chemical clarification – coagulation methods
DESCRIPTION
CHEMICAL CLARIFICATION – COAGULATION METHODS. Prepared By Michigan Department of Environmental Quality Operator Training and Certification Unit. CLARIFICATION. Removal of Settleable and Floatable Solids. CHEMICAL CLARIFICATION. Increase Removal Amount (More Solids Out) - PowerPoint PPT PresentationTRANSCRIPT
CHEMICAL CLARIFICATION – CHEMICAL CLARIFICATION – COAGULATION METHODSCOAGULATION METHODS
CHEMICAL CLARIFICATION – CHEMICAL CLARIFICATION – COAGULATION METHODSCOAGULATION METHODS
Prepared ByMichigan Department of Environmental Quality
Operator Training and Certification Unit
CLARIFICATIONCLARIFICATIONCLARIFICATIONCLARIFICATIONRemoval of
Settleable and Floatable Solids
•Increase Removal Amount(More Solids Out)
•Increase Removal Rates(Solids Settle Faster)
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
•Less Solids
•More Sludge
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
(in effluent)
(for disposal)
Stoke’s LawStoke’s Law
2(p - po)g 9n
(d/2)2VF =
VF = Fall Velocity(p - po) = Density difference between
particle and watern = viscosity of waterg = gravitational acceleration constantd = diameter of the particle
2(p - po)g 9n
(d/2)2VF =
VF = Fall Velocity(p - po) = Density difference between
particle and watern = viscosity of waterg = gravitational acceleration constantd = diameter of the particle
Stoke’s LawStoke’s Law
2(p - po)g 9n
(d/2)2VF =
VF = Fall Velocity(p - po) = Density difference between
particle and watern = viscosity of waterg = gravitational acceleration constantd = diameter of the particle
Stoke’s LawStoke’s Law
2(p - po)g 9n
(d/2)2VF =
VF = Fall Velocity(p - po) = Density difference between
particle and watern = viscosity of waterg = gravitational acceleration constantd = diameter of the particle
Stoke’s LawStoke’s Law
•Increase Particle Size(Average Diameter)
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
Particle Size versus Settling Time
Particle Sizemm Order of Size Time to Settle
1.0 Coarse Sand 3 Seconds
0.1 Fine Sand 38 Seconds
0.01 Silt 33 Minutes
0.001 Bacteria 55 Hours
0.0001 Colloidal 230 Days
0.00001 Colloidal 6.3 Years
•Increase Particle Size
•Encourage Contact
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICAL CLARIFICATION
1. Coagulation2. Flocculation
3. Separation
Coagulation
•Rapid Mixing
•“Pin-point” Floc Formation
•Chemical Addition
FlocculationFlocculation• Slow Mixing
• Floc Growth
• Increased Diameter
Solids SeparationSolids SeparationSolids SeparationSolids Separation
• Clarified Liquid• Concentrated Suspension
(sludge)
Usually Gravity Settling
Other Processes(dissolved air flotation, etc.)
•Increase Particle Size
•Encourage Contact
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
* Fine Suspended Particles Have an Electrostatic Charge (Usually +)
* Encourage Contact
* Destabilize Charges
Natural Stabilizing ForceKeeps Solids Apart
Like Charges Repel
Purpose of Chemical Clarification
Mechanisms
•Electrostatic Charge Reduction
•Interparticle Bridging
•Physical Enmeshment
Electrostatic Charge Reduction
• Solid Particles have an Electrostatic Charge
usually negative
solids repel one another
• Add Chemical to Neutralize Charge
positive charge (cationic)
• Must Not Overdose
excess positive charge
Interparticle Bridging• Polyelectrolytes (polymers)
long chainselectrostatic charges
• Adsorb on the Charged Particles
bridges particles together
NegativeColloidalParticles
Cationic Polymer Unit
Interparticle Bridging
Interparticle Bridging• Polyelectrolytes (polymers)
long chainselectrostatic charges
• Adsorb on the Charged Particles
bridges particles together
•Must Not Overdose
Physical Enmeshment• Ions Combine with Hydroxyl Ions
OH -
• Gelatinous Precipitate Forms
flakes
void spaces
• Collects Particles as it Forms
co-precipitate
enlarges the floc
Mechanisms
•Electrostatic Charge Reduction
•Interparticle Bridging
•Physical Enmeshment
CHEMICAL CHEMICAL CLARIFICATIONCLARIFICATION
CHEMICAL CHEMICAL CLARIFICATIONCLARIFICATION
1. Coagulation1. Coagulation2. Flocculation2. Flocculation3. Separation3. Separation
COAGULATION
FLOCCULATION
Rapid MixAdequate Contact
Slow MixingIncrease Floc Size
PROCESS CONTROL
1. Provide complete mixing.
2. Control mixing for floc.
3. Control chemical dose.
Chemical TreatmentChemical TreatmentChemical TreatmentChemical Treatment
Addition of
Positive Ions (Cations)
orPolymers
CHEMICAL TREATMENTCHEMICAL TREATMENT
Aluminum Sulfate (Al+3)
Calcium Hydroxide (Ca+2)
Ferric (Iron) Chloride (Fe+3)
Positive Ions Added by AddingMetal Salts
Such As
Metal Salts UsedMetal Salts UsedMost Common
Alum (Aluminum Sulfate)Alum (Aluminum Sulfate)Ferric ChlorideFerric ChlorideLime ( Calcium Hydroxide)Lime ( Calcium Hydroxide)
Others
Sodium AluminateSodium AluminateFerric SulfateFerric SulfateFerrous SulfateFerrous SulfateFerrous ChlorideFerrous Chloride
Aluminum Sulfate (Dry)Al2(SO4)3
. 14 H2O
“Alum” or “Filter Alum”
Available in Various GradesLump (rarely used)
Ground (granulated)Rice
Powdered
Feeds Easilydoesn’t “bulk”
Aluminum Sulfate (Dry)Al2(SO4)3
. 14 H2O
Irritantskinmucus membraneseyes
Irritantskinmucus membraneseyes
Must be kept dryMust be kept drycake to solid lumpcake to solid lumpcorrosivecorrosiveequipment must be cleanedequipment must be cleaned
Dosage Approximately 75 - 250 mg/LDosage Approximately 75 - 250 mg/L
Aluminum Sulfate (Liquid)Al2(SO4)3
Approximately 11 pounds / gallonApproximately 5.4 pounds of “dry”/gal
Ease of Handling vs. Transportation Costs
Corrosiveequipment must be protected
Supports Bacterial Growth / Deposits
Reduces Alkalinity
Ferric Chloride Ferric Chloride (FeCl(FeCl33))Anhydrous
Absorbs Moisture from the AirCorrosive with WaterReleases Heat as it is Dissolved
CrystalAbsorbs MoistureReleases Less Heat
LiquidLined ContainersShipped at 30 - 40 %Approximately 12 pounds per gallon
Ferric Chloride Ferric Chloride (FeCl(FeCl33))
Corrosiveequipment must be protected
Stains
Safety Concerns
Dosage Approximately 45 - 90 mg/L
LIMEHydrated Lime
Ca(OH)2
CoagulantpH AdjustmentAbsorbs Moisture
Quicklime (anhydrous)CaOAbsorbs MoistureMust be “Slaked”Heat GeneratedCosts vs. Handling
LIMEErode or Wear Equipment
Scale Build-up
LIMEErode or Wear Equipment
Scale Build-up
Dosage Approximately 200 - 400 mg/L
Irritantskineyesmucus membraneslungs
Polymeric Flocculants“Polyelectrolytes”
“Polymers”
Organic Compounds - Repeating Units
Long Chain - High Molecular Weight
PolymersPolymersPolymersPolymers
Classified By:Classified By:
ChargeCharge
Charge DensityCharge Density
Size (Length)Size (Length)
PolymersPolymersPolymersPolymers
Charge:Charge:
““Cationic” - positive chargeCationic” - positive charge
““Anionic” - negative chargeAnionic” - negative charge
““Nonionic” - no free chargeNonionic” - no free charge
PolymersPolymersPolymersPolymersCharge Density:Charge Density:
Relative Number of Locations Along Relative Number of Locations Along the Chain That Carry a Chargethe Chain That Carry a Charge
Percent of Maximum PossiblePercent of Maximum Possible
Low Charge (<25%)Low Charge (<25%)Medium Charge (25 -50%)Medium Charge (25 -50%)High Charge (>50%)High Charge (>50%)
PolymersPolymersPolymersPolymersSize (Length):Size (Length):
Designated by Molecular WeightDesignated by Molecular Weight““Low” - <10,000 gm/moleLow” - <10,000 gm/mole
““Medium” - 10,000 to 100,000 gm/moleMedium” - 10,000 to 100,000 gm/mole
““High” - 100,000 to 1,000,000 gm/moleHigh” - 100,000 to 1,000,000 gm/mole
““Very High” - 1,000,000 to 10,000,000 gm/moleVery High” - 1,000,000 to 10,000,000 gm/mole
““Ultrahigh” - >10,000,000 gm/moleUltrahigh” - >10,000,000 gm/mole
AnionicPolymers
CationicPolymers
NonionicPolymers
0 % +100 %-100 % +50 %-50 %
MW = 104 gm/moleLow MW
MW = 105 gm/moleMedium MW
MW = 106 gm/moleHigh MW
MW = 107 gm/moleVery High MW
MW > 107 gm/moleUltrahigh MW
Flocculatingafter
Coagulation
SludgeDewatering
Coagulation
POLYMER MAP
PolymersPolymersPolymersPolymersAvailable as:
LiquidDryGelEmulsion
Must be Dilutedusually <1%
Can Be Very Viscousmay build up in pipes and pumpsclean regularly
salt water - dilute bleach
PolymersDry Polymers:
absorb moisture - ineffectivemay form “fish-eyes”aged for maximum efficiency
2 hours minimum7 days maximum
Polymers
Considered Non-Hazardous
Extremely SlipperyClean Up Immediately
SaltChlorineDrying AgentsAbsorbent Materials
PolymersPolymers
Dosage Rateusually less than 1 mg/L(0.25 to 1.5 mg/L)
Overdose Worse Than No PolymerOverdose Worse Than No Polymer
CHEMICAL CHEMICAL CLARIFICATIONCLARIFICATION
CHEMICAL CHEMICAL CLARIFICATIONCLARIFICATION
1. Coagulation1. Coagulation2. Flocculation2. Flocculation3. Separation3. Separation
PROCESS CONTROLPROCESS CONTROLPROCESS CONTROLPROCESS CONTROL
1. Provide complete 1. Provide complete mixing.mixing.
2. Control mixing for 2. Control mixing for flocculation.flocculation.
3. Control chemical dose.3. Control chemical dose.
Equipment
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
CHEMICALCHEMICALCLARIFICATIONCLARIFICATION
Dry Chemical Feeders
VOLUMETRIC
Measures chemical amount by VOLUME
GRAVIMETRIC
Measures chemical amount by WEIGHT
VOLUMETRIC FEEDERSLess Expensive
Low Delivery Rate
Less Accurate
Screw Feed Mechanism
Volumetric Screw Feeder
ChemicalChemicalHopperHopper
ChemicalChemicalHopperHopper
DriveMechanism
RotatingFeed Screw
MixingTank
Gravimetric Feeders
Loss-in-Weight Gravimetric Feeders
Belt Gravimetric Feeders
Highly AccurateClose Dosage Control
Chemical Cost Savings
Intermediate Cost
Accurate & Reliable
Gravimetric FeederGravimetric FeederGravimetric FeederGravimetric Feeder
HopperScale Beam
Control Wedge
Endless Belt
Slide Gate
GRAVIMETRIC BELT FEEDER
WEIGH BELTWEIGH BELT
CHEMICALHOPPER
WEIGHDECK
VERTICALVERTICALGATEGATE
WEIGHBEAM
GRAVIMETRIC FEEDERS
ADVANTAGES
1. Calibration normally not required
2. Greater accuracy and dependability
3. Incorporation of totalizer
4. Automatic proportioning
5. Low maintenance; simple operation
BULKSTORAGE
BINDAY HOPPER
FEEDER
DISSOLVER
HOLDINGTANK
WATER SUPPLY
PUMP TOAPPLICATION
GRAVITY TOAPPLICATION
TYPICAL DRY CHEMICAL FEED SYSTEMTYPICAL DRY CHEMICAL FEED SYSTEM
CHEMICALHOPPER
MIXER
WATERSUPPLY
TOAPPLICATION
FEEDER
Loss-in-weight Gravimetric Feeder
SCALE DRYFEEDER
DISPERSER
WATER SUPPLY
MIXER
MIXING TANK
SCALE
DRYFEEDER
DISPERSER
WATER SUPPLY
MIXER
MIXING TANK
TRANSFERPUMPMETERING
PUMP
APPLICATIONPOINT
POLYMER FEED SYSTEM
AGINGTANK
HOLDINGTANK
Liquid Feeders
Rotary Dippers
Rotometers
Metering Pumps
METERING PUMPS
POSITIVE DISPLACEMENT
Gear
Diaphragm
Plunger
GEAR PUMP
Gear
Gear
Suction Discharge
GEAR PUMP
Suction Discharge
PLUNGER PUMP
PLUNGERSUCTION
VALVE
DISCHARGEVALVE
DIAPHRAGM METERING PUMP
SUCTION STROKE
INTAKE
OPEN
CLOSED
ECCENTRIC DRIVE
DIAPHRAGM
PLUNGER
PUMPINGCHAMBER
CHECK VALVEASSEMBLY
DIAPHRAGM METERING PUMP
DISCHARGE STROKE
OPEN
CLOSED
ECCENTRIC DRIVE
DIAPHRAGM
PLUNGER
PUMPINGCHAMBER
CHECK VALVEASSEMBLY
HYDRAULICFLUID
OUTLET
DIAPHRAGM PUMP
Treatment Process
Coagulation
Flocculation
Separation
MIXING
Initial Rapid Mixing
Uniform Dispersion
Efficient Application
Feed
Impeller
Overflow
FLASH MIX TANKFLASH MIX TANK
FLASH MIX TANKFLASH MIX TANK
FLOCCULATIONFLOCCULATIONFLOCCULATIONFLOCCULATION
Gentle Mixing
Particle Contact
In Biological Process
Feed
ImpellerOverflow
FLOCCULATION TANKFLOCCULATION TANK
Typical Mechanically Mixed Flocculating ClarifierTypical Mechanically Mixed Flocculating Clarifier
Influent
Effluent
Flocculation
Chamber
SlowMixers
CircularBaffle
Treatment Process
Coagulation
Flocculation
Separation
Prepared ByMichigan Department of Environmental Quality
Operator Training and Certification Unit
CHEMICAL CLARIFICATION – CHEMICAL CLARIFICATION – COAGULATION METHODSCOAGULATION METHODS
CHEMICAL CLARIFICATION – CHEMICAL CLARIFICATION – COAGULATION METHODSCOAGULATION METHODS