1. Michael Bourke – Wigen Water Technologies
Case Studies of Two Small Systems Using NF/RO to Improve Drinking Water Quality
Michael Bourke – Wigen Water Technologies

2. Potable Applications of NF/RO
Aesthetic
TDS
Hardness
Sulfate
Color
Regulatory
Nitrate
Arsenic
Radionuclides
Fluoride
Selenium
Pesticides
Heavy Metals

3. 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%

4. Pressure Membrane Feed Water Permeate Concentrate
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
Membrane
Permeate
Concentrate
Pressure

5. 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.
Feed Water
Concentrate
Permeate
Membrane Material
Spacer Material
Permeate Carrier Material

6. NF/RO Membrane Operation

7. NF/RO System Components

8. 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

9. Cleaning Frequency?
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 12

10. Case Studies City of Wellman, IA City of Creighton, NE
New RO System for Radium & Ammonia Removal and General Water Quality Improvement.
City of Creighton, NE
Upgraded RO System to Improve Nitrate Removal.

11. Case Study #1: RO Pilot Study Evaluates Removal of TDS, Sulfate, Ammonia and Radionuclides at Wellman IA
Background
Trial Objectives
Pilot Plant Selection
Results
Full-scale System Design

12. Wellman, Iowa Population ~1400 Groundwater supply Greensand Filters
DW violations for:
Nitrite
Combined radium

13. Raw Water Characteristics
Parameter
Range (Ave)
TDS, mg/L
1600 – 3620 (1914)
Ammonia, mg/L as N
(3.8)
Total Hardness, mg/L as CaCO3
Sulfate, mg/L
(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
TOC, mg/L
1.3 – 1.8

14. Trial Objectives Three month trial required by IA DNR.
Parameter (actual)
Target
Combined Radium ( )
< 5.0 pCi/L*
Sulfate ( )
< 250 mg/L#
TDS ( )
< 500 mg/L#
Hardness ( )
< 250 mg/L as CaCO3
Ammonia ( )
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.

15. Pilot Criteria 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

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

17. Pilot Plant Set-up

18. Trial Design 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)

19. Data Normalization
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 4

20. Trial Results
Potential Membrane
Damage
No decrease = minimal fouling

21. Trial Results
CIP Performed

22. Trial Results 98.9% TDS Reduction 16-28 mg/L 99.9% Hardness Reduction
mg/L as CaCO3 (slight increase in last week)

23. Trial Results 99.94% Sulfate Reduction
mg/L (slight increase in last week)
Below detection (<0.09 mg/L)

24. Membrane Autopsies 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.

25. Results Summary
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.

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

27. Full-Scale Installation
July 2011

28. Case Study #2: Upgrade of Creighton’s RO System brings City back in to Compliance with Nitrate MCL
Background
RO System Capabilities for NO3 Removal & Factors Impacting Performance
Overhaul of City’s RO System
System Performance – Before & After

29. City of Creighton Population ~1200 Groundwater supply
Raw Water Nitrate mg/L

30. RO System History – First in NE
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)

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

32. RO System History
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.

33. WWT Investigation
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

34. Projection Results Parameter Raw Feed Permeate Nitrate, 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)

35. 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%

36. Recommendations
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.

37. Individual Train Performance
Trains 1 & 2 Membranes Replaced

38. Overall Nitrate Removal Data
Trains 1 & 2 Membranes Replaced

39. Individual Train Performance
Trains 1 & 2 Membranes Replaced

40. Low Energy Membrane Savings
Previous RO Membranes:
Operating Pressure: 150 psi
Pump Power: 20 HP per train
Annual Power Cost*: $7,840 per 10c/kWh
Low Energy RO Membranes:
Operating Pressure: 110 psi
Pump Power: 15 HP per train
Annual Power Cost*: $5,880 per 10c/kWh
Annual Power Savings: $7,840 (25% reduction)
*Assuming 60% plant utilization

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

42. Results Summary
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!

43. Questions?