CNRL Extraction Water Treatment Plant Pilot Study

Transcription

CNRL Extraction Water
Treatment Plant Pilot
Study
Basal Water Phase
Final Report 2012
May 29, 2013
Prepared for:
Canadian Natural Resources Ltd.
Calgary, Alberta
Attn. Kavithaa Loganathan
Manager, Water Treatment
Pilot Projects
Prepared by:
EPCOR
Suite 1210, 401-9 Avenue SW
Calgary, AB T2P3C5
epcorwatersolutions.com
phone: 403-717-4600
STATEMENT OF QUALIFICATIONS AND LIMITATIONS
EPCOR and all persons involved in the preparation of these materials disclaim any
warranty as to accuracy or currency of the contents. These materials are provided for
informational purposes only and on the basis that none of EPCOR or other persons
involved in the creation of these materials will be responsible for the accuracy or
currency of the contents or for the results of any action taken on the basis of the
information contained in these materials or for errors or omissions contained herein.
None of EPCOR or other persons involved in the creation of these materials is
attempting to render business, scientific, legal, accounting or other professional advice.
The materials contained herein should in no way be construed as being either official or
unofficial policy of any governmental body.
Version
1.1
Date
(DD/MM/YY)
05/12/12
2.0
20/02/13
2.0
29/05/13
Revision Notes
Originator(s)
DRAFT for comments from
Technical Team
DRAFT accounting for comments
from technical team review
Finalized version of report
B Leinan
S Molla
B Leinan
S Molla
B Leinan
S Molla
CNRL EWTP Pilot - Basal Water Treatment Phase
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ACKNOWLEDGEMENTS
Kavithaa Loganathan
Joy Romero
Ashok Babu
Charles Williams
Mike Rogers
Steve Stanley
Audrey Cudrak
Jamie Gingrich
Lee Ward
Rob Brown
Don Macuch
David Rector
Vicki Campbell
Ryan Litwinow
Brent Leinan
Saif Molla
Andrew Rose
Ryan Thomas
Zach Pruden
Lyle Deines
Stan Epp
Leonardo Paternina
Stephen Peters
Brian Mottershead
Glen Sinclair
Garry Germscheid
David Parker
Steve Kroll
John Korpiel
Jean-Francois Beaudet
Ryan Colley
Jeremy Jones
Martin Gendron
CNRL
CNRL
CNRL
CNRL
ATSI
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
EPCOR
LSI
LSI
Veolia
Veolia
Veolia
Veolia
Veolia
Veolia
Veolia
Project Manager
VP Technology Development
Lead Technology Development
Project Coordinator
Technical Advisor
SVP Water Services
Director, Project and Technical Services
Senior Manager, Operational and Technical
Senior Manager, Project Development
Manager, Water Project Development
Project Controls
Director, Oil Sands, Industrial Water
Manager, Northern AB W & WW
Project Manager
Project Manager
Piloting Engineer
Lead Hand Operator Crew A
Lead Hand Operator Crew B
Operator
Operator
Operator
Operator
Operator
Operator
Director, Water Projects
Project/Construction Manager
Project Manager
VP Business Development
Senior Process Engineer
Manager - Technical Services
Pilot Project Engineer
Applications Engineer
Field Engineer
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Overall Project Management
Project Executive
Project Support
Project Support
Project Support
Project Executive
Executive Sponsor
Senior Pilot Engineering Advisor
Program Manager
Project Oversight
Project Support
Project Support
Project Support
Project Manager – Construction Phase
Project Manager – Piloting Phase
Pilot Design and Analysis
On-site Liaison and Operations Lead
On-site Liaison and Operations Lead
Operations and Process Optimization
Project Support
Construction Support
Project Manager – Vendor
Project Support
Project Support
Project Support
Operations Support
Operations Support
Operations Support
May 29, 2013
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EXECUTIVE SUMMARY
Canadian Natural Resources Ltd. initiated an Extraction Waters Pilot Study to determine
the lowest cost option for an Integrated Water Management Plan. Source water for
treatment included Basal Water and Recycled Water (RCW) from the Tailings Pond. The
pilot study is divided into two phases based on source water type. Phase 1 involved the
treatment of basal water. Phase 2 involved the treatment of tailings pond recycle water.
This report is focused on the basal water treatment piloting phase of the project, which
took place between June 7th and October 8th, 2012. A separate report will address Phase
2 pilot testing subsequent to completion of the pilot in early 2013.
The experimental phase of the pilot was started in April 2012 and is scheduled for
completion in early 2013. EPCOR has been contracted to execute the pilot in concert
with a CNRL project team, with support from equipment vendors. Lockerbie Stanley Inc.
(LSI) was contracted to carry out the construction and maintenance of the pilot facility.
All process equipment used in the Basal treatment phase was supplied by Veolia.
EPCOR led the reporting and analysis of pilot scale data, with input from both CNRL and
Veolia personnel. Veolia has prepared a document (included as an Appendix in this
report) with input from both CNRL and EPCOR, that details scaling up the piloted
equipment to a full scale treatment facility.
The pilot facility was located on CNRL Horizon site adjacent to 99A plant, which is on the
north side of the site, adjacent to the tailings pond. Basal water was trucked directly from
the basal water wellheads to the pilot influent water storage tank.
Basal water is typified by neutral pH, low to moderate TSS and high TDS (Table E1).
TDS is primarily composed of sodium, chloride, bicarbonate and hardness-causing
compounds. Organic compounds were at low concentrations, with the ability to measure
low levels compromised by high detection limits resulting from the high salinity of the
water. TOC was less than the detection limit (13 mg/L) for 88% of samples taken. Oil
and Grease (O&G) was consistently low.
Table E1. Primary water quality characteristics of untreated basal water
Parameter
Units
Average
Std. Deviation
pH
SU
7.0
0.1
TSS
mg/L
23.4
81.5
TDS
mg/L
21,300
3,456
Chloride
mg/L
12,456
509
Bicarbonatemg/L as CaCO3
3,638
193
Total Hardness
mg/L as CaCO3
1,450
102
Total Organic Carbon
mg/L
<13 mg/L
2.8
Oil & Grease
mg/L
1.1
0.3
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Potassium
Permanganate
Sulphuric Acid (option)
Metabisulphite
& Anti-Scalant
Ferric Chloride
& Caustic (option)
Basal Tank
Reaction
Tank
Polymeric
Ultra-Filtration
(PUF)
Reverse
Osmosis
(RO)
Figure E1. Basal water treatment process train
The treated water quality goals for the basal water treatment phase included effluent
Total Dissolved Solids (TDS) < 1000 mg/L, Sodium < 500 mg/L and the maximum
possible recovery for reuse. An overview of the treatment train is provided in Figure E1.
The goal of each treatment step and optimal operating conditions determined by the pilot
are described below.
Oxidation/Precipitation/Coagulation
The goal of including an oxidation treatment step in the treatment train was to precipitate
out sulfides, iron, and manganese, which had the potential to negatively impact fouling
rates on the UF and RO membrane systems. Based on pilot observations on
downstream membrane fouling, optimal operation was identified as maintaining a neutral
pH in the oxidation/precipitation stage, adding permanganate at a fixed dose in order to
precipitate iron and sulphides, but keeping manganese in dissolved form. Bench scale
experimentation using sodium hypochlorite was carried out as an alternative oxidant to
potassium permanganate, but not examined at the pilot scale. Use of sodium
hypochlorite instead of potassium permanganate would reduce the dissolved
manganese concentration in RO feed water.
Optimal chemical dosages for this unit process identified in the pilot are presented in
Table E2.
Table E2. Optimal process settings for Oxidation/precipitation/coagulation
Parameter
Optimal Setting
Potassium permanganate = 1 to 1.5 mg/L
Ferric chloride
= 0 to 2 mg/L as Fe
Sodium Hydroxide
= 0 mg/L
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Ultrafiltration (UF) System
The primary goal of the ultrafiltration step was solids removal. The UF system used
during the pilot was a polyvinylidene fluoride (PVDF) hollow fiber outside - in type (DOW
SFD 2860 module) membrane. The strategy for managing fouling of the membranes was
primarily through a combination of frequent physical backwashes combined with the use
of Chemically Enhanced Backwashes (CEBs) at regular intervals. Clean-In-Place (CIP)
procedures were also utilized when a more significant membrane clean was required.
Backwashes (non-chemically enhanced) were less effective at restoring performance
than anticipated.
Solids removal was consistently good, with UF filtrate turbidity averaging 2.0 NTU and
Silt Density Index (SDI) averaging 0.9 over the course of the pilot (well water source).
RO feed requires an SDI of less than 5 at a minimum and ideally less than 3.
UF filtrate concentrations of iron and sulphides were consistently low enough to achieve
targets based on the perceived ability of anti-scalant chemicals to manage fouling on the
downstream RO membranes.
Pilot data and the results of the membrane autopsy indicate iron was the primary foulant
on the UF membrane, with a notable concentration of sodium present as well. Two pH
ranges were trialed during the pilot: elevated (pH 7.5 – 8.0) and neutral (pH 6.9 – 7.2).
The impact of iron fouling is more significant at the neutral pH than the elevated pH
initially used in July and early August. Minimizing the ferric chloride dose would also
likely assist in reducing overall UF fouling rate and maximization of UF system recovery.
Other compounds identified as present on the membrane surface in much smaller
quantities include calcium, manganese and sulfur. Visible inspection of the UF module
noted the presence of an oily subsance and a petrochemical smell was detected.
However, the membrane deposits were noted to be primarily inorganic in the membrane
autopsy.
The basal water was trucked directly from the basal wellheads for most of the pilot.
Basal pond water use was explored in the pilot due to the presumed benefits of water
equalization and water aging (introduction of oxygen into the water from the
atmosphere). However, the presence of significant algae in the pond water was a
dominant factor which ultimately resulted in an immediate negative impact on UF
performance.
Optimal operational settings for this unit process identified in the pilot are presented in
Table E3. The typical cleaning pH levels recommended by DOW for the modules are 2
and 12 for inorganic and organic cleaning phases respectively. Exposing the
membranes to extreme high and low pH levels over time contribute to membrane
degradation and therefore should be minimized.
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Table E3. Optimal process settings for Ultrafiltration
Parameter
Optimal Setting
Flux (normalized to 20˚C) = 53 lmh
Recovery range
= 70 to 80% based on pilot waste streams observed
(improved recovery may be possible at full scale due to
waste stream scalability)
Operational flow mode
= Cross-flow operation
CEB sequence
= Acid CEB – Caustic CEB – Acid CEB
Acid CEB
 approximately 2.5 pH
 5000 mg/L citric acid
 200 mg/L sodium metabisulphite
 30 min soak time
Caustic CEB
 approximately 12 pH using caustic
 600 mg/L NaOH
 600 mg/L NaOCl
CEB frequency
= Once every 24 hours at optimum operating conditions
CIP sequence
= Caustic CIP – Acid CIP - Caustic CIP
Acid CIP
 ≤2.3 pH using citric acid,
 38°C solution
 10 hr soak/ recirculation period
 intermittent air scour
Caustic CIP
 2000 mg/L NaOCl
 32°C solution
CIP frequency
= Every 2 to 4 weeks
Reverse Osmosis (RO) System
The primary goal of the RO system was to reduce total dissolved solids (TDS), with a
specific target for sodium. The pilot RO system consisted of a three stage design with
fiberglass pressure vessels containing Polyamide Thin-Film Composite elements (DOW
Filmtec SW30-4040). The anticipated challenge was running the RO system at a high
recovery while at the same time managing fouling with standard cleaning methodologies
and frequencies. Recoveries of 50% (pilot target) and 60% were examined during the
study.
At all times, the RO permeate was below the 1000 mg/L target for TDS and 500 mg/L
target for sodium. At 50% recovery, permeate conductivity was reduced to 593 µS/cm, a
98.4% reduction relative to UF filtrate and untreated basal water. TDS was reduced to
304 mg/L on average with a standard deviation (SD) of 90 mg/L. Total sodium was
reduced to an average of 123 mg/L with a standard deviation of 25 mg/L. Operation at
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60% recovery was for a brief period, but saw similar rejections as was observed at 50%
operation.
Pilot data does not indicate irreversible fouling is occurring as full permeability recovery
was achieved from the CIP and operational pressures remained relatively stable during
regular operation.
Iron was a significant foulant for the RO membranes and of all parameters examined in
the CIP, had the highest levels relative to RO influent concentrations. The membrane
autopsy identified iron and barium as the primary scalants present. Sulfur, phosphorous,
and strontium were all present in the CIP solution at elevated concentrations as well,
indicating some level of scaling on the RO membranes. Total Organic Carbon (TOC)
deposit on the membrane accounted for 4.4% of the total fouling material by weight on
the front RO element (where organic fouling tends to be most significant). Evidence of
biological fouling was not observed in this pilot.
Calcium carbonate was a significant scale-causing compound for the RO system due to
the high calcium hardness and alkalinity in basal water. However, use of pH adjustment,
and anti-scalant dosing during the pilot appeared to effectively manage the impact of
hardness causing ions on the membrane.
Optimal operational settings for this unit process identified in the pilot are presented in
Table E4.
Table E4. Optimal process settings for Reverse Osmosis
Parameter
Optimal Setting
Sulphuric acid dose
= 700 to 800 mg/L as H2SO4
(to achieve 6.5 pH in RO feed)
Sodium metabisulphite dose
= 160 to 200 mg/L
(Dose was based on maintaining an RO feed
ORP value of 100 to 150 mV as
recommended by the equipment vendor.
-Maintaining manganese in a reduced dissolved
form was a key consideration in dosing
metabisulphite as manganese in a dissolved
and reduced state did not act as a significant
RO foulant. Higher than industry standard Mn
levels were often present in the RO feed so
this was a significant consideration. Lower
doses of metabisulphite may be possible.
Anti-scalant dose (50% recovery)
= 6.6 mg/L
= 6.6 mg/L
Biocide dose
= 200 mg/L for 30 min, once per week
(Nalco Permaclean PC-11)
Time between CIPs
= 1 to 2 months
Flux rate (normalized to 25°C)
= 23 lmh at 50% recovery
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TABLE OF CONTENTS
1
Background _______________________________________________ 14
1.1.
Project Overview _________________________________________________ 14
1.2
Project Objectives ________________________________________________ 15
1.3
Roles and Responsibilities _________________________________________ 15
2.
Pilot Plant Design __________________________________________ 17
2.1
Design Basis Basal Water Quality ___________________________________ 17
2.2
Treatment Train Overview _________________________________________ 17
3
Experimental Plan __________________________________________ 21
3.1
Analytical Sampling Plan Overview __________________________________ 21
3.2
Analytical Methods and Considerations ______________________________ 24
4
Untreated Basal Water Quality ________________________________ 26
5.
Treatment Performance _____________________________________ 28
5.1
Oxidation _______________________________________________________ 28
Bench Scale Testing ______________________________________________________29
Pilot Scale ______________________________________________________________34
5.2
Polymeric Ultrafiltration (PUF) ______________________________________ 35
Treatment Performance____________________________________________________40
Comparison of Pond and Well Water on UF Fouling _____________________________59
5.3
Reverse Osmosis (RO) ____________________________________________ 61
Operating Conditions ______________________________________________________61
Treatment Performance____________________________________________________67
Fouling Rate and Cleaning Effectiveness ______________________________________72
CIP Analysis ____________________________________________________________72
6.
Summary and Conclusions __________________________________ 77
6.1
Treated Water Quality _____________________________________________ 77
6.2
Operational Experiences and Lessons Learned _______________________ 77
6.3
Optimal Operational Settings Observed in Pilot (by Unit Process) ________ 77
6.4
Primary Factors Impacting Process Performance ______________________ 79
6.5
Stability of Operation _____________________________________________ 79
6.6
Comparison of Operation with Pond and Wellhead Basal Water
Sources ________________________________________________________ 80
6.7
Impact of Not Softening ___________________________________________ 80
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LIST OF APPENDICES
APPENDIX A:
APPENDIX B:
APPENDIX C:
APPENDIX D:
APPENDIX E:
APPENDIX F:
APPENDIX G:
APPENDIX H:
Summary of Untreated Basal Water Quality
Summary of Unit Process Effluent Water Quality
Operational Settings Overview
UF and RO CIP Procedures
UF and RO Membrane Autopsy (Veolia)
RO Concentrate Evaporator Testing (Veolia)
Full Scale Equipment Sizing and Considerations (Veolia)
Photos
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LIST OF ACRONYMS
BW
CEB
CIP
CNRL
CUF
DBE
DOC
gfd
gpm
kPa
lmh
LSI
MDL
NAWS
ND
NDP
NPF
NSP
NSR
NTU
ORP
psi
PUF
PVDF
RCW
RO
ROSA
SCADA
scfm
SD
SDI
SDSI
SP
SU
TDS
TMP
TOC
TSS
RO
UF
UPVC
ZLD
Backwash
Chemically Enhanced Backwash
Clean-In-Place
Canadian Natural Resources Limited
Ceramic Ultra-Filtration
David Bromley Engineering
Dissolved Organic Carbon
gallons (US) per square foot per day
gallons (US) per minute
kilo pascal
litres per square meter per hour
Langelier Saturation Index
Method Detection Limit
North American Water Systems
Non-Detectable
Net Driving Pressure
Normalized Permeate Flow
Normalized Salt Passage
Normalized Salt Rejection
Nephelometric Turbidity Unit
Oxidation-Reduction Potential
pounds per square inch
Polymeric Ultra-Filtration
Polyvinylidene Fluoride
Recycled Water
Reverse Osmosis
Reverse Osmosis System Analysis
Supervisory Control and Data Acquisition
standard cubic feet per minute
Standard Deviation
Silt Density Index
Stiff & Davis Stability Index
Sample Point
Standard Units (pH)
Total Dissolved Solids
Trans-membrane Pressure
Total Suspended Solids
Reverse Osmosis
Ultra-Filtration
Unplasticized Polyvinyl Chloride
Zero Liquid Discharge
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LIST OF FIGURES
Figure 1. Photo of basal water treatment pilot facility on CNRL Horizon Site. _______ 14
Figure 2. Basal water treatment process train ________________________________ 17
Figure 3. Overview of the pilot timeline _____________________________________ 20
Figure 4. Manganese Solubility at various pH values and ORP (Pourbaix Diagram) ___ 29
Figure 5. Change in basal water pH and Oxidation-Reduction Potential (ORP) with
aeration (fully aerated) and mixing observed in bench scale testing ______ 31
Figure 6. Overview of the impact of a high potassium permanganate dose on ORP with
time for basal water taken from the wellhead _______________________ 32
Figure 7. Overview of dissolved manganese in basal water at various permanganate
dosages observed in bench scale testing ____________________________ 33
Figure 8. Overview of UF recovery, flux and TMP increase rate during the pilot. _____ 42
Figure 9. Overview of UF recovery relative to water usage for membrane cleaning cycles
during the pilot. _______________________________________________ 44
Figure 10. Overview of fouling rate development for the UF. ____________________ 46
Figure 11. Comparison of backwash effectiveness using UF filtrate, UF filtrate with 100
mg/L of sodium metabisulphite and RO permeate as source water _______ 51
Figure 12. Plot of TMP and normalized permeability at various influent pH settings __ 52
Figure 13. Solubility plot for ferric iron relative to pH __________________________ 53
Figure 14. Solubility plot for CaCO3 at various calcium and dissolved carbonic acid
concentrations relative to pH_____________________________________ 54
Figure 15. Comparison of residual iron in untreated and UF filtrate water at various
coagulant doses and pH ranges in the oxidation/precipitation stage ______ 55
Figure 16. TMP development rates for individual UF runs at different coagulant and
permanganate doses ___________________________________________ 56
Figure 17. Plot of TMP and permeability for dead-end and cross-flow UF operation __ 58
Figure 18. Comparison overview of flux, run length, baseline TMP and TMP increase rate
for piloting periods when pond water versus wellhead water were used as
feed water for the pilot _________________________________________ 60
Figure 19. Simplified view of RO system configurations at 50% and 60% recovery. ___ 63
Figure 20. Overview of RO flux rate and normalized (to 25°C) flux rate over the course of
the pilot _____________________________________________________ 64
Figure 21. Overview of normalized (to 25°C) RO flux rate broken down by stage over the
course of the pilot _____________________________________________ 65
Figure 22. Overview of Normalized Salt Rejection (NSR) and Normalized Salt Passage
(NSP) over the course of the pilot _________________________________ 68
Figure 23. NPF of the RO membrane overall and for each stage __________________ 75
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LIST OF TABLES
Table 1. Overview of basal well water quality data used as the pilot design basis ____ 18
Table 2. Overview of operating targets for key process equipment _______________ 19
Table 3. Overview of sample point locations _________________________________ 21
Table 4. Overview of online instrumentation used in the pilot ___________________ 22
Table 5. Overview of initial on-site and external laboratory analytical sampling frequency
____________________________________________________________ 23
Table 6. Summary of analytical methods and detection limits (external laboratory) __ 25
Table 7. Summary of select water quality parameters for untreated basal water ____ 27
Table 8. Summary of UF system specifications and operating conditions ___________ 35
Table 9. Overview of a typical UF backwash sequence _________________________ 36
Table 10. Overview of a typical UF CEB _____________________________________ 36
Table 11. Overview of UF system related chemical usage and operational settings at
optimal conditions _____________________________________________ 38
Table 12. Summary of select water quality parameters for UF permeate ___________ 41
Table 13. High level overview of chemical dosing zones during the pilot ___________ 42
Table 14. Overview of UF CIP cleaning solution analysis for key fouling compounds __ 48
Table 15. Overview of RO membrane specifications ___________________________ 61
Table 16. Overview of RO system operating conditions_________________________ 62
Table 17. Overview of RO system related chemical usage and operational settings at
optimal conditions _____________________________________________ 66
Table 18. Summary of RO treatment performance (permeate water quality) at 50%
recovery _____________________________________________________ 69
recovery _____________________________________________________ 70
Table 20. Summary of RO reject water quality characteristics at 50% recovery ______ 71
Table 21. Summary of RO reject water quality characteristics at 60% recovery ______ 71
Table 22. Overview of RO CIP cleaning solution analysis for key scaling compounds __ 73
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1
Background
Canadian Natural Resources Ltd. initiated an Extraction Waters Pilot Study to determine
the lowest cost option for an Integrated Water Management Plan. Source water for
treatment included Basal Water and Recycled Water (RCW) from the Tailings Pond.
The experimental phase of the pilot was started in April 2012 and is scheduled for
completion in early 2013. EPCOR has been contracted to execute the pilot in concert
with a CNRL project team, with support from equipment vendors. Lockerbie Stanley Inc.
was contracted to carry out the construction and maintenance of the pilot facility.
1.1.
Project Overview
The Basal Water Treatment Pilot Facility was located on CNRL Horizon site, adjacent to
99a Pump House which is on the north side of the site, next to the tailings pond. Basal
water was trucked directly from the wellhead main header into a 60 m 3 storage tank
used as the plant influent water source.
Figure 1. Photo of basal water treatment pilot facility on CNRL Horizon Site.
The pilot study is divided into two phases based on source water type. Phase 1 involved
the treatment of basal water. Phase 2 will involve the treatment of tailings pond recycle
water. The following is a list of the major equipment:
Phase 1 (Basal Water Treatment):
 Polymeric Ultrafiltration (UF) and Reverse Osmosis (RO) from North American
Water Systems (NAWS - Veolia)
Phase 2 (Tailings Water Treatment):
 Nanoflotation from David Bromley Engineering (DBE)
 Degasification, Multiflo Softening, Ceramic Ultrafiltration (CUF), Ion Exchange,
Reverse Osmosis from Veolia Water Solutions (Veolia)
This report is focused on the basal water treatment piloting phase of the project, which
was carried out from June to October 8th, 2012. The main body of the report is focused
on analysis of pilot scale process performance analysis and identification of optimal
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operating conditions. Appendices in this report include summaries of water quality data
and operational settings, details on membrane cleaning procedures, results of
membrane autopsy (Veolia) and zero liquid discharge testing (Veolia) and details on
scaling up the piloted treatment processes as identified by the equipment supplier
(Veolia).
Reports analyzing the piloting of tailings water treatment processes (as identified in
Phase 2 above), will be prepared independently of this report, and will be available in
early 2013.
1.2
Project Objectives
The project treated water quality goal for the basal water treatment phase included
effluent TDS < 1000 mg/L, Sodium < 500 mg/L and the maximum possible recovery for
reuse.
The project treated water quality goal for the tailings pond water treatment phase
includes effluent TDS < 50 mg/L and Sodium < 30 mg/L.
Piloting data was collected in order to permit scaling up of the pilot system to a
commercial water treatment plant with a capacity to treat 3000 m3/hr of basal and tailings
water.
1.3
CNRL




Roles and Responsibilities
Project initiator and primary stakeholder
Overall project management and oversight
Provision of power supply and basal water to pilot site
Chair the Basal Water Treatment Technical Group which made all critical process
related decisions during pilot experimentation
EPCOR
 Lead and oversee all aspects of pilot facility operation
 Provide construction oversight and coordination
 Manage chemical procurement, inventory and storage for all processes
 Provide environmental and safety management for the project and all personnel
on site
 Provision of certified operations staff for 24 hrs per day, 7 days per week pilot
facility operation
 Plan and execute bench and pilot scale experimentation to optimize treatment
processes
 Troubleshoot equipment and processes
 Setup and operation of an onsite analytical laboratory to provide rapid results to
support operational setting changes and optimization
 Provide detailed logs of operations activity and equipment settings
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

Provide detailed data summary and analysis to present to the project technical
group (CNRL, EPCOR & Veolia personnel) throughout the piloting phase
Provide a basal water testing phase
summary report detailing process
performance at pilot and bench scale, summary of operational activities and
recommended optimal process settings for use in full scale facility design
LSI



Design and construction of pilot infrastructure excluding process treatment
trailers provided directly from equipment vendor (Veolia), office facilities and
power supply
Receive and install pilot treatment process trailers/skids and design/construct
mechanical and electrical interconnections between equipment
Provide electrical and mechanical support during commissioning and pilot
operation
Veolia
 Provision of primary process equipment for basal treatment pilot phase (oxidation
reaction tanks, chemical dosing systems, polymeric ultrafiltration system and
reverse osmosis system)
 Provide recommendations on chemical types and initial operational setting
targets for the supplied process equipment
 Assist in process optimization
 Provision of remote and field technical support for Veolia supplied equipment
 Conduct autopsy on the used membranes at the end of pilot operation and
provide results
 Conduct a zero liquid discharge (ZLD) study on RO reject from the pilot and
report results
 Provision of a report detailing scaling up of pilot results to a full scale facility
design
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2.
Pilot Plant Design
2.1
Design Basis Basal Water Quality
The basal water treatment pilot system was designed according to historical basal water
quality parameters provided by CNRL and are given in Table 1. In general, water quality
observed during the pilot was similar to the design basis water quality data. However,
notable variations that potentially impacted treatment system performance include
suspended solids (TSS and turbidity) as well as pH. TSS was observed to average 23
mg/L, and reached as high as 430 mg/L which is significantly higher than the design
basis number of 23 mg/L. The pH observed in the pilot averaged 7.0 which is notably
different than the design basis value of 7.9. Observed basal water quality before
treatment and at key locations throughout the treatment train are examined in depth in
later sections of this report.
2.2
Treatment Train Overview
Due to high TDS values in basal well water (Average TDS = 21,300 mg/L), low fouling
potentials due to low organic carbon present and minimal silica present, a combination of
polymeric UF, and Reverse Osmosis technologies was selected for this application. An
oxidation step was included up front to precipitate out substances (iron, manganese and
sulphides) that could foul the membranes. Water was trucked to site, directly from
wellheads, and stored in a 60 m3 tank which was used to feed the pilot facility. Figure 2
illustrates the treatment train.
Potassium
Permanganate
Sulphuric Acid (option)
Metabisulphite
& Anti-Scalant
Ferric Chloride
& Caustic (option)
Basal Tank
Reaction
Tank
Polymeric
Ultra-Filtration
(PUF)
Reverse
Osmosis
(RO)
Figure 2. Basal water treatment process train
In the initial planning stages of system design, the treatment train included processes for
degasification (alkalinity reduction) and softening (divalent metal ion reduction) upstream
of the UF system. Significant consideration was given to the hardness levels in basal
water and the advantages and disadvantages of softening the water before treatment by
UF and RO membranes. It was decided to pilot basal water treatment without softening
based on the projected high chemical usage requirements for removing hardness
causing ions, and modeling results that suggested negative impacts on the RO could be
managed using anti-scalant chemicals.
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Table 1. Overview of basal well water quality data used as the pilot design basis
Compound
Cations
Calcium, mg/L
Magnesium, mg/L
Sodium, mg/L
Potassium, mg/L
Aluminum, mg/L
Barium, mg/L
Strontium, mg/L
Ammonium, mg/L (cal.)
Ferrous Iron, mg/L
Ferric Iron, mg/L
Manganese, mg/L
Arsenic, mg/L
Antimony, mg/L
Beryllium, mg/L
Cadmium, mg/L
Chromium, mg/L
Cobalt, mg/L
Copper, mg/L
Lead, mg/L
Lithium, mg/L
Mercury, mg/L
Molybdenum, mg/L
Nickel, mg/L
Selenium, mg/L
Silver, mg/L
Thallium, mg/L
Tin, mg/L
Titanium, mg/L
Vanadium, mg/L
Uranium, mg/L
Radium, mg/L
Thorium, mg/L
Zinc, mg/L
Organics
TOC, mg/L
CBOD, mg/L
COD, mg/L
VOC, mg/L
Semi-VOC, mg/L
Naphthenic Acids, mg/L
Conc.
222
303
10,000
78.4
< 0.15
0.32
19.2
Compound
Anions
Bicarbonates, mg/L
Carbonates, mg/L
Sulfates, mg/L
Bisulfide, mg/L (cal)
Bromide, mg/L
Chloride, mg/L
Phosphate, mg/L
Nitrate, mg/L
Fluoride, mg/L
Other Constituents
pH, standard units
Temperature Range, °C
Silica, mg/L
Boron, mg/L
Total Dissolved Solids, mg/L
Conductivity, μS (est.)
Total Alkalinity, mg/L as CaCO3
Carbon-dioxide, mg/L (cal.)
Total Ammonia, mg/L as N
Free Ammonia, mg/L a N (cal.)
Total Sulfides, mg/L as S
Hydrogen Sulfide, mg/L (cal)
TSS, mg/L
Total Residual Chlorine, mg/L
Total Inorganic Nitrogen, mg/L
Total Oil & Grease, mg/L
Soluble Oil, mg/L (< 1μ)
Emulsified Oil, mg/L (1 ~ 20μ)
Free Oil, mg/L (> 20μ)
Diesel Range Organics, mg/L
Gasoline Range Organics, mg/L
Total Hardness, mg/L as CaCO3
Benzene, mg/L
Toluene, mg/L
Ethyl Benzene, mg/L
Xylenes, mg/L
Methanol, mg/L
n-Hexane, mg/L
CONFIDENTIAL
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Conc.
3,480
<5
20
14,000
<1
<1
7.9
5 (constant)
26,300
40,200
2,850
26
1,800
-
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The basal water was dosed with potassium permanganate to oxidize iron, sulphides and
manganese. The water was then processed through the polymeric ultra-filtration
membrane system operated in dead-end mode for the removal of solids to lower
concentrations. Cross flow operation was tried briefly at the end of the piloting period to
address limitations of dead-end UF operation.
At the beginning of the study, when manganese was being targeted for removal, the
feed to the Ultrafiltration (UF) system was pH adjusted from near neutral to
approximately 7.6 using caustic soda. For the second half of the study, when
manganese was being maintained in a reduced soluble state, the UF filtrate was pH
adjusted from near neutral to approximately 6.5 using sulphuric acid and fed to the RO
system. Anti-scalant was also added upstream of the RO system to address mineral
scaling. The RO system was operated in a three stage, single pass configuration with a
target recovery of 50%.
Reverse Osmosis (RO) reject water from this study was shipped to Veolia laboratory in
Plainfield, IL for an evaporation/crystallization study using Veolia technology. This will
simulate ZLD conditions. Details of this testing are located in Appendix F.
Table 2. Overview of operating targets for key process equipment
System
Target
Polymeric Ultra-Filtration
Filtrate Flow, m3/hr
Filtrate Flux, lmh
4.1
~ 51 to 85
Recovery, %
90
Single Pass, RO
Feed Flow, m3/hr
3.5
3
Permeate Flow, m /hr
3
~ 1.8
Reject Flow, m /hr
~ 1.8
Permeate Flux, lmh
13.5
Recovery, %
50
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Overall Basal Water Treatment Pilot Timeline
26-Jun: Start of 24/7
Pilot Operations
7-Jun: Power supplied
to the Pilot
8-Oct: End of Basal water
treatment Pilot Operation
15-Jun: Commissioning
with Basal water
5 Jun, 2012
12 Jun, 2012
19 Jun, 2012
26 Jun, 2012
3 Jul, 2012
10 Jul, 2012
17 Jul, 2012
24 Jul, 2012
31 Jul, 2012
26 Jun - 12 Jul: Attempt to optimize pH
adjustment and KMnO 4 dosing
strategy based on ORP
UF Operation
Timeline
19 Jun, 2012
26 Jun, 2012
3 Jul, 2012
10 Jul, 2012
12-17 Jul: Pond Water
Trials; Process units flushed
at the end of trial
17 Jul, 2012
24 Jul, 2012
14 Aug, 2012
21 Aug, 2012
Change in Dosing Strategy:
Operate at neutral pH to
prevent CaCO 3 scaling, not
targeting Mn removal
12-Jul: Mixing introduced in
the influent water tank
17-Jun: UF system
start-up
7 Aug, 2012
31 Jul, 2012
7 Aug, 2012
14 Aug, 2012
28 Aug, 2012
4 Sep, 2012
11 Sep, 2012
24-30 Sep:
UF Feed pH 7.6-8.0 (with Caustic)
KMnO 4 Dosage ~5 mg/L
FeCl 3 Dosage ~3 mg/L
21 Aug, 2012
28 Aug, 2012
4 Sep, 2012
18 Sep, 2012
25 Sep, 2012
2 Oct, 2012
9 Oct, 2012
1-8 Oct:
UF Feed pH ~7.0 (no Caustic)
KMnO 4 Dosage ~1.5 mg/L
FeCl 3 Dosage 0 mg/L
11 Sep, 2012
18 Sep, 2012
25 Sep, 2012
2 Oct, 2012
13-14 Sep: UF CIP
23 Jul - 13 Aug:
UF Feed pH ~7.5 (with Caustic)
KMnO4 Dosage 5 - 7 mg/L
FeCl 3 Dosage ~7 mg/L
16 Aug - 24 Sep:
UF Feed pH ~7.0 (no Caustic)
KMnO 4 Dosage 1 - 1.5 mg/L
FeCl 3 Dosage 1.5 - 7 mg/L
1-8 Oct: Cross-flow UF operation
2-8 Oct: New UF modules
RO Operation Timeline
24 Jul, 2012
31 Jul, 2012
24-Jul: RO operation started at
16.5 gpm feed and ~20%
recovery in 3×2×1 array
7 Aug, 2012
14 Aug, 2012
15-17 Aug: RO CIP
21 Aug, 2012
28 Aug, 2012
4 Sep, 2012
11 Sep, 2012
18 Aug - 8 Oct:
RO Feed pH adjusted to ~6.5to
prevent CaCO 3 scaling, also adding
Na 2 S2 O 5 to keep Mn in reduced state
7 Aug: RO recovery
increased to 50%
18 Sep, 2012
25 Sep, 2012
2 Oct, 2012
3-8 Oct: RO recovery
increased to 60% in
2×1×1 array
Figure 3. Overview of the pilot timeline
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3
Experimental Plan
3.1
Analytical Sampling Plan Overview
Consistent and representative sampling was one of the most important tasks performed
by operations personnel during the pilot project at the Extraction Water Treatment Pilot
Plant. Daily operator tasks included collecting and analyzing samples in the onsite lab,
and entering data in the log sheets and electronic records. Sample point locations used
in the study are outlined in Table 3.
Table 3. Overview of sample point locations
Sample Point
1. Untreated basal water
2. Reaction tank influent
3.
UF influent
4.
5.
UF filtrate
RO influent
6.
RO permeate
7.
8.
RO reject
UF backwash
Description
From the outlet of the influent storage tank
After potassium permanganate and caustic soda
(not always dosed) addition
After ferric chloride addition
Immediately after the membrane
UF filtrate after passage through cartridge filters and
addition of sulphuric acid and anti-scalant
From the combined RO permeate line from all 3 RO
stages
From the RO reject waste stream
Intermittent flow only during cleaning cycles
A key aspect of this pilot study was the collection of a continuous data set of key process
parameters through the use of online instrumentation. The online instruments were
linked to the pilot plant SCADA (Supervisory Control and Data Acquisition) system which
permitted instantaneous feedback to operations personnel. This data was also historized
to assist in troubleshooting and data analysis.
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Table 4. Overview of online instrumentation used in the pilot
Parameter
pH
Turbidity
ORP
Flow
Water temperature
Air temperature
UF TMP
Pressure
Location
 Untreated basal water
 UF influent
 UF filtrate
 RO influent
 UF influent
 UF filtrate
 Oxidation reaction tank (location
varied during pilot based on
operational requirements) – data
not historized
 RO influent – data not historized
 UF influent
 UF filtrate
 RO influent
 RO permeate
 RO reject
o (Stages 1, 2 & 3)
 All process buildings
 Surrounding the UF membrane
 RO influent
 RO permeate
 RO reject
o (Stages 1, 2 & 3)
The baseline analytical sampling plan used in the pilot study is summarized in Table 5. In
addition to the baseline testing plan, analytical testing was carried out as the pilot progressed and
experimental data requirements arose. Complete testing results are located in Appendix A and B.
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Table 5. Overview of initial on-site and external laboratory analytical sampling frequency
Parameter
Suspended Solids
Turbidity
SDI
Dissolved Solids
Conductivity
TDS
General
pH
Alkalinity
Calcium Hardness
ORP
Temperature
Anions
Sulfate
Chloride
Fluoride
Phosphate
Silica
Total Sulfide
Dissolved Sulfide
Organics
TOC
DOC
Total Oil & Grease
Naphthenic Acids
Cations
Dissolved Iron
Dissolved Manganese
Total Aluminum
Total Barium
Total Boron
Total Calcium
Total Iron
Total Magnesium
Total Manganese
Total Potassium
Total Sodium
Total Strontium
Untreated
Reaction Tank Infl.
UF Infl.
UF Filtrate
UF Backwash
RO Infl.
RO Permeate
RO Reject
Ons i te
Offs i te
Ons i te
Offs i te
Ons i te
Offs i te
Ons i te
Offs i te
Ons i te
Offs i te
Ons i te
Offs i te
Ons i te
Offs i te
Ons i te
Offs i te
Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency Frequency
Daily
Daily
Weekly
Weekly
Daily
Daily
Weekly
Weekly
Daily
Daily
Weekly
Weekly
Daily
Bi-daily
Daily
Weekly
Daily
Weekly
Weekly
Daily
Weekly
Weekly
Weekly
Daily
Daily
Daily
Daily
Daily
Weekly
Weekly
Weekly
Weekly
Weekly
Daily
Weekly
Daily
Weekly
Weekly
Weekly
Daily
Weekly
Weekly
Bi-daily
Weekly
Weekly
Weekly
Daily
Weekly
Weekly
Weekly
Daily
Weekly
Weekly
Daily
Weekly
Weekly
Weekly
Daily
Weekly
Weekly
Weekly
Daily
Daily
Daily
Weekly
Weekly
Weekly
Daily
Daily
Weekly
Weekly
Daily
Weekly
Daily
Weekly
Daily
Weekly
Weekly
Weekly
Daily
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
5 time /wk
6 time /wk
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
4 time /wk
4 time /wk
3 time /wk
Weekly
Weekly
3 time /wk
Weekly
Weekly
Weekly
Daily
3 time /wk
3 time /wk
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
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3.2
Analytical Methods and Considerations
Onsite testing included pH, temperature, Oxidation-Reduction Potential (ORP), Silt
Density Index (SDI), turbidity, TSS, alkalinity, and conductivity. This testing was primarily
intended to provide rapid feedback on process conditions in order to guide operational
settings and adjustment. External lab results are primarily used in this report due to the
higher level of accuracy possible from a full scale commercial lab. However, key on-site
parameters are more relevant than external lab results due to the tendency for
change/instability during sample transportation to and preparation at the external lab
facility. For this reason, onsite test results for parameters such as pH, temperature, SDI
and ORP were used as the primary data source. Detailed water quality results are
provided in Appendix A, where onsite and external analytical results are clearly
distinguished.
External analytical testing was carried out by Maxxam Analytics in Calgary, Alberta. A
summary of analytical methods and detection limits are provided in Table 6.
In this report non-detectable analytical results are considered to equal 50% of the
detection limit in order to carry out statistical analysis of results. Also of note, Method
Detection Limits (MDL) occasionally varied based on dilutions carried out for a given
sample. Typically MDLs were the same for all water types with the exception of RO
permeate. The high salinity of basal water resulted in high MDLs for tests such as TOC.
In low salinity water such as RO permeate, MDLs were at more typical levels.
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Table 6. Summary of analytical methods and detection limits (external laboratory)
Analysis
Alkalinity @25C (pp, total), CO3,HCO3,OH
Biochemical Oxygen Demand
BTEX/F1 in Water by HS GC/MS
Cadmium - low level CCME – Dissolved
Chlorine (Free)
Chloramines, Residual
Chlorine (Total)
Chloride by Automated Colourimetry
Chemical Oxygen Demand
Total Coliforms and E.Coli
Oxygen (Dissolved, winkler)
Carbon (DOC)
Conductivity @25C
Fluoride
CCME Hydrocarbons (F2-F4 in water)
Hardness
Mercury - Low Level (Total)
Elements by ICP – Dissolved
Elements by ICPMS – Dissolved
Ion Balance
Sum of cations, anions
Nitrogen (total), Calc. TKN, NO3, NO2
Naphthenic Acids by IR
Ammonia-N (Total)
Nitrate and Nitrite
Nitrate + Nitrite-N (calculated)
Nitrogen, (Nitrite, Nitrate) by IC
Oil and Grease by IR
Polycyclic Aromatic Hydrocarbons
pH @25°C (Alkalinity titrator)
Orthophosphate by Konelab
Sodium Adsorption Ratio
Sulphate by Automated Colourimetry
Cyanide (Total) Low level
Total Dissolved Solids (Filt. Residue)
Total Dissolved Solids (Calculated)
Total Trihalomethanes Calculation
Total Kjeldahl Nitrogen
Carbon (Total Organic)
Total Suspended Solids (NFR)
Turbidity
VOCs in Water by HS GC/MS (Std List)
Lab SOP
AB SOP-00005
AB SOP-00017
AB SOP-00039
AB SOP-00043
AB SOP-00032
CAL SOP 00045
AB SOP-00032
AB SOP-00020
CAL SOP-00042
CAL SOP-00013
CAL SOP-00053
CAL SOP-00077
AB SOP-00005
AB SOP-00005
CAL SOP-00086
AB WI-00065
CAL SOP-00007
AB SOP-00042
AB SOP-00043
AB WI-00065
AB WI-00065
AB WI-00065
CAL SOP-00085
AB SOP-00007
AB SOP-00023
AB SOP-00023
AB SOP-00023
CAL SOP-00096
AB SOP-00003
AB SOP-00005
AB SOP-00025
AB WI-00065
AB SOP-00018
CAL SOP-00073
CAL SOP-00074
AB WI-00065
CAL SOP-00104
AB SOP-00008
CAL SOP-00077
CAL SOP-00075
CAL SOP-00081
CAL SOP-00227
CONFIDENTIAL
Ver 2.0
Analytical Method
SM 2320-B
SM 5210 B
CCME, EPA 8260C
EPA 200.8
SM Method 4500-Cl G
HACH 8167
SM Method 4500-Cl G
EPA 325.2
SM5220D
SM 9223 A,B
SM 4500-O C
MMCW 119
SM 2510-B
SM 4500-F C
EPA3510C/CCME PHCCWS
SM 2340B
EPA 1631
EPA 200.7
EPA 200.8
SM 1030E
SM 1030E
SM 4500-N A
EPA 3510C/IR
EPA 350.1
SM 4 1 1 0 B
SM 4110-B
SM 4110-B
SM 5520C
EPA 3510C/8270D
SM 4500-H+B
SM 4500-P
SSMA 15.4.4
EPA 375.4
EPA 335.2
SM 2540-C
SM 1030E
EPA 8260 C
EPA 351.1, 351.2
MMCW 119
SM 2540-D
SM 2130B
EPA 8260 C
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4
Untreated Basal Water Quality
Basal water is typified by neutral pH (average 7.0; SD 0.1), low to moderate TSS
(average 23.4 mg/L; SD 81.5mg/L) and high TDS (average 21,300; SD 3,457 mg/L).TDS
is primarily composed of sodium (average 8,086 mg/L), chloride (average 12,458 mg/L),
bicarbonate (average 3,638 mg/L as CaCO3) and hardness causing compounds
(average 1,450 mg/L as CaCO3). Table 7 contains a summary of key water quality
parameters for untreated basal water delivered to the pilot facility from the basal water
wellheads. A more comprehensive summary of water quality parameters is provided in
Appendix A.
Organic compounds were at low concentration, with ability to measure low levels
compromised by high detection limits resulting from the high salinity of the water. TOC
was less than 13 mg/L for 88% of samples taken (average 6.9 mg/L; SD 2.8 mg/L). Oil
and Grease (O&G) was consistently low (average 1.1 mg/L; SD 0.3 mg/L). However,
these levels of organic compounds can theoretically contribute to RO membrane fouling.
The compounds of most significance to this pilot had the potential to form scale on UF
and RO membranes and subsequently reduce process performance. Of particular note
were calcium, magnesium, manganese, iron, barium, strontium, boron, and silica.
Prior to initiating the pilot study, untreated influent water quality and the RO system
configuration were input into the modeling software ROSA (Reverse Osmosis System
Analysis) in order to identify scaling compounds of most significant concern. The
software predicts the concentration of common RO membrane scaling compounds in the
RO reject for a given operational setting. If a given compound is near or in excess of its
solubility limit in the RO reject (which is the feed water for the end of the final membrane
element in the last stage), significant scaling is expected unless mitigative measures are
taken. The most common mitigative measures include choosing an appropriate antiscalant chemical and dose as well as adjusting feed pH in order to increase compound
solubility. Prior to piloting operation, compounds with the highest likelihood of causing
scaling issues (without mitigation) identified were barium sulphate (BaSO4) and calcium
fluoride (CaF2). Due to the high alkalinity and hardness present in untreated basal water,
calcium carbonate (CaCO3) was also a concern.
Compounds in a reduced state coming out of the well were unstable over the short term,
but displayed relatively consistent results in aged samples. These included iron,
manganese, and sulphides including hydrogen sulphide. These compounds have a
tendency to precipitate out of solution as they are exposed to oxidizing compounds. It
was important to control this reaction in order to ensure it was not occurring on the
membrane surfaces.
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Table 7. Summary of select water quality parameters for untreated basal water
Parameter
Units
pH (on-site lab)
SU
mg/L
Turbidity
NTU
Conductivity
µS/cm
mg/L
Dissolved Chloride (Cl)
mg/L
Total Sulphide
mg/L
Dissolved Sulphate
mg/L
Alkalinity
mg/L
(Total as CaCO3)
Bicarbonate (HCO3)
mg/L
Total Reactive Silica
mg/L
Hardness (CaCO3)
mg/L
Total Ammonia
mg/L
mg/L
Dissolved Organic Carbon mg/L
Naphthenic Acids
mg/L
Oil and grease
mg/L
F1 (C6-C10)
µg/L
Hydrocarbons
Total Aluminum (Al)
mg/L
Total Barium (Ba)
mg/L
Total Boron (B)
mg/L
Total Calcium (Ca)
mg/L
Total Iron (Fe)
mg/L
Total Magnesium (Mg)
mg/L
Total Manganese (Mn)
mg/L
Total Strontium (Sr)
mg/L
Dissolved Aluminum (Al)
mg/L
Dissolved Barium (Ba)
mg/L
Dissolved Boron (B)
mg/L
Dissolved Calcium (Ca)
mg/L
Dissolved Iron (Fe)
mg/L
Dissolved Magnesium (Mg) mg/L
Dissolved Manganese (Mn) mg/L
Dissolved Strontium (Sr)
mg/L
SD =
ND =
Average
(ND=
50%
MDL)
7.0
23
23
36,167
21,300
12,458
0.22
10.4
Min
Max
SD
# of
Obs.
%ND
MDL
6.6
1
8
34,000
11,503
12,000
<0.002
<1
7.4
430
110
37,000
23,000
13,000
4.6
34.0
0.1
81
20
637
3457
509
0.72
10.3
79
27
27
24
10
24
41
12
0
0%
0%
0%
0%
0%
20%
33%
0
2.5
0.1
1
10
100
0.002
1
2975
2,800
3,200
157
24
0%
5
3638
5.10
1,450
11.8
6.9
6.1
3.5
2.1
3,400
4.60
1,100
11.0
<13
<13
1.6
<2
3,900
7.78
1600
13.0
17.0
<13
5.1
5.3
193
0.64
102
0.8
2.8
1.2
1.2
1.4
24
24
24
10
16
11
11
12
0%
0%
0%
0%
88%
100%
0%
50%
5
0.05
0.5
0.5
13
13
1
2
316
<100
730
203
9
11%
100
0.2
2.3
5.0
188
2.0
233
0.27
13.3
0.045
2.3
4.9
189
1.2
235
0.27
13.1
0.039
2.2
4.8
160
1.1
210
0.16
12.0
<0.025
2.1
4.6
150
<0.6
210
0.21
12.0
0.380
2.5
5.3
210
3.3
260
0.70
14.0
0.110
2.6
5.3
210
3.1
260
0.37
14.0
0.167
0.2
0.2
16
0.5
22
0.07
1.0
0.040
0.2
0.2
12
0.7
14
0.03
0.8
4
4
4
16
42
4
52
4
14
14
14
26
41
16
42
14
0%
0%
0%
0%
0%
0%
0%
0%
36%
0%
0%
0%
22%
0%
0%
0%
0.025
0.1
0.2
3
0.6
2
0.04
0.2
0.025
0.1
0.2
3
0.6
2
0.04
0.2
standard deviation;
analytical result below the MDL result;
MDL =
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5.
Treatment Performance
The primary water quality objectives for this treatment train were to reduce TDS to less
than 1000 mg/L and sodium levels to less than 500 mg/L. Based on the use of RO
membrane technology it was expected that these objectives would be met. However,
another primary objective in piloting was to identify the maximum sustainable recovery
rates and fouling characteristics for the UF and RO membranes as this impacts the
sizing of the membrane systems and expected membrane module service life. Key
considerations in evaluating this treatment train relate to the fouling rate characteristics
and cleaning requirements for both the UF and RO membranes.
Significant consideration was given to the hardness levels in basal water and the
advantages and disadvantages of softening the water before treatment by UF and RO
membranes. It was decided to pilot basal water treatment without softening based on the
projected high chemical usage requirements for removing hardness causing ions, and
modeling results that suggested negative impacts on the RO could be managed using
anti-scalant chemicals. However, hardness related scaling on pilot equipment was
determined to be an issue at the original treatment target pH of >7.5, but was
manageable at the revised neutral pH used from August 16th to the end of the study in
October.
5.1
Oxidation
Basal water comes out of the ground in a reduced oxidative state due to the lack of
oxygen underground. When the basal water is exposed to atmospheric oxygen,
compounds such as dissolved iron, manganese and sulphides have a tendency to
oxidize and potentially precipitate out of solution as a solid. It is important to control this
precipitation in a membrane based treatment process, so that the solids do not
precipitate out on the surface or inside of the membrane structure. If fouling of the
membrane is excessive it can reduce the sustainable recovery rate of the system (due to
additional backwashes and chemical cleanings) as well as reduce the membrane service
life (if frequent high strength chemical cleanings are required).
The goal of including an oxidation treatment step in the treatment train was to precipitate
out sulfides, iron and manganese which had the potential to negatively impact fouling
rates on the UF and RO membrane systems. Iron and sulphide compounds will tend to
be oxidized before manganese compounds. Oxidation of manganese by dissolved
oxygen at ambient conditions is a slow reaction that requires significant timespans.
As can be clearly seen in Figure 4, for the Oxidation-Reduction Potential (ORP) values
observed for untreated basal water (-0.5 v to -0.1 v) Mn tends to remain soluble as Mn2+
below a pH of 7.5, but theoretically will precipitate out of solution at pH values above this
level.
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2.2
MnO4- (purple)
pH range observed in pilot
Figure 4. Manganese Solubility at various pH values and ORP (Pourbaix Diagram)
Bench Scale
A number of bench scale experiments were carried out over the course of the pilot by
both EPCOR and Veolia technical staff, in order to optimize oxidation related chemical
dosing. However, bench scale results did not always prove scalable to the pilot. Factors
such as short circuiting, tank hydraulics, reaction times and potential complexation
reactions have all been identified as possibly playing a role in variations between bench
and pilot treatment results.
Bench scale testing has identified several key requirements in designing a basal water
treatment plant. Basal water taken from the well head is in a reduced state and as it is
exposed to atmospheric oxygen, oxidation reactions slowly take place over several
hours which result in increases in pH, reduction in sulphides (and H2S) and to some
degree iron. Large rapid changes tend to occur over the first few hours after being taken
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from the well head, afterwards changes are much more gradual but can continue over
the course of the next one or two days.
Several methodologies were examined in order to stabilize water quality changes in
order to facilitate optimal dosing of oxidation chemicals (Figure 5). In this set of bench
scale trials, basal water was subjected to three different oxidizing conditions and
changes in pH and ORP were monitored with time. Replicates were carried out for all
three conditions. As a control, one set of samples was stored in a covered container with
no mixing (indicative of minimal oxidation due to exposure to atmospheric oxygen). The
second condition was an open container with some mixing provided (indicative of
exposure to atmospheric oxygen such as may be encountered in an open equalization
pond or tank). The third condition was full aeration of the basal well water using air
(indicative of maximum possible aeration achievable).
Natural aging of the water does result in stability, but requires significant time-spans, and
therefore also potentially requires large equalization storage volumes upstream of the
treatment facility (see the “No Mixing, Covered 1 and 2” curves in Figure 5). Aeration of
the water tends to speed up the natural aging process, but due to the slow kinetics
involved in oxidizing some species in the water, some gradual changes in water quality
still tend to occur over the long term (see Aerated curves in Figure 5). This bench scale
testing occurred over a six hour timeframe, but slow gradual changes can be expected
over the course of several days.
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9.5
9
No Mixing, Covered 1
pH
8.5
8
Aerated, Open 1
7.5
Aerated, Open 2
Mixing, Open 1
7
Mixing, Open 2
6.5
0
1
2
3
4
5
6
Time (hr)
300
250
200
ORP (mV)
150
100
50
Aerated, Open 1
0
-50
Aerated, Open 2
-100
Mixing, Open 1
-150
Mixing, Open 2
-200
0
1
2
3
4
5
6
Time (hr)
Figure 5. Change in basal water pH and Oxidation-Reduction Potential (ORP) with
aeration (fully aerated) and mixing observed in bench scale testing
Chemical oxidation of the water using potassium permanganate was shown to have a
rapid stabilization effect on basal water quality in the bench scale, but this result did not
scale up at the pilot scale and therefore was not pursued (Figure 6). Addition of mixing in
the feed tank was the primary mechanism used to stabilize influent ORP and pH at the
pilot scale as opposed to relying on the effects of permanganate dosing. Potassium
permanganate was dosed at the pilot scale to provide oxidation, but stabilization of ORP
and pH was not an objective due to the limitations stated above.
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500
400
300
ORP (mV)
200
16 mg/L KMnO4
100
0
-100
-200
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
Time (minutes)
Figure 6. Overview of the impact of a high potassium permanganate dose on ORP
with time for basal water taken from the wellhead
Based on pilot results, provision of aeration and some equalization of fresh basal water
provide sufficient stability to dose the required treatment chemicals upstream of the UF
treatment process. However, optimal chemical dosing is important in order to manage
fouling rates of the UF membranes. Equalization time of basal water varied significantly
throughout the pilot due to the feed water being trucked from the mine and stored in a 60
m3 feed tank at the pilot site. Trucking fill/unload times, delivery times and consumption
rates at the pilot all impacted the equalization time for the water entering the treatment
plant. Appendix G contains a report detailing full scale equipment sizing that addresses
recommended equalization time for a full scale facility.
Permanganate dose was optimized through a combination of bench scale and pilot scale
experimentation. Figure 7 displays the impact of pH and permanganate dose on
dissolved manganese concentration in the oxidized basal water. As predicted using the
Pourbaix diagram (Figure 4), elevated pH provides the lowest residual concentration,
while lower pH results in the highest residual. Use of an alternative oxidizing chemical
such as sodium hypochlorite could resolve the potential for elevated dissolved
manganese subsequent to oxidation/precipitation due to non-optimal permanganate
dosing and complexation issues.
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pH 7.2
pH 7.6
pH 8.0
Raw
0.25
Total Mn (mg/L)
0.20
0.15
0.10
0.05
0.00
0
1
2
3
4
5
6
Permanganate Dosage (mg/L)
Figure 7. Overview of dissolved manganese in basal water at various
permanganate dosages observed in bench scale testing
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7
Pilot Scale
Manganese removal did not scale up well from bench scale testing, as dissolved
manganese levels in UF filtrate were frequently higher than what was observed at bench
scale. It is likely that other compounds were complexing with manganese, keeping it in
dissolved form, despite being in the zone of the Pourbaix diagram (Figure 4) where
precipitation should have occurred.
Bench scale work identified a strong relationship between ORP and permanganate
dosing required for precipitating out iron, sulphides and manganese. However, ORP
proved to be an impractical parameter to base chemical dosing on due to the tendency
for compounds in the water to rapidly foul ORP probes (often within an hour), such that
reliable online readings were not possible. The rapid change and stabilization of ORP
subsequent to permanganate addition did not scale up from bench to pilot scale as
detailed in the previous section.
The chemical dosing strategy was changed on August 16th, after extensive attempts to
achieve reliable manganese removal were unsuccessful. This involved stopping pH
adjustment upstream of the UF and adding permanganate at a fixed dose in order to
precipitate iron and sulphides, while attempting to keep manganese in dissolved form.
The fixed permanganate dose was notably lower as only sufficient oxidation was
required to address iron and sulphide precipitation.
The dosing strategy was modified for several additional reasons. Firstly, the elevated
manganese levels observed in the UF filtrate did not show measureable negative impact
on downstream RO operation. Secondly, operation at the high pH, theoretically required
for manganese precipitation, resulted in excessive calcium carbonate scaling on pilot
plant equipment and potentially the UF and RO membranes. Operation at neutral pH
also resulted in a significant reduction in volume of caustic required for upstream pH
adjustment and therefore significant savings for ongoing chemical operating costs.
The optimal operational settings for the Oxidation treatment step are as follows:
 Potassium permanganate = 1 to 1.5 mg/L
 Ferric chloride = 0 to 2 mg/L as Fe
 Sodium Hydroxide = 0 mg/L
 Equalization (with mixing and exposure to the atmosphere) of water upstream of
the oxidation system in order to stabilize ORP and pH
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5.2
Polymeric Ultrafiltration (PUF)
Hollow fibre PVDF membranes (DOW SFD 2860) were used as the sole solids removal
mechanism in the treatment train. As expected, suspended solids (gauged by turbidity
and TSS) were consistently low in UF filtrate, regardless of influent solids or chemical
dosing upstream.
A significant portion of the pilot was used to identify optimal operating conditions and
upstream chemical dosing in order to maximize water production while attempting to
maintain fouling rates at practically manageable levels.
Operating Conditions
The UF system used during the pilot consisted of a single membrane module. Detailed
specifications and operational settings for the system are provided in Table 8. Flux rates
are normalized to 20°C as recommended by the manufacturer in order to permit
comparison of operational results as water temperature varied.
Table 8. Summary of UF system specifications and operating conditions
Parameter
Membrane type
Membrane model
Membrane surface area per module
Number of modules operated
Rated filtration flux at 25°C
Rated filtration flux at 20°C
Chemical resistance
- Operating pH range
- NaOCl maximum concentration
Temperature range (UPVC limited)
Maximum feed pressure at 20°C
Maximum operating TMP
Nominal pore diameter
External fiber diameter
Internal fiber diameter
Module diameter
Module length
Operating flow in pilot
Feed flux rate in pilot
Feed flux rate in pilot
(normalized to 20°C)
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PVDF Hollow Fiber Outside - In
DOW SFD 2860 module
51 m2
1
40 to 120 lmh
35 to 105 lmh
pH: 2 – 11
2000 mg/L
1 to 40°C
625 kPa (93.75 psi)
210 kPa (30 psi)
0.03 µm
1.3 mm
0.7 mm
225 mm
1500 mm
1.5 to 4.2 m3/hr
28 to 80 lmh
28 to 105 lmh
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The strategy for managing fouling of the membrane was primarily through a combination
of frequent physical backwashes combined with the use of Chemically Enhanced
Backwashes (CEBs) at regular intervals. Triggers for initiating a CEB included a Trans
Membrane Pressure (TMP) increase to maximums of approximately 97 to 159 kPa (14
to 23 psi) (target varied as the pilot progressed), a permeability drop of more than 15%
or time between CEBs. The fouling management philosophy used during the pilot was to
carry out frequent small duration CEBs before excessive fouling occurred and became
difficult to restore performance to baseline levels. CEBs were initiated based on a
maximum time interval of 24 hrs (though fouling rates and not time interval generally
governed CEB frequency during the pilot) if neither TMP nor permeability thresholds
were reached. A summary of a typical UF backwash sequence and UF CEB sequence
are provided in Table 9 and Table 10 respectively.
Table 9. Overview of a typical UF backwash sequence
Step
1
Time (s)
Flux (lmh)
5
---
Stand by
3
2
Air Scour #1 – 5 m /hr (3 scfm)
10
---
3
4
5
Standby
3
Drain
5
10
60
----150
6
BW top + air
45
60
7
BW bottom
45
150
8
BW rinse
0
0
Time (s)
Flux (lmh)
Table 10. Overview of a typical UF CEB
Step
1
Stand by
30
---
2
0
---
3
Standby
0
---
3
3
4
0
---
5
Drain
5
100
6
BW Bottom
15
100
7
Dosage Bottom
90
100
8
Dosage Top
90
100
Soak
BW rinse
900
180
0
100
9
10
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Chemically Enhanced Backwashes (CEBs) were experimented with significantly during
the course of the pilot in order to optimize the fouling rate control of the system.
Parameters experimented with in order to optimize CEB sequences include the
following:








# of acid and caustic CEBs executed in a sequence
# of physical backwashes (BW) in a CEB sequence
Order of executing CEB types and BWs
Use of RO permeate instead of UF filtrate (to gauge negative impact of dissolved
metals in UF permeate)
Addition of hypochlorite to BW water (enhanced organics removal)
Addition of sodium metabisulphite to BW water (enhanced manganese removal)
Production cycle length
Maximum permissible TMP
Chemical Usage and Operational Settings at Optimal Conditions
Table 11 provides a summary of the chemical dosing and operational settings
recommended for UF system operation at optimal settings. A brief summary of the
reasoning for each setting is also provided, with the detailed analysis contained in the
following sections of this report.
It should be noted when interpreting these recommendations, that the standard cleaning
methodology identified by the membrane manufacturer is use of acid CEBs at a pH of 2
(using HCl, H2SO4, citric or oxalic acid), and caustic CEBs at a pH of 12 (using NaOH).
Membrane exposure to extreme high or low pH levels should be minimized as these
conditions contribute to gradual degradation of the membrane surface which ultimately
impacts the service life of the membrane module.
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Table 11. Overview of UF system related chemical usage and operational settings at optimal conditions
Parameter
Potassium
permanganate
Ferric chloride
Optimal Setting
= 1 to 1.5 mg/L
Reasoning
-Targets iron and sulfide precipitation, but not Mn
= 0 to 2 mg/L as Fe
Sodium Hydroxide
= 0 mg/L
Flux
(normalized to 20˚C)
Recovery range
= 53 lmh
-Low dose if/as required to potentially increase particle size
and rejection by the UF, but not too high in order to avoid
contributing to UF scaling
-Operation at neutral pH significantly reduces chemical
consumption due to pH adjustment.
-The primary goal of operating at elevated pH was Mn
precipitation, which is not an objective at the optimum
conditions identified in this pilot. Mn in a dissolved
reduced state was shown to not be a significant RO
scalant.
-Operation at elevated pH resulted in severe CaCO3 scaling
throughout the pilot facility. Impact of full scale
equalization on pH must be considered in full scale
design
-Based on TMP development rate and observed time
required between CEBs
-Based on pilot waste streams observed (improved recovery
may be possible at full scale due to waste stream
scalability)
-Based on TSS levels observed
-Provides physical scouring of the membrane surface which
reduces membrane fouling and a mechanism to deal with
elevated TSS levels occasionally experienced.
= 70 to 80%
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Table 11 (con’t)
Parameter
CEB sequence
- Acid CEB
-
Caustic CEB
CEB frequency
CIP sequence
- Acid CIP
-
Caustic CIP
CIP frequency
Optimal Setting
 approximately 2.5 pH
 5000 mg/L citric acid
 approximately 12 pH
 600 mg/L NaOH
 600 mg/L NaOCl
= once every 24 hours at optimum operating
conditions
 ≤2.3 pH using citric acid,
 38°C solution
 2000 mg/L NaOCl
 32°C solution
= every 2 to 4 weeks
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A summary of select water quality parameters for UF permeate is provided in Table 12.
A complete listing of water quality parameters examined is located in Appendix B, while
detailed plots of online instrumentation data is locate in Appendix C.
As shown in Table 12, solids removal was consistently good, with effluent turbidity
averaging 2.0 NTU and Silt Density Index (SDI) averaging 0.9 over the course of the
pilot (well water source). RO feed requires an SDI of less than 5 at a minimum and
ideally less than 3.
UF filtrate concentrations of iron and sulphides were consistently low enough to achieve
targets based on the perceived ability of anti-scalant chemicals to manage fouling on the
downstream RO membranes. Subsequent analysis of RO fouling compounds did
indicate iron was a major foulant for the RO system. The RO system is discussed in
detail in a later section of this report. Iron residual concentration in the UF filtrate
appeared to be lowest during the initial chemical dosing regimen with high pH (≥7.4) in
the oxidation/precipitation phase.
Manganese removal did not scale up from bench to pilot scale testing. Typical
manganese water quality targets upstream of an RO system are a maximum of 0.1 mg/L
and preferably less than 0.05 mg/L. These levels were not consistently met with the UF
system as a number of factors resulted in high concentrations of manganese remaining
in dissolved form and passing through the UF membrane. These factors included
oxidation chamber influent water quality fluctuations in ORP and pH over short
timeframes, complexation with compounds in the water resulting in elevated dissolved
manganese levels, potential short circuiting of tanks, and other flow related effects.
High levels of organics can be a significant factor in UF and RO membrane fouling, but
this did not appear to be a factor in this pilot. Organic compounds in untreated basal
water were consistently at low levels. Due to the high salinity of the water the method
detection limit for TOC and DOC ranged from 10 to 13 mg/L, and the majority of tests on
both untreated basal and UF filtrate were below detection. Oil and grease was also
typically of low concentration in basal water (average 2.1 mg/L), with an average
reduction of 48.9% after treatment by the UF. Naphthenic acids averaged 3.5 mg/L in
untreated basal water and displayed no reduction due to treatment by the UF unit. The
membrane autopsy indicated membrane deposits were primarily inorganic.
Overview of Dosing Strategy
The chemical dosing strategy was primarily governed by and modified based on UF
filtrate quality and desired RO influent water quality (and to a lesser extent UF
operational performance). The piloting period can be broken down into nine operational
zones as presented in Figure 8. The primary operational and chemical dosing aspects of
each zone and accompanied advantages and disadvantages are provided at a high level
in Table 13.
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Table 12. Summary of select water quality parameters for UF permeate
Parameter
Average
Units (ND= 50%
MDL)
SU
pH (on-site)
NTU
Turbidity (on-site)
SDI (on-site)
Total Suspended Solids mg/L
NTU
Turbidity
µS/cm
Conductivity
mg/L
Dissolved Chloride (Cl)
Total Sulphide
mg/L
Dissolved Sulphate (SO4) mg/L
Alkalinity (Total as
mg/L
CaCO3)
mg/L
Bicarbonate (HCO3)
mg/L
(C)
mg/L
Oil and grease
mg/L
Total Aluminum (Al)
mg/L
Total Barium (Ba)
mg/L
Total Boron (B)
mg/L
Total Calcium (Ca)
mg/L
Total Iron (Fe)
mg/L
mg/L
mg/L
Dissolved Aluminum (Al) mg/L
mg/L
mg/L
Dissolved Boron (B)
mg/L
mg/L
Dissolved Iron (Fe)
Dissolved Magnesium
mg/L
(Mg)
Dissolved Manganese
mg/L
(Mn)
Dissolved Strontium (Sr) mg/L
7.2
2.0
0.9
0.6
1.5
36,500
12,500
0.001
358
Min
Max
6.9
8.0
0.1
38.6
0.2
3.2
<1.0
1.0
<0.1
9.0
36,000 37,000
12,000 13,000
<0.002 0.006
<1
5,000
SD
Count
%ND
MDL
%
Reduction
(from Raw)
0.3
4.9
0.8
0.2
2.5
707
707
0.001
1,336
16
80
33
13
27
2
2
42
14
85%
4%
0%
0%
81%
93%
1.0
0.1
1
100
0.002
1
97.5%
93.5%
<1%
<1%
99.4%
<1%
2864
2,800
3,200
122
14
0%
5
<1%
3500
3,400
3,900
162
14
0%
5
<1%
6.7
<13
14.0
1.5
27
96%
13
3.0%
1.1
0.047
2.4
5.1
200
0.4
250
0.44
13.5
0.025
2.5
5.3
205
0.7
<2
<0.025
2.4
5.0
200
<0.6
250
<0.04
13.0
<0.025
2.4
5.3
200
<0.6
2.1
0.081
2.4
5.2
200
1.7
250
1.10
14.0
0.038
2.5
5.3
210
1.7
0.3
0.048
0.0
0.1
0
0.4
0
0.31
0.7
0.018
0.1
0.0
7
0.6
14
2
2
2
2
45
2
55
2
2
2
2
2
5
93%
50%
0%
0%
0%
60%
0%
2%
0%
50%
0%
0%
0%
40%
2
0.025
0.1
0.2
3
0.6
2
0.04
0.2
0.025
0.1
0.2
3
0.6
48.9%
74.9%
<1%
<1%
<1%
77.6%
<1%
<1%
<1%
44.5%
<1%
<1%
<1%
40.1%
255
250
260
7
2
0%
2
<1%
0.41
0.10
0.78
0.33
5
0%
0.04
<1%
14.0
14.0
14.0
0.0
2
0%
0.2
99.8%
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Table 13. High level overview of chemical dosing zones during the pilot
Operational Settings
Wellhead water source
Pond water source
Elevated pH in oxidation zone
Neutral pH in oxidation zone
Flux range (Low/Moderate/High)
Dead end operation
Cross flow operation
Mn targeted for precipitation
New membrane modules (burn in period)
Advantages
Low chemical usage
Stable influent ORP & pH
Physical scouring of membrane surface
Disadvantages
CaCO3 scaling throughout pilot facilities
CEBs not sufficient to restore baseline TMP
Elevated Mn residuals in UF filtrate
Elevated Fe residuals in UF filtrate
Not relevant to scaling up UF design
A
X
X
B
X
X
C
X
D
X
Zone
E
X
X
H
X
X
M
X
X
L
X
L
X
H
X
X
X
X
X
F
X
G
X
X
X
M
X
L
X
X
X
H
X
I
X
X
L
X
M
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Figure 8. Overview of UF recovery, flux and TMP increase rate during the pilot.
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UF Recovery
Water recovery for the UF system was purely a function of the proportion of treated
water used for membrane cleaning cycles (backwashes and CEBs). The inverse
relationship of UF recovery to total water used for cleaning cycles is visible in Figure 9.
During production cycles there is no waste stream, such that 100% of water fed to the
system passed through the membrane and becomes UF filtrate. In the UF system the
primary operational variables that can be used to impact recovery are:






backwash frequency;
chemically enhanced backwash (CEB) frequency;
clean-in-place (CIP) frequency;
Water usage during a single cleaning cycle (BW, CEB, CIP);
flux; and
optimization of upstream chemistry to target UF membrane fouling reduction.
In this pilot the severity of fouling on the UF membrane (as gauged by TMP increase
rate) had a major impact on the UF recovery rate, due to the treated water requirements
for cleaning cycles.
Recovery for the UF varied significantly during the couse of the pilot as is visible in
Figure 8. Recovery is calculated as a balance between the water treated by the UF
system, minus the treated water used for backwashes and chemically enhanced
backwashes (CEBs). Clean in Place (CIP) chemical cleaning events were not
considered in the calculations used in this report. From late August onwards there was a
significant increase in the volume of water used per day for both backwashes and CEBs
in response to increased fouling on the membrane. The increased fouling was due to
increased flux rates (and therefore volume of water treated per day) as well as the
chemistry of the water contacting the UF membrane.
Initially UF recovery was lower (typically in the 60 to 70% range) as upstream chemical
process optimization was the focus. Recovery was gradually increased to 80% and to as
high as 89% in late August. Significant issues related to scaling on the UF membrane
were encountered at the end of August and persisted through much of September.
Experimentation with a variety of cleaning methodologies during this period was
responsible for the rapid reduction/variation in recovery. It is likely that relative water
volumes for cleanings could be reduced in a full scale facility relative to the pilot.
Inherent facility design issues unique to the pilot (e.g. length of pipe runs, sizing of pipes
and vessel volumes) likely increase the total volume of clean water used during this
study relative to a full-scale facility. However, it is clear that frequency and type of
cleanings used for the UF have a significant and notable impact on system recovery.
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Figure 9. Overview of UF recovery relative to water usage for membrane cleaning
cycles during the pilot.
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Fouling Rate Development and Cleaning Effectiveness
Ideally, execution of a CEB sequence would provide complete removal of fouling
material and initial membrane TMP would return to baseline levels. At the beginning of
the pilot, the CEB sequence and frequency were effective in maintaining TMP within a
manageable range. However, in late August, CEBs were not restoring TMP and
permeability to baseline values despite significant effort in modifications to CEBs,
including sequence order, chemical strength, duration, frequency and use of
accompanied backwashes (Figure 10). For reference, plots of UF TMP throughout the
entire piloting period are located in Appendix C.
The overall fouling characteristic of the UF membrane during the pilot is depicted in
Figure 8 and Figure 10. The TMP increase rate indicates the increase in TMP per unit
time during a run and the Baseline TMP indicates the TMP level at which a run is started
right after a CEB has been completed. A complete run is defined as the period of UF
operation in between two CEBs and is referenced in Figure 10 as “Time Between
CEBs”.
In order to remove foulants not addressed by the CEBs, a CIP was conducted on
September 13 to 14, which was effective in restoring membrane TMP and permeability
to baseline values. However issues reappeared in less than a week of operation. At this
point, rapid TMP development was occurring and CEBs were required on a frequency
(approximately every 3 hours) that had negative implications for recovery as well as
practical operational factors.
In general, CIPs are more effective than CEBs at removing fouling material and restoring
permeability. This is due to the use of higher cleaning chemical concentrations in
combination with prolonged soaking periods, where the cleaning solution is in contact
with the membrane surface. However, CIPs negatively impact the service life of a
membrane more than CEBs due to the combination of higher strength chemical
solutions and contact time. As previously mentioned, the number of CIPs carried out
should be minimized.
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Baseline TMP (psi)
Time Between CEBs (Hrs)
TMP Increase Rate (psi/day)
Flux Corrected to 20°C (lmh)
140
120
Pond
Pond
Water
Water
Trial
Trial
Flushing system of
pond organics
pH 7.4-7.6
pH 7.6-8.0
100
Crossflow
pH 6.8-7.0
pH 6.8-7.0
80
Major change in
dosing strategy
CIP
60
New
modules
40
20
0
20-Jun 30-Jun 10-Jul
20-Jul
30-Jul 09-Aug 19-Aug 29-Aug 08-Sep 18-Sep 28-Sep 08-Oct 18-Oct
Figure 10. Overview of fouling rate development for the UF.
CIP Solution Analysis and Membrane Autopsy Overview
The autopsy conducted on the UF membrane (Appendix E) used during the pilot
indicated deposits were mainly inorganic, with iron and chloride being the main elements
present. Low levels of sulphur, calcium and manganese were also detected, but at
significantly lower levels that iron and sodium. A brown orange deposit on the UF
strands was noted to have penetrated deep into the membrane structure, not just on the
membrane surface.
The cleaning solutions used during the CIP were sampled and sent for analysis in order
to isolate key compounds that were present on the membrane surface and contributing
to reduced performance (Table 14). The CIP consisted of multiple steps designed to
remove typical organic foulants and mineral scalants. High pH cycles are typically
effective in removing organic material, while low pH cycles target removal of mineral
scalants.
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The detailed procedure used for CIPs is located in Appendix D. An abbreviated
summary of the CIP cycle is as follows:





2 hr recirculation (#1) with cleaning solution at 40 lmh
o Sample solution
6 hr soak in cleaning solution
2 hr recirculation (#2) at 40 lmh
o Sample permeate and concentrate solution
Drain cleaning solution
Rinse with potable water until neutral pH at 20 lmh
o Sample solution
Organic compounds were not found in significant concentrations in the high pH CIP
solution, which targeted removal of organic foulants on the membrane. Additionally,
untreated basal water TOC concentrations were consistently below detection limits
(though detection limits were 13 mg/L due to high water salinity). These two factors
suggest organic fouling is not the governing issue in UF performance. However, it should
be noted that even the low levels of TOC and O&G observed can result in membrane
fouling. The maximum O&G concentration specified by the manufacturer for the UF
membranes is 2 mg/L. Though 93% of analytical results were reported to be < 2mg/L,
several results were marginally above this limit (Table 12).
Fouling on the UF membrane was correlated to upstream chemical dosing. Iron was
present in the most significant concentration in the low pH CIP solution, which targeted
mineral scale removal from the membrane. Subsequent investigation into the impact of
lower coagulant dosing suggests that dosing of ferric chloride coagulant immediately
upstream of the UF membrane was a significant contributor to rapid membrane fouling
rates observed. Coagulant dose across the various chemical dosing strategies is
examined in greater depth in a later section of this report. The elevated TOC present in
the low pH CIP solution is due to the use of citric acid to lower the pH and does not
indicate organics removal from the membrane. Organics tend to precipitate out of
solution at low pH.
In addition to iron, there was also elevated barium, calcium, strontium, sulfur and zinc in
the low pH CIP cleaning solutions. Minimal organic material was observed in the high pH
CIP solution. This suggests mineral scaling and not organic fouling is the primary source
of reduced performance instigating the CIP. In the membrane autopsy, iron was the
dominant metal deposit by a wide margin.
Ferric chloride was selected as the coagulant for this application due to its proven use in
similar treatment scenarios and effectiveness over a wide pH range. However, iron and
chloride were the most significant deposits on the UF membrane, indicating the
coagulant significantly contributed to membrane fouling. This is backed up by both the
CIP solution analysis and membrane autopsy data. It is likely possible to reduce the
impact of iron fouling by the ferric chloride dose used in the application in combination
with the use of CIP chemicals specifically targeting the iron deposits.
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Table 14. Overview of UF CIP cleaning solution analysis for key fouling
compounds
Parameter
pH
Acid CIP
Recirc#1
Solution
Acid CIP
Recirc#2
Conc.
Units
UF Effl.
SU
7.2
2.21
9000
b
a
2.36
a
Acid CIP
Recirc#2
Filtrate
Acid
CIP
BW
Flush
Caustic
CIP
Conc
Caustic
CIP
Filtrate
MDL
2.61
6.15
12.1
12.1
0
7700
a
Total Organic Carbon (C)
mg/L
<13
7700
120
38
30
13
Carbonate (CO3)
mg/L
<0.5
Dissolved Sulphate (SO4)
mg/L
358
<0.5
130
<0.5
120
<0.5
170
<0.5
42
1300
100
1300
<1
0.5
1
Total Aluminum (Al)
mg/L
0.046
0.9
6.7
2.7
1.7
4.1
4
0.025
Total Antimony (Sb)
mg/L
<0.015
<0.015
<0.015
0.002
<0.015
<0.015
<0.015
0.015
Total Arsenic (As)
mg/L
<0.005
0.0021
0.0045
0.012
0.0048
0.0016
0.0016
0.005
Total Barium (Ba)
mg/L
2.4
1.5
1.5
2.3
0.77
0.14
0.16
0.1
Total Beryllium (Be)
mg/L
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
0.025
Total Boron (B)
mg/L
5.1
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
0.2
Total Cadmium (Cd)
ug/L
<0.13
1
1.6
2.6
1.1
0.32
0.25
0.13
Total Calcium (Ca)
mg/L
200
110
200
220
57
28
27
3
Total Chromium (Cr)
mg/L
<0.025
0.022
0.063
0.11
0.032
0.013
0.0082
0.025
Total Cobalt (Co)
mg/L
<0.0075
0.0012
0.0036
0.0088
0.0022
<0.0075
<0.0075
0.0075
Total Copper (Cu)
mg/L
0.0025
0.032
0.061
0.3
0.14
0.017
0.015
0.005
Total Iron (Fe)
mg/L
<0.6
39
80
230
38
3
0.69
0.6
Total Lead (Pb)
mg/L
<0.005
0.016
0.033
0.091
0.023
0.0021
0.0014
0.005
Total Lithium (Li)
mg/L
2.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
0.2
mg/L
250
12
25
17
15
<2
2.3
2
mg/L
0.44
0.84
2.6
3.8
2.5
0.054
<0.04
0.04
Total Molybdenum (Mo)
mg/L
<0.005
0.0012
0.0028
0.0082
0.0026
0.0032
0.0029
0.005
Total Nickel (Ni)
mg/L
0.014
0.0069
0.021
0.072
0.016
<0.013
<0.013
0.013
Total Phosphorus (P)
mg/L
<1
<1
<1
2.4
1.4
<1
<1
1
Total Potassium (K)
mg/L
66
<3
<3
<3
<3
7.6
8.6
3
Total Selenium (Se)
mg/L
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.005
Total Silicon (Si)
mg/L
2.5
2.4
3
4.1
3.3
1.5
1.7
1
Total Silver (Ag)
mg/L
<0.0025
<0.0025
<0.0025
0.0013
0.0004
<0.0025
<0.0025
0.0025
Total Sodium (Na)
mg/L
7600
100
120
190
170
2000
2300
25
mg/L
13.5
3.6
7.9
9.3
1.1
0.36
0.26
0.2
Total Sulphur (S)
mg/L
4.4
66
53
58
11
11
10
2
Total Thallium (Tl)
mg/L
<0.005
<0.005
<0.005
0.0009
<0.005
<0.005
<0.005
0.005
Total Tin (Sn)
mg/L
<0.025
<0.025
0.0078
0.02
0.0037
<0.025
<0.025
0.025
Total Titanium (Ti)
mg/L
<0.025
0.011
0.036
0.087
0.04
<0.025
<0.025
0.025
Total Uranium (U)
mg/L
<0.0025
0.0003
0.0004
0.0005
0.0003
<0.0025
<0.0025
0.0025
Total Vanadium (V)
mg/L
<0.025
0.0057
0.01
0.02
0.0073
<0.025
<0.025
0.025
Total Zinc (Zn)
a
mg/L
<0.075
2.8
68
450
0.4
0.29
0.14
0.075
TOC elevated in Acid CIP due to use of an organic acid for cleaning (citric acid)
b
Onsite pH
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Table 14 (con’t)
Acid CIP
Recirc#1
Solution
Acid CIP
Recirc#2
Conc.
Acid CIP
Recirc#2
Filtrate
Acid
CIP BW
Flush
Caustic
CIP
Conc
Caustic
CIP
Filtrate
7.2
2.21
2.36
2.61
6.15
12.1
12.1
0
mg/L
0.025
0.88
6.7
2.3
0.58
4.6
4.3
0.025
Dissolved Antimony (Sb)
mg/L
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
<0.015
0.015
Dissolved Arsenic (As)
mg/L
<0.005
0.002
0.0037
0.0041
0.00092
0.002
0.0013
0.005
mg/L
2.45
1.4
1.4
1.9
0.38
0.13
0.15
0.1
Dissolved Beryllium (Be)
mg/L
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
0.025
Dissolved Boron (B)
mg/L
5.3
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
0.2
Dissolved Cadmium (Cd)
µg/L
<0.13
1.2
1.6
0.81
0.3
0.39
0.27
0.13
mg/L
205
110
210
230
55
28
28
3
Dissolved Chromium (Cr)
mg/L
<0.025
0.022
0.06
0.091
0.0087
0.015
0.0088
0.025
Dissolved Cobalt (Co)
mg /L
<0.0075
0.0011
0.0034
0.007
0.00047
<0.0075
<0.0075
0.0075
Dissolved Copper (Cu)
mg/L
<0.005
0.032
0.031
0.017
0.011
0.019
0.015
0.005
Dissolved Iron (Fe)
mg/L
0.7
41
85
230
17
1.5
<0.6
0.6
Dissolved Lead (Pb)
mg/L
<0.005
0.015
0.027
0.049
0.005
0.0025
0.0014
0.005
Dissolved Lithium (Li)
mg/L
2.2
<0.2
<0.2
<0.2
<0.2
<0.2
<0.2
0.2
Dissolved Magnesium (Mg)
mg/L
255
12
14
16
14
<2
<2
2
Dissolved Manganese (Mn)
mg/L
0.41
0.88
2.8
3.8
0.9
<0.04
<0.04
0.04
Dissolved Molybdenum (Mo)
mg/L
<0.005
0.0012
0.0024
0.0046
0.00093
0.0037
0.0035
0.005
Dissolved Nickel (Ni)
mg/L
0.016
0.0069
0.019
0.05
0.0049
<0.013
<0.013
0.013
Dissolved Phosphorus (P)
mg/L
<1
<1
<1
<1
<1
<1
<1
1
Dissolved Potassium (K)
mg/L
67.0
<3
<3
<3
<3
7
7.7
3
Dissolved Selenium (Se)
mg/L
0.0074
<0.005
0.00077
0.00072
<0.005
<0.005
<0.005
0.005
Dissolved Silicon (Si)
mg/L
2.5
2.7
3.6
4.1
2.6
1.9
1.9
1
Dissolved Silver (Ag)
mg/L
<0.0025
<0.0025
<0.0025
<0.0025
<0.0025
<0.0025
<0.0025
0.0025
Dissolved Sodium (Na)
mg/L
8,300
100
120
180
180
2200
2200
25
Dissolved Strontium (Sr)
mg/L
14
3.8
8.6
9.5
0.98
0.35
0.26
0.2
Dissolved Sulphur (S)
mg/L
5.7
1500
760
520
15
13
12
2
Dissolved Thallium (Tl)
mg/L
<0.005
<0.005
<0.005
0.00058
<0.005
<0.005
<0.005
0.005
Dissolved Tin (Sn)
mg/L
<0.025
<0.025
0.0071
0.01
0.0013
<0.025
<0.025
0.025
Dissolved Titanium (Ti)
mg/L
<0.025
0.015
0.035
0.072
0.0048
<0.025
<0.025
0.025
Dissolved Uranium (U)
mg/L
<0.0025
0.0003
0.00042
0.00045
0.00026
<0.0025
<0.0025
0.0025
Dissolved Vanadium (V)
mg/L
<0.025
0.0059
0.011
0.017
0.0016
<0.025
<0.025
0.025
Dissolved Zinc (Zn)
b
mg/L
<0.075
2.9
53
480
0.33
0.28
0.15
0.075
Parameter
Units
UF Effl.
SU
Dissolved Aluminum (Al)
pH
b
Onsite pH
Refer to Appendix D for the detailed CIP procedure
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MDL
Impact of Flux Rate
Flux rate of a membrane is a measure of the volume of water passing through a unit
area of membrane surface. At high flux rates, more water is being forced through the
membrane, so it is expected that fouling rate would also be elevated. UF flux rate was
normalized to 20°C in order to permit comparison of membrane performance as the
water temperature varied. Normalization was carried out in accordance with the USEPA
Membrane Filtration Guidance Manual (EPA 815-R-06-009) as recommended by the
membrane manufacturer.
The UF system was run at normalized flux rates as high as 105 lmh (Figure 8 and Figure
10) to maximize recovery, but ultimately was reduced to a more optimal level of 53 lmh
in order to permit use of standard cleaning methodologies and frequencies.
Operation at the lower flux rate permits longer run times between CEBs, but ultimately
requires a larger UF system and capital expenditure. UF backwash waste essentially
contains basal water with elevated levels of coagulated solids, which should not
represent an issue for reintroduction into the basal storage pond, as solids would
naturally separate out in the pond. It is anticipated that UF reject can be directed back to
the basal water storage pond, such that management of UF waste streams is not a
significant issue. If waste stream management is not a significant issue, then the primary
impact of system flux and recovery is on equipment sizing.
Backwash Effectiveness
Backwashing is a physical cleaning of the membrane that should result in a significant,
though typically short-lived, improvement in TMP and membrane permeability. The goal
of backwashing is to maintain performance and extend the timeframe required between
chemical cleaning cycles such as CEBs and CIPs.
In this pilot, backwashes were less effective at restoring performance than anticipated.
During the initial part of the study, marginal but somewhat visible decrease in UF TMP
could be observed with each backwash. However, after sustained operation and
potential build-up of scalants on the membrane surface, fouling rate and TMP were not
observed to decrease substantially with the backwashes. Nevertheless, backwashes
were continued to be used because the backwash cycle was the primary mechanism
used to remove accumulated solids in the UF vessel and maintain them at manageable
levels. During a production cycle all flow was forced into the UF vessel and the only flow
out was from water passing through the UF membrane, such that solids concentration in
the membrane vessel continually increased during a production cycle (dead-end
operation). Ultimately, when chemical dosing was not optimized during the pilot,
backwashing was not an effective mitigative measure to remove fouling from the
membranes.
UF filtrate was used as the source of backwash water during the pilot. Brief
experimentation with sodium metabisulphite (for enhanced manganese removal) added
to backwash water was carried out in late September and is presented in Figure 11. No
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appreciable improvement in backwash effectiveness was observed relative to UF filtrate
alone. Low doses of sodium hypochlorite (for enhanced organics removal) in
combination with UF filtrate were also examined, with no benefit observed either.
Brief experimentation was carried out using RO permeate for backwash water in order to
identify if a higher quality of water would improve backwash effectiveness (Figure 11).
No improvement in backwash effectiveness was observed using RO permeate relative to
UF filtrate.
Figure 11. Comparison of backwash effectiveness using UF filtrate, UF filtrate with
100 mg/L of sodium metabisulphite and RO permeate as source water
Impact of Manganese Concentration
Manganese concentration was targeted primarily due to its anticipated impact on the RO
membrane as opposed to the UF membrane. The initial UF filtrate target for Mn was
0.05 mg/L, while a common industry standard maximum for RO influent is 0.1 mg/L of
Mn. Due to the complexities of oxidizing and precipitating Mn out of solution as detailed
in previous sections, these targets were not consistently met. Precipitated Mn was
removed from solution by the UF, while dissolved Mn passed through the membrane. As
shown in Table 12, dissolved Mn concentrations in the UF filtrate ranged from 0.1 to
0.78 mg/L.
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Manganese was not significantly elevated in the UF CIP solution relative to iron and
other common scalants. This indicates that manganese was not the governing factor in
the fouling issues encountered with the UF membrane system.
Impact of UF Influent pH
Analysis of pH impact on UF fouling is possible due to the dosing strategy change that
occurred on August 16th. Elevated pH was attempted at approximately 7.4 to 7.6 in order
to minimize manganese solubility, but this was ultimately unsuccessful. High pH
increased the impact of the high alkalinity of the water, which impacted the plant and UF
membranes through CaCO3 precipitation. Reduction of the pH correlates to a negative
impact on UF TMP development, TMP baseline and permeability (Figure 12). However,
the pH change occurred at the same time as an increase in UF flux rate and a major
change in chemical dosing strategy, which involved a reduction in permanganate dosing
and deliberately not attempting to precipitate out all the manganese upstream of the UF.
Due to the multiple changes that occurred alongside the pH change in the
oxidation/precipitation stage upstream of the UF on August 16th, several key factors
must be considered in order to identify the overall impact. Key considerations are
manganese, iron, and calcium carbonate solubility and residuals, coagulant dosage and
potassium permanganate dosage. The SDSI was positive at elevated pH of 7.5,
indicating calcium carbonate scaling potential. At neutral UF effluent pH, the SDSI was
slightly negative, indicating scaling was not theoretically expected. Each of the above
noted factors contributing to scaling are discussed further below.
Baseline TMP (psi)
Time Between CEBs (Hrs)
Flux Corrected to 20°C (lmh)
40
UF Feed pH ~7.0
KMnO4 Dosage 1-1.5 mg/L
FeCl3 Dosage ~7 mg/L
UF Feed pH 7.4-7.5
KMnO4 Dosage 5-7 mg/L
FeCl3 Dosage ~7 mg/L
110
30
100
25
90
20
80
15
70
10
60
5
50
0
30-Jul
04-Aug
09-Aug
14-Aug
19-Aug
24-Aug
29-Aug
03-Sep
Flux
TMP & Time Between CEBs
35
120
40
08-Sep
Figure 12. Plot of TMP and normalized permeability at various influent pH settings
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Metal solubility and the ability to prevent metal precipitation on the surface of the UF
membrane were critical to achieving acceptable system performance. Manganese
solubility was discussed in depth and it was determined that the inability to obtain
consistently low Mn residuals in the UF filtrate was due to complexation reactions
causing an increase in Mn solubility. CIP solution analysis does not indicate Mn
precipitation on the UF was the governing factor in UF performance.
Figure 13 shows the point of minimum Fe3+ solubility at pH 8.8, with solubility increasing
as pH is reduced from that point. The target of the pilot was to precipitate iron ahead of
the UF in order to minimize residual onto the RO system. Operation of the oxidation
stage upstream of the UF at the higher range of pH experimented with has a clear
benefit in lowering iron residuals in UF effluent. However, the benefits provided from the
slightly reduced iron concentration in UF effluent must be weighed against the negative
aspects of operating at elevated pH.
pH range
observed in pilot
Figure 13. Solubility plot for ferric iron relative to pH
Calcium carbonate solubility is significantly increased as pH decreases from a pH of 11.
Scaling tends to increase as pH increases for the operating range experienced in the
pilot (Figure 14). Significant CaCO3 scaling was observed throughout the pilot
infrastructure and calcium was present in elevated concentrations in the CIP solution.
Calcium carbonate scaling was an issue for the UF and the pilot as a whole, but the
amount of scaling would be more significant at the high pH operational setting. In this
pilot CaCO3 was not targeted for precipitation ahead of the UF system, and was
addressed through the use of anti-scalant chemicals ahead of the RO system. Chemical
dosing upstream of the UF was not designed to address CaCO3 as CEBs were
anticipated to be sufficient to remove deposited material. Softening and degasification
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were initially contemplated for inclusion in the process train, but were ultimately not
included due to the extremely high chemical consumption anticipated.
In the CIP solution analysis, iron was found in significantly elevated concentrations,
warranting further analysis. While operating with the original dosing strategy, with both
elevated pH and high coagulant and permanganate dosages, iron residual in UF filtrate
was consistently below the detection limit (0.6 mg/L as Fe) as visible in Figure 15. In
contrast, when the revised dosing strategy was employed with neutral pH in the
oxidation/precipitation stage, iron residual in the UF filtrate was frequently elevated to
near the 1 mg/L range. At the neutral pH, influent iron levels remained similar and
coagulant dose range was used at both high and low levels with similar results. Minimum
ferric solubility occurs at pH 8.8, which supports the observation of higher dissolved iron
levels in UF filtrate at lower pH values.
Approximate ranges in pilot :
pH: 6.5 to 8.0
log (Ca): -2.28 to -2.40
CT: 0.014 to 0.030
Figure 14. Solubility plot for CaCO3 at various calcium and dissolved carbonic
acid concentrations relative to pH
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Raw Fe (mg/L)
UF Effluent Fe (mg/L)
Coagulant Dosage (mg/L as Fe)
10
9
Low Fe residual
Elevated Fe residual
pH approx 7.4 to 7.6
pH approx 6.8 to 7.0
pH 7.4
to 8.0
Coagulant Dose; Total Iron Concentration
8
7
6
5
4
3
2
1
0
01-Jul
08-Jul
15-Jul
22-Jul
29-Jul 05-Aug 12-Aug 19-Aug 26-Aug 02-Sep 09-Sep 16-Sep 23-Sep 30-Sep
Figure 15. Comparison of residual iron in untreated and UF filtrate water at various
coagulant doses and pH ranges in the oxidation/precipitation stage
Analysis of coagulant dosing relative to pH and UF filtrate residuals provides insight into
the impact of oxidation/precipitation operating pH on UF performance. Addition of ferric
chloride (FeCl3) coagulant upstream of the UF was intended to destabilize colloidal
particles and increase the average size of particulate coming in contact with the
membrane surface. A secondary objective identified initially was for increased removal
of organic material and a concurrent reduction in organic fouling of the UF. However,
organic fouling was determined to not be significant as identified in the autopsy report
(Appendix E).
Several changes to coagulant dosing were made over the course of the pilot (Figure 16).
It is clear that high coagulant dose alone is not responsible for elevated fouling rates as
dose was maintained in the 6.0 to 7.5 mg/L (as Fe) range from the start of the trial until
roughly a week after the operating pH was lowered to the 6.8 to 7.0 range. Fouling rate
was stable during this period initially, but started to increase only after the pH change
was made. During the period of exponential fouling rate increase in early September, the
coagulant dose was increased from low levels (approximately 1.5 mg/L as Fe) in an
attempt to counteract the rise, but fouling rate continued to increase. Stopping all
coagulant dosing was briefly experimented with, but mostly using new UF membrane
modules (initiated in order to provide sufficient flow to operate the downstream RO
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system due to flow limitations caused by operating the UF system at the optimized UF
flux of 40 lmh). Pilot data indicates iron fouling on the membrane is more significant at
the neutral pH than the elevated pH initially used in July and early August. Ferric
chloride dose is secondary relative to this consideration, but it is logical to conclude that
minimizing the ferric chloride dose would assist in reducing iron fouling on the
membrane surface and therefore result in the reduction of overall fouling rate and
maximization of UF system recovery. However, operation at elevate pH introduces
issues with calcium carbonate scaling as discussed previously.
Permanganate dosing levels and philosophy changed substantially through the pilot
(Figure 16). Initial attempts to dose the oxidant to achieve a target ORP level proved
ineffective. When the major change in dosing strategy was carried out on August 16th,
permanganate was dosed at a constant low dose typically in the 1.0 to 1.5 range. High
and low permanganate doses (regardless of pH) did not reliably produce low Mn levels
in the UF filtrate. The reduction in permanganate dosing occurred at the same time pH
was reduced, such that their impacts cannot be fully separated. However, fouling rate
changes appear to more closely follow pH changes than permanganate dosing changes
for periods such as the high pH period between September 27th and 30th (Figure 16).
Baseline TMP (psi)
Coagulant Dose as Fe (mg/L)
Permaganate Dose (mg/L)
80
60
TMP
50
Flushing system of
pond organics
pH 7.4-7.6
10.5
Major change in
dosing strategy
pH 6.8-7.0
9.0
pH 7.6-8.0
CIP
Crossflow
pH 6.8-7.0
40
7.5
6.0
30
New
modules
4.5
20
3.0
10
1.5
0
0.0
20-Jun 30-Jun 10-Jul 20-Jul 30-Jul 09-Aug 19-Aug 29-Aug 08-Sep 18-Sep 28-Sep 08-Oct 18-Oct
Figure 16. TMP development rates for individual UF runs at different coagulant
and permanganate doses
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Chemical Dose
70
12.0
Pond
Water
Trial
Impact of Not Softening Upstream of the UF
Initially, the basal water treatment process train included both a degasification (alkalinity
reduction) step as well as a softening process step upstream of the UF system. Prior to
initiation of pilot testing, a review of the advantages and disadvantages of including
these process steps was carried out and the decision was made by CNRL to exclude
them from pilot testing. The primary disadvantage in including these processes is the
large volumes of chemicals (sulphuric acid, caustic soda and lime) required. This initial
configuration would have required three significant pH adjustments to permit
degasification (low pH), softening (high pH) and finally neutral pH going into the RO
system. Based on preliminary modeling of the system it was determined that the
pretreatment provided by oxidation/ coagulation and the UF in combination with use of
appropriate anti-scalant chemicals would be sufficient pre-treatment for piloting the RO
system.
Not carrying out softening upstream of the UF system results in a trade-off between
different negative impacts that occur when operating at elevated (7.6 to 8.0) to neutral
(approximately 6.9 to 7.0) pH in the oxidation/precipitation stage. At elevated pH the iron
oxidation reaction is more easily controlled such that precipitation occurs ahead of the
membrane instead of scaling on the membrane surface. Elevated pH also tended to
reduce iron concentrations in the UF filtrate. However, in the pilot when the elevated pH
scenario was used, there were widespread issues with CaCO3 precipitation throughout
the pilot plant infrastructure (due to the high scaling potential of the water as evidenced
by the high SDSI value of 0.56 at a pH of 7.5 and water temperature of 15°C as
experienced in the pilot trials). Even if water temperature was at the temperature it
comes out of the wellhead (reported to be approximately 5˚C by CNRL) SDSI calculates
to be 0.37, which indicates high scaling potential. This resulted in repeated issues with
scaling up of equipment such as pumps and the Amiad pre-screening filter (standard
equipment used upstream of UF systems to protect UF membranes from damage),
though only a minor impact on UF performance.
At neutral pH, the calcium carbonate precipitation was reduced such that it was no
longer a governing operating factor. At a pH of 6.9 and water temperature of 15°C (as
observed in the pilot trials), the SDSI was approximately -0.04, indicating calcium
carbonate scaling was not theoretically expected. A new concern relating to iron
precipitation (among other compounds) on the UF membrane surface began to be a
significant factor which resulted in a dramatic increase in observed fouling rate and
reduced intervals between required CEBs.
The major benefit of not including softening in the treatment train is the elimination of the
need for softening infrastructure as well as significant ongoing chemical dosing costs.
Significant reduction in sulphuric acid, caustic soda and lime were achieved, though
additional anti-scalant chemical was required.
Cross Flow versus Dead End UF Operation
The UF pilot system was designed for dead end operation and was operated in this
manner for the majority of the basal piloting period. Dead end operation was initially
deemed acceptable for this application as the untreated basal water contained
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consistently low solids concentrations. However, chemistry of the UF influent water
resulted in higher than desirable fouling rates, necessitating experimentation with cross
flow operation in the final weeks of basal piloting. Cross flow was obtained by
recirculation of 25% of influent flow back to the coagulation tank from October 1st to 2nd.
Introducing a cross flow stream causes scouring action across the surface of the UF
membrane. The scouring acts to physically remove a portion of the fouling material that
has deposited on the membrane and theoretically increases the timeframe between
CEBs or CIPs. Figure 17 clearly shows improved TMP and normalized permeability after
the transition from dead-end to cross-flow UF operation. During this period the flux rate
was set at a normalized flux of approximately 53 lmh (with some minor variations due to
temperature fluctuations). Cross flow operation is a more optimal operational condition
than dead end operation for this treatment application. The membrane used in this pilot
is primarily intended for low solids, dead end applications. Alternative membrane types
designed for cross flow operation should be considered when scaling up the results from
this pilot study.
Figure 17. Plot of TMP and permeability for dead-end and cross-flow UF operation
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Comparison of Pond and Well Water on UF Fouling
Pond water use was explored in the pilot due to the presumed benefits of water
performance when pond water was fed to the pilot infrastructure (Figure 18). The TMP
increase rate and baseline TMP dramatically increased upon introduction of pond water
into the system. After extensive flushing of the system and resumption of using wellhead
water as feed water, TMP increase rates returned to levels similar to before the pond
water was introduced.
Key differences between untreated basal water taken from the pond relative to basal
water taken from the wellhead are as follows:




easily oxidized compounds have been oxidized and in some cases precipitated
out of solution
reduced dissolved hydrogen sulphide
algae in the water was significant and easily observable in both water at the pilot
plant and in the source pond
organic material (algae) were most probably responsible for the immediate and
rapid decrease in UF performance when basal water source was changed from
the wellhead common header to directly from the pond. Algae was visibly present
in significant quantity in the basal water pond at the time of the trial
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Figure 18. Comparison overview of flux, run length, baseline TMP and TMP
increase rate for piloting periods when pond water versus wellhead
water were used as feed water for the pilot
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5.3
Reverse Osmosis (RO)
Reverse Osmosis provides the highest level of treatment of all membrane types. The
microscopic pores reject organic compounds salts and minerals. In designing this pilot it
was expected that RO would be capable of producing water of sufficient quality to
achieve project objectives. However, the level of pre-treatment required is typically high
for this technology.
The initially proposed pre-treatment train included degasification with sulphuric acid
followed by softening upstream of the UF system. Based on a review of the untreated
basal water quality and the significant cost savings in chemical usage, the upstream
treatment was reduced to chemical oxidation, coagulation and UF treatment followed by
pH reduction, anti-scalant dosing and ORP reduction immediately upstream of the RO
membranes. With the revised pre-treatment train, the anticipated challenge was running
the RO system at a high recovery while at the same time managing fouling with standard
cleaning methodologies and frequencies.
Operating Conditions
The pilot RO system consisted of a three stage design with fiberglass pressure vessels
containing three 102 mm (4 inch) diameter, 1016 mm (40 inch) long elements. Detailed
specifications on the membranes are provided in Table 15. Provision of adequate flow
rates through a pilot sized system resulted use of a three stage design for the pilot study.
System configurations and operating ranges used over the course of the pilot are
provided in Table 16 and Figure 19. Detailed plots of RO system operating parameters
over the entire course of the pilot are located in Appendix C.
Table 15. Overview of RO membrane specifications
Parameter
Membrane Model
Membrane Type
Maximum Operating Temperature
Maximum Operating Pressure
Maximum Pressure Drop
pH Range, Continuous Operation
pH Range, Short Term
Maximum Feed Silt Density Index
Feed Chlorine Tolerance
Membrane Element Active Surface Area
Stabilized Salt Rejectiona
Max Feed Flow Ratea
Details
DOW Filmtec SW30-4040
Polyamide Thin-Film Composite
45 °C
6895 kPa (1000 psi)
103 kPa (15 psig)
2 to 11
1 to 13
SDI 5
<0.1 mg/L
7.4 m2 (80 ft2)
99.4%
3.6 m3/hr (16 gpm)
a
Based on standardized test conditions as follows: 32,000 mg/L NaCl, applied pressure of 800 psig, 25C, and 8%
recovery rate
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Table 16. Overview of RO system operating conditions
Parameter
Number of Stages
Number of elements per pressure vessel
Membrane Array (50% recovery)
Membrane Array (60% recovery)
Recovery
Feed Pressure
Permeate Pressure
Influent Flow
Operating flux (normalized to 25°C)
Value
3
3
3 (stage 1) X 2 (stage 2) X 1 (stage 3)
2 (stage 1) X 1 (stage 2) X 1 (stage 3)
50% and 60%
3447 to 6895 kPa (500 to 1000 psi)
Stage 1: 0 to 414 kPa (0 to 60 psi)
Stage 2 & 3: 0kPa (0 psi)
3.6 m3/hr (16 gpm)
Overall: 7 to 46 lmh (4 to 27 gfd)
Operating pressure (50% recovery)
Stage 1: 4 to 50 lmh (2 to 29 gfd)
Overall: 3613 to 4737 kPa (524 to 687 psi)
Operating pressure (60% recovery)
Stage 2: 3530 to 4537kPa (512 to 658 psi)
Overall: 4633 to 6419 kPa (672 to 931 psi)
Time between CIPs
Antiscalant chemical
Antiscalant dose range
Biocide chemical
Cleaning Agents
Approx. 1 to 2 months
Hydrex 4102 - Liquid
2.7 – 7.6 mg/L
Nalco Permaclean PC-11 - Liquid
Citric Acid,
Sodium Hydroxide,
Sodium Metabisulphite
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50% Recovery
Configuration
Stage 1
Stage 2
Stage 3
RO
Influent
Permeate
Concentrate
60% Recovery
Configuration
Stage 1
Stage 2
Stage 3
Permeate
Concentrate
RO
Influent
Figure 19. Simplified view of RO system configurations at 50% and 60% recovery.
Flux and pressures for each stage are provided in Table 16, and
detailed plots in Appendix C
Flux rate is a key parameter in the design of a RO treatment system. RO system flux
rates in this report have been normalized to 25°C in accordance to ASTM standard
D4516 - 00 (Standard Practice for Standardizing Reverse Osmosis Performance Data)
and the membrane supplier technical manual. Initial flux rate for the system was set at
around 14 lmh (8 gfd), with notably high flux rates through the third stage membranes
(Figure 21 and Figure 22). During this period, overall recovery was determined to be in
the 25 to 30% range due to a malfunctioning reject flow meter. On August 11th, the
recovery rate was increased to the target rate of 50%, at an influent flow of roughly 16
gpm and an overall normalized flux of around 20 to 22 lmh (12 to 13 gfd). A recovery
rate of 60% was operated from October 4th to 8th using a 3 stage, 2 X 1 X 1 pressure
vessel array at an overall normalized flux of approximately 43 lmh (25 gfd).
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Figure 20. Overview of RO flux rate and normalized (to 25°C) flux rate over the
course of the pilot
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Figure 21. Overview of normalized (to 25°C) RO flux rate broken down by stage
over the course of the pilot
Chemical Usage and Operational Settings at Optimal Conditions
A summary of operational settings and chemical usage for operation of the RO unit at
optimal conditions is provided in Table 17.
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Table 17. Overview of RO system related chemical usage and operational settings at optimal conditions
Parameter
Sulphuric acid dose
(to achieve 6.5 pH)
Optimal Setting
= 700 to 800 mg/L as H2SO4
Reasoning
= 160 to 200 mg/L
Anti-scalant dose
(50% recovery)
Anti-scalant dose
(60% recovery)
Biocide dose
= 6.6 mg/L
-Dose was based on maintaining an RO feed ORP value of
100 to 150 mV as recommended by the equipment
vendor.
-Maintaining manganese in a reduced dissolved form was a
key consideration in dosing metabisulphite as manganese
in a dissolved and reduced state did not act as a
significant RO foulant. Higher than industry standard Mn
levels were often present in the RO feed so this was a
significant consideration. Lower doses of metabisulphite
may be possible.
-Alternate anti-scalant chemicals could be considered to
address the iron scaling issues identified in this study
-Alternate anti-scalant chemicals could be considered to
address the iron scaling issues identified in this study
-Weekly application of biocide was carried out as a
preventative measure
-Biological growth in the RO system was not observed in
this study.
-The short duration of the pilot study may not have given
biological activity in the system sufficient time to establish
Time between CIPs
Flux rate normalized to 25°C
(50% recovery)
= 1 to 2 months
= 23 lmh
= 6.6 mg/L
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Treated water quality from an RO unit is highly dependent on parameters such as
recovery, temperature and influent water quality. Water temperature was relatively stable
throughout the study as is typical with groundwater. Brief temperature excursions were
primarily due to limitations of the pilot facility. For example, there was a brief period in
August where water temperature increased to above 20˚C, due to an operations
shutdown resulting in extended hold times in the untreated water storage tanks
combined with high ambient temperatures. Two recovery settings of significance (50%
and 60%) were used and are worthy of analysis. However, the vast majority of the study
was focused on the 50% recovery as this was originally identified as the primary target
for the pilot. The 60% recovery was examined briefly at the end of the study in an
attempt to push the operational limits of the technology. Influent water quality was
relatively stable throughout the study, but did undergo a reduction in TDS at the latter
portion of the study, when the 60% recovery setting was examined.
High TDS levels in the basal water and RO feed water result in high osmotic pressures
and resulting high feed water pressures. The resulting high osmotic pressure was the
primary factor that limited the achievable RO recovery levels to the range of 50 to 60%
observed in the pilot. Scaling at pH of 7.6 a higher contributed to scaling during the pilot.
However, operation at a pH below 7.0 and maintaining manganese in a reduced state
largely mitigated the impact of scaling on achievable RO recovery.
Normalized Salt Rejection (NSR)
Normalized salt rejection is a standard parameter used in assessing performance of RO
membranes. NSR takes into account the effect of changes in temperature, recovery,
feed TDS and permeate flow on salt passage. Declines in NSR over time can indicate an
issue with membrane integrity or fouling. Ideally the NSR remains relatively stable over
the course of operation. The initial two weeks of RO operation displayed a higher
normalized salt rejection (NSR) than the remainder of the pilot study (Figure 22). This is
typical of the breaking in period for an RO membrane. In mid-August, there were
significant deviations in NSR, which were later attributed to improperly set valves in the
RO system that were permitting a small portion of RO reject water to pass through to the
permeate flow. During this period, elevated TDS was observed in the permeate. Once
this issue was resolved, TDS levels dropped and NSR stabilized to between 98% and
99%. Based on the NSR trend, the membrane maintained its treatment integrity
throughout the course of the pilot study.
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Figure 22. Overview of Normalized Salt Rejection (NSR) and Normalized Salt
Passage (NSP) over the course of the pilot
50% Recovery
Table 18 summarizes the RO treatment performance at 50% recovery. Organic material
in UF filtrate was below detection limits, but due to the high salinity of the water, the
detection limit for TOC was 13 mg/L. In RO permeate, salinity is greatly reduced which
eliminated the detection limit issue. In RO permeate the TOC was reduced to 0.3 mg/L
on average. Naphthenic acids were reduced to < 1 mg/L from 3.5 mg/L in the untreated
basal water. UF treatment did not appreciably reduce naphthenic acid concentration.
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recovery
Average
(ND=
50%
MDL)
Min
psi
639
624
858
SU
5.4
4.7
µS/cm
770
SU
µS/cm
Parameter
Feed Pressure
(on-line
instrumentation)
pH (onsite)
Conductivity (onsite)
pH
Conductivity
Total Dissolved
Solids
Total Organic
Carbon
Naphthenic Acids
Total Sodium (Na)
% Reduction Relative to
Std.
Dev
# of
Obs
6.7
0.4
37
448
1652
273
39
5.90
593
5.47
220
6.44
810
0.35
169
9
9
0%
0%
mg/L
304
120
430
90
9
mg/L
0.3
<0.5
<0.5
0.0
mg/L
mg/L
0.5
123
<1
87
<1
160
0.0
25
Units
Max
%ND
MDL
UF
Effl
RO Infl
Raw
0
1
98.4%
98.4%
0%
10
98.6%
98.6%
9
100%
0.5
95.0%
96.4%
9
9
100%
0%
1
25
95.0%
73.7%
98.4%
Dissolved solids were the primary target for reduction by the RO system. Permeate
conductivity was reduced to 594 µS/cm, a 98.4% reduction relative to UF filtrate and
untreated basal water. TDS was reduced to 304 mg/L on average, with a standard
deviation of 90 mg/L.
Sodium was also a primary target for reduction. Total sodium was reduced to an
average of 123 mg/L (SD = 25 mg/L) in the RO permeate at a recovery of 50%. This
represents a 98.4% reduction relative to the dissolved sodium concentration in untreated
basal water.
At all times, the RO permeate quality stayed well below the maximum targets of 1000
mg/L for TDS and 500 mg/L sodium (Table 18).
60% Recovery
The RO was operated at 60% recovery at the beginning of October; during a period
where influent temperature was lower than average for the piloting period. Over the 50%
recovery period, average RO influent temperature was 16.2°C, while during the 60%
recovery period, average temperature was 13.0°C. As temperature decreases, diffusion
activity across the membrane also decreases which typically results in an increase in
rejection by the membrane. In order to confirm that there are no issues with the
membrane and results are accurate, the Normalized Salt Rejection (NSR) trend can be
examined for anomalies. The NSR accounts for changes in feed water temperature and
recovery changes in addition to salt concentration gradient changes. Comparing the two
periods, the NSR was relatively constant in the 97% to 98% range before and after the
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transition from 50% to 60% rejection (Figure 22). This indicates that the membrane
performed as expected in terms of salt rejection, with variations in permeate TDS and
conductivity attributable to the changes in temperature and recovery.
At all times, the RO permeate quality stayed well below the maximum targets of 1000
mg/L for TDS and 500 mg/L sodium (Table 19).
recovery
Parameter
Feed Pressure
(on-line
instrumentation)
pH (on-site)
Conductivity(onsite)
pH
Conductivity
Total Dissolved
Solids
Total Organic
Carbon
Naphthenic Acids
Total Sodium (Na)
Average
(ND=
50%
MDL)
Min
psi
856
672
931
SU
4.8
4.7
µS/cm
471
SU
µS/cm
% Reduction Relative to
Std.
Dev.
# of
Obs.
4.9
0.1
5
374
611
117
5
5.43
5.30
5.53
0.12
3
0%
0
410
360
480
62
3
0%
1
mg/L
207
180
250
38
3
0%
10
mg/L
2.3
<0.5
<0.5
3.6
3
100%
0.5
mg/L
mg/L
0.5
<1
<1
0.0
3
100%
1
90
81
95
8
3
0%
25
Units
Max
%ND
MDL
UF
Effl
RO
Infl
Raw
98.9%
98.9%
98.9%
99.1%
64.1%
64.1%
64.1%
86.1%
87.8%
98.9%
98.8%
RO Reject Water Quality
RO reject disposal is an important consideration, which was independently investigated
by Veolia using reject water produced during this pilot. The quality of the RO reject is
critical for designing related treatment processes. The methodology used for the ZLD
testing was further treatment of the reject by evaporators and crystallizer. Details of this
testing is presented in Appendix F of this report. Table 20 and Table 21 provide a
summary of RO reject water quality characteristics for 50% and 60% recovery operation
during the course of this pilot.
At a 50% recovery, it is expected that the concentration factor for most compounds
would be 2.0 times the RO influent water. At a recovery of 60%, concentration factor
should theoretically be 2.5.
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Table 20. Summary of RO reject water quality characteristics at 50% recovery
Min
Max
Std.
Dev.
# of
Obs.
SU
µS/cm
SU
µS/cm
mg/L
Average
(ND=
50%
MDL)
6.9
65,687
7.49
65,222
43,222
6.6
41,600
7.09
64,000
42,000
7.8
68,900
7.97
66,000
44,000
0.3
4,467
0.26
667
667
mg/L
4,944
4,100
5,900
mg/L
3
<5
mg/L
mg/L
mg/L
mg/L
6,033
3
3
2,567
mg/L
Parameter
Units
%ND
MDL
C.F.
pH (on-site)
Conductivity (on-site)
pH
Conductivity
CaCO3)
Alkalinity (PP as
CaCO3)
Bicarbonate (HCO3)
Carbonate (CO3)
Hydroxide (OH)
Hardness (CaCO3)
(C)
Naphthenic Acids
Total Calcium (Ca)
Dissolved Calcium
(Ca)
Dissolved Magnesium
(Mg)
37
39
9
9
9
0%
0%
0%
0
1
10
1.81
1.96
629
9
0%
5
2.35
<5
0.0
9
100%
5
5,000
<5
<5
1,800
7,200
<5
<5
2,800
760
0.0
0.0
308
9
9
9
9
0%
100%
100%
0%
5
5
5
0.5
2.32
7
<13
15
2.9
9
89%
13
1.46
mg/L
mg/L
7
337
<1
300
9
370
2.8
23
9
9
11%
0%
1
3
2.24
mg/L
337
260
370
37
9
0%
3
2.10
mg/L
420
420
420
1
0%
2
2.14
C.F = Concentration factor
Table 21. Summary of RO reject water quality characteristics at 60% recovery
Parameter
Units
pH (on-site)
Conductivity (on-site)
pH
Conductivity
CaCO3)
Alkalinity (PP as
CaCO3)
Bicarbonate (HCO3)
Carbonate (CO3)
Hydroxide (OH)
Hardness (CaCO3)
(C)
Naphthenic Acids
Total Calcium (Ca)
Total Potassium (K)
Dissolved Magnesium
(Mg)
SU
µS/cm
SU
µS/cm
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
Average
(ND=
50%
MDL)
6.6
81,120
7.3
78,667
55,333
Min
Max
Std.
Dev.
# of
Obs.
6.5
79,600
7.0
78,000
55,000
6.7
82,200
7.6
79,000
56,000
0.1
1,028
0.28
577
577
4,033
3,800
4,400
3
4,867
3
3
3,633
<5
4,600
<5
<5
3,600
21.3
12.7
487
160
477
593
%ND
MDL
C.F.
5
5
3
3
3
0%
0%
0%
0
1
10
2.19
2.52
321
3
0%
5
2.69
<5
5,300
<5
<5
3,700
0.0
379
0.0
0.0
58
3
3
3
3
3
100%
0%
100%
100%
0%
5
5
5
5
0.5
<13
12.0
470
150
470
25.0
13.0
500
170
480
4.7
0.6
15
14
6
3
3
3
2
3
33%
0%
0%
0%
0%
13
1
3
3
3
580
610
15
3
0%
2
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2.42
3.52
2.43
12.31
2.38
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Fouling Rate and Cleaning Effectiveness
Particulate fouling was not considered a major factor for the RO due to the reliable and
near complete solids removal by the upstream UF system. SDI values in UF filtrate
averaged 0.9 with a standard deviation of 0.8. The RO system requires an SDI of less
than 5 at a minimum and ideally less than 3. SDI values underwent a small increase
after passage through the cartridge filter, pH adjustment and anti-scalant addition, with a
resulting average SDI of 2.8 (standard deviation 1.3). This could be due to post filtration
precipitation caused by pH changes or from the chemical additions themselves.
Regardless, SDI values for water contacting the RO membrane were consistently low.
Mineral scaling on the RO membranes was modelled using DOW software (ROSA) prior
to starting the pilot in order to identify priority compounds in the untreated water that
needed addressing. Initially, manganese was focused on as requiring reduction due to
anticipated negative impact on the RO membrane. However, observation of the RO
performance showed that if manganese was maintained in a reduced state (as gauged
by an ORP of approximately 100 to 200 mV) with pH reduction and anti-scalant addition,
scaling impact was minimal.
Biological fouling is always a consideration in RO systems, but no evidence of biological
fouling was observed in this pilot when feeding well water. As a preventative measure,
biocide was applied to the RO membranes on a weekly basis.
CIP Analysis
The chemical cleaning methodology used for the RO membrane was an infrequent
clean-in-place (CIP), which used a combination of citric acid and sodium metabisulphite
to address mineral scaling. The CIP was carried out in 3 stages in order to permit
isolation of each of the three RO system stages. All phases of the CIP were carried out
at low pH as the focus of the cleaning was removal of mineral scalants. A plot of the RO
system stage layout is provided in Figure 19. A sample of the cleaning solution used in
each of the three CIP steps was sent to an external lab for analysis of common scalants.
Only a single RO CIP was carried out during the pilot study.
The pilot strategy for an RO CIP had the following trigger events:
 Normalized permeate Flow (NPF) decrease by 10 to 15%
 Trans-membrane Pressure (TMP) drop increase by 15 to 25%
Iron was a significant foulant of the RO membranes and of all parameters examined in
the CIP cleaning solution, had the highest levels relative to RO influent concentrations
(Table 22). For all three stages in the system, iron had notable concentrations in the CIP
solution. It is likely that iron fouling could be addressed by modification of the type or
dose of anti-scalant. Most significant is that iron was present at extremely high levels in
all three RO stages indicating iron scaling had occurred throughout the RO system. All
other metals analysed for were only present in high concentration in the final RO stage,
which is where mineral scaling is expected to first manifest as an issue.
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Table 22. Overview of RO CIP cleaning solution analysis for key scaling
compounds
Iron
(total)
Manganese
(total)
Aluminum
(total)
Barium
(total)
Calcium
(total)
Magnesium
(total)
Strontium
(total)
mg/L
0.66
mg/L
0.56
mg/L
0.22
mg/L
1.7
mg/L
186
mg/L
248
mg/L
12.6
Phase 1
(Stage 3 focused)
26
26
2.5
7.7
1800
89
64
Phase 2
(Stage 2 focused)
95
1.6
2.2
1.7
660
9.1
8.7
0.54
0.27
100
67
6.8
8.4
1.2
2.4
1.4
630
12
9.7
Analyte
Units
RO Influent Avg
CIP Solution
Phase 3
(Stage 1 focused)
110
0.7
1.4
Control (unused)
2.4
0.26
0.6
Metabisulphite
CIP
23
2
1.3
Ratio of CIP Concentration to RO Influent Concentration
Phase 1
(Stage 3 focused)
3,965%
4,631%
1,133%
451%
969%
36%
509%
Phase 2
(Stage 2 focused)
14,488%
285%
997%
100%
355%
4%
69%
16,776%
366%
3,508%
125%
46%
356%
634%
272%
589%
32%
16%
82%
54%
36%
339%
3%
3%
5%
10%
19%
77%
Phase 3
(Stage 1 focused)
Control (unused)
Metabisulphite CIP
Calcium was present in very high concentrations in the CIP step that focused on the
third RO stage. Elevated levels were present in the second stage CIP solution, but were
negligible in the first stage CIP solution. The high levels of calcium are expected based
on the high hardness (average 1,429 mg/L as CaCO3) in the RO influent.
Manganese, aluminum, barium and strontium were all present in the CIP solution, with
the highest concentrations observed in the third stage CIP solution. Scaling is typically
most severe in the final RO element, which is what was observed in this pilot.
Normalized Permeate Flow
One of the primary tools available to gauge membrane performance is the analysis of
the normalized permeate flow (NPF) trends. Gradual reductions in the NPF can indicate
mineral scaling, colloidal or organic fouling. Rapid declines in NPF are commonly
associated with metal oxide fouling or biological fouling. In contrast, dramatic increases
in NPF can indicate structural damage or chemical attack on the membrane surface.
Normalized permeate flow takes into account the effect of changes in temperature and
net driving pressure (NDP) on the permeate flow. The NDP is calculated by subtracting
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average osmotic pressure and permeate back pressure from the average feed pressure.
Thus NPF is normalized for any changes in the NDP and changes in pressure drop
across the membrane element. If all other operating parameters remain constant, any
change in the average TDS concentration in the RO feed will affect the osmotic
pressure, which in turn will affect the NDP and NPF. However the salt passage or
permeate TDS concentration should not affect the NPF unless some underlying problem
like scaling or membrane damage is affecting both.
The initial three weeks of RO operation resulted in a rapid reduction in NPF due to
several factors. New RO membranes typically display extremely high but short lived
permeability which stabilize to levels that typically become the baseline permeability
(which is ideally returned to after standard CIP cleaning). Significant calcium carbonate
precipitation was observed in the CIP carried out on August 15th to 18th. This was
attributable to operation at elevated pH upstream of the UF and precipitation during
periods where the RO system was in standby. Subsequent to the CIP, operation at
neutral pH and flushing the RO with permeate upon shutdown, resolved the issue.
It is also possible to further isolate membrane fouling across the system by examining
NPF trends for each individual RO stage (Figure 23). After the RO CIP was completed
on August 19th, the second and third stages of the RO system were stable and flat. The
majority of variation in NPF occurred in the first stage for the system. The significant rise
in Stage 1 NPF from approximately September 27th to October 1st is noteworthy and
significant as it correlates with a major change in RO pre-treatment operation. During
this period, the oxidation dosing strategy was reverted back to what was pursued before
August 17th. The pH upstream of the UF was increased to greater than 7.5 and
permanganate dose increased to 5.0 mg/L in order to achieve complete oxidation and
precipitation of reduced species such as iron, sulphide and manganese. RO influent pH
was unchanged from before during and after this period due to sulphuric acid dosing
immediately upstream of the RO system. This indicates that the compounds being
oxidized, precipitated and eventually filtered out of solution by the UF have an immediate
impact on the RO membrane operation. External lab results for RO influent indicate nondetectable iron levels (< 0.6 mg/L), but higher than average manganese levels (0.19 to
0.78 mg/L) during this time span, and all other examined compounds remain at similar
levels to the immediately preceding period. Water quality results do not clearly identify
the compounds or species involved in this short term improvement in RO performance.
The fact that the change in NPF was focused on the first stage, and iron was the only
scaling compound measured in significant quantity in the Stage 1 CIP solution, indicates
that its tendency to foul the membrane at low concentrations may be involved.
The RO membrane autopsy indicated that the most significant deposits on the
membrane were iron and barium scaling, with much lower concentrations of sulphur and
phosphorous (Appendix E). The autopsy also confirmed that membrane deposits were
primarily inorganic. Only very low concentrations of organic material were measured in
the deposits.
The reduction in NPF on October 4th is due to increasing system recovery from 50% to
60%. Increased recovery is expected to impact NPF due to the resulting increase in RO
feed pressure and consequently the increase in Net Driving Pressure.
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Pilot data does not indicate irreversible fouling is occurring as full permeability recovery
was achieved from the CIP and operational pressures remained relatively stable during
regular operation. Improved performance can likely be achieved through the use of
reduced ferric coagulant doses upstream of the UF system. Alternatively, the antiscalant type and dosage could be adjusted to target iron fouling on the membrane.
Based on the data from this pilot, CIPs would likely be required on a monthly or
bimonthly basis. This is in line to slightly more frequent than would occur at a
desalination facility. However, the mineral composition and upstream chemical dosing of
the RO influent has been shown to be the governing factor in membrane fouling and
scaling, so the two applications are not directly comparable.
Figure 23. NPF of the RO membrane overall and for each stage
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Impact of Not Softening
Calcium carbonate was a significant scale-causing compound for the RO system due to
the high calcium hardness and alkalinity in basal water. Other notable hardness-causing
ions present in the influent in significant concentrations were iron, manganese, barium
and strontium.
Use of pH adjustment, ORP control and anti-scalant dosing during the pilot appeared to
effectively manage the impact of hardness causing ions on the membrane. Influent
pressure was relatively stable and the time interval before a CIP was required was within
industry standards. Based on this data, softening is not essential for operation of the
piloted treatment train. The scenario where softening may provide an advantage, is if the
high hardness in the RO reject was problematic for disposal of the waste stream. RO
reject disposal is examined in detail in Appendix F.
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6.
Summary and Conclusions
6.1
Treated Water Quality
The piloted treatment train proved capable of meeting the water quality objectives of
TDS < 1000 mg/L and sodium < 500 mg/L for all operational settings examined.
6.2














6.3
Operational Experiences and Lessons Learned
Untreated basal water is chemically unstable and requires equalization and
potentially aeration or mixing in order to achieve stability
Equalization and aging of the untreated basal water results in an increase in pH and
ORP with the precipitation of mainly sulfides. Aeration of the water substantially
accelerates this process. Any full scale design would need to account for any pH
change due to water equalization or aeration incorporated into the system
Bench scale chemistry did not always scale up to pilot scale, particularly for
oxidation/precipitation reactions
Chemical dosing (permanganate or metabisulphite) based on ORP measurement is
difficult to implement because of unstable nature of basal water and rapid fouling of
probe
Water usage in UF CEB and BW cycles had a dramatic impact on UF recovery
UF CEB frequency was governed by fouling rate
UF CIPs were effective in removing fouling material
More frequent cleanings are likely be required for the UF if operated in dead-end
mode relative to cross-flow mode
Pond water causes rapid fouling of UF due to algae and other organics
Untreated basal well water contains low organics and O&G levels making organic
fouling a lesser concern for membranes
Elevated Mn levels (relative to industry standard of <0.1 mg/L in RO feed water)
when maintained in a reduced state did not compromise RO performance, thus
targeting Mn removal may not be required for optimum membrane performance
Iron was identified as a major scalant for both UF & RO. Even small dosages of ferric
based coagulants at low pH conditions can deteriorate this situation
Hardness causing compounds in the basal water can rapidly scale up membranes
and associated equipment at high pH conditions
Overdosing of metabisulphite can cause higher than optimal sulphate levels in RO
feed that can potentially lead to increased Barium Sulfate scaling
Optimal Operational Settings Observed in Pilot (by Unit Process)
Oxidation/Precipitation/Coagulation
Parameter
Potassium permanganate
Ferric chloride
Optimal Setting
= 1 to 1.5 mg/L
= 0 to 2 mg/L as Fe
Sodium Hydroxide
= 0 mg/L
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Ultrafiltration (UF) System
Parameter
Flux
(normalized to 20˚C)
Recovery range
CEB sequence
- Acid CEB
-
Caustic CEB
CEB frequency
CIP sequence
- Acid CIP
-
Caustic CIP
CIP frequency
Optimal Setting
= 53 lmh
= 70 to 80%

approximately 2.5 pH

5000 mg/L citric acid

200 mg/L sodium metabisulphite

30 min soak time
- approximately 12 pH using caustic
- 600 mg/L NaOH
- 600 mg/L NaOCl
- 30 min soak time
= once every 24 hrs at optimum operating conditions

≤2.3 pH using citric acid,

200 mg/L sodium metabisulphite

38°C solution

10 hr soak/ recirculation period

intermittent air scour

approximately 12 pH using caustic

2000 mg/L NaOCl

32°C solution

10 hr soak/ recirculation period

intermittent air scour
= every 2 to 4 weeks
Reverse Osmosis (RO) System
Parameter
Optimal Setting
Sulphuric acid dose (to achieve 6.5 = 700 to 800 mg/L as H2SO4
pH)
= 160 to 200 mg/L (observed dosage to
achieve targeted ORP at RO feed;
lower dosage could be possible)
= 6.6 mg/L
= 6.6 mg/L
Biocide dose
Time between CIPs
= 1 to 2 months
Flux rate (50% recovery)
= 23 lmh
(normalized to 25°C)
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6.4
Primary Factors Impacting Process Performance












6.5
Presence of algae growth in feed water (pond water vs. well head source)
Iron scaling of the UF membrane
Water pH in the Oxidation/ Precipitation stage
Coagulant dose
UF flux rate
Effectiveness of UF CEBs and CIPs
Flushing of RO immediately after shutdown (precipitation from stagnant water will
occur due to loss of effectiveness of anti-scalants over extended period)
RO influent pH
Iron and barium scaling of the RO membrane
RO recovery
RO anti-scalant type and dosage
High TDS in the RO feed water resulted in high osmotic pressure, which was the
primary factor which limited RO recovery to the 50% to 60% range examined in
the pilot
Stability of Operation
Untreated Basal Water
Basal feed water undergoes significant variation in Oxidation-Reduction potential
immediately after exiting the well head. Aeration combined with equalization ahead of a
treatment facility should be able to effectively counteract this issue and provide stable
feed water.
UF
Fouling rate on the UF membrane is critical and susceptible to exponential increases if
upstream chemistry is not optimized. Due to the high scaling nature of the water, cross
flow operation of the membrane is deemed essential, in order to provide physical
scouring of the membrane surface and extend production run times between CEBs and
CIPs. Normalized (to 20°C) flux rates in excess of 53 lmh were not appropriate for this
application due to the scaling tendencies of the feed water. Carrying out a CIP was
effective in removing fouling material and restoring UF performance. However, the UF
autopsy indicated that the use of a cleaning chemical targeting iron deposits may
provide additional benefits.
RO
RO operation was stable and sustainable at a recovery of 50%, even when the upstream
UF system was experiencing scaling issues. Operation at 60% recovery was also
relatively stable, though examined for a significantly smaller timeframe. Anti-scalant type
and dose could be re-examined in order to address iron, which was identified as the
primary scaling compound.
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6.6
Comparison of Operation with Pond and Wellhead Basal Water
Sources
Pond water use was explored in the pilot due to the presumed benefits of water
performance
Key differences between untreated basal water taken from the pond relative to basal
water taken from the wellhead were as follows:
 Easily oxidized compounds had been oxidized and in some cases precipitated
out of solution
 Reduced dissolved hydrogen sulphide
 Algae in the water was significant and easily observable in both water at the pilot
plant and in the source pond
 Organic materials (algae) were most probably responsible for the immediate and
rapid decrease in UF performance when basal water source was changed from
the wellhead common header to directly from the pond
6.7
Impact of Not Softening
Softening and degasification were initially contemplated for inclusion in the treatment
train, but were ultimately not included due to the extremely high chemical consumption
anticipated. Exclusion of softening eliminates the capital costs for softening infrastructure
as well as the significant ongoing costs related to chemicals required for the treatment
process and sludge disposal. The primary adverse impacts of not carrying out upstream
softening vary based on the operational pH used in the oxidation/precipitation treatment
stage.
At neutral pH (6.8 to 7.0) the impacts were as follows:
 increased iron fouling of the UF membrane, potentially requiring frequent CEBs
 reduced or near eliminated issues with CaCO3 scaling on pilot plant infrastructure
At elevated pH (7.4 to 8.0) the impacts were as follows:
 reduced impact of iron fouling on the UF membrane
 severe CaCO3 precipitation throughout the pilot facility, often requiring equipment
such as pre-filters and pumps to be taken off line for descaling
The use of anti-scalant chemicals, metabisulphite and neutral pH upstream of the RO
was effective in mitigating the impact of high hardness on the RO system. However, high
hardness levels in RO reject are also a major consideration in disposal of the waste
stream.
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CNRL Extraction Water Treatment Plant Pilot Study

Transcription

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