The wastewater containing fluoride is usually treated by the coaguration and sedimentation method using calcium hydroxide, with the resultant sludge being dischaged as industrial waste. Because of the shortage of landfill place, the reduction of such the industrial waste sludge is now an essential issue in the wastewater treatment.
The author have recently succeeded in practical application of fluoride regeneration to calcium floride using granular calcium carbonate. So far three full-scale industrial treatment plants have been under operational.
In this technology, wastewater is fed to the reactor with granular calcium carbonate, which remove fluoride from the wastewater and converted them to granular calcium fluoride which purity can be compared to natural fluorite.
In this study, the author analyzed kinetifically the reaction rate by applying the unreacted shrinking core model. It was found that the rate of reaction is contorolled by chemical reaction on the interface between the reactant cell phase and the unreacted core. Moreover, the author carried out a simulation analysis based on a fluoride regeneration pilotplant test data, and the results were in good agreement with the actual measured values.

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UV absorbance: DOC ratios were determined for the dissolved component of the water samples obtained from several specific sources, influent rivers and in-lake points of the three lakes as well as the evaluation of their changes during long-term incubations. There were significant differences in the ratios between influent rivers and in-lake points, which were consistently due to the difference between allochthonous sources mainly composed of pedogenic humic substances and autochthonous sources e.g. substances excreted through primary production. The nearly constancy of the ratio during the biodegradation process was confirmed for both allochthonous and autochthonous components; hence a two-component model could be applied to these lakes in order to calculate the proportion of DOC in each of the two components. Because of its usefulness to the model, easiness of measurement, and the close relation to trihalomethane productivity, this ratio could be one of the important indices for lake environmental management.

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In order to investigate the occurrence of Giardia cysts and Cryptosporidium oocysts in raw sewage and the removal in sewage treatment processes, we conducted a field survey at 9 sewage treatment plants. The results can be summarized as follows : 1) In all plants, Giardia cysts were detected in raw sewage and effluent of primary sedimentation. Cyst densities in raw sewage ranged from 130 to 5,500 cysts·l^-1 (geometric mean 1,350 cysts·l^-1). Cyst densities in effluent of primary sedimentation ranged from 150 to 5,200 cysts·l^-1 (geometric mean 800cyst·l^-1). 2) Cryptosporidium oocysts were detected from only one raw sewage sample with the density of 28 oocysts·l^-1. 3) Indicator bacteria counts tested, C.perfringens spores, coliforms and E.coli, were statistically correlated with Giardia cyst densities and the most significant relationship was observed between C.perfringens spore counts and Giardia cyst densities. 4) No correlation was observed between Giardia cysts removal and indicator bacteria removal. However, significant relationship was observed between average removal of C.perfringens spores and Giardia cysts. These results indicated that C.perfringens spores can be useful indicator for the evaluation of protozoan densities and removal. 5) Turbidity appeared to be the most appropriate indicator for Giardia cysts removal in activated sludge treatment process.

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An investigation on relationship between sea bottom environment and macrobenthic fauna was carried out at 29 points of Tokyo Inner Bay in different seasons. Concentrations of COD and total sulfide and thickness of sedimentary accumulation in all investigated areas except some coastal areas and waterways were over 30 mg·g^-1, 1.0 mg·g^-1 and 0.7 m respectively, which suggested that the sediment of the above area had suffered from serious organic pollution. The number of macrobenthic species decreased at the places where concentrations of COD and total sulfide and ignition loss of sediment were over 20 mg·g^-1, 0.3 mg·g^-1 and 8%. More than 10 species of macrobenthos were hardly observed at the places where COD concentration, ignition loss, total sulfide concentration of sediment and thickness of sedimentary accumulation were over 50 mg·g^-1, 14%, 2 mg·g^-1 and 1 m, respectively. No macrobenthos was observed in the offshore areas with serious organic pollution and macrobenthic fauna at the places surrounding was very poor in summer. The inner area of central waterbreak, where the sediment condition was comparatively good, could have diverse and rich macrobenthic fauna in spring, however it became an area with no or poor macrobenthos in summer due to the decrease of DO in sea bottom layer.

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Strong acid water generation from mudstone exposed to the atmosphere through excavation and dredging was observed in sedimentary layers corresponding to the period from the Neogene to the Pleistocene. This phenomenon has been recently related to environmental problems associated with large-scale construction.
This paper describes the phenomenon on the acid leachate from mudstone using a batch test and an experimental landfill test. Generation of acid water is estimated as the leaching of sulfate from pyrite contained in mudstone due to oxidation reactions in the presence of oxygen and water. Rut, it is shown that leaching of sulfate is depressed under coexistence with chlorine. In this test, pH decreased to 2.8 and SO₄^2- concentration increased to 2,300mg·l^-1. Oxidation reactions and acid-water migration in the field were examined using an experimental landfill 2.5m in height composed of mudstone dredged from the sea bed and cap soil. From observations of oxygen concentration in pore, we determined that the zone affected by oxidation is limited to about 0.5 to 0.6m penetration under the cap soil with 0.5m of depth due to consumption and diffusion of oxygen in pores.

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Concentration of rare earth elements in bottled drinking water was analyzed by inductively coupled plasma mass spectrometry. Concentration of rare-earth elements (Y, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, Yb, Lu) were measured about bottled drinking water of 55 kinds marketed in Japan. Concentration of rare-earth elemnts measured were under 1 ng/ml. Rare-earth elements were able to be classified to 5 groups by cluster analysis. By cluster analysis of bottled drinking water, bottled drinking water showing very near rare-earth elements composition existed. However, trend of certain constant by water resouces of bottled drinking water and classification was not recognized.

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