What this tool does
Keep oxygen used by the sample separate from oxygen used by the seed. Review several bottles without silently averaging different samples or discarding failed controls.
When to use it
After bench readings and governing criteria are available. Check sample identities and the effective original-sample volume before entering any row. Stop if the seeding geometry is not one of the three supported cases.
Inputs and supported units
Use the labelled laboratory units and a consistent sample basis. Values are not silently interpreted as a regulatory method. Numeric input changes clear earlier results; CSV files are read locally, without uploading. The demonstration values only illustrate the arithmetic.
Calculation or decision method
Sample fraction P = sample mL / bottle mL. Calculated demand is (initial DO − final DO − seed correction) / P, in mg/L on the original-sample basis.
Direct seeding
For each usable seed control, divide its DO depletion by the mL of seed suspension it contains. Average those unit demands, then multiply by the seed mL in each sample bottle. Controls must use the same suspension and bottle volume. The analyzer applies your entered depletion and residual checks before including a control.
Seeded dilution water
A full bottle of the same seeded water supplies its depletion. Multiply that depletion by the fraction of each sample bottle occupied by seeded dilution water: (bottle mL − sample mL) / bottle mL. Do not use the direct-seed volume ratio as a substitute. Extra direct seed additions, extra reagents or unequal control-bottle volumes require a different reconciled method outside this tool.
Unseeded
No seed demand is subtracted. An unseeded dilution-water blank is a separate QC observation, not a seed control to subtract automatically.
How to interpret the result
Read the breakdown, exclusions and input record before the headline. Meeting an entered numeric condition is not a complete analytical quality decision. Retain the original bench sheet and resolve differences with the laboratory reviewer.
Worked example
For directly seeded 300 mL bottles, two usable controls give 0.34 and 0.41 mg/L depletion per mL seed; their average is 0.375. With 2 mL seed, correction is 0.75 mg/L. A 15 mL sample depleting from 8.5 to 3.5 mg/L gives (5−0.75)×300/15 = 85 mg/L. The demonstration's first seed control remains visible but does not enter the average because its final DO is below the entered 1 mg/L example criterion.
Assumptions
The entered measurements describe the same stated sample, method and basis. Inputs must already account for any upstream dilution not explicitly modeled. Criteria come from the governing SOP, not from this website.
Limitations
This is not a complete BOD method or batch-release decision. It does not assess incubation, sample handling, instrument calibration, GGA, blanks, inhibitors, toxicity or method reporting conventions. BOD and CBOD require their own appropriate observations/controls; choosing a label does not convert one into the other. Do not convert a five-day test to another duration or temperature with this tool. It reports eligible bottle counts and per-row arithmetic, never an automatic average or a permit result.
Sources
- Wisconsin DNR — BOD Seed: direct bottles and seeded dilution water
- Wisconsin DNR — Laboratory Study Guide