Red Sea Water Research Articles

Anomalous distribution of distinctive water masses over the Carlsberg Ridge in May 2012

Abstract. In May 2012, we conducted a hydrographic survey over the Carlsberg Ridge in the northwest Indian Ocean. In this paper, we use these station data, in combination with some free-floating Argo profiles, to obtain the sectional temperature and salinity fields, and subsequently, the hydrographic characteristics are comprehensively analyzed. Through the basic T–S diagram, three salty water masses, Arabian Sea High-Salinity Water, Persian Gulf Water, and Red Sea Water, are identified. The sectional data show a clear ventilation structure associated with Arabian Sea High-Salinity Water. The 35.8 psu salty water sinks at 6.9∘ N and extends southward to 4.4∘ N at depths around the thermocline, where the thermocline depth is in the range of 100 to 150 m. This salty thermocline extends much further south than climatology indicates. Furthermore, the temperature and salinity data are used to compute the absolute geostrophic current over the specific section, and the results show mesoscale eddy vertical structure different from some widely used oceanic reanalysis data. We also find a west-propagating planetary wave at 6∘ N, and the related features are described in terms of phase speed and horizontal and vertical structures.

Optimization and immobilization of amylase produced by Aspergillus terreus using pomegranate peel waste

BackgroundAmylases are amongst the most important hydrolytic enzymes that are used in numerous industrial uses reaching for food to pharmaceuticals. Immobilization of enzymes can proposal several assistances as reusability and retrieval from their products improve strength under both operating and storing environments.ResultsMarine fungal isolate was recovered from red sea water at Sharm El-Sheikh Province and was tested for amylase activity using different agricultural wastes as substrate. It was found that pomegranate peel was the best substrate for amylase production (339 U/ml). Thus, it was subjected for identifying by 18S rDNA gene. The phylogenetic analysis results indicated that this fungal isolate belonged to Aspergillus species with similarity of 99% and named as Aspergillus terrus SS_RS-NE. Its nucleotide sequences were deposited in NCBI GenBank under accession no. of MN901491. Some parameters affecting amylase activity using pomegranate peel as substrate were studied. The results denoted that, the highest amylase activity of 340.69 U/ml using 1.5% pomegranate peel at 30 °C, pH 6.0 on 5 days incubation time by Aspergillus terreus. The produced crude enzyme was partially purified with 80% ammonium sulfate followed by dialysis. The enzyme activity was 1246 U/ml and 2411 U/ml employing ammonium sulfate precipitation and dialysis respectively.The partially purified amylase was immobilized with 2% sodium alginate and the results showed the highest immobilized enzyme yield was 92.8%. The characterizations of immobilized amylase were studied and the results indicated that, the maximal immobilized amylase activity was 2522.5 U/ml with 2% starch as a substrate at optimum pH value of 6.5, temperature at 60 °C and 10 min reaction time in comparison to maximal free amylase enzyme at pH 5, 50 °C after 40 min. The results also indicated the immobilized amylase was stable at 60 °C for 20 min.ConclusionsAspergillus terrus SS_RS-NE (MN901491) was isolated and genetically identified. It has the ability to produce amylase enzyme using pomegranate peel waste with a yield of 339 U/ml. The crude enzyme was partially purified by ammonium sulfate followed by dialysis. The maximal immobilized amylase activity of 2522.5 U/ml was obtained under optimized some culture conditions and medium nutrient parameters.

A review on the impact of salinity on foundation soil of coastal infrastructures and its implications to north of Red Sea coastal constructions

The present paper summarizes previous studies on the characteristics and soil properties of Red Sea water and how it is impacting civil engineering infrastructures; the review also looks at various geotechnical parameters. Seawater may have negative effects on soil as well as on infrastructures such as airports, seaports, highways, and buildings. The average value of salinity (psu) is 40.60 ± 0.10 with significant positive or negative differences among years, months, and depths. However, along the northern coast of the Red Sea, turbidity is in the range of 1 to 3 Formazin Nephelometric Units (FNU). Moreover, while surface average pH is 8.1 ± 0.02 during winter, higher values occur in the north due to lower temperatures. Similarly, during the summer, average Red Sea surface pH is 8.07 ± 0.03, with higher values occurring in the north due to temperature differences. The water pH at Gulf of Aqaba fluctuates around 8.3. The mean value of Red Sea temperature is 27.88 ± 2.14 °C. The average value of dissolved oxygen is 6.77 ± 0.41 mg/L. During the present work, the geotechnical parameters are investigated. In general, salts decrease the plasticity index, soil compressibility, swelling characteristics, and optimum moisture content while increasing the permeability, maximum dry density, shear strength, and bearing capacity of soil.

Observations of a Deep Submesoscale Cyclonic Vortex in the Arabian Sea

AbstractSubmesoscale coherent vortices (SCVs) are numerous in high‐resolution numerical simulations, but their observations are scarce. Among the few in situ available measurements of SCVs, a vast majority concern anticyclones. No cyclonic SCV with large dynamical Rossby number (|ζ/f| > 1) has ever been sampled. This suggested that such small cyclones may lack robustness. Here, we present in situ measurements of an intense cyclonic SCV in the Arabian Sea. This eddy lay at 600 m depth, with a Rossby number and a dynamical Rossby number |ζ/f| > 1.5. This cyclone was most likely generated at the mouth of the Gulf of Aden. It trapped and advected Red Sea Water, from there on. This highlights the role of deep SCVs in the spreading of salty waters across the Arabian Sea.

Demographic structure and stock status of Lethrinus lentjan in Saudi coastal waters of the Red Sea.

Fishes of the family Lethrinidae form a considerable portion of the catch from both the Red Sea and the Arabian Gulf in Saudi Arabia, and the species Lethrinus lentjan (Lacepède, 1802) is one of the most important among these fishes. This study was conducted to evaluate the demographic structure coefficients, survival rate, and stock status of L. lentjan from the Red Sea coast of Saudi Arabia. A total of 593 samples were collected on a monthly basis for a period of one year from the landing site for fishing boats operating in Red Sea waters off Jeddah. The results indicated that 88.87% of the specimens were female; the maximum total length recorded was 43.5 cm with the most frequent length (14.67%) being 23–23.9 cm. The maximum age recorded for both males and females was 6 year-plus, and the 1 year-plus age category represented the majority of the samples (57.67%). The total mortality coefficient, natural mortality coefficient, and fishing mortality coefficient were 1.538, 0.315, and 1.223, respectively; all mortality coefficients in the female fishes were higher than those in the male fishes. The survival rate of males was higher (0.617) than that of females (0.214). The results of the present study indicate that L. lentjan is subjected to overfishing and a new management strategy is necessary to improve the stock status of this fish species.

On the dynamics of an idealised bottom density current overflowing in a semi-enclosed basin: mesoscale and submesoscale eddies generation

The Red Sea Water enters the Gulf of Aden through the Strait of Bab El Mandeb as a density current. The Red Sea Water subsequently spreads into the Gulf of Aden under the influence of surface mesoscale eddies, which dominate the surface flow, of topographic features such as rift and capes, and of the monsoon regimes. The dynamics of a bottom density current overflowing in a semi-enclosed basin, as the Red Sea Water outflows in the Gulf of Aden, is investigated by performing idealised numerical simulations, at submesoscale resolution, in which we progressively add topographic and dynamical elements. The rift and cape play an important role, respectively, on the vertical and the horizontal mixing as well as baroclinic and barotropic instabilities undergone by the bottom density current. Mesoscale and submesoscale eddies are generated depending on the model configuration. In the presence of surface mesoscale eddies, the bottom density current water is mainly advected at their periphery. In winter, both mesoscale and submesoscale eddies are generated, while in summer only submesoscale eddies are present. Finally, to put our results based on idealised numerical simulations and Lagrangian experiments in perspective, we analyse the trajectories of three Argo floats, deployed in the Rift of Tadjurah. Clues of submesoscale eddies generation at capes are observed which is in agreement with our idealised numerical simulations.

Laser-Printed, Flexible Graphene Pressure Sensors.

While the outstanding properties of graphene have attracted a lot of attention, one of the major bottlenecks of its widespread usage is its availability in large volumes. Laser printing graphene on polyimide films is an efficient single‐step fabrication process that can remedy this issue. A laser‐printed, flexible pressure sensor is developed utilizing the piezoresistive effect of 3D porous graphene. The pressure sensors performance can be easily adjusted via the geometrical parameters. They have a sensitivity in the range of 1.23 × 10−3 kPa and feature a high resolution with a detection limit of 10 Pa in combination with an extremely wide dynamic range of at least 20 MPa. They also provide excellent long‐term stability of at least 15 000 cycles. The biocompatibility of laser‐induced graphene is also evaluated by cytotoxicity assays and fluorescent staining, which show an insignificant drop in viability. Polymethyl methacrylate coating is particularly useful for underwater applications, protecting the sensors from biofouling and shunt currents, and enable operation at a depth of 2 km in highly saline Red Sea water. Due to its features, the sensors are a prime choice for multiple healthcare applications; for example, they are used for heart rate monitoring, plantar pressure measurements, and tactile sensing.

Life cycle of mesoscale eddies in the Gulf of Aden

The Red Sea Water is a warm and salty water produced in the Red Sea by evaporation induced by strong solar radiation. This dense water mass exits the Red Sea through the Strait of Bab El Mandeb, and enters the Gulf of Aden as a density current between 400 and 1000 metre depth. In the Gulf of Aden, in situ and satellites observations have shown the impact of the deeply reaching eddies dominating the mesoscale dynamics, on the spreading of the Red Sea Water. In this paper, we study the life cycle of these mesoscale eddies in the Gulf of Aden by using a regional primitive equation model at mesoscale resolution, and an eddy-tracking algorithm. The mesoscale anticyclonic eddies are formed at the mouth of the Gulf of Aden, and subsequently drift westward into the gulf. Mesoscale anticyclones are long-lived compared to the cyclones. The cyclones result from the interaction of anticyclones with the coast and the sloping topography. The wind stress, the bathymetry and the surrounding eddy field drive the life cycle of eddies. Finally, Kelvin and internal waves are triggered along the northern and southern coasts.

The life cycle of submesoscale eddies generated by topographic interactions

Abstract. Persian Gulf Water and Red Sea Water are salty and dense waters flowing at intermediate depths in the Gulf of Oman and the Gulf of Aden, respectively. Their spreading pathways are influence by mesoscale eddies that dominate the surface flow in both semi-enclosed basins. In situ measurements combined with altimetry indicate that Persian Gulf Water is stirred in the form of filaments and submesoscale structures by mesoscale eddies. In this paper, we study the formation and the life cycle of intense submesoscale vortices and their potential impact on the spreading of Persian Gulf Water and Red Sea Water. We use a primitive-equation three-dimensional hydrostatic model at a submesoscale-resolving resolution to study the evolution of submesoscale vortices. Our configuration idealistically mimics the dynamics in the Gulf of Oman and the Gulf of Aden: a zonal row of mesoscale vortices interacting with north and south topographic slopes. Intense submesoscale vortices are generated in the simulations along the continental slopes due to two different mechanisms. First, intense vorticity filaments are generated over the continental slope due to frictional interactions of the background flow with the sloping topography. These filaments are shed into the ocean interior and undergo horizontal shear instability that leads to the formation of submesoscale coherent vortices. The second mechanism is inviscid and features baroclinic instabilities arising at depth due to the weak stratification. Submesoscale vortices subsequently drift away, merge and form larger vortices. They can also pair with opposite-signed vortices and travel across the domain. They eventually dissipate their energy via several mechanisms, in particular fusion into the larger eddies or erosion on the topography. Since no submesoscale flow clearly associated with the fragments of Persian Gulf Water was observed in situ, we modeled Persian Gulf Water as Lagrangian particles. Particle patches are advected and sheared by vortices and are entrained into filaments. Their size first grows as the square root of time: a signature of the merging processes. Then, it increases linearly with time, corresponding to their ballistic advection by submesoscale eddies. On the contrary, without intense submesoscale eddies, particles are mainly advected by mesoscale eddies; this implies a weaker dispersion of particles than in the previous case. This shows the potentially important role of submesoscale eddies in spreading Persian Gulf Water and Red Sea Water.

Differential Bioaccumulation of Trace Elements and Rare Earth Elements in the Muscle, Kidneys, and Liver of the Invasive Indo-Pacific Lionfish (Pterois spp.) from Cuba.

The Indo-Pacific lionfish is a saltwater fish that inhabits the Red Sea waters and the Indian and Pacific oceans; it is an invasive species in the western Atlantic and was recently introduced into the local diet in the USA, Central and South America, and the Caribbean with the aim of controlling the invasion of this species. Due to its predatory nature, it tends to bioaccumulate metals and other contaminants via the marine food web and could thus constitute a suitable species for monitoring aquatic ecosystems. The presence and distribution of 23 trace elements and 16 rare earth elements (REEs) were investigated by inductively coupled plasma-mass spectrometry (ICP-MS) in the muscle, liver, and kidneys of lionfish from Cuba. Significant differences in metal concentrations were found in the different fish organs. The liver and kidneys registered the highest concentrations for most trace elements and for ΣREE, thus demonstrating that they are effective bioindicators of possible pollution on the environment in which fish live, and assuming great importance in the choice of early biomonitoring. Trace element concentrations in the muscle are instead of crucial interest for consumer safety. The limits set by EU regulations and Cuban guidelines for Cd and Pb in fish muscle were never exceeded, suggesting that lionfish from Cuba could therefore represent a good source of minerals and proteins for the local population. Graphical abstract.

Thuwalallenes A-E and Thuwalenynes A-C: New C15 Acetogenins with Anti-Inflammatory Activity from a Saudi Arabian Red Sea Laurencia sp.

Thuwalallenes A–E (1–3, 5 and 8) and thuwalenynes A–C (4, 6, 7), new C15 acetogenins featuring uncommon ring systems, along with cis-maneonene D (9), thyrsiferol (10) and 23-acetyl-thyrsiferol (11) were isolated from the organic extract of a population of the red alga Laurencia sp., collected at Rose Reef off the village of Thuwal in the Red Sea waters of the Kingdom of Saudi Arabia. The structure elucidation of the isolated natural products was based on extensive analysis of their spectroscopic data. Compounds 1–6, 8, 10 and 11 were evaluated for their anti-inflammatory activity by quantifying nitric oxide (NO) release in response to TLR4 stimulation in macrophages. Besides compound 4 that did not exhibit any activity, all other tested metabolites inhibited NO production from activated macrophages. Among them, thyrsiferol (10) and 23-acetylthyrsiferol (11) displayed activity with IC50 values in the low nM scale without cytotoxicity.

The Guard Coral Crabs of Familes Trapeziidae and Domeciidae (Superfamily Trapezoidea) from the Egyptian Red Sea Coasts, and Its Asscoiated Gulfs, Aqaba and Suez, Egypt

A total of 6 species belong to families Domciidae and Trapeziidae (superfamily Trapezoidea: Brachyura: Decapoda) live in symbionts with branching stony corals in the shallow waters of the Egyptian coasts of the Red Sea, Gulf of Aqaba and Gulf of Suez were recorded during this study. These species were carefully examined and revised. The first family (Domciidae) was represented by only one species, Domecia hispida; while family Trapeziidae has 5 species comprised: Trapezia bidentata, Tr. cymodoce, Tr. digitalis, Tr. guttata and Tr. tigrina. All 5 species of genus Trapezia are well represented in the Red Sea waters; while Gulf of Aqaba was inhabited with Tr. cymodoce, Tr. bidentata and Tr. tigrina, and Gulf of Suez was occupied with Tr. cymodoce and Tr. gutata, in addition to Domecia hisipida. A brief description on general character, size, localities, color, habitats, and distribution was given. Constructed keys for identification of genera and species were also given.

On the Effect of Red Sea and Topography on Rainfall over Saudi Arabia: Case Study

This paper aimed to investigate the impact of Red Sea topography and water on the development and rainfall of a case of cyclogenesis occurs over Saudi Arabia during the period 16–18 November 2015 using the Weather Research and Forecasting (WRF) model. The WRF Control Run (WRF-CR) experiment was performed with presence of actual topography and surface water of the Red Sea, while the other three sensitivity experiments were carried out without (i) Red Sea Topography (NRST), (ii) Red Sea Water (NRSW), and (iii) Red Sea Topography and Water (NRSTW). The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission (TRMM) rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results demonstrate that rainfall intensity and spatio-temporal distribution significantly changes through each sensitivity experiment compared to the WRF-CR, where the significant variation was found in the NRST experiment. The absence of topography (NRST) leads to formation of strong convergence area over the middle of Red Sea which enhanced uplift motion that further strengthened the low-level jet over Red Sea and the surrounding regions, which enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the cyclonic system. The absence of Red Sea water (NRSW) changed rainfall spatial distribution and reduced its amount by about 30–40% due to affecting of the dynamics of the upward motion and moisture gradient, suggesting that surface fluxes play an important role in regulating the low-level moist air convergence prior to convection initiation and development.

Hydrography of a shelf ecosystem inshore of a major Western Boundary Current

The Agulhas Current, the largest Western Boundary Current in the Southern Hemisphere, strongly influences the oceanographic conditions of its adjacent shelf system. As a result of limited societal drivers, such as large-scale fisheries and marine mining, the South African southeast shelf, between Port Elizabeth and Port Shepstone, is one of the least studied and under-sampled shelf systems in Southern Africa. This study describes hydrographic conditions from the first two shelf-wide high-resolution surveys (January/February and July/August 2017) of this region. These data provide a baseline of environmental conditions and hydrographic processes across the shelf. The Agulhas Current, as well as cyclonic mesoscale eddies along the inshore edge of the Current, were observed to strongly drive conditions on the shelf. Substantial differences in the impacts of these cyclonic eddies were evident, with the smaller less intense January/February eddy inducing much stronger upwelling than the larger more intense July/August eddy. Indications of seasonality in temperature, salinity and chlorophyll-a were observed in the surface layers. Surface waters were 4 °C warmer in January/February than in July/August. Considerably lower salinities (33.77 g kg−1) were observed in January/February as a result of high rainfall and subsequent increased river outflow. Upwelling mechanisms such as divergence-induced upwelling, Ekman veering in the bottom boundary layer, Ekman pumping associated with cyclonic eddies, were observed to uplift colder, nutrient-rich water from deeper layers onto the mesotrophic shelf. These colder waters ultimately reached the surface as a result of wind-driven Ekman transport and vertical mixing. Tropical Surface Water, Subtropical Surface Water and South Indian Central Water were observed on the shelf. Red Sea Water as well as Antarctic Intermediate Water generally occupied the slope regions except where cyclonic eddies uplifted intermediate waters onto the shelf. The shelf-wide dissolved oxygen levels (>3 ml l−1) suggested that oxygen availability adequately facilitated the survival of the existing shelf biology.

Cut‐off low systems over Iraq: Contribution to annual precipitation and synoptic analysis of extreme events

AbstractWe combine daily in situ precipitation data with meteorological reanalysis data in order to explore the contribution of cut‐off low systems to the seasonal and inter‐annual rainfall variations over Baghdad from 2005 to 2016. During these 12 years (average rainfall of 131 ± 67 mm/year), 38 rainy cut‐off lows brought 43% of the total precipitation, with extreme inter‐annual variations. Indeed, precipitation associated with autumn cut‐off lows was the principal factor that turned an arid into a wet year: during the three most arid years cut‐off lows contributed about 25% of the average rainfall (10 out of 40 mm/year) while during the three wettest years they contributed near 67% (171 out of 254 mm/year). The extreme‐rain cut‐off low systems displayed analogous synoptic characteristics: upper‐atmosphere divergence, upwards vertical motions in the middle atmosphere, and lower‐atmosphere winds into central Iraq at times when the surface Red Sea and Persian Gulf waters were warmer than the surface air. During those days previous to an extreme event, the surface waters cooled substantially and the amount of precipitable water increased largely, suggesting high latent heat transfer. In order to characterize those conditions that favour rainfall, we focus on the November 18–20, 2013 cut‐off low system, which led to the largest flooding and wettest year in Baghdad between 2005 and 2016. The distribution of properties in the middle (500 hPa) and upper (250 hPa) troposphere shows that the region was affected by intense horizontal divergence and upwards motions, coinciding with a surface low over the Arabian Peninsula that caused intense northwards winds over the Persian Gulf and brought substantial moisture to central Iraq. The analysis of several stability indexes indicates that convective instability played a secondary role during the episode.

Elucidation of dual-mode inhibition mechanism of a typical polymer-based antiscalant on Red seawater for thermal desalination at higher temperatures and higher concentration factors

Scale deposition in the thermal process for desalination is quite inevitable. This study is about scale formation, crystal modification, and prevention mechanism of a tetrapolymer based antiscalant on Red Seawater. Red seawater at concentration factors (CF) of 1.5 and 2.5 was studied under reflux condition at 70 °C and 98 °C respectively for seven hours with 1 ppm, 2 ppm, and 4 ppm concentration of the antiscalant. Eventually, the mechanism of inhibitory action of the antiscalant has been reconnoitered after seawater analysis and imaging the morphological changes in the crystal formation patterns with Scanning electron microscope (SEM). The changes in the values of pH, turbidity and alkalinity (both phenolphthalein alkalinity (PA) and total alkalinity (TA)) were measured to apprehend various fluctuations happening as a result of the addition of antiscalant. The variations in the pH of seawater with antiscalant were in concurrence with the changes in alkalinity and was also reflected in turbidity. These changes explicitly demonstrated the threshold mechanism of scale inhibition. SEM micrographs exhibited distorted round shaped depositions supporting crystal modification mechanism as well. The efficiency and dominance of inhibitory mechanism varied from 2 h to 6 h for the antiscalant and was observed to be directly related to CF of seawater used, the temperature applied, and a dose of antiscalant added.

Production of pectin lyase from agricultural wastes by isolated marine Penicillium expansum RSW_SEP1 as dye wool fiber

Enzyme technology is considered one of the most promising tools in the field of biotechnology as applied biocatalysts. The marine fungal strain Penicillium expansum RSW_SEP1 isolated from red sea water at Sharm El-Shiekh province and identified by 18S rRNA gene (accession number MH754656). The strain was able to produce pectin lyase from different agricultural wastes as the cheapest and most economical carbon source. The maximal enzyme activity of 88.83 U/mL was obtained from the pea peel (Pp) and sugar cane bagasse (Scb) at ratio 5:5 (w/w) and pH 6 by 8 mL of spore suspension as inoculum. Different concentrations of pectin lyase were examined on green dyed. The highest value of color strength (K/S) at 15% of wool fibers dyed with green algae by microwave after 5 min of the pretreated wool at pH 5.0. Different concentrations % of pectin lyase was examined on green dyed. The results indicated that, the highest value of color strength (K/S) at 15% of wool fibers dyed with green algae by microwave after 5 min of the pretreated wool at pH 5.0. This study focused on isolation and molecular identification of marine fungal strain as pectin lays producer from agriculture wastes and its application of dyeing wool fibers.

Seasonality of marine plastic abundance in central Red Sea pelagic waters

The Red Sea holds one of the lowest concentrations of floating plastic worldwide and no evident congregation zones were identified so far, despite peculiar oceanographic features that candidate the basin as an accumulation area for floating debris. However, the Red Sea exhibits a complex pattern of surface currents, which changes according to the monsoon season, possibly affecting the abundance of plastic throughout the year. To explore the effect of seasonality on plastic concentration in surface waters, we conducted a fortnightly time series sampling, using a neuston net, for 21 months at a pelagic station in the central Red Sea, where the major seasonal overturn of the Red Sea surface circulation occurs. The estimated average abundance (±SE) was 58,563 ± 19,272 items Km−2 (73.5 ± 40.75 g Km−2), highly variable according to season, lower during the summer monsoon. Indeed, the winter monsoon pushes oceanic surface waters inside the Red Sea, transporting alongside floating plastic items, whilst surface currents exit the basin during the summer monsoon, depleting central Red Sea waters from floating plastic. Composition of plastic items also changes through time. Particularly, the higher proportion of films and foams during summer months suggests that the main source of plastic at the sampling station from June to September is a short-range transport, while during winter months, the higher contribution of small fragments indicates that, from October to May, plastic is also transported to the central Red Sea through surface currents for long distances, possibly coming all the way from the Indian Ocean.

Flux Optimization in Reverse Osmosis via the Solution-Diffusion Model

This paper suggests a new method of predicting flux values at reverse osmosis (RO) desalination plants. The study is initiated by using the solution-diffusion model that is applied to the groundwater source at Abqaiq plant (500 RO plant) at Saudi Aramco, Dhahran, Saudi Arabia in order to calculate the osmotic pressure of the treated water for Shedgum/Abqaiq groundwater. For modelling purposes, the same technique is used to determine the osmotic pressure drops at the same plant configuration and operating conditions when using seawater sources such that of Arabian Gulf and the Red Sea waters. High rejection brackish water RO (BWRO) element Toray TM720D-400 with 8" is the RO membrane type that is used at Abqaiq plant. The calculated osmotic pressures of the three water sources, assuming that they are all treated at Abqaiq plant, are utilized to determine the appropriate flux values as well as membrane resistances of different BWRO Toray membranes. Values of numerous parameters such as water permeability constant, applied pressure, gas constant, water temperature, water molar volume and membrane thickness, water salinity/TDS are taken into account to develop our calculations through the solution-diffusion model. A comparison between low-pressure, standard and high-pressure BWRO Toray membranes performance have been established to select the ideal membrane type for the treatment of water from various sources at Abqaiq plant. The model results confirm an inverse relationship between the membrane thickness and the water flux rate. Also, a proportional linear relation between the overall water flux and the applied pressure across the membrane is identified. Higher flux rates and lower salinity indicate lower membrane resistance which yields to the higher water production. Modelled data predict that BWRO Toray TM720D-440 with 8" membrane is the optimal BWRO membrane choice for the three water sources at Abqaiq plant.

Co-axial hollow fiber module for air gap membrane distillation

A novel air gap membrane distillation (AGMD) module in which non-porous polymeric hollow fiber condensers (i.e., heat exchangers) were inserted inside the porous hollow fiber membranes was developed. In this module the hot feed was circulated on the outer side of the membrane's lumen and the coolant was circulated counter-currently inside the condenser fibers. The condensation of water vapor occurred in the air gap between the inner surface of the membrane fibers and the outer surface of the condenser fibers. By varying the number of condenser fibers inside the lumen, a different ratio of membrane fiber active surface area to the total surface area of condenser fibers and corresponding packing densities were achieved and examined in desalination of Red Sea water. The effect of membrane type on process performance was investigated with three different hollow fiber membranes with varied wall thickness (two capillary and one tubular). At a feed temperature of 85 °C, the water vapor flux increased from 12 kg/m2h to 18 kg/m2h with the increase in condenser fibers packing density from 9% to 28%, and then decreased to 14 kg/m2h when packing density was increased to 36% due to condensing surface constrain inside the lumen. A higher efficiency of the AGMD process was observed in the case of capillary membranes as compared to tubular membranes due to reduction in wall thickness which facilitated lower mass transfer resistance. The effect of operating conditions including feed and coolant flow rates and temperature difference between the feed and coolant solutions was also investigated. The increase in the feed flow rate had significant effect on vapor flux comparing to that of coolant for all tested AGMD configurations. This effect was more pronounced at high feed temperatures. Based on observed results, an optimal module design was suggested.