In order to improve DO condition of lake or sea, this paper proposes a method of increment of DO in the water and gives an experimental investigation for the method. A vertical pipe connected to the waters where DO is poor is set in the water, inside of which are located an air -stone and a honeycomb above it. Bubbles formed accumulate on the top of the honeycomb, and all water to be treated becomes the elements of thin film of bubbles. Thus high performance gas dissolution is achieved. Quantities such as DO, rate of treatment etc. were examined for various conditions. It has been shown that there is an optimal size of honeycomb from gas resolution rate and that the optimal condition is realized when the relative velocity of the gas and liquid is almost the same as the slug velocity.

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In wastewater treatment systems, a pre-coagulation process increases the amount of sludge. Therefore, we examined carbonization as a material recovery method from sewage sludge.
We postulated that there would be differences between the char derived from pre-coagulated sludge and that from the sludge generated in typical wastewater treatment processes. This study investigated the effects of sludge pre-coagulated with ferric chloride on the carbonization process. We used pre-coagulated sludge and mixed sludge in a carbonization experiment and investigated the solid yield, surface area, and adsorptive capacity for hydrogen sulfide.
We found that the solid yield was higher for pre-coagulated sludge than for mixed sludge, because of the increase in iron resulting from use of the coagulating agent and the inorganic content. The surface area of the char from pre-coagulated sludge was greater than that from mixed sludge when the carbonization temperature was 700°C, because iron compounds affected the organic content. Moreover, char from pre-coagulated sludge had a greater adsorptive capacity for hydrogen sulfide than that from mixed sludge.

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To design methods of bio-remediation and soil vapor extraction to remove gasoline, kerosene, and light oil from contaminated soils, and to estimate the results of such purification, it is important to establish the principles of gas-phase substance transfer in soil. However, few experiments on gas phase dispersion in soil have been published to date. Therefore column experiments on the dispersion of oxygen and nitrogen or nitrogen and carbon dioxide were carried out with Toyoura sand of volumetric moisture content 0%. This study found peculiarities in the flow direction of gas phase dispersion in soil. Using the results of this study, the dispersivity and the molecular diffusion could be determined by means of dispersivity theory. The results suggest that the theory of dispersivity applied to substance transfer in underground water can also be applied to the dispersion of gas components in the gas-phase of soil.

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It is significant to evaluate the social and environmental benefits of the civil engineering structures. However, the environmental benefit has not been treated in the design of a structure. In this study, a direct environmental impact due to the construction of RC underpass in a traffic-congestion intersection and an indirect environmental-impact reduction effects by the clearance of traffic congestion are comprehensively evaluated. The results showed that CO₂ and SOx are mostly discharged at the manufacturing of materials and NOx at the execution of the structure and that the environmental impact at the construction of the underpass is counterbalanced in an approximately 9 year by the environmental-impact reduction from the car traffics.

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Phytoremediation is one of the environmental rehabilitation techniques that take advantage of plant physiology and metabolism. In this study, a greenhouse experiment was carried out in order to examine the applicability of plants for the remediation of lead (Pb) contaminated soil. Buckwheat (Fagopyrum esculentum) was the best plant for Pb phytoextraction in the first cultivation. Rye(Secale celeale), oat(Avena sativa) and phacelia (Phacelia campanularia) was a useful Pb accumlator for autumn sowing. In effect of leachate reduction by vegetation, the total amount of leachate for vegetation cultivation period was less than the control (no vegetation). As a result,it was concluded that vegetative coverage reduces downward water movement in the profile of Pb contaminated soil.

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The demonstration experiment of nitrate-contaminated groundwater in situ remediation was performed from 2000 January to 2003 March at Kakamihara-city. The permeable reactive barrier was constructed at the aquifer and observation wells were setted around the barrier. It was able to denitrify biologically by permeable reactive barrier containing biodegradable plastics and iron powder for reactants. The nitrate concentration of groundwater decreased after filtered out the barrier, and the performance of purification had been maintained for three years.

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Expansion of pH condition for thermophilic L-lactate fermentation of unsterilized artificial garbage was examined in batch mode culture with using L-lactate fermented broth as inoculum. The conditions were set at pH 6.0 and 55°C in order to bring pH condition close to optimal growth condition of Bacillus coagulans. The results showed that the fermentation with using L-lactate fermented broth of 400 mL/1L-Reactor as inoculum led to L-lactate fermentation instead of butyrate fermentation. Lactate concentration of 34 g/L, lactate yield based on initial carbohydrate concentration of 0.5 and optical purity of lactate of 99% were obtained in this fermentation. Then, possibility of semi-continuous fermentation was examined, because inoculation was conducted by the residual broth in fill-and-draw operation. The conditions set for the semi-continuous fermentation were pH 6.0, 55°C and COD loading of 44.8 g-COD/L-Reactor/day (HRT of 2 days and once a day operation). The fermentation resulted in lactate concentration of 26 g/L, the yield of around 0.5 and optical purity of produced lactate of 99% without any butyrate detection during 10 days operation.
A device for recording consumption of neutralization reagent by which pH condition was kept at given value was set up to the reactor for the sake of monitoring the fermentation process of lactate. Comparison between its records and analyzed lactate concentration through operation time revealed that the records described the lactate fermentation process well. Volumetric production rate of lactate could be calculated as 1.26 g/L/hr with the data monitored by this device.

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The present paper empirically examines Walras tatonnement processes of bads, focusing on the Japanese scrap papers market. The demand and supply function of the scrap papers and the reproduced paper products are estimated by using the time series data. The dynamic price adjustment formula of the scrap papers is then derived from the demand and supply function and the related inventory control model. The result reveals that the Walras tatonnement processes can be applied to the scrap papers market, if we definitely consider the control of bads in stock.

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A questionnaire survey of 199 dams was conducted to clarify the volume of woody debris entering dams in Japan. The following results were obtained: 1) Dams managed by the Ministry of Land, Infrastructure and Transport (MLIT) and Japan Water Agency (JWA) had more data on woody debris than prefectural dams; 2) The volume of woody debris was measured based on apparent volume at most dams; 3) The volume of woody debris varied widely and most of it was produced by specific local downpours; 4) Though we could not find factors correlated with the volume of woody debris, large volumes of woody debris are produced at dams throughout Japan every year, indicating that woody debris could be a useful resource.

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