Zero Liquid Discharge Desalination

1. Zero Liquid Discharge Desalination Rick Bond, Vasu Veerapaneni

2. Concentrate Management Options • Direct discharge to surface water. • Discharge to POTW. • Underground injection. • Zero Liquid Discharge. Discharge options Where discharge is constrained or restricted

3. Discharge options that do not remove salt from the water cycle are unsustainable. Viewed as a resource rather than waste, concentrate can be treated to recover potable water and salt products. Complete treatment to recover all of the concentrate as potable water is referred to as Zero Liquid Discharge (ZLD) desalination. Motivation to Treat and Recover Concentrate

4. Established ZLD Technologies Are Expensive • Thermal desalination – expensive and energy intensive. • Evaporation ponds – expensive, require large land areas, and evaporated water is a lost resource.

5. New ZLD Approaches Have Four Basic Steps Product Water Primary Desalination Concentrate Recovery in RO is limited by sparingly soluble salts Concentrate Secondary Treatment Desalination salts Final ZLD Evaporation Concentrate is treated to remove salts Allowing further recovery by desalination salts

6. Costs Are Minimized by Maximizing Recovery in Secondary Desalination Product Water Primary Desalination Concentrate Secondary Treatment Desalination Concentrate $2 -$3 /kgal salts Final ZLD Evaporation $13 /kgal salts

7. Technology options Chemical Softening Fluidized Bed Crystallizer MIEX Ion Exchange Coagulation Activated Alumina Biological Concentrate Treatment Forward Osmosis Capacitative Distillation Thermo- Ionic Desalination Membrane Distillation RO Electro-dialysis Reversal Electro-dialysis Metathesis Vibratory Shear Enhanced Process Secondary Desalination Thermal Evaporation Pond Salt Gradient Solar Pond Wind aided intensified evaporation (WAIV) Dew-vaporation Turbomister Final ZLD Evaporation

8. Inorganic scalants - CaCO3, BaSO4,CaSO4, SiO2. Natural organic matter (NOM). Fouling potential of NOM is increased by complexation reactions between NOM and Ca. Recovery in Secondary Desalination Is Limited by Membrane Fouling

9. Zero Liquid Discharge for Inland Desalination AwwaRF Project #3010 (2005 – 2007) Brackish groundwater, surface water, reclaimed water Zero Liquid Discharge Desalination of Waters with High Organic Content Water Research Foundation Project #4163 (2008 – 2010) Brackish water with high concentrations of natural organic matter Two different approaches were evaluated in research conducted to reduce ZLD costs

10. ZLD with Fluidized Bed Crystallization (Project #3010) Primary RO • Product Water • Product Water Filter Secondary RO • Concentrate Fluidized bed crystallizer Brine Concentrator • Concentrate Evaporation pond

11. Fluidized Bed Crystallizer (Crystalactor) • Ca and Ba are removed by precipitation onto CaCO3 crystals. • Used extensively in Europe for softening. • Produces near anhydrous crystals (90% dry) therefore low solids volume. • High loading rate, (80 m/h (33 gpm/sf) small footprint.

12. Fluidized Bed Crystallizer vs. Chemical Softening

13. Treatment costs were reduced by 50 to 60 percent

14. Energy consumption was reduced by 65 to 75 percent

15. Primary RO product water product water EDM concentrate Pond, WAIV, or thermal salts ZLD Desalination Using Electrodialysis Metathesis (EDM) (Project #4163) concentrate

16. Innovative arrangement of membranes used to separate concentrate into two streams of highly soluble salts. Although this variation is new, the technology and the membranes have been used for decades. Electrodialysis Metathesis (EDM) Is a New Electrodialysis Technology

17. Electrodialysis Is a Membrane Separation Process Driven by Electric Potential • Driving force is electric potential between anode and cathode. • Cell pair comprises cation and anion exchange membranes, diluate cell, and concentrate cell. • Ions are extracted from diluate compartment and held in concentrate compartment. • A stack contains hundreds of cell pairs.

18. In Basic Electrodialysis All Removed Ions Are Contained in a Single Concentrate Stream Cell pair CaSO4 BaSO4 CaCO3 Diluate Concentrate C C A Mg2+ (+) (-) Cl- Na+ SO42- anode cathode Ca2+ Concentrate Feed

19. EDM Concentrate Is Separated into Two Highly Soluble Streams Cell set (4 membranes, 4 cells) Na with anions Cl with cations C SC A SA SC Mg2+ Cl- (+) (-) Cl- Na+ Na+ anode cathode SO42- Ca2+ NaCl Concentrate 2 Cl with cations NaCl Concentrate 1 Na with anions Feed

20. Solubilities of Na2SO4, CaCl2, and NaCl are 15 to 35 Times Solubility of CaSO4 Solubility of Salts in water CaCl2 Maximum 3.1M at 33°C NaCl Na2SO4 CaSO4

21. Development of solid products with EDM approach Primary RO product water recycled NaCl NaCl recycled to EDM concentrate NaCl EDM NaOH NaOH Pond, WAIV, or thermal CaCO3 Mg(OH)2 CaSO4 salt

22. EDM effectively separated the concentrate into two streams of highly soluble salts. Silica and TOC went through EDM largely unaffected and therefore posed no membrane fouling risk. No inorganic or organic compound concentrations were found in any of the EDM streams that would be considered potential membrane fouling threats. EDM water quality results

23. EDM Pilot results with NF concentrate EDM concentrate was effectively separated into two streams of highly soluble salts: sodium with anions and chloride with cations.

24. EDM recovery in the pilot tests exceeded 99% Recovery in EDM depends of the rate of water transfer by osmosis and electroosmosis. The rate of water transfer in electrodialysis is proportional to the equivalents of ions transferred.

25. EDM recovery decreased with TDS

26. EDM energy consumption increased as TDS increased

27. EDM treatment costs compared with thermal EDM less expensive Transition range Thermal less expensive

28. EDM Method was particularly cost effective for low TDs sources

29. Summary • Concentrate management will become increasingly important as we strive to manage salinity and meet water demands. • Two ZLD methods were evaluated in AwwaRF/WRF research projects: fluidized bed crystallization and EDM. • Each showed potential to reduce ZLD treatment costs by more than 50 percent. • Best ZLD method may depend on water quality characteristics and treatment goals.

30. Acknowledgements • City of Phoenix • City of Scottsdale • San Antonio Water & Sewer • City of Beverly Hills • SNWA • California Energy Commission • Orlando Utilities Commission • Tampa Bay Water • South Florida WMD • Southwest Florida WMD • St. Johns River WMD • Water Research Foundation

31. MSSC2011 Annual Salinity SummitFEBRUARY 17-18SAN ANTONIO, TEXAS Zero Liquid Discharge Desalination Rick BondBondRG@bv.com