REVERSE OSMOSIS

Reverse Osmosis

A Seminar Report Report

MAHATMA GANDHI MISSION`S College of Engineering & Technology Kamothe, Navi Mumbai

SEMINAR REPORT ON

REVERSE OSMOSIS Submitted By Mr. Pandhare Baliram V. Under the guidance of Prof. Nishant Sawale

University of Mumbai 2011-2012

MGMCET, Kamothe

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Reverse Osmosis


MAHATMA GANDHI MISSION`S COLLEGE OF ENGINEERING AND TECHNOLOGY KAMOTHE NAVI MUMBAI

Certificate this is to certify that mr.pandhare baliram v has submitted the seminar report titled

REVERSE OSMOSIS under the guidance of

“

”

prof. Nishant Sawale for B.E(sem sem viii). this is the partial fulfillment of the requirements towards the award of degree of bachelor of engineering chemical of mumbai university.

Prof. NISHANT SAWALE Project Guide Department of Chemical Engg

MGMCET, Kamothe

Prof. C K MISTRY

HOD Chemical Dept

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ACKNOWLEDGEMENT

When the compilation of the project comes to an end, the time comes to acknowledge all persons who have made it a success. It gives me immense pleasure to express my gratitude to each individual associated directly or indirectly with the successful completion of my seminar report. I would like to take this opportunity to especially thank my guide, Prof. NISHANTSAWALE of Chemical Engineering Department, MGM CET for having trust in me and giving me such a challenging and demanding topic for my seminar. I would also like to thank him for all the materials he has provided me which proved to be of great importance in understanding the topic and also providing me the lab and internet facilities. I would like to express my gratitude and appreciation to my friends and seniors for providing me with some valuable suggestions.

BALIRAM PANDHARE BE CHEMICAL

MGMCET, Kamothe

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ABSTRACT

Earth is the only planet, which has water in abundant and in ready to use forms. So we have to consider only his water in our discussion. About 97% of water available on earth from the area under sea, remaining 3 % is found in continent and in atmosphere. But more than 70% of this later portionis locked in glaciers and icecaps. The main reason for water shortage is uneven distribution of rain. Many other reasons are also there. Most of the water available is being polluted. So though there is water, we cannot use it as in the same form. For using the water we have to do some chemical and physical operation on this water. Bio-filtration is one of the operations for the purification of water. But we have large part of water by desalinizing the seawater. Seawater has salination value is 35000 ppm. But according to WHO for human consumption salinity should be 500 ppm. In desalination process actual value is brought to 500PPM.

.

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INDEX

S.NO.

TOPIC

1

INTRODUCTION  WHAT IS OSMOSIS AND REVERSE OSMOSIS  PRINCIPLE OF REVERSE OSMOSIS

2 3



OPERATION

PAGE NO.

6

8

MEMBRANE SELECTION 9 



MEMBRANE MATERIAL TYPES OF MAMBRANE MODULE. MAMBRANE SCALING MAMBRANE FOULING



APPLICATION OF RO SYSTEM.



4

5



18

20

6

ADVANTAGES AND DISADVANTAGES

23

7

CONCLUSION CONCLUSION

25

8

REFERENCE

26

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INTRODUCTION

Reverse osmosis is a physical process by which the dissolved Material in the solvent may be separated from that solvent with the assistance Of a semi-permeable membrane. By application of pressure in excess of the natural osmotic pressure to the feed water the membrane will preferentially allow the solvent (i.e. water) molecules to pass through and high percent of electrolytes and dissolved organic materials will be rejected. The raw water is pressure fed into a chamber containing semipermeable membrane. Only the pure water (known as permeate) can pass through the membrane, while the impurities are rejected and ruin to waste (known as concentrate). Reverse osmosis is operated as a continuous process.

WHAT IS OSMOSIS AND REVERSE OSMOSIS It is the phenomenon of water flow through a semi-permeable membrane that blocks the transport of salt or other solutes through it. Osmosis is a fundamental effect in allbiological system. Osmosis is applied to water purification and desalination, waste material treatment and many other chemical and biochemical laboratory and industrial process.

Reverse Osmosis: When two water or other solvent volumes are separated by a semi permeable membrane, water will flow from the side of low solute concentration to side of high solute concentration. The flow may be stopped or even reversed, by applying external pressure on the side of higher concentration. In such a case the phenomenon is called reverse osmosis. RO is a-physical process. If there are solute molecules only in one side of the system, then the pressures that stop the flow is called osmotic pressure. By the application of pressure in excess of the natural osmotic pressure to the feed water the membrane will preferentially allow the solvent MGMCET, Kamothe

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Reverse Osmosis

molecules to pass through and high percent of electrolytes and dissolved organic materials will be rejected. The raw water is pressure fed into a chamber containing semi permeable membrane. Only the pure water can pass through the semi permeable membrane, while the impurities are rejected and run to waste. Reverse osmosis is operated as a continuous process.

PRINCIPLE OF REVERSE OSMOSIS Reverse osmosis is a membrane process that act as a molecular filter to remove 99% of all dissolved minerals, upto97% of most dissolved organic matter, more than 98% of biological and colloidal matter can be removed from water having concentration from 50 ppm to 60,000 ppm. Reverse osmosis is a misnomer, since application of pressure lo overcome osmotic pressure reverses only the flow of solvent but not the direction of flow of solute. As shown fig. (a), which depicts a semi permeable membrane separating pure water and a salt solution is pure water passes in opposite direction in process called natural osmosis. The driving force for the two flows is the difference in chemical potential between the two solutions. The water now continues until the pressure aerated by osmotic head equals-the osmotic pressure of salt solution in fig. (b). The two liquids are in equilibrium, by applying an external pressure; a salt solution in fig. (c) the flow of solvent may be revised. The reversal of flow has given the process the name REVERSE OSMOSIS.

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OPERATION

By squeezing ordinary tap water (using your house water pressure) against a special membrane, pure water molecules are separated from impurities. What's even more impressive is that these rejected impurites are automatically rinsed down the drain leaving bottled quality water for you that's pure and delicious. We have combined this fantastic Eagle Reverse Osmosis process with other quality components to create a compact drinking water appliance that fits neatly under your kitchen sink. It provides you with an abundant supply of true bottled quality water without the bottles from its own attractive spigot. We can even hook up your icemaker and refrigerator water dispenser!

1. Sediment filter : sand, sediment, silt 2. Pre-carbon filter : insecticides, pesticides, herbicides, chlorine 3. Pre. 5-micron filter :dirt, rust, turbidity 4. RO membrane: inorganic minerals, nitrates, arsenic, barium, copper 5. Post carbon filter :final polish

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MEMBRANE

Definition : Membrane can be defined as essentially as a barrier; which separates two phases and restricts transport of various chemicals in a selective manner. Membrane is a heart of every membrane process. The membrane can be made of an inorganic or organic, synthetic or biological product. Membrane of reverse osmosis system permeable for solvent and impermeable for solute.

Material used for membranes in RO Membranes are prepared from almost every available material. In large-scale production commercial thermoplastic and cellulosics are primarily used. 1. Cellulose acetate. 2. Aromatic polyamide 3. Polyamide 4. Polyphyenylene oxides

MODULES TYPES FOR REVERSE OSMOSIS SYSTEM The several forms of Reverse Osmosis membranes are sold packaged in devices to contain the steam pressure and to separate the feed and reject stream from the permeate streams. The device; usually called a module, is designed to control the feed stream-velocity and turbulence in order to reduce concentration polarization. There are four types of modules related to the types of membrane a) Spiral wound b) Tubular c) Plate and frame d)hollow module membrane

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1)Spiral wound module A variation of the basic plate-and-frame concept is the spiral-wound module, which is widely used today in reverse osmosis, ultrafiltration, and gas separation. Its basic design is illustrated in Figure 1.

Fig. 1 Schematic drawing of a spiral-wound membrane module

The feed flow channel spacer, the membrane, and the porous membrane support form an envelope which is rolled around a perforated central collection tube and inserted into an outer tubular pressure shell. The feed solution passes in axial direction through the feed channel across the membrane surface. The filtrate is moves along the permeate channel and is collected in a perforated tube in the center of the roll. Small spiral wound units consist of just one envelope which limits the total membrane area that can be installed in 2 one unit to about 1 to 2 m . The main reason for the limitation of the surface area which can be installed in a module containing one single envelope is the pressure drop encountered by the permeate moving down the permeate channel to the central collection tube. Because the channel in a practical unit is very narrow its length is limited to 2 to 5 m. A significantly longer path would resultr in an unacceptable pressure drop in the permeate channel. To install larger membrane surfaces in a spiral wound module a multileaf arrangement in used as indicated in the Figure 1b.

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concentrate

permeate outlet f ee eed d f low membrane permeate flow

f eed solution spacer

membrane porous centre tube permeate spacer

Fig. 1b Schematic drawing illustrating the construction of a multi-leaf spiralwound module

Commercial spiral wound modules are about 1 meter long and have a diameter of 10 to 2 60 cm. The membrane area in a spiral-wound element is 3 and 60 m . Generally, 2 to 6 elements are placed in series in a pressure vessel. The spiral-wound module provides a relatively large membrane area per unit volume. The large scale production is quite cost effective and module costs per membrane area quite low. The major application of the spiral-wound module is in reverse osmosis sea and brackish water deslination. But it is also extensively used in ultrafiltration and gas separation. However, the spiral-wound module is quite sensitive to fouling, and the feed channels can easily be blocked and particles or fibers should be removed from the feed solution by a proper pretreatment procedure.

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2)The plate-and-frame membrane module Another module type used on an industrial scale for various membrane separation processes including ultrafiltration, reverse osmosis, and gas separation is the plate-andframe module. Its design has its origin in the conventional filter press-concept. The membranes, porous membrane support plates, and spacers forming the feed flow channel are clamped together and stacked between two endplates and placed in a housing as indicated in the schematic diagram of Figures 2a and 2b.

permeate channel space feed channelspacer permeate feed solution

retentate

permeate

Fig. 2a module

Schematic drawing illustrating the concept of a plate-and-frame membrane

The feed solution is pressurized in the housing and forced across the surface of the membrane. The permeate is leaving the module through the permeate channel to a permeate collection manifold which in circular devices is central tube as indicated in the Figure b. Often the device contains one or more baffels to extend the path-length of the feed solution in the device.

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feed sol sol ution

retentate permeate

Fig. 2b Circular plate-and-frame filter device with one baffel to extend the feed flow path length

There are various types of plate-and-frame modules on the market which offer, however, only slight variations in their basic configuration . In many plante-and-frame membrane modules the membranes can easily be exchanged. This makes the module suitable for batch-type operations and multi-purpose applications using different membranes for different separation tasks. Plate-and-frame units are mainly used in small scale applications such as in the production of certain pharmaceuticals, bioproducts, or fine chemicals. The housings and other components of plate-and – frame frame modules to be used in the food and pharma industry are made from stainless steel so that they can easily be MGMCET, Kamothe

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steam sterilized. These units, however, are quite expensive and the exchange of the membranes is labor intensive. Therefore, the plate-and-frame module is quite expensive.

3 )The tubular membrane module While the previously described some membrane module types required flat sheet membrane material for their preparation, special membrane configurations are needed for the preparation of the tubular, capillary, and hollow fiber modules. The tubular membrane module consists of membrane tubes placed into porous stainless steel of fiber glass reinforced plastic pipes. The pressurized feed solution flows down the tube bore and the permeate is collected on the outer side of the porous support pipe, as indicated in Figure 3. The diameters of tubular membranes are typically between 1-2.5 cm. In some modules, the membranes are cast directly on the porous pipes and in others they are prepared separately as tubes and then installed into the support pipes. Today, tubular modules are used in ultrafiltration at low hydrostatic pressures. This allows the membrane tubes to be made by a welding or glueing procedure of flat sheet membranes that are cast on a relatively thick and mechanacilly strong porous polyester support material. These tubes which have a diameter of 0.5 to 1 cm do not need additional support when operated at hydrostatic pressures of less than 2 to 4 bars. Usually, 10 to 30 individual tubes are installed in a larger tube and potted at the end of the tube. The feed solution is fed in parallel through the tubular bundel while the permeate of the individual tubes is collected in the outer shell tube as indicated in the schematic drawing of Figure 4b. The main advantage of the tubular module is that concentration polarization effects and membrane fouling can be easily controlled, and plugging of the membrane module is avoided even with feed solutions that have very high concentration of solid matter and thus high viscosity. The disadvantage of the tubular module design is the low surface area, that can be installed in a given unit volume, and the very high costs. Therefore, tubular membrane modules are generally only applied in applications where feed solutions with high solid content, and high viscosity have to be treated and other module concepts fail due to membrane fouling and module plugging. This is the case in certain applications in the food and pharma industry and in the treatment of certain industrial effluents.

MGMCET, Kamothe

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f eed eed permeate

concentrate

permeate

f eed solution

membrane porous tube

Fig. 3a Schematic drawing illustrating the tubular membrane module

retentate

permeate feed

Fig. 3b Tubular module with seven individual tubes bundled in a shell tube

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.

4 The hollow fiber membrane module The same basic spinning process is used for the preparation of hollow fiber membranes, which have an outer diamter of 50 to 100 µm. In hollow fiber membranes, the selective layer is on the outside of the fibers, which are installed as a bundle of several thousand fibers in a half loop with the free ends potted with an epoxy resin in a pressure tube as indicated in Figure 4. The filtrate passes through the fiber walls and flows up the bore to the open end of the fibers at the epoxy head. feed solution

shell tube concentrate

permeate

hollow fiber fiber

epoxy resin

Fig. 4 Schematic drawing illustrating the construction of a hollow fiber module

The hollow fiber membrane module has the highest packing density of all module types available on the market today. Its production is very cost effective and hollow fiber membrane modules can be operated at pressures in excess of 100 bars. The main disadvantage of the hollow fiber membrane module is the difficult control of concentration polarization and membrane fouling. When operated with liquid solutions the modules do not tolerate any particals, macromolecules or other materials that may MGMCET, Kamothe

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easily precipitated at the membrane surface. Therefore, an extensive pretreatment is required when hollow fiber membranes are used for the treatment of liquid mixtures. The main application of the hollow fiber module is today in reverse osmosis desalination of sea water and in gas separation. Both application require high operating pressures and low cost membranes which have a long useful life. In reverse osmosis, of sea water an extensive pretreatment of the sea water is required.

Tab. I Commercially available membrane modules, there costs and major applications Membrane Module Spiral-wound Module Plate-and-frame Module Tubular module Hollow fiber Module

Membrane area per unit volume 2 -3 (m m ) 800 – 1200

Membrane costs Low

Control of concentration polarization good

400 – 800

Medium

good

20 – 100 2000 – 5000

very high very low

very good very poor

Application

UF, RO, GS MF, UF, RO, D, ED MF, UF, RO RO, GS

MF = microfiltration UF = ultrafiltration RO = reverse osmosis ED = electrodialysiS GS = gas separation

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FOULING Membrane fouling is one of the most serious problems in case of Reverse Osmosis system. This affects directly on the performance of the reverse osmosis system. It may cause permanent damage to membrane. The main reasons of fouling are: 1. Membrane scaling 2. Metal oxide ppt. 3. Device plugging 4. Biological growth inside device. 5. Colloidal fouling.

Membranes scaling : Membrane scaling is caused by ppt of the salts dissolved in feed water. The salts in feed water are usually concentrated by a factor of two to ten in RO process, their solubility limits can be exceeded thus ppt can occur. The most common scales encountered in water treatment application are calcium carbonate and calcium sulfate. But ether compounds such as silicate, strontium sulfate, beryllium sill late and calcium fluoride also can scaling.

Metal Oxide Precipitation : Soluble species in feed water can be oxidized in the reverse osmosis system ahead of the permiator or in the permiator itself, to form insoluble species, which can deposit into permiator. Both manganese and iron can cause fouling by this mechanism, but iron fouling is most prevalent. Device plugging : Plugging is caused by mechanical filtration in which particles too large to pass through the feed brine passage are trapped in device. Device plugging problem. Biological fouling : Biological fouling occurs mainly due to growth of micro-organism in RO device. Microorganisms may itself grow in membrane and when feed water is filtered these bacteria's may enter in product water. Colloidal fouling : Colloidal fouling is caused by entrapment of colloids on membrane surface in RO. Colloidal fouling is also caused by coagulation of colloids during RO process.

MGMCET, Kamothe

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NEW DEVELOPMENT Prefiltration of high fouling waters with another, larger-pore membrane with less hydraulic energy requirement, has been evaluated and sometimes used, since the 1970s. However, this means the water passes through two membranes and is often repressurized, requiring more energy input in the system, increasing the cost. Other recent development work has focused on integrating RO with electrodialysis to improve recovery of valuable deionized products or minimizing concentrate volume requiring discharge or disposal

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APPLICATION OF REVERSE OSMOSIS TECHNIQUE Reverse osmosis system or technique has a many application over other conventional techniques; so in industry it is most widely used technique. Some of them are as follows. a. The most wide use of RO is in the desalination of sea water. b. RO is also used in sewage water treatment plants for the removal of nitrates phosphates or the non-biodegradable surfractants. c. RO is used in the treatment of hard water. d. Paper and pulp industry also use this technique for the treatment of waste water. e. Electroplating and electro painting industries also needs RO. f. RO is used in the removal of common water pollutants like nitrates, borate, fluorides, phosphates, alkyl benzene sulphonate. g. RO is used in pharmaceutical and electronic industries.

Water and wastewater purification Rain water collected from storm drains is purified with reverse osmosis water processors and used for landscape irrigation and industrial cooling in Los Angeles and other cities, as a solution to the problem of water shortages. In industry, reverse osmosis removes minerals from boiler water at power plants. plants . The water is boiled and condensed repeatedly. It must be as pure as possible so that it does not leave deposits on the machinery or cause corrosion. The deposits inside or outside the boiler tubes may result in under-performance of the boiler, bringing down its efficiency and resulting in poor steam production, hence poor power production at turbine. It is also used to clean effluent and brackish groundwater. The effluent in larger volumes (more than 500 cu. meter per day) should be treated in an effluent treatment plant first, and then the clear effluent is subjected to reverse osmosis system. Treatment cost is reduced significantly and membrane life of the RO system is increased. The process of reverse osmosis can be used for the production of deionized water . RO process for water purification does not require thermal energy. Flow through RO system can be regulated by high pressure pump. The recovery of purified water depends upon various factors including membrane sizes, membrane pore size, temperature, operating pressure and membrane surface area. In 2002, Singapore announced that a process named NEWater would be a significant part of its future water plans. It involves using reverse osmosis to treat domestic wastewater before discharging the NEWater back into the reservoirs.

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Food industry In addition to desalination, reverse osmosis is a more economical operation for concentrating food liquids (such as fruit juices) than conventional heat-treatment processes. Research has been done on concentration of orange juice and tomato juice. Its advantages include a lower operating cost and the ability to avoid heat-treatment processes, which makes it suitable for heat-sensitive substances like the protein and enzymes found in most food products. Reverse osmosis is extensively used in the dairy industry for the production of whey protein powders and for the concentration of milk to reduce shipping costs. In whey applications, the whey (liquid remaining after cheese manufacture) is concentrated with RO from 6% total solids to 10 – 20% 20% total solids before UF (ultrafiltration) processing. The UF retentate can then be used to make various whey powders, including whey protein isolate used in bodybuilding formulations. Additionally, the UF permeate, which contains lactose, is concentrated by RO from 5% total solids to 18 – 22% 22% total solids to reduce crystallization and drying costs of the lactose powder.

Car washing Because of its lower mineral content, reverse osmosis water is often used in car washes during the final vehicle rinse to prevent water spotting on the vehicle. Reverse osmosis is often used to conserve and recycle water within the wash/pre-rinse cycles, especially in drought stricken areas where water conservation is important. Reverse osmosis water also enables the car wash operators to reduce the demands on the vehicle drying equipment, such as air blowers.

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Future Advancements Improvements will be necessary as RO is used to treat the ever greater expanding candidate feed waters, including municipal and industrial wastewater effluents, and other source waters that are less than optimal for conventional RO membranes (e.g., wastewaters containing high concentrations of biological chemical demand (BOD), chemical oxygen demand (COD), TOC, silica, and suspended solids, such as foodprocessing condensates and cooling tower blowdown). Membranes will need to be developed that are tolerant of chlorine for microbial growth control, and resist to fouling with suspended solids and organics. Other membrane technologies, such as microfiltration and ultrafiltration, are finding fresh application in pre-treating RO systems operating on these challenging water sources. There is also continuing research into higher-performance (high flux and high rejection) membranes to further reduce the size and cost of RO systems. Nanotechnology shows promise for having a role in the development of these high-performance membranes. Improvements will be required in the chemistries used to treat RO. These chemistries include antiscalants, which will be needed to address higher concentrations of scale formers such as silica, and membrane cleaners, which will have to address microbes, biofilms, and organics.

MGMCET, Kamothe

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ADVANTAGES AND DISADVANTAGES Advantages of reverse osmosis 1. Thermal damage of product is eliminated 2. Retention of original aroma and taste is retained 3. Reduction is energy consumption 4. Easy in operation 5. Compact size 6. Low maintenance. Disadvantages ; 1 High Cost 2 Less membrane life Factors Influencing Reverse Osmosis Performance Permeate Flux and Salt Rejection are the key performance parameters of a reverseosmosis process. They are mainly influenced by variable parameters which are as follows: 1)Pressure 2)Temperature 3)Recovery 4)Feed water salt concentration . Pressure With increasing effective feed pressure, the permeate TDS will decrease while the permeate flux will increase. Temperature If the temperature increases and all other parameters are kept constant, the permeate flux and the salt passage will increase. Recovery The recovery is the ratio of permeate flow to feed flow. In the case of increasing recovery, the permeate flux will decrease and stop if the salt concentration reaches a value where the osmotic pressure of the concentrate is as high as the applied feed pressure. The salt rejection will drop with increasing recovery .

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RO product water cost calculations: The most critical parameters in cost evaluation are the fixed charges and the energy cost for the production of desalinated water. Other parameters that may have lower effect on the unit product cost include the cost of chemicals and labor. The following method of calculation may be used for knowing the cost of water desalinated by Reverse Osmosis technology. The calculations proceed as follows: - Calculate the amortization factor a = i(1+i)n(up) (1+i)n -1 - Calculate the annual fixed charges A1 = (a) (DC) - Calculate the annual electric power cost A2 = (c) (w) (f) (m) (365) - Calculate the annual chemical cost A3 = (k) (f) (m) (365) - Calculate the annual membrane replacement cost A4 = 10% of membrane purchase cost - Calculate total annual labor cost A5 = (l) (f) (m) - Calculate total annual cost At = A1 + A2 + A3 + A4 + A5 - Calculate unit product cost (m3) As = At/ ((f) (m) (365)) - Calculate unit product cost (m3/d) As = At / ((f) (m) (365)

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CONCLUSION

Today's day water is basic need and the availability of pure water is little quantity on earth. So desalination is necessary for today's world and selecting Reverse Osmosis process we can solved water problem to some extend to use of membrane technology. 1. Reverse osmosis is most efficient and convenient hyper filtration process of water purification. 2. Reverse osmosis process gives more promising result. 3. Reverse osmosis is simple and effective method than any other purification method. 4. Organic matter removal and particle colloidal reduction are effectively controlled by RO.

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REFERENCES &INTERNET SITES

1) Technical Management of RO System, S.El-Manharawy, A.Hafez/329-344 2) Desalination Plant Seawater Reverse Osmosis (SWRO) Plant. Watertechnology.net 3) www.scribd.com 4) Reverse osmosis industrial application and processes by Jane kucera 5) Environment engineering by cs rao

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