Dissolved Air Flotation (DAF): Commissioning and Operations at the

White Tanks Regional Water Treatment Plant

Jeremiah Mecham, Agua Fria District Operations Superintendent

Timothy J. White, P.E., Project Engineer

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Agenda Plant Background Dissolved Air Flotation

Process Overview White Tanks Design

Operational Experience Q&A

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Background Overuse of groundwater in Agua Fria district

Declining water levels, ground subsidence Water quality issues

Surface Water Plant recommended by WESTCAPS AAW takes lead for WTRWTP

Planning 2001 Advertise Design Concept / RFP 2003 Design 2003 through 2005 Groundbreaking 2007 Startup 2009

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White Tanks Regional Water Treatment Plant

Treats CAP water from Beardsley Canal in Surprise, AZ

Capacity 13.4 MGD initial 80 MGD ultimate

Major Treatment:

DAF GAC filtration UV Cl2 Disinfection

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Clarification Options Conventional Sedimentation

Plate and Tube Settlers

Solids Contact / Solids Blanket Clarifiers

Dissolved Air Flotation (DAF) Ballasted Flocculation (Actiflo)

Direct Filtration

Raw Water Pump Station

Flocculation

Settle / Flotation

GAC/Sand Filtration

UV Light Disinfection

Clearwell Storage

Clarification

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DAF Selection Overview Based upon raw water quality and overall treatment

goals, process selection recommended using Dissolved Air Flotation

Fundamentals of DAF treatment similar to conventional treatment (coag/floc/sed)

Small footprint / high loading rates

Effective on low turbidity water, highly efficient at removing algae

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What is Dissolved Air Flotation? Why chose it? Separation process similar to gravity sedimentation

Target is Small, Uniform Floc That Readily Floats Uses thousands of microbubbles to attach and lift particles / floc Chemistry critical to maximize particle attachment to bubbles More Concentrated Solids with DAF

Clarified Water Turbidity Often Lower than Conventional/ Filtered Water Turbidity Typically Similar

Treatment of <1 NTU, 99% algae count reduction, and 15% TOC removal Flexibility to Improve Performance by Adjusting Recycle

Lower Capital Cost for DAF/Higher Power Cost

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Process Coagulant Usage

0

10

20

30

40

50

0 15 25 50 75 100 125 150

Turbidity, NTU

Coa

gula

nt D

ose,

mg/

l

DAF

Gravity Clarification

Direct Filt.

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DAF Components Saturator tanks – air and water are

combined under pressure to super saturate the water with air

Recycle pumps – uses clarified water to generate super saturated stream

Nozzles – create pressure drop to release supersaturated air as microbubbles. Pressure drop critical in providing correct size bubble

False floor – promotes hydraulics Sludge removal – sludge floats and

collects at top of basin – basins are periodically flooded hydraulically to remove solids

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White Tanks DAF Schematic

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AquaDAF Flow Diagram

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White Tanks DAF Flow Limits

Plant Flow Two in Service Three in Service Four in Service

Q total, mgd

Q mgd

Loading Rate,

gpm/ft2 Q

mgd

Loading Rate,

gpm/ft2 Q

mgd

Loading Rate,

gpm/ft2

5.0 2.5 3.0 1.7 2.0 1.3 1.5

10.0 5.0 6.0 3.3 4.0 2.5 3.0

13.4 6.7 8.0 4.5 5.3 3.4 4.0

20.0 - - 6.7 8.0 5.0 6.0

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Operational Experience Background Experience

Plant Supervisor experienced with DAF

Well Field Operators Plant Maintenance

Training Lab Classroom Field Other Facilities

Operations Results

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Facility Layout

Intake

Screening Structure

Raw Reservoirs

Raw PS

DAF/ Filters

WW Basins

Chemical Storage

UV Finished Water Basin

Admin Building

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Training

Lab Training/Testing Team Management/Vendors

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Training

Classroom Training Provided by vendors

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Training

Field Training Provided by vendors/Project

management team

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Training

Field Training Provided by vendors/Project

management team

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Site Visit Site Visits to Operating American Water Facilities

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Operations

Challenges Staffing Nozzles Training

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Raw & Settled Water Turbidities

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

11/5/2009 0:00 11/5/2009 12:00 11/6/2009 0:00 11/6/2009 12:00 11/7/2009 0:00 11/7/2009 12:00

Date

Turb

idity

(NTU

)

WT_AIT_21001 WT_AIT_22010 WT_AIT_31101 WT_AIT_31201 WT_AIT_31301

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Operations CHEMICAL USAGE DURING VALIDATION TESTING

CHEMICAL[1

]

11/05/09 11/06/09 11/07/09 Dose (mg/L) Gallons Dose

(mg/L) Gallons Dose (mg/L) Gallons

Ferric Chloride 18.0 125.7

18.0 141.3 15.0 42.7

13:00 = 15

Sodium Hydroxide

08:00= 10.0

17.1 0.0 (offline) 0 0.0

(offline) 0 10:30= 8.0

13:00= 0.0 (offline)

Sodium Hypochlorite 0.70 20.8 0.70 25.4 0.70 8.5

[1] FeCl3 at 41% strength, S.G. 1.43. NaOH at 33% strength, S.G. 1.36. NaOCl at 12.5% strength, S.G. 1.10

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Results Analyte

11/5/2009 11/6/2009 11/7/2009

Raw Finished Raw Finished Raw Finished

OPERATOR MEASUREMENTS

Turbidity (NTU)[1] 0.40 0.13 0.42 0.13 0.36 0.17

Chlorine, Free (mg/L) N/A Inf: 0.44

Eff: 0.38 N/A Inf: 0.46 Eff: 0.36 N/A Inf: 0.58

Eff: 0.46

Alkalinity (mg/L as CaCO3)

123 N/A 114 111 118 109

TDS (mg/L) 169 N/A 161 160 161 159

GRAB SAMPLES

E. Coli N/A Negative N/A Negative N/A Negative[2]

Total Coliform N/A Negative N/A Negative N/A Negative2

TOC (mg/L) 2.94 (RW)[3] 2.52 (SW)[4] 0.90 2.88 (RW)

2.50 (SW) 0.67 2.89 (RW) 2.53 (SW) 0.70

TOC Removal N/A 69% N/A 77% N/A 76%

[1] Finished Water turbidity samples were taken from Combined Filter Effluent Sample measurements [2] Samples were only required for 2 days of testing. Additionally, 11/7/09 was a Saturday when the laboratory was closed, meaning analysis of this sample would have been delayed until outside of the allowable hold time. [3] RW = Raw Water as collected from the Screening Structure Sample tap. [4] SW = Settled Water as collected from the DAF Effluent Sample tap.