The organic loading influences the performance of the filter. The organic loading is the amount of B.O.D. applied to the filter per day per volume of filter media. So the units of organic loading are typically pounds B.O.D./day/1000 ft

The organic loading can be calculated using the formula below. This formula does not include recirculation, so the flow used is the influent flow rather than the total flow.

The B.O.D. is the concentration of B.O.D. in the filter influent. The units of the filter volume are "1000 ft

So let's calculate the organic loading of a 23,500
ft^{3} filter with an influent B.O.D. of 200 mg/L, and a flow of
3 mgd.

So the organic loading of the filter is 213 lbs/day/1000 ft