To pursue development of rill networks on sloping fields during a short period, intermittent field surveys and hydrologic measurements were performed in 4 months since the construction of the sloping fields were finished. All of the rill networks formed on the fields had tree-like type of network structures and rill networks of 3rd order (Strahler ordering) were formed at early stage in the observation period. There existed close relationships between rill numbers in the rill networks and their orders but there existed no relationship between rill lengths in most of the networks and their orders at the last stage in the observation period. Furthermore, factors influencing rill formation and development of rill networks were investigated.

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The behavior and characteristics of pollution loading amount and water quality of wastewater were investigated by using observed data on rural sewerage facilities. In this paper, the pollution loading amount of wastewater was examined on the basis of the water quality of wastewater obtained from composite tests conducted during 24 hr and inflow of wastewater observed in the flow meters installed in rural sewerage facilities. It was found that probability distribution of pollution loading amount obeyed normal or logarithmic normal distribution and water quality also agreed with logarithmic normal distribution. It was found that behavior of pollution loading amount over a wide rage of water quality is nonlinear and dependent upon the magnitude of the water quality obtained from the investigation. The relationship between pollution loading amount and water quality is represented by hyperbola equations. Water quality of wastewater were influenced by inflow rate of wastewater so that water quality of wastewater were in inverse proportion to inflow rate of wastewater. Pollution loading amount and water quality of wastewater cloud be predicted by considering known conditions such as numbers of users and amount of used city water of rural sewerage facilities.

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The tests for shrinkage parameters of clays were carried out for natural and mineral clays. The relationships among shrinkage limit (w_s) which is one of the shrinkage parameters, other consistency limits and pH were examined. The results obtained can be listed as follows, (1) Kaolinite has markedly higher shrinkage limit than bentonite, and the shrinkage limit of clay having more bentonite is lower.(2) The shrinkage index (I_s) (=plastic limit w_p-shrinkage limit w_s.) increases in proportion to plasticity index (I_p) in the range of I_p<100 and I_s is a constant being independent of I_p in the range of I_p>100.(3) The liquid limit (w_L) increases in proportion to the square of the pH approximately.(4) The relationship between I_s and pH was found to be a linear relation.

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A pressure infiltrometer method based on the theory of constant-head infiltration from a single ring has been widely used to determine a field-saturated hydraulic conductivity of soil. An apparatus as well as a procedure to measure the steady-state infiltration rate into soil is quite simple. In this study, accuracy of the field-saturated hydraulic conductivity of soil measured by the pressure infiltrometer method was assessed using field tests. The sands with low content of fine soil particles were selected for the study. The field-saturated hydraulic conductivity of soil was measured at 142 points in the fields and compared with permeability of the 100cc-in-volume soil cores bored from the test sites. The field tests show that the former are about 27% in average larger than the latter. Then numerical calculation using the finite element method was conducted to investigate the dimensions of soil region which is tested by the pressure infiltrometer method. The numerical results suggest that, when the constant head of 10-2 cm above the soil surface is employed in the sand soil, the field-saturated hydraulic conductivity measured by the pressure infiltrometer method represents the permeability of the soil region approximately 20cm in depth from the soil surface.

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The paper presents the results of field tests that were conducted to reveal the mechanical performance of large flexible pipe buried in shallow cover with enhancement of the uplift capacity of buried pipelines by the use of geogrids.
Twin type flexible pipes, whose diameter was 2400mm, were installed in the field with 1.5m cover. The mechanisms involved in the uplift process under increasing ground water level and the behavior of pipe during construction were discussed. After measurement for the performance of pipe, about 1 year duration, the results indicate that the deflection of pipe is less than 1% of diameter and the force onto the geogrid is about 10% for the ultimate strength of that. The results of field test reveal that the pipe with geogrid protection is restrained its deflection during the installation of pipe, and that the uplift resistance of buried pipeline can be increased significantly by the incorporation of geogrids.

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A laboratory scale automation system for the extended aeration process was installed to study the effects of DO controlling and intermittent aeration on energy saving and nitrogen removal. ORP reaches to the peak (P 1) when nitrification finishes in the constant DO condition. The ORP peak can be used as the indicator for finishing aeration. The ORP inflection point appears at the end of denitrification is already known as ‘the nitrate knee’. Therefore, optimum DO control for nitrogen removal can be realized, by detecting the both inflection points on the ORP curve.
Especially, in the conditions showing both of peak and nitrate knee on the ORP curves, the average T-N removal rate were kept over 90%.
Treated water qualities (T-N, BOD, COD, TOC) could be kept stable ever on condition that the input load varied largely.
Farther more, the energy for aeration could be largely saved using this treatment system.

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The automatic control system based on detected the inflection points on ORP curves was developed for extended aeration wastewater treatment system. In this system, the blowers were stopped at the end points of nitrification and restarted just after setting time for anaeration phase since nitrate knee was shown on ORP curves. Thus, aerobic, anoxic, and anaerobic phase were alternately made in an aeration tank for an aeration and non-aeration cycle. The removal rates of BOD, COD, TOC, T-N, and T-P in automatic control system were 97.9%-99.0%, 89.4%-95.4%, 91.1%-96.6%, 93.0%-95.9%, and 54.3%-85.1%, respectively. Overall, the results showed that this automatic control system was strongly reliable for the treatment of wastewater.

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The examined dam (Nishitakao Dam in Touhaku National Irrigation Project) is possible to be eutrophicated because of an excess of nutrient load effluent from livestock area and fodder fields on the dam basin. Although now, the water quality is categorized as an eutrophic lake, the water-bloom has not occurred. It is considered that the dam operation which they exhaust the dam of water at the end of irrigation period affects the formation of water environment, The aim of this study is to examine the dynamics of water quality, including the effect of the term-end discharge, an ecosystem water quality model was constructed in this study. Simulation results showed that, under the condition without term-end discharge, the maximum value of Chemical Oxygen Demand (COD) was decreased because the inflow which imports pollutant to the dam decreased by 26%. However, it was also shown that the concentration of Total Nitrogen (T-N) increased gradually and the concentration of Total Phosphate (T-P) kept almost no changes

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A robust optimization (RO) model to manage water quality in rivers is presented. RO is a framework that is characterized by defining solution robustness and model robustness and controlling the effects of data uncertainties in the model on optimal solutions. Discharge, water depth and water temperature are assumed to vary stochastically in rivers and several scenarios are generated. To maximize expected total BOD loads from outfalls, solution robustness and model robustness are objectives in the RO model. Constraints consist of BOD and DO transport equations discretized by the finite element method, water quality standards and effluent limitation standards in rivers. Optimal allocations of effluent BOD loads can be determined by simulating the stream flow and operating the RO model with various values of multiobjective weights. Application to a hypothetical river system demonstrates that the model can be more effective tool for providing alternative solutions than a commonly used stochastic programming model.

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This paper aims at the proposal of the cost benefit analysis using Contingent Valuation Method about the village park project, based on the investigation data of 19 parks where the projects were completed. The findings are as follows. Firstly, appraised value by CVM is stable in both investigation and analysis procedures. Secondly, when we calculate an average CV, it is practical to use the method that Boyle et.al. showed. And it is desirable to design the questionnaire including personal income and attribute. Thirdly, the number of household in benefits range influences results of cost benefit analysis greatly. In order to reduce such influence it is effective to divide the benefits range from the similar park on the map. Finally, correlation between the benefit and the construction-and-maintenance cost is very low in the village park project. This suggests that it might be insufficient to apply the current method substituting the construction cost for the environmental benefit of village park.

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The objective of this study is to find whether or not it is possible to use melting slag powder from municipal solid waste (MSW slag powder) as a concrete admixture. In this paper, MSW slag powder (blaine's specific surface area=3, 920cm²/g) made by coke-bed melting processes was examined.-I inspected the quality of the MSW slag powder and properties of mortar, and concrete that used the MSW slag powder in research. As a result, the following have been clarified:(1) The chemical compositions of the MSW slag is same of that of blast-furnace slag, but the alkali content is much more than that of it.(2) T he slag elutes hardly any heavy metals at all.(3) MSW slag powder has the characteristics equivalent to the blast-furnace slag powder (flow value, stable, setting time, early period heat of hydration, strength, Freeze-thaw resistance).

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This paper reported the changes in microbial flora and an attempt carried out to identify the genus, which are playing an active role in the reactor to decompose kitchen garbage. The results may be summarized as follows.(1) The viable cell account shows the peak values, 3 hours after putting the garbage into the reactor and gradually decreased.(2) The active isolates (bacilli) are predominant right after putting the garbage in to it. As the organic matters are being decomposed, the non-active isolates (cocci) increase in comparison with the active isolates.(3) The involved microbial floras grow well at 40°C, and can not survive at 60°C. Then, the flora is judged mesophile.(4) Microbial flora consists of biota belonging to Bacillus.

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This study dealt with effective strainer structure of porous underdrain pipes installed in a settling pond. On the basis of experimental results observing the discharge through the different shapes of a strainer, it became clear that the discharge through constant radius strainer was smaller than that through funneled radius strainers. Especially, in the case of high suspended concentration, the discharge through funneled radius strainers was much larger than that through constant radius strainer. However, there was no differences in discharge among the funneled types of strainer, in which the enlargement degree of strainer radius ranged from 17° to 50°.
Two types of underdrain pipe were installed in a settling pond to compare the discharge of pipe with constant radius strainers and that with funneled radius strainers. Until 4 hours from the suspension inflow to the settling pond, the discharge of pipe with funneled radius strainers was almost in agreement with that of pipe with constant radius strainers. However, after 5 hours passed, the discharge of pipe with funneled radius strainers was much larger than that with constant radius strainers. Also, suspended solids of underdrainage from both pipes were lower than 820mg/l. It was much smaller than the concentration of inflow to the settling pond. According to these experimental results, it was concluded that the structure of a funneled radius strainer is effective for maintaining underdrainage in a settling pond.

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The clogging of filter and emitter in microirrigation system are serious problems for keeping water constant supply during cropping season. The effects of algae clogging were discussed by using various kinds of filters and emitters of the microirrigation system under conditions of polluted and unpolluted irrigation water. There are high relationships between concentration of chlorophyl a in algae and turbidity or suspended solid. Since size of algae contained was smaller than the opening diameter of filter element when polluted water was used, the emitter clogging was slightly improved by the volume type filter rather than the areas type of filter.
In the case of unpolluted irrigation water where natural spring water was used, longer size algae extremely increased during irrigation season. The area type filter was not effective to remove algae but suspended solids contained in irrigation water. The volume type filter was effective to decrease the emitter algae clogging when algae were filtrated in the short irrigation periods of two to three months. Under longer irrigation periods, however, the algae were absorbed with filter element too tightly to clean up by the system of automatic back washing of filter.

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[in Japanese]

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[in Japanese]

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