A lime-alum treatment method for wastewater discharged from tunnel costruction works which contains water glass (soluble silicate) and portland cement for chemical grouting was designed. The wastewater was treated with calcium hydroxide and aluminum sulfate simultaneously. The operational characteristics of model suspensions containing water glass, portland cement and kaolin were examined by the jar test. The results are summarized as follows :
(1) Turbidity was not removed to less than several turbidity units by lime treatment alone when the S. SiO₂ concentration of wastewater was under 145 mg·l^-1.
(2) In the case of the lime-alum treatment, regardless of the S. SiO₂ concentration of wastewater, turbidity was removed completely by adjusting the pH to more than 10.7 with lime and alum dosages depending on the effluent turbidity.
(3) The lime and alum requirements for treatment of the model suspensions (S. SiO₂ 43.5-290mg·l^-1, kaolin 1,000mg·l^-1 and portland cement 100-5000mg·l^-1) were 60-100mg·l^-1 and 0-40mg·l^-1, respectively.
(4) The sediment volume of 60min. sedimentation (SV₆₀), which increased with S. SiO₂, concentration of wastewater, was 0.5-5.0% throughout all of the experiments.
(5) The contact time required was 5-10min.
(6) S. SiO₂ was only slightly removed.
From these results, the lime-alum treatment method was considered to be useful for the wastewater discharged from a tunnel construction site using chemical grouting.

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Mutagenic activity was examined on dichloromethane extracts of leachate samples collected from a municipal solid waste landfill by means of the Ames Salmonella assay. Mutagenicity was found among 51% of 101 leachate samples and most of the positive samples showed mutagenicity for both strains TA100 and TA98 irrespective of metabolic activation by S9, indicating that the active ingredients consisted mainly of direct mutagens. A four-year survey revealed that mutagenic activity in landfill leachate was high (200-1,500 net revertants·l^-1) during the operation of the landfill, whereas it decreased gradually after the landfill was closed. Detailed study on clesed landfill sites showed that younger landfill sites discharged leachate with higher mutagenic activity. No correlation was observed between mutagenic activity and conventional water pollution indicators such as BOD, COD, TOC, DO, and water temperature except for T-N which showed a weak positive correlation. These results demonstrated the significance of the mutagenicity assay for evaluating the possible presence of micropollutants in landfill leachate.

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The concentrations of tributyltin (Bu₃Sn⁺), triphenyltin (Ph₃Sn⁺) and their degradated products including dibutyltin (Bu₂Sn²⁺), butyltin(BuSn³⁺), diphenyltin (Ph₂Sn²⁺) and phenyltin (PhSn³⁺) in the inside and in the outside of Dokai Bay were measured to investigate their distributions and behavior by GC-FPD.
No organotins were detected in the sediment samples taken from the outside of Dokai Bay. The highest concentrations of Bu₃Sn⁺ and Ph₃Sn⁺ were 0.42 and 0.29mg·kg^-1·dry in the inside of Dokai Bay, respectively. Relatively high concentrations of Bu₃Sn⁺ and Ph₃Sn⁺ were found in the areas of heavy shipping traffic, shipyards and docks, where they are used as antifouling agents in paints for boats and ships. Coefficients of sediment-water partition of organotins were also calculated as the ratio of the concentration of organotins in the sediment to those in the water column just above it. Coefficients of the range of partition of BuSn³⁺, Bu₂Sn²⁺, Bu₃Sn⁺, PhSn³⁺, Ph₂Sn²⁺ and Ph₃Sn⁺ were in the range of 10² to 10³. By using the dendrograms based on concentration ratio of butyltin homologues, we attampted to estimate the persistent periods of butyltins in water environments.

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The structural analysis of bacterial phase in an aerobic submerged biofilter was carried out on the basis of quinone profiles. The predominant quinones at 5°C, 20°C and 35°C were, ubiquinone (Q)-8(57.3 mol%), Q-8(56.1%) and Q-7(32.8%), respectively. The predominant bacteria inhabiting the microbial film of biofilter were Proteobacteria classified into β-group at 5°C and 20°C, while those of α- and γ-groupes were inhabiting at 35°C as well.
The dissimilarity (D) between 5°C and 20°C, i.e. D (5°C, 20°C), was 23%, and D (5°C, 35°C) and D (20°C, 35°C) were 45% and 53%, respectively. It was clarified that increased temperature brought about a change in the bacterial phase inhabiting the microbial film of biofilter.

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The performance of the ANAMET anaerobic-aerobic system for treating the alcohol stillage wastewater was investigated by conducting pilot plantscale experiments. The ANAMET system is combined with a thermophilic anaerobic contact process and a conventional activated sludge process.
In the anaerobic contact process unit, BOD removal efficiency of 87% and COD removal efficiencies ranging from 82 to 83% were obtained under the following operational conditions : the temperature ranged from 53 to 55°C, the HRT ranged from 4 to 5 days and the COD loading rate ranged from 9.11 to 11.7 kg-COD·m^-3·d^-1. The optimum ranges of influent COD concentration, COD loading rate and sludge age in the aerobic activated sludge process unit were 2,000-3,000mg·l^-1, 0.55-1.10kg-COD·m^-3·d^-1 and 8-15days, respectively. Through this investigation, it was found that the ANAMET anaerobic-aerobic system provided efficient performance in the methane production, the improvement of effluent water qaulity and the decrease of sludge production. This anaerobic-aerobic combination system is considered to be suitable for the treatment of wastewater with high concentration of solids.

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