Advancements in Membrane Technology: Standardizations and Innovations in Drinking Water Applications

June 17, 2016

Jarrett Kinslow, PE

Jill Hudkins, PE

● Introduction and Review of

Membrane Technologies

● Membrane Filtration (MF/UF)

Overview, Applications &

Innovations

● Membrane Separation (NF/RO)

Overview, Applications &

Innovations

● Summary

Agenda

SAWS Brackish Groundwater Desalination Approaching Completion (Yesterday)

1

Introduction

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.

Increasing regulatory standards

especially regarding disinfectant

by-products and waterborne pathogens

Limited and deteriorating

supplies require the use of

alternative water sources

Growing demand due to

population growth

Technological innovation

leading to development of

low cost, high quality water

treatment solutions

Retrofit of old technology

to protect the public from

aging or underperforming

systems

Membranesoffer costeffectivesolutions

Drivers for Membrane Treatment

Flat Sheet Thin Film Composite (RO/NF)

Support Material

Membrane

Hollow Fiber (MF/UF)

Contaminants

Membrane Types

99.0498.000ppt_4-29-02_djh04.ai

MICROFILTRATION

ULTRAFILTRATION

NANOFILTRATION

RO

Giardia

Salts

SOC’s

NOMHardness

Cryptosporidium

Turbidity

Viruses

Algae

Radionuclides

Bacteria

Asbestos

H2O

Color

Organic Macromolecules

> 0.1 micron

0.1 - .003 micron, >2000 MW

> 0.001 micron, >180 MW

> 0.0001 micron, Ions > 20 AW

Membrane Selection

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

1

Membrane Filtration

● 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)

Membrane Filtration (MF/UF)

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

• 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

• Pores form a physical barrier to

impurities but allow pure water

to pass

UF Membranes = Effective Barrier

MembraneFiber

Electron microscope view of membrane surface

Operating Modes

Outside In

Inside Out, Flow Thru

Inside Out, Dead End

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

● 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 System Design Parameters

● 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)

MF/UF Applications

Ultrafiltration Pathogen Removal

4 to 6 micron

0.1 micron pore size

Giardia(4 - 14 microns in diameter) Cryptosporidium

(4 - 6 microns in diameter)

Wastewater Treatment/Reuse

Reclaimed Water

Feed Pump

DisinfectionPermeate

MembraneFiltrationModules

Strainer

Secondary Treatment w/Tertiary Filtration

Secondary Treatment w/Membrane Filtration

Raw

Was

tew

ater

Membrane Filtration System

Membrane Bioreactor

Vacuum Pump

● 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 Additional Considerations

● 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 Innovations

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

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)

MF/UF Systems - Market Trends (cont.)

1

Membrane Separation

●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 Separation (RO/NF)

Semipermeable

membrane layer~2000 Angstrom

Microporous

polymeric support

Fabric backing

0.2 mm0.008"

Membrane Sheet Surface

Fabric backingPolymeric support

PA membrane surface

Membrane Construction

● 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

Membrane Separation (NF/RO)

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.

Water

1,500 mg/L 100 mg/L

Dia

ph

ragm

P>PO

Length: 1 m, 40 “

Diameter: 200 mm, 8”

Membrane Element Dimensions

Feed

Concentrate

Product

Membrane

Permeate

Carrier

Brine Spacer

RO/NF Membrane Element

Feed

Concentrate

Permeate

Head End Adapter R.O. Element

InterconnectorO-rings Brine Seal

Pressure Vessel

Retaining Ring

Head Seal Thrust Cone

RO/NF Pressure Vessel Assembly

44 gpm feed

22 gpm permeate

22 gpm concentrate

Pressure Vessel Flow-streams

Interconnector

End plate

Trust ring

Connector -adaptor

Pressure vessel

Feed or concentrate port

Section of RO element

Element Cross-Section

Reverse Osmosis System Schematic

FinishedWater

RawWater

Pretreatment

High Pressure Pumps

Post Treatment

Permeate

Concentrate toDisposal

Membrane Treatment Stage 1

Stage 2

Raw Water Blend

● 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)

RO/NF System Design Parameters

● 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

NF/RO Applications

Membrane Softening vs. Lime Softening

Fin

ish

ed

Wat

er

Pretreatment High Pressure Pumps

Post Treatment

Permeate

Concentrate to Disposal

MembraneSoftening SkidsStage 1

Stage 2

Raw Water Blend

Solids Contact Unit (Softener)

Rapid Media Filtration

Blending Basin

Lime/PolymerLime-Soda Ash Process

Raw Water w/Hardness, Color, Iron Nitrates and Organics

Membrane Softening Process

Dissolved Inorganic Solutes (Brackish GW)

FinishedWater

RawWater

Pretreatment High Pressure Pumps

Post Treatment

Permeate

Concentrate to Disposal

NF/RO Membrane SkidStage 1

Stage 2

Raw Water Blend

Blending Basin

Existing Treatment Process

Reverse Osmosis Treatment Process

● 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 Additional Considerations

NF/RO Innovations

● Energy Reduction

Low Energy (Higher Permeability)

Membranes

Optimized Feed Channel Spacers

Energy Recovery Devices

● Process Optimizations

Fouling Resistant Membranes

Improved Pretreatment Chemicals

High Recovery RO Designs

(Concentrate Minimization)

Multi-ported Pressure Vessels

Center Feed Vessels (Nanofiltration)

Port St. Lucie Energy Recovery Device

NF/RO Innovations

● Product Innovations

Large Diameter Elements

High Surface Area Elements

(Automated Manufacturing)

Interlocking Membrane

Elements

8” element vs. 16” element

● 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

Summary