Water is the most important chemical component on Earth. Seawater distillation processes have a considerable promise as a technique suitable for producing large scale quantities of potable water from the seawater. Distillation process flowsheets consist of a number of interconnected units. The development of the mathematical model describing the behaviour of these units, and the subsequent solution of this model are fundamental steps in process flowsheeting. The first objective of this work is to develop a specialized flowsheeting program for performing design and simulation calculations for different types and configurations of seawater distillation processes. Many numerical methods have been used for solving linear and nonlinear sets of equations representing distillation processes. Most of these methods involve the direct manipulation of the mathematical model equations without exploiting the special properties, such as the sparsity and the weak nonlinearities, of these equations. The second aim of this study is to develop a new approach taking advantages of these properties. Hence, the model equations can be linearized, and grouped according to the variable type. These groups can then be solved by linear matrix technique. The performance of the developed program is investigated by solving many distillation process problems. The results from design and simulation calculations for large practical desalination plants are discussed. In addition to that the convergence characteristics of the new approach (such as stability. number of iterations. computing time. sensitivity to starting values, and general ease of use) are presented. Also. the validity of the approximation assumptions proposed to develop the new approach is examined.

Dissolved oxygen was studied in distilled water and salt solutions by means of nuclear magnetic resonance. The free induction technique was employed to measure the spin lattice relaxation time, T-^, for oxygen-free distilled water and for water containing oxygen under one atmosphere of air and one atmosphere of oxygen at temperatures of 1° to 75°C. The same measurements were made for solutions of 0.5 M sodium chloride at temperatures of 1° to 40°C. The spin lattice relaxation probability, 1/T[subscript 1(c)], in the presence of paramagnetic oxygen, was attributed to two relaxation mechanisms: the first a dipole-dipole interaction and the second a hyperfine interaction. The two terms were evaluated from measurements of T[subscript 1(c)] at two different magnetic field strengths at 20°C. Using the theoretical relationship between the dipole-dipole term and η/T, the results were used to evaluate the hyperfine term at different temperatures. The activation energy obtained from the variation of the dipole-dipole term with temperature was assumed to represent the energy required to break one hydrogen bond between two water molecules. The activation energy found for the hyperfine term was taken as a measure of the breaking of a hydrogen bond between one oxygen molecule and an aggregate of water molecules. The activation energy of the hyperfine term was found to be a function of temperature. Comparison of this quantity with heats of solution of dissolved oxygen in distilled water and salt solution showed a similar pattern of change in both. Oxygen supersaturation was studied in sea water cultures of Nitzschia closterium and Chlorella strain "A" at a temperature of 12°C. Saturation values up to 200% were reached under illumination with light energy of 9.2x10[power -3] langlies/min. Nitzschia was found to be more photosynthetically active, under the same culture conditions, than Chlorella. Oxygen production by Nitzschia was shown to be a function of the difference in photosynthetic pigment concentrations (chlorophyll-a — non-astacin carotenoid), total alkalinity, and the change in catalytic activity of the medium. Variation of oxygen concentration in Nitzschia cultures under light and dark periods indicated a mechanism by which oxygen may escape as microbubbles to the atmosphere. The rate of oxygen desupersaturation was measured in water free of organisms. The rate increased with increase of ion content and with the surface to volume ratio of the water column, but was not influenced by addition of siliceous particulate matter to the supersaturated water. Small addition of a surface active agent (heptanoic acid) increased the oxygen desupersaturation rate but further addition decreased the rate. / Science, Faculty of / Chemistry, Department of / Graduate

A method is described for measuring the preferential responses of fish to alterations in the chemical and physical nature of their environment. Changes in the responses of young chum salmon at various stages of growth to alterations in the environmental sea water content have been studied. The effects of small alterations in temperature (2 to 3 C° ) and in rates of flow of environmental liquids on the fishes' responses to salinity change, were also studied. Preliminary experiments on the responses of coho salmon fry to sea water are described. The results indicate that changes in the environmental sea water content, such as those encountered in the estuaries of salmon streams may exert a directive influence on the seaward movement of chum salmon fry. / Science, Faculty of / Zoology, Department of / Graduate

The conversion of ammonia to 2:4-dinitroaniline by reaction with 1-fluoro, 2:4-dinitrobenzene and the subsequent conversion of dinitroaniline to a diazo-dye with N-(1-naphthyl)ethylenediamine has been investigated as an analytical method for determining ammonia at the micromolar concentration level. Particular emphasis was placed upon the possibility of applying this method to the analysis of sea water. Dinitroaniline was formed under alkaline conditions (pH greater than 8) and required the presence of the fluoro-dinitrobenzene as a separate phase for initiation of the reaction. The conversion, which was light sensitive, was accelerated by increases in pH and temperature, but neither of these factors improved the final yield. The yield of dinitroaniline had a marked dependence on the amount of fluorodinitrobenzene; initially increasing with increasing fluorodinitro-benzene content, it then decreased with higher fluorodinitrobenzene concentrations suggesting further reaction between dinitroaniline and fluorodinitrobenzene. In both distilled and sea water, the maximum yield of dinitroaniline from solutions containing ammonia at the micromolar concentration level was found to be 55-58%. The absorbance of the diazo-dye in sea water of salinity 30.4% was only 42% of that observed in distilled water. Although sufficiently sensitive for application to sea water analysis, the precision of the conversion of dinitroaniline to the diazo-dye in sea water was poor compared to that achieved in distilled water. / Science, Faculty of / Chemistry, Department of / Graduate

An analytical technique for the differentiation of biologically active copper (Cu) in seawater was developed. The procedure involves passing a seawater sample through an ion exchange resin of the sulponate type until complete breakthrough of metal ion is achieved. The sorbed Cu is then eluted and its total concentration is determined by anodic stripping voltammetry. Comparison with Cu adsorption from standard seawater samples of similar composition, pH, and ionic strength yields a Cu equivalent measurement that is related to the free cupric ion activity of the sample. Since the cupric ion is believed to be the toxic form of the metal, the Cu equivalent measurement can be related to the biologically active fraction of Cu. The measurement of biologically active Cu by the resin technique was verified by comparing the analytical results with results from phytoplankton bioassays. Tests were first conducted in artificial seawater that had its chemistry well defined and where model organic ligand (EDTA, NTA, histidine and glutamic acid) were used to control the speciation of the metal. In the experiments using the organic ligands EDTA, NTA, or glutamic acid added to Cu spiked artificial seawater, a strong relationship between the Cu equivalent values and growth rates of the bioassay organism was found (r=0.92). However, in experiments with histidine, this relationship was much weaker and was attributed to the adsorption of positively charged Cu-histidine complexes onto the resin. The adsorption of these complexes results in overestimating the amount of biologically active Cu present in the sample. The few studies on the electrochemical nature of organic complexing agents in seawater suggests, however, that most are negatively charged. Thus the technique would be suitable in many seawater systems. The analytical and bioassay techniques were then applied to natural seawater samples collected from five depths in a local fjord. A discrepancy was found between some of the bioassay and resin test results. However, the discrepancy was attributed to a physiological Cu-Mn interaction in the bioassay organism and not to a problem with the resin technique. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The effect of S.W. on the osmoregulatory processes of Rainbow trout was studied. Rainbow trout were monitered for various acid--ba.se and respiratory parameters during F.W. - S.W. transfer. Plasma Cl⁻, total CO₂ and HCO₃⁻ concentrations were measured, as well as blood pH, Pa0₂ and PC0₂- V02₂, VG, VCO₂, and VH⁺ were calculated from the measured parameters. During the exposure to S.W. for 3 hours none of the measured variables changed significently, indicating that the Rainbow trout is indeed euryhaline. It appears that unlike the goldfish the trout has a branchial Cl⁻/HCO₃⁻ exchange diffusion pump that is of small capacity, because changes in the external concentrations of CI⁻ and HCO₃⁻ did not affect internal levels of these ions. Raising external Cl⁻ levels would cause a lowering in plasma HCO₃⁻ if there was a Cl⁻/HCO₃⁻ exchange diffusion pump in the gills. A second group of experiments involved the use of Cl⁻ to measure Cl⁻ fluxes in the gills of intact trout. Injections of HCO₃⁻ into the fish did not stimulate Cl⁻ efflux, indicating that if there is a Cl⁻/HCO₃⁻ exchange diffusion pump, it is of small capacity. Gill carbonic anhydrase levels were measured in the gills of F.W. and S.W. trout, S.W. and F.W. coho, and goldfish. Goldfish have a high level as does the S.W. coho. Carbonic anhydrase catalyses the formation of HCO₃ from C02 for the Cl⁻/HCO₃⁻ pump, and is thus indicative of the importance of the pump in Cl⁻ and HCO₃⁻ fluxes.. The significance of the differences in the ionic pumps of trout, coho, and goldfish are discussed in relation to their life histories. Trout having a flexible osmoregulatory system (being euryhaline) while the coho and goldfish are more specialised being essentially stenohaline. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (viewed May 26, 2009) Includes bibliographical references (p. 49-56)

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: 47-48)

Thesis (M.S.)--Texas A & M University, 1980. / Vita. Includes bibliographical references (leaves 88-92).

Owing to the maldistribution of precipitation in the harsh climatic region has resulted in the deficit between freshwater demand and natural supply or water scarcity in these countries. Seawater desalination has emerged as one of the most reliable methods to bridge this gap. However, the thermal desalination (MED and MSF) process faces challenges related to surface scaling phenomena, such as temperature and seawater concentration. Innovative thermodynamic processes and technologies have the potential to overcome these limitations. On one hand, the top brine temperature (TBT) limit can be raised by partially removing the multivalent ions such as SO42-, Mg2+, Ca2+, Cl-, and Na+ dissolved in the seawater. One of the main drawbacks of the current MED processes is their vulnerability to scaling at temperatures above 70°C.. This limitation deprives the technology to be energy efficient and reduces its optimal productivity. However, by implementing an optimized pre-treatment of seawater feed using NF membranes, the efficiency of the process can be significantly improved. In the pilot plant, the experiment was conducted to investigate the efficacy of NF (nanofiltration) as a physical pre-treatment method for partially removing undesirable ions of dissolved salts in Red Sea water, thereby mitigating scaling issues beyond the upper TBT limit in thermal desalination systems. Utilizing the NF-270 membrane, the optimal operating feed pressure of 15 bar was determined to ensure effective ion removal while minimizing operational expenditures (OpEx). The results demonstrated high removal rates, with 97% removal of Sulfate (SO42-), 73% removal of Magnesium (Mg2+), 49% removal of Calcium (Ca2+), 17% removal of Sodium (Na+), and 16% removal of Chloride (Cl-). By employing NF as a pre-treatment method, the concentrations of these ions were significantly reduced, allowing for thermal desalination plants to operate at higher temperatures, with a maximum TBT of 120°C. This, in turn, has the potential to substantially increase water production yield in thermally driven plants by incorporating a greater number of stages in a green new design plant or by exploiting larger temperature differences in existing plants.