Calculation of Range of Dilutions forAcceptable BOD Results

Prepared ByMichigan Department of Environmental Quality

Operator Training and Certification Unit

BOD PROCEDUREBOD PROCEDURE

DILUTE SAMPLE

Minimum Residual, 1.0 mg/LMinimum Depletion, 2.0 mg/LAt Least Two Dilutions

Calculation of Range of Acceptable BOD Results

BOD Sample =Depletion

X 300 mLSample Volume

Minimum BOD =Minimum Depletion

X 300 mLSample Volume

Minimum BOD =2.0

X 300Sample Volume

Minimum BOD = 600Sample Volume

Lowest (Minimum) Acceptable Results – Lowest Acceptable Depletion

Example

What is the Lowest Acceptable BOD results if 20 mL of sample is used?

Minimum BOD = 600Sample Volume

Minimum BOD = 60020

Minimum Acceptable BOD = 30 mg/L

Minimum BOD That May Be Reported =600

Sample Volume

Example 2

What is the Lowest Acceptable BOD results if 150 mL of sample is used?

Minimum BOD = 600Sample Volume

Minimum BOD = 600150

Minimum Acceptable BOD = 4 mg/L

Calculation of Range of Acceptable BOD Results

Maximum BOD =D.O. In – 1.0

X 300 mLSample Volume

Maximum BOD =7.0

X 300Sample Volume

Maximum BOD = 2100Sample Volume

Highest (Maximum) Acceptable Results

ASSUMING Initial D.O. of 8.0 mg/L

Lowest Acceptable Residual

– Highest Acceptable Depletion

Depletion = 8.0 - 1.0 = 7.0

Example

What is the highest Acceptable BOD results if 20 mL of sample is used?

Maximum BOD = 2100Sample Volume

Maximum BOD = 210020

Maximum Acceptable BOD = 105 mg/L

Maximum BOD That May Be Reported =2100

Sample Volume

Example 2

What is the highest Acceptable BOD results if 150 mL of sample is used?

Maximum BOD = 2100Sample Volume

Maximum BOD = 2100150

Maximum Acceptable BOD = 14 mg/L

Maximum BOD That May Be Reported =2100

Sample Volume

Calculation of Range of Acceptable BOD Results

Minimum BOD = 600Sample Volume

Lowest (Minimum) Acceptable Results – Lowest Acceptable Depletion

Summary

Highest (Maximum) Acceptable Results

Lowest Acceptable Residual

– Highest Acceptable Depletion

Maximum BOD = 2100Sample Volume

(Assuming D.O. In =8.0 mg/L

Calculation of Range of Acceptable BOD Results

Minimum BOD = 600Sample Volume

Wait A Minute

Maximum BOD = 2100Sample Volume

600 X 3.5 = 2100600 X 3.5 = 2100

So (assuming D.O. In is 8.0)

Minimum BOD x 3.5 = Maximum BODMinimum BOD x 3.5 = Maximum BOD

Calculation of Range of Acceptable BOD Results

Minimum BOD = 600Sample Volume

Lowest (Minimum) Acceptable Results – Lowest Acceptable Depletion

Summary (again)

Highest (Maximum) Acceptable Results

Lowest Acceptable Residual

– Highest Acceptable Depletion

(Assuming D.O. In =8.0 mg/L

Maximum BOD = 3.5 X Minimum BOD

Example

What is the Lowest Acceptable BOD results if 30 mL of sample is used?

Minimum BOD = 60030 = 20 mg/L

What is the Highest Acceptable BOD results if 30 mL of sample is used?

20 mg/L X 3.5 = 70 mg/L

Total Range when using a 30 mL sample:

20 to 70 mg/L

Total Range when using a 100 mL sample = 6 to 21 mg/L

Total Range when using a 150 mL sample = 4 to 14 mg/L

Total Range when using 100 mL and 150 mL (two Bottles)

Total Range when using a 50 mL sample = 12 to 42 mg/L

= 4 to 21 mg/L

Total Range when using 50 mL and 150 mL (two Bottles)

= 4 to 42 mg/L

OVERLAP From 6 to 14 mg/L

OVERLAP From 12 to 14 mg/L

Total Range when using a 25 mL sample = 24 to 84 mg/L

Total Range when using a 125 mL sample = 4.8 to 16.8 mg/L

Total Range when using 25 mL and 125 mL (two Bottles)

NO: Does Not Include 16.8 to 24 mg/L

= 4.8 to 84 mg/L

Range To Wide (No Overlap)

?

Calculate Range of Acceptable BOD Results

Use Two Volumes that Expand the RangeBut

Give a “Comfortable” Overlap

Calculate Range of Acceptable BOD Results

Use Two Volumes that Expand the RangeBut

Give a “Comfortable” Overlap

Calculate Range of Acceptable BOD Results

Use Two Volumes that Expand the RangeBut

Give a “Comfortable” Overlap

Calculation of Range of Dilutions forAcceptable BOD Results

Prepared ByMichigan Department of Environmental Quality

Operator Training and Certification Unit