Will Reverse Osmosis Replace Thermal Desalination in GCC Region

Novel Tri Hybrid Desalination Plants

Libya, like many arid countries, relies heavily on groundwater resources, which are increasingly scarce. With a 1950 km Mediterranean coastline offering an abundant but highly saline water source (35,000 38,000 ppm), seawater desalination is essential to meet national water demands. This study presents a techno-economic evaluation of three desalination technologies—Reverse Osmosis (RO), Multi-Stage Flash (MSF), and Multi-Effect Distillation (MED)—for a 1200 m³/day plant. RO design was conducted using ROSA software, while MSF and MED were modeled thermodynamically.RO requires significantly lower seawater intake (117 m³/h) compared to MSF (475.7 m³/h) and MED (200 m³/h), with corresponding plant efficiencies of 43%, 10.5%, and 25%. RO produces potable water (190 ppm TDS), while MSF and MED yield ultra-pure water (~50 ppm TDS), necessitating remineralization. RO operates without steam input, unlike MSF and MED (7.3 m³/h steam), and demands 235 kW of electrical power versus 245 kW (plus steam) for MSF and 50 kW (plus 7.5 m³/h steam) for MED. RO’s high brine pressure (53.5 bar) enables energy recovery, whereas MSF and MED discharge warm brine at low pressure, posing environmental challenges. Economically, unit water costs are $0.37/m³ for RO, $1.52/m³ for MSF, and $1.21/m³ for MED. Overall, RO is the most technically and economically viable option for this capacity under Libyan conditions.

Two-stage FO-BWRO/NF treatment of saline waters

It is well established that to sustain the growth in human population commensurate growth in potable water resources is a necessity. Thus, to produce “extra” water in potable form, technologies like sea-water or brackish water desalination is resorted which include thermally driven technologies like multi-stage flash (MSF) or multi effect distillation (MED) or pressure driven like reverse osmosis (RO). It is well established that operation of “State of Art” RO plants are energetically closest (3–6 kWh/m3) to thermodynamic limits (1.56 kWh/m3 for 50% recovery of 35,000 ppm feed) of desalination whereas MSF or MED are more energy intensive (20 kWh/m3 and higher). Hence, RO has gained widespread popularity over the last few decades. However, as fresh water is extracted from seawater, what remains is concentrated brine, which has almost twice the salt concentration of sea-water and is(increasingly becoming) an environmental concern. Therefore, Zero Liquid Discharge (ZLD) desalination processes for brine or hypersaline streams management from land locked desalination is an absolute necessity. As RO itself is a mature technology, there is little scope in improvement of the same as far as membrane configuration and chemistry is concerned. Hence, in this book chapter, the authors discuss sustainability of desalination from two perspectives. One is to explore the potential to integrate solar/wind energies to desalinate water through RO. This would lead future efforts into solar and wind related developments as well as energy storage devices influencing RO. Then the chapter delves into handling the RO reject. The reject brine of RO (or any hypersaline stream) can be subjected to three approaches: (i) Water for Energy (WFE), (ii) Energy for Water (EFW) and (iii) Brine to Chemicals (BTC). The selection of WFE and EFW depends on the degree of salinity (DOS). If the DOS is large, indicating high osmotic pressures, then it is advisable to recover the osmotic energy of the stream to generate power (WFE) through technologies like Pressure Retarded Osmosis or Reverse Electrodialysis. However, EFW approach can also be undertaken utilizing brine concentrator (BC) to generate water and recover salts from brine. Zero Liquid Discharge approach utilizing BC and aided by membrane-based forward osmosis (FO)/electrodialysis reversal (EDR)/membrane distillation (MD) to achieve 10% concentration of brine followed by BC (to attain 22% concentration) is also discussed. To achieve ZLD, Forced Circulation Crystallizer (FCC) is utilized downstream of BC. This process will recover salts as valuable byproduct and thereby improve the overall techno-economics. Challenges involved in design and development of ZLD desalination processes for wider scale application of these technologies in desalination and other industries is discussed. A new avenue worth exploring is BTC, which involves integration of Chlor-Alkali processes to recover Chlorine and Hydrogen from brine which are extremely important to the chemical industry to produce water treatment chemicals (using Chlorine) as well as for producing urea (using hydrogen through Haber process) for agriculture. Thus, the book chapter focuses not only on making RO sustainable but also provides futuristic avenues to make the Water-Energy and Water-Energy-Food Nexus more sustainable.KeywordsDesalinationReverse osmosisWater-energy nexusBrine handlingSustainability

Performance analysis of hybrid system of multi effect distillation and reverse osmosis for seawater desalination via modelling and simulation

Comparison between Forward Osmosis-Reverse Osmosis and Reverse Osmosis processes for seawater desalination

Optimization of Integrated Forward – Reverse Osmosis Desalination Processes for Brackish Water

An optimization strategy for a forward osmosis-reverse osmosis hybrid process for wastewater reuse and seawater desalination: A modeling study

A two-step forward osmosis (FO) desalination process combining both FO and reverse osmosis (RO) systems has been developed by the Centre for Osmosis Research and Applications at the University of Surrey and commercialised by Modern Water plc. In the FO + RO process seawater was used as feed water (FW) and a concentrated aqueous solution was used as a draw solution (DS). By taking advantage of natural osmosis, pure water is transferred from the FW to the DS and then recovered from the DS by the RO process utilising low resistance membranes, and hence lower specific energy consumption (SEC). This paper presents results of FO experiments conducted on flat sheet membrane using a bench-scale rig. The osmotic agent investigated in this study was magnesium sulphate, which is non-toxic, and highly soluble in water. Furthermore experiments were carried out on the RO pilot in order to regenerate the DS for reuse in the FO process and produce clean water. This paper also presents some pilot plant results and data from commercial plants in Oman and Gibraltar. The data demonstrates the efficiency of the FO + RO compared with the conventional RO process in terms of SEC and membrane fouling performance.

Water is not just the essential ingredient for life, but also a fundamental factor in the economy and security of any country. Coupled with increased population and climate change effect, the availability of food, water, and energy are the biggest challenges that the world faces. There is also the dependency of these essential gradients and basic needs on each other; i.e., water is needed to produce energy and energy is needed to produce water as well as both water and energy are needed to produce food. Over the next two decades water demand will exceed water supply by about 40% according to many scientific studies and reports. Food and energy demands will exceed supply by 50% and have also been described by the UK government's chief scientific advisor, Prof. John Beddington, to create the ''perfect storm'' by 2030. The provision of drinkable supplies through desalination could offer a sustainable solution to the drinking water problem but also presents a technical challenge too as well as all existing methods involve high operating and investment costs. A novel manipulated/forward osmosis (MfO) desalination process has been invented and developed at the Centre for Osmosis Research and Applications at the University of Surrey in collaboration with Modern Water plc (Modern Water). In the MfO process seawater is converted into an osmotic agent's solution by taking advantage of the natural osmosis process. Pure water is then recovered from the osmotic agent's solution using a membrane process, where the agent is reused. The technical obstacles being overcome in this process are the avoidance of all scaling, bio-fouling, high operating pressures, and necessity for pre-treatments and the associated chemical wastes, which result in direct and indirect reduction of cost. The concepts also serve as a platform for applications in power generation and other industrial applications. The pilot plant and Modern Water's commercial plants data in Oman and Gibraltar that follow from the manipulated osmosis (MO) process route offers up to 30% saving in the specific energy consumption over a conventional reverse osmosis (RO) process. The MO process also offers an increase in fresh water recovery rate coupled with minimal membrane fouling propensity and brine disposal. Additionally, the process can be incorporated into existing RO and thermal plants with reasonable modifications. New plant based on the MO principle should also have lower capital costs and smaller footprint. The new technology can be used to obtain clean water from any available water source irrespective of its purity, such as waste streams, seawater, brackish water, river water, etc. The provision of drinkable supplies through desalination could offer a sustainable solution to the drinking water problem but also presents a technical challenge too as well as all existing methods involve high operating and investment costs. A novel Manipulated/Forward Osmosis (MfO) desalination process has been invented and developed at the Centre for Osmosis Research and Applications at the University of Surrey in collaboration with Modern Water plc. In the MfO process seawater is converted into an osmotic agent's solution by taking advantage of the natural osmosis process. Pure water is then recovered from the osmotic agent's solution using a membrane process, where the agent is reused. The technical obstacles being overcome in this process are the avoidance of all scaling, bio-fouling, high operating pressures, and necessity for pre-treatments and the associated chemical wastes, which result in direct and indirect reduction of cost. The concepts also serve as a platform for applications in power generation and other industrial applications. The pilot plant and Modern Water's commercial plants data in Oman and Gibraltar that follow from the MO process route offers up to 30% saving in the specific energy consumption over a conventional RO process. The MO process also offers an increase in fresh water recovery rate coupled with minimal membrane fouling propensity and brine disposal. Additionally, the process can be incorporated into existing RO and thermal plants with reasonable modifications. New plant based on the MO principle should also have lower capital costs and smaller footprint. The new technology can be used to obtain clean water from any available water source irrespective of its purity, such as waste streams, seawater, brackish water, river water, etc.

The forward osmosis and desalination

State-of-the-art of reverse osmosis desalination

Machine learning models for predicting the rejection of organic pollutants by forward osmosis and reverse osmosis membranes and unveiling the rejection mechanisms

Evaluation of organic matter characteristics of FO and RO concentrates

Cost-based feasibility study and sensitivity analysis of a new draw solution assisted reverse osmosis (DSARO) process for seawater desalination