The water quality before and after the secondary treatment in domestic wastewater treatment facilities in Chiba prefecture Japan were surveyed. T-N removal performance was high in the plants operated in intermittent aeration mode as compared with those operated in continuous aeration mode because of occurence of biological denitrification in their process. The performance of T-N removal was low in the facilities of which influent BOD concentration was low even though it was operated in intermittent aeration mode. The decease of BOD was observed in equalization tanks in the facilities of resort condominiums of which influent BOD load was extremely low. The mean value of influent BOD/T-N ratio in such facilites was below 2. That caused lack of proton donor resulting in difficulty in progress of denitrification while nitrification was advanced sufficiently. The relation between influent BOD/T-N ratio and T-N removal in surveyed 37 facilities suggested that the maximum T-N removal for a certain value of BOD/T-N ratio smaller than 4 decreased by the equation approximately: R_N,Max=20×(BOD/T-N)+10, where R_N,Max is the maximum T-N removal(%). This equation can be applied to estimate the amounts of proton donor to be added in facilities of which influent BOD/T-N ratio is low.

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In this study, actual river water, that was pretreated by coagulation sedimentation, was treated in a fixed bed mini-column of biological activated carbon (BAC) or sand for a very long term about 1,800days, and the changes of effects to remove organic compounds by biodegradations and adsorption were investigated. In sand column which has only biodegradation effect by biofilm, 34% of organic compounds as TOC could be removed after one or two months of lag time. Biodegradation of organic compounds which had adsorbed once in pores brought about the extension of adsorption ability of BAC, and pore volume was recovered. Adsorption ability decreased with pore volume decrease by adsorption of organic compounds which were hardly degradable, and TOC removal ratio of BAC decreased gradually and became as same as that for sand after a long time.

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Headloss and longitudinal dispersion coefficients were investigated for steady uniform flow through rock beds with different gravel sizes in a range of flow rates or Reynolds numbers relating to operation of the rock bed contact-purification channel. The empirical equation for volume to surface of rock media was obtained to compare the equivalent spherical surface with the actual surface of a large number of rocks. The shape factor (α/β) of rock media was considerably larger than that of filtration sand, and α/β was 7.2-8.5 for the 350-1,200cm³ rocks. The headloss equation by Fair-Hatch explains approximately the experimental results by the use of the above shape factor. The dimensionless coefficients aL and bL for the longitudinal dispersion equation given by D_L/ν=a_L·Re^bL were obtained from the one-dimensional tracer tests in a Reynolds number range from 10¹-10³ through rock beds of 9mm-113mm media. Such a kind of experimental study is necessary and important in the region of large Reynolds numbers (beyond the range of Darcy's law) because of the pore-system geometry and the effects of inertia and turbulence which can no longer be neglected as the mechanical dispersion becomes dominant. The coefficient is 12.38 for a_L and 0.72 for b_L within the limit of this experiment. The longitudinal dispersion coefficient is calculated to be 3.6-17.6cm²·sec^-1 for the fluid interstitial velocities (=(flow rate)/(cross sectional area of voids)) of 0.1-0.9cm·sec^-1 in a bed of 113mm media using the above coefficients of a_L and b_L.

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It's reported that the trihalomethane was produced from the 1,3-diketone structural compounds such as acetylacetone by chlorination for water supply, and the water treatment methods should be necessary to prevent their production. In this report, each 5 mM diketone was treated by ozone alone, UV irradiation alone or ozone + UV irradiation (ozone/UV), and their degradation pathways were investigated from the decomposition products.
The main pathway of diketone was considered to have released a longer side-chain prior to the other shorter chain for the one side ketone group. The released groups were oxidized to keto-aldehydes and keto acids. When the shorter side-chain was methyl group, the residue group was oxidized to acetic acid. In the side pathway, a small quantity of keto acids was produced from the residue group when the methyl group as a shorter side-chain was released as formaldehyde.
The decomposition behaviors of three diketones themselves by ozone/UV were compared, and acetylacetone was decomposed most rapidly among them. Acetylacetone was decomposed comparatively rapidly even by UV irradiation alone, as it has UV absorption spectrum at about 254 nm which is the main irradiation wavelength of low pressure mercury lamp.
TOC (total organic carbon) removal(%) was very high by ozone + UV irradiation, and most efficient decomposition to inorganic carbon dioxide compared with ozone alone treatment was assumed.

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1 . Biological water quality of streams on campus was measured by observing aquatic invertebrates during 1994-1996. Results were compared with those in spring and autumn and with those at Sandankyo in 1996.
2 . The number of species observed on campus in the spring were 28-35 and in the autumn was 19-32. At Sandankyo the numbers were 35 in the spring and 33 in the autumn.
3 . Insects represented 75-83% of the species on campus and 91-94% of the species at Sandankyo. The dominant species on campus were Amphipoda, Diptera, Ephemeroptera and at Sandankyo were Ephemeroptera and Tricoptera.
Because the numbers arc small, the red Chironomidae, which are pollution resistant, are of little problem at both sites.
4 . The pollution index of the water samples was measured by the Beck-Tsuda biotic index method. The indices on campus were 25-34 in the spring, 16-37 in the autumn and at Sandankyo were 39 in the spring and 34 in the autumn. The cleanest water quality was in the mid-and upper streams on campus and in the streams at Sandankyo.

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