EFFECTS OF SLIGHT VARIATIONS IN NUTRIENT LOADINGS ON PORE PLUGGING INSOIL COLUMNS

The high nutrient concentrations that would exist near the nutrient in jection well during the application of cometabolic in situ bioremediat ion may lead to the development of significant quantities of biomass a t this point in the subsurface. This biomass can decrease the porosity of the soil to such an extent that nutrient injection is no longer po ssible. In this work, experiments were conducted using a porous media biofilm reactor, operated under constant substrate loading conditions, such that the pressure drop across the reactor was allowed to increas e to maintain a constant volumetric flow rate through the reactor. Res ults suggest that biomass production, and hence biofilm thickness, nea r the injection feed port is highly sensitive to substrate loading. In addition, these variations in biofilm thickness produce dramatic diff erences in the pressure drop that is attained across the reactor. Use of the Kozeny-Carman equation can be used to predict that once a criti cal depth has been exceeded, the pressure drop across the bed will inc rease exponentially within biofilm depth. This result means that press ure is not a reliable indicator of the onset of pore plugging.