Advancements in Membrane Technology:
Standardizations and Innovations in
Drinking Water Applications
June 17, 2016
Jarrett Kinslow, PE
Jill Hudkins, PE
Agenda
● Introduction and Review of
Membrane Technologies
● Membrane Filtration (MF/UF)
Overview, Applications &
Innovations
● Membrane Separation (NF/RO)
Overview, Applications &
Innovations
● Summary
SAWS Brackish Groundwater Desalination
Approaching Completion (Yesterday)
Introduction
1
Introduction
• Typically, water treatment processes can be broken down into the
following categories:
Chemical
Physical
Biological
• Membrane treatment processes can be generally classified as
physical processes in which constituents are separated from the
raw water.
Drivers for Membrane Treatment
Limited and deteriorating
supplies require the use of
alternative water sources
Technological innovation
leading to development of
low cost, high quality water
treatment solutions
Increasing regulatory standards
especially regarding disinfectant
by-products and waterborne pathogens
Membranes
offer cost
effective
solutions
Growing demand due to
population growth
Retrofit of old technology
to protect the public from
aging or underperforming
systems
Membrane Types
Contaminants
Membrane
Support Material
Flat Sheet Thin Film Composite (RO/NF)
Hollow Fiber (MF/UF)
99.0498.000ppt_4-29-02_djh04.ai
Membrane Selection
Algae
Turbidity
Cryptosporidium Bacteria
Giardia
MICROFILTRATION
> 0.1 micron
Organic Macromolecules
Viruses
Asbestos
0.1 - .003 micron, >2000
MW
ULTRAFILTRATION
Hardness Color
NOM
Radionuclides SOC’s
NANOFILTRATION
> 0.001 micron, >180 MW
Salts
RO
H2O
> 0.0001 micron, Ions > 20 AW
Membrane Processes
● Membrane Filtration: Size Exclusion (Sieving)
 Microfiltration, MF
 Ultrafiltration, UF
● Membrane Separation: Diffusion Controlled
 Nanofiltration, NF
 Reverse Osmosis, RO (Low Pressure/Brackish Water)
 Seawater Reverse Osmosis, SWRO
● Non-Water Permeable: Charge Controlled Processes
 Electrodialysis, ED
 Electrodialysis Reversal, EDR
Membrane Filtration
1
Membrane Filtration (MF/UF)
● Hollow Fiber Membranes – Bundles or Cassettes
● Microfiltration (MF)
 Process removes particles / turbidity / bacteria / and protozoa
 Pressure Range: 4 - 70 psi
 Configuration: Hollow Fiber
● Ultrafiltration (UF)
 Process removes particles / turbidity / bacteria / protozoa and virus
 Pressure Range: 10 - 90 psi
 Configuration: Hollow Fiber
Membrane Filtration (MF/UF)
● Various forms are available
 Vacuum Driven (submerged in tank)
 Pressure Driven (in pressure vessels, normally vertical)
● Typically operates in dead end mode (like a media filter)
● System operates for a prescribed run period (determined by
recovery)
● Concentrate waste from a short duration backwash (backpulse
cycle)
MF/UF Membranes
• Membranes are
manufactured as hollow
fibers
• Materials include PP,
PVDF, PES, and others
• Most are resistant to
high levels of chlorine
• Hollow fibers are
engineered to provide a
specific pore size
UF Membranes = Effective Barrier
• Hollow strands of porous plastic
fibers with billions of
microscopic pores on the
surface
• The pores are thousands of
times smaller in diameter than a
human hair
Membrane
Fiber
Electron microscope view of
membrane surface
• Pores form a physical barrier to
impurities but allow pure water
to pass
Operating Modes
Inside Out, Flow Thru
Inside Out, Dead End
Outside In
MF/UF Treatment Units
• Hollow fibers are bundled
into cassettes for immersed
service or enclosed vessel
modules
• Operated in inside-out or
outside-in and dead end or
recirculation modes
• Pressure is applied to the
feed or a vacuum is applied
to the fibers
MF/UF System Design Parameters
● Flux rates decrease with increasing fouling potential
● To Increase Capacity: Add membrane area (more membrane
elements in parallel)
● To Increase Recovery: Add pretreatment
● To Increase Quality: Membrane material, pore size
● Recovery limited feed pressure limitations and effectiveness of
backwash cycles
MF/UF Applications
●
●
●
●
Retrofit for Existing Media Filters
Surface Water Treatment (LT2ESWTR)
GroundWater Under Direct Influence (GWUDI)
Pretreatment to RO/NF (Integrated Membrane Systems)
 Seawater RO (SWRO)
 Brackish Surface Water
 Water Reuse (IPR/DPR)
Ultrafiltration Pathogen Removal
0.1 micron pore size
4 to 6 micron
Giardia
(4 - 14 microns in diameter)
Cryptosporidium
(4 - 6 microns in diameter)
Raw Wastewater
Wastewater Treatment/Reuse
Secondary Treatment w/Tertiary Filtration
Permeate
Disinfection
Vacuum
Pump
Reclaimed
Water
Membrane Bioreactor
Membrane
Filtration
Modules
Strainer
Secondary Treatment w/Membrane Filtration
Feed
Pump
Membrane Filtration System
MF/UF Additional Considerations
● Commercial offerings are typically proprietary systems ,
packaged by the membrane manufacturer (Pall, GE, Evoqua)
● Most components are not inter-changeable
● Recent market trends are towards standardization of membrane
elements
● Many state regulatory agencies require pilot testing
● Challenge testing
● Direct integrity testing (pressure decay test)
MF/UF Innovations
● Solids and Turbidity Resiliency
● Membrane Fibers
 Low Fouling PVDF Membrane Chemistry
 Improved Durability of Membrane Fibers
● Membrane Cassettes/Bundles –
Modular Construction and Flexibility for
Expansion
● Encased vs. Submerged Installations
● Enhanced Methods for Maintaining
System Performance (CEB, Mini-Cleans,
CIP)
MF/UF Systems - Market Trends
MF/UF Market has traditionally been
dominated by suppliers of complete
pre-engineered systems:
● Significant differences in modules,
operational conditions, and cleaning
required custom tailored systems
● Required selection of system supplier
prior to completing the plant design
● Owner often must sole-source future
membrane replacements and future
service/parts
MF/UF Systems - Market Trends (cont.)
Interchangeable rack MF/UF systems
are changing the ways systems are
designed and constructed:
● Piping and supporting equipment are
designed to work with multiple membrane
manufacturers (non-proprietary alternative)
● Allows detailed design to be completed
without a final membrane manufacturer
selection
● Compatibility with 3-6 different membrane
manufacturers
● Improved convergence of suppliers of
MF/UF with NF/RO (benefits applications
for integrated membrane systems)
Membrane Separation
1
Membrane Separation (RO/NF)
●Thin Film, Flat Sheet Membranes – Spiral Wound
●Nanofiltration (NF)
 Process removes turbidity / virus / color / pesticide / NOM /
pesticide / and hardness
 Pressure Range: 70 - 140 psi
 Configuration: Spiral Wound Sheet
●Reverse Osmosis (RO)
 Process removes turbidity / color / pesticide / NOM / pesticide /
hardness / salinity removal / nitrate / arsenic
 Pressure Range: 140 - 700 psi
 Configuration: Spiral Wound Sheet, Hollow Fiber
Membrane Sheet Surface
Semipermeable
membrane layer
~2000 Angstrom
Microporous
polymeric support
Fabric backing
0.2 mm
0.008"
Membrane Construction
Polymeric support
PA membrane surface
Fabric backing
Membrane Separation (NF/RO)
● Always pressure driven (normally
horizontal pressure vessels)
● Operates in cross flow mode, producing a
constant flow of concentrate (volume
determined by recovery)
● System operates continuously, and the
higher TDS concentrate is produced in
proportion to the permeate flow stream
Reverse Osmosis
● “Reverse” osmosis is achieved by providing adequate pressure to
overcome the osmotic pressure so that the feed water flows from
the more concentrated solution to the “fresh” water side of the
membrane.
Diaphragm
P>PO
1,500 mg/L
100 mg/L
Water
Membrane Element Dimensions
Diameter:
200 mm, 8”
Length:
1 m,
40 “
RO/NF Membrane Element
Feed
Brine Spacer
Concentrate
Product
Membrane
Permeate
Carrier
RO/NF Pressure Vessel Assembly
Feed
O-rings
Interconnector
Brine Seal
Permeate
Head Seal
Pressure Vessel
Head
End Adapter
Retaining Ring
Thrust Cone
R.O. Element
Concentrate
Pressure Vessel Flow-streams
44 gpm feed
22 gpm
permeate
22 gpm concentrate
Element Cross-Section
Trust ring
End plate
Interconnector
Feed or concentrate
port
Connector adaptor
Pressure vessel
Section of RO
element
Reverse Osmosis System Schematic
Post Treatment
Pretreatment
Raw Water Blend
Raw
Water
Finished
Water
Stage 1
High Pressure
Pumps
Membrane
Treatment
Stage 2
Concentrate to
Disposal
Permeate
RO/NF System Design Parameters
● Flux rates decrease with increasing fouling potential
● To Increase Capacity: Add membrane area (more pressure
vessels in parallel)
● To Increase Recovery: Concentrate Staging - 1st stage
concentrate becomes 2nd stage feed
● To Increase Quality – Permeate Staging – 1st stage permeate
becomes feed to 2nd Pass
● Recovery limited by limiting salts and/or feed pressure limitations
(energy costs)
NF/RO Applications
●
●
●
●
●
●
●
●
●
●
Membrane Softening (NF)
Color / Organics Removal (NF, Stage 2 DBPR)
Brackish Water (BWRO)
Nitrate Removal
Arsenic Removal
Industrial Water Treatment (Boiler, Manufacturing, ect.)
High Purity / Ultrapure Water
Seawater Desalination (SWRO)
Water Reuse (LPRO)
Food & Beverage, Bottled Water
Membrane Softening vs. Lime Softening
Lime-Soda Ash Process
Raw Water
w/Hardness, Color,
Iron Nitrates and
Organics
Solids Contact
Unit (Softener)
Rapid Media
Filtration
Raw Water Blend
Blending
Basin
Stage 1
Pretreatment
High Pressure
Pumps
Membrane Softening Process
Membrane
Softening Skids
Stage 2
Post
Treatment
Permeate
Concentrate to Disposal
Finished Water
Lime/Polymer
Dissolved Inorganic Solutes (Brackish GW)
Existing Treatment Process
Raw
Water
Raw Water Blend
Blending
Basin
Stage 1
Pretreatment
High Pressure
Pumps
Reverse Osmosis Treatment
Process
NF/RO Membrane
Skid
Post
Treatment
Finished
Water
Permeate
Stage 2
Concentrate to Disposal
NF/RO Additional Considerations
● Commercial offerings are standardized with inter-changeable
vessels and membrane elements
● Systems packaged by Membrane OEMs
● State regulatory agencies may accept membrane projections
(software), some still require pilot testing
● Method of concentrate disposal
NF/RO Innovations
● Energy Reduction
 Low Energy (Higher Permeability)
Membranes
 Optimized Feed Channel Spacers
 Energy Recovery Devices
● Process Optimizations
Port St. Lucie Energy Recovery Device
 Fouling Resistant Membranes
 Improved Pretreatment Chemicals
 High Recovery RO Designs
(Concentrate Minimization)
 Multi-ported Pressure Vessels
 Center Feed Vessels (Nanofiltration)
NF/RO Innovations
● Product Innovations
 Large Diameter Elements
 High Surface Area Elements
(Automated Manufacturing)
 Interlocking Membrane
Elements
8” element vs. 16” element
Summary
● Membrane technology is rapidly becoming more
mainstream throughout the US
● Costs can be competitive with conventional
treatment
● Membrane technology continues to evolve with
innovation
● Pilot Scale and Demonstration Scale Testing is
always beneficial