Night-soil sludge contains a high percentage of nitrogen and generates a large amount of ammonia, a malodorant compound during composting. The purpose of this research was to study on the effects of operational conditions of composting on the decomposed amount of organic compounds and that of ammonia emission. The optimum conditions for high speed composting of night-soil sludge for speedy decomposition of organic compounds were a temperature around 60°C, weakly alkaline conditions with a pH 7.2 or higher and a moisture content ranging from about 40 to about 60%, respectively. It was also found that the type of seeding material scarcely affected the decomposition speed of organic compounds. The amount of ammonia emission was almost directly proportional to that of organic compound decomposition for most cases of composting operational conditions. There was elucidated, however, that there were some cases where the decomposed amount of organic compound was not directly proportional to the amount of ammonia emission, where the moisture content was low, the proportion of the amount of ammonia emission was larger than that expected from the decomposed amount of organic compounds; and where the temperature was high or where the pH was low, the proportion of the amount of ammonia emission was smaller than that expected from the decomposed amount of organic compounds.

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Water quality was evaluated from the viewpoint of mutagenicity of drinking water. And, this study focused on the evaluation of the genotoxic characteristics of chlorinated and brominated substances produced by chlorination of the river waters containig bromide ions. Thus, the mutagenic activities of drinking waters, and disinfected river waters and sewage effluents were measured by Ames tests using S.typhimurium strains TA100 and TA98, and by chromosomal aberration test using cultured Chinese hamster lung cells (CHL/IU) in vitro. After flowing samples through CSP800 or XAD-2 resin column, absorbed substances were dissolved in dimethyl sulfoxide, and submitted to the mutagenicity assays.
Mutagenic activities of the drinking waters produced by chlorination were observed to be higher than those by ozonation. Mutagenic activities showed different characteristics in mutagenic potentials and induced aberrant cells caused by by-products when bromide ions were substituted for chloride ions with various ratios.

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