Make Water Anywhere
with Pall Integrated Membrane Systems
Tim Lilley, Pall Corporation
Portsmouth, April 2012
COPYRIGHT 2012
The information contained in this document is the
property of the Pall Corporation, and is supplied for
the use of the assigned recipient only.
Unauthorised use or reproduction is prohibited, and
the information contained herein is not to be
supplied to others without the specific approval of
an officer of the Pall Corporation.
Contents
ƒ Constituents of source water
ƒ Fundamentals of membrane desalination
ƒ Membranes – functions and properties
ƒ Sustainable operation
ƒ Conclusions
Constituents of source water
Water contaminants will include dissolved solids and suspended solids
Range where contaminants may exist
or behave as a dissolved/suspended state
Dissolved
Dissolved
Suspended
Inorganic salts Organics Colloidal Virus/Bacteria
Size (µm)
0.0001
0.001
0.01
0.1
Membrane RO Nanofiltration Membrane UF & MF
Mineral/General/Mixed
1.0
Depth/Media
10
100
Size (µm)
Settlement
Seawater contains between 30 and 50 g/l of dissolved salts. Depending on the
water source, other contaminants will be present across the entire range
with huge problems associated with the suspended components
© 2012, Pall Corporation
Constituents of water
3
10
Suspended Solids
10
5
10
4
Dissolved Solids
Seawater
10
1
10
Seawater
0
10
-1
10
10
-2
Contaminant Loading TDS (mg/l)
Contaminant Loading TSS (mg/l)
2
10
10
2
10
1
10
Optimum membrane range
3
0
Alternative technology range
© 2012, Pall Corporation
Constituents of water
Suspended solids - Removed by a filtration media or membrane processes
Dissolved contaminants - Removed by Reverse Osmosis (RO)
R
a
w
S
e
a
w
a
t
e
r
Strainer
Pretreatment:
Chemical addition
MF Membrane
Filtration
Monitoring
Backwash
RO Membrane
Post Treatment
Remineralisation and
chlorination
Conc Retentate
R
a
w
S
e
a
w
a
t
e
r
Strainer
MF Membrane
SASRF
RO Membrane
Conc Retentate
Post Treatment
Remineralisation and
chlorination
D
i
s
t
r
i
b
u
t
i
o
n
D
i
s
t
r
i
b
u
t
i
o
n
© 2012, Pall Corporation
Contaminants in Water
R
a
w
S
e
a
w
a
t
e
r
Strainer
MF Membrane
Post Treatment
Remineralisation and
chlorination
RO Membrane
SASRF
Conc Retentate
D
i
s
t
r
i
b
u
t
i
o
n
Range where contaminants may exist
or behave as a dissolved/suspended state
Dissolved
Dissolved
Suspended
Inorganic salts Organics Colloidal Virus/Bacteria
Size (µm)
0.0001
0.001
0.01
0.1
Membrane RO Nanofiltration Membrane UF & MF
Mineral/General/Mixed
1.0
Depth/Media
10
100
Size (µm)
Settlement
© 2012, Pall Corporation
Membrane separation
Direct or “dead-end” flow
Crossflow
Feed
Feed
Microporous/Semipermeable
membrane
Filtrate/Permeate
Filtrate
Feed contaminants
© 2012, Pall Corporation
Membrane configurations
Microfiltration
Complete uniform pore structure through the
thickness (no skin) polyvinylidene fluoride (PVDF)
membrane construction
Ultrafiltration
Uniform inner and outer skinned
UF membrane with narrow pore
range ensures highly efficient
rejection characteristics
© 2012, Pall Corporation
Membrane vs conventional filtration
Features / Performance
Evaluation
Membrane
MF
Benefit of Pall MF
+
++++
0.1 µm rating removes particulate fines (colloids
and oxidized metals eg. Fe, Mn, As) & micro
organisms
Silt Density Index (SDI)
+
++++
Filtrate with SDI <3
Turbidity
++
++++
Filtrate with turbidity < 0.1 NTU
Microbial removal
+
++++
6 log removal of microorganism and pathogens
Consistency in performance
+
++++
Continuous
Integrity testable
-
++++
Assurance of safe potable water supply
Flexibility to cope with variable
feeds and hydraulic loads
++
++++
Broad operation range, handles upsets
Reliability & longevity
++
++++
Superior strength of HC-PVDF membranes
Modular & expandable
+
++++
Future needs, by modules or banks
Waste minimization
+
+++
Unique Air-scrub-feature for high recovery
Footprint and weight
+
+++
Compact design, small footprint
Response to oil in feed
++
+++
CIP will clean membranes while SF blocks
++++ : excellent
+++ : good
++ : fair
Protection of potential RO
Sand Filter /
MMF/DMF
+ : poor
- : not available
© 2012, Pall Corporation
Membrane filtration vs conventional
Differences of filtrate qualities between traditional prefiltration
and Microza® prefiltration (Deposits during SDI measurements)
Feedwater
After
traditional
pre-filtration
After MF
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Transmembrane Pressure
Pre-treatment membrane operation
Previously
filtered seawater
Filtered seawater
Backwash
outlet
Air inlet
Raw seawater
Time
© 2012, Pall Corporation
Pre-treatment membrane operation
Filtration
Filtered seawater
Backwash & air scrub
Previously
filtered seawater
Backwash
outlet
Raw seawater
Air inlet
© 2012, Pall Corporation
Pre-treatment performance imperatives
Performance metrics
ƒ Particulate (RO pre-treatment)
ƒ Turbidity < 0.1 NTU
ƒ SDI < 2 (RO feed requires SDI <3)
ƒ Total suspended solids - background
ƒ Microbiologicals (RO pretreatemnt and drinking water production)
ƒ Giardia, Crypstosporidium > 6 log removal (99.9999%)
ƒ Virus 0.5-3 log
ƒ Animal Parasites
Given the broad range of inlet solids and the life expectancy
It is vital to use a physically robust and chemically resistant
Membrane:
ƒ Homogenous construction
ƒ Chemically inert PVDF
ƒ High degree of crystallinity
Skinned ultrafiltration membranes will not withstand the rigours
of repeated backwashing and air scrub. Resulting in deterioration
of performance with time
© 2012, Pall Corporation
Membrane integration
Homogenous fibre
material imparting high
mechanical strength
0.1µm rated
membrane fibre,
1.2mm OD,
0.8mm ID
Highly crystalline PVDF
pre-treatment membrane
Conventional spiral wound composite
polyamide RO membrane configuration
© 2012, Pall Corporation
DTRO configuration
Disc Tube RO (DTRO) membrane alternative configuration
© 2012, Pall Corporation
Membrane properties & considerations
Pre-treatment
ƒ Protection of downstream equipment, processes & functions
ƒ Control of inlet suspended solids (SDI >3 for RO/NF)
ƒ Microbial barrier
ƒ Integrity assurance
ƒ Sensitive, automated test to confirm performance
ƒ Sustainable operation
ƒ Ability to reverse pore occlusion (filtration process)
ƒ Withstand aggressive cleaning procedures
ƒ Chemical resistance
RO
ƒ Desired rejection rates for ionic species
ƒ Minimal loss of production through flow channel and membrane fouling
© 2012, Pall Corporation
Operational considerations - sustainability
ƒ The pre-treatment stage can face extremely challenging and sometimes often
variable feed water conditions
ƒ As the filtration membrane retains solids, it exhibits an increase in
transmembrane pressure (TMP) as previously demonstrated
ƒ The increase in TMP must be completely recoverable, this is achieved with
physical and chemical cleaning regimes
ƒ Reverse filtration with previously filtered water in combination with air scour
ƒ Regular (24 hr – infinite) flux maintenance clean (ClO-)
ƒ CIP (~monthly – infinite) Chemical clean (ClO- + NaOH)
ƒ Chemical cleaning can be eliminated with low flux operation
ƒ Membrane prefiltration dramatically reduced cleaning burden of downstream
RO
ƒ Membrane prefiltration reduces scale formation in RO by reduced precipitation
nucleation
© 2012, Pall Corporation
Sustainable operation
MF TMP trends in heavily contaminated feed water
Stable TMP
restoration value
Rapid increasing TMP associated with elevated algae
Normally increasing TMP
© 2012, Pall Corporation
Sustainable operation
Robust and chemically resistant membranes are required to withstand
the rigours of feed water duty and the associated aggressive cleaning
procedures over the years of their service life
Highly crystalline PVDF exhibit greater mechanical and
chemical resistance (Liu, C. 2007). Factors affecting stability..
• Morphology of polymers: crystalline vs. amorphous polymers
• Chemical composition, inc structure of monomers
• Molecular architecture - average mol wt & distribution, branching, cross linking.
• Chain orientation with respect to the major stresses during operation
• Structure and geometry of membranes
• The presence of catalysts and inhibitors for chemical reactions relevant to
chemical degradation of polymeric membranes
© 2012, Pall Corporation
Shipboard Series
AT25 - 20m3/day
MF pre-treatment
upgrade
AT32 - 40m3/day
DTRO special
Submarine
© 2012, Pall Corporation
Conclusions
ƒ Membrane technology has a long history in water treatment but recent
developments in construction and polymer chemistry have enabled
significant broadening of this scope – particularly as a conventional media
filter replacement option
ƒ Robust polymeric prefiltration membranes remove virtually all suspended
solids and produce a high quality filtrate with background levels of TSS and
SDI
ƒ Membranes provide dependable barriers to microorganisms in drinking water
supply and as such enable treatment of freshwater sources (Bunker feed)
ƒ Combining MF membranes as pre-treatment to RO enables the latter to
function under optimum conditions and produce a treated water quality that is
reliably within demanding target limits
ƒ The control of TSS and microbial burden reduces bio fouling of RO
membranes and delays scale formation enabling optimum RO production
and extended life
ƒ The robust MF membranes can continuously maintain throughput when
challenged with a wide range of inlet solids and algae conditions with
effective TMP regeneration
© 2012, Pall Corporation