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

Agenda  Plant Background  Dissolved Air Flotation  Process Overview  White Tanks Design  Operational Experience  Q&A

2 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

3 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

4 Clarification Options  Conventional Sedimentation  Plate and Tube Settlers  Solids Contact / Solids Blanket Clarifiers  Dissolved Air Flotation (DAF)  Ballasted Flocculation (Actiflo)  Direct Filtration Clarification

Raw Water Flocculation Settle / GAC/Sand UV Light Clearwell Pump Station Flotation Filtration Disinfection Storage

5 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

6 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

7 Process Coagulant Usage

50 Gravity Clarification

30 DAF 20

10 Direct Filt. 0 Coagulant Dose, Coagulant mg/l 0 15 25 50 75 100 125 150 Turbidity, NTU

8 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

9 White Tanks DAF Schematic

10 AquaDAF Flow Diagram

11 White Tanks DAF Flow Limits

Plant Flow Two in Service Three in Service Four in Service Loading Q Loading Loading Rate, total, Q Rate, Q Rate, Q gpm/ft2 mgd mgd gpm/ft2 mgd gpm/ft2 mgd

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

12 Operational Experience  Background Experience  Plant Supervisor experienced with DAF  Well Field Operators  Plant Maintenance  Training  Lab  Classroom  Field  Other Facilities  Operations  Results

13 Facility Layout

Raw PS DAF/ Chemical Admin Filters Storage Building Raw Reservoirs

Screening Structure

Intake WW Basins UV Finished Water Basin

14 Training

 Lab Training/Testing  Team Management/Vendors

15 Training

 Classroom Training  Provided by vendors

16 Training

 Field Training  Provided by vendors/Project management team

17 Training

 Field Training  Provided by vendors/Project management team

18 Site Visit  Site Visits to Operating American Water Facilities

19 Operations

 Challenges  Staffing  Nozzles  Training

20 Raw & Settled Water Turbidities

4.00

3.50

3.00

2.50

2.00 Turbidity (NTU) Turbidity 1.50

1.00

0.50

0.00 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

WT_AIT_21001 WT_AIT_22010 WT_AIT_31101 WT_AIT_31201 WT_AIT_31301

21 Operations CHEMICAL USAGE DURING VALIDATION TESTING 11/05/09 11/06/09 11/07/09 CHEMICAL[1 Dose Dose Dose ] Gallons Gallons Gallons (mg/L) (mg/L) (mg/L) Ferric 18.0 18.0 125.7 141.3 15.0 42.7 Chloride 13:00 = 15 08:00= 10.0 Sodium 10:30= 0.0 0.0 17.1 0 0 Hydroxide 8.0 (offline) (offline)

13:00= 0.0 (offline)

Sodium 0.70 20.8 0.70 25.4 0.70 8.5 Hypochlorite

[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

22 Results 11/5/2009 11/6/2009 11/7/2009 Analyte 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 Inf: 0.44 Inf: 0.46 Inf: 0.58 N/A N/A N/A (mg/L) Eff: 0.38 Eff: 0.36 Eff: 0.46 Alkalinity (mg/L as 123 N/A 114 111 118 109 CaCO3) 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 2.94 (RW)[3] 2.88 (RW) 2.89 (RW) TOC (mg/L) 0.90 0.67 0.70 2.52 (SW)[4] 2.50 (SW) 2.53 (SW) 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. 23