Lessons Learned from the Development of Advanced Life Support Systems for Space Applications Emerging Applications for Water Treatment and Potable Water.

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 SystemsJuly 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

SolventParticle or Solute Molecule

Membrane

PermeateFeed

P

Pressure-Driven Membrane Processes

Suspended Solids (Particles)

Macromolecules (Humics)

Multivalent Ions (Hardness)

Monovalent Ions (Na+,Cl-)

UFUF NFNFRROO

MMFF

Water Molecules

Limitations of Pressure-Driven Membrane Processes

Membrane fouling Limited application

Membrane scaling Limited water recovery

Energy

Membrane Fouling

particlesmacromolecules ionsmicrobes

Membrane Fouling

MFMF UFUF NFNF RORO

Membrane Scaling

Osmotic- and Thermally-Driven Membrane Processes

Process Mass Transport Driving Force

Forward Osmosis (FO) Diffusion Osmotic Pressure

Membrane Distillation (MD)

Evaporation Partial Vapor Pressure

The driving force is temperature or concentration gradients across the membrane

Combination with each other and with pressure-driven membrane processes

Osmosis / Forward Osmosis

Brine Water

Equilibrium

osmoticpressure

Brine Water

membrane

Osmosis

Water/Feed

Forward Osmosis(FO)

Brine

Brine ≡ Draw Solution (DS)

Draw Solutions

0 2 4 6 8 100

400

800

1200

1600O

smot

ic P

ress

ure

(@25

o C),

atm

Concentration, M

MgCl2

CaCl2

NaCl KCl sucrose KNO

3

NH4HCO

3

Forward Osmosis Pretreatment for Reverse Osmosis

Concentrated DS

Diluted DS

solute

ReverseOsmosis

ForwardOsmosis

RawFeed Solution

ConcentratedSolution Clean

Water

Membrane Distillation

adapted from: http://www.water-technology.net/

**pfm PPAJ

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

P F

Traditional DCMD

P F

VEDCMD

Effect of Permeate-Side Vacuum on FluxΔT = 20C

vf = vp = 1.4 m/sec

Pf = 1.1 bar (abs)

- + Results from Traditional Configuration

New Hybrid System for Fouling-Protected MD

0 5 10 15 20 25 300.0

0.5

1.0

1.5

2.0

2.5

3.0

Wat

er F

lux,

L/m

2 -hr

Elapsed Time, hr

MD Water Flux

DS ~ 50 g/l NaCl DS ~ 200 g/l NaCl

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

MembraneContactors

Schematic of Original DOC Test Unit

DOC #1 DOC #2

Final Waste

RO

Hygiene WW

+HC

Catalytic Oxidation

Conc. WW

+ Urine

Schematic of New DOC Test Unit

FO MD

Final Waste

RO

Hygiene WW

Hum.Cond.

+ Urine

Catalytic Oxidation

Construction of New Prototypes

Performance of Forward Osmosis feedDSmmw APAJ )(

MD for Potable Reuse of Urine and Humidity Condensate

(Tf = 40ºC, Tp = 20ºC)

Specific Power Consumption

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

Estrone (E1)Estrone (E1)17-17-ββ Estradiol (E2) Estradiol (E2)

Hormone Rejection by Membrane Distillation

Wastewater FeedDI Water Feed(urine + humidity condensate)

Hormone Rejection by Forward Osmosis

0 10 20 30 40 50 60 70 8050

60

70

80

90

100

ED

C R

ejec

tion,

%

Water Recovery, %

H2 in Soap Solution E1 in Soap Solution E1 in DI Water

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

Pretreated CentrateRaw Centrate

11

22

33

44

55

66

77

88

99

FO Performance Tests

Average Rejection (%)

Ammonia TKNOrtho-

phosphate

>87 >89 >99.5

Forward Osmosis vs. Reverse Osmosis

MembraneMembraneCleaningCleaning

FO for Brackish Water Desalination

Performance of VEDCMD

CDS = 55 g/l NaCl

Tfeed = 20C

Tlow = 40C

Thigh = 60ºC

Performance of VEDCMD

Forward Osmosis vs. VEDCMD

CDS = 55 g/l NaCl

Tfeed = 20C

Tlow = 40C

Thigh = 60ºC

Scale Inhibition Study

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