Using the secondary effluents from 4 domestic wastewater treatment plants and their advanced effluents by flocculation-sedimentation, activated carbon adsorption and ozonation processes, reduction effect of their trihalomethane and total organic halide formation potentials (THMFP and TOXFP), and removal effect of each component in TOXFP samples by GC-MS analysis were examined, respectively.
It was shown that effective removal of NH₄-N concentration in the secondary effluent was very important in order to reduce its THMFP and TOXFP, since both potentials were very susceptible to NH₄-N component. The averaged 32-34% of THMFP and 25-24% of TOXFP in the secondary effluents were reduced by flocculation-sedimentation and ozonation processes, respectively. In case of the combination process of activated carbon adsorption after flocculation-sedimentation, high removal effciencies of COD and TOC were obtained and reduction efficiencies of THMFP and TOXFP were 76% and 71% on the average, respectively. Main components of halogenated organic compounds in the secondary effluents were trichloroacetic acid. dichloroacetic acid and chloral hydrate, and their components could be reduced effectively by the same combination process.

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Developing solution for photography is a mixed solution that contains some organic substances and about 10% of sodium sulfite, an antioxidant of the organic substances. Therefore, the waste developer solution displays a high COD and the treatment is difficult because the contained organic substances, p-methylaminophenol sulfate and hydroquinone (p-dihydroxy-benzene), are also hardly decomposed. In order to reduce the COD in the solution, a combined method of oxidation with ozone and coagulative precipitation with iron (III) chloride was examined.
By ozone oxidation, about 85% of the COD in the developer solution was reduced. In detail, the sulfite ions were thoroughly oxidized and most of the organic substances were also oxidized. Furthermore, the oxidized organic substances were decomposed to carboxylic acids and a part of the carboxylic acids were estimated to be decomposed to carbon dioxide. However, the conversion rate of the carboxylic acids to carbon dioxide was so slow that the acids could not be decomposed completely during that a short period. The coagulative precipitation with iron (III) after the partial decomposition by ozone oxidation enabled the concentration of COD to be reduced about 90-96%.

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Bioaccumulation of di-2-ethylhexyl phtalate (DEHP) and di-n-butyl phtalate (DBP) by a wintering diving duck, Aythya fuligula, was studied by a conventional analysis modified to minimize contamination. The 0.061 μg · g^-1 for DEHP and the 0.041 μg · g^-1 for DBP were detected in a blank sample throughout whole procedure. Added DEHP and DBP were recovered at 105.2% and 106.3%, respectively. Trophic level of A. fuligula was examined using carbon and nitrogen stable isotope ratios. Nitrogen stable isotope ratios suggested that organic component of the liver of A. fuligula was changed with its food bivalve, Corbicula japonica, by 70 days after duck's arrival. Mean concentrations of DEHP and DBP on basis of fat in the livers of ducks and the flesh of C. japonica were 332μg · g^-1 and 7.51μg · g^-1 for DEHP, and 12.1μg · g^-1 and 6.88μg · g^-1 for DBP, respectively. Concentrations of DEHP in the livers of ducks increased towards the middle of December 1994, and decreased afterwards, suggesting that both bioaccumulation and decomposition of DEHP occurred in the liver of ducks. Increase of DEHP concentrations towards the middle of December 1994 was attributed to the backflow of saline water from urbanized area, because carbon isotope ratios and the concentrations of DEHP in the liver of ducks showed positive correlation.

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Hydrogen and oxygen isotope measurements of rain and of snow samples collected from Nagaoka in Niigata pref., Japan, were examined. Their variations of isotopic composition changed considerably within a few days. The rain samples were collected daily from 10/15 to 10/18 during the 10^th typhoon of 1998. The snow samples were collected on 2/24 and 2/25 in 1999. Oxygen and hydrogen isotope ratios of the rain and the snow samples were measured with a Micromass PRISM mass spectrometer using an equilibrium technique of carbon dioxide and hydrogen with platinum, respectively.
The following two results were obtained:
(1) The average values of δD and δ¹⁸O of the rain and the snow samples were between -32.5 and -62.9 per mil, and between -7.7 and -9.8 per mil, respectively.
(2) The d value calculated using the obtained δD and δ¹⁸O were between 2.46 and 22.06 for the rain and between 28.84 and 37.46 for the snow.
Surprisingly, the isotopic composition of water precipitated in Japan changed rapidly based on the obtained results. The implication of these results suggests that analyzing isotopic ratios may lead to a prediction of a possible disaster caused by heavy rain or snow.

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Aiming the recovery of ferromagnetic powder, the excess activated sludge supplemented with magnetite (magnetic sludge) was solubilized with the thermochemical treatment using alkaline solution, the ultrasonic treatment, and was decomposed with the aerobic digestion treatment. The incineration of sludge was not carried out. There is no problem for the reuse of magnetic powder including small amount of organic materials. We expected to remove more than 85% of activated sludge from the magnetic sludge. As the results, both the thermochemical treatment and the ultrasonic treatment were found to be effective for the sludge solubilization. However, in the case of thermochemical treatment, we obtain alkaline suspension of sludge as a byproduct after the recovery of magnetic powder. In another case, the ultrasonic treatment takes less than 10 minutes to recover the magnetic powder. This method is not available for the treatment in large quantity. On the other hand, the aerobic digestion treatment was the most effective with only the aeration. By adding magnetic sludge into the aeration tank at regular intervals, the MLVSS decreased under aeration and the magnetic powder was accumulated. We made the aerobic digestion treatment to an end, when the ratio of magnetic powder against sludge reached to more than 4 times in the aeration tank. The magnetic powder was separated easily as the digested magnetic sludge by magnetic attraction.

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An experimental investigation of the removal of suspended matter from an aqueous solution was carried out with a foam separation batch system using fish mucus as the chemical. Flounder and eel mucus showed a high foaming capacity. The capacity was influenced by changes in pH and by the presence of salts in the solution. The capacity of eel mucus was weaken in the weak acidic solution (pH 5), and was enhanced in the alkaline solution (pH 10). The capacity of both types of mucus were elevated with addition of NaCl. The capacity of flounder mucus was extremely high in seawater, and the height of foaming layer was 7 times higher than in distilled water at the same concentration. When the flounder mucus was added to the bubbling solution (above 3mg · l^-1), the suspended kaolin particles were adsorbed on the foam layer and were removed from the seawater by separation. The removal efficiency was 99%. The eel mucus also removed the kaolin in the presence of salts. Foam separation is a suitable method for removing suspended matter from fish rearing water that contains fish mucus.

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