elucidation of flocculation growth kinetics using a microfluidic approach." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1498776/.
Testo completoAbstract (sommario):
The inter-disciplinary work in this thesis entails the development of a microfluidic device with bespoke imaging methodology to study flocculation growth kinetics dynamically in real-time. Flocculation is an advantageous downstream operation that increases the product-separation efficiency by selectively removing impurities. Yet, there is no unifying model defining the effect of different physico-chemical parameters on the rates of flocculation. Conventional setups for said analyses require large experimental space that are tedious to perform, and are limited by their dependence on end-point analysis, requiring sample-handling and further dispersion into typical particle-sizing instruments. In spite of the counter-intuitiveness of implementing microfluidics to study flocculation due to the anticipated channel-clogging issue, it is hypothesised that the growth kinetics can be measured by achieving a continuous, steady-state flocculation under a lower-shear environment. Flocculation within a spiral microfluidic device (~151.8 µl volume) is evaluated against a bench-scale setup (~50 ml volume) through the comparison of floc size and zeta potential. The fluid hydrodynamics in the microchannel is assessed by an experimental mixing-time analysis (tmix = 7.5 s) and a residence time distribution study (tm = ca. 70 s). In situ measurement of floc size and morphology is facilitated through high-speed imaging, with an image-processing script for robust analysis. Different flocculants are tested and growth rates calculated (~ 8 and ~12 µm s-1 for PEI and pDADMAC). Flocs grew linearly up to 250 µm for cationic polymers, while no growth was observed with a non-ionic PEG. Using an improved parameter-fitting step, the growth rates are compared to a simplified model for monodisperse perikinetic flocculation. The work presented should thus, enable an experimental estimation of flocculation growth kinetics and pave way for the development of accurate flocculation models for polydisperse particles. The developed system also facilitates a rapid screening of new flocculants useful for quicker process development.
50
Dicks, Reay Gary. "Microalgae flocculation and sedimentation by physico-chemical property exploitation." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10366.
Testo completoAbstract (sommario):
The purpose of this research was to characterise the physical properties of microalgae, as a function of growth and suspension conditions, to enable exploitation of these characteristics for improved separation whilst allowing for water recycle.