A Novel Hybrid Forward Osmosis Process for Drinking Water AugmentaQon using Impaired Water and Saline Water Sources 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 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.ide-tech.com/Index.asp
http://www.energyrecovery.com/
OsmoQc Pressure as an Energy Guzzler membrane Seawater
Conc.
Seawater
(~50% rec.)
Δπ ≈ 350 psi
Δπ ≈ 700 psi
OsmoQc Pressure as an Energy Source OsmoQcally-­‐driven Membrane Processes 

Forward osmosis (wastewater treatment, pretreatment, desalina5on) Pressure retarded osmosis (power genera5on) membrane membrane Brine /
Draw
Solution
Osmosis Draw
Solution
Forward Osmosis (“engineered osmosis”) 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 NH4HCO3 NaCl CaCl2 MgCl2 KCl sucrose KNO3 OsmoQc Pressue, atm 1400 1200 1000 800 20000 15000 10000 600 400 5000 200 0 0 0 1 2 3 4 5 ConcentraQon, M 6 7 OsmoQc Pressure, psi 1600 Forward Osmosis: Draw SoluQons NH4HCO3 NaCl CaCl2 MgCl2 KCl sucrose KNO3 OsmoQc Pressue, atm 250 200 150 4000 3500 3000 2500 2000 1500 100 1000 50 500 0 0 0 1 ConcentraQon, M 2 OsmoQc Pressure, psi 300 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 13 Water flux, LMH 12 11 10 9 8 LFC-­‐1 RO Mode CA-­‐2 RO Mode CA-­‐2 FO Mode 7 6 0 2 4 Membrane
cleaning
6 8 Time, Hours 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.
10 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 Jw = A (ΔP – Δπ) 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.
What are the LimitaQons? The Complexity of Mass Transport Js = B Δc Jw = A (ΔP – Δπ) FO
Concentrated BW Brine
Draw
Solution tank
Js,RO
BW Brine

Unlike RO, FO exhibits bi-­‐direc5onal diffusion of ions RO
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 Additional flux
Solvent (water) Flux, J

Decreasing
Feed Conc.
Δπ
FO Decreased
Osmotic
Pressure
RO ΔP Membrane
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 Seawater
Conditions:
19ºC
1.5 LPM
pH 7.5
Feed Cond:
SE: 850 µS/cm
DI: 80 µS/cm
Pilot TesQng Feed
(Recycled)
water
Temp.
Control
Seawater
Draw
Solution
RO Cell
Permeate
FO Cell
Waste
Pilot Test Results Secondary Effluent Feed PC
PC
CC
Pilot Test Results Secondary Effluent Feed Feed
(Recycled)
water
Temp.
Control
Seawater
Draw
Solution
FO Cell
Waste
FO Cell
Waste
RO Cell
Permeate
Feed
(Recycled)
water
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 Ammonia rejection: FO: 75%, RO: 75%, Total: 94%
Conditions:
2.4 LPM
pH 7.5
35 g/L Seawater
Feed Cond:
SE: 850 µS/cm
Solute Transport: NH3, NO3, UV Nitrate rejection: FO: 79%, RO: 82%, Total: 97%
Conditions:
2.4 LPM
pH 7.5
35 g/L Seawater
Feed Cond:
SE: 850 µS/cm
Solute Transport: NH3, NO3, UV UV rejection: FO: 86%, RO: >99.9%, Total: >99.9%
Conditions:
2.4 LPM
pH 7.5
35 g/L Seawater
Feed Cond:
SE: 850 µS/cm
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 Seawater stream
Impaired water stream
Forward Osmosis
RO influent stream
Reverse Osmosis
Concentrated impaired
water stream
Permeate (finished water)
RO reject stream
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
$/m2
45.00
Forward osmosis membrane
cost
Minimum return on
investment ratio
1
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