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.

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Biodegradability of twelve organic compounds found in coal liquefaction wastewater was examined by using acclimated activated sludge. The compounds tested were phenol, three isomers of cresol, cyclohexanol, 3, 5-xylenol, aniline, ο-toluidine, pyridine, α-picoline, quinoline and pyrrole.
The results are as follows :
1) The limit concentration of each compounds for biodegradation were determined. The limit concentrations ranged from 100mg·l^-1 (ο-toluidine and 3, 5-xylenol) to 4000mg·l^-1 (pyridine).
2) The limit concentration of a compound in the presense of other one became lower than that of the compound alone. Namely, the additive effects of inhibition were seemed to exist.
3) The activated sludge acclimated to a high concentration of a compound obtained higher resistivity to a certain degree.

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During the past four decades many investigators have considered the use of Oxidation-Reduction Potential (ORP) measurements for the management and control of operations in activated sludge process, anaerobic digestion process and toxic substance treatment process. These reports indicated available and interesting results in the exemplification and utility of the value of ORP measurement. But what kind of factors influenced the value of ORP was not indicated.
This paper aims to evaluate the relationship between temperature, DO, H₂S, pH and the value of ORP in the Nernst Electrode Potential Equation and attempts to discuss on the degree of influence for ORP value on the following items.
(1) The temperature of the solution.
(2) Relationship between DO and ORP in case of gradual DO increasing and decreasing.
(3) Relationship between artificial H₂S solution and ORP.
(4) The hydrogen-ion concentration (ΔEh/ΔpH and ΔrH/ΔpH).

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[in Japanese]

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