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<p>One of the main problems our actual society faces is the shortage of water. Despite the great effort made by authorities and researchers, multiple countries with poor economic resources are experiencing serious difficulties derivative of water scarcity. Desalination provides a feasible solution for inland and coastal areas. Through literature and reviewed articles analysis the reader will meet the actual issues regarding designing a desalination plant, and more over with reverse osmosis (RO) processes, which are the main arguments of this work. One of the big deals is the environmental concern when handling the concentrate disposal. Another important point about desalination processes is the increasingly interest in coupling the units with renewable energy sources (RES). The results point out that regardless of the efforts made until today, additional achievement is required in fields such as membrane’s structure materials for RO method, concentrate disposal systems, governmental water policies review and update, and greater distinction researches between brackish water and seawater RO desalination processes. Taking into consideration the previous outcomes it is finally concluded that some particular steps must be accomplished when beginning a desalination plant design.</p>

One of the main problems our actual society faces is the shortage of water. Despite the great effort made by authorities and researchers, multiple countries with poor economic resources are experiencing serious difficulties derivative of water scarcity. Desalination provides a feasible solution for inland and coastal areas. Through literature and reviewed articles analysis the reader will meet the actual issues regarding designing a desalination plant, and more over with reverse osmosis (RO) processes, which are the main arguments of this work. One of the big deals is the environmental concern when handling the concentrate disposal. Another important point about desalination processes is the increasingly interest in coupling the units with renewable energy sources (RES). The results point out that regardless of the efforts made until today, additional achievement is required in fields such as membrane’s structure materials for RO method, concentrate disposal systems, governmental water policies review and update, and greater distinction researches between brackish water and seawater RO desalination processes. Taking into consideration the previous outcomes it is finally concluded that some particular steps must be accomplished when beginning a desalination plant design.

A survey performed over existing two pilot-scale and two full-scale RO desalination facilities to study the current status of boron rejection showed a highest rejection 85% leading to permeate boron concentration of 0.52 mg/L, and recent studies predicted a cost increase due to incorporation of boron reduction systems. Mathematical models were developed to study the process performance and related cost implications. The deterministic process model was verified with pilot-scale experiment performed using a single spiral wound module and was later modified to represent the full-scale design options available to meet the required water quality criteria. Then the selected full-scale design options were simulated to predict their performance in terms of recovery and boron rejection. For cost analysis, to account for uncertainty probability models were developed for stochastic inputs to the cost estimation model and were used with operating parameters from the full-scale simulations to determine the expected total cost of water produced. Later, a sensitivity analysis was performed to observe the effect of change in uncertainty of inputs. Further, the applications of the deterministic process model are suggested.

Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Ravindran Chella, Florida State University, FAMU-FSU College of Engineering, Dept. of Chemical Engineering. Title and description from dissertation home page (viewed Sept. 26, 2003). Includes bibliographical references.

Theoretical studies are presented in this thesis on the hydrodynamic dispersion due to electro-osmotic flow (EOF) through a parallel-plate or circular channel under the combined effects of wall heterogeneities, including surface topography, hydrodynamic slip, and zeta potential. These wall properties, which are periodically varied along the channel, are called wall patterns in general. The electric potential field and the velocity field of the EOF are determined by solving the linearized Poisson-Boltzmann (P-B) equation and the Stokes equation, respectively, subject to the spatially varying electrohydrodynamic boundary conditions caused by the wall patterns. In particular, for wall patterns with discrete step changes (in contrast with slowly varying and continuous ones), the solutions are expressed by Fourier series that satisfy the mixed-type boundary conditions. The effective expression for the dispersion is derived using the theory of homogenization by introducing multiple-scale variables and expansions. The effective dispersion coefficient is determined either by purely analytical analysis or numerical methods combined with analytical deduction, depending on the complexity of the problem formulation. This thesis consists of two parts. In the first part, the aggregate effect on the flow due to non-uniformly distributed wall properties is studied in two problems. The first problem considers the combined effects of wall corrugations and slippage modulation on pressure-driven cross (transverse) flow through a thin parallel-plate channel in terms of the hydrodynamic effective slip length and flow enhancement. The second problem considers the combined effects of charge distribution and slippage modulation on both longitudinal and transverse EOF through a channel with the same geometry in terms of the electroosmosis (EO) mobility and flow morphology. It is shown that the interaction between different wall patterns due to surface heterogeneity can play a significant role in determining the flow velocity as well as the local convection pattern, both quantitatively and qualitatively. In the second part, hydrodynamic dispersion due to EOF under the aggregate effect of surface heterogeneities in wall potential and hydrodynamic slippage is studied also in two problems. The first problem considers a limiting case where certain geometric and dynamic requirements are satisfied so that the theory of lubrication approximation can be applied to simplify the analysis, for which analytical solutions are obtained for the flow as well as the dispersion. The second problem is for a similar but more general case without using the lubrication approximation, in which the velocity of the flow, the dispersion coefficient and the plate height for the mass transfer are numerically determined after the mathematical formulation of the problem. It is remarkable that the introduction of hydrodynamic slippage can dramatically change the dispersion arising from EOF in various aspects, especially when both the slippage and electric potential are non-uniformly distributed on the channel wall. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

This thesis investigates the technical problems associated with large-scale stand-alone wind powered desalination employing a short-term energy store, particularly the complexities associated with the intermittent operation of the desalination plant. To achieve this, a non-linear, time domain system model of an existing wind powered desalination plant has been developed using the propriety code Simulink. Two desalination techniques have been considered: reverse osmosis and electrodialysis, due firstly to their relatively low specific energy consumption, and secondly, their efficient coupling to a wind turbine generator. As a way of reducing power mismatch, optimising water production, and above all reducing the switching rates of the desalination units, operation of the reverse osmosis and electrodialysis units under variable power conditions is suggested. Little information is available on plant performance under such conditions. A mathematical model has therefore been developed to ascertain the performance of reverse osmosis and electrodialysis processes under transient power conditions. The model consists of the set of partial differential equations (PDEs) describing the conservation of mass, momentum and chemical species coupled with the appropriate boundary conditions. A numerical solution based on the finite volume method has been employed to solve for the system of PDEs, as no analytical solution is available for the particular set of model equations derived. Sensitivity of plant performance to key design parameters (such as operating pressure and energy storage capacity) and operational strategies is predicted from simulation results. This technology is economically attractive for islands where wind energy density is high and water resources are scarce.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 83-86). Also available via the Internet.

Thesis (Ph. D.)--University of New South Wales, 2000. / Also available online.

Proefschrift--Leyden. / Erratum slip and "Stellingen" ([2] p.) inserted. Includes bibliographical references.