John Dunford - Bond Water Technologies - Dissolved Air Flotation (DAF) Overview & Optimization Presentation At The 32nd Annual Waste & Pretreatment Conference In Charlottesville, VA March 2016

1. 1
John Dunford, CWT
Wastewater Product Manager
Bond Water Technologies
Dissolved Air Flotation (DAF)
Overview & Optimization

2. 2
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 off
 Dense solids are collected at the bottom of the tank

3. 3
What is Dissolved Air Floatation?

4. 4
Where is Dissolved Air Floatation Used?
 DAF systems are most commonly used in industrial
applications to treat waste streams to locality standards
prior to discharge
 Common Industries:
 Food processing
 Paper mills
 Oil refineries
 Chemical plants
 Large-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

5. 5
Pre-DAF Chemical Conditioning
 Waste stream can be introduced to DAF untreated
 Some manufactures claim as high as 85% solids removal
or
 To aid in the efficiency of floatable particle formation, it
is very common to chemically condition the wastewater
prior to the DAF
 Coagulant (inorganic, organic or blend)
 Flocculant (anionic or cationic polymer)
 Solids removal as high as 98%
 Removal efficiencies depend on many factors!

6. 6
Pre-DAF Chemical Conditioning
Untreated Wastewater
 Waste streams carry a consistent charge; usually slightly
negative, but can also be positive
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Pre-DAF Chemical Conditioning
Coagulant Applied
Charge neutralization of colloidal particles in the waste
stream to promote clumping together to form light floc
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Pre-DAF Chemical Conditioning
Flocculant Applied
 Promotes clumping of floc particles
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9. 9
Pre-DAF Air Introduction
Dissolved Air Applied
 Air is introduced to the waste stream under pressure to
adhere to particles
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10. 10
Pre-DAF Air Introduction
Dissolved Air Applied
 Air bubbles expand in floatation basin at (close to)
atmospheric pressure causing particles to rise
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11. 11
DAF Design Considerations
 Design Factors/Considerations
 Flow rate
 Water Temperature
 Waste characteristics
 Chemical pre-treatment
 Solids loading (lbs/hr/ft2)
 Hydraulic loading (gpm/ft2)
 Air to solids ratio (lbs of air/lbs of solids)

12. 12
DAF Design Considerations
 Saturator Pressure: Usually 60 – 90 PSI
 As water temperature increases, saturator pressure needs to
increase to achieve similar saturation levels
 Bubbles: 10-100 micrometers
 Too large, the bubbles wont interact with enough solids and
wont “grab” the particles
 Too small, not enough buoyant force
 Hydraulic loading: 0.3 to 3.0, 4.0 gpm/ft2 MAX
 (Q + R) ÷ DAF surface area
 Q = DAF influent flow rate (gpm)
 R = internal recycle rate (gpm)
 Typically between 15 and 25% of Q

13. 13
DAF Design Considerations
 Solids loading: 1.0 – 6.0 lbs/ft2/hr
 (TSS x Q x 8.34 ÷1,000,000)/ DAF surface area
 Air/Solids ratio (lbs air/lbs solids): 0.015-0.05

A
S
=
1.3 × Sa P−1 ×R
TSS ×Q
 Sa = solubility ratio = ma/mw
 P = atmospheric pressure
 R = recirculation rate
 Particle Rise Rate ≥ D/TR
 D = basin depth
 TR = basin hydraulic retention time

14. 14
DAF Optimization
 Adjusting Variables
 Flow rate
 Recycle Rate
 pH adjustment
 Coagulant & Flocculant Types
 Chemical Injection Points
 Skimmer Rate
 Air Pressure/Rate
 Water Level
 Mixing Rates
CORRECT ADJUSTMENTS CAN
RESULT IN YOU SAVING MONEY!!!!!

15. 15
FOG & TSS Effluent Testing
WE WILL MEET OR
BEAT YOUR
CURRENT COSTS!
Which one has the lowest FOG & TSS?
Our goal is to be <200 ppm FOG & 100 ppm TSS
FOG 168 ppm
TSS 45 ppm
Chemical Cost - $32/day
FOG 100 ppm
TSS 30 ppm
Chemical Cost - $45/day
FOG 50 ppm
TSS 10 ppm
Chemical Cost - $65/day

16. 16
Bond Water Case Study
WE WILL MEET OR
BEAT YOUR
CURRENT COSTS!
Wastewater Treatment Case Study
FOG (Fats, Oils & Greases), TSS, BOD Removal

17. 17
Case Study Background
FOG, TSS and BOD can be one of
the most challenging aspects for a
plant to maintain compliance with
their discharge permit. A
customer was facing pressure
from both the city and sanitation
district for violating their permit
on FOG, TSS and BOD in addition
to causing major pump station
issues for the municipality. The
customer had a DAF system in
place that was designed years ago
for lower flows and FOG/TSS.

18. 18
Before Bond Water

19. 19
Case Study Solution
• The current DAF system was designed for 45 gpm flows and the plant
was sending 70 gpm to this system.
• The amount of TSS and FOG had increased significantly in the
influent stream.
• Air to solids ratio was too low so we put together a treatment
program that will produce a “lighter” floc (unlike the alum approach)
and lowered the pH set point resulting in less caustic addition and
better protein/oil breaking.
• Automated acid and caustic feed via proportional control.
• Trained operators in making adjustments plus routine service visits.
• Minor piping changes were made to allow for longer air to solids
contact time, thus increasing their chances of collision and
floatation.
• Removed “hand made” modifications to DAF box and put back to
original mechanical specs.

20. 20
After Bond Water
Reduced surcharges = $15,000 per year savings!!!!!
Reduced chemical usage = $15,000 per year savings!!!!!

21. 21
Wastewater Treatment Services
• BondClear Inorganic & Organic Coagulants
• BondPoly Flocculants – Dry and Liquid Forms
• BondDF Defoamers – Silicone, Oil and Water
• Comprehensive On-site Service Plans - KPIs
• Operator Training
• Custom Made Blends
• Metals Removal Technology
• Emulsion Breakers
• Non Chemical Treatment Alternatives
• Faster Delivery Times
• Free Trials
• Dewatering Aids
• Economical Feed Systems
• GRAS and NSF Approved Products
• Routine On-site Jar Testing
• Continuous Improvement Programs
WE WILL MEET OR BEAT
YOUR CURRENT
OVERALL COSTS!