MWEA Annual Conference
June 26, 2012
ORP Improves Operational Efficiency
Mark Prein, P.E.
What is ORP
ORP Definition
Oxidation
Reduction
Potential
What
Is
ORP?
ORP Definition
Bing says 8,650,000 definitions
1. A chemical reaction in which oxygen is
added to an element or compound
2. The process of losing electrons from a
chemical element or compound
Example: Nitrification
2NH4+ + 3O2 -> 2H+ + 2H2O + 2NO22NO2- + O2 -> 2NO3-
OXIDATION
(CHEMICAL)
ORP Definition
Bing says 50,300,000 definitions
Any chemical reaction in which the atoms in a
material take on electrons.
Note: Reduction is the opposite of oxidation.
REDUCTION
(CHEMICAL)
Example: Denitrification
2NO3- + organic matter -> N2(Gas) + CO2 + H2O
ORP Definition
Bing says 204,000,000 definitions
1.Possible but as yet not actual: having a
latent possibility or likelihood of occurring, or
of doing or becoming something
2.Capacity for development: a capacity to
develop, succeed, or become something
How steep is the
hill you are standing on?
POTENTIAL
ORP Definition
In wastewater treatment, ORP is:
A measure of the ability or potential of a
wastewater to permit specific biological
reactions (oxidation and or reduction).
ORP Biological Values
Biochemical Reactions and Corresponding ORP Values
Biochemical Reaction
Nitrification
cBOD degradation with free molecular oxygen
Biological phosphorus removal
ORP, mV
+100 to +350
+50 to +250
YSI Environmental
+25 to +250
–Application Note
Denitrification
+50 to -50
Sulfide (H2S) formation
-50 to -250
Biological phosphorus release
-100 to -250
Acid formation (fermentation)
-100 to -225
Methane production
-175 to -400
ORP Equipment
Where Might You Use ORP
• Collection System
• Lift Stations
• Sewers
• Treatment Plant
• Activated Sludge
• Anaerobic
• Anoxic
• Aerobic
• Digesters
• Fermenters
• Final Clarifiers
How Use ORP
• Collection System
• Hydrogen Sulfide Control
• Treatment Plant
•
•
•
•
CBOD removal
Nitrification
Denitrification
Biological Phosphorous
Removal
• Fermentation
• Methane production
ORP Biological Values
Biochemical Reactions and Corresponding ORP Values
Biochemical Reaction
Nitrification
cBOD degradation with free molecular oxygen
Biological phosphorus removal
ORP, mV
+100 to +350
+50 to +250
YSI Environmental
+25 to +250
–Application Note
Denitrification
+50 to -50
Sulfide (H2S) formation
-50 to -250
Biological phosphorus release
-100 to -250
Acid formation (fermentation)
-100 to -225
Methane production
-175 to -400
Placement ORP Probe
• Understand the process
• Location is Critical
• Avoid influence of process
equipment
• Be aware of process phases
• Maintenance required
Examples
Please:
Ask Questions As We Go
Collection System
Large Community
Random Odor
complaints
•
Could not be tied
to operational
changes
•
Could not be tied
to wet/dry
weather events
Sewer Collapse in
Area
Have high H2S levels
but why?
Collection System
OdaLogger
Red Arrow Odalogger
Results
Collection System
Units
8/28/2010
8/29/2010
8/30/2010
BOD5
Sulfate
Total Sulfide
TSS
Field
pH
Temp
D.O.
Dis Sulfide
mg/l
mg/l
mg/l
mg/l
380
4.21
5.4
568
89
21.7
3
46
285
10.6
3.9
307
s.u.
°C
mg/l
mg/l
7.75
21
3.93
4.55
7.63
22.95
2.62
5.35
7.99
25.02
3.01
3.25
H2S, Air
ppm
37
66
27
% O2
LEL
%
s.u.
20.9
0
20.9
0
20.9
0
Lab
Sample
Event
Results
Collection System
Units
8/28/2010
8/29/2010
8/30/2010
BOD5
Sulfate
Total Sulfide
TSS
Field
pH
Temp
D.O.
Dis Sulfide
mg/l
mg/l
mg/l
mg/l
380
4.21
5.4
568
89
21.7
3
46
285
10.6
3.9
307
s.u.
°C
mg/l
mg/l
7.75
21
3.93
4.55
7.63
22.95
2.62
5.35
7.99
25.02
3.01
3.25
H2S, Air
ppm
37
66
27
% O2
LEL
ORP
%
s.u.
mv
20.9
0
-68.6
20.9
0
-89.3
20.9
0
-61.4
Lab
The
Rest
Of
The Story
ORP Conversion
Re-aeration
Example
WWTP Upset
Treatment
and
Odor
Event
WWTP Upset Background
• Plant
1. Aerated Lagoon System
2. Settling Ponds
3. Storage Ponds
• Operations
1. Monitor Influent and Effluent
for standard parameters
2. DO measured at effluent
3. As Effluent DO varies, adjust air
feeds
• Event
1. Over very short period went
anaerobic
2. With all aeration on, could not
meet demand
WWTP Upset - Investigation
7.0
14
6.0
12
5.0
10
4.0
8
3.0
6
hjg
2.0
4
Aerators
1.0
2
0.0
0
Date
Number of Aerators
Average DO, mg/l
Effluent Dissolved Oxygen vs. Aerators
WWTP Upset - Investigation
•
•
Mixers turned off to save energy
when DO demand low
When mixers turned on:
1.
2.
3.
•
Re-suspend solids
Initial increase in DO demand
Some Odor
During spring warm-up
1.
Increasing biological activity
2. Influent Loading
3. Stored Loading
•
Mixer selection based on effluent
DO, which indicated wastewater
carrying a positive DO
WWTP Upset Background
DO
Temperature
hjg
WWTP Upset Background
Aerators vs. Temperture
16
24
14
21
12
18
15
8
12
6
9
Aerators
4
6
2
3
0
0
Date
Temperature, Degree C
Aerators
Temperature
10
WWTP Upset Background
8.0
150
7.0
100
6.0
50
5.0
0
4.0
-50
3.0
hjg
-100
2.0
-150
1.0
-200
0.0
-250
Date
ORP, mv
DO, mg/l
DO vs. ORP Results
WWTP Upset - Findings
•
•
•
•
Operator placed in a no win
situation by positive DO probe
results
Actual events
1. Spring with warm
temperatures
2. Entire volume went
anaerobic
3. Turned on mixers for more
air, which in turn added
more demand
DO probe under influence of
point of re-aeration
Mixers must be turned on
before demand
Aerobic Digestion/Holding
Biosolids
Holding
Tank
Aerobic Digestion/Holding
• Holds Activated Sludge
• Fully Automated Controls
1. Level Sensor
2. DO Sensor
3. ORP Sensor
• Process Operations
•
•
•
•
Fill – Selected Tank
Mix/Aerate
Settle/Decant
Feed ISPs
SCADA CONTROL
Typical Operation
A Little Easier to Read
What Is Really Happening?
2
Energy Savings
1
Its Only A Tool
1 - Air Off, Start Press
3-Decant
2-Settled
Thank You