Reverse osmosis (RO)

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GOOD MORNING
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Deepak Pani SJES,BBSR
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Reverse Osmosis Seminar
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If You Have Questions...

• Ask Them at Any time!

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Technical Presentation

• Reverse Osmosis Terminology
• Principles of Reverse Osmosis
• Types of R O Membranes
• O M of Reverse Osmosis System

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Typical Applications of Reverse Osmosis
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Principles ofReverse Osmosis
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Separation Processes
Reverse Osmosis
Ultrafiltration
Particle Filtration
Separation Process
Microfiltration
Nanofiltration
Carbon Black
Giardia Cyst
Aqueous Salt
Paint Pigment
Human Hair
Beach Sand
Bacteria
Virus
Metal ion
Relative Size of Common Materials
Yeast Cell
Tobacco Smoke
Mist
Coal Dust
Colloidal Silica
Granular Activated Carbon
Sugar
Pollen
Asbestos
Milled Flour
Atomic Radius
Micrometers 0.001 0.01 0.1
1.0 10 100 1000
Approximate Molecular Weight 100
200 1,000 10,000 100,000
500,000
Note 1 micrometer (micron) 4 x 10-5 inches
1 x 104 Angstrom units
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Osmosis
semi-permeable membrane
Dilute Solution
Concentrated Solution

• The spontaneous flow of water from a dilute
  solution to a concentrated solution, when the two
  solutions are separated by a semipermeable
  membrane.

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Osmotic Pressure
Dilute Solution
Concentrated Solution
P ??

• The pressure that must be applied to a
  concentrated solution to prevent osmosis.

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Reverse Osmosis
P
Dilute Solution
Concentrated Solution
P gt ??

• Reversing osmotic flow by applying a
  pressure in excess of the osmotic pressure

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Three Cases of Osmosis
osmosis
equilibrium
reverse osmosis
P ??
P gt ??
?? lt ??
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Reverse OsmosisTerminology
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Block Diagram of RO
PRODUCT WATER
SALT WATER
MEMBRANE
(PERMEATE )
HIGH PRESSURE PUMP
REJECT WATER (CONCENTRATE)
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Reverse Osmosis Terminology

• Recovery Water Recovery ()
• Rejection Salt Rejection ()

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Recovery Rate

• Ratio of permeate flow to feed flow
• Expressed as
• Recovery (permeate flow/feed flow) 100

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Salt Rejection

• of salts rejected.
• 100 - (Permeate TDS/Feed TDS) 100

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Reverse Osmosis MembraneTypes
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RO Membranes Types of Construction

• Tubular
• Hollow Fiber
• Spiral

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Hollow Fiber R. O.
Brine
Product water
Feed
EpoxyNub
Hollow Fiber Membrane
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Thin Film CompositeMembrane / Fabric
Cross Sectional View
25 ?m 1 mil 1/1000 inch
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Element Leaf
Cross Sectional View
Fabric
Permeate Channel
Membrane
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Cross section ofSpiral Wound Membrane
Permeate Tube
Membrane Backing
O Ring
Mesh Spacer
Outer Cover
Permeate Carrier
Membrane
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Membrane Assembly
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Reverse OsmosisMembranes - Spiral woundTypes

• Cellulose Acetate
• Thin Film Composite
• Polysulfones

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Benefits of R.O.

• High recovery rates.
• Predictable water quality--regardless of TDS
  content.
• Simple operation and control.
• Limited chemical problems.
• No daily regeneration hassels.
• Can be skid mounted,hence less space.
• Very few components for maintenance.
• Less operator attention

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Critical Design Parameters
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Source of Water
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Water Temperature
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Silt Density Index - SDI
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Feed Water Analysis
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RO System Design
Parameters required for designing

• Mangenese
• Barium
• Strontium
• Chlorite
• Sulphate
• Nitrate
• Ammonia
• Phosphate
• Fluoride
• Silica
• Total Dissolved Solids
• Hydrogen Sulphate
• Carbon Di Oxide

• Temperature (Max, Min Average)
• Chlorine Residual
• Turbidity
• Suspended Soilds
• Colour
• Silt Density Index
• pH
• Coliform Count (bacteria)
• Total Plate Count
• Calcium
• Magnesium
• Potasium
• Iron

Note Variation in these parameters should be
noted and odours, traces of industrial pollutant,
clay, sand, rust, or other unusual
characteristics should be described.
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Reverse OsmosisSystem Design
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System Design

• The Reverse Osmosis system design process
  consists of three principal steps.
• Membrane selection
• Defining the R.O. configuration and operating
  conditions.
• Determining pretreatment requirements

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Membrane SelectionBasis

• Application or end use
• Quality Desired
• Water Temperature

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Estimating System configuration

• Establish system flux.
• Estimate number of elements.
• Estimate array.

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Water Flux

• Unit flow of water through a unit area of
  membrane per unit of time.
• The most common units of measure are GFD (Gallons
  / Square Foot - Day)

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Water Flux

• Operating Flux is the water flux at actual system
  operating conditions.
• Used as a system design criterion to select
  optimum membrane area
• Describes current operating conditions

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Recovery Limits

• Concentration of scale forming salts
• Osmotic Pressure
• Permeate Quality
• Concentrate Disposal

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RO System components

• The basic expanded design of a single system
  includes the following
• Raw water feed pump to supply water to the pre
  treatment
• Pre treatment system for Turbidity,TSS,Colloidal
  particles Organic matter.
• Cartridge filter to remove micron size particle
  to control the SDI( Silt density index) of feed
  water
• Anti scalant dosing system.
• High pressure pumpfeed control valve to
  pressurize the feed water.
• Membranes housed in Pressure tubes.

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RO System components

• The basic expanded design of a single system
  includes the following
• Raw water feed pump to supply water to the pre
  treatment
• Pre treatment system for Turbidity,TSS,Colloidal
  particles Organic matter.
• Cartridge filter to remove micron size particle
  to control the SDI( Silt density index) of feed
  water
• Anti scalant dosing system.
• High pressure pumpfeed control valve to
  pressurize the feed water.
• Membranes housed in Pressure tubes.

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• A reject control valve to control the recovery of
  the RO system.
• Askid to mount to all mechanical equipment .
• Flow indicators to measure permeate and reject
  flowrates.
• Pressure gauges for monitoring the differential
  pressures across the RO feed, reject and
  intermediate stages.
• Conductivity pH meter for measuring the quality
  of the permeate water.
• And other necessary instruments for monitoring
  easy operation and critical parameters.
• A cleaning system consisting of Tank,CF,Pump and
  necessary instruments.

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Role of Pretreatment in RO

• To reduce particulates improve SDI.
• Clarification / Filtration.
• Polymer/coagulant addition.
• Micro-filtration.
• Minimiza Scaling fouling.
• Softening.
• Acid antiscalant addition.
• Antiscalant addition.
• Chlorine Removal.
• Carbon Filtration.
• Bisulfite Addition.

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Role of Pretreatment in RO

• Minimize Silica Scaling.
• Antiscalant addition.
• Softening pH control.
• Turbocirculator.
• Controlling Organic.
• Dissolved Organic.
• Colloidal Orgabic.

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Typical RO Pretreatment

• S Solids Removal
• Clarification
• Media Filter
• Scale control pH adjustment
• Antiscalant Addition
• Acid Addition
• Safety Filter
• Cartridge Filter

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Role of Pretreatment in RO

• Silt Density Index It is the second parameter
  used to determine colloidal quantity of the RO
  Feedwater. A test is run to determine the rate of
  the pluggage of a 0.45 micron filter at 30 psig
  for 15 minutes. This test consists of determining
  amount of time it takes to collect a 500 ml
  sample at the start of the 15 minutes test and
  comparing this time to the amount of time it
  takes to collect a 500 ml sample at the end of
  the 15 minutes.

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Reverse osmosis system
Cleaning tank Pump (SS) Cartridge filter
Pretreatment
Cartridge filter
RO hydra block
Cleaning system
RO/ DM plant pH adjustment Degassification
Dosing system
De-chlorination
Membrances Pressure tubes HP pumps Control
pannel
Filteration
Coagulation
Post treanment
Clarification
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Schematic diagram of RO unit for brackish water
Activated carbon filter
Lime or lime - soda coagulant aids
Sand filter
S.H.M.P.
Acid
coagulation and sedimentation
Mn greensand filter
DESALATION SECTION Membrane modules
Polishing filter

Product water
High pressure pump
Waste brine
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Data Normalization

• Performance Parameters which are tracked
• Water Flow
• Salt Passage
• Differential Pressure

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Probing

• Probing is done while the system is operating at
  normal conditions.
• Insertion is normally done from the end opposite
  the permeate collection manifold.

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Probing
Feed
Conc.
Permeate
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Leakage Flow

• Passage of water and salt directly from the feed
  to the permeate.
• O-ring leaks
• Membrane imperfections
• Element structural damage

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Leakage Flow
Leakage flow can be estimated by determining the
rejection of a highly rejected species such as
the sulfate ion or hardness.
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High Differential Pressure

• Increase of normalized Differential Pressure
  indicates fouling of feed / brine channel.
• Identify location of the increase.
• Upstream indicates suspended solids in the
  feedwater.
• Downstream indicates scaling.
• Uniform increase could be biological.

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Fouling

• The deposition of suspended particles on the
  membrane surface.
• Foulant on the membrane surface increases the
  resistance to the flow of water through the
  membrane.
• Fouling causes lower productivity at constant net
  pressure or higher net pressure at constant
  productivity.

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Scaling

• The deposition of sparingly soluble salts onto
  the
• membrane surface and/or the feed channel
  material.
• Scaling occurs primarily in the downstream
  elements because of the higher concentrations
  existing in this portion of the RO system.
• Common scalants include calcium sulfate, silica
  and calcium carbonate.