The initial formation process of mixed fouling of Pseudomonas fluorescent and CaCO3 on the different solid surfaces in a simulated cooling water system was investigated. The mixed fouling behavior on different solid surfaces under the conditions of different CaCO3 saturation levels and bulk velocities was examined

and the growth curves of mixed fouling were obtained. The results showed that the average mass of mixed fouling was less than that of biofouling. In the unsaturated CaCO3 solution

the average mixed fouling mass was little; but in the saturated CaCO3 solution

with the saturation level of CaCO3 and bulk velocity increasing

the average mass and induction period of the mixed fouling decreased. The mixed fouling mass on non- metallic material surfaces was more than that on metal material surfaces. It was also found that CaCO3 particles were adsorbed to the surfaces firstly

then microbes were adsorbed. The existence of CaCO3 inhibited the combination of microbes with surfaces

on the other hand

the adsorption and growth of microbes suppressed CaCO3 fouling development.