Direct wet surface imaging of an anaerobic biofilm by environmental scanning electron microscopy: Application to landfill clay liner barriers

To contain domestic waste and its associated pollution within a landfill, e ngineered mineral (clay) barriers are used and are designed to have a perme ability of 1x10(-9) m/s (Westlake 1995). The rate of permeability of variou s porous media has shown to be influenced by the clogging of flow paths (me dia pores) due to biofilm formation (Charckalis and Marshall 1990, Cunningh am et al. 1991). The term biofilm is given to describe the colonies of surf ace adherent microorganisms (Donlan et al. 1994). In this study, permeabili ty experiments were built and modified to act as microcosms to investigate the influence of biofilm formation on the permeability of clay barriers. Tr aditional scanning electron microscopy methods disrupt or destroy the biofi lm and previous anaerobic studies have involved building closed cells (such as miniature continuous culture chambers) that utilise light microscopes ( Robin Jones et al. 1997). This paper examines the application of the enviro nmental scanning electron microscope (ESEM) to the direct examination of th e clay interface and biofilm formation in situ within the microcosm.