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Dissolved Air Flotation (DAF): Commissioning and Operations at the White Tanks Regional Water Treatment Plant

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Dissolved Air Flotation (DAF): Commissioning and Operations at the White Tanks Regional Water Treatment Plant 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 40 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 .
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