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Removal of Arsenic from Drinking Water by Nanofiltration

ACTION 637: Metals and Related Substances in Drinking Water. M E T E A U. Removal of Arsenic from Drinking Water by Nanofiltration . Zdravka Lazarova Austrian Research Centers GmbH – ARC Department WATER. ACTION 637: Metals and Related Substances in Drinking Water. M E T E A U.

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Removal of Arsenic from Drinking Water by Nanofiltration

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  1. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Removal of Arsenic from Drinking Water by Nanofiltration Zdravka Lazarova Austrian Research Centers GmbH – ARC Department WATER

  2. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U • Outline • Pressure-Driven Membrane Processes • Nanofiltration – Main Characteristics • Experimental Results on NF of As(III) and As(V) • Comparison NF90, NF200, NF270 • Effect of Process Parameters • pressure difference • arsenic concentration • pH value of feed • Conclusions

  3. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U • Arsenic Removal Technologies for Drinking Water Treatment • VIABLE TREATMENT TECHNOLOGIES • Coagulation & Precipitation • Adsorption • Ion Exchange • Oxidation • Biological Techniques • MEMBRANE SEPARATIONS

  4. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U • Arsenic Removal Technologies for Drinking Water Treatment • Best Available Technologies (BAT) for Arsenic removal ? • USEPA suggested for As(V): • Ion exchange • Activated alumina • Reverse osmosis • Coagulation/filtration • Lime softening

  5. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U • Arsenic Removal Technologies for Drinking Water Treatment • Technologies with increasing importance ! • Granular Ferric Hydroxide (GFH) • Iron-based Coagulation/Microfiltration • Iron Oxide-Coated Sand • NANOFILTRATION

  6. RO NF UF MF F ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Pressure-Driven Membrane Processes COMPARISON MF - UF – NF- RO

  7. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U COMPARISON - SOLUTES REJECTED MICROFILTRATION 0.15 to 50 µm or higher water monovalentions 0.003 to 0.2 µm ULTRAFILTRATION multivalent ions NANOFILTRATION 0.001 to 0.003 µm viruses bacteria REVERSE OSMOSIS 0.0005 µm suspended solids Source: adapted from http://www.kochmembrane.com

  8. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U NF - Process Characteristics • Performance characteristics between RO and UF • Essentially lower pressure than RO (P ~ 0.5-6 MPa) • Removes molecules in the 0.001 µm range (MWCO ~ 0.2 to 200) • Applications: water softening, removing of organic matter, desalting of organic reaction products, removal of nitrates, removal of metal ions Source: adapter from http://www.kochmembrane.com

  9. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Membrane Process Applied for Large-Scale Cross-Flow Membrane Filtration R(C) RETENTATE (As-Concentrate) Feed p PERMEATE (pure water) P

  10. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U FACTORS AFFECTING ARSENIC RETENTION • SOLUTION CHEMISTRY • pH • As-concentration • As-species • Ionic strength • Co-solutes • FUNCTIONAL PHYSICAL PARAMETERS • Pressure • Temperature • Flow Rate (cross-flow velocity) • Recovery • MEMBRANE CHARACTERISTICS • Porosity/MWCO • Charge • Salt separation ability • Hydrophilicity • Fouling…

  11. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U EXPERIMENTS COMPARISON performance of NF90, NF200, NF270 for removal of As(III) and As(V) from drinking water • Effect of pressure difference • Effect of pH • Effect of As-concentration FilmTec TM NF Membranes, Dow, USA

  12. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Membrane Test Unit AMAFILTER Flow Rate 100- 1000 L/h Pressure 0-60 bar Membrane contact surface 63,5 cm2

  13. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U • Drinking water – Seibersdorf • Warer quality parameters • pH ~7,17 • hardness ~22°dH (3,9 mmol/L) • conductivity~722 µS/cm • Ions cations anions Feed solution for membrane experiments: tap water spiked As(V) Na2HAsO4.7H2O As(III) As2O3

  14. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Comparison NF270-NF200-NF90 permeate flux as a function of pressure difference As(V)- As(III) at 400 L/h; pH 8; [As]=100µg/L;T°=25°C

  15. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Comparison NF270-NF200-NF90 As-retention as a function of pressure difference As(V)- As(III) at 400 L/h; pH=8; [As]=100µg/L;T°=25°C

  16. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U As(V) -retention as a function of As-concentration in feedMEMBRANES NF-90 NF-270 (T) Q =400 L/h; pH= 8; pressure= 5 bar; T°=25°C

  17. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U As(III) -retention as a function of As-concentration in feedMEMBRANES NF-90 NF-270 (T) Q 400 L/h; pH 8; pressure 5 bar; T°=25°C

  18. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U As- Retention/Flux as a function of pH-value MEMBRANES NF-90 Q = 400 L/h; pH 8; pressure 5 bar; T°=25°C

  19. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U COMPARISON As(V)- Sb(V) 20 bar 15 bar 20 bar 10 bar 15 bar 5 bar 10 bar 5 bar

  20. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U CONCLUSIONS • COMPARISON NF-MEMBRANES NF-90, NF-200, NF270 • Membrane performance depends on arsenic forms (As(III) & As(V)) and experimental conditions (feed concentration, pH, ionic strength?, feed matrix (co-ions …)? • Arsenic retention efficiency follows the order : NF90>NF200>NF270 • Removal of As(V) is substantially higher; not sensitive to pressure changes (96%-99% at 5-20 bar) • Effect of feed concentration on As- rejection depends on the membrane type • As(III) treatment is more sensitive to the pH-value of the feed • Pilot experiments are needed for process optimisation

  21. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Electrochemical Oxidation of As-containing waters FLOW SHEET DIAGRAMM H2O -e- H++OH- • ORGANIK As(III) mobile electrochemical plant As(V)

  22. ACTION 637: Metals and Related Substances in Drinking Water M E T E A U Austrian Research Centers GmbH -ARC Thank you for your attention

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