In the present study, the rate of oxygen consumption of the Microcystis floc corrected from surface bloom of lake Kasumigaura was measured as a function of mixing strength of the flow field in the bottle agitated by a magnetic stirrer. The strength of the applied flow field was characterized by the rate of energy dissipation per unit mass, ε, which was obtained from the rate of rapid coagulation of uniform polystyrene latex particles measured by means of coulter counter. It was found that the rate of oxygen consumption is constant against the strength of flow field for the range 1.0<ε<10³ (erg/g.s.). With this result, the validity of the method to apply the commercial BOD tester composed of a closed bottle with a magnet stirrer for the measurement of the rate of oxygen consumption of Microcystis floc was confirmed. The obtained result also implied that the aggregation behaviour of Microcystis is considered to have little effect on the rate of oxygen consumption.

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This study dealt with surface runoff of nitrogen and phosphorus components with soil losses in upland field of Japan. The USLE standard frames were constructed in the upland field, then soil losses and surface water quality were evaluated in each frame. Total nitrogen and phosphorus in suspension and supernatant were analysed by means of absorption spectrophotometry after the decomposition. To obtain the supernatant from each eroded suspension, suspended solids such as soil particles and organic matters were eliminated from each sample by centrifugal separation or by filtering. Additionally, anmonium, nitrate and nitrite nitrogen in supernatant were analysed.
The results indicated that total nitrogen and phosphorus concentration in eroded suspension were higher than in supernatant. Also, there was a tendency that total nitrogen and phosphorus concentration in suspension increased with suspended solids. It follows that soil particles and organic matters transported nitrogen and phosphorus components. Although there were poor agreement between inorganic nitrogen concentration and suspended solids, the loads of nitrogen and phosphorus components, even for inorganic nitrogen, were in agreement with soil losses. Additionally, the loads of nitrogen and phosphorus in most fertilized frame (628.5 kg/10 a) were higher comparing with other frames. These results apparently indicate the surface runoff of nitrogen and phosphorus increases with soil losses, especially in much fertilized fields.

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The densities of kaolin floc have been obtained as a function of floc diameter by measuring the terminal settling velocities of gravitational fall for stationary fluid. The trajectories and terminal settling velocities ofkaolin floc in sinusoidally oscillating fluids, were then studied by obtaining numerical solutions to the nonlinear Lagrangian momentum equation with a particle-fluid drag which is a function of the particle Reynolds number. The terminal settling velocities obtained numerically for vertical and horizontal oscillating flows, were found to be lower thanthose for stationary fluid. The retardation of the settling velocity occurred for fd₀>0.1cm/s, where f is the frequency of the oscillating flow and d₀ is the diameter of floc. This retardation was primarily attributed to the increase of phase lag and the decrease of amplitude of floc oscillation, with appreciable secondary influences arising from the increase in the turbulence intensity, the diameter of floc, and the frequency of oscillating flow. It was concluded that the mechanism of this retardation obtained for terminal settling velocities of kaolin floc, in sinusoidally oscillating fluids, was similar to the results obtained for sand particles in other studies previously presented.

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For land improvement project-related work, in the case where legal procedures for the initiation of such work have been performed as stipulated under the LIL, such work may be performed even on the land of persons who are not in agreement with the performance of such work. Therefore, there is no question of either civil or criminal liabilities in cases where such work has actually been performed.
According to the LRL, in regards to the performance of land readjustment-related work without having obtained the consent of owners or possessors, it is necessary to perform such work on the basis of Article 80 of the LRL. Thus there is a need for first obtaining, through a designation of replotting, etc., a suspension of usage and profiting in regards to the land which is to be the subject of such work.
Although the text of Article 123-2 of the LIL is almost identical to the stipulations of Article 80 of the LRL, the legal purposes, spirit, objects, and legal constructions, etc., of these two laws are in fact different. Therefore, the legal basis for implementation of work under the LIL should not be understand as being the same as that for implementation of work under the LRL.

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The beach shoreline change and its factors in the Nozumi-Teradomari coast, where the outlet of discharge channel is located, are analyzed by the aerial photographs and bottom sounding surveys. Flood index is introduced as a factor to forecast the shoreline change, instead of estimating the volume of sediment run-off from the river Shinano. It is analyzed the relationship between shoreline change and flood index that is obtained from daily discharge at the reference point of flood plan in the river Shinano.
By the analysis above, the followings were recognized regarding to the shoreline change.
1) The left side shoreline of discharge channel was to be advanced after the period of frequent occurrence of large-scale flood, on the other hand it was to be retreated when large-scale flood occurred few or none.
2) The amount of change in the right side shoreline was less than the left side one, and it began to change about 1-2 years later than the left bank.
3) It was shown that by using the flood index of the year at the reference point of the basin, it is able to forecast the trend of shoreline change in the next year.

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The variations in grain size accumulation curve and zeta potential of kaolinite due to the addition of dispersing agents were experimentally investigated. The sufficient effect for dispersion of the kaolinite suspension was obtained when more than 0.15mL/g of saturated solution of sodium hexametaphosphate was used as the dispersing agent. The sufficient effect for dispersion of the kaolinite suspension was also obtained when more than 0.20mL/g of solution of sodium silicate, which specific gravity was 1.023 at 15°C, was used as the dispersing agent. However, the effect for dispersion of the kaolinite suspension was not obtained when even 0.40mL/g of 1N solution of sodium hydroxide was used as the dispersing agent. On the other hand, it was found out that the zeta potential was less than at least-35mV in order to obtain the sufficient effect for dispersion of the kaolinite suspension.

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The functional form of the Gouy-Chapman theory on the interaction of electric double layer is tested to calculate the yield stress, T_o, of the dilute suspension of sodium montmorillonite in a electrostatically dispersed state as a function of the volume fraction of clay particles, φ The result showed that the proposed expression can explain the large increase ratio of To against φ which were experimentally obtained by Fujii et al., Sudo et al. and Yasutomi et al. However, the quantitative difference in the absolute value of τ₀ implies it is necessary to introduce the efficiency factor of φ in term of the appearance of double layer force accounting for the orientation of the dispersed sheets and purity of montmorillonite sheets.

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The objectives of this study are whether or not are it is possible to use melting slag from municipal solid waste as fine aggregate for concrete. In this paper, 3 kinds of melting slag made by electronic arc, electronic plasma and cokes-bed melting processes were examined. As a result, the following have been clarified:(1) All of the slag have excellent physical and chemical properties as fine aggregate for concrete. All almost of the slag elutes hardly any heavymetals at all. The slag made by electronic plasma and cokes-bed has latent hydraulic properties.(2) The concrete using slag aggregates were not expanded, because aluminum contained in slag aggregates were chemically stable.(3) The strength of concrete using slag aggregates were equal to or higher than river sand concrete strength.(4) Since amount of bleeding of concrete using slag aggregates increases with the amount of mixed slag increase, the setting time were retarded, and the freeze-thaw resistance of concrete using slag aggregates were decreased slightly with a high replacement.

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We carried out the water purification test using oyster shells of which we had been making effort to fmd disposal measures as industrial waste, especially on the assumption that agricultural water amenity park. In the experiment, the daily variation of water quality was examined, using deteriorated agricultural water and making it circulate through an oyster shell tank.
As a result, the following findings were obtained.
1) Hydrogen ion concentration was about 8 and dissolved oxygen concentration was more than 5mg/L throughout a whole observation period. The concentration of suspended solids decreased from 20mg/L to 2mg/L in a few days. The value of biochemical oxygen demand also decreased from 8mg/L to about 4mg/L in about a week and dcreased to 1mg/L in 30 days. An improvement effect in electric conductivity was not found. 2) The number of coliform bacteria group decreased from 5, 000 MPN/100mL to 1, 000 MPN /100mL in a few days after the starting of experiment, showing further decreasing tendency also afterwards. 3) Total nitrogen concentration decreased from the value of 1.4mg/L to 0.6mg/L, a value less than half of the initial concentration, in about 10 days, showing further decreasing tendency after then. Especially, large decrease of ammonium was found. Total phosphorus concentration increased to 0.20mg/L in about 10 days due to the phosphorus elution from oyster shells in initial stage, but afterwards, it turned to decrease. Namely, it decreased to 0.1mg /L after 20 days and to about 0.05mg /L after 30 days. 4) As the decreasing tendency of coliform bacteria was found, the water purification is expected from the sanitary point of view. Further, we judge the supply of new oyster shells to be necessary every 7 years or so to keep their function, because the reduction of their volume due to elution is about 5% a year by our investigative cases.
From the above result, it is concluded that oyster shells are useful for the purification of agriculutural water.

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Arsenic is highly concentrated in the groundwater of the Ganges delta, with 220 thousand chronic arsenic disease patients identified in the state of West Bengal in India. In Bangladesh, however, the number of patients is not yet clarified, nor the arsenic-polluted area. In order to address the matter, Samta village in Bangladesh was selected as a model village for achieving arsenic free water for drinking and cooking.
Arsenic concentration of the ground water in all the village tube wells was analyzed from 26ththrough 30th of March 1997 to determine the distribution of arsenic pollution. A follow-up survey was carried out from 8th through 15th of October, 1997 so as to determine the contour line of the groundwater and the arsenic concentration in the rainy season. From the above surveys the following were revealed: 1) The ground water arsenic pollution in Samta village is the worst in the Ganges alluvial plain; 2) The arsenic concentration in the ground water during the rainy season is higher than in the dry season; and 3) The high arsenic distribution in Samta village corresponds to a buried channel judging from the relationship between the contour line sand the flow direction of the ground water.

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The purpose of this study is to clarify the relations between river water quality and watershed landuse, river bank conditions, and river channel form (artificial or natural) in the dairy farming area of eastern Hokkaido, Japan. The concentration and specific load of nitrogen showed a tendency to increase with: 1) the rate of grassland area to the watershed, 2) the population of cattle, and 3) the percentage of artificial river channel.
From these results, the management of river water quality and the conservation of the rural environment should be assured by the following measures: 1) control of total load production, 2) management of point-source load, 3) management of non-point source load, 4) enhancement of natural purification, and 5) conservation of runoff water passing to rivers.

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We conducted a field test on a pressure-reducing pipeline system equipped with a new type of automatic control valves for field irrigation, and verified its pressure reducing function, reproducing the results of measurement by simulation using a mathematical model. The simulation of generating status of water hammering pressure brought about by the operation of a diversion device at the end of pipeline revealed that the rapid closeout of the terminal valve propagated pressure wave upstream through the automatic control valves. As a countermeasure for restraining the water hammering pressure, the installation of a surge relief valve was studied. As a result, it was found effective to install the surge relief valve at the end of the pipeline for the downstream side of a pressure-reducing valve (automatic control valve), and it was found effective to additionally install it at the upstream side of a pressure-reducing valve. It was also found that the size of the surge relief valve requires about the same level as the main pipe in terms of diameter.

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Air-seeding was carried out in an area of 120, 000ha between 1983 and 1995 for controlling desertification. Using vegetation data of 138 plots of seeded area, suitable plant species and seeding rate have been concluded with the following results.(1) Suitable plant species are Hedysarum mongolicum, Artemisia sphaerocphala, Astragalus adsurgens, Melilotus suavealens.(2) Low seeding rate of 6.0-7.0kg/ha gives better results with seed treatment. Secondly the relation of seeding time, average sand dune height, sand dune density and natural plant cover rate with the plant cover rate after air-seeding was established using the Quantification Theory I. The results are as follows:(3) Suitable seeding time is from May 25 to June 25.(4) Land types suitable for air-seeding have average sand dune height between 0-10m, sand dune density below 75%, and a natural plant cover rate of 12-25%.

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The upland field improvement projects, mainly integrated upland field improvement projects, have been carried out to secure crop production and to enlarge the degree of freedom of crop selection. The rate of upland irrigation improvement reached 16% at the end of FY 1995 while the fourth long-term plan of land improvement aims at increasing the rate to 30%. As it becomes more difficult to secure satisfactory water resources, many projects would adopt water conveyance system by using pump. A case study of T irrigation project has shown that establishment of irrigation farming needs considerable time in projects with water conveyance system by using pump. It is important that the irrigation project in different phases should be adopted to reduce the difference between plan and actual condition of water utilization, and to establish water utilization suitable to area condition. This paper discusses favorable design condition of the project in different phases with diameter of pipe and actual pump head, in view of reducing total cost of construction and maintenance in projects with water conveyance system by using pump. The result shows that introduction of the project in different phases suitable to area condition including project implementation system is necessary in high pump head area (actual pump head is above 80m).

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Agricultural pipeline is demanded a large-scale flow area in the case of renewing an old or damaged open channel. Recently, plural large pipes are buried into the same trench in order to bury shallowly and to make maintenance easy. But the behavior of these parallel buried pipes has not been cleared enough, and these cases are designed as similar to single buried condition. This paper discusses the behavior of twin buried pipes (φ 2400mm FRPM) that was obtained by in situ test during construction and one year passage. Results are summarized as follows:
1) Sheet-pile extraction remarkably increases the deflection of near side pipeline only.
2) The pipe strain of spring line restrains to 80% at adjacent side compared with sheet-pile side.
3) The strain distribution of pipe inclines to sheet-pile side and appears symmetrical phase with adjacent pipes.
4) Even so, in case of twin buried condition, the properties of pipes that increase deflection during construction and interact with backfill materials are basically similar to single pipe installation.

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