Submitted in fulfillment for the requirements of the degree of Master of Technology: Chemical Engineering,Durban University of Technology. Durban. South Africa, 2015. / Access to safe drinking water supply is still a major problem especially in remote rural areas of developing countries. These communities rely solely on untreated surface and ground waters for survival due to the lack of financial resources to provide access to piped water. The consumption of this water in turn makes them easily susceptible to water related diseases. Hence, there is a need for an interim solution while the government is still sourcing funds for the distribution of water to these communities. Membrane filtration is a promising technology for the treatment of surface water as it does not alter the taste or smell of the end product. The main limitation for the implementation of membrane technology in rural areas is still energy demand, fouling and the skills required for membrane cleaning. Biological ultrafiltration is an emerging technology that produces water of high quality in terms of turbidity, organics and bacteria removal. The technology has been evaluated using a gravity driven dead-end mode on European waters and it offered acceptable stabilisation of fluxes for extended periods without any chemical cleaning or backwashing. This is a promising technology which can be implemented to act as an interim solution for the treatment of surface water in remote rural areas prior to consumption. This study concerns the evaluation of a biological ultrafiltration membrane system on local three South African rivers, namely, Tugela River, Umbilo River and Umgeni River. A laboratory systems comprising of a feed tank and six membrane modules connected in parallel was set up to assess the performance of a bio-UF membrane on a range of surface waters. The performance was assessed on the system’s ability to produce stable fluxes from the three rivers, the system ability to produce water with acceptable quality in terms of SANS 241:2011 for turbidity, TOC, total coliforms and E-coli. The membranes were initial cleaned and the flux rates for ultra-pure water were determined for each membrane prior to being exposed to raw water. Raw water samples were collected from three rivers with varying turbidity, total coliforms and organics. The concentrations of these contaminants were tested prior to running the raw water through the system. Thereafter, permeate was collected with time and its quality was evaluated in terms of turbidity, TOC and coliforms. The impacts of algae on flux stabilisation were evaluated by allowing the bio-UF system to run for a minimum of 3 months with and without algae growth. The system was found to be able to produce water that is compliant with the SANS 241:2011 standard in terms of turbidity, total coliforms, E-coli and TOC concentration. The system was also found to be unable to produce stable fluxes for all three rivers. The observed responses were noted to be similar to normal dead-end response, however, a slow declining flux rates was observed for Umgeni River. The presence of algae during the operation was a bio-UF membrane system was noted to further decrease the rate of flux decline. There appears to be a correlation between the raw water quality and the rate of flux decline. A further investigation was carried out aimed at assessing the relationship between the concentration of bacterial counts, TOC and turbidity. From the obtained results, it was noted that feed water with low turbidity (≤ 5 NTU), high bacterial count (≥30 000) and high total organic carbon (≥70 mg/L) is able to reduce the rate of flux decline. Hence, it can be concluded that a dead-end gravity driven Bio-UF membrane system can be used for the treatment of surface water in remote where the most main contaminants are from natural organic matter, micro-organisms and turbidity. Furthermore, it is able to produce slower declining flux rates which will increase the filter run time. It is recommended that the impacts of algae, type of bacteria and organics that enable slow decline in flux rates during the operation of Bio-UF should be investigated in order to identify means of enhancing the flux rates. Microfiltration membranes are available on the local markets hence it is also recommended that the performance of Bio-UF should be evaluated in comparison to Bio-MF.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The hydrodynamics of a hollow fibre membrane module for the ultrafiltration of potable water were investigated. The purpose was to use a hydrodynamic model to predict the permeate flux for modules of various dimensions. Various models were considered, but most of them could not account for important effects such as macroscopic radial gradients and wet fibre expansion, found in hollow-fibre membrane modules. The Porous Medium Model was found to be a suitable model and it was used together with a finite element software package, Fastflo, to solve for the pressure distributions inside the membrane modules and predict permeate flux. The permeability of the membranes was obtained using a combination of numerical and experimental procedures and was found to be 2.3 x 10-13m. A cost analysis was performed to find the most economical module dimensions (outer diameter and length) for any required product flow rate. It was assumed that the cost of the fibres and module housing comprised the capital cost, while the operating cost consisted of the pumping energy. A capital recovery factor of 0.3 was used to convert capital costs to a yearly cost. It was found that the optimum module dimensions are an outer diameter of between 90mm and 160mm and a length of 0.6m. Finally the pressure distributions on the lumen and shell sides during both cross-flow filtration and backwash were examined. Shade plots proved useful for identifying possible areas of stagnant flow, as well as indicating where backwash is the most effective. / AFRIKAANSE OPSOMMING: Die hidrodinamika binne-in 'n holvesel membraanmodule vir die ultrafiltrasie van drinkwater is ondersoek. Die doel was om 'n hidrodinamiese model te gebruik om die permeaatvloed vir modules van verskeie dimensies te voorspel. Verskillende modelle is oorweeg, maar die meeste kon nie belangrike faktore soos makroskopiese radiale drukqradiente of nat veselverlenging in ag neem nie. Die Poreuse Medium Model was die mees geskikte model en is gebruik saam met Fastf/o, 'n sagteware pakket wat gegrond is op die eindige element metode, om vergelykings vir die drukverspreiding binne-in die module op te los en permeaatvloed te voorspel. Die permeabiliteit van die membrane is verkry met behulp van numeriese en eksperimentele prosedures en 'n waarde van 2.3 x 10-13 m is bepaal. Hierna is 'n koste-analise uitgevoer om die mees ekonomiese module afmetings (Iengte en buitedeursnit) te bepaal vir 'n gegewe produk vloeitempo. Daar is aanvaar dat kapitaalkoste bestaan uit die koste van vesels en module-omhulsel, terwyl bedryfskoste bereken is deur die hoeveelheid energie benodig om die pomp aan te dryf. 'n Kapitaalherwinningsfaktor van 0.3 is gebruik om kapitaalkoste om te skakel na 'n jaarlikse koste. Die optimum module afmetings is 'n lengte van 0.6m en 'n buite-deursnit van tussen 90mm en 160mm. Laastens is die drukverspreidings tydens beide kruisvloeifiltrasie en die terugspoelproses ondersoek. Areas van stagnante vloei kan deur middel van skadu-grafieke geYdentifiseer word, terwyl dit ook moontlik is om die terugspoelproses te optimeer.

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......

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2018. / A membrane distillation crystallization (MDC) experimental setup was designed, constructed and commissioned with rectangular mixing crystallizer tanks. The advantages and disadvantages of a rectangular mixing tank are compared to the traditional cylindrical mixing tank with baffling by means of a computational fluid dynamic (CFD) analysis in Ansys Fluent. The effect of tank configuration and geometry on the hydrodynamic and mixing characteristics for efficient momentum, solid suspension, heat and mass transfer were investigated. The hydrodynamic conditions in a crystallizer-mixing tank determine the quality of fluid mixing essential for optimal crystallization. Forty-five degree pitched blade turbines (PBT) were used to provide the agitation in the stainless steel rectangular jacketed tanks. Clear polycarbonate replicas of the rectangular tanks were manufactured to visually observe the mixing process in the tanks. Silica particles were used to represent the calcium carbonate crystals in the experiment. The data gathered from these experiments showed that the tanks should be operated between 600 to 750 rpm in the CFD simulations to simulate partial to complete suspension. In the numerical simulations a rectangular tank was compared to a cylindrical tank with baffling of the same volume. The partial differential equations solved in the numerical simulation were the conservation of mass (continuity), conservation of momentum and additional turbulence equations. In order to solve the turbulent fluid flow characteristics, the industry standard two-equation model, namely the K-epsilon model was used. This model was refined by the addition of the Wen-Yu drag model, the Simonin turbulent dissipation and the Simonin et al. turbulence interaction models. The RANS based RNG (k-ε), derived from the instantaneous Navier-Stokes equation was selected as the preferred model to analyse the hydrodynamic flow fields in the tanks. The 3D sliding mesh method was used to compute a time accurate solution. The Eulerian-granular multiphase model was used to predict the degree of solids suspension in the tanks. The efficiency of mixing within the tank was measured by the tank’s ability to keep the crystals in suspension and preventing any particle from settling at the bottom for more than 1-2 second(s). The mixing tanks were initially loaded with 5% v/v, which equates to a loaded height of approximately 10 mm. The simulations were done with the use of the volume fraction function to visually observe the cloud height and gauge the homogeneity and distribution of the particulates within the fluid flow fields. The results from the experimental setup were compared to the CFD simulations to qualify the use of CFD simulations for the comparison of the geometrically different tanks. Lastly, the findings from the CFD simulations were used to compare the tanks and determine if the rectangular tank built for the MDC experiment perform satisfactorily to replace a standard cylindrical tank with baffling for this application.

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Globally, water is considered an essential resource as it sustains human, animal and plant life. Water is not only essential for all forms of life but imperative for economic growth. The world’s population is increasing at a disquieting rate, which will result in an increased demand for fresh water and food security. The agricultural industry is the main consumer of global freshwater and utilises fertilisers in order to meet food demands. The demand for water in South Africa (SA) has increased considerably due to the rapid expansion of the agricultural industry, and of the municipal and industrial sectors. Agricultural developments in SA are affected greatly as the country is facing a current drought crisis as a result of low rainfall and large water demands. With an abundance of saline water globally, desalinisation will be a major contributor to solving the global freshwater crisis. With limited fresh water resources accompanied by the agricultural industry as a major consumer, alternative measures are required to desalinate water specifically for agricultural use. Forward osmosis (FO) is a membrane technology that gained interest over the past decade because it has several advantages over pressure-driven membrane processes such as reverse osmosis (RO). FO technology is based on the natural osmotic process which is driven by a concentration gradient between two solutions separated by a semi-permeable membrane. Naturally, water will permeate through the membrane from a solution of low solute concentration or low osmotic pressure (OP) known as a feed solution (FS) to a solution of a higher concentration or higher OP also known as a draw solution (DS). Whilst various research studies have contributed to several advances in FO, several process limitations such as reverse solute flux (RSF), concentration polarisation (CP) and membrane fouling remain problematic, hindering FO for large-scale applications. Further investigation is therefore warranted and crucial in order to understand how to mitigate these limitations to develop/improve future processes. The aim of this study was to evaluate a fertiliser-drawn forward osmosis (FDFO) system by investigating the effects of membrane orientation, system flow rate, DS concentration, and membrane fouling on an FDFO systems performance and energy consumption. The FS used was synthetic brackish water with a sodium chloride (NaCl) content of 5 g/L whereas a potassium chloride (KCl) synthetic fertiliser was used as a DS. The membrane utilised was a cellulose triacetate (CTA) membrane and was tested in forward osmosis mode (FO mode) and pressure retarded osmosis mode (PRO mode) whilst the system flow rate was adjusted between 100, 200 and 400 mL/min. Additionally, the DS concentration was altered from 0.5, 1 and 2 M KCl, respectively. Experiments were performed using a bench scale FO setup which comprised of an i) FO membrane cell, ii) a double head variable peristaltic pump for transporting FS and DS’s respectively, iii) a digital scale to measure the mass of the DS, iv) a magnetic stirrer to agitate the FS, v) two reservoirs for the FS and DS, respectively, vi) a digital multiparameter meter to determine FS electrical conductivity (EC) and vii) a digital electrical multimeter to measure system energy consumption. Each experiment comprised of seven steps i) pre-FDFO membrane control, ii) membrane cleaning, iii) FDFO experiment, iv) post-FDFO membrane control, v) membrane cleaning, vi) membrane damage dye identification and vii) membrane cleaning. Pre- and post-FDFO membrane control experiments operated for 5 h whilst each membrane cleaning procedure operated for 30 min. The FDFO experiment operated for 24 h whilst the membrane damage dye identification operated until a minimum of 10 mL water was recovered. The process parameter which largely contributed to a beneficial system performance and specific energy consumption (SEC) was the increase in DS concentration. Water fluxes increased approximately threefold from a DS concentration increase from 0.5 to 1 M, followed by an additional 30 to 50 % rise in water flux at a DS concentration increase 1 to 2 M. SEC decreased by 58 and 53 % for FO and PRO modes, respectively, with a DS concentration increase from 0.5 to 1 M. An additional 35 and 37 % SEC reduction for FO and PRO modes was obtained for a DS concentration increase from 1 to 2 M. Altering the membrane from FO to PRO did not contribute to a beneficial system performance nor did it improve SEC. However, at a DS concentration of 0,5 M, the PRO mode obtained a 5.3 % greater water recovery compared to the FO mode. Conversely, at a DS concentration of 1 and 2 M, the FO mode achieved 5.4 and 7.0 % greater water recoveries compared to the PRO mode. The increase in flow rate also did not increase system performance significantly, however, a fluctuation in system SEC was observed. Throughout the study, no membrane fouling was observed, however, possible minute traces of membrane fouling could be observed from the membrane surface electron microscope (SEM) images. Additionally, minor changes in post- FDFO membrane control water recovery results were noticed which support the possible occurrence of membrane fouling during the FDFO experiment.

Co-produced water from the oil and gas industry represents a significant waste stream in the United States. Produced water is characterized by high levels of total dissolved solids (TDS), dissolved organics and oil and grease. Among the wide variety of organics present in the water, the concentration of hazardous substances such as benzene, toluene, ethylbenzene, and xylenes (BTEX) can reach 600 mg/L and the concentration of non-hazardous carboxylate can be as high as 10,000 mg/L (API, 2002). Regulations governing the disposal of produced water are tightening and the interest in reusing treated produced water is increasing in the United States particularly in regions with scarce water supplies. In order to reuse produced water, removal of both the inorganic dissolved solids and hazardous organics such as BTEX may be necessary. The main goal of this research was to investigate the feasibility of using a combined physicochemical/biological treatment system to remove the organic constituents present in saline produced water. In order to meet this objective, two separate biological treatment techniques were investigated: a vapor phase biofilter (VPB) to treat the regeneration off-gas from an upstream surfactant-modified zeolite (SMZ) adsorption system and a membrane bioreactor (MBR) to treat the carboxylate and BTEX constituents that penetrate an upstream SMZ system. Each of the biological pretreatment systems was investigated first in the laboratory treating synthetic produced water and then in the field coupled to an SMZ adsorption system treating produced water. Both of the biological treatment systems were capable of removing the BTEX constituents both in the laboratory and in the field over a range of operating conditions. For the VPB, separation of the BTEX constituents from the saline aqueous phase yielded high removal efficiencies. However, carboxylates remained in the aqueous phase and were not removed in the combined VPB/SMZ system. In contrast, the MBR was capable of directly treating the saline produced water and simultaneously removing the BTEX and carboxylate constituents. The major challenge of the MBR system was controlling membrane fouling, particularly when the system was treating produced water under field conditions.

Thesis (Master of Engineering in Chemical Engineering))--Cape Peninsula University of Technology, 2018. / Fresh, clean water has always been critical for the world's social development. Supply of water can be reinforced through recycling and reuse; and secondary treatment of municipal wastewater effluent with a membrane bioreactor (MBR) followed by a reverse osmosis (RO) process, has emerged as a crucial treatment process for water reuse. However, fouling of RO membranes in such process is unavoidable. This leads to poor performance, increase in operational cost and degradation of the membrane material, which reduces the membrane life span. Various researches have been conducted to provide an understanding of the mechanism of fouling, and methods have been developed to minimize it. In this research, the effect of surface modification to minimise fouling on a thin film composite polyamide RO membrane was investigated. This study was divided into three parts, namely: membrane modification, biofouling and filtration using RO. Two modifying agents, PVA and DMAEMA, were used as grafting solutions. Escherichia coli (E. coli) were used as the biofoulant to study the ant-biofouling properties of the membranes. A make-up synthetic MBR secondary effluent feed was used in a bench scale RO process. During the membrane modification process, the membrane was treated using two different approaches. Firstly, the covalent attachment of polyvinyl alcohol (PVA) through Glutaraldehyde (GA) onto the surface and secondly the redox initiated grafting of dimethyl amino ethyl methacrylate (DMAEMA PVA and DMAEMA grafting solutions were applied at four different concentrations). The PVA and DMAEMA modifying agents were successfully grafted onto the membrane top layers and were confirmed by the functional groups, present, using the Attenuated Total Reflectance–Fourier Transform Infrared spectroscopy (ATR-FTIR) spectra. The morphology of the membrane surfaces was investigated using Scanning Electron Microscopy (SEM), before and after treatment. SEM analysis showed better membrane structures with PVA grafting compared to DMAEMA.

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.

No description available.

MSc. (Applied Chemistry) / Remediation of POPs particularly the chlorinated compounds in water is therefore crucial. This research work describes the modification of polyethersulfone (PES) thin-film membrane composite (TFC) with functionalised carbon nanotubes (f-CNTs) using the phase invasion method. The oxidised CNTs were successfully decorated with Zero-Valent (ZV) Fe/Ni nanoparticles for the adsorption and degradation studies of polychlorinated organic pollutants (in this case the dichlorodiphenyltrichloroethanes (DDTs)). The in situ modification procedure was carried out using different quantities (0.04 wt%, 0.1 wt% and 0.2 wt%) of Fe/Ni-f-CNTs nanohybrids dispersed in a DMAc solution and dipping the polyethersulfone powder into a suspension containing the Fe/Ni-f-CNTs to form a nano-composite membrane. The formed composite membrane characteristics were investigated with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) and X-ray diffraction spectroscopy (XRD). The incorporation of nanohybrid in the PES membrane was found to increase the surface smoothness and the hydrophilicity of the composites. In addition, there was an increase in the adsorption of DDTs with increase in the nano-hybrid loading as indicated by the adsorption studies using the Langmuir isotherm and Freundlich isotherm studies. The data obtained from the batch studies closely fitted with the Langmuir isotherm based on the characteristic parameter RL found to lie within the standard range 0 < RL < 1 .