Transcript H-titanate nanofibres for water remediation

Fertiliser drawn forward osmosis process as low
energy desalination for fertigation in the
Murray Darling Basin
Sherub Phuntsho1*, Ho Kyong Shon1 & Amit Chanan2
1Centre
2NSW
for Technology in Water & Wastewater, University of Technology, Sydney (UTS)
State Water
*Email: [email protected]
Outline
 Water consumption and issues in Australia
 Role of desalination
 Principles of Forward osmosis
 Motivation for this research
 Performances of fertilisers as draw solutions
 Limitations for FDFO process and their options
 Future research works
Water consumption and issues in Australia
 Water sources for water supply industry:
 Surface water (95.7%),
 Groundwater (3.4%)
 Desalination (0.8%)
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Agriculture consumes 52% of total water
However, Australia is considered as the driest continent
Frequent drought affects water security & agricultural productivity
Global warming & climate change impacts on water security
Household
13.9%
Other industries
Water supply
8.9%
14.0%
51.8%
Agriculture
Electricity & gas 2.2%
Manufacturing 4.9%
Mining 3.6% 0.6% Forestry & fishing
Source: ABS
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Role of desalination
Desalination: reliable and alternate source to augment fresh water
Desalination technology has significantly improved
However, desalination process is still energy intensive for irrigation
In Australia, Desalination accounts <1% for water supply industry
(2009-2010) mainly for domestic water supply
 Energy: 60% of the total operation cost of RO desalination
 Low energy and Low-cost desalination technologies are necessary for
irrigation
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Source: NWC, Australia
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Types of desalination technologies
State of the art RO desalination consumes energy ~3.0 kWh/m3
Forward osmosis is emerging technology
FO for potable water requires 0.84 kWh/m3
FDFO desalination for fertigation <0.2 kWh/m3
6
5.66
5
4.05
Energy (kWh/m3)
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4.00
4
3.21
MSF
MED
MED-low temp/electrical
RO
RO-energy recovery
NH3-CO2 FO (1.5 M feed)
FO for direct fertigation
3.00
3
2
0.84
1
0.24
5
0
Desalination Technologies
What is Forward Osmosis Process?
membrane
Driving force = External energy
osmotic
pressure
Forward Osmosis
Water
Brine
Water
membrane
Brine
Brine
Water
Reverse Osmosis
ΔP
Osmosis
Equilibrium
Brine as Draw Solution (DS)
Driving force = concentration/osmotic gradient
FO desalination process for potable water
 Forward osmosis desalination for potable water
 However, diluted DS solution cannot be used directly with separation
 Separation of draw solute is not easy and still require energy
Fertiliser drawn FO (FDFO) desalination for fertigation
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FO desalination for non-potable purpose such as irrigation is ideal
Highly concentrated fertiliser draw solution is used in FDFO process
Diluted fertilizer solution can be used directly for fertigation
Novelty: FDFO does not require separation process, low energy
Fertilisers anyway used for agriculture
Motivation: Water issues in the Murray Darling Basin
 MDB>1 million sq.km
 65% of Australia’s irrigated land
 40% of Australia’s Agricultural
production
Source: MDBA
 A$ 15 billion to economy
 60% of basin’s total annual inflow
diverted for irrigation
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Motivation: Water issues in the Murray Darling Basin
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Over allocation of river water for consumptive
Reduced river flow down stream & impact on the river ecosystem
Urgent need to restore river ecosystem
Proposed plan by MDBA to cut 2,750 GL of water for environment
Potential implications on food production and food prices
Environmental issues in the basin
Economic need of the basin
Overuse of water
Salinity
Drought
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Motivation: Salt Interception Scheme in the MDB
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Brackish groundwater (BGW) causes increased river water salinity
SIS consists of bore holes at certain distance from rivers
Pumps 22 million m3/yr & removes half million tons of salts by evaporation
Existing SIS: unsustainable use of groundwater resources
Integrate FDFO with existing SIS – sustainable use of BGW for irrigation
Reduce pressure on the river water for irrigation & increase environmental
flows
Fertigation
FDFO
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Performances: Fertilisers as draw solutes (DS)
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Most soluble fertilisers can used as draw solutes for FDFO desalination
Investigated 11 different fertilisers as draw solutions
Osmotic pressure: important factor for FO process
All fertilisers generates osmotic pressure higher than seawater (28 atm)
Osmotic pressure of
seawater ~ 28 atm
Performance: Water extraction capacity of fertilisers
 Estimate volume of water a kg of fertiliser can extract depends on:
 MW of the compound
 Osmotic pressure
 TDS of the feed water
 More water extracted from low TDS feed water source
 Important for nutrient concentrations in the final product water
Feed TDS→ 35,000 mg/L
NH4Cl
28
KCl
20
NH4NO3
14
NaNO3
17
DAP
13
KNO3
13
SOA
12
Urea
13
MAP
13
Ca(NO3)2
10
KH2PO4
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20,000 mg/L 10,000 mg/L 5,000 mg/L
52
107
216
37
76
155
28
61
130
32
66
135
26
56
116
25
54
112
23
49
104
25
51
103
24
49
100
20
43
90
18
40
83
2,000 mg/L
542
389
342
340
299
284
277
254
252
236
210
Performance: Water flux in the FDFO process
 Water flux: rate of water transport per unit area in a unit time
 Water flux depends on the types of fertilisers used, osmotic pressure
and concentration of DS and the feed TDS
 At higher fertiliser concentrations, water flux is comparable to RO
desalination process
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9
Pure water flux (μm/s)
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NH4NO3
(NH4)2SO4
NH4Cl
Ca(NO3)2
NH4H2PO4
(NH4)2HPO4
KNO3
NaNO3
KCl
7
6
5
4
3
2
1
0
0
0.5
1
1.5
2
Draw solution concentration (M)
2.5
3
Limitations of FDFO proces: reverse diffusion of DS
 Reverse diffusion of fertiliser salts to feed water
 Economic loss of fertiliser
 Complicates concentrate management due to presence of fertiliser
in the feed concentrate
Saline
water
FO
membrane
Fertiliser
solution
Feed solutes
Fertiliser solutes
Water flux
Limitations of FDFO process: nutrient concentrations
 Final nutrient concentrations important for direct fertigation
 Target concentrations:
 Types of crops, growing seasons, soil conditions, etc.
 Eg. tomato: 100-200 mg/L N, 40-50 mg/L P and 200-300 mg/L K
 Final concentrations depend on feed TDS & osmotic pressure
 Low final nutrient concentrations using blended fertilisers containing all
nutrients
Fertilisers
Urea
NH4NO3
SOA
NH4Cl
Ca(NO3)2
NaNO3
MAP
DAP
KH2PO4
KNO3
BW2
BW5
BW10
1829/0/0
1020/0/0
761/0/0
482/0/0
720/0/0
483/0/0
482/1066/0
706/781/0
0/1077/1359
486/0/1365
4500/0/0
2670/0/0
2020/0/0
1210/0/0
1870/0/0
1210/0/0
1200/2660/0
1820/2010/0
0/2720/3440
1230/0/0
4500/0/0
2700/0/0
2000/0/0
1200/0/0
1900/0/0
1200/0/0
1200/2700/0
1800/2000/0
0/2700/3400
1200/0/0
Option 1: Final nutrient concentrations by dilution
Option 2: Integrated FDFO-NF desalination process
FDFO desalination with NF
as post-treatment process
FDFO desalination with NF
as pre-treatment process
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Option 3: hybrid system integrated with WWTP
FDFO – WWT hybrid system
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Future research works
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Pilot-scale operation of FDFO desalination process
Improve the process efficiency of the FDFO desalination
Pilot-scale will be tested at Buronga SIS at Mildura, NSW
Energy estimations and the Life Cycle Analysis of the FDFO
desalination
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Acknowledgements
Research funded by the National Centre for Excellence in
Desalination Australia (NCEDA)