Saudi Arabia Water Challenge - Term Paper Example

Saudi Arabia Water Problem Table of contents Purpose statement Introduction Background Desalination process Nano membrane technology Reverse osmosis Comparison between reverse osmosis, and Nano membrane technology Conclusion Saudi Arabia Water Problem Purpose Statement This report will mainly discuss nanotechnology used for water purification, and how it works, and then discusses the currently used approach “Reverse osmosis.” Finally, the report will study the advantages and the disadvantages of two desalination approaches. A. Introduction Water refers to a neutral compound chemical substance containing hydrogen and oxygen, which are covalently joined together. Water exists in liquid (at ambient conditions), gaseous (vapour), and solid forms as ice. In addition, water covers a vast percentage of the earths’ surface and is very essential for living and non-living forms of life. According to Bragg and Bragg (2005), the oceans contain about 97% of the entire water on the earths’ surface; in Saudi Arabia, water has been supplied in three forms, mainly surface water, which accounts for about 10%, the underground aquifers that provide the majority percentage of more than 80%, and the various desalination plants, which provide about 5% of water. The availability of essential water supply continued to deplete and the water resources become limited, prompting the adoption of desalination plants. Natural resources define all the resources that occur freely within the environment that exist in a natural form, such as natural forests, minerals, water, and natural gases. 1. Background Desalination refers to the several processes of conversion of salt water to fresh water through the removal of salt and other minerals. Several approaches are used to treat seawater including thermal evaporation of seawater and use of modern desalination plants, osmosis in reverse. Nanomembranes are filters made from organic polymers with less thickness that are used to separate the liquids and gases at the molecular levels. Such technology is also used in desalination of seawater, purification of polluted water, and the removal of carbon dioxide and other pollutants from exhaust gases. The modern technology adopted in Saudi Arabia has enabled the exploitation of underground water by companies such as Saudi Aramco, an oil company, and hence increasing availability of water in the country. 2. Desalination process In Saudi Arabia, there has been water scarcity because of the rising population, which led to the adoption of desalination technology through the development of modern polymer materials producing semi-permeable membranes, which allow selective passage of water and other ions. The technology is categorized according to content extracted (water or salt from the main stream), separation process, and the energy used in the entire process (Anon, 1997). Evaporative processes have been used for extraction of fresh water from the mainstream. Such evaporative desalination processes consist of various methods. Multi stage flash (MSF) method involves the evaporation of seawater in chambers with low pressure as compared to the vapor pressure. The low-grade steam from the turbines heats the tubes within the distiller, which heat the seawater intake. The heated seawater then passes into low-pressure vessels, and boils into steam. The steam is condensed on heat exchanger tubes, which are cooled by the incoming water, feed to the heater. The conversion of seawater to steam depends on the pressure maintained within the vessel. In multiple effect distillation (MED), condensing steam heats tube bundles, resulting into evaporation. The vapor produced is used as steam in the next chamber operating at low pressure and temperature (Micale, Cipollina and Rizzuti, 2009). B. Nano membrane technology Membranes are selective barriers between two phases. The use of Nano membrane technology is vital in the reclamation of wastewater, for example, from the domestic sewage. This technology is also used in the desalination process to avail more water to the increasing population and demand for water. Membrane filters are created including nanofiltration, ultrafiltration, and microfiltration. In ultrafiltration, the high hydrostatic pressure used forces the liquid against a semi permeable membrane, which retains the high molecular weight solutes and suspended solids, while allowing water to pass through, while microfiltration uses pressurized systems to remove contaminants from fluids by the passage through microporous membrane. The cross flow principle is used with both ultra and micro filtration, where the feed flow (seawater) travels tangentially across the filter surface; the solids are trapped in the filter, while the filtrate passes to the other end. The membranes inner surface consists of sponge like structures, which provides fluid resistance, and retains particles and other coagulates. It is a pressure driven process that uses semi permeable membranes for the selective removal of dissolved solutes. The Nanomembranes are thin (more permeable) made of polyamides and require less pressure for nanofiltration to take place. In order to reduce the costs of desalinating water, solar energy is to be used to provide the required energy for the process; the plant uses ultrahigh concentrator photovoltaic cells. The process consists of seven stages namely; pretreatment, coagulation, flocculation, sedimentation, disinfection, aeration and filtration. The force applied which can be a concentration gradient, temperature difference, electrical or potential difference, or pressure difference, to the fluid mixture, allows selective passage through the membranes, the solutes remain while the low molecular solvent passes through the membrane. Membrane technology combines membrane bioreactors and membrane technology (ultrafiltration, microfiltration, and nanofiltration). Reverse osmosis Reverse osmosis refers to movement of solvent molecules from a more concentrated environment to a more dilute environment when the pressure applied is greater than the osmotic pressure (Bettelheim, et al, 2009). This type is categorized basing on the separation process involved. It consists of various forms such as semi-permeable membranes, and ionic membranes (electro dialysis). In reversed osmosis, the semi-permeable membranes used allow selective passage between water and the mineral salts, whereby, water being a solvent, passes through the membrane into the permeate stream, leaving the solutes due to pressure difference. There are two compartments, one containing the seawater and the other external pressure, which is more than the osmotic pressure. Seawater forces the water molecules to move towards the dilute compartment against the concentration gradient. The membranes used are made of dense barrier layers (cellulose acetate) that allow only the solvent to pass through. There are no heating or phase changes that are required, energy is efficiently provided by the abundant oil reserves within Saudi Arabia. The reversed osmosis system consists of three subsystems namely pretreatment, membrane process, and post treatment. There are two output streams - the less saline water, and the concentrated saline stream. In the pretreatment process, various substances are added to the seawater or feed water from the ocean or underground, as it enters the first chamber; acids and scale inhibitors, which prevent salt precipitation especially of the sparingly soluble salts. After this, the seawater is fed into the membrane process, consisting of tough barrier layers, which are semi-permeable, allowing selective movement of solvent and solute. External pressure, which is greater than the osmotic pressure of the seawater, is applied, allowing selective passage of solvent, and leaving the solutes (mineral salts). This ensures the movement of the solvent towards the dilute solution. After this process, the solvent in the compartment is passed through the post treatment process, where aeration and degasification are performed, after which stabilization and disinfection chemicals are added and then fed into the distillation system. The concentrate is discharged into a separate chamber (Bergman, p.7, 2007). Figure showing the process of reverse osmosis Source: http://www.oas.org/dsd/publications/unit/oea59e/ch20.htm. C. Comparison Between, Reveres Osmosis, and Nanomembranes The Nano membranes developed utilize a significantly less amount of power compared to the reverse osmosis, which requires high pressure, and will filter out toxins, such as arsenic. The process consists of pretreatment, membrane process and the post treatment subsystems. Nano membrane technology is a cost effective process of desalination and water purification and a safer technology being adopted in Saudi Arabia, in the city of Al Khafji that will serve numerous population with clean water (Zhang, et al, 2009). Both reverse osmosis and Nano membrane are technologies that are used in Saudi Arabia for desalination and purification of water from the sea. Nano membrane technology is being used in Saudi Arabia as compared to reverse osmosis because of the abundance of cheap solar energy that efficiently drives the desalination and purifying plants is cheaply available. In addition, the nanomembrane technology utilizes less external pressure that is required in the membrane process for filtration process to take place, hence resulting into a large-scale production of freshwater from the seawater for consumption. Nanofiltration membranes reduce water hardness by removing divalent ions that cause hardness, hence saving energy cost; they also remove watercolor, and inorganic contaminants. Conclusion Water is an essential commodity that supports life of all forms on earth, a natural resource that is facing depletion like the other natural resources, and hence needs to be conserved. Saudi Arabia has employed modern methods to conserve its water resources such as desalination and purification measures; for example, multi stage flash, multi effect distillation both of which use evaporation process depending on the content extracted. Basing on the separation process, there are two membrane processes for desalination, reversed osmosis and electro dialysis (ED), which require high pressure compared to the liquid pressure and large amount of energy supply as compared to the nanomembrane technology. The membranes are made of varied thicknesses and materials. All these processes are pressure dependent for the elimination of mineral salts from the solvent (water). Nanomembrane technology is safer compared to reverse osmosis due to elimination of toxic substances from the water. Annotated Bibliography Anon. Desalination by reverse osmosis. 1997. 16 May 2011. http://www.oas.org/dsd/publications/unit/oea59e/ch20.htm. The article elaborates desalination process, more so focusing on reverse osmosis. In addition, the article provides the technical description of the process, as well as highlighting the four major components of reverse osmosis. Bergman, Robert. Reverse osmosis and nanofiltration. Denver: American Water Works Association, 2007. 16 May 2011. http://books.google.com/books?id=GwATsvphRLEC&printsec=frontcover&dq=reverse+osmosis&cd=4#v=onepage&q&f=false. The author discusses the process of reverse osmosis as well as nanofiltration system, more so in relation to their application in water treatment. Bettelheim, Frederick, et al. Introduction to General, Organic and Biochemistry. OH: Cengage Learning, 2009. 16 May 2011. http://books.google.com/books?id=mM-Ulksh9PAC&pg=PA201&dq=reverse+osmosis&cd=7#v=onepage&q=reverse%20osmosis&f=true. In this book, among other topics, the process of reverse osmosis is clearly presented including its definition and application in desalination of water. Bragg, Paul and Bragg, Patricia. Water: The Shocking Truth That Can Save Your Life. California: Health Science Publications, 2005. 16 May 2011. http://books.google.com/books?id=o-pWlzjZTjgC&printsec=frontcover&dq=water&hl=en&ei=l77QTebvL4rt-gasvvTrCQ&sa=X&oi=book_result&ct=result&resnum=5&ved=0CF8Q6AEwBA#v=onepage&q&f=true. This book dwells more on usability of water for drinking by presenting a comprehensive discussion on composition of drinking water for sustainable world. Micale, Giorgio, Cipollina, Andrea and Rizzuti, Lucio. Seawater Desalination: Conventional and Renewable Energy Processes. London: Springer, 2009. 16 May 2011. http://books.google.com/books?id=NXEmcGHScV8C&pg=PA86&dq=desalination+in+saudi+arabia&hl=en&ei=otHQTZC1B8ar-QayloXrCQ&sa=X&oi=book_result&ct=result&resnum=6&ved=0CHgQ6AEwBQ#v=onepage&q=desalination%20in%20saudi%20arabia&f=true. The authors in this book discuss the process of desalination, specifically dwelling on purification of seawater for human consumption. The authors also give a case study of Middle East region specifically Saudi Arabia as the place where desalination process is more prevalent. Zhang, Tian C. et al. Nanotechnologies for water environment applications. Virginia: ASCE Publications, 2009. 16 May 2011. http://books.google.com/books?id=fLFIZeAXzoIC&printsec=frontcover#v=onepage&q&f=false. This book discusses nanotechnology process, with special focus on nanomembranes. The authors also provide a vivid discussion of pros and cons of this process in relation to other desalination processes such as reverse osmosis. Works Cited Anon. Desalination by reverse osmosis. 1997. 16 May 2011. http://www.oas.org/dsd/publications/unit/oea59e/ch20.htm. Bergman, Robert. Reverse osmosis and nanofiltration. Denver: American Water Works Association, 2007. 16 May 2011. http://books.google.com/books?id=GwATsvphRLEC&printsec=frontcover&dq=reverse+osmosis&cd=4#v=onepage&q&f=false. Bettelheim, Frederick, et al. Introduction to General, Organic and Biochemistry. OH: Cengage Learning, 2009. 16 May 2011. http://books.google.com/books?id=mM-Ulksh9PAC&pg=PA201&dq=reverse+osmosis&cd=7#v=onepage&q=reverse%20osmosis&f=true Bragg, Paul and Bragg, Patricia. Water: The Shocking Truth That Can Save Your Life. California: Health Science Publications, 2005. 16 May 2011. http://books.google.com/books?id=o-pWlzjZTjgC&printsec=frontcover&dq=water&hl=en&ei=l77QTebvL4rt-gasvvTrCQ&sa=X&oi=book_result&ct=result&resnum=5&ved=0CF8Q6AEwBA#v=onepage&q&f=true. Micale, Giorgio, Cipollina, Andrea and Rizzuti, Lucio. Seawater Desalination: Conventional and Renewable Energy Processes. London: Springer, 2009. 16 May 2011. http://books.google.com/books?id=NXEmcGHScV8C&pg=PA86&dq=desalination+in+saudi+arabia&hl=en&ei=otHQTZC1B8ar-QayloXrCQ&sa=X&oi=book_result&ct=result&resnum=6&ved=0CHgQ6AEwBQ#v=onepage&q=desalination%20in%20saudi%20arabia&f=true. Zhang, Tian C. et al. Nanotechnologies for water environment applications. Virginia: ASCE Publications, 2009. 16 May 2011. http://books.google.com/books?id=fLFIZeAXzoIC&printsec=frontcover#v=onepage&q&f=false. Read More