Lime neutralization of acidic drainage is the most common process to produce an environmentally acceptable effluent. The process involves neutralization, precipitation of metal hydroxides, flocculation, settling and storage of the sludge. The sludge is not entirely stable over the long term due to the natural pH decline in the storage area that can re-solubilize metals. The use of activated silica sol could be an alternative to flocculants in the lime neutralization process. The nature of the metal hydroxide---silica bond could make the sludge more stable on short and long term. / It was observed that similar settling characteristics can be obtained with the standard flocculant and a low dosage of activated silica sol. Using activated silica sol, the settling rate is dependent on the concentration of magnesium and iron in the mine effluent. / There was an improvement in sludge stability when using a high dosage of activated silica sol. Two mechanisms have a role in the increased stability: the adsorption bond and the buffering capacity of activated silica sol. The tests suggested that a dosage of 0.1 gSiO2/gFe optimizes the settling characteristics and the sludge stability.

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.

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.

In order to ensure aircraft safety during winter conditions, glycol-based deicing and anti-icing fluids are employed prior to takeoff. These products can exert a severe impact on the environment if allowed to go untreated. The present study is related to the treatment of glycol-contaminated wastewaters by the activated sludge process. / The specific objectives of the research were to: (1) determine the effects of process parameters such as biomass concentration, deicing fluid concentration and temperature on the biodegradation kinetics. (2) determine the mechanism of deicing fluid removal and model the reaction rates. (3) determine the effects of microbial changes on the treatment process. (4) evaluate the advantages of a sequencing batch reactor for the treatment of deicing wastes. (5) corroborate our laboratory results with field data from an operating wastewater facility treating deicing wastes. / The results from the field show that despite the increases in influent organic matter during the deicing season, there were very little changes in effluent values of organic matter. Furthermore, influent concentrations of deicing fluid between 10 and 30 mg/L were reduced to trace amounts (i.e. below 5 mg/L) throughout the deicing season. However, as witnessed by the high sludge volume index during the deicing season, the presence of deicing fluid creates settling problems in the clarifier. / The laboratory batch experiments indicate optimal substrate removal rates at biomass concentrations of 1000 mg/L and 2000 mg/L. Very low biomass levels lead to inhibition whereas a high biomass level of 3000 mg/L is unnecessary since the food to microorganism ratio is such that only a fraction of the biomass participates in the degradation reaction. With regards to deicing fluid concentration, organic matter removal rates tend to increase as the deicing fluid is increased. However, at the highest level of deicing fluid, certain inhibitory effects are present. As expected, higher temperatures produce much higher removal rates with the ethylene glycol substrate showing less variation with temperature than the other organic compounds present in the wastewater. / With regards to the mechanism of removal, the results showed very little adsorption of organic matter onto the biomass within the first hour of contact. In addition, the total organic matter removal (TOC and COD) followed first order kinetics with respect to substrate concentration. / Lastly, sequencing batch reactor operation allowed for much higher removal rates as the microbial population is acclimatized to the substrate with increasing cycles. With regards to the microbial population, the Biolog results showed that there was a decrease in the variety of compounds that could be degraded as the biomass was exposed to the deicing fluid. Furthermore, most population changes occurred at the very beginning of the deicing season and in the first half of the SBR experiments.

Infrastructure is the foundation and the basic framework which permits cities to function. However, there are significant infrastructure problems in North America. In cities across North America, the infrastructure is deteriorating. The efficiency of a community depends on the condition of its infrastructure. The health and welfare of the residents and the economy of a country requires an efficient and sound infrastructure. North America will not achieve prosperity if it allows its urban infrastructure to decay to the Developing World's levels. / Increased new sources of revenue need to be explored by political officials to pay for the cost of upgrading our infrastructure to an acceptable level. In addition, developing an effective management, approach is a long-term way to handle a problem as large and as serious as our current infrastructure crisis. Current engineering and construction practices have proved to be detrimental to our environment and depletion of natural resources. The future role of civil engineers should be the prevention of any damage to our environment and natural resources, and this can be achieved by incorporating sustainability into the current engineering and construction practices. (Abstract shortened by UMI.)

The study identifies the major problems associated with the current approach to the planning and engineering of large development projects with respect to the objectives of sustainable development and the requirements of the environmental impact assessment process. The Great Whale Hydroelectric Project is used as an example to illustrate some of these deficiencies. The author argues that the economic and technical criteria traditionally used by engineers in designing projects are no longer sufficient to meet society's objectives, and that a new multidisciplinary approach must be adopted that allows for the accommodation of environmental and social factors from the very beginning of the planning and design process. A protocol is proposed as a structured approach to engineering for sustainable development and recommendations are made regarding the need to adapt engineering ethics and training to reflect this new reality.

For many decades, tetrachloroethylene (PCE) has been used as a dry-cleaning solvent and as a degreaser. Owing to its improper storage and disposal, PCE has become one of the most widely detected pollutant in groundwaters. PCE has been classified as a potential threat to the environment and as a possible carcinogen to humans. It has been shown that PCE can be completely dechlorinated to non-toxic compounds under anaerobic conditions. / In this study, the PCE treatment efficiency of two anaerobic fluidized bed reactors (AFBRs) were investigated and compared under different hydraulic loads. Granular activated carbon (GAC) and biolite were used as a support media in the first and second reactor, respectively. / The results showed that the GAC AFBR achieved close to 100% PCE removal under all the loading conditions studied. Both adsorption and dechlorination accounted for this total PCE dechlorination. With the exception of one hydraulic loading, adsorption was the main PCE removal mechanism for the duration of this investigation for the GAC reactor. The maximum PCE removal efficiency achieved by the biolite$ rm sp{TM}$ AFBR was approximately 70%. Dechlorination was the only removal mechanism for this reactor. / The highest specific chloride ion production rate for both reactors was achieved under the lowest loading condition and methanol activity. Very few metabolites were detected in the reactors' effluents showing that the chloride ion production was almost entirely due to the total dechlorination of PCE.

<p> One of the most difficult endeavors in filamentous algal growth models is predicting the occurrence of sloughing. Algal sloughing can stem from various sources such as from biological or mechanical means. The focus of this study is to investigate the role of fluid shear on the benthic filament mass. This research proposes a method to model the external forces on a benthic filament from the aquatic environment and the internal forces from the movement of the filament mass itself. To accomplish this, three parallel endeavors were pursued. First, a fluid-structure force interaction model was developed that can be applied to a multi-node cylindrical benthic filament model. Second, a finite element modeling approach was used to estimate the internal structural properties based on the filament mass displacement under a specified external force. Third, motion capture techniques from experimental video footage were utilized to provide data for the fluid-structure interaction model and validation of the finite-element model. In laboratory application of this methodology on an experimental sample of mixed-culture filamentous algae, a value of 4.2 MPa was calculated for the internal stress in a filament, a value in close agreement with literature values. This method can provide an in-situ approach to investigate the structural properties of the algal filament in its natural aquatic environment without the use of expensive equipment. </p>

Researchers have linked resin and fatty acids (RFAs) to acute toxicity, especially in thermomechanical and chemithermomechanical pulp and paper mill effluents. Thus, the measurement of total RFAs may be a rapid, inexpensive alternative to standard methods of toxicity monitoring, such as 96-hour rainbow trout testing. Current procedures for the analysis of RFAs typically involve solvent extraction and concentration, derivatization, and analysis by GC, HPLC, or TLC. These procedures are far too expensive, complicated, and time-consuming for implementation at mill sites. / This thesis reports the development of a rapid, colourimetric assay based on the dye methylene blue (MB) for the quantification of resin and fatty acids in pulp and paper mill effluents. This MB assay uses the complexation of the cationic organic dye molecule to the carboxylic acid groups of RFAs to form a measurable chromophore. The electrically neutral, blue-coloured complexes are then extracted into a poorly polar organic solvent, dichloromethane. The measured absorbance at 655 nm is directly related to the total RFA concentration in the effluent sample. / The methylene blue assay is inexpensive and simple to use. It has a method detection limit of 0.589 mg/L total RFA. There are good correlations between the results obtained using the methylene blue assay and a well-established GC assay, and between RFA concentrations measured by the MB assay and acute toxicity measured by Microtox. The assay is sufficiently simple and rapid to be practical for routine in-mill monitoring.

Organic liquids such as crude oils, creosotes and coal tar often remain in contact with groundwater or surface waters for long periods of time before or during any attempted remediation. Potentially toxic solutes such as polycyclic aromatic hydrocarbons (PAHs) are continuously released from pollutant oil phases described above to the water phase. The research was aimed at understanding how physicochemical as well as biological phenomena affect dissolution and biodegradation of PAH compounds from pollutant oil phases. These phenomena were investigated for a simple two-component non-aqueous phase liquid (NAPL) and for creosote, a multi component NAPL. / Mass transfer experiments of naphthalene from a synthesized two-component NAPL were conducted to assess the extent of variation of mass transfer rate coefficients between column and completely mixed flow-through (CMFT) systems. The differences in the hydrodynamics between column and CMFT systems, employed in this study, resulted in a difference in the mass transfer rate coefficients of a factor of 3. Several reported empirical correlations for the estimation of mass transfer coefficients in batch and column systems were verified. Good agreement between Sherwood numbers, a dimensionless quantity reflecting the magnitude of the mass transfer coefficient, predicted by the reported correlations and those calculated from mass transfer coefficients obtained from the experiments was obtained in all cases. / The biodegradation kinetic coefficients mumax and Ks for the biodegradation of naphthalene from a two-component NAPL, coated onto uniformly sized nonporous particles, were evaluated in completely mixed batch reactor (CMBR) systems and in flow-through column systems. The values obtained for mumax and Ks from column systems were very close to those obtained from CMBR systems. This suggests that both coefficients estimated from CMBR or column systems can be applied for modeling studies. The development of biofilms at the NAPL-water interface reduced mass transfer rates of naphthalene by 70% in column systems and 60% in CMBR systems. / Viscous interfacial films develop at the creosote-water interface when creosote is aged in water for a period of time. The mass transfer rate coefficient of naphthalene from creosote to water was reduced by 30% over a one-week aging period. Minor additional reductions were observed with further aging. Hindered diffusion through the bulk creosote phase and changes in composition of creosote as a result of extended dissolution did not account for the observed reductions.