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Tzahi Cath, Carl Lundin, Jörg Drewes
Advanced Water Technology Center (AQWATEC) Division of Environmental Science and Engineering
Colorado School of Mines Golden, CO
24th Annual WateReuse Symposium September 14th, 2009
SeaJle, WA
A Novel Hybrid Forward Osmosis Process for Drinking Water AugmentaQon using Impaired Water and Saline Water Sources
PresentaQon Overview The Water-‐Energy nexus
Emergence of osmo5cally-‐driven membrane processes
Poten5al applica5ons and implementa5ons
Desalina5on and the energy-‐water nexus
Osmo5c dilu5on of seawater
AwwaRF 4150
Concluding remarks
The Water – Energy Nexus Water to Energy…
Energy to Water…
Energy Recovery in DesalinaQon
http://www.energyrecovery.com/ http://www.ide-tech.com/Index.asp
OsmoQc Pressure as an Energy Guzzler
Seawater
membrane
Δπ ≈ 350 psi
Conc. Seawater
(~50% rec.) Δπ ≈ 700 psi
OsmoQc Pressure as an Energy Source OsmoQcally-‐driven Membrane Processes
Forward osmosis (wastewater treatment, pretreatment, desalina5on)
Pressure retarded osmosis (power genera5on)
Forward Osmosis (“engineered osmosis”)
Draw Solution
membrane
Osmosis
Brine / Draw
Solution
membrane
OsmoQc Pressure as an Energy Source OsmoQcally-‐driven Membrane Processes
Forward osmosis (wastewater treatment, pretreatment, desalina5on)
Pressure retarded osmosis (power genera5on)
Pressure Retarded Osmosis: OsmoQc Power
From: R. J. Aaberg, Osmotic power - A new and powerful renewable energy source, ReFocus, 4 (2003) 48-50
Forward Osmosis: Draw SoluQons
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20000
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Osm
oQc Pressure, p
si
Osm
oQc Pressue, atm
ConcentraQon, M
NH4HCO3
NaCl
CaCl2
MgCl2
KCl
sucrose
KNO3
Forward Osmosis: Draw SoluQons
0
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1000
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0 1 2
Osm
oQc Pressure, p
si
Osm
oQc Pressue, atm
ConcentraQon, M
NH4HCO3
NaCl
CaCl2
MgCl2
KCl
sucrose
KNO3
State of Development of OsmoQcally-‐driven Membrane Processes
ApplicaQon of OsmoQcally-‐driven Membrane Processes
Aaberg (2003)
So… what are the advantages and limitaQons of osmoQcally-‐driven
membrane processes?
FO vs. RO
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Water flux, LMH
Time, Hours
LFC-‐1 RO Mode CA-‐2 RO Mode CA-‐2 FO Mode
Membrane cleaning
Holloway, R.W., Childress, A.E., Dennett, K.E., Cath, T.Y., “Forward osmosis for concentration of centrate from anaerobic digester”, Water Research, Vol. 41 (17), September 2007, 4005-4014.
Power ConsumpQon Rela5vely good economy at small scale…
Economy of scale holds promise for successful implementa5on
Effect of Feed Chemistry on FO Process Performance Driving force decreases when recovery increases
Good rejec5on of contaminants of concern
Cath et al., “Membrane Contactor Processes for Wastewater Reclamation in Space. Journal of Membrane Science, Vol. 257, (1-2), July 2005, 111-119.
Cartinella, Cath, et al. “Removal of Natural Steroid Hormones from Wastewater Using Membrane Contactor Processes”, Environmental Science and Technology, 40 (23), (2006) 7381-7386.
Jw = A (ΔP – Δπ)
FO
RO
Draw Solution tank
BW Brine
Concentrated BW Brine
What are the LimitaQons? The Complexity of Mass Transport
Js = B Δc
Js,RO
Unlike RO, FO exhibits bi-‐direc5onal diffusion of ions
Jw = A (ΔP – Δπ)
How can we simultaneously reduce energy demand in SWRO, protect RO membrane, and provide mulQ barrier
treatment of impaired water?
Energy Demand of DesalinaQon High energy demand of SWRO desalina5on due to high osmo5c
pressure of the brine
Δπ
Additional flux
Decreasing Feed Conc.
Decreased Osmotic Pressure
Membrane
Solv
ent (
wat
er) F
lux,
J
RO
ΔP
FO
The beginning…
T.Y. Cath, A.E. Childress, System and Methods for Forward Osmosis Assisted Desalination of Liquids, Patent Application No. 11/295,807, December 2005.
Water Research FoundaQon (AwwaRF) 4150 Cath, T.Y., Drewes, J.E., Lundin, C. (2009). “A Novel Hybrid Forward Osmosis Process for Drinking Water Augmentation using Impaired Water and Saline Water Sources.” Draft Final Report. Awwa Research Foundation (AwwaRF #4150), Denver, Colorado.
FO/RO Hybrid for Water AugmentaQon: OsmoQc DiluQon of Seawater Low energy desalina5on / enhanced recovery
Dual barrier
Bench-‐scale TesQng in the Lab Bench scale forward osmosis system
Closed loop system Doses concentrated salt to maintain DS concentra5on
SCADA control of salt dosing, temperature, and data acquisi5on
Bench Scale Results: Short term fouling test
No flux decline seen in short term secondary effluent experiments
Conditions: 19ºC
1.5 LPM pH 7.5
Bench Scale Results: OperaQng Envelope
Conditions: 19ºC
1.5 LPM pH 7.5
Feed Cond: SE: 850 µS/cm
DI: 80 µS/cm
Seawater
Pilot TesQng Temp. Control
RO Cell
Permeate
FO Cell
Feed (Recycled)
water
Waste
Seawater Draw
Solution
Pilot Test Results Secondary Effluent Feed
PC PC CC
Pilot Test Results Secondary Effluent Feed
Temp. Control
RO Cell
Permeate
FO Cell
Feed (Recycled)
water
Waste
Seawater Draw
Solution
FO Cell
Feed (Recycled)
water
Waste
Pilot Test Results Secondary Effluent Feed
Pilot Scale Results: TerQary effluent feed
Conditions: 2.4 LPM
pH 7.5 35 g/L Seawater
Feed Cond: TE: 850 µS/cm
Solute Transport: NH3, NO3, UV
Conditions: 2.4 LPM
pH 7.5 35 g/L Seawater
Feed Cond: SE: 850 µS/cm
Ammonia rejection: FO: 75%, RO: 75%, Total: 94%
Solute Transport: NH3, NO3, UV
Conditions: 2.4 LPM
pH 7.5 35 g/L Seawater
Feed Cond: SE: 850 µS/cm
Nitrate rejection: FO: 79%, RO: 82%, Total: 97%
Solute Transport: NH3, NO3, UV
Conditions: 2.4 LPM
pH 7.5 35 g/L Seawater
Feed Cond: SE: 850 µS/cm
UV rejection: FO: 86%, RO: >99.9%, Total: >99.9%
Solute Transport: Micropollutants Rejec5on of organic micropollutants
Accumula5on over 7-‐day experiment Some compounds were not detected in feed water
Clofibric acid, dichlorprop, diclofenac, fenofibrate, gemfibrozil, ibuprofen, ketoprofen, mecoprop, naproxen, salicylic acid
Compound Bench FO Pilot FO Pilot RO Pilot Total Diclofenac >99.9% 89% >99.9% >99.9% Gemfibrozil 80% 78% 78% 97% Ibuprofen n/a 87% 64% 93% Mecoprop 95% >99.9% - >99.9% Naproxen 90% 85% 94% 98% Salicylic Acid 72% >99.9% >99.9% >99.9%
Economic Feasibility Simple model
constructed
Helps to determine the level of recovery of impaired water possible
Parameter Unit Value Finished water flow rate m3/day 100 Impaired water flow rate m3/day 200 Seawater TDS concentration g/L 35 Impaired water TDS
concentration g/L 0.5
RO recovery % 50 Energy cost $/kWh 0.20 Forward osmosis membrane
cost $/m2 45.00
Minimum return on investment ratio
1
Impaired water stream
Concentrated impaired water stream
Permeate (finished water)
RO reject stream
Reverse Osmosis
Forward Osmosis
RO influent stream
Seawater stream
Economic Feasibility
Economic Feasibility
Economic Feasibility
Concluding Remarks
High rejec5on of suspended solids and macromolecules and rela5vely high rejec5on of most dissolved ions and molecules
Very low membrane fouling
Low energy consump5on and energy benefits to downstream SWRO
Mul5 barrier protec5on leading to direct potable reuse
Preparing for a large scale demonstra5on project
Acknowledgements Funding Agencies
Water Research Foundation (formerly AwwaRF)
California Department of Water Resources
National Aeronautics & Space Administration
Russell Plakke and Brian Good, Denver Water
Christiane Hoppe, Brandy Laudig, Ryan Holloway, Josh Cartinella, Dean Heil
Edward Beaudry, Hydration Technologies Inc.
Thank You