Abstract
Soil structure is heterogeneous with cracks or macropores where bypass flow would waste applied decontamination chemicals without interaction with soil matrix. We investigated the efficiency of bioremediation for oil contaminated soils by changing infiltration rate, i.e., saturated and unsaturated flow, for two types of soils, one had macropores inside and the other did not. Resultant biological activities in effluent increased dramatically for the experiment with an unsaturated flow with macropores. Unsaturated condition prevented bypass flow, allowed dispersion of nutrient in soils, and achieved appropriate water content for biological activity, while macropores prevented clogging during the infiltration experiment.