Nutrient Removal Efficiency Calculator

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

About Nutrient Removal Efficiency Calculator

Nutrient removal efficiency is the percentage reduction in total nitrogen and total phosphorus. Biological nutrient removal typically achieves 70-85% nitrogen and 80-95% phosphorus with chemical polishing. The Redfield ratio of 16:1 by moles indicates which nutrient limits algal growth in the receiving water.

Formula

Removal efficiency

Removal % = (influent - effluent) x 100 / influent, for each nutrient

Worked example

With the default values below, Nutrient Removal Efficiency Calculator returns Nitrogen Removal Efficiency of 77.778%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Influent Total Nitrogenminimum 0 mg/L: 45 mg/L
Effluent Total Nitrogenminimum 0 mg/L: 10 mg/L
Influent Total Phosphorusminimum 0 mg/L: 7 mg/L
Effluent Total Phosphorusminimum 0 mg/L: 1 mg/L

Results

Nitrogen Removal Efficiency: 77.778%
Phosphorus Removal Efficiency: 85.714%
Influent N To P Ratio: 6.429
Likely Limiting Nutrient: Nitrogen limiting - prioritise N removal

Step by step

1Values used
2Removal efficiency
3Nitrogen Removal Efficiency= 77.778
4Phosphorus Removal Efficiency= 85.714
5Influent N To P Ratio= 6.429
6Likely Limiting Nutrient= Nitrogen limiting - prioritise N removal

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 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Nutrient consent limits protect against eutrophication and are legally enforceable. Confirm limits and averaging periods in the specific permit.

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

Nutrient consent limits protect against eutrophication and are legally enforceable. Confirm limits and averaging periods in the specific permit.

Frequently Asked Questions

Why does the limiting nutrient matter?

Removing the non-limiting nutrient does not reduce algal growth. Freshwater is usually phosphorus limited and marine water nitrogen limited, which is why consent priorities differ between inland and coastal works.

What limits nitrogen removal?

Available carbon for denitrification. Where the influent COD to nitrogen ratio is below about 8, an external carbon source such as methanol or acetate is needed to reach low total nitrogen.