Transcript Forward Osmosis: Principles, Applications, and Recent

Lessons Learned from the Development of
Advanced Life Support Systems for Space
Applications
Emerging Applications for Water Treatment and
Potable Water Reuse
Tzahi Y. Cath
Environmental Science and Engineering Division
Colorado School of Mines
2006 International Conference on Environmental Systems
July 17-20, 2006
Presentation Outline



Overview of Membrane Processes for Water Treatment

Pressure-driven membrane processes

Membrane contactor processes
Combination of processes for process intensification

Potable Reuse of Wastewater

Volume Minimization of Wastewater

Brackish Water Desalination
Summary and Future Directions
Pressure-Driven Membrane Processes
Membrane
Feed
Permeate
P
Particle or
Solute Molecule
Solvent
Pressure-Driven Membrane Processes
MF
UF
NF
RO
Suspended Solids (Particles)
Macromolecules (Humics)
Multivalent Ions (Hardness)
Monovalent Ions (Na+,Cl-)
Water Molecules
Limitations of Pressure-Driven
Membrane Processes

Membrane fouling
 Limited application

Membrane scaling
 Limited water recovery

Energy
Membrane Fouling
macromolecules
microbes
particles
ions
Membrane Fouling
MF
UF
NF
RO
Membrane Scaling
Osmotic- and Thermally-Driven
Membrane Processes


The driving force is temperature or concentration
gradients across the membrane
Process
Mass Transport
Driving Force
Forward Osmosis (FO)
Diffusion
Osmotic Pressure
Membrane Distillation
(MD)
Evaporation
Partial Vapor Pressure
Combination with each other and with pressure-driven
membrane processes
Osmosis / Forward Osmosis
membrane
osmotic
pressure
Brine
Water
Osmosis
Brine
Water
Equilibrium
Brine ≡ Draw Solution (DS)
Brine
Water/
Feed
Forward Osmosis
(FO)
o
Osmotic Pressure (@25 C), atm
Draw Solutions
1600
MgCl2
CaCl2
NaCl
KCl
sucrose
KNO3
NH4HCO3
1200
800
400
0
0
2
4
6
Concentration, M
8
10
Raw
Feed Solution
Forward
Osmosis
Forward Osmosis Pretreatment
for Reverse Osmosis
Reverse
Osmosis
Concentrated DS
solute
Diluted DS
Concentrated
Solution
Clean
Water
Membrane Distillation
adapted from: http://www.water-technology.net/

J  Am Pf*  Pp*


heated aqueous feed solution is
brought into contact with feed side of
hydrophobic, microporous membrane

hydrophobic nature of membrane
prevents penetration of aqueous
solution into pores

cold pure water is in contact with
permeate side of membrane

vapors diffuse through pores and
directly condense into cold stream
Vapor Pressure and Partial Vapor Pressure in
Microporous Membrane Evaporation Processes
Water +
NaCl
Vacuum Enhanced
Direct Contact Membrane Distillation
Traditional DCMD
VEDCMD
P F
P F
Effect of Permeate-Side Vacuum on Flux
ΔT = 20C
45
TS45
TS22
PP22
2
Water Flux, l/m -hr
40
vf = vp = 1.4 m/sec
Pf = 1.1 bar (abs)
35
30
25
20
15
10
- +
5
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
Permeate Absolute Pressure, bar
Results from
Traditional
Configuration
New Hybrid System for Fouling-Protected MD
2.5
2
Water Flux, L/m -hr
3.0
2.0
DS ~ 50 g/l NaCl
DS ~ 200 g/l NaCl
1.5
1.0
0.5
MD Water Flux
0.0
0
5
10
15
20
Elapsed Time, hr
25
30
Advantages of Membrane Contactors

High rejection of wide range of contaminants/solutes

Low-grade energy / waste heat sources can be used

Reduced fouling potential – less pretreatment required

Operate at low pressure – less constraints / safety issues

In MD, driving force not reduced by osmotic pressure

Can provide enhanced recovery through brine desalination
Evaluation of
Forward (Direct) Osmosis Concentration (DOC)
for Direct Potable Reuse of Wastewater in
Long-Term Space Missions
Project History

Mid 1990s – Forward osmosis incorporated into a water reclamation
systems

1999 – Osmotek Inc. completed first phase of technology
demonstration

2002-2003 – University of Nevada, Reno completed optimization study
with recommendations to modify DOC architecture

2004-2007 – Rapid Technology Development Team (RTDT) program
to develop a more reliable system – appropriate for
human testing at TRL 5-6
Original DOC Concept


Integration of three membrane processes in one system
 Reverse osmosis – core process
 Forward osmosis – pretreatment for RO
 Forward osmosis/osmotic distillation – pretreatment for RO
Treat variety of wastewater streams, including:
 Hygiene wastewater
 Humidity condensate (HC)
 Urine
Membrane
Contactors
Schematic of Original DOC Test Unit
Hygiene
WW
+
HC
DOC #1
DOC #2
Conc.
WW
+
Urine
RO
Catalytic
Oxidation
Final Waste
Schematic of New DOC Test Unit
Hygiene
WW
FO
MD
Hum.
Cond.
+
Urine
RO
Catalytic
Oxidation
Final Waste
Construction of New Prototypes
Performance of Forward Osmosis
2
Water Flux, L/m -hr
J w  Am (P   )  Am  DS   feed 
18
Deionized water feed
hygiene feed
hygiene/urine/humidity feed
16
14
12
10
8
6
4
20
30
40
50
60
70
Draw Solution Concentration, g/L NaCl
MD for Potable Reuse of Urine and
Humidity Condensate
(Tf = 40ºC, Tp = 20ºC)
40
1
20
2
Water Flux, l/m -hr
2
Water Flux, L/m -hr
60
80
2
operating at constant recovery
60
40
1
20
Water Flux
% Recovery
0
0
20
40
60
80
Elapsed Time, hr
0
100 120
fresh feed solution added
0
0
20
40
60
Elapsed Time, hr
80
0
100
Water Recovery, %
2
Water Flux
Water Recovery
Water Recovery, %
80
100
3
100
3
Specific Power Consumption
3
50
kWh/m
Specific Energy Consumption
60
40
1000 g Salt / RO Pump @ 100%
1000 g Salt / RO Pump @ 90%
1000 g Salt / RO Pump @ 80%
500 g Salt / RO Pump @ 100%
500 g Salt / RO Pump @ 90%
500 g Salt / RO Pump @ 80%
30
20
10
0.1
0.2
0.3
0.4
DS Flowrate, l/min
0.5
Removal of Endocrine Disrupting Chemicals (EDCs)

Continually released to environment by humans and most
often not destroyed by conventional wastewater treatment

May be a significant problem in closed water reclamation
systems
17-β Estradiol (E2)
Estrone (E1)
Hormone Rejection by Membrane Distillation
DI Water Feed
Wastewater Feed
(urine + humidity condensate)
3.5
2
2.5
90
2.0
1.5
1.0
0
5
10
15
85
Water Flux
E1 Rejection
E2 Rejection
80
20 25 30 35
Elapsed Time, hr
3.0
95
2.5
90
2.0
1.5
1.0
0
5
10
15
Water Flux
85
E1 Rejection
E2 Rejection
80
20 25 30 35
Elapsed Time, hr
Rejection, %
95
100
2
3.0
Water Flux, l/m -hr
100
Rejection, %
Water Flux, l/m -hr
3.5
Hormone Rejection by Forward Osmosis
EDC Rejection, %
100
90
80
70
60
H2 in Soap Solution
E1 in Soap Solution
E1 in DI Water
50
0
10 20 30 40 50 60 70 80
Water Recovery, %
Forward Osmosis for Concentration
of Liquids from Anaerobic Digester
Anaerobic Digesters

Liquid fraction (“centrate”) recycled back to beginning of
treatment process

Problems:


High loading of organic matter, nutrients, and suspended
solid to the main treatment train

Increased operating cost

Difficult to employ pressure-driven membrane processes

Environmental concerns
Potential benefits:

commercial products ?
FO Performance Tests
FO Performance Tests
Raw Centrate
2
14
12
16
1
9
3
5
7
10
8
2
4
6
8
6
4
14
12
10
8
6
4
2
2
0
0
20
30
PCC 1
PCC 2
PCC 3
PCC 4
PCC 5
DDW
2
16
Water Flux, l/m -hr
18
RCC 1
RCC 2
RCC 3
RCC 4
RCC 5
DDW
Water Flux, l/m -hr
18
Pretreated Centrate
40
50
60
70
DS Concentration, g/l NaCl
20
30
40
50
60
70
DS Concentration, g/l NaCl
FO Performance Tests
Average Rejection (%)
Ammonia
TKN
Orthophosphate
>87
>89
>99.5
2
Water Flux, l/m -hr
Forward Osmosis vs. Reverse Osmosis
14
13
12
11
10
9
8
7
6
5
4
FO
RO
Membrane
Cleaning
0
10 20 30 40 50 60 70 80
Elapsed Time, hr
FO for Brackish Water Desalination
Performance of VEDCMD
45
CDS = 55 g/l NaCl
High Temperature VEDCMD
Low Temperature VEDCMD Tfeed = 20C
Tlow = 40C
35
2
Water Flux, l/m -hr
40
Thigh = 60ºC
30
25
20
15
10
5
0
0
10
20
30
40
50
Feed Concentration, g/l TDS
Performance of VEDCMD
Forward Osmosis vs. VEDCMD
45
High Temperature VEDCMD
Low Temperature VEDCMD
FO (DS @ 55 g/l NaCl)
35
2
Water Flux, l/m -hr
40
CDS = 55 g/l NaCl
Tfeed = 20C
Tlow = 40C
Thigh = 60ºC
30
25
20
15
10
5
0
0
10
20
30
40
50
Feed Concentration, g/l TDS
Scale Inhibition Study
14
2
Water Flux, L/m -hr
12
10
8
6
4
2
Without Scale Inhibitor
With 10 ppm Scale Inhibitor
0
0
5
10
15
Time, hr
20
25
Summary and Future Directions

Membrane contactors perform very well and are suited for unique
applications as the treatment process or as pretreatment

Integration of membrane contactors or membrane contactors with
pressure-driven membrane processes can lead to process enhancement

Further development of membranes for MD and FO is crucial for future
advancement of these processes and their potential applications
Acknowledgements

NASA, Ames Research Center

DOD, Office of Naval Research

Prof. Glenn Miller and Prof. Ken Hunter at UNR

Joshua Cartinella, Ryan Holloway, Riz Martinetti
Thank You