FIG. 8. (a) Glass beads column (0.5–1.0 mm diam.) containing blobs of extracellular polymeric substance (EPS) prior addition of dyed water, (b) column saturated with dyed water for 15 min (no dye diffusion in EPS), (c) saturated column after 12 h (including saturated EPS blobs), and (d) column drained and flushed with water (retention of water by EPS blobs after drainage).