Residence Time Distribution in Submerged Biofilters

A mathematical model is presented for the residence time distribution in a submerged denitrification filter, in which pronounced tailing is experienced due to hold-up in the biofilm. Experiments with a dye tracer, Eosine-Y, and with Tritium show that adsorption of the dye makes it impossible to determine biofilm characteristics.

The same is true for any tracer if nitrogen bubbles are present in the filter. An experiment with Tritium in the filter without bubbles indicates that the surface of the media is only partly covered with biofilm. Biofilm characteristics can be determined only with great uncertainty, due to uneven distribution.