A conventional activated sludge process for a night soil treatment plant requires dilution water as much as approximately 20 times of the influent volume. One plant with a standard design had an uneven ground sinking problem, because ground water was the its only source for dilution water. The modified denitrification process was applied to that particular plant in order to reduce dilution water consumption.
The experiment was successful and the following results were obtained ;
1) The modified denitrification process is feasible, because it saved approximately 85% of dilution water consumption without deterioration of the effluent quality. The use of a certain amount of ground water is inevitable to ensure easy liquid/solid separation.
2) Effluent quality improved with 98% nitrogen removal.

抄録全体を表示

This paper describes the analytical method of earthy-musty odorants from laboratory culture, and growth characteristics and 2-methylisoborneol (2-MIB) production of blue-green algae, Phormidium tenue. As headspace-gaschromatography is simple and rapid, it was used to determine for odorants from culture medium. The detection limit in the present method was 10ppb in the case of 1.0ml gas injection. The recoveries of 100ppb 2-MIB and geosmin were 99.5% and 90.9%, respectively. Three strains of P. tenue were used in these experiments. Meijyo strain was isolated from the moat around the Nagoya Castle, whereas the other two (Kure strain and Muroo strain) were received from Tokyo Metropolitan Research Laboratory of Public Health and Osaka Municial Water Works Bureau. These strain were cultured on two kinds of CT medium and modified Fitzgerald medium. As a result CT medium was found to promote much better than modified Fitzgerald medium on growth and 2-MIB production. The maximum quantity of 2-MIB which was produced in Meijyo strain, was 204ppb in the culture medium after 4 weeks. It was observed that the optimum temperature, pH and light intensity for growth and 2-MIB production were 20-25°C, 8-9 and 1000-2000lux, respectivery. And it became clear that temperature and pH agreed well with those of field observations.

抄録全体を表示

The studies on formation mechanism and removal techniques of halogenated organic compounds are popular among many investigators.
But “The Origin of Precursor” has been rarely reported and is not clearly known.
We investigated “The Origin of Precursor” at Lake Biwa-Yodo River catchment area.
The result showed that the load ratio of precursor in Lake Biwa (Uji River) is about 50% to Yodo-River.
Also we found that the contribution persentage of natural soils to particulate precursor in water is about 3040% at Kizu River, less than 10% at Lake Biwa, Uji River and Katsura River.

抄録全体を表示