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

Novel Tri Hybrid Desalination Plants

Desalination is probably the only means for fresh water supply to countries in decertified climate. The majority of GCC counties rely on desalinated water for fresh water supply to major cities. Over 70% of the desalinated water in the GCC comes from thermal desalination plants including Multi Stage Flash (MSF) and Multi Effect Distillation (MED). The new trend in the desalination plant in the GCC is 30% Reverse Osmosis (RO) and 70% thermal. However, these percentages vary from one to another country depending on feed water quality and expertise. For example, Oman Sea has lower salinity than the Gulf water and hence Oman uses more RO for desalination than MED and MSF. This decision is also driven by economy as RO process less energy intensive and hence the produced water is less expensive as compared to thermal plants. On the contrary, Qatar and Kuwait use more MSF followed by MED due to the high salinity and low quality feed water. This is also because trials of RO in both Qatar and Kuwait were not successful because of the problems of membrane fouling and restrict pre-treatment requirements due to the quality of the water intake.The advantages of RO over thermal technologies are well known in terms of lower energy consumption and the cost of produced water; but are not yet taken advantage of in the GCC zone. One of the reasons is blamed on high feed water salinity and bad water quality; other reasons such as lack of experience, red tides and reliability are contributed to the dominance of thermal plants. However, field experience showed that good pretreatment and optimized RO design may overcome the problems of high feed salinity and bad water quality. Several RO plants, such as Fujairah in UAE, are good examples of a working RO technology in the harsh water environment. Good RO design includes design and optimization of both pretreatment and post-treatment. Field experience showed that most of RO plants failure was due to inefficient pretreatment which resulted in providing low quality water to the RO membrane that caused fouling. Fouling, including biological and scaling, can be handled once an efficient pretreatment process is available. Recent advances in pre-treatment techniques include the combination of Forward Osmosis (FO) with RO among other methods. Recent studies by the authors including commercial implantations have shown that the combination of FO with RO addresses the most technical challenge of RO process and that is fouling, which results in lower energy consumption and less chemical additives. Experience showed fouling in FO process in reversible, i.e. can be removed by backlashing while fouling in conventional RO process is irreversible.In this study, the feasibility of integrating FO with RO process for the desalting of the Gulf water in Qatar is presented. The results are expressed in terms of specific energy consumption, process recovery, produced water quality, chemical additives and overall process cost.The implementation of RO for desalination is not only reducing the cost of desalination but also the environmental impact. More R&D should be done to provide useful data about RO application and suitability for the Gulf water. The R&D should be focused on laboratory to market development of RO technology using rigorous lab scale and pilot plant testing program.

Cost evaluation and optimisation of hybrid multi effect distillation and reverse osmosis system for seawater desalination

Minimisation of Energy Consumption via Optimisation of a Simple Hybrid System of Multi Effect Distillation and Permeate Reprocessing Reverse Osmosis Processes for Seawater Desalination

Potential of solar desalination in Israel and in its close vicinity

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

In recent times two or more desalination processes have been combined to form integrated systems that have been widely used to resolve the limitations of individual processes as well as producing high performance systems. In this regard, a simple integrated system of the Multi Effect Distillation (MED)/Thermal Vapour Compression (TVC) and Permeate Reprocessing Reverse Osmosis (PRRO) process was developed by the same authors and confirmed its validity after a comparison study against other developed configurations. However, this design has a considerable amount of retentate flowrate and low productivity. To resolve this issue, two novel designs of MED and double reverse osmosis (RO) processes including Permeate and Retentate Reprocessing designs (PRRP and RRRO) are developed and modelled in this paper. To systematically assess the consistency of the presented designs, the performance indicators of the novel designs are compared against previous simple designs of MED and PRRO processes at a specified set of operating conditions. Results show the superiority of the integrated MED and double permeate reprocessing design. This has specifically achieved both economic and environmental advantages where total productivity is increased by around 9% and total retentate flowrate (disposed to water bodies) is reduced by 5% with a marginally reduced energy consumption.

Hybrid solar desalination systems driven by parabolic trough and parabolic dish CSP technologies: Technology categorization, thermodynamic performance and economical assessment

This work presents a detailed thermo-economic analysis of unit water costs from dual-purpose cogeneration plants. The power levelized cost was first calculated for stand-alone steam, nuclear, and combined-cycle power plants. The cost of energy needed to operate the desalination systems connected to power plants was evaluated based on two different approaches: power- and heat-allocated methods. Numerical models based on the heat and mass balances of the power and desalination plants’ components were developed and validated. Comprehensive and updated data generated using Desaldata libraries were correlated to estimate the capital, labor, overhead, and maintenance costs for different desalination systems. The levelized water cost produced by multi-effect distillation, multi-effect distillation with vapor compression, multi-stage flash, and reverse osmosis systems connected to different power plants was estimated. The impact of various controlling parameters, including the price of natural gas, nuclear power plant installation cost, and the desalination capacity on water cost, was investigated. For all simulated cases, the levelized water cost evaluated using the heat-allocated method was found to be lower by 25–30% compared to that estimated using the power-allocated method. The cost of water produced using reverse osmosis remains below that produced by other desalination technologies. However, using the heat-allocated method to estimate the levelized water cost narrows the gap between the costs of water produced by multi-effect distillation and that produced by seawater reverse osmosis. The results also show that the use of the multi-effect distillation process in a cogeneration configuration rather than multi-effect distillation with vapor compression can result in a lower water cost. The profit analysis shows slight differences between the profit of a power plant connected to a reverse osmosis system and the profit of a power plant connected to a plain multi-effect distillation system.

Minimisation of energy consumption via optimisation of a simple hybrid system of multi effect distillation and permeate reprocessing reverse osmosis processes for seawater desalination

Lack of clean water is one of the world’s most challenging concerns, and as pollution levels rise, the availability of clean water is rapidly diminishing, necessitating the development of an appropriate remedy. A possible solution to this problem is to transform salty or brackish water into pure water using a variety of desalination technologies. This chapter covers the fundamental techniques and contemporary advancements in thermal-based high-capacity desalination systems, such as multi-stage flash (MSF) evaporation, multi-effect distillation (MED), vapour compression distillation (VCD), low-temperature thermal desalination (LTTD), and others. In addition, the viability of a solar energy integrated desalination system as a long-term solution to the problem of water scarcity and also the case study of existing solar energy-based large-scale desalination has been presented. Improved thermal efficiency, performance ratio, and yield rate of the desalination system through hybridization of MSF, MED, and VCD processes among themselves as well as with the reverse osmosis (RO) process has been reported. Furthermore, it has been observed that the LTTD is one of the eco-friendly approaches to desalinating water on a large scale with the least level of carbon footprint and global warming potential (GWP). Besides that, the future direction of large-scale solar desalination development has been indicated.

PurposeIn this paper the performance and effectiveness of the reverse osmosis (RO) process for the biologically pretreated leachate was investigated. The RO process was carried out separately for two different pH: 8.0 and 9.3.MethodsA general pollution parameters as well as organic and inorganic indicators were determined in raw, biologically pretreated and RO treated leachate. The performance characteristics of the reverse osmosis system were made on the basis of permeate flux, electroconductivity removal rate, concentration factor and efficiency in removal of analyzed parameters.ResultsThe use of SBR pretreatment had very good efficiency in BOD (97.3%) and ammonia nitrogen (95.4%) removal. The lowest effectivity was observed for chloride (11.6%), boron (3.9%) and TDS (1.2%). Pretreated leachate was subjected to RO system. The normalized average flux was 0.53 (42.3 L/m2·h) for pH = 8.0 and 0.68 (33.5 L/m2·h) for pH = 9.3. The lower membrane fouling at higher pH can be explained by electrostatic repulsion between the negatively charged membrane surface and organic substances. Independently of the process pH, a two-step membrane fouling was observed. The greatest differences in removal rates were observed for boron, which had a higher retention rate at higher pH, and ammonia nitrogen, whose removal rate decreased at higher pH. The obtained permeate pH after RO process was lower than the feed pH in two analyzed value of pH.ConclusionsThe higher flux value at pH = 9.3 is result of high content of organic matter in leachate, which is better rejected at higher pH because of higher electrostatic repulsion between organic matter and membrane surface. This indicates that the organic matter content should be taken into account when determining the operating parameters (pH values) of the RO system.

The feasibility of nanofiltration membrane bioreactor (NF-MBR)+reverse osmosis (RO) process for water reclamation: Comparison with ultrafiltration membrane bioreactor (UF-MBR)+RO process

Performance analysis of a hybrid system of multi effect distillation and permeate reprocessing reverse osmosis processes for seawater desalination

Distillation vs. membrane filtration: overview of process evolutions in seawater desalination