AWWA ACE70858

This powerpoint presentation begins by providing a brief overview of the general mechanisms of biofilm formation. Study hypothesis is stated as: unique solution chemistry condition of seawater: the high ionic strength (eliminate electrostatic double layer interaction van der Waals and short-range interactions become dominant), divalent cations; and, a given bacteria at a particular growth state will deposit more rapidly on more hydrophobic, rough surfaces. The experimental method included direct observation. Experimental materials were bacteria, membrane, and solution chemistry. Topics presented include: multi-probe liquid contact angle; bacteria and membrane properties; summary of adhesive energies; deposition result of different SWRO membranes and different chemistry solution; and, hydrodynamic condition - effect of cross flow velocity and permeate flow rate. Concluding remarks: H. pacifica is extremely hydrophilic; SWHR is very hydrophilic; SWC3+ is relatively hydrophobic; and, it is not clear why the more complex seawater matrix produces more hydrophilic membranes, less adhesion force, and lower deposition. Includes tables, figures.