BOD Removal Efficiency Calculator

Work out bod removal efficiency instantly with clear inputs, formula shown and shareable results.

About BOD Removal Efficiency Calculator

BOD removal efficiency is the fractional reduction in concentration. Conventional activated sludge achieves 90-96%, trickling filters 80-90% and primary settlement alone 25-40%. Because consent limits are absolute, a strong influent requires a higher percentage removal to reach the same effluent quality.

Formulas

Removal efficiency

Efficiency % = (influent BOD - effluent BOD) x 100 / influent BOD

Consent requirement

Required efficiency = (influent - consent limit) x 100 / influent

Worked example

With the default values below, BOD Removal Efficiency Calculator returns BOD Removal Efficiency of 93.5714%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Influent BODminimum 0 mg/L: 280 mg/L
Effluent BODminimum 0 mg/L: 18 mg/L
Flowminimum 0 m3/day: 5,000 m3/day
Consent Limitminimum 0 mg/L: 20 mg/L

Results

BOD Removal Efficiency: 93.5714%
BOD Load Removed: 1,310.000
BOD Load Discharged: 90.000
Efficiency Required For Consent: 92.8571%

Step by step

1Values used
2Removal efficiency
3Consent requirement
4BOD Removal Efficiency= 93.5714
5BOD Load Removed= 1,310.000
6BOD Load Discharged= 90.000
7Efficiency Required For Consent= 92.8571

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Effluent quality limits are legally binding consent conditions with sampling and reporting requirements. Verify against the specific consent.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Effluent quality limits are legally binding consent conditions with sampling and reporting requirements. Verify against the specific consent.

Frequently Asked Questions

Why do stronger influents need better plants?

The consent is a fixed concentration. Doubling influent BOD from 250 to 500 mg/L means removal must rise from 92% to 96% to hit 20 mg/L, which needs longer sludge age and more aeration.

Are percentage and absolute limits both used?

Yes. Many consents impose both a maximum concentration and a minimum percentage removal, so a plant cannot comply simply by dilution.