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Biological Nutrient Removal Applications for Monitoring ORP

Biological Nutrient Removal Applications for Monitoring Oxidation Reduction Potential YSI WATER RESOURCE RECOVERY WEBINAR

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Today’s Topics

• The Science of ORP (oxidation reduction potential) or Redox • Putting ORP to Use • Applications • Sensor Care and Parting Thoughts

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The Science of ORP

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Growing Bugs are Happy Bugs!

• Carbon • Nutrients • Energy • Reducing Power – the ability to transfer electrons

Bacteria require 4 things for growth

5 Source: Biological Wastewater Treatment, 2nd ed., Grady, C.P., Daigger, G.T., Lim, H.C., 1999.

Bugs Get Energy and Reducing Power from Oxidation-Reduction (Redox) Reactions Redox transfers electrons

Function e- donor e- acceptor BOD removal Organic C O2

Nitrification NH4+ O2

Denitrification Organic C NOx

Fermentation Organic C Organic C

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What Has ORP Got To Do with It?

It measures electron donating ability • Electron tower: most negative (e- donors) at

top to most positive (e- acceptors) at bottom. • Electrons donated from the top of the tower

can be “caught” by acceptors at various levels.

• The greater the “fall” the more energy is released

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1.2 v

Source: Brock Biology of Microorganisms, 10th Ed., Madigan, M., Martinko, J., Parker, J., 2002

What Has ORP Got To Do with It?

It measures electron donating ability • Electron tower: most negative (e- donors) at

top to most positive (e- acceptors) at bottom. • Electrons donated from the top of the tower

can be “caught” by acceptors at various levels.

• The greater the “fall” the more energy is released

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0.8 v

Source: Brock Biology of Microorganisms, 10th Ed., Madigan, M., Martinko, J., Parker, J., 2002

What Has ORP Got To Do with It?

It measures electron donating ability • Electron tower: most negative (e- donors) at

top to most positive (e- acceptors) at bottom. • Electrons donated from the top of the tower

can be “caught” by acceptors at various levels.

• The greater the “fall” the more energy is released

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0.15 v

Source: Brock Biology of Microorganisms, 10th Ed., Madigan, M., Martinko, J., Parker, J., 2002

Sounds Complicated, Huh?

It is, but…. • Can be very simple if only interested in measuring e-

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ORP Sensor is Very Similar to a pH Sensor

The measurement is the raw signal, millivolts (mV)

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Reference electrode Reference junction

Electrolyte Measuring electrode

*YSI SensoLyt PtA electrode (109 125Y)

Putting ORP to Use

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Terminology

• Oxic = aerobic = DO is the primary e- acceptor • Anoxic = DO; NO3 • Anaerobic = DO; NO3

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What Does ORP Tell Us About Our Process?

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0 -100 -200 -300 -400 +400 +300 +200 +100

Nitrification

BOD removal

‘P’ uptake

Denitrification

Fermentation

‘P’ release

ORP, mV

Oxic Anaerobic Anoxic

ORP as a DO Sensor

• DO > 1.0 mg/L: primarily O2 • No direct meaning as to the status of nitrification

• DO < 1.0 mg/L: O2 + other e- acceptors • No direct meaning as to the status of denitrification

• When DO is < 0.1 primarily other e- acceptors

Think of ORP as a DO sensor that measures negative

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ORP as a ‘N’ Sensor

• NO3 and NO2

• Ammonium and TKN

• Little to no dissolved ‘N’ (and no DO)

ORP can indicate what forms of N are present

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+

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ORP as a ‘P’ Sensor

• ‘P’ is neither oxidized or reduced • However, it can tell you when conditions are ripe for uptake and release

Well, it can’t really do that

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Monitoring Methods

Spot sampling

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YSI Pro10 Field pH/ORP YSI EcoSense pH100A

Monitoring Methods

Online continuous monitoring

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YSI SensoLyt® 700 IQ

Applications

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Intermittent Aeration Process

SBR, cyclic activated sludge

Reproduced G Olsson, M Nielsen, Z Yuan, A Lynggaard-Jensen, J-P Steyer (2005) Science & Technical Report No. 15, Instrumentation, Control, and Automation in Wastewater Systems, with permission from the copyright holders, IWA Publishing

ORP DO NH3-N NO3-N

Legend:

Intermittent Aeration Process

SBR, cyclic activated sludge

Reproduced G Olsson, M Nielsen, Z Yuan, A Lynggaard-Jensen, J-P Steyer (2005) Science & Technical Report No. 15, Instrumentation, Control, and Automation in Wastewater Systems, with permission from the copyright holders, IWA Publishing

ORP DO NH3-N NO3-N

Legend:

Intermittent Aeration Process

SBR, cyclic activated sludge

Reproduced G Olsson, M Nielsen, Z Yuan, A Lynggaard-Jensen, J-P Steyer (2005) Science & Technical Report No. 15, Instrumentation, Control, and Automation in Wastewater Systems, with permission from the copyright holders, IWA Publishing

ORP DO NH3-N NO3-N

Legend:

Cyclic Activated Sludge System

Operation: Enhanced Bio P removal • ORP high / air stop: ~250 mV • Anaerobic to Oxic • DO SP: 1.7 to 1.9 mg/L • Nitrification • P uptake

• ORP low / timer start: ~0 mV • Oxic to Anoxic • Denitrification • Timer start

• Anaerobic Timer: 40 min. • Anaerobic • P release • Blower start

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Concentration and Mass Limits Met Without Chemicals

Smith, R.C., Goble, L., “To Everything There is a Season; Lessons from Four Seasons of Phosphorus Removal at Greene County Sugarcreek WRRF”, WEFTEC 2010

Continuous Flow Systems

• Effluent ammonia control / chloramination • Aeration control • Simultaneous nitrification denitrification

Applications

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Extended Aeration Process

Goal: minimize aeration & chlorine • ORP in anoxic zone • NH3-N target: 2 – 3

mg/L

27 Myers, M., Myers, L, Okey, R., “The use of oxidation-reduction potential as a means of controlling effluent ammonia concentration in an extended aeration activated sludge system”, WEFTEC 2006

Extended Aeration Process Upstream from Chloramination Trial control strategy • Upper ORP SP: -200 mV

• Lower ORP SP: -270 mV • NH3-N maintained

between 1 and 3.5 mg/L • D.O. near 0 • Nitrate also low

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Anoxic DO Nitrate

Myers, M., Myers, L, Okey, R., “The use of oxidation-reduction potential as a means of controlling effluent ammonia concentration in an extended aeration activated sludge system”, WEFTEC 2006

Sensor Care and Parting Thoughts

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Calibration, Cleaning, Replacement

• Calibration: 1-point offset correction • YSI 3682 Zobell solution: +231 mV @25°C (platinum – Ag/AgCl)

• Cleaning: • In general use the same practices as you would a pH sensor • Junction: running water / soft brush • Platinum: Wet and blot dry (avoid rubbing) • Short-term soak in household dish soap for grease removal

• Replacement: • Electrodes should last many months to years (YSI electrodes warrantied

for 6 months)

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Parting Thoughts

• ORP is relative – not comparable between brands, between applications • ORP accuracy +/- 20 mV • Response may be slow – up to 24 hours to stabilize in natural waters (but

very fast in Zobell) • ORP measurement is affected by temperature but not corrected for it.

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Feeling Better?

ORP is cool!

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For More Information…

IQ SensorNet

• YSI.com/IQ • +1 (937) 767-7241 • (800) 897-4151 • info@ysi.com

• Application Note

ORP Management in Wastewater as an Indicator of Process Efficiency

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