Reverse Osmosis

To The ChairmanDepartment of Chemical EngineeringAnd Technology UET Lahore

Subject: Grant of revenues to purchase Reverse Osmosis EquipmentRespected Sir,It is being brought into your attention that Chemical Engineering Department is lacking Reverse Osmosis Equipment which is very important for the education of Chemical Engineering Students. By this equipment students will be able to learn about effect of different membranes, and other factors like temperature, pressure, flow rate etc. on Reverse Osmosis. It is widely being used in industry for water purification. It is a modern, clean and economic technology and every industry is adopting it. So to keep students upto date with the industry we are in intense need of this equipment. Kindly grant us revenues to purchase this valuable equipment we shall be very thankful to you for this kind favor. Regards

WATER PURIFICATION BY REVERSE OSMOSISOBJECTIVES:The objective of this Laboratory Equipment is to evaluate the performance of various membranes when used for reverse osmosis (RO) applications. The impact of operating conditions such as solute concentration, pressure, flow rate, and temperature on separation efficiency will be examined. This experiment combines several aspects of fluid mechanics and mass transport, illustrating how flow conditions impact mass transport through the membrane. Ultimately, students will be able to determine which process the provided membranes are best-suited for, as well as optimal operating conditions for each process.INTRODUCTION:There are a number of methods ofwater treatment, for example, media filtration, activated carbon filtration, water softening, and de-ionization. These methods of water treatment remove one impurity or a selected group of impurities from contaminated water. Unfortunately, water being a universal solvent, it seldom contains only one or a selected group of impurities. Typical natural water contains dozens of impurities from natural sources. The term water purification refers to a process, which selectively extracts pure water from an impure solution, leaving all kinds of impurities behind, regardless of their source or their nature. This is quite different than water treatment described above.[1]Reverse Osmosisis a water purification technique that reduces the quantity of dissolved solids in solution. It was first developed in the 1950's by the US government to provide fresh drinking water for the Navy, and since then, advances have made it much more feasible for obtaining purified water from wastewaters produced in many industrial applications.[2]

There are only three scientifically recognized methods of water purification. These are: Distillation, freeze-thawing, and reverse osmosis ("RO"). Of these, reverse osmosis offers the most practical and economical approach to water purification. The equipment is compact, easy to operate, and it is highly energy-efficient, in comparison with distillation and freeze-thawing equipment. Whether your goal is to upgrade municipal water for medical treatment or to desalinate sea water for municipal uses, reverse osmosis is the process of choice. [1]

REVERSE OSMOSIS PRINCIPLE:In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential, a thermodynamic parameter. Reverse osmosis can remove many types of molecules and ions from solutions, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely.DIFFERENCE BETWEEN OSMOSIS AND REVERSE OSMOSIS:Osmosis is a natural phenomenon which can be defined as the movement of pure water through a semi permeable membrane from a low to a high concentration solution (see Figure 1). The membrane is permeable to water and some ions but rejects almost all ions and dissolved solids. This process (movement of water) occurs until the osmotic equilibrium is reached, or until the chemical potential is equal on both sides of the membrane. A difference of height is observed between both compartments when the chemical potential is equalized. The difference in height expresses the osmotic pressure difference between the two solutions. Reverse osmosis is a process which occurs when pressure, greater than the osmotic pressure, is applied to the concentrated solution. Water is forced to flow from the concentrated to the diluted side and solutes are retained by the membrane (see Figure 1).UNIVERSITY OF ENGINEERING & TECHNOLOGY LAHORE, KSK CAMPUS

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Figure 1: REVERSE OSMOSIS OPERATING PRINCIPLERO MEMBRANE:RO membranes can be supplied in both flat sheet and HFF (Hollow Fine Fiber) structural formats. The flat sheet RO membrane is composed of three layers. There is a nonwoven polyester support layer, a polysulfone layer, and on top the polyamide barrier layer. The barrier layer is formed by the polyamide layer.APPLICATIONS:Reverse Osmosis has tones of applications in almost all industries because of its ease and no use of chemicals and reduced manpower. Some of the applications are given as: Drinking Water Purification Humidification Ice-Making Biomedical Applications Laboratory Applications Pharmaceutical Production Kidney Dialysis Water used in chemical processes Boiler Water

REFERENCES:1. http://www.bluspr.com/reverse_osmosis_introduction.html2. http://www.rpi.edu/dept/chem-eng/Biotech-Environ/MISC/biotreat/reverseo.html