ABSTRACT
Formation of biofilms has long been recognized as an important mechanism of interaction between porous media and biological processes, with practical applications to cngineering problems. For example, studies of soil "plugging" (decreases in hydraulic conductivity) began appearing in the 1940s, principally in response to problems associated with reduced flow through sewage infiltration ponds [11 and in plugging of sandstone formations during injection of water for enhanced oil recovery [21-More recent work demonstrated that biofilm formation can reduce the effectiveness of in situ bioremediation when injection of nutrients stimulates the production of biofilm by indigenous bacteria [3]. These and other studies conducted over the past 50 years have led to a general understanding of the nature of biofilms and their interaction with porous media. In essence, some species of aquatic bacteria show a strong tendency to adhere to surfaces of porous media [4-61-Following initial colonization, bacteria adhere irreversibly to solid surfaces by means of their exopolysaccharide (EPS) surface structures and begin to form a confluent film within which the bacterial cells are enmeshed in a matrix of acidic mucopolysaccharide [7].
