Simple models for the release kinetics of dissolved organic carbon from woody filtration media

The mechanisms and kinetics of dissolved organic carbon (DOC) release from woody materials (pine, hardwood and compost) under non-equilibrium leaching conditions was examined through batch and column tests. Mechanistically based kinetic models (first and second order) had a low predictive power for DOC release compared to those based solely on regression (Elovitch, power law). The DOC release data showed a bi-phasic response, with an early period of rapid release (<24 h) controlled by film diffusion followed by a slower rate controlled by intra-particle diffusion. After flow interruption, DOC release was primarily controlled by intra-particle diffusion; however, the specific rate parameters generally varied with each flow cycle and between different wood types.