Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr....

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Water Softening Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE

Transcript of Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr....

Page 1: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Water SofteningWater Softeningby Precipitation with Lime

at the Bloomington, Illinois Water Treatment Plant

Dr. John T. O’Connor, PETom O’Connor, PE

Page 2: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Water HardnessWater Hardness

Hardness is the sum of calcium and magnesium concentrations,

expressed as mg/l as CaCO3 equivalent in waterworks practice.

Page 3: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Hardness ValuesHardness Valuesmg CaCO3 equivalent / liter

City Source Raw SoftenedKansas City 75% MO River, 25% alluvial wells 218 85

St. Louis 66% MS River, 34% MO River 208 107

Columbia Alluvial wells, MO R. flood plain 350 155

Chicago Lake Michigan, South Dist. Plant 128 128

Highland Silver Lake 104 141

Normal 14 Wells 419 108

Bloomington Lakes Bloomington, Evergreen 195 111

Page 4: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Benefits of SofteningBenefits of Softening

• Reduced film formation on household fixtures, glassware, pots and pans, silverware

• Reduced scale formation in pipes, hot water heaters and plumbing fixtures (if stabilized)

• Removal of metals (Fe, Mn, Cu, Pb, Cd, Zn, Ni)

• Removal of radionuclides (radium, uranium)

• Disinfection (due to high pH of lime)

• Marginal removal of TOC (lime co-precipitation)

Page 5: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Cation ExchangeCation Exchangeas alternative to lime precipitationas alternative to lime precipitation

Washington. Illinois

• Sodium ion exchanged for calcium and magnesium ionsSodium ion exchanged for calcium and magnesium ions

• Increases in Total Dissolved Solids (TDS), conductivityIncreases in Total Dissolved Solids (TDS), conductivity

• Regeneration with NaCl (brine); brine disposal requiredRegeneration with NaCl (brine); brine disposal required

• Potential adverse health effects of sodium ion increasePotential adverse health effects of sodium ion increase

Page 6: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Cati

on

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Cati

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Throughput set for

Ammonium Ion RemovalMorton, Illinois

Page 7: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

SSAALLTT

SSTTOORRAAGGEE PPIITT

NaCl ~ $27 / ton (2007)

NaCl + H2O Na+ + Cl– (brine)

Page 8: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Brine Transfer PumpBrine Transfer Pump

Brine ~11% NaCl (1 lb/gal)

Corrosive to metal, concrete

Page 9: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Spent Spent Brine Brine

DisposalDisposal

•Sewer•Evaporation• Injection•Ocean•Deicing

Page 10: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lim

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1 meq/ l = 50 mg CaCO3 eq./ l

Page 11: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lime Softening - PrecipitationLime Softening - Precipitation

Single-stageSingle-stage—when source water has high calcium —when source water has high calcium and low magnesium hardness - and low magnesium hardness - CaCOCaCO3 3

Excess limeExcess lime—source water is high in both calcium —source water is high in both calcium and magnesium hardness - and magnesium hardness - CaCOCaCO3 3 + Mg(OH) + Mg(OH)22

Mg(OH)Mg(OH)2 2 may be recovered at lowered pH for use as a ‘recycled’ coagulant.may be recovered at lowered pH for use as a ‘recycled’ coagulant.

Page 12: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.
Page 13: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.
Page 14: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.
Page 15: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.
Page 16: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

‘Overfeed’ of Lime leads to post-precipitation upon Recarbonation

Page 17: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lime Contact ClarifierLime Contact Clarifier

Lime Feed

CaO(s) + H2O Ca(OH)2 (s)

Page 18: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Recarbonation BasinRecarbonation Basin

Page 19: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lime Hopper and Slaking FacilitiesLime Hopper and Slaking Facilities

Page 20: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lime AugerLime Auger

Page 21: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lime Feed LineLime Feed Line

Page 22: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Dorr-Oliver, Permutit and and CBI-WalkerDorr-Oliver, Permutit and and CBI-WalkerUpflow Contact ClarifiersUpflow Contact Clarifiers

Bloomington, Illinois, Water Treatment Plant

Page 23: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Dorr-Oliver Softener with V-notch overflow weirs;

effluent channels in center and perimeter of tank

Page 24: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Dorr-Oliver Softener drained for

maintenance

Influent pipe, lime feed and

mixing

Page 25: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Dorr-Oliver Softener: Detail of dewatered peripheral effluent

channel

Page 26: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Permutit Softener•Conical reaction well

•Solids contact with slurry recirculation

Page 27: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Permutit Softener•Settling compartment with radial launders

•Submerged orifices minimize variations in effluent discharge

Page 28: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Permutit SoftenerTwo effluent launders convey softened water to recarbonation basin

Page 29: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Sludge Rake

steel truss with squeegees to plow solids to center hopper

Page 30: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Carbon dioxide (COCarbon dioxide (CO22 or H or H22COCO33) -) - Recarbonation Recarbonation lowers pH; alkalinity unchangedlowers pH; alkalinity unchanged

Sulfuric AcidSulfuric Acid lowers pH and alkalinity; adds sulfate ionlowers pH and alkalinity; adds sulfate ion (microbial activity may lead to H(microbial activity may lead to H22S formation)S formation)

ChlorineChlorine produces hydrochloric acid (HCl); lowers pHproduces hydrochloric acid (HCl); lowers pH

StabilizationStabilization

Page 31: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Bloomington, Illinois’ ‘Old’ Plant (1929, 1956, 1966)

Page 32: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Recarbonation BasinRecarbonation Basin Settling CompartmentSettling Compartment

CO2 was Injected20 feet below

surface; no

bubbles evident; almost

total absorption of applied

gas.

Clear water indicates no

post-precipitation of calcium carbonate.

Page 33: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Removal of Softening Sludge from Storage LagoonRemoval of Softening Sludge from Storage LagoonChampaign, Illinois

Page 34: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Sidewall Sludge Cutting DeviceSidewall Sludge Cutting DeviceChampaign, Illinois

Page 35: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Utilization of Utilization of Reclaimed Reclaimed

SludgeSludgeChampaign, Illinois

Sludge pumped to tanker truck for

application to farmland as ‘soil sweetener’.

Page 36: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Contact Clarifier - Floating SolidsContact Clarifier - Floating SolidsMissouri Lime Softening Plant

Page 37: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Floating SolidsFloating Solids

Page 38: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Micrograph of Floating SolidsMicrograph of Floating Solids

Green crystals = calcium carbonate

Orange strands = algal filaments

Page 39: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Lime Softening SolidsLime Softening Solids

Calcium carbonate crystals (green)

Algal cells (orange)

Page 40: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

EVALUATE

• Chemical dosages

• PAC, polymer feeds

• Flocculation time and paddle speed

• Floc size, density

• Floc settling rates

• Temperature effects

• Organism removals

Jar TestingJar Testing

Page 41: Water Softening by Precipitation with Lime at the Bloomington, Illinois Water Treatment Plant Dr. John T. O’Connor, PE Tom O’Connor, PE.

Why lime softening also removes trace metals.