Relationship between Desalination of Sea Water and Principles of Osmosis - Essay Example

Relationship Between Desalination of Sea Water and Principles of Osmosis al Affiliation) Introduction Desalination is the process of acquiring clean and pure water expelling saline or salt from sea water using different methods (Wetterau, 2011). There are different degrees of salt in water, which influence the cost of treatment. The level of saline in sea water is commonly measured in parts per million (ppm) (Wetterau, 2011). There are various methods used for desalination for instance, reverse osmosis, forward osmosis and multistage flash distillation, which presently is the most preferred. This paper explains definitions of terms under desalination, the process of desalination in relation to osmosis, the importance of desalination and a brief summary of the whole process. Definition of terms Reverse osmosis is a process where pressure is utilized to push water through a membrane which keeps bigger solutes like salt from going through (Wetterau, 2011). Reverse osmosis is thought to be the least expensive method in terms of energy consumption when used in large scale. On the other hand, forward osmosis uses the natural osmotic methodology; a substance moving from a zone of low focus to a region of high fixation. Most part of it requires about 50% of the expense of opposite osmosis, because of less energy being utilized to finish the procedure (Sato & Nakao, 2015).As opposed to forcing the solution through a pressure gradient, this procedure permits the process to occur naturally. There are a few terms in the water desalination process that identify with the salinity of the water source. Salinity is the concentration of disintegrated salt in the water and is normally measured in parts per thousand (ppt). Brackish water is a critical term describing water that is more saline than fresh. The saltiness of salty water can extend to around 0.5 and 30 ppt and usually reflects the nature of groundwater in unconfined aquifers close to estuaries or beachfront (Venketeswari, Leong, & Yong, 2014). Seawater has a salinity range of approximately 30ppt to 50 ppt. This difference in the salinity of seawater is as a result of closeness to fresh water stores. Brine solution describes any amount of water with salinity exceeding 50 ppt (Venketeswari, Leong, & Yong, 2014). Brine solution also refers to wastewater that is as a result of desalination, which must be dealt with before being discharged into nature. Technical Description The two main processes that use the concept of semi permeable membranes for desalination include electrodialysis and reverse osmosis. In the reverse osmosis, water from coming from saline solution under high pressure is sidelined from the disintegrated salts by moving all the way through a membrane or a water-porous layer. The saturate (the fluid moving through the layer) is forced through the water- permeable membrane as a result the pressure difference produced between the product water and the pressurized feedwater that is close to the pressure in the atmosphere.The residue of feedwater proceeds to the part of the reactor that has high pressure in form of brine solution. There is no heating at this stage. Most of the energy in this stage is used to initiate pressurization process.The process of desalination of brackish water operates under pressures ranging between 250 psi and 400 psi while seawater desalination requires pressure range of between 780 psi and 1 010 psi(Low, 2009). In order to increase the pressure in the compartments, the collected feedwater is forcefully pumped against the crust. As the result water goes through the crust, the left overs of brine solution and feed water become increasingly concentrated (Low, 2009). In order to decrease the amount of broke down salts that are remaining, a segment of this feedwater-salt water solution is removed from the compartment. In the absence of this free ejection, the amount of disintegrated salts continue to increase in the feedwater. The osmosis system comprises of four segments: the pre-treatment stage,pressurization stage, membrane separation stage, the post-treatment or stabilization stage. Figure 1 represents the fundamental parts of a converse osmosis framework (Low, 2009). Pretreatment: in this step, the feedwater undergoes pretreatment to make it match with the layer of membranes by uprooting suspended solids, modifying the pH, and adding an inhibitor to minimize any form of scaling created by constituents, for example, calcium sulfate(Sato & Nakao, 2015). Pressurization: in this step, forces from pump increase the pressure of the feedwater coming from the prêt-reatment step to a working pressure suitable for the membrane and salinity of feed water. Separation: The porous layer allows desalinated water to go through and inhibits dissolved salts. Since not all the membranes are perfect in separating salts in water, a less rate of salt goes through the film and stays in the resultant water. The films of reverse osmosis arrive in a mixed bag of arrangements (Bamaga, Yokochi, & Beaudry, 2009).Examples of membranes that are mostly used include the void fine fiber and spiral wound membranes. They are large and are made of sweet-smelling polyamides ,cellulose acetic acid derivatives. They are both utilized in seawater and brackish water desalination, in spite of the fact that the particular membrane and the pressure vessel differ as per the distinctive working pressures (Bamaga, Yokochi, & Beaudry, 2009). Stabilization: Products of water coming from membranes more often requires pH conformity and degasification prior to being transported to the supply framework for consumption. The resultant material goes through an air circulation section where the pH is increased from an estimation of more or less 5 to 7(Low, 2009). The water is then released to a stockpiling reservoir for future use. Figure 1: The process of Osmosis Desalination. Source: O.K. Buros, et. Al., The USAID Desalination Manual, Englewood, N.J., U.S.A., IDEA Publications. Practical desalination basically concentrates on converting brackish water into water that is nature friendly and safe for consumption. Brackish water is pumped from the aquifer by a few wells and diverted into a solitary gathering tank. Saline water then returns to pre-treatment, wherein bigger minerals are quickly removed by sand channels and the remaining water moves to invert osmosis. After the recently treated water leaves the reverse osmosis membranes, it must go through a last step before being safe for utilization. Reverse osmosis is just viable in expelling solids from water particles and cannot uproot gas, therefore the last piece of the process includes evacuating CO2 and guaranteeing that water PH is near to 7.5 (Low, 2009). Conclusion Desalination acts as a water source for people living in arid and semi arid regions. There are two particular issues: desalination requires extreme energy utilization and brackish water transfer can result in natural harm if not properly disposed. The energy requirements for power and pumping of water are high. These energy prerequisites significantly add to the expense of desalination and put a strain on effectiveness. At the point when too much energy is being consumed, extra environmental assessments must occur to determine every exceptional circumstance. Saline solution transfer is an essential process inside desalination and must be maneuvered carefully. Brackish water must be diluted to match the saltiness of the water into which it is disposed and improper disposal can result in critical ecological harm to the natural waterways. References Bamaga, O., Yokochi, A., & Beaudry, E. (2009). Application of forward osmosis in pretreatment of seawater for small reverse osmosis desalination units. Desalination And Water Treatment, 5(1-3), 183-191. doi:10.5004/dwt.2009.574 Bamaga, O., Yokochi, A., & Beaudry, E. (2009). Application of forward osmosis in pretreatment of seawater for small reverse osmosis desalination units. Desalination And Water Treatment, 5(1-3), 183-191. doi:10.5004/dwt.2009.574 El-Dessouky, H., & Ettouney, H. (2002). Fundamentals of salt water desalination. Amsterdam: Elsevier. Li, M. (2011). Reducing specific energy consumption in Reverse Osmosis (RO) water desalination: An analysis from first principles. Desalination, 276(1-3), 128-135. doi:10.1016/j.desal.2011.03.031 Low, S. (2009). Preliminary studies of seawater desalination using forward osmosis. Desalination And Water Treatment, 7(1-3), 41-46. doi:10.5004/dwt.2009.698 Manes, C., Khan, M., Molina, V., & Croue, J. (2013). The use of microbial and chemical analyses to characterize the variations in fouling profile of seawater reverse osmosis (SWRO) membrane. Desalination And Water Treatment, 51(4-6), 944-949. doi:10.1080/19443994.2012.705507 Sato, Y., & Nakao, S. (2015). Theoretical estimation of semi-permeable membranes leading to development of forward osmosis membranes and processes as a future seawater desalination technology. Desalination And Water Treatment, 1-8. doi:10.1080/19443994.2015.1005692 Venketeswari, P., Leong, O., & Yong, N. (2014). Seawater desalination using forward osmosis process. Journal Of Water Reuse And Desalination, 4(1), 34. doi:10.2166/wrd.2013.009 Wetterau, G. (2011). Desalination of seawater. 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