Trickling Filter Loading Calculator

Work out trickling filter loading instantly with clear inputs, formula shown and shareable results.

About Trickling Filter Loading Calculator

Trickling filters are assessed on organic loading in kilograms of BOD per cubic metre of media per day and hydraulic loading in cubic metres per square metre per day. Low-rate filters run 0.08-0.4 kg BOD/m3/day with high removal; high-rate filters accept 0.4-1.6 with lower removal and require recirculation.

Formulas

Loading rates

Organic loading = BOD load / media volume; hydraulic loading = flow / plan area

Removal estimate

Efficiency approximated by the NRC-type relationship with organic loading

Worked example

With the default values below, Trickling Filter Loading Calculator returns Organic Loading Rate of 1.2732. Change any input above and every figure here is recalculated in your browser.

Inputs used

Applied Flowminimum 0 m3/day: 4,000 m3/day
Filter Diameterminimum 0 m: 20 m
Media Depthminimum 0 m: 2 m
Applied BODminimum 0 mg/L: 200 mg/L

Results

Organic Loading Rate: 1.2732
Hydraulic Loading Rate: 12.732
Media Volume: 628.32
Estimated BOD Removal: 66.672%

Step by step

1Values used
2Loading rates
3Removal estimate
4Organic Loading Rate= 1.2732
5Hydraulic Loading Rate= 12.732
6Media Volume= 628.32
7Estimated BOD Removal= 66.672

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.

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

Frequently Asked Questions

Why does recirculation help?

It maintains a minimum wetting rate to keep the biofilm active and dilutes strong influent, allowing higher organic loading without ponding. It also improves nitrification on lightly loaded filters.

What causes ponding?

Excessive biofilm growth blocking the void space, usually from high organic loading with insufficient hydraulic shear. Increasing recirculation or reducing load restores sloughing balance.