feasibility of forward osmosis for desalination and water reclamation
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The 13th IWA Leading Edge Conference on Water and Wastewater Technologies
DEVELOPMENT AND APPLICATION OF SUSTAINABLE MEMBRANE DESALINATION TECHNOLOGY: REVERSING WATER SCARCITY AND FAST FORWARDING TO THE FUTURE
FEASIBILITY OF FORWARD OSMOSIS FOR DESALINATION AND WATER RECLAMATION: APPLICATION EXAMPLE AT PILOT SCALE
BEATRIZ CORZO
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INDEX
Water Scarcity and Wastewater Reuse
Hybrid FO advantages
FO challenges
OFREA Project
Design
Demonstration plant
Cost evaluation
Conclusions
Acknowledgments
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WATER SCARCITY AND WASTEWATER REUSE
>3 Billion people will live under water stress in 2025 (Valladares et al., 2014)
Options:‒ Water desalination‒ Water reuse‒ Improve water efficiency
Can we compete using FO in water reuse for agricultural purposes?
A combination of the three is needed
Challenges for water reuse are both technological and economical: technologies that can assure safe water at a
competitive price are needed
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Water Recycling Guidelines: Depend on local context Mainly bacteriological parameters
E.coli Nematode eggs Giardia Criptosporidium
Others: Nutrients (N and P) Suspended solids Turbidity Dissolved salts Heavy metals Boron Harmful organic substances
WASTEWATER REUSE
Sand filtration/O3/AC/MBR/biological treatment/floculation….
MF/UF+RO (one or two passes)F+EDR+Disinfection+AOPsHybrid FO?
What water quality do we need?
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HYBRID FO ADVANTAGES
Multibarrier concept ‒ High permeate quality
Low and reversible fouling ‒ Less pretreatment ‒ Less chemical cleaning
Product water customization (e.g. boron removal, fertigation)
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FO CHALLENGES
Low flux (ICP & ECP) and expensive elements‒ Improvements in FO membranes:
# Thinner membranes with less tortuosity (S parameter) → less ICP and higher flux # More providers → lower prices
DS recovery is energy intensive.‒ Diluted DS has more osmotic pressure than feed water
DS replacement costs ‒ Reverse salt diffusion and incomplete DS recovery
Permeate quality ‒ DS content
No real data‒ Main studies are lab-scale, synthetic feed, short term and batch conditions. Realistic
studies are still needed → OFREA PROJECT
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OFREA PROJECT
According to a workshop on water reuse: (Optimizing water reuse in EU. Dec 2014)
‒ Water reuse in Spain: 35%‒ Region of Murcia: 98%
of wastewater is reused, mostly in agriculture.
The rest presents high salinity
Reuse Datebase (CEDEX). R. Iglesias, 2007
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OFREA PROJECT
FO-NF pilot plant is operating with real feed, continuous and long-term (> 1 year): Feed water: San Pedro del Pinatar 3 m3/h WWTP
effluent– Conductivity: 4-6 mS/cm – Boron: 1.2 ppm – SAR: 10.6
RD 1620/2007 limit:– Conductivity: 3 mS/cm – Boron: 0.5 ppm – SAR: 6
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OFREA PROJECT: PREVIOUS DESIGN
FO MEMBRANE SELECTION5 membrane brands tested with different configuration.
‒ TFC membrane showed the best performance.
‒ TFC was the selected for the demonstration plant.
Porifera membrane
was selected
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OFREA PROJECT: PREVIOUS DESIGNDS SELECTIONDifferent families. Different Van’t Hoff and diffusivity properties.
• High osmotic pressure obtained by formate• Conductivity must be carefully used as control variable
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OFREA PROJECT: PREVIOUS DESIGNDS SELECTION Dynamic test. Spiral wound commercial element. Asymptotic behavior is caused by internal concentration polarization. For 10 bar no significant differences.
KCOOH the best in terms of flux. Expensive. Compromise between CAPEX and OPEX. NF recovery method has been chosen.
Draw Solution
FOFlux
Reversal flux
losses
DS losses in permeate
Cost of product
Cost of replacement
Recovery method
HMWP + - - - - ++ - NFNaCl + + + - - - RO
HCOOK ++ + + ++ ++ ROMgSO4 - - - - - NFK4P2O7 + ++ ++ + ++ NF
- Low+ High
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OFREA PROJECT: DEMONSTRATION PLANT
The first and largest Hybrid-FO demonstration plant worldwide for
reclamation in agricultural purposes.
84 m2
30 m2
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OFREA PROJECT: DEMONSTRATION PLANT DATA
Stable operation of the FO (22% of loss of flux the first days)
NF permeability decreased due to fouling: ‒ Using an organic DS.‒ Using an inorganic DS
and increasing permeate flowrate. Silicates and gypsum presence.
Specific flux or permeability FO=Flux/(пDS – пfeed)
NF=Flux/(NDP)
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OFREA PROJECT: PERMEATE QUALITY
Stable permeate quality Low conductivity except
for initial NF membranes
B < 0.4 mg/L (>70% removal)
High quality for agricultural use!
A change in NF: savings in chemical consumption
but more energy is used
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OFREA PROJECT: COST EVALUATION
DS reposition and energy consumption
No chemical cleaning in FO membranes
(1) DS price is referred to a small-scale order(2) It is assumed 0.10€/KWh(3) NF Membranes fouled
NF HF
NF HR
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COST EVALUATION AND CONCLUSIONS
UF+RO€/m3
FO+NF€/m3
0.35-0.45 0.96
TERTIARY TREATMENT
LET’S GO DOWN THE PRICES! We demand:
An improvement in FO membranes permeability. To find a really cheap DS with ↑Van’t Hoff coefficient. To regenerate the DS with other systems: MD (waste heat or solar
energy)
LARGE SCALE PILOT SCALE
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CONCLUSIONS
FO-NF operated in the long term with real feed:‒ NF membrane was fouled with the organic DS and the first inorganic DS.‒ FO membrane is working with stable permeability. No fouling in the long-term.‒ High permeate quality (conductivity, SAR and boron are below legislation).
Costs‒ NF chemical cleaning is related to DS. No cleaning in FO membranes. ‒ No remineralization is needed.‒ Relevant costs due to low permeability of FO membranes, DS losses and DS
reconcentration energy.‒ To implement our new DS has decreased the prices relevantly.
Economic feasibility of hybrid FO is highly dependent on all these factors.IN A NEAR FUTURE COULD BE CHEAPER THAN CONVENTIONAL SYSTEMS!
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ACKNOWLEDGMENTS
The research leading to these results has received funding from the LIFE+ Programme of the European Commission (LIFE12/ENV/ES/000632 LIFE OFREA) and from La Generalitat de Catalunya (Industrial PhD program).
All my colleagues from Acciona Agua and Carme Sans from the University of Barcelona.
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