We analyzed the optical and hydraulic conditions of phytoplankton population competition based on the characteristics of antenna pigment absorption. From the analytical results of competition between th two types of antenna pigment, we found that the underwater light conditions in which short-wave blue or green light is superior (e. g. in clear water bodies), and the hydraulic conditions in which the ratio of mixed depth to euphotic depth is greater, are favorable for phycoerythrin-rich type (PE type) cyanobacteria. Conversely, under the optical conditions such as those in reservoirs where water tends to have lower transparency compared to oceans, it is assumed that shallow mixed depth can make phycocyanin-rich type (PC type) cyanobacteria more advantageous than PE type. Furthermore, for large-colony PC type cyanobacteria (LCPC) such as bloom-forming Microcystis, a mixed depth of several times the euphotic depth is the its critical depth. Therefore, LCPC requires shallow mixed depth from the optical point of view.

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We investigated the optical and hydraulic conditions of cyanobacteria growth using the field observation data for two reservoirs in Japan. When the buoyancy frequency (N²) is greater than O(10^-4)(s^-2) - O(10^-3)(s^-2), the populations of PC type Phormidium and Microcystis increase, however, for N² values less than that, the population of PE type Phormidium increases. From a theoretical analysis using the Wedderburn number (W), it is considered that the above level of N² is estimated as the critical condition for vertical mixing of density stratification. Therefore, it is assumed that two antenna pigments types, that is PC and PE, of Phormidium have different suitable hydraulic conditions. Furthermore the hydraulic stability requirement for large-colony cyanobacteria that form water bloom can be estimated based on N².

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The separation of insoluble solids from wastewater from shochu distillation is very difficult because of their high viscosity. Thus a large amount of shochu waste has been dumped into the ocean. The purpose of this study is to establish a new separation technique for shochu waste. Filamentous fungus was inoculated to shochu waste at 1×10⁶ cells/ml and the culture solution was incubated for several days. After that, the culture solution was filtered on a filter paper for 15 minutes using an aspirator. Accordingly the shochu waste was condensed to about 6 to 10 times. We consider that the elongated filaments of fungi should grasp and aggregate the solid particles in shochu waste, and this is expected to be the major accelerated separation mechanism in this study. Aspergillus oryzae RIB128 showed the highest separation efficiency among in the tested strains. With the treatment of shochu waste with filamentous fungi, the pH of shochu waste was changed from 3.9 to 7 by the decrease of organic acid. Organic carbon, nitrogen, and phosphorus decreased to about 70%, 60%. and 90%, respectively.

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Coagulation-precipitation treatment using ferric chloride was carried out in wastewater taken from a solid waste incinerator wet scrubbing system. The treated wastewater was fractionated with 1 μm and 0.1μm filter, and the dioxin concentration in each fraction was determinde. The isomer profiles indicated that 1) dioxin concentration in the “<0.1μm” fraction decreased, and 2) dioxin in the “≥0.1,<1μm” fraction between temproary increased by the conagulation process. Hence, it become clear that dioxin particle size increases and dioxin can be removed with conagulation-precipitation treatment. The relationship between dioxin isomer concentrations in montreated warte (X) and treatde water (Y), and Flocculant concentration (A) is expressed by the following regression formula. Y=2.3×10¹⁰×(X/A)+1.8 This result suggests that a dioxin concentration of more than 1,000 pg TEQ·l^-1 in highly contaminated wastewater can be reduced to below the wastewater effluent regulation value (10 pg TEQ·l^-1) by a combination of coagulation-precipitation treatment and membrane filtration.

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Alkylphenols are used in various industries in Japan. These substances are found to be endocrine disruptors that affect the gonad system. One alkylphenol that is often detected in the aquatic environment and has been found to have an estrogenic effect is nonylphenol (NP). The objectives of this study were to degrade NP using chlorine and ozone, the two major disinfectants used in treatments of drinking water and wastewater, and to investigate the effects of other coexisting substances. The results showed that NP in buffered water could easily be degraded by chlorine and ozone. The presence of ammonia however affected the degradation of NP by chlorine. Humic acid showed a negative effect on the removal of NP by chlorine and ozone but the effect of humic acid was small. Comparison of the amount of total chlorinated carbon (TOX) formed during chlorination of buffered NP solution and of sewage effluent was likewise conducted. Under normal chlorination conditions, the amount of TOX formed per mg dissolved organic carbon (DOC) was higher in buffered NP solution (138μg-Cl/mg-DOC) than in sewage effluent (84μg-Cl/mg-DOC). The results of the study further showed that 15-min chlorine contact time considerably decreased the NP concentration and its estrogen receptor binding effect. The aromatic ring however was not decomposed. Degradation of the aromatic ring was only observed after 24-h contact time. Ozone contact time of 1-min was found to degrade the aromatic ring.

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