ACKNOWLEDGEMENTSTo prepare this text, several people have helped me. It is my pleasure to express my gratitudeto all of them. First of all I want to thank Mr.A.Sathish Kumar, TSO, Hindustan unilever-Water Div, Krishnagiri, who gave me the opportunity to do internship in one of the world’s prestigious organization. My grateful thanks to Mr.J.Samson Selvakumar, TSO, Hindustan unilever-Water Div, Coimbatore, who initiated and encouraged me to prepare this text. Mr.Sesha, CCO, Hindustan unilever-Water Div, Coimbatore, who directed me in the right path to prepare this text. I am grateful to him. My sincere thanks to Mr.R.Sridhar, Symphony Supervisor, Hindustan unilever-Water Div, Coimbatore, for training me and giving me a wonderful experience. I thank him for answering my queries patiently. Last but not least my hearty thanks to Dr.R.Nanda Gopal, Director, PSG Institute Management. and Deepa Ranganathan Assistant Professor PSG Institute of Management. Saravanan Ragothaman +91-9003881369 firstname.lastname@example.org
A Reference text for PWE, Pureit PSG Institute of Management Coimbatore - 641 004
REVERSE OSMOSISINTRODUCTION: Water is a one of the basic needs for human being. Without water, human being cannot survive.But the reason for 90% of disease is drinking of unpurified water. This project helps to understand theoverall process of RO purifier and how it helps to prevent waterborne diseases.Why should we purify water? If you see the condition of water in reservoir you won’t drink that water. The figure belowshows how the water are being stored in dam. Before distributing water for potable purpose theyjust added chlorine into water. It is called chlorinating by-products, also known as "chlorinatedhydrocarbons" or trihalomethanes (THMs). Most THMs are formed in drinking water when chlorine reactswith naturally occurring substances such as decomposing plant and animal materials. But the chlorinemust be added at a certain ratio about 0.05 ml for a liter of water. Health officials doesn’t concernedthe ratio level and mixed it with water as their wish. This excess of chlorine can cause odor and changethe taste of water. So most of the people would vomit after drinking this chlorinated water. It also causestomach pain and risk for certain types of cancer is now being correlated to the consumption ofchlorinated drinking water. The Presidents Council on Environmental Quality states that "there isincreased evidence for an association between rectal, colon and bladder cancer and the consumption ofchlorinated drinking water."Methods in Water Treatment:
We can treat Water in two ways. They are, Purification of existing potable water Converting Non potable water into purified potable waterPurification of existing potable water: In this type of water treatment the water which is going to purify, doesn’t contain excess salts.The TDS level of this type of water is normally below 200 ppm. But it contains other impurities likeBacteria’s, Viruses and other micro organisms. So this type of water purification system used to removethe above microorganisms.Converting Non potable water into purified potable water: In this type of water treatment the water which is going to purify, contains excess salts. TheTDS level of this type of water is normally above 200 ppm. It also contains other impurities likeBacteria’s, Viruses and other micro organisms. So this type of water purification system used to removesalt as well as above microorganisms. We use RO technology for this type of water treatment.RO technology converts salt water intopotable water. In this book we will have a depth look about RO.RO: RO stands for Reverse Osmosis. Before going to look about RO, we are just going to see whatthe concept of osmosis is. Osmosis is a natural phenomenon in which any diluted/light solution tends to move towards aconcentrated/heavy solution. In a simple words Osmosis is the natural tendency of water with a lowconcentration of dissolved particles (pure water) to move across a semi-permeable membrane to anarea of water with a high concentration of dissolved particles (water with high TDS). Still if u have any problems to understand osmosis process just have a look on the below image.In this image, The nails have attracted towards magnet. How it is happened? The magnet has highconcentration than the nail. The low concentrated nails attracts towards the highly concentratedmagnet. The same concept used in osmosis process.
For example we all know that honey has higher concentration than the normal water(containssolids). When we put these two solutions in a single vessel by separating it using a membrane then thewater alone (low concentration) moves towards the honey (high concentration).Membrane: Membrane is a heart of RO purifier. Membrane is nothing but a thin, film-like structure thatcontains number of tiny pores which separates two fluids. It acts as a selective barrier, allowing someparticles or chemicals to pass through, but not others. The size of hole is about 0.0001 Microns. Thesymbolic representation of micron is μ. One micron is 0.000001 meter. The average width of humanbeing hair is generally 100 μm (varies between 70 -120 μm). Just imagine , if you slice vertically humanhair into 100 pieces, that one part is one micron. Again if u slices that one part of human hair into 10000pieces, that piece only can pass through RO membrane. From that we can conclude that even we can’timagine pore size of RO membrane. It’s very very smallest one.
An Experiment of Osmosis and Reverse Osmosis between Two Solutions: The figure shows there are two solutions named Dilute solution and Concentrated solution havetaken in two glass vessels. Dilute solution has low concentration and concentrated solution has highconcentration and the membrane has placed exactly between two solutions.
Fig. 1: Initially there was high level of dilute solution and low level of concentrated solution. As statedin earlier, due to Osmosis process, dilute solution is trying to move through membrane towardsconcentrated solution. But membrane will allow only water (H2O) and act as a barrier for othermolecules. Therefore the water (H2O) in the dilute solution is moving continuously to concentratedsolution.Fig. 2: After a while the water gets arrived to concentrated solution side and other molecules likeviruses, bacteria’s stays in dilute solution side. So the level of concentration solution gets increased. The important thing is Osmosis process happened automatically without any external force. ButReverse Osmosis requires external pressure.4
Fig. 3: After Osmosis process, we have to apply external pressure on concentrated solution side toachieve Reverse Osmosis process. Due to high level pressure on top of the concentrated solution side the contents inside theconcentrated solution like water, salt, virus and bacteria and other impurities try to escape to dilutesolition side through membrane. But membrane allows only water and keeps other contents inconcentrated solution side. This process continuously happen until the pressure level equals to levelincreased in concentrated solution.Fig. 4: Then finally we will get the figure as same as fig. 1. After Osmosis we may remove the wastewater from dilute solution side and can do Reverse Osmosis process. If we do like this way, we can getpurified potable water in dilute solution side at the end of process.Process inside Membrane:Major Parts in Membrane: There are six parts in membrane.These are, Outer Wrap Feed Channel Spacer Membrane Permeate Collection Material Perforate Central Tube Anti Telescoping DeviceOuter Trap: It is the outer layer of membrane. It is made by .Feed Channel Spacer: The figure shows outer trap and feed channel spacer.
It is used to facilitate gap to pass water inside spiral wound membrane element. The waterpasses only through feed channel spacer. The figure shows the inner structure of feed channel spacer.
After entering feed solution into feed channel spacer, the waste water inside the feed solutiongets move straightly and gets out as a waste water.Membrane: Membrane is placed next to feed channel spacer. The water inside the feed solution can onlypass through the cavity of membrane and rest of feed solution gets out as waste water.Permeate Collection Material:
It is placed next to membrane and it collects the water from membrane.Perforate Central Tube: The end of Permeate Collection Material is connected to Perforate Central Tube. Therefore,finally it carries potable water and its output connected to device tap.Anti Telescoping Device: Longitudinal extension and consequent destruction of spirally wound membrane modulesarranged in paired axial alignment within a pressure vessel of an ultra filtration unit are prevented by apair of end-cap anti-telescoping devices (ATDs)Overview Process: Feed solution containing ions, organics and impurities like microorganism, salt etc. is fed intothe spiral wound membrane element. In output side there are two types named permeate andconcentrate. Permeate part carrying pure water and concentrate part carrying brine and otherimpurities.
The above figure shows how Water molecules get separate from other molecules (salt, microorganic etc.).The feed channel spacer allows to pass feed solution. But the outside of feed channelspacer covered by membrane. The membrane has number of holes size about 0.0001 μm. So the watercan only escape through that hole and other particles passes straightly and getting out as waste water.