Bond Overview

John Dunford, CWTWastewater Product ManagerBond Water Technologies

Dissolved Air Flotation (DAF)Overview & Optimization

#What is Dissolved Air Floatation?A process using air bubbles to assist with the removal of suspended matter such as oil or solids.

Compressed air is introduced to the waste stream and mixed with suspended particles causing them to become buoyant.Flow is slowed in a settling/floatation tank allowing buoyant particles to float to the top of the tank where they are skimmed offDense solids are collected at the bottom of the tank

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What is Dissolved Air Floatation?

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Where is Dissolved Air Floatation Used?DAF systems are most commonly used in industrial applications to treat waste streams to locality standards prior to dischargeCommon Industries:Food processingPaper millsOil refineries Chemical plantsLarge-scale DAF systems can also be used for municipal wastewater treatment Sludge thickening Solids clarification

Textile industry Meat processing Bakeries Other high-solids waste streams

Algae removal

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Pre-DAF Chemical ConditioningWaste stream can be introduced to DAF untreatedSome manufactures claim as high as 85% solids removal orTo aid in the efficiency of floatable particle formation, it is very common to chemically condition the wastewater prior to the DAFCoagulant (inorganic, organic or blend)Flocculant (anionic or cationic polymer)Solids removal as high as 98%

Removal efficiencies depend on many factors!

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Pre-DAF Chemical ConditioningUntreated WastewaterWaste streams carry a consistent charge; usually slightly negative, but can also be positive--------

#Pre-DAF Chemical ConditioningCoagulant Applied Charge neutralization of colloidal particles in the waste stream to promote clumping together to form light floc --------++++++++++++

#Pre-DAF Chemical ConditioningFlocculant AppliedPromotes clumping of floc particles-+-++-++-+-++-+-+-++

#Pre-DAF Air IntroductionDissolved Air Applied Air is introduced to the waste stream under pressure to adhere to particles--------++++++++++++

#Pre-DAF Air IntroductionDissolved Air Applied Air bubbles expand in floatation basin at (close to) atmospheric pressure causing particles to rise --------++++++++++++

#DAF Design ConsiderationsDesign Factors/ConsiderationsFlow rateWater TemperatureWaste characteristicsChemical pre-treatmentSolids loading (lbs/hr/ft2)Hydraulic loading (gpm/ft2)Air to solids ratio (lbs of air/lbs of solids)

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DAF Design ConsiderationsSaturator Pressure: Usually 60 90 PSIAs water temperature increases, saturator pressure needs to increase to achieve similar saturation levels

Bubbles: 10-100 micrometersToo large, the bubbles wont interact with enough solids and wont grab the particlesToo small, not enough buoyant force

Hydraulic loading: 0.3 to 3.0, 4.0 gpm/ft2 MAX(Q + R) DAF surface areaQ = DAF influent flow rate (gpm)R = internal recycle rate (gpm)Typically between 15 and 25% of Q

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DAF Design Considerations

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DAF OptimizationAdjusting VariablesFlow rateRecycle RatepH adjustmentCoagulant & Flocculant TypesChemical Injection PointsSkimmer RateAir Pressure/RateWater LevelMixing RatesCORRECT ADJUSTMENTS CAN RESULT IN YOU SAVING MONEY!!!!!

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FOG & TSS Effluent TestingWE WILL MEET OR BEAT YOUR CURRENT COSTS!

Which one has the lowest FOG & TSS?Our goal is to be