This document evaluates the potential of forward osmosis (FO) processes for wastewater reuse purposes. It describes long-term experimentation with two FO pilot plants: an FO-membrane bioreactor plant and an FO-nanofiltration plant. The FO-MBR plant operated continuously for a month using activated sludge with two different draw solutions, achieving stable water fluxes and minimal fouling. The FO-NF plant treated municipal wastewater effluent, consistently producing high-quality permeate low in conductivity and boron over time. While FO processes have higher energy costs than reverse osmosis, they have potential niches in potable reuse, agricultural reuse, and industrial applications due to lower fouling

1. EVALUATION OF POTENTIAL OF FORWARD OSMOSIS
PROCESSES FOR WASTEWATER REUSE PURPOSES
De la Torre, T., Arnaldos, M., Corzo, B., Ferrero, E., Navea, S.,
Simón, P., Rodríguez, C., Malfeito, J.J.
ACCIONA Agua and ESAMUR

2. Index
1.FO opportunities and challenges
2.Long-term experimentation
 FO-MBR pilot plant
 FO-NF demonstration plant
3.Costs: first impressions
4.Conclusions

3. Index
1.FO opportunities and challenges
2.Long-term experimentation
 FO-MBR pilot plant
 FO-NF demonstration plant
3.Costs: first impressions
4.Conclusions

4. FO opportunities and challenges
Why?
 Low and reversible fouling
 Less pretreatment
 Less chemical cleaning
 Product water customization (e.g.
boron removal, fertigation)
 Improvements in FO membranes:
 Thinner membranes with less
tortuosity (S parameter)
 less ICP and higher flux
 More providers  lower prices
(Mi and Elimelech, 2009)
(Achilli et al., 2010)

5. Market niches in wastewater reclamation
Industrial wastewater
• Requiring high quality and complex treatment
• With fouling problems (requiring extensive pretreatment)
• Applications with no DS separation
• Residual heat
• Case-specific
Municipal wastewater
Potable reuse
•Indirect or direct (Singapur/Namibia…)
•Multibarrier concept is state of the art
Industrial
•Cooling towers
Agriculture
•Boron
•Micropollutants
•Salinity
•Heavy metals
Source: AQUAREC, 2006
FO opportunities and challenges

6. FO Challenges
 Low flux (ICP & ECP)
 DS recovery is energy intensive
 DS costs (Js and incomplete DS recovery)
 Permeate quality
 No data: main studies are lab-scale, synthetic feed, short
term and batch
Realistic studies are still needed
This study: 2 FO-pilot plants operating with real feed,
continous, long-term (months):
 FO-NF
 FO-MBR
FO opportunities and challenges

7. Index
1.FO opportunities and challenges
2.Long-term experimentation
 FO-MBR pilot plant
 FO-NF demonstration plant
3.Costs: first impressions
4.Conclusions

8. FO-MBR
Pilot scale FO-MBR plant
• Feed: 4L/min, 1 bar
• DS: 1L/min, 0.5 bar
• DS concentration: 1.5 M
• Activated sludge (AS) conductivity: 1000 S/cm
• Continuous operation during one month per
selected DS using real activated sludge
Membrane test cell (CTA, HTI)

9. FO-MBR: Results
• 2 DS selected after modelling: K4P2O7 and HCOOK
• Sustained long-term operation with minimal fouling and
consistent water fluxes for K4P2O7 and HCOOK
• No chemical cleaning
• Similar Js and Jw for both DS
K4P2O7 HCOOK

10. Index
1.FO opportunities and challenges
2.Long-term experimentation
 FO-MBR pilot plant
 FO-NF demonstration plant
3.Costs: first impressions
4.Conclusions

11. FO-NF plant
LIFE-OFREA FO-NF demonstration plant
• Region of Murcia: 98% of wastewater is reused, mostly in
agriculture. The rest present high salinity
• San Pedro del Pinatar WWTP effluent:
• Conductivity: 4-6 mS/cm
• Boron: 1.5 ppm
• www.life-ofrea.com

12.  Simulation between modules in series using Matlab
 Experimentation with commercial elements in batch
Feed water
FO-NF plant: design

13. FO-NF plant
LIFE-OFREA FO-NF demonstration plant
• Commisioning December 2014
• 3 m3/h effluent from WWTP of San Pedro del Pinatar (Murcia,
Spain)

14. FO-NF plant: permeability evolution
• Stable operation of the FO
• NF permeability decreased due to fouling but then stabilized
• Permeability FO=Flux/( DS feed T corrected
• Permeability NF=Flux/NDP (T corrected)

15. FO-NF plant: permeate quality
• Stable permeate quality
• Low conductivity
• B < 0.4 mg/L (>70% removal)
• High quality for agricultural reuse except for SAR > 100 mequ/L

16. Index
1.FO opportunities and challenges
2.Long-term experimentation
 FO-MBR pilot plant
 FO-NF demonstration plant
3.Costs: first impressions
4.Conclusions

17. UF+RO vs. FO+RO:
CAPEX:
 Membrane prices for FO should go down in the future years
OPEX:
 Energy consumption is higher for the FO+RO (this study;
McGovern and Lienhard, 2014,..)
 Chemicals
• Low fouling:
• Membrane replacement and chemicals for cleaning and shutdowns
will be lower for the FO option.
• Low or zero pretreatment: no antiscalant, pH adjustment, FeCl3,…
• Draw solution costs due to Js and incomplete recovery 
economical DS must be found
Cost comparison

18. Index
1.FO opportunities and challenges
2.Long-term experimentation
 FO-MBR pilot plant
 FO-NF demonstration plant
3.Costs: first impressions
4.Conclusions

19. Conclusions
• Niches of FO in wastewater reclamation:
• Potable reuse
• Agricultural reuse: specially if 2-RO passes are needed
• Industrial uses
• FO-NF & FO-MBR operated in the long term with real feed:
• Stable operation
• High permeate quality (conductivity and boron)
• SAR must be adjusted
• No fouling in the long-term
• Costs
• Relevant cost due to DS losses and DS reconcentration energy
• Balance between cost of DS, membranes and energy needed
FO application is still challenging…but is becoming a reality!

20. Acknowledgements
We would like to thank the collaboration of Aguas y Servicios de la Costa Tropical
and HTI for the membrane coupons.
The research leading to these results has received funding from:
• LIFE+ Programme of the European Commision (LIFE12/ENV/ES/000632 LIFE
OFREA) www.life-ofrea.com
• People Programme (Marie Curie Actions) of the European Union’s Seventh
Framework Programme FP7/2007-2013 under REA agreement 289193 (SANITAS
Project). www.sanitas-itn.eu
teresa.torre.garcia@acciona.com
This presentation reflects only the author's views and the European Union is not
liable for any use that may be made of the information contained therein.