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Membrane Filtration Basics 101 Paul J. Delphos, Black & Veatch 757-456-5380, ext 12 VA AWWA Plant Operations Committee Operators Conference Virginia Beach, VA May 19-21, 2014
Membrane Filtration
Basics 101 Paul J. Delphos, Black & Veatch 757-456-5380, ext 12
VA AWWA Plant Operations Committee Operators Conference Virginia Beach, VA
May 19-21, 2014
Presentation Overview
Market Assessment
Membrane Theory
Example Applications
What’s The Big Deal??
1st Significant MF/UF System in North America in 1993 (Saratoga, CA – 3.6 mgd)
Over 250 plants now on-line
Historically, small facilities (i.e. < 1 mgd) for small clients
Trend is to fewer, but larger facilities
Minneapolis – 70 and 90 mgd
Singapore – 72 mgd
Lancaster – 24 mgd, expandable to 36 mgd
Desalination Is Growing As Well
SWRO
BWRO
EDR
BWRO
SWRO EDR BWNF
250
20 15 71
110
92 44 110
BWNF
Number of Installations Capacity (mgd)
Other Perspectives
Membrane System Sales To Reach $9 Billion by 2008 (Mcllvaine Company, 2006)
$6.8 Billion in 2005 (33% Top End Growth)
Includes Desalination and Low-Pressure Membranes
Microfiltration from $1.9 to $2.5 Billion
Only 2.5% of US Drinking Water is Treated with MF/UF Membranes
Expected to Reach $10 Billion by 2010
Nearly All New Revenues Are
From New Projects
What Are Membranes?
Cartridge/Pressure
Submerged/Vacuum
Membrane Theory Overview
Colloids
Bacteria
Pollens Yeasts
Organic macromolecules
Organic compounds
Viruses Dissolved
salts
Reverse osmosis
Nanofiltration
Microfiltration
Sand filter
1 0.1 0.01 0.001 0.0001 10 100 um
hair visible
to
naked
eye
Giardia Smallest
microorganisms
Polio
virus
Ultrafiltration
How Do Membranes Work?
Membranes can remove anything that
is larger than its pores.
Giardia
Cryptosporidium
• Membranes fail incrementally – one fiber at a time.
• Statistically, individual fiber breaks are insignificant
to the overall microbial water quality.
Membrane Failure Mode
Bubble point
Air pressure
Sonic wave
Bio-challenge
Turbidity
Particle
monitoring
Direct
Measures
Indirect
Measures
The accepted standard is moving towards
continuous (safety interlock) turbidimeters.
Detection limit 0.001 NTU.
On-Line Integrity Testing
Some Key (and New) Terms
NEW
Flux
Flux Decline
Specific Flux/Permeability
Reverse Filtration
Membrane Integrity
Log Removal
Recovery
Transmembrane Pressure
OLD
Overflow Rate
Declining Rate
????
Backwash
Filter Breakthrough
Filtered Turbidity
Backwash Volume
Filter Head Loss
Piloting Overview
Number of Systems?
Regulatory Acceptance
Verified Membrane Applicability
Basis of Design
Operator Experience
Data Evaluation
City of Lancaster MF Pilot
0
10
20
30
40
50
60
Nov Jan Mar Apr Jun
gfd
p
si
0
2
4
6
8
10
12
ZW 500-C, Sp Permeability @ 20°C ZW 500-C, Instantaneous Flux ZW 500-C, Average TMP
Flux
Recovery/Waste Disposal
Cold Water TMP Issues
Daily Cleans vs. Monthly Cleans
Turbidity
TOC/UV254
Particle Counts – log removal
MIT’s
Membrane Fouling
Causes
Biological
Organic/Colloidal/
Particle
Chemical Scaling
Membrane Compression
Synthetic Polymers
Mitigation Measures
Chlorination
Cross-Flow
Backwash
Chemical Cleaning
Additives/Coagulants
Pretreatment
Membrane Fouling Directly Impacts Costs
Fouling is the limiting factor in most membrane system designs
By removing organics, or natural organic matter (NOM), membranes become much more effective
Coagulation removes NOM by:
Charge Neutralization
Adsorption To Precipitates
With membranes, coagulation is geared to TOC removal
The “cake layer” on pressure systems improves TOC removal
Membrane Fouling
0
2
4
6
8
10
12
14
16
0 50 100 150 200 250 300
Time
Pre
ssu
re -
psi
Membrane
Fouling
Backwash
Irreversable
Fouling
Backwash &
Chemical Cleaning
Membrane Fouling Example
Before and After Backwashing
0
2
4
6
8
10
12
14
16
18
20
22
22-
Jul
24-
Jul
26-
Jul
28-
Jul
30-
Jul
1-
Aug
3-
Aug
5-
Aug
7-
Aug
9-
Aug
11-
Aug
13-
Aug
15-
Aug
17-
Aug
19-
Aug
21-
Aug
Date
TM
P (
ps
i)
Before BP VacuumAfter BP Vacuum
(1) Vacuum increase due to flux increase corresponding
to re-adjusted permeate flow.
(2) Rain event - organics/color raw water spike, alum
dosage not increased to compensate.
(3) High vacuum alarm --> tank dumped, re-started with
higher alum dosage.
(4) Caustic dosing interrupted.
(5) High vacuum alarm --> clean
(6) Clean - vacuum recovers to 4"Hg.
(7) Ferric dosing interrupted? (Floc tank pH = 6.8).
(8) High vaccum alarm --> system off for 6.5 hours and
then re-started.
(1) (2) (3) (5)(4) (6) (7) (8)
SEM Images of Fouling Layer (UF Membrane, CA, 100k MWCO)
Clean Membrane
Growth of NOM Fouling Layer Over Time
Effect of Backwashing on Fouling Layer
HIOP Cake Layer with Sorbed NOM
Effect of Backwashing on Cake Layer
Clean Membrane, CA 100k MWCO
Dead-End Filtration – 30 Minutes
Dead-End Filtration – 1 Hour
NOM Layer Before Backwash
NOM Layer After Backwash
Coagulant Aid (HIOPS) + NOM Before BW
Coagulant Aid + NOM After BW
Turbidity/pathogen/TOC removal on raw water
Replace conventional filters following flocculation/sedimentation
Treatment of conventional filter backwash water
Pretreatment ahead of RO or NF membrane system
Fe/Mn removal following oxidation
Arsenic Removal
Pathogen removal following conventional treatment
Potential Applications For Low Pressure
Membranes
Typical Pressure MF/UF System
Air System B/W Water
Cl2
Raw
Water
Source
Supply
Pump
Particle
Strainer
CIP System
Membrane
Modules Backwash Waste/
Concentrate
To
Disposal
Finished
Water
Storage
Finished
Water
Pumping
Permeate
Submerged - Enhanced Coagulation
Air
Permeate Pump
Feed Water
Bleed/Concentrate
Flocculation Chamber
Coagulant
Flash Mixer
High solids concentration in tank
Filtered Water
5 to 50 psi
Filtered Water
Filtered Water
Solids and
Liquids Under
Pressure
Pressure vs. Submerged
Pressure vs. Submerged
Pressure
Advantages
Skid-mounted
Easy to install
Great for small systems
Easy competition
High Fluxes
Disadvantages
Larger systems
Fouling/energy
Low Dosages of Coagulant
Backwashing
Submerged
Advantages
Use of existing tanks
Larger systems
Low energy
Great for poor raw water
Low fouling
Backwash recovery
Disadvantages
Modifications can be expensive
Low flux rates
Concentrate with fiber breakage
Filtered Water
5 to 50 psi
Filtered Water
Filtered Water
Solids and
Liquids Under
Pressure
Outside-In vs. Inside-Out
Outside-In vs. Inside-Out
Outside-In
Advantages
Submerged option
Larger active area
Higher solids
Lower Pressure
Dead-end flow
Disadvantages
Lower comparative flux
Irreversible fouling?
Inside-Out
Advantages
Great with clean water
Cross-flow operation minimizes irreversible fouling
Disadvantages
Recirculation required
Higher flux requirements
High fouling potential
Increased energy
MF/UF Modes of Operation
Conventional (Dead-End)
Feed
membrane filter
Cross-flow
Fe
ed
me
mb
ran
e f
ilte
r
Principal Suppliers of Low Pressure Drinking
Water Membrane Systems
Membrane System Suppliers
Pall Corporation (MF/UF)
GE - Zenon Environmental, Inc. (MF/UF)
Evoqua Water Technologies
(Siemens - US Filter/Memcor (MF) )
Wigen, Inc. (UF)
H2O Installations
WesTech
Kruger
Membrane Module Suppliers
GE (UF
Evoqua (MF)
Dow (UF)
Toray (UF)
Hydronautics, Inc. (UF)
Asahi (MF)
Primary Elements of Low-Pressure Membrane
System
Feed water/vacuum pumps
Ancillary pumps
Automatic screens
Skids with PLC-based controls
Clean-in-place (CIP)
SCADA system/PLC network
Air delivery system
Waste holding tank/pumps
Neutralization tank/pumps
Roanoke, VA – Crystal Spring
Spring has been used for drinking water since 1880s
In summer of 2000, VDH determine spring was GWUI as coliform counts increased
Virginia Membrane Plants - Memcor - 14
Koch - 1
VDH “Approved” Other Membrane Manufacturers
Competitive Bid Between Memcor and Pall
Crystal Spring WTP - Design Conditions
5 mgd firm (one rack out of service)
99.5% recovery (backwash recovery)
No pretreatment (chlorine was recommended by Pall)
30 day cleaning cycle
60 minute backwash frequency
10-year membrane warranty
Performance testing for successful bidder
Crystal Spring WTP - Bid Summary
Cost Component
US Filter - Memcor
Pall
Capital $1,600,317 $1,960,000
O&M (20-yr PW)
$436,625 $303,176
Membrane Repl. (20-yr PW)
$357,822 $429,130
Total 20-yr PW $2,394,764 $2,692,306
Performance Testing Operating Results
Flux: 34.8 gfd @ 15oC
TMP: 1 psi increase per 15 to 18 days
Average TMP: 10.5 psi
Backwashing: 150 sec/90 minutes
97% Recovery
CIP Interval of Over 90 days
Crystal Spring WTP – Performance Testing
Criteria
Flux: 34.6 gfd
Recovery: 95% w/o backwash recovery 99.5% w/ backwash recovery
Backwash: 150 sec/60 min
CIP Interval: 30 days
Chemical Consumption Limits
Power Consumption Limits
100 – day Duration
Performance Testing Water Quality Results
Turbidity
Raw: 0.06 NTU to 0.14 NTU
Permeate: 0.02 NTU (lower limit of turbidimeter)
Particle Counts
Raw: 25 to 75 >2 um/mL
Permeate: 2 to 8 >2 um/mL
1 to 1.5 log removal
Pilot Turbidity Spike Data
9.8
9.9
10
10.1
10.2
10.3
10.4
10.5
10.6
14:15 14:40 15:11 15:39 15:44 16:12 16:23 16:40 16:46
Time
TM
P (
ps
i)
0
5
10
15
20
25
30
35
Fe
ed
Tu
rbid
ity
(N
TU
)
TMP
Turbidity``
Permeate <0.023 NTU
Crystal Spring WTP
Spring, Pumps and Screens
Installed Membrane System
Installed Membrane System
CIP System
Membrane System Piping
Operating Data - Flow
0.00
1.00
2.00
3.00
4.00
5.00
6.00
Dece
mber
Janu
ary
Febuar
y
Mar
chApri
l
May
June
July
August
Month
Flo
w (
mg
d)
Operating Data - Flux
20
22
24
26
28
30
32
34
Dec
ember
Januar
y
Febuar
y
Mar
chApri
lM
ay
June
July
August
Month
Flu
x (
gfd
)
Operating Data - Recovery
90%91%92%93%94%95%96%97%98%99%
100%
Dec
embe
r
Janu
ary
Febu
ary
Mar
chApr
il
May
June
July
Aug
ust
Month
Reco
very
(%
)
Operating Data - Turbidity
00.20.40.60.8
11.21.41.61.8
2
Dece
mber
Janu
ary
Febuar
y
Mar
chApri
l
May
June
July
August
Month
Tu
rbid
ity
Operating Data - TMP
0
5
10
15
20
25
30
Febuar
y
Mar
chApri
l
May
June
July
August
Month
TM
P (
psi)
Filter 1
Filter 2
Filter 3
Filter 4
Filter 5
Other 1st Year Results
CIP Interval: 1 per 6 months
Zero Fiber Breaks (over 10 million fibers)
Manpower Reqt’s: < 2 h/d, 5 d/wk
“The Plant Runs Itself” – Greg Belcher, City of Roanoke
Chesapeake, Virginia
7.5 MGD Submerged Membrane Plant
Dedicated in April 2006
Raw Water TOC – 4 to 6 mg/L
Raw Water Turbidity 25 to 50 NTU
Coagulant Feed – 20 to 25 mg/L
Coagulant pH – 5.5 to 6.0
Chesapeake TOC Data
Sample May 8 May 22 May 30 Jun 7
Raw 4.10 4.22 4.50 4.29
Permeate 1.36 1.77 1.88 1.82
% Reduction 67% 60% 58% 58%
Alum Dose (mg/L)
25 20 20 20
pH 5.46 5.87 5.90 5.85
Raw Water Strainers
Pretreatment Tanks
Membrane Tanks
Multiple Membrane Trains with Crane
Lancaster Pennsylvania
24 and 12 MGD WTPs
Regulatory Drivers
LT2 ESTWR (Crypto Removal)
Stage 2 D/DBP Rule
Future Rules
Conventional Facilities
Zenon 500 Upgrade
Direct vs. Clarified Feed
Lancaster, PA
24 and 12 mgd Membrane Facilities
Two of the Largest on the East Coast
Includes State-of-the-Art Thickening Process
Include Two-Stage Membrane Treatment with UV Disinfection
Over $70 million
Great client reference
Lancaster, PA - Pilot Operation
Raw
Pre-screened River Water
Alum Feed
Acid
15 minute floc
99.7% recovery
PACl later
Clarified
Post-clarification
Daily Cleans vs. Monthly Cleans
95% Recovery
EC Jar Tests
Data Evaluation - Permeate
Parameter Raw MF/UF Clarified
MF/UF
EC
Alum Dose 50 mg/L 30 mg/L 70 mg/L
Turbidity <0.03 NTU <0.03 NTU <0.3 NTU
Particle Cts
(#/mL)
<10 <10 NA
TOC Removal 35-50% 15-25% 35-50%
DBP’s 1 3 2
Lancaster – Other Findings
Raw will work on flashy river water
Need to pay attention closely during flashy events
Daily cleans – Helped when working
Heated daily cleans/backwashes helped short-term
High fluxes can be unstable
Lancaster – Other Findings (cont.)
Clarification process is not necessarily an additional barrier or a reduction of risk
Constructability and retrofit costs can be very difficult to quantify
Cold water (<3oC) was difficult
PACl worked best in cold water
Raw water membrane costs (capital and operating) – 30 to 40% above clarified
Swansea Water District, MA
First Desalination Project on East Coast for HDR
1.5 mgd Desalination plus 1 mgd Fe/Mn Groundwater Membrane Plant
Upon completion, will be the 2nd surface water desalination facility north of Florida
Pall/Toray
Summary
Membranes are here and will become a more technology in the future.
Membranes are a great particle removal mechanism
Significant fractions of organics are not normally removed with MF/UF, but when coupled with a coagulant, removals are equal to or better than conventional facilities
Membranes will work on all waters, cost is just the major factor – so, pick the correct system!!!!!!
For more information, contact:
Paul J. Delphos
757-456-5380, ext 12
Membrane Filtration
Basics 101
