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Aeration Tank Volume Calculator

Work out aeration tank volume instantly with clear inputs, formula shown and shareable results.

About Aeration Tank Volume Calculator

Aeration volume follows from the food-to-microorganism ratio: the biomass inventory needed is BOD load divided by F/M, and volume is that inventory divided by the MLVSS concentration. Conventional activated sludge runs F/M of 0.2-0.4 and extended aeration 0.05-0.15, with correspondingly larger tanks.

Formulas

Biomass inventory

Biomass (kg MLVSS) = BOD load / F:M ratio

Volume

Volume (m3) = biomass x 1000 / MLVSS (mg/L)

Worked example

With the default values below, Aeration Tank Volume Calculator returns Aeration Tank Volume of 2,133.33. Change any input above and every figure here is recalculated in your browser.

Inputs used

BOD Loadminimum 0 kg/day
1,400 kg/day
Design MLSSminimum 0 mg/L
3,500 mg/L
Food To Microorganism Ratiominimum 0 kg BOD/kg MLSS/day
0.25 kg BOD/kg MLSS/day
MLVSS Fraction Of MLSSaccepts 0–100 %
75 %

Results

Aeration Tank Volume
2,133.33
Biomass Inventory Required
5,600.00
MLVSS Concentration
2,625.0
Volumetric BOD Loading
656.250

Step by step

  1. 1Values used
  2. 2Biomass inventory
  3. 3Volume
  4. 4Aeration Tank Volume= 2,133.33
  5. 5Biomass Inventory Required= 5,600.00
  6. 6MLVSS Concentration= 2,625.0
  7. 7Volumetric BOD Loading= 656.250

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 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.

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

Frequently Asked Questions

What does a low F/M ratio give?

Longer sludge age, more complete oxidation, nitrification and a well-mineralised sludge, at the cost of a larger tank and more aeration energy. Very low F/M can cause pin floc and deflocculation.

Why use MLVSS rather than MLSS?

Only the volatile fraction is active biomass; the rest is inert inorganic material. Using MLSS overstates the active population, particularly where inorganic loading is high.

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