Saline Water Conversion Corporation Research Articles

Control of Bromate Formation in Desalinated Seawater Production and Transmission with Ammoniation

Bromate is a potentially carcinogenic disinfection by-product of potential concern in desalinated waters, where bromide derived from seawater can be converted to bromate by the oxidising species used for disinfection. Historically, it has been difficult to maintain complete adherence to national standards of no more than 10 ppb for bromate at all locations served with desalinated seawater by the Saline Water Conversion Corporation (SWCC) in the Kingdom of Saudi Arabia. In this full-scale study, the addition of 100–200 ppb of ammonia to the produced water of a Multi-Stage Flash Desalination plant effectively controlled the formation of bromate in the transmission system supplying inland centres in the Makkah Province of the Kingdom of Saudi Arabia (Arafa, Taif) on a time scale sufficient for the distribution of water to the consumer, even when the bromide content of the produced water was artificially enhanced (up to 132 ppb) via the addition of seawater.

Pathways to magnesium supplementation of drinking water: An overview of the saline water conversion corporation experience

Magnesium (Mg) in drinking water is essential for human health, with low concentrations in drinking water being reported to be correlated with poor cardiovascular health outcomes. Based on the literature and suggestions that the World Health Organization would soon announce guidelines for Mg content of drinking water, the Saline Water Conversion Corporation (SWCC) announced specifications in October 2020 targeting 15–25 ppm of Mg in product water. SWCC produces approximately 6 million m3 of potable water daily for domestic and industrial use in the Kingdom of Saudi Arabia, so meeting this Mg target will require the allocation of significant resources. In this report the different approaches to adding Mg in post-treatment of the product water from the SWCC's network of desalination plants are reviewed in order to optimise the additional capital investment and ongoing operational expenses. The most cost-effective option is to mix produced water with groundwater containing Mg, but where this is not feasible the next most cost-effective method for achieving a 15 ppm target was assessed to be treating desalination brine with nanofiltration (NF) to generate a magnesium-rich brine fraction that can be mixed with produced water. A one-stage NF process can meet the 15 ppm Mg target only with levels of chloride and total dissolved solids exceeding regulatory maximums in the produced water, so a multi-stage NF process with intermediate dilution was designed. While this has a significantly higher capital expenditure and energy requirement than one-stage NF, at the cost of energy in the Kingdom of Saudi Arabia it is still significantly less expensive than alternative approaches (0.009 USD/m3). This solution was implemented at an SWCC desalination plant on the Red Sea and has been delivering Mg-enriched water (∼15 ppm) to approximately 1.3 million people since May 2022 at an estimated additional operational cost of 0.007 USD per m3. For lower target levels of Mg supplementation (∼5 ppm), replacement of limestone with dolomite in post-treatment limestone contactors has been found to be a cost-effective process in plant-scale trials at another SWCC plant on the Red Sea.

Film-forming amine product as an alternative to carbohydrazide oxygen scavenger in high pressure boilers

Hydrazine has been largely replaced by carbohydrazide (CHZ) as an oxygen scavenger due to safety and health concerns and CHZ is now used in Saline Water Conversion Corporation (SWCC) high pressure boilers. However, the operational problem of phosphate hide-out has become a continuous challenge for the plant operators. Advances in boiler water treatment have shown that effective corrosion control and prevention of scaling can be achieved by using a mixture of film-forming and alkalizing amines and polycarboxylates [Film Forming Amine Product (FFAP)]. With the use of FFAP, carbohydrazide/ammonia treatment of make-up water and phosphate treatment in the drum will not be required. A uniform FFAP formulation was used throughout the test.The evaluation study was carried out at a boiler of the Yanbu Phase 1 Desalination and Power Plant (Mitsubishi) generating 60 MWh, with make-up water of 15 t h−1 producing 330 t h−1 steam at a pressure of 67 barg and temperature of 480 °C.The trial provided evidence that FFAP was a good alternative to use of an oxygen scavenger. Changeover from CHZ to FFAP without phosphate addition in the drum was done initially by dosing FFAP from both hydrazine tank and phosphate tank so that pH was maintained to the required values in both feed water and drum water. With the optimal dose rate (0.6 ppm) maintaining FFAP in the range of 0.3–1.0 ppm in feed water, all the key parameters (pH, ammonia and specific conductivity) were within the specified boiler design limits. The average corrosion rates on the water side were low for both CHZ and FFAP treatment (0.009 ± 0.001 mm y−1), however FFAP treated coupons showed much lower corrosion rates compared to CHZ in the steam side (0.0006 ± 0.0003 mm y−1 cf. 0.0075 ± 0.0006 mm y−1).

Thermal Performance of MED-TVC Pilot at 95°C Elevated Temperature with Acid-anti-scalant Blend Treatment

Enhancing the efficiency of desalination plants and economics of desalinated water are the major goal to researchers. In desalination industry; Multi Effect Desalination (MED) has an economic potential which proves its maturity among different desalination technologies. Large MED plants were built and operated with satisfactory performance in the last decade. They have been operated at low temperature compared to MSF and competitive operation efficiency. The Desalination Technology Research Institute (DTRI) which belongs to the Saline Water Conversion Corporation (SWCC) of Saudi Arabia has tested MED pilot plant with hybrid acid and anti-scalant treatment to control the scale. The test was conducted under 95 °C compared to 65 TBT which the current commercial standard operational temperature and previously tested 85 TBT within DTRI-SWCC pilot plant. Increase in the TBT would allow to increase the number of effects which lead to more system efficiency (the performance ratio) and then reduce fuel consumption which reflected in water unit cost of the desalinated water. The results showed that the thermal performance including fouling factor and performance ratio was constant and have very minor degradation during the test. The good thermal performance was confirmed by the post-operation visual inspection, which revealed that the heat transfer tubes were maintained in a clean condition after testing.

Strategy of endoscopic skull base reconstruction in endoscopic transsphenoidal approaches

Background Saline Water Conversion Corporation (SWCC) is the main source of water in the Red Sea coast in Jeddah, KSA, the workers and their families are exposed to vapor and chemicals that affect their upper respiratory tract. Aim Our aim was to study the prevalence of unified airway disease [allergic rhinitis (AR) and bronchial asthma] in SWCC Society accommodations, serum immunoglobulin E (IgE) level and its relation to the duration of bronchial asthma, and duration of living in the accommodations. Patients and methods This randomized study included 400 patients with bronchial asthma, the included patients comprised two groups: group I (GI) (n=200) from SWCC Society accommodations and group II (GII) (n=200) patients from outside the accommodations. Both groups were classified according to Allergy Classification of allergic rhinitis and its impact on asthma and blood samples for IgE taken from them. Results According to the classification of allergic rhinitis and its impact on asthma, the persistent and moderate–severe allergy were more common in GI (80%) and the intermittent allergy and mild severity was 20%, while the persistent and moderate–severe allergy were less common in GII (22%) and the intermittent allergy and mild severity was 78%. GI patients experienced a significantly high IgE level compared with GII, higher in males than females, and increases with the duration of living in the accommodations and duration of bronchial asthma. Conclusion Unified airway disease is common in SWCC Society with a high level of IgE compared with outside the accommodations. Keywords: allergic rhinitis, bronchial asthma, environmental diseases, serum total immunoglobulin E.

Prevalence of unified airway disease in Saline Water Conversion Corporation Society

Prevalence of unified airway disease in Saline Water Conversion Corporation Society

The Effect of Leadership Behavior on Managerial Creativity of Saline Water Conversion Corporation Employees: Applied Study on Shuqaiq Desalination Plants Employees: تأثير السلوك القيادي على الإبداع الإداري للعاملين بالمؤسسة العامة لتحلية المياه المالحة: دراسة تطبيقية على العاملين بمحطات تحلية الشقيق

The study aimed to identify the data of some variables of leadership behavior, and to identify the reality of managerial creativity of employees and administrators in the Saline Water Conversion Corporation. Also, to identify the data of some personal and functional variables of workers at the level of their managerial creativity. To achieve the study's aims, the researcher followed the descriptive approach. The study was applied to a sample consisted of 100 employees of the Saline Water Conversion Corporation, using a questionnaire distributed to them. The study came with some conclusions, most important of with are: 1) The level of managerial creativity of the Saline Water Conversion Corporation employees was high. 2) The analysis and connectivity were the least available elements of managerial innovation. 3) The elements of managerial creativity can be arranged according to their availability as: (flexibility, originality, sensitivity to problems, intellectual fluency, and ability to analyze and connect). 4) There are positive and statistically significant data between the behavior of the administrative leader who is interested in the staff and the level of their creativity. 5) There is no statistically significant data between the interest of the administrative leader in the work and the level of managerial creativity of the employees. 6) There are statistically significant relationships between personal and functional variables and some variables of leadership behavior, which are: (The presence of positive data statistically significant between the educational qualification, the functional rank of workers, and the level of managerial creativity, and the presence of negative data statistically significant between the functional rank of workers and the interest of the administrative leader to work). The study recommended the emphasis on the principle of delegation as a means and tool to develop the skills of creative staff by providing expertise and direct contact with situations and events, and support the concept of serious participation of workers in decision-making.

Toyobo and SWCC to pilot test membrane technology

Japan's Toyobo Co Ltd and Saudi Arabia's Saline Water Conversion Corporation (SWCC) have signed a memorandum of understanding (MoU) on a joint pilot test aimed at realizing the practical application of a new brine concentration (BC) membrane technology that uses concentrated brine discharged by seawater desalination plants.

Fungal and marine shell fouling in desalination plant equipment

Abstract The Saudi Arabian Saline Water Conversion Corporation (SWCC) aims to maintain an uninterrupted desalinated water output and has tasked its Desalination Technologies Research Institute (DTRI) with trouble-shooting operational problems and unusual events faced by its desalination plants. Three events were reported and investigated by DTRI. Two were found to involve fungal fouling, and one was found to involve fouling by marine shells. One case of fungal fouling involved a new seawater reverse osmosis membrane and the plant was advised to review the handling and storage practice of membranes. The other case involved product water hoses and manifested itself in the form of black slimy deposits arising from dense fungal growth. The fungus originated from new product hoses and was eliminated by shock-dosing replacement hoses with chlorine. The marine shell fouling involved a feed water line of a combined power/desalination plant. Chlorine, hydrochloric acid, ethylenediaminetetraacetic acid, and fresh water were used to assess their ability to control marine shell fouling in laboratory experiments, with varying results. Since high doses of chlorine were not effective in controlling marine shell fouling, the practice of continuous chlorination should be abandoned in favor of an alternative chlorination regimen, e.g., pulse chlorination.

A Demonstration of High Temperature MED-TVC Desalination Technology in the Gulf Area

This work focuses on a multiple effect desalination system with thermal vapor compressor (MED-TVC) operating at a top brine temperature (TBT) of 85°C which is significantly above the common operation temperatures of conventional MED-TVC systems, limited to a range below 70°C mainly due to scale risk. Such increase in TBT would enhance the production and system economics. A pilot plant installed at the Desalination Technologies Research Institute (DTRI) of the Saline Water Conversion Corporation (SWCC) in Jubail, Saudi Arabia was operated at the TBT of 85°C over a 5-month test period. Visual inspection of tube bundles after the test, in conjunction with chemical scale analysis showed that scaling was limited to a soft thin film scale, which was easily removed by flushing with water, which confirmed a low fouling potential analyzed from operation data. Techno-economic analysis of the MED-TVC system operating at a TBT of 85°C, indicated up to 34% reduction in steam consumption and up to 16% reduction in the levelized cost of water (LCOW), when compared with a MED-TVC unit operating at a conventional TBT of 65°C. Accordingly, the high temperature MED-TVC systems operating at a TBT of 85°C can be considered as a financially competitive and technologically reliable desalination option for the Gulf area which has challenging seawater characteristics.

Power Plant Output Augmentation by Evaporative Cooling Based on HRSG Blowdown Water Recycling in the Kingdom of Saudi Arabia: A Novel Approach

Water is a scarce natural resource fundamental for human life. Power plant architects, engineers, and power utilities owners must do everything within their hands and technical capabilities to decrease the usage of water in power plants. This paper illustrates the research carried out by Pöyry Switzerland to reduce the water consumption on power and desalination combined cycle power plants, on which there are gas turbine evaporative cooling systems in operation. The present study analyzed the potential re-utilization and integration of the heat recovery steam generator (HRSG) blowdown into the evaporative cooling system. Relatively clean demineralized water, coming from the HRSG blowdown, is routed to a large water tank, where it is blended with distillate water to achieve the required water quality, before being used on the gas turbine evaporative cooling system. To prove the feasibility of the HRSG blowdown recycling concept, the Ras Al Khair Power and Desalination Plant owned and operated by the Saline Water Conversion Corporation (SWCC), located in the Eastern Province of the Kingdom of Saudi Arabia, was used as case study. Nevertheless, it is important to mention that the principles and methodology presented on this paper are applicable to every power and desalination combined cycle power plant making use of evaporative cooling. Sea water desalination is the primary source for potable water production on Saudi Arabia, with secondary sources being surface water and groundwater extracted from deep wells and aquifers. Saving water is of utmost importance for power plants located in locations where water is scarce, and as such, this paper aims to demonstrate that it is possible to decrease the water consumption of power and desalination combined cycle plants, on which evaporative cooling is used as gas turbine power booster, without having to curtail power production. The outcome of the study indicates that during the summer season, recycling the HRSG water blowdown into the gas turbine evaporative cooling systems would result on the internal water consumption for the gas turbine evaporative coolers decreasing by 545 ton/day, or 23.79%, compared with the original plant design which does not contemplate blowdown re-use. Using evaporative cooling results on an overall gain of 186 MW, or 10.27%, on gross power output, while CO2 emissions decrease by 46.8 ton CO2/h, which represents a 13.8% reduction compared with the case on which the evaporative cooling system is not in operation. A brief cost analysis demonstrated that implementation of the changes would result in a negligible increase of the operational expenses (OPEX) of the plant, i.e., implementation of the suggested modification has an unnoticeable impact on the cost of electricity (CoE). The payback of the project, due to limited operating hours on evaporative cooling every year, is of 12 years for a 30 year plant lifetime, while 2.22 M USD of extra-revenue on potable water sales are generated as a result of implementing the proposed solution. Although in principle this value is modest, the effect of government subsidies on water tariffs as well as political and strategic cost of water is not included on the calculations. In conclusion, the study results indicate that water recycling, and reduction of plant's water footprint for power and desalination combined cycle plants using evaporative cooling, is not only technically possible but commercially feasible.

Long term experience in the operation of nanofiltration pretreatment unit for seawater desalination at SWCC SWRO plant

Abstract Saline Water Conversion Corporation is the pioneer in developing applications and operation of nanofiltration (NF) pretreatment for seawater desalination which was developed by its research arm, namely, the Saline Water Desalination Research Institute. Initial work on a pilot plant scale, resulted in its application in one of the commercial seawater reverse osmosis (SWRO) plants at Ummlujj currently in operation since September 2000. During this long term of operation of NF–SWRO system, a number of improvements were made on the system operation based on operational experiences as well as research, which ultimately resulted in smooth operation of the same. This long-term operation revealed that it is possible to operate NF at 65% recovery at pH = 6 utilizing only low feed pressure of <25 bar. This led to increase in SWRO production by 42%. Also, no chemical cleaning or membrane replacement was required for SWRO membranes. These achievements make the NF–SWRO process economically attractive and feas...

Lessons learnt from the operational performance of SWCC MSF desalination plants

Around 88% of water production by the Saline Water Conversion Corporation (SWCC) is provided by large MSF desalination plants which operate as power/water cogeneration plants. Despite the fact that the majority of SWCC MSF plants have been operating for more than two decades, their availability and water production as well as energy effi ciency are still maintained within—or even sometimes higher—than the original design values. This is attributed to SWCC strict requirements of operation and maintenance which resulted in extending the life of the plants to more than thirty years. In this paper, the energy efficiency of SWCC existing MSF desalination plants will be assessed. SWCC successful economic implementation of scale control techniques and the use of appropriate corrosion resistant materials will be highlighted. Benefi ts obtained from operating SWCC MSF desalination plants within the context of dual purpose plants employing either back pressure or extraction condensing turbine for the simultaneous p...

Performance analysis of a trihybrid NF/RO/MSF desalination plant

The Saline Water Desalination Research Institute (SWDRI) of the Saline Water Conversion Corporation (SWCC), Saudi Arabia has been actively involved in developing the application of nanofiltration (NF) pretreatment to both seawater reverse osmosis (SWRO) and multistage flash (MSF) desalination processes. Full integration of NF, SWRO and MSF processes would result in enhancing the reliability, flexibility, plant productivity and ultimately reduce water production cost. Extensive experimental studies on a pilot-scale were conducted recently by SWDRI to establish the operational boundaries and constraints of the trihybrid NF/RO/MSF desalination system. The system was configured in such a way that the NF unit received seawater feed from the heat rejection of the MSF pilot plant and was able to operate at a fairly constant temperature of about 33°C which produced NF permeate (NFP) at a recovery ratio of about 64%. The SWRO unit which received the NFP as a feed yielded a permeate recovery of about 47%. Average chemical analysis of the RO reject (ROR) revealed that the sulphate and calcium concentrations were only 124 and 281 ppm, respectively, and was subsequently used as a make-up to the MSF pilot plant. The very low concentration of the sulphate and calcium ions in the brine recycle which were below the saturation limits enabled to operate the MSF unit safely up to a top brine temperature of 130°C (unit temperature design limit) and water recovery ratio of about 69%. In this paper, the operational performance of the trihybrid NF/RO/MSF desalination pilot plant will be presented. The established optimum operating conditions can be used as a guide to assess the techno-economic viability of the trihybrid desalination scheme.

Seawater desalination — SWCC experience and vision

In order to appreciate Mankind's technological advancements, one needs to present a historical overview. This applies to desalination technology (among all other human developments). Over the millennia, desalination did develop very slowly at the start and then its development started to accelerate. The author has so far traced this technology to as far back as to the third millennium BC. Arabian Peninsula and its surroundings had been the cradle of this, like quite many other, fields of knowledge and technology. Such development has left its mark also around the Mediterranean, especially in Alexandria and Athens, then much later in Italy. The Arabian Islamic Civilization has engraved several thumbprints on the path of distillation. An ingenious distiller with built-in internal reflux was found with Arabic writing below, to describe the device. Moreover, Demusquain glass was used in making lenses as solar heat concentrators for distillation. During this millennium colonialism, which brought prosperity to some through exploitation of resources and the deprivation of the colonized masses, implemented desalination as one of its tools on board ships and within the so-called prosperous new found lands. With the increase of water demand and emphasis on desalination technology due to shortage of underground resources in the kingdom, the government of Saudi Arabia established the Saline Water Conversion Corporation (SWCC) in 1974. Since the SWCC has grown and become the authority to look after all matters related to seawater desalination. At present SWCC has 27 plants producing 668MGD of desalinated water and 4115MW of electricity from existing operating plants. Additional four plants with a total capacity of 218MGD of water and 999MW of electrical power are under construction. This will take total desalinated water production to 886MGD and electrical power generation of 5114MW. The last three decades have seen a tremendous growth of SWCC along a few different lines, such as: a) enhanced production capacity of desalinated water, b) self administered operation and maintenance, c) execution of trouble shooting and applied projects, d) development of experience-based design concept, e) venturing into new technology and/or carry out modifications, into existing ones, f) promote Saudization in all disciplines of desalination. With the immense interest and concern in developing seawater desalination industry to minimize cost, upgrade performance and prolong life of plants, a Research and Development Center (RDC) was established and inaugurated in 1987 to achieve these objectives. Teh center has five sections, Thermal, Reverse Osmosis, Corrosion, Chemistry, and Ecology and Marine Biology. The center is equipped with most advanced and sophisticated equipment in addition to a multistage flash (MSF) and several RO pilot plants. The RDC helps in solving problems in operating plants thus leading to higher efficiencies and longer plant life. RDC also helps in the selection of ideal materials and chemicals for eventually achieving lower production cost. Studies to protect the environment have also been carried out. Since its inception the RDC has completed 117 projects in various aspects of desalination, some of which begot from problems encountered during plant operation. Moreover, SWCC Research and Development (R&D) and Studies and Designs (S&D) Departments are the corporate THINK TANKS for the future. SWCC activities have opened eyes into new horizons far behind the traditional ones. Lofty stands up high, as a new milestone which was brought into adaptation is nanofiltration of seawater as pretreatment, potentially for all desalination processes. In other words recent efforts at the center yielded a novel approach to membrane and thermal seawater desalination processes using nanofiltration (NF) membrane. This patented concept of using NF as pretreatment to both RO and MSF processes enhances the production of desalted water by more than 60% and reduces the cost by about 30%, yet it is an environmentally friendly process. Preliminary results of studies on NF indicate that this new concept could one day revolutionize desalination technology. Other prospective horizons are by conducting applied research on: a) design, commissioning then operation of large capacity distillers, b) hybridization of desalination processes, c) exploration of alternative energy sources for desalination, e.g., solar and nuclear, d) search for suitable and cost effective chemicals, alloys and synthetic materials, e) new design for very large number membrane elements housing (the proposed vessel is envisioned to be like a heat exchanger and/or a steam drum), f) designing, building and testing elevated top brine temperature (TBT) MSF process at (and/or above) 160°C, g) treatment and safe disposal of waste generated through better understanding of environment interactive impacts related to desalination, h) magnetically enhanced separation of seawater hardness.

Available safety margins of time and antiscalant dose rate

Saline Water Conversion Corporation (SWCC), Research & Development Center (RDC) was encountered with a request to establish available safety margins of time and antiscalant dose rate. This request came to RDC from operating plants in order to set limits of available time and for clear identification of operating procedures in case of antiscalant dose rate interruption. This paper will review past works of scale control in SWCC. Results obtained during the past couple of decades (1981–2000 AD) are cited as background information. Such results include scale control techniques of ball cleaning and antiscalant dose rate optimization and costs. The paper will also describe some preliminary ground work carried out in laboratory and on the 20 kl/d pilot plant MSF distiller available at SWCC-RDC in Al-Jubail. Laboratory work will show threshold scale information potentials as a function of time using change in solution alkalinity. In these tests were various antiscalant types of polyphosphonate and polymaleic and polycarboxylic acids were dosed into natural seawater and artifcially concentrated brine solutions. On the other hand, operating results of the 20 kl/d MSF pilot plant will be shown at low down to very low antiscalant dose rates. In addition, operating results on pilot plant MSF distiller for limited duration will be discussed while suspending either antiscalant dosing or on-line rubber ball cleaning scale control technique.

Optimization of hybridized seawater desalination process

Saline Water Conversion Corporation (SWCC), Research and Development Center (RDC) came up in recent years with a breakthrough in feed treatment to all desalination processes. Selective ions, biomass and suspended solids rejection characteristic of nanofiltration (NF) membranes were utilized to retard the ingress of hardness forming ions and other foulants into desalination downstream processing steps, e.g. SWRO and MSF. NF pretreatment using brackish water hardness removal membranes were applied to seawater pilot, demonstration and eventually commercial desalination plants. A good number of such membranes were tested in order to select the best. The screening scheme revealed couple of interesting facts related to characteristics of various brands and grades of NF membranes. In an earlier stage of this multi phase project these membranes were categorized as groups A, B and C. These groups in the same order were found to give from high hardness and salinity rejection with low flow and product recovery down to low rejection with high flow and recovery. Based on the above findings, it was decided that the most suitable membranes would be those of group B which could give good flow and recovery with reasonable rejections. Membranes of group B were tested at various plant sizes, production schemes and configurations. This paper will concentrate on 4, 8 and 9 inch membrane elements used in NF or NF/SWRO combination to provide make-up to pilot plant MSF of 20 kl/d distiller. Such hybridized production configurations were optimized by testing overall performance. Few prime parameters were closely analyzed to come up with the best combination of NF membrane brand and their operating parameters along with MSF and/or SWRO—MSF hybrid conditions. In the latter case SWRO reject was used as make-up to the MSF pilot plant distiller. Moreover, the testing program locked into further hybridization, whereby MSF heated reject water was used as feed to NF pretreatment section. This was done to establish the effect of feed temperature rise benefits on NF and/or NF—SWRO energy input, yield(s) and product(s) flow and quality. The MSF operation was monitored and its operating results were analyzed. Main components of such analyses were gain output ratio (GOR), fouling factor (FF), top brine temperature (TBT), chemical consumption and product to make-up yield ratio and its quality.

A demonstration plant based on the new NF—SWRO process

Earlier work at Saline Water Conversion Corporation (SWCC) R&D Center showed that nanofiltration (NF) pretreatment of seawater feed to seawater desalination plants removed from its turbidity and microorganism, caused significant rejection of the scale forming hardness ions, reduced TDS in Gulf seawater and produced a new, partially desalinated seawater product, considerably different and superior to seawater in qualities and without the problems normally associated with seawater of high concentration of scale forming ions, high TDS, high turbidity and high bacteria count. Integration of the NF unit with one of the conventional desalination processes to form for example an NF-SWRO lead to a significant improvement in the seawater desalination processes, for example by doubling the SWRO product water output and recovery ratio and the production of high purity permeate (TDS <200 ppm) from one single stage SWRO. However, all previous works were done on a pilot plane scale by integrating NF spiral wound membrane elements in series, size 4″×40″, with a SWRO unit employing 2.5″×40″ membrane elements. In view of the positive and encouraging results obtained on a pilot plant scale, trial on an NF—SWRO demonstration unit was not only logical but essential to determine the operating conditions as well as to establish plant performance parameters for commercial size NF-SWRO plants. The demonstration unit built for this purpose consisted of 6 NF spiral wound membrane elements, size 8″×40″ arranged in series followed by a SWRO unit comprising 3 HFF SWRO elements 8″×40″ or 9″×40″ also arranged in series. The paper describes the NF—SWRO demonstration unit along with the experimental approach used in this investigation dealing with the performance of several selected NF membranes integrated with SWRO membrane to form an NF—SWRO desalination system. The results obtained from the demonstration unit confirm the earlier results which were obtained from the pilot plant study. The results shall be utilized in the operation of the now under construction NF—SWRO plant at Umm Lujj, Saudi Arabia.

Studies on a polyoxypropylene glycol-based antifoaming agent in MSF plants

Salt carry-over due to excessive foaming in a multistage flash (MSF) distiller and detrimental foaming in the deaerator section have been reported in the Saline Water Conversion Corporation (SWCC) of Saudi Arabia and other desalination plants. The application of a suitable antifoaming agent has prevented distillate contamination and improved release of dissolved oxygen in the deaerator section, thus improving the operating efficiency of MSF plants. The developer of a polyoxypropylene glycol-based antifoaming agent collaborated with SWCC in carrying out trial runs to show that their product was as effective and economical as the one currently being used (a polyglycol blend in a hydrocarbon solvent) in SWCC plants. Trial tests were carried out at laboratory, pilot and commercial plant levels. Miscibility of this agent in water was determined initially in the laboratory, followed by field trial runs in an MSF pilot plant and the commercial plants of Al-Jubail I and II. Foam control, non-interference with antiscalant performance, distillate purity and stability at a low dose rate over a wide range of temperatures were some of the important criteria evaluated during testing of this antifoaming agent. During MSF plant runs, distillate conductivity and dissolved oxygen level in the feed were regularly monitored and found within the acceptable limits. Compatibility of this agent with antiscalant was also assessed. Heat transfer and plant performance data were found satisfactory confirming that this agent did not exhibit any adverse effect on the antiscalant used in Al-Jubail plants. Results of laboratory and field trial runs of this antifoaming agent are discussed.

Thermal performance of multi-stage flash distillation plants in Saudi Arabia

The Saline Water Conversion Corporation (SWCC) of Saudi Arabia is currently producing around 16% of the total worldwide capacity of desalted water [1]. The majority of SWCC desalination plants employs the multistage flash (MSF) distillation process which produce 94% of SWCC's total desalinated water. SWCC various MSF distillers are characterized by a wide range of operating and design conditions. The capacity of operating distillers ranges between 2.5 to 7.5 migd. Some large distillers of rated capacity up to 10 migd are under construction in Shoibah and Yanbu. The number of stages of these distillers varies between 16 and 34, while the operating top brine temperature varies between 90°C and 115°C. Design and operating parameters of various SWCC MSF distillers have been collected and effectively utilized to simulate and analyze the thermal performance of these distillers. The thermal performance of each distiller is quantitatively assessed using a computer program which is based on the first and the second law of thermodynamics. A comparative study on energy and exergy analyses is conducted for different MSF plants. This paper also presents a comprehensive micro-thermal analysis to identify the potential for improving plant efficiency. The exergy losses due to irreversibility in different subsystems of each MSF distiller are evaluated. Exergy destruction in the brine heater, heat recovery and heat rejection stages and friction in liquid paths are determined. The impact of different design and operating parameters such as top brine temperature and number of stages on the thermal performance of the MSF system is evaluated.