The cation-exchange equilibrium of toxic metal cations were investigated in wide concentration range to predict their behavior in contaminated soils. When the concentration of toxic metal cation in water was high enough, the exchange amount became saturation at the cation exchange capacity of each soil. The exchange isotherms in low concentration range showed the linear relation ship in logC₁ vs. logQ₁ diagram with slope n₁. The value of n₁ was not based on the kind of soil, but was determined for each cation. The influence of coexisting cation was expressed quantitatively by the multiple isotherm equation proposed in this study. The concentrations of H⁺ and Al³⁺ gave the strong effects to the exchange of toxic cations.

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A new soil washing technique is developed and its actual example of work is shown, which can clean up oil-contaminated soil by using micro-bubbles produced from self resolution of hydrogen peroxide in alkali solution. This method has ability that can extract 90%-99% oil from highly contaminated soil with heavy oil like fuel oil C. This method also has merits: One is that extracted oil can be collected at the surface of solution for recycling. The second is that the water can be reused in the remediation process as solution is easily treated. The third is application of bioremediation after the treatment may lead to an extreme level of remediation, as resin and asphalten components are to be extracted well.

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A study on evaluating from the viewpoint of saving cost and preventing global warming gas emission on municipal sewers was conducted applying both LCC converted present worth and overall LC-CO₂ emission accumulated for two-generations during an evaluating period for 100 years describing [LCC]² and [LC-CO₂]². For the next-age systems, applying shallow buried pipelines, reducing solid wastes and applying material recycles of used pipes, apparatus, parts, etc. were considered for conventional, multi-pumping gravity and vacuum sewer systems as the alternatives. The evaluations were carried out proposing two kinds of integrated indicators as well as individual factors for the comparisons.

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The amount of reduced CSO loads and the amount of CO₂ emission by the construction and operation of the reservoir were calculated. The authors have proposed the evaluation index in consideration of CO₂ emission. which is considered not only CSO loads reduced but also CO₂ emission. The calculation cases are 6 examples as following: without reservoir (case1), capacity of reservoirs are 10, 000-50, 000m³ (case2-6). According to this evaluation index, the case3 which capacity of reservoir to 20, 000m³ is the best. When projects are selected to improve social infrastructure, the index gives us an important information about efficient of project effect and CO₂ emission.

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We used a questionnaire to gain an understanding of inhabitants' ideas about what they want from the facilities along the watersides. We learned that many inhabitants are concerned about the purity of the water in streams and rivers. They also conveyed that they want improvements to riverside spaces to be geared to different uses that suit various age brackets. People thought revetments should be designed for safety and provide easy access to the river. Elderly peoples expressed an especially strong desire to participate in activities related to river maintenance. We believe that maintenance provided by the inhabitants themselves is an effective means of preserving the waterside and making sure that it is used effectively.

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Process behavior of a novel bioreactor for sewage treatment, in which a net membrane unit was installed as an alternative of final settling chamber, was examined by conducting a continuous flow experiment. A polyester-made net membrane unit having 77μm mesh size and 37% of opening area was employed. Permeate flux was ranged 0.6 to 1.5 m·d^-1 and permeate SS was maintained below 10mg·L^-1 under 100mm H₂O pressure. The proposed net membrane bioreactor system achieved simultaneously over 90% SS removal, over 90% COD removal, and 85% ammonium removal, demonstrating the system could be an attractive alternative for final settling chamber of activated sludge process.

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Bamboo groves expanding is a geoenvironmental problem caused by a decrease in demand of food and architecture materials, and aging of owners or shortage of labor in the farm villages. The total areas of bamboo groves distributed in Toyota-cho, Yamaguchi prefecture have increased up to about 157% for 18 years on the basis of analysis of aerial photographs. Also field survey of the bamboo groves was carried out on 18 sites. Main conclusions are summarized as follows. 1) The cause of bamboo groves expanding is dependent on the type of surrounding vegetation and the predominance of bamboo. 2) Bamboo groves expanding results in the death of conifers. 3) Bamboo have a tendency to grow in silt ground having characteristics of low liquid limit and comparatively low N_d value.

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A new reactor configuration called reversible flow anaerobic baffled reactor (RABR) was applied to palm oil mill effluent (POME) which contains high proportions of particulate COD. A laboratory-scale RABR having a working volume of 20 liters was operated under thermophilic condition (at 55°C) for 500 days. The reactor accommodated a volumetric COD loading rate of 20 kgCOD·m³·d^-1, keeping soluble-COD removal of above 90% on average and overall-COD removal of 76% on average. There was no tendency for lipids to accumulate within the sludge bed over the entire period. Specific methanogenic activity tests revealed a uniform distribution of methanogenic sludge along the RABR compartment

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