ORP Improves Operational Efficiency Mark Prein, P.E. What is ORP - - PowerPoint PPT Presentation

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

• f 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.

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. 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

2 4 6 8 10 12 14 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Number of Aerators Average DO, mg/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

3 6 9 12 15 18 21 24 2 4 6 8 10 12 14 16 Temperature, Degree C Aerators Date

Aerators vs. Temperture

Temperature Aerators

hjg

WWTP Upset Background

• 250
• 200
• 150
• 100
• 50

50 100 150 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 ORP, mv DO, mg/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