The ability to produce potable water economically is the primary purpose of seawater desalination research. Reverse osmosis (RO) and multi-stage flash (MSF) cost more than potable water produced from fresh water resources. As an alternative to RO and MSF, this research investigates a high-efficiency mechanical vapor-compression distillation system that employs an improved water flow arrangement. The incoming salt concentration was 0.15% salt for brackish water and 3.5% salt for seawater, whereas the outgoing salt concentration was 1.5% and 7%, respectively. Distillation was performed at 439 K (331oF) and 722 kPa (105 psia) for both brackish water feed and seawater feed. Water costs of the various conditions were calculated for brackish water and seawater feeds using optimum conditions considered as 25 and 20 stages, respectively. For brackish water at a temperature difference of 0.96 K (1.73oF), the energy requirement is 2.0 kWh/m3 (7.53 kWh/kgal). At this condition, the estimated water cost is $0.39/m3 ($1.48/kgal) achieved with 10,000,000 gal/day distillate, 30-year bond, 5% interest rate, and $0.05/kWh electricity. For seawater at a temperature difference of 0.44 K (0.80oF), the energy requirement is 3.97 kWh/m3 (15.0 kWh/kgal) and the estimated water cost is $0.61/m3 ($2.31/kgal). Greater efficiency of the vapor compression system is achieved by connecting multiple evaporators in series, rather than the traditional parallel arrangement. The efficiency results from the gradual increase of salinity in each stage of the series arrangement in comparison to parallel. Calculations using various temperature differences between boiling brine and condensing steam show the series arrangement has the greatest improvement at lower temperature differences. The following table shows the improvement of a series flow arrangement compared to parallel: ?T (K) Improvement (%)*1.111 2.222 3.333 15.21 10.80 8.37 * Incoming salt concentration: 3.5% Outgoing salt concentration: 7% Temperature: 450 K (350oF) Pressure: 928 kPa (120 psig) Stages: 4

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.

The ability to produce potable water economically is the primary purpose of seawater desalination research. Reverse osmosis (RO) and multi-stage flash (MSF) cost more than potable water produced from fresh water resources. As an alternative to RO and MSF, this research investigates a high-efficiency mechanical vapor-compression distillation system that employs an improved water flow arrangement. The incoming salt concentration was 0.15% salt for brackish water and 3.5% salt for seawater, whereas the outgoing salt concentration was 1.5% and 7%, respectively. Distillation was performed at 439 K (331oF) and 722 kPa (105 psia) for both brackish water feed and seawater feed. Water costs of the various conditions were calculated for brackish water and seawater feeds using optimum conditions considered as 25 and 20 stages, respectively. For brackish water at a temperature difference of 0.96 K (1.73oF), the energy requirement is 2.0 kWh/m3 (7.53 kWh/kgal). At this condition, the estimated water cost is $0.39/m3 ($1.48/kgal) achieved with 10,000,000 gal/day distillate, 30-year bond, 5% interest rate, and $0.05/kWh electricity. For seawater at a temperature difference of 0.44 K (0.80oF), the energy requirement is 3.97 kWh/m3 (15.0 kWh/kgal) and the estimated water cost is $0.61/m3 ($2.31/kgal). Greater efficiency of the vapor compression system is achieved by connecting multiple evaporators in series, rather than the traditional parallel arrangement. The efficiency results from the gradual increase of salinity in each stage of the series arrangement in comparison to parallel. Calculations using various temperature differences between boiling brine and condensing steam show the series arrangement has the greatest improvement at lower temperature differences. The following table shows the improvement of a series flow arrangement compared to parallel: ?T (K) Improvement (%)*1.111 2.222 3.333 15.21 10.80 8.37 * Incoming salt concentration: 3.5% Outgoing salt concentration: 7% Temperature: 450 K (350oF) Pressure: 928 kPa (120 psig) Stages: 4

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.

This study presents a two-step desalination process, in which produced water is cleaned by forming gas hydrate in it and subsequently dewatering the hydrate to remove the residual produced water trapped in between the hydrate crystals. All experiments were performed with pressure in the range of 450 to 800psi and temperature in the range of -1 to 1°C using CO? as guest molecule for the hydrate crystals. The experiments were conducted using artificial produced waters containing different amounts of NaCl, CaCl₂ and MgCl₂ at varying temperature (T) and pressure (P). The results are presented as functions of %Reduction of difference chemical elements, CO? requirements and applied T and P conditions. The impact of dewatering techniques, including centrifuge and filtration process, on gas hydrate solid product is studied. The results showed that over 99% of dissolved NaCl and MgCl2 can be removed from artificial saline water in laboratory experiments. This was achieved in a process involving a single-stage hydrate formation step, followed by a single-step solid-liquid separation (or dewatering). The results also show that the %Reduction (percentage of the concentration decrease) of artificial produced water increases with centrifugation time and rotational speed (rpm). The %Reduction was increased considerably after hydrate crystals were crushed and filtered, indicating that the artificial process water was entrapped in between the hydrate crystals. It was found also that the finer the particle size, the higher the extent of salt removal. In general, filtration was a better than centrifugation for the removal of TDS (Total Dissolved Solids). / Master of Science

This study investigates the desalination needs and available technologies in Sri Lanka. Lack of rainfall, pollution due to agricultural chemicals, presence of fluoride, increasing demand, exploitation of ground water and brackishness have created scarcity of fresh pure water specially in near costal and dry zones in Sri Lanka. Due to Cronic Kidney Disease (CKD) around 500 people died in dry zones annually which is suspected to cause by Arsenic and Cadmium contain in ground water due to agriculture chemicals.   The available desalination methods are Reverse Osmosis (RO), Solar distillation and conventional methods. The cost for RO is Rs.0.10 cents per liter and solar distillation Rs.2.96 per liter. Although the price shows that the RO is better but due to high initial investment as a third world country it is very difficult to afford huge initial investment without government intervention. The experimental solar desalination units only produce nearly 5liters of potable water per day and directly impacted by availability of solar radiation. The energy availability of Sri Lanka and future potable water demand predicted as 2188.3 Mn liters as maximum demand which will be in 2030, therefore by that time the government should have a proper plan to cater the demand and desalination plants need to be planned and built based on the demand of dry zones and specially agriculture areas.   The applicability of renewable energy for desalination in local arena was also simulated taking the Delf Reverse Osmosis plant for the simulation. Results show that the optimum design is combination of Solar PV and existing 100kW Diesel generator Set with Battery bank and converter.

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.

Sulfonated polysulfones BisAS and BPS were fabricated into dense polymer films, and their water and ion transport properties were systematically characterized. Fundamental NaCl and water transport properties were correlated with polymer chemistry, and water and NaCl permeability were found to increase with degree of sulfonation due to the increasing polymer water content. The BisAS backbone structure was found to result in greater water uptake, increasing water and salt permeability, though the polysulfones show evidence of sensitivity to the thermal casting process as well. Additionally, water and ion permeability and sorption values were determined for select polymers when exposed to a feed consisting of mixtures of monovalent and divalent cation salts. The divalent cations were found to sorb into the polymer much more favorably than the monovalent sodium, similarly to charged materials found in the literature. The sodium permeability of sulfonated polysulfones was found to increase in the presence of divalent cations by ratios of 2 to 5 times more than when exposed to an equivalent increase in feed charge concentration of monovalent cations. It has been hypothesized the more strongly charged divalent cations are neutralizing the sulfonate charges and suppressing Donnan exclusionary effects that reduce salt transport in charged polymers. / text

Growing populations and periodic drought conditions have exacerbated water stress in many areas worldwide. Consequently, it would be valuable to manage both supply and demand of water to fully address water sustainability. Additionally, the inextricable link of water and energy -- energy is required to pump, treat, and distribute water and water is often used in the production of energy -- creates the need to study the use of these resources together. In response to water stress, some municipalities have considered desalination of saline water as a freshwater supply. Unfortunately, desalination requires a sizeable energy investment and causes significant carbon emissions with conventional approaches. However, renewable energy technologies can be paired with desalination to mitigate concern over the environmental impacts of increased energy use. At the same time, desalination can be operated in an intermittent way to match the variable availability of renewable resources. Both wind and brackish groundwater resources are plentiful in the Panhandle region of West Texas, making an integrated wind-powered desalination facility an option for meeting increasing water demands. Integrating wind power and brackish groundwater desalination generates a high-value product (drinking water) from two low-value resources (saline water and wind power without storage). This thesis presents a thermoeconomic, geographic, and operational analysis of an integrated wind-powered reverse osmosis facility treating brackish groundwater in West Texas. The results demonstrate the favorability of the integrated facility under certain economic, geographic, and operating conditions. Also in response to water stress, corporations are becoming increasingly interested in identifying water vulnerabilities in their operational portfolios to minimize physical, reputational, regulatory, and financial risks associated with potential water shortages. The water footprint is one tool available to assess water use, identify vulnerabilities, and guide mitigation strategies. This thesis provides an accounting methodology for water reporting that includes direct water uses and indirect (embedded in energy, services, and products) water uses in the operations. Further, a case study is considered to illustrate the methodology by assessing the water impact of a mixed-use facility in Palo Alto, California. The results demonstrate the importance of considering the indirect water uses, which requires a more exhaustive analysis. / text

Yes / Models’ accuracy and reliability are important factors for designers of the humidification-dehumidification (HDH) desalination systems. A model used for designing the system must consider all important parameters in order to maintain high accuracy over the wide range of fluctuating conditions. The empirical models for HDH systems which are mostly available in literature are simple and easy to develop but also have limited predictive accuracy for extreme conditions because of consideration of only a few of many influential parameters. Usage of these models may lead to an expensive redesign at latter stages in development of the real system. Therefore, the aim of this paper is to propose the mechanistic model of the HDH desalination process with an improved prediction accuracy as an alternative to conventional models. This model is developed by coupling the heat and mass transfer equations at the water–air interface into enthalpy equations. Performances of the proposed model and an empirical model from literature are compared against experimental data obtained from the HDH system, which is also designed in this work. Results show the proposed model has relatively low mean square error (0.4) hence more accurate than the empirical model with mean square error of 7. It was also found that, the recovery ratio attained by the system increases substantially with an increase of the feed water temperature, but decreases with an increase of water-to-air flow ratio. Freshwater productivity increases with an increasing packing's specific area while doubling of dehumidifiers’ surface area improves the recovery ratio by 16%.