ENVIRONMENTAL-IMPACT AND MECHANISMS OF THE BIOLOGICAL CLOGGING OF SATURATED SOILS AND AQUIFER MATERIALS

The biological clogging of natural porous media, often in conjunction with physical or chemical clogging, is encountered under a wide range of conditions. Wastewater disposal, artificial groundwater recharge, i n situ bioremediation of contaminated aquifers, construction of water reservoirs, or secondary oil recovery are all affected by this process . The present review provides an overview of the techniques that are u sed to study clogging in the laboratory, or to monitor it in field app lications. After a brief survey of the clogging patterns most commonly observed in practice, and of a number of physical and chemical causes of clogging, the various mechanisms by which microorganisms dog soils and other natural porous media are analyzed in detail. A critical ass essment is also provided of the few mathematical models that have been developed in the last few years to describe the biological clogging p rocess. The overall conclusion of the review is that although informat ion is available on several aspects of the biological clogging of natu ral porous media, further research is required to predict its extent q uantitatively in a given situation. This is particularly true in cases that involve complicating factors such as predation or competition am ong organisms.