Water Distillation - Literature review Example

Water Distillation Name Institution Date Outline Water Desalination Introduction Water desalination is a water treatment process used to remove dissolved salts from the water and convert otherwise unusable water useful for drinking, irrigation and even industrial applications. The increased water demands as well as the increasing susceptibility to drought and the waning availability of water supply sources signifies the important of developing alternative water supply sources, and desalination is a viable water supply source. According to the World Health Organsation, the acceptable limit of salinity for human beings and domestic animals is 500 ppm. Therefore, in case the salinity range is above 500 ppm, it is essential to desalinate the water. There are various methods used in water desalination. Brief History Water desalination using distillation process might was performed as early as 4th century B.C. In 18th and 19th century, desalination became very common Explanation Water desalination has been practiced for a long time and it is currently feasible to produce high quality and large water quantities using desalination processes. Applications There is reverse osmosis that utilizes the osmotic pressure difference between the salt water and the pure water to remove the salts from water and membrane distillation that is a thermal, vapor-driven transportation process Evaluation Advantage include water desalination provides solution for water scarcity while disadvantages include high use of energy and high cost. Conclusion Water desalination is the removal of salts from the water and is a viable water supply option. Desalination has been there since 4th century and currently it’s a popular technique. Some of the common desalination processes include reverse osmosis and membrane distillation. The technique has its advantages and drawbacks as well. Water Desalination Introduction Water desalination is a water treatment process used to remove dissolved salts from the water and convert otherwise unusable water useful for drinking, irrigation and even industrial applications (Gryta, 2010). The elevated water demands as well as the increasing susceptibility to drought and the waning availability of water supply sources signifies the important of developing alternative water supply sources, and desalination is a viable water supply source (Cath et al, 2004). According to World Health Organization, the acceptable limit of salinity for human beings and livestock is 500 ppm (Mutai, 2013). Therefore, in case the salinity range is above 500 ppm, it is essential to desalinate the water. There are various methods used in water desalination and they include reverse osmosis and membrane distillation, among other methods. (US. Department of interior , 1972). Water desalination has been practiced for a long time and it is currently feasible to produce high quality and large water quantities using desalination processes (Mutai, 2013). However, water desalination has both advantages and disadvantages and they will be analyzed as well. Cath et al (2004) provide that water desalination using distillation process might was performed as early as 4th century B.C. in 18th and 19th century, desalination became very common where sea water was desalinated using submerged tubes and multi effect desalination process. In late 1950s, huge seawater distillation plants were built with UAE while within 1970s, membrane based desalination procedures, reverse osmosis and membrane distillation began gaining popularity (Gryta, 2010). Between 1972 and1999, the installed water desalination capacity globally rose to 370 million gallons daily, annually. Currently, desalination capacity has been rising at about 12% annually. With the rising awareness on desalination technology, more desalination projects are expected to be installed in future. Desalination has increased substantially for the last two decades because of the impending water scarcity globally (Cath et al, 2004). Currently, desalination plants are being built worldwide. Studies show that if water usage continues at this rate, the supply of water will no longer be there by 2090. Desalination is definitely a solution for water scarcity because it converts water previously unsuitable for human consumption into water fit for consumption and other uses (Stein, 2008). According to Niemczynowicz (2015), the scarcity of fresh water is an increasing problem globally since only 1 percent of earth’s water is available for human consumption. Studies further show that the location of 96.5 percent of earth’s water is within the seas and oceans, while 1.7 percent of earth’s water is sited within the ice caps. The remaining percentage of water consists of brackish water that is somewhat saline and is in form of surface water within estuaries and as groundwater (Niemczynowicz, 2015). The need for supply of fresh water is among the most critical global priorities and as a result desalination is increasingly being used to avail fresh water. Pure and clean water is essential for survival of human beings as well as for various industrial purposes, agricultural purposes, among other uses (Younos & Tulou, 2005). During water desalination, various techniques are used. One of the water desalination methods is reverse osmosis which is a technique that utilizes the osmotic pressure difference between the salt water and the pure water to remove the salts from water. Another method is membrane desalination which is a thermal, vapor-driven transportation process through microporous and hydrophobic membranes (Pangarkar et al, 2011). Pangarkar et al (2011) explain that reverse osmosis is a “pressure-driven membrane procedure where a feed stream flows under pressure via a semi-permeable membrane; two aqueous streams, one stream rich in salt and the other stream weak in salt are separated using the semi-permeable membrane”. Water passes via the membrane, if the applied pressure is higher than the osmotic pressure, and the salt is preserved (Price et al, 2002). Consequently, a low salt concentration infuse stream is attained and a concentrated brine remains at the feed side. Basically, a reverse osmosis system is made of four key subsystems that encompass: pretreatment system, high-pressure pump, membrane module, in addition to post-treatment system (Pangarkar et al, 2011). Generally, for reverse osmosis to occur, an extremely high pressure is affected on the concentrated solution. A high pressure pump is used to force the pre-treated feed water to flow through the membrane surface. The high pressure pump utilizes high energy when pumping the feed water. NREL (2012) opines that the applied energy is directly proportional to the feed pressure and the flow rate. Practically, the high salt concentrations in the water being desalinated necessitates increased pressure and the higher the salt concentration, the higher the pressure and pumping energy is required for generating the targeted permeate flux. Younos & Tulou (2005) further add that the needed hydrostatic pressure is supposed to be higher than the osmotic pressure on the feed membrane’s side. With the increase of the recovery of reverse osmosis unit, there is an increase of the osmotic pressure of the membrane’s feed side and hence the needed feed pressure elevates (Mutai, 2013). The reverse osmosis membranes are high salt rejection membranes because salinity can impact salt passage across the membrane. The key disadvantages of reverse osmosis include the negative environmental impact of rejected brine as well as the restricted recovery. Restriction of the recovery and brine concentration occurs due the high concentration of the brine within the reverse osmosis can elevate osmotic pressure and hence increase energy consumption (Younos & Tulou, 2005). An example is the Sydney Desalination Plant that supplies water within Sydney. The location of Sydney Desalination Plant is within Southern Sydney, New South Wales, Australia. The plant produces about 450 gigawatt-hours (1,600 TJ) annually (NREL, 2012). The other method is used in water desalination is membrane distillation. As per Mutai (2013) “membrane distillation is a thermal, vapor-driven transportation process through micro-porous and hydrophobic membranes”. Application of membrane distillation occurs as a non-isothermal membrane process where the motivating force is normally the partial pressure gradient across a porous membrane. Khayet (2011) emphasizes that the membrane should not be wetted by the process liquid. For the membrane distillation, heating of the saline water occurs in order to elevate the vapor pressure and this produces the disparity between partial pressure at the two membrane sides (Gryta, 2010). The evaporation of hot water occurs via non-wetted pores of the membranes that are normally hydrophobic. Normally, the membranes cannot be wetted using the aqueous solutions that come in contact with it and normally only vapor and gases that cannot be condensed are found in the membrane pores. As the process continues, condensation of the passing vapor occurs on a cooler surface and as a result fresh water is produced (Khayet, 2011). An example is the Victorian desalination plant located in southern Australia. The plant produces 410 mega litres per day and 50 gigalitres (5.3×109 cu ft) per year and supplies 33% of water in Melbourne (NREL, 2012). The membrane distillation process has various advantages that include that the procedure can be conducted at lower operating pressure and lower temperatures and hence less energy is required. The procedure also need lower vapor space, it is not limited to osmotic pressure and also the process allows extremely high separation factor of non-volatile solute (Cath et al, 2004). Other advantages of membrane distillation include that the process produces extremely purified water and the process can utilize any type of low-grade waste heat or solar energy systems and this makes membrane distillation a procedure of choice in generation of potable water within arid areas (Price et al, 2002). Water desalination comes with many advantages that include provision of high quality water, irrespective of the source. The key benefit of water desalination is that it adds drought-proof supplies to water supply range (Khayet, 2011). Another advantage is the sizing of water facilities because water desalination is achieved using pumps, filters and other equipment features. This aspect of sizing results to lesser size facilities in comparison to other traditional water supply options. Mutai (2013) also adds that water desalination can be modularly expended and this implies that it is possible to add capacity easily by increasing the number of filtration components. This flexibility is critical during minimization or optimization of the initial capital investments to adequately meet the estimated water demands. Finally, in water desalination, it is possible to incorporate technological innovations that produce water at lower cost and with less energy use (NREL, 2012). The most striking disadvantage of water desalination is that it requires high energy levels because almost a half of the operational costs of water desalination process are associated with energy use (Mutai, 2013). Another disadvantage of water desalination is the high costs. The high costs can be associated with high energy/power costs, costs of concentrate disposal, and also high costs associated with post-treatment phase. Generally, the high costs associated with the desalination process results to the high cost of the desalinated water (Younos & Tulou, 2005). Conclusion Water desalination is the removal of salts from the water and is a viable water supply option. Water Desalination has been there for a long time and currently it’s a popular technique. The process of desalination is a feasible solution for the problem of water shortage globally and also will help in meeting the increasing water demands. Some of the common desalination processes include reverse osmosis and membrane distillation. Advantages of using water desalination to provide fresh water include; provision of already scarce water, sizing facilities, and its ability to integrate technology innovations. However, water desalination has major disadvantages that include high use of energy and high cost. References Al-Karaghouli, D, Renne & L. Kazmerski. (2010). Review technical and economic assessment of photovoltaic-driven desalination systems. Renewable Energy. 35(2), pp. 323–328. Cath Y, Adams D & Childress A. (2004). Experimental study of desalination using direct contact membrane distillation: a new approach to flux enhancement. Journal of Membrane Science. 228(1), pp. 5–16. Gryta M. (2010). Desalination of thermally softened water by membrane distillation process. Desalination. 257(1–3), pp: 30–35.. Khayet M. (2011). Membranes and theoretical modeling of membrane distillation: a review. Advances in Colloid and Interface Science. 164(1-2), pp. 56–88. Mutai A. (2013). A Research Paper on Desalination in Australia. Water Resource Management. 1(2). NREL (2012). Comparison of Technical and Economic Performance of the Main Desalination Processes with and without Renewable Energy Coupling. NREL. Niemczynowicz, J. (2015). Present challenges in water management. Water International. 25: 139-147. Pangarkar B, Sane M & Guddad M. (2011). Reverse Osmosis and Membrane Distillation for Desalination of Groundwater: A Review. International Scholarly International Network. 2011(1), pp:1-9. Price, H, Lupfert, E., Kearney, D., et al. (2002). Advances in parabolic trough solar power technology. Journal of Solar Energy Engineering. 124 (5), 109–125. Younos T & Tulou K. (2005). Overview of desalination techniques. Journal of Contemporary Water Research and Education. 132(3), pp:1-10. Stein, M. (2008). When Technology Fails: A Manual for Self-Reliance, Sustainability, and Surviving the Long Emergency, 2nd Edition. London: Chelsea Green Publishing. US. Department of interior (1972). Sea Water Distillation Module, Orange County: Environmental Impact Statement. 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