Water quality parameters in the water column of a dam reservoir were measured monthly in 2001. From July to November, the vertical profiles of alkaline phosphatase activity (APA) and related parameters were examined in detail. APA increased during the summer in epilimnion while it was almost stable in hypolimnion. A small increase in APA was observed at a depth immediately above the bottom of the lake. APA fluctuation was independent of soluble reactive phosphorus. It was assumed that APA is not indicative of the phosphorus status of aquatic microorganisms in the lake. A positive correlation was observed between chlorophyll a content and APA in the photic zone. In the aphotic zone, APA correlated positively with the colony count of heterotrophic bacteria, but not with microscopic total bacterial count.

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To effectively use sewer system resources, experiments were carried out to recover phosphorus and aluminum from incinerator ash of sewage sludge. I found that, if an alkali solution is added to sewage ash, phosphorus and aluminum can be selectively eluted to the solution and separated by adding calcium hydroxide. Phosphorus and aluminum were recovered in the form of calcium phosphate and sodium aluminate respectively. The recovered phosphorus compound was 100% citric acid-soluble, and contained 36% phosphoric acid. With respect to toxic heavy metals specified by the Fertilizer Control Law, the Cd and As contents were below the specified standards, and Ni, Cr, Pb and Hg were not detected in the available chemical analyses. The recovered phosphate was of acceptable quality for use as fertilizer. The recovered aluminum solution contained 17000mg/1 Al, and may be used as flocculant in the removal of phosphorus from sewage.

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A bench-scale anaerobic/oxic sequencing batch reactor (SBR) was operated for 35 days with peptone and acetate fed as carbon sources during the start-up phase. In order to find quinone biomarkers representing bacteria the play important roles in priming the enhanced biological phosphorus removal (EBPR) process, the time variations of 12 quinone species and EBPR activities were quantitatively compared in the SBR. Both phosphate release rate and specific phosphate release rate increased at the beginning of the operation and reached maximum on the 21st day. It was interpreted kinetically that the concentration of phosphate-accumulating organisms (PAOs) in the reactor and the fractional percentage of PAOs in the sludge increased in the first 21 days. Only MK-10 showed a good correlation with EBPR activity through out this period, and therefore, MK-10 could be a candidate biomarker. Since Q-9 and MK-7 showed good correlations only in the first seven days, these two quinone species may be present in bacteria that play certain roles during the early phase of EBPR development.

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The inhibition of freshwater algal growth was investigated using powdered TiO₂ as a photocatalyst under artificial sunlight irradiation with a combination of fluorescent lamp and black light in order to develop a new method of water quality improvement in lakes or reservoirs using natural energy. The growth of Microcystis aeruginosa, Anabaena solitalia and Coelastrum astroideum was effectively inhibited by using powdered TiO₂ photocatalyst at a concentration of 100mg·l^-1, whereas that of Fragilaria capucina wasn't.

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In this study, we attempted to quantify the risk of enteric virus infection due to wastewater reuse, and to clarify the necessary reclamation methods to ensure safety. To assess the potential risk associated with the use of reclaimed wastewater in various reuse applications, some exposure scenarios were assumed, and enteric virus concentrations in secondary effluents were monitored at ten wastewater treatment plants for 2 years. The virus concentrations in secondary effluents distributed according to a log normal curve. Annual infection risks (r) corresponding to the scenarios were calculated using the Monte Carlo method. Then, assuming a number of virus removal efficiencies (x), annual infection risks (r) were calculated and the relationship between virus removal efficiency and annual infection risk (r=f (x)) was obtained for each scenario. The necessary virus removal efficiency (x0), satisfying the assumed acceptable annual risk (r0) under the given scenario, was calculated using r=f (x). A virus removal method satisfying the virus removal efficiency (x0) was chosen using the existing data of enteric virus removal efficiencies of several reclamation methods.

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Samples of water and suspended solids (SS) collected from the Hinuma river system over one year were analyzed by PIXE (Particle Induced X-ray Emission) to determine elemental concentrations.
The average SS concentrations at the 11 sampling sites ranged from 1.4 to 12.7mg·l^-1 during ordinary water discharge. The SS concentrations were the highest in the upstream reaches of the Hinuma River, but were lower from the middle to downstream reaches, suggesting that the SS may have settled to the riverbed. All of the SS samples contained relatively high concentrations of Al, Fe, Ca, K and Mg, suggesting that the SS consist of particles from the earth's crust. Variations in elemental ratios to Al of Na, Mg, K, Ca and Cu in the SS among the sampling sites may have been due to differences in geology, land use, drainage from quarries, or brackishness of the water. Moreover the highest Fe: Al ratio was observed at a site where a large microbial mat had developed; the Cu: Al ratio was remarkably high at another site where intensive pig farming was practiced.

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