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Ballasted Sedimentation for Water & Wastewater Treatment

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Ballasted Sedimentation for Water & Wastewater Treatment Ballasted Sedimentation for Water & Wastewater Treatment PNWS-AWWA Conference May 5, 2017 Jeff Marrs, Plant Manager, City of Anacortes Water Treatment Plant Jeff Lundt, P.E., King County Tina Hastings, P.E., CH2M Jason Curl, P.E., CH2M Agenda Technology Overview Water Treatment • City of Anacortes Water Treatment Plant • Woodland-Davis Regional Water Treatment Plant Wastewater Treatment Technology Overview Ballasted Sedimentation QMJ, November 2003 3 Ballasted Sedimentation Process Overview Sludge Separator Sand COAG Polymer Influent Effluent Clarifier Mixing / Flocculation / Coagulation Maturation 4 Solids RapiSand™ Ballasted Sedimentation Technology Selection • Veolia/Kruger: Actiflo® • Degremont: DensaDeg® Evoqua: CoMagTM Actiflo® • • WesTech: RapiSandTM DensaDeg® 5 Actiflo® 6 Sand Pumps 7 Plates vs. Tubes Plate Tubes Material 316 SST Polystyrene, black UV resistance Good Recommend to submerge in water Expected Life > 30 years 10 - 15 years Hose down < 90 psi < 40 psi pressure Performance Good Slightly better Installation Easier (lighter) Cost + $0.25M for a 35MGD train Applications Optional Standard (most (Salem, drinking water Tacoma, plants, Anacortes) 8 Bremerton) Water Treatment Case Study: City of Anacortes Water Treatment Plant 9 City of Anacortes Water Treatment Plant . Project drivers and objectives . Skagit River Basin and Raw Water Quality Characteristics . Treatment process systems . Reliability / Sustained Operations - considerations and features . Optimization . Operator Challenges and Response 10 Anacortes Water System Service Area Anacortes Tesoro & Shell Oil Refineries Mount Del Mar Vernon La Conner Swinomish Tribe Skagit PUD Naval Air Oak Harbor 11Station Project Drivers – Challenges/Limitations • Floodplain elevation • Challenging Raw Water Quality Dramatic fluctuation of Turbidity and Color • Ineffective Pre-treatment • Need to Expand Treatment Capacity 2007 max. day demand: 29 MGD 2030 max. day demand: 40.7 MGD • Condition of existing structures • Reliability and Redundancy needed for continuous operations 12 Skagit River Basin 13 Source: Skagit County Source: USDA Forest Service Raw Water Quality (2003-2008) • Turbidity Average: 28 NTU 95th-%: 81 NTU 98th-%: 164 NTU Maximum: 5475 NTU • Color: 1 – 4872 Pt Co • pH: 6.5 - 7.8 • Alkalinity: 16-38 mg/L • TOC 0.5 to 3.0 mg/L 14 Selected Treatment Scheme • Ballasted sedimentation • Rapid sand filtration • Chlorine contacting – CT compliance • Finished water pH adjustment 15 HIGH SERVICE PUMPS LOW LIFT / BW / FTW CLEARWELL PUMPS BALLASTED SEDIMENTATION 16 2013 Treatment Process Ballasted Lagoons Sedimentation Standby High Service (2 trains) Generators Pumps FW Storage Tank Decant PS Pipe Gallery (Lower), Electrical and Operation Control (Upper) 8 Filters 17 Design Production Requirements • Treatment capacity – 42 MGD • Future expansion capacity – 55 MGD • Emergency conditions treatment capacity – 21 MGD 18 Ballasted Sedimentation Process Microsand Add Coagulant Microsand Particle to Grow Large Particle Floc particles Large Solid Floc Particles Particle Flocculate Add Ballast and Polymer Organic Particle Distance Attach Particles to Ballasted Flocculation Ballast to Increase Settling Ballast Velocity Settling – use plate 19 settlers to enhance separation Time Ballasted Sedimentation - Actiflo SLUDGE (0.5 to 1%) HYDROCYCLONE BALLASTED FLOCS TO HYDROCYCLONE POLYMER MICRO-SAND CLARIFIED WATER ALUM / CAUSTIC / SODA ASH COAGULANT RAW WATER INJECTION COAGULATION MATURATION TUBE SETTLER WITH SCRAPER 20 Manufacturer: Kruger Key Design Parameters from Actiflo Pilot Testing Hydraulic Raw Coagulant Polymer Target Settled Mixing Loading Rate Turbidity Dose Dose Water pH with Speed (HLR) (NTU) (mg/L) (mg/L) Lime Dose (Hz) (gpm/ft2) Low Not 18 0.4 90 18 - 43 (< 15) Required High (up to 50* 0.5 7.55 90 18 - 43 2200) 21 Treatment Goals for Ballasted Sedimentation Raw Water Turbidity Range Settled Water Turbidity Less than or equal to 200 NTU Less than or equal to 2 NTU Between 201 NTU and 500 NTU Less than or equal to 3 NTU Greater than 500 NTU Less than 5 NTU Settled Water Quality Performance Requirements Parameters Settled Water Quality Criteria Target: Not greater than 1 NTU Turbidity, 95th percentile: Not greater than 2 NTU* NTU 98th percentile: Not greater than 5 NTU * Washington Department of Health (DOH) Treatment Optimization Program 22 turbidity goal Ballasted Sedimentation System Two parallel trains with 27 MGD capacity each 23 Ballasted Sedimentation Equipment Ballasted Sedimentation System – Micro-sand Recycle Pumps 24 Ballasted Sedimentation - Equipment Ballasted Sedimentation Ballasted Sedimentation System System Hydrocylones Mixer Drives 25 Filtration System – 8 Cells, each with 2 bays 26 Residuals Handling Three lagoons: . Floating decanter each lagoon . One in-service . Decant water booster . One in standby pumps for high river . One out-of-service level conditions 27 Residuals Handling 28 Optimization 29 Optimization • Aluminum Sulfate – Range from 5 – 40 mg/L depending on river changes. • Coagulant Polymer – Ranges from 0.40-0.50 mg/L – Not frequently adjusted. – Carry over to filters • Caustic Soda – Used for pH control when raw water does not meet treatment requirements. – Ranges from 1.0 – 6 mg/L 30 Optimization • Microsand – Maintain 3-6 grains per liter. (manufacturers recommendation) – Rarely add sand due to high sediment in source water – Regular monitoring with infrequent adjustments. – Highest amount of maintenance required. • Soda Ash – Used for alkalinity control – Not regularly used 31 Optimization • Following year 1 of operation, operators began experimenting with chemical dose ranges. • Resulted in reduced chemical costs with improved results. • Added laboratory analysis for quality control 32 Challenges with Operating a Surface Water Plant • Frequent Changes in Source Water • Seasonal Challenges • Equipment Failure • Chemical Feed Issues – Late to respond – Over/under dosing – Operator Interpretation 33 Operator Challenges • Frequent changes in source water conditions • Imbalance in chemical doses in pre- treatment process affects filter operations • Changes can occur in minutes due to short detention time (This is a good and bad thing). • Due to high flow demand and limited storage operators have little time to correct any problems. 34 35 36 Typical Results • Raw Water – 5 – 1100 NTU – 7.00 -7.40 pH – Alkalinity is 15 – 30 mg/L • Settled Water – Target is less than 1.0 NTU at all times. Typical is less than 0.50 NTU. 95% or greater removal typical. – pH range is 6.80 -7.20 – Alkalinity is 15-25 mg/L 37 Typical Results • Filtration – Alum is added to aid in filter performance (1.0-1.5 mg/L) – Filter Aid Poly is added for enhanced performance – Typical run time varies but normally is 72-96 hours. – Finished water turbidity is typically 0.020 NTU or less. 38 Results 1050 Raw Water NTU 0.90 NTU Settled 99.9 % Removal 39 Tips For Success • Operator Training is Essential • Preventive Maintenance Program • Corrective Action Program • Plant SOP’s • Process Instrumentation Maintenance Program • Post Incident Analysis and Review • Communication 40 Water treatment Case Study: Woodland-Davis Clean Water Agency (WDCWA) Regional Water Treatment Facility 41 Overall Regional System Length: 4.5 miles Diameter: 36 inches Location: River mile 70.8 Maximum Combined Diversion: 400 cfs Total Capacity: 30 mgd Woodland: 18 mgd Davis: 12 mgd Length: 9.9 miles Diameter: 36 inches 42 42 Process Locations Maintenance Operations Solids Drying Bed Chem SBC Ozone Backwash Filtration Thickeners Pump Station Clearwell Clearwell Solids Drying Effluent Pump Bed Station 43 43 Woodland-Davis Process Flow Diagram Chemical Addition Pump Ballasted Sedimentation Ozone Filtration Clearwells Raw Water Station Gravity Effluent Thickener Solids Effluent Woodland Pump Backwash Station Solids Drying Effluent Davis Beds Pump Station 44 Landfill Sand Ballasted Clarification • Purpose: Flocculation of destabilized particles into settleable floc and settling of particles • Treatment Criteria: – Turbidity: 85 – 99% removal – DBP precursors: 20 – 35% removal – Manganese: 85 – 99% removal – Iron: 85 – 99% removal – TOC: 20 – 35% removal – Aluminum: 85 – 99% removal 45 SBC – Design Criteria Item Values Units Max Combined Flow* 31.6 mgd Min Combined Flow 7.0 mgd Number of Trains 3 Design Flow per Train 10.53 mgd Coagulation Tank HRT 2 min Minimum Pump Flow 831 gpm Maturation Tank HRT 4.2 min Tube Settler Overflow Rate 30 gpm/ft2 Settling Basin Loading Rate 30 gpm/ft2 Max Settled Water Turbidity 2 NTU Sand Recirculation Flow per Train 225 gpm Sand Recirculation Pumps per Train 1 duty, 1 standby Hydrocyclones per Train 1 duty, 1 standby *Max combined flow based on raw water treatment flow, plus unthickened solids flow, plus backwash supply flow Trains are sized so that max combined flow can be treated with one unit offline. Settled effluent turbidity may increase, requiring more frequent filter backwashing as filter loading increases. 46 Overview – Actiflo® TURBO • Fundamentals – Coagulation tank – coagulated water mixed to form floc Veolia Water, 2009 – Flocculation/Maturation tank – add polymer and microsand, mix, enhance floc – Settling tank – lamella tubes decrease distance floc needs to fall – Scrapers – moves unthickened sludge, sand recirc pumps withdraw sludge – Hydrocyclones –separate microsand from sludge, sand returned to maturation tank, sludge 47 to thickeners Combined Sewer Overflow treatment Case Study: Georgetown Wet Weather Treatment Station 48 Brandon and Michigan
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