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Water Conditioning Process

Water Conditioning Process. Dr.Lek Wantha. Contents. Water usage in industries Water sources Water quality related to end-use Water treatment for industrial supply Water softening Ion exchange process Lime-soda process Demineralization Desalting or Desalinization Electrodialysis (ED)

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Water Conditioning Process

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  1. Water Conditioning Process Dr.LekWantha

  2. Contents • Water usage in industries • Water sources • Water quality related to end-use • Water treatment for industrial supply • Water softening • Ion exchange process • Lime-soda process • Demineralization • Desalting or Desalinization • Electrodialysis (ED) • Reverse osmosis (RO)

  3. Water Usage in Industries • Component in products • Energy carrying media (heat media), i.e. steam • Cooling media • Cleaning • Separating & Purification • Transportation of raw material & products • Mixing • Complete reaction

  4. Water Sources(exclude tap water) • Sea water • Salt >>>2.6% by mass NaCl, MgCl2, sulfate • Gases>>> N2, O2,CO2 • Surface water • Flowing in river, cannel • Contain of inorganic and organic compounds depend on climatic • Underground water • Artesian well • Water table well • Spring • Geysers(hot spring)

  5. Water Sources

  6. Water Quality Related to End-use • Inorganic salts • Ca2+ • Mg2+ • Na+ • K+ • Sulfate carbonate • Chloride ion • Organic compounds & dissolved gasses • CO2 • O2 • H2S • Organisms • Aquatic animals • Aquatic insects • Microorganisms

  7. Water Quality Related to End- use

  8. Water quality Requirement for Agriculture • Livestock • Low bacteria, <40/100 mL • Low toxic concentration • Irrigation • Low dissolved solids, <500 mg/L • Total bacteria, 100,000/100 mL • Low heavy metal • Fish, aquatic life, wide life requirements • Low toxic concentration • pH near neutral (6.5-8.5) • Low BOD (1-2 mg/L) • High DO • Cold: 6-7 mg/L (15 ºC) • Warm: 4-5 mg/L (20 ºC) • Low temperature, turbidity BOD= Biochemical oxygen demand OD = Dissolved oxygen

  9. Water quality Requirement for Industries • Cooling • Low hardness, 50 ppm of (Mg2+ + Ca2+) • Low corrosivity • Food processing, brewing & soft drinking • As public drinking water, but F- <1 ppm • Thermal power • Total Dissolved Solid (TDS) < 0.1 ppm • Public recreational requirements • Free of color, odor, taste and turbidity • Total bacteria, <1000/100 mL • Coliform bacteria <100/100 mL • Low nutrients

  10. Water quality Requirement for Industries • Public drinking water (treated) • No bacteria • Low nitrate, nitrite (< 10 ppm) • Very low pesticide (none or < 0.05 ppm) • Fluoride allowable to 2.4 ppm • Toxic substances (below criteria level) • TDS < 500 ppm

  11. Water Treatment for Industrial Supply

  12. Hydrated lime (Ca(OH)2)  Quicklime (CaO) Soda ash (Na2CO3)  Caustic soda (NaOH) • Ion exchange process • Reverse osmosis (RO) • Electrodialysis (ED)

  13. Water Softening • Reduce/remove hardness • Hardness • Dissolved salts: Calcium and magnesium • Problems Calcium bicarbonate → Calcium carbonate + Water + Carbon dioxide Ca(HCO3)2 → CaCO3 + H2O + CO2 • deposition of calcium carbonate scale in pipes and equipment • causes corrosion of iron or steel equipment • culprit in forming soap scum

  14. Softening Boiling Adding lime Adding sodium carbonate Exchange process Softening Adding sodium carbonate Exchange process

  15. Ca(HCO3)2 + heat  CaCO3 +CO2+H2O • Mg(HCO3)2 + heat  MgCO3 +CO2+H2O • Ca(HCO3)2 + Ca(OH)2  2CaCO3 +2H2O • MgCl2 + Ca(OH)2  Mg(OH)2  + CaCl2 • CaCl2+Na2CO3  CaCo3  + 2NaCl • MgSO4+Na2CO3+ Ca(OH)2  Mg(OH)2  +CaCo3  + Na2SO4 Sodium Cation Exchange Ion Exchange Process Hydrogen Cation Exchange Anion Exchanger

  16. Ion Exchange Process Zeolite softening

  17. Ion Exchange Process • Advantages  • Ion exchange can be used with fluctuating flow rates. • Makes effluent contamination impossible. • Resins are available in large varieties from suppliers and each resin is effective in removing specific contaminants. • Limitations  • Pretreatment is required for most surface waters. • Waste is highly concentrated and requires careful disposal. • Unacceptable high levels of contamination in effluent. • Units are sensitive to the other ions present.

  18. Sodium Cation Exchange

  19. Hydrogen Cation Exchange

  20. Anion Exchanger

  21. Lime-soda Process • Lime = CaO + Soda = soda ash (Na2CO3) • Carbonate hardness (temporary) • Ca(HCO3)2 + Ca(OH)2  2CaCO3 +2H2O • Mg(HCO3)2 + Ca(OH)2  MgCO3+CaCO3 +2H2O • MgCO3+ Ca(OH)2  Mg(OH)2 +CaCO3 • Non-carbonate hardness (Permanent) • MgCl2 + Ca(OH)2  Mg(OH)2  + CaCl2 • CaCl2+Na2CO3  CaCo3  + 2NaCl • CaSO4+Na2CO3  CaCo3  + Na2SO4 • MgSO4+Na2CO3+ Ca(OH)2  Mg(OH)2  +CaCo3  + Na2SO4

  22. Types of Lime Hydrated lime (Ca(OH)2)  quicklime (CaO) Soda ash (Na2CO3)  Caustic soda (NaOH)

  23. Demineralization Process • Removal of minerals and nitrate from the water • Ion exchange: • removal of hardness ions (magnesium and calcium) • water demineralization • 90% of barium, arsenic, cadmium, chromium, silver, radium, nitrites, selenium and nitrates can be effectively removed from water • Reverse osmosis • Electrodialysis • membrane processes, remove dissolved solids from water using membranes

  24. Desalting or Desalinization Process • Treatment of highly saline water: • sea water • 3,500 ppm of dissolved salt • Lowing saline contents • < 500 ppm • Two methods • Electrodialysis (ED) • Reverse Osmosis (RO)

  25. Electrodialysis (ED) 2H2O + 2e-2OH- +H2(g) 2Cl- 2e- +Cl2 (g)

  26. Osmosis vs. Reverse Osmosis (RO) Reverse Osmosis Osmosis Contaminants Contaminants Direction of water flow Direction of water flow

  27. Sources • http://water.me.vccs.edu/courses/ENV115/lesson9.htm

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