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Dr.Lek Wantha
Water Conditioning Process
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)
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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
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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 compoundsdepend on climatic
Underground water Artesian well Water table well Spring Geysers (hot spring)
Water Sources5
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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
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Water Quality Related to End- use
Water quality parameter
Measurement parameter
pH pHSuspended solid SSTurbidity TurbidityCa2+ and Mg2+ HardnessDissolved ion Conductivity
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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
Water quality Requirement for Agriculture
BOD= Biochemical oxygen demandOD = Dissolved oxygen
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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
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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
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Water Treatment for Industrial Supply
Water treatment
Clarification Disinfection Hardness removal (softening)
Physical
methods
Thermal
Distillation
Freezing-out
Chemical
methods
Lime soda process
Phosphat
e process
Physico-chemic
al method
s
Cation
exchange
process
Deaeration
Chemical
Physical
Distillation
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Water treatmentWater
softening
Ion exchange process
Sodium Cation
Exchange
Hydrogen Cation
Exchange
Lime-soda process
Demineralization
Desalinization
Electrodialysis (ED)
Reverse osmosis (RO)
Hydrated lime (Ca(OH)2) Quicklime (CaO)Soda ash (Na2CO3) Caustic soda (NaOH)
Ion exchange processReverse osmosis (RO)Electrodialysis (ED)
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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
Hardness of WaterCarbonate Hardness
(Temporary hardness)Calcium &
magnesium bicarbonate
Non-Carbonate Hardness
(Permanent hardness)Calcium &
magnesium sulfate
Calcium & magnesium
nitrate
Calcium & magnesium
chloride
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BoilingAdding lime
Adding sodium carbonate
Exchange process
Softening
Adding sodium carbonate
Exchange process
Softening
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Water Softening
Boiling
Adding lime
Adding sodium carbonate
Exchange process
Ca(HCO3)2 + heat CaCO3 +CO2+H2OMg(HCO3)2 + heat MgCO3 +CO2+H2O
Ca(HCO3)2 + Ca(OH)2 2CaCO3 +2H2OMgCl2 + Ca(OH)2 Mg(OH)2 + CaCl2
CaCl2+Na2CO3 CaCo3 + 2NaClMgSO4+Na2CO3+ Ca(OH)2
Mg(OH)2 +CaCo3 + Na2SO4
Ion Exchange Process
Sodium Cation
Exchange
Hydrogen Cation
ExchangeAnion Exchanger
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Ion Exchange Process
Zeolite softening
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.
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Sodium Cation Exchange
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Hydrogen Cation Exchange
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Anion Exchanger
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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
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Types of LimeHydrated lime (Ca(OH)2) quicklime (CaO)
Soda ash (Na2CO3) Caustic soda (NaOH)
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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
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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)
Electrodialysis (ED)25
2Cl- 2e- +Cl2 (g)
2H2O + 2e- 2OH- +H2(g)
Osmosis vs. Reverse Osmosis (RO)
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Osmosis
Direction of water flow
Con
tam
inan
ts
Reverse Osmosis
Direction of water flow
Con
tam
inan
ts
27
Sources
http://water.me.vccs.edu/courses/ENV115/lesson9.htm