nutrient removal in oxidation ditches
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Webinar for Tennessee Wastewater Treatment Plant OperatorsFebruary 24, 2021
Grant Weaver, PE & wastewater [email protected]
Nutrient Removal in Oxidation Ditches
Strategies for Optimizing Nutrient Removal
Week 1: Nitrogen RemovalWeek 2: Phosphorus RemovalWeek 3: N&P Review and Case Studies
Today: Nitrogen & Phosphorus Removal in Oxidation Ditch wwtps
Mar 3: N&P Removal in SBRsMar 10: N&P Removal in Conventional Activated Sludge
Mar 17: Brainstorming N&P Removal Opportunities for Tennessee Wastewater Treatment Plants
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Wastewater ScienceDO (Dissolved Oxygen)ORP (Oxidation Reduction Potential)
Oxidation Ditch Knowledge
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Step 1: Convert Ammonia (NH4) to Nitrate (NO3)
Step 2: Convert Nitrate (NO3) to Nitrogen Gas (N2)
Oxygen-rich Aerobic ProcessDon’t need BOD for bacteria to growBacteria are sensitive to pH and temperature
Oxygen-poor Anoxic ProcessDo need BOD for bacteria to growBacteria are hardy
Ammonia Removal -1st Step of N Removal
Ammonia (NH4)
Ammonia RemovalAmmonia (NH4) is converted to Nitrate (NO3)
Ammonia Removal
Ammonia (NH4)
Oxygen (O2)
Ammonia Removal
Ammonia (NH4)
Alkalinity
Oxygen (O2)
H+
Ammonia (NH4)
Nitrite (NO2)
Alkalinity
Oxygen (O2)
H+
Ammonia Removal
Ammonia Removal
Ammonia (NH4)
Nitrite (NO2)
Alkalinity
Oxygen (O2) Oxygen (O2)
H+
Ammonia Removal
Ammonia (NH4)
Nitrite (NO2)
Nitrate (NO3)
Alkalinity
Oxygen (O2) Oxygen (O2)
H+
Nitrate Removal - 2nd
Step of N removal
Nitrate Removal
Nitrate (NO3)
Nitrate Removal
Nitrate (NO3)
BOD
Nitrate Removal
Nitrate (NO3)
Nitrogen Gas (N2)
BOD
Nitrate Removal
Nitrate (NO3)
Nitrogen Gas (N2)
OxygenBOD
Nitrate Removal
Nitrate (NO3)
Nitrogen Gas (N2)
Alkalinity
OxygenBOD
Adds DO (dissolved oxygen)Consumes BOD … Denitrifiers out compete bio-P bugs for VFAs!Gives back alkalinity … beneficially raises pH
Nitrogen Removal
DO: Dissolved Oxygen
ORP: Oxygen Reduction Potential
MLSS: Mixed Liquor Suspended Solids
HRT: Hydraulic Retention Time
BOD: Biochemical Oxygen Demand
Alkalinity
Note: All numbers are approximations, “rules of thumb”
Step 1: Nitrification (Ammonia Removal)
1 mg/L or more
+100 mV or more +
2500 mg/L or more
6 or more hours
less than 20 mg/L
60 mg/L or more
Alkalinity is lost
Step 1: Denitrification (Nitrate Removal)
Less than 0.2 mg/L
Less than -100 mV
Same
1 or more hours
100 mg/L or more … VFAs preferred!
Alkalinity is gained
Phosphorus Removal:What an Operator needs to know
ONE. Convert soluble phosphorus to TSS (total suspended solids)…BiologicallyChemically
TWO. Remove TSS
Biological Phosphorus Removal
Step 1: prepare “dinner”
VFA (volatile fatty acids) production in anaerobic/fermentive conditions
Step 2: “eat”
Bio-P bugs (PAOs, “phosphate accumulating organisms”) eat VFAs in anaerobic/fermentive conditions … temporarily releasing more P into the water
Step 3: “breathe” and grow
Bio-P bugs (PAOs) take in almost all of the soluble P in aerobic conditions as they grow and reproduce
Optimizing Bio-P Removal: Mainstream or Sidestream Fermentation
Anaerobic Tank2 hour HRT (hydraulic retention time)*ORP of -200 mV* 25 times as much BOD as influent ortho-P*Ortho-P release (3 times influent ortho-P)*
*Approximate: Every Plant is Different
Aeration TankDO of 2.0 mg/LORP of +150 mVpH of 7.0+*Ortho-P concentration of 0.05 mg/L*
Survey Question (soon):Which Oxidation Ditch is yours?
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Orbal Oxidation Ditch
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Oxidation Ditch with Anaerobic and Anoxic Zone
Oxidation Ditch Anoxic Zone Anaerobic Zone
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Oxidation Ditch with Anaerobic Zone
Oxidation Ditch Anaerobic Zone
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Oxidation Ditch with Anoxic Zone
Oxidation Ditch Anoxic Zone
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Oxidation Ditch with no Anoxic Zone and no Anaerobic Zone
Oxidation Ditch
Which Oxidation Ditch is Yours?
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Oxidation Ditch with Anaerobic and Anoxic Zones
Designed for Nitrogen and Phosphorus Removal
Anoxic Zone Anaerobic Zone
Oxidation DitchOptimizing Nutrient RemovalAnaerobic zone: VFA production & uptake Anoxic zone: Nitrate → Nitrogen GasAerobic zone: Ammonia → Nitrate / Phosphorus uptake
Anaerobic Zone:VFA production / VFA uptake / Phosphorus release
Anoxic Zone:Nitrate removal (Denitrification)
Oxidation Ditch:Ammonia removal (Nitrification) / Phosphorus uptake
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Oxidation Ditch with Anaerobic and Anoxic ZonesLansing, KS Choteau, MT
Garden Plains, KSRose Hill, KS
Lansing, Kansas Population: 12,000 3.2 MGD design flow
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Lansing, KS
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Lansing, KSNitrogen Removal
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Lansing, KSNitrogen Removal
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Lansing, KSPhosphorus Removal
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Lansing, KSPhosphorus Removal
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Oxidation Ditch with Anoxic Zone
NOT designed for Phosphorus Removal
Anoxic ZoneOxidation Ditch
Optimizing Nutrient RemovalPlan A. Nitrify and Denitrify in Ditch
Make Anoxic Zone anaerobicPlan B. 3D/4D ferment in ditchPlan C. Sidestream fermenter
Anoxic Zone:Nitrate removal (Denitrification)
Oxidation Ditch:BOD and Ammonia removal (Nitrification)
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Oxidation Ditch with Anoxic ZoneGreat Bend, KS Collierville, TN
Derby, KSGreat Bend, KSHamilton, MTKingman, KSLaFollette, TN
Great Bend, Kansas Population: 13,400 3.6 MGD design flow
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Great Bend, KS
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Great Bend, KS
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Great Bend, KS
Great Bend, Kansas
Nitrogen Removal in DitchRotor equipped with VFD and controlled by in-tank DO probeAmmonia → NitrateNitrate → Nitrogen Gas
Anoxic Zone converted to Fermenter Gate CLOSEDMixers turned OFF
Phosphorus Uptake in Ditch
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Oxidation Ditch with Anaerobic Zone
Designed for Ammonia Removal but NOT total-Nitrogen Removal
Oxidation Ditch
Optimizing Nutrient RemovalNitrogen: Nitrify and Denitrify in Ditch: 1 rotor and/or cycle rotor(s) on & offPhosphorus: Strengthen Anaerobic Zone by cycling mixer(s) off & on
Anaerobic Zone:VFA production / VFA uptake / ortho-P release
Oxidation Ditch:BOD and Ammonia removal (Nitrification)
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Oxidation Ditch with Anaerobic ZoneLaFollette, TN
LaFollette, Tennessee Population: 6,800 1.87 MGD design flow
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LaFollette, TN
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LaFollette, TN
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LaFollette, TN
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Oxidation Ditch with no Anoxic Zone and no Anaerobic Zone
Designed for Ammonia Removal butNOT designed for total-Nitrogen or Phosphorus Removal
Oxidation Ditch
Optimizing Nutrient RemovalNitrogen Removal: Nitrify and Denitrify in Ditch: 1 rotor and/or cycle rotor(s) on & offPhosphorus Removal:
A. Create anaerobic sludge blankets in ditch / resuspend MLSSB. Create sidestream fermenter and recycle sludge into ditch
Oxidation Ditch:BOD and Ammonia removal (Nitrification)
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Oxidation Ditch w/o Anoxic or Anaerobic ZonesHarriman, TNCookeville, TN
Athens Mouse Creek, TNBartlett, TNChinook, MTColstrip, MTCowan, TNForsyth, MTHalstead, KS
Hardin, MTPratt, KSLewistown, MTLibby, MTLyons, KSMiles City, MTMillington, TN
Harriman, Tennessee Population: 6,200 1.5 MGD design flow
Harriman, Tennessee
Actual Flow Effluent Nitrogen (mg/L) Effluent Phosphorus (mg/L)
(MGD) Historical Average After Optimization Historical Average After Optimization
1.2 21.5 2.3 2.9 1.4
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Harriman - As Designed
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Harriman - As Operated
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Harriman - As Operated
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Harriman - As Operated
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Harriman - As Operated
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Harriman - As Operated
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Harriman - As Operated
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Oxidation Ditch w/o Anoxic or Anaerobic ZonesHarriman, TNCookeville, TN
Athens Mouse Creek, TNBartlett, TNChinook, MTColstrip, MTCowan, TNForsyth, MTHalstead, KS
Hardin, MTPratt, KSLewistown, MTLibby, MTLyons, KSMiles City, MTMillington, TN
Cookeville, Tennessee Population: 33,500 15 MGD design flow
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Cookeville
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Cookeville, TN
Cookeville - As Designed
Cookeville - As Now Operated
Cookeville - As Now Operated
Cookeville - As Now Operated
Cookeville - As Now Operated
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Orbal Oxidation Ditch
Designed for Nitrogen Removal …often for Phosphorus Removal too
Opportunities for enhancing nutrient removalNitrogen Removal: Aerobic & Anoxic zonesPhosphorus Removal:
A. Optimize ditch … maybe bypass portion of influent around two outer ringsB. Sidestream fermenter
Outermost Ring:Anoxic (Denitrification)Oftentimes, Anaerobic (VFA production)
Middle Ring:Simultaneous Nitrification / Denitrification
Innermost Ring:Aerobic (Nitrification)
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Orbal SystemAthens, TN Oostanaula wwtp
Athens, Tennessee Population: 13,850 6.0 MGD design flow
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Athens Oostanaula (TN)
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Athens Oostanaula (TN)
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Athens Oostanaula (TN)
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Acknowledgements, Part 1
TENNESSEE DEPARTMENT OF ENVIRONMENT & CONSERVATION (TDEC)Karina Bynum, Sherry Wang, George Garden, Jenny Dodd, Jason Benton, Eddie Bouzied, Bryan Carter, David Duhl, Jordan Fey, Oakley Hall, Michael Murphy, Steve Owens, Rob Ramsey, Sherwin Smith, Robert Tipton, Sandra Vance, John West, Ariel Wessel-Fuss, Tim Hill, Brianne Begley & Alle Crampton ATHENSGreg Hayes, Russell Coleman & John SullivanCOOKEVILLERonnie Kelly, Tom Graham & John BufordHARRIMANRay Freeman LAFOLLETTENick CowanNASHVILLEJohnnie MacDonald & David TuckerNORRISTony Wilkerson & Doug Snelson
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Acknowledgements, continued
TENNESSEE, continued Brett Ward (UT-MTAS), Dewayne Culpepper (TAUD), Larry Gamblin (Bartlett), Danny Neely (Baileyton), David Harrison (Collierville), Nic Willis (Cowan), Darryl Green (Henderson), Jack Hauskins & Rocky Hudson (Lafayette)
KANSAS Tom Stiles, Rod Geisler (retired), Shelly Shores-Miller, Nick Reams & Ryan Eldredge (KDHE), Jason Cauley, Reuben Martin, April Batts & James Gaunt (Great Bend), Tony Zell, Gordon Cunning & Kris Bennetts (Lansing), Jamie Belden & Becky Lewis (Wichita)
MONTANA Paul LaVigne (retired), Pete Boettcher, Josh Viall, Ryan Weiss, Bill Bahr (retired), Dave Frickey (retired) & Mike Abrahamson (DEQ), Drue Newfield (Havre), Curt Konecky (retired), Del Phipps & Aaron Losing (Kalispell), Grant Burroughs (Big Sky), Gene Connell (Missoula), Eric Miller & Cory Fox (Chinook), Keith Thaut (Conrad), Mark Fitzwater & entire staff (Helena)
EPA Paul Shriner & Tony Tripp (HQ), Tina Laidlaw (R8), Brendon Held & Craig Hesterlee (R4), Sydney Weiss (R5)
… and, many more!
Oxidation Ditch Knowledge
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Nutrient Removal in SBRs (Sequencing Batch Reactors) with Case StudiesWednesday, March 310:00 - 11:45 AM Eastern Time
March 10: Nutrient Removal in Conventional and Extended Aeration Activated Sludge wwtps
March 17: Brainstorming Nutrient Removal Opportunities for YourPlants
