Retro-Fit Denitrification Retro-Fit Denitrification for Small Wastewater for Small Wastewater Treatment FacilitiesTreatment Facilities

Tenth AnnualTenth AnnualVail Professional Wastewater Operators SeminarVail Professional Wastewater Operators Seminar

Friday, October 29, 2004Friday, October 29, 2004

Zachary J. Matyja, E.I.T.Jacobson Helgoth Consultants, Inc.

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Presentation OutlinePresentation Outline

• Denitrification Process• Improvements at Genesee Water and Sanitation District• Implementation Process• Questions

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Denitrification ProcessDenitrification Process

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Denitrification ProcessDenitrification Process

• Ammonia (NH3)• In WW Process, Nitrogen bonds to Organic Molecules to form Ammonia-Nitrogen (NH3 & NH4)• NH3 Converted to Nitrates in Aeration Process

• Nitrates (NO3)• Common in Natural Water• Sources include: Ag Runoff, Organic Matter, WWTF Discharges• 10 mg/L Limit for Drinking Water• Can Cause “blue baby syndrome”

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Denitrification ProcessDenitrification Process

• Denitrification• The biological conversion of nitrate-nitrogen to nitrogen gas (N2), nitrous oxide (N2O), and nitric oxide (NO)• Occurs under anoxic conditions (no free oxygen available)

• Various Denitrification Processes• Attached Growth• Proprietary Processes• Single-Sludge Nitrification/Denitrification

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Single-Sludge Nitrification / DenitrificationSingle-Sludge Nitrification / Denitrification

• All modifications to existing nitrification facility take place in aeration basin• Anoxic Zone precedes Aeration• Internal Water Recycle (400-500% of Influent Flow)

Anoxic Zone(Denitrificatio

n)

RECYCLE

Aeration Zone

(Nitrification)

Influent Effluent

N2 Gas

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Effect of Recycle on Nitrate ReductionEffect of Recycle on Nitrate Reduction

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0 100 200 300 400 500 600 700 800

Recycle Rate (%)

Nitra

te R

educt

ion (%

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Denitrification ChemistryDenitrification Chemistry

• Ammonia First Passes Through Anoxic Zone• Ammonia is Converted to Nitrate in Aeration Zone• Nitrate are Recycled to Anoxic Zone• Nitrate are Converted to Nitrogen gas in Anoxic Zone

Anoxic Zone(Denitrificatio

n)

RECYCLE

Aeration Zone

(Nitrification)

InfluentEffluent

N2 Gas

NO3 Converted to N2NO3 Converted to N2 NH3 Converted to NO3NH3 Converted to NO3

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Denitrification CalculationsDenitrification Calculations

• Conventional Nitrification Calculations Required First• Denitrification Calculations, Solve For

• Recycle Ratio• Aerobic / Anoxic Residence Times• Aerobic / Anoxic Tank Volumes• Aerobic / Anoxic Ratio

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Genesee Water and Sanitation DistrictWastewater Treatment Facility

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Project BackgroundProject Background

• In Foothills West of Denver, Near I-70 • District Serves 4,000+ People• Activated Sludge Facility• Discharge to Bear Creek

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Need for ProjectNeed for Project

• 2002 Drought – Low Flows in Bear Creek• Bear Creek Water Quality for Downstream Users• Potential District Water Quality Problems• Potential Water Reuse• “Stay Ahead of the Game”• Potential Future Nitrate Effluent Regulations

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Existing Wastewater Process SchematicExisting Wastewater Process Schematic

•Two Aeration Basins Operated in Parallel (0.25 MGD Capacity, Each)•Three Secondary Clarifiers Operated in Series

Aeration Basins(typ.)

ClarifierClarifier Clarifier SandFilter

Grit

Scre

enin

g

ChlorineRAS

DISCHARGE

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Existing ConditionsExisting Conditions

• Activated Sludge Facility• Design Flow 0.5 MGD• Actual Flows ≈ 0.25 MGD• Achieving Near Complete Nitrification • Previous Average Conditions:

Influent EffluentLimits

• Ammonia (mg/L) 25-40 < 1.09-18.5

• Nitrates (mg/L) < 0.5 15-23 None

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Denitrification Calculation ResultsDenitrification Calculation Results

• Estimated Recycle Ratio = 295% • Aerobic Residence Time Required = 4.8 hours• Anoxic Residence Time Required = 2.0 hours• Aerobic Tank Volume Fraction = 71%• Anoxic Tank Volume Fraction = 29%

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Denitrification Design DrawingsDenitrification Design Drawings

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Denitrification DesignDenitrification Design

• Baffle Wall in Aeration Basin• Install Reinforced Flexible Baffle Curtain to Divide Basins• Attached on all sides to Basin• 3’ x 4’ Hole in Bottom Corner• Furnished and Installed by Lange Containment Systems, Inc.

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Baffle Wall InstallationBaffle Wall Installation

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Denitrification DesignDenitrification Design

• Submersible Mixer• Ensure Successful Mixing of Entire Anoxic Basin• Primary purpose to keep all solids in suspension, and prevent settling in Anoxic Basin• Evaluated Two Mixers, Flygt required two mixers to accomplish same mixing• Selected USFilter EMU Uniprop

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Mixer InstallationMixer Installation

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Denitrification Design DrawingsDenitrification Design Drawings

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Denitrification Design DrawingsDenitrification Design Drawings

• Piping Design From Pump

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Denitrification DesignDenitrification Design

• Submersible Pump• Designed for 900 gpm, 10’ TDH• 5 hp, 1750 rpm, submersible motor• Guide Rails to Raise Pump • ITT Flygt Submersible Sewage Pump Purchased

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Pump InstallationPump Installation

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Denitrification DesignDenitrification Design

• Flow Measurement• Electromagnetic Flow Meter –

Endress + Hauser, Promag 50W

• Flow Control• Ballcentric Plug Valve with Handwheel Gear – Pratt

• Piping and Related Equipment• C900 PVC Pipe, Fittings, and Glue• Ductile Iron Pipe, Fittings, and Hardware• Pipe Hangers, Support Brackets, and Hardware

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Flow and Piping InstallationFlow and Piping Installation

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Denitrification DesignDenitrification Design

• Electrical Modifications• Breakers, Starters, Controls• Installed for Pump, Meter, Mixer• Installed by Sub-Contractor

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Denitrification InstallationDenitrification Installation

• Aeration Basin Offline• Basin Power Washed• Diffusers Removed / Plugged• Baffle Wall Installed by Sub-Contractor• Pump, Piping, Mixer Installed• Electrical Hook-up by Sub-Contractor

• 200 Man-Hours by District Staff• 100 Man-Hours Electrical Sub-Contractor• 300 Man-Hours Total

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Denitrification Results at GeneseeDenitrification Results at Genesee

• Current Recycle Rate set at ≈ 230% • Effluent Nitrate Levels 3-5 mg/L (78% Reduction)

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Additional Benefits found at GeneseeAdditional Benefits found at Genesee

• A Substantial Decrease in Added Alkalinity Requirements has been Noted

• Alkalinity is recovered in Recycled Water in Anoxic Zone

• Better Settling and Clarity has been Noted in Clarifiers• A Decrease in Aluminum Sulfate Usage has been Noted

• Due to Increased Biological Phosphorous Uptake

• More Effective Dewatering Process (Centrifuge) • Reduced Air Requirement in Aeration Basins

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Negatives to Denitrification found at Negatives to Denitrification found at GeneseeGenesee

• Initial Electrical Consumption has increased 15%

• From Pump, Mixer, and Meter Usage• May Decrease because of Reduced Air Requirements

• Initial Operation Requirements to Determine Recycle Ratio• More Frequent Monitoring for Filamentous Control in the Anoxic Zone

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Total Costs Total Costs

• $46,000 for One (0.25 MGD) Aeration Basin Conversion

• Engineering – $ 6,500• Baffle Wall – $ 6,200• Pump & Equip. – $ 4,900• Jib Crane & Trolley – $ 1,400• Mixer & Equip. – $10,300• Flow Meter – $ 2,900• Plug Valve – $ 500• Pipe, Supports, Etc. – $ 3,300• Electrical – $ 9,900

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Design ImplementationDesign Implementation

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Design ImplementationDesign Implementation

• Determine Need• Establish Funding• Engineering Calculations / Design• Equipment / Materials Selection• Determine Resources Available• Installation• Financial / Chemical Changes

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Questions?Questions?

Zach Matyjazmatyja@jacobsonhelgoth.com

Jacobson Helgoth Consultants, Inc.www.jhcinc.com(303) 986-0733