Abstract
Development process of biofilm, attaching on surfaces of various kinds of substratum, i.e., polyvinylchloride, glass and polypropyrene, each being treated chemically so as to prepare different surface roughness, was analyzed in the light of oxygen consumption rate and spacial structure of biofilm.
The spacial structure of biofilm was complicated in that the biofilm surface attached on the substratum surface was not uniform and the vertical structure was not homogeneous, sometimes vacant space existing within the biofilm. From the oxygen consumption activity the formation of biofilm is considered to be composed of two processes in series, i.e., a monotonous development of biofilm and a random process in which separation and reformation of biofilm occured on different surfaces at the same time. However, the microscopical analysis of structure revealed that even in the initial biofilm development the attachment and detachment of biofilm constituents occured locally.
Among the factors experimented the liquid flow velocity showed most significant effect on the biofilm development as that the biofilm obtained under the fluid velocity of 15 cm·s-1 was stabler and thicher than the one obtained under the liquid flow rate of 5 cm·s-1. Substratum of hydrophobic nature seemed to be the most ineffective for the initial biofilm development, but in the random process mentioned above its effect became insignificant. The surface roughness of substratum was effective for the initial biofilm development indpendently of liquid flow rate, but the biofilm developed on the rougher surface was apt to detach easily compared with the one formed on smooth surface.
