We propose applying the fuzzy reasoning with four input variables (organic matter, total hardness, iron, bicarbonate) to the evaluations of palatable water.
Firstry, the membership functions of them were prepared from the standard on palatable water from Ministry of Welfare in Japan. After that, a learning rule based on a desent method is applied to the consequent part of each fuzzy rule. The usefulness of generated fuzzy rules for test data (N=35, other district) was examined, so the correlation coefficient was given as 0.7829. Furthermore, we generated new rules iteratively in the fuzzy partitioned input regions by tuning. The correlation between sensory test and evaluation by fuzzy rules with the minimum inference error was improved on and the correlation coefficient was given as 0.8621.
These results suggest it is possible to apply fuzzy if-then rules with non-fuzzy singletons in the consequent part and four input variables to the evaluations of palatable water.

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The characteristics of accumulated substances were examined in two types of the anaerobic reactor membrane separation (ARMS) system.
For the ARMS process, the gas production rate from anaerobic digestion of wastewater containing long-chain fatty acid was higher than that in the chemostat type anaerobic reactor. Volatile fatty acids (VFAs) didn't accumulate in the ARMS process, but a VFAs concentration of 1,500 mg·l^-1 accumulated in the chemostat type anaerobic reactor. The removal rate of COD in the ARMS process was over 99%, and 80% of COD components in the influent was converted to the methane gas. In the ARMS process, number of bacteria increased by one order after 90-days operation but no significant change was observed in the chemostat type anaerobic reactor. But, the bio-activities per bacterial number decreased in spite of the increase of the bacterial number in the ARMS process.
The accumulated organic substances in the ARMS process were fractionated by membrane filtration and ultra membrane filtration. Results showed that bio-activity of permeate decreased as time of operation increased, but that of particulate substances increased.

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A mathematical model was developed to predict the effect of vertical water circulation caused by air-lift on water quality restoration in a lake. In this model, several ecosystem paths such as Algal growth, predation by zooplankton, degradation of organics and so on were combined with completely-mixing series tank model, in which a water body was divided vertically to two districts, epilimnion and hypolimnion. This model was applied to Lake Yogo, where two sets of the vertical water circulation unit were set, and verified by comparing the simulated results with observed data. The vertical circulation effects on lake restoration were discussed with this model from the viewpoints of concentrations of dissolved oxygen in hypolimnion, phytoplankton, total nitrogen and total phosphorus.

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Effects of suspended photocatalyst concentration and reactor radius on the decomposition rate of total organic carbon (TOC) were studied to elucidate a design concept of the internal radiation-type cylindrical photoreactor. For this purpose, the transmittancy of UV light through Pt loaded TiO₂ suspension and the rate of photocatalytic decomposition of TOC, caused by methanol as raw material, within cylindrical type photoreactors equipped with a high pressure Hg lamp were measured. The transmittancy of UV light through photocatalyst suspension was empirically correlated with light pass length and photocatalyst concentration. The decomposition rate of TOC was independent of TOC concentration. By using these obserbed results and assuming that the photocatalytic decomposition rate was proportional to photocatalyst concentration and square root of light intencity, an equation was presented to obtain the average reaction rate within the cylindrical type photoreactor. Experimental results of TOC decomposition in reactors with different diameters were well correlated with this equation.

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In the current investigation of the cause for ground water pollution by arsenic speices, speciation and quantitative analysis of arsenic compounds in water and soil samples were performed by using high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). In water samples, arsenic acid and arsenious acid were detected, but methanearsonic acid (monomethylarsonic acid ; MAA) and dimethylarsonic acid (cacodylic acid ; DMAA) were not detected. On the other hand, in soil samples, MAA was detected at low concentration.

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