As a result of the simulation of nitrogen budgets in Ariake Bay utilizing a box-type model, we concluded that the lack of nitrogen in nori farms was caused by the following facts: First, when nitrogen loading was delayed, some phytoplankton types consumed large amounts of nitrogen, which then created a lack of nitrogen because of the poor supply of nitrogen from the catchment area during the rainy period of autumn. Second, when the standing stocks of nitrogen in the fields of a nori fishery contributed significantly to the level of available nitrogen, and the fields had a high level of nitrogen consumption by phytoplankton, the supply of nitrogen was not sufficient to restore the nitrogen level to that required for a healthy fishery. Finally, phytoplankton was able to bloom at a favorable water temperature even at the beginning of nori production. Because the uptake of nitrogen depends on the population of phytoplankton, the plankton blooming in August and September causes a lack of nitrogen at the beginning of October.

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A system combining Up-flow anaerobic sludge blanket (UASB) and aerobic down-flow hanging sponge (DHS) reactors, which is cost-effective and has low-energy requirements, was applied to an actual dye wastewater treatment. The system performance was investigated for a duration of about 500 days operated in 12 different modes with a HRT of 8 hr for each reactor. The results demonstrated that the actual dye wastewater containing a high concentration of sulfate decreased treatment efficiency because of hydrogen sulfide inhibition in UASB. However, changing to UASB effluent circulation system, in which the effluent was introduced to a desulfurization unit before recycling, effectively improved treatment. As an important finding, the operational mode with the recycling of DHS effluent to the UASB inlet improved the final effluent quality with color removal compared with the UASB-DHS one-through mode. We conclude that the actual dye wastewater that originally contained 1000 mg COD·l^-1, 700 mg BOD·l^-1, and a transparency index of 2.5 cm on average, was effectively treated using the system combining anaerobic/aerobic UASB and DHS reactors, achieving approximately 80% COD removal, more than 95% BOD removal, and of a transparency index over 30 cm.

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The effects of low pressures (down to 0.01 MPa) on the mesophilic anaerobic fermentation of glucose (10 g COD·l^-1) were examined in this fundamental study. The anaerobic fermentation was developed to produce either low-molecular-weight fatty acids, lactic acid, hydrogen or methane as the primary product, by adjusting HRT, temperature and characteristics of the seed sludge. In the fermentation experiments producing acids and hydrogen, lactic acid and propionic acid concentrations decreased and acetic acid concentration increased in a completely mixed anaerobic reactor as operating pressure was decreased. Also, low-pressure operation yielded more hydrogen. In the fermentation experiment producing methane, the reactor recovered quickly at 0.01 MPa compared with 0.1 and 0.07 MPa. Low-pressure operation is thus considered favorable overall. Most of these observations are in accordance with thermodynamic predictions.

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The effects of inoculum on the characteristics of thermophilic hydrogen fermentation were investigated by performing a long-term continuous experiment lasting more 50 days. Continuous hydrogen fermentation of starch was conducted under thermophilic condition (55°C) by using five types of inoculum, including thermophilically digested sludge of activated sludge, cattle manure and sewage sludge, compost, and thermophilic acidogenic sludge. Five chemostat-type reactors were operated at an HRT (hydraulic retention time) of 24h. Stable hydrogen production was achieved in each culture without any methane production during the long-term continuous experiment. The highest hydrogen yield (2.32 mol H₂/mol hexose converted) was obtained by thermophilically digested sludge of activated sludge. The thermophilic hydrogen fermentation of starch by thermophilically digested sludge of activated sludge was expressed using the following stoichiometric equation : starch → 2.32n H₂ + 2.14n CO₂ + 0.5n acetate + 0.63n butyrate + 0.11n biomass (C₅H₉O₃N).

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To identify the cause of the high turbidity of the Murasaki River estuary, we investigated variations in suspended particle (SS) concentration and SS composition during the tide cycle in the Murasaki River estuary in June 2001 (rainy season) and September 2001 (nonrainy season). Additionally, the stable isotope ratio of carbon and nitrogen in the sediment and SS concentration and chemical composition were determined in the Murasaki River watershed over the investigation period.
In September, the turbidity and SS concentration were high in the bottom layer. The SS compositions in the surface and middle layers depended on the tide phase, although in the bottom layer, SS composition did not depend on the tide phase. Moreover, the average SS composition in the bottom layer showed relatively low particulate organic carbon (POC) and chlorophyll a (Chl a) contents and high C/N and C/Chl a ratios, and the sinking particle compositions was similar to the SS composition in the bottom layer. This suggests that the origin of SSs in the bottom layer differed from those in the surface and middle layers, and the resuspension of sediment was a significant source of SSs during the nonrainy season. In June, the variation in SS composition in the surface layer did not correlate with tide level, and the average SS composition was similar to that in the river. This finding suggests that surface layer SSs were predominantly river-borne SSs.
Sediments in the upper and middle reaches had a high δ ¹⁵N (+4.5‰∼+5.2‰) because of artificial pollution (small reservoir, agriculture effluent and human sewage). However, the δ ¹³C and δ ¹⁵N contents of the sediment in the Murasaki river estuary suggest that terrestrial C3 plants were the main source of organic matter in the sediment (δ ¹³C=-25.8‰, δ ¹⁵N=+2.9‰). Additionally, the δ ¹³C and δ ¹⁵N of sinking particles in the Murasaki river estuary suggest that the contribution of particles from the forest was higher in June (δ ¹³C=-25.2‰, δ ¹⁵N=+3.2‰) than in September (δ ¹³C=-24.4‰, δ ¹⁵N=+3.9‰). This suggests that the load from the forest brought when a storm was the main source of the organic matter in the the Murasaki River estuary sediments, and that the high turbidity of the Murasaki River estuary was caused by the resuspension of the sediment originating from the forest.

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The efficiency of removing boron from industrial wastewater by coagulation sedimentation with the coagulant cerium chloride (CeCl₃) was determined. The optimum processing conditions were investigated in a batch processing experiment conducted by supplying 100 mg ·l^-1 boron to a reactor. The optimum processing conditions were a pH of about 10, cerium addition to give a Ce/B molar ratio (molarity of Ce/molarity of B ) of 2 or more, and a processing time in the range of 5-30 minutes. The removal efficiency for boron decreased when sulphate ions were coexisted at a concentration of about six times or more of boron concentration. However, it was improved by performing coagulation sedimentation using calcium chloride (CaCl₂) and by increasing CeCl₃ concentration. When the effect of processing was examined using actual industrial wastewater under the determined optimum processing conditions, the removal efficiency for boron was in the range of 87-92%. When a field processing experiment was conducted by setting up small batch experiment equipment next to the wastewater treatment equipment, the removal efficiency for boron was 93%. This was about 58% higher than that of actual wastewater treatment equipment. Moreover, fluorine and SS (suspended solid) were successfully removed in addition to boron.

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The removal of arsenic(III) and arsenic(V) from water solution was carried out using a chelating resin, Diaion CRB02 (Mitsubishi Chem., Japan). As(III) and As(V) were removed at the pH range of 6-10 using the resin. At the optimum pH of 7, the average quantities of adsorbed arsenic on the resin determined by an analysis of adsorption isotherms were 15.5 mg·g^-1 for As(III) and 4.9 mg·g^-1 for As(V). When the sample solution {As(III) and As(V): 50.0 mg·l^-1} passed through the column at a space velocity of 40 h^-1, the breakthrough points of arsenic appeared was at 110 fold the resin volume for As(III) and 40 fold the resin volume for As(V). Adsorbed arsenic was recovered at 89∼103% for As(III) and 94∼96% for As(V) using 0.1 M and 1 M sodium hydroxide solutions. The results suggest that AS(III) and As(V) in waste water can be successfully removed using the resin and recovered using 0.1 M and 1 M sodium hydroxide solutions.

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To reuse the coagulant contained in water supply sludge, the coagulant was extracted using H₂SO₄ and its removal ratios for 117 types of pesticide and 14 types of metal on coagulation and sedimentation were studied compared with those of Al₂(SO₄)₃ and polyaluminum chloride (PAC). For inflow (pH 6.0) at a sewage treatment plant using 2 μl · ml^-1 (11.6 μg · ml^-1 as Al) recovered coagulant, the removal ratios were as follows: organochlorine pesticides, 13.1-100%; organophosphorus pesticides, 10.8-100%; carbamate pesticides, 5.1-67.7%; nitrogen-containing pesticides, 0-100%; pyrethroid pesticides, 39.1-100%; other pesticides, 5.5-100%; and decomposition products of pesticides, 0-100%. The removal ratios of the recovered coagulant for 93 pesticides were higher than or the same as those of Al₂(SO₄)₃ [50 μg · ml^-1 (7.9 μg · ml^-1 as Al)] and PAC [50 μg · ml^-1 (3.2 μg · ml^-1 as Al)]. On the other hand, the removal ratios of the recovered coagulant for metals were —106-100% and the remaining ratios for six metals including Al and Mn were more than 100% because those metals were contained in the recovered coagulant.

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The monitoring of 99 pesticides in drinking water from private wells in the Tama district in Tokyo was conducted from July 2004 to November 2005. Six pesticides (i.e., simazine, dichlorvos, bentazone, terbucarb, atrazine, and diuron) were detected in water samples. The frequencies of detecting bentazone, simazine, and the others were 5.2, 2.8, and less than 1%, respectively, in 250 water samples examined. The maximum concentration of each pesticide was less than 0.0001 mg · l^-1 and was less than one-hundredth of maximum contaminant level. A degradation product of the herbicide chlorthal dimethyl (TCTP) was detected at a concentration of 0.0037 mg · l^-1 in groundwater and at a concentration of 0.0008 mg · l^-1 in tap water after disinfection using sodium hypochlorite.

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