Fluid mechanics of a channel with one porous wall was studied from first principles as the initial step towards understanding polarization phenomena in membrane modules. A regular perturbation method was used to solve the steady-state Navier-Stokes equations for an incompressible, constant property fluid in two dimensions with uniform suction and slip at the permeable boundary. The effects of solute and hydrodynamic parameters on concentration polarization during potable water treatment applications are investigated numerically. Inertia dominated and permeation drag dominated particle transport is discussed. Experimentally determined residence time distributions of particles in a microporous channel are interpreted in the light of inertial and permeation forces. Inertial lift theory is shown to predict initial particle transport. Experimentally observed long trailing edges in particle residence time distributions indicate the importance of other transport mechanisms even in dilute suspension mechanics. It is seen that inertial effects are negligible under conditions typical of microfiltration.

Diurnal variations of flow rate and organic load cause difficulties in the operation of wastewater treatment plants. The man-made hydraulic shocks produced by the installation of fixed speed pumps upstream of the treatment processes further amplify the frequency and magnitude of these variations. The major objective of this study is to develop control strategies to minimize these variations. A dynamic model has been developed for the operation of fixed speed pumping stations. The optimum control strategy based on this model can reduce the on-off pump cycles up to 86% for a typical day as compared with ordinary two point control. Optimum models and corresponding control algorithms have also been developed for the operation of in-line equalization basins. These models have shown potential for the reduction of the required equalization volume and can provide smoother outflow to the downstream processes. A reduction of tank volume by 63.5% has been obtained in the simulation using the optimum control strategy.

A database for surface impoundments (SIs) consisting of hydrogeologic and operational parameters was developed and statistically analyzed. The database was used to evaluate infiltration, groundwater mounding, contaminant transport (dilution), and the relationships between each of these mechanisms. Analytical, numerical, and statistical solutions were used for the evaluation. Hydraulic heads calculated with Hantush's analytical solution for mound growth compared well to those computed by a two-dimensional numerical transport model for unconfined aquifers (UNMOC). Infiltration from the "typical" surface impoundment (defined by the database) was modeled with UNMOC. Dilution effects were quantified and compared to those predicted by the one-dimensional Monte Carlo model (EPACML) used by EPA in specifying acceptable waste concentrations for disposal. The SI-specific database in conjunction with UNMOC predicted much less dilution than EPACML and provide an alternative approach to regulating surface impoundments.

Much attention has been devoted to the design and construction of wastewater treatment plants. However, relatively little attention has been devoted to plant operations. Knowledge based or expert systems are oriented toward improving operational procedures and thus have significant potential for solving control problems. This paper presents the results of a study conducted to examine the use of expert systems technology for computer assisted operation of the anaerobic digestion process. Knowledge was divided into mechanistic understanding of the process and that which comes from experience (heuristic). Effective operation requires both types of knowledge. A process task analysis identified four major tasks. These are monitoring, state assessment, control decision and execution tasks. The analysis suggested an expert system configuration consisting of software modules corresponding to these tasks. Development of the state assessment and control action modules was stressed. The capture of mechanistic knowledge was emphasized. Knowledge was represented using if-then rules. Diagnostic rule development was accomplished using computer simulations of hydraulic, organic, toxic and ammonia upsets which could cause process failure. Rules relating to control included decision rules which specified appropriate control actions and fuzzy rules which specified the amount of control. Additional simulations of process upsets were used to examine the behavior of the system. Several different upset states were properly identified and corrected by the system. The control actions used were influent flow control, dilution, organism recycle and acid or base addition. The rule-based approach was found to be flexible and transparent. Theoretical knowledge from the mechanistic model could be converted into a language understood by operations personnel. However, the expressive capabilities of the rule language and the inability to ensure consistency and completeness in the rule base limited the system. An expert system is knowledge intensive and knowledge transfer from the expert to the computer and from the computer to the operator are important factors. Field testing will be needed to validate the rules developed for the expert system. Future research should emphasize the development of a body of knowledge about process operation. Alternative knowledge representations and hybrid systems integrating expert, fuzzy and stochastic control techniques should be studied. In combination these provide powerful tools for solving the problems of control in wastewater treatment.

A model is developed that calculates capital and operating cost of cross-flow membrane filtration as a function of relevant design parameters. An expression for capital cost is empirically derived from information gathered from membrane manufacturers. Operating cost is divided into components for energy consumption, chemical demand, membrane replacement and concentrate disposal and is determined from attributes of the membrane system. The effect of operating parameters and membrane characteristics on cost are examined. The flux of permeate across a membrane is the principle factor determining cost. Energy cost, although important to the daily operating cost of a water treatment plant, is overshadowed by the membrane replacement cost. The effect of backflushing procedures on cost is evaluated using empirical functions for permeate flux derived from a microfiltration pilot study. Microfiltration is determined to be a cost-competitive alternative to ultrafiltration. Costs calculated by this study are compared to reported costs for membrane filtration.

Recent evidence indicates that ferrous carbonate (FeCO$\sb3$, siderite) plays a critical role in forming corrosion resistant scale. Although FeCO$\sb3$ also limits the solubility of iron in some anaerobic systems, its precipitation kinetics have received little attention. The temperature dependent precipitation kinetics of ferrous carbonate were studied using a powerful new "temperature ramped" approach. Activation energies calculated using three second order and two first order precipitation models (53.8-123 kJ/mol) all qualitatively indicate that precipitation is controlled by surface reaction rate. Precipitation is extremely slow at ambient temperatures, but becomes limited by diffusion above approximately 110 C. Surface reaction rate equations must, therefore, be used to model low temperature precipitation, and mass transfer equations should be used to estimate high temperature FeCO$\sb3$ growth. Seed crystals were prepared and Ostwald ripened in a reactor under anoxic conditions. Precipitation was induced by linearly increasing (ramping) the temperature and recording the change in iron concentration with respect to time and temperature. Rather than performing a series of isothermal experiments, temperature dependent kinetics were determined by fitting nonlinear models to temperature ramped experiments. The techniques developed in this research could easily be adapted for use with a number of other reduced metal systems.

Leather tanning, one of mankind's oldest industries, is in a time of environmental transition. Traditionally a "wet" industry, many processes result in pollution loads which are not acceptable in today's legislative environment. For this study, the largest Canadian Retanner, located outside of Montreal, Quebec, allowed its processes and associated waste products and loads to be characterized. A physico-chemical treatment regime, utilizing precipitation, coagulation, and flocculation technology, was then proposed and implemented on the laboratory level. The results were positive, but the solid waste product from treatment was found to present its own set of environmental problems. Finally, the various reuse, recycling, and reduction opportunities applicable to the tanning industry were explored, as was their applicability to the re-tanner in question.

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.