Caracteristiques Hydrodynamiques De Tourbe En Colonne Trib. Cebedeau
Hydrodynamic characteristics of peat columns
Water treatment processes which use peat bed or columns may be limited by hydrodynamic properties of this material. Ascending water experiments, using 1,5 m hight and 20 cm diameter columns, allowed us to determine hydraulic conductivity (Darcy coefficient) K : it ranges between 0.14 and 0.88 cm/s for eutrophic Heurteauville peat and between 0.011 and 0.093 cm/s for oligotrophic Floratorf peat, depending upon column filling conditions. For both peat types pore volume V(p) is near to 32,000 cm3, corresponding to a 74-87 % kinematic porosity. Mathematical analysis of concentration profiles at column outputs, when 10 mM KCl plug injection were performed, gave dispersion coefficient D ranging between 0.23 and 0.31 cm2/s for eutrophic peat and between 0.10 and 0.21 cm2/s for oligotrophic peat. Comparison of concentration profiles when KCl is introduced or rinced by water shows that interactions between KCl and peat is mainly diffusional and that KCl may be used as hydrodynamic tracer. If diffusion is supposed to be under purely kinetic dispersion regime, intrinsic dispersion coefficients ?’ range between 7 and 30 cm.