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Synthesis, characterization and assessment of nanocomposites-based ultrafiltration membrane with reduced fouling and better wastewater disinfection23 April 2015 (has links)
Ph.D. (Chemistry) / This study addressed the incorporation of nanotechnology-based materials, either through incorporating nanomaterials or by introducing nanostructures onto the membrane matrix, to form nano-enabled polymeric membranes with high specific flux and better anti-fouling profile. The aim of the study was to integrate nanotechnology and membrane science in order to improve the performance of water filtration membranes by alleviating some of the specific shortcomings of water treatment membranes......
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Microbial inactivation using ultraviolet light-emitting diodes for point-of-use water disinfectionGabbai, Udi Edward January 2015 (has links)
No description available.
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Investigating the efficacy of medium pressure UV and hydrogen peroxide as on-farm treatment methods to reduce the microbial load of irrigation waterKotze, Madelize J. 04 1900 (has links)
Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Many South African farmers are forced to use water from nearby rivers for crop irrigation, since it is
the most affordable and sometimes only source of water available to them. During this research
project, a baseline study was performed on a farm irrigating fresh produce with water obtained
from the Eerste River. The baseline study was done over a five month period, at six preselected
sampling points, to determine the microbial and physico-chemical parameters of the water so a
baseline could be established to compare the results to when the ultraviolet (UV) apparatus was
installed (February 2013). Aerobic colony count (ACC), total coliforms (TC) and Escherichia coli
(E. coli) were tested for during the microbiological study, while the physico-chemical analysis
comprised of temperature, pH, conductivity, chemical oxygen demand (COD), alkalinity and total
soluble solids (TSS). The UV treatment study was also performed over a five month timeline, at
eight different sampling points (original six sampling points, with additional sampling points before
and after UV). The same microbiological tests were performed during the UV treatment study, but
turbidity and percentage ultraviolet transmittance (% UVT) were performed additionally during
physico-chemical analysis.
During the baseline study ACC, TC and E. coli counts as high as 9 600 cfu.mL-1, 13 799
MPN.100 mL-1 and 2 098 MPN.100 mL-1 were isolated at the river (Sampling Point 1), respectively.
While performing the UV treatment study ACC, TC and E. coli counts as high as 142 000 cfu.mL-1,
241 960 MPN.100 mL-1 and 6 867 MPN.100 mL-1 were isolated at the river, respectively. As a
result it was concluded that the Eerste River was mostly unsuitable for irrigation of fresh produce
that are consumed raw. The higher counts in the river, during the UV treatment study might be
attributed to the increase in rainfall that occurred in the sampling months (March to July 2013).
The counts as measured at the point of irrigation are considered of greater importance,
since the counts present in the river might still decrease to below the guideline levels after passing
through sand filters and the addition of hydrogen peroxide (current mode of treatment) or after
passing through the UV in the UV treatment study. The ACC, TC and E. coli counts during the
baseline study were as high as 8 800 cfu.mL-1, 24 196 MPN.100 mL-1 and 85 MPN.100 mL-1 at the
point of irrigation (Sampling Point 6), respectively. After hydrogen peroxide addition average logreductions
ranging between 0.65 and 1.13 were seen, but reduction was never constant. The counts at the point of irrigation remained more or less constant compared to the river
due to contamination that occurred at the sand filters, making the water unsuitable for irrigation of
fresh produce in terms of ACC and TC counts. In the UV treatment study ACC, TC and E. coli
counts were as high as 35 000 cfu.mL-1, 10 462 MPN.100 mL-1 and 63 MPN.100 mL-1 at the point
of irrigation (Sampling Point 8), respectively. Average log-reductions in the range of 0.90 to 1.25
were achieved, but it was inconsistent. After treatment with chlorine and re-sanding of the sand
filters, no further contamination occurred and counts decreased to below guideline limits, making
the water safe for irrigational use in terms of all of the microbiological parameters. Not only is UV treatment more effective in reducing microbiological counts than H2O2, it is also relatively less
expensive in the long term. Hydrogen peroxide treatment of water amounts to a very high capital
expense every month, whereas UV may seem expensive when starting up, but the monthly
operating cost thereafter is marginally less than for H2O2.
It is of great importance to farmers to find a treatment that would reduce the counts in the
river water to below the guideline limits required for safe irrigation since pathogens can be carried
over from water onto fresh produce, resulting in an increase in produce-associated foodborne
outbreaks and loss of consumer trust. / AFRIKAANSE OPSOMMING: Menigte Suid-Afrikaners is afhanklik van nabygeleë riviere om hulle oeste te besproei aangesien
dit meestal die mees bekostigbare en soms enigste bron tot hul beskikking is. Tydens hierdie
projek is ‘n grondslag sowel as ‘n UV behandelingsmetode studie uitgevoer op ‘n plaas wat vars
vrugte en groente besproei met water water wat hul vanuit die Eersterivier verkry. Die
grondslagstudie is oor ‘n tydperk van vyf maande uitgevoer by ses voorafgekose punte. Dit is
gedoen om die mikrobiologiese sowel as chemiese parameters van die water te bepaal sodat ‘n
grondslag beskikbaar kon wees om met resultate te vergelyk wat met behulp van die
ultravioletmasjien verkry is (in Februarie 2013 geïnstalleer). Tydens die mikrobiologiese studie is
daar vir aerobiese koliform tellings (ACC), totale koliforme (TC) en Escherichia coli (E. coli)
getoets. Tydens die chemiese analise is temperatuur, pH, konduktiwiteit, chemiese suurstof
benodiging, alkaliniteit en totale oplosbaie vastestowwe in die water getoets. Die UV
behandelingsmetode studie is ook oor ‘n tydperk van vyf maande uitgevoer, met twee addisionale
toetspunte by. Presies dieselfde mikrobiologiese analises as wat tydens die grondslag studie
uitgevoer is, is tydens die UV behandelingsmetode studie uitgevoer, maar vir die chemiese analise
het turbiditeit en persentasie ultraviolet transmissie van die water bygekom.
Gedurende die grondslag studie was ACC, TC and E. coli tellings so hoog as 9 600
cfu.mL-1, 13 799 MPN.100 mL-1 en 2 098 MPN.100 mL-1 onderskeidelik uit die rivier geïsoleer
(Punt 1). Tydens die UV behandelingsmetode studie was ACC, TC en E. coli tellings so hoog as
142 000 cfu.mL-1, 241 960 MPN.100 mL-1 en 6 867 MPN.100 mL-1 onderskeidelik by die rivier
geïsoleer. Gevolglik is daar afgelei dat die Eersterivier se water meestal ongeskik is om te gebruik
vir die besproeiing van vars groente en vrugte wat rou geëet word sonder dat enige verdere
behandeling plaasvind. Die hoër tellings wat tydens die UV behandelingsmetode in die rivier
sigbaar was kan hoofsaaklik toegeskryf word aan die toename in reënval in daardie tyd (Maart tot
Julie 2013).
Tellings soos gemeet by die punt van besproeiing is wel van groter belang as die wat
aangeteken is by die rivier; aangesien die tellings wat in die rivier aangeteken is steeds kan
afneem tot onder aanvaarbare hoeveelhede soos in die standaarde uiteengesit, want die water
moet steeds deur sandfilters beweeg en word ook huidiglik deur waterstofperoksied behandel
tydens die die grondslagstudie of beweeg deur die UV apparaat in die UV behandelingsmetode
studie. Die ACC, TC en E. coli tellings soos gemeet by die besproeiingspunt (Punt 6) was so hoog
as 8 800 cfu.mL-1, 24 196 MPN.100 mL-1 en 85 MPN.100 mL-1, onderskeidelik. Na
waterstofperoksied byvoeging was die gemiddelde log-reduksies sigbaar, tussen 065 en 1.13,
maar afnames was nooit konstant nie. Die tellings by die punt van besproeiing het ongeveer
konstant gebly in vergelyking met die tellings wat by die rivier aangeteken is; moontlik as gevolg
van die hoë kontaminasie vlakke in die sandfilters. Kontaminasie van sandfilters het veroorsaak
dat die water ongeskik was vir die gebruik van besproeiing van vars groente as gevolg van die hoë ACC en TC vlakke. Tydens die UV behandelingsmetode studie is ACC, TC en E. coli tellings so
hoog as 35 000 cfu.mL-1, 10 462 MPN.100 mL-1 en 63 MPN.100 mL-1, onderskeidelik aangeteken
(Punt 8). Gemiddelde log-reduksies tussen 0.90 tot 1.25 was verkry, maar behandeling en
afnames in tellings was nie konstant nie. Nadat die sandfilters met chloor behandel is en die sand
daarin vervang is, het geen verdere kontaminasie by die punt voorgekom nie. Nadat al die
voorafgenoemde behandelings afgehandel is, het die tellings tot laer as die van die standaarde
gedaal en dus was die water nou veilig om te gebruik vir besproeiingsdoeleindes in terme van die
mikrobiologiese parameters. Die UV behandelingsmetode is nie net meer effektief in die verlaging
van mikrobiologiesese tellings as waterstofperoksied nie, dis ook heelwat goedkoper in die
langtermyn. Waterstofperoksied behandeling van water lei tot ‘n baie hoë kapitale onkoste per
maand, terwyl UV baie duur mag voorkom in die beginfase, maar die maandelikse kostes is
aansienlik laer as die van waterstofperoksied en maak sodoende op daarvoor.
Dit is van uiterste belang vir boere om ‘n water behandelingsmetode te vind wat die hoë
tellings in die rivier sal afbring tot laer as Suid-Afrikaanse en Kanadese riglyne; aangesien
patogene oorgedra kan word van vars vrugte en groente. Laasgenoemde kan tot ‘n drastiese
toename in vars voedsel geassosieerde siektes en gevolglik ‘n afname in die vertroue wat ‘n kliënt
in ‘n produk plaas, lei.
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Electrospun nanofibers decorated with silver nanoparticles for fouling controlMsomi, Phumlani Fortune 02 July 2015 (has links)
M.Tech. (Chemistry) / This work focused on the in-situ decoration of polyethersulfone (PES) nanofiber mats with silver nanoparticles (AgNPs) using an electrospinning technique. The biocidal and organic properties of the Ag decorated nanofibers were evaluated. Electrospinning of Ag decorated nanofibers was also carried out on a mixed matrix membrane support composed of nitrogen doped carbon nanotube (N-CNTs) and PES to fabricate a unique bi-faceted membrane. PES was dissolved in a solution containing silver nitrate (AgNO3) and N,Ndimethylacetamide (DMAc). The polymer solution was dissolved at 80ºC for 3 h under reflux until a yellow homogeneous solution was obtained which indicated the in-situ formation of AgNPs. The polymer solution was cooled and stored to remove air-bubbles. An ultraviolet - visible (UV – Vis) spectrometer was used to confirm the presence of AgNPs, while a Malvern nanosizer was used to estimate the size distribution of the AgNPs in the PES polymer matrix. The solution was electrospun on an aluminium (foil) collecting plate. Biocidal properties of the material were evaluated using Gram-positive (G+) Staphylococcus aureus (S. aureus) and ram-negative (G-) Escherichia coli (E. coli) by the zone inhibition method. The silver decorated polyethersulfone nanofibers showed good antibacterial activity against both G+ S. aureus and G- E. coli.
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Synthesis of TiO2 nanoparticles by spray-lyophilization process : characterization and optimization of properties of photocatalytic water purification and gas sensing applicationsKibasomba, Pierre Mwindo 28 March 2021 (has links)
Monodisperse titanium dioxide (TiO2) nanoparticles were synthesized by a novel freeze-drying process herein called lyophilization. The process of lyophilization is described in detail. The materials were characterized by scanning electron microscopy SEM) including energy dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), Raman spectroscopy and UV-Vis-IR spectrophotometry. The TiO2 nanoparticles have narrow size distribution, mono-disperse, strained with most of the characteristics showing presence of the four phases of TiO2 thus: anatase, brookite, rutile with each lyophilization process producing its own phase mostly controlled by pH and precursor concentration and anneal/calcining temperatures. With specific reference to HRTEM, Raman spectroscopy results and XRD, it was found that the Scherrer equation, the Williamson-Hall method and others of similar nature were not enough to explain the strain and the grain sizes of these particles. Therefore the Williamson-Hall method was revised to properly explain the new results. The obtained TiO2 nanoparticles were used in three applications: (1) gas sensing (2) degradation of organic water-borne pollutants using methylene blue as an indicator (3) anti-bacterial activity. / Physics / D. Phil. Physics)
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Removal of E. coli with alternative media Biosand filtersFulton, Nathan J. 16 August 2012 (has links)
When Biosand filters cannot be constructed with crushed quarry rock due to resource limitations, a suitable alternative filter media is needed. In this research, two crushed quarry rock alternatives were examined. Three bench-scale Biosand filters with crushed rock, beach sand, and heat-treated beach sand media were simultaneously dosed with Willamette River water seeded with K-12 E. coli for 31 days. Influent and effluent filtrate was analyzed for E. coli using 3M Petrifilm E. coli/Coliform plate counts; influent and effluent pH, conductivity, turbidity, dissolved oxygen, and temperature were monitored. All three filters achieved stable E. coli removal efficiencies of 99% or greater after filter maturation, suggesting that it is possible to effectively use beach sand and heat-treated beach sand in Biosand filters for pathogenic bacteria removal. Mean effluent E. coli concentrations for crushed rock, beach sand, and heat-treated beach sand filters were 12, 29, and 30 CFU/mL respectively. Crushed rock filter effluent was significantly lower in mean effluent E. coli concentration than beach sand (P < 0.001) and heat-treated beach sand (P < 0.001)
filter effluents, suggesting that beach sand and heat-treated beach sand media should only be used as a secondary option to crushed rock media due to potentially greater exposure risk to pathogenic bacteria. / Graduation date: 2013
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