The document discusses the application of oxidation reduction potential (ORP) in biological nutrient removal processes, emphasizing its role in assessing the electron donating ability of bacteria during wastewater treatment. It covers topics such as the science behind ORP, its monitoring methods, and practical applications within different aeration processes to optimize nutrient removal. Additionally, it addresses sensor care, calibration, and the importance of ORP measurements in evaluating the efficiency of wastewater treatment systems.

1. 1
Biological Nutrient Removal Applications for Monitoring ORP

2. Biological Nutrient Removal Applications for Monitoring Oxidation Reduction Potential
YSI WATER RESOURCE RECOVERY WEBINAR
2

3. Today’s Topics
•
The Science of ORP (oxidation reduction potential) or Redox
•
Putting ORP to Use
•
Applications
•
Sensor Care and Parting Thoughts
3

4. The Science of ORP
4

5. 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.

6. 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
6

7. 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
7
1.2 v
Source: Brock Biology of Microorganisms, 10th Ed., Madigan, M., Martinko, J., Parker, J., 2002

8. 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
8
0.8 v
Source: Brock Biology of Microorganisms, 10th Ed., Madigan, M., Martinko, J., Parker, J., 2002

9. 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
9
0.15 v
Source: Brock Biology of Microorganisms, 10th Ed., Madigan, M., Martinko, J., Parker, J., 2002

10. Sounds Complicated, Huh?
It is, but….
•
Can be very simple if only interested in measuring e-
10

11. ORP Sensor is Very Similar to a pH Sensor
The measurement is the raw signal, millivolts (mV)
11
Reference electrode
Reference junction
Electrolyte
Measuring electrode
*YSI SensoLyt PtA electrode (109 125Y)

12. Putting ORP to Use
12

13. Terminology
•
Oxic = aerobic = DO is the primary e- acceptor
•
Anoxic = DO; NO3
•
Anaerobic = DO; NO3
13

14. What Does ORP Tell Us About Our Process?
14
0
-100
-200
-300
-400
+400
+300
+200
+100
Nitrification
BOD removal
‘P’ uptake
Denitrification
Fermentation
‘P’ release
ORP, mV
Oxic
Anaerobic
Anoxic

15. 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
15

16. 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
16
+
-

17. 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
17

18. Monitoring Methods
Spot sampling
18
YSI Pro10 Field pH/ORP
YSI EcoSense pH100A

19. Monitoring Methods
Online continuous monitoring
19
YSI SensoLyt® 700 IQ

20. Applications
20

21. 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:

22. 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:

23. 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:

24. 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
24

25. 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

26. Continuous Flow Systems
•
Effluent ammonia control / chloramination
•
Aeration control
•
Simultaneous nitrification denitrification
Applications
26

27. 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

28. 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
28
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

29. Sensor Care and Parting Thoughts
29

30. 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)
30

31. 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.
31

32. Feeling Better?
ORP is cool!
32

33. 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
33