Fertiliser drawn forward osmosis process as low energy desalination for fertigation in the Murray Darling Basin

1. Fertiliser drawn forward osmosis process as low energy desalination for fertigation in the Murray Darling Basin Sherub Phuntsho1*, Ho Kyong Shon1 & Amit Chanan21Centre for Technology in Water & Wastewater, University of Technology, Sydney (UTS)2NSW State Water *Email: sherub.Phuntsho@uts.edu.au

2. 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

3. Water consumption and issues in Australia • Water sources for water supply industry: • Surface water (95.7%), • Groundwater (3.4%) • Desalination (0.8%) • 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 Other industries Agriculture Water supply Electricity & gas Manufacturing Forestry & fishing Mining Source: ABS

4. 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 Source: NWC, Australia

5. 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 Source: Phuntsho et al. 2012

6. osmotic pressure Brine Water Water Brine Brine Water membrane Equilibrium Osmosis What is Forward Osmosis Process? Reverse Osmosis Forward Osmosis ΔP membrane Brine as Draw Solution (DS) Driving force = External energy Driving force = concentration/osmotic gradient

7. 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

8. Fertiliser drawn FO (FDFO) desalination for fertigation • 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

9. 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 • A$ 15 billion to economy • 60% of basin’s total annual inflow diverted for irrigation Source: MDBA

10. Motivation: Water issues in the Murray Darling Basin • 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

11. Motivation: Salt Interception Scheme in the MDB • 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

12. Performances: Fertilisers as draw solutes (DS) • 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

13. 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

14. 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

15. 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 FO membrane Fertiliser solution Saline water Feed solutes Fertiliser solutes Water flux

16. 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

17. Option 1: Final nutrient concentrations by dilution

18. Option 2: Integrated FDFO-NF desalination process FDFO desalination with NF as post-treatment process FDFO desalination with NF as pre-treatment process

19. Option 3: hybrid system integrated with WWTP FDFO – WWT hybrid system

20. Future research works • 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

21. Acknowledgements • Research funded by the National Centre for Excellence in Desalination Australia (NCEDA)

22. Thank you