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Small-scale estuarine plume discharges into adjacent seas are common inshore features responsible for the transportation and dispersion of brackish water in the coastal zone. However, the physics that govern small-scale mixing in the frontal regions of river plumes are still poorly understood. The current study quantified and compared the observed hydrodynamic properties present inside a radially spreading river plume discharge from the River Teign, Teignmouth, Devon, UK, to those predicted by a generic plume model. Numerical simulations designed to replicate time dependent radial plume spreading from a constant source predicted the development of an internal interfacial bore that lagged the surface plume front through radial distance and time from initial plume release. The model was scaled from time lapse X-band radar imagery that recorded several plume discharge events. Scaled model output predicted the internal bore to form approximately 180 m behind the leading surface front. Subsequent field studies employed instrumentation capable of recording high-resolution measurements of temperature, salinity and velocity, spatially and vertically throughout the plume's buoyant layer over two ebb tidal cycles. Results suggested the plume advanced at a rate dependent on a super-critical interfacial Froude number of O(1.3) and was a region of intense mixing and downward mass entrainment. Temperature contours recorded through the stratified plume gave no indication of an internal bore in its predicted position but did show an abrupt shallowing of the interfacial region some 40 to 60 m behind the surface plume front. Super-critical interfacial Froude and critical Gradient Richardson numbers present in this region of the plume implied that this was the position of the predicted bore. The form of the bore often appeared as an ensemble of undular internal hydraulic jumps rather than a singular discontinuity as predicted by the model. Bulk mixing analysis inside the leading front based on established gravity current theory suggested that the extent of turbulent exchange in the model frontal boundary condition P, was underestimated by about a factor of 2. With the required increase in P, model simulations showed a decrease in the lag distance of internal bore formation to one where critical Froude numbers were detected inside the actual plume. Throughout both surveys, the gravity head remained a reasonably constant size due to any increase in across frontal velocity over the ebb tidal cycle being matched by an increase in entrainment and mixing. The subsequent conclusions from the study show the outflow and mixing dynamics are controlled by the estuary's tidal modulation of estuarine brackish water outflow / plume inflow rate behind the leading plume frontal discontinuity.

The Lawrence Livermore National Laboratory (LLNL), in Berkley, California, developed a laboratory scale non-membrane electrosorption process known as Capacitive Deionization Technology™ (CDT™) for the continuous removal of ionic impurities in water. A saline solution flows through an unrestricted capacitor type module consisting of numerous pairs of high-surface area (carbon-aerogel) electrodes. The electrode material (carbon aerogel) contains a high specific surface area (400 – 1 100 m2/g), and a very low electrical resistivety (< 40 m<font face="symbol">W</font>.cm). Anions and cations in solution are electrosorbed by the electric field upon polarization of each electrode pair by a direct current (1,4 Volt DC) power source. Testing conducted on a laboratory scale unit at LLNL has proved that CDT™ has the potential to be an alternative desalination technology (Farmer5 et al., 1995). The primary objective of this research was to continue, where the laboratory scale research ended. Thus taking CDT™ from a laboratory scale technology to an industrial scale process, by developing and evaluating an industrial CDT™ prototype system. First, a process was developed to manufacture a cost effective industrial sized CDT™ module. During this process various manufacturing techniques were evaluated to produce an optimum prototype. As part of the developmental process the prototype was tested and water treatment efficiency results were first compared to results obtained on the laboratory scale module and secondly to established desalination technologies like reverse osmosis, electrodialysis, and distillation. Due to the wide variety of potential saline feed water sources, research for this dissertation focused on brackish water applications (which includes wastewater reuse applications). After establishing a cost effective small-scale model of a potential industrial manufacturing process, the prototype was tested with regard to water treatment efficiency. Test results on brackish type waters (1 000 mg/l), indicated that the industrial CDT™ prototype had an energy requirement of 0,594 kWh/1000 liters. Research results compared well to the laboratory scale energy consumptions of 0,1 kWh/1000 liters (Farmer5 et al, 1995) and to the best available existing brackish water membrane based desalination systems with energy requirements of 1,3 to 2,03 kWh/1 000 liters (AWWA, 1999). The thermodynamic minimum energy required (due to osmotic pressure) to desalinate a 0,1% or 1 000 mg/l sodium chloride solution, is 0,0234 kWh/1 000 liters. Development and evaluation results indicated that CDT™ industrial modules could be manufactured cost effectively on a large scale and that such units have the potential to be very competitive with existing technologies with regards to overall operational and maintenance costs. Therefore Capacitive Deionization Technology™ can be viewed as a potential alternative to membrane technologies in the future. Regardless of the benefits to the potable water industry, CDT™ have the potential to incur a dramatic step reduction in the operational costs of desalination plants, which will make desalination a more viable alternative technology for large-scale agricultural and industrial uses. / Dissertation (MEng (Waterutilization))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

Yes / The Reverse Osmosis (RO) process has been expansively used in water treatment as a result of its low energy consumption compared to thermal distillation processes, leading to reduced overall water production cost. Evaluation and minimisation of energy consumption (expressed in kWh/m3 of fresh water production) in a medium-scale spiral wound brackish water RO (BWRO) desalination plant of the Arab Potash Company (APC) are the main aims of this research. The model developed earlier by the authors has been integrated to simulate the process and achieve the main aims. Energy consumption calculations of low salinity BWRO desalination plant, with and without an energy recovery device, have been carried out using the gPROMS software suite. In other words, this research evaluated the impact of adding an energy recovery device on the RO process energy consumption of the APC, which is introduced for the first time. Also, the effects of several operating conditions of BWRO process include the feed flow rate, pressure and temperature on the performance indicators, which include the energy consumption and total plant recovery at different energy recovery device efficiencies, were studied. The simulation results showed that the total energy consumption could be reduced at low values of feed flow rates and pressures and high values of temperatures. More importantly, there is an opportunity to reduce the total energy consumption between 47% and 53.8% compared to the one calculated for the original design without an energy recovery device.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references.

Thesis (Ph. D.) - L'Université de Clermont II (U.E.R. Sciences exactes et naturelles à dominante recherche), 1978. / At head of title: Série : E ; No. d'ordre : 260.

Yes / The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

Yes / Reverse Osmosis (RO) process has become one of the most widely utilised technologies for brackish water desalination for its capabilities of producing high-quality water. This paper emphasis on investigating the feasibility of implementing the retentate recycle design on the original design of an industrial medium-sized multistage and multi-pass spiral wound brackish water RO desalination plant (1200 m³/day) of Arab Potash Company (APC) located in Jordan. Specifically, this research explores the impact of recycling the high salinity stream of the 1st pass (at different recycled percentages) to the feed stream on the process performance indicators include, the fresh water salinity, overall recovery rate, and specific energy consumption. The simulation is carried out using an earlier model developed by the same authors for the specified RO plant using gPROMS suits. This confirmed the possibility of increasing the product capacity by around 3% with 100% recycle percentage of the high salinity retentate stream.

With the continual concern over the presence of naturally occurring and anthropogenic inorganic and trace organic contaminants in the aquatic environment there is a growing need for the implementation of innovative treatment processes for the elimination of these contaminants from natural waters and wastewater effluents. While conventional treatment methods are ineffective in the removal of emerging contaminants such as steroidal hormones and pesticides, membrane technology, including electrodialysis (ED), has been highlighted as a potential treatment option. However, the clear lack of fundamental understanding of the behaviour of contaminants in ED is a current limitation for its extensive utilisation and is a critical issue that needs to be addressed. ED processing potentialities have not been fully exploited and more research is needed to account for all the key parameters such as contaminant physicochemical properties, solution chemistry and the presence of organic matter. The purpose of this study was to elucidate the mechanisms of inorganic and trace organic contaminant removal by ED. The inorganic contaminants fluoride, nitrate and boron were selected due to their ubiquitous nature in the environment and public health concerns resulting from longterm exposure. The hydrated radius and strength of hydration shells played a significant role in ionic transport, whereby nitrate with a smaller hydrated radius was removed more effectively (94.1 %) than fluoride (68.3 %) with a larger hydrated radius. While fluoride and nitrate removal was pH independent, the pH dependent speciation of boron enhanced its removal with increasing pH. Territorial binding and/or complexation of the inorganics with organic matter enhanced removal. The removal of a range of trace inorganics (e.g. arsenic, calcium, magnesium, uranium) from a brackish groundwater from a remote Australian community was investigated. Undissociated inorganics were not transported through the membranes, whereas dissociated inorganics were due to electrostatic attraction. At acidic-neutral conditions ionic transport was the dominant removal mechanism. At neutral to alkaline conditions insoluble carbonate species precipitated and deposited as a membrane scaling layer (60 μm). This has serious implications for the long-term practical applicability of ED to treat real waters as scaling increased ED stack resistance (pH 3: 27.5 4, pH 11: 50 4) and decreased total dissolved solids removal (pH 3: 99 %, pH 11: 89.5 %). While the treatment of trace organics by other membrane processes has been widely studied, their fate in ED and interaction with ED membranes is relatively unknown. Trace contaminant-membrane interaction studies were undertaken to quantify the partitioning of trace organics; namely steroidal hormones and the pesticide endosulfan, to ED membranes by measuring membrane-water partition coefficients (log KM). The extremely high sorption capacity of the membranes was attributed to hydrogen bonding between the trace organic and membrane functional groups. Hormone sorption during ED was influenced by solution pH and organic matter. In the case of estrone, membrane sorption decreased at pH 11 (487 μg/cm3) compared to pH 7 (591 μg/cm3) due to dissociation and membrane electrostatic repulsion .At pH 11, repulsion between dissociated estrone and HA coupled with membrane electrostatic attraction resulted in increased sorption. The findings from this study highlight that the transport of trace contaminants will depend largely on the characteristics of the membranes used in the ED process as well as the physicochemical characteristics of the contaminants, their interaction with the ED membranes and the presence of other inorganic and/or organic compounds. The knowledge gained has direct applications to current problems and uncertainties in water and wastewater treatment with regards to the fate and transport of contaminants.

The Mekong Delta, which is considered as the main 'rice bowl and fish basket', is one of seven distinct agro-ecological regions of Vietnam and plays an important role in the economy of the country. Several rice-based farming systems have been developed in various areas of the MD. Rice-shrimp integrated system in brackish areas is a special farming system developed in this delta. It is a profitable system and seems to be environmentally safe on the one hand without the use of pesticides. On the other hand, use of brackish water in this system may result in degradation of land, as some previous studies have found. To understand how this farming system works and to identify the external and internal factors influencing its sustainability, the project 'Sustainability of rice-shrimp farming system in a brackish area in the Mekong delta of Vietnam' was carried out in 1992-1993 by an interdisciplinary team of researchers from the University of Cantho and staff of local district Agricultural Office, representing different fields of sciences. The research methodology was the Farming Systems Research approach with modifications towards soft systems thinking, involving farmers into the research process. One main result of this study is an insight into the rice-shrimp farming system. It includes various physical, biological, technological, economical and sociological aspects of rice production prior to integration and in integrated farm, naturally supplied shrimp growing and giant shrimp rearing, upland crop production as well as off-farm and non-farm work of farm households. Sustainability of the system studied is assessed, in comparison with rice monoculture, through various criteria of the three view points productivity, environmental safety and socio-economic effectiveness. In terms of such points of view, rice-shrimp farming system is rated higher than rice monoculture system. Thus the integrated system so far is considered to be more sustainable than the others. / Master of Science (Hons)