A new approach to membrane and thermal seawater desalination processes using nanofiltration membranes (Part 1)

Seawater desalination — SWCC experience and vision

A demonstration plant based on the new NF—SWRO process

Dual-stage nanofiltration seawater desalination: water quality, scaling and energy consumption

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.

Optimization of hybridized seawater desalination process

One of the main applications of nanofiltration (NF) is in the pretreatment stage of seawater desalination. NF has high rejection rates for divalent ions and could eliminate the scaling species that pose serious fouling problems in seawater desalination. This review comprehensively examines recent advances in NF membrane research in seawater desalination. Significant progress has been made in understanding the mechanism of solute transport through NF membranes and has resulted in the development of predictive models based on the Spiegler–Kedem model and the modified Nernst–Planck equation. The contributions of each type of transport mechanism through NF membranes, i.e., convection, diffusion, and electro-migration, have been reported. A review of recent progress made in the development of integrated NF membrane and seawater desalination processes is included. Work related to membrane fouling, which is a key problem in NF, is also discussed.

A holistic review on how artificial intelligence has redefined water treatment and seawater desalination processes

Pre-treatment with nanofiltration (NF) in seawater desalination—Preliminary integrated membrane tests in Urla, Turkey

Advances in seawater desalination technologies

Seawater desalination technology is an important solution to global water scarcity, yet conventional methods such as reverse osmosis (RO) and distillation face challenges including high energy consumption and costly infrastructure. Graphene, as a novel nanomaterial, has demonstrated promising application prospects in desalination due to its unique physical and chemical properties. This study focuses on the applications of graphene in seawater desalination. Through comprehensive collection, organization, and analysis of relevant literature, the promotion effect of graphene on seawater desalination process in various forms such as permeable membrane and photothermal conversion membrane is analyzed and summarized. Finally, the existing research results, shortcomings and future development directions of graphene in the field of seawater desalination are summarized.

Both brackish water desalination and seawater desalination processes are well established and in common use around the globe to create new water supply sources. The farther the location of the source water from the ocean or seashore, the lower the salinity (TDS) of the water and the lower the osmotic pressure that needs to be overcome when desalinated water is produced. This is one of the major reasons that brackish desalination is often considered less costly than seawater desalination. A number of project considerations, however, indicate that seawater desalination can be beneficial and more cost-effective than brackish water desalination. To make a fair comparison, we need to properly compare all major aspects of both types of projects to define the best and most appropriate desalination technology. While brackish water has less feed water TDS, it is more challenging to dispose of the produced concentrate. Also, although brackish water desalination needs less energy to overcome osmotic pressure, it usually requires more energy to draw the water from the well than it takes to pump seawater from the open ocean intake. Another factor is that the temperature of the brackish well water may be lower than the temperature of ocean water, giving seawater desalination an advantage in energy demand. In comparing brackish to seawater desalination, these major aspects should be evaluated: (1) Locations of seawater and brackish water plants, relative to the major consumers of the desalinated water, (2) Transportation (pumping and disposal) costs of the feed water and produced water, (3) Potential colocation of a seawater plant with a large industrial user (e.g., power plant) of the seawater for cooling or other purposes, (4) Produced quality of brackish water and seawater desalination in terms of major minerals and emerging contaminants, (5) Sustainability of the water source: capacity and depth of the brackish water wells, as well as the type of soil. (6) Technical and economic aspects of produced concentrate disposal, (7) Permitting process costs for brackish and seawater desalination, and (8) The economics of both brackish and seawater desalination treatment processes: capital costs, operational and maintenance (O&M) costs, lifetime water cost, and total water cost (TWC). This paper discusses the major evaluation criteria and considerations involved in properly comparing the economic and technical aspects of brackish and seawater desalination to determine the more favorable desalination technology for a given desalination project.

Progress in membrane science and technology for seawater desalination — a review

Energy-efficient hybrid FCDI-NF desalination process with tunable salt rejection and high water recovery

Solar energy, amongst all renewable energies, has attracted inexhaustible attention all over the world as a supplier of sustainable energy. The energy requirement of major seawater desalination processes such as multistage flash (MSF), multi-effect distillation (MED) and reverse osmosis (RO) are fulfilled by burning fossil fuels, which impact the environment significantly due to the emission of greenhouse gases. The integration of solar energy systems into seawater desalination processes is an attractive and alternative solution to fossil fuels. This study aims to (i) assess the progress of solar energy systems including concentrated solar power (CSP) and photovoltaic (PV) to power both thermal and membrane seawater desalination processes including MSF, MED, and RO and (ii) evaluate the economic considerations and associated challenges with recommendations for further improvements. Thus, several studies on a different combination of seawater desalination processes of solar energy systems are reviewed and analysed concerning specific energy consumption and freshwater production cost. It is observed that although solar energy systems have the potential of reducing carbon footprint significantly, the cost of water production still favours the use of fossil fuels. Further research and development on solar energy systems are required to make their use in desalination economically viable. Alternatively, the carbon tax on the use of fossil fuels may persuade desalination industries to adopt renewable energy such as solar.

Optimisation of multi effect distillation based desalination system for minimum production cost for freshwater