???? Types of Filtration

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???? Types of Filtration

• ???? Direct Filtration
• ????? Sand or Multi Media
• ?? Cartridge
• ???? Cross Flow Filtration
• ??? Reverse Osmosis
• ?? Nanofiltroation
• ?? Ultra Filtration
• ?? Micro Filtration

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??Feed Water
???? Direct Filtration
??? Product Water
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???? Direct Filtration
Product
???????????? Solids on surface quickly foul the
membrane
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????? Back Wash to Sewer
????
?? Back Wash
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???? Cross Flow Filtration
???Permeate
??Feed Water
??Concentrate
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???? Cross Flow Filtration
??? Membrane Surface
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????Concentration Polarization
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???? Cross Flow Filtration ??????? Things to
Remember

• ????????????????
• Water velocity of the feed must be sufficient to
  keep the solids moving.
• ???????????
• Low water velocity will allow the membrane
  surface to foul.
• ???????(???????)?????????
• Higher water recoveries (greater water
  utilization) means lower water velocity.

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???? The Filtration Spectrum
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???? Cross Flow Filtration

• ??? Reverse Osmosis
• ??????? Dissolved Solids
• ?? Nanofiltration
• ???? Divalent Ions (Ca Mg)
• ?? Ultrafiltration
• ?????? Organics Colloids
• ?? Microfiltration
• ????? Suspended Solids

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?? Osmosis
Osmotic Head
H2O
??Pure Water
??? Strong Solution
H2O
H2O
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?? Equilibrium
????? Applied Pressure, PF
????Osmotic Pressure, PO,F
H2O
?? Pure Water
Strong Solution
H2O
H2O
Osmotic Pressure, PO,P
?? Equilibrium
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??? Reverse Osmosis
Applied Pressure, PF
????? Permeate Pressure, PP
Osmotic Pressure, PO,F
H2O
Pure Water
Strong Solution
H2O
H2O
Osmotic Pressure, PO,P
???? Pure Water Flow
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????Net Driving Pressure (NDP)
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???? Net Driving Pressure

• NDP PF PO,P - PP - PO,F
• Available Pressure to Drive the Process
• ??? Brackish water PO,P 0

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????????? Osmotic Pressure of Various Compounds
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??? Osmotic Pressure

• 100 ppm Salt 1 PSI Osmotic Pressure
• 1000 ppm NaCl 11.4 psi
• 1000 ppm NaHCO3 12.8 psi
• 1000 ppm Sucrose 1.5 psi
• 35,000 ppm Seawater 374 psi

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????? Impurities in Water

• ???? Ionic

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????? Impurities in Water
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????? Impurities in Water

• ??? Ionic
• ????
• Non Ionic

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Impurities in Water
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Impurities in Water

• Ionic
• Non Ionic
• ??? Particulate

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Impurities in Water
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????? Impurities in Water

• Ionic
• Non Ionic
• Particulate
• ??? Gases

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????? Impurities in Water
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??????Reverse Osmosis Removes

• ???Ionic
• ????Non Ionic
• ???Particulate

??? ??? Not Gases !
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?????? Ions in Solution

• ????????
• Compounds dissolve in water to form charged ions
• ??? (?? ? ????)
• Anions (Negative Charge - extra electrons)
• ??? (?? ????)
• Cations (Positive Charge - missing electrons)

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?? Ions

• ???????????? ???
• Ions missing or having one electron monovalent
• ???????????? ???
• Ions missing or having two electrons
  divalent
• ???????????? ???
• Ions missing or having three electrons
  trivalent

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?? Ions

• ??? Monovalent NaCl ? Na Cl-
• ??? Divalent CaSO4 ? Ca2 SO42-
• ??? Trivalent Na3PO4 ? 3Na PO43-

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????????Relative Permeation Rates of Ions

• ??? Monovalent 1 x 10-5 cm/sec ?
• ??? Divalent 1 x 10-6 cm/sec
• ??? Trivalent 1 x 10-7 cm/sec ?

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???????Typical Passage of Ions
Determined at 200 psi, 25 recovery, pH 7.8 on
de-chlorinated city feed water with TFC membrane
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Things to Remember ?????? Rejection Increases
with Increasing????????

• Degree of dissociation????
• Ionic charge????
• Molecular weight???
• Degree of molecular branching????

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How small is small?
Inches Meter Micrometer 39.37 1 1,000,000 3.9
4 .1 100,000 .39 .01
10,000 .04 .001 1,000 .004 .000,1
100 .000,4 .000,01 10 .000,04 .000,001
1 .000,008 .000,000,2 .1 5 x 10
-9 .005 UF 4 x 10 -10 .000,4 RO 1
Angstrom 1 10 -10 m
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Salt Rejection
H2O
Membrane
Cl-
Na
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??? Membrane Pore Channel
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??? Reverse Osmosis

• ? Membranes

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???RO? First RO Membrane ROGA? Module 1 1964?
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Semi???Semi Permeable Membranes???? Materials
of Construction

• ????? Cellulose Acetate
• TFC? Thin Film Composite
• ??? (Polyamide)
• ?? Polysulfone

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???/????Asymmetric Membrane ????? Cellulose
Acetate
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?????????Thin Film Composite Polyamide Membrane
Compaction is not an issue
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Barrier Layer
?? Polysulfone
??? Support Layer
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Barrier Layer
Polysulfone
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TFC ?? Surface
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??? ????Salt Rejection - Salt Passage
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??? Salt Flux
Js K2(Cm - Cp)
Js ??? Salt Flux K2 ???? Mass Transfer
Coefficient Cm ????? Concentration at the
membrane Cp ?????? Concentration in the permeate
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??? Permeate Flux
Jw ??? Water Flux K1 ????/??System
Constant P ????? Transmembrane Pressure ???
Osmotic Pressure
P
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????? Permeate Flux
???????????????? The rate of permeate flow
through one square foot of membrane.

• 10 - 25 GFD
• ?? Temperature
• ?? Pressure

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????? Membrane Comparison
??Characteristic
TFC
Opr. pH
2 - 11
Feed Pressure
gt 400 PSI
lt 200 PSI
Salt Rejection
? Excellent
Water Flux
? Excellent
Bacteria Stability
? High
Cl
Stability
? Poor
2
Physical Stability
?? Better
o
Max T (
F)
113
Element Cost
1.50
System Cost
1.16
???? Relative Cost
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???????? Membrane Characteristics and Typical
Operating Conditions
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???? Membrane Manufacturers

• Dow Filmtec
• Fluid Systems - Koch
• Hydranautics - Nitto Denko
• Osmonics - Desal
• Dupont - Out of membrane business
• Torray
• Toyobo
• Trisep

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??? Reverse Osmosis

• ???
• Membrane Configurations

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???Membrane Configurations

• ?? (R/O gt 99 USA) Spiral Wound
• ???? Hollow Fiber
• ?? Tubular
• ?? Plate and Frame

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??? Spiral Wound Membranes

• ????? Cellulose Acetate
• ????? Thin Film Composite
• ??? (Polyamide)
• ?? Polysulfone

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????? Spiral Wound Membrane Elements
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??????? Flow Pattern for a Spiral Wound Element
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??? Permeate Recovery
???Permeate
?? Feedwater
?? Concentrate
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????????? Flow Through a Pressure Vessel
????? Brine becomes more concentrated
???Product
?? Feed
??Concentrate
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Minimum Element Flow
?????????????????? The minimum flow rate through
the last element of a pressure vessel
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??? Reverse Osmosis

• ???????
• System Design Operation

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RO????RO System Variables

• ??? Permeate Recovery
• ???Permeate Flux
• ??(?????)????
• Min. Element Concentrate Flow

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????? ???Concentration Factor vs. Recovery
?? Evaporation
?? Make UP
Blow Down
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????????Concentration Factor vs. Recovery
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????????Recovery vs. Concentration Factor
Recovery Concentration Factor 50 2 75 4
80 5 90 10 95 20 97.5 40 98
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???????? Factors Influencing Recovery

• ???????
• Concentration of scale forming salts
• ???? Osmotic pressure
• ????? Permeate quality

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????????Factors Influencing Flux

• ?????????
• Dependent on fouling characteristics of the feed
  water
• Wastewater (SDI lt 5) 8 - 12 GFD
• Surface Water (SDI lt5) 10 - 14 GFD
• Well Water (SDI lt3) 14 - 18 GFD
• RO Permeate 18 - 30 GFD

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RO ??

• ?? Reject Staging
• AKA multi-stage??
• ????? Improves water recovery
• Multi - Pass
• AKA product staging
• ???? Improves water quality

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Single-Stage RO System
TRAIN 1
??FEED
??? PERMEATE
??? HIGH PRESSURE PUMP
TRAIN 2
?? BRINE
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Two Stage RO System 21 Array
?? Recovery 75 Salt Rejection 87
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??RO??????? Typical Operating Data for Two Stage
RO System
Item 1st Stage 2nd Stage Total System ???? Feed
flow 100 GPM 50 GPM 100 GPM ????? Permeate
flow 50 GPM 25 GPM 75 GPM ???? Concentrate
flow 50 GPM 25 GPM 25 GPM ??? Recovery 50
50 75 Feed TDS 1000 ppm 1960 ppm 1000
ppm Permeate TDS 40 ppm 70 ppm 50
ppm Concentrate TDS 1960 ppm 3850 ppm 3850
ppm Feed Conductivity 1414 mmho 2700 mmho 1414
mmho Permeate Conductivity 60 mmho 104 mmho 75
mmho Concentrate Conductivity 2700 mmho 5030
mmho 5030 mmho Percent Salt Rejection 96
96.4
95 ???? Feed Pressure 250 psi 230 psi 250
psi ????? Permeate Pressure 10 psi 10 psi
10 psi ???? Concentrate Pressure 230 psi 210
psi 210 psi Feed/Concentrate P 20
psid 20 psid 40 psid ????Transmembrane P 240
psid 220 psid 240 psid Membrane area /
vessel 3720 ft2 1860 ft2 5580 ft2 Flux
????(avg.) 19.4 gsfd 19.4 gsfd 19.4 gsfd
D
D
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Reject Staging

• ???????
• Increased Utilization of Water
• ????
• Incremental Increase in Investment
• ???????????
• Minimal Degradation in Water Quality

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Average Rejection ?????

• ?????TDS
• Average Membrane Feed TDS
• ??Feed TDS ??Concentrate TDS
• 2
• Membrane Rejection
• Average Feed TDS - Permeate TDS x100
• Average Feed TDS

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???? Average Concentration

• ???? Log Mean Calculation
• CAVG CF ln (CF/CC)
• 1 - (CF/CC)
• CAVG ??????? Average Concentration in System
• CC ???? Concentration of Concentrate
• CF ???? Concentration of Feedwater

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??RO?? Double Pass RO System 21 Array
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Double PassProduct Staging

• ?? Applications
• ?? Seawater (High TDS)
• ?????? Ultra-high purity applications
• ??pH???? Interstage pH adjustment w/ NaOH
• Improved Alkalinity Rejection
• Improved Silica Rejection
• Improved TOC Rejection

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