Coupling of standard condensing nuclear power stations to horizontal aluminum tubes multieffect distillation plants

No large nuclear back-pressure turbines are available to day. Standard condensing nuclear turbines could operate continuously with a back-pressure of up to 7″ Hg, exhausting huge amounts of steam at 56°C - 640°c with a loss of electricity production of only 6%–10%. p]The horizontal aluminium tube multieffect distillation process developed by “Israel Desalination Engineering Ltd.” is very suitable for the use of such low-grade heat. A special flash-chamber loop constitutes a positive barrier against any possible contamination being carried over by the steam exhausted from the turbine to the desalination plant. The operation is designed to be flexible so that the power plant can be operated either in conjunction with the desalination plant, or as a single purpose plant. Flow sheets, heat and mass balances have been prepared for eight different combinations of plants. Only standard equipment is being used in the power plant.

The desalination plant consists of 6 to 12 parallel double lines, each of them similar to a large prototype now being designed.

Water production varies between 50 and 123 MGD and water cost between 90 and 137 ¢/1000 gallons.

Costs are based on actual bids.     

Thermoeconomic design of a multi-effect evaporation mechanical vapor compression (MEE–MVC) desalination process

Desalination of seawater accounts for a worldwide water production of 24.5 million m³/day. A “hot spot” of intense desalination activity has always been the Arabian Gulf, but other regional centers of activity emerge and become more prominent, such as the Mediterranean Sea and the Red Sea, or the coastal waters of California, China and Australia. Despite the many benefits the technology has to offer, concerns rise over potential negative impacts on the environment. Key issues are the concentrate and chemical discharges to the marine environment, the emissions of air pollutants and the energy demand of the processes. To safeguard a sustainable use of desalination technology, the impacts of each major desalination project should be investigated and mitigated by means of a project- and location-specific environmental impact assessment (EIA) study, while the benefits and impacts of different water supply options should be balanced on the scale of regional management plans. In this context, our paper intends to present an overview on present seawater desalination capacities by region, a synopsis of the key environmental concerns of desalination, including ways of mitigating the impacts of desalination on the environment, and of avoiding some of the dangers of the environment to desalination.     

The Libyan experimental on the environmental impact assessment for desalination plants

The desalination industries are considered to have a major role in developing human life. Recently this technology became widely distributed, and its construction along the coastal area has been widely reported. Many countries are adopting these technologies for securing the fresh water supply for consumer consumption all over the world. This situation has raised the need for researches to evaluate the environmental impact assessment (EIA) of these technologies on coastal line environment.

This study has been directed to monitor sea water quality used for feeding desalination plants to determine the concentrates of selected pollutants such as heavy metals by using chemical monitoring system to know their effects on the desalination units and other components. This study was conducted in the year 2003 from January to June. Samples were collected from feed water intake of Benghazi North desalination plant and Tobrouk desalination plant, both plants were chosen because of their importance for supplying fresh water for potable water and industrial uses.

The results of this study showed monthly differences in most tested parameters, these differences lead to the scale and corrosion by precipitation on the components of the desalination unites. The objectives of this study is to know the main reasons which caused increasing these concentrates in the sea water (study area) and know how to deal with.     

Sustainable fuel cell integrated membrane desalination systems

According to the United Nations, between two and seven billion people will face water shortages by the year 2050. Further, it is estimated that the amount of water available per person will shrink by a third during the next two decades. Inadequate supply of good-quality water coupled with higher water demand due to rapid population growth and industrialisation in developing countries are among the major reasons for the worsening water situation. Current shortages of potable water around the world and looming water scarcity especially in the developing countries is the driving force behind the implementation of membrane technologies for seawater and brackish water desalination. Typical energy consumption in seawater reverse osmosis (RO) plants operating at 40–45% product water recovery and with energy recovery from the high pressure reject stream currently is about 3–4 kWh/m³. The near-term goal of the industry is to reduce energy consumption to less than 2 kWh/m³ by using a combination of energy efficient RO pumps, more efficient energy recovery devices, high performance low energy RO membranes, hybrid membrane systems, advanced pretreatment technologies and alternate energy integrated membrane systems. The beneficial aspects of using alternate energy systems such as on-site distributed fuel cell systems integrated with membrane desalination units in remote locations are discussed.     

Desalination of non-chlorinated surface seawater using TFC membrane elements

The Umm Lujj II reverse osmosis (RO) desalination plant in Saudi Arabia has produced high quality potable water [< 200 mg/L total dissolved solids (TDS) concentration] at better than design capacity [4,400 m³/d (1.16 MGD)] from non-chlorinated Red Sea surface seawater (42 g/L TDS concentration) since May 1986. The plant employs thin-film composite (TFC^R) spiral-wound membrane elements manufactured by UOP Fluid Systems. During the two years of operation, there have been no element additions or replacements and no element cleaning has been required. The only meaningful biological concern for surface seawater RO plants containing TFC^R membrane is algae growth, which is effectively controlled by a low concentration of copper sulfate. The seawater is not pretreated with a general disinfectant such as chlorine because other live microorganisms in the surface seawater do not attack or excessively foul UOP's TFC^R membrane. There has been no evidence of fouling by microorganisms or other foulants at Umm Lujj. This is reflected in the normalized membrane water flux after the two-year period being at the predicted value for a non-fouling feedwater. It is proposed that the long-term stability of TFC^R membrane with non-chlorinated surface seawater is due to its surface properties.     

Desalination in the development of Libya problems of implementation and impact on environment

In Libya, many desalination plants of different working principles and various manufacturers are being installed. Practically all important plants are dual purpose installations, the total desalting capacity being about 140,000 m³/day for sea water and 21,000 m³/ day for brackish water.

The paper points out the main problems faced by the different manufacturers during the erection and maintenance of their plants, particular attention being given to those related to Libyan specific conditions. Suggestions are made in order to decrease the acuteness of these problems in the future.

Also, the impact on the environment of the installation of such desalting plants is considered in all its aspects (social, economic, . . . ), particularly those related to a developing nation.     

Ashkelon seawater desalination project — off-taker’s self costs, supplied water costs, total costs and benefits

Total desalinated water costs to the Israeli Government, the “off-taker”, from the Ashkelon seawater desalination plant consist of the contracted water costs at the plant’s battery limits plus the government’s own expenditures: a) its initial investments (tender administration, out-of-plant infrastructure required to integrate the product within the national and regional water supply systems, etc.), b) its annual infrastructure O&M, supervisory and administrative costs, and c) the projected additional costs associated with certain project risks assumed by it throughout the life of the project. The paper presents and reviews these risks and quantifies the Government’s anticipated direct and indirect, fixed and variable costs, including several cost escalation scenarios anticipated due to the linkage of the contracted water price to various indices (using an item by item and index by index cost sensitivity analysis). The escalated desalinated water costs are then compared to the similarly anticipated but differently escalating costs of other water sources in Israel, to project, long-term, the resultant gap. The benefits foreseen from the project, and particularly those related to its specific site location, and its mandated daily, monthly and annual water supply schedules and product quality, are presented against: a) the background of Israel’s current water supply system’s water sources’ sustainable capacity, reliability, quality and costs, b) the anticipated growth in demand by various consumer sectors and c) the continuous deterioration of groundwater quality. The resulting risk and cost-benefit analyses are relevant not only to the Ashkelon project, which, as the first large scale government sponsored seawater desalination project in Israel, is a pioneering case study, but also to all pending and future seawater desalination projects in Israel. Some of these are not and will not be BOT, as the Ashkelon project was, but BOO and turnkey contracts, but, though government’s participation and the division of project risks may vary, the key cost-benefit issues, from the government’s point of view, will remain the same. In this context, Israel’s overall seawater desalination program, which is currently fixed at 315 million m³/y by 2010, and its role within the Israeli Water Commission’s long-range planning are briefly reviewed.     

Effective scale control for seawater RO operating with high feed water pH and temperature

An effective scale control program for seawater RO is widely recognized as an important factor in ensuring trouble free and cost effective operation. This is especially important under the high feed water pH and temperature conditions found in Southern Europe and Middle East.

In addition, regulatory issues concerning maximum acceptable boron levels in drinking and irrigation water necessitate the growing need to operate plants at higher feed water pH. Operating at increased pH increases boron rejection but also increases the scaling tendencies of the water. This can lead to calcium carbonate and magnesium hydroxide precipitation in the membranes.

A complete scale control program needs to control calcite and brucite saturation at the maximum operating reject pH and temperature. Antiscalant chemistry, optimum dose rate as well as accurate monitoring and control of the scale inhibitor are key factors in long-term cost effective “scale free” operation.

This paper details the operating strategies and scale control issues related to both single and two pass seawater RO plants operating at elevated feed water pH and temperature.     

Implementation of ISO 14001:2004 (environmental management system standard) for reverse osmosis desalination plants for the first time in Iran

Implementation of ISO 14001:2004 (environmental management system) has been executed for reverse osmosis desalination plants for the first time in Iran at Noor Vijeh Company (N.V. Co), a water and wastewater firm based in Tehran. The scope of work was the activities and product of company's BWRO desalination plant in the city of Qom (3000 m³ per day) and SWRO desalination plant in Assaluyeh, Pars Special Economic and Energy Zone, Iran. The aims of this project were in line with company’s approach to sustainable development and its direction towards conducting environmental friendly activities and production characteristics.

Initially the famous PDCA (Plan, Do, Check, Act) was used to identify the aspects and evaluate their effects. The significant aspects of each plant affecting the environment are then identified and preventive control measures and reducing their probabilities of loss are anticipated. These cover the normal activities within each plant and those aspects arising from emergency conditions such as earthquakes, fire, etc.

Elements of this system are

• Environmental policy and its targets and programmes

• Practical methods for environmental management system processes

• Executive manuals for implementing special activities

• Tables and indexes for environmental aspects for each plant

• Organizational charts, positions, qualifications, and necessary trainings for the involved personnel.

Environmental aspects are evaluated through their interaction with and effects over, releases to water, emissions to air, land contamination, waste management, energy use, and use of natural resources and raw material.     

An autonomous wave-powered desalination system

The potential for an autonomous wave-powered desalination system is considered and it is identified that the most promising configuration is a reverse osmosis (RO) plant utilising a pressure exchanger-intensifier for energy recovery. A numerical model of the RO plant with a pressure exchanger-intensifier is developed that shows that a specific energy consumption of less than 2.0 kW h/m³ over a wide range of sea-water feed conditions, making it particularly suitable for use with a variable power source such as wave energy. A numerical model of the combined wave-power and desalination plant is also developed that shows that it is possible to supply the desalination plant with sea-water directly pressurised by the wave energy converter, eliminating the cost and energy losses associated with converting the energy into electricity and back to pressurised water. For a typical sea-state the specific hydraulic energy consumption of the desalination plant is estimated to be 1.85 kW h/m³ whilst maintaining a recovery-ratio of less than 25 to 35% to avoid the need for chemical pre-treatment to eliminate scaling problems. It is suggested that the economic potential for wave-powered desalination depends on these energy and cost savings more than compensating for the reduction in membrane life that occurs with variable feed conditions.     

Sea water desalination by reverse osmosis in chigasaki laboratory

For the purpose of constructing a reverse osmosis [RO) sea water desalination plant of 800 m³/day capacity, a series of tests on the following themes have been carried out in the Chigasaki Laboratory:

1. Performance and durability of 8B modules made in Japan

2. Simplification of pretreatment system

3. Establishment of energy recovery system.

Domestic modules showed good and stable performance during long term operation, and water recovery ratio of these modules have been raised to 40%.

In-line coagulation and filtration system has been established for the pretreatment of feed sea water, instead of coagulation, sedimentation and filtration system.

The energy recovery equipment is consisted of a high-pressure pump, a motor and a hydraulic turbine on a common base. Recovered energy from pressurized brine is used for the auxiliary motive power of the high-pressure pump. The experimental data show that about 20% of required power for the pump was recovered.     

Future role of desalting for water quality improvement - Colorado River Basin, U.S.A.

Up to the present time, the development of desalting technology has been mainly directed at water supply augmentation. In view of Federal and State legislation in the U.S.A. to support water pollution control and water quality improvement, along with advances in membrane desalting processes, an expanded new role for desalting is discussed.

Potential desalting applications now under study by the Bureau of Reclamation's “Colorado River Water Quality Improvement Program” are examined along with general constraints, cost-effective criteria, planning strategies, and water resources impacts. Specific desalting sites and time frames are briefly addressed from a planning viewpoint generally limited to the upper region of the Colorado River Basin. Estimates of plant capacities, general feedwater conditions, costs, and various types of processes under planning investigation are provided.

The paper suggests key areas of membrane desalting research needs related to salinity control. Finally, this planning overview concludes that the economic differences between conventional salinity control techniques and desalting may be narrowing.     

Integration of seawater desalination with power generation

The economic benefits of integrating seawater desalination with power plants are discussed, starting from the first principles of thermodynamics. The concepts of the “fuel-use performance ratio” and the “power loss” method are described in the context of their usage for thermal cycle evaluation and desalination process selection, both with conventional steam cycles and with combined cycle power plants. A thermo-economic model is introduced to evaluate water and power costs and rates of return in dual-purpose power/desalination applications. The future of integrated power and desalination plants is discussed with reference to the growing role of seawater reverse osmosis (SWRO) in the desalination arena. A case study is presented to evaluate the benefits of integrating SWRO with existing power/desalination plants in the Middle East. Subject to the assumptions of the study, it is concluded that repowering and retrofitting would result in a nearly three-fold increase in the power generating capacity and an over six-fold increase in the water output, without requiring any expansion of the seawater intake system. Based on natural gas fuel, the repowered plant would also result in a 70% increase in the fuel efficiency of the station and a drastic reduction in the cost of water production. For a privatization scenario, an economic analysis is used to show that attractive rates of return would be obtained if a developer were to purchase and refurbish the existing plant, selling the products on a build own and operate (BOO) basis. In preparation for this promising application, the need for pilot plant testing at existing power/desalination stations, together with research and development work in membrane technology for high temperature operation, is emphasized.     

Environmental impacts of the mega desalination project: the Red–Dead Sea conveyor

The Dead Sea is the lowest point on the earth. Historically, its level was 392 m below sea level. Due to the diversion of the water that is feeding the sea from the north and to the construction of industrial facilities in the south to extract minerals, the Dead Sea level nowadays has been lowered to 417 m. Furthermore, the surface area of the sea has been reduced from 940 km² in 1960s to 637 km² today.

In an attempt to restore the Dead Sea to its original level, and to find a reliable source of fresh water in the region which suffers from chronic water scarcity, the Red Dead Sea conveyor (RDSC) project has been proposed. RDSC would convey seawater from the Red Sea (Gulf of Aqaba) to the Dead Sea to save it from vanishing, and to produce desalinated water and hydroelectric power by utilizing the difference in elevations between the Red and Dead seas.

The proposed project is expected to have great impact on the regional socio-economic development. However, many questions need to be answered before proceeding with such a mega project. Some of the answers needed are related to the environmental impacts of the project. The present paper is an attempt to address the major environmental impacts associated with the implementation of the RDSC project. Both positive and negative impacts were considered in the analysis.

The analysis revealed that brine reject is the main adverse environmental problem. The amount of brine has been estimated to be 1050 MCM/y. In addition to salt content, the reject brine contains several chemical additives, chemical cleaning solutions and pretreatment chemicals that are discharged with the brine. Another significant adverse impact that is identified is the impact on the fragile marine environment of the Gulf of Aqaba. The semi enclosed nature of this marine environment, which encourages its unique biological diversity, also makes it particularly susceptible to pollution. Therefore, measures that should be taken during the construction and operation of the project to protect the marine environment were recommended.     

Desalination costs in Australia: A survey of operating plants

A survey of desalination costs in Australia was conducted using data obtained from plant operators, and is reported in second quarter 1986 A$. Unit water costs range from $0.76/kL (for a precursor to deionisation for boiler feed) to $14/kL (for emergency supplies for an island resort).

However, an average figure for desalination of brackish water is $3–$4/kL, and for seawater, $5–10/kL in medium-sized installations.

Capital costs for brackish water plants have been correlated with plant design capacity ranging from 10 to 3400 kL/d.

There is insufficient information to allow a proper comparison between reverse osmosis and electrodialysis for brackish water desalination.     

The futuke of water supply to tripoli

The recent expansion of the city of Tripoli has resulted in an inadequate water supply for the present demand. Means of improvements are indicated.

Presuming effective measures for conserving water, the peak day demand for municipality water is expected to increase from its present value of 0.26 Mm³/d to 0.6 Mm³/d in the year 2000. Schemes to meet future demands are surveyed.

For all feasible schemes, the increase of irrigation water is not allowable except by re-use, the sea water desalting is inevitable, the capital investment for the next 5 years is more than $ 400 × 10⁶ and the cost of potable water is unlikely to be less than $ 0.7/m³ under careful management.

Schemes and research projects for brighter conclusions are welcome.     

Riyadh''s reverse osmosis water treatment plants - the largest demineralization complex in the world

The water demand in Riyadh has increased very rapidly during recent years owing to the rapid expansion of the city with a population growth of about 50,000 per year. The water from the main source, an aquifer of Minjur sandstone at a depth of 1,200–1,500 m reached, by drilling, has high hardness, sulphate and TDS. The existing water works with raw water cooling, lime-soda softening, sedimentation, filtration and disinfection have been in operation at Malez, Shemessy and Manfouha since 1969. VBB, a member of Swedish Consulting Group (SWECO), is consultant to the Ministry of Agriculture and Water (MAW) regarding the water supply in Riyadh.

In 1973, VBB made an investigatory study on additional water treatment. The aims were to consider the possible need for further improvement of the actual water quality, to point out how such improvements could be achieved and finally, to discuss alternative treatment methods suitable for the purification of water taken from the new well fields.

The purpose of this paper is to give an overview of the technical design and construction of the new water treatment plants in Riyadh, with a total capacity of about 254,000 m³ /d. The treatment of Minjur deep-well water includes not only chemical softening but also demineralization with reverse osmosis (RO) as a final purification stage. The Salbukh plant (50,700 m³/d) should come onstream in autumn 1979.     

An atomic force microscope study of calcium carbonate adhesion to desalination process equipment: effect of anti-scale agent

Whilst carbon dioxide is water soluble the system is somewhat complex and results in the presence of carbonate anions which interact with cations such as Ca²⁺ and Mg²⁺ present in seawater to form insoluble carbonates, especially at high temperatures. In multistage flash (MSF) desalination plants CO₂ gas becomes less soluble in the brine as a result of the brines high temperature and high salinity which causes the pH to be in the range of 8–9. The presence of these conditions causes the release of CO₂, simultaneous to the formation of scale deposits since its solubility is a function of the solution pH.

The formation of scale deposits, such as CaCO₃ causes fouling in the MSF distillers which has previously been studied by many researchers. A great amount of work has been carried out and more is yet to come in order to fully understand the role of various components and their interaction including the effectiveness of scale control techniques. The deposits may serve as an adsorbing film raising the speed of the loss of crystals or promoting the formation of scale deposits and therefore further adhesion on the wall surfaces of the MSF distillers and other process plant equipment leading to deterioration in the performance and efficiency of the whole desalination plant.

This paper shows direct quantification of the adhesion forces between CaCO₃ crystals and different process equipment surfaces under different conditions. This was carried out using an atomic force microscope (AFM) with an attached CaCO₃ crystal as a colloid probe to bring the CaCO₃ directly into and out of contact with the surfaces and measuring the resultant adhesion. This involved using surfaces different grades of roughness and carrying out measurements in synthetic sea water solutions of differing ionic strengths as well as with real seawater samples. Furthermore, the effect on measured adhesion of adding anti-scalant to the solutions was examined.     

Comparative economics of current and advanced desalting systems

A comparative investigation of the economics of desalting based on current and projected technology has been made. Current operating cost of various plant types operating in Israel are reported. These costs range from less than $.4/m³ for membrane plants desalting brackish water to more than three times as much for thermal plants desalting seawater. For new systems, two plant sizes were evaluated: 4,000 m³/day plants applying current technology and 100,000 m³/day plants applying projected technology. The water costs obtained for the various plant types and applied economic parameters, especially energy prices, range between $.2/m³ and $.6/m³ for brackish water desalting and from $.5/m³ to $2.4/m³ for seawater desalting.     

Reverse osmosis to achieve water control and recycle

A 648,000 GPD reverse osmosis (RO) facility at ERDA's Rocky Flats Plant near Golden, Colorado will convert tertiary sewage plant effluent for recycle as cooling tower makeup to reduce external water demand and achieve “zero discharge” off-site of tertiary sewage effluent.

Design parameters for the facility, determined by three years of pilot plant testing, include 98% feedwater recovery, 100 ppm T.D.S. product water, and minimum brine production for evaporation to dryness.

Pretreatment consists of RO feed attenuation in a large pond, chlorination, sand filtration, softening, diatomaceous earth filtration, feed-water heating and pH adjustment. The RO plant will have three 150 GPM trains, each with a combination of HFF modules producing about 90% of the permeate, followed by SW modules producing the final 10%. Permeate from the SW modules can be combined with permeate from the HFF modules or returned to the RO feed stream.

Unique design considerations include heating the 40–70°F fee to 77°F by means of heat recovery from the permeate and supplemental steam heating, recycling of pretreatment backwash streams wherever possible to reduce the volume of brine, and precautions to avoid silica scaling of the modules.