Michael Bourke – Wigen Water Technologies .
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Transcript of Michael Bourke – Wigen Water Technologies .
Michael Bourke – Wigen Water Technologies
www.wigen.com
Potable Applications of NF/ROAesthetic
TDSHardnessSulfateColor
RegulatoryNitrateArsenicRadionuclidesFluorideSeleniumPesticidesHeavy Metals
Contaminant Removal Rates using RO & NF
Comparative Removal Rates NF RO
Monovalent Ions (Sodium, Potassium, Chloride, Nitrate, etc) <50% >98%
Divalent Ions (Calcium, Magnesium, Sulfate, Carbonate, Iron, etc)
>90% >99%
Microsolutes (<100 Mw) 0-50% 0-99%
Microsolutes (>100 Mw) >50% >90%
Feed Water
Membrane
Permeate
Concentrate
Pressure
Membrane separation is a process in which properly pretreated source water is delivered at moderate pressures against a semipermeable membrane. The
membrane rejects most solute ions and molecules, while allowing water of very low mineral content to pass through.
Feed Water
Concentrate
Permeate Membrane Material
Spacer Material
Permeate Carrier Material
The most common RO membrane material today is aromatic polyamide, typically in the form of thin-film composites. They consist of a thin film of membrane bonded to layers of other porous materials that are tightly wound to support and strengthen the
membrane.
NF/RO Membrane Operation
NF/RO System Components
1. Feed water characteristics- Cations- Anions- Silt Density Index (SDI)- Temperature- Oxidants
2. Pre-treatment requirements
- Mechanical and/or chemical- Solids removal (turbidity < 1 NTU)- Fe/Mn removal- Anti-scalant and sodium bisulfite dosing
3. Determine desired permeate quality & flow- Membrane selection- Recovery achievable/waste volume- Amount of bypass
4. O&M Requirements- Power & Pretreatment chemicals- Cartridge filter replacement- CIP Chemicals- Membrane Replacement
10-15% increase in normalized 10-15% increase in normalized differential pressuredifferential pressure
10-15% decrease in normalized 10-15% decrease in normalized permeate flowpermeate flow
10-15% decrease in permeate quality10-15% decrease in permeate quality
Prior to sanitizationPrior to sanitization
Regular Maintenance ScheduleRegular Maintenance Schedule
Every 3 to 12 monthsEvery 3 to 12 months
Cleaning Frequency?
Case StudiesCity of Wellman, IA
New RO System for Radium & Ammonia Removal and General Water Quality Improvement.
City of Creighton, NE Upgraded RO System to Improve Nitrate Removal.
• Background• Trial Objectives• Pilot Plant Selection• Results• Full-scale System Design
Wellman, Iowa
• Population ~1400• Groundwater supply• Greensand Filters• DW violations for:
- Nitrite- Combined radium
Raw Water Characteristics
Parameter Range (Ave)TDS, mg/L 1600 – 3620 (1914)
Ammonia, mg/L as N 0.2-4.2 (3.8)
Total Hardness, mg/L as CaCO3 780-1070
Sulfate, mg/L 91- 2230 (1219)
Combined Radium, pCi/L 2.0 – 21.3 (6.5)
Fluoride, mg/L 0.6 – 1.1
Silica, mg/L as SiO2 13 – 14
Iron, mg/L < 0.03 mg/L
Manganese, mg/L 0.006 – 0.055
Chloride, mg/L 6.5 – 85.6
Sodium, mg/L 150 - 764
TOC, mg/L 1.3 – 1.8
Trial Objectives
Three month trial required by IA DNR.Demonstrate RO system performance on a pilot
plant representative of a full-scale system.
Parameter (actual) Target
Combined Radium (2.0-21.3)
< 5.0 pCi/L*
Sulfate (910-2230) < 250 mg/L#
TDS (1600-3620) < 500 mg/L#
Hardness (780-1070) < 250 mg/L as CaCO3
Ammonia (0.2-4.2) As low as possible*EPA Primary DW Regulation#EPA Secondary DW Regulation
Pilot CriteriaRepresentative of Full-scale Design
Average flux ratesArray Length (6L) – representative flux per
elementMembrane element diameter/type
Representative Pre-treatmentFiltrationFe/Mn RemovalChemical Dosing
Representative Feed Water
Pilot Plant Set-up
S1 Feed(elements 1-3)
S1 Feed(elements 4-6)
S2 Feed
Concentrate
2-2:1-1, 3-Long Pilot Plant, Simulates 2:1, 6-Long System
Trial DesignDuration – cover minimum CIP frequencyData Collection
Automatic (pressure, flows, conductivity, temperature)
Normalized data to monitor system performance, early signs of fouling or membrane damage.
Manual (feed, permeate & concentrate samples)Membrane Autopsy
Detect/identify cause of fouling (lead and end elements)
Takes changes in pressure and temperature and then normalizes, or adjusts, the recorded permeate flow rate accordingly.
Data Normalization
Graphically shows the permeate flow rate without the effects temperature
Indicates the need for cleaning Helps troubleshoot system
System Flows vs. Time
3.00
8.00
13.00
18.00
26-Jun-09 06-Jul-09 16-Jul-09 26-Jul-09 05-Aug-09 15-Aug-09 25-Aug-09 04-Sep-09 14-Sep-09 24-Sep-09 04-Oct-09
Date
Flo
w (
gp
m)
Normalized Permeate Flow Permeate Flow Concentrate Flow Linear (Normalized Permeate Flow)
No decrease = minimal fouling
Potential MembraneDamage
Normalized Permeate Conductivity vs. Time
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
26-Jun-09 06-Jul-09 16-Jul-09 26-Jul-09 05-Aug-09 15-Aug-09 25-Aug-09 04-Sep-09 14-Sep-09 24-Sep-09 04-Oct-09
Date
No
rma
lize
d P
erm
ea
te C
on
du
cti
vit
y (
uS
/cm
)
Normalized Permeate Conductivity (uS/cm) Permeate Conductivity
Linear (Normalized Permeate Conductivity (uS/cm))
CIP Performed
TDS vs. Time
0
500
1000
1500
2000
7/14
7/21
7/28 8/4
8/11
8/18
8/25 9/1
9/8
9/15
9/22
9/29
Date
TD
S (
mg
/l)
Feed TDS
Permeate TDS
• 98.9% TDS Reduction• 16-28 mg/L
Hardness vs. Time
0
100
200
300
400
500
600
700
800
900
1000
7/14
7/21
7/28 8/4
8/11
8/18
8/25 9/1
9/8
9/15
9/22
9/29
Date
Har
dn
ess
(m
g/la
s C
aCO
3)
Feed Hardness
Permeate Hardness
• 99.9% Hardness Reduction• 0.9-2.0 mg/L as CaCO3
(slight increase in last week)
Sulfate vs. Time
0
200
400
600
800
1000
1200
1400
7/14
7/21
7/28 8/4
8/11
8/18
8/25 9/1
9/8
9/15
9/22
9/29
Date
Su
lfat
e (
mg
/l)
Feed Sulfate
Permeate Sulfate
Ammonia vs. Time
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
7/14
7/21
7/28 8/4
8/11
8/18
8/25 9/1
9/8
9/15
9/22
9/29
Date
Am
mo
nia
(m
g/l
as N
)
Feed Ammonia
Permeate Ammonia
• 99.94% Sulfate Reduction• 0.9-4.2 mg/L (slight increase
in last week)
• Below detection (<0.09 mg/L)
•First membrane in bank 1 and last in bank 2
•No visible signs of fouling.
•∆P and Flowrate within acceptable ranges
•Conductivity rejections of 97.3% & 97.1% below spec of 99.5% - possible chlorine damage.
•Fujiwara test was positive for halogen on membranes indicating oxidative attack.
• TDS, sulfate, hardness & ammonia reduced to well below targets.
• Combined radium (226/228) reduced to below detection <1.0 pCi/L (feed levels only ~2.0 pCi/L during trial).
• Increase in permeate flow and some salts determined to be due to chlorine oxidation. Possible chlorine peaks in feed or loss of sodium bisulfite dosing.
• No fouling experienced over trial period with 2.3 mg/L dose of Vitec 3000, and CIP frequency likely to be every 4-6 months.
• Two x 100 gpm RO skids
• 20% Bypass stream
• Design flux of 14.4 GFD & 75% recovery
• Array: 3:1, 6-Long
• Toray TMG20-400 membranes
• ORP meter on feed to shut down RO on detection of Cl2 residual.
• Waste to sewer.
July 2011
• Background• RO System Capabilities for NO3
Removal & Factors Impacting Performance
• Overhaul of City’s RO System• System Performance – Before & After
City of Creighton• Population ~1200• Groundwater supply• Raw Water Nitrate 15-20 mg/L
RO System History – First in NEInstalled in 1993 – first
RO system in Nebraska
Two skids each with two RO trains.
Array per RO train:3:2, 6-long
Feed: 130 gpm per train
Permeate: 100 gpm per train (76% recovery)
RO Concentrate120 gpm
RO Train 4
Greensand Filters
RO Train 3
RO Train 2
RO Train 1
Well Pumps
Bypass – 125 gpm
Finished Water 525 gpm
Permeate 400 gpm
RO System HistoryBypass: 50% reduced to 25% with increasing
raw water nitrate levels to stay in compliance.Trains 1 & 2 historically had significantly
more use:Membranes replaced most recently in 1 & 2
due to greater TDS and nitrate leakage.No improvement in Train 1 and 2
performance after membrane replacement.System placed on compliance order in early
2011 – given 90 days to get in compliance.
Projection conducted for Toray TMG20N-400C low energy RO membranes.
With 20 mg/L NO3-N in feed, theoretical permeate level was 1.67 mg/L.
Nitrate from trains 1 & 2 was >5.0 mg/L.Determined that reconditioned RO
membranes had been recently installed in trains 1 and 2.Typically used for hardness removalNot suitable for nitrate removal
Projection ResultsParameter Raw Feed PermeateNitrate, mg/L as N 20 1.67 (actual ~5.5)
Hardness, mg/L as CaCO3 223 2.5
Sulfate, mg/L 22 0.05
Calcium, mg/L 77 0.66
Magnesium, mg/L 12.9 0.11
Silica, mg/L as SiO2 13 0.21
Chloride, mg/L 10 0.04
Sodium, mg/L 15.3 0.17
TDS, mg/L 11.0 (actual ~140)
Contaminant Removal Rates using RO & NF
Comparative Removal Rates NF RO
Monovalent Ions (Sodium, Potassium, Chloride, Nitrate, etc) <50% >98%
Divalent Ions (Calcium, Magnesium, Sulfate, Carbonate, Iron, etc)
>90% >99%
Microsolutes (<100 Mw) 0-50% 0-99%
Microsolutes (>100 Mw) >50% >90%
Install Toray Low Energy Membranes (TMG20N-400C) in worst performing trains (1 & 2).
Fastest and lowest cost to get system back in compliance.
Future:Replace existing pumps with
more efficient low energy pumps.Replace membranes in trains 3 &
4.
Trains 1 & 2 Membranes Replaced
Trains 1 & 2 Membranes Replaced
Trains 1 & 2 Membranes Replaced
Previous RO Membranes:Operating Pressure: 150 psiPump Power: 20 HP per trainAnnual Power Cost*: $7,840 per train @ 10c/kWh
Low Energy RO Membranes:Operating Pressure: 110 psiPump Power: 15 HP per trainAnnual Power Cost*: $5,880 per train @ 10c/kWh
Annual Power Savings: $7,840 (25% reduction)
*Assuming 60% plant utilization
Operating Costs: c/1000 galPower 10.4Chemicals# & cartridge filters 14.9Membrane replacement (5 years) 16.5Total* 41.8
*Assuming 60% plant utilization, 75% recovery & 20% bypass.
#Bisulfite, antiscalant, CIP chemicals
• Determined that reconditioned membranes were not effectively removing nitrate and resulting in MCL violations.
• Replacement of train 1& 2 membranes immediately brought system back in to compliance.
• Low energy membranes will save City ~$8000 per year in pumping power.
• Don’t assume any RO membrane can remove >90% nitrate!
Questions?
www.wigen.com