published_or_final_version / Civil Engineering / Master / Master of Philosophy

D.Phil. (Chemistry) / Polycaprolactone (PCL), a linear, biodegradable polymer, and ethylene vinyl acetate (EVA), a branched copolymer, were used to prepare PCNs via the melt-blending method. Organoclay of the type Cloisite® 20A (C20A) and bentonite clay were used as fillers. The results show that the structure of a polymer matrix plays a significant role towards compatibilisation with the silicate layers of the clay. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed an exfoliated-intercalated mixed morphology for the PCL matrix. However, for the EVA matrix, silicate layers agglomerated to form tactoids and resulted primarily in an intercalated morphology. Fourier transform infrared (FT-IR) spectroscopy was used to determine the nature of the interactions between the polymer and the filler. The thermal properties were investigated using thermogravimetric analysis (TGA) and indicated that, with an increase in clay loading, the thermal stability was reduced for both matrices, notwithstanding the type of polymer or clay used. Using EVA and C20A, this study revealed that more exfoliated nanocomposite structures can be obtained by using a modified solution-blending technique. This technique is a hybrid of the melt-blending and solution-blending methods. When compared to the melt-blending method, the modified solution method was found to be an efficient method for producing nanocomposite strips with uniform dispersion of the clay at organoclay loading of 8% and crystallinity by extrusion. However, the melt-blending method produced nanocomposites with high porosity, intercalation and thermal stability whereas the modified solution-blending technique resulted in more intercalated-exfoliated morphology, but less porosity and thermal stability. Despite the positives drawn from the modified solution method, the melt-blending method was used throughout for nanocomposites intended for application in water treatment. This was done because the solution used in the modified solution method could not be completely removed from the nanocomposite. Organic solvents can have a negative effect on the environment and human life.

Ph.D. (Chemistry) / The ultrafiltration membranes presented in this study were synthesized using the phase inversion method by casting on a nonwoven fabric. The polymer solutions were mixed with synthetic and bio additives in order to improve the resultant membrane performance. Synthetic additives (polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP)) were compared with a novel and cheap bio additive, lignin. Based on the knowledge that the additives must be soluble in water in order to increase the pore sizes of the membranes, sodium hydroxide was used to elute residual additives that remain in the membrane during coagulation. In order to trace the residual additives remaining, ATR-FTIR was used. Contact-angle analysis and water-absorption experiments were used to elucidate the hydrophilic properties of the prepared membranes. Membranes modified with lignin (Lig) were found to absorb more water (94% water uptake) when compared to the other membranes. In general, the contact angles were found to be low for membranes that were treated with NaOH. Membrane permeability followed the trend, Lig_PSf>PVP_PSf>PEG_PSf which is similar to the trend followed during water uptake. Pore size and pore distribution analysis showed that membranes modified with lignin and PVP had a narrow range (had pore sizes ranging from 10 to 24 nm) compared to that of PEG-PSf membrane (which ranged from 2.5 to 22 nm). A Robeson plot showed that Lig_PSf membranes had high separation factors regardless of the size of the solute being rejected. This study shows the possibility of using cheap and readily available additives to increase the performance of membranes......

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017. / Water scarcity in South Africa (SA) and more specifically Cape Town, Western Cape, has escalated to disaster levels in 2018. Agriculture and irrigation account for 62% of SA’s accessible potable water (Thopil & Pouris, 2016), and although the agriculture sector plays a pivotal role in SA’s socio-economic development, the future of the sector is dependent on critical issues such as climate variability and population growth (Besada & Werner, 2015). Wine production in SA is an important agricultural activity, contributing great economic value to the agri-food sector. However, despite this, the wine industry is responsible for vast water consumption and the unsafe disposal of winery wastewater, which are critical issues from an environmental and economic standpoint. The ever-imminent crisis pertaining to the limited supply of fresh water from conventional water resources has necessitated the need to develop alternative water resources to supplement an increased water supply, which include the reuse of wastewater, ground water, brackish water (BW) and seawater (SW) desalination. When fresh water supplies are limited, agricultural irrigation is penalised. The reuse of agricultural wastewater as a substitution for potable water irrigation may prove beneficial in areas where water shortages are severe. Forward osmosis (FO) is a developing desalination technology that has received increased attention as a promising lower-energy desalination technology. FO technology relies on the natural osmotic process, driven by a concentration gradient as opposed to significant hydraulic pressures like reverse osmosis (RO). Water is extracted from a lower concentrated feed solution (FS) to a highly concentrated draw solution (DS). The term “lower energy” is only applicable for applications where the recovery of the DS is not required. FO technology offers several advantages. However, the lack of suitable membrane modules and DSs hinder its practical application. FO offers novelty applications in which specialised DSs are selected to serve as the final product water, most notably concentrated fertilisers for direct fertigation. The aim of this study was to evaluate the performance and compatibility of commercially available cellulose triacetate (CTA) and aquaporin biomimetic FO membranes with commonly used fertilisers for direct fertigation within the SA wine industry, using a fertiliser drawn forward osmosis (FDFO) system.

Submitted in fulfillment of the academic requirements for the Master’s Degree in Technology: Chemical Engineering, Durban University of Technology. Durban. South Africa, 2015. / Increased public concern over health and the environment, the need to expand existing wastewater treatment plants due to population increase, and increasingly stringent discharge requirements, have created a need for new innovative technologies that can generate high quality effluent at affordable cost for primary and secondary re-use. The membrane biological reactor (MBR) process is one of the innovative technologies that warrant consideration as a treatment alternative where high quality effluent and/or footprint limitations are a prime consideration. MBR processes have been applied for the treatment of industrial effluent for over ten years (Harrhoff, 1990). In this process, ultrafiltration or microfiltration membranes separate the treated water from the mixed liquor, replacing the secondary settling tanks of the conventional activated sludge process. Historically, energy costs associated with pumping the treated water through the membranes have limited widespread application for the treatment of high volumes of municipal wastewater. However, recent advancements and developments in membrane technology have led to reduced process energy costs and induced wider application for municipal wastewater treatment (Stephenson et al., 2000). This report describes a small and pilot scale demonstration study conducted to test a woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) process for use in domestic wastewater treatment. The study was conducted at Durban Metro Southern Wastewater Treatment Works, Veolia Plant, South Africa. The main objective of this project was to develop and evaluate the performance of an aerobic woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) for small scale domestic wastewater treatment. The experiments were oriented towards three sub objectives: to develop the membrane pack for immersed membrane bioreactor based on WF microfilters; to evaluate the hydrodynamics of WF membrane pack for bioreactor applications; and to evaluate the long-term performance and stability of WFM-IMBR in domestic waste water treatment. The literature was reviewed on membrane pack design for established commercial IMBR. The data collected from literature was then screened and used to design the WF membrane pack. Critical flux was used as the instrument to measure the WF membrane pack hydrodynamics. Long-term operation of the WFM-IMBR was in two folds: evaluating the performance and long term stability of WFM-IMBR. The membrane pack of 20 flat sheet rectangular modules (0.56 m by 0.355 m) was developed with the gap of 5 mm between the modules. The effects of parameters such as mixed liquor suspended solids or aeration on critical flux were examined. It was observed that the critical flux decreased with the increase of sludge concentration and it could be enhanced by improving the aeration intensity as expected and in agreement with the literature. Hence the operating point for long term subcritical operation was selected to be at a critical flux of 30 LMH and 7.5 L/min/module of aeration. Prior to the long term subcritical flux of WFM-IMBR, the operating point was chosen based on the hydrodynamic study of the WF membrane pack. The pilot scale WFM-IMBR demonstrated over a period of 30 days that it can operate for a prolonged period without a need for cleaning. Under subcritical operation, it was observed that there was no rise in TMP over the entire period of experimentation. Theoretically this was expected but it was never investigated before. Good permeate quality was achieved with 95% COD removal and 100% MLSS removal. The permeate turbidity was found to be less than 1 NTU and it decreased with an increase in time and eventually stabilized over a prolonged time. Woven fibre membranes have demonstrated great potential in wastewater treatment resulting in excellent COD and MLSS removal; low permeate turbidity and long term stability operation. From the literature surveyed, this is the first study which investigated the use of WF membranes in IMBRs. The study found that the small scale WFM-IMBR unit can be employed in fifty equivalence person and generate effluent that is free of suspended solids, having high levels of solid rejection and has acceptable discharge COD for recycle. Future work should be conducted on energy reduction strategies that can be implemented in WFM-IMBR for wastewater treatment since high energy requirements have been reported by commercial IMBRs.

M.Sc. (Nanoscience) / Polychlorinated biphenyls (PCBs) are endocrine disrupting compounds (EDCs) and are harmful to humans and the environment. These PCBs are grouped under chlorinated organic compounds (COCs). The PCBs find their way to the environment through human activity such as industrialization and farming. Such activity produces wastes and runoffs that eventually end up in the water we use for drinking, farming and sanitation. It has then become necessary for researchers to find viable methods to remove these compounds from the environment. This is because current water treatment methods are not effective in the removal of the PCBs from water. The stages in the conventional treatment methods may include sand filtration, advanced oxidative processes and coagulation among others. These methods need to be energetically eco-friendly to drive the PCB dechlorination processes. Researchers have used a variety of metallic nanoparticles including bimetallic nanoparticles for the removal of COCs from water. However, nanoparticles tend to agglomerate when not supported - leading to a decrease in their activity. Hence it has become necessary to stabilize or immobilize these nanoparticles on suitable support materials, such as, polymer solutions or solid substrates. Solid substrates including metal oxides, carbon and membranes, are currently being explored. Poly(vinylidene difluoride) microfiltration membranes are especially suitable for this function given the high porosity, chemical inertness and other outstanding physical properties. In this work, the objective was to modify commercially hydrophilized poly(vinylidine)difluoride (PVDF) membranes with poly(ethylene glycol) (PEG). PEG is a bidentate polymer with two –OH groups found on either side of the molecule. The -OH groups allows PEG binding to the PVDF polymer backbone and hence high ability to capture or chelate the metal ions followed by their reduction. Nano-zerovalent metal nanoparticles were formed from these metal ions and chelated into the PEG grafted PVDF membrane to give the composite PVDF-PEG-Fe0. Post addition of the secondary metal was then followed by the introduction of the precomposite to a Pd solution to give the final catalytic membrane (PVDF-PEG-Fe0/Pd0). The use of PEG in this system allows for an even dispersion of the nanoparticles in the composite. The resulting nanocomposite membrane was used for the dechlorination of a polychlorinated biphenyl (PCB 77). Attenuated total reflection- Fourier transform infra red spectroscopy (ATR-FTIR) showed that PEG was successfully grafted onto the PVDF backbone. Optical contact angle measurements (OCA) were taken to determine the change in hydrophilicity of the membrane upon modification. X-ray diffraction spectroscopy (XRD) proved that the Pd and Fe nanoparticles immobilized on the system were indeed zerovalent. Scanning electron microscopy (SEM) images and contact angle measurements suggested a less porous membrane and slightly decreased hydrophilicity after modification. On the SEM micrographs the nanoparticles were observed to be quite evenly distributed in the membrane. Transmission electron microscopy (TEM) showed that the nanoparticles were in the range 20-30 nm in diameter, confirming the particle size values as determined by SEM. For the preliminary dechlorination studies done under ambient conditions, two dimensional column gas chromatography- time of flight- mass spectrometry (GCxGC-TOF-MS) results showed a complete dechlorination of PCB 77. A comparative study of the bare PVDF and catalytic membranes showed a slight difference in adsorption of the total PCB 77 concentrations. The catalytic membrane maintained its activity towards the dechlorination of PCB 77 after multiple regeneration cycles.

Submitted in fulfilment of the academic requirements for the Degree of Masters in Technology: Chemical Engineering, M.L. Sultan Technikon, 2002. / Crossflow microfiltration (CFMF) using a fabric support has been successfully used to treat a range of problematic waters. Experimental evidence indicates that the formation of a dynamic membrane or precoat on a woven-fibre microfilter can significantly increase the performance of the filter, that is, the production rate and rejection. The use of precoats in filtration applications is based on the precoat's unique microstructure that is able to trap sub-micron particles while maintaining a permeable filter cake. However, to date the precoating step has been more of an art than a science. Very little knowledge exists on the best type of precoat to use, or the the optimal velocity, pressure and concentration to form a stable precoat. Further, although various models have been proposed for CFMF, their still exists a lack of knowledge of the mechanisms by which precoats improve performance. / M

D.Phil. (Chemistry) / The application of dendritic-based materials has attracted great interest. For the first time this research has investigated the feasibility of poly (propyleneimine) (PPI) dendrimers and hyperbranched polyethyleneimine (HPEI) in combination with beta-cyclodextrin (β-CD) embedded in polysulfone (PSf) membrane for water treatment. The advantage of embedding these conjugates (β-CD-PPI and β-CD-HPEI) in PSf membranes is the presence of numerous nanocavities which can act as water channels allowing easy water passage through the membrane improving water permeability. Secondly, the presence of functional groups such as –OH and –NH greatly improves hydrophilicity of membranes. Commercial polysulfone (PSf) ultrafiltration membranes were crosslinked with β-cyclodextrin-poly (propyleneimine) (β-CD-PPI) and β-cyclodextrin-hyperbranched polyethyleneimine (β-CD-HPEI) using trimesoyl chloride (TMC) by interfacial polymerisation. These membranes were used in the rejection of Aldrich humic acid (molecular weight: 4.1 kDa) from synthetic water samples prepared in the laboratory. Moreover, β-cyclodextrin-poly (propyleneimine) (β-CD-PPI) was used as a host for the preparation of Fe/Ni nanoparticles. The new membranes were synthesised by crosslinking β-CD-PPI with trimesoyl chloride and subsequently loading Fe/Ni nanoparticles and this was supported on a commercial polysulphone (PSf) layer for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The membrane surfaces were characterised using Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) spectroscopy , scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HR-TEM), water-contact angle, and water-intake capacity...

M.Sc. (Chemistry) / Water purification technologies based on membranes are prone to fouling by natural organic matter (NOM) and other biological species in water. This leads to the short lifespan of the membranes and high demand in energy than normal due to high pressure needed to pump water across the fouled membrane. In a quest to address these challenges, polyethersulfone (PES) and polyvinylidene flouride (PVDF) membranes supported on 3 different types of non-woven fabrics NWF1(polyester), NWF2 (polyphenylene sulphide) and NWF3( thicker polyester) were fabricated using the phase inversion method. This enabled the modification the active top layer of PES and PVDF thin film while maintaining the high mechanical strength offered by the NWFs. FTIR spectroscopy, sessile drop contact angle measurements, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the membranes. The membrane flux and rejection were studied using the cross-flow membrane unit. The contact angle results revealed that the hydrophilicity of PES and PVDF membranes increased as the polyvinyl pyrrolidone (PVP) concentration was increased. TGA revealed that the PES and PVDF membranes were thermally stable up to 580ºC and 530ºC respectively. The cross-sectional SEM revealed that membrane pores become enlarged when PVP has been added. AFM showed that membrane roughness improved when PVP was added. A rejection of 98% humic acid was obtained for PES membranes supported on NWF1, compared to 94 % and 96 % for membranes supported on NWF2 and NWF3 respectively. The highest rejection of humic acid (HA) recorded for PVDF membranes supported on NWF1 was found to be 97 % compared to the 95% for membranes supported on NWF2 and NWF3 fabrics respectively. PES membranes supported on NWF2 exhibited low but best As(III) metal ions rejections whilst PVDF membranes supported on NWF3 exhibited low but best rejections for Cr(III) metal ions.

Submitted in fulfilment of the requirements of the Degree of Master of Technology: Chemical Engineering, Durban University of Technology, 2013. / Lack of access to clean and safe potable water, especially for people living in rural areas of developing economies, is a matter of great concern in different parts of the world. Measures taken to address the challenges arising from this problem include the improvement of existing water purification methods and development of new appropriate technologies such as point of use (POU) water treatment technologies. One such appropriate POU technology is the Remote Rural Water Treatment System (RRWTS) developed at Durban University of Technology (DUT) in South Africa. The RRWTS is based on polyester woven fabric microfiltration (WFMF) membranes and other locally sourced materials. The filtration unit consists of flat sheet modules assembled into a pack and permeate outlets connected to a manifold and then to a tap. The system is gravity driven and therefore eliminates the use of pumps and electricity. This system has shown potential for use in water treatment as it produces permeate with turbidity below 1 NTU, has a high permeate flow rate, and is easy to use and maintain. However, the major challenge facing its use is that permeate does not meet the set microbiological standards for drinking water (zero E. coli in 100 mL treated water). The RRWTS can ideally remove 95 to 99 per cent of the influent E. coli. This necessitates the use of a separate disinfection step, often using chlorine for complete removal of microbial contaminants. The objectives of this study were: to investigate the incorporation of silver nanoparticles (AgNPs) into the WFMF membrane; to evaluate the disinfection efficacy of the AgNPs impregnated filter (coated filter); and to determine the long term performance of the coated filter in terms of disinfection and silver elution (90 days). The study was conducted in four stages. Firstly, AgNPs were incorporated on the membrane using in situ chemical reduction of silver nitrate using sodium borohydride. Secondly, the filters were characterized using scanning electron microscopy (SEM) to determine the morphology, and the Sessile drop method for contact angle measurement was employed to determine the membrane hydrophilicity. In addition, X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy and UV- Visible Spectroscopy iii were used to investigate the presence of AgNPs on the coated filter. Thereafter, the antibacterial efficacy of the filters was evaluated using a laboratory scale experimental rig and different microbial assays. Raw river water and deionized water spiked with E.coli (synthetic feed) were used as feed. Lastly, the effects of concentration of E.coli in the feed and silver elution on the disinfection performance of the coated filter over time were investigated. The performance criteria were based on permeate quality and they included: turbidity, concentration of E.coli, and silver concentration. The characterization results depicted that AgNPs were successfully immobilized on the WFMF membranes by in situ chemical reduction. The incorporation of AgNPs was ascertained using UV-Vis Spectrophotometry, FT-IR and XRD. The Sessile drop test indicated that the membrane became more hydrophilic (77 per cent decrease in water contact angle) and the permeability increased significantly as a result of the coating (p <0.05). The coated filters demonstrated excellent filtration performance producing permeate with turbidity less than 1 NTU for feed turbidities between 40 and 700 NTU. The disinfection efficacy was found to be excellent, producing permeate with zero E.coli concentration for feed concentrations between 10,000 CFU/ 100 mL and 85,000 CFU/100 mL. The E.coli removal efficiency was 100 per cent for a period of 63 days of continuous filtration. The ICP Atomic Emission Spectrometer (ICP-AES) results showed that the leaching of silver from the coated filters over time (90 days) was always below 0.1 mg/L which is the widely accepted guideline for potable water. From the literature surveyed, this is the first study which investigated the use of AgNPs in WFMF membranes for potable water disinfection. The coated filters treated water to the set international standards for potable water in terms of physical and microbiological quality. However, the study did not comprise investigation into the effect of different silver loadings on the filter performance. The study also employed E.coli as the indicator organism for faecal contamination. The results obtained can be used as a model for future work using other microorganisms and different silver loadings in order to compare the performance.