Complete description of Reverse osmosis process - Historical background - Membrane sheets - Applications - Case study

1. REVERSE OSMOSISMEMBRANETECHNOLOGYINWATERTREATMENT
PRESENTED BY :-
NAVSAL KUMAR
T.E. CIVIL ‘A’
ROLL – 3840
Civil Engineering Department
Vishwakarma Institute of Information Technology
Pune

2. OVERVIEW
• INTRODUCTION
• HISTORY
• WORKING
• RO FUNDAMENTALS
• RO MEMBRANE
• PARAMETERS AFFECTING RO
• CONTAMINANTS REMOVED
• TYPICAL RO SYSTEM
• EFFICIENCY OF RO SYSTEM
• RANGE OF APPLICATIONS
• RO SYSTEM MAINTENANCE
• CASE STUDY
• CONCLUSION
• REFERENCES

3. INTRODUCTION
• Osmosis is a natural phenomenon in which Water moves from a high
concentration of water (less sugar/salt dissolved in it) to a low
concentration of water (more salt/sugar dissolved in it) across a semi-
permeable membrane
• This means that water can cross a selectively permeable membrane from
a dilute solution (less dissolved in it) to a concentrated solution (more
dissolved in it)
OSMOSIS

4. Reverse Osmosis: What is it?
• RO is a form of filtration using osmosis in reverse
• Water passes from a more concentrated solution to a less
concentrated solution
• To accomplish this, a force or pressure must be applied
• RO requires 1 psi of pressure for every 100 ppm of TDS
• RO is used to remove dissolved solids from water but it can also
improve taste, odor & color of water
• RO membranes have the capability to remove particles as small as
ions i.e. magnesium ions or sodium ions
• RO membrane will reject most compounds based largely on size
• Dissolved ions, such as salts, carry an electric charge and will also
be rejected by membrane

5. HISTORY
• The process of osmosis through semipermeable membranes was first
observed in 1748 by Jean-Antoine Nollet
• In 1949, the University of California at Los Angeles (UCLA) first investigated
desalination of seawater using semipermeable membranes
• In 1950, the first commercially viable membranes were discovered by
Sidney Loeb and Srinivasa Sourirajan.
• By the end of 2001, about 15,200 desalination plants were in operation or
in the planning stages worldwide

6. Reverse Osmosis: How does it work?
• Feed water flows into RO unit with the force of line
pressure
• Water is forced through membrane by cross flow filtration
• Cross flow filtration is most commonly used in RO as it
allows membrane to continually clean itself
• Membrane then either rejects or repels contaminants
• Two exit streams generated: waste & product stream
• Waste stream consists of: A concentrate (reject) stream
which carries contaminants (compounds too large to pass
through membrane)
• Permeate stream consists of: Product water which has
been forced through the membrane & is virtually free of
TDS

7. Reverse Osmosis Schematic

8. Reverse Osmosis Fundamentals:
FEED WATER: Main flow of impure water to be treated;
PRODUCT WATER: Portion of feed water which passes through
membrane as permeate
REJECT WATER: Portion of feed water which did not pass
through membrane; carries impurities to drain
MODULE: Combination of spiral round membrane
element & pressure vessel

9. Difference between a 1 and 2 stage RO System
• In a one stage RO system, the feed water enters the RO system as one s
stream and exits the RO as either concentrate or permeate water.
• In a two‐stage system the concentrate (or reject) from the first stage then
becomes the feed water to the second stage. The permeate water is
collected from the first stage is combined with permeate water from the
second stage. Additional stages increase the recovery from the system
1 stage
2 stage

10. Single Pass RO vs Double Pass RO
• the difference between a single pass RO system and a double pass RO
system is that with a double pass RO, the permeate from the first pass
becomes the feed water to the second pass (or second RO) which ends up
producing a much higher quality permeate because it has essentially gone
through two RO systems

11. RO Membrane:
• Membrane is the work-horse of an reverse osmosis system
• When choosing an RO system you must do so wisely – taking into account water
quality is very important
• Two main types of membranes:
CTA membrane: Cellulose acetate/triacetate blend
• Provides lowest cost per litre of water
• Resists chlorine but has a lower flow rate limit in applications of high water
consumption
TFC membrane: Thin film/thin layer composite
• Can handle high flow, has a high rejection rate & can handle high water consumption
• Cannot handle chlorine concentrations; water must be carbon pre-filtered

12. Membrane Comparison:
CTA Membrane TFC Membrane
Advantages: Advantages:
High Rejection
High Flow
Low price pH tolerant
Disadvantages: Disadvantages:
pH intolerant Chlorine intolerant
Medium rejection High price
Applications: Applications:
Low temperature water
Low pressure water
High nitrate water
High pH
Chlorine tolerant
Municipal water
Chlorinated Wells

13. Parameters that affect RO:
• Water Temperature: RO system ratings are based on 770F/ 250C water
temperature i.e. : RO system rated at 20 GPD (gallons per day) at
340F/10C will only produce 6 GPD
• Feed Water Pressure: A lack in water pressure (less than 40 PSI) will
reduce product water; this can be helped with the aid of a booster pump
• Contaminants in Feed Water: Large particles, iron concentration or high
levels of hardness in feed water can cause clogging of the membrane
• Clogging of the membrane can decrease its life
• Microorganisms: RO membranes can filter out bacteria, depending on
the bacteria size, however this may cause fouling of the membrane as
bacteria can begin to grow through pores of membrane causing
BACTERIA CREEP – RO systems should not be installed on non-potable
water

14. RO Systems can remove the following
contaminants:
• Dissolved solids = TDS (salts & minerals) – UP TO 2000 ppm
• Most Heavy metals (lead, mercury, silver)
• Most radioactive elements
• RO systems may not be capable of removing nitrates to recommended
levels
Type of contaminant Name of contaminants
Ions & Metals Arsenic (As), Aluminum (Al), Barium (Ba), Bicarbonate (HCO3--),
Cadmium (Cd), Calcium (Ca), Carbonate (CO3--), Chloride (Cl),
Chromium (Cr), Copper (Cu), Fluoride (F), Iron (Fe), Lead (Pb),
Magnesium (Mg), Manganese (Mn), Mercury (Hg), Nitrate / Nitrite (NO3-/
NO2-), Potassium (K), Radium (Ra), Selenium (Se), Silver, Sodium (Na),
Sulfate (SO4--), Zinc (Zn)
Organic chemicals Benzene, Carbon tetrachloride, Dichlorobenzene, MtBE, Toluene
Trichloroethylene, Total Trihalomethanes (THMs)
Particles Asbestos, Protozoan cysts
Pesticides 1,2,4-trichlorobenzene, 2,4-D, Atrazine, Endrin, Heptachlor, Lindane,
Pentachlorophenol

15. Typical Consumer RO System:

16. EFFICIENCY OF RO SYSTEM
• Percent Recovery is the amount of water that is being ‘re
covered’ as good permeate water.
• The higher the recovery % means that you are sending le
ss water to drain as concentrate and saving more permea
te water.
• For example, if the recovery rate is 25% then this means
that for every 100 litres of feed water that enter the RO
system, you are recovering 25 litres as usable permeate
water and 75 litres are going to drain as concentrate.
waterfeedofVolumeTotal
100*producedwatertreatedofVolumeRecovery% 

17. RO System Maintenance:
When to Replace Pre-filters:
•Every 6 months for
normal installations.
•After a Boil Water
Advisory (BWA)
When to Replace Post-filters:
• Every 6 months, depending on water
conditions.
• Noticeable decrease in water production
indicates that the prefilter should be
changed.
• After microbiological contamination, such
as in a Boil Water Advisory (BWA)
When to Replace the Membrane
• Typically, every 18 months to 3 years
• Test using a TDS (total dissolved solids) meter. Replace a membrane below 80%
TDS reduction.
• This will depend on influent water quality, usage, pre & post filter maintenance
• Maintain filters, lengthen life of membrane!!!

18. RANGE OF APPLICATIONS
• Water and wastewater purification
• Food industry
• Desalination
• Maple syrup production
• Hydrogen production
• Reef aquariums
• Window cleaning

19. CASE STUDY
• Implementing institution: Central Salt and Marine Chemicals Research
Institute
• (CSMCRI)
• Head: Dr. Pushpito Kumar Ghosh (director)
• Details of institution: Address: Central Salt and Marine Chemicals
Research Institute, Gijubai Badheka Marg, Bhavnagar-364 002, Gujarat,
India
• Implementation period: Each part of the project (two-stage seawater
reverse osmosis and animal-powered reverse osmosis) took two years to
implement.
• Costs: Two-stage seawater reverse osmosis phase: US$300,000
• Technology used : Thin film composite (TFC) reverse osmosis (RO)

21. CONCLUSION
Reverse Osmosis is an effective and proven technology to
produce water that is suitable for many industrial applications
that require demineralized or deionized water.
Further post treatment after the RO system such as mixed bed
deionization can increase the quality of the RO permeate and
make it suitable for the most demanding applications. Proper
pretreatment and monitoring of an RO system is crucial to
preventing costly repairs and unscheduled maintenance. With the
correct system design, maintenance program, and experienced
service support, your RO system should provide many years of
high purity water.

22. REFERENCES
• Puretech industries Technical Papers
• Central Salt and Marine Chemicals Research
Institute – Case study
• Reverse Osmosis and Nanofiltration M46,
American Water Works Association
• Wikipedia