The work summarizes the results of a studies conducted with six different flushing agents, i.e. two anionic surfactants (SDS and DOWFAX 8390), two complexing agents (cyclodextrins), a humid acid, and an alcohol (ethanol), for solubilizing and removing residual-phase immiscible liquid from porous media. Batch experiments were conducted to measure the degree of trichloroethene (TCE) and tetrachloroethene (PCE) solubilization induced by these agents. These studies revealed that the solubility of TCE and PCE was enhanced significantly. Column experiments were conducted to compare water and agent-enhanced flushing of Borden sand containing residual saturations of TCE and PCE. The results of these studies indicate that the total flushing volume necessary to remove the contaminant was reduced substantially in the presence of all applied agents. The relative effectiveness of the agents varied based on the method of evaluation. It was shown that a volatile contaminant, e.g. toluene, TCE, and PCE, can be separated from cyclodextrin solution by mean of air-sparging. The cyclodextrin solution was successfully reused for continuos flushing of a contaminated porous material. The simulation of selected experiments revealed that the mass transfer rate coefficients are generally increasing if evaluated based on the aqueous driving force approach. However, a relation based on the enhanced driving force approach was found to be less significant. Even though areas of additional research have been identified, this research contributes to a better understanding of the processes governing chemically enhance flushing of contaminated porous media.

D. Tech. Environmental, Water and Earth Sciences / Pollution of water sources with heavy metals is currently a global concern due to the detrimental effect of these metals on both human and animal health. To address this issue, biological treatment methods have been seen as the most effective and eco-friendly option of the available treatment processes of wastewater. The aim of this study was to compare the ability of selected bacterial isolates and indigenous protozoan to tolerate nickel and vanadium in wastewater systems in order to determine which group of organisms might play a major role in the removal of nickel and vanadium, even at high concentrations, in wastewater treatment systems.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Le blanchiment est toujours l’un des points critiques en termes d’impact environnemental lors de la production de pâte de bois. Une nouvelle séquence « propre » de blanchiment sans réactifs chlorés (TCF) et à base d’ozone a permis d’obtenir une pâte à dissoudre blanchie dont les propriétés sont semblables à celles de pâtes blanchies par des séquences conventionnelles ECF à base de dioxyde de chlore. Il est montré que la pâte TCF a une meilleure stabilité de blancheur que la pâte ECF correspondante. Les phénomènes de jaunissement dont les mécanismes sont toujours mal compris ont été étudiés en mettant en œuvre diverses méthodes dont la spectroscopie RPE et la spectroscopie UV Raman et l’analyse des groupements carbonyle et carboxyle par fluorescence. Les groupes carbonyle que peut porter la cellulose se sont montrés néfastes pour la stabilité de la pâte, à la fois dans les conditions d’un vieillissement accéléré et en conditions alcalines de mercerisation. Ils peuvent néanmoins être partiellement éliminés par un traitement alcalin, ce qui se traduit par une meilleure stabilité de blancheur. L’addition de peroxyde d’hydrogène dans ce traitement permet d’obtenir des résultats encore meilleurs, sans élimination supplémentaire des carbonyles. Il aurait pour effet d’éliminer des chromophores résiduels de type quinonique et ayant un très fort impact sur le jaunissement des pâtes. La pâte TCF possèderait moins de chromophores quinoniques qu’une pâte ECF. / Bleaching of wood pulp is still an environmental issue. A new ozone-based TCF bleaching sequence made it possible to produce a bleached dissolving pulp whose properties were comparable to those of a pulp bleached with a conventional bleaching sequence using chlorine dioxide (ECF). It was noticed that the TCF bleached pulp had better brightness stability. The origin of yellowing is still poorly understood. It was studied here by the implementation of several analytical methods including EPR spectroscopy, UVRaman spectroscopy and also fluorescence spectroscopy for the specific analysis of carbonyl and carboxyl groups. It was shown that the carbonyl groups present on the cellulose are detrimental to the brightness stability, both during accelerated ageing and mercerization. They can be partly eliminated by an alkaline treatment, which improves the brightness stability. Addition of hydrogen peroxide allows for a further increase of the brightness stability, but without any extra carbonyl removal. It would have an effect on some conjugated residual chromophores, mainly quinones, involved in the yellowing mechanism. The TCF pulp would possess less quinones than a ECF pulp.

An activated unsaturated sand filter (AUSF) is one of only a few of the filtration technologies utilized to treat waters and wastewaters that use unsaturated filter media. AUSF employs sand coated with potassium permanganate and operates with an open chamber allowing free air flow into the column of sand. The AUSF also benefits from operation without the need for a sedimentation unit. Previous studies have demonstrated the efficient removal of iron and manganese using an AUSF, however, to date there are still very limited studies available that use AUSF technology for the removal of metals from waters and wastewaters. Thus, there is an urgent need and opportunity to exploit this technology further. This research was conducted in order to develop and study the characteristics and subsequent operational performance of a novel AUSF media. The study focuses on the removal of copper, manganese, zinc and nickel from a synthetic wastewater and extends current knowledge to a passive aeration process rather than the active aeration used in the previous study by Lee et. al. (2004). The characterisation involved the use of sieving, Brunauer- Fmmett-Teller (BET) analysis, water evaporation studies and scanning electron microscopy (SEM) for structural analysis such as particle size, surface area, porosity and topography. Energy dispersive X-ray analysis (EDX), acid/alkali resistance, isoelectric point determination and acid digestion analysis were used to determine the chemical constituency, chemical stability, electrical charge properties and the binding efficiency of the media. Finally, tracer studies were employed to determine the flow characteristics through the particle media. The manganese coated sand was proven effective for the removal of copper in both agitated tank batch studies and continuous column studies. The batch studies showed that the equilibrium sorption of copper followed a Langmuir isotherm and the sorption rate was best modelled using the pseudo-second-order kinetic model. This suggests that adsorption is taking place as a single homogeneous layer on the surface of the sand particle via the chemisorption method. The Weber-Morris and Bangham models were used to determine the rate-controlling mechanism and this was found to be predominantly intra-particle diffusion. This was confirmed for column studies using the Bohart-Adams model that demonstrated that liquid-film mass transfer was not significant. Several mechanisms of metal removal are proposed and these include precipitation, electrostatic attraction, adsorption, ion exchange and complex ion formation. The column studies demonstrated that dispersion was low under the operating conditions and plug flow performance could be inferred, thus justifying the use of the AUSF model employed. Copper was best removed when operating as an unsaturated particle bed and the removal capacity was increased by approximately 100% when compared to a saturated particle bed. Moreover, the pH increase that occurs on exposure of the process water to the unsaturated column further improves removal capacity. Thus, there is no requirement for an expensive pH adjustment as a pre-treatment process prior to this unit operation. In addition, the removal capacity of the AUSF was demonstrated to increase with lower metal concentrations, lower water flow rates, smaller sand particles, an increase in manganese to sand ratio and an increase in particle bed height. The AUSF performance in removing metals followed the order Cu > Mn > Zn > Ni for individual and mixed component solutions and Cu > Ni > Zn > Mn for a synthetic wastewater typical of the electroplating industries. In conclusion, the novel manganese coated AUSF developed is effective in the removal of metals from solution and offers the potential of a sustainable low cost treatment method for the purification of waters and wastewaters.

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Thesis (MTech (Engineering))--Cape Peninsula University of Technology, 2007 / The removal of the colour-eausing natural organic matter (NOM) from natural brown water (NSW) to be used for drinking purposes is of paramount importance. One of the methods available to remove NOM from NSW is the use of pressure-driven membrane separation systems. One of the limitations in efficiently applying membrane filtration in the treatment of NOM-eontaining water is membrane fouling that is caused by foulants, such as NOM, that accumulate on the membrane surface and in the membrane pores. Microfiltration (MF), as a membrane separation system, is susceptible to severe membrane fouling during membrane filtration of NSW. Fouling is characterized by a rapid decline in permeate flux and loss of productivity. Progress in developing more effective control and prevention of fouling is impeded by the absence of suitable fouling measurement and characterization techniques. An in situ method for measuring membrane fouling is necessary for detection of membrane fouling during MF of NSW at the eartiest stages so that the corrective actions can be taken before fouling is permanently adsorbed onto the membrane surface. In this study, an ultrasonic-based method was effectively used to detect and measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling exp~riments results showed the formation of a new peak on the ultrasonic response echo signal due to the presence of a fouling layer on the surface of the membrane. The ultrasonic signals acquired during the in-situ detection of membrane fouling were analysed using wavelet transforms (WTs). Wavelet analysis was applied to differential signals to obtain additional information about fouling. Differential signals were calculated by subtracting the baseline measurement signals from the test signals. The presence of the fouling layer on membranes was verified by atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses of the fouled membranes.

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This research was directed at reducing arsenic levels in the effluents generated at the Canelands facility that manufactures monosodium methyl arsenate. Two effluent streams containing arsenic have to be considered, a raw water stream that is treated on site and a brine stream that is disposed of by sea outfall. Removal of arsenate from aqueous media by coagulation was investigated and models were developed describing selected variables that influence the removal of the arsenate. Three coagulant systems were investigated, namely aluminium(III) coagulation, iron(III) coagulation and binary mixtures of aluminium(III) and iron(III). Researchers have studied individual aluminium (III) sulphate and iron(III) chloride coagulation. No detailed research and modelling had, however, been carried out on the use of binary mixtures of aluminium (III) sulphate and iron (III) chloride coagulation of aqueous arsenate, nor had individual aluminium(III) sulphate and iron(III) chloride coagulation of arsenate been modelled at relatively high arsenate concentrations. The models that were generated were validated statistically and experimentally. The variables investigated in the aluminium(III) model included initial arsenate concentration, pH, polymeric flocculent concentration, aluminium(III) concentration and settling time. The variables modelled in the iron(III) coagulation were initial arsenate concentration, pH, polymeric flocculent concentration, and iron(III) to arsenic mole ratio. The modelling of the binary coagulant system included initial arsenate concentration, pH, iron (III) concentration, aluminium(III) concentration, and flocculent concentration as variables. The most efficient arsenic removal by coagulation was iron(III), followed by the binary mixture of aluminium(III) and iron(III) and the weakest coagulant was aluminium(III) sulphate. Scale-up coagulations performed on real raw water samples at a 50 litre volume showed that iron(III) was the most efficient coagulant (on a molar basis) followed closely by the binary mixture, while aluminium(III) coagulation was considerably weaker. The residual arsenic levels of the iron(III) and the binary coagulation systems met the effluent discharge criteria, but the aluminium coagulation system did not. Leaching tests showed that the iron(III) sludge was the most stable followed by the sludge of the binary mixture and the aluminium(III)-based sludge leached arsenic most readily. Settling rate studies showed that the flocs of the iron(III) coagulations settled the fastest, followed by binary mixture flocs and the aluminium flocs settled the slowest. The flocs of the binary mixture had the lowest volume, followed by the iron(III) flocs, while the aluminium(III) flocs were the most voluminous. Based on current operations of the raw water treatment plant the aluminium(III)-based coagulation is the most cost efficient. Given a relative costing of 1.00 for the aluminium(III) coagulation, the iron(III) chloride-based coagulation would be 2.67 times more expensive and the equimolar binary mixed aluminium(III)/iron(III) system would be 1.84 times the cost of aluminium(III) coagulation.

M.Tech. (Chemistry) / This study investigated the functionalization of coke particles and their utilization for the preparation of coke-polymer composite. Looking at the possibility of using it for the removal of lead and chromium ions from their aqueous solutions. Due to various inorganic materials in coke, it was treated with acid to demineralize the ash content. The demineralized coke was further oxidized with hydrogen peroxide to add functional groups on its surface as well as in the bulk of coke particles before coating of the polymers. The composite preparation entails modifying the surface properties of coke with hydrophilic polymers like polyvinyl alcohol (PVA), poly ethylene glycol (PEG) and poly vinyl pyrrolidone (PVP) followed by the crosslinking to improve the interfacial interaction between the polymer and coke to make the synthesized composite stable in water. The structural composition of coke and modified coke was examined by FT-IR spectroscopy, X-ray diffraction, X-ray fluorescence, Raman Spectroscopy, thermal analysis and scanning electron microscopy combined with energy dispersive X-ray analysis. It was also observed that the modified coke samples have enhanced carbon reactivity which indicates that the non-carbon phases were removed by the treatment with acid. The adsorption studies for the removal of Pb (II) and Cr (III) ions from contaminated water was done in batch mode using variables such as pH, contact time and the initial concentration. The synthesized material was found to have better adsorption capacity as compared to raw coke. To understand the adsorption isotherm processes, Freundlich and Langmuir isotherms were applied. The monolayer adsorption capacity for the removal of lead ions was found to be 2.41 mg/g, 2.95 mg/g, 8.32 mg/g, 9.70 mg/g and 9.84 mg/g for raw coke, acid treated coke, PVA coated coke, PEG coated coke and PVP coated coke, respectively. The chromium monolayer adsorption capacity was found to be 9.48 mg/g, 9.94 mg/g, 35.84 mg/g, 32.79 mg/g and 34.13 mg/g for the same order of adsorbents mentioned for lead. Studies were carried out at the optimum pH of 6.0 for both the metal ions. The adsorption kinetic studies showed that both the metal ions followed pseudo second order rate equation and the adsorption equilibrium was attained in 60 minutes and 120 minutes for Pb (II) and Cr (III) ions, respectively.