2.4.4. Effect of hydrodynamic shear force on bacterial adhesion
To estimate the effect of the hydrodynamic shear force on the bacterial adhesion, the pre-formed biofilm on the membrane surface was exposed to the different stirring rates, and the detached bacteria were measured. After biofilm pre-formation using the same protocol as described in Section 2.4.1 at 1.50 MPa of the TMP and 100 rpm of the stirring rate, we continuously supplied 5-fold diluted FAB medium in to the cell at 1.50 MPa of the TMP and at various stirring rates from 100 to 300 rpm. The bacterial concentration in the condensate water was measured by a pour platemethod to evaluate the bacteria detached fromthe membrane surface due to the shear force caused by stirring. Briefly, 1 mL of condensate water was added to 27 mL of warm FAB medium containing 1.5 g/L agar. The mixed solution was poured onto plastic plates, cooled at room temperature, and solidified. The prepared plates were incubated for 24 h at 30 °C, and the bacterial colonies on the plates were then counted.