• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 421
  • 67
  • 61
  • 27
  • 18
  • 15
  • 12
  • 12
  • 12
  • 12
  • 12
  • 11
  • 3
  • 2
  • 1
  • Tagged with
  • 792
  • 792
  • 166
  • 100
  • 99
  • 99
  • 93
  • 93
  • 91
  • 88
  • 83
  • 82
  • 77
  • 71
  • 68
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Particle and biomass detachment during biological filter backwashing : impact of water chemistry and backwash method

Richman, Marjorie Timmerly 08 1900 (has links)
No description available.
12

Effectiveness of static mixers for disinfection of cryptosporidium oocysts

Hardy, Scott Andrew 05 1900 (has links)
No description available.
13

The development of appropriate brine electrolysers for disinfection of rural water supplies.

Siguba, Maxhobandile January 2005 (has links)
<p>A comparative study of electrolysers using different anodic materials for the electrolysis of brine (sodium chloride) for the production of sodium hypochlorite as a source of available chlorine for disinfection of rural water supplies has been undertaken. The electrolyser design used was tubular in form, having two chambers i.e. anode inside and cathode outside, separated by a tubular inorganic ceramic membrane. The anode was made of titanium rod coated with a thin layer of platinum and a further coat of metal oxide. The cathode was made of stainless steel wire. An assessment of these electrolysers was undertaken by studying the effects of some variable parameters i.e.current, voltage and sodium chloride concentration. The cobalt electrolyser has been shown to be superior as compared to the ruthenium dioxide and manganese dioxide electrolysers in terms of hypochlorite generation. Analysis of hydroxyl radicals was undertaken since there were claims that these are produced during brine electrolysis. Hydroxyl radical analysis was not successful, since sodium hypochlorite and hypochlorous acid interfere using the analytical method described in this study.</p>
14

The electrogeneration of hydroxyl radicals for water disinfection.

Mangombo, Zelo January 2006 (has links)
<p>This study has shown that OH˙ radicals can be generated in an Fe/O2 cell from the electrode products via Fenton&rsquo / s reaction and used for water disinfection. The cell system in which the experiments were carried out was open and undivided and contained two electrodes with iron (Fe) as the anode and oxygen (O2) gas diffusion electrode. Typically, 100 ml of Na2SO4.10H2O (0.5M) solution was used as a background electrolyte. OH˙ radicals were produced in-situ in an acidic solution aqueous by oxidation of iron (II), formed by dissolving of the anode, with hydrogen peroxide (H2O2). The H2O2 was electrogenerated by reduction of oxygen using porous reticulated vitreous carbon (RVC) as a catalyst.</p>
15

The development of appropriate brine electrolysers for disinfection of rural water supplies

Siguba, Maxhobandile January 2005 (has links)
>Magister Scientiae - MSc / A comparative study of electrolysers using different anodic materials for the electrolysis of brine (sodium chloride) for the production of sodium hypochlorite as a source of available chlorine for disinfection of rural water supplies has been undertaken. The electrolyser design used was tubular in form, having two chambers i.e. anode inside and cathode outside, separated by a tubular inorganic ceramic membrane. The anode was made of titanium rod coated with a thin layer of platinum and a further coat of metal oxide. The cathode was made of stainless steel wire. An assessment of these electrolysers was undertaken by studying the effects of some variable parameters i.e.current, voltage and sodium chloride concentration. The cobalt electrolyser has been shown to be superior as compared to the ruthenium dioxide and manganese dioxide electrolysers in terms of hypochlorite generation. Analysis of hydroxyl radicals was undertaken since there were claims that these are produced during brine electrolysis. Hydroxyl radical analysis was not successful, since sodium hypochlorite and hypochlorous acid interfere using the analytical method described in this study. / South Africa
16

Hydrophobic partitioning of the bacteriophage MS-2

Kroeger, Thomas William, 1952- January 1989 (has links)
In batch experiments at pH's 5 and 7, the partitioning of MS-2 between water and silica (unbonded) was compared with the partitioning between water and silica with 6.5 percent of the surface covered by hydrophobic C18 chains (bonded). The roles of double-layer and van der Waals forces in partitioning were explored by modeling the potential energies of interaction. MS-2 adsorption to unbonded silica was negligible at pH 7, but did occur at pH 5. Adsorption was independent of pH with the bonded silica and approximately 2.6 orders of magnitude greater than the unbonded at pH 5, suggesting the importance of hydrophobic partitioning. The total potential energies of interaction, which closely approach the pH-independent van der Waals potentials, are similar in magnitude for all pH's or silica types, and have no positive (repulsive) values. The insignificant contribution of the double-layer potentials suggests that these pH-dependent forces may not account for the pH-dependent adsorption observed with the unbonded silica.
17

Modelling the effect of deposition on removal efficiency in deep-bed filtration

Mackie, Robert Ian January 1984 (has links)
No description available.
18

Polymeric nitrogen donor macro(meso)porous sorption materials for selected transition metals

29 June 2015 (has links)
Please refer to full text to view abstract
19

The use of impulse response tracer experiments in horizontal subsurface flow constructed wetland development

Pieters, Werner January 2016 (has links)
A research proposal submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / In the past three decades there has been an increased interest in constructed wetlands (CW) and their effectiveness in treating water. The hydraulic efficiency of a CW can be determined by using chemical reactor theory to develop residence time distribution (RTD) parameters such as effective volume (Veff), normalized variance (σ2) and mean residence time (τm). Five experiments were conducted to study the effects on these RTD parameters in a CW by using a glass pilot-scale laboratory rig and varying the inlet-outlet positions. The rig made use of a glass tank 250x250x500mm filled with clear superabsorbent polymer balls as a packing. The clear tank and balls made it possible for the flow to be observed when a FWT red impulse tracer dye was inserted into the system. The flow was photographed at specific time intervals for visual analysis and comparison. . The visual results showed the formation of a hull-shaped velocity profile in all the experiments. The RTD was obtained by collecting tracer samples at specific outlet positions during the course of each experiment. The five inlet-outlet configurations RTD parameters results showed; a straight flow path from a single inlet to outlet yielded the lease desirable hydraulic performance with dead volumes contributing to up to 67% of the CW. An increase in the number of outlets and changing the direction of flow diagonally showed up to a 96% improvement to the effective volume of the system could be achieved when compared with single inline inlet-outlet flow. The best result was achieved by combining the visual and RTD data to make changes to the rigs geometry in order to eliminate dead zones and yielded up to a 148% improvement in the effective volume of the system when compared with single inline inlet-outlet flow. A well designed CW with respect to inlet-outlet position can result in reduced land requirements and construction costs by minimizing the dead volume and improving hydraulic efficiency. / MT2016
20

Synthesis and application of novel functionalized nanostructured membranes incorporating N-doped CNT supported metal nanoparticles in water treatment

Phao, Neo 06 August 2013 (has links)
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment for the degree of Master of Science in Chemistry. May 2013. / In relation to conventional water treatment methods, membrane separation has acquired a great audience due to its wide applicability, reliability, low cost, low energy demands, and ease of use. However, membrane fouling has been identified as the main downsizing factor in the application of this technology. To address this issue, several studies have suggested the use of inorganic additives for enhancement of the membrane antifouling properties. In this study, silver (Ag) decorated nitrogen doped carbon nanotubes (N-CNTs) dispersed into polyethersulphone (PES) membranes for potential use in water treatment. Firstly, N-CNTs were synthesised using the chemical vapour deposition (CVD) method. The black soot was functionalised and characterised using transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Brunner-Emmett-Teller (BET). The N-CNTs were found to have an average diameter of 15 nm. The functionalised N-CNTs were then decorated with Ag nanoparticles (AgNPs) using the Polyol method. The resultant product was also characterised using TEM, the AgNPs were found to have an average diameter of 6 nm. The N-CNTs and Ag/N-CNTs were then uniformly dispersed into (PES) membranes to form N-CNT/PES and Ag/N-CNT/PES blend membranes, respectively. The membranes were then characterised using several series of techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle analyser and a cross-flow filtration system. The blend membranes were investigated for any improved properties and tested for their efficiency in removing model pollutants (polyethylene glycol, humic acids, and bacteria) from water. The AFM results revealed a reduction in surface roughness from 23.9 nm for the pristine PES to 12.7 nm in the N-CNT/PES blend membranes. The mechanical stability increased from 3.7 MPa for the pristine PES to 4.4 MPa with a small addition of N-CNTs. Furthermore, the performance studies showed a 46% increase in pure water flux and a 13% increase in rejections for N-CNT blend PES membranes as compared to the pristine PES membrane. Antibacterial studies were also performed where Ag modified N-CNTs were found to inactivate Enterohaemorrhagic E. coli by almost twice the initial concentration in the bacterial suspensions. Finally, Ag/N-CNTs were immersed into PES membranes. The Ag/N-CNTs/PES membranes were then tested for their activity towards the bacteria.

Page generated in 0.1396 seconds