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Seawater intakes for desalination plants
Abstract
The seawater intake has to ensure sufficient seawater in terms of quantity and quality independently from the type of desalination plant (RO, MED, MSF) installed downstream. The best seawater quality can be reached by beach wells, but in these cases the amount of water which can be extracted from each well is limited by the earth formation, and therefore the amount of water available by beach wells is very often far below the demand of the desalination plant. In these cases the developer has the choice between (1) an intake from deep seawater with the advantage to have less polluted seawater and the disadvantage of high investment cost which normally limits this type of seawater intake to 20,000 m³/h; (2) open seawater intakes with the advantage of low investment cost but the disadvantage of biologically more active water which requires more efforts to treat the seawater. Offshore seawater intakes require a submerged pre-screening device minimizing the amount of sand sucked into the pipeline and ensuring that no particles able to damage or block the pump can enter. A description with pros and cons of the different available pre-screening devices will be given in the presentation, with special consideration of how the different types influence the total project cost. Open seawater intakes have to handle much higher amounts of coarse debris as well as micro organisms. The different kinds of available open seawater intakes will be presented in the presentation as well, demonstrating how efficiently and economically the different intake types fulfil this requirement.
... As an important part of a desalination plant, seawater intake ensures that sufficient, continuous, and suitable raw water is provided throughout the life cycle of the plant. The selection of a water intake location has important impacts on the investment in the seawater desalination plant, water production cost, stable operation of the system, and ecological environment (KRESHMAN, 1985;Morton et al., 1996;Gille, 2003;Andrianne and Ftlix, 2004;Tsiourtis, 2008;Darwish et al., 2016;Shahabi et al., 2017;Missimer and Maliva, 2018;Al-Kaabi and Mackey, 2019;Aydin and Sarptas, 2019). The water intake methods of seawater desalination include indirect water intake, such as beach well and seabed filtration water intake, shallow water intakes, such as direct water intake on the shore and artesian open channel water intake, and deep-sea water intake, of which shallow water intake is the most widely used (Gille, 2003;Lin et al., 2021). ...
... The selection of a water intake location has important impacts on the investment in the seawater desalination plant, water production cost, stable operation of the system, and ecological environment (KRESHMAN, 1985;Morton et al., 1996;Gille, 2003;Andrianne and Ftlix, 2004;Tsiourtis, 2008;Darwish et al., 2016;Shahabi et al., 2017;Missimer and Maliva, 2018;Al-Kaabi and Mackey, 2019;Aydin and Sarptas, 2019). The water intake methods of seawater desalination include indirect water intake, such as beach well and seabed filtration water intake, shallow water intakes, such as direct water intake on the shore and artesian open channel water intake, and deep-sea water intake, of which shallow water intake is the most widely used (Gille, 2003;Lin et al., 2021). ...
... 2) Water depth condition. To ensure that the water intake at a seawater desalination plant is effective, a certain depth criterion must be met (Gille, 2003). Generally, sea areas with water depths greater than 2 m at the lowest tide are suitable for the construction of desalination projects of various scales. ...
Seawater desalination water intake site selection has an important impact on the investment, water production cost, stable operation, and safety of seawater desalination plants. Site selection is affected by many factors, such as the natural geography, ecological environment, and social economy of coastal zones; some constraints can be directly identified as unsuitable areas for these construction projects. For the shallow water intake method of seawater desalination, this study selects suitability evaluation indicators for seawater desalination water intake site selection from the three influencing factors of basic geography, water environment, and industrial development and constructs a suitability evaluation model based on the multifactor spatial overlay analysis of the Geographic Information System platform. This model carries out a quantitative suitability evaluation of the seawater desalination water intake site selection and realizes the suitable spatial zoning for spatially selecting the water intake, thus forming a scientific, quantitative, and spatial suitability evaluation system for this process. The evaluation method was applied in the Rongcheng city offshore area of China and analyzed. The evaluation results showed that the suitable areas for seawater desalination water intake site selection comprised 304.8 square kilometers, which were mainly distributed in the offshore areas in northern Rongcheng city and near the coastline areas of its central and southern regions. The unsuitable areas covered 292.4 square kilometers, mainly distributed in the marine ecological red line areas and the coastal aquaculture areas of Rongcheng city. The evaluation results met the site selection needs of the seawater desalination water intake project in Rongcheng city. This study improves upon the existing method of seawater desalination intake site selection at the theoretical and technical levels and provides a scientific basis for the location selection and planning for water intake in large spatial ranges of coastal waters.
... At present, desalination plants can use seawater, urban or industrial wastewater, or brackish water from aquifers. Moreover, seawater may be obtained from open near-surface intakes on the shoreline, from submerged intakes bringing in deeper water layers, or from intakes under the seafloor that draw seawater through permeable strata [41][42][43][44]. The latter intakes may be constructed as vertical or radial beach wells, infiltration galleries/beds, or horizontally drilled drains. ...
... Open intakes are the simplest way to provide sufficient seawater flow for large desalination plants; however, the presence of organic matter, microorganisms, and suspended solids requires employing aggressive pretreatment, adding chemical additives, and frequent cleaning of filters and membranes. If this intake option cannot be avoided, remedial strategies, such as using a screen or coarse filter, reducing intake water velocity, or placing the intake system at a certain depth beneath the water surface, should be used [41,42]. ...
... Consequently, to minimize the environmental impacts of brine discharges, obtaining seawater through permeable strata (i.e., beach wells, infiltration galleries, or directed drilling of horizontal drains; Fig. 1) is preferable. This is because such feed water is prefiltered, thereby optimizing pretreatment processes and reducing pollutant concentrations of the subsequent reject water [8,42,[45][46][47]. These kinds of intakes also reduce impingement and entrainment of marine organisms [3]. ...
Seawater desalination is a potential solution for addressing water shortages. The number of desalination plants projected and constructed in some regions has substantially increased in recent decades. However, desalination process poses some undesirable environmental impacts in terms of energy consumption, land use, and seawater intake, but particularly the most significant impacts are related with effluent disposal and discharge. Thus, the challenge for the desalination industry is to produce new water resources without increasing pressure on the marine environment. The effluent characteristics depend on the feed water and desalination technology used. Negative environmental impacts of brine discharge from a desalination plant can be minimized by appropriate planning. The countermeasures should vary depending on plant size and type, the biological communities in the discharge area, and the area’s hydrogeological features. This study overviews the available information about minimizing the harmful effects of the desalination industry. It highlights that an appropriate discharge location must be selected and the mixing of brine with ambient seawater must be maximized to reduce the environmental impacts of brine. Moreover, it is helpful to establish a carefully designed environmental monitoring program to assess brine plume distribution over time while monitoring biota. Frequent environmental monitoring programs of desalination plants normally show that the impacts are small, localized, and unimportant; however, significant effects have been detected in some cases. In these cases, effects can be mitigated by introducing devices that increase the mixing of effluent and surrounding seawater or/and by diluting the effluent before discharge.
... For large plants-with production capacities of more than 200,000 m 3 /day-this is practically the only viable option from an economic point of view (Voutchkov 2004). In other situations, the most suitable intake solution is by means of a water intake works in the coastal aquifer, and this is the least costly solution in the medium-long term, provided of course, that there is an aquifer along the coastal strip that possesses the necessary characteristics (Gille 2003). There is always a hybrid option, namely, for part of the water to be abstracted via headworks in the coastal aquifer, supplemented with a direct seawater intake in times of higher demand. ...
... This improvement in water quality reduces the final desalination costs significantly (by 5-30%) ( Missimer et al. 2013). Fig. 1 Scheme showing typical pre-treatment processes for an SWRO plant using direct or subsurface intake (SW seawater, RO reverse osmosis) Small-and medium-sized desalination plants (< 200,000 m 3 /year) are fed from collection wells tapping coastal aquifers, below the fresh water-seawater contact (Gille 2003;Pulido-Bosch et al. 2002;Rodríguez-Estrella and Pulido-Bosch 2009). The various phases of work need to be carefully designed to avoid seasonal operational problems. ...
Many coastal areas of our planet receive only scarce precipitation, and have limited or often non-existent surface water resources. Over the last four decades, the intensive agriculture and tourism along the Spanish mediterranean coast have led to a large increase in water demand. The economic development of this, the most arid stretch of the Mediterranean coast has been dependent on the availability of good quality groundwater. Desalination in Spain has contributed to the progress and development of these areas, being considered as the solution to this increased demand. Along the Spanish mediterranean coast, around 30 desalination plants of medium–high capacity, between 20,000 and 125,000 m³/day, have been built over the last 25 years, and there are several plants in the planning stage, to be constructed in the near future. In addition, 100 small plants desalinate brackish water. Desalination plants are usually supplied from coastal boreholes if there is a coastal aquifer with hydraulic connection to the sea. Nevertheless, the water to desalinate in other cases comes from evaporitic aquifers or even fossil water. Regarding the water intake systems, horizontal directional drilling can give good results, not to mention a number of other sophisticated and curious designs, each with their particular advantages and drawbacks. This paper describes the main problems and also the benefits concerning water intake systems to some desalination plants along the Spanish mediterranean coast.
... Therefore, coastal facilities, such as seawater desalination technology, are increasing as supplementary or primary water sources for various countries. Most of the desalination activity has always been concentrated in the Persian Gulf, but they are emerging and becoming prominent in other areas, such as the Mediterranean Sea, the coastal waters of California, China, and Australia (Gille 2003). The Persian Gulf is surrounded by arid desert land, particularly in its southern part. ...
Seawater desalination is increasing due to the global water crisis, and velocity caps are widely used at intake entrances to protect marine life and facilitate the required flow. Despite various investigations of seawater intake, a lack of precise research on the discharge coefficient of these structures is evident. The discharge characteristics of seawater intake are investigated both analytically and experimentally. Results show that the circle velocity caps have higher capacity than square ones, about 2% to 3.5%. Also, the Froude number of approach flow and the area of the velocity caps are the two parameters with the greatest impact on discharge coefficients. However, the height of caps and the number of separator blades have the least effect. Furthermore, some equations of discharge coefficients are developed based on machine-learning techniques with appropriate accuracy. Additionally, the Taguchi method, evaluated as an economical approach, significantly reduces the number of tests while the accuracy of results decreases. Nomenclature ANOVA Analysis of Variance B Main channel width, (m) DoE Design of Experiment h Height of the velocity cap, (m) MTs Model trees Re Reynolds number V m Velocity in main channel, (m/s) V in Velocity in intake, (m/s) Y m Water depth in main channel, (m) ρ Mass density, (kg/m 3) A Area of velocity cap (m 2) C d Discharge coefficient D i Diameter of the orifice, (m) Fr Froude number in the main channel P water pressure, (N/m 2) H Head of water above the centerline of the orifice, (m) N Number of blades Q in Discharge through the intake, (m 3 /s) Q m Discharge in the main channel, (m 3 /s) w The distance of opening of intake from the channel bed, (m)
... Based on current practical operations, it is assumed that the distance between the installation and the seawater intake is equal to 3500 m. The pressure drop for seawater transport is estimated to be 3.2 bar (Gille, 2003). The electricity consumption for the pumps is estimated as presented in the previous section. ...
This study proposes a new seawater desalination process using concentrated solar energy. Compared with conventional desalination technologies, the proposed process produces tap water with high energy efficiency and a lower environmental impact.
The proposed process is based on a new type of solar boiler using solar energy concentrated via a “beam-down” optical system. To improve the productivity, the steam produced is used to feed an adapted multiple-effect distillation (MED) system. A complete process model from seawater and sun to tap water is proposed, coupling an in-house Python program for the solar boiler component and ProSim software for the MED component. Ancillary calculations concerning the pretreatment, post-treatment, and sizing of the components are performed using a spreadsheet program. The environmental impacts of the tap water production by the proposed system are evaluated using the life cycle assessment method.
The theoretical feasibility of the proposed process is demonstrated by modeling a reference case, with an estimated annual productivity of 10,000 m³ of tap water. According to the calculation, the energy performance is estimated at 1.57 kWh of electricity and 117.7 kWh of solar energy per cubic meter of tap water produced. An estimated land area of 3845 m² is required for the solar field. The life cycle assessment indicates that the performance of the proposed process is significantly improved compared with conventional MED, with an 84% reduction in the total impact according to the ReCiPe endpoint method. In addition, the proposed system displays a competitive environmental performance compared with reverse osmosis. The emissions of the new process are estimated at 2.36 kg CO2-eq per cubic meter of tap water produced versus 3.67 kg CO2-eq and 2.97 kg CO2-eq for low- and high-performance reverse osmosis, respectively.
... The extracted feedwater at this depth has lesser quality due to the presence of organic content, suspended solids, and photosynthetic microbes. In deep-water intake, the seawater is obtained at depths of more than 35 m; thus, such water is generally of higher quality [48]. In general, an offshore intake terminal that extends farther and deeper into the ocean may help to avoid regions in which biomass may accumulate, as well as the seawater's photic zone, where HAB organisms tend to grow [7]. ...
Arid countries throughout the world are massively reliant on seawater desalination for their supply of drinking and municipal water. Harmful algal bloom (HABs), frequently referred to as 'red tides' due to their vibrant colors are predicted to grow in recurrence and distribution in the coming years where numerous desalination facilities will become increasingly susceptible to damage or shutdown during HAB events. Such a phenomenon, one of the operational challenges facing the industry, can cause significant operational issues that result in increased chemical consumption , increased membrane fouling rates, and in extreme cases, a plant to be taken off-line due to the high biomass of microalgae and a variety of substances that some of these algae produce. Hence, understanding the HABs' nature, their challenges, and ways in which they can be monitored, treated, and mitigated will allow engineers and operators to address HAB hazards and maintain the integrity of new and existing desalination facilities.
... The intake mouth is normally located at least 500 m away from the shore to take care of low tides as well as to draw water from a depth of about 5 m or more from the surface to ensure the quality. Deep seawater intake is viable in most instances for capacities equal to or higher than 500,000 m 3 /day (Gille, 2003). ...
The present water and energy crisis facing the world at
large with the ever-growing population is one that
demands careful attention by the research community.
The treatment of seawater and brackish water by
integrating renewable energy technologies into desalination
processes holds a promising future for availing
freshwater in areas of water scarcity across the globe.
This chapter captures the different desalination technologies
(such as thermal and membrane technologies) and
different renewable energy technologies (like solar, wind
and geothermal energies) that can be integrated into the
process of water treatment for salt removal. Utilizing
renewable energy technologies in desalination systems
will serve as alternative where grid electricity is not
available, reduce environmental pollution and cost.
... The intake mouth is normally located at least 500 m away from the shore to take care of low tides as well as to draw water from a depth of about 5 m or more from the surface to ensure the quality. Deep seawater intake is viable in most instances for capacities equal to or higher than 500,000 m 3 /day (Gille, 2003). ...
The present water and energy crisis facing the world at large with the ever-growing population is one that demands careful attention by the research community. The treatment of seawater and brackish water by integrating renewable energy technologies into desalination processes holds a promising future for availing freshwater in areas of water scarcity across the globe. This chapter captures the different desalination technologies (such as thermal and membrane technologies) and different renewable energy technologies (like solar, wind and geothermal energies) that can be integrated into the process of water treatment for salt removal. Utilizing renewable energy technologies in desalination systems will serve as alternative where grid electricity is not available, reduce environmental pollution and cost.
... The intake mouth is normally located at least 500 m away from the shore to take care of low tides as well as to draw water from a depth of about 5 m or more from the surface to ensure the quality. Deep seawater intake is viable in most instances for capacities equal to or higher than 500,000 m 3 /day (Gille, 2003). ...
In the last few decades, desalination processes have played a crucial role in meeting the growing demand for water. Desalination process consists of raw water, desalination device, product water and energy. Among the desalination processes, membrane-based reverse osmosis desalination has become popular because of its characteristics such as ambient temperature operation, low specific energy consumption, modularity, and tolerance to intermittent operation. The chapter discusses the mechanism of desalination using preferential sorption-capillary flow model. A brief description of membrane preparation techniques is followed by a discussion on the merits and demerits of the membrane element configuration based on tubular and flat sheet geometries. The various steps involved in the design of RO desalination plants are indicated with the reason for each operation including pretreatment involving fouling and scaling control, design considerations for fixing the recovery, the arrangement of modules including the concept of stages and passes. The monitoring methods including silt density index are indicated. The need for post treatment and the methods used are discussed including control of boron concentration in the permeate. The developments of various types of pumps and the corresponding energy recovery devices over the years resulting in the reduction of specific energy consumption to less than 3 kWh/m³ are highlighted. While discussing inland brackish water desalination, it is indicated that the design strategy should focus on resource conservation and sustainability rather than minimisation of cost. The specific energy consumption of reverse osmosis desalination plants nowadays is around or less than about 3 kWh/m³ and further improvement in this direction will be only marginal. Major improvements are expected in the development of membranes that resist fouling.
... The intake mouth is normally located at least 500 m away from the shore to take care of low tides as well as to draw water from a depth of about 5 m or more from the surface to ensure the quality. Deep seawater intake is viable in most instances for capacities equal to or higher than 500,000 m 3 /day (Gille, 2003). ...
Several investigations have established that due to population expansion and land use, fresh water scarcity has increased tremendously placing immense burden on desalination process as the major alternative remedy to freshwater supply. The increase in problems related to energy across the globe due to exhaustibility of fossil fuels. Hence, there is a need to search for other sources of energy to meet up with the growing demand. Globally, the existing methods of desalination are not cost effective; hence, scientists are searching for alternative ways to reduce the financial burden in the setup of water desalination techniques. One of the suggested areas is in the utilization of microorganisms. One of the suggested methods is in the area of energy conservation, when using water to produce energy via utilization or engaging the use microbial desalination. Therefore, this chapter intends to provide comprehensive information on the application of microorganisms for the water desalination. Several types of microorganisms that could be applied for water desalination were also highlighted. The modes of action through which they exhibited their action were also discussed. The principles involved in the process of desalination were also elucidated.
... The intake mouth is normally located at least 500 m away from the shore to take care of low tides as well as to draw water from a depth of about 5 m or more from the surface to ensure the quality. Deep seawater intake is viable in most instances for capacities equal to or higher than 500,000 m 3 /day (Gille, 2003). ...
... The use of beach wells as a pretreatment strategy for the treatment of seawater is attractive because of the potentially lower operations and maintenance cost as compared to other pretreatment options, including media or cartridge filtration. The use of traditional vertical beach wells, however, is limited to smaller systems due to the large number of wells that would need to be drilled in order to fulfill the pretreatment needs and are an economical alternative to open sea intakes for desalination plants with capacities less than 20,000 m 3 /d only [9]. ...
Fresh water production by desalination of seawater is an expensive affair. During the last few years, seawater reverse osmosis (SWRO) desalination technology has gone through a remarkable transformation and gained widespread acceptance, which is evident from the increased share of SWRO. Typical SWRO desalination consists of four major components: an intake; a pre-treatment system; a high-pressure pumping system; and a membrane module. The performance of the entire system is dependent upon the proper design and operation of each component and assessed by its ability to produce required quantity of water with acceptable quality at lowest possible cost. Recent advances in seawater reverse osmosis (RO) that has allowed a drastic reduction in the cost of desalinated water include the application of highly efficient energy recovery devices (ERDs) and the utilization of advanced RO membranes. However, fouling and membrane degradation are some of the major challenges faced by the RO systems, which need to be carefully addressed. The chapter discusses various parameters, which are typically used to assess RO desalination plant performance. It will also cover the challenges faced by SWRO plants and measures adopted to address these challenges to maintain the best plant performance.
... This example is developed for a particular type of popular disk filter (SpinKlin, manufactured by Arkal, Israeldsee Fig. 5.10). These filters have found applications on a number of desalination plants with membrane pretreatment such as the 300,000 m 3 /day (80 MGD A number of other manufacturers provide similar equipment, and the specific unit sizes and design criteria vary (Gille, 2003). Equipment manufacturer should be consulted to identify the microscreen system design criteria for a specific desalination project. ...
... This example is developed for a particular type of popular disk filter (SpinKlin, manufactured by Arkal, Israeldsee Fig. 5.10). These filters have found applications on a number of desalination plants with membrane pretreatment such as the 300,000 m 3 /day (80 MGD A number of other manufacturers provide similar equipment, and the specific unit sizes and design criteria vary (Gille, 2003). Equipment manufacturer should be consulted to identify the microscreen system design criteria for a specific desalination project. ...
... This example is developed for a particular type of popular disk filter (SpinKlin, manufactured by Arkal, Israeldsee Fig. 5.10). These filters have found applications on a number of desalination plants with membrane pretreatment such as the 300,000 m 3 /day (80 MGD A number of other manufacturers provide similar equipment, and the specific unit sizes and design criteria vary (Gille, 2003). Equipment manufacturer should be consulted to identify the microscreen system design criteria for a specific desalination project. ...
... A number of other manufacturers provide similar equipment, and the specific unit sizes and design criteria vary (Gille, 2003). Equipment manufacturer should be consulted to identify the microscreen system design criteria for a specific desalination project. ...
... Most large-capacity seawater reverse osmosis (SWRO) desalination facilities use conventional surface-water intake systems, such as a velocity cap attached to a large diameter pipeline which conveys raw seawater to an onshore screenhouse and a series of other pretreatment processes (Gille 2003;Missimer 2009;Chap. 1). ...
Passive screen intake systems provide a higher degree of reduction in impingement and entrainment compared to open-ocean intake structures, such as channel and velocity cap intake systems. The system consists of a wedgewire screen structure with a conveyance pipeline to the plant facility and a pumping station. Commonly, the screen structure contains a semi-automated cleaning system that uses bursts of compressed air. Passive screen intake systems exclude a large part of the marine biota by using a relatively small screen aperture and a low inflow velocity. Screen slot aperture is commonly less than 3 mm and depends on environmental regulations pertaining to the specific site location. The range in design intake velocities through the screen ranges from 10 to 15 cm/s, again depending on local regulations. The current motion across the screen structure also sweeps small organisms off the screen and helps exclude them from entrainment into the inflowing water. The degree of environmental impact on entrainment of ichthyoplankton is greatly dependent on the design of the passive intake system and the current velocity. Some environmental impacts occur when constructing the connecting pipeline across or beneath the seabed and surface zone of the shoreline. Passive screen intake systems can provide a high-capacity SWRO plant with the required feed water. However, when the passive screens are located offshore, there is some complexity in the maintenance of the screens that can limit use of the technology.
... Another concern is the effect of brackish/saline groundwater abstraction on the quality of the fresh groundwater. In addition, deep beach wells might be costly, compared to surface water takes, if drilling is needed to large depths ( Gille 2003). Other problems of beach wells could be those related to well installations and maintenance such as screen corrosion or boreholes collapse. ...
Qatar is an arid country, with limited water resources. The country relies on desalination of seawater to meet the increasing water demand for municipal and industrial needs, while the agricultural sector uses the precious fresh groundwater. Groundwater underneath Qatar is mostly saline or brackish with small lenses of fresh water in the northern part of the country. Brackish groundwater in Qatar has a Total Dissolved Solids of less than 10,000 mg/l, compared to seawater, which is 35,000 mg/l. Using brackish and saline groundwater for desalination via beach wells is less costly and more environmental friendly than direct sea water intake, which is being used in Qatar. The main challenge facing beach wells usage is their questionable capacity to provide enough quantities for desalination plants. This study investigates the optimal location and the maximum yield of beach wells in Qatar, using Sea Water Intrusion model (SWI2), coupled with MODFLOW. Model results show the maximum yield of wells at a depth of 100 m is 16,000 m3 per km2. This quantity is good enough for a medium size reverse osmosis plant. Based on hydrogeological settings, the proposed location for the beach wells is near Al-Khor town and to the north of it.
... 36 Even with very narrow mixing zones, seawater will likely have to be collected at least 1 km away from the facility, as in desalination plants, to avoid anthropogenic contaminants. [106][107][108] Thus, the energy for pumping raw water from the ocean and rivers will likely range from 0.02-0.05 kW h m À3 . ...
The enormous potential of harvesting energy from salinity gradients has been discussed for decades, and pressure-retarded osmosis (PRO) is being increasingly investigated as a method to extract this energy. Despite advancements in membranes and system components, questions still remain regarding the overall viability of the PRO process. Here, we review PRO focusing on the net energy extractable and the ultimate feasibility of the most widely explored configurations. We define the maximum energy that can be obtained from the process, quantify losses and energetic costs that will reduce the net extractable energy, and explain how membrane modules can be improved. We then explore the potential of three configurations of PRO: systems designed to control mixing where rivers meet the sea, power plants that utilize the high concentration gradients available from hypersaline solutions, and PRO systems incorporated into reverse osmosis desalination plants to reduce electricity requirements. We conclude by considering the overall outlook of the process and identifying the most pressing challenges for future research.
... It has been reported that a well intake system at Sur plant in Oman plays a vital role in improving the water quality significantly by removing all of the algae, most of the bacteria, and a significant percentage of the TEP, and organic substances from the feedwater [10,11]. Similarly, the use of a deep ocean intake has been reported to provide better feedwater quality compared to the shallow open-ocean intakes due to lower biological productivity in deep water compared to shallow water [12]. Therefore, the risk of biofouling caused by TEP can be reduced by construction and operation of the appropriate intake type and pretreatment process. ...
Transparent expolymer particles (TEP) are believed to be a key organic compound that leads to membrane biofouling in SWRO systems. The sticky nature, high surface reactivity and micro-gel character of TEP play a major role in a membrane fouling, because deposition on the membrane surface acts as culture media for bacterial growth and as a depositional substrate. In turn, the TEP contributes to biofilm formation and membrane clogging with time. The removal of TEP at early stages of the desalination process is important to avoid any adverse effect on membrane operation. The intake system can play a significant role in TEP reduction. In this research, the impact of intake systems on TEP reduction was investigated. Two RO desalination plants in Jeddah, Saudi Arabia were studied. One of the SWRO desalination plants uses a deep-open ocean intake (9 meter depth) and the other uses four wells. Water samples were collected from the seawater surface, the intake, and after the pre-treatment processes. The efficiency of TEP removal by each treatment stage was evaluated. Organic compounds, bacterial and algae concentrations were determined for both sites. The results revealed that the use of well intake system reduced the TEP significantly compared to the raw seawater. By comparing the TEP concentrations in the surface seawater to those determined in the deep intake, it was found that the particulate TEP concentration was 70% lower in the deep intake, but colloidal TEP concentrations were much higher. These data provide insight into improved design of SWRO intake systems that take into consideration potential TEP occurrence and reduction scenarios.
... It has been suggested that seawater to be used as feed water for seawater reverse osmosis (SWRO) facilities improves with depth because of lower primary productivity caused by light absorbance and a lower concentration of suspended sediment in the water column (Gille 2003;Cartier and Corsin 2007). Therefore, some have concluded that " deep water " intakes can produce a higher quality feed water that has potential to reduce the pretreatment requirements and to lower the cost of SWRO desalination. ...
It has been suggested that using a deep open-ocean intake would improve feed water quality and would reduce the cost of SWRO water treatment by lessening membrane biofouling potential. The feasibility of developing deep intake systems for large-capacity SWRO plants located on the Red Sea was assessed. A bathymetric survey showed that the continental shelf along the Red Sea nearshore has a nearly vertical drop into deep water beginning at depths between 20 and 40 m. The vertical nature of the bathymetric profile and the issue of active seismicity make the development of a SWRO intake at a depth of greater than 100 m below surface a very risky venture along the Red Sea coast of Saudi Arabia. Detailed assessment of temperature and salinity with depth show a decrease of 5 °C and an increase of 1100 mg/L respectively over 90 m. Concentrations of algae, bacteria, total organic carbon, particulate and colloidal TEP, and the biopolymer fraction of natural organic carbon all showed declines in concentration. However, the general water quality improvements in reduced concentrations of organic matter were insufficient to reduce the intensity of pretreatment for an SWRO system. Overall, the Red Sea does not appear to be a good location for the use of deep SWRO intakes because of the structural risk of installing and maintaining an intake at near or below 100 m of water depth.
... The best location of the intake structure in terms of source water quality is at ocean floor depths of 30 meters or higher (deep water intake). Debris load in the source water and algal content during red tides at such depths are typically 20 times lower than that in the surface water or the shallow waters of the tidally influenced nearshore area (2). It is also fluctuate between summer and winter due to occasional storms. ...
Introduction Seawater Desalination Plant Configuration Water Production Costs Future Trends Conclusion References
... Physical pretreatment of the source water is often limited to only intake screening to remove coarse debris in order to prevent equipment erosion by suspended solids and prevent equipment from blocking. MSF is very robust with the allowable particle size for sea-water entering the tubes varying between 5 and 15 mm [38]. On the other hand, MED needs finer filtration, with the allowable particle size for sea-water going through the spray nozzles <0.5 mm. ...
Most marine algal species are beneficial, not harmful, as algae are the foundation of the food chain and provide the bulk of Earth’s oxygen through photosynthesis. Mankind also commercially harvests algae for a myriad of uses in the food, pharmaceutical and medical industries to name but a few. However, the sudden prolific growth in algal cell numbers, referred to as harmful algal blooms (HAB), can constitute an operational and/or health risk to desalination plants, threatening water supply security and safety, respectively. The excessive biomass and organics associated with HAB can lead to the closure of desalination plants, particularly sea-water reverse osmosis (SWRO) plants due to overloading of the pretreatment facilities or potential irreversible RO membrane fouling. While these impacts are well documented, the removal of potent marine algal toxins, which represent a potential public health risk if not removed by desalination plant processes, is not well researched. The incidence of HAB has escalated throughout the world with algal specialists reporting that “compared to 30 years ago, we have more algal toxins, more toxic algal species and more areas affected”. Therefore, this paper examines the major marine algal toxins that may be present at the intake of a desalination plant, their fate in thermal and SWRO desalination plant processes and the potential residual risk to public health in desalinated drinking water. Toxin removal in the various process steps is predicted based on the physico-chemical properties of these marine toxins. Results from bench and pilot studies investigating the efficacy of barriers in the desalination technology processes to remove cell-bound toxins and extracellular toxins from ruptured algal cells are also reviewed.
... It has been reported that a well intake system at Sur plant in Oman plays a vital role in improving the water quality significantly by removing all of the algae, most of the bacteria, and a significant percentage of the TEP, and organic substances from the feedwater [10,11]. Similarly, the use of a deep ocean intake has been reported to provide better feedwater quality compared to the shallow open-ocean intakes due to lower biological productivity in deep water compared to shallow water [12]. Therefore, the risk of biofouling caused by TEP can be reduced by construction and operation of the appropriate intake type and pretreatment process. ...
... Due to lack of data and ability to quantify the rates of impingement and entrainment, the associated environmental impacts are often overlooked even though they may represent the most significant and direct effects from desalination (Pankratz 2004). The threat of intake pipes on the marine environment is highly variable and dependent on the technology employed for seawater intake; how far the intake pipe is from the shore as well whether the intake pipes are open sea or subsurface (Pankratz 2004;Gille 2003). ...
The Gulf Cooperation Council (GCC) of Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates (UAE) inhabits of one of the most water-scarce regions in the world, once comprised small impoverished desert principalities. However, since the 1970s, the GCC has witnessed rapid population growth and economic develop-ment, brought on by sharp increases in oil revenues. Popula-tion growth coupled with increased urbanization, industriali-zation, and agricultural output has placed tremendous pressure on the region's scarce groundwater resources. GCC countries are all using hundreds to thousands times more water than sustainable recharge would allow. Their water footprints, among the highest in the world, are sustained by unconven-tional sources of water such as desalination, wastewater reuse, and the import of "virtual" water via agricultural goods. This paper analyzes the current state of water in the GCC using a water–energy–food (WEF) nexus approach. The paper dis-cusses various proposals for meeting future water needs in the GCC such as renewable energy-powered desalination and foreign direct investment in agricultural land and addresses the various tradeoffs involved.
... In general, two types of seawater intake systems are available, the open intake and the beach-well method. The open intake system has the advantage of low investment cost but requires more pre-treatment of the raw water before it is fed to an RO system (which requires a Silt Density Index-SDI of <3.5); whereas the beach well system has the advantage of less polluted seawater but higher investment cost [55]. Since the intake system and pre-treatment system are inter-dependent, a simple correlation to estimate the combined capital cost of the intake and pre-treatment system is used here [52,56] (10) where E N is the total number of RO elements. ...
This paper focuses on a Hybrid Process that uses feed salinity dilution and osmotic power recovery from Pressure Retarded Osmosis (PRO) to achieve higher overall water recovery. This reduces the energy consumption and capital costs of conventional seawater desalination and water reuse processes. The Hybrid Process increases the amount of water recovered from the current 66.7% for conventional seawater desalination and water reuse processes to a potential 80% through the use of reclaimed water brine as an impaired water source. A reduction of up to 23% in energy consumption is projected via the Hybrid Process. The attractiveness is amplified by potential capital cost savings ranging from 8.7%-20% compared to conventional designs of seawater desalination plants. A decision matrix in the form of a customizable scorecard is introduced for evaluating a Hybrid Process based on the importance of land space, capital costs, energy consumption and membrane fouling. This study provides a new perspective, looking at processes not as individual systems but as a whole utilizing strategic co-location to unlock the synergies available in the water-energy nexus for more sustainable desalination.
... It must ensure a sufficient volume of water and, at the same time, minimize the suspended solid contents and the presence of pollutants and biological matter. Indirect seawater intake systems such as beach wells offer advantages because beach sand acts as a filter reducing marine biological matter and other pollution sources (Gille, 2003). However, much care must be taken when designing the beach wells in order to ensure the adequate volume of seawater and to minimize the extraction of freshwater from coastal aquifers. ...
The Tordera Desalination Plant located in Blanes (NE Spain) has seawater intake through 10 beach wells located a few meters inland on the shoreline at the Tordera River Delta. Between October 2002 and October 2003, the extracted groundwater showed a decrease in conductivity, especially in the wells located in the northern area, prompting the present study. A multi-isotopic approach (δD, δ18OH2O, 3H, δ34SSO4, 87Sr/86Sr and 228Ra/226Ra) coupled with chemical data was applied in order to assess the origin of the water collected for the desalination plant and to quantify the extent of freshwater collection from the Tordera aquifer, when applicable. Three multi-piezometers located in the Tordera aquifer were also sampled in order to characterize the freshwater end-member. A seasonal survey was performed in order to assess the evolution of mixed freshwater-seawater intake. Tritium isotopes showed values ranging from 0.6 to 2.5TU indicating recent origin of the collected waters. This was further confirmed using radium isotopes (226Ra and 228Ra), as the 228Ra/226Ra activity ratio (AR) indicated a continuous input of seawater on a yearly time scale. The water extracted from the beach wells was at least 95% seawater, except for wells 8-10. The latter two were extracting up to 15% of freshwater from the Tordera aquifer system. From a methodological point of view, while δ34S of dissolved sulphate and the ratio 87Sr/86Sr are good tracers of seawater mixing with freshwaters, the isotopic composition of water (δD and δ18OH2O) and the Cl-/Br- ratio are conservative tracers that allow for quantifying the contribution of freshwater to the extracted water. Although slight variations linked to seasonality were observed in all wells during the 3-year study period (November 2003 to December 2006), wells 1 and 7 showed an increase in freshwater contribution from 4% to 11% and well 10 a decrease from 15% to 10% over this period.
This study aims to assess feedwater, brine, and drinking water quality related to eight full-scale Egyptian seawater desalination plants. Collected water quality records from plants on the Mediterranean and Red Seas were monthly analyzed to identify different physical, chemical, and biological parameters during 2022. Statistical analysis and water quality indices (WQIs) approaches were applied to evaluate the various water quality states based on the available international and Egyptian guidelines. Analyzed seawater quality properties showed compliance with the most operating permissible limits except for high concentrations of turbidity, fats, oils, and greases, total bacteria in one plant, and iron, manganese, and silica in another plant. The monthly measured Weighted Arithmetic WQI classified 71 % and 100 % of desalination plants as having “Excellent” water rank according to the standard limits of the World Health Organization and the Egyptian Water Quality Standard, respectively. However, 65 % and 52 % of desalination plants were projected into the “good” water quality rank based on the Canadian Council of Ministers of the Environment WQI for the same guidelines. The results indicate that the feed intake type and the location of a desalination plant can optimize its performance efficiency, minimize contamination sources, and mitigate the potential environmental impacts of brine.
Determining the optimal seawater intake types and is influenced by factors including location, geology, ecology, costs, regulations, and stakeholder input. Employing multicriteria analysis, this approach systematically evaluates factors through objective scoring, ensuring a methodical decision-making methodology. This analysis focuses on crafting a decision support interface that meticulously coordinates a range of vital factors to assess the viability of seawater intake locations both offshore and onshore. These factors encompass geological, geographical, hydrological, and hydrogeological conditions, as well as topographic and bathymetric data, water capacity, demand, environmental constraints, technical specifications, economic impacts, and local requirements. The cornerstone of our multicriteria analysis approach is the methodical organization of the gathered data within a structured Excel database. Concurrently, an interactive VBA-based interface is designed to extract insights from this integrated database. Stakeholders can evaluate potential sites based on predefined criteria, customize outcomes, and engage interactively based on preferences. The interface adapts to user selections, expertly guiding them toward the optimal intake type. This process is governed by rules in the VBA code and carefully defined constraints, ultimately providing a precise intake type via a comprehensive elimination and ranking process.
Microplastics (MPs) have gained increasing attention as an emerging contaminant in drinking water. However, there is no definitive conclusion on the deleterious effects of MPs on human health. Herein, we consider the potential threats of these anthropogenic particles that have been increasingly found in drinking water sources (DWSs) based on reviewing their occurrence and removal from a water treatment perspective. As revealed by 53 publications on MP presence in conventional DWSs, bulk sampling can better reflect the current knowledge on the pollution in DWSs; the median MP concentration in conventional water sources was 2.2 × 10³ items m⁻³ with the size of particles identified usually >50 μm. Next, the removal efficiency of MPs across multiple barriers in drinking water treatment plants was also elaborated. Almost all MPs (>10 μm) were removed after coagulation, sedimentation and filtration processes. For smaller MPs (>1 μm), removal rates of >80 % were typically observed. Two size-dependent threats associated with MPs in DWSs were identified: 1) the increased probability of the accumulation of potential pathogenic bacteria and the transmission of antibiotic resistance genes where larger MPs in DWSs may serve as important carriers; 2) the release of nanoplastics and dissolved organic carbon from the photodegradation process of MPs. Additionally, MPs in alternative DWSs were given special attention due to their potential to accumulate MPs. The review provides new information for practitioners and scientists alike with respect to the potential threats posed by MPs in DWSs.
Due to extremely high rates of evaporation and low precipitation in the Persian Gulf, discharges from desalination plants (DPs) can lead to ecological stresses by increasing water temperatures, salinities, and heavy metal concentrations, as well as decreasing dissolved oxygen levels. We discuss the potential ecological impacts of DPs on marine organisms and propose mitigating measures to reduce the problems induced by DPs discharges. The daily capacity of DPs in the Persian Gulf exceeds 11 million m3 d‐1, which is approximately half of global daily fresh‐water production; multi‐stage flash distillation (MSF) is the dominant desalinization process. Results from field and laboratory studies indicate that there are potentially serious and chronic threats to marine communities following exposure to DPs discharges, especially within the zoobenthos, echinodermata, seagrasses, and coral reefs. DP discharges can lead to decreases in sensitive species, plankton abundance, hard substrate epifauna, and growth rates of seagrasses. However, the broad applicability of any one of these impacts is currently hard to scale because of the limited number of studies that have been conducted to assess the ecological impacts of DP discharge on Persian Gulf organisms. Even so, available data suggest that appropriately sited, designed, and operated DPs combined with current developments in impingement and entrainment reduction technology can mitigate many of negative environmental impacts of DPs.
Water Supply has been the most comprehensive guide to the design, construction and operation of water supply systems for more than 40 years. The combined experience of its authors make it an unparalleled resource for professionals and students alike. This new sixth edition has been fully updated to reflect the latest WHO, European, UK and US standards, including the European Water Framework Directive. The structure of the book has been changed to give increased emphasis to environmental aspects of water supply, in particular the critical issue of wastage reduction and conservation of supplies. Written for both the professionals and students, this book is essential reading for anyone working in water engineering. .Comprehensive coverage of all aspects of public water supply and treatment .Details of US, European and WHO standards and practice .Based on decades of practical professional experience. © 2009 D. D. Ratnayaka, M. J. Brandt and K. M. Johnson. Published by Elsevier Ltd All rights reserved.
97% of water on earth exists in the form of seawater. Therefore, the use of marine resources is one of the most important research issues at present. The use of seawater is expanding in various fields (seawater desalination, cooling water for nuclear power plants, deep seawater utilization, etc.). Seawater intake systems utilizing sand filters in order to take in clean seawater are being actively employed. For the intake pipe used in this system, assuring equal intake flows through the respective holes is very important to improve the efficiency of the intake and filtering process. In this study, we analyzed the efficiency of the dual structure perforated pipe used in the seawater intake system using 3D numerical simulations and the inflow rate according to the gap of the up holes. In the case of decreasing gaps in the up holes toward the pipe end, the variation of the total inflow rate was small in comparison with the other cases. However, the standard deviation of the inflow rate through the up holes was the lowest in this case. Also, stable flow occurred, which can improve the efficiency of the intake process. In the future, a sensitivity analysis of the various conditions should be performed based on the results of this study, in order to determine the factors influencing the efficiency, which can then be utilized to derive optimal designs suitable for specific environments.
This chapter describes the principles behind the design and operation of intakes on upland streams and off rivers, canals, reservoirs, estuaries and the sea. Separate sections cover intake location, hydrology, water quality, pollution protection, screen design, sediment transport and exclusion, fish behaviour, dealing with ice and biological fouling and operation and maintenance. Environmental considerations are discussed including abstraction restrictions, effect on other users as well as fish exclusion and protection systems.
Desalination is a growing option as a source of drinking water. Consistent and reliable feedwater is required to efficiently produce potable water. Existing intake scenarios are limited. Direct intake of surface seawater is hampered by impingement and entrainment of planktonic organisms that require additional filtration and pretreatment. Vertical beach wells are restricted by their infiltration rate, whereas radial collector wells have a greater infiltration rate, but are restricted by hydrogeological properties of the subsurface geology. Infiltration galleries provide sizeable infiltration rates, but are constrained to select geological provinces. A synthetic beach well designed to overcome the existing limitation is proposed. Copyright ©2006 by The International Society of Offshore and Polar Engineers.
A beachwell intake system was proposed to provide water with higher temperature for seawater source heat pump. Pumping tests were conducted on a beachwell intake system to study the characteristics of seepage and heat transfer. Experimental results showed that the maximum temperature variation appeared in aquifer and there were obvious temperature attenuation and lag in other soil layers during the process of seepage and heat transfer. Supply water temperature was higher than that of seawater because heat was transferred from soil to fluid when seawater was filtered through the aquifer. Besides, the supply water temperature decrease could slow down during the intermittent heating. So this intake system guaranteed relatively stable higher temperature supply water as heat source.
The Test Bed for seawater reverse osmosis desalination plant having a capacity of 10 million imperial gallons per day, located in Gijang-Gun, Busan, South Korea, is under construction by Doosan Heavy Industries and Construction. Generally, beach well-type intake system furnishes a good seawater quality, but the amount of water which can be extracted from each well is limited by the geological formation surrounding the wells. In case of the Test Bed, unfortunately, beach well-type intake could not be adopted, therefore, in order to achieve a similar level of seawater quality, as being able to get by adopting the beach well intake, the Test Bed intake system is directly connected with a newly developed dissolved air flotation with ball filtration system. The Test Bed intake system consists of passive offshore screen, intake pipe, and air-burst cleaning system. In order to avoid possible clogging of the offshore screen by oceanic substances, compressed air-bursting system is installed onshore. In addition, underground tunnel is adopted to minimize the environmental impact during construction. Also, to avoid possible brine recirculation, a simulation study on the recirculation of brine discharge was carried out. The simulation study has been conducted using Environmental Fluid Dynamics Code model which is a three-dimensional hydrodynamic and water quality model. Grid generation is arranged 11.5 km horizontally and 15.5 km vertically. Mesh is varied from 20 to 200 m with 10 layers. Using tidal current and tide data of Korea hydrographic and oceanographic administration (KHOA), this model was verified. The result shows that if the distance between intake and outfall is 50 m, brine is induced to intake and excessive salinity at intake increases to 800 ppm in summer. If the distance between intake and outfall is increased to 70 m, the resulting maximum excessive salinity is 340 ppm. Finally, the outfall is displaced 70 m from intake.
In this work, the design and operation of multistage flash (MSF) desalination processes are optimized and controlled in order to meet variable demands of freshwater with changing seawater temperature throughout the day and throughout the year. On the basis of actual data, the neural network (NN) technique has been used to develop a correlation which can be used for calculating dynamic freshwater demand/consumption profiles at different times of the day and season. A storage tank is linked to the freshwater line of the MSF process which helps avoiding dynamic changes in operating conditions of the process. A steady state process model for the MSF process coupled with a dynamic model for the storage tank is developed which is incorporated into the optimization framework within gPROMS modeling software. For a given design (process configuration), the operation parameters are optimized at discrete time intervals (based on the storage tank level which is monitored dynamically and maintained within a feasible limit) while the total daily cost is minimized.
Seawater heat pump (SWHP) systems are considered as an ideal approach to heat and cool buildings in coastal areas due to its attractive advantages of high efficiency, low carbon emission and using renewable energy instead of electricity for heating and cooling. A great many of SWHP systems have been applied in residential and commercial buildings successfully. In this paper, models describing the coupled seepage and heat transfer process of beach well infiltration intake systems for a SWHP were established and validated by field experiment. In addition, the performance of the beach well infiltration intake system was simulated. And effect of the parameters related to the beach well and the operation of the system on pumping water temperature was explored through a series of simulations. As a result, application of SWHP systems with beach well infiltration intake system in coastal areas in China is feasible due to the favorable geographical conditions and environment.
The most commonly explored salinity-gradient scheme in the pressure retarded osmosis (PRO) process is based on the pairing of seawater and river water as a salinity gradient resource. However, due to the lack of a high-performance PRO membrane, a sufficient osmotic pressure differential across the membrane active layer to produce high power density cannot be attained with this seawater–river water pair. While high-performance PRO membranes have to be developed, there are other approaches to increase power density that combine several salinity gradient resources more efficiently. This study analyzes scenarios of osmotic power generation by PRO based on a variety of salinity gradient resources. Brine from RO (or future FO) desalination plants and municipal wastewater effluent (or brackish water) may be used as a high-salinity draw solution and low-salinity feed solution, respectively. The use of high salinity brines (as draw solution) from future FO desalination plants paired with seawater (as feed solution) may be an especially viable approach for a hybrid process of FO desalination and PRO power generation. In this approach, seawater is the only input resource, and there is no need to have separate intake and pre-treatment for the feed and draw solutions as in the conventional seawater–river water PRO scheme. From the analysis of these scenarios, we performed experiments with seawater (0.5 M NaCl) as feed solution to investigate the feasibility of the PRO process with the various proposed schemes. For the 2 M draw/0.5 M feed solution scheme at a solution temperature of 30 °C, a water flux of 13.9 L m−2 h−1 and corresponding projected power density of 4.7 W/m2 were obtained at a hydraulic pressure difference of 12.5 bar using a commercial cellulose triacetate FO membrane. This study demonstrates that osmotic power generation by pressure retarded osmosis using seawater as a feed solution is potentially viable through the introduction of a hybrid process of FO desalination and PRO osmotic power generation.
This Comment argues that the federal and state standards for reducing marine life mortality from power-plant intakes should be applied to a statewide policy for new desalination projects in California. Under this framework, open seawater intakes should not be permitted for new desalination plants. Part II of this Comment provides an overview of the history and technology of desalination as well as environmental impacts of open seawater intakes and alternative intake technologies. Part III surveys existing state and federal laws addressing open seawater intakes and suggests a framework for applying these laws to desalination projects. Part IV argues that new desalination plants should not be permitted to use open seawater intakes because doing so would be inconsistent with California law and would undercut other California efforts to protect marine life. Part V presents the Carlsbad Desalination Project as a case study of how existing state law has been improperly applied to grant water permits. Part VI concludes with a summary of why a statewide desalination policy should be implemented consistent with state law.
This study focuses on the role of the aquifer media as a tool to improve the characteristics of seawater used to supply desalination plants, quantifying this improvement from a considerable number of physicochemical parameters. The evolution of both physi-cochemical and microbiological characteristics through the aquifer media has been deter-mined by comparing the composition of seawater samples taken via direct intake with those taken over the aquifer. The principal improvements are due to the process of filtration. It includes up to a 95 % reduction in turbidity and up to a 50 % reduction in SDI. Other parameters are also notably reduced (TOC is cut on average by 60 %, and DO by 80 %), due to bacterial activity in the aquifer. It is also important to highlight that only a short distance of water flow through the aquifer is needed to achieve this improvement. If it used the seabed as the filter material, it would be necessary a minimum thickness of a few meters due to biological activity involves a significant increase in the TOC. An understanding of the filtration processes occurring within the aquifer provides a natural analogue on which future improvements in artificial pre-treatment can be based.
The prospects of using the membrane water treatment technologies for deeply removing organic compounds from steam-water paths
at thermal power stations are considered. It is shown that the membrane technologies allow organic substances to be removed
from water more efficiently than do the traditional technologies.
Seawater desalination, especially with reverse osmosis, is developing as an alternative source of drinking water resource in coastal states. Desalting seawater requires a consistent and reliable source of feedwater to operate and produce potable water effectively and efficiently. Problems with the launch of Tampa Bay Desalination Plant related to characterization of the feedwater and pretreatment issues. Review of existing intake scenarios and their limitations provides a planning tool for seawater reverse osmosis facilities. Direct intake of surface seawater is hampered by impingement and entrainment of planktonic organisms that require additional filtration and pretreatment. Vertical beach wells provide high quality feedwater, but are limited by their infiltration rate. The radial collector wells with generally higher infiltration rates are also limited. Infiltration galleries provide large infiltration rates, but are restricted to select geological provinces. For reverse osmosis systems, the system preference is for water and salt with the widely fluctuating organic material removed. We suggest a generalized model to provide consistent source of screened water with biological materials eliminated. Several guidelines for placement of intakes are also provided from learnt rules of coastal engineering.
The effluent of concentrated seawater results from desalting ocean water, whether thermal or pressure processes are used. Disposal of the concentrated seawater needs to be addressed during the early stage of planning the design and site selection of the desalination facility. Recent developments in energy recovery technology have significantly improved the economics of producing fresh water from seawater. Optimized specific power consumption yields recovery rates that are lower than those employed historical, resulting in a lower concentration of dissolved salts in the plant effluent. With seawater desalination becoming a growing option for a secure source of drinking water, management of the waste streams becomes significant. We highlight a ‘total systems engineering approach’, which encompasses several key attributes that lessen the environmental burden of the seawater desalination option. Included among these approaches are smaller distributed systems with no chemical pre-treatment. For RO systems, reject water with lower salt concentrations is achieved by incorporating pressure exchange technology. For thermal distillation systems, reject water 1°C above ambient seawater temperature can be achieved by employing thermoplastic heat exchangers with no significant increase in capital costs. A case study utilizing a retrofit of an existing municipal seawater desalination plant will highlight our approach.
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