ORP Improves Operational Efficiency

Mark Prein, P.E.

MWEA Annual Conference

June 26, 2012

What is ORP

Oxidation

Reduction

Potential

ORP Definition

What

Is

ORP?

OXIDATION

(CHEMICAL)

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 + 2NO2-

2NO2- + O2 -> 2NO3

-

REDUCTION

(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. Example: Denitrification 2NO3

- + organic matter -> N2(Gas) + CO2 + H2O

POTENTIAL

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?

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).

YSI Environmental

–Application Note

ORP Biological Values

Biochemical Reactions and Corresponding ORP Values

Biochemical Reaction ORP, mV

Nitrification +100 to +350

cBOD degradation with free molecular oxygen +50 to +250

Biological phosphorus removal +25 to +250

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

YSI Environmental

–Application Note

ORP Biological Values

Biochemical Reactions and Corresponding ORP Values

Biochemical Reaction ORP, mV

Nitrification +100 to +350

cBOD degradation with free molecular oxygen +50 to +250

Biological phosphorus removal +25 to +250

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

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

Results

Collection System

Red Arrow Odalogger

Sample

Event

Results

Collection System

Units 8/28/2010 8/29/2010 8/30/2010

Lab

BOD5 mg/l 380 89 285

Sulfate mg/l 4.21 21.7 10.6

Total Sulfide mg/l 5.4 3 3.9

TSS mg/l 568 46 307

Field

pH s.u. 7.75 7.63 7.99

Temp °C 21 22.95 25.02

D.O. mg/l 3.93 2.62 3.01

Dis Sulfide mg/l 4.55 5.35 3.25

H2S, Air ppm 37 66 27

% O2 % 20.9 20.9 20.9

LEL s.u. 0 0 0

The

Rest

Of

The Story

Collection System

Units 8/28/2010 8/29/2010 8/30/2010

Lab

BOD5 mg/l 380 89 285

Sulfate mg/l 4.21 21.7 10.6

Total Sulfide mg/l 5.4 3 3.9

TSS mg/l 568 46 307

Field

pH s.u. 7.75 7.63 7.99

Temp °C 21 22.95 25.02

D.O. mg/l 3.93 2.62 3.01

Dis Sulfide mg/l 4.55 5.35 3.25

H2S, Air ppm 37 66 27

% O2 % 20.9 20.9 20.9

LEL s.u. 0 0 0

ORP mv -68.6 -89.3 -61.4

Re-aeration

Example

ORP Conversion

Treatment

and

Odor

Event

WWTP Upset

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

hjg

WWTP Upset - Investigation

0

2

4

6

8

10

12

14

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Nu

mb

er

of

Aera

tors

Av

era

ge D

O, m

g/l

Date

Effluent Dissolved Oxygen vs. Aerators

Aerators

WWTP Upset - Investigation

• Mixers turned off to save energy when DO demand low

• When mixers turned on: 1. Re-suspend solids

2. Initial increase in DO demand

3. 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

hjg

WWTP Upset Background

Temperature

DO

WWTP Upset Background

0

3

6

9

12

15

18

21

24

0

2

4

6

8

10

12

14

16

Tem

pera

ture

, D

eg

ree

C

Aera

tors

Date

Aerators vs. Temperture

Temperature

Aerators

hjg

WWTP Upset Background

-250

-200

-150

-100

-50

0

50

100

150

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

OR

P, m

v

DO

, m

g/l

Date

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

Biosolids

Holding

Tank

Aerobic Digestion/Holding

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?

1

2

Energy Savings

Its Only A Tool

1 - Air Off, Start Press

3-Decant

2-Settled

Thank You