Presented at the Arizona Water and Pollution Control Association Conference, Tucson, May 2002.

1. Optimization of Coagulation process by Evaluating Adhesion forces using Atomic Force Microscopy Ajay Kashi 1 , Anneta Razatos 2 and Morteza Abbaszadegan 1 1 Department of Civil & Environmental Engineering 2 Department of Chemical and Materials Engineering U A S

5. A C D B E 1) Line A 2) Line B 3) Line C 4) Line D 5) Lines E & F AFM Force Measurement A, B & C - Approach D & E - Retraction Distance of Separation (nm) Cantilever Deflection (nm) Z X F

6. Possible Configuration to Study Bacterial Adhesion by AFM Planar surface (Glass Plate) Bacteria Cantilever with Silicon Nitride Tip

7. MATERIALS AND METHODS CELLS + GLUTARALDEHYDE FIXED CELLS POLYETHYLENEIMMINE COATED GLASS POLYETHYLENEIMMINE POLYETHYLENEIMMINE

8. MODIFIED AFM CANTILEVERS CELLS + GLUTARALDEHYDE POLYETHYLENEIMMINE Coated Si 3 N 4 Tips Bacterial Lawn on Si 3 N 4 Tip FIXED CELLS

9. AFM Image of Immobilized E. coli and SEM Micrograph of AFM cantilever tip

10. Lipid A Glucose KDO Heptose Galactose Legend D21 LIPOPOLYSACCHARIDE STRUCTURE OF E. coli K-12 N-acetyl Glucosamine

11. Control Experiments

12. Results and Discussion Force, F = k x Δ X Spring Constant of Cantilever, k = 0.06nN/nM Δ X = Tip Deflection for the Approach curve.

13. Results and Discussion -0.45 ± 0.02 -0.35 ± 0.06 Experiment in PBS+NaCl Experiment in PBS only E. coli bacteria on tip and on glass surface E. coli bacteria on tip and on glass surface Configuration Experiment Force Values in nN

14. Approach Retraction Approach Retraction Approach Retraction 35nm 45nm 55nm 12mg/l 18mg/l 24mg/l Experiment #2

15. Results and Discussion Force values for Bacteria – Bacteria Interaction in Different Concentrations of Alum -1.77 ± 0.2 -0.77 ± 0.02 -0.70 ± 0.06 Force in (nN) 24 18 12 Alum Conc. in (mg/l)

17. Future Work Microbes Microbial Lawn Other Microbial cells commonly found in water 1. Inorganic Particles Microbes 2. Microbe-coated cantilever probing sediment-coated substrate Sediment-coated cantilever probing sediment-coated substrate Inorganic Particle Inorganic Particles 3.

18. Questions ?