Residence time distribution model for soil filters.

Abstract

Pulse tracer tests were carried out to determine the residence time distribution (RTD) in earthworm-cultured and uncultured, laboratory-scale soil filters. A two-parallel-cell dispersion model for the mixing behavior in soil filters is presented; the model showed excellent fit to experimental data. Results showed a fitted Peclet number of 0.83 to 0.89 for the uncultured soil filter and 0.18 to 0.29 for the cultured soil filter. Results also determined that the cultured soil filter dispersion number (1/Pe) was relatively high, showing the significant effect of earthworms on mixing. Reactor performance data and dispersion model predictions based on present RTD model parameters also reveal good agreement, indicating the usefulness of RTD parameters for describing real situations.