The objective of this study was to determine the effect of biological treatment, using a trickling filter, on recycle water from a sulphide concentrator. Activated carbon (AC) treatment was studied for comparative purposes. / Both biological AC treatment increased the recovery of chalcopyrite in a single mineral microflotation test, from approximately 5.5% to 14.4% and 7.2% respectively. However, major differences were observed between various samples when comparing the number and types of bubbles produced during frothing tests. As expected, the number of bubbles produced per given volume decreased following AC treatment, approaching that of tap water. However, after biological treatment, the number of bubbles was increased. It is suspected that the changes produced by biological treatment in the recycle water might produce organic matter more surface active than that initially found in the wastewater.

The protection of public health is the basis behind any waste management system while its sophistication is dictated by environmental impact concerns and constraints on the ideal solution. Waste management systems can and should be designed from a sustainable basis. This thesis examines the theoretical basis of sustainable waste management systems and explores their application in Trinidad and Tobago. The transformation of Trinidad's existing waste management system into one which is sustainable begins with a thorough characterization of the existing formal and informal waste management sectors. Their linkages are identified and understood, leading to recommendations towards the alteration of the existing policy/legislation basis, system structure and operations to create a sustainable system. The resources and expertise are in place to complete such a transformation and the resulting system will benefit the nation; converting an antiquated policy of environmental neglect into that which will provide for the earth and future generations.

Consideration of alternative methods for the disposal of bauxite waste by the aluminum industry has generated interest in the ability of bauxite waste solid constituents to attain a certain degree of physical integrity upon drying to yield a material of suitable strength properties. This thesis study seeks to provide insight into the development of physical integrity in bauxite waste through elucidation of potentially operative bonding mechanisms in a selected Jamaican bauxite waste which is observed to dry to a material of relatively high post-dehydration strength properties. Interest in the ability of bauxite waste solids to attain a certain degree of physical integrity extends to an application, proposed in this study, involving the potential use of bauxite waste as a contaminant stabilization/solidification medium. Efforts at facilitating elucidation of potentially operative bonding mechanisms are accomplished by means of a comparative study involving a second bauxite waste derived from Guinea bauxite which, despite its similar mineralogy to the selected Jamaican bauxite waste, was observed to dry to a material of low post-dehydration strength properties. Results obtained from the study revealed the apparently important role of hydroxylated oxide/hydrous oxide surfaces of high specific surface in governing the development of physical integrity. / A parallel study concerned with the ion adsorption properties of Jamaican bauxite waste was as well conducted in efforts to further aid in establishing the potential for use of bauxite waste as a contaminant stabilization/solidification medium. Adsorption tests were conducted using four ions (Cl$ sp-$, SO$ sb4 sp-$, K$ sp+$, and Pb$ sp{++}$) selected on the basis of valency and sign of charge. The results indicated the marked ability of the bauxite waste solids to adsorb lead both below and above the measured point of zero charge (PZC) of the bauxite waste solids. The results also indicated sulphate, contrary to chloride, was readily adsorbed provided it was added as its acid. When added as its salt (Na$ sb2$SO$ sb4$), no sulphate adsorption was observed even at pH values well below the PZC. The postulated chemisorption-type interaction of lead and other heavy metals with hydroxylated oxide/hydrous oxide surfaces suggests that certain bauxite wastes, particularly those which exhibit high post-dehydration strength properties, may be well suited for use in contaminant stabilization/solidification applications.

The low capital and operating costs of aerated lagoons has lead to their extensive use in rural areas as a method of wastewater treatment. Although the performance of the system depends directly on the hydraulic mixing, there is currently no consensus on the key hydraulic parameters that influence the mixing of these lagoons. Tracer studies were performed on the St-Hermas aerated lagoon and a dynamically similar laboratory model to determine the effects of the water flow rate and the aeration rate on the performance of these aerated lagoons, to evaluate the method of dynamic similarity used to design the laboratory model and to evaluate the accuracy of predictive empirical dispersion models. The results were analysed using flow visualisation, simple observational and mathematical Retention Time Distribution (RTD) techniques and various hydraulic models. From these results it is concluded that the water flow rate and the aeration rate both significantly affect the hydraulic mixing of aerated lagoons, with the water flow rate being the dominant parameter. Furthermore, it is proven that the method of dynamic similarity used in this research is valid and that the only dispersion model that predicted reasonably accurate results was Arcievala (1981). An additional finding during the course of this research indicates that tracer study E-curves must be developed to completion in order to ensure conservation of mass and accurate analytical results.

This study is concerned with the biodegradation of polycyclic aromatic hydrocarbons (PAHs), particularly the utilization of biological processes in the bioremediation of PAH-contaminated soils. In this regard, the effects of the contaminant bioavailability and the redox environment on the biodegradation process have been investigated. / First, the mineralization of naphthalene in soil/water systems under denitrifying conditions has been studied. Results showed that naphthalene mineralization is influenced by its availability to the microbial population, which in turn is a function of the compound initial concentration, the sorption/desorption characteristics of the soil/contaminant complex and the organic content of the soil. / Second, the biodegradation of four PAH compounds, acenaphthene, acenaphthylene, fluorene and anthracene, in a soil/water system under four redox environments has been studied. Both aerobic and denitrifying environments supported appreciable PAH biodegradation rates. The denitrifying environment was chosen for a further experiment to investigate the performance of a bioreactor system in treating PAH-contaminated soils. Results showed that by enlarging the scale of the reactor by approximately eight times and simultaneously reducing the mixing intensity of the soil slurry, the biodegradation rates of the PAH compounds remained virtually unchanged.

No description available.

No description available.

Mushroom tyrosinase (polyphenol oxidase, EC 1.14.18.1) was investigated as an alternative to peroxidase, enzymes for the catalytic removal of phenolic compounds from wastewaters. The maximum catalytic activity was observed at pH 7; however, significant activity was observed at pHs ranging from 5 to 8. Tyrosinase was unstable under acidic conditions and at elevated temperatures. The activation energy for thermal inactivation of tyrosinase was determined to be 1.85 kJ mol-1 at pH 7. The transformation of phenols catalysed, by tyrosinase was investigated as a function of pH, initial phenol concentration, and additives. Phenol was transformed successfully with tyrosinase, over a wide range of pH (pH 5--8) and a wide range of initial concentrations (0.5 mM--10 mM). Some chlorinated phenols were also successfully transformed with tyrosinase. Polyethylene glycol and chitosan did not improve the transformation efficiency of phenol. However, chitosan was successfully used to remove coloured, products resulting from treatment Since coagulation with aluminium sulfate failed, the colour removal induced by chitosan addition appeared to be the result of simultaneous coagulation and adsorption mechanisms. Minimum doses of chitosan required to achieve 90% of colour removal were logarithmically related to the quantity of phenol treated. All solutions of phenol and chlorophenols treated with tyrosinase, had substantially lower toxicities, than their corresponding initial toxicities. Chitosan addition enhanced the reduction in toxicity very effectively. The toxicities of the phenol solutions treated with tyrosinase were markedly lower than previously reported toxicities of solutions treated with peroxidase enzymes.

This thesis is the result of five years research into road traffic emissions of air pollutants. It includes a review of traffic pollution studies and models, and a description of the PREDICT model suite and PREMIT emissions model. These models were used to evaluate environmentally sensitive traffic control strategies, some of which were based on the use of Advanced Transport Telematics (ATT). This research has improved our understanding of traffic emissions. It studied emissions of the following pollutants: carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx). PREMIT modelled emissions from each driving mode (cruise, acceleration, deceleration and idling) and, consequently, predicted relatively complex emission characteristics for some scenarios. Results suggest that emission models should represent emissions by driving mode, instead of using urban driving cycles or average speeds. Emissions of NOx were more complex than those of CO and HC. The change in NOx, caused by a particular strategy, could be similar or opposite to changes in CO and HC. Similarly, for some scenarios, a reduction in stops and delay did not reduce emissions of NOx. It was also noted that the magnitude of changes in emissions of NOx were usually much less than the corresponding changes in CO and HC. In general, the traffic control strategies based on the adjustment of signal timings were not effective in reducing total network emissions. However, high emissions of pollutants on particular links could, potentially, be reduced by changing signal timings. For many links, mutually exclusive strategies existed for reducing emissions of CO and HC, and emissions of NOx. Hence, a decision maker may have to choose which pollutants are to be reduced, and which can be allowed to increase. The environmental area licensing strategy gave relatively large reductions in emissions of all pollutants. This strategy was superior to the traffic signal timing strategies because it had no detrimental impact on the efficiency of the traffic network and gave simultaneous reductions in emissions of CO, HC and NOx.

Various workers have shown the asphaltene fraction of crude oil to be responsible for the highly stable W/O emulsions formed after marine oil spillages. Electron microscope studies on crude oil emulsions using the freeze etching technique showed the oil/water interface to be smooth on the aqueous side but to have a particulate structure on the oil side. In Brega crude oil emulsions, waxy plates were aligned along the interface. Also observed were the coherence of the interfacial film and droplet coalescence. Allowing a method error of ± 10%, good agreement was found between computer calculated droplet diameters from the log-normal distribution equation and standard statistical mean diameters. Sc (interfacial area/unit volume oil phase) was larger for salt water emulsions. An equation proposed for Sc as a function of stirring time fitted very well for all three crude oil emulsions. The maximum Sc increased with φ (volume fraction) indicating a minimum possible diameter droplet fold by the stirrer. A rate parameter in the equation is probably related to the asphaltene diffusion to the interface. A good fit with the data was obtained when the equation was modified to account for detergent addition delaying emulsion formation. A second rate parameter may reflect the irreversible replacement of detergent at the interface by asphaltenes. Ageing studies showed that once stabilisation was complete, detergent present only slowly affected coalescence. A heating effect explained the non-linearity of Kuwait and Tia Juana emulsion rheograms. The greater viscosity of Tia Juana stabilised emulsions was explained by a thicker supporting asphaltene layer. The elasticity of the-interfacial film accounted for anomalous behaviour in emulsions of asphaltenes dispersed in m-xylene/n-octane. The extrapolated yield point and critical shear rate were used as empirical measures of deformability and attractive forces respectively.