Michael Bourke – Wigen Water Technologies www.wigen.com

 Aesthetic

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TDS
Hardness
Sulfate
Color
 Regulatory
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Nitrate
Arsenic
Radionuclides
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Fluoride
Selenium
Pesticides
Heavy Metals

Contaminant Removal Rates using RO & NF
Comparative Removal Rates
Monovalent Ions (Sodium, Potassium, Chloride, Nitrate, etc)
Divalent Ions (Calcium, Magnesium, Sulfate, Carbonate, Iron, etc)
Microsolutes (<100 Mw)
Microsolutes (>100 Mw)
NF RO
<50%
>90%
>98%
>99%
0-50% 0-99%
>50% >90%

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.
Pressure
Feed Water
Membrane
Permeate
Concentrate

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.
Concentrate
Feed Water
Spacer Material
Permeate Membrane
Material
Permeate
Carrier
Material

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 differential pressure
 10-15% decrease in normalized permeate flow
 10-15% decrease in permeate quality
 Prior to sanitization
 Regular Maintenance Schedule
 Every 3 to 12 months

 City 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

•
Population ~1400
•
Groundwater supply
•
Greensand Filters
•
DW violations for:
Nitrite
Combined radium

Parameter
TDS, mg/L
Ammonia, mg/L as N
Total Hardness, mg/L as CaCO3
Sulfate, mg/L
Combined Radium, pCi/L
Fluoride, mg/L
Silica, mg/L as SiO2
Iron, mg/L
Manganese, mg/L
Chloride, mg/L
Sodium, mg/L
TOC, mg/L
Range (Ave)
1600 – 3620 (1914)
0.2-4.2 (3.8)
780-1070
91- 2230 (1219)
2.0 – 21.3 (6.5)
0.6 – 1.1
13 – 14
< 0.03 mg/L
0.006 – 0.055
6.5 – 85.6
150 - 764
1.3 – 1.8

Parameter (actual) Target
Combined Radium (2.0-21.3) < 5.0 pCi/L*
Sulfate (910-2230)
TDS (1600-3620)
< 250 mg/L #
< 500 mg/L #
Hardness (780-1070)
Ammonia (0.2-4.2)
< 250 mg/L as CaCO3
As low as possible
*EPA Primary DW Regulation
# EPA Secondary DW Regulation


Three month trial required by IA DNR.
Demonstrate RO system performance on a pilot plant representative of a full-scale system.

 Representative of Full-scale Design
 Average flux rates
 Array Length (6L) – representative flux per element
 Membrane element diameter/type
 Representative Pre-treatment
 Filtration
 Fe/Mn Removal
 Chemical Dosing
 Representative Feed Water

S1 Feed
(elements 4-6)
2-2:1-1, 3-Long Pilot Plant, Simulates 2:1, 6-Long System
Concentrate
S2 Feed
S1 Feed
(elements 1-3)

 Duration – cover minimum CIP frequency
 Data 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.
 Graphically shows the permeate flow rate without the effects temperature
 Indicates the need for cleaning
 Helps troubleshoot system

Trial Results
18.00
System Flows vs. Time
13.00
8.00
No decrease = minimal fouling
Potential Membrane
Damage
3.00
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
Normalized Permeate Flow Permeate Flow Concentrate Flow Linear (Normalized Permeate Flow)

Trial Results
Normalized Permeate Conductivity vs. Time
40.00
35.00
30.00
25.00
20.00
CIP Performed
15.00
10.00
5.00
0.00
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
Normalized Permeate Conductivity (uS/cm) Permeate Conductivity
Linear (Normalized Permeate Conductivity (uS/cm))

Trial Results
TDS vs. Time
2000
1500
1000
500
0
7
/1
4
7
/2
1
7
/2
8
8
/4
8
/1
1
8
/1
8
8
/2
5
Date
9
/1
9
/8
9
/1
5
9
/2
2
9
/2
9
Feed TDS
Permeate TDS
•
99.9% Hardness Reduction
•
0.9-2.0 mg/L as CaCO3
(slight increase in last week)
•
98.9% TDS Reduction
•
16-28 mg/L
Hardness vs. Time
500
400
300
200
100
1000
900
800
700
600
0
7/
14
7/
21
7/
28
8/
4
8/
11
8/
18
8/
25
Date
9/
1
9/
8
9/
15
9/
22
9/
29
Feed Hardness
Permeate Hardness

Trial Results
4,5
4
1400
3,5
1200
Sulfate vs. Time
•
99.94% Sulfate Reduction
•
0.9-4.2 mg/L (slight increase in last week)
400
1,5
200
1
0
0,5
7/
14
0
1
7/
21
7/
28
2
8/
4
3
8/
11
4
8/
18
8/
25
Date
5
9/
1
6
9/
8
9/
15
7
9/
22
9/
29
Feed Sulfate
8 9
•
Below detection (<0.09 mg/L)
10
Ammonia vs. Time
3.5
3
2.5
2
5
4.5
4
1.5
1
0.5
0
7/
14
7/
21
7/
28
8/
4
8/
11
8/
18
8/
25
Date
9/
1
9/
8
9/
15
9/
22
9/
29
Feed Ammonia
Permeate Ammonia

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First membrane in bank 1 and last in bank 2
•
No visible signs of fouling.
• ∆P and Flowrate within acceptable ranges
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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.
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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.

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Two x 100 gpm RO skids
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20% Bypass stream
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Design flux of 14.4 GFD & 75% recovery
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Array: 3:1, 6-Long
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Toray TMG20-400 membranes
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ORP meter on feed to shut down RO on detection of Cl2 residual.
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Waste to sewer.

July 2011

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•
•
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Background
RO System Capabilities for NO3 Removal &
Factors Impacting Performance
Overhaul of City’s RO System
System Performance – Before & After

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Population ~1200
•
Groundwater supply
•
Raw Water Nitrate 15-20 mg/L

 Installed 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)

Bypass – 125 gpm
RO Train 1
Well Pumps
Greensand
Filters
RO Train 2
RO Train 3
RO Train 4
Permeate 400 gpm
Finished Water
525 gpm
RO Concentrate
120 gpm

 Bypass: 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 removal
 Not suitable for nitrate removal

Parameter
Nitrate, mg/L as N
Hardness, mg/L as CaCO3
Sulfate, mg/L
Calcium, mg/L
Magnesium, mg/L
Silica, mg/L as SiO2
Chloride, mg/L
Sodium, mg/L
TDS, mg/L
Raw Feed
20
223
22
77
12.9
13
10
15.3
Permeate
1.67 (actual ~5.5)
2.5
0.05
0.66
0.11
0.21
0.04
0.17
11.0 (actual ~140)

Contaminant Removal Rates using RO & NF
Comparative Removal Rates
Monovalent Ions (Sodium, Potassium, Chloride, Nitrate, etc)
Divalent Ions (Calcium, Magnesium, Sulfate, Carbonate, Iron, etc)
Microsolutes (<100 Mw)
Microsolutes (>100 Mw)
NF RO
<50%
>90%
>98%
>99%
0-50% 0-99%
>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 psi
Pump Power: 20 HP per train
Annual Power Cost*: $7,840 per train @ 10c/kWh
Low Energy RO Membranes:
Operating Pressure: 110 psi
Pump Power: 15 HP per train
Annual Power Cost*: $5,880 per train @ 10c/kWh
Annual Power Savings: $7,840 (25% reduction)
*Assuming 60% plant utilization

Operating Costs:
Power
Chemicals # & cartridge filters
Membrane replacement (5 years)
Total* c/1000 gal
10.4
14.9
16.5
41.8
# Bisulfite, antiscalant, CIP chemicals
*Assuming 60% plant utilization, 75% recovery & 20% bypass.

•
Determined that reconditioned membranes were not effectively removing nitrate and resulting in MCL violations.
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Replacement of train 1& 2 membranes immediately brought system back in to compliance.
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Low energy membranes will save City ~$8000 per year in pumping power.
• Don’t assume any RO membrane can remove >90% nitrate!

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